JPH11200529A - Short fiber for placing concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide short fibers for placing concrete having a function that the short fibers are decomposed and extinguished with time after concrete placing and fine hollow passages are left, a cured concrete structure is manufactured and voids existing in the inside and the outside air are channeled by mixing freshly mixed concrete with hydraulic cement and water when the freshly mixed concrete to be used for placing concrete is adjusted. SOLUTION: Short fibers contain a resin composition consisting of 100 pts.wt. fatty polyester and 1-100 pts.wt. at least one kind selected from polyalkylene glycol, polyvinyl alcohol and starch having structural units displayed by formula. When a freshly mixed concrete is adjusted, the short fibers are mixed with hydraulic cement and water and used. In the formula, R1 and R2 represent a hydrogen or a 1-6C saturated or unsaturated hydrocarbon group separately independently and (n) an integer of 1-5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic cement and a short fiber for concrete casting which is used by mixing it with water when preparing fresh concrete for concrete casting. The present invention relates to a concrete structure casting method, which comprises casting ready-mixed concrete prepared by mixing hydraulic cement, water, and short fiber concrete.

[0002]

2. Description of the Related Art Conventionally, concrete construction methods include: 1) a step of preparing hydraulic cement and fresh concrete containing water; 2) embedding concrete panels and constructing a concrete casting formwork. 3) filling the ready-mixed concrete into the concrete casting formwork; 4) curing the hardened concrete structure; 5) the concrete after the ready-mixed concrete becomes a hardened concrete structure. Disassembling the casting formwork.

However, in such a conventional method of constructing a concrete structure, voids of various sizes, such as bubbles, voids, microvoids, and cavities, are formed inside the walls of the concrete structure to be formed. Including tees) in which air is trapped. Most of these voids are closed spaces isolated from the outside world or the outside air. If such a concrete structure is in a fire,
The air trapped in the voids inside the walls of the concrete structure expands rapidly, causing explosions and cracks, not only destroying the concrete structure, but also scattering due to the destruction Concrete fragments could injure humans.

As a means for solving such a drawback, in the process of preparing ready-mixed concrete, in addition to hydraulic cement and water, short fibers (staple fiber, staple fiber) of chemical fibers such as polyolefin (polyethylene, polypropylene, etc.). ), Channeling the void present inside the wall of the concrete structure with the outside world or the outside air and the short fiber, and dispersing the air rapidly expanded in the void into the outside world or the outside air. Has been devised by some of those skilled in the art.

[0005] However, in such a method, the void existing inside the wall surface of the concrete structure is not channeled directly by the minute passage of the cavity, but is channeled by the short fiber of the chemical fiber. It was only. In addition, in such a method, when the concrete structure is in a fire, the short fibers of the chemical fibers remaining as they are in the concrete structure are thermally decomposed by the high heat of the fire, and toxic decomposition gas is generated. , There was a risk of harm to humans. As described above, according to the conventional technique, it is difficult to sufficiently solve the problem to be solved by the present invention described below.

[0006]

The problem to be solved by the present invention is a short fiber for concrete casting having a specific composition, which is used for preparing ready-mixed concrete for use in concrete casting. By mixing with hydraulic cement and water, it is eliminated over time in an environment of pH 11 or more during the curing process after placing concrete, leaving a fine cavity passage, and the voids, with respect to the outside world or the outside air,
Having a function that can be an open space, and after the ready-mixed concrete becomes a hardened concrete structure, it has a function of channeling a void existing inside the wall surface of the concrete structure with the outside world or outside air, An object of the present invention is to provide short fibers for concrete casting. By using the short fiber for concrete casting of the present invention, a void existing inside the wall surface of the concrete structure is made to be an open space with respect to the outside world or the outside air by a fine cavity passage, thereby causing a fire. Even if it is generated and heated to a high temperature, it is possible to provide a concrete structure that is less likely to generate an explosion or crack and that is less likely to generate a decomposition gas.

[0007]

Means for Solving the Problems The inventors of the present invention have a temperature of 25 ° C.
A short fiber that is stable to water near neutrality without causing a decrease in molecular weight due to hydrolysis and has a function of hydrolyzing under alkaline conditions (pH 11 or more) is mixed with hydraulic cement and water to produce a short fiber. Concrete was prepared, and the ready-mixed concrete was cast to construct a concrete structure. The present inventors have conducted intensive studies on the characteristics of this concrete structure, and as a result, the void existing inside the wall surface of the concrete structure is closed to the outside or the outside air by the short fibers immediately after casting. However, in the process of curing the hardened concrete, the short fibers disintegrate and disappear over time in an environment of pH 11 or more in the hardened concrete structure, leaving a fine cavity passage, and the void is exposed to the outside world or the outside air. It was found that the space was open, and the present invention was completed.

That is, the present invention provides the following [1] to
It is specified by the items described in [6]. [1] (A) 100 parts by weight of an aliphatic polyester, and (B) a polyalkylene glycol or a polyvinyl alcohol having a structural unit represented by the formula (1) or (2):
And a short fiber containing a resin composition consisting of at least 1 to 100 parts by weight of at least one selected from the group consisting of starch, when preparing ready-mixed concrete for concrete casting, hydraulic cement, and Staple fiber for concrete casting used by mixing with water.

Embedded image (In the formula, R ₁ and R ₂ each independently represent a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 6 carbon atoms, and n represents an integer of 1 to 5.) ] The short fiber for concrete casting according to [1], wherein the short fiber is a monofilament. [3] The short fiber for concrete casting according to [1], wherein the short fiber is a multifilament. [4] The average length of the short fiber is 1 to 50 mm [1] to
The short fiber for concrete casting according to any one of [3]. [5] (B) is a polyalkylene glycol [1]
-The short fiber for concrete casting according to any one of [4] to [4]. [6] The short fiber for concrete casting according to claim 5, wherein the polyalkylene glycol is polyethylene glycol and / or polypropylene glycol.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The resin composition constituting the short fibers for casting concrete according to the present invention is stable under neutral conditions such as rainwater before casting concrete, and alkalis during curing after casting concrete. Decomposition must proceed rapidly under the conditions. Generally, the pH inside concrete is 1
Since it is 1 to 13, the resin composition constituting the short fibers for concrete casting according to the present invention must be easily decomposed at a pH of 11 or more. Therefore, a resin composition that can be decomposed under alkaline conditions is a resin composition that is hardly decomposed by neutral water near pH 7 and that is rapidly hydrolyzed by alkaline water having a pH of 11 or more. is there. Aliphatic polyesters are effective as a resin composition in which hydrolysis proceeds under alkaline conditions having a pH of 11 or more.

Examples of the aliphatic polyester of the present invention include polyhydroxycarboxylic acids, polyesters comprising aliphatic polyhydric alcohols and aliphatic polybasic acids, mixtures of polyhydroxycarboxylic acids and polyesters, hydroxycarboxylic acids and aliphatic polyesters. Examples include a random copolymer containing two or more types of monomer components selected from the group of polyhydric alcohols and aliphatic polybasic acids, and a block copolymer. Particularly preferred are polylactic acid, a mixture of polylactic acid and another aliphatic polyester, and a random copolymer and a block copolymer of polylactic acid and another aliphatic polyester.

The hydroxycarboxylic acids used in the aliphatic polyester of the present invention include glycolic acid, lactic acid,
Examples thereof include 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxylvaleric acid, 5-hydroxyvaleric acid, and 6-hydroxycaproic acid.

The aliphatic polyhydric alcohol used in the aliphatic polyester of the present invention includes ethylene glycol,
Diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, , 9-nonanediol, neopentyl glycol, polytetramethylene glycol, 1,4-cyclohexanedimethanol, 1,4
-Benzene dimethanol, etc., and examples of the aliphatic polybasic acid include succinic acid, oxalic acid, malonic acid, glutaric acid, adipic acid, bimeric acid, suberic acid, azelaic acid, sebacic acid, undecandioic acid and dodecanediacid. Acids, phenylsuccinic acid, 1,4-phenylenediacetic acid and the like. One or more of these may be included.

Examples of the method for producing the aliphatic polyester used in the present invention include a direct polymerization method in which lactic acid is dehydrated and polycondensed in an organic solvent in the presence or absence of a catalyst (JP-A-6-65360). Lactic acid cyclic dimer (lactide)
Polymerized by melt polymerization (US Pat. No. 2,758,98).
No. 7), a ring-opening polymerization method in which a mixture of a cyclic dimer of lactic acid and ε-caprolactone is melt-polymerized in the presence of a catalyst (US Pat. No. 4,057,537), and the like. There are no restrictions. Further, the copolymer may be partially copolymerized with a polyhydric alcohol such as a polysaccharide, or the chain may be extended using a binder such as diisocyanate.

The molecular weight of the aliphatic polyester used in the present invention is not particularly limited as long as it exhibits substantially sufficient mechanical properties so that it can be processed into a film or a container.
Generally, the weight average molecular weight is preferably from 100,000 to 500,000, preferably from 30,000 to 400,000, more preferably from 50,000 to 300,000 from the viewpoint of ease of molding. If the weight average molecular weight is less than 10,000, the mechanical properties are not sufficient,
If it exceeds 10,000, handling may be difficult or uneconomical.

The hydrolysis of these aliphatic polyesters proceeds under alkaline conditions in concrete, but the rate is not sufficient to achieve the object of the present invention. To quickly hydrolyze in concrete curing,
It is necessary to add a component that promotes decomposition (decomposition accelerator).

Such compounds include, for example, starch, polyvinyl alcohol and its derivatives, polyethylene glycol and its derivatives, polypropylene glycol and its derivatives, polyoxytetramethylene glycol and its derivatives, etc. )) And hydrophilic polymer compounds such as polyalkylene glycols.

Embedded image (In the formula, R ₁ and R ₂ each independently represent a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 6 carbon atoms, and n represents an integer of 1 to 5.) The polyalkylene glycol represented by the formula (1) has good compatibility with the aliphatic polyester, and is preferable.
Of the polyalkylene glycols, polyethylene glycol or polypropylene glycol is preferred.

When a polyalkylene glycol represented by the formula (1) or a derivative thereof is used as a decomposition accelerator for an aliphatic polyester, the decomposition rate of the aliphatic polyester in an environment of pH 11 or more depends on the molecular weight of the polyalkylene glycol. , May be different. In order to obtain a high decomposition rate, the weight average molecular weight of the polyalkylene glycol is preferably 100 to 10,000, and 200 to 8,000.
Is more preferable, and 400 to 6000 is further preferable.
If it is smaller than 100, bleed out from the aliphatic polyester is remarkable, and if it is larger than 10,000, the decomposition promoting effect may not be so much exhibited.

The starch is not particularly limited, but corn starch and potato starch are preferably used. These decomposition accelerators may be added alone, or may be added as a mixture of two or more kinds, and it is more preferable to use starch and / or polyvinyl alcohol in combination with polyalkylene glycol, and it is more preferable to use them in combination. Hydrolysis rate can be obtained. The addition amount is 1 to 100 parts by weight, preferably 2 to 75 parts by weight, more preferably 3 to 5 parts by weight based on 100 parts by weight of the aliphatic polyester.
0 parts by weight, more preferably 4 to 30 parts by weight.

The resin composition according to the present invention may be optionally used to improve physical properties such as flexibility and impact resistance. Can also be added.

Examples of the plasticizer used in the present invention include phosphoric acid esters, phthalic acid esters, aliphatic polybasic acid esters, polyhydric alcohol esters, and oxyacid esters. Examples of the phosphate esters include tributyl phosphate, tri-2-ethylhexyl phosphate, triphenyl phosphate, and tricresyl phosphate. Examples of the phthalate esters include dimethyl phthalate, diethyl phthalate, and dibutyl phthalate. , Diheptyl phthalate, dioctyl phthalate, di-2-ethylhexyl phthalate,
Diisononyl phthalate, octyl decyl phthalate, diisodecyl phthalate, butyl benzyl phthalate, and the like.Examples of the aliphatic polybasic esters include butyl oleate, glycerin monooleate, dibutyl adipate, and di-adipate. n-hexyl, di-2-ethylhexyl adipate, alkyl 610 adipate, di-2-ethylhexyl azelate, dibutyl sebacate, di-2-ethylhexyl sebacate and the like,
As polyhydric alcohol esters, diethylene glycol dibenzoate, triethylene glycol di-2-
Ethyl butyrate, glycerin triacetate glycerin tripropionate and the like can be mentioned, and oxyacid esters include methyl acetyl ricinoleate, butyl acetyl ricinoleate, butyl phthalyl butyl glycolate, tributyl acetylene citrate and the like.

Other examples include chlorinated paraffin, dinonylnaphthalene, toluenesulfonethylamide, camphor, methyl abietate and the like. These may be used alone or as a mixture of two or more. The amount used depends on the desired softness, but is 1 to 30% by weight based on the polymer.

In the present invention, another relatively soft polymer may be added for the purpose of imparting flexibility to the aliphatic polyester. The method of imparting flexibility by adding a soft polymer is substantially bleeding by selecting the type and amount of the polymer to be added or the weight-average molecular weight as appropriate in addition to being able to soften as compared with the method of adding the plasticizer. There is no change with time due to out, and it can be preferably used.

The soft polymer that can be used in the present invention is a polyalkylene glycol having a structural unit represented by the formula (1) (formula 4), such as polyethylene glycol or polyprolene glycol.

Embedded image (Wherein, R ₃ and R ₄ each independently represent a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 6 carbon atoms, and n represents an integer of 1 to 5). In order to impart flexibility to the polyester substantially without bleed-out even when molded, the weight average molecular weight of the polyalkylene glycol to be added is 2 × 10
^It is preferably from ^{3 to} 5 × 10 ^6, more preferably from 4 × 10 ^{3 to} 3 × 10 ⁶ , even more preferably from 1 × 10 ⁴ to 1 × 10 ⁶ . The addition amount is appropriately selected depending on the desired softness, but is 1 to 40% by weight based on the aliphatic polyester.

In the present invention, when spinning the resin composition according to the present invention, an inorganic filler may be added for the purpose of preventing blocking between fibers. Examples of the inorganic filler include talc, magnesium silicate, calcium carbonate, aluminum powder, silica, kaolinite and the like.

As an embodiment of the method for producing short fibers for concrete casting according to the present invention, a method comprising the following steps 1) to 5) is exemplified. 1) Pelletizing step A step of mixing the resin composition obtained by mixing the aliphatic polyester, the decomposition accelerator, and in some cases, a plasticizer and an inorganic filler by using a general mixer or an extruder, and pelletizing. There are no restrictions on the kneading machine, homogenizer, extruder, extrusion die, etc. employed in this step. 2) Spinning step A step of spinning the pellets obtained in the pelletizing step by a melt spinning method, a dry spinning method, a wet spinning method, or the like. The specific contents are described, for example, in Textile Handbook / Raw Materials (edited by The Textile Society of Japan, Maruzen, Tokyo, 1968), pages 823 to 832. There are no restrictions on the spinning method, spinning equipment, and the like employed in this step. Usually, melt spinning is preferably employed as the spinning method. When melt spinning is employed, the die temperature is preferably from 180 to 190C.

3) Drawing Step A step of drawing the yarn spun in the spinning step. The specific contents thereof are described in, for example, Textile Handbook / Raw Materials (edited by The Textile Society of Japan, Maruzen, Tokyo, 1968), pages 833 to 841. There are no restrictions on the stretching method, stretching equipment, etc. employed in this step. When employing melt spinning, the stretching ratio is preferably 3 to 10 times. 4) Heat treatment / post-treatment step A step of heat treatment / post-treatment of the yarn drawn in the drawing step. The specific contents thereof are described in, for example, Textile Handbook / Raw Materials (edited by The Textile Society of Japan, Maruzen, Tokyo, 1968), pages 833 to 841. There are no restrictions on the heat treatment method and post-treatment method employed in this step.

5) Cutting Step A step of turning the yarn treated in the heat treatment / post-treatment step into short fibers. The specific contents are, for example, Textile Handbook / Raw Materials (edited by The Society of Fiber Science, Maruzen, Tokyo, 1968), 837-841
Page. There are no restrictions on the cutting method or cutter used in this step. By such a manufacturing method, for example, monofilament short fibers having a fineness of 200 to 400 denier and a strength of 3 to 10 g / denier can be obtained.

In the present invention, the term "short fiber" means a tow-like yarn cut based on a certain staple diagram. In the present invention, the term “yarn” refers to a textile handbook / processing edition (edited by the Japan Society of Fiber Science, Maruzen, Tokyo, 1969)
It includes the concept of “raw yarn” described on pages 393 to 421, and includes, for example, monofilament, multifilament, staple fiber (swoof), tow, high bulk swoof, high bulk tow, spun yarn, blended yarn, processed yarn, and false twist yarn. , Irregular shaped yarn, hollow yarn, conjugate yarn, POY
(Partially oriented yarn), DTY (drawn yarn), POY-DT
Y, sliver, etc. are also included.

[0029] The short fibers for concrete casting of the present invention are composed of the resin composition described in detail above, and are not particularly limited in cross-sectional shape and fineness, and may be monofilaments.
It may be a multifilament. Specific examples of the cross-sectional shape of the short fiber for concrete casting of the present invention include a perfect circle, an ellipse, a hollow, and a different shape (for example, a triangle, a square, a pentagon, a hexagon, etc.), and the like. Specifically, a perfect circular shape is preferable. The fineness of the short fibers for casting concrete of the present invention is usually preferably 200 to 400 denier, and the strength is preferably 3 to 10 g / denier. The staple diagram of the short fiber for concrete casting according to the present invention is not particularly limited, but usually, it is preferably rectangular and the average length of the short fiber is preferably 1 to 50 mm.

As an embodiment of the method of placing concrete using the short fibers for placing concrete according to the present invention, a method comprising the following steps 1) to 5) is exemplified. 1) Ready-mixed concrete preparation process The short fiber for concrete casting of the present invention, hydraulic cement,
And a step of preparing ready-mixed concrete containing water. 2) Concrete casting formwork construction process The process of building concrete panels and constructing concrete casting formwork. 3) Filling the ready-mixed concrete A step of filling the ready-mixed concrete into the concrete casting formwork. 4) Curing step A step of curing the hardened concrete structure. 5) Concrete dismantling formwork dismantling step A step of dismantling the concrete casting formwork after the ready-mixed concrete becomes a hardened concrete structure.

There is no particular limitation on the method for mixing the short fibers for casting concrete of the present invention with hydraulic cement or water to obtain ready-mixed concrete. Generally, the short fibers for casting concrete of the present invention are mixed with hydraulic cement or water to obtain ready-mixed concrete. Further, the short fibers for concrete casting of the present invention, hydraulic cement, aggregate (for example,
Sand, gravel, overgrown stone, etc.), and optionally, additives (eg,
Binders, thickeners, etc.) may be premixed at a fixed composition ratio in advance.

[0032]

EXAMPLES The weight average molecular weight (Mw) in the examples was determined by gel permeation chromatography (GPC) (column temperature; 40 ° C., chloroform solvent) by comparison with a standard polystyrene sample.

Synthesis Example 1 In a 500 ml four-neck flask equipped with a stirrer and a thermometer, 104.3 g of 90% lactic acid and diphenyl ether 2 were added.
25.0 g and 2.0 g of metallic tin were added, and 130 ° C./140
The mixture was heated and stirred at 7 mmHg for 7 hours while distilling the generated water out of the system. A Dean Stark Trap was attached thereto, and azeotropic dehydration was performed at 140 ° C./130 mmHg for 8 hours. Then, a drying tube filled with 40 g of molecular sieves 3A was attached. And heated to reflux at 130 ° C./17 mmHg for 30 hours. After cooling, the reaction mass was dissolved in 600 ml of chloroform, added to 4 l of acetone, reprecipitated, and the precipitated solid was separated by filtration. Next, an isopropyl alcohol (hereinafter referred to as IPA) solution 5 in which 5 g of hydrochloric acid is dissolved in the filter cake.
And stirred for 30 minutes.
The resulting wet cake was dried at 60 ° C./100 mmHg for 15 hours. The resulting solid was white powdered polylactic acid in a yield of 69.1 g, a yield of 92.2%, and a weight average molecular weight (M
w) 29.5 million.

Synthesis Example 2 In a 1000 ml four-neck flask equipped with a stirrer and a thermometer, 730.3 g of 90% lactic acid and 5.0 g of zinc powder were added, and the produced water was distilled out of the system at 130 ° C./50 mmHg for 3 hours. After the mixture was heated and stirred while being discharged, the pressure was further reduced to 5 mmHg. At this time, lactide, which is a cyclic dimer of white lactic acid, was distilled off. The obtained lactide was recrystallized from ethyl acetate to obtain 420.0 g of purified ratatide. The yield was 80.0%. In a 500 ml reactor equipped with a thermometer, a stirring blade, a nitrogen inlet tube, and a reaction mass outlet at the bottom, 200 g of purified lactide and 0.02 tin otatanate were added.
g and lauryl alcohol (0.06 g) were charged and heated and stirred at 200 ° C./10 mmHg for 2 hours in a nitrogen stream. After completion of the reaction, a melt of polylactic acid was extracted from the lower outlet, cooled, and cut with a pelletizer. The obtained polylactic acid had a yield of 164.0 g, a yield of 82.0%, and a weight average molecular weight (Mw) of 138,000.

Synthesis Example 3 The procedure of Synthesis Example 1 was repeated, except that 50.5 g of 1,4-butanediol and 66.5 g of succinic acid were used instead of lactic acid. As a result, polybutylene succinate in the form of white powder was obtained. I got The yield was 92.2 g, the yield was 95.0%, and the weight average molecular weight (Mw) was 122,000.

Synthesis Example 4 Polylactic acid obtained in Synthesis Example 2 (Mw = 1380,000) 30
0 g, polybutylene succinate obtained in Synthesis Example 3
(Mw = 1220,000) 200 g was charged into a ribbon blender and mixed well to obtain a mixture of polylactic acid and polybutylene succinate (lactic acid component: 60% by weight).

Synthesis Example 5 The weight average molecular weight (M
w) Reaction mass of 220,000 polylactic acid (75 g of polylactic acid,
Diphenyl ether (225.0 g) was charged with 18.8 g of the polybutylene succinate having a weight average molecular weight (Mw) of 122,000 obtained in Synthesis Example 3, and further charged at 130 ° C./17.
Other than reacting for 20 hours at mmHg. As a result of the same procedure as in Synthesis Example 1, a block copolymer of polylactic acid and polybutylene succinate (lactic acid component: 80% by weight) was obtained. The yield was 87.4 g, the yield was 93.2%, and the weight average molecular weight (Mw) was 135,000.

Synthesis Example 6 Instead of lactic acid, 104.0 g of 6-hydroxycaproic acid
Was carried out in the same manner as in Synthesis Example 1, except that polycaproic acid in the form of white powder was obtained. The yield is 81.0 g,
The yield was 92.2% and the weight average molecular weight (Mw) was 11.1
It was 10,000.

Synthesis Example 7 Polylactic acid obtained in Synthesis Example 2 (Mw = 1380,000) 30
0 g of the polycaproic acid obtained in Synthesis Example 6 (Mw = 1
11,000) 200 g was charged into a ribbon blender and mixed well to obtain a mixture of polylactic acid and polycaproic acid (lactic acid component: 60% by weight).

Synthesis Example 8 18.8 g of the polycaproic acid obtained in Synthesis Example 6 was synthesized.
Was charged into a reaction mass of polylactic acid having a weight average molecular weight (Mw) of 111,000 (75 g of polylactic acid, 225.0 g of diphenyl ether) obtained by the same method as in Example 1.
As a result of performing the reaction in the same manner as in Synthesis Example 1 except that the reaction was carried out at mmHg for 20 hours, a block copolymer of polylactic acid and polycaproic acid (lactic acid component: 80% by weight) was obtained. The yield was 86.5 g, the yield was 92.2%, and the weight average molecular weight (M
w) was 135,000.

Example 1 1) Production of Short Fiber 80 parts by weight of polylactic acid having a weight average molecular weight of 2950,000 and a polymer alloy of polyvinyl alcohol / starch [trade name: Matterby: manufactured by Nippon Synthetic Chemical Co., Ltd.] 20 parts by weight Were extruded at a temperature of 180 ° C. using a twin-screw extruder (36 mm) and pelletized with a pelletizer. The pelletized resin composition is heated at an extruder cylinder temperature of 170-19.
It was melt-spun at 0 ° C. and a die temperature of 190 ° C., immediately stretched 5 times, and had a fineness of 350 denier and a strength of 3.0 g / denier.
A monofilament having a perfect circular cross section was manufactured. This monofilament is cut by a cutter and has a length of 30 ± 5 mm.
Short fibers. 2) Manufacture of hardened concrete board 100 parts by weight of ordinary Portland cement, standard sand 100
After mixing 5 parts by weight and 5 parts by weight of short fibers with a high-speed mixer for 5 minutes, water was added so that the water / cement weight ratio (W / C ratio) became 0.4, and mixed well to prepare ready-mixed concrete. . This ready-mixed concrete was filled into a formwork made of concrete panels to produce a hardened concrete plate of 250 × 250 × 25 mm. The hardened concrete slabs were cured for 6 months in the shade outdoors. 3) Evaluation of hardened concrete board After hardening, the hardened concrete board was heated in an electric furnace kept at 1000 ° C. for 20 minutes. After the heating was completed, it was taken out of the electric furnace and cooled naturally. After cooling to room temperature, the surface of the hardened concrete plate was observed, but there were no cracks, and no difference was observed from before heating.

Example 2 1) Production of Short Fiber 80 parts by weight of polylactic acid having a weight average molecular weight of 138,000 and polyethylene glycol (weight average molecular weight is 2000) 20
The resin composition was obtained by mixing parts by weight. This resin composition was melt-spun at an extruder cylinder temperature of 170 to 190 ° C. and a die temperature of 190 ° C., and immediately stretched 5 times to a fineness of 35.
A monofilament of 0 denier, 4.0 g / denier strength and a perfect circular cross section was produced. This monofilament was cut by a cutter to obtain a short fiber having a length of 30 ± 5 mm. 2) Production of hardened concrete plate 250 × 250 × 25 m in the same manner as in Example 1.
m of hardened concrete board was manufactured and cured for 6 months in the shade outdoors. 3) Evaluation of hardened concrete board After hardening, the hardened concrete board was heated in an electric furnace kept at 1000 ° C. for 20 minutes. After the heating was completed, it was taken out of the electric furnace and cooled naturally. After cooling to room temperature, the surface of the hardened concrete plate was observed, but there were no cracks, and no difference was observed from before heating.

Example 3 1) Production of Short Fiber 70 parts by weight of polylactic acid obtained in Synthesis Example 1 and starch 20
Parts by weight, polyethylene glycol (weight average molecular weight is 2
000) of 10 parts by weight to obtain a resin composition. This resin composition was heated at an extruder cylinder temperature of 170 to 190.
The mixture was melt spun at a die temperature of 190 ° C. and immediately stretched 5 times to produce a monofilament having a fineness of 350 denier, a strength of 3.1 g / denier and a perfect circular cross section. This monofilament was cut by a cutter to obtain a short fiber having a length of 30 ± 5 mm. 2) Production of hardened concrete plate 250 × 250 × 25 m in the same manner as in Example 1.
m of hardened concrete board was manufactured and cured for 6 months in the shade outdoors. 3) Evaluation of hardened concrete board After hardening, the hardened concrete board was heated in an electric furnace kept at 1000 ° C. for 20 minutes. After the heating was completed, it was taken out of the electric furnace and cooled naturally. After cooling to room temperature, the surface of the hardened concrete plate was observed, but there were no cracks, and no difference was observed from before heating.

Example 4 1) Production of Short Fiber 70 parts by weight of polylactic acid obtained in Synthesis Example 1 and a polymer alloy of polyvinyl alcohol / starch (trade name: Matterby: manufactured by Nippon Synthetic Chemical Co., Ltd.) 20 parts by weight 10 parts of polyethylene glycol (5 parts by weight average molecular weight 400, 5 parts by weight average molecular weight 4000) were mixed to obtain a resin composition. The resin composition was extruded at an extruder cylinder temperature of 170.
~ 190 ° C, melt spinning at a die temperature of 190 ° C.
The monofilament was drawn twice to produce a denier of 350 denier, a strength of 3.1 g / denier, and a perfect circular cross section. This monofilament is cut by a cutter and has a length of 30 ±
5 mm short fibers were used. 2) Production of hardened concrete plate 250 × 250 × 25 m in the same manner as in Example 1.
m of hardened concrete board was manufactured and cured for 6 months in the shade outdoors. 3) Evaluation of hardened concrete board After hardening, the hardened concrete board was heated in an electric furnace kept at 1000 ° C. for 20 minutes. After the heating was completed, it was taken out of the electric furnace and cooled naturally. After cooling to room temperature, the surface of the hardened concrete plate was observed, but there were no cracks, and no difference was observed from before heating.

Example 5 1) Production of staple fiber 70 parts by weight of polybutylene succinate obtained in Synthesis Example 3 and a polymer alloy of polyvinyl alcohol / starch [trade name: Matterby: manufactured by Nippon Synthetic Chemical Co., Ltd.] 20 parts by weight Parts, polyethylene glycol (weight average molecular weight is 40
0) 10 parts were mixed to obtain a resin composition. The resin composition was melt-spun at an extruder cylinder temperature of 170 to 190 ° C. and a die temperature of 190 ° C., and immediately stretched 5 times to obtain a fineness of 3
A monofilament of 50 denier, strength of 2.9 g / denier and a perfect circular cross section was produced. This monofilament was cut by a cutter to obtain a short fiber having a length of 30 ± 5 mm. 2) Production of hardened concrete plate 250 × 250 × 25 m in the same manner as in Example 1.
m of hardened concrete board was manufactured and cured for 6 months in the shade outdoors. 3) Evaluation of hardened concrete board After hardening, the hardened concrete board was heated in an electric furnace kept at 1000 ° C. for 20 minutes. After the heating was completed, it was taken out of the electric furnace and cooled naturally. After cooling to room temperature, the surface of the hardened concrete plate was observed, but there were no cracks, and no difference was observed from before heating.

Example 6 1) Production of Short Fiber A polymer alloy of 70 parts by weight of a mixture of polylactic acid / polybutylene succinate (weight ratio: 6/4) obtained in Synthesis Example 4 and polyvinyl alcohol / starch [trade name: Matterby : Manufactured by Nippon Synthetic Chemical Co., Ltd.] and 10 parts of polyethylene glycol (weight average molecular weight: 1000) were mixed to obtain a resin composition. This resin composition was melt-spun at an extruder cylinder temperature of 170 to 190 ° C. and a die temperature of 190 ° C., immediately stretched 5 times, and had a fineness of 350 denier.
A monofilament having a strength of 3.0 g / denier and a perfect circular cross section was produced. This monofilament was cut by a cutter to obtain a short fiber having a length of 30 ± 5 mm. 2) Production of hardened concrete plate 250 × 250 × 25 m in the same manner as in Example 1.
m of hardened concrete board was manufactured and cured for 6 months in the shade outdoors. 3) Evaluation of hardened concrete board After hardening, the hardened concrete board was heated in an electric furnace kept at 1000 ° C. for 20 minutes. After the heating was completed, it was taken out of the electric furnace and cooled naturally. After cooling to room temperature, the surface of the hardened concrete plate was observed, but there were no cracks, and no difference was observed from before heating.

Example 7 1) Production of staple fiber 80 parts by weight of the polylactic acid / polybutylene succinate block copolymer (weight ratio 8/2) obtained in Synthesis Example 5 and a polyvinyl alcohol / starch polymer alloy [trade name] Matterby: manufactured by Nippon Synthetic Chemical Co., Ltd.] 10 parts by weight, polyethylene glycol (weight average molecular weight is 200
0) 10 parts were mixed to obtain a resin composition. The resin composition was melt-spun at an extruder cylinder temperature of 170 to 190 ° C. and a die temperature of 190 ° C., and immediately stretched 5 times to obtain a fineness of 3
A monofilament of 50 denier, strength 3.3 g / denier and a perfect circular cross section was produced. This monofilament was cut by a cutter to obtain a short fiber having a length of 30 ± 5 mm. 2) Production of hardened concrete plate 250 × 250 × 25 m in the same manner as in Example 1.
m of hardened concrete board was manufactured and cured for 6 months in the shade outdoors. 3) Evaluation of hardened concrete board After hardening, the hardened concrete board was heated in an electric furnace kept at 1000 ° C. for 20 minutes. After the heating was completed, it was taken out of the electric furnace and cooled naturally. After cooling to room temperature, the surface of the hardened concrete plate was observed, but there were no cracks, and no difference was observed from before heating.

Example 8 1) Production of Short Fiber 80 parts by weight of polycaproic acid obtained in Synthesis Example 6 and a polymer alloy of polyvinyl alcohol / starch (trade name: Matterby: manufactured by Nippon Synthetic Chemical Co., Ltd.) 10 parts by weight Polyethylene glycol (weight average molecular weight is 2000) 10
The parts were mixed to obtain a resin composition. This resin composition was heated at an extruder cylinder temperature of 170 to 190 ° C. and a die temperature of 190.
The mixture was melt-spun at a temperature of ° C and immediately stretched three times to produce a monofilament having a fineness of 350 denier, a strength of 2.6 g / denier and a perfect circular cross section. This monofilament was cut by a cutter to obtain a short fiber having a length of 30 ± 5 mm. 2) Production of hardened concrete plate 250 × 250 × 25 m in the same manner as in Example 1.
m of hardened concrete board was manufactured and cured for 6 months in the shade outdoors. 3) Evaluation of hardened concrete board After hardening, the hardened concrete board was heated in an electric furnace kept at 1000 ° C. for 20 minutes. After the heating was completed, it was taken out of the electric furnace and cooled naturally. After cooling to room temperature, the surface of the hardened concrete plate was observed, but there were no cracks, and no difference was observed from before heating.

Example 9 1) Production of Short Fiber 70 parts by weight of the mixture of polylactic acid / polycaproic acid (weight ratio 6/4) obtained in Synthesis Example 7 and polyvinyl alcohol /
A resin composition was obtained by mixing 20 parts by weight of a polymer alloy of starch [trade name: Matterby: manufactured by Nippon Synthetic Chemical Co., Ltd.] and 10 parts of polyethylene glycol (weight average molecular weight: 2000). This resin composition is melt-spun at an extruder cylinder temperature of 170 to 190 ° C. and a die temperature of 190 ° C.
Immediately stretched 5 times, fineness 350 denier, strength 3.0
g / denier, a monofilament with a perfect circular cross section was produced. This monofilament was cut by a cutter to obtain a short fiber having a length of 30 ± 5 mm. 2) Production of hardened concrete plate 250 × 250 × 25 m in the same manner as in Example 1.
m of hardened concrete board was manufactured and cured for 6 months in the shade outdoors. 3) Evaluation of hardened concrete board After hardening, the hardened concrete board was heated in an electric furnace kept at 1000 ° C. for 20 minutes. After the heating was completed, it was taken out of the electric furnace and cooled naturally. After cooling to room temperature, the surface of the hardened concrete plate was observed, but there were no cracks, and no difference was observed from before heating.

Example 10 1) Production of staple fiber A polymer alloy of 80 parts by weight of the polylactic acid / polycaproic acid block copolymer (weight ratio 8/2) obtained in Synthesis Example 8 and a polyvinyl alcohol / starch polymer [trade name: Matterby: 10 parts by weight of Nippon Synthetic Chemical Co., Ltd.] and 10 parts of polyethylene glycol (weight average molecular weight: 2000) were mixed to obtain a resin composition. This resin composition is melt-spun at an extruder cylinder temperature of 170 to 190 ° C. and a die temperature of 190 ° C., and immediately stretched 5 times to produce a monofilament having a fineness of 350 denier, a strength of 3.2 g / denier and a perfect circular cross section. did. This monofilament was cut by a cutter to obtain a short fiber having a length of 30 ± 5 mm. 2) Production of hardened concrete plate 250 × 250 × 25 m in the same manner as in Example 1.
m of hardened concrete board was manufactured and cured for 6 months in the shade outdoors. 3) Evaluation of hardened concrete board After hardening, the hardened concrete board was heated in an electric furnace kept at 1000 ° C. for 20 minutes. After the heating was completed, it was taken out of the electric furnace and cooled naturally. After cooling to room temperature, the surface of the hardened concrete plate was observed, but there were no cracks, and no difference was observed from before heating.

Comparative Example 1 1) Production of a hardened concrete plate 100 parts by weight of ordinary Portland cement, standard sand 100
After mixing the parts by weight with a high-speed mixer for 5 minutes, water was added so that the water / cement weight ratio (W / C ratio) would be 0.4 and mixed well to prepare ready-mixed concrete. This ready-mixed concrete is filled into a formwork made of concrete panels,
A hardened concrete board of 250 × 250 × 25 mm was manufactured. The hardened concrete slabs were cured for 6 months in the shade outdoors. 2) Evaluation of hardened concrete board The hardened concrete board after curing was heated in an electric furnace kept at 1000 ° C for 20 minutes. After the heating was completed, it was taken out of the electric furnace and cooled naturally. After cooling to room temperature, the surface of the hardened concrete plate was observed, and many cracks, cracks, and craters were found.

Comparative Example 2 1) Production of hardened concrete board 100 parts by weight of ordinary Portland cement, standard sand 100
After mixing 5 parts by weight of vinylon staple fiber (monofilament, 500 denier, length 30 ± 5 mm) with a high-speed mixer for 5 minutes, the water / cement weight ratio (W / C ratio)
Water was added so as to be 0.4 and mixed well to prepare ready-mixed concrete. This ready-mixed concrete is filled into a formwork made of concrete panels, and 250 × 250 × 25
mm hardened concrete boards were produced. The hardened concrete slabs were cured for 6 months in the shade outdoors. 2) Evaluation of hardened concrete board The hardened concrete board after curing was heated in an electric furnace kept at 1000 ° C for 20 minutes. After the heating was completed, it was taken out of the electric furnace and cooled naturally. After cooling to room temperature, the surface of the hardened concrete plate was observed, and cracks and craters were found.

Comparative Example 3 1) Production of a hardened concrete board 100 parts by weight of ordinary Portland cement, standard sand 100
Parts by weight, 5 parts by weight of polypropylene short fiber (monofilament, fineness of 350 denier, length 30 ± 5 mm) were mixed with a high-speed mixer for 5 minutes, and then the water / cement weight ratio (W / C)
(Ratio) was 0.4 and mixed well to prepare ready-mixed concrete. This ready-mixed concrete is filled into a formwork made of concrete panels, and 250 × 25
A hardened concrete board of 0 × 25 mm was manufactured. The hardened concrete slabs were cured for 6 months in the shade outdoors. 2) Evaluation of hardened concrete board The hardened concrete board after curing was heated in an electric furnace kept at 1000 ° C for 20 minutes. After the heating was completed, it was taken out of the electric furnace and cooled naturally. After cooling to room temperature, the surface of the hardened concrete plate was observed, and cracks and craters were found.

[0054]

According to the present invention, when preparing ready-mixed concrete for use in concrete casting, the concrete-laying short fibers having the specific composition of the present invention are mixed with hydraulic cement together with water. In an environment of pH 11 or higher in the later curing process, it disappears over time and leaves fine hollow passages, and after the ready-mixed concrete becomes a hardened concrete structure, the voids inside the concrete structure are removed from the outside or the outside air. Can be channeled. According to the present invention, the void existing inside the wall surface of the concrete structure is made to be an open space with respect to the outside world or the outside air by the fine cavity passage, so that a fire occurs and even if the concrete structure is heated to a high temperature. It is possible to provide a concrete structure that is less likely to generate an explosion or a crack and that is less likely to generate a decomposition gas.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hisashi Aihara 1190 Kasama-cho, Sakae-ku, Yokohama City, Kanagawa Prefecture (72) Inventor Tomoyuki Nakata 1190 Kasama-cho, Sakae-ku, Yokohama City, Kanagawa Prefecture Mitsui Chemicals ( 72) Inventor Kazuhiko Suzuki 1190 Kasama-cho, Sakae-ku, Yokohama City, Kanagawa Prefecture (72) Inventor Masanobu Ajioka 1190 Kasama-cho, Sakae-ku, Yokohama City, Kanagawa Prefecture Mitsui Chemicals Corporation

Claims (6)

[Claims] 1. A group consisting of (A) 100 parts by weight of an aliphatic polyester, and (B) a polyalkylene glycol having a structural unit represented by the formula (1), a polyvinyl alcohol, and a starch. Short fibers containing at least one selected from 1 to 100 parts by weight of a resin composition, and used in mixing with hydraulic cement and water when preparing ready-mixed concrete for concrete casting. Short fibers for concrete casting. Embedded image (In the formula, R ₁ and R ₂ each independently represent a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 6 carbon atoms, and n represents an integer of 1 to 5.) 2. The short fiber for casting concrete according to claim 1, wherein the short fiber is a monofilament. 3. The short fiber for casting concrete according to claim 1, wherein the short fiber is a multifilament. 4. The short fiber for concrete casting according to claim 1, wherein the short fiber has an average length of 1 to 50 mm. 5. The short fiber for casting concrete according to claim 1, wherein (B) is a polyalkylene glycol. 6. The short fiber for placing concrete according to claim 5, wherein the polyalkylene glycol is polyethylene glycol and / or polypropylene glycol.