JPH0346422B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for molding ceramics with excellent moldability in which one or more selected from the group consisting of starch derivatives and vegetable seed mucilage derivatives is used as a binder in the ceramic manufacturing process. Conventionally, in the manufacturing process of ceramics, a binder is added to a base material that does not have a plastic viscosity that can be molded or to an element that does not have sufficient dry strength. A binder is used during molding to impart plasticity and maintain the shape after molding. In the molding process, properties such as good dry strength, uniformity, leakage, etc., short mixing time, and no shrinkage or bubble generation are required. In the sintering process, properties such as burnout at 400 to 500°C, no thermal distortion, no foaming, etc. are required. There are a wide variety of binders that have been used in the past, depending on the type of substrate and the molding method employed, and each type is used appropriately, but starch, cellulose derivative polyvinyl alcohol, etc. are usually used. The starches used include unprocessed raw starch, dextrin made cold-water soluble by acid hydrolysis, and alpha-alpharated starch made cold-water swellable by heat treatment.
The adhesion or deposition on the mold, the strength and uniformity of the molded product, the drying properties of the molded product, etc. are unfavorable and unsatisfactory. Carboxymethylcellulose or methylcellulose are used as cellulose derivatives, but these have high porosity and are prone to pinholes when mixed with ceramic substrates, and the molded product after demolding is easily deformed and warped. However, it is not satisfactory as it has drawbacks such as slow drying rate, rapid deposition, lack of smooth and dense surface after sintering, and high price. Polyvinyl alcohol has a high porosity and pinholes are likely to occur when mixed with ceramic substrates, the dry strength of the molded product is weak, the combustion range is narrow and it burns explosively, causing thermal distortion, and it is difficult to obtain appropriate fluidity. It is not satisfactory as it has the following drawbacks. The present inventors have conducted extensive research in order to solve the above-mentioned drawbacks, and as a result, we have found that the plasticity is such that it can be molded using one or more types selected from the group consisting of starch derivatives and vegetable seed mucilage derivatives as a binder. The present invention was completed based on the discovery that the above-mentioned drawbacks can be solved by adding it to a ceramic base that does not have viscosity or a ceramic base that does not have sufficient dry strength and molding it. The starch derivatives used in the present invention refer to etherified starch, esterified starch, graft copolymerized starch, and those obtained by converting these into dextrin or alpha. Etherified starches include natural starches such as wheat starch, potato starch, sweet potato starch, tapioca starch, rice starch, sago starch, corn starch, high amylose corn starch, their derivatives, amylose and amylopectin fractions, wheat flour, rice flour, and corn flour. ,
Using starch-containing substances such as dried potato powder and dried tapioca powder as raw materials, ethylene oxide, propylene oxide, monochloroacetic acid, dimethyl sulfate, methyl iodide, allyl chloride, acrylonitrile, acrylamide, benzyl chloride, diethylaminoethyl chloride, 3-chloro, 2 - Obtained by the action of an etherifying agent such as hydroxypropyltrimethylammonium chloride. Esterified starch is obtained by treating the starch with an esterifying agent such as concentrated sulfuric acid, acetic anhydride, vinyl acetate, maleic anhydride, succinic anhydride, propionic acid, butyric acid, orthophosphate, polyphosphate, metaphosphate, etc. can get. Cross-linked etherified starch and cross-linked esterified starch are treated with formaldehyde,
It is obtained by the action of a crosslinking agent such as epichlorohydrin, phosphorus oxychloride, polyphosphate, metaphosphate, diisocyanate, bisethylene urea, adipic acid, and acrolein. Graft copolymerized starch is produced by homopolymerizing monomers such as acrylic acid, methacrylic acid, acrylamide, methacrylamide, vinyl acetate, methyl acrylate, methyl methacrylate, ethyl acrylate, and ethyl methacrylate to the above starches. Alternatively, it can be obtained by copolymerization. Similarly, graft copolymerized etherified starch or graft copolymerized esterified starch can be obtained by graft copolymerization before and after etherification or esterification. Furthermore, these may be made cold water soluble by subjecting them to acid hydrolysis treatment at high temperature to form dextrin, or may be made cold water swellable by heat treatment and alpha conversion. Examples of the plant seed mucilage in the present invention include guar gum, locust bean gum, and tamarind. The plant seed mucilage derivatives in the present invention include those obtained by reacting the plant seed mucilage with the etherifying agent, those obtained by reacting the esterifying agent, and those obtained by reacting the crosslinking agent. Examples include those obtained by graft copolymerization of the above monomers, and those obtained by combining these. Here, etherified starch, esterified starch, crosslinked etherified starch, crosslinked esterified starch, graft copolymerized etherified starch, graft copolymerized esterified starch, etherified vegetable seed mucilage, esterified vegetable seed Mucilage, cross-linked etherified vegetable seed mucilage, cross-linked esterified vegetable seed mucilage, graft copolymerized ether vegetable seed mucilage, graft copolymerized esterified vegetable seed mucilage in etherification and esterification The degree is the degree of substitution (substituent DS per mole of anhydroglucose residue)
expressed in moles), degree of substitution 0.01 to 1.0, preferably 0.05
~0.3 is preferably used. In addition, the degree of crosslinking in cross-linked etherified starch, cross-linked esterified starch, cross-linked vegetable seed mucilage, cross-linked etherified vegetable seed mucilage, and cross-linked esterified vegetable seed mucilage is expressed by the swelling degree, and the swelling degree is 1 to 1.
8 ml, preferably 2 to 5 ml is suitably used. The degree of swelling is defined as 100 mg of starch sample, suspended in 10 ml of electrolyte solution (a solution containing 10% zinc chloride and 26% ammonium chloride in distilled water), and placed in a hot water bath (95°C or higher) for 5 minutes. After heating, cool to 20℃, shake thoroughly, transfer this to a 10ml graduated cylinder, and calculate the swelling volume of the sample when it is left standing at 20℃ for 12 hours.
It means a numerical value expressed in ml, and the smaller the value, the greater the degree of crosslinking. Graft copolymerized starch, graft copolymerized etherified starch, graft copolymerized esterified starch,
The graft ratio in graft copolymerized crosslinked starch, graft copolymerized vegetable seed mucilage, etc. is 1 to 100.
%, preferably 3 to 40%. Although these binders are usually used alone, it is more effective to use two or more kinds in combination depending on the molding method and the desired properties. The amount of the binder used in the present invention is preferably 0.2 to 35 parts by weight, preferably 0.5 to 20 parts by weight, per 100 parts by weight of ceramic bodies that do not have a plastic viscosity that can be molded or that do not have sufficient dry strength. added to. Other molding aid additives include plasticizers (abietic acid derivatives, diethyl oxalate, polyethylene glycol, polypropylene glycol, phthalate esters, dibutyl phthalate, sucrose, acetate, isobutyrate, glycerin, etc.), peptizers (glycerin, octadecyl amine,
Trichloroacetic acid, oleic acid, octadiene, glyceryl oleate, glyceryl trioleate, glyceryl tristearate, menhaden oil, etc.) Solvents (toluene, methyl ethyl ketone, etc.)
can be mentioned. The amount of these molding aids added to the ceramic base,
Depending on the molding method, drying properties, decomposability, binding properties, plasticity, peptization properties, etc. are examined as appropriate, and an appropriate amount is added to obtain appropriate properties. By using the binder of the present invention, suitable plasticity and fluidity can be obtained with a lower moisture content than conventional ones, and the porosity during mixing is low, so pinholes are difficult to form, and the moisture retention stability is good, making it resistant to changes over time. On the other hand, it is stable. In addition, the sedimentation rate of particles and the movement rate of water are good, the surface is smooth and homogeneous, demolding is easy, and dry strength is excellent. Furthermore, it has a wide combustion temperature range and can be molded with less shrinkage after molding. The molding method using the binder of the present invention includes:
Various known methods can be used, and regardless of the type of molding method, superior properties can be obtained at lower costs than conventional methods. It is particularly suitable for slurry casting, plastic molding, dry and semi-dry pressure molding, but is not limited thereto. During molding, appropriate amounts of the ceramic base, the binder of the present invention, and the various molding aids mentioned above are added in order to obtain appropriate properties by examining drying properties, decomposability, binding properties, plasticity, peptization properties, etc. The present invention will be described in more detail with reference to Examples. Example 1 10 parts of the binder of the present invention (etherified starch 35% aqueous solution, crosslinked etherified starch 35% aqueous solution , a mixed solution of a 25% aqueous solution of 6 parts of crosslinked etherified starch and a 9% aqueous solution of 4 parts of etherified guar gum), 0.1 part of polyethylene glycol (degree of polymerization 1000) as a plasticizer, 0.6 part of dibutyl phthalate, and glycerin as a peptizer.
0.1 part of a surfactant as a dispersant was fed into a pack mill and mixed, and the clay-like mixture was plastically molded to obtain a good molded product. Comparative Example 1 In Example 1, instead of the binder of the present invention, a 20% aqueous solution of 10 parts of corn starch, a 10% aqueous solution of 10 parts of methyl cellulose (degree of polymerization 4000), and 10 parts of polyvinyl alcohol (degree of polymerization partially saponified 300) were used. 35%
Plastic molding was carried out in the same manner as in Example 1 except that an aqueous solution was used as the binder. Example 2 The physical strength (bending strength, bending elongation) of the molded products obtained in Example 1 and Comparative Example 1 was measured. The test method is 70mm x 20mm x 1 obtained by plastic forming.
A molded plate of mm was used as a test piece, and the bending strength and bending elongation at breakage were measured by applying an external force (pressure) due to a drop to the lateral center line. Here, the bending strength represents the maximum external force (pressure) required for the molded plate to collapse, and the bending elongation represents the maximum deformation value when the molded plate collapses as a ratio to the vertical length of the molded plate. At a descending speed of 5 mm/min using a Tensilon test machine
Measured at 20℃ and 65%RH. The results are shown in Table 1.

[Table] Example 3 5 parts of the binder of the present invention per 100 parts of a ceramic base containing 99% or more of alumina (average particle size 5μ)
parts (2% aqueous solution of etherified guar gum, 6% aqueous solution of etherified starch, 5% aqueous solution of crosslinked etherified starch, mixed solution of 5% aqueous solution of 3 parts of crosslinked etherified starch and 2% aqueous solution of 2 parts of etherified guar gum),
Polyethylene glycol as a plasticizer (polymerization degree
1000) 0.1 part, dibutyl phthalate 0.6 part, glycerin 0.1 part as a deflocculant, surfactant as a dispersant
0.1 part is fed into a ball mill and mixed to obtain a slurry-like mixture. This slurry-like mixture was obtained as a good molded product by slurry casting. Comparative Example 2 In Example 3, instead of the binder of the present invention, a 6% aqueous solution of 5 parts of cornstarch, a 1.5% aqueous solution of 5 parts of methyl cellulose (degree of polymerization 4000), and 5 parts of polyvinyl alcohol (degree of polymerization by partial saponification 300) were used. twenty five
Slime casting was carried out in the same manner as in Example 3, except that a % aqueous solution was used as the binder. Example 4 The physical strength (hardness, plasticity ratio) of the molded products obtained in Example 3 and Comparative Example 2 was measured. Here, the hardness and plasticity ratio are expressed by the following formula. Hardness = (Total external force) - (Bingham drop value) / Rate of change Plasticity ratio = Bingham drop value / Lower limit drop value Good slurry casting means that the hardness is small;
A material with a large plasticity ratio is good, and the plasticity ratio controls the casting properties (fluidity, solidification state of the molded body, warping, cracking, shrinkage rate and strength of the dry base). The results are shown in Table 2.

[Table] Example 5 The binder of the present invention (alpha-formed crosslinked etherified starch, alpha-formed etherified starch, alpha-sodium polyacrylate Graft copolymerized starch, tamarind)
10 parts of glycerin as a plasticizer, and 0.1 part of a surfactant as a dispersant were added to a ball mill and mixed to obtain a powdery mixture. Next, the moisture content of this powdery mixture was adjusted to 0.5% and 1.0%, and a good molded product was obtained by dry pressure molding. Comparative Example 3 Dry pressure molding was carried out in the same manner as in Example 5, except that 10 parts each of roasted dextrin and pullulan (molecular weight 300,000) were used as binders instead of the binder of the present invention. Summer. Example 6 The physical strength (collapse strength) of the molded product obtained in Example 5 and Comparative Row 3 was measured. Test method: moisture adjusted to 0.5% and 1.0%, 25
An external force (pressure) was applied by falling in the longitudinal direction of a test piece that had been dry-formed into a cylindrical shape with a diameter of 10 mm and a height of 20 mm at a pressure of Kg/cm ² to measure the collapse strength. At a descending speed of 50 mm/min using a Tensilon test machine
Measured at 20℃ and 65%RH. The results are shown in Table 3.

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Claims (1)

[Claims] 1 Etherified starch, esterified starch, cross-linked etherified starch, cross-linked esterified starch, graft copolymerized starch, starch derivatives such as dextrinized and alphalyzed starch, guar gum, locust bean gum, and tamarind with ether A method for molding ceramics, characterized by using as a binder one or more types selected from the group consisting of plant seed mucilage derivatives, which are esterification, esterification, graft copolymerization, and combinations thereof. .