JP2000015390A - Binder composition for carbon dioxide curing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the surface stability of a casting mold while maintaining high casting mold strength by using a compsn. contg. a water-soluble phenolic resin for carbon dioxide curing and phosphate. SOLUTION: The water-soluble phenolic resin for carbon dioxide curing is composed of an aq. alkaline resol phenolic resin soln.; an oxyanion compd. and preferably other additives for improving the casting mold strength. The particularly preferable phosphate to be added is expressed by formula, where R1, R2, R3 are 1-8C alkyl group and aryl group into which ether groups may be inserted. Such phosphate is more specifically, trimethyl phosphate, triethyl phosphate, tributyl phosphate, tributoxyethyl phosphate, triphenyl phosphate, triisopropyl phosphate, tricredyl phosphate and tri-2-ethylhexyl phosphate. These materials may be used in combination of >=2 kinds.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a binder composition for curing carbon dioxide, which is used when a mold is formed using carbon dioxide as a curing agent, and a mold composition for curing carbon dioxide containing the same.

[0002]

2. Description of the Related Art As a binder used for producing a mold, an organic binder which is excellent in safety and can be cured with carbon dioxide has been receiving attention.

[0003] Organic binders curable by carbon dioxide are disclosed, for example, in Japanese Patent Publication No. 4-76947 and Japanese Patent No. 2723376. Further, as an improvement in the mold strength of such a binder, JP-A-4-147743, JP-A-5-320477, and JP-A-8-206775 disclose glycol ethers, pyrrolidone compounds and the like as binder resins. It discloses using it as an additive. However, the binder containing these additives does not sufficiently improve the strength of the mold, and has poor surface stability of the mold.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a binder capable of improving the surface stability of a mold while maintaining high mold strength.

[0005]

SUMMARY OF THE INVENTION The present invention is a binder containing a water-soluble phenolic resin for curing carbon dioxide and a phosphate ester.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The water-soluble phenolic resin for curing carbon dioxide of the present invention comprises an aqueous solution of an alkaline resole phenolic resin, an oxyanion compound, and preferably other additives for improving the strength of the mold.

An aqueous solution of an alkaline resole phenolic resin is prepared by converting phenols in the presence of a large amount of an alkaline substance.
It can be obtained by reacting with aldehydes in water. The phenols may be one kind selected from a phenol compound and a bisphenol compound, or a mixture of two or more kinds or a co-condensation resin. Examples of the phenol compound include phenol, cresol, resorcinol, 3,5-xylenol, novolak phenol, and other substituted phenols.As the bisphenol compound,
Bisphenol A, bisphenol F, bisphenol S and the like can be mentioned. Aldehydes include formaldehyde, acetaldehyde, furfural and the like and mixtures thereof. The aldehyde is preferably 1.0 to 6.0 moles, more preferably 1.1 to 5.5 moles, based on the phenol.

As the alkaline substance, it is preferable to use an alkali metal hydroxide in an amount of 0.01 to 6.0 times, preferably 0.1 to 5.0 times the mole of the phenol.
Preferred alkali metal hydroxides are sodium hydroxide, potassium hydroxide, lithium hydroxide and mixtures thereof, with potassium hydroxide being most preferred.

The reaction conditions may be appropriately determined according to the desired molecular weight.
It is preferably set to 10 to 300 mPa · S, for which 25 to 9
The reaction solution of 0% by weight may be reacted at 50 to 100 ° C. for 0.5 to 10 hours.

The oxyanion compound is a boric acid compound such as borax or boric acid, and is indispensable for the organic carbon dioxide curing method. This is because it is considered that the ionomer is formed only after the oxyanion compound absorbs carbon dioxide, and the water-soluble phenolic resin is polymerized. Borates such as boric acid, sodium tetraborate decahydrate (borax), potassium tetraborate decahydrate, sodium metaborate, sodium pentaborate and potassium pentaborate are preferred. The amount of the oxyanion compound added to 100 parts by weight of the aqueous solution of the alkaline resole phenolic resin is determined based on the curing speed and strength of the mold.
0.1 to 30 parts by weight, preferably 3 to 15 parts by weight are good. Other oxyanion compounds include aluminates, stannates and the like.

For the purpose of improving the mold strength, for example, γ-
Silane coupling agents such as aminopropyltriethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, and γ-glycidoxypropyltriethoxysilane can be used. These may be added to the kneading sand and used, but are preferably used in combination with the binder composition. The addition amount is 0.01 to 10 parts by weight, preferably 0.1 to 5.0 parts by weight based on 100 parts by weight of the aqueous solution of the alkaline resole phenolic resin.

In the present invention, a phosphate ester is added to a water-soluble phenolic resin for curing carbon dioxide. The phosphate ester of the present invention refers to a compound represented by the formula (1).

[0013]

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(R ₁ , R ₂ , R ₃ : a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms into which an ether group may be inserted, at least one of which is a hydrocarbon group) In the ester, R ₁ , R ₂ , and R ₃ are an alkyl group or an aryl group having 1 to 10 carbon atoms into which a hydrogen atom or an ether group may be inserted, and specifically, methyl phosphate, ethyl phosphate, Butyl phosphate, butoxyethyl phosphate, phenyl phosphate, isopropyl phosphate, cresyl phosphate, 2-ethylhexyl phosphate, dimethyl phosphate, diethyl phosphate, dibutyl phosphate, dibutoxyethyl phosphate, diphenyl phosphate, phosphorus Diisopropyl acid, dicresyl phosphate, di-2-ethylhexyl phosphate, trimethyl phosphate, triethyl phosphate, tributyl phosphate, tributoxyethyl phosphate, trife phosphate Le, phosphoric acid triisopropyl phosphate, tricresyl phosphate, phosphoric acid tri-2-ethylhexyl. Phosphoric acid triesters are more preferred,
Particularly preferably, R ₁ , R ₂ , and R ₃ are each an alkyl group or an aryl group having 1 to 8 carbon atoms into which an ether group may be inserted, and specifically, trimethyl phosphate, triethyl phosphate, phosphorus Tributyl acid, tributoxyethyl phosphate, triphenyl phosphate, triisopropyl phosphate, tricresyl phosphate, and tri-2-ethylhexyl phosphate. These may be used as a mixture of two or more.

These phosphoric esters are used by being added to the binder composition, but may be added at the stage of synthesizing the water-soluble phenolic resin for curing carbon dioxide. The addition amount is preferably 0.1 to 30 parts by weight, more preferably 1 to 20 parts by weight, based on 100 parts by weight of the water-soluble phenolic resin for curing carbon dioxide in order to efficiently achieve the object of the present invention.

The solid content (2 g of the binder composition dried at 105 ° C. for 3 hours) of the binder composition for curing carbon dioxide of the present invention is used to obtain excellent mold strength by uniform kneading with molding sand. Preferably 30 to 90% by weight, more preferably 40 to 85% by weight
It is.

In the case of molding using the binder composition of the present invention, the refractory granular material and the binder composition of the present invention are kneaded with a mixer or the like, and the kneading sand is filled in a gas curing mold model. After that, carbon dioxide gas is ventilated to form a mold. When kneading using a mixer, a refractory granular material 100
The binder composition of the present invention is preferably 0.1 parts by weight.
To 15 parts by weight, more preferably 0.5 to 5 parts by weight. The amount of carbon dioxide used is 0.01 to 30 parts by weight, preferably 0.1 to 15 parts by weight, based on 100 parts by weight of the refractory granular material in order to prevent uncuring of the mold and maintain the productivity of the mold. The carbon dioxide gas may be aerated by a reduced pressure substitution hardening method.

As a method for obtaining kneaded sand, a water-soluble phenolic resin for curing carbon dioxide and a phosphoric acid ester may be prepared in advance, and these may be separately added to the refractory granular material and kneaded. The phosphate ester can also be used in a solvent solution or dispersion using a lower alcohol, a polyhydric alcohol, acetone, an ester compound, or the like. At this time, the amount of the water-soluble phenolic resin for curing carbon dioxide is 0.1 to 10 parts by weight based on 100 parts by weight of the refractory granular material.
It is preferable that the amount of the phosphoric acid ester be 0.001 to 5 parts by weight, and the obtained kneaded sand can be used to form a mold as described above.

Examples of the refractory granular material include quartz sand, chromite sand, zircon sand, olivine sand, and the like.
Examples include alumina sand, mullite sand, synthetic mullite sand, and alumina ball sand. As the refractory granular material, fresh sand, reclaimed sand, or a mixed sand thereof can be used.

The binder composition, the mold composition and the mold obtained by the molding method of the present invention can be used for the production of non-ferrous alloys such as aluminum castings, cast steels and cast iron castings. Absent.

[0021]

The use of the binder composition of the present invention can improve the surface stability of a mold while maintaining high mold strength.

[0022]

EXAMPLES In the following examples, kneading and molding conditions were 25
° C and 60% RH. [Synthesis Examples 1 to 4 of aqueous phenol resin aqueous solution for curing carbon dioxide gas] A solution of an alkali compound (A) and a phenol (P) in a molar ratio shown in Table 1 is shown in Table 1 with respect to phenol at 70 ° C. The molar ratio of the aldehyde compound (F) was gradually added. The temperature was raised to 80 ° C., and the reaction was continued until the viscosity of the aqueous solution of the water-soluble phenolic resin in the reaction solution reached 83 mPa · s at 25 ° C. 8% by weight of borax, γ-
1% by weight of aminopropyltriethoxysilane is added,
A resin aqueous solution was obtained.

[0023]

[Table 1]

Examples 1 to 18 and Comparative Examples 1 to 5 [Adjustment of Blending of Binder Composition for Curing Carbon Dioxide Gas]
10% by weight of the additives shown in Table 2 in the resin solution obtained in
By adding and blending, a binder composition for curing carbon dioxide gas was prepared. [Measurement of mold strength] To 1.5 kg of Mikawa R6 silica sand with a sand temperature of 25 ° C,
45 g of each of the binder compositions shown in Table 2 were added, kneaded with a batch mixer for 1 minute, and filled into a gas curing wooden mold having eight test pieces of 50 mmφ × 50 mmh.
30 liters of carbon dioxide gas at an air flow rate of 20 l / min and a gas pressure of 0.2 MPa
Aerated for seconds. Then, immediately remove the test piece,
After standing for 24 hours, the coercive pressure (mold strength) and the surface stability were measured. The surface stability was calculated by shaking the test piece on a sieve having a mesh of 1680 μm for 120 seconds and following the formula below. Table 2 shows the results.

[0025]

(Equation 1)

[0026]

[Table 2]

Examples 19 to 23 and Comparative Example 6 The binder obtained in Synthesis Example 1 was mixed with the amount of triethyl phosphate shown in Table 3 and the mold strength and surface stability were measured in the same manner as described above. .

[0028]

[Table 3]

Examples 24 to 25 and Comparative Example 7 2.7 parts by weight of the binder composition obtained in Synthesis Example 1 and 0.3 parts by weight of the additives shown in Table 4 were prepared, and 100 parts by weight of domestic silica sand No. 7 was prepared. The mixture was kneaded with a mixer, and the pressure resistance and surface stability after 24 hours were evaluated in the same manner as described above.

[0030]

[Table 4]

Claims (5)

[Claims] 1. A binder composition for curing carbon dioxide, comprising a water-soluble phenolic resin for curing carbon dioxide and a phosphate ester. 2. The binder composition for curing carbon dioxide according to claim 1, wherein the phosphate ester is contained in an amount of 0.1 to 30 parts by weight based on 100 parts by weight of the water-soluble phenolic resin. 3. The binder composition for hardening carbon dioxide according to claim 1, wherein the phosphate ester is a phosphate triester. 4. A mold for curing carbon dioxide containing 0.1 to 15 parts by weight of the binder composition for curing carbon dioxide according to claim 1 with respect to 100 parts by weight of the refractory granular material. Composition. 5. A mold composition for hardening carbon dioxide, comprising 0.1 to 10 parts by weight of a water-soluble phenolic resin for hardening carbon dioxide and 0.001 to 5 parts by weight of a phosphoric ester based on 100 parts by weight of the refractory granular material.