JPH04147743A - Manufacture of mold or core - Google Patents

Abstract

PURPOSE:To manufacture a mold having excellent mold strength and surface stability and a little deterioration caused by moisture absorption by using organic series binder and carbon dioxide. CONSTITUTION:Molding sand and the undermentioned component of binder, i.e., containing 60-96wt% alkali phenol form-aldehyde resin water solution, 3-20wt% alkali metal borate and 1-20wt.% glycol ether group and/or furfuryl alcohol, are mixed and molded. The carbon dioxide gas is permeated to this and cured to manufacture a mold or a core. The carbon dioxide gas used in this invention, is low toxicity, and as toxic gas used in, such as 'Isocure process' and 'Hardex process', is unnecessary, this is desirable on the working surroundings and sanitation, and as the binder containing no nitrogen bringing about gas defect, etc., in the casting, is used, the quality of casting is improved.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method for manufacturing a mold or core.

Specifically, by mixing foundry sand and a specific organic binder, molding the mixture, and then curing it by aerating carbon dioxide gas, it is possible to create molds or medium-sized molds with excellent mold strength and surface stability, and with little moisture deterioration. Concerning a method of producing children.

Conventional technology The method for producing molds or cores using gas-curing binders is to mix an inorganic binder such as water glass with foundry sand, mold the mixture, and then harden it with carbon dioxide gas (carbon dioxide). (gas curing method), a method in which a mixture of a benzylic ether type phenol resin and a polyisocyanate is mixed into molding sand, the molded product is then hardened with amine gas (ink core method), a mixture of furan resin and peroxide is mixed into molding sand A method of curing the mixed and molded material with sulfur dioxide gas (Burdox method) is known. However, the carbon dioxide curing method that uses an inorganic binder has problems such as poor mold disintegration after casting, increased finishing time, poor sand recovery, and environmental damage caused by waste sand. .

On the other hand, the isocure method and bardox method, which use organic binders, have better mold disintegration and sand recovery than the carbon dioxide curing method, which uses inorganic binders.
Not only is this method undesirable in terms of working environment hygiene due to the use of toxic gas, but also there is the problem that gas defects, soot defects, and Hoening defects are likely to occur in castings because the binder component contains nitrogen needles.

Therefore, in recent years, attempts have been made to use organic binders and harden them with low-toxic carbon dioxide gas. For example, there is a method in which carbon dioxide gas is bubbled through a mixture of foundry sand and an alkaline phenol-formaldehyde resin aqueous solution, and a method in which a binder containing an alkali metal salt of boric acid is added to the above-mentioned alkaline phenol-formaldehyde resin aqueous solution and foundry sand. Methods of venting carbon dioxide gas have been proposed, but all of them have problems in that the strength of the casting is low, the surface stability is poor, and furthermore, it deteriorates due to moisture absorption under high humidity.

Problems to be Solved by the Invention The present invention provides a method for manufacturing a mold or core with excellent mold strength and surface stability, and with little moisture deterioration, using an organic binder and carbon dioxide gas. The purpose is to

Means for Solving the Problems The present invention provides foundry sand and the following components (a) to (c) (a) alkaline formaldehyde resin aqueous solution 60 to
(b) 3 to 20% by weight of an alkali metal salt of boric acid (C) A binder containing 1 to 20% by weight of glycol ethers and/or furfuryl alcohol are mixed and molded, and then carbonated The present invention relates to a method for manufacturing a mold or core, which is characterized by curing by passing gas through it.

The present invention will be explained in detail below.

Examples of the alkali metal in the alkaline phenol formaldehyde resin aqueous solution used in the present invention include lithium, sodium, potassium, and the like.

The molar ratio of phenol and alkali metal is phenol:alkali metal=i, O:Q, 4 to 1.0:2.5, preferably 1.0:1.0 to 1.0:2.0. If the molar ratio is less than 1.0:0.4, the water solubility of the resin will be poor, and if it is greater than 1.0:2.5, insufficient strength will be obtained. One or more alkali metals may be present in the reaction system, or may be added after the reaction is complete. The molar ratio of phenol to formaldehyde 1 is 1
．． 0:1.0-103, O1 preferably 1.0:1.2
~1.0:2.5. If the molar ratio is less than 1.0:1.0, the strength obtained will be insufficient, and if the molar ratio is more than 1°0.30, not only will the viscosity of the resin increase, but the formaldehyde The working environment deteriorates due to the irritating odor.

Alkaline phenol formaldehyde resin is 30~
Prepare a 70% by weight aqueous solution. If the resin content is less than 30% by weight, the water content is too high and the strength of the mold or core is insufficient, and if the resin content is more than 70% by weight, the viscosity of the resin becomes high, causing problems in handling. .

The amount of the aqueous alkaline formaldehyde resin solution based on the total amount of the binder is 60 to 96% by weight, preferably 75 to 90% by weight. If the blending amount is less than 60% by weight, the strength immediately after aeration of carbon dioxide gas will be insufficient, and
If it exceeds 96% by weight, the effect of improving mold strength will be small.

Examples of the alkali metal salt of boric acid used in the present invention include sodium borate and potassium borate.

The alkali metal salt of boric acid is used by being added and dissolved in an aqueous alkaline phenol formaldehyde resin solution.

The amount of the alkali metal salt of boric acid added to the total amount of the binder is 3 to 20% by weight, preferably 5 to 15% by weight.

If the amount is less than 3% by weight, the strength immediately after carbon dioxide gas ventilation is insufficient and is not practical, and if it is more than 20% by weight, not only the viscosity of the resin increases but also the strength obtained decreases.

Typical examples of glycol ethers used in the present invention include diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, ethylene glycol monomethyl ether, ethylene glycol, monoethyl ether, ethylene glycol monopropyl ether, Ethylene glycol-motsbutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether,
/Ethylene glycol monopropyl ether, diethylene glycol monobutyl ether, Brochtung glycol monomethyl ether, and dipropylene glycol monomethyl ether.

The amount of glycol ethers and/or furfuryl alcohol based on the total amount of the binder is 1 to 20% by weight,
Preferably it is 3 to 15% by weight.

When the amount is less than 1% by weight, the effect of improving the strength and surface stability of the mold is small, and when it is more than 20% by weight, the effect on mold strength and surface stability is reduced, and it is not economical.

Examples of foundry sand used in the present invention include silica sand, olivine sand, chromite sand, and zircon sand.

In the present invention, a mold or a core can be manufactured by mixing the foundry sand and a binder, molding the mixture into a desired shape, and then passing carbon dioxide through the mixture.

The binder of the present invention may contain 6 L of a 7-rankanobbling agent in order to improve the caking properties of the alkaline phenol formaldehyde resin and foundry sand. Preferred examples of antiblining agents include γ-aminopropyltriethoquinone, γ-(2-aminoethyl)aminofuropyltrimethoquinone, and the like.

The amount of the binder added to 100 parts by weight of foundry sand is 0.
．． The amount is 4 to 10 parts by weight, preferably 0.8 to 5 parts by weight.

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

Examples 1 to 5 and Comparative Example 1 Phenol 949 was charged into a 1e four-bottle flask equipped with a thermometer, a stirrer, and a condenser, and 50% was added to it without stirring.
101 g of potassium hydroxide and 65.2 y of 92% paraformaltehyde were gradually added.

Next, this solution was heated to 90°C and reacted at 90'C for 3 hours to obtain an alkali phenol formaldehyde resin.

Next, 12'3.49 50% potassium hydroxide, 309 borax and 1.9 g of γ-aminopropyltriethoxysilane were added to the alkali phenol formaldehyde resin which had been cooled to below 40°C after the completion of the reaction, and the alkali phenol formaldehyde resin was added. A solution was obtained.

Preparation of Binder> To the alkali phenol formaldehyde resin solution, 10% by weight of various glycol ethers or frifuryl alcohol shown in Table 1 were added and mixed to prepare a binder.

<Performance evaluation> Silica sand (product name "Miura 6 Kosand", manufactured by Mikawa Siliceki Co., Ltd.) 1
The above-mentioned binder 359 was added to Step 9 and kneaded for 1 minute.

This kneaded sand was molded into a test wooden mold (50φX 50 bmm, 6
After molding the carbon dioxide gas at a flow rate of 2012/mi
The mixture was cured by bubbling with n for 60 seconds.

Using the obtained cured test piece, immediately after ventilation and at 20°C 60%RH
Then, the compressive strength and surface stability were measured after being left for 24 hours in an atmosphere of 20'C-100% RH. The results are shown in Table-1.

Compressive strength was measured using an Amsler compression tester.

Surface stability was calculated by shaking a standard 50φ x 50hmm test piece for 60 seconds on a sieve with a mesh size of 3360μ and using the following formula.

Examples 6 to 12 Preparation of binder> For the same alkali phenol formaldehyde resin solution as used in Examples 1 to 5 and Comparative Example 1,
A diethylene glycol monobutythyl ether binder was prepared as shown in 2.

<Performance evaluation> Performance evaluation was performed in the same manner as in Examples 1 to 5. The results are shown in Table-2.

Examples 13 to 15 Preparation of binder Table 3
A binder was prepared by adding and mixing 5% by weight of the various glycol ethers shown below.

Performance Evaluation> 35 g of the above-mentioned binder was added to silica sand (trade name ``Miura 6 Kosan'', manufactured by Mikawa Siliceki Co., Ltd.) and kneaded for 1 minute.

After molding this mixed sand into a test wooden mold (50φx5Qhmm, 6 pieces), carbon dioxide gas was applied at a pressure of 2,0 kg/
ctn'' and a flow rate of 20 ρ/min for 60 seconds to cure.

Immediately after aeration and at 20'C-6 using the obtained cured test piece.
The compressive strength was measured after being left for 24 hours in an atmosphere of 0% RH. The results are shown in Table-3.

Effects of the Invention According to the method of the present invention, it is possible to produce a mold or core that has excellent mold strength and surface stability, and is less susceptible to deterioration due to moisture absorption.

In addition, since the present invention hardens the mold with low-toxic carbon dioxide gas, it does not require toxic gas unlike the conventional isocure method, hard method, and lath method, which is preferable in terms of working environment hygiene. Using a binder that does not contain nitrogen needles improves the quality of the casting.

Claims (1)

[Claims] 1. Foundry sand and the following components (a) to (c) (a) 60 to 96% by weight of an alkaline phenol formaldehyde resin aqueous solution (b) 3 to 20% by weight of an alkali metal salt of boric acid (c ) A method for producing a mold or core, which comprises mixing a binder containing 1 to 20% by weight of glycol ethers and/or furfuryl alcohol, molding the mixture, and then curing by blowing carbon dioxide gas through the mixture. .