Preparation of rubber-modified molding materials by means of gro

Details Preparation of rubber-modified molding materials by means of gro Preparation of rubber-modified molding materials by means of gro

1997-05-12

1999-06-08

Acquah, Samuel A.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

522 32, 522 60, 522 65, 522113, 522150, 526328, 5262325, 526345, 525309, C08F11802

Patent

active

059105534

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a process for the preparation of rubber-modified molding materials, groups which form free radicals on thermal decomposition being incorporated in the rubber, and to rubber-modified molding materials prepared by the process.
Rubber-modified molding materials are materials in which domains of elastomers, for example rubbers, are embedded in a matrix comprising a thermoplastic. There is considerable demand for rubber-modified molding materials which have surface gloss, impact strength and tensile strength. The characteristic domain structure is responsible for the desired mechanical properties.
The multiphase character and hence also the domain structure of rubber-modified molding materials is based on the fact that they are composed of different polymer components which are immiscible or only partly miscible with one another. The impact strength thereof results from increased energy absorption during deformation up to fracture. The energy is consumed for the formation of microcavities or for initiating sliding processes of the matrix polymer chains. The multiphase character is therefore essential for achieving high impact strengths.
The following are also applicable: of defined particle size, which neither exhibits phase separation in the thermoplastic melt (processing) nor tends to homogenization with formation of a macromolecular solution at high temperatures. it must be possible to transmit forces at the phase boundaries.
The most effective phase coupling at the boundaries of the elastomer particles is achieved by graft copolymerization. For example, in the preparation of acrylonitrile/styrene/acrylate (ASA) molding materials, the procedure generally adopted is one in which an acrylate rubber is initially taken and, by polymerization with a monomer mixture comprising styrol and acrylonitrile, copolymers based on the latter two monomers are then grafted on.
EP 0 095 919, EP 0 143 991, EP 0 438 418, EP 0 001 782, DE 11 828 11, JP-A 71003-182, JA 60 21 0666 and B. Vollmert, Angewandte Makromolekulare Chemie, 3, 18 (1968), 1-27, describe the preparation of thermoplastics modified with acrylate rubbers.
It is an object of the present invention to provide a process for the preparation of rubber-modified molding materials having improved mechanical properties, in particular higher impact strengths, notched impact strengths and hole impact strengths.
We have found that this object is achieved by the novel process in which, in a first stage, a first mixture (A) which contains at least one alkyl acrylate or methacrylate (a) of the general formula (1) ##STR2## where R.sup.1 is hydrogen or methyl and R.sup.2 is alkyl of 1 to 32 carbon atoms, at least one first monomer (b) which forms free radicals on thermal decomposition and, if required, a second monomer (c) or a plurality thereof is polymerized, preferably in solution, with free radicals to give a rubber (B), (d) or a plurality thereof, preferably dissolved or swollen therein, to form a second mixture (C), and to give the rubber-modified molding material (D). The polymerization being carried out either continuously as a solution or mass polymerization or being continued as a suspension polymerization after a conversion of at least 15%, the rubber-modified molding material (D), containing from 1 to 60% by weight of the rubber (B) and the rubbers (B) in grafted form being present in said molding material (D) as particles having a diameter of from 0.1 to 20 .mu.m.
The first monomer (b) which forms free radicals on thermal decomposition should form only a few free radicals, if any at all, during its own polymerization.
The novel process has the advantage that, apart from the abovementioned properties, the weather resistance and the rigidity of the molding materials is also improved. By varying the preparation parameters, the gloss of the molding materials prepared can be varied over a wide range.
A graft copolymerization takes place in the third stage, the backbone of the resulting graft copolymer being formed by the rubber (B), and t

REFERENCES:
Von Bruno Vollmert, Die Ang. Makromol. Chem., vol. 3, 1968, No. 18, pp. 1-27.

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