JPS6228042A - Binder resin composition for casting mold - Google Patents

Abstract

PURPOSE:To improve the productivity of a casting mold by mixing a resol type resin obtd. by condensing a specific phenol compd. alone or mixture composed of >=2 kinds thereof and aldehyde and furan resin under specific conditions thereby forming a binder. CONSTITUTION:The resol type resin is obtd. by condensing the un-substed.or substd. monovalent or divalnet phenol compd. such as phenol or cresol alone or the mixture composed of >=2kinds thereof and aldehyde. Such resin and the furan resin are then mixed or the furan resin and phenol compd. are subjected to co-condensation to obtain the resin compsn. The resin compsn. is formed by satisfying the conditions given by formula [I] and the binder for the casting mold is constituted of such compsn. The initial strength of the casting mold is improved by the above-mentioned method without deteriorating the other performacnes thereof. The productivity of the casting mold is consequently improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a binder resin composition for self-hardening molds and acid-curing cold box molds. More specifically, the present invention relates to an improved binder resin composition for molds containing a phenol-furan resin as a main component, and particularly to a binder resin composition suitable for acid-curable cold box molds.

[Conventional technology]

The self-hardening mold method, the cold box mold method, and the cloning method (shell method) are known as molding methods for producing molds such as main molds and cores using organic binders. In particular, organic self-hardening molds are used mainly in the mechanical casting field to improve productivity, casting quality, and
It has already become a general-purpose molding method in place of inorganic molding methods from a safety and health standpoint.

On the other hand, conventionally, in order to manufacture molds at medium to high speeds, a cloning method has been widely used in which molds are manufactured by heating and curing so-called coated sand in which granular refractories are coated with phenolic resin.

However, in order to save energy during mold manufacturing, improve mold production speed, and improve the quality of molds and castings, the cold box mold manufacturing method, which hardens at room temperature using gaseous or aerosol substances, has become an alternative mold manufacturing method to the cloning method. Serious attempts are being made to introduce it in the foundry industry.

The cold box method involves an acid-curing cold box in which acid-curing resins, typically furan-based resins, are cured with sulfur dioxide using peroxide as an oxidizing agent, and polyols and polyisocyanates are cured in an aerosol form of tertiary amine as a catalyst. There is a urethane cold box that hardens as

Among these, molds using urethane cold boxes are
There are disadvantages such as poor disintegration of casting sand during casting production, and the tendency to cause casting defects such as sand trapping, scooping, pinholes, and soot defects.

On the other hand, acid-curing cold boxes have been rapidly attracting attention in recent years as a method for solving the above-mentioned difficulties.

[Problem that the invention seeks to solve]

BACKGROUND ART Phenol resins, furan resins, urea resins, melamine resins, or modified products thereof have conventionally been used as binders for self-hardening molding methods in the field of casting, which focuses on small-lot, high-mix production. However, for reasons of mold properties and quality of castings, binders based on furan resins have recently been widely used. In particular, phenol resins are cheaper than furan resins, but they have problems with storage stability and initial strength, so it is difficult for not only phenol resins but also phenol furan resins to be fully put into practical use. This has not been achieved yet, and further improvements are desired.

In addition, for acid-curing cold boxes that produce molds in small quantities and in large quantities at medium to high speeds, acid-curing resins include furan resins, phenol resins, urea resins, and modified resins of these. In particular, at present, only furan-based resins are being put into practical use. In other words, automatic molding machines are used to manufacture medium to large quantities of molds using the cold box method, in which acid-curing resin and peroxide are added and kneaded to the refractory granular material to coat the surface of the refractory granular material. Covering, filling, molding, curing, and removal are performed continuously in a cycle of less than one minute automatically using air pressure or the like.

In particular, phenolic resins are cheaper than furan resins, but they have various problems, especially their initial strength, which is significantly reduced.
In the acid-curing cold box method, which requires high-speed mold production, not only phenol resins but also phenol furan resins have not yet been put to practical use.

The present invention particularly relates to a binder resin composition for castings mainly composed of phenolic furan resin that improves the initial strength of molds1, and is particularly applicable to acid-curing cold boxes that require high-speed mold manufacturing. The object of the present invention is to provide a binder resin composition for molds, which is mainly composed of a phenolic furan resin, which can be used to improve the initial strength of molds.

[Means for solving problems]

As a result of intensive research, the present inventors have determined that the number of moles of aldehydes, the number of furan skeletons, the number of moles of phenolic compounds contained in the form of reactants or monomers in acid-curing resins mainly composed of phenol-furan resins, and The present invention was completed based on the discovery that there is a close relationship between the number of reaction points and the initial strength of the mold.

That is, the present invention relates to a binder resin composition used in a mold manufacturing method using an acid-curable resin as a binder, wherein the acid-curable resin contains an unsubstituted or substituted monohydric or dihydric phenol compound. A resin composition obtained by mixing a resol-type resin obtained by condensing an aldehyde alone or in a mixture of two or more types with a furan-based resin, or by co-condensing a furan-based resin, the phenolic compound, and an aldehyde, and (h x B) / (3 x B + k x C) = 0.3 to 1.0 However, A: Number of moles of aldehyde contained in 100 g of the composition as a reactant or monomer B: Number of moles of aldehyde contained in 100 g of the composition The number of furan rings C: &u The number of phenolic hydroxyl groups contained in 100 g of an adult animal: The total number in one molecule of the above phenolic compound in ortho and rose positions capable of addition reaction with formaldehyde. The present invention relates to a characteristic binder resin composition for molds.

The binder resin composition of the present invention significantly improves the initial strength of the mold. This effect is particularly remarkable in the acid-curing cold box method, and mold productivity is greatly improved.

The initial strength of a mold is determined by a complex balance of various factors such as wettability, fillability, curing reaction rate, and molecular structure during the curing process.

The above conditional expression (A+B) / (3X B+k x C)
Among these factors, it seems to be closely related to the curing reaction rate and the molecular structure of the curing process, and has a large influence on the initial strength of the mold. The appropriate range is 0.3 to 1.0
, preferably from 0.3 to 0.7, and if it is outside this range, the initial strength will be extremely reduced.

Until now, there has been no research that has investigated the improvement of the initial strength of phenolic furan resins from the viewpoint of the above conditional expression, but the present invention makes it possible to significantly improve the initial strength of molds using phenolic furan resins as a binder. It became.

Specific examples of unsubstituted or substituted monohydric or dihydric phenol compounds used in the present invention include phenol, cresol, xylenol, butylphenol, nonylphenol, resorcinol, methylenebisphenol, catechol, etc., and preferably compounds of the general formula (I ) H (wherein R1 and Rt are hydrogen atoms or hydrocarbon groups having 1 to 9 carbon atoms), and more preferably at least one phenol compound selected from phenol, cresol, and xylenol. be.

The value of k in the above conditional expression is the total number of ortho- and rose-position phenol compounds in one molecule that are capable of addition reaction with formaldehyde. The value is 3. or,
A mixture of two or more types of phenol compounds is expressed as an average number depending on the mixing ratio.

The furan resin in the present invention refers to furfuryl alcohol, furfuryl alcohol/aldehyde condensate, furfuryl alcohol condensate, furfuryl alcohol/urea/
Aldehyde condensate, furfuryl alcohol/melamine/
It is an acid-curing resin mainly composed of aldehyde condensates, etc.
It is not particularly limited.

The aldehydes in the present invention include aromatic aldehydes,
Although aliphatic aldehydes and the like are used, aliphatic aldehydes are preferred. Preferred aliphatic aldehydes are at least one of formaldehyde, paraformaldehyde, glyoxal, and acetaldehyde, and more preferred are at least one of paraformaldehyde and formaldehyde, or a portion thereof modified with other aldehydes such as glyoxal and acetaldehyde. It is an aldehyde.

Aldehydes are usually contained not only in condensation with phenolic compounds but also in furan resins. Therefore, the aldehyde in the above conditional formula is an aldehyde included in both of them.

The binder resin composition of the present invention is mainly composed of a phenolic resin mixed with or co-condensed with a furan-based resin, but it can also be mixed with or co-condensed with, for example, urea or a urea/aldehyde condensate as a modifier. However, it is also possible to mix or co-condense at least one of conventionally known modifiers. Specific examples of conventionally known modifiers include coumaron/indene resin, petroleum resin, polyester, alkyd resin, polyvinyl alcohol, epoxy resin, ethylene/vinyl acetate, polyvinyl acetate, polybutadiene, polyether, polyethyleneimine, and polychloride. Polymers and oligomers such as vinyl, polyacrylic acid ester, polyvinyl butyral, phenoxy resin, cellulose acetate, xylene resin, toluene resin, polyamide, styrene resin, polyvinyl formal, acrylic resin, urethane resin, nylon, lignin,
Lignosulfonic acid, rosin, ester gum, vegetable oil,
Bitumen, heavy oil, crushed cashew nut, vanillin,
Natural products such as tannins, saccharides and their derivatives such as starch, corn starch, glucose, and dextrin, resorcin residues, cresol residues, 2.2, 4-trimethyl-4-(hydroxyphenyl)coumarone, and isopropenylphenol. Reaction by-products, reaction residues and by-products such as reaction by-products of terephthalic acid and ethylene glycol,
Polyhydric alcohols such as polyethylene glycol, condensates with ketones and aldehydes such as acetone, cyclohexanone, and acetophenone, amino or imino compounds such as dicyandiamide, acrylamide, and thiourea, and their aldehyde condensates, furfural, glyoxal, etc. These include aldehyde compounds, and ester compounds such as isocyanuric acid esters and unsaturated fatty acid esters. The modification rate of these modifiers is preferably 20% or less.

Furthermore, the viscosity of the binder resin composition in the present invention can be adjusted to 1 to 1000 at 25°C by controlling the reaction conditions and using a diluent.
By using cps, the initial strength of the mold can be further improved. If the viscosity is too low, the resin will be adsorbed into the microscopic pores on the surface of the sand grains, which will prevent the resin from effectively coating the surface of the sand grains. If the viscosity is too high, the wettability and uniform dispersibility of the resin to foundry sand will decrease.

Specific examples of diluents that can be used for the above purpose 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, cellosolves such as 2-methoxyethanol and 2-ethoxyethanol. ,
Examples include at least one of cellosolve acetates such as 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-butoxyethyl acetate, and 2-phenoxyethyl acetate, and carpitol acetates such as diethylene glycol 7-noethyl ether acetate. Note that the diluent may be mixed into the resin composition in advance or immediately before kneading the foundry sand. The blending amount thereof is preferably 20% or less based on the composition.

Further, the amount of water contained in the composition of the present invention is 10
% or less. If more water is contained, the effects of the present invention will be significantly reduced. Furthermore, the amount of monomer phenol compounds contained as unreacted substances, etc. is also 10%.
It is preferable that it is below. If more monomer phenol compounds are contained, the initial strength will be significantly lowered or the storage stability will be deteriorated. Furthermore, it is preferable that the amount of monomer aldehyde contained as unreacted substances is 10% or less; if more monomer aldehyde is contained, the workability will be significantly deteriorated due to the odor caused by the monomer aldehyde.

Furthermore, a silane coupling agent may be added for the purpose of further improving the strength of the mold. Examples of the silane coupling agent include γ-(2-amino)aminopropylmethyldimethoxysilane, γ-aminopropyltrimethoxysilane, T-aminopropyltriethoxysilane,
Examples include γ-mercaptopropyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane.

In the present invention, as the hardening agent for the self-hardening mold method, organic sulfonic acids such as para-toluenesulfonic acid and xylene sulfonic acid, inorganic acids such as phosphoric acid and sulfuric acid, and mixtures thereof are used, but there are no particular limitations. It's not a thing. In addition, organic peroxides such as ketone and aromatic peroxides and inorganic peroxides such as hydrogen peroxide are used as peroxides in the acid-curing cold box method, but are not particularly limited. .

In order to manufacture a mold, silica sand containing quartz as a main component, zircon sand, chromite sand, oripin sand, etc. are used as a refractory granular material together with the binder according to the present invention, but there are no particular limitations. It is not something that will be done.

In addition, the time of addition of the binder resin composition may be before or after kneading the curing agent or peroxide into the foundry sand, but
In view of the longer pot life of the kneaded sand, it is preferable to use it after adding a curing agent in the case of self-hardening, or before adding peroxide and kneading in the case of the acid-curing cold box method.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited to these Examples.

Examples 1 to 6 and Comparative Examples 1 to 2 Various reaction amounts of phenol, furfuryl alcohol, and paraformaldehyde were reacted for a predetermined time using a conventional method, and after the reaction was completed, the mixture was neutralized with an aqueous solution of para-toluenesulfonic acid, and 5% methanol was added. , conditional expression (A+8) / (3x B+
Various binder resin compositions having k x C) values shown in Table 1 were obtained, and their initial strengths in an acid-curing cold box method and a self-hardening mold method were measured.

The initial strength of the acid-curing cold box method was determined by adding 1.4 parts by weight of the resulting binder resin composition to 100 parts by weight of Australian flattery silica sand and Ml! KPO peroxide 0.5
The mixture obtained by adding and kneading parts by weight was 25 x 25 x 2
Pressurized air was blown into a 50 m/m mold to fill it, and then sulfur dioxide gas was blown into the mold to form a mold, and the bending strength of the mold was measured 30 seconds after the sulfur dioxide gas was blown into the mold.

The initial strength of the self-hardening mold method is 100% of Freemantle silica sand.
7 parts by weight of para-toluenesulfonic acid as a curing agent
0.5 parts by weight of a 5% aqueous solution and 1.4 parts by weight of the obtained binder resin composition were added and kneaded, and the mixture was immediately mixed into 50 m/
It was filled into a test piece model of wφ×5 ah, and the compressive strength was measured after 30 minutes.

The results are shown in Table-1.

Table-1 Examples 7 to 12 and Comparative Examples 3 to 4 Various reaction amounts of phenol and paraformaldehyde were reacted for a predetermined time using a conventional method, and after the reaction was completed, neutralization was performed with an aqueous solution of para-toluenesulfonic acid to obtain a phenol resin. Furthermore, a furfuryl alcohol/formaldehyde condensate with a known reaction amount of furfuryl alcohol and formaldehyde is mixed, and the conditional formula (A+B) / (3X B+k
Various binder resin compositions having the values of x shown in Table 2 were obtained.

Using the obtained binder resin compositions, the initial strengths in the acid-curing cold box method and the self-hardening mold method were measured by the methods shown in Examples 1 to 6.

The results are shown in Table-2.

Table 2 [Effects of the Invention] As is clear from this example, the present invention enables the self-hardening mold method and the acid-hardening cold box method to use an acid-curing resin mainly composed of phenolfuran resin as a binder. In this case, the initial strength of the mold can be significantly improved without deteriorating other performances. The effect is particularly remarkable in the acid-curing cold box method, and the productivity of molds can be significantly improved.

Claims (1)

[Scope of Claims] 1. A binder resin composition used in a mold manufacturing method using an acid-curable resin as a binder, wherein the acid-curable resin is an unsubstituted or substituted monohydric or dihydric phenol. It is a resin composition obtained by mixing a resol type resin obtained by condensing a single compound or a mixture of two or more compounds with an aldehyde and a furan resin, or by cocondensing a furan resin, the above phenol compound, and an aldehyde. , and (A+B)/(3×B+k×C)=0.3 to 1.0 However, A: Number of moles of aldehyde contained in 100 g of the composition in the form of a reactant or monomer B: Number of moles of aldehyde contained in 100 g of the composition The number of furan rings contained C: the number of phenolic hydroxyl groups contained in 100 g of the composition k: the total number of the above phenolic compounds in one molecule at ortho and para positions capable of addition reaction with formaldehyde. A binder resin composition for molds, characterized by: 2. The value of (A+B)/(3×B+k×C) is 0.3 to 0
．． 7. The composition according to claim 1, wherein the composition is 3. The composition according to claim 1, wherein the phenol compound is a compound represented by general formula (I), and k in the conditional formula is 3. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (In the formula, R_1 and R_2 are hydrogen atoms or carbon atoms from 1 to 9.
4. The composition according to claim 1, wherein the aldehyde is an aliphatic aldehyde. 5. The composition according to claim 3, wherein the phenol compound represented by general formula (I) is at least one of phenol, cresol, and xylenol. 6. The composition according to claim 4, wherein the aliphatic aldehyde is at least one of formaldehyde, paraformaldehyde, glyoxal, and acetaldehyde.