Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1998-10-08
2000-04-18
Gorr, Rachel
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
523201, 525 70, 525293, 525301, 525902, C08L 5100
Patent
active
060516569
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the preparation of molding materials modified with acrylic rubber by polymerization of monomers forming the graft shell in the presence of an acrylic rubber which is dissolved or swollen in the monomers and contains monomers having chemically reactive groups.
The preparation of rubber-modified molding materials has long been known. Furthermore, the use of elastomeric acrylate polymers having glass transition temperatures of less than 0.degree. C., preferably less than -10.degree. C. (acrylic rubber), for molding materials modified in this manner has been known for almost 40 years. They have improved weathering resistance compared with the molding materials prepared using diene rubbers. In the modified multiphase molding materials, domains of the rubber are embedded in a matrix of a thermoplastic, the domain structure playing a major role in determining the mechanical properties of the resulting molding materials. The toughness of the molding materials results from increased energy absorption during deformation up to fracture, energy being consumed for the formation of microcavities or for the initiation of sliding processes of the matrix polymer chains. The multiphase character is therefore an essential precondition for achieving high impact strengths.
There is still a considerable need for molding materials modified with acrylic rubber and in particular styrene/acrylonitrile copolymers modified with acrylic rubber (ASA molding materials) which have high impact strength and good flow properties and give shaped articles having reduced surface gloss.
The preparation of ASA molding materials in emulsion is described in many patent publications (cf. for example DE-A 19 11 882, DE-A 28 26 925, DE-A 31 29 378, DE-A 31 29 472, DE-A 31 49 046, DE-A 31 49 358, DE-A 32 06 136, DE-A 32 27 555). The disadvantage of this preparation is the necessity of removing assistants during working up of the molding materials, in order to avoid subsequent problems during their processing (discoloration, speck formation, corrosion). In particular, however, the impact strength, tensile strength and gloss properties of shaped articles produced therefrom are unsatisfactory.
DE-B 11 82 811 published more than 30 years ago discloses the polymerization of the acrylate with a crosslinking monomer in solution for the preparation of the acrylic rubber, the monomers styrene and acrylonitrile to be grafted on being added after a conversion of only from 20 to 40% by weight of the monomers and then being polymerized by mass or solution polymerization. Owing to the varying composition in the grafting reaction and because of the incorporation of rubber units into the graft shell by polymerization, this leads to a reduction in the Vicat softening temperature and a deterioration of further mechanical properties of the resulting molding materials.
It is an object of the present invention to prepare molding materials which are modified with acrylic rubber and can be processed to give shaped articles having improved impact strength, good flow properties and reduced surface gloss.
We have found that this object is achieved by a process for the preparation of molding materials modified with acrylic rubber if monomers having chemically reactive groups are incorporated into the acrylic rubber by polymerization, the completely polymerized acrylic rubber is dissolved or thoroughly swollen in the monomers forming the graft shell, and monomers and/or polymers which contain chemically reactive groups capable of reacting with the chemically reactive groups contained in the acrylic rubber (A2) or capable of being linked with these with the aid of an added crosslinking agent (AMV) are added to the mixture. The added crosslinking agent (AMV) may react both with the chemically reactive groups in the acrylic rubber (A2) and with the chemically reactive groups of the added monomer and/or polymer. The graft polymerization can then be carried out in one or more stages, at least the first stage of the polymerization being c
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Heckmann Walter
Mc Kee Graham Edmund
Rosenau Bernhard
BASF - Aktiengesellschaft
Gorr Rachel
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