Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2002-12-02
2004-11-09
Mullis, Jeffrey (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S156000, C524S157000, C524S379000, C524S505000, C525S271000, C525S316000, C525S338000
Reexamination Certificate
active
06815475
ABSTRACT:
This invention relates to compositions of hydrogenated block copolymers.
BACKGROUND OF THE INVENTION
Partially hydrogenated block copolymers of vinyl aromatic and conjugated dienes such as hydrogenated styrene-butadiene-styrene copolymers are well known in the art. U.S. Pat. Nos. 3,333,024; 3,431,323; 3,598,886; 5,352,744; 3,644,588 and EP-505,110 disclose various hydrogenated block copolymers. Partially hydrogenated refers to hydrogenation of the diene portion of the block copolymer without aromatic hydrogenation or aromatic hydrogenation of 90 percent or less. Although these partially hydrogenated copolymers have been tested in various applications, they suffer from one or more shortcomings, including low heat resistance, poor physical properties, poor processability, low heat resistance and poor light stability. Attempts have been made to remedy these shortcomings by increasing the hydrogenation of the aromatic ring of the block copolymer. However, polymer scientists contend that fully hydrogenated styrene-butadiene-styrene copolymers have no useful properties at elevated temperatures, even if only slightly elevated.
Thermoplastic Elastomers
, 2
nd
edition, 1996, page 304, lines 8-12 states “Thus, polystyrene remains the choice for any amorphous hydrocarbon block copolymer. This last fact is clearly demonstrated in the case of the fully hydrogenated VCH-EB-VCH polymer. The interaction parameter is so severely reduced by hydrogenation that at only slightly elevated temperatures, the polymer loses all strength and appears to be homogeneously mixed at ordinary melt temperatures.”
Specifically, hydrogenated diblock copolymers tend to have low viscosities and melt strengths making them difficult to process. Diblocks also have other disadvantages due to their poor tensile properties. For the same reason they are not useful for making flexible materials, while rigid materials made from diblocks tend to be brittle.
Blends of partially hydrogenated block copolymers with other polymers are also known. For example, blends of cyclic olefin (co)polymers have been attempted as disclosed in EP-0726291, wherein cyclic olefin (co)polymers are blended with vinyl aromatic/conjugated diene block copolymers or hydrogenated versions thereof. Cyclic olefin (co)polymers (COC's) are known to have excellent heat distortion temperature, UV stability and processability. However, such copolymers suffer from poor impact resistance. Blends of COC's with partially hydrogenated block copolymers still suffer from an imbalance of physical properties due to the absence of aromatic hydrogenation within the block copolymer.
Therefore, there remains a need for compositions of fully or substantially hydrogenated block copolymers which have adequate viscosity and melt strength to ease processability, can be used in elastomeric applications and have a desirable balance of physical properties.
Additionally, uses for clear, substantially or fully hydrogenated hydrogenated block copolymers of vinyl aromatic and conjugated diene monomers, and polymer blends thereof, are still desired, wherein the copolymers are processable by conventional manufacturing technologies and possess useful physical properties at standard and elevated temperatures.
SUMMARY OF THE INVENTION
One aspect of the present invention is directed to compositions comprising fully or substantially hydrogenated block copolymers and various end-use applications thereof. The hydrogenated block copolymer is a rigid hydrogenated block copolymer, which comprises at least two distinct blocks of hydrogenated polymerized vinyl aromatic monomer, herein referred to as hydrogenated vinyl aromatic polymer blocks, and at least one block of hydrogenated polymerized conjugated diene monomer, herein referred to as hydrogenated conjugated diene polymer block, wherein the hydrogenated copolymer is further characterized by:
a) a weight ratio of hydrogenated conjugated diene polymer block to hydrogenated vinyl aromatic polymer block of 40:60 or less;
b) a total number average molecular weight (Mn
t
) of from 30,000 to 150,000, wherein each hydrogenated vinyl aromatic polymer block (A) has a Mn
a
of from 6,000 to 60,000 and each hydrogenated conjugated diene polymer block (B) has a Mn
b
of from 3,000 to 30,000; and
c) a hydrogenation level such that each hydrogenated vinyl aromatic polymer block has a hydrogenation level of greater than 90 percent and each hydrogenated conjugated diene polymer block has a hydrogenation level of greater than 95 percent.
Hydrogenated block copolymers having these Mn and hydrogenation characteristics are transparent to light at visible wavelengths and are ideally suited for various applications, while possessing excellent properties at both standard and elevated temperatures. The combination of transparency, high glass transition temperature, low water absorption, good strength, toughness, weatherability and excellent melt processability makes these materials and blends thereof, ideal candidates for many applications including fabricated articles, thermoformed articles, extruded articles, injection molded articles, films and the like.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
One aspect of the present invention is directed to applications for rigid hydrogenated block copolymers and end-use applications thereof. Hydrogenated block copolymers are prepared by hydrogenating a block copolymer produced from a vinyl aromatic monomer and a conjugated diene monomer.
The vinyl aromatic monomer is typically a monomer of the formula
wherein R′ is hydrogen or alkyl, Ar is phenyl, halophenyl, alkylphenyl, alkylhalophenyl, naphthyl, pyridinyl, or anthracenyl, wherein any alkyl group contains 1 to 6 carbon atoms which may be mono or multisubstituted with functional groups such as halo, nitro, amino, hydroxy, cyano, carbonyl and carboxyl. More preferably Ar is phenyl or alkyl phenyl with phenyl being most preferred. Typical vinyl aromatic monomers include styrene, alpha-methylstyrene, all isomers of vinyl toluene, especially paravinyltoluene, all isomers of ethyl styrene, propyl styrene, butyl styrene, vinyl biphenyl, vinyl naphthalene, vinyl anthracene and the like, and mixtures thereof. The block copolymer can contain more than one specific polymerized vinyl aromatic monomer. In other words, the block copolymer can contain a polystyrene block and a poly-alpha-methylstyrene block. The hydrogenated vinyl aromatic polymer block can also be a copolymer wherein the hydrogenated vinyl aromatic component is at least 50 weight percent of the copolymer.
The conjugated diene monomer can be any monomer having 2 conjugated double bonds. Such monomers include for example 1,3-butadiene, 2-methyl-1,3-butadiene, 2-methyl-1,3 pentadiene, isoprene and similar compounds, and mixtures thereof. The block copolymer can contain more than one specific polymerized conjugated diene monomer. In other words, the block copolymer can contain a polybutadiene block and a polyisoprene block.
The conjugated diene polymer block can be prepared from materials which remain amorphous after the hydrogenation process, or materials which are capable of crystallization after hydrogenation. Hydrogenated polyisoprene blocks remain amorphous, while hydrogenated polybutadiene blocks can be either amorphous or crystallizable depending upon their structure. Polybutadiene can contain either a 1,2 configuration, which hydrogenates to give the equivalent of a 1-butene repeat unit, or a 1,4-configuration, which hydrogenates to give the equivalent of an ethylene repeat unit. Polybutadiene blocks having at least approximately 40 weight percent 1,2-butadiene content, based on the weight of the polybutadiene block, provides substantially amorphous blocks with low glass transition temperatures upon hydrogenation. Polybutadiene blocks having less than approximately 40 weight percent 1,2-butadiene content, based on the weight of the polybutadiene block, provide crystalline blocks upon hydrogenation. Depending on the final application of the polymer it may be desirable to incorporate a crystalline
Donald Robert J.
Esneault Calvin P.
Hahn Stephen F.
Hahnfeld Jerry L.
Parsons Gary D.
Dow Global Technologies Inc.
Mullis Jeffrey
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