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
2001-06-05
2003-10-21
Nutter, Nathan M. (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...
C525S222000, C525S232000, C525S238000, C525S240000, C525S241000
Reexamination Certificate
active
06635712
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a molding material comprising a dry blend of a styrenic resin, a process for producing moldings using the molding material and the moldings produced thereby. More particularly, it is concerned with a molding material comprising a dry blend of a styrenic polymer having an atactic configuration and a styrenic polymer having a mainly syndiotactic configuration and specific physical properties; a process for producing moldings using the molding material; and the moldings produced thereby.
BACKGROUND ART
A styrenic polymer which has an atactic configuration hereinafter sometimes referred to as “atactic polystyrene”) and which is produced by radical polymerization has heretofore been used for a variety of applications because of its availability at a low cost. However, the aforesaid atactic polystyrene, which is non-crystalline because of its atactic configuration in stereostructure, is not necessarily satisfactory in regard to solvent resistance, thus restricting its applicable field as a molding material. A resin composition of the atactic polystyrene and a polyphenylene ether blended therewith is known, but likewise it is not necessarily satisfactory in regard to solvent resistance.
In order to improve the solvent resistance, there has been adopted a method in which styrene is copolymerized with a polar monomer such as acrylonitrile, methacrylates, acrylates, maleic anhydride and maleimides. However, the copolymer thus obtained has involved such problems as random copolymerization ratio being limited, low productivity, unfavorable color tone, malodor and difficulty in recycling by mixing with an other styrenic resin.
It being so, as an alternative for non-crystalline atactic polystyrene, crystalline syndiotactic polystyrene was developed, and further, there are proposed resin compositions each comprising the syndiotactic polystyrene and other resin blended there with so as to improve heat resistance thereof {Japanese Patent Application Laid-Open Nos.104818/1987(Showa-62), 257948/1987 (Showa-62), 257950/1987(Showa-62), 182344/1989(Heisei-1), etc.}.
Nevertheless, the problems still remain unsolved in that in the case of producing a styrenic resin composition by blending the atactic polystyrene with the syndiotactic polystyrene, it is necessary to carry out melt kneading prior to the production of the composition by molding in order to sufficiently manifest such physical properties as solvent resistance and mechanical strength, and carry out molding working of the composition at a temperature higher than a molding working temperature of a conventional atactic polystyrene, thereby deteriorating the molding cycle and causing sinks at thick-walled portions.
DISCLOSURE OF THE INVENTION
In such circumstances; an object of the present invention is to provide a molding material which is capable of affording moldings that are excellent in solvent resistance and mechanical strength in the case of molding a styrenic polymer, even if molding working is carried out at a molding working temperature of a conventional atactic polystyrene, dispensing with a melt kneading step; a process of producing the moldings which use the aforesaid the molding material, and in which the molding cycle is shortened and the production cost is curtailed.
As a result of investigation accumulated by the present inventors in order to solve the foregoing problems involved in the prior arts, it has been found that it is made possible to obtain moldings excellent in various physical properties such as solvent resistance and mechanical strength, even if molding is carried out at a molding working temperature of a conventional atactic polystyrene, dispensing with a melt kneading step, by blending an atactic polystyrene with a syndiotactic polystyrene endowed with specific physical properties. The present invention has been accomplished by the aforesaid findings and information.
That is to say, the present invention is summarized as follows.
{1} A molding material which comprises a dry blend of 10 to 95% by weight of a (A) styrenic polymer having atactic configuration and 2 to 90% by weight of a (B) styrenic polymer which has a melting point of 250° C. or lower, a weight average molecular weight of at most 200,000 and mainly syndiotactic configuration.
{2} The molding material as defined in item {1} in which the styrenic polymer having mainly syndiotactic configuration as the component (B) has a melting point of 245° C. or lower, and is blended in an amount of 5 to 90% by weight.
{3} The molding material as defined in item {1} in which the styrenic polymer having mainly syndiotactic configuration as the component (B) has an initial relative crystallinity as measured with a differential scanning calorimeter being at most 60%.
{4} A process for producing a molding which comprises molding the molding material as defined in any of items {1} to {3} at a a resin temperature of 260° C. or lower.
{5} A molding which is produced by the process as defined in item {4}.
THE MOST PREFERRED EMBODIMENT TO CARRY OUT THE INVENTION
The present invention is constituted of a molding material which comprises a dry blend of 10 to 95% by weight of a (A) styrenic polymer having atactic configuration and 2 to 90% by weight of a (B) styrenic polymer having a melting point of 250° C. or lower, a weight average molecular weight of at most 200,000 and mainly syndiotactic configuration.
As the styrenic polymer having atactic configuration as the component (A) to be used in the present invention, use is made of an atactic polystyrene which is produced by any of solution polymerization, bulk polymerization, suspension polymerization and bulk-suspension polymerization. As a monomer to be used as a starting material for the atactic polystyrene, use is made of an aromatic vinyl compound represented by the general formula (1):
wherein R is independently of one another, is a substituent group having at least one atom selected from the group consisting of a halogen atom, carbon atom, oxygen atom, nitrogen atom, sulfur atom, phosphorus atom, selenium atom, silicon atom and tin atom; m is an integer of 1 to 3; and when m is plural, each R may be same or different. The atactic polystyrene may be a copolymer of the forgoing aromatic vinyl monomer and an other vinyl monomer copolymerizable with at least one aromatic vinyl monomer or rubbery polymer. Also, the atactic polystyrene may be a hydride of the polymer or the copolymer, or a mixture thereof.
Examples of the aromatic vinyl compound represented by the general formula (1) include styrene, &agr;-methylstyrene, methylstyrene, ethylstyrene, isopropylstyrene, tert-butylstyrene, phenylstyrene, vinylstyrene, chlorostyrene, bromostyrene, fluorostyrene, chloromethylstyrene, methoxystyrene and ethoxystyrene. Of these are particularly preferable styrene, p-methylstyrene, m-methylstyrene, p-tert-butylstyrene, p-chlorostyrene, m-chlorostyrene and p-fluorostyrene. Any of those may be used alone or in combination with at least one other.
Examples of an other vinyl monomer copolymerizable with the aromatic vinyl compound include vinylcyanide compounds such as acrylonitrile and methacrylonitrile; acrylic esters such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, amyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, dodecyl acrylate, octadecyl acrylate, phenyl acrylate and benzyl acrylate; methacrylic esters such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, amyl methacrylate, hexyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, phenyl methacrylate and benzyl methacrylate; and maleimide based compounds such as maleimide, N-methyl maleimide, N-ethyl maleimide, N-butyl maleimide, N-lauryl maleimide, N-cyclohexyl maleimide, N-phenyl maleimide and N-(p-bromophenyl) maleimide.
Examples of rubbery polymers copolymeri
Aoyama Takuma
Okada Akihiko
Idemitsu Petrochemical Co. Ltd.
Nutter Nathan M.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
LandOfFree
Molding material, process for producing molded article, and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Molding material, process for producing molded article, and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Molding material, process for producing molded article, and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3174905