JPH044123B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a molding matrix made of a sintered porous body of sulfonated polyolefin resin and suitable for shaping ceramic slurry or stone slurry. More specifically, it is a molding mold made of a sintered porous body of sulfonated polyolefin resin, and the average pore size between the resin particles constituting the sintered porous body is 5 to 100 μm.
The surface of the particles is sulfonated, and the degree of sulfonation is in the range of 1 x 10 ^-4 to 7 milliequivalents per gram of polyolefin resin. Regarding the mother mold. A molding mold made of a sintered porous body of sulfonated polyolefin resin is produced by filling a mold with a predetermined shape with a predetermined amount of sulfonated polyolefin resin particles, and heating the mold from the outside to reduce the points of contact between the particles. It can be manufactured by fusing it at a temperature, then cooling and solidifying it. It can also be produced by making a similar porous sintered body of polyolefin resin particles and then sulfonating it. Conventionally, molds made of gypsum have been most commonly used as molds for casting, which is used to shape slurry made from a mixture of ceramic raw material soil and water into a predetermined shape in the ceramic manufacturing process. This is because gypsum is cheap, has good shaping processability, and when ceramic slurry is cast, it quickly absorbs some of the water, making it easier to solidify the slurry. However, on the other hand, a matrix made of gypsum is heavy, easily scratched, and easily damaged, which poses a major problem in handling. Furthermore, since the slurry is alkaline, it chemically changes and causes clogging, resulting in a decrease in the solidification rate of the slurry and shortening the lifespan of the mold. The slurry casting mold made of a sintered porous body of sulfonated polyolefin resin according to the present invention was developed using polyolefin resin as a material, which has excellent moldability among plastics. Polyolefin resin is originally hydrophobic,
The porous body obtained by sintering the powdered resin is
Although it has countless continuous pores, it is hydrophobic,
Because it is water repellent, water does not penetrate into the sintered body with a pore size below a certain size. However, when the surface of the resin particles constituting the sintered porous body is rendered hydrophilic by sulfonating, water quickly penetrates into the sintered body by capillary action. Further characteristic properties include water absorption, swelling and swelling seen in hydrophilic substances.
It has no solubility. The molding mold according to the present invention has the properties of polyolefin resin, which are lightweight, hard to scratch, has excellent impact resistance and alkali resistance, and is easy to mold, as well as imparting hydrophilicity through sulfonation, and further sintering. It was completed by combining several techniques to make use of the capillary phenomenon caused by the countless pores that communicate with each other by making the material porous. Specific applications of the molding mold of the present invention include, in addition to the already-mentioned molding mold for ceramic slurry casting, molds for making plaster reproductions of arts and crafts, etc. It is very useful as a matrix in cases where solidification is promoted by losing part of the water content. The sulfonated polyolefin constituting the porous sintered body of the present invention is an olefin polymer such as polyethylene, polypropylene, or polybutene, or a copolymer mainly composed of ethylene or propylene, such as an ethylene/propylene copolymer or an ethylene/butene copolymer. Powder of ethylene/vinyl acetate copolymer or mixture of these polymers
The granules, or their sintered bodies, may be treated directly in a sulfonating agent such as fuming sulfuric acid, hot concentrated sulfuric acid, sulfuric acid, sulfuric anhydride, etc., or in a sulfonating agent such as carbon tetrachloride, carbon dichloride, or fluorinated hydrocarbon. It can be obtained by reacting in a conventional manner in a system using a solvent. Further, in order to further increase hydrophilicity or to suppress corrosion of a mold during sintering and molding, it is preferable to neutralize the sulfonic acid group reacted and added to the polyolefin resin with an alkali to form a salt. These sulfonated polyolefin powders
In both cases where granules are made into sintered bodies or sintered bodies of polyolefin powder or granules are sulfonated, only the surface layer of the particles constituting the sintered body is sulfonated. Therefore, the porous sintered body, which is easily wetted by water, absorbs water by its capillary phenomenon until the voids are filled, and is also easy to re-dry. More preferably, the polyolefin resin used in the present invention has a melt index value (ASTM-D1238) of 1 (g/10 min) or less and a powder particle size mainly in the range of 50 to 500μ. be. This prevents excessive sintering between resin particles during sintering and forming, and also facilitates controlling the average pore diameter of the obtained sintered body within the range of 5 to 100 μm. This means that if the melt index value of the polyolefin resin powder during sintering is 1 g/10 minutes or more, the fluidity of the particles during melting is high, so mutual fusion progresses rapidly. It is difficult to maintain voids between particles. In addition, when the powder particle size is mainly 50μ or less, the voids between the particles are extremely small, and the voids rapidly disappear at the same time as the fusion. In addition, 5 μ is used for water absorption in slurry.
Although it is advantageous in terms of water absorption to have a pore diameter of
In order to obtain a sintered body having a pore diameter of 5μ or more, it is preferable that the particle size of the raw material powder for the sintered body is 50μ or more. On the other hand, if the particle size of the powder is 500μ or more, the pore diameter of the sintered body will exceed 100μ, causing slurry particles to enter the sintered body and cause clogging. Therefore, the particle size of the powder is in the range of 50 to 500 μm, and the average pore diameter of the sintered body can be controlled to 5 to 100 μm depending on the particle size distribution. The pore size of the sintered body is appropriately selected depending on the particle size of the base clay in the ceramic slurry, the particle size of the gypsum slurry, etc., but the pore size of the sintered porous body that is the matrix is coarse. If this occurs, clay particles may enter and cause clogging, or the surface of the solidified slurry may become rough. Therefore, the average pore diameter of the sintered porous body is more preferably 50μ or less, most preferably 25μ or less.
On the other hand, the sulfonation exchange equivalent for the polyolefin resin particles constituting the sintered porous body is 1×10 ⁻⁴ milliequivalent or more per 1 g of polyolefin, and if it is less than this, the hydrophilicity is poor. In addition, when sulfonating polyolefin powder after sintering,
Depending on the size and shape of the molded product, there are restrictions due to the sulfonation reaction vessel and other restrictions, but there is no particular upper limit restriction on the sulfonation exchange equivalent. However, the desired hydrophilic effect reaches an equilibrium state when the amount of sulfonation exceeds a certain value, and as the degree of sulfonation increases, the strength of the sintered compact itself tends to decrease. Therefore, about 7 milliequivalents/g or less is sufficient. On the other hand, a method in which a sulfonated polyolefin resin powder is prepared and then sintered into a desired shape has the advantage that a large amount of material can be processed in a sulfonation reaction vessel of the same size. However, in this case, depending on the MI value of the polyolefin resin, there is a drawback that as the sulfonation exchange equivalent increases, sintering becomes more difficult. Therefore, the upper limit of the sulfonation exchange equivalent in this case is approximately 5×10 ⁻¹ (milliequivalents/g). Incidentally, non-sulfonated resin powder, cellulose powder, glass fiber, inorganic filler, etc. are added to and mixed with the sulfonated polyolefin resin powder to the extent that hydrophilicity is not substantially impaired, and sintering is imparted with characteristics based on this. It may be a porous body. Incidentally, the average pore diameter between the resin particles of the sintered body defined in the present invention and the degree of sulfonation on the surface of the resin particles are values measured by the following method. Average pore diameter: Any part of the surface of the sintered body, especially the surface that comes into contact with the slurry, is magnified using a microscope, and the shape of the voids interposed between the resin particles constituting the sintered body is determined. is considered to be a similar circle, ellipse, or rectangle, and 1/2 of the sum of the measured values of its major and minor axes is taken as the pore diameter of the void. The average value of the pore diameters thus determined for 100 or more individual pores in close proximity within the field of view is taken as the average pore diameter. Degree of sulfonation: Accurately weigh approximately 20g of the sample,
Add 150 ml of 1N HCl and stir for 1 hour. Then filter and wash with water (washing is continued until the liquid becomes neutral). Add 70 ml of ethyl alcohol and 70 ml of 2N-CaCl ₂ aqueous solution to the washed sample,
Stir for 1 hour. Add 2 ml of 1.5% phenolphthalein solution to this as a titration indicator,
Titrate with 0.01N-NaOH solution. The sulfonation exchange equivalent is calculated from these values using the following formula. Sulfonation exchange equivalent (milliequivalent/g) = (A-B)・f・N/W In the above formula, A: Amount of 0.01-NaOH solution required for titration (ml) B: 0.01 required for blank test -NaOH solution volume (ml) f; 0.01N -NaOH solution titer W; weight of sample (g) The degree of sulfonation is determined by the sulfonation exchange equivalent value obtained by the above measurement method. . Hereinafter, the present invention will be illustrated in more detail with reference to Examples. Example 1 95% by weight of the total particle size is 75 to 150μ, and the
A 50% by weight polymerized powder of high-density polyethylene having an average particle size of 100 μ (MI value: 0.04 g/10 min, density: 0.955 g/cm ³ ) is sulfonated in an ethylene dichloride solution dissolved in sulfuric anhydride, When the sulfonation exchange equivalent reached 1.5×10 ⁻³ meq/g·PE, it was neutralized with caustic soda, and then thoroughly washed with water and dried to produce a sulfonated polyethylene powder. This sulfonated polyethylene powder is 22×22cm
Filled into an aluminum mold with a square, 5mm deep cavity, heated and sintered in a hot air oven at 180℃.
Then, it was cooled to obtain a porous sintered body. The average pore diameter of this sintered body was about 20μ. For comparison, a porous sintered body was also prepared by sintering and molding the above-mentioned high-density polyethylene polymer powder in the same manner. Furthermore, a mixture of 100 parts of calcined gypsum and 30 parts of water was poured into a mold measuring 22 x 22 cm square and 1 cm deep, and left indoors for 30 days to harden and dry. A rod-shaped object with a length of 20 cm, a width of 5 mm, and a thickness of 5 mm was made from each piece by cutting. The obtained plates and bars were used as test specimens, and their hydrophilicity and water permeability were evaluated using the following methods. ;Water suction speed Draw a 1 cm diameter circle in the center of a 10 x 10 cm square, 5 mm thick plate specimen, and drop 3 c.c. of water into it using a pipette. At this time, the amount of dripping is controlled so that uninfiltrated water does not overflow outside the circle and the water on the sintered body does not dry, and the time until the water is completely sucked is measured. ;Hydrophilicity When a rod-shaped specimen measuring 5 x 5 mm square and 20 cm in length is stood vertically and the lower end 1 cm is immersed in water, the height at which water permeates into the specimen by capillary action is read over time. The height is expressed as hydrophilicity. The results are listed in Table 1. As is clear from this result, the sintered compact of the present invention has better water permeability than that made of gypsum.

[Table] Example 2 Using the sulfonated polyethylene powder used in Example 1, a hemispherical sintered porous body with an inner diameter of 20 cmφ and a thickness of 1 cm, and a hemispherical sintered porous body with an outer diameter of 16 cmφ and a thickness of 1 cm were prepared. One set of male and female molds was made, as well as two male and female molds of the same shape made of gypsum. Inside each matrix cavity, a slurry (water content: approximately 30% by weight, suspended particle size: approximately 30μ, acidity; PH approx. 9.5) was cast. This slurry solidifies by losing about 10% of its water content and can be removed from the matrix. The time until the mold could be demolded from this matrix was measured, and the performance as a matrix was evaluated. In addition, Table 2 also shows the results of repeatedly measuring the time required for solidification and demolding by pouring slurry into the demolded mother mold again. As is clear from this result, the matrix according to the present invention exhibited extremely superior performance compared to the solidification time of the slurry when a matrix made of gypsum was used. Furthermore, whereas the gypsum matrix suffered from a decline in performance due to the alkali in the slurry, the product of the present invention showed almost no decline in performance even after repeated use.

[Table] Example 3 The same matrix as used in Example 2 was evaluated for its ease of being scratched by nails and its drop impact strength. The results are listed in Table 3. While plaster molds are easily damaged and cracked, the product of the present invention was hardly damaged or cracked.

[Table] Example 4 High-density polyethylene (MI value: 0.2 g/10 min, density: 0.955 g/cm ³ ) was mechanically pulverized to obtain particles with a particle size of 75~
A powder having 95% by weight of the total in 250μ was obtained. This powder was sulfonated and neutralized in the same manner as in Example 1, then sintered and formed, and the powder was directly sintered and then the sintered body was sulfonated and neutralized. I formed a body. For the sintering molding, a dipped brass mold with a cavity of diameter 9cmφ and depth of 5mm was used, and the cavity was filled with powder.
After being sintered by immersing it in an oil bath at °C for 5 minutes, it was taken out and cooled to solidify. The average pore diameter of the obtained sintered body with continuous pores is 50%, and the average pore diameter is 50μ.
It was before and after. Regarding this disc-shaped sintered body, the water suction speed was measured in the same manner as in Example 1. The results are listed in Table 4. According to this, the sulfonation exchange equivalent is 1×10 ^-4 (milliequivalent/
g・PE) or higher, it was found that the material had sufficient water absorbency as a matrix material for ceramic casting.

【table】

【table】

Claims (1)

[Claims] 1 A molding matrix made of a sintered porous body of sulfonated polyolefin resin, wherein the average pore diameter between the resin particles constituting the sintered porous body is in the range of 5 to 100μ, and the surface of the particles is sulfonated. 1. A molding mother mold characterized in that the degree of sulfonation is in the range of 1×10 ⁻⁴ to 7 milliequivalents per gram of polyolefin resin.