Vol. 18, No. 7, Page 17

CONFERENCE REPORT

HIGH PERFOR?4ANCE 1st EUROPEAN CONFERENCE ON HIGH PERFORMANCE ADDITIVES held in A~DITI~ London, lo-11 May, 1988.

The term "high performance" signifies the growing demand being made of the additives sector in terms of overall property and/or cost effectiveness. The conference succeeded in its aim to high- light the more recent and important developments in a wide spec- trum of technical papers presented to a large audience of inter- national delegates. Two critical points - which can be levelled at similar conferences of this size - concern:

1) the projection of typed tabulated data on the screen which is virtually unreadable except by the front row: and

2) the decision to publish the papers in an A5 format which is easily "lost" on a bookshelf among standard textbooks etc.

Opinions vary on the definition of "an additive"; in the over-view paper no mention was made of catalysts for polyurethanes, and yet the Americans devote a section to these in their regular surveys of the additives sector. (The title of this publication "Additives for Polymers"was specifically selected to more clearly define the spectrum limits, which precludes polymerization catalysts etc.).

LIGHT STA3ILIZERS FOR POLYOLEF~NES can be sub-divided into four main classes: radical scavengers; quenchers; absorbers; and screens. The hindered amine light stabilizers (HALS), which are radical scavengers, are extremely effective in use and also cost-effective in the sense that only small quantities are necessary. They have allowed the polyolefines to be used in demanding environments hitherto a "no-go" area with regard to life expectancy. One of the most effective HALS described in the paper by Ciba-Geigy was said to be CHIMASSORB 119, a high molecular weight compound.

ORGAN0 PHOSPHATE ANTIOXIDANTS can be used as a partial replacement for HALS since they will give equivalent UV light protection at a lower cost in polyolefines, PVC, polyesters, etc. These com- pounds are generally used to provide protection against discolour- ation, melt degradation and oxidation. The paper presented by Borg Warner Chemicals described the effectiveness of two commer- cial products - ULTRANOX 626 and WESTON 619 - when used in comb- ination with HALS and phenolic-type antioxidants in polypropylene fibres. The synergistic effect of combining HALS and phosphites is characteristic of active pentaerythritol phosphites but not other phosphites.

THE LU3RICRTION/CO-STABILIZATION OF PVC AND ITS ALLOYS was the subject of a paper by Henkel Chemicals. This company specialise in lubricants for the PVC sector and the paper outlined the devel- opment and application of a range of lubricant/co-stabilizer blends, which,it was stressed, must be individually tailored to the require-

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A,DDITIVES FOR o 1988 Blrcvicr Science Publishers Ltd.. Englud.~.OO + %20

POLYMERS No part of this publication may be reproduced. stored in a retrieval system, or transmitted by any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the publishers (Readers in the U.S.A. - please see special regulations listed on back cover.)

Vol. 18, No. 7, Page 18

ments of the processor to achieve optimum performance. In common with other additive sectors, present emphasis is on new synergis- tic blends with the aim of reducing the metal stabilizer levels and to meet the more demanding technical requirements. Tests carr- ied out on a new range of LOXIOL lubricant/co-stabilizers have shown them to be synergistic in combination with many of the pri- mary metal stabilizers in current use. The most common oleochemi- cal based lubricants used for rigid PVC are fatty esters, partial esters, fatty acids, fatty alcohols and metal soaps. Non-oleochem- ical lubricants are derived from petrochemical sources and primar- ily consist of polythene and paraffin waxes.

REACTIVE PROCESSING AND MIXING IN TWIN-SCREW COMPOUNDING EXTRUDERS was described by Betol Technical ServicesU.K., and emphasised the need for advanced and more versatile forms of compounding equip- ment, and closely intermeshing twin-screw extruders have unique characteristics which relate to flow and mixing, both of which are of importance in a) achieving intimate distribution of the reactants, b) the uniform and controlled residence time distribu- tion, c) the efficient melt devolatization capability, and d) the maintenance of a low heat of reaction during polymerization reac- tions.

THE NUCLEATION OF POLYPROPYLENE using PDTS (1,3:2,4-O-p' ditoluy- lidene sorbitol), a low molecular weight organic molecule contain- ing both hydrophilic and hydrophobic segments, formed part of a paper by the New Japan Chemical Co. Low additions of this com- pound - designated GELLAL-MD (PDTS) - improve the clarity, increase the rigidity and radiation stability, and reduce the moulding cycle time. The melting point of the polypropylene remains unchang- ed but the degree of supercooling of the melt decreases dramatically

IONOMERS AS PROCESSING AIDS have proved to be particularly effec- tive in engineering plastics, according to Allied Corporation Inter- national. (The term ionomer relates to polymeric materials having a number of salt groups attached to the polymer chain). These low molecular weight ionomers - designated AClyn - possess a unique balance of physical and chemical properties due to the ionomer morphology, and this paper elaborated on the benefits of this state in the processing and performance of thermoplastics. The adhesive properties of these low molecular weight ionomers make them suit- able as coupling agents in filled/reinforced systems.

Some of the more recent developments in CHEMICAL EXPANSION SYSTEMS were outlined in a paper by Schering Industrial Chemicals (U.K.). The interest in chemical blowing agents has been stimulated by the demand for expanded engineering plastics and crosslinkable olefin/rubber blends. After reviewing the existing systems, the paper considered the possible advantages of using selected carrier systems to modify the performance of such systems. In practice, any developments in the future are likely to be based upon modi- fied forms of existing products, unless any one entirely new comp- ound shows considerable market potential in terms of performance. This forecast excludes the ammonia-free high temperature expan- sion systems. Azodicarbonamide, in the opinion of Schering, repre- sents the most likely candidate for subsequent modification.

GETTING THE MOST FROM YOUR TITANIUM DIOXIDE PIGMENT was the sub- ject of a paper by the Tioxide Group in the U.K. which explained the significance of pigment variations that arise from one supplier

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POLYMERS No part of this publication may be reproduced. stored in a retrieval system, or transmitted by any form or by any

means. electronic. mechanical, photocopying, recording or otherwise. without the prior permission of the publishers.

(Readers in the U.S.A. - please see special regulations listed on back cover.)

Vol. 18, No. 7, Page 19

SPE Rl!TI’EC

to another, some of whom have up to 30 grades available. These variations are due to differences in base crystal structure and composition, the mean crystal size, and surface modification of the particles etc. Specific requirements, such as very high disper- sibility, durability or very low evolution of volatiles, can be met by optimizing pigment selection, the balance between such prop- erties being dependent upon both the polymer and the end-use. The paper gave reasons for the selection of specific grades, and highlighted areas where particular grades should be used. Poly- olefines and PVC account for about 80% of titanium dioxide pigment consumption by the plastics industry worldwide, and some 35% of’ this total is in the form of masterbatches. These pigments will influence the ageing characteristics of plastics since they absorb UV light but, in consequence, act also as photocatalysts. They have a negligible-to-deleterious effect on the mechanical proper- ties, particularly the impact strength. Large agglomerates will act as centres of stress or weakness. Areas for further develop- ment include high temperature processing and applications, high impact materials, thin weatherable films and improving throughput rates.

(Part 2 of this Report will be given in the next issue of ADDITIVES FOR POLLERS).

John Shelton

5IARY

International conference to be held at the Leenwenhorst Conference Centre in Holland 26-28 September 1988.

Organised by the U.K. Plastics & Rubber Institute supported by the British Composites Society.

Further details:

PRI Conference Office, 11, Hobart Place, LONDON SWlW OHL

To be held 2-4 October, 1988 at the Crown Plaza Holiday Inn, Newport R.I.

Further details:

The Colour & Appearance Division and Polymer Modifiers & Addi- tives Division of the SPE.

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POLYMERS No part of this publication may be reproduced, stored in a retrieval system, or transmitted by any form or by any means, electmnic, mechanical, photocopying, recording or otherwise, without the prior permission of the pubtishers. (Readers in the U.S.A. - please see special regulations listed on back cwer.)