Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1998-05-27
2000-09-19
Woodward, Ana
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525 66, 525 67, 525 92A, 525 70, 525 72, 525123, 525166, 525176, 525183, C08L 6700, C08L 7700, C08L 6900, C08L 7500
Patent
active
061213748
DESCRIPTION:
BRIEF SUMMARY
The invention relates to multiphase thermoplastic resin compositions and more particularly to compositions in the form of a matrix in which nodules are dispersed.
Many thermoplastics have to be modified by incorporating rubbers or other polymers, for example in order to modify the flexural modulus thereof or to improve the impact strength.
The Applicant has discovered that if, in a matrix (M) containing nodules (S) part of (S) is replaced by a polymer (K), the tensile strength could be improved while maintaining the flexural modulus. In addition, this also very often results in a reduction in the size of the nodules of the phase dispersed in (M).
This has many advantages, for example when the polymer of the matrix is transparent or even translucent, the reduction in the size of the nodules increases the transparency or makes the polymer more translucent for a constant level of dispersed phase. The impact strength is also improved.
U.S. Pat. No. 5,070,145 describes compositions consisting of 80 parts of nylon-6 (PA-6) or nylon-6,6 (PA-6,6) in which 20 parts of a mixture (i) of a copolymer of ethylene and of an ethyl or butyl acrylate and (ii) of a copolymer of ethylene, ethyl acrylate and maleic anhydride have been dispersed. These compositions have good impact strength.
EP 284,379 describes multiphase compositions consisting of a polyamide and of an ethylene copolymer in the form of a polyamide matrix in which nodules (1) of an ethylene-ethyl acrylate-maleic anhydride copolymer are dispersed, and dispersed in these nodules (1) are nodules of polyamides. These nodules (1) are firstly prepared by dispersing a polyamide in the ethylene copolymer, and then these nodules are crosslinked and then dispersed in a polyamide. These compositions are also presented as having a good impact strength.
Patent FR 2,719,849 describes thermoplastic compositions consisting of a matrix of a thermoplastic polymer in which nodules of a second thermoplastic polymer, partially or totally encapsulated by an ethylene copolymer, are dispersed. These compositions are prepared by firstly encapsulating the second polymer and then the other polymer forming the matrix is added under conditions such that the capsules are not destroyed. This preparation is carried out in two steps which are completely separate or with one step following the other in the same extruder. These compositions have both good flexibility and good impact strength. The examples show PA-6, PA-12 or PBT (polybutylene terephthalate) matrices in which are dispersed nodules of PA-6,6 encapsulated by an ethylene-ethyl acrylate-glycidyl methacrylate copolymer. A comparative example shows that in a PA-6 matrix the PA-6,6 nodules encapsulated by the ethylene copolymer are coarser than the nodules formed only from the ethylene copolymer.
The present invention is therefore a thermoplastic composition comprising at least one polymer (M) forming a matrix in which are dispersed at least one polymer (S) and at least one polymer (K) and such that its tensile strength is greater than that of a composition comprising only (M) and (S), the proportion by weight of (M) being the same.
In order to modify the impact properties or the flexural modulus of a polymer (M), it is necessary to add a plasticizer and/or a polymer (S) to it. The drawback of a plasticizer is that, above a certain amount, it exudes and therefore the properties are not preserved. If the amount of (S) is increased too much, there may be compatibility problems and another property may also be affected. For example, if the amount of (S) in (M) is increased, a decrease in the flexural modulus is indeed obtained, but there is a reduction in the tensile strength, which may also be expressed by a decrease in the burst strength of an extruded tube.
The Applicant has therefore discovered that, by adding a polymer (K) to a mixture of (S) in (M), the tensile strength was improved. More specifically, by replacing a part of (S) by (K), so as to maintain the flexural modulus, an improvement in the tensile strength was obtained. This
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Guibouin Chrystelle
Hert Marius
Montanari Thibaut
Perret Patrice
Roumilhac Didier
Elf Atochem SA
Woodward Ana
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