Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1995-04-28
1997-10-14
Zemel, Irina S.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525174, 525184, 525432, 525445, 525436, 528170, 528184, 528193, C08L 7908, C08G 7316
Patent
active
056773943
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to block copolymers and to a method for manufacturing them.
Liquid crystalline polymers are polymers which in melt state exhibit optical anisotropy. The strength and stiffness of many thermoplastics can be substantially improved by blending them with thermotropic, main-chain liquid crystalline polymers. This is because the liquid crystalline polymers form fibres which orientate in the flow direction of the thermoplastic matrix melt. As a result there is an improvement of the mechanical properties, such as tensile strength and modulus of elasticity, of the thermoplastic in this direction. Often, the addition of the liquid crystalline polymer also improves the heat resistance and dimensional stability of the thermoplastics and makes it easier to process them. Liquid-crystal polymers are, for the above reasons, being investigated widely.
The actual liquid crystal in liquid crystalline polymers is formed by a rigid structural unit called a mesogen. Mesogens are generally formed by two or more linearly substituted ring units linked to each other via a short, rigid bridging group known as a spacer. As examples of mesogenic structural units, the polyester groups formed by hydroxy benzoic acid, terephthalic acid and hydroquinone should be mentioned. Liquid-crystal polymers can be divided into two main categories, viz, main-chain and side-chain liquid-crystal polymers, depending on whether the mesogenic groups are located in the main chain or in the side chain. Main-chain liquid crystalline polymers are generally polymers of highly rigid character whose stable crystalline structure can only be melted by using abundant energy. Therefore, their melting occurs at high temperatures, whereby thermal decomposition is simultaneously involved.
As far as liquid crystalline polymers and their properties are concerned, reference is made to the review article by Chung et al. in Handbook of Polymer Science and Technology, 2 (1989) pp. 625 to 675.
Block polyesterimides with liquid crystalline properties are known in the art. Said polymers have been described in, for instance, U.S. Pat. Nos. 4,727,129, 4,728,713 and 4,728,714. The prior art aromatic compounds have, according to the patent specifications, good strength and heat and wear resistance. At temperatures below 320.degree. C. the polymers provide melts which form liquid crystalline fibers. The prior an compounds do not, however, have the properties needed for thermoplastic elastomer applications, such as good flexibility at low temperatures and thermal and hydrolytical stability.
It is an object of the present invention to solve the problems relating to the prior an and to provide an entirely novel kind of a liquid crystalline polyesterimide, which can be used as a thermoplastic elastomer component in polymer compounds.
According to the present invention, there is provided a novel (A-B).sub.t -type block copolymer wherein t is an integer, typically about 3 to 100, the second block (B) being formed by a rigid aromatic polyester segment. According to the invention, block A comprises a flexible trimellitimide terminated polyether or a polysiloxane. The structure of block A is typically ##STR4## wherein R stands for a polyether or polysiloxane.
In more detail, the liquid crystalline polymer according to the invention is mainly characterized by what is stated in the characterizing part of claim 1.
The method according to the invention is, again, characterized by what is stated in the characterizing part of claim 10.
The compounds according to the invention are characterized by what is stated in the characterizing part of claim 14.
To complete the survey of the prior art, it should be mentioned that block copolymers containing polyether, in particular poly(tetrahydrofuran) are known per se. Reference is made to the article by Wang and Lenz in Polymer known polymer is ##STR5## and it does not contain a polyesterimide structure according to the present invention. Its properties are also different from those of the present polymers.
High molecular wei
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Alanko Heli
Bergstrom Christer
Bohme Frank
Harkonen Mika
Passiniemi Pentti
Neste Oy
Zemel Irina S.
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