Vinylcyclohexane-based block copolymers

Details Vinylcyclohexane-based block copolymers Vinylcyclohexane-based block copolymers

2001-05-22

2002-12-10

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...

C525S089000, C525S091000, C525S333300, C526S308000

Reexamination Certificate

active

06492468

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to block copolymers which are predominantly based on vinylcyclohexane and to a process for producing them. The block copolymers can be processed to form mouldings by extrusion or injection moulding. The mouldings which result therefrom are distinguished by their high resistance to thermal deformation, good mechanical properties, high transparency in the visible and near UV range, and by their particularly low birefringence and water absorption.
BACKGROUND OF THE INVENTION
Hydrogenated polystyrene (polyvinylcyclohexane) was described for the first time by Hermann Staudinger in 1929. This material exhibits very low birefringence, very low water absorption and satisfactory resistance to thermal deformation, and is particularly suitable as a substrate material for optical data storage media. U.S. Pat. No. 4,911,966 describes the use of the hydrogenation product of polystyrene as a substrate material for optical disks. Processes which result in hydrogenated polystyrenes of different microstructures, and in which special catalysts are used, are in described in WO 94/21694 and U.S. Pat. No. 5,352,744. Processes are known for the hydrogenation of atactic polystyrene to form atactic hydrogenated polystyrene by the use of special catalysts (EP-A 0 322 731, EP-A 0 423 100, U.S. Pat. No. 5,654,253; U.S. Pat. No. 5,612,422; WO 96/34896).
WO 94/21694 describes a process for the complete hydrogenation of aromatic alkenyl polymers and aromatic polyalkenyl/polydiene block copolymers by heterogeneous catalysis.
Completely hydrogenated block copolymers formed from styrene derivatives and conjugated dienes with a di- and triblock structure are also known. Compared with hydrogenated polystyrene, completely saturated block copolymers of this type on the one hand exhibit improved mechanical properties (increased impact strength and elongation at break), but on the other hand exhibit lower levels of transparency and a lower resistance to thermal deformation.
Partially or completely hydrogenated diblock and triblock copolymers have been described which are based on monomers of styrenes and conjugated dienes (represented by the symbols SB, SI, SBS or SIS, wherein S, B and I represent styrene, butadiene and isoprene, respectively) and which comprise a uniform block component (a “pure block”), and mixed diblock copolymers have been described (represented by the symbols SB
M
and S
1
M) which comprise a soft block which consists of diene and styrene (JP 10 116 442-A, GB 1 156 932, Polymer Preprints (1972), 13(1), 427-432; Advan. Chem. Ser. (1973) No. 129, 27-38).
Compared with polyvinylcyclohexane, the block copolymers which are described there and which have a vinylcyclohexane content of at least 70% exhibit an increased elongation at break, and are described as rigid and transparent. However, the quoted optical transmission data (75-82%) indicate a level of haze which is quite high.
EP-A 505 110 describes blend systems comprising hydrogenated block copolymers of styrene, of a conjugated diene and of hydrogenated polystyrene, wherein the olefinic double bonds are completely hydrogenated and the aromatic bonds are 60-80% hydrogenated, and describes the use thereof as a substrate material for optical disks.
SUMMARY OF THE INVENTION
The present invention relates to a block copolymer which comprises at least three blocks, and which contains at least one hard block and at least one soft block, wherein the hard block contains at least 65, preferably 70, particularly 75, most preferably 80, most particularly 84% by weight of recurring units of general formula (I)
wherein
R
1
and R
2
independently of each other, denote hydrogen or a C
1
-C
6
alkyl, preferably a C
1
-C
4
alkyl,
R
3
represents hydrogen or a C
1
-C
6
alkyl, preferably a C
1
-C
4
alkyl, particularly methyl and/or ethyl, or an alkylene comprising a condensed-on ring, preferably a C
3
or C
4
alkylene (comprising a condensed-on 5- or 6-membered cycloaliphatic ring),
p represents an integer of 0 or 1 to 5, preferably 0 or 1 to 3,
and the soft block contains
99-50% by weight, preferably 95-70% by weight, of recurring units based on a straight chain or branched C
2
-C
14
alkylene, preferably a C
2
-C
8
alkylene, and
1-50% by weight, preferably 5-30% by weight, of recurring units of general formula (I).
DETAILED DESCRIPTION OF THE INVENTION
The recurring units in the soft block can be distributed randomly, alternately or in the form of a gradient.
The proportion of hard blocks (with respect to the total polymer) is generally 65 to 97% by weight, preferably 75 to 95% by weight, and the proportion of soft blocks is 3 to 35% by weight, preferably 5 to 25% by weight.
The recurring units corresponding to formula (I) in the hard and soft blocks can either be identical or different. In turn, a hard block and a soft block can themselves contain different recurring units which correspond to formula (I).
The hard blocks of the block copolymers according to the invention can contain up to 35% by weight at most of other recurring units, which are based on customary olefinic comonomers which are optionally substituted, and which preferably comprise cyclohexadiene, norbornene, dicyclopentadiene, dihydrocyclopentadiene, tetracyclo-dodecene, vinyl esters, vinyl ethers, vinyl acetate, maleic acid derivatives and (meth)acrylic acid derivatives which are optionally substituted by a C
1
-C
4
alkyl.
The block copolymer according to the invention can optionally contain other soft blocks comprising recurring units based on saturated aliphatic hydrocarbon chains which comprise 2 to 10, preferably 2 to 5 carbon atoms and which are optionally substituted by a C
1
-C
4
alkyl group, and isomeric forms thereof.
The block copolymer according to the invention generally has a molecular weight (number average) of 5000-1,000,000, preferably from 50,000-500,000, most preferably 80,000-200,000, as determined by gel permeation chromatography using a polystyrene calibration standard. The (number average) molecular weight of the hard blocks is generally 650-970,000, preferably 6500-480,000, most preferably 10,000-190,000. The molecular weight of the soft blocks is generally 150-350,000, preferably 1500-170,000, most preferably 2400-70,000. The block copolymer can contain hard and soft blocks which each have different molecular weights.
Apart from stereoregular head-to-tail linkages, the linking between the chain components can also comprise a small proportion of head-to-head linkages. The copolymers can be linear or can be branched via branching centres. They can also have a star-shaped structure. Linear block copolymer are preferred within the scope of the present invention.
The block copolymer according to the invention can comprise different block structures, wherein the terminal blocks, independently of each other, can constitute a hard or a soft block. They can be built up as follows, for example:
A
1
−(B
i
−A
i
)
n
;
B
1
−(A
i
−B
i
)
n
;
(A
i
−B
i
)
n
;
wherein
A represents a hard block, B represents a soft block.,
n≧1, and preferably represents 1, 2, 3 or 4, and
i represents an integer between 1 and n (1≦i≦n).
The hard and soft blocks in the block copolymer according to the invention are generally incompatible with each other. This incompatibility results in phase separations on a microscopic scale.
On account of micro-phase separation phenomena, the block copolymer according to the invention exhibits more than one glass transition. The glass transition temperature of the hard phase, which predominantly consists of hard blocks, is at least 100° C., preferably at least 120° C., most preferably at least 140° C., as determined by differential thermal analysis. The glass transition temperature of the soft phase, which predominantly consists of soft blocks, ranges from −120° C. to 60° C., preferably −100° C. to 20° C., most preferably −80° C., to 0° C., as determined by dynamic mechanical analysis (DMA).
The present invention further relates to a process for producing b

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