AU622024B2

AU622024B2 - Expandable styrene polymers

Info

Publication number: AU622024B2
Application number: AU54929/90A
Authority: AU
Inventors: Uwe Guhr; Klaus Hahn; Hans Hintz; Dietmar Wittenberg
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1989-05-12
Filing date: 1990-05-11
Publication date: 1992-03-26
Anticipated expiration: 2010-05-11
Also published as: AU5492990A

Description

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822024 COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-69 Form COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete SeicaonLodgvd: Published: 'Priority: ti R~elated Art 'Ii ii Name of Applicant Address of Applicant Actual Inventor: Address -for Service BASF AKTIENGESELLSCH-AFT D-6700 Ludwigshafen, Federal Republic of Germany DIETMAR WITTENBERG, KLAUS HAHN, UWE GUHR, HANS HINTZ WATERMARK PATENT TRADEMARK ATTORNEYS.

LOCKED BAG NO. 5, HAWTHORN, VICTORIA 3122, AUSTRALIA Complete Specification for the Invention entitled: EXPANDABLE STYRENE POLYMERS rqe following statement Is a full description of this Invention, Including the bett method of performing It known to

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1- O.Z. 0050/40807 0 0 0i 00 0 o I a 0 0 0000 0 00 0 0Q 0 i 0 0 0 4 i 1' e Expandable styrene polymers The present invention relates to novel expandable sty'ene polymers which are suitable for the preparation of resilient foams.

Foams based on styrene polymers have become very important industrially as heat insulation and packaging materials. They are produced industrially on a large scale by first preparing expandable styrene polymers by suspension polymerization of styrene in the presence of a blowing agent, expanding the raid polymers by heating to give foam particles and then welding the latter in molds to form moldings.

Polystyrene foams are rigid foams. It is an object of the present invention to increase the resil- 15 ience of the polystyrene foams and to provide a raw material for the preparation of resilient polystyrene foams.

We have found, surprisingly, that these objects are achieved by admixing styrene-soluble elastomers.

The present invention thus relates to expandable styrene polymers containing a) from 50 to 98% by weight of polystyrene and/or of a styrene copolymer containing not less than 50% by weight of polymerized styrene, b) from 2 to 50% by weight of a styrene-soluble elastomer, c) from 1 to 15% by weight, based on the sum of a) and b) of a low boiling blowing agent and, if required, d) conventional additives in effective amounts.

The present invention furthermore relates to foams having a density of from 0.01 to 0.1 g/cm 3 and containing a) from 50 to 98% by weight of polystyrene or of a styrene copolymer containing not less than 50% by weight of polymerized styrene, b) from 2 to 50% by weight of a styrene-soluble elastomer and, if required, 4 i

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c) conventional additives in effective amounts.

The novel products contain, as main components from 50 to 98, preferably from 50 to 90, in particular from 70 to 85, by weight of polystyrene and/or a styrene copolymer containing not less than 50, preferably not less than 80, by weight of polymerized styrene. Examples of suitable comonomers are ae-methylstyrene, styrenes halogenated in the nucleus, styrenes alkylated in the nucleus, acrylonitrile, esters of acrylic or methacrylic acid with alcohols of 1 to 8 carbon atoms, N-vinylcarbazole, maleic acid and maleic anhydride. Advantageously, the polystyrene contains a small amount of a crosslinking agent as polymerized units, ie. a compound having more than one, preferably 15 two, double bonds, such as divinylbenzene, butadiene or butanediol diacrylate. The crosslinking agent is used in general in amounts of from 0.005 to 0.05 mol based on styrene.

To achieve particularly high expandability, it is advantageous for the styrene polymer to have a mean molecular weight M, (weight average) of from 100,000 to 200,000, in particular from 130,000 to 180,000, measured by the GPC method. The foam has improved processing properties when the high molecular weight slope of the molecular weight distribution curve measured by the GPC method is so steep that the difference between the mean values (Mz+ 1 -Mz) is less than 150,000. The GPC method is described in G. Glockler, Polymercharakterisierung, Chromatographische Methoden Volume 17, Huthig-Verlag, Heidelberg 1982. The stated mean values are described in H.G. Elias, MakromolekUle, Huthig-Verlag, Heidelberg 1971, pages 52-64.

Styrene polymers which have the abovementioned mean molecular weights can be obtained if regulators are present during the polymerization. Advantageously from 0.01 to 1.5, preferably from 0.01 to 0.5, by weight of a bromine-free organic compound having a chain transfer I(IB~UI LI~ II--sl -PIIC~ 3 O.Z. 0050/40807 94 r toot O t o o O* 0 0 0Q r0 0c t a tr constant K of from 0.1 to 50 are used as the regulator.

Advantageously, the regulator is added during the polymerization only when a conversion of from 29 to 90% ias been reached, in order to achieve a steep high molecular weight slope of the molecular weight distribution curve.

Advantageous high expandability Can also be achieved if component a) contains from 0.1 to 10, advantageously from 0.5 to 10, by weight of a styrene polymer having a mean molecular weight (weight average) of from 500 to 5,000.

Further details of molecular weight regulation in the preparation of expandable styrene polymers are given in EP-B 106 129.

Styrene polymers which contain from 0.1 to 2, 15 preferably from 0.15 to 1.5, by weight of polymerized acrylonitrile lead to foams which are substantially free of shrinkage. A mixture of from 95 to 99.5% by weight of polystyrene and from 0.5 to 5% by weight of a styrenesoluble styrene/acrylonitrile copolymer also has these properties if the total content of acrylonitrile in the mixture is from 0.1 to 2, preferably from 0.15 to 2, by weight.

Styrene polymers which contain from 3 to preferably from 5 to 15, by weight of polymerized acrylonitrile lead to foams having high resistance to oil. A mixture of from 50 to 85% by weight of polystyrene and 15 to 50% by weight of a styrene-soluble styrene/acrylonitrile copolymer also has this advantageous property if the total content of acrylonitrile in the mixture is from 3 to 20, preferably from 5 to by weight. Such mixtures are prepared in a simple manner by dissolving the intended amount of the styrene/ acrylonitrile copolymer in styrene prior to the polymerization.

Styrene polymers which contain from 2 to 15, in particular from 3 to 12, by weight of maleic acid or maleic anhydride as the comonomer lead to foams which i s. 11 I 1. -1 7 '1 4 O.Z. 0050/40807

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The products contain, as further component a styrene-soluble elastomer in an amount of from 2 to preferably from 5 to 40, in particular from 10 to 30, by weight. The elastomer is generally essentially noncrosslinked, ie. the degree of crosslinking may be so low that the solubility in styrene is not adversely affected as a result. Elastomers whose gel content does not exceed 10% by weight are still considered as essentially 15 noncrosslinked and are suitable as an additive. The elastomer generally has a glass transition temperature of less than 0°C, preferably less than -10 0 C, in particular less than -20 0 C. For example, styrene-soluble ethylene/ propylene rubbers, which may contain small amounts of a diene as polymerized units, and polyisobutylene, styrenesoluble vinyl ether rubbers, acrylate rubbers, in particular those based on C 2

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8 -alkyl acrylates, styrenesoluble silicone rubbers and styrene-soluble polyurethane rubbers are suitable.

25 The expandable styrene polymers contain from 1 to preferably from 2 to 10, in particular from 3 to 8, by weight of a low boiling blowing agent as component homogeneously distributed. The blowing agents should not dissolve the polystyrene but should be soluble in polystyrene. The boiling point should be below the softening point of the polystyrene. Examples of suitable blowing agents are propane, butane, pentane, hexane, cyclopentane, cyclohexane, octane, dichlorodifluoromethane, trifluorochloromethane and 1,1,1-difluorochloroethane. Pentane is preferably used.

The expandable styrene polymers may furthermore contain effective amounts of conventional additives, such i i I I 1 j i 5 O.Z. 0050/40807 0 C 9 00 0 0 00 0000 0000 0 00 o 0 0 000oooo 0,o o ooo oo0 o oo o n Sooo o as dyes, fillers, stabilizers, flameproofing agents, synergistic agents, nucleating agents, lubricating agents, antistatic agents, substances which have an antiadhesive effect during expansion and agents for reducing the demolding time in final expansion.

Other suitable additives are poly-(2,6-dimethyl)- 1,4-phenylene ether and poly-1,4-phenylene sulfide. In amounts of from 1 to 20% by weight, based on component these additives increase the heat distortion resistance of the foam.

The expandable styrene polymers are generally present in the form of particles, ie. in bead form, granular form or in the form of fragments, and advantageously have a mean diameter of from 0.1 to 6 mm, in particular from 0.4 to 3 mm.

The preparation can be carried out, for example, by mixing the components in the melt in an extruder, the extrudate being cooled so rapidly that no expansion takes place, and then being comminuted.

20 The preparation is advantageously carried out by suspension polymerization in a conventional manner. For this purpose, the elastomer and any additives are dissolved in styrene, and this solution is polymerized in aqueous suspension. A regulator or a small amount, for example from 0.005 to 0.05 mol based on styrene, of a crosslinking agent is advantageously added during the polymerization. The blowing agent may be initially taken in the polymerization or may be added in the course of the polymerization. It may also be added to the batch after polymerization is complete.

The resulting bead-like expandable styrene polymers are then isolated from the aqueous phase, washed and dried.

For the production of foams, the expandable styrene polymers are expanded in a known manner by heating above their softening point, for example with hot air or preferably with steam. After cooling and, if neces-

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i t 6 O.Z. 0050/40807 sary, intermediate storage, the resulting foam particles can be further expanded by heating again. They can then be welded in a known manner, in molds which close without i a gas-tight seal, to give moldings.

The foams obtained have a density of about 0.01- 0.1 g/cm 3 Because of their resilience, they are used in particular for shock-absorbing packaging, as core material for automobile bumpers, for interior trim in automobiles, as upholstery material and as heat and sound insulation material.

In the Examples which follow, parts are by weight.

i EXAMPLE 1 IIn a pressure-resistant stirred kettle, a mixture 15 of 200 parts of water, 0.1 part of sodium pyrophosphate, 100 parts of a solution of 9 parts of polyisobutylene having an intrinsic viscosity of 28 [cm 3 and a glass t' transition temperature of -64 0 C (Oppanol B10 from BASF AG) in 91 parts of styrene, 7.5 parts of pentane, 0.15 part of tert-butyl peroxide, 0.45 part of benzoyl peroxide and 4 parts of a 10% strength aqueous solution of .tc. polyvinylpyrrolidone was heated to 90 0 C while stirring, kept at this temperature for 5 hours and then heated at 100°C for 2 Lours and at 120°C for a further 2 hours.

After cooling, the resulting bead polymer having a mean particle diameter of about 1 mm was isolated from the i aqueous phase, washed and dried.

The resulting expandable styrene polymer was i subjected to preexpansion in a commercial stirred S 30 Rauscher-type preexpander, using a stream of steam, to a bulk density of about 30 g/l. After storage for 24 hours, the foam particles were welded in a Rauscher-type block mold by treatment with steam and under a pressure of 1.8 bar to give a block having a density of about g/1.

The resilience was tested by measuring tlhe tensile strength (DIN 53,430) and the modulus of elasticity 7 O.Z. 0050/40807 (DIN 53,426) using samples of the foam block. The results are summarized in Table 1.

EXAMPLE 2 The procedure described in Example 1 was followed, except that a solution of 11 parts of polyisobutylene in 89 parts of styrene was used.

EXAMPLE 3 I The procedure described in Example 1 was fol- 'I lowed, except that a solution of 21.5 parts of polyisobutylene in 78.5 parts of styrene was used.

EXAMPLES 4 AND The procedure described in Example 1 was followed, except that a solution of 11 (or 21.5) parts of i polyisobutylene having an intrinsic viscosity of 38.5 (Oppanol B12 from BASF AG) in 89 (or 78.5) parts of styrene was used.

.000 o EXAMPLES 6 TO 8 io f The procedure described in Examples 1 to 3 was followed, except that 0.01 part of divinylbenzene was present during the polymerization.

EXAMPLE 9 (COMPARISON) t The procedure described in Example 1 was followed, except that 100 parts of styrene were polymerized in the absence of an elastomer.

i 8 O.Z. 0050/40807 TABLE 1 Example Polyisobutylen~.

by wt. Intrinsic viscosity Tensile strength DIN 53,430 rkn /cm 2 1 Modulus of elasticity DIN 53,426 rkcr mn 2 1 1 9 2 11 3 21.5 4 11 5 21.5 6 9 7 11 8 21. 5 9 (comparison) rr-T /aT1 28 28 28 38.5 38.5 28 28 28 4.6 5.5 6.4 6.3 6.9 5.2 5.7 6.7 3.6 210 224 241 239 249 220 228 250 151

Claims

1. An expandable styrene polvyer containing a) from 50 to 98% by weight of polystyrene and/or of a styrene copolymer containing not less than 50% by weight of polymerized styrene, b) from 2 to 50% by weight of a styrene-soluble elastomer, c) from 1 to 15% by weight, based on the sum of a) and b) of a low boiling blowing agent and, if requTired, d) conventional additives in effective amounts.

2. An expandable styrene polymer as claimed in claim 1, wherein component a) has been prepared in the presence of from 0.005 to 0.05 mol of a crosslinking agent, S3. An expandable styrene polymer as claimed in claim $o 1, wherein component a) has a mean molecular weight M, (weight average) of from 100,000 to 200,000, measured by the GPC method. S" 4. An expandable styrene polymer as claimed in claim 3, wherein the high molecular weight slope of the molecu- lar weight distribution curve of component measured by the GPC method, is so steep that the difference bet- ween the mean values (Mz+ 1 -Mz) is less than 150,000. An expandable styrene polymer as claimed in claim 1, wherein component a) contains from 0.1 to 10% by weight of styrene polymers having a mean molecular weight (weight average) of from 500 to 5,000.

6. An expandable styrene polymer as claimed in claim 1, wherein component a) has been prepared in the presence of from 0.01 to 1.5% by weight of a bromine-free organic compound having a chain transfer constant K of from 0.1 to

7. An expandable styrene polymer as claimed in claim 1, wherein component b) is essentially noncrosslinked and has a glass transition temperature of less than 0°C.

8. An expandable styrene polymer as claimed in claim 1, wherein componlta b) is an ethylene/propylene rubber, polyisobutylene rubber, polyvinyl ether rubber, acrylate 10 O.Z. 0050/40807 rubber, silicone rubber or polyurethane elastomer.

9. An expandable styrene polymer as claimed in claim 1, wherein component a) is a styrene/acrylonitrile copolymer containing from 0.1 to 2% by weight of acrylo- nitrile or is a mixture of from 95 to 99.5% by weight of polystyrene and from 0.5 to 5% by weight of a styrene- soluble styrene/acrylonitrile cop olysx having a total content of from 0.1 to 2% by weight of acrylonitrile in the mixture. An expandable styrene polymer as claimed in claim 1, wherein component a) is a styrene/acrylonitrile copolymer containing from 3 to 20% by weight of acrylo- nitrile or is a mixture of from 50 to 85% by weight of polystyrene and from 15 to 50% by weight of a styrene- soluble styrene/acrylonitrilo copolymer having a total O t content of from 3 to 20% by weight of acrylonitrile in the mixture.

11. An expandable styrene polymer as claimed in claim 1, wherein component a) is a mixture of polystyrene and a styrene/maleic acid or maleic anhydride copolymer having a total content of from 2 to 15% by weight of maleic acid or maleic anhydride.

12. A process for the preparation of an expandable styrene polymer as claimed in claim 1, wherein the elas- tomer is dissolved in styrene and polymerized in aqueous suspension, and the blowing agent is added during or after the polymerization.

13. A foam having a density of from 0.01 to 0.1 g/cm 3 i and containing a) from 50 to 98% by weight of polystyrene and/or of a styrene copolymer containing not less than ISb by weight of polymerized styrene, b) from 2 to 50% by weight of a styrene-soluble elastomer and c) conventional additives in effective amounts.

14. A process for the production of foam moldings, wherein an expandable styrene polymer as claimed in claim 11 O.Z. 0050/40807 1, in the form of particles, is expanded by heating above the softening point, and the resulting foam par- ticles are welded to one another by heating in molds which close without a gas-tight seal. DATED this 10th day of May 1990. BASF AKTIENGESELLSCHAFT WATERMARK PATENT TRADEMARK ATTORNEYS "THE ATRIUM" 290 BURWOOD ROAD HAWTHORN. VIC. 3122. .A L