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
1999-03-22
2001-08-07
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...
C525S238000, C525S239000, C525S240000, C525S294000, C524S504000, C524S505000
Reexamination Certificate
active
06271308
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to block copolymers comprising at least one polyalkadiene block and at least one (aromatic vinyl-co-acrylonitrile) block, and the use thereof as additive for polymers.
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, particularly at lower temperatures, the dimensional stability and the processability.
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.
Moreover, mixtures of different polymer fractions often occur when reprocessing polymers. In fact, a waste fraction will seldom consist 100% of the same polymer. To yet obtain a product having stable mechanical properties, a homogeneous polymer product must also be realized.
Thus, mixtures of polyethylene, e.g. low density PE, and polyvinyl chloride are inherently brittle. These mixtures are interesting both from the viewpoint of modifying the (mechanical) properties of PVC and for considerations of recycling.
2. Description of the Related Art
In the prior art a lot of research has been done on block copolymers to be used as compatibilizing agent for mixtures of polymers, in particular 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 have improved ductility.
In spite of the large number of research studies from the prior art, it is still not completely clear which criteria a 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 have been proposed which have an effectiveness higher than that of the simple diblock copolymers.
For the above-mentioned example of polyethylene and polyvinyl chloride, inter alia graft copolymers of PVC or polymethyl methacrylate grafts on polyethylene polymers have been proposed. Thus, an article by Boutevin et al. in Polymer Bulletin 14 (1985) 25-30 describes that the mechanical properties of a PE/PVC mixture can be optimized by adding at least 5 wt. % of a graft copolymer of polyethylene with methyl methacrylate. Besides, the optimization in properties is qualitatively and quantitatively hardly spectacular.
An article by Hajian et al. in Eur. Polym. J. 20 (1984), 135-138 describes the effect of specific copolymers on mixtures of PE and PVC and of PE and polystyrene. Acceptable results are only obtained if the copolymers are used in amounts above 10%.
Block copolymers of, e.g., polybutadiene (PB) and polystyrene (PS) are used to compatibilize, 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.
By the term “iniferter” are designated specific free radical initiators which simultaneously also function as chain transfer agent and as polymer radical terminator.
SUMMARY OF THE INVENTION
According to the present invention it has now been found that specific block copolymers of polyalkadiene which may or may not be hydrogenated and poly(aromatic vinyl-co-acrylonitrile) form very effective compatibilizers, in particular for mixtures of polyolefins or polyalkadienes, on the one hand, with polystyrene acrylonitrile (SAN) and with homopolymers with which the poly(aromatic vinyl-co-acrylonitrile) properly mixes, such as poly(methyl methacrylates), polycarbonates, polyvinyl chloride and poly (&egr;-caprolactam), on the other hand.
These specific block copolymers are copolymers comprising at least one blok of a polyalkadiene and at least one block of random poly(aromatic vinyl-co-acrylonitrile). The compatibilizing properties of these block copolymers are substantially better than those of known copolymers, such as copolymers in which random copolymer blocks are grafted on a polymer chain. In the case of using known compatibilizing agents in amounts of 5-10 wt. % and more, based on the complete composition comprising at least two non-compatible polymers, an amount of about 1 wt. % is sufficient when using the copolymers according to the present invention.
More in particular, the invention relates to a polymer composition comprising a first polymer and a second polymer, which second polymer is not compatible with the first polymer, and an amount of a copolymer comprising at least one block of a polyalkadiene and at least one block of random poly(aromatic vinyl-acrylonitrile), the ratio of the block copolymer to the second polymer ranging between 1:50 and 1:5. In a preferred embodiment the first polymer forms a continuous phase in which the second polymer is dispersed. However, blends, such as 50/50 blends, are also possible.
Any random copolymer block, also referred to in this specification as SAN block, which is present in the block copolymer used according to the present invention, is build up from at least acrylonitrile units and units of an aromatic vinyl compound.
The aromatic vinyl compound to be used can be represented by formula I,
in which R
1-3
may be independently selected from a hydrogen atom, a C
1-4
alkyl group or a C
1-4
alkyl group substituted with an inert group; and in which R
4-8
may independently represent a hydrogen atom, a halogen atom, a C
1-4
alkyl group or a C
1-4
alkyl group substituted with an inert group.
Preferably, however, the aromatic vinyl compound is styrene.
The above random copolymers, which can be used according to the present invention, are miscible with polymers, with which also known block copolymers of acrylonitrile and aromatic vinyl are miscible, such as, e.g., with poly(methyl methacrylate), polycarbonate, polyvinyl chloride, poly(&egr;-caprolactone), and with those known poly(aromatic vinyl-acrylonitrile) block copolymers, such as styrene-co-acrylonitrile copolymers. In the preferred polymer composition according to the invention these polymers can form both the first polymer phase and the second polymer phase.
If required, the degree of miscibility can be adapted to the ratio of acrylonitrile/arornatic vinyl compound in the SAN blocks.
In a preferred embodiment the polymer composition according to the invention comprises a copolymer in which the polyalkadiene blocks present are based on polybutadiene which may or may not be hydrogenated. However, good results are also obtained by using other polyalkadienes, such as polymers of isoprene, pentadienes which may or may not be conjugated, hexadienes which may or may not be conjugated, etc.
These polyalkadiene blocks properly mix with all polymers with which the corresponding homopolymers of the alkadiene monomers also properly mix, in particular with polyalkenes. However, depending on the purpose of adding the copolymer according to the invention, the po
de Boer Bert
Hadziioannou Georges
Kroeze Erik
ten Brinke Gerrit
Asinovsky Olga
Norris McLaughlin & Marcus P.A.
Rijksuniversiteit te Groningen
Seidleck James J.
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