JPH0153141B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a resin composition for bonding foundry sand grains. Currently, the manufacturing methods for casting molds and cores are as follows:
The shell mold method is the mainstream, and phenolic resin is generally used as the sand grain binder. However, during the coating, molding, and pouring steps of the shell molding process, phenolic resin generates gases with toxic and unpleasant odors such as phenol, ammonia, aldehyde, and carbon monoxide during heating, and is used in aluminum castings. However, in order to improve these drawbacks, unsaturated polyester resins have recently begun to attract attention as casting sand grain binders. Japanese Patent Publication No. 49-48520
Publication No. 50-30114, Japanese Patent Publication No. 1973-30114
Publication No. 104721, Japanese Patent Publication No. 51-29318, Japanese Patent Publication No. Sho 51-29318
Although it is disclosed in Japanese Patent Laid-Open No. 54-80234 and Japanese Patent Application Laid-Open No. 56-59560, it is still used in only a few cases. Polyester resin coated sand using unsaturated polyester resin as the foundry sand grain binder improves the above-mentioned drawbacks of phenol resin coated sand using phenol resin as the binder, but on the other hand, it has the drawback of poor moldability. It's matching. In other words, when molding a shell core by filling resin-coated sand into a mold heated to 280-300℃ using a blow-in shell mold-making machine,
The clogging of the mold making machine magazine and the resulting decrease in filling performance are considered to be drawbacks of the current polyester resin coated sand, and the disadvantage is that the conventional mold making machine cannot be used as is. Practical implementation is delayed. This clogging of the mold making machine magazine is related to the fusion point, which is one of the properties required of resin coated sand. Since the temperature of the mold used to form the core and mold is as high as 280-300°C, the temperature of the mold-making machine magazine also rises to about 70-90°C. Therefore, if the welding point is low, the binder will melt in the magazine of the mold making machine and cause clogging due to adhesion to the magazine or blocking of the resin coated sand. The problem is that the commonly used phenol resin coated sand has a melting point of 90 to 115°C, whereas the melting point of polyester resin coated sand made by known techniques is as low as 85°C or less. The melting point of resin coated sand is influenced by the softening point of the binder used. Therefore, in order to raise the melting point of polyester resin coated sand, it is easy to think of raising the softening point of the unsaturated polyester as a binder. According to studies by the present inventors, in order to raise the melting point of polyester resin coated sand to the melting point of phenol resin coated sand (90°C or higher), the softening point of unsaturated polyester must be 120°C.
However, molds using resin-coated sand that uses unsaturated polyester as a binder with a softening point of 120°C or higher have low strength, and it is necessary to raise the softening point of unsaturated polyester to 120°C or higher. It is necessary to increase the degree of condensation, and there is a high probability of gelation during synthesis, causing problems such as difficulty in supplying in a stable state. In view of the drawbacks of such unsaturated polyester resin compositions for bonding foundry sand grains, the present inventors have determined that
In order to obtain polyester resin coated sand with a temperature of 90°C or higher, as a result of extensive research into resin compositions for bonding foundry sand grains, we have discovered a resin composition for bonding foundry sand grains that can compete with phenolic resins in terms of melting point and strength. . That is, the present invention relates to an unsaturated polyester that is solid at room temperature, an unsaturated monomer or prepolymer having one or more unsaturated bonds in the molecule, a polymerization catalyst, and a metal selected from magnesium oxide, zinc oxide, and calcium oxide. The present invention relates to a resin composition for bonding foundry sand grains containing one or more oxides. In the present invention, by blending the above-mentioned metal oxides, it is possible to improve the fusion point, which was a drawback of conventional polyester resin coated sand, without reducing the strength. The present invention will be explained in more detail below. The unsaturated polyester that is solid at room temperature used in the present invention is an α,β-unsaturated dibasic acid, its acid anhydride, or a mixture thereof, and if necessary, a saturated dibasic acid or its anhydride with a polyhydric alcohol. It can be obtained by reacting with a known method. As the α,β-unsaturated dibasic acid or its anhydride, maleic acid, itaconic acid, fumaric acid, maleic anhydride, citraconic acid, chloromaleic acid, etc. are used. As the saturated dibasic acid or its anhydride, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, succinic acid, adipic acid, sebacic acid, methylsuccinic acid, etc. are used. Examples of polyhydric alcohols include propylene glycol, dipropylene glycol, 1,2-propanediol, ethylene glycol, diethylene glu, 1,3-butanediol, neopentyl glycol, 1,6-hexanediol, hydrogenated bisphenol A, etc. Glycols, glycerin, trimethylolpropane, pentaerythritol, etc. are used, and a monohydric alcohol may be partially used in combination if necessary. In order for an unsaturated polyester to be solid at room temperature, its softening point measured by the ring and ball method must be 50
℃ or higher, but it is preferably in the range of 80℃ to 110℃. If the softening point is less than 80°C, the amount of metal oxide added will increase, and if it exceeds 110°C, the strength of the mold or core will tend to decrease. Examples of unsaturated monomers or prepolymers having one or more unsaturated bonds in the molecule include styrene monomer, chlorostyrene, divinylbenzene, diallyl phthalate, methyl methacrylate, acrylic acid, vinyl acetate, acrylamide, and phenyl. Maleimide, maleimide, styrene bromide, tertiary butyl styrene, triallyl isocyanurate,
N-methylacrylamide, N,N'-dimethylacrylamide, N-methylmethacrylamide,
N,N'-dimethylmethacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N,N'-methylenebisacrylamide, N,N'-methylenebismethacrylamide,
Zinc acrylate, calcium acrylate, aluminum acrylate, zinc methacrylate, calcium methacrylate, diallyl phthalate prepolymer, triallyl isocyanurate prepolymer,
Examples include alkyl acrylates of epoxy resins. As the unsaturated monomer or prepolymer having one or more unsaturated bonds in the molecule, it is preferable to use one with a melting point of 60°C or higher, and the amount added is 100 parts by weight of the unsaturated polyester. 5 parts by weight to 100
Parts by weight are common. When using an unsaturated monomer or prepolymer with a melting point of less than 60°C, the melting point of the resin coated sand tends to decrease, so the amount added is 5 parts by weight per 100 parts by weight of unsaturated polyester. Parts by weight or less are preferred. One type of unsaturated monomer or prepolymer may be used alone, or two or more types may be used in combination. As the polymerization catalyst used in the present invention, organic peroxides are usually preferred, such as dicumyl peroxide, benzoyl peroxide, tertiary butyl perbenzoate, di-tertiary butyl perbenzoate, cumene hydroperoxide,
1,3-bis-(tert-butylperoxyisopropyl)benzene, 1,1-bis-(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 2,5-dimethyl-(2,5
-dibenzoylperoxy)hexane, 2,2-
Bis-(4,4-di-tert-butylperoxycyclohexyl)propane, 2,5-dimethyl-2,5-di(tert-butylperoxy)-
Examples include hexyne-3,n-butyl-4,4-bis-(tertiarybutylperoxy)valerate, lauroyl peroxide, and cyclohexanone peroxide. If the amount of these organic peroxides is less than 0.5 parts by weight per 100 parts by weight of unsaturated polyester, sufficient curing properties will not be obtained, and if it exceeds 20 parts by weight, curing properties commensurate with the amount blended will not be obtained. It is preferably used in a range of 0.5 parts by weight to 20 parts by weight, and usually in a range of 1 part by weight to 10 parts by weight. These polymerization catalysts may be used alone or in combination of two or more. Magnesium oxide, zinc oxide, and calcium oxide are preferable in terms of their effects on the melting point of resin-coated sand and their cost. The amount of metal oxide added varies depending on the type of metal oxide, the softening point of the unsaturated polyester, and the melting point of the unsaturated monomer or prepolymer, but is usually from 1 part by weight to 100 parts by weight of the unsaturated polyester. It is considered to be within the range of 30 parts by weight. For example, magnesium oxide is 0.5 to 5 parts by weight, zinc oxide is 2 parts by weight.
A range of 15 parts by weight will almost achieve the objective.
These metal oxides may be used alone or in combination of two or more. The resin composition for binding foundry sand grains according to the present invention includes:
A lubricant, a curing accelerator, a polymerization inhibitor, a filler, a silane coupling agent, etc. may be included as necessary. As the lubricant, calcium stearate, zinc stearate, methylolamide, bisamide, etc. are used. Examples of curing accelerators include metal naphthenates such as cobalt naphthenate and cobalt octenoate, metal salts of octenoate, and amines. Examples of polymerization inhibitors include hydroquinone, parabenzoquinone,
2,5-diphenylparabenzoquinone, tolbenzoquinone, monotertiarybutylhydroquinone, etc. are used. As the filler, calcium carbonate, barium sulfate, aluminum hydroxide, clay, silica, talc, etc. are used. Examples of silane coupling agents include vinyltriethoxysilane, vinyl-tris-(β-methoxyethoxy)silane, γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, vinyl Examples include trichlorosilane. When actually using the resin composition for binding foundry sand grains according to the present invention, the resin composition may be mixed in advance by an appropriate method, or each component may be added and mixed at the time of preparing the resin coated sand. Good too. Resin-coated sand is prepared by the semi-hot method, in which sand grains are coated with a resin using a solution of the resin composition dissolved in a suitable solvent, such as acetone, methyl ethyl ketone, toluene, benzene, or xylene, and then the solvent is evaporated and dried. This is done using a solvent-based hot melt method. The present invention will be explained below with reference to Examples. Parts are by weight. Example 1 7 moles of maleic anhydride, 3 moles of isophthalic acid,
6 moles of propylene glycol and 3 moles of glycerin are reacted by heating at 210℃ in an inert gas stream, and the softening point (measured by the ring and pole method, the same applies hereinafter) is 86.
An unsaturated polyester A having an acid value of 60 and a temperature of 60° C. was obtained. 100 parts of this unsaturated polyester, 30 parts of diallyl phthalate prepolymer, 2 parts of dicumyl peroxide.
1 part of silica sand, 1 part of tertiary butyl perbenzoate, 1 part of magnesium oxide, and 10 parts of zinc oxide were preheated to 160°C and 0.24 kg of the resin composition was mixed with 8 parts of silica sand.
By stirring for 5 minutes with Kg and a speed mixer manufactured by Enshu Tekko Co., Ltd., model NSC-1, coated sand in which the surface of the sand was uniformly coated with the resin composition was obtained. About this coated sand JACT
The fusion point and room temperature bending strength were measured based on the resin coated sand standard test method of (Casting Technology Promotion Association). The results are shown in Table 1. Comparative Example 1 Example 1 was prepared except that the metal oxides magnesium oxide and zinc oxide were removed from the resin composition of Example 1.
Resin-coated sand was obtained in the same manner as above. Table 1 shows the measurement results of the melting point and room temperature bending strength.

[Table] Example 2 7 moles of maleic anhydride, 3 moles of terephthalic acid,
3 moles of glycerin, 3 moles of hydrogenated bisphenol A, and 2.5 moles of propylene glycol were reacted by heating at 220℃ in an inert gas stream to obtain a softening point of 100℃ and an acid value.
65 unsaturated polyester B was obtained. To 100 parts of this unsaturated polyester, 10 parts of N,N'-methylenebisacrylamide, 3 parts of dicumyl peroxide,
By stirring 0.24 kg of a resin composition prepared by adding and mixing 1 part of magnesium oxide and 5 parts of zinc oxide with 8 kg of silica sand preheated to 160°C using a speed mixer, the resin composition was uniformly coated on the sand surface. Resin coated sand was obtained. Table 2 shows the measurement results of the melting point and room temperature bending strength. Comparative Example 2 Example 2 was prepared except that the metal oxides magnesium oxide and zinc oxide were removed from the resin composition of Example 2.
Resin-coated sand was obtained in the same manner as above. Table 2 shows the measurement results of the melting point and room temperature bending strength. Example 3 Obtained using the same material as Example 2, softening point
115℃, 100 parts of unsaturated polyester with acid value 55,
10 parts of N,N'-methylenebisacrylamide, 3 parts of dicumyl peroxide, 1 part of magnesium oxide
0.24 parts of resin composition mixed with 5 parts of zinc oxide
By stirring for 5 minutes with 8 kg of silica sand preheated to 160° C. using a speed mixer, a resin coated resin composition was obtained in which the surface of the sand was uniformly coated with the resin composition. Table 2 shows the melting point and room temperature bending strength. Comparative Example 3 Obtained using the same material as Example 2, softening point
115℃, 100 parts of unsaturated polyester with acid value 55, N,
Silica sand prepared by preheating 0.24 kg of a resin composition containing 10 parts of N'-methylenebisacrylamide, 3 parts of dicumyl peroxide, and 1 part of ultrafine anhydrous silicic acid (trade name Aloesil 200, manufactured by Nippon Aloesil Co., Ltd.) to 160°C. By stirring with a speed mixer for 5 minutes with 8 kg, resin coated sand in which the resin composition was uniformly coated on the sand surface was obtained. Table 2 shows the measurement results of the fusion point and bending strength. When ultrafine silicic anhydride is used as the metal oxide as in this comparative example, the fusion point of the resin-coated sand is lower than when magnesium oxide and zinc oxide are used as in Example 2. is shown. Example 4 Using the same blending ratio as Example 2, unsaturated polyester B, N,N'-methylenebisacrylamide, dicumyl peroxide, magnesium oxide, and zinc oxide were each weighed separately so that the total was 0.24 kg. The mixture was added to 8 kg of silica sand preheated to 160° C. while stirring using a speed mixer, and by stirring for a total of 5 minutes, resin coated sand in which the resin composition was uniformly coated on the sand surface was obtained. The measurement results of the melting point and room temperature bending strength are shown in Table 2, and the properties are almost the same as those of the resin coated sand obtained using the resin composition of Example 2.

[Table] Resin-coated sand using the resin composition for bonding foundry sand grains according to the present invention has a higher melting point than conventional polyester resin-coated sand and has mold formability equivalent to that of phenol resin-coated sand. It is something. Furthermore, the resin-coated sand preparation process may be the same as that for phenol resin-coated sand, and no modification of equipment is required.

Claims (1)

[Claims] 1. An unsaturated polyester that is solid at room temperature, an unsaturated monomer or prepolymer having one or more unsaturated bonds in the molecule, a polymerization catalyst, and a metal oxide selected from magnesium oxide, zinc oxide, and calcium oxide. A resin composition for binding foundry sand grains containing one or more species.