JPH0153605B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a molding material used to create shapes using molds, such as ceramics and ceramic molded bodies. When molding ceramics, etc., a slurry-like slurry made by dispersing raw material powder in water, etc. is poured into a female mold, and after the part close to the mold loses its fluidity, the surplus fluid slurry is poured out. This is done by discharging the material, taking out the semi-solidified material from the mold, and then subjecting it to a process such as firing. Gypsum, which has excellent water absorption, has been commonly used as the material for this female mold. Because gypsum has excellent water absorption, it takes less time to semi-solidify the slurry, making it a suitable material for casting molds, but it has a rather rough surface.
In addition, because it is easily affected by the basic components in the slurry, repeated use causes the surface to gradually wear out, wear out, crack, or chip, so it has to be discarded after being used a few dozen times. . Especially in the case of ceramics used for industrial purposes, it is necessary to have high surface smoothness, flatness, and dimensional accuracy.
Accordingly, a high level of surface precision is required for casting molds. In view of the above-mentioned drawbacks of gypsum casting molds, the present inventors conducted extensive research on materials for molding and completed the present invention.The purpose of this invention is to have toughness, Unaffected by mud,
It is an object of the present invention to provide a material for molding that has excellent water absorbency and can be easily molded using general processing tools or machining means such as NC processing. The above purpose is to use polyvinyl acetal resin A.
and a phenolic resin B, which are finely mixed and dispersed in such a range that the ratio of the resins constituting the structure is B/A = 0.2 to 5 in terms of weight ratio, This is achieved using a molding material that is characterized by a porous structure with continuous pores. What is important in the present invention is that a phenolic resin is finely mixed and dispersed in a polyvinyl acetal resin (PVAt resin) to form a porous structure having continuous pores. The amount of phenolic resin mixed and dispersed in the PVAt resin is PVAt.
The amount is in the range of 0.2 to 5 parts by weight based on the system resin.
The amount of phenolic resin to PVAt resin is 0.2
If it is less than 1 part by weight, it becomes brittle, has poor toughness and workability, and has poor water absorption. On the other hand, the amount of phenolic resin is 5
If the amount exceeds parts by weight, the strength and dimensional stability will be insufficient. In addition, the water absorption performance, which is a feature of the molded material according to the present invention, is achieved by using a hydrophilic resin as one of the raw materials.
This is achieved by using PVAt-based resin and having a porous structure with continuous pores, and such continuous pores can only be achieved by the pore formation method described below. If the porosity is less than 50%, the proportion of continuous pores among the pores will be low and the water absorption performance, which is a characteristic of this material, will be inhibited, and if it exceeds 80%, the strength of the structure will be insufficient. Furthermore, those with an average pore diameter of less than 0.5 microns are difficult to manufacture, and those with an average pore diameter of more than 100 microns are too coarse and unsuitable as materials. In the molding material according to the present invention, the PVAt resin and the phenolic resin do not form a uniform polymer through copolymerization or polycondensation, but are mixed in an extremely microscopic state. It can be produced, for example, by the method described below. The first method is to mix a PVAt-based resin and a phenolic resin precursor or prepolymer in a fluidized state and proceed with a curing reaction. That is, first, a predetermined amount of a polyvinyl alcohol aqueous solution and a liquid phenolic resin prepolymer are mixed, and an aqueous dispersion of a pore-forming agent such as starch or a modified product thereof as a pore-forming agent, and a crosslinking agent such as an aldehyde are added. Add the required amount of curing catalyst such as acid for each agent, stir and mix uniformly to make a reaction stock solution, pour it into the required mold, and react at 40 to 80℃ for 10 to 20 hours to form a porous body. and pre-cure. It is then manufactured by washing with water, dehydrating, drying, and curing at 100 to 200°C, preferably 120 to 160°C, to complete the curing reaction of the phenolic resin. The time required depends on the size and porosity of the material, with larger and lower porosity materials requiring longer curing times. That is, the curing time must be carefully selected depending on each case. A water-soluble resol resin is suitable as the phenolic resin used in the present invention. Resole resin is an initial product produced by reacting phenols with aldehydes in the presence of a basic catalyst, and generally 1.5 to 3.5 mol of aldehyde is added in slight excess to 1 mol of phenol. A water-soluble resol resin can be obtained by maintaining the initial condensate reacted in the presence of an alkali catalyst in a stable water-soluble state. Phenols used in the production of resol resins most commonly include phenols and cresols. However, other phenols can also be used, such as phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol,
2,5-xylenol, 2,4-xylenol,
2,6-xylenol, 3,4-xylenol,
3,5-xylenol, o-ethylphenol,
m-ethylphenol, p-ethylphenol,
Examples include p-phenylphenol, p-tert-butylphenol, p-tert-aminophenol, bisphenol A, resorcinol, and mixtures of these phenols. Formaldehyde is most commonly used as the aldehyde for polycondensation with the phenols. However, monoaldehydes and dialdehydes such as paraformaldehyde, hexamethylenetetramine, furfural and glutaraldehyde, adipaldehyde and glyoxal may also be used. As the basic catalyst used in the resol resin synthesis reaction, known catalysts such as caustic alkali, alkali carbonate, barium hydroxide, calcium hydroxide, ammonia, quaternary ammonium compounds, and amines may be used. is most commonly used. The polyvinyl alcohol used in the present invention is generally obtained by saponifying vinyl acetate, and
There are no particular restrictions on its degree of polymerization, degree of saponification, branching, copolymerization with other monomers, etc., and it can be used alone or in combination of two or more, but preferably has a degree of polymerization of 100.
~5000, preferably with a saponification degree of 70% or more. As the curing catalyst used in the present invention, catalysts generally used for curing phenolic resins can be used, such as hydrochloric acid, sulfuric acid, oxalic acid, lactic acid, formic acid,
Acetic acid, para-toluenesulfonic acid, benzenesulfonic acid, etc. are suitable. The amount of the curing catalyst to be added may be appropriately determined in consideration of the type of catalyst used, the composition of raw materials, the curing temperature, etc. At this time, if a reactive granular or powdery phenolic resin is used as the phenolic resin, high strength can be obtained. Reactive granular or powdered phenolic resin is completely different from pulverized cured products of conventionally known resol resins or cured novolak resins, or pulverized cured novolak resin fibers. This is a phenolic resin made of spherical primary particles and secondary aggregates thereof, which is manufactured according to the manufacturing method described in JP-A-57-177011. Since this reactive granular or powdered phenolic resin has a nearly spherical shape, it is easier to mix with polyvinyl alcohol or liquid phenolic resin than powder obtained by pulverizing known cured phenolic resins. By using this resin, it is possible to obtain a high-strength PVAt resin-phenol resin mixed resin porous body with continuous pores in which a large amount of phenolic resin powder is uniformly mixed. . When using this reactive granular or powdered phenolic resin as part of the phenolic resin, it may be added to a liquid phenolic resin prepolymer, an aqueous polyvinyl alcohol solution, or a mixture thereof and stirred uniformly. Also,
When the entire amount of the phenolic resin is to be made into the granular or powdered phenolic resin, it may be added to an aqueous polyvinyl alcohol solution or a mixed solution containing other additives and stirred uniformly. The second method is to prepare a porous PVAt-based resin in advance, impregnate it with a predetermined amount of liquid phenol-based resin or its precursor, and then proceed with a heat treatment curing reaction. In this case, in an aqueous polyvinyl alcohol solution, an aqueous dispersion of a pore forming agent such as starch or its modified product, a crosslinking agent such as an aldehyde, etc.
After adding the required amount of each catalyst such as acids and stirring uniformly, the reaction stock solution is cast into the required mold and reacted at 40 to 80°C to obtain a porous PVAt-based resin by a known method. It is obtained by immersing the resin in a liquid phenolic resin or its precursor, and curing at a temperature of 100 to 200° C. after reducing a predetermined pressure to complete the curing reaction of the phenolic resin. In this method, the porous body is basically formed of PVAt resin, and the phenol resin is uniformly impregnated into it, so the structure is slightly different from that in the first method. It is suitable for producing products with a relatively low proportion of phenolic resin. In the present invention, when a melamine resin, for example, a melamine resin, a phenol compound, a hindered phenol compound, an amine compound, a hydroxylamine compound, etc. is blended, oxidation and heat accumulation phenomena, especially during curing, can be avoided. This is effective in suppressing the so-called punking phenomenon. In addition to the above effects, the melamine resin also has the effect of improving the hardness of the porous body. In addition, salts such as calcium carbonate, mirabilite, calcium sulfate, etc., for the purpose of increasing volume or improving strength,
Appropriate amounts of glass or glass fiber powder, talc, asbestos, asbestos, mica, metals and their oxides, carbide powders, whiskers, clay, etc. may be added. The material for molding of the present invention obtained in this way is finished into a predetermined mold using ordinary hand tools and machining methods such as NC processing. There are extremely few undesirable phenomena such as "burning" and the workability is extremely good. Moreover, even after repeated operations such as humidification, washing, and drying after being processed into molds, "misalignment" hardly occurs. In particular, compared to gypsum, it has the great advantage of being less prone to wear and tear and being able to withstand repeated use. The present invention will be specifically described below with reference to Examples. Example 1 As a phenolic resin, a water-soluble phenolic resin aqueous solution (PR-961A (purity 64%) manufactured by Sumitomo Duress),
Kuraray PVA as polyvinyl alcohol
-117 powder was used. Polyvinyl alcohol was dissolved in water to make an aqueous solution, and the above PR-961A was mixed to prepare a homogeneous viscous liquid. The mixing ratio was adjusted to the proportions shown in Table 1 in terms of the weight of each pure resin. Furthermore, 500g of wheat starch was dispersed in water and steamed in this liquid,
800 g of 37% formalin and 700 g of 30% sulfuric acid were added, and water was further added so that the total amount was 10%. After stirring thoroughly, the mixture was cast into a mold made of vinyl chloride. In this case, the ratio of the resin content was 10 to 4 kg. The mold was placed in warm water set at 50° C. and left to react for 20 hours, after which the contents were taken out from the mold. Thereafter, it was washed under running water under a shower for three days, and then dried. The dried material was cured at 150°C under a nitrogen stream. The physical properties of the obtained product were measured and the results are shown in Table 1.

[Table] Example 2 As the third component, reactive granular phenolic resin (trade name: Bell Pearl S, manufactured by Kanebo Co., Ltd., average particle size
50 μm) or melamine resin (product name: Milben Resin, manufactured by Showa Kobunshi Co., Ltd. purity 50%), and the water-soluble phenolic resin and polyvinyl alcohol having the composition shown in Example 1 were reduced, and the amount of these resins was reduced accordingly. Added ingredients. The additives, composition, etc. were the same as in Example 1, and the resin mixing ratio was also listed in Table 2. Furthermore, the reaction conditions were also the same as in Example 1. The results are shown in Table 2.

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Claims (1)

[Scope of Claims] 1. A resin structure made of a mixture of polyvinyl acetal resin A and phenol resin B, wherein the ratio of the resins constituting the structure is B/A=0.2 to 0.2 by weight. 5. A molding material characterized by having a porous structure having continuous pores and being finely mixed and dispersed within a range of 5. 2 Porous body structure with continuous pores has a porosity of 50~
80% by volume and an average pore diameter of 0.5 to 100μ.