Preparation of rubber-modified molding materials from reaction m

Details Preparation of rubber-modified molding materials from reaction m Preparation of rubber-modified molding materials from reaction m

1997-05-12

1999-03-23

Warzel, Mark L.

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

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

525293, 525 80, 525 85, C08L 3300, C08L 3326

Patent

active

058861050

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a process for the preparation of rubber-modified molding materials and to rubber-modified molding materials prepared by the process, derivatives of acrylamides or of methacrylamides being used in the process.
Rubber-modified molding materials are materials in which domains of elastomers, for example rubbers, are embedded in a matrix comprising a thermoplastics material. There is a 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 partially 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 applicable besides: 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 higher 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 styrene and acrylonitrile, copolymers based on the latter two monomers are then grafted on.
The preparation of ASA molding materials in emulsion is described, for example, in DE 32 06 136, 31 49 046, 31 49 358, 32 27 555, 31 29 378, 31 29 472, 29 40 804, 28 26 925 and 19 11 882. The rubber is prepared in emulsion from n-butyl acrylate and small amounts of monomers containing two double bonds. However, the molding materials prepared by the process do not have impact strength or rigidity and tensile strength sufficient for all applications, and the gloss of the moldings produced therefrom cannot be varied over a wide range.
The emulsion polymerization of styrene/acrylonitrile in the presence of a rubber which contains monomer units comprising derivatives of acrylamides or methacrylamides is described in DE 21 26 151.
For these reasons, the molding materials are most advantageously prepared in solution. Such processes are described in EP 0 095 919 and DE 11 82 811.
According to EP 0 095 919, no grafting of the comonomers onto the rubber, i.e. no effective coupling at the boundary, takes place. According to DE 11 82 811, the rubber is prepared from n-butyl acrylate with 0.5 to 10% by weight of a comonomer having two double bonds capable of radical polymerization. The polymerization of the styrene/acrylonitril (SAN) monomer mixture is initiated at a rubber conversion of from 10 to 80%. Consequently, the grafted part of the rubber does not have the same composition as the polymer matrix, leading to poorer mechanical properties of the molding materials. Furthermore, incorporation of rubber units in the graft shell, i.e. the graft branches, by polymerization leads to a reduction in the Vicat softening temperature of the products.
It is an object of the invention to provide a process for the preparation of rubber-modified molding materials having improved mechanical properties, in particular higher impact strength, notched impact strength and hole impact strength.
We found that the subject 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 (I) ##STR3## where R.sup.1 is hydrogen or methyl and R.sup.2

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