JPH11244991A - Manufacture of resin coated sand - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a resin coated sand for molding a shell mold which is low in odor, high in strength and resistant in blocking property. SOLUTION: In a manufacturing method, novolac phenol resin of 0.5-5 pts.wt. is added to a refractory aggregate of 100 pts.wt. heated to 100-180 deg.C is added, melted and kneaded, the novolac phenol resin is uniformly coated on the surface of the refractory aggregate, and resol phenol resin emulsion or suspension of 0.5-5 pts.wt. is added thereto. In addition, the volatile component is evaporated and removed through further kneading, and the resin is coated on the surface of the refractory aggregate.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a resin coated sand for shell mold casting.

2. Description of the Related Art In general, a resin-coated sand for molding a shell mold is a novolak-type phenol resin obtained by reacting phenol and formaldehyde under an acidic catalyst, or a solid or liquid at room temperature obtained by reacting under a basic catalyst. Is added to a refractory aggregate heated to 100 to 180 ° C., and the resin is melted by heat and coated on the surface of the refractory aggregate. To the novolak type phenol resin, a solution obtained by dissolving hexamethylenetetramine in water as a curing agent is added. At this time, the role of water is to uniformly disperse hexamethylenetetramine and to lower the temperature of the refractory aggregate during kneading. On the other hand, the resole type phenol resin does not require hexamethylenetetramine, but water is used for cooling the refractory aggregate.

The novolak type phenolic resin is most commonly used as a binder for shell mold casting. However, this binder requires hexamethylenetetramine as a curing agent. In mold making by baking using a heating mold at 250 to 350 ° C., it is a major problem from the viewpoint of the working environment that this hexamethylenetetramine is thermally decomposed to generate irritating odors such as ammonia and formaldehyde. In particular, formaldehyde has the potential to be a harmful air pollutant from the viewpoint of global environmental problems, and is a subject substance of the Air Pollution Control Law. On the other hand, when a resol type phenol resin, particularly a solid resol resin, is used as a binder for shell mold molding, hexamethylenetetramine is not required as a curing agent, and since the mold can be molded only by heat curing, the generation of the above-mentioned odorous substances is avoided. It was expected as a low-odor odor binder. However, solid resole resin, when manufacturing resin coated sand,
The cured reaction proceeds by the heated refractory aggregate, and the molecular weight increases. For this reason, it is generally known that the melt viscosity is higher than that of the novolak type phenol resin, it is difficult to uniformly coat the surface of the refractory aggregate with the resin component, and the mold strength is lowered. In addition, if the molecular weight of the resole type phenol resin is reduced in advance in consideration of the above reaction in order to increase the strength, there is a problem that the softening point is lowered and the blocking property of the resin and its resin-coated sand during storage is increased. In order to compensate for the problem of the resole type phenolic resin, an invention using an emulsion of the resole type phenolic resin has also been invented. Too low, the melting point of the resin-coated sand decreases, and blocking occurs. Also, if you raise the temperature of the refractory aggregate to solve this problem,
The reaction of the resole type phenol resin has progressed, and sufficient strength has not been obtained.

SUMMARY OF THE INVENTION In view of these problems, the present invention provides a new resin-coated sand for shell mold molding by curing a novolak-type phenol resin with a resol-type phenol resin emulsion or suspension. I do. That is, the present invention
To 100 parts by weight of the refractory aggregate heated to 100 to 180 ° C., 0.5 to 5 parts by weight of a novolak-type phenol resin is added and melt-kneaded, and the novolak-type phenol resin is uniformly applied to the surface of the refractory aggregate. After coating, 0.5 to 5 parts by weight of a resol type phenol resin emulsion or suspension was added, and further kneaded to remove volatile components by evaporation to coat the resin component on the surface of the refractory aggregate, low odor, This is a method for producing a resin coated sand for shell mold casting having high strength and difficult blocking properties. Compared with the curing of novolak-type phenolic resin and hexamethylenetetramine and the condensation polymerization reaction of resol-type phenolic resin, the obtained resin-coated sand has extremely low generation of irritating odors such as ammonia and formaldehyde generated during mold molding, and is stored. Blocking at the time is hard to occur,
High strength molds can be molded. This is because the resol type phenol resin emulsion or suspension used as a curing agent is added after the novolak type phenol resin is uniformly coated on the surface of the refractory aggregate, so that the coatability on the refractory aggregate becomes good and the reaction is improved. This is because it is possible to appropriately control the progress of the operation. The novolak-type phenol resin used in the present invention is prepared by reacting a phenol and an aldehyde under an acidic catalyst or a divalent metal salt catalyst.
1 to 5 parts by weight of a coupling agent, 0.1 to 5 parts by weight of a lubricant, and 0.1 to 5 parts by weight of an organic acid are added. The phenols may include all those having one or more phenolic hydroxyl groups in the molecule. If specifically exemplified, phenol, bisphenol A, bisphenol F, bisphenol S, biphenol, cresol, xylenol, propylphenol, tert-
Examples thereof include butylphenol, phenylphenol, aminophenol, resorcinol, catechol, and hydroquinone, and these can be used alone or as a mixture of two or more. Examples of aldehydes include formalin, paraformaldehyde, trioxane,
Glyoxal, malondialdehyde, terephthalaldehyde, acetaldehyde, benzaldehyde and the like can be mentioned, and these can be used alone or as a mixture of two or more. Examples of the acidic catalyst include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, and organic acids such as oxalic acid, phenolsulfonic acid, paratoluenesulfonic acid, and benzoic acid. Examples of the divalent metal salt catalyst include lead naphthenate, zinc acetate, ferric octoate, and cobalt neodecanoate. Examples of the coupling agent include β- (3,4 epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-
β- (aminoethyl) -γ-aminopropyltrimethoxysilane, and the like. The addition amount of the coupling agent is desirably 0.1 to 5 parts by weight. When the amount is 0.1 parts by weight or less, the effect of the coupling agent is not exhibited, and when the amount is 5 parts by weight or more, the curing is inhibited. Examples of the lubricant include ethylene bis stearoamide, methylene bis stearoamide, methylol stearoamide, stearic amide, oleic amide and the like. The added amount of the lubricant is preferably 0.1 to 5 parts by weight. When the amount is 0.1 part by weight or less, the effect of the lubricant is not exhibited, and when it is 5 parts by weight or more, the curing is inhibited. As the organic acid, those similar to the acidic catalyst can be used. The addition amount of the organic acid is desirably 0.1 to 5 parts by weight. When the amount is 0.1 parts by weight or less, the effect of improving the curability is not exhibited, and when the amount is 5 parts by weight or more, the curing is inhibited. The method for producing the novolak type phenol resin can be produced by a technique already known in JP-A-08-003257 and the like, and is not particularly limited.
The resol type phenol resin emulsion or suspension used in the present invention is obtained by reacting a phenol with an aldehyde under a basic catalyst, and 1 to 20 parts by weight of an emulsifier or 100 parts by weight of a resole type phenol resin in terms of solid content. A colloid protective agent is added, and if necessary, 1 to 30 parts by weight of an organic nitrogen compound, 0.1 to 5 parts by weight of a coupling agent, Add ５5 parts by weight of lubricant and 1１５15 parts by weight of hexamethylenetetramine. The phenols and formaldehydes used here can be the same as those used in the production of the novolak type phenol resin. Examples of the basic catalyst include hydroxides and oxides of alkali metals and alkaline earth metals such as sodium hydroxide, potassium hydroxide, calcium oxide and magnesium oxide, and amines such as ammonia, hexamethylenetetramine and triethylamine. Is mentioned.
Examples of the emulsifier or colloid protective agent include, but are not limited to, polyvinyl alcohol, hydroxymethylcellulose, hydroxyethylcellulose, gum arabic, casein, acrylamide, and the like. The addition amount of the emulsifier or the colloid protective agent is desirably 1 to 20 parts by weight, and if it is 1 part by weight or less, the effect of the emulsifier or the colloid protective agent is not exhibited, and if it is 20 parts by weight or more, the curing is inhibited. Examples of the organic nitrogen compound include urea, melamine, aniline, benzoguanamine, ethylenediamine, acetamide, oxamide, glutarimide, dicyandiamide, glutamic acid, sodium glutamate and the like. The amount of organic nitrogen compound added is 1
If the amount is less than 1 part by weight, the effect of suppressing formaldehyde generation is not exhibited, and if it is more than 30 parts by weight, curing is inhibited. As the coupling agent and the lubricant used here, the same ones as described for the novolak type phenol resin can be used. The amount of hexamethylenetetramine added is 1
~ 15% by weight is desirable, and when it is 1% by weight or less, the strength is improved,
The effect of improving the curability is not exhibited, and if it is 15% by weight or more, the amount of formaldehyde and ammonia generated is large. The method of producing the resol type phenol resin emulsion or suspension can be produced by a technique already known in Japanese Patent Publication No. 62-003855 or the like, and is not particularly limited. The refractory aggregate is, for example, silica sand, alumina sand,
Zircon sand, chromite sand, olivine sand, mullite sand,
Although fly ash and the like can be mentioned, it is not particularly limited as long as it is used for mold making. That is, 0.5 to 5 parts by weight of a novolak type phenol resin is added to 100 parts by weight of the refractory aggregate heated to 100 to 180 ° C., and the mixture is heated and melted to uniformly coat the surface of the refractory aggregate. Next, 0.5 to 5 parts by weight of an emulsion or suspension of a resol type phenol resin is added and kneaded. As the kneading progresses, the temperature of the refractory aggregate decreases to the softening point of the phenol resin, and the refractory aggregate enters a dry state. Then, calcium stearate, zinc stearate, and the like are added to the refractory aggregate and mixed to obtain a resin-coated sand. The obtained resin-coated sand has characteristics of hardly causing blocking, low odor and high strength.

The present invention will be described in more detail with reference to the following examples. Note that the present invention is not limited to these examples. [Example 1] 400 g of phenol, 50% formalin 1
79 g was charged into a reaction vessel, and 4 g of oxalic acid was added to add 10 g.
The reaction was performed at 0 ° C. for 4 hours. Reactant temperature is 180 at normal pressure
The solution was dehydrated and concentrated until the temperature rose to ℃ to obtain an initial condensate of a novolak type phenol resin. To 100 parts by weight of this initial condensate, 1 part by weight of γ-aminopropyltriethoxysilane and 1 part by weight of ethylenebisstearamide were added to obtain a novolak type phenol resin (binder A)
). Next, 300 g of phenol and 387 g of 42% formalin were charged into a reaction vessel, and 25% aqueous ammonia 1
5 g and 24 g of a 40% aqueous solution of hexamethylenetetramine were added and reacted at 60 ° C. for 3 hours. Dehydration concentration was performed under a reduced pressure of 15 kPa until the temperature of the reaction product increased to 60 ° C.
An initial condensate of a resol type phenol resin was obtained. The saponification degree is 88 mol% based on 100 parts by weight of the initial condensate,
After adding 300 g of a 7% aqueous solution of polyvinyl alcohol having an average degree of polymerization of 1,700 and uniformly stirring the mixture, the mixture was cooled to room temperature to obtain an oil-in-water type fine particle size resole phenol resin emulsion (referred to as curing agent A). ). The non-volatile component of this resol-type phenol resin emulsion was 105
It was 50% by weight as a result of measurement at 3 ° C. for 3 hours. Using a speed mixer for hot coat made by Enshu Tekko, flattery sand is used as a fire-resistant aggregate. For 100 parts by weight (8 kg) of the refractory aggregate previously heated to 140 ° C., 1 part by weight of the binder A obtained above (8 parts by weight)
0g) After addition and heat melting to uniformly coat the surface of the refractory aggregate, 2 parts by weight (1
60 g) of the curing agent A is added and kneaded. As the kneading progresses, the water evaporates and changes to a dry state. Next, 0.1 part by weight (8 g) of calcium stearate was added and mixed with 100 parts by weight of the refractory aggregate, and sand was removed from the mixer to obtain a resin-coated sand. The obtained resin-coated sand was free of lumps and wetness, and had an appearance similar to that of a resin-coated sand made of a normal novolak resin. The fusion point of the obtained resin-coated sand was measured (according to JACT test method C-1). The obtained resin coated sand was heated to 10 × 1 using a mold.
A test piece of 0 × 60 mm was molded under the conditions of baking at 250 ° C. for 60 seconds, and the bending strength was measured (JACT test method S
M-1). Resin coated sand 5 obtained
0 g was calcined at 300 ° C. for 5 minutes, and the amount of formaldehyde in the generated gas was measured. The obtained resin coated sand is placed in a container at a temperature of 30 ° C. and a humidity of 70%.
It was left for a week to check the occurrence of blocking (JAC
According to T test method C-4). [Example 2] 5 parts by weight of urea was added to the above-mentioned resole type phenol resin emulsion (curing agent A) based on 100 parts by weight of the resole type phenol resin in terms of solid content,
A resol type phenol resin emulsion was obtained (referred to as curing agent B). 1 part by weight (80 g) of binder A obtained in Example 1 per 100 parts by weight of refractory aggregate, curing agent B
Was used in the same manner as in Example 1 to obtain a resin-coated sand. The same measurement as in Example 1 was performed on the obtained resin coated sand. Example 3 1 part by weight of γ-aminopropyltriethoxysilane and 1 part by weight of ethylene were added to the above resole type phenol resin emulsion (curing agent A) based on 100 parts by weight of the resole type phenol resin in terms of solid content. Bisstearoamide was added to obtain a resole type phenol resin emulsion (referred to as curing agent C). A method similar to that of Example 1 using 1 part by weight (80 g) and 2 parts by weight (160 g) of hardener C per 100 parts by weight of the refractory aggregate obtained in Example 1 above. To obtain a resin coated sand. The same measurement as in Example 1 was performed on the obtained resin coated sand. Example 4 5 parts by weight of hexamethylenetetramine was added to the above-mentioned resol-type phenolic resin emulsion (curing agent A) based on 100 parts by weight of the resol-type phenolic resin in terms of solid content, to give a resol-type phenolic resin emulsion. (Referred to as curing agent D). A method similar to that of Example 1, except that 1 part by weight (80 g) of binder A obtained in Example 1 and 100 parts by weight of refractory aggregate and 2 parts by weight (160 g) of hardener D are used. To obtain a resin coated sand. The same measurement as in Example 1 was performed on the obtained resin coated sand. Comparative Example 1 1.5 parts by weight (120 g) of water to 100 parts by weight (8 kg) of refractory aggregate and 15 parts by weight (24 g) of hexamethylenetetramine to 100 parts by weight of binder A were added. A molten aqueous solution was obtained (referred to as curing agent E).
Using 2 parts by weight (160 g) of binder A obtained in Example 1 with respect to 100 parts by weight of the refractory aggregate and 144 g of hardener E, resin coat sand was prepared in the same manner as in Example 1. I got The same measurement as in Example 1 was performed on the obtained resin coated sand. [Comparative Example 2] Using 4 parts by weight (320 g) of the curing agent A obtained in Example 1 with respect to 100 parts by weight of the refractory aggregate,
Resin coated sand was obtained in the same manner as in Example 1. The same measurement as in Example 1 was performed on the obtained resin coated sand. [Comparative Example 3] 300 g of phenol, 42% formalin 2
74 g was charged into a reaction vessel, and 30 g of 25% aqueous ammonia was added.
Was added and reacted at 60 ° C. for 3 hours. The reaction product was dehydrated and concentrated under a reduced pressure of 15 kPa until the temperature of the reaction product rose to 90 ° C. to obtain a solid resol-type phenol resin (referred to as a binder B). The binder B obtained above is used for the refractory aggregate 100
Resin coated sand was obtained in the same manner as in Example 1 using 2 parts by weight (160 g) and 1.5 parts by weight (120 g) of water with respect to parts by weight. The same measurement as in Example 1 was performed on the obtained resin coated sand. When the obtained resin-coated sand was left in a container at a temperature of 30 ° C. and a humidity of 70% for one week, the resin-coated sand was blocked to the extent that it could be broken down by hand (according to JACT test method C-4).
Tables 1 and 2 show the characteristics of the resin-coated sands of Examples 1 to 4 and Comparative Examples 1 to 3.

[Table 1] (Note) RCS in the table stands for resin coated sand.

[Table 2] (Note) RCS in the table stands for resin coated sand.

According to the present invention, the following effects can be obtained by using a resol type phenol resin emulsion or suspension as a hardener and a novolak type phenol resin as a binder. (1) A resin-coated sand having low odor is obtained. (2) A resin-coated sand from which a high-strength mold can be obtained can be manufactured. (3) A resin coated sand having difficult blocking properties is obtained. (4) No new equipment or equipment is required for the production of resin-coated sand.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hitoshi Mashio 700, Shukudaidaicho, Takasaki City, Gunma Prefecture Inside Gunei Chemical Industry Co., Ltd.

Claims (7)

[Claims] 1. A refractory aggregate 1 heated to 100 to 180 ° C.
With respect to 00 parts by weight, 0.5 to 5 parts by weight of a novolak type phenol resin is added, melt-kneaded, and the novolak type phenol resin is uniformly coated on the surface of the refractory aggregate.
0.5 to 5 parts by weight of a resol type phenol resin emulsion or suspension was added, and further kneaded to evaporate and remove volatile components to coat the resin component on the surface of the refractory aggregate. Low odor, high strength, difficult blocking A method for producing a resin coated sand for shell mold molding having a property. 2. A resol type phenol resin emulsion or suspension reacts a phenol with an aldehyde under a basic catalyst, and the emulsifier is used in an amount of 1 to 20 parts by weight based on 100 parts by weight of the resol type phenol resin in terms of solid content. The method for producing a resin-coated sand for shell mold casting according to claim 1, further comprising a colloid protective agent. 3. The resol-type phenolic resin emulsion or suspension contains 1 to 30 parts by weight of an organic nitrogen compound based on 100 parts by weight of the resol-type phenolic resin in terms of solid content. 2
A method for producing the resin-coated sand for shell molding described in the above. 4. The method of claim 3, wherein the organic nitrogen compound is urea, a urea compound, an amide compound, an amine compound, a triazine compound, an imide compound, or an amino acid compound. 5. The resol-type phenol resin emulsion or suspension contains 0.1 to 5 parts by weight of a coupling agent based on 100 parts by weight of the resol-type phenol resin in terms of solid content. One, two
4. The method for producing the resin-coated sand for shell mold casting according to any one of the above items 3 and 3. 6. The resol-type phenol resin emulsion or suspension contains 0.1 to 5 parts by weight of a lubricant based on 100 parts by weight of the resol-type phenol resin in terms of solid content. 2, 3, and 5
The method for producing a resin-coated sand for shell mold molding according to any one of the above. 7. The resol-type phenol resin emulsion or suspension contains 1 to 15 parts by weight of hexamethylenetetramine based on 100 parts by weight of the resol-type phenol resin in terms of solid content. 7. The method for producing a resin-coated sand for shell mold casting according to any one of 3, 5, and 6.