Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1997-05-02
1998-02-10
Foelak, Morton
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
521134, 521180, 521189, 521 79, C08J 902
Patent
active
057169993
DESCRIPTION:
BRIEF SUMMARY
The invention relates to polyarylene sulfide foams and a process for their production by heating polyarylene sulfides which contain sulfoxide groups or a polyarylene sulfoxide.
Polyphenylene sulfide foams have been produced to date from polyphenylene sulfide (PPS for short) by addition of 3 to 5% by weight of a blowing agent concentrate (EP-A-0 406 634 or U.S. Pat. No. 5,114,983). Azo compounds, anhydrides or azoles are used as blowing agents. The mixture is processed and foamed at temperatures of 300.degree. to 360.degree. C., which are customary for polyarylene sulfides. A reduction in density of about 40 to 45% can be achieved in the polyphenylene sulfide foamed in this way, the term "reduction in density" being understood as meaning a percentage reduction in the density of the foamed material, based on the density of the non-foamed starting material.
Foam sheets of high heat distortion resistance can be produced from a mixture of 80 to 99% of styrene polymer and 1 to 20% by weight of 1,4-polyphenylene sulfide and customary blowing additives, such as propane, butane, pentane, chlorohydrocarbons, fluorochlorohydrocarbons or CO.sub.2, by extrusion at 100.degree. to 200.degree. C. (EP-A-0 443 393; U.S. Pat. No. 5,106,684). These foam sheets have thermal conductivities of between 0.024 and 0.030 watt.meter.sup.-1.kelvin.sup.-1 and contain 90 to 95% of closed cells having a cell diameter of 0.1 to 0.2 mm.
Polyphenylene sulfide with a low degree of foaming (U.S. Pat. No. 4,471,247), which can be used as an electrical insulating or heat removal medium for coils and pole shoes in railway electric motors, can be obtained by heating PPS material which comprises volatile impurities. The density of the heat-treated material is between 5 and 10% below the density of the starting material. This reduction in density is too low for many uses, for example as thermal insulation material. A blowing agent must also be added here for greater foaming of the material.
Foaming of high-melting polymers without the customary blowing agents or blowing gases with a degree of reduction in density of more than 10% is either not possible or presents difficulties.
The object of the invention was the development of a process for the production of polyarylene sulfide foams which does not require the addition of customary blowing agents to the polymer to be foamed and which nevertheless allows a high degree of foaming.
It has been found that polyarylene sulfoxides and mixtures thereof with polyarylene sulfides form a foam when heated. On heating, sulfoxide groups of the polyarylene sulfoxides are converted into sulfide groups and oxygen, which acts as an expanding agent, is released in the process.
The invention thus relates to a process for the production of polyarylene sulfide foam, which comprises heating at least one polyarylene sulfoxide or a mixture of one or more polyarylene sulfides and at least one polyarylene sulfoxide.
Polyarylene sulfides, which are also called polyarylene thioethers, are understood as meaning compounds which contain at least one arylene sulfide unit (--Ar--S--; Ar=arylene). Arylenes are, for example, phenylene, biphenyldiyl (--C.sub.6 H.sub.4 --C.sub.6 H.sub.4 --), naphthalenediyl, anthracenediyl or phenanthrenediyl, which can be mono- or polysubstituted. Substituents are, for example, straight-chain, cyclic or branched C.sub.1 -C.sub.20 --hydrocarbon radicals, such as C.sub.1 -C.sub.10 --alkyl radicals, for example, methyl, ethyl, n-propyl, iso-propyl, n-butyl, t-butyl or n-hexyl, or C.sub.6 -C.sub.14 --aryl radicals, for example phenyl or naphthyl; and halogens or sulfonic acid, amino, nitro, cyano, hydroxyl or carboxyl groups.
Polyarylene sulfides are, for example, compounds which contain units of the formula independently of one another are identical or different. The indices n, m, i, j, k, o and p independently of one another are zero or the integers 1, 2, 3 or 4, and their sum must be at least 2, and Ar.sup.1, Ar.sup.2, Ar.sup.3 and Ar.sup.4 in formula (I) are arylene systems having 6 to 18 carbon atom
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Frank Georg
Kulpe Jurgen
Scheckenbach Helmut
Schleicher Andreas
Foelak Morton
Hoechst Aktiengesellschaft
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