Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Utility Patent
1999-03-22
2001-01-02
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S207000, C525S240000, C525S066000, C525S098000
Utility Patent
active
06169147
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a specific block copolymer and to a polymer composition comprising a continuous phase formed by at least a first polymer and a second phase dispersed therein of at least a second polymer, which second polymer is not compatible with the first polymer, in which polymer composition the specific block copolymer is included.
Besides, the invention relates to the use of the specific block copolymer as impact modifier in polymer composition.
The invention further relates to specific triblock copolymers.
Mixtures of polymers can in principle give a wide variety of mechanical properties by adjusting the type and the amount of polymers in mixtures. In particular, mixtures are prepared for the purpose of modifying the impact strength, in particular at lower temperatures, the dimensional stability and/or the processability.
Besides, when reprocessing polymers, mixtures of different polymers are often obtained. In fact, a waste fraction will seldom consist 100% of the same polymer.
However, most polymers show no proper miscibility with other polymers, so that no homogeneous product is formed, but a polymer product with many (macroscopic) domains formed by the individual polymers. Such products have no good mechanical properties, in particular not as regards ductility.
2. Description of the Related Art
In the prior art a lot of research has been done on block copolymers that can be used as compatibilizing agent for mixtures of polymers, in particular of homopolymers, which per se do not mix together; and as modifier for specific mechanical properties of polymers. Compatibilizing agents reduce the interfacial tension between the immiscible components, so that the polymer mixture can form a dispersion with much smaller domains. These dispersions often show improved ductility.
In spite of the large number of research studies from the prior art it is still not completely clear which criteria a block copolymer must satisfy so as to act as an effective compatibilizing agent. Besides simple diblock copolymers which, on the basis of theoretical predictions, should have the most effective compatibilizing activity, different more complex copolymers have been proposed. Thus, in the prior art random copolymers, graft copolymers, tapered diblock copolymers and low molecular triblock copolymers are proposed the effectiveness of which is higher than that of the simple diblock copolymers.
An attractive manner of compatibilizing is the forming in situ of block copolymers or graft copolymers via interfacial reactions with functionalized polymers during mixing in the melt, e.g. by melt kneading, of polymers. This so-called reactive compatibilization has been discussed in different places in the prior art, e.g. by Wu in Polymer 26 (1985) 1855; by Armat et al in Polymer 34 (1993) 977, and by Yeh et al., Polym. Bull. 35 (1995) 371.
SUMMARY THE INVENTION
The present invention substantially relates to polymer mixtures based on polyamides, in particular nylons. These synthetic materials form an attractive class of polymers for engineering uses. However, they possess a number of disadvantageous properties. Thus, this material is rather brittle, readily absorbs much moisture, and is dimensionally hardly stable. To improve these properties, polyamides are mixed with other polymers, e.g. with polyphenyleneoxide (PPO), acrylonitrile/butadiene/styrene copolymers (ABS), polyalkenes, polycarbonate and rubbers. The improvement of the above properties often involves a loss of mechanical properties, so that measures for compatibilization are required.
According to the invention a class of block copolymers has now been found which are eminently suited for compatibilizing synthetic mixtures on the basis of polyamides and for modifying polyamide compositions. These block copolymers comprise at least one polyalkadiene block and at least one (aromatic vinyl compound-co-maleic anhydride) block.
More in particular, the invention relates to a block copolymer comprising at least one polyalkadiene block and at least one random (aromatic vinyl compound-co-maleic anhydride) block.
Block copolymers of, e.g., polybutadiene (PB) and polystyrene (PS) are used for compatibilizing, inter alia, polyethylene/polystyrene and polypropylene/polystyrene mixtures. These block copolymers are usually prepared by anionic techniques. Anionic techniques have a number of evident disadvantages. They require strict polymerization conditions, e.g. very pure monomers, an absolute moisture- and oxygen-free atmosphere and cryogenic temperatures. These conditions are hard to realize on an industrial scale.
Moreover, no random copolymers can be obtained by using anionic techniques.
European patent application 0 418 118 describes copolymers prepared by using iniferters.
In an article in Polym. J. 17 (1985) 97, Otsu and Kuriyama describe a process in which random and alternating copolymer sequences could be prepared by using the iniferter technique.
REFERENCES:
patent: 5278231 (1994-01-01), Chundury
patent: 5321081 (1994-06-01), Chundury
Hadziioannou Georges
Kroeze Erik
ten Brinke Gerrit
Asinovsky Olga
Norris McLaughlin & Marcus P.A.
Rijksuniversiteit te Groningen
Seidleck James J.
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