JPH0118818B2 - - 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 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 to 750°C, as in aluminum alloy castings, the core collapses. In the thick inner part of the core, the heat of the molten metal hardens the phenolic resin after casting, increasing its strength.Also, even in the thin part of the core, when it is wrapped in the molten metal, the core becomes oxygen-free, so the benzene rings mainly form. Carbonization occurs 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, in general, aluminum alloy castings using phenol resin coated sand as cores of complex shapes,
The reality is that in most cases sand baking is performed at 400 to 500°C for 4 to 10 hours to improve the disintegration property before demolding using a knockout machine. Recently, attention has been paid to the low thermal decomposition temperature of unsaturated polyester resin, and polyester resin coated sand, which uses unsaturated polyester resin as the sand grain bonding resin and improves the above-mentioned drawbacks of phenol resin coated sand, has been developed for aluminum alloy casting. (Japanese Patent Application Laid-Open No. 54-80234,
54-162622, etc.). However, although the current polyester resin coated sand can improve the drawbacks of poor disintegration properties of phenol resin coated sand, on the other hand, compared to phenol resin coated sand, it has (1) poor mold formability, and (2) high temperature. The disadvantage is that the strength of the mold is low. In other words, using a blow-in shell mold making machine.
When molding a shell core by filling a mold heated to 280 to 300°C with resin-coated sand, problems occurred in mold formability due to clogging of the mold machine magazine and the resulting reduction in filling performance. The mold making machine cannot be used as is. In addition, because the strength of the mold at high temperatures is low, when removing the hardened mold and core from a mold heated to 280 to 300°C, it often breaks, making it difficult to mold cores and molds with complex shapes. The practical application of polyester resin coated sand has been delayed because it is difficult and limited to molding of molds and cores of very simple shapes. The clogging of the modeling machine magazine related to the defect (1) above is related to the fusion point, which is one of the characteristics required of resin coated sand. The temperature of the mold used to form the core and mold is 280℃.
Because the temperature is as high as ~300℃, the temperature of the mold making machine magazine normally decreases while continuously molding cores and molds.
If the temperature rises to around 70-90℃ and the melting point is low, the resin for binding sand grains will melt in the magazine of the mold making machine, causing clogging 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 moldability of polyester resin coated sand, it is necessary to raise the melting point to 90°C or higher, which is the same level as that of phenol resin coated sand. Furthermore, in order to improve the strength of the mold at high temperatures, which is the drawback of (2) above, it is necessary to essentially improve the heat resistance of the unsaturated polyester resin. In view of the drawbacks of such polyester resin coated sand, the present inventors have conducted intensive research to develop polyester resin coated sand that has a melting point of 90°C or higher and has excellent mold strength at high temperatures. We have now discovered a resin composition for bonding foundry sand grains that can compete with phenolic resins in both melting point and mold strength at high temperatures. The present invention comprises an acid component containing an α,β-unsaturated dibasic acid and optionally a saturated dibasic acid, and a polyhydric alcohol component in which 10 to 100 mol% of the polyhydric alcohol component is hydrogenated bisphenol A. An unsaturated polyester having a softening point of 50°C or higher by the ring and ball method (hereinafter referred to as the ring and ball method) specified in JIS K5850 Section 3.8, obtained by reacting 1
Castings containing an unsaturated monomer or prepolymer having one or more polymerizable double bonds in the molecule, a polymerization catalyst, and an oxide of a metal belonging to or group of the Periodic Table of the Elements This invention relates to a resin composition for binding sand grains. In the present invention, an acid component containing an α,β-unsaturated dibasic acid and, if necessary, a saturated dibasic acid, and a polyhydric alcohol component in which 10 to 100 mol% of the polyhydric alcohol component is hydrogenated bisphenol A. An unsaturated polyester with a ring and ball softening point of 50°C or higher obtained by reacting with is blended, which improves heat resistance and greatly improves the strength of the mold at high temperatures. By blending hydrogenated bisphenol A with 10 to 100 mol% of the polyhydric alcohol component, the heat resistance of unsaturated polyester is improved, the softening point of unsaturated polyester can be easily raised, and hydrogenated bisphenol The viscosity at temperatures above the softening point is lower than that of unsaturated polyester that does not contain A. Currently, the manufacturing method for resin-coated sand is to heat the sand grains in advance to a temperature higher than the softening point of the resin to be coated, and then mix the resin into the heated sand and stir it. A hot-melt method is used in which the resin is heated and melted to coat the resin, but in this case, the lower the melt viscosity of the resin, the easier it is to coat the surface of the sand grains uniformly. Furthermore, during mold molding, it is expected that the lower the melt viscosity, the easier the bond between the resin-coated sand grains will be, and the stronger the bond will be during the process of curing by heating.
It is presumed that as a result of these, it becomes possible to significantly improve the strength at room temperature and the strength at high temperature. If the amount of hydrogenated bisphenol A is less than 10 mol% of the polyhydric alcohol component, the desired strength of the mold at high temperatures cannot be obtained. In the present invention, in the periodic table of elements,
, or one or more oxides belonging to the group. The method of fusing resin-coated sand is naturally influenced by the softening point of the resin used to bind the sand grains. Therefore, in order to raise the melting point of polyester resin-coated sand, it is conceivable to raise the softening point of the unsaturated polyester, which is the resin for binding sand grains. However, unsaturated polyester has a softening point of 20~
In order to raise the melting point of polyester resin coated sand to 90℃ or higher, the softening point of unsaturated polyester must be 120℃ or higher because it has a wide softening temperature range, starting to soften at a temperature 30℃ lower. 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 of the periodic table of elements,
There is no need to raise the softening point of the unsaturated polyester to 120°C or higher, making it possible to improve the melting point without reducing strength. In the present invention, maleic acid, maleic anhydride, fumaric acid, itaconic acid, citraconic acid, chloromaleic acid, etc. are used as the α,β-unsaturated dibasic acid. Saturated dibasic acids include phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, adipic acid, sebacic acid, etc. In some cases, polybasic acids such as trimellitic acid, benzoic acid, etc. Acids of high valence are used in combination. In addition to hydrogenated bisphenol A, polyhydric alcohols include propylene glycol, dipropylene glycol, ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-
Butanediol, neopentyl glycol, 1,
6-hexanediol, glycerin, trimethylolpropane, pentaerythritol, etc. are used, and if necessary, a monohydric alcohol may be used in combination. 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 to 110°C. The above-mentioned unsaturated polyester having a softening point of 50° C. or more by the ring-and-ball method used in the present invention is produced by blending the above-mentioned materials by a known method. When the softening point is less than 80°C, the amount of metal oxide added increases, and when it exceeds 110°C, the strength of the mold tends to decrease. Examples of unsaturated monomers or prepolymers having one or more unsaturated bonds in one molecule include styrene, chlorostyrene, divinylbenzene, diallyl phthalate, diallyl phthalate prepolymer, acrylic acid, methyl acrylate, methacrylic acid, Methyl methacrylate, vinyl acetate, acrylamide, phenylmaleimide, maleimide, styrene bromide,
Tertiary butyl styrene, triallyl isocyanurate, triallyl isocyanurate prepolymer, N-methylacrylamide, N,N'-dimethylacrylamide, N-methylmethacrylamide, N,N'-dimethylmethacrylamide, N
-Methylolacrylamide, N-methylolmethacrylamide, N,N'-methylenebisacrylamide, N,N'-methylenebismethacrylamide, zinc acrylate, calcium acrylate,
Examples include aluminum acrylate, zinc methacrylate, calcium methacrylate, and acrylic acid or methacrylic acid adducts of epoxy resins. As the unsaturated monomer or prepolymer having one or more unsaturated bonds in one molecule, it is preferable to use one with a melting point of 60°C or higher, and the amount added is 5 parts by weight per 100 parts by weight of unsaturated polyester. 100 parts by weight
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 to be added is 5 parts by weight per 100 parts by weight of unsaturated polyester. The following are preferred. These unsaturated monomers or prepolymers may be used alone or in combination of two or more. The polymerization catalyst used in the present invention includes:
Organic peroxides are preferred, such as dicumyl peroxide, benzoyl peroxide, tertiary butyl perbenzoate, cumene hydroperoxide, 1,3-bis(tertiary butylperoxyisopropyl)benzene, 1,1-bis- (tertiarybutylperoxy)-3,3,5-trimethylcyclohexane, 2,5-dimethyl-(2,
5-dibenzoylperoxy)hexane, 2,2
-bis-(4,4-ditertyabutylperoxycyclohexyl)propane, 2,5-dimethyl-2,5-di(tertiarybutylperoxy)-
Hexyne-3,n-butyl-4,4-bis-(tertiarybutylperoxy)valerate, lauroyl peroxide, cyclohexanone peroxide, and the like are used. The amount of these organic peroxides is determined based on the curability of the resin based on 100 parts by weight of the unsaturated polyester mentioned above.
The range is preferably from 0.5 parts by weight to 20 parts by weight, particularly preferably from 1 part by weight to 10 parts by weight. These polymerization catalysts may be used alone or in combination of two or more. Metal oxides are listed in the periodic table of elements.
, or oxides of metals belonging to the group
In particular, magnesium oxide, zinc oxide, and calcium oxide are useful, considering their price and effect on the fusion point of resin-coated sand. The amount of metal oxide added varies depending on the type of metal oxide, the softening point of the unsaturated polyester, the melting point of the unsaturated monomer or prepolymer, the amount blended, etc., but is preferably based on 100 parts by weight of the unsaturated polyester. teeth
It is used in a range of 0.5 parts by weight to 30 parts by weight.
For example, magnesium oxide is used in a range of 0.5 to 5 parts by weight, and zinc oxide is used in a range of 2 to 15 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 may contain a lubricant, a curing accelerator, a polymerization inhibitor, a filler, a silane coupling agent, etc., as necessary. As the lubricant, calcium stearate, zinc stearate, methylolamide, bisamide, etc. are used. As curing accelerators, naphthenic acid metal salts such as cobalt naphthenate, octenoic acid metal salts such as cobalt octenoate, and amines are used, and as polymerization inhibitors, hydroquinone, parabenzoquinone,
2,5-diphenylparabenzoquinone, tolbenzoquinone, monotertiarybutylhydroquinone, etc. are used. Calcium carbonate, barium sulfate, aluminum hydroxide, clay, silica, talc, etc. are used as the filler. Silane coupling agents include vinyltriethoxysilane, vinyl-tris-(β-methoxyethoxy)silane, γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, vinyltris-(β-methoxyethoxy)silane, Chlorosilane etc. 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. The resin-coated sand is prepared by a semi-hot method in which the resin composition is dissolved in a suitable solvent such as acetone, methyl ethyl ketone, toluene, benzene, or xylene to coat the surface of the sand grains with the resin, and then the solvent is evaporated and dried. This is carried out using a solvent-free hot melt method. Examples of the present invention will be described below. Parts are by weight. Example 1 8 moles of maleic anhydride, 2 moles of isophthalic acid,
4 moles of hydrogenated bisphenol A, 3 moles of glycerin, and 2 moles of ethylene glycol were reacted by heating at 200℃ in a nitrogen gas stream to obtain a softening point of 100℃, an acid value of 50, and a viscosity (65% diallylphthalate solution, JIS K6901 bubble viscometer method). ) 4.6 poise unsaturated polyester (A)
I got it. To 100 parts of this unsaturated polyester (A), 20 parts of diallyl phthalate prepolymer (trade name: Daisodap, manufactured by Osaka Soda Co., Ltd.), 2 parts of dicumyl peroxide, and 1 part of tertiary butyl perbenzoate.
8 parts of silica sand preheated to 160°C and 0.24 kg of a resin composition prepared by adding and mixing 1 part of magnesium oxide, 2 parts of zinc oxide, 3.5 parts of calcium stearate, and 1 part of a silane coupling agent (KBM-503 manufactured by Shin-Etsu Chemical).
By stirring with Kg for 5 minutes using a speed mixer manufactured by Enshu Tekko Co., Ltd., model NSC-1, coated sand in which the surface of the sand grains was uniformly coated with the resin composition was obtained. The fusion point (according to JACT: Casting Technology Promotion Association, test method C-1), room temperature bending strength (according to JIS K6910), and high temperature bending strength (according to JACT test method SM-5) were measured for this coded sand. did. The results are shown in Table 1. Example 2 6 moles of maleic anhydride, 4 moles of isophthalic acid,
3 moles of hydrogenated bisphenol A, 4 moles of propylene glycol, and 2 moles of glycerin were reacted by heating at 200℃ in a nitrogen gas stream, resulting in a softening point of 100℃ and an acid value.
An unsaturated polyester (B) having a viscosity of 60 and 5.0 poise (diallyl phthalate 65% solution, bubble viscometer method) was obtained. For 100 parts of this unsaturated polyester (B), 20 parts of diallyl phthalate prepolymer (trade name: Daisodap, manufactured by Osaka Soda Co., Ltd.), 2 parts of dicumyl peroxide, 1 part of tertiary butyl perbenzoate
10 parts zinc oxide, 3.5 parts calcium stearate
Part, silane coupling agent (Shin-Etsu Chemical KBM-
503) 0.24Kg of resin composition added and mixed with 1 part
Enshu Tekko Co., Ltd. with 8 kg of silica sand preheated to ℃
By stirring for 5 minutes with an NSC-1 type speed mixer, coated sand in which the resin composition was uniformly coated on the surface of the sand grains was obtained. The fusion point, normal temperature bending strength, and high temperature bending strength of this corded sand were measured in the same manner as in Example 1, and the results are shown in Table 1. Comparative Example 1 6 moles of maleic anhydride, 4 moles of isophthalic acid,
7 moles of propylene glycol and 2 moles of glycerin were reacted by heating at 200℃ in a nitrogen gas stream, resulting in an unsaturated polyester with a softening point of 100℃, an acid value of 65, and a viscosity (65% solution of diallyl phthalate monomer, foam viscometer method) of 12 poise. I got (C). For 100 parts of this unsaturated polyester (C), 20 parts of the same diallyl phthalate prepolymer as in the example, 2 parts of dicumyl peroxide, 1 part of tertiary butyl perbenzoate,
10 parts zinc oxide, 3.5 parts calcium stearate,
Silane coupling agent (Shin-Etsu Chemical KBM-503)
Enshu Tekko Co., Ltd. NSC-
By stirring for 5 minutes using a Type 1 speed mixer, coated sand in which the surface of the sand grains was uniformly coated with the resin composition was obtained. The melting point, normal temperature bending strength, and high temperature bending strength of this coated sand were measured in the same manner as in Example 1, and the results are shown in Table 1. Comparative Example 2 A coated sand was obtained in the same manner as in Example 2, except that the metal oxide zinc oxide was removed from the resin composition of Example 2. Regarding this coated sand, the melting point, room temperature bending strength,
Table 1 shows the results of measuring the bending strength at high temperatures. Comparative Example 3 8 mol of maleic anhydride, 2 mol of isophthalic acid,
4 moles of hydrogenated bisphenol A, 3 moles of glycerin, and 2 moles of ethylene glycol were reacted by heating at 200℃ in a nitrogen gas stream to obtain a softening point of 100℃, an acid value of 50, and a viscosity (65% diallylphthalate solution, JIS K6901 bubble viscometer method). ) 4.6 poise unsaturated polyester (D)
I got it. 100 parts of this unsaturated polyester (D), 20 parts of zinc acrylate, 2 parts of dicumyl peroxide,
Enshu Tekko ( By stirring for 5 minutes using a Speed Mixer Model NSC-1 manufactured by Co., Ltd., coated sand in which the surface of the sand grains was uniformly coated with the resin composition was obtained. The melting point, room temperature bending strength, and high temperature bending strength of this 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 high melting point and low temperature at high temperatures, which was a drawback of conventional polyester resin coated sand. It is confirmed that the strength of the mold is improved and the mold has excellent formability. Further, the preparation of resin-coated sand using the resin composition for bonding foundry sand grains according to the present invention may be the same as that for phenol resin-coated sand, and does not require any improvement in equipment.

Claims (1)

[Claims] 1. An acid component containing an α,β-unsaturated dibasic acid and, if necessary, a saturated dibasic acid, and a polyhydric alcohol component.
JIS obtained by reacting with a polyhydric alcohol component in which 10 to 100 mol% is hydrogenated bisphenol A
K5850 Unsaturated polyester with a softening point of 50℃ or higher by the ring and ball method specified in Section 3.8,
Contains an unsaturated monomer or prepolymer having one or more polymerizable double bonds in one molecule, a polymerization catalyst, and an oxide of a metal belonging to or group of the periodic table of elements. Resin composition for bonding foundry sand grains.