Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-08-07
2001-07-10
Teskin, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S216000, C526S225000, C526S237000, C526S219000, C526S219600, C526S313000, C568S749000, C568S750000, C568S756000
Reexamination Certificate
active
06258901
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process for producing a light-colored p-vinylphenol-based polymer. More particularly, the present invention relates to a process for producing, in simple steps, a p-vinylphenol-based polymer which is superior in transmittance of far-ultraviolet light, has a high molecular weight and is light-colored.
BACKGROUND ART
p-Vinylphenol-based polymers are in use in various industrial fields, as functionalized polymer materials such as photosensitive resin, thermosetting resin, coating material, material for rust preventive, and the like. When an ordinary unpurified p-vinylphenol monomer is used as a polymerization raw material, however, the obtained polymer (p-vinylphenol-based polymer) has a yellowish brown color and has had limited applications.
Further, in recent years, p-vinylphenol-based polymers have drawn attention as a substance essential for use in a photoresist for production of super integrated semiconductor circuit, in the field of photosensitive electronic materials. In order to use a p-vinylphenol-based polymer in this photoresist application, the solution of the polymer is required to be superior in transmittances of visible light and far-ultraviolet light (KrF excimer laser beam of 248 nm) as well as in heat resistance. The heat resistance of a p-vinylphenol-based polymer can be evaluated by, for example, glass transition temperature; in order for the polymer to have excellent heat resistance, the polymer is required to have a molecular weight not lower than a certain high value, specifically a weight-average molecular weight of about 7,000 or higher. Incidentally, this specific value of molecular weight differs depending upon the kind of the polymer.
As to the process for production of p-vinylphenol-based polymer, various processes are known and they can be largely divided into two kinds of processes.
The first process comprises subjecting a p-vinylphenol monomer which is obtained by hydrolysis of acetoxystyrene, decarboxylation of hydroxycinnamic acid, catalytic decomposition of bisphenolethane, dehydrogenation of ethylphenol or the like, to homopolymerization or copolymerization in the presence of a radical polymerization initiator or a cationic polymerization catalyst. The second process comprises subjecting a monomer which is obtained by protecting the hydroxyl group of p-vinylphenol with an acetyl group, a trialkylsilyl group, a tert-butyl group, a tert-butoxycarbonyl group or the like, to homopolymerization or copolymerization in the presence of a radical polymerization initiator or an anionic polymerization catalyst and then removing the protective group for reversion to hydroxyl group.
Since a p-vinylphenol monomer is used as a polymerization raw material, the first process has a merit of being able to obtain an intended p-vinylphenol polymer directly. However, the p-vinylphenol-containing reaction mixture obtained in the synthesis of p-vinylphenol monomer contains impurities considered to hinder the formation of polymer, as part of coloring-causing substances; therefore, in the cationic polymerization of p-vinylphenol monomer, it becomes necessary to purify the p-vinylphenol monomer which is a polymerization material. However, since p-vinylphenol is very unstable thermally and causes polymerization easily, it is difficult to increase its purity to a high level by distillation. Hence, for example, JP-A-51-39788 discloses a method of repeating recrystallization using a hydrocarbon type solvent such as hexane or the like. This method enables production of a polymer of high molecular weight and substantially no coloring, but has not been fully satisfactory for practical application because the purification method by recrystallization is complex and brings about large loss of intended product.
As to the radical polymerization of p-vinylphenol monomer, for example, JP-A-61-291606 or JP-A-63130604 discloses a method of polymerizing a p-vinylphenol monomer in the presence of a phenol having no unsaturated side chain and water for suppression of runaway reaction. In this method, however, since the p-vinylphenol-containing reaction mixture obtained in the synthesis of p-vinylphenol monomer contains coloring-causing substances as mentioned previously, the polymer obtained from the reaction mixture per se (not subjected to any purification) is colored and has been insufficient in transmittances of visible light and far-ultraviolet light. Further, since the concentration of the raw material p-vinylphenol monomer in the reaction system is inevitably low, it has been difficult to obtain a polymer of high molecular weight.
Meanwhile, in the second process, the hydroxyl group-protected p-vinylphenol, unlike the above-mentioned p-vinylphenol monomer, is generally distillable. Therefore, the second process has a merit of being able to polymerize a high-purity monomer obtained by distillation. In the second process, however, it is necessary to remove the protective group of a formed polymer from the polymer in order to obtain an intended polymer; therefore, coloring of polymer may occur in the removal of the protective group and the post-treatment of the formed polymer increases the number of process steps, which have been the drawbacks of the second process.
The object of the present invention is to solve the above-mentioned problems of conventional processes for production of p-vinylphenol polymer and provide a process for producing a light-colored polymer superior in transmittances of visible light and far-ultraviolet light and high in molecular weight, efficiently and economically. As a target for improvement in coloring in visible light wavelength region, a transmittance of 90% can be employed because coloring is hardly noticeable at a light transmittance of higher than 90% and is easily noticeable at a light transmittance of lower than 90%.
DISCLOSURE OF THE INVENTION
In view of the above situation, the present inventors made an intensive study. As a result, the present inventors found out that in subjecting p-vinylphenol to homopolymerization or copolymerization with a vinyl compound copolymerizable with p-vinylphenol to produce a p-vinylphenol-based polymer, there can be produced, by using a raw material p-vinylphenol subjected to a distillation treatment under particular conditions, a light-colored (white to light yellow) p-vinylphenol-based polymer high in transmittances of visible light and far-ultraviolet light and also high in molecular weight. The present invention has been completed based on the above finding.
The gist of the present invention lies in a process for producing a light-colored vinylphenol-based polymer by subjecting p-vinylphenol to homopolymerization or subjecting p-vinylphenol and a vinyl compound copolymerizable with p-vinylphenol to copolymerization, in the presence of a cationic polymerization catalyst or a radical polymerization initiator, which process comprises subjecting a p-vinylphenol-containing raw material to vacuum flash distillation in the presence of a phenolic compound having no unsaturated side chain and water, and subjecting the resulting p-vinylphenol-containing fraction to polymerization.
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention is described in detail below.
The light-colored p-vinylphenol-based polymer of the present invention includes a homopolymer of p-vinylphenol; a copolymer between p-vinylphenol and a vinyl compound copolymerizable with p-vinylphenol, such as m-vinylphenol, styrene or derivative thereof, acrylic acid or ester thereof, methacrylic acid or ester thereof, maleic anhydride, maleic acid or ester thereof, maleimide or the like; a benzene nucleus-substituted product of said polymer; a chemically modified polymer obtained by esterifying or etherifying the phenolic hydroxyl group moiety of said polymer; and so forth.
p-Vinylphenol, which is a polymerization raw material in the process of the present invention, can be produced by any of various known methods. The known methods include, for example, hydrolysis of acetoxystyrene, decarboxylation
Kaneko Masao
Matsumoto Tadashi
Ohtsu Kunishige
Oka Nobuyuki
Maruzen Petrochemical Co. Ltd.
Stoltz Melvin I.
Teskin Fred
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