JPH08301941A - Binder for production of inorganic sinter and inorganic sinter - Google Patents

Abstract

PURPOSE: To provide a binder which decomposes gently under the firing and sintering conditions and gives a sinter free from any undecomposed carbide and to provide an inorganic sinter produced by using the same. CONSTITUTION: A binder for the production of an inorganic sinter, containing a copolymer of an alkylene glycol vinyl ether of the formula: CH2 =CHO(AO)n R (wherein A is 2-4 C alkylene; R is H or 1-4 C alkyl; and n is an integer of 1-20) with maleic anhydride, and an inorganic sinter produced by using this binder.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a binder for producing an inorganic sintered body.

[0002]

2. Description of the Related Art In the production of various types of sintered compacts, inorganic powders such as ferrite, alumina, silica, zirconia, mullite and barium titanate are mixed with an organic polymer binder such as polyvinyl alcohol to produce green compacts. A method of firing this to sinter the inorganic powder while decomposing and scattering the binder is widely used. However, when heating a normal green compact molded using an organic polymer binder, part of the organic polymer binder does not decompose and burn out, and remains as carbide in the sintered body or is rapidly decomposed and scattered during the sintering process. As a result, the molded body may crack, warp or swell,
Further, there is a problem that density is reduced and the sintered body becomes fragile due to the presence of carbides remaining in the sintered body and void defects caused by the rapid decomposition and scattering of the binder. No binder is obtained.

[0003]

DISCLOSURE OF THE INVENTION The present invention aims to solve the above-mentioned problems and gently decomposes and scatters under firing and sintering conditions, and remains as undecomposed carbide in the sintered body. As a result of conducting a research on a binder for producing an inorganic sintered body without doing, it was found that a binder containing a copolymer of alkylene glycol vinyl ether and maleic anhydride achieves the above object. Obtained.

[0004]

That is, the present invention comprises a copolymer of alkylene glycol vinyl ether represented by the following general formula (I) and maleic anhydride for producing an inorganic sintered body. The present invention relates to a binder and an inorganic sintered body produced using the binder. General formula (I)

Embedded image (A in the formula is an alkylene group having 2 to 4 carbon atoms, R is hydrogen or an alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 20)

The alkylene glycol vinyl ether used in the present invention is a polyalkylene glycol and / or an alkyl polyalkylene glycol vinyl ether. Examples of the vinyl ether include vinyl ether compounds of alkylene oxide adducts having 2 to 4 carbon atoms such as ethylene oxide (EO), propylene oxide (PO), and tetramethylene oxide (TMO), and the above alkylene oxides of alcohols having 4 or less carbon atoms. The vinyl ether form of an adduct is mentioned. Also these 1
It may be one kind or a mixture of two or more kinds. When the alkyl group of the alkylene glycol vinyl ether has 5 or more carbon atoms, it becomes hydrophobic and sufficient water dispersibility may not be obtained. The average number of moles of alkylene oxide added to alkylene glycol vinyl ether is 1 to
Used in the range of 20 mol. If the average number of moles of alkylene oxide added exceeds 20, it is not preferable because abrupt decomposition and scattering occur under firing and sintering conditions, and cracks or warp swelling occur in the molded body.

The alkylene glycol vinyl ether used in the present invention can be produced by a known method. For example,
It is obtained by the Reppe reaction of acetylene with polyalkylene glycol and / or alkyl polyalkylene glycol.

The maleic anhydride used in the present invention includes
It may contain a maleic anhydride derivative or an α, β-unsaturated carboxylic acid such as citraconic anhydride or itaconic anhydride.

As the molecular weight of the copolymer of alkylene glycol vinyl ether and maleic anhydride used in the present invention, the weight average molecular weight measured by GPC is preferably 10,000 to 1,000,000 in terms of polyethylene glycol, and more preferably 100,000 to 500,000.
When the weight average molecular weight is less than 10,000, the binding force as a binder is lowered and sufficient green moldability and shape retention cannot be obtained, and when the weight average molecular weight exceeds 1,000,000, the viscosity as a binder increases due to an increase in viscosity. Workability may be reduced.

A known polymerization method can be applied to the method for producing the copolymer used in the present invention. The charge ratio of alkylene glycol vinyl ether and maleic anhydride is
Although it can be arbitrarily selected, it is preferable to use 1 mol or more of alkylene glycol vinyl ether per 1 mol of maleic anhydride in order to achieve a complete reaction rate of maleic anhydride.

The polymerization operation is benzoyl peroxide,
Using a radical initiator such as azobisisobutyronitrile, usually benzene, toluene, benzene derivatives such as ethylbenzene, ethyl acetate, esters such as isopropyl acetate, ketones such as methyl ethyl ketone and methyl isobutyl ketone, carbon tetrachloride, Radical copolymerization is performed at a temperature of 5 to 150 ° C. in a solvent such as an organic halide such as chloroform. It is also possible to dissolve maleic anhydride in alkylene glycol vinyl ether without using a solvent and then perform bulk polymerization with the above-mentioned radical initiator. In addition, within the range that does not change the characteristics of the obtained copolymer,
It is also possible to copolymerize olefins such as styrene and α-olefins, and monomers such as alkyl vinyl ethers such as methyl vinyl ether and ethyl vinyl ether. Further, the obtained copolymer can also be used as an alkali salt excluding alkali metal. As the alkali salt, ammonium salt and organic amine salt are preferable.

The kind of the inorganic powder used in combination with the binder for producing an inorganic sintered body of the present invention is not particularly limited, and examples thereof include oxides such as alumina, silica, zirconia, ferrite, mullite, barium titanate. And other complex oxides.

As a general method for producing an inorganic sintered body using the binder of the present invention, the inorganic powder as described above is uniformly kneaded with the binder of the present invention and a suitable solvent, and then, if necessary. After defoaming, it is molded into an arbitrary shape to obtain a green molded body. As a molding method, a conventional method such as press molding or extrusion molding can be adopted. Further, the green compact is heat-treated to remove the binder and fire and sinter.

The amount of the binder of the present invention to be used can be appropriately determined depending on the kind of the inorganic powder, the processability of the green molded product, the desired properties, etc., but the copolymer component of the present invention is added to 100 parts by weight of the inorganic powder. 1 to 30 parts by weight is suitable in terms of conversion. At this time, as long as there is no hindrance, dispersants (esters of polyhydric alcohols such as glycerin and sorbitan, amine dispersants, etc.), plasticizers (polyethylene glycol, etc.), or sintering aids (glass powder, magnesia, etc.) It is also possible to mix an appropriate amount.

[0014]

EXAMPLES Hereinafter, examples and comparative examples will be described in more detail. Production Example of Copolymer (1) A glass autoclave equipped with a thermometer, a stirrer, a suitable device, and a nitrogen gas introducing tube was charged with 72 g of methoxytriethylene glycol vinyl ether, 40 g of maleic anhydride and 448 g of methyl ethyl ketone, and a nitrogen atmosphere. Heated below to 80 ° C. To this, 100 ml of an initiator solution consisting of a 1% by weight methyl ethyl ketone solution of azobisisobutyronitrile was added, and a polymerization reaction was carried out for 10 hours. The polymerization rate at this time was 100%. Then, the solvent was removed by drying under reduced pressure to obtain a copolymer (1). The weight average molecular weight of this copolymer was 200,000.

Copolymers (2) to (3) and comparative polymers
Production Example of (1) By changing the composition of raw materials, as in the production example of the copolymer (1),
Methoxypolyethylene glycol vinyl ether and maleic anhydride were charged and a polymerization reaction was carried out. Table 1 shows the weight average molecular weights of the methoxy polyethylene glycol vinyl ether used and the copolymer obtained.

[0016]

[Table 1]

(Note) 1) Average number of moles of ethylene oxide (EO) added per molecule of methoxy polyethylene glycol vinyl ether used. 2) Measured by GPC manufactured by Tosoh Corporation, and calculated based on polyethylene glycol- and polyethylene oxide-converted molecular weights. Column: GPWP + G5000PW + G3000P
W Column temperature: 40 ° C. Eluent: 0.1N-NaCl aqueous solution Solvent flow rate: 1.02 ml / min Detector: Differential refractometer (RI)

Example 1 Ferrite (manufactured by Saikai Kogyo Co., Ltd., trade name: KMG-29) 1
00 parts by weight and 10 parts by weight of a 10% aqueous solution of the copolymer (1) were placed in a Menor mortar and uniformly kneaded, and then dried at 105 ° C. for 12 hours. Next, the obtained dried and solidified product was finely crushed and used as a test sample, and a thermal decomposition curve was determined using a thermobalance under the following measurement conditions. The result is shown in FIG.

(Measurement conditions) Temperature rising rate: 10 ° C./min, temperature was raised to 600 ° C. Atmosphere: In Air From FIG. 1, the heating temperature at which the heating loss reaches 20% to 80% is 265 ° C. to 500 ° C., The average weight loss rate during this period was 2.55% / min. No residue was observed at the end of heating at 600 ° C.

Example 2 A sample was prepared and tested in the same manner as in Example 1 except that the copolymer (1) used in Example 1 was changed to the copolymer (2). The result is shown in FIG. The heating temperature at which the weight loss upon heating reached 20% to 80% was 245 ° C to 470 ° C, and the average weight loss rate during this period was 2.67% / min. No residue was observed at the end of heating at 600 ° C.

Example 3 A sample was prepared and tested in the same manner as in Example 1 except that the copolymer (1) used in Example 1 was changed to the copolymer (3). The result is shown in FIG. The heating temperature at which the weight loss on heating reached 20% to 80% was 305 ° C to 440 ° C, and the average weight loss rate during this period was 4.44% / min. No residue was observed at the end of heating at 600 ° C.

Comparative Example 1 A sample was prepared and tested in the same manner as in Example 1 except that the copolymer (1) used in Example 1 was changed to the copolymer (4). The result is shown in FIG. The heating temperature at which the weight loss upon heating reached 20% to 80% was from 260 ° C to 335 ° C, and the average weight loss rate during this period was a large value of 8.00% / min. No residue was observed at the end of heating at 600 ° C.

Comparative Example 2 Instead of the copolymer (1) used in Example 1, polyvinyl alcohol (saponification degree: 88 mol%, polymerization degree: 120) was used.
A sample was prepared and tested in the same manner as in Example 1 except that 0) was used. The results are also shown in FIG. The heating temperature at which the weight loss on heating reaches 20% to 80% is 265 ° C to 345 ° C, and the average weight loss rate during this period is 7.50% /
It showed a large value with minutes. No residue was observed at the end of heating at 600 ° C.

[0024]

EFFECTS OF THE INVENTION The green molded body using the binder for producing an inorganic sintered body of the present invention has no cracks, warpage, swelling, etc., and has a moderate thermal decomposition rate, and the sintered body has no residual carbide. It has excellent performance without vacancy defects due to rapid decomposition and scattering of binder.

[Brief description of drawings]

FIG. 1 is a diagram showing thermal decomposition curves of Examples 1 to 3 and Comparative Examples 1 and 2.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display area C09J 129/10 JCR C04B 35/00 108

Claims (2)

[Claims] 1. A binder for producing an inorganic sintered body, which comprises a copolymer of an alkylene glycol vinyl ether represented by the following general formula (I) and maleic anhydride. General formula (I) (A in the formula is an alkylene group having 2 to 4 carbon atoms, R is hydrogen or an alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 20) 2. An inorganic sintered body produced by using the binder for producing an inorganic sintered body according to claim 1.