JPH06234555A - Fiber reinforced cement product - Google Patents

Abstract

PURPOSE:To obtain a fiber reinforced cement product improved in bending property, water resistance and impact resistance by using a polybenzazol fiber having a specific physical property as a cement reinforcing material. CONSTITUTION:This fiber reinforced cement product is obtained by using the polybenzazol fiber having at least 4.0 GPa tensile strength and at least 140 GPa initial elasticity and <=25Angstrom in void diameter as a reinforcing material. A method for making the void diameter <=25Angstrom is, for instance, that the conc. of phosphoric acid in a coagulation bath is adjusted to >=5% at the time of producing the fibers by spinning from a dope composed of a polymer containing polybenzazol as a main component and a polyphosphoric acid and, in post treating process, giving an oily agent is effective.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a fiber reinforced cement product having improved bending properties, water resistance and impact resistance.

[0002]

2. Description of the Related Art Conventionally, in order to improve mechanical properties, especially tensile properties, bending properties or impact resistance of cement products such as concrete, it is necessary to mix metal fibers, glass fibers, synthetic fibers, ceramic fibers and the like. Has been tried. Metal fibers typified by stainless steel fibers and ceramic fibers typified by carbon fibers have excellent alkali resistance and high tensile strength, but have a problem of low toughness during bending. In addition, metal fibers have a high specific gravity, and there is a problem that the construction method for uniformly dispersing them in a cement product is limited, and carbon fibers have a problem that impact resistance is poor. Furthermore, although glass fiber has high tensile strength and tensile modulus,
Poor alkali resistance.

On the other hand, when synthetic fibers such as polyvinyl alcohol fibers, polyamide fibers, polypropylene fibers and polyester fibers are used as a reinforcing material for cement products, the toughness at bending is better than that of metal fibers and glass fibers, but the tensile strength is high. However, the tensile modulus was not sufficient. Therefore, it has been studied to use wholly aromatic polyamide fibers having a tensile strength of 20 g / denier or more as a reinforcing material for cement products as a material capable of improving the tensile properties of synthetic fibers. On the other hand, polybenzazole fibers (PBZ) such as polyparaphenylenebenzbisthiazole (PBT) and polyparaphenylenebenzbisoxazole) (PBO) are used as aromatic polyamides as new high heat resistance, high elastic modulus and high strength organic fibers. It has been reported to have better performance than. Therefore, it is of course considered that the application of cement products as a reinforcing material is more promising than that of wholly aromatic polyamide. However, the PBZ fiber produced by the conventionally known spinning method has a void diameter of more than 25 Å and tends to have a reduced water resistance. Therefore, high strength cannot be maintained in the presence of water. It was

[0004]

[Problems to be Solved by the Invention]
INDUSTRIAL APPLICABILITY The present invention improves hydrolysis resistance, water resistance, and bending resistance by reducing the void diameter generated during production without impairing the excellent properties of PBZ fibers, that is, high strength, high elastic modulus, and high heat resistance. An object of the present invention is to provide a cement product which uses PBZ having excellent properties and impact resistance as a fiber reinforcing material.

[0005]

It has been heretofore known that PBZ fibers have particularly excellent properties as a high elastic modulus and high strength material, but their tensile strength decreases with the presence of water. It turns out that I have. The present inventors have investigated the cause of the decrease in the tensile strength of PBZ due to water, and as a result, the decrease in strength is caused by water.
It was found that it is due to the hydrolysis of the Z molecular chain and that it accelerates the infiltration hydrolysis action of water from the relatively large voids. This means that reducing the void diameter improves hydrolyzability. As a result of experiments, it was found that the hydrolyzability was remarkably improved when the average diameter of voids was 25 Å or less. As a result of examining the factors that determine the void diameter, it was found that the concentration of phosphoric acid in the coagulation bath had a great influence. As a result of diligent studies, as one of the methods for reducing the void diameter to 25 Å or less, when producing a fiber by spinning from a dope composed of a polymer containing PBZ as a main component and polyphosphoric acid, the phosphoric acid concentration of the coagulation bath is 5% or more. It has been found that doing has great effects. The PBZ fiber produced in this way has a void diameter of 25Å or less, and the cement product using the reinforcing material produced using this has little strength reduction even if it comes into contact with moisture such as rain during use. It has been found that the material exhibits excellent water resistance, and has arrived at the present invention.

That is, the present invention is at least 4.0 GP.
A fiber-reinforced cement product having a tensile strength of a, an initial elastic modulus of at least 140 GPa, and a PBZ fiber having a void diameter of 25 Å or less as a reinforcing material.

Polybenzazole fiber (PBZ) of the present invention
Means a fiber made of polybenzoxazole (PBO) or polybenzthiazole (PBT) or a random or block copolymer thereof. The tensile strength is 4.0 GPa, preferably 4.1 GPa or more, and the tensile elastic modulus is 140 GPa or more, preferably 150 GPa or more. In order to exhibit such mechanical properties, the intrinsic viscosity of the PBZ polymer measured in methanesulfonic acid should be 10 or more. The average diameter of the fibers is preferably 50 μm or less, more preferably 25 μm or less.

The PBZ fiber of the present invention has a void diameter of 25.
Å It has the characteristic of being less than or equal to. Void diameter 2
As one of the methods for reducing the concentration to 5 Å or less, it was found that the concentration of phosphoric acid in the coagulation bath is set to 5% or more when a fiber is produced by spinning from a dope composed of a polymer containing PBZ as a main component and polyphosphoric acid. Further, it is effective to apply an oil agent in the post-treatment process. The type of oil agent used in the present invention may include a component acting as a lubricant. It goes without saying that an emulsifier, a stabilizer and the like are used in combination if necessary. As components contained in the oil agent, animal oils, vegetable oils, fatty acid esters, hydrocarbons, higher alcohols, neutral oils such as higher fatty acids, soaps, sulfuric acid esters, sulfonic acids, phosphoric acid esters, surfactants such as ether derivatives, And mixtures thereof, silicone oil, etc. can be used. The oil agent can be applied at one place or at two or more places at the same time during the process from the spinneret to the final winding, and can be performed at any place. It is preferably applied after solidification. If a heat treatment step for increasing the elastic modulus is further required, it is preferable to add a finishing agent after the heat treatment step.

The method of applying the oil agent to the yarn includes spray application in which the oil agent is atomized, dip application through the oil agent bath,
Any method such as kiss roll application or guide application may be used.
An oil agent may be added to the coagulation bath. The adhesion amount of the oil agent is 0.05 to 7.0 with respect to the dry weight of the fiber to which the oil agent is applied.
Weight% is good. If it is less than 0.05% by weight, the oil agent does not sufficiently cover the fiber surface, and if it is more than 7.0% by weight, an excessive amount of the oil agent scatters, which is not preferable. More preferably 0.
It is 1 to 3.0% by weight. Most preferred is 0.3-
It is 2.0% by weight.

When it is necessary to remove the oil agent after applying the oil agent, an oil agent removing step may be provided in a separate step. The fine powder insoluble in the oil agent means that which acts as a solid lubricant. For example, diameter 10m
Colloidal silica or colloidal alumina of μ or less, or titanium oxide or calcium carbonate of several hundred mμ or less in diameter
Silica gel, calcium phosphate, talc, clay, mica, graphite, molybdenum sulfide and the like having a diameter of several μ can be used. It is necessary that these are smaller than the single yarn diameter in the yarn. The fine powder acts as a solid lubricant on the fiber surface,
It has an effect of preventing adhesion between fibers and an effect of improving water resistance by preventing contact of water. The amount of these fine powders deposited is preferably 5.0% by weight or less based on the dry weight of the fibers. If it is 5.0% by weight or more, the effects of water resistance and adhesion prevention reach the ceiling, which is not preferable. 1.0% by weight
The following is more preferable. Most preferably 0.5
It can be said that the content is less than or equal to weight%.

When the fiber used as the reinforcing material of the fiber-reinforced cement product of the present invention is used as a short fiber, the fiber length is not particularly limited, but is preferably 5 to 100 mm, particularly preferably 7 to 70 mm. Further, it can be used in the form of long fibers, woven or knitted fabric, or non-woven fabric.

The PBZ fiber for reinforcing material of the fiber-reinforced cement product of the present invention can sufficiently exhibit the performance of the fiber when used alone, but other fibers may be used depending on the purpose.
For example, it is also possible to mix and use carbon fiber, wholly aromatic polyamide fiber or glass fiber.

The fiber-reinforced cement product of the present invention comprises, for example, the PBZ fiber produced by the above-mentioned method, as it is or in the form of a monofilament cut into a suitable length, as a cement to be a molding matrix, water, and if necessary. It can be easily obtained by combining and mixing with sand and crushed stone.

As a method for mixing and adjusting the fiber-reinforced cement composition which is a raw material of the fiber-reinforced cement product of the present invention, for example, 30 parts of water to 100 parts of cement on a weight basis are used.
˜70 parts, and if necessary, sand or crushed stone 20˜600 parts are mixed to prepare an aqueous mixture, and fibers cut to a predetermined length are preferably added in an amount of 0.2˜8% by volume to the mixture. The method of mixing is mentioned. If necessary, it is also possible to use it together with fibers such as other metal fibers.

The use of the fiber-reinforced cement product of the present invention is not particularly limited, but examples thereof include various building components, pipes, piles, poles, assembled walls, grooves, foundation blocks, roof tiles, and the like. Here, the fiber-reinforced cement product of the present invention also includes a fiber-reinforced cement mixture that is not yet solidified and is used in on-site construction such as a casting method and a spraying method.

[0016]

EXAMPLES The present invention will be specifically described below with reference to Examples, but the methods for measuring the physical properties used in the evaluation of the present invention are as follows. <Void diameter measurement method> Small angle X-ray scattering intensity measurement
This is done using a Kratki camera. Wrap the sample fiber around the 6 m measuring holder. X-ray output is 45 kv 150 mA
Then, the Cukα ray is used after being monochromaticized with a nickel filter. The vertical limit slit of the Krafty camera was 42 mm, the width limit slit was 0.07 mm, and the length of the light receiving unit slit was 10 mm, and the width limit was 0.14 mm. The measuring range is 0.1 to 3 degrees. The step width is 0.025 degree increments and is accumulated for 30 seconds or more. The background scattering is corrected using the following equation from the measurement results of the sample and air scattering. I = μIsample−Iair μ = Iair (0) / Isample (0) where I is the true scattering intensity, Isample is the measured scattering intensity with the sample, and Iair is the intensity measured without the sample. . After measuring the sample, the intensity is measured at a scattering angle of 0 degree to determine the absorption coefficient of the sample. The void size is measured using a Guinier plot. The logarithm of the scattering angle (I) and the square of the scattering vector (k) are plotted, and a linear approximation is performed for data in which the value of the square of k is 0 to 0.01Å ² , and the following equation is used from the slope (s) of the straight line. Calculate. D = 2 (2S) ^1/2 Water resistance test: Tensile strength in a wet state was used as an evaluation measure of water resistance. After the test piece was immersed in water (20 ° C.) for 200 hours, the sample was taken out of the water and the tensile strength was measured within 1 minute according to the method specified in JIS-L1096 (1979). However, the width of the test piece was 3 cm. Method for measuring bending strength of cement products: JIS-A110
6 (1976). Method for measuring impact strength of cement products: JIS-A130
According to the method prescribed in 1 (1975), an operation of dropping a shaped weight having a weight of 1 kg from a height of 1.5 m to the center of the sample was repeated 10 times, and the number of times the sample was not broken was expressed.

Example 1 Spin dope (polyparaphenylene benzobisoxazole having an intrinsic viscosity of 25 at a concentration of 14.7% by weight was dissolved in polyphosphoric acid having a composition expressed in terms of phosphorus pentoxide of 83.7% by weight) Was passed through a metal mesh filter medium and spun at a discharge rate of 0.22 g / min per single hole from a spinneret having a diameter of 0.20 mm and a number of holes of 334 kept at 150 ° C. Flow velocity of the spun yarn is rectified 0.5 m / sec, temperature 70
It cooled with the air cooling airflow of (degreeC). Then, the yarn was placed 15 cm below the spinneret surface at a concentration of 10% phosphoric acid placed 40 cm below.
It was introduced into a coagulation bath at 0 ° C., and cooled to remove the solvent. After that, the yarn was passed through a first roller having a diameter of 200 mm, then a washing roller having the same diameter, a drying roller, and a heat treatment kneader online, and was wound at a yarn speed of 200 m / min without being substantially stretched. . The drying roller temperature was heated at 170 ° C., 190 ° C., and 210 ° C. for 20 seconds, respectively. After that, the yarn was cooled to a temperature of 80 ° C. or lower and wound by a winder. At that time, an air blower was installed at the outlet of the washing roller to remove water adhering to the yarn, and then a molecular weight of 900
1% by weight of a polyethylene oxide / polypropylene oxide copolymer of 0 was dispersed. The obtained PBO multifilament was cut into a length of 20 mm, 100 parts by weight of boltland cement, 50 parts by weight of water, 850 parts by weight of fine aggregate (sea sand), coarse aggregate (crushed stone with a particle size of 15 mm or less)
2% by volume in an aqueous mixture of 700 parts by weight,
Stir in the mixer until the fibers are evenly dispersed. Mix the kneaded mixture into a sample form (thickness 3 cm, width 15 c
m, length 50 cm) and allowed to stand for 28 days to obtain a fiber reinforced cement product. Table 1 shows the results of measuring the characteristics of cement products.

Comparative Example 1 PB was carried out in the same manner as in Example 1 except that the coagulating bath was water.
O multifilament was obtained. From this, a fiber-reinforced cement product was obtained in the same manner as in Example 1. Table 1 shows the results of measuring the properties of the fiber and cement products.

[0019]

[Table 1]

As is clear from Table 1, the void diameter can be reduced to 25 Å or less by setting the phosphoric acid concentration in the coagulation bath to 5% or more of the PBO fiber.
It is possible to improve the hydrolysis resistance, which is the greatest drawback, without impairing the excellent heat resistance, high strength, and high elastic modulus properties of O fiber. It can be seen that a cement product excellent in impact resistance and water resistance was obtained.

[0021]

As described above, according to the present invention, PBZ
Bending properties, by improving the hydrolysis resistance of the fiber,
A fiber-reinforced cement product having excellent water resistance and impact resistance could be obtained.

Claims (1)

[Claims] 1. A fiber-reinforced cement product having a tensile strength of at least 4.0 GPa and an initial elastic modulus of at least 140 GPa, and a polybenzazole fiber having a void diameter of 25 Å or less as a reinforcing material.