Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1994-10-24
2004-03-02
Pezzuto, Helen L. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S189000
Reexamination Certificate
active
06699946
ABSTRACT:
The present invention relates to polyphenylene sulphide-based compositions with improved impact strength. It relates more precisely to compositions containing a polyphenylene sulphide and a product resulting from the crosslinking of an olefinic elastomer containing epoxy groups. It also relates to a process for preparing these compositions.
Poly(phenylene sulphide) (referred to briefly as PPS hereinafter) exhibits an outstanding thermal stability and a very good chemical resistance, which make it a material of choice for the moulding of components which can be employed especially in electrical and electronic applications and in the motor vehicle industry.
However, PPS has the disadvantage of having a low impact strength and hence of being brittle.
Attempts have already been made to overcome this disadvantage by incorporating into PPS elastomeric copolymers derived from olefins and from glycidyl esters of alpha,beta-unsaturated carboxylic acids (Japanese Patent Application published under number 58-154757 (1983) (Toray Industries)). The insufficient reactivity of the molecular chains of PPS towards the elastomeric copolymer nevertheless means that the interfacial cohesion between the disperse elastomeric phase and the continuous phase containing the PPS is mediocre and that the improvement in the impact strength of PPS remains inadequate. Attempts have therefore been made to increase the chemical affinity of PPS for the elastomeric copolymer by subjecting PPS beforehand to a treatment with acid and/or hot water (U.S. Pat. No. 4,889,893 (Toray Industries)). However, the morphology and the processability of the compositions obtained is not satisfactory.
Patent Application FR-A-2,617,176 (Société Chimique des Charbonnages) describes compositions containing a material which may be a polyarylene sulphide and which is strengthened against impact by addition of a copolymer containing ethylene-derived units, units derived from at least one aliphatic ester of an &agr;,&bgr;-unsaturated carboxylic acid and units derived from maleic anhydride. The compositions may also contain a chemical agent capable of crosslinking the copolymer and incorporated at the time of the blending of the other constituents of the composition. The morphology of the compositions obtained is not satisfactory either.
It has also been proposed to improve the cohesion between the continuous phase containing the PPS and the disperse phase containing the elastomer by first melt-blending PPS with a polyfunctional isocyanate (4,4′-diphenylmethane diisocyanate) (Patent Application EP-A-0,406,553 (Asahi Kasei)). The composition obtained contains thiourethane bonds which impair its stability.
Patent Application EP-A-0,360,544 (Ube Industries) described thermoplastic compositions comprising PPS and a vinyl copolymer containing epoxy groups and which can also contain a styrene copolymer modified with carboxylic acid anhydride groups.
The mechanical and thermal properties and the processability of these compositions are, however, actually improved only when they additionally contain a polyphenylene ether.
It has now been found that the impact strength of compositions containing PPS can be improved by incorporating therein a particular crosslinked elastomer, using a particular method which makes it possible to disperse it homogeneously in the PPS matrix without impairing the latter's other properties.
Consequently, the present invention relates chiefly to polyphenylene sulphide-based compositions essentially containing 60 to 99.5% by weight of polyphenylene sulphide and 0.5 to 40% by weight of a combination (C) containing a compound (C1) chosen from olefinic elastomers containing epoxy groups and a compound (C2) chosen from crosslinking agents containing functional groups which are reactive towards the epoxy groups of the compound (C1) and chosen from amino, hydroxyl, carboxyl and carboxylic acid anhydride groups.
The polyphenylene sulphide (PPS) present in the compositions according to the invention is a polymer containing at least 70 mol %, preferably at least 90 mol % of p-phenylene sulphide repeat units of formula
PPSs containing at least 70 mol % of p-phenylene sulphide repeat units impart sufficient thermal stability and chemical resistance to the compositions according to the invention. 30 mol % or less of the repeat units present in the PPS may be chosen from those which have the following structural formulae:
Processes for the manufacture of PPSs which can be employed according to the invention are well known. They can all be employed. A process comprises heating an alkali metal sulphide, in most cases sodium sulphide hydrate, in a polar solvent in order to remove the water of hydration therefrom, followed by the addition of a dihalogenated aromatic compound, in particular p-dichlorobenzene, and polymerisation at higher temperature (see, for example, U.S. Pat. No. 3,354,129 (Phillips Petroleum)). The molecular weight of the PPS obtained can be increased in a known manner by oxidative aftertreatment resulting in branched products or by addition of known agents for increasing the molecular weight (water, esters, anhydrides and alkali metal carboxylates and sulphonates, etc.) to the polycondensation mixture, resulting in linear products of high molecular weight.
The molecular weight of the PPS which can be employed according to the invention may vary within wide measures. It is generally such that the melt index of the PPS is between 5 g/10 min and 10,000 g/10 min, preferably between 10 g/10 min and 500 g/10 min (determined according to ASTM standard D 1238-74 T at a temperature of 315° C. under a 5-kg load).
The PPS which can be employed according to the invention may contain conventional additives in quantities which are not detrimental to the properties of the compositions according to the invention. By way of such additives there may be mentioned in particular: anti-oxidants and heat stabilisers such as, for example, hindered phenols, thioesters and phosphites, anti-UV agents such as, for example, resorcinol, benzotriazole and benzophenone, flame-retardant agents such as, for example, antimony salts, aryl chlorophosphates and chlorinated paraffins, antistatic agents such as, for example, dodecylbenzenesulphonate and polyalkylene glycols, lubricants such as, for example, graphite, molybdenum disulphide and silicones, corrosion inhibitors such as, for example, alkali metal carbonates, pigments such as, for example, titanium dioxide and zinc sulphide, processing aids such as, for example, aromatic esters of phosphoric acid and microtalc, agents for controlling the degree of crosslinking such as, for example, peroxides, crosslinking accelerators such as, for example, metal salts of thiophosphinic acid, crosslinking inhibitors such as, for example, dialkyltin dicarboxylates or aminotriazole, and the like.
Small quantities of other polymers may also be added to the PPS.
The PPS which can be employed according to the invention may also be treated to improve its affinity for the compound (C1) defined later, with an acid, hot water and/or an organic solvent. Details relating to this treatment, which is known to a person skilled in the art, can be found in U.S. Pat. No. 4,889,893 (Toray Industries).
The compositions according to the invention are obtained by introducing a combination (C) containing a compound (C1) and a compound (C2).
The compound (C1) which can be employed in the compositions according to the invention is an olefinic elastomer containing epoxy groups. An “olefinic elastomer containing epoxy groups” is intended to denote elastomeric copolymers derived from olefins and from monomers containing at least one epoxy group and at least one ethylenically unsaturated radical (comonomer (1)).
The olefins from which these copolymers are derived may be &agr;-monoolefins or diolefins containing conjugated double bonds.
Specific examples of &agr;-monoolefins are ethylene, propylene, 1-butene, isobutylene and the like. Ethylene is preferred as &agr;-monoolefins.
Specific examples of diolefins containing conjuga
Collard Marie-Paule
Lambla Morand
Lin Dar-Jong
Mestanza Raphaël
Vandevijver Eric
Pezzuto Helen L.
Schneller Marina V.
Solvay ( Societe Anonyme)
Venable Baetjer Howard & Civiletti LLP
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