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
2001-06-07
2004-11-30
Woodward, Ana (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S09200D
Reexamination Certificate
active
06825270
ABSTRACT:
The present invention relates to antistatic styrene polymer compositions and more specifically to a composition comprising a styrene polymer (A), a copolymer (B) containing polyamide blocks and polyether blocks essentially comprising ethylene oxide units —(C
2
H
4
—O)— and a compatibilizer (C).
The aim of the invention is to give the styrene polymer (A) antistatic properties. The formation and retention of static-electricity charges on the surface of most plastics are known. The presence of static electricity on thermoplastic films results, for example, in these films sticking to each other, making them difficult to separate. The presence of static electricity on packaging films may cause the accumulation of dust on the articles to be packaged and thus impede their use. Styrene resins such as, for example, polystyrene or ABS are used for making casings for computers, telephones, televisions, photocopiers and many articles. Static electricity causes dust to accumulate, but above all it can damage the microprocessors or the components of the electronic circuits contained in these articles.
The prior art has described antistatic agents, such as ionic surfactants of the ethoxylated amine or sulphonate type, which are added to polymers. However, the antistatic properties of the polymers depend on the ambient moisture and are not permanent since these agents migrate to the surface of the polymers and disappear. It has therefore been proposed to use, as antistatic agents, copolymers containing polyamide blocks and hydrophilic polyether blocks, these agents having the advantage of not migrating and therefore of giving permanent antistatic properties which are also independent of the ambient moisture.
Japanese Patent Application JP 60,170,646 A published on 4 Sep. 1985 describes compositions consisting of 0.01 to 50 parts of a polyether-block-amide and 100 parts of polystyrene, these being useful for making sliding parts and wear-resistant parts. The antistatic properties are not mentioned.
Patent Application EP 167,824 published on 15 Jan. 1986 describes compositions similar to previous ones and, in one embodiment of the invention, polystyrene may be blended with a polystyrene functionalized by an unsaturated carboxylic anhydride. These compositions are useful for making injection-moulded parts. The antistatic properties are not mentioned.
Japanese Patent Application JP 60,023,435 A published on 6 Feb. 1985 describes antistatic compositions comprising 5 to 80% of polyetheresteramide and 95 to 20% of a thermoplastic resin chosen from among polystyrene, ABS and PMMA, this resin being functionalized by acrylic acid or maleic anhydride. The amount of polyetheresteramide in the examples is 30% by weight of the compositions.
Patent EP 242,158 describes antistatic compositions comprising 1 to 40% of polyetheresteramide and 99 to 60% of a thermoplastic resin chosen from styrene resins, PPO and polycarbonate. According to a preferred embodiment, the compositions also comprise a vinyl polymer functionalized by a carboxylic acid, which may, for example, be a polystyrene modified by methacrylic acid.
The prior art shows either blends (i) of styrene resin and polyetheresteramide without a compatibilizer, or blends (ii) of polyetheresteramide and functionalized styrene resin, or else blends (iii) of polyetheresteramide, non-functionalized styrene resin and functionalized styrene resin.
The blends (i) are antistatic if the polyetheresteramide is properly chosen, but they have poor mechanical properties—in particular, the elongation at break is very much less than that of the styrene resin by itself.
As regards the blends (ii) and (iii), it is necessary to use a functionalized styrene resin which is complicated and expensive. The aim of the invention is to render antistatic the ordinary styrene resins used for making the abovementioned articles, these resins not being functionalized. It has now been discovered that, by using particular compatibilizers, it is possible to obtain antistatic styrene resin compositions which retain the properties of the base styrene resin and even have a markedly improved elongation at break.
SUMMARY
The present invention relates to a composition comprising, per 100 parts by weight:
99 to 60 parts of a styrene polymer (A),
1 to 40 parts of (B)+(C),
(B) being a copolymer containing polyamide blocks and polyether blocks comprising essentially ethylene oxide units —(C
2
H
4
—O)—,
(C) being a compatibilizer chosen from low-mass copolymers (C1) of styrene and of an unsaturated carboxylic acid anhydride, copolymers (C2) of ethylene and of an unsaturated carboxylic acid anhydride and copolymers (C3) of ethylene and of an unsaturated epoxy, blocks copolymers (C4) SBS or SIS grafted by an unsatured carboxylic acid or an unsatured carboxylic acid anhydride and mixtures thereof, (B)/(C) being between 2 and 10.
By way of example of styrene polymer (A), mention may be made of polystyrene, elastomer-modified polystyrene, styrene-acrylonitrile copolymers (SAN), elastomer-modified SAN, particularly ABS which is obtained, for example, by grafting (graft polymerization) of styrene and acrylonitrile on a polybutadiene or butadiene-acrylonitrile copolymer backbone, and blends of SAN and ABS. The abovementioned elastomers may be, for example, EPR (the abbreviation for ethylene-propylene rubber or ethylene-propylene elastomer), EPDM (the abbreviation for ethylene-propylene-diene rubber or ethylene-propylene-diene elastomer), polybutadiene, acrylonitrile-butadiene copolymer, polyisoprene or isoprene-acrylonitrile copolymer.
In the polymers (A) that have just been mentioned, part of the styrene may be replaced with unsaturated monomers copolymerizable with styrene; by way of example, mention may be made of alpha-methylstyrene and (meth)acrylic esters. As examples of styrene copolymers, mention may also be made of chloropolystyrene, poly-alpha-methylstyrene, styrene-chlorostyrene copolymers, styrene-propylene copolymers, styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-vinyl chloride copolymers, styrene-vinyl acetate copolymers, styrene-alkyl acrylate (methyl, ethyl, butyl, octyl or phenyl acrylate) copolymers, styrene-alkyl methacrylate (methyl, ethyl, butyl or phenyl methacrylate) copolymers, styrene-methyl chloroacrylate copolymers and styrene-acrylonitrile-alkyl acrylate copolymers. In these copolymers, the comonomer content will generally be up to 20% by weight. The present invention also relates to metallocene polystyrenes having a high melting point.
It would not be outside the scope of the invention if (A) were a blend of two or more of the above polymers.
The polymers (B) containing polyamide blocks and polyether blocks result from the copolycondensation of polyamide blocks having reactive end groups with polyether blocks having reactive end groups, such as, inter alia:
1) polyamide blocks having diamine chain ends with polyoxyalkylene blocks having dicarboxylic chain ends;
2) polyamide blocks having dicarboxylic chain ends with polyoxyalkylene blocks having diamine chain ends obtained by cyanoethylation and hydrogenation of aliphatic dihydroxylated alpha,omega-polyoxyalkylene blocks called polyetherdiols;
3) polyamide blocks having dicarboxylic chain ends with polyetherdiols, the products obtained being, in this particular case, polyetheresteramides. The copolymers (B) are advantageously of this type.
The polyamide blocks having dicarboxylic chain ends stem, for example, from the condensation of alpha,omega-aminocarboxylic acids, of lactams or of dicarboxylic acids and diamines in the presence of a chain-stopper dicarboxylic acid.
The number-average molar mass {overscore (M)}n of the polyamide blocks is between 300 and 15,000 and preferably between 600 and 5000. The mass {overscore (M)}n of the polyether blocks is between 100 and 6000 and preferably between 200 and 3000.
The polymers containing polyamide blocks and polyether blocks may also include randomly distributed units. These polymers may be prepared by the simultaneous reaction of the polyether and of the
Atofina
Millen White Zelano & Branigan P.C.
Woodward Ana
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