JPS6364259B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a resin composition for bonding foundry sand grains. Currently, the shell molding method is the mainstream method for manufacturing casting cores and complex molds, and phenolic resin is generally used as the resin for binding sand grains. When the casting temperature is as high as 1300°C to 1400°C, such as in cast iron castings, the disintegration properties of phenol resin coated sand are good, but when the casting temperature is as low as 650°C to 750°C, as in aluminum castings, it is moderate. In the thick part of the inner core, after casting, the phenolic resin hardens due to the heat of the molten metal, increasing its strength, and even in the thin part of the core, when wrapped in molten metal, the core becomes oxygen-free, so benzene rings mainly form. is carbonized and the sand grains or the sand grains and the aluminum alloy casting are bonded together, so the strength hardly decreases and the collapsibility is very poor. Therefore, aluminum alloy castings that use phenol resin coated sand as cores of complex shapes are usually sand-baked at 400℃ to 500℃ for 4 to 10 hours before breaking down using a knockout machine. The reality is that they are improving their sexuality. Recently, attention has been drawn to the low thermal decomposition temperature of unsaturated polyester, and polyester resin coated sand, which improves the above-mentioned drawbacks of phenol resin coated sand and uses unsaturated polyester resin as the resin for binding sand grains, has been introduced for use in aluminum alloy casting. (Japanese Unexamined Patent Application Publication No. 1983-80234,
162622, etc.). However, although the current polyester range coated sand can improve the disadvantage of poor disintegration properties of phenol resin coated sand, it also has the disadvantage of poor mold formability compared to phenol resin coated sand. There is. In other words, using a blow-in shell mold making machine.
When filling a mold heated to 280°C to 300°C with resin-coated sand to form a shell core, there was a problem of clogging of the mold making machine magazine and the resulting decrease in filling performance, which made it necessary to replace the existing mold making machine. The practical application of polyester resin coated sand has been delayed because it cannot be used as is. This clogging of the mold making machine magazine is related to the fusion point, which is one of the characteristics required of resin coated sand. Since the temperature of the mold used to form cores and molds is high at 280℃ to 300℃, the temperature of the mold making machine magazine usually rises to about 70℃ to 90℃ while continuously molding cores and molds. If the melting point is low, the resin for binding sand grains will melt in the magazine of the mold-making machine, and the sand will become clogged due to adhesion to the magazine or blocking of the resin-coated sand. The problem is that while the commonly used phenol resin coated sand has a melting point of 90 to 115°C, the melting point of the current polyester resin coated sand is as low as 85°C or less. Therefore, in order to improve the mold formability of polyester resin coated sand, the melting point should be set at 90°C, which is the same as that of phenol resin coated sand.
It is necessary to increase this to a higher level. In view of the drawbacks of such polyester resin coated sand, the present inventors have conducted extensive research to develop a polyester resin coated sand with a melting point of 90°C or higher, and as a result, they have found that it is competitive with phenolic resin in terms of melting point and strength. We have now discovered a resin composition for binding wet foundry sand. In the present invention, mono(dihydrodicyclopentadienyl) maleate represented by formula (1) is reacted with a polyhydric alcohol, and if necessary, a saturated polybasic acid and/or an α,β-unsaturated dibasic acid. A self-polymerizable unsaturated polyester polymerization catalyst having a softening point of 50°C or higher obtained by the ring-and-ball method (JIS K2207) and an oxide of a metal belonging to, or group of the periodic table of elements. This invention relates to a resin composition for bonding foundry sand grains. According to the resin composition for bonding foundry sand grains according to the present invention, there is no decrease in strength seen in molds obtained using conventional polyester resin coated sand, and polyester resin coated molds with a melting point of 90°C or higher are produced. Sand can be obtained, and mold forming properties equivalent to those of phenol resin coated sand can be obtained. In the present invention, polyhydric alcohol is added to mono(dihydrodicyclopentadienyl) maleate, and if necessary, saturated polybasic acid and/or α, β
- A self-polymerizable unsaturated polyester obtained by reacting an unsaturated dibasic acid is used. The conventional unsaturated polyester obtained by reacting an acid component containing an α,β-unsaturated dibasic acid with a polyhydric alcohol component has poor self-polymerizability, so it contains only one polyester in the molecule. It has been necessary to use one or more of the above unsaturated monomers or prepolymers having unsaturated bonds. The unsaturated monomers or prepolymers include liquid substances such as styrene, divinylbenzene, vinyltoluene, diallyl phthalate, diallyl phthalate prepolymers,
There are products such as triacrylic formal and triallyl isocyanurate that are solid at room temperature, but when liquid products are used, the softening point of unsaturated polyester resin drops significantly, and when polyester resin coated sand is made, the melting point is lower. The disadvantage is that it is low. Further, if a solid material is used, the effect on the fusion point is relatively small, but it has the disadvantage that it is generally expensive and lacks versatility. On the other hand, the mono(dihydrodicyclopentadienyl)maleate represented by the above formula (1) used in the present invention is added to an alcohol, and if necessary, a saturated polybasic acid and/or an α,β-unsaturated dibasic acid. Unsaturated polyester obtained by reacting with an acid has self-polymerizability, so it does not necessarily contain 1 in the molecule.
There is no need to blend an unsaturated monomer or prepolymer having more than 1 unsaturated bond, and the disadvantages seen in conventional general unsaturated polyester resins are eliminated by blending unsaturated monomers or prepolymers. Improved. In the present invention, in the periodic table of elements,
, or oxides of metals belonging to the group. The melting point of resin-coated sand is naturally influenced by the softening point of the resin used to bind the sand grains. Therefore, in order to increase the melting point of polyester resin coated sand, it is considered to increase the softening point of the unsaturated polyester which is the resin for binding sand grains. However, the softening point of unsaturated polyester is 20°C higher than the softening point determined by the ring and ball method.
Since it has a wide softening temperature range, starting to soften at ~30℃ lower temperature, in order to raise the melting point of polyester resin coated sand to over 90℃, the softening point of unsaturated polyester must be 120℃.
In this case, the following problems arise and it is difficult to put it into practical use. 1. A mold formed using resin-coated sand using a resin composition containing an unsaturated polyester with a softening point of 120° C. or higher as the resin for binding sand grains has low strength. 2. In order to raise the softening point of unsaturated polyester to 120°C or higher, it is necessary to increase the degree of condensation.
During synthesis, there is a high probability of gelation and it is difficult to supply it in a stable state. However, by blending oxides of metals belonging to groups , , or groups of the periodic table of elements, it is not necessary to raise the softening point of unsaturated polyester to 120°C or higher, and the fusion point can be improved at the same time without reducing strength. becomes possible. Mono(dihydrodicyclopentadienyl)maleate used in the present invention is, for example, 5- or 6-hydroxy-3a,4,5,6,7,7a-
It can be obtained by a ring-opening esterification reaction between hexahydro-4,7-methanoindene (hydroxylated dicyclopentadiene) and maleic anhydride, an addition reaction between dicyclopentadiene and maleic acid, and the like. This compound is already known and can be produced by a known production method. Note that during these reactions, di(dihydrodicyclopentadienyl) maleate shown in formula (2) may be partially produced, but the presence of this di(dihydrodicyclopentadienyl) maleate is It does not affect the effectiveness of the product in any way. Examples of polyhydric alcohols include propylene glycol, dipropylene glycol, 1,2-propanediol, ethylene glycol, diethylene glycol, 1,3-butanediol, neopentyl glycol, 1,6-hexanediol, hydrogenated bisphenol A, and glycerin. , trimethylolpropane, pentaerythritol, etc. are used,
A monohydric alcohol may be used in combination if necessary. As the α,β-unsaturated dibasic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, citraconic acid, chloromaleic acid, etc. are used.
Saturated dibasic acids include phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, adipic acid, sebacic acid, etc. If necessary, monovalent acids such as benzoic acid may be used in combination. Good too. The unsaturated polyester used in the present invention has a softening point of 50°C or higher as measured by the ring and ball method, but is preferably in the range of 80°C to 110°C. 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 will tend to decrease. The above-mentioned self-polymerizable unsaturated polyester having a softening point of 50° C. or higher by the ring-and-ball method used in the present invention is produced by blending the above-mentioned materials by a known method. The polymerization catalyst used in the present invention is preferably an organic peroxide, such as dicumyl peroxide, benzoyl peroxide, tertiary butyl perbenzoate, tertiary butyl perbenzoate, cumene hydroperoxide, 1,3
-Bis(tertiarybutylperoxy)-3,
3,5-trimethylcyclohexane, 2,5-dimethyl-(2,5-dibenzoylperoxy)hexane, 2,2-bis-(4,4-di-tertiarybutylperoxycyclohexyl)propane,
2,5-dimethyl-2,5-di(tertiarybutylperoxy)-hexyne-3,n-butyl-
4,4-bis-(tertiarybutylperoxy)
Valerate, lauroyl peroxide, cyclohexanone peroxide, etc. are used. The amount of organic peroxide blended is preferably in the range of 0.5 parts by weight to 20 parts by weight, particularly 1 part by weight to 100 parts by weight of the above unsaturated polyester, in view of the softening properties of the resin.
A range of 10 parts by weight is preferred. These polymerization catalysts may be used alone or in combination of two or more. As metal oxides, in the periodic table of elements,
, or oxides of metals belonging to the group
Especially considering the price and the effect on the melting point of resin coated sand, magnesium oxide,
Zinc oxide and calcium oxide are useful. The amount of the metal oxide added varies depending on the type of metal oxide and the softening point of the unsaturated polyester, but is preferably used within the range of 0.5 parts by weight to 30 parts by weight per 100 parts by weight of the unsaturated polyester.
For example, magnesium oxide is used in a range of 0.5 to 20 parts by weight, and zinc oxide is used in a range of 2 to 20 parts by weight. The 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 contains a lubricant, a curing accelerator, a polymerization inhibitor, a filler, a silane coupling agent, and one or more polymerizable double bonds in one molecule, as necessary. Unsaturated monomers or prepolymers, etc. may also be included. As the lubricant, calcium stearate, zinc stearate, methylolamide, bisamide, etc. are used. As curing accelerators, naphthenic acid metal salts such as cobalt naphthenate, octene salt metal salts such as cobalt octenoate, amines, etc. are used, and as polymerization inhibitors, hydroquinone, parabenzoquinone, 2,5-diphenyl para Benzoquinone, turpenzoquinone, monotertiary butylhydroquinone, 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 Trichlorosilane or the like is used. Examples of unsaturated monomers or prepolymers having one or more polymerizable double bonds in one molecule include styrene, chlorostyrene, divinylbenzene, diallyl phthalate, diallyl phthalate prepolymer, methyl methacrylate, acrylic acid, Vinyl acetate, acrylamide, phenylmaleimide, maleimide, styrene bromide, triallylisocyanurate, triallylisocyanurate prepolymer, N-methylacrylamide, N,N'-dimethylacrylamide, N-methylmethacrylamide, N,N' -dimethyl methacrylamide, N,
N'-methylenebisacrylamide, N,N'-methylenebismethacrylamide, zinc acrylate,
Calcium acrylate, aluminum acrylate, zinc methacrylate, calcium methacrylate, acrylic acid or methacrylic acid adducts of epoxy resins, and the like are used. When the resin composition for bonding foundry sand grains according to the present invention is actually used, each component may be mixed in advance, or each component may be added and mixed at the time of preparing resin-coated sand. 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. Examples of the present invention will be described below. Parts are by weight. Example 1 4 moles of mono(dihydrodicyclopentadienyl) maleate, 1 mole of isophthalic acid, 2 moles of glycerin, and 1 mole of propylene glycol were reacted by heating at 200°C in a nitrogen gas stream to obtain a softening point of 90°C and an acid value.
50 self-polymerizable unsaturated polyester (A) was obtained. For 100 parts of this self-polymerizable unsaturated polyester (A), 15 parts of zinc oxide, 2 parts of dicumyl peroxide,
0.24 kg of a resin composition prepared by adding and mixing 1 part of tertiary butyl perbenzoate and 3.5 parts of calcium stearate was mixed with 8 kg of silica sand preheated to 160°C for 5 minutes using a speed mixer manufactured by Enshu Tekko Co., Ltd. NSC-1. A resin coated sand whose surface was uniformly coated with the resin composition was obtained. About this resin coated sand JACT
The fusion point was measured based on the resin-coated sand standard test method of the Casting Technology Promotion Association, and the room temperature bending strength (flexural strength) was measured based on JIS K6910. The results are shown in Table 1. Comparative Example 1 4 mol of maleic anhydride, 1 mol of isophthalic acid,
An unsaturated polyester (B) having a softening point of 90°C and an acid value of 55 was obtained by heating and reacting 2 moles of glycerin and 2.5 moles of propylene glycol at 200°C in a nitrogen gas stream.
To 100 parts of this unsaturated polyester (B), 20 parts of diallyl phthalate, 15 parts of diaphragm oxide, 2 parts of dicumyl peroxide, 1 part of tertiary butyl perbenzoate, and 3.5 parts of calcium stearate were added and mixed. Silica sand preheated to 160℃8
By stirring with a speed mixer for 5 minutes with Kg, resin coated sand in which the sand surface was uniformly coated with the resin composition was obtained. The melting point and room temperature bending strength of this resin coated sand were measured in the same manner as in Example 1, and the results are shown in Table 1. Comparative Example 2 A resin coated sand was obtained in the same manner as in Example 1 except that zinc oxide as a metal oxide was removed from the resin composition of Example 1. The melting point and room temperature bending strength of the resin coated sand were measured in the same manner as in Example 1, and the results are shown in Table 1.

[Table] As is clear from Table 1, the resin coated sand using the resin composition for bonding foundry sand grains according to the present invention has a higher strength than the mold obtained using the conventional polyester resin coated sand. It is possible to obtain a polyester resin-coated sand with a melting point of 90°C or higher without any decrease in temperature, and to provide mold formability equivalent to that of phenol resin-coated sand. Further, the preparation of resin-coated sand using the resin composition for binding foundry sand grains according to the present invention may be the same as when using a phenolic resin composition, and no modification of equipment is required.

Claims (1)

[Scope of Claims] 1 Mono(dihydrodicyclopentadienyl)maleate represented by formula (1), polyhydric alcohol, and if necessary further saturated polybasic acid and/or α,β-
Self-polymerizable unsaturated polyesters with a softening point of 50°C or higher obtained by the ring-and-ball method obtained by reacting unsaturated dibasic acids, polymerization catalysts, and oxides of metals belonging to groups , , or of the periodic table of elements. A resin composition for binding foundry sand grains, comprising: