Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Staple length fiber
Reexamination Certificate
2001-09-25
2003-11-11
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Staple length fiber
C428S407000, C523S217000, C523S205000, C523S206000
Reexamination Certificate
active
06645620
ABSTRACT:
The present invention relates to a material based on a halogenated thermoplastic resin, comprising long fibers, its manufacturing processes and its applications.
The incorporation of mineral fibers in order to reinforce and improve the mechanical properties of molded articles based on a thermoplastic polymer is known.
Thus, to produce thermoformable structures having a flexural modulus which approaches the theoretically possible levels, document EP 56703 teaches to wet the reinforcing filaments, in parallel alignment, with a molten thermoplastic polymer.
Document FR 2579133 discloses a fiber-reinforced thermoplastic polymer composite in which the intimate bonding between the polymer and the fibers is provided by a second thermoplastic polymer, compatible with the first, promoting fiber wetting. It teaches that this composite results in articles having improved mechanical properties because of the interposition, between the standard thermoplastic polymer and the fibers, of a second thermoplastic polymer promoting wetting.
Moreover, French Patent FR 2 630 967 has described a process for manufacturing thermoplastics reinforced by long fibers, consisting in impregnating each fiber with a thermoplastic wetting polymer before sheathing the fibers by a thermoplastic polymer compatible with the wetting thermoplastic.
When glass fibers are incorporated in order to reinforce and improve the properties of articles based on a vinyl chloride resin, it is found that the increase in stiffness of these articles is often accompanied by a degradation in their impact strength.
Given the high viscosity of a vinyl chloride resin, when implementing the reinforcing process problems specific to it are encountered that cannot be solved by the teaching of the abovementioned prior art on reinforced thermoplastics.
Thus, on the one hand the wetting of the glass fibers with a vinyl chloride resin is unsatisfactory and, on the other hand, during mixing, the glass fibers are subjected to high stresses, and are therefore often broken, and end up with a reduced length.
Consequently, it is virtually impossible to obtain a uniform dispersion of long fibers in a material based on a vinyl chloride resin.
In addition, a poor dispersion of glass fibers in a material based on a vinyl chloride resin is in general manifested by flaws in the surface appearance of the articles made from such a material.
The problems specific to materials based on a vinyl chloride resin were disclosed in document EP 773 259. That document proposes to solve these problems and teaches, by its example 10, to prepare, in a first step, glass fibers coated with a graft copolymer (G1) consisting of 27% by weight of acrylonitrile units, 68% by weight of styrene units and 5% by weight of glycidyl methacrylate units, by impregnating glass fibers 3 mm in length and 13 &mgr;m in diameter in a homogeneous solution comprising acrylonitrile, styrene, glycidyl methacrylate and benzoyl peroxide, then by adding water to the solution and, finally, heating the mixture at a polymerization temperature of 80° C. for 5 hours. After polymerization, the coated glass fibers are washed with water and then dried at 60° C. in order to give a material (G1) containing 80% glass fibers by weight.
In a second step, a copolymer (e3) is prepared by heating, under nitrogen at 170° C. for 2 hours, a reaction mixture consisting of polypropylene, an antioxidant, dicumyl peroxide and methyl methacrylate. After polymerization, the copolymer is washed with acetone and then dried in order to give a block copolymer (e3) consisting of 70% by weight of a polypropylene block and 30% by weight of a polymethyl methacrylate block.
Finally, in a third step, 35 parts by weight of the material (G1), 5 parts by weight of block copolymer (e3), 100 parts by weight of a vinyl chloride resin (A), 3 parts by weight of a dibutyltin mercaptide and 0.5 parts by weight of stearic acid are mixed and then the mixture is extruded in order to give a sheet 3 mm in thickness and 30 mm in width.
Although the solution proposed in document EP 773 259 makes it possible to obtain articles, based on a vinyl chloride resin, having good mechanical properties and a correct surface finish, it nevertheless has the drawback of being complex and expensive.
It is an object of the present invention to provide a novel material based on a halogenated thermoplastic resin, comprising long fibers, capable of giving articles having good impact strength together with sufficient rigidity and a correct surface finish.
This material is characterized in that at least one long fiber is in intimate contact with an alkyl-(meth)acrylate-based polymer or polymer blend.
The subject of the invention is more particularly a material based on a halogenated thermoplastic resin, comprising long fibers, characterized in that each long fiber is in intimate contact with an alkyl-(meth)acrylate-based polymer or polymer blend.
Preferably, the material based on a halogenated thermoplastic resin comprises long fibers which are in intimate contact with an alkyl-(meth)acrylate-based polymer or polymer blend and are in almost parallel alignment.
According to the invention, the material is advantageously in granule form.
The cross section of these granules preferably consists of a core of long fibers in intimate contact with the alkyl-(meth)acrylate-based polymer and of an outer layer based on a halogenated thermoplastic polymer. In addition, the length of these granules corresponds to that of the fibers and is preferably greater than 3 mm.
As halogenated thermoplastic polymer, mention may be made especially of vinyl-chloride-based or vinyl-fluoride-based polymers, polymers based on vinylidene fluoride, polytetrafluoroethylene, polyfluoroalkyl vinyl ether, polyhexafluoropropylene and polychlorotrifluoroethylene. Vinyl-chloride-based polymers and those based on vinylidene fluoride are preferred.
In the foregoing and hereafter:
the term “long fibers” is understood to mean fibers whose length is generally greater than 1 mm, advantageously greater than 3 mm and preferably between 4 and 100 mm;
the term “alkyl-(meth)acrylate-based polymer” is understood to mean homopolymers and copolymers, the latter containing at least 70% and preferably at least 90% by weight of an alkyl methacrylate and/or acrylate and at least one other monomer chosen especially from olefins, unsaturated polycarboxylic acids, such as maleic, fumaric and itaconic acids, and their aliphatic, cycloaliphatic and aromatic esters, their amides and their nitrites, amides and nitrites of an unsaturated carboxylic acid such as acrylic or methacrylic acid, and vinyl esters of monocarboxylic and polycarboxylic acids, such as vinyl acetate, propionate and benzoate;
the term “vinyl-chloride-based polymers” is understood to mean homopolymers and copolymers, the latter containing at least 50% by weight of vinyl chloride and at least one monomer copolymerizable with vinyl chloride. The copolymerizable monomers are those generally used in conventional vinyl chloride copolymerization techniques. Mention may be made of vinyl esters of monocarboxylic and polycarboxylic acids, such as vinyl acetate, propionate and benzoate; unsaturated monocarboxylic and polycarboxylic acids, such as acrylic, methacrylic, maleic, fumaric and itaconic acids, and their aliphatic, cycloaliphatic and aromatic esters, their amides and their nitrites; vinyl and vinylidene halides; alkyl vinyl ethers; olefins.
Among vinyl-chloride-based polymers, vinyl chloride homopolymers are preferred.
The vinyl-chloride-based polymers may be prepared by known methods, such as emulsion polymerization, suspension or microsuspension polymerization and mass polymerization.
As vinylidene-fluoride-based polymers, mention may especially be made of vinylidene fluoride (VF2) homopolymers and copolymers preferably containing at least 50% by weight of VF2 and at least one other fluoromonomer such as chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), trifluoroethylene (VF3) and tetrafluoroethylene (TFE); trifluoroethylene (VF3) homopolymers and cop
Dupuy Carole
Jacquemet Regis
Renouard Philippe
Atofina
Kiliman Leszek
Pennie & Edmonds LLP
LandOfFree
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