JPH0148234B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) This invention relates to a method for manufacturing porous ceramic molded products,
In particular, the present invention relates to a method of manufacturing a porous ceramic molded product by molding a mixed composition comprising a ceramic raw material and a urethane foam forming composition in a mold, and firing the urethane foam molded product. (Prior art) Porous ceramic materials have excellent properties such as corrosion resistance, heat resistance, and strength, so they are used in a wide variety of applications such as materials, ion exchange resin materials, diaphragms, adsorbents, catalyst carriers, and kiln packing tools. has been done. As a method for producing the above-mentioned porous ceramic molded product, a porous ceramic molded product is obtained by firing a urethane foam mixed with a ceramic raw material, removing the polyurethane, and sintering the ceramic raw material. It is attracting attention as an excellent manufacturing method because molded products can be obtained relatively easily. As a method for producing porous ceramic molded products, a slurry ceramic obtained by adding water to a ceramic raw material is reacted with a polyoxyalkylene polyol and a polyisocyanate compound having two or more isocyanate groups at the end, and the product is free at the end. A method in which a hydrophilic urethane prepolymer having an isocyanate group is mixed, this mixed composition liquid is poured into a mold to cause reaction foaming, and then the urethane foam molded product is dried and fired (Japanese Patent Publication No. 12927/1983). Unexamined Japanese Patent Publication 1986
-Refer to Publication No. 145153, etc.) are known. The above-mentioned known hydrophilic urethane prepolymer method uses a hydrophilic polyol with an ethylene oxide content of 60 mol% or more, so the polyurethanization reaction is fast, and the amount of urethane resin relative to the ceramic raw material is reduced to create porous pores with high specific gravity. It has the advantage of being able to obtain high-quality ceramic molded products, but on the other hand, it is necessary to mix a large amount of water due to the high ethylene oxide content, and as a result, the urethane foam molded products have a high moisture content and become dry when dried. Shrinkage is large, which can lead to cracking, warping, etc., resulting in products with defective shapes. Further, in the hydrophilic urethane prepolymer method, the urethane prepolymer is produced in advance and then mixed into the muddy slurry, so the production process is complicated. On the other hand, as a method for manufacturing urethane foam molded products,
A one-shot method in which a mixture of ceramic, water, polyol, surfactant, catalyst, etc., and a polyisocyanate compound having two or more isocyanate groups at the end is poured into a mold and reacted and foamed. is known (for example, see Japanese Patent Application Laid-open No. 54-3110). In this known one-shot method, since the urethane resin content in the urethane foam molded product is high, the resin removal and firing time of the molded product becomes long, which may cause cracks in the ceramic molded product, and It is not possible to obtain large ceramic molded products. In this one-shot method, if the amount of urethane resin in the urethane foam molded product is reduced, the urethane foam will not solidify and a molded product will not be obtained. (Problem to be solved) In the one-shot method, which has a simple manufacturing process, even if the amount of urethane resin in a urethane foam molded product is reduced, it is sufficiently solidified and a porous ceramic molded product with a high specific gravity can be manufactured. , and to reduce the shrinkage rate during drying of the urethane foam molded product. (Means for Solving the Problems) This invention provides 100 parts by weight of ceramic raw material, 20 to 50 parts by weight of water, an average molecular weight of 1000 to 10000,
A polyoxyalkylene polyol having 3 or more functional groups with an ethylene oxide content of 30 parts by weight or less and capped with an ethylene oxide group at the end, a crosslinking agent consisting of ethanolamines, and 0.01 to 1.0 parts by weight of a catalyst are added to the upper polyoxyalkylene polyol.
A ceramic slurry (referred to as component A) blended so that the equivalent ratio of OH groups of ethanolamine to OH groups is 3 to 120, and a surfactant consisting of polyalkylene polysiloxane 1 to 100 parts by weight of the polyisocyanate compound. An isocyanate component (referred to as component B) containing 5 parts by weight,
The equivalent ratio of the OH group of the above A component to the NCO group of the B component is 0.5 to 3.0, and the total amount of the polyoxyalkylene polyol, crosslinking agent, catalyst, and B component in the above A component is adjusted to 100 parts by weight of the ceramic raw material. A porous material characterized by forming a urethane foam molded product by injecting a mixed composition liquid into a mold so that the amount of urethane resin is 19 parts by weight or less, and drying and firing this molded product. This is a method for manufacturing ceramic molded products. The ceramic raw material used in this invention generally becomes a sintered body by heating at high temperature, and is preferably a non-clay type material such as alumina, zirconia, silicon carbide, magnesia, or sillimanite. If added, it should not exceed 20% by weight, preferably 10% by weight, in the ceramic raw material.
It is as follows. If the content of the clay type exceeds 20% by weight, it is necessary to increase the amount of water added to create a low viscosity ceramic slurry, resulting in poor solidification of the urethane foam molded product. The amount of water added to 100 parts by weight of ceramic raw materials is
20 to 50 parts by weight, preferably 30 to 40 parts by weight,
If it is less than 20 parts by weight, the fluidity of the ceramic slurry will be poor and it will be difficult to mold urethane foam.
If the amount exceeds 1 part by weight, the urethane foam will fail to solidify. The amount of water blended is adjusted depending on the particle size of the ceramic raw material, and it is preferable that the amount of water blended is small when the particle size is large, and relatively large when the particle size is small. Next, the polyoxyalkylene polyol blended as the ceramic slurry (component A) has an average molecular weight of 1000 to 10000, preferably 3000 to 10000, and an ethylene oxide content of 30% by weight or less, preferably 10 to 30% by weight. , a trifunctional group or more whose terminal end is capped with an ethylene oxide group. When the average molecular weight of the polyoxyalkylene polyol is less than 1,000 or more than 10,000, the urethane foam is difficult to solidify. Furthermore, if the ethylene oxide content exceeds 30% by weight, the urethane foam becomes difficult to solidify because of its increased hydrophilicity. The crosslinking agent is an ethanolamine containing a tertiary amine, and examples thereof include triethanolamine, N-methyldiethanolamine, and N-ethyldiethanolamine. Examples of the catalyst include triethylenediamine (DABCO), diethylenetriamine, morpholine, etc. as amine-based catalysts, and dibutyltin laurate as examples of tin-based catalysts, but amine-based catalysts that are not hydrolyzed are preferred. The amount of catalyst blended is based on the ceramic raw material.
0.01 to 1.0 parts by weight per 100 parts by weight, preferably
It is 0.05 to 0.5 part by weight. If the amount of the catalyst is less than 0.01 part by weight, the reaction will be slow and the urethane foam will not solidify, and if it exceeds 1.0 part by weight, the urethane foam will solidify abnormally, resulting in a flexible urethane foam molded product. I can't. The equivalent ratio of the OH group of ethanolamine to the OH group of the above polyoxyalkylene polyol is 3
-120, preferably 20-40; if the equivalent ratio is less than 3, the crosslinking effect will be insufficient and the strength of the urethane foam will decrease; on the other hand, if the equivalent ratio exceeds 120, the urethane foam will become brittle. . Next, the polyisocyanate compound in component B is
Examples include methylene diisocyanate (MDI), tolylene diisocyanate (TDI), and isophorone diisocyanate (IPDI), but crude MDI is preferable in terms of reactivity and cost. As the polysiloxane surfactant in component B, it is suitable to use dimethylpolysiloxane partially modified with carboxyl, alcohol, or polyoxyalkylene polyol, which imparts water dispersibility to the polyisocyanate compound. ing. The blending amount of the surfactant is 1 to 5 parts by weight per 100 parts by weight of the polyisocyanate compound.
Preferably it is 2 to 3 parts by weight. If the amount is less than 1 part by weight, the polyisocyanate compound will be difficult to disperse in water and the urethane foam will not solidify. In addition, if the amount exceeds 5 parts by weight, active hydrogen (water,
(alcohol, etc.) reduces the NCO groups in the polyisocyanate compound, so the urethane foam does not solidify. In order to mix the above A component and B component, the equivalent ratio of the OH group in the A component to the NCO group in the B component, that is, the OH/NCO equivalent ratio is 0.5 to 3.0, and The amount of urethane resin, which is the total amount of the polyoxyalkylene polyol, crosslinking agent, catalyst, and component B in the above A component, is
A mixed composition liquid is obtained by mixing the ingredients so that the amount is 19 parts by weight or less. When the OH/NCO equivalent ratio is less than 0.5, abnormal foaming occurs when the urethane foam is produced, resulting in poor solidification of the urethane foam, and when the equivalent ratio exceeds 3, foaming due to insufficient NCO groups and poor solidification occur.
Further, if the amount of urethane resin exceeds 19 parts by weight, it becomes difficult to fire the ceramic foam molded product, and a ceramic molded product with a high specific gravity cannot be obtained. The above-mentioned ceramic slurry (component A) and component B are mixed and thoroughly stirred, and the mixed composition liquid is poured into a mold, and is reacted and foamed in the mold to obtain a urethane foam. The reaction in the mold is at room temperature to 35℃, 3 to 5
done in minutes. The urethane foam molded product solidified and molded in the mold is removed from the mold and then dried at 80 to 100°C for 15 to 24 hours to remove moisture contained in the urethane foam. The dried urethane foam molding is then heated in a high temperature furnace. This heating is
The process involves thermal decomposition of polyurethane and sintering of ceramic raw materials; the former process is carried out at temperatures ranging from room temperature to 400°C.
during which the polyurethane undergoes gradual oxidative decomposition or thermal decomposition in an oxygen-poor atmosphere. The latter process differs depending on the type of ceramic raw material, but is usually
It is carried out at a temperature of 1100℃ or higher. After sintering, the product is allowed to cool gradually and then taken out from the heating furnace. (Function) In this invention, by blending a surfactant into a polyisocyanate compound, the dispersibility of components A and B is improved when they are mixed, and the reaction is made smoother. In addition, polyoxyalkylene polyol improves the dispersibility of ceramic raw materials in water, and when component B is mixed with component A, it promotes the hydrophilicity between the polyisocyanate compound and water, and it also reacts with the polyisocyanate compound. In particular, the urethane foam molded product has overall flexibility. Furthermore, since the crosslinking agent made of ethanolamines blended into component A has catalytic ability, it imparts a certain degree of hardness and strength to the urethane foam molded product. The above-mentioned effects act synergistically with each other so that solidification can be achieved even if the amount of urethane resin is reduced, and since the urethane foam molded product has appropriate flexibility, it can be easily removed from the mold. In addition, since this invention uses a hydrophobic polyoxyalkylene polyol with a low ethylene oxide content, the water absorption and water holding properties of the urethane foam are low, and therefore the shrinkage rate of the urethane foam molded product when drying is low. No more cracks or warping. The detailed reason for the above effect is not clear. (Example) Component A was produced by blending water, polyoxyalkylene polyol, a crosslinking agent, and a catalyst with a ceramic raw material prepared by appropriately blending various ceramics.
Component B is manufactured by blending MDI surfactant,
A predetermined amount of the mixed composition liquid, which was stirred to uniformly mix the above A component and B component, was poured into a polyvinyl chloride mold (100 x 100 x 10 mm) whose inner surface was coated with a silicone mold release agent in advance. The mixture is allowed to react at room temperature for 5 minutes to foam and solidify. Immediately after removing the urethane foam molded product from the mold, it is dried in a dryer at 80°C for 24 hours. Next, this dry urethane foam was placed in an electric furnace and heated to 400℃ for 5 minutes.
The temperature was then raised to a predetermined temperature at a rate of 150° C. per hour, maintained for 1 hour for firing, and slowly cooled 15 hours after firing. Table 1 below shows the composition of component A, and Table 2 shows the composition of component B, the mixed composition liquid of components A and B, the state of the urethane foam molded product, and the properties of the fired product.

【table】

[Table] Among the crosslinking agents in Table 1, A is triethanolamine, B is N-methyldiethanolamine, and C is ethylene glycol (not included in this invention).
The catalyst (d) is tetraethylene diamine, and the catalyst (e) is dibutyltin dilaurate. In the table, for the surfactants, F is the product name PRX-607 (manufactured by Toray Silicone Co., Ltd.), G is the product name SH-193 (manufactured by Toray Silicone Co., Ltd.), and C is the product name Y-6827 (manufactured by Nippon Unica). . In Comparative Example 1, a polyoxyalkylene polyol having an ethylene oxide content of 70% was used in Example 1, and the urethane foam did not solidify in the mold. Comparative Example 2 is one in which the surfactant of component B in Example 1 is blended with component A,
It took 10 minutes for the urethane foam to solidify, and the urethane foam was hard and brittle and cracked when removed from the mold. Comparative Example 3 uses ethylene glycol (not containing tertiary amine) as the crosslinking agent in component A in Example 2, but after abnormal foaming in the mold, the foam breaks and solidifies, but the urethane foam remains. No molded product was obtained. Comparative Example 4 is a conventional one-shot method in which a surfactant is added to component A and the amount of urethane resin is increased. Although it solidifies in 3 minutes, the urethane foam molded product is brittle. It cracked when fired. (Effects of the Invention) A porous ceramic molded product having a relatively large bulk specific gravity and high bending strength can be obtained by a one-shot method with a simple manufacturing process.

Claims (1)

[Claims] 1. 20 to 20 parts of water per 100 parts by weight of ceramic raw material.
50 parts by weight, average molecular weight 1000-10000, ethylene oxide content of 30 parts by weight or less, polyoxyalkylene polyol with three or more functional groups capped with ethylene oxide groups at the end, crosslinking agent consisting of ethanolamines, catalyst 0.01-1.0 weight part, the equivalent ratio of the OH group of the ethanolamine to the OH group of the polyoxyalkylene polyol is 3 to 3.
Ceramic slurry (referred to as component A) blended to have a composition of 120% and a polyisocyanate compound
The above-mentioned A
The equivalent ratio of the OH group of the component and the NCO group of the B component is 0.5
~3.0, and mixed so that the total amount of urethane resin, which is the total amount of the polyoxyalkylene polyol, crosslinking agent, catalyst, and B component in the above A component, is 19 parts by weight or less based on 100 parts by weight of the ceramic raw material. A method for producing a porous ceramic molded product, which comprises injecting a composition liquid into a mold to form a urethane foam molded product, and drying and firing the molded product. 2 The ceramic raw material is non-clay based, and the clay based content is at most 20% by weight.
A method for manufacturing a porous ceramic molded product as described in 2.