JPH0643047B2 - Method for producing fiber-reinforced cement compact - Google Patents

Description

The present invention relates to a method for producing a fiber-reinforced cement molded product having improved fiber dispersibility and shapeability and excellent strength.

(Prior Art) Asbestos is mixed as a reinforcing material in a cement molded product in order to improve the moldability at the time of molding and to improve the mechanical strength after curing. In recent years, asbestos is used. Some health problems have been pointed out. For this reason, various synthetic fibers are used as a reinforcing material in place of asbestos.

As a method for obtaining a fiber-reinforced cement molded product using such a synthetic fiber, for example, JP-A-58-213666, a cement is mixed with an inorganic filler and a synthetic fiber, and 100 parts by weight of the cement. 15 to 30 parts by weight of water is added to a kneader having a sharp protrusion, a pressure kneader, and a barber, which is used as a molded product after mixing using a kneader that easily scratches the fiber surface during kneading. A technique has been disclosed in which water necessary for shaping is added and shaped by pressing to form a molded body.

However, when using a synthetic fiber as a reinforcing material, its dispersibility is not as good as asbestos, the fiber balls are easily entangled to form a fiber ball, the fiber ball once formed is not easily defibrated, It tends to stay in the cement matrix in its original shape and the fibers are not evenly dispersed. As a result, there is a problem that the obtained molded product cannot have sufficient strength.

In addition, there is a problem in that the fibers undergo numerous scratches and breaks during the kneading of the synthetic fibers, and the strength of the fibers themselves decreases, resulting in a decrease in the strength of the molded body.

Furthermore, when pressing and shaping a mixture containing 30 parts by weight or more of water in the die of a press, separation of water occurs in the die before the shaping is completed, and the mixture partially fails to flow and complete shaping is performed. There is a problem that the strength of the molded body becomes non-uniform even if the molding is not performed or the shaping is performed.

(Problems to be Solved by the Invention) The present invention is to solve the above-mentioned problems, and an object thereof is to improve the dispersibility of synthetic fibers and the shapeability of a cement mixture, and to improve the strength. An object of the present invention is to provide a method for producing an excellent fiber-reinforced cement molded product.

(Means for Solving Problems) That is, the method for producing a fiber-reinforced cement molded product of the present invention is the method of dissolving 0.1 parts by weight or more of a water-soluble polymer substance in 30 parts by weight or more of water, or at the same time when dissolving. , 20 inorganic fillers
Add 0 parts by weight or less and mix, add 0.3 to 7 parts by weight of synthetic fiber to the first step and perform oscillating mixing, and add 100 parts by weight of cement to the mixture obtained in the first step. A second step of further performing oscillating mixing, a third step of adding 0.1 to 5 parts by weight of a water reducing agent to the mixture obtained in the second step, and further oscillating mixing, and a third step of The present invention is characterized in that it comprises a fourth step of putting the mixture obtained in the step of (4) into a mold that can be opened and closed and pressing and shaping at a speed of 0.3 mm / sec or more, whereby the object of the present invention is achieved. It

Then, as the water-soluble polymer substance used in the present invention, there are methyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, hydroxyethyl cellulose, polyacrylic acid and the like.

Examples of the synthetic fiber used in the present invention include fibers of vinylon, polyamide, polyester, polypropylene, etc., whose thickness is 2 to 40 denier and length is 3 to
A length of 15 mm is used.

The cement referred to in the present invention refers to a hydraulic cement such as Portland cement, alumina cement and blast furnace cement.

Further, as the inorganic filler used in the present invention, silica sand,
River sand, fly ash, silica flower, bentonite, sepiolite, wollastonite, calcium carbonate,
There are mica and blast furnace slag.

The inorganic fillers as described above are preferably used in combination of two or more kinds for the following reasons. That is, for example, when silica sand is used as the inorganic filler, an extremely high strength can be obtained by molding immediately after kneading.
After a lapse of about a time, the synthetic fibers agglomerate, and the more complicated the shape, the more difficult the molding becomes.

On the other hand, for example, when fly ash, which is a spherical particle having a specific surface area of 2400 cm ² / g or more, is used, the strength is inferior to that of silica sand, but the moldability immediately after kneading is good and the moldability is impaired even after about 1 hour. It is easy to mold even complicated shapes.

Therefore, each defect is compensated by combining an inorganic filler such as silica sand that provides high strength with an inorganic filler having a specific surface area of 2400 cm ² / g or more and having excellent formability such as fly ash that is spherical particles. be able to.

As the water reducing agent used in the present invention, conventionally known ones can be used, those containing lignin sulfonate or a derivative thereof as a main component, those containing a sulfonate of a higher polyhydric alcohol as a main component, and oxyorganic compounds. Acid-based, alkylallyl sulfonate-based,
Those containing polyoxyethylene alkylallyl ether as the main component, those containing polyol complex as the main component, those containing sulfonate of an aromatic polycyclic condensation product as the main component, and those of water-soluble melamine formalin resin There are those that have the main component.

The oscillating mixing referred to in the present invention is a mixing method performed by using a device in which a flexible rubber container is mounted on a disc-shaped oscillating plate without using stirring blades. By continuously changing its inclination direction and angle, the rubber container containing the material to be mixed is deformed and rocks, which accelerates the contents and changes its speed and direction. It is scattered in a random direction and mixed. One cycle of the movement of the rocker is usually 1 to 3 times / sec. An example of the rocking mixer is an omni mixer manufactured by Chiyoda Giken Co., Ltd.

Next, the manufacturing method of the present invention will be described for each step along with its action.

In the first step, first, by dissolving 0.1 parts by weight or more of a water-soluble polymer substance in 30 parts by weight or more of water, viscosity of water is given, and the precipitation of an inorganic filler added afterwards or at the time of dissolution is suppressed and dispersed. You can improve your sexuality.

To the above aqueous solution, 200 parts by weight or less of an inorganic filler is added and mixed. In particular, when a water-soluble polymer substance such as methyl cellulose which is easily dissolved in water is used, an inorganic filler is added and mixed at the same time when the water-soluble polymer substance is dissolved. As this inorganic filler, one kind may be used alone, but two or more kinds 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 cm ² / g or more. As a result, the fluidity of the mixture can be further improved, the shape can be more easily shaped, and the decrease in strength can be suppressed to a minimum.

In this way, by adding the synthetic fibers to the viscous aqueous solution in which the inorganic filler is dispersed and mixing by shaking, the synthetic fibers are uniformly formed without forming fiber balls, being scratched, or being cut. Distributed. In this case, if the average particle size of the inorganic filler is 100 μm or more, it becomes difficult for the particles of the inorganic filler to enter between the fibers of the synthetic fiber, and the fibers tend to aggregate without being dispersed. 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. If the amount of synthetic fiber added is less than 0.3 parts by weight, the desired strength of the molded product cannot be obtained, and if the amount added exceeds 7 parts by weight, the dispersion of the fibers becomes poor and the 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 rocking mixing is further performed. Thereby, the fine particles of cement are easily dispersed between the inorganic filler and the synthetic fiber to obtain a uniform mixture. The synthetic fibers are not damaged or cut even in this process.

Furthermore, in the third step, 0.1 to 5 parts by weight of the water reducing agent is added to the mixture obtained in the second step, and the mixture is subjected to rocking mixing. The synthetic fibers are not damaged or cut even in this process. The water reducing agent functions to suppress the increase in viscosity of the mixture caused by the temperature decrease of the aqueous solution in which the polymer substance is dissolved.

That is, the water-soluble polymer substance used in the present invention generally has temperature dependence, and when the temperature falls below 10 ° C., the viscosity of its aqueous solution increases. When the cement is rock-mixed by using a high-viscosity aqueous polymer solution, the viscosity of the kneaded mixture becomes high and becomes hard. If the kneading hardness of the mixture is hard, the fluidity is poor, and it becomes difficult to shape the mixture into a predetermined shape at the time of press shaping, and moreover, the time required for dehydration by pressing becomes long.

In this case, it is considered that the hardness of the mixture is adjusted by increasing the amount of water or the temperature of the aqueous solution is adjusted by a heating device, but in the former case, the time for dehydration by pressing becomes long, In the latter case, a special device is required, and there is a problem in any 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 the water reducing agent is added in the first step, the viscosity of the aqueous solution is drastically reduced, and the dispersion of the synthetic fiber is extremely deteriorated. When the synthetic fibers are dispersed, it is better to use an aqueous solution having a viscosity as high as possible.

Therefore, if the water reducing agent is added in the third step, it is possible to suppress an increase in the viscosity of the mixture kneaded without impairing the dispersion of the synthetic fibers, and yet to increase the viscosity of the mixture kneaded in the second step. It is convenient because the amount of the water reducing agent can be adjusted while actually checking the value.

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

In the final fourth step, the mixture obtained in the third step is put into an openable mold to be pressed and shaped. Since the mixture contains 30 parts by weight or more of water, water is easily separated from the mixture. Therefore, it is necessary to complete the shaping before the separation of water occurs. In this case, 0.3m of the mixture in the mold
By pressing at a speed of m / sec or more, moisture is not separated in the mold, and the mixture is rapidly filled in the mold with sufficient fluidity and completely shaped.

The molded product obtained by the above-mentioned steps is dehydrated in a shape to the extent that shape retention is maintained, then demolded, and cured by a conventionally known method to obtain a molded product.

(Example) Hereinafter, the Example and comparative example of this invention are shown.

Example 1 0.2 parts by weight of methyl cellulose was dissolved in 45 parts by weight of water at a temperature of 5 ° C., 30 parts by weight of silica powder was added to and mixed with this aqueous solution, and 2 parts by weight of aramid fiber having a fiber length of 6 mm was added thereto. Then, rocking mixing was performed. (First step) Next, 100 parts by weight of cement was added to the above mixture, and the mixture was subjected to rocking mixing. (Second step) Further, a water reducing agent containing alkylallyl sulfonate as a main component in the above mixture (trade name: Mighty 150, manufactured by Kao Corporation)
0.5 part by weight was added and further mixed by rocking. (Third
Step) Finally, the above mixture is put into a mold that can be opened and closed, and it is subjected to wavy pressing at a speed of 0.5 mm / sec and a pressure of 50 kg / cm ^{2 and} is dehydrated, and after demolding, the temperature is 60 ° C. and 90%. A molded body was produced by curing and curing at a relative temperature for 1 week. (Fourth step) The oscillating mixing in the first to third steps was performed using an omni mixer (capacity 70) manufactured by Chiyoda Giken Kogyo Co., Ltd.

As a result of evaluating the shapeability and the dehydratability in the fourth step, all were good. The shapeability was evaluated by whether or not the mixture flowed to the details including the end of the mold, and the dehydratability was evaluated by whether or not it could be dehydrated within 15 seconds. As a result of observing the dispersed state and broken state of the fiber in the mixture before shaping, both were good. The bending strength of the obtained molded body measured according to JIS A 1408 is 270 kg / cm ^2.
Met.

Comparative Example 1 A molded article was produced under the same conditions as in Example 1 except that no water reducing agent was used, and the shapeability and the dehydratability were evaluated in the same manner as in Example 1, and as a result, all were poor. . The bending strength was 250 kg / cm ² .

(Effect of the Invention) In the production method of the present invention, an inorganic filler is added and mixed at the same time after or after dissolving a water-soluble polymer substance in water, and synthetic fibers are added to this viscous mixture. Therefore, the synthetic fiber has good dispersibility without forming a fiber ball. Further, the mixture containing the synthetic fibers is mixed by oscillating mixing without using any stirring blades, so that the synthetic fibers are not damaged or cut and are uniformly dispersed to obtain a high-strength molding. .

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 the viscosity of the mixture at the time of temperature decrease caused by the aqueous solution is Since it is suppressed by adding the water reducing agent in the step, that is, the step immediately before shaping, the shaping property of the kneaded mixture can be improved without impairing the dispersion of the synthetic fiber.

Moreover, since the kneaded mixture is pressed in the mold at a speed of 0.3 mm / sec or more to shape it, the shaping can be completed before the water content of the mixture is separated in the mold. In combination with the effect of (1), the mixture can be quickly filled with the mixture while having sufficient fluidity and complete shaping can be performed, and a uniform and strong molded product can be obtained.

Claims (4)

[Claims] 1. After dissolving 0.1 part by weight or more of a water-soluble polymer substance in 30 parts by weight or more of water, simultaneously with or when dissolving, 200 parts by weight or less of an inorganic filler is added and mixed, and synthetic fiber 0.3
A first step of adding ~ 7 parts by weight to perform oscillating mixing, a second step of adding 100 parts by weight of cement to the mixture obtained in the first step, and further performing oscillating mixing; Add 0.1 to 5 parts by weight of a water reducing agent to the mixture obtained in the step 2 and further perform a third mixing by rocking, and put the mixture obtained in the third step in a mold that can be opened and closed. And a fourth step of shaping by pressing at a rate of 0.3 mm / sec or more. 2. The method for producing a fiber-reinforced cement molded product according to claim 1, wherein two or more kinds of inorganic fillers are used in combination. 3. The method for producing a fiber-reinforced cement molded product according to claim 1, wherein the inorganic filler has an average particle diameter of 100 μm or less. 4. At least one of the two or more types of inorganic fillers has a particle shape close to a sphere and has a specific surface area.
The method for producing a fiber-reinforced cement molded product according to claim ^{2, which has a} density of 2400 cm ² / g or more.