Abstract: It is intended to provide the following resin composition for stereolithography which is superior in storage stability and aging stability during operation, shows no increase in viscosity upon prolonged storage, has a high light-curing sensitivity and, therefore, makes it possible to produce, upon photo irradiation, an object by stereolithography, which is superior in dimensional accuracy, fabricating accuracy, water resistance, moisture resistance and mechanical properties at a high fabricating speed and a high productivity.

Abstract: A monosulfonium salt in which very little unreacted raw material remains, which has a purity of at least 96%, and which has one sulfonio group in its molecule is manufactured without a refining step. After (a) an aryl compound, (b) a sulfoxide compound, (c) a dehydrating agent, and (d) a BF4, PF6, AsF6, or SbF6 salt of an alkali metal or an alkaline earth metal are introduced into a reaction system, (e) an inorganic acid is added, so that the aryl compound (a) and the sulfoxide compound (b) are subjected to dehydration condensation.

Abstract: A monosulfonium salt in which very little unreacted raw material remains, which has a purity of at least 96%, and which has one sulfonio group in its molecule is manufactured without a refining step. After (a) an aryl compound, (b) a sulfoxide compound, (c) a dehydrating agent, and (d) a BF4, PF6, AsF6, or SbF6 salt of an alkali metal or an alkaline earth metal are introduced into a reaction system, (e) an inorganic acid is added, so that the aryl compound (a) and the sulfoxide compound (b) are subjected to dehydration condensation.

Abstract: A monosulfonium salt in which very little unreacted raw material remains, which has a purity of at least 96%, and which has one sulfonio group in its molecule is manufactured without a refining step. After (a) an aryl compound, (b) a sulfoxide compound, (c) a dehydrating agent, and (d) a BF4, PF6, AsF6, or SbF6 salt of an alkali metal or an alkaline earth metal are introduced into a reaction system, (e) an inorganic acid is added, so that the aryl compound (a) and the sulfoxide compound (b) are subjected to dehydration condensation.

Abstract: It is intended to provide the following resin composition for stereolithography which is superior in storage stability and aging stability during operation, shows no increase in viscosity upon prolonged storage, has a high light-curing sensitivity and, therefore, makes it possible to produce, upon photo irradiation, an object by stereolithography, which is superior in dimensional accuracy, fabricating accuracy, water resistance, moisture resistance and mechanical properties at a high fabricating speed and a high productivity.

Abstract: A monosulfonium salt in which very little unreacted raw material remains, which has a purity of at least 96%, and which has one sulfonio group in its molecule is manufactured without a refining step. After (a) an aryl compound, (b) a sulfoxide compound, (c) a dehydrating agent, and (d) a BF4, PF6, AsF6, or SbF6 salt of an alkali metal or an alkaline earth metal are introduced into a reaction system, (e) an inorganic acid is added, so that the aryl compound (a) and the sulfoxide compound (b) are subjected to dehydration condensation.

Abstract: It is an object of the invention to provide a method which makes it possible to manufacture the desired sulfonium salts directly without using a metathesis process and without using acids in large excess amounts. An aryl compound (A) in which a hydrogen atom is bonded to at least one of the carbon atoms of the aryl group, and a sulfoxide compound (B) which can be expressed by the formula: R1 SO R2 (where R1 and R2 indicate hydrocarbon groups or heterocyclic groups which may be substituted, and which may be the same or different) are reacted in the presence of a strong acid (C) which can be expressed by the formula: HMXmYn (where M indicates an element of group IIIa or group Va of the periodic table, X indicates a halogen atom, Y indicates a hydroxyl group, m and n are integers which are such that m+n=4 and n=0 to 3 in cases where M is an element of group IIIa, and m and n are integers which are such that m+n=6 and n=0 to 2 in cases where M is an element of group Va).

Abstract: It is an object of the invention to provide a method which makes it possible to manufacture the desired sulfonium salts directly without using a metathesis process and without using acids in large excess amounts. An aryl compound (A) in which a hydrogen atom is bonded to at least one of the carbon atoms of the aryl group, and a sulfoxide compound (B) which can be expressed by the formula: R1SOR2 (where R1 and R2 indicate hydrocarbon groups or heterocyclic groups which may be substituted, and which may be the same or different) are reacted in the presence of a strong acid (C) which can be expressed by the formula: HMXmYn (where M indicates an element of group IIIa or group Va of the periodic table, X indicates a halogen atom, Y indicates a hydroxyl group, m and n are integers which are such that m+n=4 and n=0 to 3 in cases where M is an element of group IIIa, and m and n are integers which are such that m+n=6 and n=0 to 2 in cases where M is an element of group Va).

Abstract: A method for producing a water absorbent resin by polymerizing a water-soluble monomer having a polymerizable unsaturated group (A) and a crosslinking agent (B) as the essential components by radical polymerization in the presence of water or, polymerizing a water-soluble monomer having an unsaturated group (A) and a crosslinking agent (B) by radical-graft copolymerization with a water-soluble polymer (C) as the backbone polymer in the presence of water, wherein a water-based solid material capable of being endothermally fused or dissolved into water (D) is added when initiating the polymerization, with at least a part of the water-based solid material (D) in a solid state. By the method of the present invention, a water absorbent resin having a high molecular weight and a high absorption capacity with little water-soluble component can be obtained with ease.

Abstract: A method for producing a water absorbent resin comprising the step of radically polymerizing a water-soluble radically polymerizable monomer having an acid group or a group of the salt thereof and optionally a polysaccharide in the presence of water using a crosslinking agent (C), wherein 0.0001 to 1 weight % of a thiol compound (D) having a radically polymerizable double bond, based on the above mentioned water-soluble radically polymerizable monomer (A), is used as the copolymerizing component to provide a water absorbent resin having a high absorbency and a good gel stability after absorbing body fluid, and a water absorbent comprising the water absorbent resin produced thereby.

Abstract: A method for preparing water-absorbent resins (D) by radically polymerizing a water soluble monomer (A), or a water-soluble monomer (A) and a polysaccharide (B) in the presence of a crosslinking agent (C) and water, wherein the polymerization is conducted under the existence of a thiol compound (E). Water-absorbent resins obtained in the method of the present invention provide high absorption while providing safety with very little amount of a water-soluble component.

Abstract: Water-absorbing resin compositions obtained by adding a water-soluble thiol compound in the process of drying or pulverizing a hydrogel of a water-absorbing resin which is obtained by polymerizing a water-soluble monomer having a polymerizable unsaturated group optionally with a polysaccharide, in the presence of a crosslinking agent and water. Composition of the present invention are highly efficient in water absorption and safe for having extremely low amounts of residual monomer and water-soluble component.

Abstract: A method for producing a water absorbent resin by polymerizing a water-soluble monomer having a polymerizable unsaturated group (A) and a crosslinking agent (B) as the essential components by radical polymerization in the presence of water or, polymerizing a water-soluble monomer having an unsaturated group (A) and a crosslinking agent (B) by radical-graft copolymerization with a water-soluble polymer (C) as the backbone polymer in the presence of water, wherein a water-based solid material capable of being endothermally fused or dissolved into water (D) is added when initiating the polymerization, with at least a part of the water-based solid material (D) in a solid state. By the method of the present invention, a water absorbent resin having a high molecular weight and a high absorption capacity with little water-soluble component can be obtained with ease.

Abstract: The present invention relates to a process for producing water absorbent resin comprising a step of adding a high-molecular crosslinking agent which has at least 2 azetidinium salt groups in the molecule and has at least 1000 weight-average molecular weight to the water absorbent resin paticles having carboxylic groups and carboxylic acid salt groups and a step of efficiently crosslinking the vicinity of the surface of the water absorbent resin particles. In the process for producing water absorbent resin according to the present invention, the use of high-molecular crosslinking agent achieves less permeation of the crosslinking agent into the water absorbent resin particles and enables efficient crosslinking of the vicinity of the surface of the water absorbent resin particles. Consequently, the water absorbent resin having high water absorbency both under pressure-free state and under loading can be manufactured.

Abstract: The invention concerns a process for producing water-insoluble water-absorbing resins, which comprises the steps of initiating polymerization of an aqueous solution containing 30 to 80% by weight of (a) a hydrophilic vinyl monomer having a functional group and (b) a crosslinking agent by supplying the aqueous solution together with (c) a polymerization initiator to a polymerizing apparatus capable of heating and/or cooling surfaces in contact with the aqueous solution, subsequently causing constant temperature polymerization of the solution without agitating the same by controlling the temperature of the system being polymerized to 20.degree. to 70.degree. C., and elevating, if necessary, the temperature ok the system to be in excess of 70.degree. C. in a stage with a polymerization percentage of 70% or above before completion of polymerization. Obtainable water-insoluble water-absorbing resins have excellent water-absorbing property and have less water-soluble components.