JPS62241865A - Ceramic binder - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a polyvinyl alcohol-based ceramic binder 1 with improved performance.

[Conventional technology 1 Polyvinyl alcohol cypress (fats) such as polyvinyl alcohol and polyvinyl butyral are used as binders for fine ceramic molding.Fine ceramic molded products have excellent heat resistance and fire resistance, and have recently been used as a raw material. This is something that is receiving a lot of attention.

However, there are two main methods for molding fine ceramics (hereinafter simply referred to as ceramics), depending on the requirements. One is to mix a ceramic material and a binder solution, dry it once, then fill it into a molding container and pressurize it, so that the ceramic material is compressed to a high density.
This is a press molding method that attempts to obtain molded products, and one of the methods is to cast and dry ceramic materials dispersed in a binder solution using the so-called doctor spray method or extrusion method to create a sheath-like ceramic molded product. This is a tape molding method that aims to obtain .

[Problem to be Solved by the Invention 1] Thus, the performance of the binder greatly affects the density and uniform dispersion during molding of the ceramic material, and the quality of this condition depends on, for example, the strength, density, and appropriate flexibility of the molded product. It is required to have a good balance of properties such as ease of handling during molding and molding, strong adhesive strength, releasability from molding equipment, and adhesive stability.

However, many of the above-mentioned general polyvinyl furfur resins still have unsatisfactory performance, and there is room for improvement. Therefore, it is necessary to introduce various modified groups into the resin.
Improving the above performance by: 1. Although it has been proposed, the introduction of modified groups has many disadvantages, such as requiring special techniques to manufacture the binder and, coupled with this, leading to an increase in price.

[Means for Solving the Problems 1] Therefore, in view of the above circumstances, the inventors of the present invention have developed a binder for ceramics that preferably has performance equal to or better than that of a modified product even if it is made of unmodified polyvinyl alcohol. Based on the idea that this would be possible, various changes were made in the degree of polymerization and saponification, but the expected results could not be easily obtained.

However, as we continued our research, we discovered that the blocking properties of hydroxyl groups (residual acetic acid groups) in polyvinyl alcohol, and finally the randomness, greatly affected the desired performance, and we gradually arrived at the present invention.

That is, the present invention has a degree of polymerization of 2,500 or less, a saponified skin of 20 to
It is characterized in that a polyvinyl alcohol resin containing 95 mol % and having a block character of 0.55 or more is used as the ceramic binder.

In the case of commercially available polyvinyl alcohol resins,
The block character is less than 0.55, and even if the resin has the same saponification and polymerization degree, it is difficult to obtain the effects of the present invention.

The block character is 0.55 or more, preferably 0.
A value of 60 or more means that the hydroxyl groups and residual vinyl acetate groups are randomly distributed in the polyvinyl alcohol resin used in the present invention. In this respect, ordinary commercially available polyvinyl alcohol (alkali-saponified product) has hydroxyl groups and residual vinyl acetate groups distributed in a fairly block-like manner, which is a big difference from the resin of the present invention.

The aforementioned block character representing the randomness of the hydroxyl group and the acetate group is calculated based on the following formula when expressed as "η".

η=(OH,○Ac)/2(OH)(OAc)where (OH,0Ac) is 0)(OH) measured in the l'c-NMR spectrum.

(b) +CH-CH2-CI-1)OHOAc
.

The absorption strength of the methylene group based on the two-unit chain structure (
The intensity of (b) in the amount of (dyad) is expressed as a mole fraction. In addition, (OH) and (OAc) are the saponified skin and residual vinyl acetate group content of polyvinyl alcohol, respectively, and are expressed as a molar fraction.6 The polyvinyl alcohol resin used in the present invention is
! There are no particular restrictions on the method of production (although it can be produced by any method, for example, a method of saponifying polyvinyl acetate with an acid, a method of re-7cetylation of polyvinyl alcohol, etc.).

Further, the polymerization degree of the resin is 2,500 or less, preferably 1.500 or less, more preferably 100 to 1,500.
is within the range of If the degree of polymerization is greater than 2.500, the viscosity of the slurry will be high, and if it is too low, film forming properties and adhesive properties will be insufficient, which is not practical.

The content of the saponified skin is in the range of 20 to 95 mol%, preferably 20 to 85 mol%, more preferably 30 to 75 mol%.

If the saponified skin is less than 20 mol%, the adhesive strength will decrease and 95
If it exceeds mol%, the flexibility of the molded product will decrease and should be avoided.

As described above, in the present invention, by using a polyvinyl alcohol resin having a unique block character, it is possible to create a ceramic binder that is highly balanced in terms of performance and has a wider range of polymerization degree and saponification than conventional ones. becomes possible.

The main objective of the present invention is that, as mentioned above, even if unmodified polyvinyl alcohol is used, if it is a resin with a high block character, it will be equivalent to or higher than polyvinyl alcohol-based resins modified with various conventional modifying groups. Although the intention is to provide a ceramic binder with excellent performance, this does not in any way prevent the resin of the present invention from being modified, and modified groups may be added as necessary without departing from the scope of the present invention. Of course, it is optional to introduce polyvinyl alcohol derivatives by means such as copolymerization, grafting, post-modification, etc.

Such derivatives include carbonyl group-containing polyvinyl alcohol, formalized polyvinyl alcohol, 7
Examples include cetal compounds, butyral compounds, urethane compounds, esterified compounds with sulfonic acids, carboxylic acids, etc., and cationized compounds. Further examples include saponified copolymers of vinyl esters and monomers copolymerizable with vinyl esters, such as ethylene, propylene, isobutylene, α-octene, α-dodecene, V eova (long-chain alkyl vinyl ester), olefins such as α-octadecene,
Unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic anhydride, itaconic acid, their salts, mono- or dialkyl esters, nitriles such as acryloni-Flyl and methacryloni-Flyl, amides such as acrylamide, methacrylamide, etc. , olefin sulfonic acids or their salts such as ethylene sulfonic acid, esters sulfonic acid, meta-allylsulfonic acid, alkyl vinyl ethers, polyoxyalkylene allyl ethers, alkyl allyl ethers, saturated carboxylic acid allyl esters,
Vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, ethylenically unsaturated monomer containing acetoacetyl group, unsaturated monomer containing oxyalkylene group, Class 1, secondary or tertiary amine, quaternary ammonium Examples include salt-containing unsaturated vinyl monomers. However, the present invention is not limited to these.

The ceramic binder using the polyvinyl alcohol resin of the present invention can be used in any system or state such as solvent-based, water-based, powdered, or block-based. The type of solvent may be appropriately selected depending on the physical properties of the resin. Especially when used in water systems,
The resin of the present invention has much improved solubility in the region of low saponification skin compared to conventional general polyvinyl alcohol, so it is possible to use this material to create ceramics that are advantageous in terms of safety and workability. It becomes a binder.

Plasticizers may be used to more effectively improve moldability and flexibility. Plasticizers include polyhydric alcohols such as sorbitol and mannitol, glycerin,
Examples include glyfurs such as siglycerin, ethylene glycol, polyethylene glycol, flopylene glycol, and methylpentanetriol, surfactants such as sorbitan aliphatic esters and their ethylene oxide adducts, and vinyl acetate oligomers. The amount added is preferably in the range of 1 to 100% by weight based on the polyvinyl alcohol resin.

Furthermore, additives that can be incorporated into the adhesive of the present invention include rosins, rosin esters, pinene polymers, hydrogenated petroleum resins, and other tackifiers that are compatible with resins.
, antioxidants, fillers, waxes, etc., which can be added in appropriate amounts. It can also be used in combination with other known ceramic binders.

When performing press molding using the ceramic binder of the present invention, Pace F is added to 100 parts by weight of the ceramic material.
The solid content of the resin dissolved in the form or water or organic solvent is o,
i to 20 parts by weight, more preferably 0, 1, -10 parts by weight, and if necessary, the plasticizer and additives are added and thoroughly mixed and dispersed. Dry at a temperature of 80 to 120°C with an appropriate particle size distribution until the residual solvent/residual moisture is 0.2% by weight or less (based on the total weight of the material), then put it into a mold and heat it under pressure at around room temperature. 0.5-3. This is often done by multiplying Ot/c+*2.

When performing tape molding, a mixed/dispersed liquid in the same ratio as above is uniformly cast onto a base material such as a Tetron sheet by a doctor blade method or an extrusion method, and dried to obtain a sheet-like product.

Of course, the present invention is not limited to this molding method.

As the ceramic material, one or a combination of alumina, silicon nitride, carbon nitride, boron nitride, silicon carbide, boron carbide, zirconia, beryllia, and the like may be used.

[Function 1] Thus, the ceramic molded product using the ceramic binder of the present invention obtained through the above molding method has excellent properties such as strength and smoothness, so it can be used for pottery stone, refractories, grindstones, and graphite electrodes. It can be used for various ceramic parts such as spark plugs, honeycombs, IC board packages, ceramic capacitors, ferrites, ceramic engines, thermistors, etc.

[Example] Next, the composition of the present invention will be explained in more detail by giving examples. "%" and "part" are based on weight unless otherwise specified.

In addition, the block character used in each example is (
The polyvinyl alcohol resin (indicated by "η" in the table) of 0.55 or more is obtained by acid saponifying the corresponding polyvinyl acetate resin using sulfuric acid at 40 to 60'C in a methanol solvent.

Example (press molding example) Alumina (manufactured by Showa Light Metal Co., Ltd., product name AL-IGO3
G) Add 6 parts of the polyvinyl alcohol resin shown in Table 1 to 100 parts and 60 parts of water, mix thoroughly in a ball mill, and dry at 80°C until the moisture content is 0.2% or less.
After pulverizing and sieving the material into 60 to 120 meshes, it was put into a mold and press-molded at room temperature under a pressure of 1.6 t/0 m2, and its performance was evaluated.

The results are shown in Table 1.

Comparative Example In place of the r-resin used in Example 1, comparative resins as shown in Table 1 were used, and press molding was carried out in the same manner as on the same side, and the results were evaluated.

The results are also shown in Table 1.

Example (tape molding example) Alumina (Showa Light Metal Co., Ltd. 91, trade name AL-15)
Add 1 ( ) part of the resin shown in Table 2 to 100 parts of water and 60 parts of water, mix well in a ball mill, defoamer using an evaporator, and spread it on a Tetron sheet using an applicator for 21 minutes. A thick film was formed. 1 hour at 50℃, 8
Green Sea F was obtained by drying in a blow dryer at 0° C. for 3 hours and at 105° C. for 2 hours, and evaluated.

The results are shown in Table 2.

Comparative Example Evaluation was carried out in the same manner except that comparative resins shown in Table 2 were used instead of the resin used in Example 2.

The above results are summarized in Table 2.

○Various evaluation methods・Slurry stability After mixing in a two-ball mill, put the slurry into a test tube with an inner diameter of 20 mm, stopper it, and heat it at 20℃ for 7 hours.
After standing for 2 hours, the state of separation of the system was observed.

・The green density was determined by the following formula.

・Compression speed 10mm/w using bending strength NIO-F graph (Shimadzu CT type compression bending tester IS-5000)
In, the test piece was repeatedly bent and measured 10 times at room temperature.

・Mold releasability: Observe the state of powder adhesion to the pre-deposited mold.

・Cracked The sheet surface after obtaining the Nigeleen sheet was observed with a magnifying glass (x6) to check for the presence or absence of cracks.

・Flexibility: Rub the cracks in the curved part when the green sheet is wrapped around a glass rod with a diameter of 8II + 1 (×6
) and evaluated as ◎: No cracks at all, ○: Almost no cracks, Δ: Slight cracks, and ×: Fully cracks.

(Left below) [Effects] As is clear from the above examples, molded products using the ceramic binder of the present invention have improved various performances in a well-balanced manner, and in particular, press-formed products have improved strength (bending strength). ,
Tape molded products have excellent flexibility. In addition, the slurry before molding maintains a suitable viscosity for a long period of time and has excellent stability, resulting in good workability.

Claims (1)

[Claims] A ceramic binder whose main ingredient is a polyvinyl alcohol resin having a degree of polymerization of 2,500 or less, a saponified skin of 20 to 95 mol%, and a block character of 0.55 or more.