Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1997-06-16
1998-06-16
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...
525307, 525 80, 525 85, C08L 5100
Patent
active
057672016
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to emulsion graft copolymers which are composed of comonomers, and c.sub.1 :b.sub.1 is from 1.3:1 to 1.9:1 and the sum of the components A to D is 100% by weight.
The present invention furthermore relates to a process for the preparation of these emulsion graft copolymers and to the use thereof.
Emulsion graft copolymers based on vinyl monomers are generally known and are used by themselves but in particular as additives in plastics, such as acrylate- and methacrylate-based homo- or copolymers. Their addition results in an improvement in the impact strength of such acrylate resins, which can be processed, for example, to moldings, sheets, films and organic glass (acrylic glass). The other important basic properties of acrylate resins, such as high light transmittance and clarity, weather resistance, heat distortion resistance and mechanical strength, may however be adversely affected by these additives. It is therefore generally desirable to keep the undesirable property changes as small as possible or--if possible--to prevent them and at the same time to achieve an increase in the impact strength by means of emulsion graft copolymers having a multistage structure and special composition.
DE-A 22 53 689 discloses multistage emulsion graft copolymers. The polymers described in detail there are composed of three stages, ie. a core and a first and a second graft shell, the core and second shell consisting of a hard, nonelastomeric polymer and the first shell of an elastomeric polymer. Furthermore, this publication points out the possibility of a multistage structure of the graft polymers comprising alternating hard and elastomeric phases.
Moreover, EP-A-512 333 describes emulsion graft copolymers which are composed of a hard core and four graft shells, hard and soft stages alternating.
If the known emulsion graft copolymers are used as additives in thermoplastics, in particular acrylate resins, such as polymethyl methacrylate, their impact strength increases but edges of moldings or coatings on moldings have a yellowish tinge, which is undesirable. In addition, the known emulsion graft copolymers cannot be sufficiently thoroughly dispersed in the thermoplastics so that the haze will be satisfactorily low for many applications.
A further problem is the formation of shell-like indentations in extruded sheets, in particular of polymethyl methacrylate toughened with the known emulsion graft copolymers. The formation of shell-like indentations is understood as meaning shell-like indentations which form at the edges when the sheets are sawn for processing. In addition, injection molded parts splinter or crack when sprues are mechanically removed.
It is an object of the present invention to provide emulsion graft copolymers as impact strength improvers for thermoplastic materials, which impart high impact strength to these materials and at the same time improve the mechanical and optical properties, such as yellow tinge of edges and haze, and reduce the tendency to form shell-like indentations.
We have found that this object is achieved by the emulsion graft copolymers defined at the outset. Preferred embodiments are evident from the description.
We have also found a process for their preparation, their use as additives in thermoplastic materials and moldings, films and coatings comprising these thermoplastic materials.
The novel emulsion graft copolymers have a four-stage composition comprising a hard, nonelastomeric stage (A), an elastomeric, second stage (B), an elastomeric, third stage (C) and finally an outer, hard, nonelastomeric, fourth stage (D), the individual stages being present in the following amounts: and
The first stage A of the emulsion graft copolymer consists of (a.sub.1), -alkyl acrylate (a.sub.2), (a.sub.3) and polyfunctional comonomers (a.sub.4).
The sum of the components a.sub.1 to a.sub.4 is 100% by weight.
Suitable C.sub.1 -C.sub.8 -alkyl acrylates a.sub.2 are both linear and branched alkyl esters of acrylic acid. The preferred C.sub.1 -C.sub.8 -alkyl acrylates i
REFERENCES:
patent: 3793402 (1974-02-01), Owens
patent: 3808180 (1974-04-01), Owens
patent: 4180529 (1979-12-01), Hofmann
patent: 5286801 (1994-02-01), Besecke et al.
Poegel Josef
Tiefensee Kristin
Zimmer Guenter
BASF - Aktiengesellschaft
Warzel Mark L.
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