JPH04371343A - Binder composition for sand core for high-pressure casting - Google Patents

Abstract

PURPOSE:To make improvements in the properties of sand molds, the quality of castings and working environment, etc., by using the above binder compsn. at the time of producing the sand core to be applied to an undercut part in die casting for casting a light alloy under a high pressure. CONSTITUTION:This binder compsn. for the sand core for high-pressure casting is the binder compsn. used at the time of producing the sand core to be applied to the undercut part die casting for casting a light alloy under several 10 to several 100kg/cm<2> pressure by adding and kneading a harder compsn. essentially consisting of the salt of a weak base and lower aliphat. sulfonic acid or arom. sulfonic acid to and with binder compsn., then curing the mixture under heating and contains a thermoplastic resin essentially consisting of the cocondensation product or mixture of at least one kind among furfuryl alcohol, furfuryl alcohol- formalin, and urea-formalin and a formalin capturing agent.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for use in manufacturing sand cores to be applied to undercut portions in die casting for casting light alloys under high pressure. More specifically, several 10 kg/cm2 to several 100
A sand core applied to the undercut part in die casting for casting light alloys at a pressure of kg/cm2 is made by adding and kneading a hardening agent and a binder composition to refractory granular aggregate and keeping it at 100℃ or higher. The present invention relates to a binder composition for high-pressure casting sand cores, which is used when manufacturing sand cores by filling it into molds and curing with heat.

0002

[Prior art and problems to be solved by the invention] Conventionally,
When manufacturing hollow products or undercut products by pressure casting, the product is cast in parts and then assembled by welding or other construction methods. However, if a collapsible sand core can be used, it will be possible to integrally cast products with complex shapes, and improvements in casting quality and cost benefits can be expected. Salt cores are used as part of these collapsible sand cores, but salt cores are difficult to mold into cores with complex shapes, and furthermore, special molds and molding machines are required. Therefore, the cost is high, and a collapsible sand core is required as an alternative for energy saving and rationalization. As a sand core molding process, a shell molding method is widely used in which so-called resin-coated sand, in which fire-resistant granular aggregate is coated with a phenol novolac resin, is molded and thermally cured. This process has the advantage of being simple in terms of equipment and easy to use, but the shell sand core has poor collapsibility and requires heat treatment to take out the sand mold in the disassembly process. This process takes 250-300
It is common practice to bake and harden the castings at a temperature of 0.degree. C., which causes various problems such as distortion of the mold, poor dimensions of the casting due to deformation, and a working environment, and there has been a desire to significantly improve these problems.

[0003] In order to deal with these problems, many studies have been conducted in the past. As one of them,
Japanese Patent Publication No. 61-29816 has been disclosed, which uses a mixture of a refractory granular aggregate, an acid-curing resin, and a catalyst consisting of a salt of a lower aliphatic sulfonic acid or an aromatic sulfonic acid with a weak base. Possibly 150~200℃
This is the so-called warm box method, which heats and hardens at a low temperature. This has greatly improved the dimensional accuracy and work environment of castings due to temperature-induced distortion and deformation of the mold, and has become widespread mainly in the cast iron field. However, as a molding system that can be applied to a wider range of applications, improvements in the physical properties of molds, the quality of castings, and the working environment are desired.

0004

[Means for Solving the Problems] The present inventors have completed the present invention as a result of intensive research to solve the above problems. That is, several 10 kg/cm2 to several 100
When manufacturing a sand core applied to the undercut part in die casting for casting light alloys under a pressure of kg/cm2, the sand core is added to the fire-resistant granular aggregate and kneaded with a curing agent and a binder composition, then heated and hardened. A binder composition used in
At least one thermoplastic resin selected from: (a) Coumarone resin (b) Ketone resin (c) Vinyl acetate resin (d) Polystyrene (e) Polyvinyl alcohol (f) Petroleum resin (g) Dicyclopentadiene resin ( h) rosin (i) organosorvolysis-lignin (j) bisphenol A residue (k) resorcinol residue, and a formalin scavenger. be.

[0005] The main component in the binder composition of the present invention is at least one co-condensate or mixture of furfuryl alcohol, furfuryl alcohol-formalin, and urea-formalin. (a) to (k) used to further improve disintegration properties and used in combination therewith
The content of the thermoplastic resin is preferably 3 to 30% by weight. If the thermoplastic resin content in the binder composition of the present invention is less than 3% by weight, the effect of improving the initial strength of the sand core will be very small, and if it exceeds 30% by weight, the viscosity of the system will increase and the kneading The fluidity of the sand is poor and the strength of the sand core is reduced. The weight average molecular weight of the thermoplastic resin is 300 to 50,00.
0 is preferable because it greatly improves the initial strength of the sand core. If the weight average molecular weight is less than 300, the effect of improving the initial strength will be very small, and if it exceeds 50,000, the viscosity of the system will increase, the fluidity of the kneaded sand will be poor, and the strength of the sand core will decrease.

The content of formalin scavenger in the binder composition of the present invention is preferably 1.0 to 10.0% by weight. If the content is less than 1.0% by weight, the effect of improving the environment due to formalin odor during production by heating and hardening the sand core will be very small, and if it exceeds 10.0% by weight, the sand core will not be heated and hardened. After this, the polymerization of the resin does not progress, and the crosslinking density also decreases, resulting in a decrease in the strength of the sand core. Preferred formalin scavengers are urea, phenol, cresol, xylenol or resorcinol. The binder composition in the present invention is 5 to 5 parts by weight per 1000 parts by weight of the fire-resistant granular aggregate.
Preferably, it is used in a proportion of 0 parts by weight. If it is less than 5 parts by weight, sufficient sand core strength cannot be obtained, and if it exceeds 50 parts by weight, it will adversely affect the fluidity of the kneaded sand. When manufacturing a mold using the binder composition of the present invention, it is kneaded together with a refractory aggregate and a curing agent, filled into a mold kept at 100° C. or higher, and heat-cured.

The curing agent composition used in the present invention is one whose main component is a salt of a weak base and a lower aliphatic sulfonic acid or an aromatic sulfonic acid, and usually contains 1000 parts by weight of fire-resistant granular aggregate. It is used in a proportion of 1 to 30 parts by weight. If it is less than 1 part by weight, sufficient initial strength cannot be obtained,
If it exceeds 30 parts by weight, excessive hardening will result, and the surface stability of the sand core will be significantly reduced. Generally, it is preferable to use the curing agent composition in an amount of 15 to 80 parts by weight based on 100 parts by weight of the binder composition. Incidentally, the curing agent composition in the present invention is usually used as a solution of water or a solvent. This curing agent composition may contain saccharides such as starch, corn starch, glucose, dextrin, derivatives thereof, and the like.

[0008] In order to improve mold strength and ease of handling, a diluent may be mixed with the acid-curable resin within a range that does not adversely affect other properties. Its blending amount is 2
It is preferably 0% by weight or less. Specific examples of diluents that can be used include aromatic hydrocarbons such as benzene and xylene, alcohols such as methanol, ethanol, and furfuryl alcohol, ethers such as diethyl ether, anisole, and acetal, acetone, Ketones such as methyl ethyl ketone, heterocyclic hydrocarbons such as tetrahydrofuran and dioxane, esters such as methyl acetate and ethyl acetate, polyhydric alcohols such as ethylene glycol and glycerin, 2-methoxyethanol, 2-methoxyethanol, etc.
- Cellosolves such as ethoxyethanol, 2-methoxyethyl acetate, 2-ethoxyethyl acetate,
Examples include cellosolve acetates such as 2-butoxyethyl acetate and 2-phenoxyethyl acetate, and carbitol acetates such as diethylene glycol monoethyl ether acetate. Furthermore, a silane coupling agent may be added for the purpose of further improving mold strength. As the silane coupling agent, for example,
Examples include γ-(2-amino)aminopropylmethyldimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, etc. . As the refractory granular aggregate used to produce sand cores in the system of the present invention, silica sand containing quartz as a main component, zircon sand, chromite sand, etc. are used.

[0009] Furthermore, the sand core produced as described above is coated with conventionally known surface coating agents, such as refractories such as zircon flour, synthetic mica, and colloidal silica, and binders such as molasses and hentonite. After coating and drying a surface coating agent made by mixing ingredients with water, lower alcohol, etc. to form a film, it is placed in a mold and
A light alloy is cast using a die-casting machine at a pressure of from kg/cm2 to several 100 kg/cm2.

0010

EXAMPLES The present invention will be explained in detail below with reference to Examples, but the present invention is not limited to these Examples. Examples 1 to 11 and Comparative Examples 1 to 6 Hardening agent composition (toluenesulfonic acid-copper salt: 40% by weight, methanol: 40% by weight, water: 20% by weight) based on 1000 parts by weight of Australian flattery silica sand 4 ．．
A sand mixture prepared by adding and kneading 5 parts by weight and 15 parts by weight of the binder composition shown in Table 1 was blown into a vertically split molding machine for furan worm boxes at an air pressure of 4.0 kg/cm2 and baked at a hardening temperature of 180°C for 30 seconds. A sand core was molded for evaluation of sand shakeout performance. The sand core of the shell was molded by blowing resin coated sand (RCS) into a vertical molding machine for shells at an air pressure of 1.5 kg/cm 2 and baking at a hardening temperature of 300° C. for 1 minute. 70 parts by weight of zircon flour in the molded sand core.
A surface coating agent consisting of 20 parts by weight of synthetic mica, 10 parts by weight of colloidal silica, 5 parts by weight of hentonite, 2 parts by weight of molasses and 40 parts by weight of water was applied and dried to form a film, and then set in a mold, An aluminum alloy (material: AC-4C) was cast using a die-casting machine at a pressure of 100 kg/cm2, and the ability to shake out sand was evaluated. The results are shown in Tables 1 and 2. Similarly, 25 x 25 x 250 m/m
A sand core for measuring bending strength was cured at a temperature of 180°C for 20
It was fired for seconds, and the bending strength was measured 15 seconds after firing. The results are shown in Tables 1 and 2.

[0011]

[Table 1]

0012

[Table 2]

[0013]

Effects of the Invention: By using the binder composition of the present invention when manufacturing sand cores that are applied to undercut parts in die casting for casting light alloys under high pressure, the physical properties of the mold can be improved and the castings can be improved. It is possible to improve quality and work environment.

Claims (4)

[Claims] [Claim 1] Several 10 kg/cm2 to several 100 k
A sand core that is applied to the undercut part in die casting for casting light alloys at a pressure of g/cm2 is manufactured by adding a curing agent and a binder composition to refractory granular aggregate, kneading it, and then heating and curing it. A binder composition used in the production of a binder containing at least one co-condensate or mixture of furfuryl alcohol, furfuryl alcohol-formalin, and urea-formalin as a main component, and further comprising the following (a) to ( k)
A binder composition for high-pressure casting sand cores, comprising at least one thermoplastic resin selected from the following and a formalin scavenger. (a) Coumarone resin (b) Ketone resin (c) Vinyl acetate resin (d) Polystyrene (e) Polyvinyl alcohol (f) Petroleum resin (g) Dicyclopentadiene resin (h) Rosin (i) Organosorvolysis-lignin (j ) Bisphenol A residue (k) Resorcinol residue 2. The thermoplastic resin and formalin scavenger (a) to (k) each have a content of 3% in the binder composition.
30% by weight and 1.0 to 10.0% by weight of the binder composition for high-pressure casting sand cores according to claim 1. [Claim 3] The average molecular weight of the thermoplastic resin is 300.
50,000. The binder composition for high-pressure casting sand cores according to claim 1. 4. The binder composition for high-pressure casting sand cores according to claims 1 and 2, wherein the formalin scavenger is urea, phenol, cresol, xylenol or resorcinol.