JPH0364463B2 - - Google Patents

Description

[Detailed description of the invention]

``Object of the Invention'' Industrial Field of Application The present invention is directed to fiber-reinforced cement molded articles, such as cement pipes, cement plates, cement corrugated plates, wall bodies, etc., using fibers as a reinforcing material, which are particularly useful for cement corrugated plates. More specifically, it has excellent mechanical properties using high-strength, high-modulus fibers made of highly polymerized acrylonitrile-based polymers as reinforcing fibers, and conventional cement moldings using asbestos as reinforcing fibers. The present invention relates to an inexpensive cement molding that can be substituted for the cement molding of. Conventional technology Cement molded products using asbestos as a reinforcing fiber have traditionally been produced and sold in large quantities, but ever since asbestos was recognized as a carcinogen, its production has been significantly restricted, and in some developed countries. Nowadays, the use of asbestos is about to be legally prohibited, and the provision of inexpensive reinforcing fibers to replace asbestos, which has until now been the mainstream reinforcing fiber in cement moldings, has become an urgent and important issue. Attempts have been made to use various synthetic fibers and natural fibers as reinforcing fibers for cement moldings. In addition to requiring many properties such as physical properties, adhesion to cement, miscibility, dispersibility, alkali resistance in cement slurry and during curing, and water resistance, asbestos is inexpensive, it also needs to be low cost. However, these fibers often did not satisfy practical performance. Special Publication No. 53-18213 and U.S. Patent No.
No. 4414031 and other publications propose attempts to use acrylic fibers as reinforcing fibers for cement moldings, but all of these methods can be substituted for cement moldings that use asbestos as reinforcing fibers. It was not possible to provide a cement molded product having physical properties exceeding a certain level. Problems to be Solved by the Invention In other words, the problems with cement molded products using acrylic fibers as reinforcing fibers are as follows: (1) Acrylic fibers with low mechanical properties such as tensile strength and initial modulus of elasticity cannot be used as reinforcing fibers. When used, it is necessary to increase the orientation ratio of acrylic fibers to cement in order to improve the mechanical properties, especially the bending strength, of cement molded products to a level that poses no practical problems. However, if the blending ratio of acrylic fibers to cement exceeds a certain level, especially about 3% by weight, the dispersibility of the fibers into the cement deteriorates, making it easier for the fibers to become entangled in the cement. (2) Conventional acrylic materials used for clothing and industrial materials may significantly reduce the operability of the molded product manufacturing process, such as wet papermaking, and the resulting cement molded products may easily become cracked or fluffed. The fibers have poor alkali resistance, water resistance, and heat resistance, and after being mixed with cement, the mechanical properties of the fibers decrease significantly during the curing of the cement, and in some cases, the fibers deteriorate or dissolve. (3) Furthermore, with conventional acrylic fiber manufacturing technology, it was possible to improve either tensile strength or initial elastic modulus, but it is impossible to improve both of these properties at the same time. , it is technically extremely difficult to improve. However, as reinforcing fibers for cement moldings, unless both tensile strength and initial elastic modulus are satisfied at the same time, it will not be possible to satisfy the bending strength, which is an essential property of cement moldings, such as slate such as corrugated sheets. However, there were problems such as impossibility of practical use. The inventors of the present invention have conducted intensive studies focusing on the above-mentioned problems of cement moldings, and have found that in order for acrylic fibers to be able to replace asbestos as reinforcing fibers for cement moldings, it is necessary to It was discovered that not only the strength, initial modulus of elasticity, bending strength, etc. are significantly improved, but also that the polymer constituting the fiber needs to have a high degree of polymerization, and the present invention was developed based on this finding. That is, an object of the present invention is to provide a cement molded product using acrylic fibers as reinforcing fibers, which solves the above-mentioned problems, and another object is to provide a cement molded product that uses asbestos as reinforcing fibers. It is an object of the present invention to provide a cement molded product which has excellent mechanical properties, is inexpensive, and can be substituted for an asbestos-reinforced cement molded product. "Structure of the Invention" Means for Solving the Problems The above objects of the present invention can be achieved by the invention described in the claims. The configuration of the present invention will be specifically explained in detail below. First, the cement molded product of the present invention is characterized in that the proportion of acrylic fibers contained in the cement molded product is approximately 1% by weight or more and less than 3% by weight, preferably 1 to 2.5% by weight, and more preferably Characteristically, the amount ranges from 1 to 2% by weight. Here, the above-mentioned blending ratio is the weight percent of the acrylic fiber in the total weight of cement and solid materials such as acrylic fiber and other additives, such as pulp and flocculant, mixed into the cement. The blending ratio of the acrylic fibers, which is one of the features of the present invention, is extremely small compared to the blending ratio of fibers in conventional cement moldings, but if this blending ratio is less than 1% by weight, the cement moldings On the other hand, if the amount exceeds 3% by weight, it becomes difficult to uniformly disperse the fibers in the cement, leading to a decrease in operability in wet papermaking, for example, and making it difficult to produce cement molded products with stable quality and performance. This is not preferable because it becomes difficult to industrially manufacture the product and the resulting cement molded product is likely to crack. Next, in order to satisfy the above-mentioned blending ratio and achieve the purpose of the present invention, the fibers blended into the cement molded product must be made of a highly polymerized polymer, and its physical properties are better than those of conventionally known acrylic fibers. Must be significantly better. That is, the acrylic fiber used in the present invention preferably has a degree of polymerization of the polymer constituting the fiber, expressed as an intrinsic viscosity, of 2.0 or more, preferably 3.0 or more, more preferably more than 4.0, and has a polymerization degree of at least 10 g. /d, preferably a tensile strength of 11 g/d or more and an initial elastic modulus of 180 g/d or more, preferably 200 g/d or more. However, even if the blending ratio of fibers in the cement molded product is within the above range, the strength, flexural strength, and flexural strength relative to density (d) cannot be improved until the degree of polymerization and physical properties are satisfied. The ratio of bending ^{strength (M) to density (d) (M/d 2 )} and impact strength are both 50Kg・cm ⁴ . /
This makes it possible to produce cement molded products with excellent physical properties that cannot be expected from conventional products, such as g ² or more and 1.5 Kg cm/cm ² or more. Here, the tensile strength and initial elastic modulus of the above fiber are:
This value was measured assuming that the sample length of the fiber used for measurement was 200 mm. In other words, unless the strength and initial elastic modulus of the acrylic fiber exceeds 10 g/d and 180 g/d, respectively, the reinforcing effect on the cement molded product will be small. It is not possible to obtain a cement molded product that satisfies the physical properties and performance required for practical use. In addition, it is advantageous that the polymer constituting the acrylic fiber is a highly polymerized acrylonitrile polymer having an intrinsic viscosity of at least about 2.0, which is advantageous in terms of developing strength and elastic modulus, and also Because of its high strength, it is possible to suppress and prevent the deterioration or dissolution of the acrylic fibers during the production of cement molded products, and to reflect the mechanical properties of the acrylic fibers as a reinforcing effect on the cement molded products. It was summer. The fibers made of the high polymerization degree polymer of the present invention are more easily cut into cut fibers than the fibers made of polymers with a low polymerization degree such as conventional clothing fibers. In addition, fusion or pseudo-fusion occurs little between single fibers, and the fibers have excellent fiber opening properties.This improves the dispersion properties in cement slurry and is effective as a reinforcement for cement molded products. It is estimated that this will make a large contribution. It satisfies the properties required for cement reinforcing fibers, such as alkali resistance, water resistance, and heat resistance, and has high physical properties such as strength, especially tensile strength and initial elastic modulus of 10 g/d or more and 180 g/d or more, respectively. Acrylic fibers having a high degree of polymerization are difficult to produce by conventional industrially known methods, such as wet spinning and dry spinning. A method for producing fibers with high strength and high elastic modulus from such a polymer with a high degree of polymerization is described in Japanese Patent Application No. 128006/1983 (Japanese Patent Application Laid-Open No. 21905/1989) previously proposed by the present inventors. The dry/wet spinning method disclosed in
In other words, basically, instead of directly discharging the acrylonitrile polymer solution into a liquid coagulation bath, there is a method in which the solution is first discharged into an inert atmosphere and then introduced into the liquid coagulation bath to complete the coagulation. It is preferable to adopt this method; otherwise, when the degree of polymerization of the polymer exceeds 2.0, it is difficult to obtain an acrylic fiber that satisfies both strength and initial elastic modulus. The acrylonitrile (hereinafter abbreviated as AN) polymer constituting the acrylic fiber of the present invention includes:
At least 96% by weight, preferably 97% by weight or more
Highly polymerized AN-based polymers consisting of AN and 4% by weight or less, preferably 3% by weight or less of an unsaturated vinyl compound, and having an intrinsic viscosity (value measured at 25°C using dimethylformamide as a solvent) of 2.0 or more. It is a combination. If the amount of copolymerized unsaturated vinyl compound in this AN polymer exceeds 4% by weight, the heat resistance of the resulting fibers will decrease, and the mechanical properties of the fibers will decrease during the manufacturing process of cement moldings, such as the curing process. However, this is not preferable because the reinforcing effect is lost. In addition, the fibers used have a single filament fineness of 0.5 to 5 d, preferably 0.5 to 3 d, and a fiber length of 1 to 10 mm, preferably 3 to 10 mm. Such acrylic fibers have a high miscibility with cement. Since it has excellent properties and is homogeneously dispersed in cement, it can be made into any cement molded product by a known method for producing cement molded products, such as a wet papermaking method.
Furthermore, it is possible to obtain a cement molded product with good operability and stability in wet papermaking, and excellent quality and performance. Effects of the Invention The cement molded product of the present invention has the following effects. Cement molded products are less susceptible to deterioration in operability due to entanglement of fibers in the cement during the manufacturing process, and less likely to cause cracks or fuzz in the resulting cement molded products. After mixing acrylic fibers into cement, the mechanical properties of the fibers deteriorate during curing of the cement molded product.
Fiber deterioration and dissolution are unlikely to occur. Bending strength (M), especially bending strength (M) relative to density (d) (i.e. M/d ² ) is approximately 50Kg・cm ⁴ /
g ² or more, impact strength is approximately 1.5Kg・cm/cm ² or more,
The main mechanical properties of cement molded articles are significantly improved. This is surprising considering that conventional cement molded products using acrylic fibers as reinforcing fibers could not be used for corrugated plates due to insufficient physical properties. Of course, the cement molded product of the present invention is not limited to use in corrugated plates, and can be used for various purposes similar to cement molded products using asbestos as reinforcing fibers. In the present invention, the physical properties of the cement molded product are values measured by the test method described below. Preparation of cement molded plate for test Reinforcing fiber acrylic fiber x parts by weight, cellulose pulp 2 parts by weight Silica powder (average particle size 0.6 microns) 10 parts by weight, Portland cement (88-
x) Mix part by weight with water so that the solids concentration is 5% by weight, add 500ppm of polyacrylamide as a flocculant to the solids, and mix the resulting slurry with a 50 mesh round wire mesh. A cement laminate is made using the same process. This board is pressure molded at a pressure of 250 kg/cm ² to form a cement board with a thickness of approximately 6 mm. Then, in water at 20°C for one day at 20°C and 100% RH.
After 28 days of wet curing, dry and cure to create cement molded plates for testing. Test method Cut a test piece from this cement board and use JIS-K
Bending strength and impact strength were measured according to -6911. Hereinafter, the present invention will be explained in more detail with reference to Examples. Examples 1, 2 and 3, Comparative Examples 1 and 2 AN99% by weight, sodium 2-acrylamido-2-methylpropanesulfonate ((AMPS)
A polymer with an intrinsic viscosity of 3.0 (measured at 25°C using dimethylformamide as a solvent) consisting of 1% by weight was dissolved in dimethyl sulfoxide (DMSO) to a polymer concentration of 14% and incubated at 45°C. A spinning stock solution with a solution viscosity of 1300 poise was prepared. This spinning stock solution was once discharged into the air through a spinneret with a hole diameter of 0.15 mmφ and a number of holes of 1000, and then introduced into a 30% DMSO aqueous solution at a temperature of 20°C. It was coagulated and taken off at a take-up speed of 10 m/min. The distance between the spinneret surface and the liquid level of the 30% DMSO aqueous solution was 5 mm. The obtained coagulated yarn was washed with water and then taken off in boiling water. It was stretched 5 times and dried at a surface temperature of 150°C with a relaxation of 3%.The dried yarn was subjected to secondary dry heat stretching to 2.8 times using a continuous roller type hot drawing machine at 150 to 190°C. The yarn was subjected to tension heat treatment using two rollers held at 230°C, and then wound onto a winder.The total stretching ratio of the obtained yarn was 13.5 times, the single yarn fineness was 1.5 d, and the single yarn strength was 12.5 g/
d, the initial elastic modulus was 225 g/d, and the elongation was 7.5%. (Measurements were made with a sample length of 200 mm and a deformation rate of 50%/min). The obtained yarn was cut into fibers with a length of 5 mm to prepare fibers for reinforcing cement. Five types of cement molded plates were prepared by changing the blending ratio of the reinforcing fibers, and their physical properties were measured. The results are shown in Table 1. For comparison, 15 parts by weight of chrysotile asbestos 5R, 2 parts by weight of cellulose pulp,
83 parts by weight of Portland cement with a solids concentration of 15
Mix with water to make the same parts by weight, wet paper making method

【table】

[Table] Paper forming property Good Good
Fair Good Paper-making impossible −

Claims (1)

[Scope of Claims] 1. Consisting of an acrylonitrile-based polymer mainly composed of acrylonitrile having an intrinsic viscosity of at least 2.0 (value measured at 25°C using dimethylformamide as a solvent), and having a tensile strength of at least
10g/d, 1% by weight of acrylic fiber obtained by wet-dry spinning with an initial elastic modulus of 180g/d or more.
The reinforcing fibers are acrylic fibers that contain acrylic fibers in an amount of less than 3% by weight and have a bending strength of 50 kg/cm ⁴ /g ² or more and an impact strength of 1.5 kg/cm ² or more based on the density of the molded product. Cement moldings. 2. A cement molded product according to claim 1, in which reinforcing fibers are acrylic fibers having a tensile strength of 11 g/d or more and an initial elastic modulus of 200 g/d or more. 3 In claims 1 and 2, the intrinsic viscosity of the acrylonitrile polymer (measured at 25°C using dimethylformamide as a solvent) is
A cement molded product whose reinforcing fibers are acrylic fibers with a rating of 3.0 or higher. 4 In claims 1 to 3, the acrylic fiber has a single yarn fineness of 0.5 to 5 d and a fiber length of 1 to 10
Cement molded product using acrylic fibers as reinforcing fibers.