JPS6317018B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a mold by bonding molding sand by polymerizing an acrylic ester or a methacrylic ester in an environment where oxygen exists. Conventional mold manufacturing methods include methods using inorganic binders such as cement and water glass, methods using organic binders such as furan, and bonding by heating and cross-linking drying oils, phenolic resins, etc. A method of hardening the mold by passing sulfur dioxide gas or amine gas through the mold is known. This method of using an acrylic ester or a methacrylic ester as an organic binder is a relatively recently known method, and is described, for example, in JP-A-50-29423. In this method, acrylic ester or methacrylic ester is polymerized and cured using peroxide in an oxygen-free environment to bond molding sand. In this method, the acrylic ester or methacrylic ester (hereinafter referred to as monomer) used does not polymerize sufficiently in the presence of oxygen, for example in the air, so polymerization proceeds in an oxygen-free environment and mold sand For this reason, it is necessary to maintain the mold in an atmosphere of nitrogen or carbon dioxide gas during curing, and equipment and operations that handle such inert gases are required. The present inventors have developed a method that self-cures at room temperature in air without the need for such extra equipment or operations, while taking advantage of the properties of the polymer of the above-mentioned monomers, and without using special gases. As a result of intensive research into methods for manufacturing molds, the present invention was achieved. That is, the present invention is characterized in that molding sand is self-hardening bonded in an environment in the presence of oxygen using a binder consisting of a monomer, an organic peroxide, and a polymerization accelerator containing an amine and a cobalt soap. This method involves the production of a mold that can be used practically even in an environment where oxygen exists by promoting the polymerization reaction using an organic peroxide and a polymerization accelerator containing an amine and a cobalt soap. It was discovered that a mold can be manufactured. The molding sand used in the present invention is common molding sand such as silica sand, zircon sand, chromite sand, and olivine sand. The monomer used in the present invention may be any acrylic ester or methacrylic ester, but from the viewpoint of curing speed and properties after curing, monomers containing two or more (meth)acrylic acid groups in one molecule are preferred. Preferably, those having three or more are particularly preferable. Examples of such monomers include monofunctional polyfunctional esters such as trimethylolpropane tri(meth)acrylate, polyhydric alcohols and polycarboxylic acid oligoesters with several (meth)
Oligoester-type (meth)acrylic ester in which acrylic acid groups are bonded with ester bonds, urethane-type (meth)acrylic ester in which several (meth)acrylic acid groups are ester-bonded at the end of a urethane oligomer, and epoxy Examples include epoxy-type (meth)acrylic esters in which several (meth)acrylic acid groups are ester-bonded to the ends of resin oligomers. Of course, these monomers may be used alone or in combination of two or more. The organic peroxide used in the present invention is a compound having a structure in which one or two hydrogen atoms of hydrogen peroxide (H-O-O-H) are replaced with an organic group, and the peroxide bond (- O—O—) and has the property of easily generating free radicals, examples of which include methyl ethyl ketone peroxide and cumene hydroperoxide. In the present invention, a polymerization promoter containing an amine and a cobalt soap is used as the polymerization promoter, and the amine is preferably a tertiary amine. Particularly preferred among the tertiary amines is N,N-dialkylarylamine, and examples of compounds belonging to this category include N,N-dimethylaniline and N,N-dimethyl-p-toluidine. Cobalt octenoate, cobalt naphthenate, etc. are used as cobalt soaps. The polymerization accelerator of the present invention is preferably a mixture of an amine and a cobalt soap, but if a carboxylic acid is used in combination with these two, the polymerization accelerating effect becomes greater, so if necessary, it is preferable to use a carboxylic acid in combination. As such carboxylic acid, acrylic acid, acetic acid, etc. are used. The standard proportions of each material used in manufacturing the mold of the present invention are as follows. The monomer is used in an amount of 0.8 to 3% (by weight, the same applies hereinafter), preferably 1 to 2%, based on the molding sand. The organic peroxide, amine, cobalt soap, and carboxylic acid used together if necessary are each used in an amount of 0.5 to 15%, preferably 1 to 7%, based on the monomer. By the method of the present invention, it is possible to manufacture a self-hardening mold in an environment substantially containing oxygen, that is, in the air, but in order to further accelerate the hardening, heating, micro- Of course, acceleration means such as wave irradiation may also be used.
Alternatively, the process may be carried out after degassing in advance to reduce the amount of oxygen present. Examples are shown below. The mold test piece used was 50 mm in diameter x 50 mm in height, and the curing properties were measured in terms of counter pressure (Kg/cm ² ). All data are after kneading, molding, and leaving in the air at a room temperature of 25°C. The order of mixing into the molding sand is preferably monomer first, but the others are not particularly significant.
Furthermore, it is a practically effective procedure to pre-mix substances that do not react with each other before kneading them into molding sand. The aggregate mainly used was silica sand, an Australian product under the brand name Fremantle, and its particle composition was as follows.

[Example 1]

Monomer 1-1 Novolac type epoxy acrylate
R-113 (manufactured by Nippon Kayaku Co., Ltd.) 1-2 Novolac type epoxy acrylate
R-011 (manufactured by Nippon Kayaku Co., Ltd.) 1-3 Oligoester acrylate M-
8030 (manufactured by Toagosei Co., Ltd.) Organic peroxide Methyl ethyl ketone peroxide 5% Polymerization accelerator Cobalt octenoate 5% N,N-dimethylaniline 5%

[Example 2]

monomer trimethylolpropane triacrylate organic peroxide Methyl ethyl ketone peroxide 2.5% Polymerization accelerator Cobalt octenoate 2.5% N,N-dimethylaniline 2.5% 2-1 Acrylic acid 2% 2-2 Acetic acid 3%

[Example 3]

Mixture organic peroxide of monomer novolac type epoxy acrylate R-113 (manufactured by Nippon Kayaku Co., Ltd.) and neopentyl glycol diacrylate 3-1 Cumene hydroperoxide 5% 3-2 Methyl ethyl ketone peroxide
5% Polymerization accelerator Cobalt octenoate 5% N,N-dimethylaniline 5%

[Example 4]

Monomer oligoester acrylate M-8030 (manufactured by Toagosei Co., Ltd.) Organic peroxide Methyl ethyl ketone peroxide 3.5% Polymerization accelerator Caprylic acid 3.5% Cobalt naphthenate 3.5% 4-1 N,N-dimethylaniline 4% 4-2 N,N-dimethyl-p-toluidine
3%

[Example 5]

Monomer novolac type epoxy acrylate R-113
(manufactured by Nippon Kayaku Co., Ltd.) Organic peroxide Methyl ethyl ketone peroxide 5% Polymerization accelerator Cobalt octenoate 5% N,N-dimethylaniline 5% Mold sand 5-1 Zircon sand 5-2 Chromite sand 5-3 Olivine sand

【table】

Claims (1)

[Scope of Claims] 1. Molding sand is molded in an oxygen-present environment using a binder consisting of an acrylic ester or methacrylic ester, an organic peroxide, and a polymerization accelerator containing an amine and a cobalt soap. A method for manufacturing a mold, characterized in that the molds are bonded together in a self-hardening manner. 2. The method of claim 1, wherein the polymerization accelerator is a mixture of an amine and a cobalt soap. 3. The method of claim 1, wherein the polymerization accelerator is a mixture of amine, cobalt soap and carboxylic acid.