Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1998-12-09
2000-08-22
Seidleck, James J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525387, 525308, C08F 434, C08L 5104
Patent
active
061074071
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the preparation of molding materials modified with acrylic rubber, monomers which contain groups which are decomposed by a redox component to give free radicals being incorporated as polymerized units in the acrylic rubber, and molding materials prepared in this manner.
The preparation of rubber-modified molding materials has long been known. The use of elastomeric acrylate polymers having glass transition temperatures of less than 0.degree. C. and preferably less than -10.degree. C. (acrylic rubber) for molding materials modified in this manner has also been known for almost 40 years. Compared with the molding materials prepared using diene rubbers, they have improved weathering resistance. In the modified multiphase molding materials, domains of the rubber are embedded in a matrix of a thermoplastic, the domain structure playing an important 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 forming microcavities and for initiating conduction processes of the matrix polymer chains. The multiphase character is therefore an essential precondition for achieving such impact strengths.
There is still a great 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. EP-0 095 919, EP-0 143 991, EP-0 438 418, JA-71 03 182, JA-60 21 0666, B. Vollmert, Die Angewandte makromolekulare Chemie 3 (1968), 1-27, and C. K. Riew, Rubber-Toughened Plastics, Advances in Chemistry Series 222, American Chemical Society, pages 15-64, describe the preparation of molding materials modified with acrylic rubber.
The preparation of ASA molding materials in emulsion is described in many publications in the patent literature (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-32 27 555). The disadvantage of this preparation in emulsion is the necessity of purifying the resulting relatively large amounts of water and the expensive essential removal of assistants in the working-up of the molding materials in order to avoid subsequent problems during processing (discoloration, speck formation, corrosion). The impact strength, tensile strength and gloss properties of shaped articles produced therefrom are also unsatisfactory.
DE-B 11 82 811 published more than 30 years ago discloses the polymerization of an acrylate together with a crosslinking monomer in solution for the preparation of a rubber-modified molding material, the monomers styrene and acrylonitrile to be grafted on being added after a monomer conversion of only from 20 to 40% by weight and the polymerization thereof then being carried out by solution or mass polymerization. Because the composition is not constant during the grafting reaction and owing to the incorporation of rubber units into the graft shell by polymerization, there is a reduction in the Vicat softening temperature and a deterioration of further mechanical properties of the resulting molding material.
In order to achieve a higher grafting yield in the grafting reaction, it is advantageous to incorporatg by polymerization, in the preparation of the acrylic rubber, comonomers with groups which undergo cleavage to give free radicals in the subsequent grafting reaction. EP-0 001 782 describes a process for the preparation of impact-resistant and ageing-resistant graft copolymers, monomers which contain peroxy groups, azo groups or labile C--C bonds being incorporated into an acrylic rubber by polymerization and then undergoing cleavage with thermal initiation and forming the graft shell with monomers forming hard polymers. Since the decomposition of the groups forming free radicals requires elevated temperatures, the polymerization of the monomers forming the graft shel
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McKee Graham Edmund
Rosenau Bernhard
Asinovsky Olga
BASF - Aktiengesellschaft
Seidleck James J.
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