Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reissue Patent
2000-06-30
2002-09-17
Lipman, Bernard (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...
C525S067000, C525S071000, C525S307000, C525S310000
Reissue Patent
active
RE037851
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an impact additive of the core/shell type as well as to a composition containing a thermoplastic polymer, in particular a vinyl chloride homopolymer or a copolymer mostly containing vinyl chloride, an impact additive of the core/shell type and optionally other additives.
Some synthetic resins, in particular resins based on poly (vinyl chloride) or on a copolymer mostly containing vinyl chloride, are widely used in the building industry, in particular due to their low cost and to their good physical and/or chemical properties.
Nevertheless, they exhibit low impact strengths at ambient temperature or at low temperature or again also after ageing.
It has been proposed to overcome these defects by incorporating, in these thermoplastic resins, products known as impact additives which are generally polymers exhibiting a degree of elastomeric properties.
A description is given in U.S. Pat. No. 3,678,133 of an impact additive of the core/shell type composed of an elastomeric core and of a more rigid thermoplastic shell.
The elastomeric core is obtained by polymerization of a mixture of monomers comprising at least 50% by weight of an alkyl acrylate, the alkyl group of which has from 2 to 8 carbon atoms, and a minor proportion of a crosslinking agent. The preferred alkyl acrylate is n-butyl acrylate.
It is also mentioned that alkyl acrylates having longer chains exhibit the disadvantage of polymerizing with greater difficulty, 2-ethylhexyl acrylate being given as an example.
The rigid thermoplastic shell is obtained by polymerization of a mixture of monomers comprising 40% to 100% by weight of alkyl methacrylate in which the alkyl group contains 1 to 4 carbon atoms.
The impact additive in this patent is produced in such a way that the polymerization of the rigid thermoplastic shell takes place at the surface of the elastomeric phase, preferably as a separate layer which more or less completely covers the elastomeric core.
Although the impact additives thus obtained significantly improve the impact strength at ambient temperature of the resins containing them, there is a loss in the mechanical properties, in particular a loss in the impact strength, at low temperature, of the said resins.
SUMMARY OF THE INVENTION
An impact additive of the core/shell type has now been found which is composed of a core based on alkyl acrylate or on a polyorganosiloxane rubber and a shell based on poly(alkyl methacrylate), or on a styrene-acrylonitrile copolymer, characterized in that the said impact additive comprises from:
(a) 70% to 90% by weight, and preferably 75% to 85%, of an elastomeric crosslinked core which is composed:
1) of 20% to 100% by weight, and preferably of 20% to 90%, of a nucleus composed of a copolymer (I) of n-alkyl acrylate, the alkyl group of which has a carbon number ranging from 5 to 12, and preferably ranging from 5 to 8, or of a mixture of alkyl acrylates, the linear or branched alkyl group of which has a carbon number ranging from 2 to 12, and preferably ranging from 4 to 8, or of a polyorganosiloxane rubber, of a polyfunctional crosslinking agent possessing unsaturated groups in its molecule, at least one of which is of CH
2
═C< vinyl type, and optionally of a polyfunctional grafting agent possessing unsaturated groups in its molecule, at least one of which is of CH
2
═CH—CH
2
—allyl type, the said nucleus containing a molar amount of crosslinking agent and optionally of grating agent ranging from 0.05% to 5% and preferably an amount of between 0.5% and 1.5%;
2) of 80% to 0% by weight, and preferably of 80% to 10%, of a covering composed of a copolymer (II) of n-alkyl acrylate, the alkyl group of which has a carbon number ranging from 4 to 12, and preferably ranging from 4 to 8, or of a mixture of alkyl acrylates as defined above in 1) and of a polyfunctional grafting agent possessing unsaturated groups in its molecule, at least one of which is of CH
2
═CH—CH
2
—allyl type, the said covering containing a molar amount of grafting agent ranging from 0.05% to 2.5% and preferably an amount of between 0.5% and 1.5%;
b) 30% to 10% by weight, and preferably 25% to 15%, of a shell grafted onto the said core composed of a polymer of an alkyl methacrylate, the alkyl group of which has a carbon number ranging from 1 to 4, or alternatively of a statistical copolymer of an alkyl methacrylate, the alkyl group of which has a carbon number ranging from 1 to 4, and of an alkyl acrylate, the alkyl group of which has a carbon number ranging from 1 to 8, containing a molar amount of alkyl acrylate ranging from 5% to 40%, and preferably of between 10% and 20, or alternatively composed of a styrene-acrylonitrile copolymer having a preferred styrene:acrylonitrile molar ratio between 1:1 and 4:1, and particularly between 7:3 and 3:1, respectively.
Mention will be made, as illustration of n-alkyl acrylates which can be used according to the present invention to form the copolymer (I), of n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate and very particularly n-octyl acrylate.
Mention will be made, as illustration of n-alkyl acrylates which can be used according to the present invention to form the copolymer (II), of n-butyl acrylate, n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate and very particularly n-octyl acrylate.
The n-alkyl acrylate which may be used to form the copolymers (I) and/or (II) can be identical or different.
Mention will be made, as illustration of linear or branched alkyl acrylates which can be used according to the present invention for the formation of the mixtures of alkyl acrylates constituting the copolymers (I) and /or (II), of ethyl acrylate, n-propyl acrylate, n-butyl acrylate, amyl acrylate, 2-methylbutyl acrylate, 2-ethylhexyl acrylate, n-hexyl acrylate, n-octyl acrylate, n-decyl acrylate, n-dodecyl acrylate or 3,5,5-trimethylhexyl acrylate.
In the case where a mixture of alkyl acrylates is used to produce the copolymers (I) and/or (II), use will be made of an amount by weight of n-alkyl acrylate at least equal to 10% by weight of the mixture of alkyl acrylates and preferably an amount of between 20% and 80%.
As above, use may be made, to form the copolymers (I) and/or (II), of a mixture of identical or different alkyl acrylates.
According to the present invention, it is preferable to use n-alkyl acrylates and very particularly n-octyl acrylate to form the copolymers (I) and (II).
If a mixture of alkyl acrylates is used to form the copolymers (I) and/or (II), use will preferably be made of 20% to 80% by weight of n-octyl acrylate and preferably of 80% to 20% by weight of n-butyl acrylate.
Mention will be made, as illustration of alkyl methacrylates which can be used to form the shell grafted onto the crosslinked elastomeric core according to the present invention, of ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate and very particularly methyl methacrylate.
According to the present invention, the crosslinking agent used to form the copolymer (I) can in particular be chosen from derivatives possessing at least two double bonds of the vinyl type or alternatively possessing one or a number of double bonds of the vinyl type and at least one double bond of the allyl type. Use will preferably be made of compounds possessing, in their molecules, a majority of double bonds of the vinyl type.
Mention will be made, as illustration of such crosslinking agents, of divinylbenzenes, polyalcohol (meth)acrylates, such as trimethylolpropane, triacrylate or trimethacrylate, allyl acrylate or methacrylate, alkylene glycol diacrylates or dimethacrylates having 2 to 10 carbon atoms in the alkylene chain and in particular ethylene glycol diacrylate or dimethacrylate, 1,4-butanediol diacrylate or dimethacrylate or 1,6-hexanediol diacrylate or dimethacrylate or polyoxyalkylene glycol diacrylate or dimethacrylate of formula
in which X represents a hydrogen atom or the methyl radical, n is an integer ranging from 2 to 4 and p is an integer ranging from
Bertelo Chris
Dargelos Pascale
Drujon Xavier
Lermite Andre
Meunier Gilles
Atofina
Lipman Bernard
Millen White Zelano & Branigan P.C.
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