Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1997-01-09
2001-04-24
Short, Patricia A. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S064000, C525S066000, C525S067000, C525S068000
Reexamination Certificate
active
06221962
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention concerns a liquid crystalline blend.
This kind of a blend comprises a polymer matrix and a liquid crystalline polymer. The blend further contains a substance which enhances the compatibility of the polymer matrix and the liquid crystalline polymer.
The invention also relates to a process for preparing liquid crystalline polymer blends and to products which essentially consist of said polymer blends.
DISCUSSION OF THE PRIOR ART
Liquid crystalline polymers are polymers which in melt state lie between the boundaries of solid substances and liquids. The liquid crystalline structure is called a mesomorphic phase or an anisotropic phase because macroscopically in the melt state the liquid crystalline polymers are fluids. Microscopically they have a regular structure similar to that of crystals. The liquid crystalline polymers are called “thermotropic” if their anisotropy depends on the temperature only. 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.
The above-mentioned polymer blends are, however, hampered by the problem that their transversal properties, such as impact strength, are inferior to those of the corresponding unblended plastics. This phenomenon is due to the anisotropic structure and to the poor adhesion between the liquid crystalline polymer phase and the thermoplastic phase.
It is known in the art that the compatibility of liquid crystalline polymers and thermoplastics and that the impact strength of blends thereof can, to some extent, be improved by adding to the blends a third component, i.e. a substance known as a compatibilizer. The task of the compatibilizer is, for instance, to diminish surface tension between the phases, to improve adhesion, and to improve dispersion.
EP Published Patent Application No. 0 369 734 describes a polymer blend which consists of a poly(alkylene terephthalate) matrix, a polyacrylate-based liquid crystalline polymer and a substance which improves the impact strengths of the processed articles at low temperatures. According to the reference, the last-mentioned substance can be comprised of polyethylene, polypropylene, an ethylene-acrylic acid copolymer or a ethylene-propylenediene rubber.
A compatibilized blend of a liquid crystalline polymer and polycarbonate is disclosed in the EP Published Patent Application No. 0 380 112. The compatibilizer used in said reference consists of a polyolefin and/or olefinic copolymers. Among the olefinic copolymers, substances containing styrene monomers may be mentioned.
Common to both of the embodiments described in the references above is that the impact strength improvements of the polymer blends have been rather small.
SUMMARY OF THE INVENTION
The present invention aims at removing the problems relating to the prior art while providing liquid crystalline polymer blends of an entirely novel kind.
Our invention is based on the concept that the substance used for promoting the compatibility of the polymers comprises a polymer containing reactive functional groups. Surprisingly, it has been found that by adding polymers containing reactive groups to blends comprising thermoplastics and liquid crystalline polymers it is possible to provide polymer blends, with tensile and flexural strength properties which are better than the corresponding properties of the polymer matrix, while the impact strength remains at least reasonably good as far as practical applications are concerned. Thus, the impact strengths of the polymer blends according to the invention are at least 20% better than the impact strengths of corresponding uncompatibilized blends.
In particular, the blend according to the invention is mainly characterized by a compatibility promoting substance that consists of a polymer containing reactive functional groups. The tensile strength and flexural strength of the blend are as a result better than the corresponding properties of the matrix polymer. Additionally, the Charpy impact strength of the blend is at least 20% better than that of the corresponding uncompatibilized blend.
The process according to the invention is characterized by melt mixing 95 to 50 parts by weight of a polymer matrix, 5 to 50 parts by weight of a liquid crystalline polymer, and 0.1 to 30% by weight of functional polymer (calculated on the basis of the total amount of the matrix polymer and the liquid crystal and polymer) in order to form a compatibilized polymer blend, whose Charpy impact strength is at least 20% better than that of a corresponding uncompatibilized blend. Additionally the blend can be further subjected to additional processing.
For the purpose of this application the term “reactive compatibilizer containing functional groups” denotes a polymer which at least in principle is capable of reacting with at least one of the components of the blend. In practice it is difficult to determine the exact nature of the interaction between the compatibilizer and the other components of the blend, to ascertain whether a chemical reaction has taken place or not. Therefore, within the scope of the present application, all polymers which contain functional groups capable of reacting with the functional groups of the matrix polymer and/or the liquid crystalline polymer, are considered to be reactive compatibilizers. In blends containing polyolefins, the reactive, functional groups of a polymer working as a compatibilizer react (or interact in some other way) with the functional groups of the liquid crystalline polymer. Generally, the last-mentioned groups are comprised of the free terminal groups of the polymer chain. The polymer chain of the compatibilizer (e.g. its polyolefin residue) interacts,with the polyolefinic matrix without there necessarily being any chemical reaction. In blends containing polyesters, such as poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT), and a liquid crystalline polymer, the compatibilizer may react both with the matrix and with the liquid crystalline polymer because PET, for instance, is not an entire inert polymer.
The functional groups of the compatibilizer comprise, for example, carboxy, anhydride, epoxy, oxazolino, hydroxy, isocyanate, acylacetam and carbodiimide groups.
The polymer residue of the compatibilizer can comprise co- and terpolymers, grafted polyolefins, grafted polystyrene and thermoplastic elastomers. The polar groups of polyolefinic copolymers are generally acrylic esters or functional acrylic acid groups. The polar groups of the terpolymers can be maleic anhydride groups, hydroxyl groups and epoxy groups, of which the last-mentioned are particularly preferred. The styrene block copolymers can consist of polystyrene segments and flexible elastomer segments. Typical styrene block copolymers are SBS (styrene/butadiene/styrene-copolymer), SIS (styrene/isoprene/styrene-copolymer) and SEBS (styrene/ethylene butylene/styrene-copolymer).
The compatibilizer used is selected depending on the other components of the liquid crystalline polymer blend. According to the present invention, particularly preferred compatibilizers are functional polyolefines or olefinic copolymers (including styrene), the functional groups preferably being epoxy, carboxy, amine or hydroxyl groups, in particular epoxy groups and glycidyl methacrylate groups. The portion of functional groups in the polymer is about 0.1 to 30%, preferably 1 to 10%.
“Liquid crystalline polymer blend” means a blend in which at least one thermoplastic has been blended with at least one liquid crys
Heino Markku
Seppala Jukka
Westman Marjut
Cohen & Pontani, Lieberman & Pavane
Neste Oy
Short Patricia A.
LandOfFree
Liquid crystal polymer blends, process for the preparation... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Liquid crystal polymer blends, process for the preparation..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Liquid crystal polymer blends, process for the preparation... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2455508