A photocurable composition is provided. A cured product formed by curing the photocurable composition has reworkability and excellent heat resistance while having flexibility. The photocurable composition includes a telechelic acrylic polymer having an acryloyl group at both ends; a polyfunctional acrylic polymer having acryloyl groups; a monofunctional acrylic monomer; and a fumed silica including at least one of a hydrophilic fumed silica or a fumed silica having a polar group. The photocurable composition has a Martens hardness of 0.07 to 0.75 N/mm.sup.2, where the Martens hardness is a hardness after the photocurable composition is cured.

The present invention relates to a cuarable resin composition, etc., having an excellent transparency, applicability, and workability. Specifically, the present invention relates to a resin composition, etc., including: (A) a polymer having two or more (meth)acryloyl groups in one molecule thereof; (B) a silica powder surface-treated with an alkyl silane; and (C) boric acid or a borate ester.

An acrylic rubber containing: an alkyl acrylate unit; a crosslinking monomer unit; a unit of a bifunctional monomer represented by the following formula (A-1):

##STR00001##

wherein n represents 1 to 9, R.sup.1 represents a hydrogen atom or a methyl group, and R.sup.2 represents an alkanediyl group having 2 to 4 carbon atoms; and an ethylene unit, wherein the acrylic rubber has a toluene insoluble content of 4 to 40% by mass.

An acrylic rubber contains a copolymer of a monomer mixture of: 25 to 46 wt. % of alkoxyalkyl acrylate, 23 to 37 wt. % of 2-ethylhexyl acrylate, 9 to 17 wt. % of alkyl methacrylate, 1 to 3 wt. % of monoalkyl fumarate and the remaining amount is ethyl acrylate. This acrylic rubber improves hydrolysis resistance by introducing a specific alkyl acrylic monomer with extremely low hydrolysis property i.e. low hydrophilicity, and at the same time satisfies all of oil resistance, cold resistance, and hydrolysis resistance in a well-balanced manner.

An acrylic rubber composition comprising 5 to 15 parts by weight of a plasticizer having a solubility parameter SP value (by Small's method) of 8.5 to 10.5 based on 100 parts by weight of super cold resistant grade acrylic rubber having a glass transition point Tg of −42° C. or less, wherein the acrylic rubber composition can give a vulcanizate with the TR10 value, which is an index of cold resistance, of −42° C. or less both initially and after oil dipping. In the acrylic rubber composition, first, the ratio of an acrylate monomer that constitutes acrylic rubber is adjusted, thereby the low temperature characteristics can be maintained even in an oil contact environment. This intentionally reduces the oil resistance of the vulcanized rubber molded product, thereby increasing the amount of oil swelling into the vulcanized rubber molded product and improving the flexibility in a low temperature environment.

A photocurable composition is provided. A cured product formed by curing the photocurable composition has reworkability and excellent heat resistance while having flexibility. The photocurable composition includes a telechelic acrylic polymer having an acryloyl group at both ends; a polyfunctional acrylic polymer having acryloyl groups; a monofunctional acrylic monomer; and a fumed silica including at least one of a hydrophilic fumed silica or a fumed silica having a polar group. The photocurable composition has a Martens hardness of 0.07 to 0.75 N/mm.sup.2, where the Martens hardness is a hardness after the photocurable composition is cured.

Described herein are sealant compositions with low shrinking volume. The sealant compositions include a glass filler. The sealant compositions are useful in a variety of building and construction applications, as well as interior or exterior trim work applications.

Provided are a novel acrylic polymer that has moderate crosslinking reactivity and is suitable for sealant applications and a sealant using the polymer. The (meth)acrylic acid alkyl ester polymer according to the invention has a weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) method of 30,000 to 150,000 and a number average molecular weight (Mn) of less than 20,000 and has 1.1 to 3.0 methyldimethoxysilyl groups, more than 0.5 methyldimethoxysilyl groups at side chains of a molecular chain, and more than 0.5 methyldimethoxysilyl groups at molecular chain terminals, per one molecule of the polymer.

A seal rubber composition contains a carboxyl group-containing acrylic rubber, silica, and two or more inorganic fibers, an amount of the silica per 100 parts by weight of the carboxyl group-containing acrylic rubber is 25 to 100 parts by weight, and a total amount of the inorganic fibers per 100 parts by weight of the carboxyl group-containing acrylic rubber is 35 to 100 parts by weight. A sealing member includes a sliding portion composed of a vulcanized product of the seal rubber composition.

An acrylic rubber composition comprising an acrylic rubber and a compound represented by General Formula (1):

##STR00001##

where R.sup.1 to R.sup.4 each independently represent a C.sub.1 to C.sub.30 organic group which may have a substituent, and R.sup.5 to R.sup.10 each independently represent a hydrogen atom or a C.sub.1 to C.sub.30 organic group which may have a substituent.