Corr Starch Adhesiveman

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Corn Products International, Inc.Quality Policy on Products, Services and Customer Relations

It is the policy of Corn Products International, Inc., to provide products that not only meet

applicable government quality and safety standards, but also seek to meet evolving customer

expectations for quality, value and service; and to assure the accuracy and propriety of all labeling,

advertising, and other representations we make concerning our products and services.

This manual is intended as a resource on starch, its

relationship to, and use in corrugating. It is designed

to make it easier to respond quickly and effectively

to adhesive and machine problems. The information

presented is based upon actual field and laboratory

work. It should not be viewed as providing advice or

solutions to particular applications, each of which

is unique and not susceptible to general advice.

We encourage you to call your representative at

Corn Products U.S., CASCO, Inc., or CPIngredientes

to discuss your specific situation. We will be happy

to lend our support.

INTRODUCTION

Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3The History of Starch . . . . . . . . . . . . . . . . . . . . . . .3The Corn Wet Milling Process . . . . . . . . . . . . . . . . .4The Role of Corn . . . . . . . . . . . . . . . . . . . . . . . . . .6Starch Basics for Corrugated Board . . . . . . . . . . . . .7

Viscosity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9Low Viscosity . . . . . . . . . . . . . . . . . . . . . . . . . . . .9High Viscosity (Thick, Heavy Adhesive) . . . . . . . . . .9Effects of Shear on Viscosity . . . . . . . . . . . . . . . . . .9The Temperature Viscosity Control System . . . . . . . .10Viscosity/Time Relationship . . . . . . . . . . . . . . . . .11Viscosity/Resin Relationship . . . . . . . . . . . . . . . . .11Microbiological Degradation . . . . . . . . . . . . . . . . .11Care with Biocides . . . . . . . . . . . . . . . . . . . . . . . .11

Gelatinization Temperature . . . . . . . . . . . . . . . . . . . .12Gel Temperature Too High . . . . . . . . . . . . . . . . . . .12Gel Temperature Too Low . . . . . . . . . . . . . . . . . . .12Gel Temperature/Time Relationship . . . . . . . . . . . .12Determination of Caustic Concentration

In Liquid Caustic . . . . . . . . . . . . . . . . . . . . . .12

Corrugating Additives . . . . . . . . . . . . . . . . . . . . . . . .13Penetrating Aids . . . . . . . . . . . . . . . . . . . . . . . . .13Antifoam Agents . . . . . . . . . . . . . . . . . . . . . . . . .13Liquid Additives . . . . . . . . . . . . . . . . . . . . . . . . .13Resins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

Corrugating Processes/Systems/Equipment . . . . . . . . . .15Stein Hall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15Jet Cook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15High Shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16No-Carrier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

Starch Properties and Testing . . . . . . . . . . . . . . . . . .17Alkali (Caustic) Sensitivity . . . . . . . . . . . . . . . . . .17Measuring Viscosity of

Finished Starch Adhesive . . . . . . . . . . . . . . . . 17Calibrating the Stein Hall Cup . . . . . . . . . . . . . . . .17Gelatinization Temperature . . . . . . . . . . . . . . . . . .17Microbiological Testing . . . . . . . . . . . . . . . . . . . . .17Starch Solids Concentration . . . . . . . . . . . . . . . . .17

Board Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

Quality Monitoring and Control atthe Adhesive Station . . . . . . . . . . . . . . . . . . . . . .21Statistical Process Control . . . . . . . . . . . . . . . . . .21

Troubleshooting CommonCorrugating Problems . . . . . . . . . . . . . . . . . . . . . .23Diagnosing Viscosity Problems . . . . . . . . . . . . . . . .23Diagnosing Typical Gel Temperature Problems . . . . .26Diagnosing Corrugating Equipment and

Board Quality Problems . . . . . . . . . . . . . . . . . .27Diagnosing Warp Problems . . . . . . . . . . . . . . . . . .31

Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40

TABLE OF CONTENTS

Corporate HeadquartersCorn Products U.S.5 Westbrook Corporate CenterWestchester, IL 60154United States(800) 443-2746www.cornproductsus.com

TorontoCasco, Inc.401 The West Mall, 2nd Floor Etobicoke, Ontario M9C 5P7Canada(416) 620-2300 (Toronto)(514) 694-4700 (Montreal/Eastern Canada)www.casco.ca

CPIngredientes, S.A. de C.V.Av. Mariano Otero #1249, Floor 9Torre AtlanticoRinconada del Basque44530 Guadalajara, JaliscoMexico(33) 3884-9000 ext. 3520www.cpimex.com

CORRUGATED MAKES IT HAPPEN FOR FARMING

2

BackgroundThe History of StarchThe first uses of starch stretch back to the ancientEgyptians and Chinese. They were quite adept at usingstarches, a fact duly recorded in Cato’s Treatise written in 184 B.C.

It was much later in Europe, however, that the industry flourished. The source of grain supply then waswheat and rice. As demand for starch increased, other raw materials, including potatoes, were tried. It was theEnglish who brought the knowledge of producing starchto the New World, where, after the Revolutionary War,numerous small potato and wheat starch plants wereoperating in the eastern United States. However, the price of wheat and potatoes was rising to the point where profit margins were seriously endangered.

The search for substitute raw materials resulted inAmerica’s most abundant crop as the answer, and the firstcorn starch factory was built in 1844 in Jersey City, NewJersey. From that point on, the industry grew by leapsand bounds. In 1906, New York Glucose and the GlucoseTrust merged into Corn Products Refining Company underthe management of E.T. Bedford.

Corn Products International, Inc., Leads the WayThrough the decades, Corn Products International continues growing. Today, we operate nine corn refiningfacilities in North America. Corn starches and sweetenersproduced in these plants are used in a wide variety offood and industrial products.

Our long history with starch and experience with the corrugating industry affords corrugators many advantages. We have consistently sought new and innovative methods of meeting the changing needs ofcorrugators. Such efforts have led to the development of quality modified and unmodified starches that corrugators have come to expect. Our commitment to the corrugating industry is further evidenced by ourpledge to excellence in technical services, sales representation and engineering assistance.

3

4

The Corn Wet Milling ProcessThe objective of processing corn is to separate the kernelinto its component parts with maximum purity. The fivebasic products that result are starch, steepwater, germ,feed and gluten.

The 40-hour steeping process softens the corn,removes some solubles (steepwater), and breaks the bondconnecting starch, gluten, germ and fiber.

Germ, gluten and fiber are dewatered and dried by useof filters, presses and dryers. The germ is further processedto recover oil, while the remaining fiber is returned for feed.

Starch slurry is converted to food and industrial grade starches for industries including corrugating. It is dewatered in centrifuges to produce a starch “cake.”This is then dispersed into a stream of heated air and flash dried to a finished moisture of about 9–12.5 percent. The dried starch is pneumatically conveyed to a storage silo where it can be loaded into bulk railcars, bulk trucks or packed into 50- or 100-pound bags, or super sacks.

During the drying process, it is common for corn wet milling plants to maintain the moisture of about 9–12.5 percent. Great care must be taken to prevent thestarch from overheating in the presence of moisture. If the process is not monitored closely, a starch productwith abnormally high sensitivity to caustic soda may result.

If the starch is to be further refined into a sugar, it is processed in a refinery. Customers use dextrose, fructoseand corn syrup sugars in many food and beverage andindustrial applications.

Many factors affect the consistent production ofstarch. As with any natural raw material, properties of corn can be affected by temperature, hours of sunlight,humidity, rainfall, year of planting, soil moisture, plant population and fertilization rate.

Different corn varieties can also result in varyingstarch properties. Corn varieties that contain all branchedstarch molecules are called waxy maize. The types of cornthat contain unusually large quantities of linear starchmolecules are called high amylose hybrids. Starchesderived from these two hybrids have vastly different properties that offer benefits in end-use applications. Waxy maize starch tends to resist retrogradation, making it ideal for certain food applications such as puddings or in textiles because it produces a clear film. Conversely,high amylose hybrids invert rapidly, which works well forprocesses including fiberglass sizing or cotton-polyesterblend sizing.

Normally, corn starch is composed of two molecularspecies. Amylose, a linear non-branched type of molecule,makes up about 25 percent of the starch in conventionalcorn starch. Amylopectin, the branched molecule in starch,accounts for the remainder, or approximately 75 percent.

Corn Oil

DextroseFamily

FoodStarches

Syrup Refining

Germ Meal

Corn Syrup

HighFructose

Corn Syrup

The Corn Wet Milling Process

Steeping Milling & Screening

Starch Separation

Steepwater

Gluten FeedStarchSlurry

IndustrialStarches

Starch Drying

Feed &Dietary Fiber

Germ

Corn

6

The Role of CornThere are factors that affect the makeup of corn. For years, seed-corn suppliers have worked to improve thecharacteristics of the corn plant. Corn hybrids haveincreased resistance to disease and pests and improvedyields. These improvements benefit all industries that use corn by-products.

For corrugators, the most important properties are viscosity and gelatinization point. These properties canvary from corn crop to corn crop.

Data shows the natural gelatinization temperaturevaries depending on the climate or growing region of the world.1 (See Figure 1.) Process modifications may be necessary to compensate for raw material variations.

Even granule size (diameter) is affected by environmentalfactors. Granule size is important since it is known that

smaller granules have reduced amounts of amylose, the linear molecule fraction in starch.2 Larger starch granulesgelatinize more easily than small particles.3 It also isknown that starches with lower gel temperature thanentire high quantities of amylose yield much higher gelatinization temperatures than conventional corn starch.(See Figure 2.)

When heated in water, native starch granules, regardlessof molecular type, hydrate (absorb water), increase in sizeand thicken to form a viscous liquid, gel or paste. This single property is probably the most important characteristicof the starch and is relied upon to provide thickening. In the corrugating industry, this gelatinizing property ofstarch is encouraged by the addition of caustic soda andused effectively to suspend or carry pearl starch that hasnot been gelatinized.

Geographic Relationship to Gelatinization Temperature

Geographic Locationand Growing Conditions

Gelatinization ofCorn Starch

Location A

Location B

143-158˚F [61.7-70.0˚C]

147-165˚F [63.9-73.9˚C]

FIGURE 1

153˚F 176˚F (Note) [67.2˚C] [80.0˚C]

143˚F 158˚F 167˚F [61.7˚C] [70.0˚C] [75.0˚C]

Reported Gelatinization Temperatures of Conventional Corn Starch and High Amylose Starches

Identification ofStarch Type(Unmodified)

Gelatinization Rangeof Starch Type

(Initiation, Midpoint, Completion)

Conventional Corn

High Amylose Corn

FIGURE 2

Note: Complete gelatinization of high-amylose starch is not affectedin boiling water, 212˚F [100˚C]. It has been stated that high amylose requires

pressure for complete gelatinization.

S. F. to bridge

236-266F[113.3-130.0C]

180-190F[82.2-87.8C]

Pressure roll

Adjustablewrap roll

Linerpreheater378F [192.2C]

180-210F[82.2-98.9C]

370F[187.8C]

370F[187.8C] Starch

applicatorroll

Doctor rollStarch

Opensteamshower

Greenlinesteamshower

Dance roll

Mediumpreconditioningroll 250F [121.1C]

Opensteamshower

The Corrugating Process

FIGURE 3

Bridge

Preheater 36"

Adjustablewrap roll

S. F. liner

150-160F[65.6-71.1C]

Preheater 18"

Hold down roll

Rider roll

Doctor roll

Starch

Starch applicator rollPreheater 36"

180-210F[82.2-98.9C]

Adjustablewrap rollD. F. Liner

Roll standFootnotes:1. F.R. Earle, “Protein and Oil in Corn: Variation by Crop Years from 1907 to 1972”, Cereal Chem., Vol 54(1), pp. 71-79.2. R.L. Whistler, J.N. BeMiller and E.F. Paschall, Starch: Chemistry and Technology, 2nd Edition, (Academic Press, 1984)

Chapter III, pp. 34 & 36, Jack C. Shannon and Douglas L. Garwood, Contributing Authors.3. R.W. Kerr, Chemistry and Industry of Starch, 2nd Edition, (Academic Press, Inc.,1950) Chapter I, p. 3

7

Starch Basics for Corrugated BoardFor 2005, the value of the corrugated board market in theU.S. is estimated to be over $24 billion. Corrugated boardis made up of liners and the fluted medium. Many weights,thicknesses and combinations of liners and medium areused for different applications. The principles of manufactureare simple. (See Figure 3.)

Starting at the single facer, flat corrugating medium is softened with heat and moisture and passed between a setof corrugating rolls to form it into flutes. Adhesive is appliedto the flute tips on one side of the medium. Then, a singlefacer linerboard is brought into contact with the fluted medium under heat and pressure to produce a single facerweb. This web is conveyed to the double backer stationwhere adhesive is applied to the exposed flute tips and thedouble backer liner is applied. The combination is finallyconveyed over a series of hot plates to set the adhesive.

Modern corrugating machines can run at speeds in excess of 1,200 feet per minute, depending on the typeof board being produced. These high speeds are possiblebecause of corn starch’s ability to gelatinize and producehigh viscosities at the glue line.

A mixture of pearl starch, borax, caustic soda and wateris suspended in a paste of cooked starch. The addition ofcaustic soda helps gelatinize the starch. An increase in theamount of caustic soda, based on the total starch, will lowerthe gel temperature of the entire adhesive.

The primary value of borax is to buffer the caustic sodapresent in the formula. It also provides viscosity controland adds tack to the finished adhesive. For equivalentamounts of borax for starch formulations, see Appendix A.

Generally, 15–20 percent of the starch is fully cookedin part of the water with caustic to provide a carrier forthe pearl starch. Starch solids levels usually are 23–35 percent to achieve finished adhesive viscosity of 30–50Stein Hall seconds. After the adhesive is applied to theflute tips and heated, the pearl starch gelatinizes in place. When the starch swells and gelatinization begins, a green bond is formed. Nearly all of the corrugated boardproduced today is bonded with a starch-based adhesive.Since the quality and bonding properties of the starchdirectly affect final board quality, decisions regardingstarch should be made carefully and treated with importance in the process.

Pearl starch, or unmodified starch, typically has been the key product used for starch adhesive. However,with the introduction of high performance papers and the increased use of recycled paper, the porosity of thecorrugated medium and liners has changed. Therefore, the adhesive must change, too. Modified, or carrier, starches, when used in conjunction with pearl starch, allow an increase in solids for better bonding and the ability to achieve higher machine speeds.

S. F. to bridge

236-266F[113.3-130.0C]

180-190F[82.2-87.8C]

Pressure roll

Adjustablewrap roll

Linerpreheater378F [192.2C]

180-210F[82.2-98.9C]

370F[187.8C]

370F[187.8C] Starch

applicatorroll

Doctor rollStarch

Opensteamshower

Greenlinesteamshower

Dance roll

Mediumpreconditioningroll 250F [121.1C]

Opensteamshower

The Corrugating Process

FIGURE 3

Bridge

Preheater 36"

Adjustablewrap roll

S. F. liner

150-160F[65.6-71.1C]

Preheater 18"

Hold down roll

Rider roll

Doctor roll

Starch

Starch applicator rollPreheater 36"

180-210F[82.2-98.9C]

Adjustablewrap rollD. F. Liner

Roll stand

8

CORRUGATED MAKES IT HAPPEN FOR SHIPPING

9

ViscosityIn the corrugating industry, the term viscosity is used to describe adhesive’s flowability. (Tests for measuringviscosity can be found on page 17.)

Low ViscosityWhen adhesive paste is too thin, or has low viscosity, the water tends to “wick” into the medium. This wickingaction may remove the needed water from the glue line,which means the pearl starch may not have enough waterto gelatinize completely.

Many times the board will be dry and brittle comingoff the corrugator, or may become brittle as it stackcures. If a pin adhesion test is performed on a sample of this board, low numbers will result. There may be very little fiber pull and the glue line will have an amberappearance. Since the bond is marginal, one solution is to open the glue settings on the machine to deliver moreadhesive to the glue line. The downside to applying moreadhesive is the potential for warp, washboarding, higherstarch consumption and slower machine speeds.

High Viscosity (Thick, Heavy Adhesive)When the adhesive is too thick (high viscosity), it tendsto sit on top of the flute tip, penetrating the medium and glue line very slowly. This will lead to a soft, wetboard coming from the corrugator. It is difficult to printon wet board and it is hard to convert in the finishingdepartment. Starch consumption will also increasebecause of the wide glue lines associated with thickadhesive. Adhesive flowability is reduced in the gluepans, which pushes adhesive to the back of the pans and allows heat to build up. This usually leads to gelling problems at the single facer.

Overflowing adhesive and poor transfer of the adhesive from the glue roll is associated with high viscosity adhesive. On some of the new, high speed single facers, the machine will shut down if the viscosity is too high.

Effects of Shear on ViscosityShear is the mechanical action of breaking down theadhesive resulting in reduced viscosity. Shear can occur at the mixers, pumps, pipes, elbows or valves, and at the actual corrugator.

In mixing systems, mixing blades shear the adhesiveto a workable viscosity. When an adhesive formula isdeveloped, the mix times are calculated to perform thistask correctly. When the mix times are changed, quality of the finished adhesive will vary.

The secondary mixer blades must be properly placedand in good repair to prevent areas of over-agitation.Missing or broken blades will add mixing time and mayreduce the flexibility of the formula.

The storage tanks should have agitators operating ontimers. Agitators should be set to mix for five minutes outof every 30 minutes. These agitators also should operate ifthe Temperature Viscosity Control (TVC) system calls for heat.

Temperature is very important when taking a viscosity reading. The viscosity of the adhesive will vary proportionally with the temperature of the adhesive. As the temperature goes up, the viscosity willdrop (become thinner). Conversely, as the temperature decreases, the viscosity will increase (become thicker).This inverse relationship of viscosity to temperature is approximately 10 percent for every 2˚F [1.1˚C] change. (See Figure 4.)

The piping system used in the plant should not havedead ends. Fewer elbows and turns help reduce friction and pressure buildup within the lines. The lines should be pitched to ensure adequate drainage for cleanups.

The pumps (often positive displacement pumps) used to transfer adhesive from the mixer to storage tanks and from storage tanks to corrugator can cause unwanted shear. It is important to have the proper size pump operating at the correct rpm. A plant’s starch supplier should be able to help calculate system needs.

10

Temperature - Viscosity Correction Table (for Stein Hall Viscosity)Vi

scos

ity

(Ste

in H

all)

90F[32.2C]

42

46

48

50

52

54

56

58

60

62

64

66

68

70

72

74

76

78

80

82

84

86

88

90

92

94

96

44

38

41

43

45

47

49

50

52

54

56

58

59

61

63

65

67

68

70

72

74

76

77

79

81

83

85

86

92F[33.2C]

40

34

37

39

41

42

44

45

47

49

50

52

53

55

57

58

60

62

63

65

66

68

70

71

73

75

76

78

94F[34.4C]

36

31

34

35

36

38

39

41

42

44

45

47

48

50

51

52

54

55

57

58

60

61

63

64

66

67

69

70

96F[35.6C]

32

28

30

31

33

34

35

37

38

39

41

42

43

45

46

47

49

50

51

52

54

55

56

58

59

60

62

63

98F[36.7C]

29

25

27

28

30

31

32

33

34

35

37

38

39

40

41

43

44

45

46

47

48

50

51

52

53

54

56

57

100F[37.8C]

26

20

22

23

24

25

26

27

28

29

30

31

32

33

33

34

35

36

37

38

39

40

41

42

43

44

45

46

104F[40.0C]

21

18

20

21

22

22

23

24

25

26

27

28

28

29

30

31

32

33

34

34

35

36

37

38

39

40

40

41

106F[41.1C]

19

16

18

19

19

20

21

22

22

23

24

25

26

26

27

28

29

29

30

31

32

33

33

34

35

36

36

37

108F[42.2C]

17

15

16

17

17

18

19

20

20

21

22

22

23

24

24

25

26

26

27

28

29

29

30

31

31

32

33

33

110F[43.3C]

15

22

24

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

43

44

45

46

47

48

49

50

51

102F[38.9C]

23

FIGURE 4

If air pumps are to be used to circulate the adhesive to and from the machine, proper air pressure is essential.Most air pumps operate at 40 to 60 psi, depending uponthe distance to pump. Too much air pressure will force theadhesive through the lines and cause shear.

Valves in the lines must be inspected regularly. A worn valve may appear open when it is only partiallyopen, causing shear of the adhesive.

The Temperature Viscosity Control SystemTo control the adhesive temperature in storage properly, a Temperature Viscosity Control (TVC) system is required.Typically, the system uses a small tank of heated waterpositioned slightly above and between the adhesive storagetanks. Water from this tank is circulated through coilsinside the storage tanks at the same time agitators aremoving adhesive. The water should be heated to a

11

temperature 10˚F [5.6˚C] lower than the lowest gel temperature of the adhesive in storage. When the temperature of the adhesive falls below 100˚F [37.8˚C], the TVC system should activate automatically. Probes insidethe TVC water tank and storage tanks monitor temperature.

If the water temperature becomes too high (higherthan the gel temperature of the adhesive), the adhesivewill begin to gelatinize on the coils. When this happens,the heat transfer from the water in the coils to the starchis reduced, which increases the agitation time of the adhesive. This can result in low viscosity. The longer ittakes for the temperature to rise, the longer the storagetank agitators must run, and the higher the risk of shear.

Plants that have complete steam shutdown on weekendsrely on electric units to heat TVC water. This is an importantconsideration in new installations to insure proper adhesive viscosity control.

Viscosity/Time RelationshipThe length of time the adhesive is held in storage can be critical. Over time, the raw portion of the adhesive will begin to separate from the cooked portion. This causes viscosity to drop. Fast turnover of the adhesive is the best solution. Reducing the amount of material for storage during down periods is also wise.

Viscosity/Resin RelationshipTo make adhesive water resistant, you must add resin. This creates a chemical reaction when the mixture is heatedon the corrugator. The result produces a water-resistantbond. The degree of water resistance is related to the ratioof resin solids to starch. However, it is difficult to generalizeabout the amount of resin needed because resin solids vary dramatically.

Never mix resin-treated adhesive with adhesive in storage. When resin is added to a batch of adhesive, it isadvisable to use all of the adhesive as soon as possible.The adhesive’s resin potency will last approximately eighthours after a batch is made. After that, the resin loses theability to react with the starch and viscosity breakdownbegins, affecting the entire batch. Also, resins have afinite shelf life.

Resin should be added slowly to the adhesive, usuallyduring the final mix. Adding the resin too fast can causeviscosity changes. It is not advisable to add resin to thestorage tanks because viscosity changes can occur in storage, to the point that the adhesive will be unable topump. In addition, the storage tank agitators are notdesigned to blend resin, and permanent damage can occur.

Some resins will react with borax in the formula causinga change in viscosity. Using the correct amount of resin in the formula is critical. The resin supplier should be contacted for proper addition rates and/or limitations.

Microbiological DegradationStarch, a carbohydrate, is often considered food for bacteria.It has been found that some bacteria will survive, and may even thrive, in a strong alkaline medium such asstarch-based corrugating adhesives. If the bacteria population increases to, or exceeds, 10,000 colony formingunits (cfu) per gram, starch adhesive could show viscosityloss. This results from the gelled starch being attacked bybacteria and converted to a soluble carbohydrate, whichwill lower viscosity.

At levels greater than 1,000,000 cfu per gram, an odor may also develop. However, odor alone should not beconsidered an indicator of microbiological growth. Whenmicrobial problems are suspected, microbiological testingcan be a valuable tool. Test laboratories generally requirean aseptically obtained sample of the corrugating adhesiveto achieve meaningful results. Contact your biocide supplier and request a test of the plant’s adhesive.

Care With BiocidesTo prevent microbiological growth, biocides should be used with care. Most manufacturers recommend changingthe biocide regularly to prevent the growth of a colonythat may resist the action of a particular biocide. (See Appendix B.)

It is recommended that the entire adhesive system be cleaned twice per year using a commercially availableindustrial strength cleaner and commercial householdbleach, or a treatment from your biocide supplier. The lines to and from the machine also should be flushed and cleaned. If the adhesive system uses bulk starch, the discharge chute should be cleaned or changed since it is a breeding ground for bacteria. Details on system cleaning should be provided by the biocide supplier.

12

GelatinizationTemperatureGelatinization temperature, or gel temperature, is the temperature at which the adhesive begins to thicken and develop its bonding properties. Although it is oftenexpressed as a single temperature unit (˚F or ˚C), in realityit is a temperature range dependent upon the molecularsize and composition of the starch.

The natural gelatinization temperature of corn starch is generally too high for normal corrugating operation.Running an adhesive with high gel temperature couldaffect bonding, especially at the double backer. Machinespeed could also be affected. Addition of caustic soda suppresses the gelatinization temperature, thus providingcorrugators the flexibility to set the gel temperature at adesirable level for the individual machine conditions andpaper combinations.

Gel temperature is measured by simply heating theadhesive as it is stirred with a glass thermometer. Whenthe paste begins to thicken (gel), the temperature thatappears on the thermometer is recorded. (See Appendix C.)

Gel Temperature Too HighIf the gel temperature is too high, there may not beenough heat present to gelatinize all the starch granules.This will result in a white glue line and a poor bond. The speed of the corrugator must be reduced to achieve an acceptable bond, particularly on double wall board. The dry end operators also may notice wet or soft boardcoming off the machine.

Gel Temperature Too LowIf the gel temperature is too low, several conditions mayresult. The adhesive will gel before it has a chance to penetrate into the paper. This may result in brittle board,dry bond, raspy-feeling glue lines and cracking board.There also may be severe gelling on the fingers of the single facer or gelling in the pans.

Gel Temperature/Time RelationshipThe gel temperature will rise the longer the adhesive is held in storage. This happens because over time thestarch will absorb some of the free caustic present in the adhesive. Periodic checks of the gel temperature will prevent unwanted high temperatures at the double backer glue station.

Determination of Caustic Concentration inLiquid Caustic (Hydrometer Method)The caustic concentration of liquid caustic can be determined by utilizing a caustic specific gravity chart and specific gravity spindle. Equipment needed is a specific gravity spindle, a clear 500-mL plastic cylinder anda specific gravity concentration chart. (See Appendix D.)

Fill the plastic cylinder so that it is about 2/3 full with liquid caustic. Make sure the sample is at or aboveroom temperature. Gently insert the spindle into the liquidso that it floats freely without touching the sides or the bottom. The spindle stem has graduated marks (specificgravity units), and the reading is taken at the point wherethe liquid level intersects the spindle stem. The specificgravity reading is applied to the chart to determine thepercent caustic (% NaOH) directly.

For example, if the sample is 50% liquid caustic, the spindle reading will be 1.530. If the reading is higher, the caustic solution is higher than 50%. Similarly, if the reading is lower, the caustic solution is diluted with waterand its concentration is less than 50%. (See Appendix D.)

13

Penetrating AidsWhen dense liners and/or mediums are used, penetratingaids may help bonding by reducing the water surface tension, so the adhesive can penetrate the sheet. If aplant suspects that a penetrating aid would be beneficial,the plant should contact the starch supplier for assistance.

Antifoam AgentsThe use of antifoam agents is common with today’s corrugators. As machine speeds increase, foam is often created in the glue pans as starch cascades off the metering roll and wiper blade. If the foaming becomessevere, it can overflow the pan, causing higher than normal starch consumption; or it can transfer from theglue roll to the flute tips, causing poor bonding. Shouldfoaming occur at the double backer, it could overflow ontothe paper, resulting in a poor bond on the double facerside. For antifoam options, contact your starch supplier.

Liquid AdditivesLiquid additives are often used to enhance the wet tack, or green bond, of starch-based adhesives. Green bond isthe measure of an adhesive’s wet tack and the major factoraffecting the potential machine speed of the corrugator.These products can potentially increase corrugator operatingspeeds. Although suited for any adhesive mixing system,liquid additives are an ideal choice for high shear mixingsystems that may be equipped with liquid dosers. For liquid additive options, contact your starch supplier.

ResinsResins are used in starch adhesive formulations to impartvarying degrees of water resistance to corrugated board.The resins react with hydroxyl groups on starch and renderthe starch insoluble to water. Degrees of water resistance,ranging from moisture resistance to waterproof, depend onthe functional use of the container. Various types of watersoluble thermosetting resins are available to the corrugatingindustry. Ketone aldehyde-type resins are particularly wellsuited for corrugating applications. They require causticand heat in order to react. For resin options, contact your starch supplier.

Corrugating Additives

14

CORRUGATED MAKES IT HAPPEN FOR CONSUMERS

15

CorrugatingProcesses/Systems/Equipment

Starch plays an important role in the corrugating process,so the integrity of the starch production process is critical.

Four processes are common in starch adhesive production: Stein Hall, Jet Cook, High Shear and No-Carrier methods. Basic adhesive preparation consists ofa cylindrical primary mixer with a low-speed, high-torquemixer situated above a secondary tank with a high-speed,lower-torque agitator. A drop valve generally controls theflow of adhesive from the primary mixer into the secondarytank. However, No-Carrier adhesives differ significantly in preparation since only one mixer tank is used and nogelatinization of starch occurs.

Stein HallThis system uses a two-phase process. The first phase is referred to as the cook phase. Here, starch, water and caustic are combined to create a gelatinized starch adhesive. This product is also referred to as the carrier.

The second phase is the blend phase where starch,water and borax are added together and mixed with thecooked portion to form a finished adhesive. (See Figure 5.)

Jet CookThe Jet Cook system is a modification of the Stein Hallprocess using a single vessel horizontal mixer.

With the Jet Cook system, all the water, caustic andborax are mixed together with approximately half of thetotal starch in a horizontal mixer. The amounts of causticand borax are determined by the gel temperature that isneeded for a given adhesive. This starch/water/chemicalslurry is then circulated through pipes and returned to themixer. Live steam is injected into the pipe, causing theslurry to swell (gelatinize) as it is being pumped back intothe mixing tank. Monitored by an automatic viscometer, theprocess continues until a given viscosity (set point) isreached. Upon reaching its set point, the steam is shut off and the remainder of the pearl starch is added to theadhesive. A timed mix then finishes the process. (See Figure 6.)

Starch Water

Slurrytank

ScalesPump

Raw

Steam

20 Gal.

Carrier 190F[87.8C]

Coolingcolumn

150F [65.6C]

Mixer

Chemical tank

To storage

Steps: (1) Raw starch water; (2) Raw starch; (3) Transfer to mixer; (4) Add chemicals; (5) Add carrier water; (6) Add starch carrier; (7) Jet cook carrier; (8) Final mix; (9) Pump to storage

To storage

Recirculation

Secondary mixer

Causticmix tank

Primarymixer

Pump

Steps: (1) Water primary and secondary; (2) Starch primary; (3) Add caustic to primary; (4) Cook primary; (5) Add borax to secondary; (6) Add starch to secondary; (7) Add cooling water to primary; (8) Drop primary into secondary; (9) Final mix; (10) Pump to storage

FIGURE 5

FIGURE 6Starch Water

Slurrytank

ScalesPump

Raw

Steam

20 Gal.

Carrier 190F[87.8C]

Coolingcolumn

150F [65.6C]

Mixer

Chemical tank

To storage

Steps: (1) Raw starch water; (2) Raw starch; (3) Transfer to mixer; (4) Add chemicals; (5) Add carrier water; (6) Add starch carrier; (7) Jet cook carrier; (8) Final mix; (9) Pump to storage

To storage

Recirculation

Secondary mixer

Causticmix tank

Primarymixer

Pump

Steps: (1) Water primary and secondary; (2) Starch primary; (3) Add caustic to primary; (4) Cook primary; (5) Add borax to secondary; (6) Add starch to secondary; (7) Add cooling water to primary; (8) Drop primary into secondary; (9) Final mix; (10) Pump to storage

FIGURE 5

FIGURE 6

16

High ShearThe High Shear system is an improvement on the conventional Stein Hall process.

When trying to achieve a high solids adhesive formulawith the conventional Stein Hall system, the limiting factor is that high viscosities develop as the amount ofprimary starch is increased. One way to overcome the highviscosity is to mechanically shear the cooked portion ofthe formula. Using a vertical mixing tank with a mixingblade designed to shear the gelled starch, batches withhigher solids can be made faster with better results.

Different manufacturers use different mixer and bladecombinations to achieve the same results. Adhesive is usually made in a single vessel resting on weight sensors.Water is added (by weight) and heated to a set point.Some automatic systems compensate for condensation by adjusting the programmed ingredient weights to meetany changes caused by the added water. Other systemsheat the water using a heat exchanger so no condensationis added to the programmed formula. Starch and caustic(usually 50% liquid) are added and mixed under highshear. Borax, secondary water and starch are then addedand mixed for a cycle timed anywhere from 12 to 35 minutes. Some systems allow for up to 20 different formulas to be programmed into the system so customizedadhesive can be made for different board combinations or special papers.

Most automatic systems incorporate level controls inthe storage tanks and automatically make a batch whenneeded. This allows for lower storage volumes, whichresults in fresher adhesive being used at the corrugator.

One major advantage of the new High Shear mixingsystem is that it dramatically reduces adhesive preparationtime, freeing up manpower to be used in other plant operations. Even though some of the systems are fullyautomatic, they still must be checked daily and put on a preventative maintenance schedule. (See Figure 7.)

No-CarrierThis process is very different from the others. No gelatinization of any of the starch takes place. In the No-Carrier process, starch, water, 50% liquid caustic andboric acid are used to “swell” the starch granule. This isaccomplished by monitoring the viscosity of the adhesive.All mixing of ingredients takes place in a lower mixer. (See Figure 8.)

Borax

Water

Caustic

Starch

ScaleTo storage

20,000 r.p.m.

Motor40 hp

FIGURE 7

High Shear Adhesive System

Pump

Bulk starch

Scale hopper

Water

Norcrossviscometer

Caustic supply line

130F[54.4F]Caustic

tank

From liquidcausticstorage

Boricacid

Boric acidadditionsystem

Pump

To storage

Steps: (1) Water; (2) Starch; (3) 130F [54.4C]; (4) Mix to X Norcross Units; (5) Add boric acid to terminate; (6) Final mix; (7) To storage

No-Carrier Adhesive System

FIGURE 8

17

StarchProperties and Testing

Alkali (Caustic) SensitivityOne critical property of the starch is the ability to perform in alkali (caustic) conditions.

During the manufacturing process, starch granules canbecome damaged. When a sample of starch containing anexcessive amount of damaged granules is mixed in a solutionof caustic (alkali), the starch swells at too rapid a rate.This results in a viscosity that is higher than normal.

There are several methods used to check for the alkalisensitivity of pearl starch. One is the settling test forunmodified starch. (See Appendix E.) This test can beaccurate and reproducible with relatively inexpensive testingequipment. Minor deviations from the procedure, or lessthan ideal conditions, may result in inaccurate results.

There is a second, more rapid test for alkali sensitivitythat is just as accurate as the settling test. However, this test uses a more costly Brookfield Viscometer. (See Appendix F.)

Measuring Viscosity of Finished Starch AdhesiveThere is one standard for measuring viscosity — SteinHall seconds, which is calculated using a Stein Hall Cup.There are, of course, some plants and manufacturers whouse other methods and tools for measuring viscosity. Love Cups, Zahn Cups, Brookfield Viscometers, NorcrossViscometers and Dynatrol Viscometers are some of theother methods and tools that are used. Some have individual charts for flowability, but most are convertedto Stein Hall seconds.

The Stein Hall Cup is a brass cylinder with a specificsize orifice in the bottom, and two brass pins located onthe inside of the cylinder wall. The distance between thetwo pins will hold a volume of exactly 100 ml of liquid.The cup is filled with adhesive and allowed to flow throughthe opening. The elapsed time it takes the adhesive tomove from pin to pin is the viscosity in seconds.

Calibrating the Stein Hall CupThe Stein Hall Cup must be calibrated properly to give anaccurate viscosity reading. Measuring water flow from pin topin is the best way to check calibration. Water should flowfrom pin to pin, through the orifice, in exactly 15 seconds.

A reading other than 15 seconds may indicate aplugged or enlarged opening, or the pins may havebecome bent. Carefully clean the orifice and check thevolume between the pins. Recheck the flow of water. If it is not correct, replace the disk.

Gelatinization TemperatureGelatinization (gel) temperature will affect the corrugatingoperation and is frequently measured. Gel point is thetemperature at which liquid adhesive is transformed intoa semi-solid mass or gel. (See page 12 and Appendix C for test procedures.)

Microbiological TestingBacterial growth in starch adhesives is detrimentalbecause it causes molecular breakdown. If the growthreaches a certain point, viscosity will be drasticallyreduced, making the adhesive unusable. This growth cannot be measured at the plant site. Typically, adhesivesamples are sent to a laboratory capable of measuringbacterial growth. The plant’s biocide supplier can assist in arranging testing. Laboratory reports speak in terms of colony forming units (cfu) per gram. When the cfulevel reaches 10,000 cfu/g, it is advisable to clean the system. (See page 11 and Appendix B.)

Starch Solids ConcentrationHigh solids (starch) adhesives are necessary to bond highperformance and recycled papers. Variation in the amount ofstarch or water changes the solids content of the adhesive.

Analyzers for moisture or solids measurement areavailable to corrugators. It is critical that the analyzersbe calibrated against strict standards. Generally, adhesivesamples are analyzed by outside laboratories using eitheroven, infrared or microwave technologies. To determinewhether excessive water is entering an adhesive system,samples of fresh and stored adhesive are analyzed forwater content and compared. If the solids levels areequal, then no excess water has entered the system. If water has entered the system, the solids level in stored adhesive will be lower.

18

CORRUGATED MAKES IT HAPPEN FOR MANUFACTURING

19

Board Testing

Traditionally, moisture is determined with a forced air orvacuum oven, but other devices that incorporate infraredor microwave technologies have shown to be just as accurate and are faster.

There are many tests for determining the quality ofcombined board. Below are some of the more frequent tests.Many of these standard tests have achieved a TAPPI designation, which is noted next to the test name. Specifictest procedures may be obtained by contacting TAPPI.

Caliper T-411Caliper, or thickness, is generally the first test performedon finished board. At plant sites it is usually conductedusing a micrometer and is considered a diagnostic test to monitor the operation of the corrugator.

Edge Crush Test (ECT) T-811Corrugators use this test to determine the edgewise compressive strength of their board. This test considersthe role of the medium in overall strength. A compressionmachine is necessary. The ECT of a combined board isdependent on the paper combination used.

Dry Pin Adhesion T-821This test measures the force necessary to separate corrugated board between the flute tips of the mediumand its linerboard facings. A special pin adhesion attachment and compression machine is necessary.

Wet Pin Adhesion (unofficial)Wet pin adhesion is a variation of the dry pin test. Ittests the water resistance or waterproof characteristics ofthe finished board. In the wet pin test, the board can besubmerged in water as long as 24 hours, removed anddrained of excess water. The pin adhesion test is thenconducted on the wet board. Wet pin results are muchlower than dry pin results. A range from about two toseven lbs. per linear foot indicates water-resistant board.Wet pin results of between 10–12 lbs. per linear footindicate waterproof board to most corrugators.

Ply Separation T-812Ply separation determines the water resistancy of finished board. Board samples are submerged in water for 24 hours, removed and drained of excess water. The linerboard facing is gently pulled apart from themedium. If there is resistance and fiber tear, the board is considered water-resistant.

Glue Pattern (unofficial)For diagnostic purposes, it is often useful to soak a sample of corrugated board in water to separate the linerboard from the medium. Then, simply spray the insidesurface of the liner with a dilute solution of 0.1 percentiodine-potassium iodide. The iodine solution will stain the glue line, or starch, blue. From the pattern it may bepossible to determine how the adhesive was applied orwhether it was applied correctly.

Top to Bottom Compression T-804This test is used to measure the ability of a corrugated or solid fiber shipping container to resist external compressive forces. A completed, but empty, box isplaced in a compression tester and an external force is applied until the box fails.

Basis Weight Combined Board T-410Basis weight is a physical measurement. A sample of measured board is weighed on a balance and expressed in pounds per MSF.

20

CORRUGATED MAKES IT HAPPEN FOR DISTRIBUTION

21

Quality Monitoring and Control at the Adhesive Station

The fitness of the adhesive is related directly to the qualityof the bond that will be produced at the corrugator.Therefore, it is critical to maintain control of several keycharacteristics of the adhesive. Adhesive temperature, viscosity and gelatinization temperatures are the criticalpoints to monitor and control in order to maintain consistent adhesive.

Many problems can be avoided and eliminatedthrough the regular use of statistical process control(SPC). Development of a data collection program is recommended to achieve meaningful statistical control of the process.

The starch supplier can be a valuable resource. Many suppliers offer SPC consultation or even training. Anotherresource for SPC training is the American Society forQuality Control (ASQC).

Generally, the SPC or Quality Control Coordinator in theplant will work closely with the starch supplier to set upcontrol and monitoring systems and determine consistent,meaningful measurement points in the system.

Statistical Process ControlThe first step in monitoring any of the three controlpoints (viscosity, adhesive temperature, gelatinizationpoint) is to gather enough data to determine the processcapability. See Figure 9 for a typical example of a chartused to gather data.

If the process is determined not to be capable in anyarea, the starch supplier should be called upon to provideassistance. The process should be corrected and additionaldata gathered to verify the improvements and determineif the process is capable. The goal is to keep the starchadhesive process in tight control.

Once the process is determined capable, then additional data should be collected and the mean (X),upper control limits (UCL) and lower control limits (LCL)should be calculated. The mean (X) should closely matchthe desired target. If the mean is not numerically close to the target, then the process must be corrected. Theseprocess corrections can be as simple as an adhesive formula change, an equipment repair or calibration. Once again, starch suppliers should be considered a resource for these process corrections.

22

FIGURE 9

INDIV

IDUAL

MEA

SUREM

ENTS

X

MOVIN

G R

AN

GES

MR

NOTES:

MEASUREMENT

PREVIOUS

MOVING RANGE

41 42 42 47 45 39 34 43 35 41 44 31 42 43 32 37 41 37 41 43 44 35 36 32 42

41 42 42 47 45 39 34 43 35 41 44 31 42 43 32 37 41 37 41 43 44 35 36 321 0 5 -2 -6 -5 9 -8 6 3 -13 11 1 -11 5 4 -4 4 2 1 -9 1 -4 10

DATE

TIME

OPER. INITIALS

CHARACTERISTICS UNIT OF MEASURE

INDIVIDUAL AND MOVING RANGE (X & MR) CHART

Starch Kitchen Adhesive Viscosity Seconds (Stein Hall)2-2 2-3 2-3 2-4 2-4 2-5 2-5 2-5 2-6 2-6 2-6 2-6 2-10 2-10 2-10 2-11 2-11 2-12 2-12 2-12 2-13 2-13 2-13 2-17 2-17

2:15

JS8:00 12:30 9:00 12:00 9:00 12:00 2:30 7:12 10:30 1:00 2:45 7:45 9:00 11:30 8:30 10:15 6:30 10:30 1:30 8:30 11:30 1:45 7:00 9:25

45

50

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

40

35

30

25

10

15

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

5

0

-5

-10

-15

23

TroubleshootingCommon Corrugating Problems

Problem:

Low viscosity at the mixer

Common Causes:

Not enough starch in the cooked portion of the formula •Scale out of calibrationToo much water in the cooked portion of the formula •Water leak •Water meter out of calibration •Improper measuring device •Condensate from steam lines •Condensate from steam leak •Unwanted wash water going into the mixerToo much water in the secondary addition or secondary mixer •Water leak •Water meter not calibrated •Improper measuring device •Condensate from steam lines •Condensate from steam leakCooked portion too hot (+160˚F [71.1˚C]) •Steam leak •Temperature controller out of calibration •Temperature gauge out of calibration (reading too low)Finished batch too hot •Cooked portion too hot •Temperature controller out of calibration •Cooling water too warm (seasonal) •Mixer shaft overheating due to bad bearings •Improper balance between the cooked portion and cooling waterToo much shearing of the cooked portion of the adhesive •Cooked portion mixed too long •Drop time too slow or slow pump over time •Too long a time on high shearFinished batch being mixed too longSubstituting incorrect borax (5 mol vs. 10 mol vs. boric acid)

DIAGNOSING VISCOSITY PROBLEMS - System: Primary/Secondary Mixing Systems, Single Tank Mixing Systems, High Shear Mixing Systems

Not enough water in the secondary addition or secondary mixer •Water meter out of calibration •Improper measuring deviceCooked portion too cold •Temperature controller out of calibration •Temperature gauge out of calibration •Cooling water too cold (seasonal)Finished batch too cold (optimum temperature 100 to 102˚F [37.8 to 38.9˚C]) •Cooked portion too cold •Temperature controller out of calibration •Temperature gauge out of calibration •Cooling water too cold (seasonal) •Bulk starch too cold (seasonal) •Improper balance between the cooked portion and cooling waterNot enough shearing of the cooked portion of the adhesive •Cooked portion not mixed long enough •Too fast a drop or fast pump over time •System not left on high shear long enoughFinished batch not being mixed long enoughIncorrect amount of boraxSubstituting incorrect borax (5 mol vs. 10 mol vs. boric acid)

High viscosity at the mixer Too much starch in the cooked portion of the formula •Scale out of calibrationToo much starch in the secondary mixer •Scale out of calibrationNot enough water in the cooked portion of the formula •Water meter out of calibration •Improper measuring device

Adhesive viscosity is a critical parameter for quality corrugated board. It is a relatively easyvariable to control when the underlying cause of a problem is understood.

24

DIAGNOSING VISCOSITY PROBLEMS - Problems Common To All Systems

Low viscosity at the storage tanks Low viscosity adhesive coming from mixer •Finished batch temperature too high •Temperature of cooked portion too high •Bad temperature controller •Insufficient amount of cooked starch in primary portion •Bulk scales out of calibrationTemperature of the adhesive too high •Temperature viscosity control (TVC) system set too high •TVC controller out of calibration •Adhesive returning from machine at an elevated temperature •Finished batch temperature too high •Bad bearings on the agitator causing the shaft to overheat •Bad bearings on the supply/return pumpStorage tank agitators running continuously •Agitator timers not operating properly •TVC system controller malfunctioning •Poor heat transfer from TVC coils •TVC water too hot •TVC coils coated with gelled adhesive •TVC water too cold •TVC circulation pumps not operatingUnwanted water in adhesive •Wash water coming back from corrugator •TVC coil leaking inside storage tankOver-shearing of the adhesive •High rpm supply and return pumps •Too many elbows in the supply and return lines •Supply and return line pipe diameter too small •Pipe size reductions in supply and return lines •Partially open valves in supply and return lines •Air pressure too high on air diaphragm pumpsOld adhesive (stored too long)Adhesive treated with resin (WPA) mixed with domestic adhesiveLow solids adhesive formulaMicrobiological contamination of adhesive

Problem: Common Causes:

High viscosity at the storage tanks High viscosity adhesive coming from the mixerAdhesive viscosity "growing" in storage •Too much caustic in the formula •Scale out of calibration •Caustic meter out of calibration •Not enough borax in the formula •Scale out of calibration •Borax timer set improperly •Wrong type of borax (5 mol vs. 10 mol)Adhesive cold •TVC system not operating properly •Loss of steam pressure in the plant •Finished batch temperature should be 100 to 105˚FStorage tank agitators not operating properlyAlkali-sensitive starch


25

DIAGNOSING VISCOSITY PROBLEMS - Problems Common to All Systems

Low viscosity at the machine

High viscosity at the machine

Viscosity decrease after overnightor weekend storage

Excessive adhesive temperature in the starch pan (between 110-120˚F)Incorrect storage tank temperatureIncorrect TVC water temperatureStarch feed and return line exposed to steam lines •Insulate these lines for better temperature controlStarch feed line running over top of single facerIncrease starch flow through the pan •Adhesive temperature increases the longer it remains in the pan •Higher temperatures lower the viscosityWater dripping into the starch pan •Condensate from steam showersPartially open valves in the starch feed and return lines •Flow restriction will create shear causing a drop in viscosityAir pumps feeding or returning adhesive running at high PSI levelsBad Viking pump (weak suction) creates too much shearPumps not sized properly for the corrugatorPlant has doser •Recirculating the adhesive causing a drop in viscosityLow viscosity adhesive coming from the storage tanks

Low adhesive temperature •Cold weather outside causing the temperature dropVery high temperature in the starch pan (in excess of 120˚F [48.9˚C])Pressurized machine running high solids over 30% •Excess heat inside the chamber causing water lossChemicals in formula are out of ratio (borax to caustic)Steam leak directly into the panSteam leak blowing into a starch linePoor agitation or no agitation of the adhesive held in storageHigh viscosity adhesive coming from the storage tanks

Clean-up water returned to storage tanksAgitators/circulating pumps left runningCirculating lines full of waterTVC system not working properlyWater leak from the TVC coilTemperature of the adhesive too highInsufficient amount of cooked starch in the formula to hold viscosity properlyPrimary portion of the formula is overcookedBacteria



26

DIAGNOSING TYPICAL GEL TEMPERATURE PROBLEMS

Not enough caustic in the adhesive •Scale out of calibration •Caustic meter set too low •Caustic meter out of calibrationToo much borax in the adhesive •Scale out of calibration •Borax timer not working properlyToo much starch in the adhesive •Scale out of calibrationToo much water in the adhesive •Water meter out of calibration •Mixer scale out of calibration

Gelatinization temperature too high


Gelatinization temperature too low Too much caustic in the adhesive •Scale out of calibration •Caustic meter set too low •Caustic meter out of calibrationNot enough borax in the adhesive •Scale out of calibration •Borax timer not working properly •Borax discharge tube pluggedNot enough starch in the formula •Scale out of calibrationSubstituted incorrect borax in the formula (5 mol vs. 10 mol vs. boric acid)Problem with caustic soda •Liquid caustic too cold •Liquid caustic crystallized in storage tanks sending high concentrations of caustic •Wrong concentration of liquid caustic (See Appendix D)

Substituted incorrect borax formula (5 mol vs. 10 mol vs. boric acid)Borax too old (dry, becomes more concentrated)Caustic soda beads too oldLiquid caustic too oldCaustic stratified in storage tank sending low concentrations of causticWrong concentration of liquid caustic (See Appendix D)Adhesive stored too longAddition of resin into adhesiveWrong or defective thermometer used by starch person •Do not use an electronic or dial thermometerTest is performed improperly or by different people

27

DIAGNOSING CORRUGATING EQUIPMENT AND BOARD QUALITY PROBLEMS

Soft Board: This causes poor pin adhesion, low top-to-bottom compression and poor print quality

Excessive adhesive applicationOperator error •Low machine temperatureOver conditioning of the mediumWet paper - medium or linersExcessive rider roll pressure at double backer glue machine, crushing flute tipsUneven roller pressure in hot places or cooling section of double backerBoard cut off knife pressure too highLow viscosity of the adhesiveLow solids of the adhesiveWater sprays being used to help control warpHot plates not level

Board quality begins at the single facer. To insure that good quality board is being produced at high speeds, it is critical to maintain the single facer in good mechanical condition.

Incorrect roller pressure in the cut off section or stacking section of the machine

Washboard Appearance:This problem usually occurs once the board has cured and causes a poor printing surface and brittle edges during conversion

Heavy adhesive application at single facer or double backerAdhesive viscosity too lowAdhesive solids too lowWet paper (roll stock stored outside)Excessive heat applied to lightweight linersGlue roll set to wrong paper speedOver-dried liners


Leaning Corrugation:This causes low board caliper, poor pin adhesion, poor top-to-bottom compression, poor printing surface

Misalignment of corrugator rollsExcessive wear on corrugator rollsPressure between corrugator rolls too lowTop and bottom belts traveling at different speedsExcessive rider roll pressure at double backer glue stationAdhesive application at single facer or double backerDrag through hot plate

Slipping Board - General Excessive tension on double facerLoose or worn beltsBelt rollers liftTop and bottom belts traveling at different speedsTreatment or finish of bottom liner causing excessive drag on the hot plates

Glue roll in double backer at wrong speed (paper comes apart easily in one direction, but has good fiber pull in the other direction)Too much heat application at single facer or double backerSlow machine speedAdhesive gel temperature too lowPoorly formed flutes (highs and lows)Slipping of the board coming through the machine

Dry Board, Zipper Board:Creates waste, low pin adhesion and poor top-to-bottom compression

Adhesive application at single facer or double backer too lightWater penetrates medium too quickly •Low viscosity adhesive •Medium with fast water dropLow solids adhesiveToo much borax in the formula

Slipping Board:This problem is produced by a surface bond only and delaminates after curing

Excessive drag on single face webLoose or worn corrugator belts in double facerHot plate rollers are upRollers in pulling section of the double facer are upCorrugator belts traveling at different speedsCoating on bottom liner creating drag

28



"Cracker" Board:This problem is identified by a cracking sound when flexed

Slippage between single facer web and double backer lineLight glue applicationGlue solids too lowExcessive unglued or high-low corrugations Excessive borax in formulaLiners too hotMedium too dryToo much drag on mediumSlow machine speedLow gel temperatureGlue roll and paper machine speeds synchronizedPoorly formed flutes

Light Glue Pattern at Double Backer:Brittle or zipper board appearance

Low glue roll settingRider roll set too highGlue roll speed too fast Smooth glue rollDirty or worn glue rollLow viscosity adhesiveToo much drag on single facer web

Adhesive Between Flutes:This problem creates warp problems, high starch consump-tion, poor bonding and overall poor quality

Starch setting too highLow viscosity adhesiveLow solids adhesiveImproper adhesive formulaRider roll set too low at double backerImproper glue roll speedBad wiper blade on metering rollSkip clutch not holding glue rollBad glue on metering rollAdhesive blown off the flute tips when running a jet assist for heavy-weight boardLong “tack” adhesive

Foaming of Adhesive in Pans:Poor bonding and high starch consumption

Light Glue Pattern at Single Facer:Delaminates, poor bonding

Air in starch lines •Leak in pumpsWiper blade improperly installed or dirty wiper blade on metering rollFlexo waste water used for adhesive make-upResin in the adhesiveAdhesive viscosity too lowNot using antifoam with adhesive made with High Shear systemHigh corrugating speeds

Glue roll too far from corrugating rollSmooth glue roll—not transferring enough adhesiveGlue roll settings too lowDirty or worn glue rollImproper pressure roll settingPoorly formed flutes (highs and lows)


Dry Streak:Poor bonding, low top-to-bottomcompression of finished carton

Dirty fingers on the single facerWorn fingers - flat spot on tipFinger running too close to lower rollToo much vacuum pressure on a vacuum style single facerDirty cleanout prongsWater jacket malfunctioningHigh adhesive viscosityPoor lateral adjustment of corrugating rollTension on medium too high

29

White Glue Line:Delaminates after curing, low pinadhesion, poor top-to-bottomcompression

Insufficient gelatinizationGel temperature too highIncorrect temperature at pressure roll, corrugator rolls or hot plates •Low boiler pressureLow viscosityWet paper •Roll stock stored outside

Spotty Glue Application on the Single Face Side:Poor bonding, low pin adhesion,low top-to-bottom compression

Glue roll motor problemFinger set too lowWorn fingerMedium not properly conditionedMedium not forming properlyMedium sticking to corrugator rollExcessive drag on mediumWater dripping on medium Dirty corrugator rollsHigh/low calibrated mediumBad glue roll/metering roll

Adhesive Sets Up on Fingers:High starch consumption,poor bonding, low pinadhesion, poor top-to-bottomcompression, low productionspeeds

Gel temperature of adhesive too lowAdhesive viscosity too highTemperature in glue pan too highImproperly conditioned medium


Loose Edge on the Single Face Side:Poor quality board, high waste, low production speeds

Wet paper roll Adhesive improperly applied to mediumNot enough brake on mediumFingers improperly adjustedDirty corrugating rollsLack of pressure on rollWet liner edgeMedium wider than linerImproperly set slitter knifeRoll stand out of parallelWrap arms on the medium or liner out of parallelLarge difference in paper temperature from one side of the machine to the other sideStarch dam out of adjustment at single facer

Loose Edge on the DoubleBack Side:High waste, low productionspeeds, poor print quality

Sheet guide compressing flutesWet streak on liner edgeWorn corrugator beltWorn rollers in hot platesWet paper rollDirty hot plates

Paper temperature too highFingers wornCleanout fingers too loose or tight against glue rollIncorrectly set taper speedWater jacket not functioning properlyPoor flow of the adhesive through the starch pan

Low adhesive solidsToo much heatImproperly set slitter knifeLow viscosityRoll stand out of parallelWrap arms on the medium or liner out of parallelBridge guides too tightLarge difference in paper temperature from one side of the machine to the other sideNot enough flutes in contact with glue rollStarch dams out of adjustment



30

Highs and Lows - Flutes Not Glued - Single Face Side/Double Back Side

Fingers set too lowPressure between corrugating rolls too lowDirty rollsCorrugating medium too wetGlue roll angled improperlyToo much drag on the single face web at the double back glue lineExcess drag on mediumLow caliper mediumMedium surface temperature too highImproper brake pressure on medium

Problem:

High and Low Corrugation:Low pin adhesion, poor top-to-bottom compression,poor print surface, overallpoor quality

Common Causes (All Machines):

Medium improperly conditioned •Lack of steam •Proper steam (wet)Surface temperature of medium too highImproper pressure on corrugating rolls •Worn or old rolls


Common Causes (Finger Machines):

Fingers improperly adjusted, worn, old or dirty

Common Causes (Vacuum Machines):

Low vacuum settings •Bad sealsPlugged holes/slots in corrugated roll

Common Causes (Pressure Machines):

Improper pressure •Leaky cabinet sealsPlugged holes/slots in corrugating roll

Blisters:Poor quality, poor print surface, low pin adhesion,poor top-to-bottomcompression

Fingers worn, old, dirtyFingers adjusted improperlyIncorrect heat in corrugator rolls, pressure rolls, hot plate sectionPoor quality paperWet paperMedium not properly conditioned

Glue roll out of parallelRoll stand out of parallelRider roll out of parallel at double backer glue stationImproper pressure on rollers in hot platesImproper brake on single face webExcess drag on mediumLow caliper medium

Low viscosity adhesiveLiner too hotMedium too hotMedium or liner out of calibrationWet streaks in the medium or linerDirty or worn glue rollImproper brake pressure on single face linerWorn corrugator rolls



31

Operating Footnote: If the moisture content of the single facer liner roll is greater than 2 percent over that of the double backer liner roll, then the roll should be changed. Preheaters on the machine can only remove 1 to 2 percent moisture from roll stock. Should the moisture imbalance be greater than 2 percent, warp will occur.

Operating Footnote: If the moisture content of the double back roll is greater that 2 percent over the single-face liner roll, then the roll should be changed.A difference of 2 percent or more in moisture between the single-face liner and the double back liner will create warp.

Problem: Common Causes / Corrective Actions:

Normal Warp (Side-to-Side Up Warp) Caused by moisture in the single facer liner •Add more heat (increasing warp) to the single face web at the double backer glue machine •Reduce heat (decreasing warp) to the double facer liner at the double backer glue machine •Increase single facer liner warp on the 36-inch preheater at the single facer •Increase the warp on the medium preconditioner •Decrease steam shower into the medium •Reduce the amount of single face web on the bridge •Increase machine speed •Reduce the amount of adhesive used at the single facer •Increase the amount of adhesive used at the double backer •Lift some ballast rolls in the hot plates

Reverse Warp (Down Warp) Caused by moisture in the double facer liner •Increase heat to the double facer liner (increase wrap on the 36-inch preheater)

DIAGNOSING WARP PROBLEMS

Warp is generally caused by moisture or tension imbalance.

•Decrease the heat in the single facer web at the double backer glue machine (decrease the wrap on the 36-inch preheater) •Increase the steam shower on the medium •Lower all rollers in the hot plate section •Check steam pressure in the hot plates and increase if possible •Increase the amount of single face web on the bridge •Reduce the speed of the machine •Reduce the amount of adhesive at the glue machine •Increase the amount of adhesive at the single facer •Add small amount of moisture to the top corrugator belt (use steam spray across the entire belt) •Use water spray on single face web

Operating Footnote: If th e moisture content of the double back roll is greater that 2 percen t over the single face liner roll, then the r oll should be changed. A difference of 2 per cent or more in moisture between the single face liner and the double back liner will create warp.

32

S Warp (combination ofnormal and reverse warp):This warp is usually causedby variations in moisture (wet streaks) across the webin a roll of liner or medium,or by machine conditionswhich apply variable amounts ofheat or adhesive across the web

Wet streak in roll liner or mediumThin streak or edge in roll of liner will warp in opposite direction to wet streakLoose edge in roll of liner does not hug preheaterWet edge in liner due to outside storageOut of level or out of square machine condition preventing liner from contracting preheater firmly across the webSingle face glue roll or doctor roll (glue roll and transfer roll) out of parallelImproper crown between single face glue roll and doctor roll loose, worn or dirty in some areasScraper blade on single face or double back doctor roll loose, worn or dirty in some areasSingle face glue or doctor roll (glue roll and transfer roll) galled in some areas or pitted on endsDouble backer rider roll out of parallelDouble back glue roll and doctor roll out of parallelApplicator roll out of parallel to the corrugating rollHydraulic lift of the glue mechanism not functioning correctly at the single facer; partially blocked steam showerDistorted steam chests causing uneven board temperatures across the machinePossible roll stand out of parallel


Machine Direction Warp (End-To-End Warp): The end-to-end warp can be either up or down, but is always in the machine direction

Tension greater in one liner than in the other

Operating Footnote: If the machine is equipped with a water spray, this is usually the best way of controlling the S warp. The water spray should be used on the single face side of the web only.

Operating Footnote: The corrugator crew may find the only way to control this type of warp will be with machine speed. The higher the speed, the less drag they see, because at higher machine speed they can operate with less brake.

End-To-End Warp Tension greater on the single face liner than on the double back linerSingle face liner is pulling back on the sheet"Drag" on the top liner, usually from a drag belt on the bridgePreheater locked down not turning, adding tension to the single face web going into the double facerRunning with too much brake on the single face liner at the single facerRunning with too much paper on the bridgeRunning with too much brake on the medium pulling back on the single face webIncorrect tension on web; increase tension

End-To-End "Down" Warp Tension greater on the double back liner than on the single face liner"Drag" on the bottom liner usually caused by a bad break on the roll stand; preheater locked down not turning, adding tension to the bottom linerDirty hot plates adding dragNeed to lubricate double face liner, especially when running coated liners

Wrap arm or roller out of parallel giving uneven contact pressure in the double facerOut of round glue roll at the single facer, applying adhesive light and heavyMachine speed from time to time will cause the adhesive to be applied heavy and lightRollstock with wet streaks or moisture content higher than normal

Operating Footnote: The corrugator crews should have a good understanding of the adhesive system within their machine and also understand the proper use of water sprays. Using the adhesive and water sprays properly is the best way to control this type of warp.

Cross Machine Direction (CD)Side-To-Side Warp:This is a warp that usually isfound within a few hours afterthe board is run. The problemis moisture and tension alongwith the temperature in the working area



33

Operating Footnote: When sheets warp after they leave the corrugator, moisture is most likely the problem. The sheets coming off the machine will be wet or damp to the touch. Storing finished sheets near open doors and windows, or loading the sheets into a cold truck before they have properly cured, will cause warp.




Twist Warp (Combination ofEnd-to-End and Side-to-Side Warp):

Roll stand out of levelPreheater out of levelSplice roll out of levelTwist warp is caused by

uneven tension or stress across the web of any or allcomponents during thecombining process

Roll stand, preheater out of square to the machineDirt on wrap roll or preheaterBridge web guide out of level, out of square or off centerCrown breaker roll in double back glue machine out of levelDouble back glue machine rider roll out of levelTop double back belt pulls unevenly across webLoose or tight edge in roll of linerUneven or diagonal stresses in roll liner

Post Warp (warp observedseveral hours or days later):The degree of this type of warp will depend greatly onthe way the sheets were stacked and the location ofthe stack. About the surestway to minimize in-storage warping has proved to be producing as dry as possibleboard on the corrugator, using as little adhesive aspossible, and using preheaters to their fullest capacity

Check liners for wet streaksReduce web tension on the single face sideReduce break drag on all roll standsPreheaters should be free turningHot plate section should be clean and free of dirt build upAdhesive formula should have the proper solids for the mix within the plantIf the machine uses a two piece belt, check the speed of the beltsSheets must be stacked properlyBoard coming off the machine should be dry and firmShould have proper storage area for the finished sheets

Operating Footnote: Twist warp is seen more often on machines that run a two piece top corrugator belt. One belt will be running faster than the other adding stress to the web. If the twist warp occurs off the machine, a wet streak will be noticed in one of the liners.

34

Appendix A

Equivalent Amounts of Borax for Starch Formulations

English Units, lb Metric Units, kg

10 Mol(decahydrate)

202122

23

2425

2627

28

29

3031

32

33

34

35

15.5016.0016.75

17.50

18.2519.00

19.7520.50

21.25

22.00

23.0023.75

24.50

25.25

26.00

26.75

12.3313.0013.50

14.25

14.7515.50

16.0016.67

17.25

18.00

18.5019.00

19.75

20.25

21.00

21.50

5 Mol(pentahydrate)

BoricAcid

10 Mol(decahydrate)

9.09.510.0

10.5

11.011.5

12.0.12.5

13.0

13.5

14.014.5

15.0

15.5

16.0

16.5

7.07.27.6

8.0

8.48.8

9.29.6

9.9

10.3

10.711.1

11.5

11.8

12.2

12.6

5.55.96.2

6.5

6.87.1

7.47.7

8.0

8.3

8.68.9

9.2

9.6

9.9

10.2

5 Mol(pentahydrate)

BoricAcid

Table courtesy of TAPPI

35

Appendix B

Microbiological Growth/Control inCorrugating Adhesives

For 666 Gallon Primary – Secondary Units

Step 1 — Primary mixer

Fill mixer with 150 gallons of water and heat to 130˚F[54.4˚C]. Add 15 pounds of a commercially available industrial strength cleaner and agitate for 30 minutes. DO NOT discard the solution. Proceed to Step 2.

Step 2 — Secondary mixer

Fill mixer with 300 gallons of water and heat to 130˚F[54.4˚C]. Add 30 pounds of a commercially available industrial strength cleaner and agitate for 30 minutes.Add the solution in the primary mixer into the secondarymixer. Pump the combined solutions into the storage tankand through the circulation lines for 30 minutes. Disposeof solution in an appropriate manner.

Step 3 — Primary mixer

Fill mixer with 150 gallons of water (DO NOT HEAT). Add 2quarts of commercial household bleach and agitate for 15minutes. DO NOT discard the solution. Proceed to Step 4.

Step 4 – Secondary mixer

Fill mixer with 300 gallons of water (DO NOT HEAT). Add 1 gallon of commercial household bleach and agitatefor 15 minutes. Add the solution in the primary mixer intothe secondary mixer. Pump the combined solutions intothe storage tank and through the circulation lines for anadditional 15 minutes. Dispose of the solution in an appropriate manner.

Step 5 — Flush all mixers, tanks and lines thoroughly withclean water to remove all trace amounts of chemicals.

For 666 Gallon No-Carrier & Single Tank Mix Systems

Step 1 — Mixer

Fill mixer with 350 gallons of water and heat to 130˚F[54.4˚C]. Add 45 pounds of a commercially available industrial strength cleaner and agitate for 30 minutes.Pump the solution to the storage tank and through the circulation lines for 30 minutes. Dispose of the solution in an appropriate manner.

Step 2 — Mixer

Fill mixer with 350 gallons of water (DO NOT HEAT). Add 6quarts of commercial household bleach and agitate for 15minutes. Pump the solution into the storage tank andthrough the circulation lines for an additional 15 minutes.Dispose of the solution in an appropriate manner.


For 300 Gallon High Shear Systems

Step 1 — High shear mixer

Fill mixer with 300 gallons of water and heat to 130˚F[54.4˚C]. Add 39 pounds of a commercially available industrial strength cleaner and agitate for a full 15 minutes with the high shear ON. Pump solution into thestorage tank and through the circulation lines for 30 minutes. Dispose of the solution in an appropriate manner.

Step 2 — High shear mixer

Fill mixer with 300 gallons of water (DO NOT HEAT). Add 5quarts of commercial household bleach and agitate for 10minutes. Pump the solution into the storage tank andthrough the circulation lines for an additional 15 minutes.Dispose of the solution in an appropriate manner.


Note for all systems: Growth can occur in an empty section of pipe or on the underside of tank covers. Using proper discretion, the solutions can also be used to clean the starch pans at the machine.

36

Testing The Gelatinization Temperatures

Introduction

With a few pieces of simple equipment and a little practice, the gel temperature of a starch adhesive can be measured quickly, accurately and reproducibly.

Equipment

a. Glass thermometer calibrated in degrees Fahrenheit (F) (See Recommendations 1 & 2 on thermometers)

b. Heat stable glass test tube

c. Test tube holder or suitable clamp

d. Heat stable glass beaker or other suitable container

e. Starch adhesive to be tested

f. Hot water at proper temperature (see Procedure)

g. UL approved hot plate, bottle warmer, etc.

Procedure

1. Fill a container (beaker) with water to within 1/2 inchof the top, place on a hot plate and heat to between170˚F and 180˚F [76.7˚C and 82.2˚C]. (DO NOT BOIL THE WATER.)

2. While the water is heating, pour the starch adhesive to be tested into the test tube (fitted with a test tube holder or clamp) to a level of 1 to 2 inches, or approximately 1/3 of the tube volume. Insert thethermometer as shown to the left.

3. When the water has reached temperature, turn the hot plate OFF and place the tube in the hot water (as shown). Immediately begin stirring the adhesivewith the thermometer, being careful to wipe the side of the tube to prevent localized heating and gelling.

4. As the temperature rises, the adhesive will begin tothicken as the gel point is approached (usually between139˚F and 152˚F [59.4˚C and 66.7˚C]). The temperature rise will pause (level off) for a few seconds at the actual gel value, then continue upward. RECORD thetemperature in degrees, where the leveling occurred.(NOTE: If the water is too hot, the temperature pausewill be shorter and often more difficult to detect.)

5. The test requires some skill; it is suggested that thetest be repeated and an average value reported.

Recommendations

1. Periodically, check the accuracy of the thermometer by placing it in boiling water. It should read exactly 212˚F [100˚C].

2. Glass thermometers are recommended over metal dial-type thermometers.

Appendix C

a

b

c

d

g

e

f

37

Specific Gravities and Concentrations of Caustic Soda SolutionsBased on International Critical Tables

%NaOH %Na2O Sp. Gr.@ 60/60˚F[15.6˚C]

Deg. Baumé@ 60/60˚F[15.6˚C]

2 1.55 1.023 3.3 .17 8.53

4 3.10 1.045 6.2 .35 8.71

6 4.65 1.067 9.1 .53 8.90

8 6.20 1.089 11.9 .73 9.08

10 7.75 1.112 14.6 .93 9.27

12 9.30 1.134 17.1 1.13 9.45

14 10.85 1.156 19.6 1.35 9.64

16 12.40 1.178 21.9 1.57 9.82

18 13.95 1.201 24.3 1.80 10.01

20 15.50 1.223 26.4 2.04 10.20

22 17.05 1.245 28.5 2.28 10.38

24 18.60 1.267 30.6 2.53 10.56

26 20.15 1.289 32.5 2.79 10.75

28 21.70 1.310 34.3 3.06 10.92

30 23.25 1.332 36.1 3.33 11.11

32 24.80 1.353 37.8 3.61 11.28

34 26.35 1.374 39.5 3.89 11.46

36 27.90 1.394 41.0 4.19 11.62

38 29.45 1.415 42.5 4.48 11.80

40 31.00 1.435 44.0 4.78 11.96

42 32.55 1.454 45.3 5.09 12.12

44 34.10 1.473 46.6 5.40 12.28

46 35.65 1.492 47.8 5.72 12.44

48 37.20 1.511 49.0 6.05 12.60

50 38.75 1.530 50.2 6.38 12.76

52 40.30 1.549 51.4 6.72 12.91

Lbs. NaOHPer Gal.

@ 60˚F [15.6˚C]

Lbs. of SolutionPer Gal.

@ 60˚F [15.6˚C]

Appendix D

38

Alkali (Caustic) Sensitivity – SettlingMethod Field Test For Corrugators

This test has been designed for testing unmodified cornstarch at the corrugator’s site. For best results, the components should be weighed. Empirical information can be obtained if the containers are calibrated andmarked with the component weights. The largest variableis the length of time the starch is in contact with thecaustic solution prior to mixing. That time must be kept to a minimum to get a valid reading. It is easy to get afalse negative result.

Equipment

• 250 ml bottles with caps• 100 ml graduated cylinders

Test Solution

From dry caustic:13.3 g caustic8.1 g 10 mol borax1434.0 g distilled water

From 50 percent caustic:

26.6 g 50 percent caustic8.1 g 10 mol borax1421.0 g distilled water

Test Procedure

1. Weigh 145 g of test solution into one 250 ml bottle.

2. Weigh 50 g starch into another 250 ml bottle. If starch is being added to a marked bottle, it should be tamped to get proper amount.

3. Quickly pour starch into bottle with test solution.

4. Quickly cap the bottle and shake for 3 to 5 minutes. It is important that steps 3 and 4 be done quickly.

5. Pour the starch slurry without delay into the graduated cylinder up to the 100 ml mark and put a piece of aluminum foil over the top as a cap.

6. Let the graduated cylinder stand for 24 hours.

Observation

Read the bottom of the clear water layer. The readingshould be less than 70 ml if the starch is not alkali (caustic) sensitive.

Appendix E

39

Alkali Sensitivity, Viscometric: Unmodified Starch

Principle

Starch granules that are heat damaged and no longerexhibit birefringence in aqueous suspension tend to swellmore readily in aqueous alkali than intact granules.Measured incremental viscosity in dilute alkali at roomtemperature is related to enhanced viscosity of corrugatedboard adhesive formulations.

Scope

This procedure was developed specifically for unmodifiedcorn starch and may not be used with modified starcheswithout further study.

Equipment

• Beaker: Griffen low form, 400 ml capacity

• Brookfield Viscometer: Model LV equipped with a laboratory stand and UL Adapter with spindle SPOO.

• Stirrer: Stainless steel 3-blade propeller, 5 cm diameter, on a 0.8 x 31.0 cm shaft

• Stopwatch

• Weighing Paper

Reagents

• 1 percent (w/v) aqueous sodium hydroxide (NaOH)

Procedure

The test is run at room temperature (about 77˚F [25.0˚C]).Transfer 150 ml of 1 percent NaOH and 50 ml of distilledwater to the 400 ml beaker. Position the stirrer in thebeaker and mix the solution at 600 rpm. Weigh 100 g (seenote 1) of starch on the weighing paper. Add the starch tothe agitated alkaline solution as quickly as possible butavoid lumping (see note 2) and start timer. Transfer 16.0 mlof slurry to the UL Adapter and measure viscosity at 30 rpm.

Calculation

(Unless the viscometer reads cps directly) Alkali Sensitivity, cps = Scale Reading x 0.2 (See note 3)

Notes

1. Variation in the normality of the sodium hydroxide solution and the moisture content of the sample canhave a significant effect depending on the alkali sensitivity. As the alkali sensitivity increases, the effects of these variables increase. Decreasing the sodium hydroxide normality from 0.25 to 0.24 decreases the measured alkali sensitivity by about 1.7 cps at 14 cps and about 0.1 cps at 5 cps. Reducingthe sample moisture content from 11.0 to 10.0 percentincreases the measured value by 0.6 cps at 14 cps and0.2 cps at 5 cps.

2. The addition is generally done in 5 to 10 seconds toavoid gelatinization of the intact granules.

3. As an alternative procedure, 200 ml of 0.1875 N NaOHcan be used in place of the combination of 50 ml waterand 150 ml 0.250 N NaOH. However, this change willeliminate the ability to adjust the formulation for variations in sample moisture content. The 0.1875 N NaOH can be obtained commercially as a special order.

4. The equipment, reagents and method are all available from:

Shape Products1127 57th AvenueOakland, CA 94621(800) 444-0015www.shapeproductsonline.com

Appendix F

40

Amylose Hybrid — A corn variety forming more linearstarch molecules

Borax — A crystalline compound used to control starchswelling and provide additional adhesive tack

Double Backer — Second glue station of corrugator;single face web glued to liner to form finished board

Carrier Starch — Primary portion of adhesive

Caustic Soda — Alkaline substance that causes starchgranules to swell; also called sodium hydroxide

Feed Gluten — Co-product of processed corn

Gelatinization — Point at which adhesive begins tothicken and develops bonding properties

Germ — Product of processed corn; usually furtherrefined into corn oil

Glue Roll — Component of corrugating machine; transfers starch to flutes at double backer or single facer

High Ring Crush — High performance paper having aring crush value of 2 pounds for every pound of basis weight

Liners — The flat paperboard portion applied to the fluted medium by applying adhesive to each flute tip

Medium — Fluted portion between the liners, whichwhen combined with the liners, makes corrugated board

Modified Starch — A starch modified chemically or mechanically

Recycle — In corrugating this refers to the reuse ofpaper products

Pearl — Unmodified starch

Shear — Mechanical action of breaking down starchadhesive

Single Facer — First glue station of corrugatingmachine; medium is fluted and bonded to liner

Starch — Complex carbohydrate from corn, potato, riceor tapioca processing

Steepwater — Water in which corn has been soaked or“steeped” during the initial stages of the corn wet millingrefining process

Viscosity — Term used to describe adhesive flowability

Waxy Maize — A corn variety producing predominantlybranched, chained starch molecules

Wick — Penetrate

Glossary

41

021-CM-99Printed in the USA June, 2006 Quantity: 2,500

©2006, Corn Products International, Inc.

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