Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-09-22
2001-05-08
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S291000
Reexamination Certificate
active
06228916
ABSTRACT:
TECHNICAL FIELD
This invention relates to a conjugated diene polymer composition which is suitable as a rubber for the modification of a styrene resin and has an excellent stability and a good color tone and to a rubber-reinforced styrene resin in which the above polymer composition is used and which has an improved color tone and impact strength.
BACKGROUND ART
Conjugated diene polymers have heretofore been broadly used for the modification of resins and in various industrial articles. However, the conjugated diene polymers cause the generation of a gel and discoloration during a long term storage at a high temperature or under a thermal shear stability, so that particularly when it is used for the modification of a resin, the presence of a gel in the polymer and the discoloration of the polymer adversely affects final resin products. Therefore, there has been earnestly desired the appearance of a conjugated diene polymer composition which is excellent in heat stability at a high temperature and shear heat stability and very small in the generation of a gel and discoloration. For these problems, phenol type stabilizers, phosphorus type stabilizers and the like have heretofore been used as stabilizers for preventing gelation.
As a technique concerning a composition of a conjugated diene polymer having an excellent stability and a good color tone, there is a method in which a low molecular weight monophenol type antioxidant is combined with a high molecular weight monophenol type antioxidant and a specific organic carboxylic acid is added (JP-A-3-31,334). There is also a method in which a coupling rubber or a monoalkenyl aromatic compound-conjugated diene block copolymer is combined with a specific phenol type stabilizer or phosphorus type stabilizer (JP-A-4-252,243 and JP-A-4-246,454).
However, these techniques require the use of a large amount of an antioxidant and are not satisfactory in respect of resistance to discoloration. An object of this invention is to solve these problems and provide a rubber-like conjugated diene polymer composition which is suitable as a toughening agent for a styrene resin and excellent in both stability and color tone. In addition, in the prior art, it has been impossible to obtain a styrene resin having an excellent color tone and an excellent impact strength. Accordingly, another object of this invention is to provide a rubber-reinforced styrene resin having an excellent color tone and an excellent impact strength.
DISCLOSURE OF THE INVENTION
The present inventors have made an examination for solving the above-mentioned problems and have consequently found that a conjugated diene polymer composition which is excellent in heat stability, color tone and resistance to discoloration is obtained by using a non-coupling diene polymer in combination with a specific sulfur-containing phenol type antioxidant and a specific phenol type antioxidant each in a specific amount range, and further found that a styrene resin having excellent characteristics is obtained when said composition is used as a toughening agent for a styrene resin, whereby this invention has been made.
That is to say, this invention relates to a conjugated diene polymer composition which is excellent in heat stability, color tone and resistance to discoloration and which comprises:
(a) 100 parts by weight of a non-coupling conjugated diene polymer consisting of at least one conjugated diene or a non-coupling random copolymer consisting of a conjugated diene and at least one monovinyl aromatic compound,
(b) 0.03 to 0.2 part by weight of a sulfur-containing phenol type antioxidant represented by the following general formula (I):
wherein R
1
and R
3
are —CH
2
—S—R
5
in which each R
5
represents independently an alkyl group having 2 to 18 carbon atoms; R
2
represents hydrogen or a methyl group; and R
4
represents an alkyl group having 1 to 8 carbon atoms, and
(c) 0.03 to 0.2 part by weight of a phenol type antioxidant represented by the following general formula (II):
wherein R
6
represents a tert-butyl group; and R
7
represents an alkyl group having 2 to 22 carbon atoms.
BEST MODE FOR CARRYING OUT THE INVENTION
In this invention, the conjugated diene polymer used as the component (a) is a non-coupling conjugated diene polymer consisting of at least one conjugated diene or a non-coupling random copolymer consisting of a conjugated diene and at least one monovinyl aromatic compound and can be obtained by a known method. For example, the conjugated diene polymer is obtained by polymerizing a conjugated diene or copolymerizing a conjugated diene with a monovinyl aromatic hydrocarbon by an anionic polymerization method using an organolithium compound in an inert hydrocarbon solvent such as n-hexane, cyclohexane or the like using n-butyllithium, sec-butyllithium or the like as an initiator. Moreover, in the production of the conjugated diene polymer, it is possible to use a Ziegler catalyst consisting of an organic compound of nickel, cobalt or the like and an organometallic component of aluminum, magnesium or the like.
The conjugated diene used in this invention is a diolefin having a pair of conjugated double bonds and there are mentioned, for example, 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene and the like. As particularly general ones, there are mentioned 1,3-butadiene and isoprene. These can be used alone or in admixture of two or more.
As the monovinyl aromatic compound used in this invention, there are mentioned styrene, o-methylstyrene, p-methylstyrene, 1,3-dimethylstyrene, &agr;-methylstyrene and the like, and as particularly general ones, there are mentioned styrene, p-methylstyrene and &agr;-methylstyrene. These can be used alone or in admixture of two or more.
The weight average molecular weight of the diene polymer used in this invention is generally 10,000 to 2,000,000, preferably 50,000 to 1,000,000, and it is essential that the polymer structure be a non-coupling conjugated diene polymer or a non-coupling random copolymer. Here, the non-coupling polymer means a polymer which has not been subjected to a process of coupling reaction in which a polyfunctional coupling agent, for example, a compound such as silicon tetrachloride, tin tetrachloride or divinylbenzene, is used. A polymer having a coupling structure is not desirable with respect to color tone. In addition, a polymer having a coupling structure and a copolymer having a block structure are not desirable because when they are used as a toughening agent for a styrene resin, only a resin inferior in color tone and impact strength is obtained.
The conjugated diene portion of the diene polymer used in this invention has a microstructure in which the vinyl bond content is preferably less than 33% though it is As not particularly limited. Here, the vinyl bond content means the proportion of the conjugated diene compounds incorporated in the bonding manner of a 1,2-bond and 3,4-bond into the diene polymer based on those incorporated in the bonding manner of 1,2-bond, 3,4-bond and 1,4-bond thereinto.
When the heat stability of the diene polymer composition itself is maintained high and simultaneously the diene polymer composition is used as a toughening agent for a styrene resin, the vinyl bond content is preferably not more than 30 mole % in order to maintain a high impact strength. Moreover, when it is used as a toughening agent for a styrene resin, the vinyl bond content is preferably not less than 10 mole % in order to maintain the impact strength high. Accordingly, the vinyl bond content is more preferably 10 to 30 mole %, and particularly preferably 10 to 25 mole %.
In the case of the random copolymer, the amount of the monovinyl aromatic compound bound is not more than 65% by weight, preferably not more than 50% by weight. The bonds of the monovinyl aromatic compound are incorporated basically at random into the conjugated diene and at least 50% by weight of the monovinyl aromatic compound is incorporated at random.
In this invention, in the sulfu
Iihara Tomohiro
Sasagawa Masahiro
Sato Masao
Asahi Kasei Kogyo Kabushiki Kaisha
Birch & Stewart Kolasch & Birch, LLP
Rajguru U. K.
Seidleck James J.
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