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
2000-06-01
2002-05-07
Short, Patricia A. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S044000, C528S298000, C523S527000
Reexamination Certificate
active
06384151
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a novel unsaturated polyester and a process for producing the same as well as a resin composition containing the unsaturated polyester and a molding material containing the resin composition and, more particularly, to an unsaturated polyester modified with dicyclopentadiene, which can be utilized effectively as casting materials, lining materials, resin concretes, artificial marbles and molding materials for reinforced plastic molded articles such as SMC (sheet molding compound) and BMC (bulk molding compound). The present invention also relates to a process for producing the above polyester, a polyester resin composition containing the polyester and a radically polymerizable monomer, and a molding material containing the resin composition.
2. Prior Art
Molded articles using an unsaturated polyester are suitably used in casting and lining because of its excellent moldability, strength, heat resistance and water resistance. The unsaturated polyester is mixed with radically polymerizable monomer and then impregnated to reinforcing fibers such as glass and carbon fibers, to form a fiber-reinforced plastic. Such a fiber-reinforced plastic are often used for materials for bathtubs, water-purifier tanks, boats, vehicles, tanks and housings. As typical examples of the molding material containing the unsaturated polyester may include SMC and BMC.
The unsaturated polyester is generally a polyester obtained by condensing a polybasic acid containing an unsaturated acid partially therein with a polyhydric alcohol, and contains an unsaturated bond derived from the above unsaturated acid.
A molded article is obtained as follows. The above unsaturated polyester is mixed with a radically polymerizable monomer (reactive diluent) such as vinyl monomer to prepare a unsaturated polyester resin composition used for a molding material. Then the molding material containing the resin composition is prepared and cured in a mold to form a molded article. Alternatively, an intermediate product such as SMC and BMC containing the resin composition is prepared, followed by press molding.
On the other hand, a dicyclopentadiene-modified unsaturated polyester is obtained by reacting dicyclopentadiene, maleic anhydride, water, polyhydric alcohol and, if desired, an additional other polyhydric basic. Then, the dicyclopentadiene-modified unsaturated polyester is mixed with such a radically polymerizable monomer as styrene, to prepare a resin composition. The molding materials containing such a modified unsaturated polyester resin composition, for example, are disclosed in the following publications.
Japanese Unexamined Patent Publication No.54-90285 discloses a molding material comprising polyester, styrene and polystyrene. The polyester is obtained by the addition condensation reaction of partially esterified dicyclopentadienecarboxylic acid, which is a reaction product of dicyclopentadiene, maleic anhydride and water at 150° C. or less, and a polyhydric alcohol. The reference makes it apparent that the molding material can provide a low-shrink molded article having low viscosity and excellent electric characteristics, particularly an excellent high-temperature insulation resistance.
Japanese Unexamined Patent Publication No. 4-132714 discloses a thermosetting resin composition comprising dicyclopentadiene-modified oligomer and a vinyl polymerizable monomer. The oligomer is obtained by dropping water to dicyclopentadiene and maleic anhydride to react them and further reacting the resulting reaction product with glycol. The thermosetting resin composition can provide a molded article having an improved surface smoothness, dimensional stability (low warpage) and hot water resistance.
Japanese Examined Patent Publication No. 6-74301 discloses a dicyclopentadiene-modified unsaturated polyester resin comprising an unsaturated polyester resin using neopentyl glycol as an alcohol component, an unsaturated polyester using dicyclopentadiene as a modifier, a thixotropic agent and a polymerizable monomer. The polyester resin can afford a product having good surface smoothness.
As an example of producing the unsaturated polyester using dicyclopentadiene as a modifying component, this publication discloses a process for adding maleic anhydride to a mixture of dicyclopentadiene and water at a small adding rate so that the reaction mixture has a temperature of 130° C. or less with utilizing the reaction heat generated in the reaction. After the addition of maleic anhydride is completed, the reaction mixture is continued to be heated at 130° C. for 3 hours. Then glycol is added thereto and the temperature of the mixture is gradually raised to react with the glycol at 210° C. When the acid value of the mixture reaches 25 or less, it is judged that the reaction has been terminated and the reaction product is cooled. Subsequently, hydroquinone or a styrene monomer is added to the mixture, to obtain a dicyclopentadiene-modified polyester resin.
Published Japanese Translation No. 62-500034 of the PCT Application discloses a softened composition comprising a dicyclopentadiene-modified unsaturated polyester alkyd, a urethane oligomer and a non-resinous vinyl monomer. As an example of producing the dicyclopentadiene-modified unsaturated polyester alkyd, the publication discloses a process for adding water more than a theoretical equivalent amount relative to the amount of maleic anhydride to prepare a reaction mixture, adding dicyclopentadiene to react with the reaction mixture, and reacting the reaction product with polyol.
In general, the dicyclopentadiene-modified unsaturated polyester is obtained by producing a dicyclopentenyl monoester of maleic acid in an addition reaction step of dicyclopentadiene, maleic anhydride and water, and esterifying the addition reaction mixture including the dicyclopentenyl monoester with a polyhydric alcohol, or a polyhydric alcohol and a polybasic acid.
In the above addition reaction step, first, maleic anhydride reacts with water to form maleic acid. Then an addition reaction between dicyclopentadiene and one of carboxylic acid of the maleic acid molecule is conducted in the absence of a catalyst due to the high dissociation degree of the carboxylic acid, to produce a dicyclopentenyl monoester as an addition reaction product. Since such a reaction causes a drastic heat generation, it is required to pay close attention in order to prevent the generated heat from accelerating further reaction (Hereinafter, the accelerated exothermic reaction is referred to as “a reckless exothemic reaction”.)
According to a conventional process described above, however, when maleic anhydride, water and dicyclopentadiene are previously mixed and heated in a reaction vessel, the reaction proceeds rapidly and the pressure in the reaction vessel increases rapidly by a rapid increase in temperature due to the reckless exothemic reaction. This pressure increase may cause such a dangerous problem as breakage of the reaction vessel. To avoid the above problem, when the above reaction is conducted, a reaction vessel with a sufficient cooling capability must be used to avoid the above problem. However, such a reaction vessel generally has a large size and thereby causes an increase in cost.
In addition, the conventional process includes an addition reaction conducted by adding dropwise water or maleic anhydride to a mixture of maleic anhydride and dicyclopentadiene or a mixture of water and dicyclopentadiene. In this process, since the mixture of maleic acid and dicyclopentadiene as well as water and dicyclopentadine do not dissolve each other, the reaction system is likely to be inhomogeneous in which concentration distributions of the respective raw materials are partially inhomogeneous. Thus, it is hard to control the reaction heat and the reckless reaction is liable to be caused by the reaction heat, resulting in a poor operation safety on production of the unsaturated polyester. To avoid such a reckless reaction, the cooling capability
Funaki Hironori
Hayashi Katsura
Hayashiya Toshio
Matsukawa Kenji
Takabatake Koji
Nippon Shokubai Co. , Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Short Patricia A.
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