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
1997-11-03
2001-02-06
Yoon, Tae (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S065000, C525S074000, C525S098000, C524S505000
Reexamination Certificate
active
06184289
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a rubber-modified styrene resin composition having an excellent appearance and impact resistance. More particularly, the present invention relates to a rubber-modified styrene resin composition which can provide a molding having a good balance between surface gloss and impact resistance.
The present invention relates to a styrene resin composition and a molding thereof having good toughness and excellent adhesion, transparency, and moldability.
PRIOR ART
Impact-resistant styrene resins are prepared by polymerizing a styrene monomer in the presence of a rubber polymer. By virtue of their excellent strength, moldability and other properties, they are extensively used as molding materials for the housing of domestic electric appliances, such as televisions, office automation equipment, packaging materials, miscellaneous goods (or sundries) and the like.
In recent years, expansion of the field of demand for the above products and, at the same time, an increasing demand for cost reduction and a trend toward a reduction in thickness have lead to a demand for improved properties, particularly, an improvement in balance between impact resistance and surface gloss.
In general, the impact resistance of the resin prepared by the above polymerization method can be improved by either increasing the amount of the rubber polymer or increasing the average particle size of the dispersed particles. Both the above methods, however, cause deteriorated surface gloss. On the other hand, the surface gloss can be improved by either reducing the amount of the rubber polymer or reducing the average particle size of the dispersed particles. Both of the above methods, however, cause remarkably lowered impact resistance.
Thus, the impact resistance and the surface gloss are mutually conflicting properties, making it difficult to obtain an impact-resistant styrene resin possessing a high impact resistance and, at the same time, an excellent surface gloss.
In order to improve the properties of these impact-resistant styrene resins, JP-B 61-50488 and JP-A 59-20334 and JP-A 60-203618 propose a method for limiting the properties of the rubber polymer used, such as the solution viscosity, microstructure, and branch structure. Further, JP-A 62-178458 and JP-A 4-100810 and the like propose the use of a rubber polymer comprising a high-molecular weight polybutadiene rubber and a low-molecular weight polybutadiene rubber. As a result of careful review of these studies, it was found that, although an improvement over the conventional methods is certainly recognized, the balance between surface gloss and impact resistance is not yet satisfactory from the practical viewpoint.
On the other hand, JP-B 42-17492, JP-B 48-18594, and JP-B 1-33485, JP-A 63-78317 and JP-A 63-165413 propose a method wherein a styrene/butadiene block copolymer rubber having a high affinity for an aromatic vinyl resin is singly used as the rubber polymer, and JP-A 4-88006 proposes the use of a blend of a styrene/butadiene block copolymer rubber having a higher molecular weight with a styrene/butadiene block copolymer rubber having a lower molecular weight as the rubber polymer. According to these methods, the resultant resin has, in many cases, a lowered impact resistance although it has an improved gloss.
JP-A 62-280211 and JP-A 4-209614 propose the use of a blend of a styrene/butadiene copolymer with a polybutadiene rubber as the rubber polymer. However, the proportion of polybutadiene rubber is so low that the impact resistance is not satisfactory.
JP-A 2-178312 and JP-A 3-28210 and the like propose the provision of a particle disperser, such as a line mixer, in a production line to prepare a styrene resin possessing excellent gloss and, at the same time, high impact resistance. This proposal, however, has a critical drawback in that a great deal of investment is required due to the necessity of a change in specifications of a plant or the like.
JP-B 5-25897 and JP-B 4-63099 propose an impact-resistant polystyrene resin composition comprising a blend of a rubber-modified polystyrene with a styrene/butadiene block copolymer. The rubber-modified polystyrene has a problem in that the rubber-modified polystyrene should be prepared by separately preparing a rubber-modified polystyrene containing a smaller-size particle rubber polymer fraction and a rubber-modified polystyrene containing a larger-size particle rubber polymer fraction and blending by means of an extruder, or by blending a rubber-modified polystyrene containing a smaller-size particle rubber polymer with a rubber-modified polystyrene containing a larger-size particle rubber polymer in a polymerizer.
A modified polystyrene containing a rubber component, such as a styrene-butadiene block copolymer, is widely used for injection molding, such as a housing of electrical apparatus, a stationery product and a toy. Unstretched or unoriented, uniaxially stretched or oriented, or biaxially stretched or oriented styrene resin films, sheets, or tubes composed mainly of a modified polystyrene containing a rubber component, such as a styrene-butadiene block copolymer, have good transparency and impact resistance and, hence, have hitherto been widely used as materials for food packaging vessels and heat shrinkable films. The modified polystyrene resin itself, however, has poor adhesion to other materials, for example, polyamides, polyesters, iron, stainless steel, and aluminum, making it necessary to use an adhesive to improve the adhesion. Further, in the case of a composition having a high rubber content, although the impact resistance can be improved, problems associated with the transparency and the toughness of the film during molding are often increased. Lowering the rubber content can improve the transparency. In this case, however, the composition is fragile and, hence, has a deteriorated moldability into a vessel.
In order to meet the demand in the market for a balance between impact resistance and surface gloss in the styrene resin mentioned above, it is necessary to provide a resin composition which is easily produced while still maintaining excellent properties. Accordingly, an object of the present invention is to provide a rubber-modified styrene resin composition having a good balance between impact resistance and surface gloss.
An object of the present invention is to provide a production process which can produce on an industrial scale a molding of a styrene resin composition having improved adhesion, transparency, and moldability while maintaining the excellent rigidity and transparency inherent in the styrene resin, and a vessel using the film, sheet, or tube.
SUMMARY OF THE INVENTION
The present inventors have made extensive and intensive studies with a view to developing the above rubber-modified styrene resin composition and, as a result, has found that the use of a rubber polymer comprising a blend of an epoxidized block copolymer of styrene with a conjugated diene (hereinafter referred to an “epoxy-modified block copolymer”) and a polybutadiene rubber in a particular proportion results in the formation of a rubber-modified styrene resin composition having a high impact resistance and high surface gloss.
The present invention have solved the above problems and provides an injection molding and an extrusion molding possessing improved adhesion, transparency, and moldability by using a styrene resin composition comprising:
(A) an epoxidized block copolymer of a styrene monomer with a conjugated diene compound,
(B) a non-modified synthetic rubber and
(C) a styrene polymer.
The invention provides a styrene resin composition comprising (A) an epoxidized block copolymer of a styrene monomer with a conjugated diene compound, (B) a non-modified synthetic rubber and (C) a styrene polymer and a molded article thereof.
A first preferable embodiment of the invention is a composition comprises a matrix of (C) and a particulate rubber polymer dispersed in the matrix, said rubber polymer comprising (A) and (B).
The invention prov
Ichikawa Haruo
Teranishi Tadashi
Daicel Chemical Industries Ltd.
Flynn ,Thiel, Boutell & Tanis, P.C.
Yoon Tae
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