JPS63312805A - Preparation of fiber reinforced cement molded item - Google Patents

Abstract

PURPOSE:To prepare a fiber reinforced cement molded item having excellent strength, by adding and mixing an inorganic filler and a synthetic fiber in a polymer aqueous solution, then adding therein a water-reducing agent, vibrationally mixing them and pouring them. CONSTITUTION:After 0.1pts.wt. or more of water soluble polymeric substance is dissolved in 30pts.wt. or more water, and optionally at the same time 200pts. wt. or less of inorganic filler are added and mixed in the dissolution, 0.3-7pts. wt. synthetic fiber are therein added and furthermore vibrationally mixed. Then, 100pts.wt. cement are added in this mixture and furthermore vibrationally mixed. 0.1-5pts.wt. of water reducing agent are added in said mixture and furthermore vibrationally mixed and the mixture is put in a mold capable of freely opening and closing and pressed and molded. Coupled with the effect of the water reducing agent, the mixture is rapidly filled in the whole mold while the mixture has sufficient flowability and perfect shaping is carried out. It is thereby possible to obtain a molded item being homogeneous and having high strength.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a fiber-reinforced cement molded article with improved fiber dispersibility and shapeability and excellent strength.

(Prior art) Asbestos is mixed into cement molded bodies as a reinforcing material in order to improve formability during molding and improve mechanical strength after hardening. Health problems caused by this have been pointed out. For this reason, various synthetic fibers are used as reinforcing materials in place of asbestos.

As a method for obtaining a fiber-reinforced cement molded body using such synthetic fibers, for example, Japanese Patent Application Laid-Open No. 58-213666
In the publication, an inorganic filler and synthetic fibers are mixed with cement, 15 to 30 parts by weight of water is added to 100 parts by weight of cement, and this is mixed with a kneader having sharp protrusions.
After mixing using a kneader such as a pressure kneader or pulper, which easily scratches the fiber surface during kneading, water necessary for shaping into a molded body is added, and this is shaped by a press to form a molded body. A technology has been disclosed.

However, when synthetic fibers are used as reinforcing materials, their dispersibility is not as good as asbestos, and the fibers tend to entangle with each other to form fiber balls, and once formed, the fiber balls are not easily defibrated. , the fibers tend to remain in the same shape in the cement matrix and the fibers are not uniformly dispersed. As a result, there is a problem that sufficient strength of the obtained molded body cannot be obtained.

Furthermore, when the synthetic fibers are mixed together, numerous scratches and cuts occur in the fibers, resulting in a decrease in the strength of the fibers themselves, which causes a problem of a decrease in the strength of the molded article.

Furthermore, when a mixture containing 30 parts by weight or more of water is pressed and shaped in the mold of a press machine, water separation occurs in the mold before the shaping is completed, resulting in partial flow failure of the mixture and complete shaping. There is a problem that shaping is not carried out, or even if shaping is carried out, the strength of the molded article becomes non-uniform.

(Problems to be Solved by the Invention) The present invention solves the above problems, and its purpose is to improve the dispersibility of synthetic fibers and the formability of cement mixtures, and to improve the strength. An object of the present invention is to provide a method for producing an excellent fiber-reinforced cement molded body.

(Means for Solving the Problems) That is, the method for producing a fiber-reinforced cement molded article of the present invention involves melting 0.1 parts by weight or more of a water-soluble polymer substance in 30 parts by weight or more of water, or during the melting process. At the same time, 200 parts by weight or less of an inorganic filler is added and mixed, and to this, 0 synthetic fibers are added.
．． A first step of adding 3 to 7 parts by weight and performing rocking mixing; a second step of adding 100 parts by weight of cement to the mixture obtained in the first step and further performing rocking mixing; A third step in which 0.1 to 5 parts by weight of a water reducing agent is added to the mixture obtained in the second step, and the mixture is further mixed by shaking, and the mixture obtained in the third step is molded into a mold that can be opened and closed. Put it inside, 0.3 crane/
and a fourth step of pressing and shaping at a speed of seconds or more, thereby achieving the object of the present invention.

The water-soluble polymer substances used in the present invention include methylcellulose, carboxymethylcellulose, polyvinyl alcohol, hydroxyethylcellulose, polyacrylic acid, and the like.

In addition, examples of the synthetic fibers used in the present invention include fibers such as vinylon, polyamide, polyester, and polypropylene, and the thickness thereof is 2 to 40 deniers and the length is 3
A length of ~151 m is used.

The term "cement" used in the present invention refers to hydraulic cement such as Portland cement, alumina cement, and blast furnace cement.

In addition, the inorganic fillers used in the present invention include silica sand,
These include river sand, fly ash, silica flour, bentonite, sepiolite, walrus night, calcium carbonate, mica, and blast furnace slag.

It is preferable to use two or more of the above inorganic fillers in combination for the following reasons.

For example, when silica sand is used as an inorganic filler, extremely high strength can be obtained if it is molded immediately after kneading, but after about an hour after kneading, the synthetic fibers aggregate and become complicated. The larger the shape, the more difficult it is to mold.

On the other hand, for example, when fly ash, which is a spherical particle with a specific surface area of 2400 cd/g or more, is used, the strength is inferior to silica sand, but the moldability is good immediately after kneading, but the moldability is not affected even after about 1 hour. It is easy to mold even complex shapes.

Therefore, it is necessary to combine an inorganic filler that provides high strength such as silica sand with an inorganic filler that has excellent moldability such as fly ash, which is a spherical particle with a specific surface area of 2400 cal/g or more, to compensate for the drawbacks of each. Can be done.

As the water reducing agent used in the present invention, conventionally known ones can be used, such as those whose main component is lignin sulfonate or its derivatives, those whose main component is sulfonate of higher polyhydric alcohol, and those whose main component is lignin sulfonate or its derivatives. The main component is acid,
Those whose main component is alkylaryl sulfonate, those whose main component is polyoxyethylene alkyl allyl ether, those whose main component is polyol complex, and those whose main component is sulfonate of aromatic polycyclic condensate. There are also those whose main component is a sulfonate of water-soluble melamine-formalin resin.

Furthermore, the term "oscillating mixing" as used in the present invention refers to a mixing method performed using a device in which a flexible rubber container is mounted on a disc-shaped oscillating plate without using a stirring blade. By continuously changing its inclination direction and angle, the rubber container containing the materials to be mixed deforms and swings, thereby accelerating the contents and changing its speed and direction. The particles are scattered and mixed in random directions. One cycle of movement of the rocking plate is usually 1 to 3 times/second. As the oscillating mixing device, there is, for example, the Omni-mixer manufactured by Chiyoda Giken Kogyo.

Next, the manufacturing method of the present invention will be explained along with the effects of each step.

In the first step, first, viscosity is imparted to the water by adding 0.bffi or more parts of a water-soluble polymer substance to 3 (l) parts of water, and then the inorganic filler is precipitated, which is added afterwards or simultaneously at the time of dissolution. can be suppressed to improve dispersibility.

Up to 200 parts by weight of an inorganic filler is added to the aqueous solution and mixed. In particular, when using a water-soluble polymeric substance that is easily soluble in water, such as methylcellulose, an inorganic filler is added and mixed at the same time as the water-soluble polymeric substance is dissolved. One type of inorganic filler may be used alone, but two or more types of inorganic fillers are used, and at least one of them has a particle shape close to a spherical shape and a specific surface area of It is preferable to select and use a large one of 2400 ci/g or more. Thereby, the fluidity of the mixture can be further improved, it can be shaped more easily, and the decrease in strength can be minimized.

By adding synthetic fibers to a viscous aqueous solution in which inorganic fillers are dispersed and mixing them with shaking, the synthetic fibers are uniformly distributed without forming fiber balls, being damaged, or cut. distributed. In this case, if the average particle size of the inorganic filler is 100 μm or more, it becomes difficult for the inorganic filler particles to enter between the fibers of the synthetic fibers, and the fibers tend to aggregate instead of dispersing. The average particle size is preferably 100 μm or less.

In the present invention, the amount of synthetic fiber added is 0.3 to 7 parts by weight. The amount of synthetic fiber added is 0.3. When the amount is less than fi parts, the desired strength of the molded product cannot be obtained, and when the amount added exceeds 7 parts by weight, fiber dispersion becomes poor and fluidity during shaping becomes poor.

Next, in the second step, 100 parts by weight of cement is added to the mixture obtained in the first step, and further oscillating mixing is performed. Thereby, the fine particles of cement are easily dispersed between the inorganic filler and the synthetic fibers, and a homogeneous mixture is obtained. The synthetic fibers are not damaged or cut during this process.

Furthermore, in the third step, 0.1 to 5 parts by weight of a water reducing agent is added to the mixture obtained in the second step, and further oscillating mixing is performed. The synthetic fibers are not damaged or cut during this step, and the water reducing agent serves to suppress the increase in viscosity of the mixture caused by the drop in temperature of the aqueous solution in which the polymeric substance is dissolved.

That is, the water-soluble polymeric substance used in the present invention is generally temperature-dependent, and when the temperature drops to, for example, 10°C or less, the viscosity of the aqueous solution increases.

When cement is mixed by shaking using a highly viscous polymer aqueous solution, the viscosity of the kneaded mixture increases and becomes hard.

If the kneaded mixture is hard, the fluidity will be poor and it will be difficult to shape the mixture into a predetermined shape during pressing, and the time required for dewatering by pressing will be longer.

In this case, it is possible to adjust the hardness of the mixture by increasing the amount of water, or to adjust the temperature of the aqueous solution using a heating device, but in the former case, the time required for dehydration by pressing will be longer; Moreover, the latter case requires special equipment, and there are problems in either case.

In the present invention, by adding a water reducing agent to the mixture, it is possible to suppress an increase in the viscosity of the mixture caused by a decrease in the temperature of the aqueous solution. In this case, when a water reducing agent is added in the first step, the viscosity of the aqueous solution decreases rapidly, and the dispersion of the synthetic fibers becomes extremely poor. When dispersing synthetic fibers, it is better to use an aqueous solution with as high a viscosity as possible.

Therefore, by adding a water reducing agent in the third step, it is possible to suppress the increase in the viscosity of the kneaded mixture without impairing the dispersion of the synthetic fibers. It is convenient because you can adjust the amount of water reducing agent added while actually checking the amount.

The amount of water reducing agent added is 0.1 to 5 parts by weight, preferably 0.1
~2 parts by weight. If the amount added is less than 0.1 parts by weight, the above effects cannot be expected, and if the amount added is more than 5 parts by weight, hardening of the cement will be delayed.

In the fourth and final step, the mixture obtained in the third step is placed in a mold that can be opened and closed and pressed to shape it. Since the mixture contains 30 parts by weight or more of water, water is likely to separate from the mixture.

For this reason, it is necessary to complete shaping before moisture separation occurs. In this case, if the mixture in the mold is pressed at a speed of 0°3 fl/sec or more, the water will not separate in the mold.
The mixture quickly fills the entire mold with sufficient fluidity and is completely shaped.

The molded body obtained by the above-mentioned process is dehydrated in a mold to the extent that shape retention is maintained, and the molded body is cured and cured by a conventionally known method to obtain a molded body.

(Example) Examples and comparative examples of the present invention are shown below.

1. 0.2 parts by weight of methylcellulose was dissolved in 45 parts by weight of water with a soil temperature of 5°C, and 30 parts by weight of silica powder was added to this aqueous solution and mixed. Parts by weight were added and mixed by oscillation. (First step) Next, 100 parts by weight of cement was added to the above mixture and further mixed by shaking. (Second Step) Further, 0.5 parts by weight of a water reducing agent containing an alkylaryl sulfonate as a main component (trade name: Mighty 150, Kao ■!!ri) was added to the above mixture, and further shaking mixing was performed. (Third step) Finally, put the above mixture into a mold that can be opened and closed and
The molded product was pressed into a wave shape at a pressure of 50 dazzles per second and dehydrated, and after demolding, it was cured for one week at a temperature of 60'C and a relative humidity of 90% to produce a molded product. (Fourth step) For the oscillating mixing in the first to third steps, an omni mixer (capacity 701) manufactured by Chiyoda Giken Kogyo ■ was used.

As a result of evaluating the shapeability and dehydration properties in the fourth step, both were good. The shapeability was evaluated by whether the mixture flowed to the details including the edges of the mold, and the dehydration ability was evaluated by whether the mixture could be dehydrated within 15 seconds. Furthermore, as a result of observing the fiber dispersion state and breakage state of the mixture before shaping, both were found to be good. Further, the bending strength of the obtained molded body measured according to JIS A 140B was 270 kg/cd.

Kitakami 1 - A molded article was produced under the same conditions as in Example 1 without using any water reducing agent, and the formability and dehydration properties were evaluated in the same manner as in Example 1. As a result, both were found to be defective. Ta. Moreover, the bending strength was 250 kg/ctA.

(Effects of the Invention) In the production method of the present invention, after or at the same time as dissolving a water-soluble polymer substance in water, an inorganic filler base material is added and mixed, and a synthetic fiber is added to this viscous mixture. Because they are synthetic fibers, they do not form fiber balls and have good dispersibility. In addition, since the mixture containing synthetic fibers is mixed by oscillating mixing without using any stirring blades, the synthetic fibers are not damaged or cut, and are uniformly dispersed, resulting in a high-strength molded product. .

Furthermore, the production method of the present invention uses an aqueous solution in which a water-soluble polymer substance is dissolved in water as described above, and the increase in viscosity of the mixture when the temperature decreases due to the aqueous solution is suppressed by a specific method. Since this is suppressed by adding a water reducing agent in the step immediately before shaping, the shaping properties of the kneaded mixture can be improved without impairing the dispersion of the synthetic fibers.

Moreover, since the kneaded mixture is pressed and shaped in the mold at a speed of 0.3 m/sec or more, shaping can be completed before the water in the mixture separates in the mold, resulting in the water reduction mentioned above. Coupled with the effect of the agent, the mixture quickly fills the entire mold with sufficient fluidity and is completely shaped, making it possible to obtain a uniform and strong molded product.

Patent applicant Sekisui Chemical Co., Ltd. Representative: Hiroshi 1) Kaoru

Claims (1)

[Claims] 1. After or at the same time as dissolving 0.1 part by weight or more of a water-soluble polymer substance in 30 parts by weight or more of water, 200 parts by weight or less of an inorganic filler is added and mixed; Synthetic fiber 0.
A first step of adding 3 to 7 parts by weight and performing rocking mixing;
A second step in which 100 parts by weight of cement is added to the mixture obtained in the first step and further mixed by shaking, and 0.1 to 5 parts by weight of a water reducing agent is added to the mixture obtained in the second step. The mixture obtained in the third step is placed in a mold that can be opened and closed, and the mixture is mixed by 0.3 mm/min.
A method for producing a fiber-reinforced cement molded body, comprising a fourth step of pressing and shaping at a speed of seconds or more. 2. The method for producing a fiber-reinforced cement molded body according to claim 1, which uses a combination of two or more types of inorganic fillers. 3. The method for producing a fiber-reinforced cement molded body according to claim 1, wherein the inorganic filler has an average particle size of 100 μm or less. 4. At least one of the two or more types of inorganic fillers has a particle shape close to spherical and a specific surface area of 2400.
The method for producing a fiber-reinforced cement molded article according to claim 2, wherein the fiber-reinforced cement molded body has a particle size of cm^2/g or more.