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
2000-10-24
2003-10-14
Lipman, Bernard (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S332900, C525S333100, C525S338000, C525S339000
Reexamination Certificate
active
06632890
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to hydrogenated block copolymers. In particular, the invention relates to hydrogenated block copolymers prepared from vinyl aromatic and conjugated diene monomers. Among the most common are those prepared from a vinyl aromatic monomer, such as styrene; and a conjugated diene, such as butadiene or isoprene. Such block copolymers have been hydrogenated to further differentiate the range of physical properties and the oxidative stability. Hydrogenation of the polymerized conjugated diene block can be achieved alone or in combination with hydrogenation of the aromatic ring of the polymerized vinyl aromatic monomer. Depending on hydrogenation conditions and the catalyst employed, it is possible to hydrogenate the conjugated diene polymer portion of the block copolymer without substantially affecting the vinyl aromatic polymer block, or to substantially saturate both block types.
Fully hydrogenated block copolymers prepared from vinyl aromatic and conjugated diene monomers, wherein both blocks are substantially saturated, are well known in the art. U.S. Pat. Nos. 3,333,024 and 3,431,323 disclose hydrogenated triblock (ABA) copolymers of vinyl aromatic and conjugated diene polymers having a 20 to 30 percent hydrogenation level and improved tensile properties, when compared to their non-hydrogenated counterparts. However, such copolymers containing very low molecular weight hydrogenated polystyrene blocks, e.g. 4,000, have low heat resistance and do not afford rigid compositions with good physical properties. U.S. Pat. No. 3,598,886 discloses hydrogenated vinyl substituted aromatic hydrocarbon-conjugated diene block copolymers having less than 3 percent aromatic unsaturation, however the compositions disclosed do not have a good balance of physical properties and processability. Moreover,
Thermoplastic Elastomers
, Chapter 14, Ed. N. R. Legge, et al., Hanser Publishers, New York, 1987 discloses that fully hydrogenated block copolymers have generally poor physical properties at only slightly elevated temperatures.
U.S. Pat. No. 4,911,966 issued to Mitsubishi discloses hydrogenated vinyl aromatic polymers and copolymers and their use in optical media applications. However, the broad composition disclosed suffer from numerous disadvantages including high birefringence, poor processability and poor dimensional stability in such applications.
Therefore, it remains desirable to obtain a hydrogenated block copolymer, wherein the block copolymer is prepared from a vinyl aromatic monomer and a conjugated diene monomer, having improved physical properties and retention of these properties at elevated temperatures.
SUMMARY OF THE INVENTION
In a first aspect, the present invention is a hydrogenated block copolymer comprising 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 characterized by:
a) a total number average molecular weight (Mn
t
) of from 30,000 to 120,000, wherein each hydrogenated vinyl aromatic polymer block (A) has a Mn
a
of from 5,000 to 50,000 and each hydrogenated conjugated diene polymer block (B) has a Mn
b
of from 4,000 to 110,000; and
b) 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 of the first aspect of the present invention having these Mn and hydrogenation characteristics are transparent to light at visible wavelengths and are ideally suited for conventional manufacturing applications, while possessing excellent properties at both standard and elevated temperatures. It has been discovered that hydrogenated copolymers having both the high hydrogenation levels and Mn limitations, as defined by the hydrogenated copolymers of the present invention, have superior properties and processability characteristics, compared to the hydrogenated copolymers of the prior art. The combination of transparency, high glass transition temperature, low water absorption, and excellent melt processability makes these materials ideal candidates for many applications including fabricated articles, thermoformed articles, extruded articles, injection molded articles, films, and foams.
In a second aspect, the present invention is a hydrogenated pentablock copolymer prepared by hydrogenating a pentablock copolymer produced from at least one vinyl aromatic monomer and at least one conjugated diene monomer, wherein the hydrogenated pentablock copolymer has a total number average molecular weight (Mn
t
) of from 30,000 to 200,000 and is of the structure ABABA, and wherein each vinyl aromatic polymer block (A) has a Mn
a
of from 10,000 to 100,000 and is hydrogenated to greater than 90 percent and each conjugated diene polymer block (B) has a Mn
b
of from 2,000 to 50,000 and is hydrogenated to greater than 95 percent.
The hydrogenated pentablock copolymers of the second aspect of the present invention having these Mn and hydrogenation characteristics, have superior properties and processability characteristics when compared to other hydrogenated block and pentablock copolymers. The hydrogenated pentablock copolymers of the present invention also exhibit higher resistance to yield, and improved impact strength. In addition, the pentablocks exhibit lower melt viscosity compared to the conventional hydrogenated diblock and triblock copolymers at identical molecular weights.
The hydrogenated pentablock copolymers of the second aspect of the present invention can be used in various applications including fabricated articles, thermoformed articles, injection molded articles, extruded articles, foams, films and the like.
In a third aspect, the present invention is a hydrogenated pentablock copolymer prepared by hydrogenating a pentablock copolymer produced from at least one vinyl aromatic monomer and at least one conjugated diene monomer, wherein the hydrogenated pentablock copolymer has a total number average molecular weight (Mn
t
) of from 40,000 to 70,000 and is of the structure ABABA, and wherein each vinyl aromatic polymer block (A) has a Mn
a
of from 8,700 to 21,000 and is hydrogenated to greater than 90 percent, and each conjugated diene polymer block (B) has a Mn
b
of from 2,000 to 12,500, further characterized in that the total amount of B blocks is from 10 to 35 weight percent of the copolymer based on the combined weights of all A and B blocks, and is hydrogenated to greater than 95 percent, while block A is hydrogenated to at least 90 percent.
The hydrogenated pentablock copolymers of the third aspect of the present invention having these Mn, block content and hydrogenation characteristics, have superior now abandoned properties and processability characteristics when compared to other block and pentablock copolymers, especially in thin wall injection molding applications such as optical media discs. These hydrogenated pentablock copolymers also exhibit higher resistance to yield, and improved toughness. In addition, these pentablocks exhibit lower melt viscosity compared to the conventional hydrogenated diblock and triblock copolymers at identical molecular weights.
The hydrogenated pentablock copolymers of the third aspect of the present invention are advantageously used in thin wall injection molded applications, such as optical media discs due to their excellent processability, birefringence, dimensional stability and other physical properties.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention relates to hydrogenated block copolymers obtained by hydrogenating a block copolymer produced from at least one vinyl aromatic monomer and at least one conjugated diene monomer.
The vinyl aromatic monomer is typically a monomer of the
Bates Frank S.
Chu Chin
Fredrickson Glenn H.
Hahn Stephen F.
Hahnfeld Jerry L.
Dow Global Technologies Inc.
Lipman Bernard
LandOfFree
Hydrogenated block copolymer compositions does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hydrogenated block copolymer compositions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hydrogenated block copolymer compositions will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3169408