JP3084139B2 - Fiber reinforced hydraulic molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic material having excellent dimensional stability and, particularly, toughness in a wet state, using a polyvinyl alcohol (hereinafter abbreviated as PVA) synthetic fiber having excellent wet heat resistance as a reinforcing material. The present invention relates to a molded product (hereinafter may be abbreviated as FRC) and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, as health problems due to asbestos have been clarified and use regulations have been advanced, there has been a strong demand for asbestos substitute materials as reinforcing materials for hydraulic molded products. PVA-based synthetic fibers have the highest strength and elasticity among general-purpose fibers, and have good adhesiveness to cement and alkali resistance. Therefore, the demand for PVA-based synthetic fibers is rapidly increasing as a substitute for asbestos. However, PVA-based synthetic fibers are inherently low in moist heat resistance, so that autoclave curing in which curing is performed under moist heat conditions is impossible, and has been used exclusively for room temperature curing.

[0003] Autoclave curing is widely used as a means for improving the dimensional stability of a hydraulic molded product and greatly shortening the curing time as compared with room temperature curing. Generally, dimensional stability is improved by performing autoclave curing, but particularly, bending strength and bending in a wet state, that is, bending toughness are reduced. Therefore, the reinforcing fiber used for the autoclave curing is required to have not only the strength but also the effect of improving the bending toughness, and it is practical that the toughness ratio in a wet state defined later is at least 1.2 or more. However, as an asbestos substitute material that can withstand the harsh treatment of autoclave curing, although carbon fiber is currently used in some cases, bending toughness is difficult to obtain due to the low elongation of the fiber, and asbestos and PVA In fact, they are not widely used because they are very expensive compared to synthetic fibers.

On the other hand, as a PVA-based synthetic fiber which can be cured in an autoclave, Japanese Patent Laid-Open Publication No.
Those having a hot water resistance of 40 ° C. or higher are shown, and those having a hot water resistance of 158 ° C. are cited in the examples. The hot water resistance here means that the fiber is dissolved in water. Temperature, and such fibers do not provide the moldings of the present invention.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an inexpensive, autoclaved, cured hydraulic molding having excellent dimensional stability and bending toughness.

[0006]

That is, the present invention has a strength of 11 g / d or more and a gel elasticity of 6.0 × 10 ↑ -3 g / c.
Using PVA-based synthetic fiber having excellent moist heat resistance of at least m · d and an elution rate of 40% or less as a reinforcing material, at 140 ° C.
Thus, the autoclave curing is performed. For the first time, dimensional stability of 0.15% or less, which was previously obtained only with asbestos and expensive carbon fiber with health problems,
Further, a hydraulic molded product having excellent dimensional stability and bending toughness having a toughness ratio of 1.2 or more in a wet state has been realized, and its significance is extremely large.

The present inventors have studied autoclave conditions and dimensional stability when various PVA-based synthetic fibers are used as reinforcing materials,
As a result of examining the relationship with the bending toughness in detail, the strength 11
g / d or more, gel elastic modulus 6.0 × 10 ↑ −3 as defined later
Autoclave curing at 140 ° C. or more in a system in which 0.3 to 10% by weight of PVA synthetic fiber having a dissolution rate of 40% or less and a dissolution rate of 40% or less is added to a hydraulic molding material significantly improves dimensional stability. It has been found that excellent bending toughness is exhibited.

A fiber for FRC having a satisfactory reinforcing effect must have a strength of 11 g / d or more. Furthermore,
In order to withstand autoclaving, the gel elasticity must be 6.0 × 10 3 g / cm · d or more and the dissolution rate should be 40%.
Must be:

In order to impart wet heat resistance to PVA-based synthetic fibers, it is necessary to introduce crosslinks between PVA molecules. The gel elastic modulus specified in the present invention is a numerical value of the degree of crosslinking, and the larger the value, the more crosslinking is introduced. The method for measuring the gel elastic modulus will be described later, but is roughly as follows. Since aqueous zinc chloride is a strong solvent for PVA,
It can melt synthetic fibers. However, when the PVA molecules are cross-linked, the PVA crystals are dissolved in the aqueous zinc chloride solution, but because of the cross-linking network, the fiber as a whole does not dissolve, but shrinks to a gel-like state. The elongation behavior of this gel with respect to tensile stress follows the Hooke's law, and the gel elastic modulus defined in the present invention corresponds to the spring constant.

The elution rate as referred to in the present invention, which will be described later in detail, is a weight reduction rate of the fiber when the fiber is cut into 6 mm and immersed in an artificial cement solution at 160 ° C. %, The reinforcing effect cannot be obtained by autoclave curing. Generally, the dissolution of the fiber proceeds from the cut end, and the elution rate is different if the cut length is different. In the present invention, what is measured at 6 mm is tentatively specified, but a fiber having an elution rate of 40% at 6 mm corresponds to about 50% at 3 mm. The aforementioned gel modulus indicates the degree of crosslinking, but does not necessarily reflect the uniformity of crosslinking in the fiber. Therefore, in the present invention, the gel elastic modulus is a so-called necessary condition for enduring autoclave curing, while the elution rate is a sufficient condition, and it is necessary to satisfy both at the same time.

The present inventors have studied various fibers having different gel elasticities, and found that the damage of the fibers after the autoclave curing is smaller as the gel having a higher gel elasticity, so that the autoclave curing can be performed. It is necessary that the value be 6.0 × 10 ↑ −3 g / cm · d or more, and the elution rate is 40% or less, preferably the gel elasticity is 8.0 × 10
↑ -3 g / cm · d or more and an elution rate of 30% or less were found to have sufficient wet heat resistance.

Hereinafter, the present invention will be described more specifically. It is not necessary to take any special method for the production of the molded product, and a general FRC production method may be used.For example, in the case of a thin plate, there is a wet papermaking method such as the Hashek method, and in the case of mortar or concrete, etc. Vibration molding, centrifugal molding, extrusion molding and the like are available.

As the hydraulic substance of the present invention, cement is typical, and portland cement and various other cements are used. Gypsum, gypsum slag, magnesia and the like can be used, and these can be used alone. , Or a mixture thereof. Further, in order to form a matrix of tobermorite crystals having excellent dimensional stability by autoclave curing, it is preferable to use a mixture of calcareous materials such as cement, slaked lime and quicklime, and silica materials such as silica sand and diatomaceous earth. . The mixed silica has a Blaine specific surface area of at least 2,000 cm 2 / g, preferably at least 4000 cm 2 / g, more preferably 600 cm 2 / g.
At 0 cm ↑ 2 / g or more, tobermorite crystals are more likely to be formed with a higher brane value, and the matrix strength is increased and the effect of reinforcing fibers is also remarkable. Further, these hydraulic substances can be mixed with sand or gravel to be used as mortar or concrete. In addition, auxiliary materials such as mica, sepiolite, attabalgite, and pearlite can be used.

The PVA-based synthetic fiber used as a reinforcing material is
The strength is 11 g / d or more, and the gel elasticity is 6.0 × 10 ↑ -3.
g / cm · d or more and an elution rate of 40% or less,
The production method is not particularly limited. For example, a method of acetalization in two stages, that is, aldehyde penetrates into the fiber center without using an acid as a reaction catalyst in the first stage, and then performs a second stage treatment with a mixed solution of aldehyde and acid, The method of reacting is preferred from the viewpoint of introducing crosslinking to the center of the fiber. As the aldehyde, formaldehyde is preferable, and in the first stage, the concentration is 20 to 70 g / l and the temperature is 7 g / l.
The second stage preferably has a concentration of 50 to 100 g / l and a concentration of 30 to 150 g / l of formaldehyde and sulfuric acid in the second stage of 70 to 90 ° C. In the first stage, a dialdehyde such as glutaraldehyde (or an acetalized product thereof) can be used in combination with a monoaldehyde such as formaldehyde. Further, in addition to the two-stage treatment, formaldehyde 100-250 g / l, sulfuric acid 3
Extremely high formaldehyde concentration of 0-80 g / l,
It is also possible to carry out the treatment in one stage under the condition of a low sulfuric acid concentration. The degree of acetalization as a guide is 15 mol% or more,
Preferably, the content is 20 to 35 mol%.

These PVA fibers subjected to acetalization have a strength of 11 g / d after acetalization.
It is necessary that the strength be 13 g / d or more. The production method is not particularly limited, and may be a known method.
It is preferable to add by weight% because it promotes penetration of the aldehyde into the fiber center. The PVA polymerization degree is 150
When the degree of polymerization is 0 or more, a higher degree of polymerization can provide a higher gel elastic modulus, so it is preferably 2000 or more, and more preferably 3000 or more.
That is all. In particular, in the case of performing a two-stage treatment without using dialdehyde, it is difficult to obtain a gel elastic modulus.
It is preferable to use fibers obtained by adding a surfactant to a spinning solution having a molecular weight of 000 or more. Further, after the phosphoric acid or methylol-based compound is added and subjected to a crosslinking treatment, it can be subjected to an acetalization treatment. However, it is necessary that the crosslinking formed here does not inhibit the penetration of the aldehyde.

Such a PVA-based synthetic fiber having excellent reinforcing properties can be used in any form depending on the method of producing a molded article, the method of construction, and the like. For example, short fibers or chopped strands that are short-cut may be used, filament yarns or bundled filament yarns may be used in the form of long fibers, or so-called fiber rods. Furthermore, it can be used as a nonwoven fabric, a mat-like material, a mesh-like material, a two-dimensional or three-dimensional woven fabric, or the like. Such PVA-based synthetic fibers can also be used in combination with other reinforcing materials such as carbon fibers and reinforcing bars.

When PVA-based synthetic fibers are used as short fibers, it is necessary for the fibers to be uniformly dispersed and distributed in the matrix in order to sufficiently exert the reinforcing effect. For this purpose, the aspect ratio of the short fibers is required. (The ratio of the fiber length to the average diameter of the short fibers) is desirably 150 to 1500, preferably 300 to 800.

The addition rate of the PVA-based synthetic fiber in the hydraulic molded article of the present invention is 0.3 to 10% by weight, preferably 0.5 to 5% by weight, more preferably 1.0 to 3.0% by weight. It is. In the lower addition region, the reinforcing property is poor, and in the higher addition region, the dispersibility is poor, and it is difficult to obtain the reinforcing effect.

When pulp is used as a molding aid, the amount is preferably 3% by weight or less in order to facilitate molding and maintain the incombustibility of the molded product.

In the autoclave curing, it is necessary that a calcareous raw material and a siliceous raw material undergo a hydrothermal reaction to form tobermorite crystals, and the temperature is 140 ° C. or more, preferably 150 ° C. or more, and more preferably 160 ° C. . A higher temperature is preferable because the reaction rate increases and the time can be shortened.

[0021]

The hydraulic molded article of the present invention thus obtained has excellent physical properties such that the dimensional stability is 0.15% or less and the toughness ratio in a wet state is 1.2 or more. It can be used for cement, concrete molded products and secondary products such as slate boards, pipes, blocks, wall panels, floor panels, roofing materials, partitions, and the like.

[0022]

The present invention will be further described below with reference to examples. In the examples,% is a value based on weight unless otherwise specified. Further, the fiber strength, gel elastic modulus, elution rate, acetalization degree, dimensional stability of the hydraulic molded product, and toughness ratio in a wet state referred to in the present invention are measured by the following methods, respectively. (1) Fiber strength; in accordance with JIS L-1015,
Measured by Instron tensile tester. In addition, when a fiber is short and a test length of 20 mm cannot be obtained, the measurement is performed with a test length of 1 mm. (2) Gel elastic modulus: An assembly of 1000 to 2000 denier fibers (the multifilament yarn of the denier is used as it is) is fixed at the upper end so as to have a length of 20 cm, and a 1-gram load is applied to the lower end. Multiply. When this is immersed in a 50% by weight aqueous solution of zinc chloride at 50 ° C., the fibers shrink. The sample length when the shrinkage completely stops is measured, and this is defined as Acm. Next, load 1
Similarly, the sample length is measured in an aqueous zinc chloride solution, changing the sample length from 30 g to 30 g, and this is defined as Bcm. Note that the load used is one having a specific gravity of 8, and A and B are each read to the order of 0.1 mm. Gel modulus = 29 / (BA) · D (g / cm ·
d) Here, D is the denier of the sample before immersion in the aqueous zinc chloride solution. If the sample is cut to several mm, first fix the upper end of the single fiber, apply a C milligram load to the lower end so that the test length becomes 2 mm, shrink the sample by the above method, and read the sample length. (L ↓ 1cm) Then, change the load to E milligrams (C <E), and read the sample length in the same manner (L ↓ 2cm). Gel modulus = (EC) / 10 ／ 5 (L ↓ 2-L ↓ 1) ・
D (g / cm · d) (3) Elution rate; cut the fiber into 6 mm, and
5 g is weighed (referred to as Ag), placed in a 4.5 mm-thick stainless steel autoclave together with 100 cc of artificial cement solution, and immersed in a 160 ° C. oil bath for 2 hours. Thereafter, the fiber is pulled up from an oil bath and cooled, the fiber is taken out and dried, and then weighed (Bg). Elution rate = (AB) / A × 100 (%) In addition, the artificial cement liquid is potassium hydroxide 3.
It is defined as a composition of 5 g / l, sodium hydroxide 0.9 g / l, and calcium hydroxide 0.4 g / l. (4) Degree of acetalization: Measured according to the vinyl formal analysis method of JIS K-6729. (5) Dimensional stability of hydraulic molded product; JIS A-54
Measured according to the length change test by water absorption of No. 18. (6) Toughness ratio in wet condition; JIS K-691
According to 1, the flexural strength in a wet state (after immersion in water for 3 days) is measured with a span of 5 cm, and a flexural strength-deflection curve is created. The highest point at which the rising linear relationship is maintained is point A. A point corresponding to a bending strength of 1/5 of the maximum value of the curve and located on the deflection side higher than the maximum value is defined as point B. The curve (from the origin to the point A), the perpendicular from the point A to the abscissa axis and the area (a) surrounded by the abscissa, and the curve (from the origin to the point B), the perpendicular and the abscissa from the point B to the abscissa axis Area enclosed by coordinate axes (b)
Next. Toughness ratio = Area (b) / Area (a) Since the toughness ratio is higher in the wet state than in the dry state, the toughness ratio in the wet state was measured in the present invention.

Example 1 Fully saponified PVA having a degree of polymerization of 1800 was dissolved in water at a concentration of 15%, and 1.5 moles each of boric acid and nonylphenol ethylene oxide adduct of 1.5 moles were added to PVA.
% And 3.0% to obtain a spinning stock solution. The spinning stock solution is wet-spun into a coagulation bath at 60 ° C. comprising 15 g / l of sodium hydroxide and 350 g / l of sodium sulfate, and subjected to roller stretching, neutralization, wet heat stretching and water washing according to a conventional method, and then to a 3 g / l phosphate bath. Dipped and dried. Subsequently, the film was stretched by dry heat at 230 ° C. so that the total stretching ratio became 23 times, and wound. The resulting fiber has a strength of 1
5.3 g / d, gel elasticity 0.5 × 10 ↑ -3 g / cm
d, elution rate was 93%. Subsequently, the fibers are in the form of
Glutaraldehyde 2 g / l, formaldehyde 50 g
/ L, immersed in a 70 ° C bath and squeezed appropriately, then formaldehyde 100g / l, sulfuric acid 70g / l, sodium sulfate 30g
/ L, 80 ° C bath. The strength of the obtained fiber is 1
2.5 g / d, gel elasticity is 9.8 × 10 ↑ -3 g / cm
D, the degree of acetalization is 18.9 mol%, and the elution rate is 2
6%. The fiber was cut into 6 mm and 2% by weight of the fiber, 3% by weight of pulp, 55% by weight of Portland cement, Blaine value of 5400 cm @ 2
/ G silica powder at 40% by weight.
Autoclave curing at 0 ° C for 10 hours, thickness 4mm
Was obtained. The dimensional stability of the slate is 0.
It was 10%, and the toughness ratio in a wet state was 2.8, which was excellent.

Comparative Examples 1 and 2 A strength of 9.7 g / d and a gel elasticity of 9.6 × 10 were obtained in exactly the same manner as in Example 1 except that the film was stretched by dry heat so that the total stretching ratio was 13 times. ↑ -3 g / cm · d, a fiber having an acetalization degree of 21.2 mol% and a dissolution rate of 28% (Comparative Example 1) and the unacetalized fiber of Example 1 were treated with formaldehyde 1
00 g / l, sulfuric acid 200 g / l, sodium sulfate 50 g / l, 80
14.8 g / d, gel elasticity 5.2 × 10 ↑ -3 g / cm · d, degree of acetalization 2
A slate plate was produced in exactly the same manner as in Example 1 using fibers having a dissolution rate of 0.1 mol% and a dissolution rate of 35% (Comparative Example 2). The physical properties of the slate plate thus obtained were poor as shown in Table 1.

[0025]

[Table 1]

Examples 2 and 3, Comparative Examples 3 and 4 Completely saponified PVA having a degree of polymerization of 3000 was dissolved in dimethyl sulfoxide at a concentration of 12%, and spin-dried into a methanol bath. Subsequently, extraction, wet stretching, and drying were performed according to a conventional method, and the film was stretched by dry heat at 235 ° C. so that the total stretching ratio was 21 times. The obtained fiber had a strength of 19.1 g / d. Subsequently, the fiber was subjected to an acetalization treatment in the same manner as in Example 1,
Strength 17.7 g / d, gel elasticity 10.2 × 10 3 g
/ Cm · d, a degree of acetalization of 19.1 mol%, and a dissolution rate of 22% were obtained. This was cut into 6 mm, and the addition rates were 0.1% by weight (Comparative Example 3), 0.5% by weight (Example 2), 5.0% by weight (Example 3), and 11% by weight (Comparative Example 4). ) To produce a slate plate in the same manner as in Example 1. Table 2 shows the dispersibility of the fibers and the physical properties of the slate plate.

[0027]

[Table 2]

In Comparative Example 3, the addition rate was too low to exert the effect of reinforcing the fiber, and in Comparative Example 4, the addition rate was too high to obtain satisfactory slate plate properties due to poor dispersion.

Examples 4 and 5, Comparative Example 5 In Example 1, the conditions for autoclaving were changed. Table 3 shows the conditions and physical properties of the slate.

[0030]

[Table 3]

As is clear from the table, when the curing temperature is low, the dimensional stability is insufficient even if the curing time is increased.

Example 5 Completely saponified PVA having a degree of polymerization of 4000 was dissolved in water at a concentration of 10%, and boric acid and a 40 mol adduct of nonylphenol ethylene oxide were added in 2.0% and 6.0% PVA, respectively.
A was added to A to give a spinning dope. The spinning stock solution was spun in the same manner as in Example 1, and was roll-drawn, neutralized, wet-heat drawn, washed with water and dried according to a conventional method. Subsequently, the film is stretched at 240 ° C. so that the total stretching ratio becomes 27 times, 2 denier, strength 2
0.5 g / d of fiber was obtained. Subsequently, the first stage was subjected to a two-stage treatment in a bath of formaldehyde 60 g / l at 75 ° C, the second stage, formaldehyde 100 g / l sulfuric acid 80 g / l and sodium sulfate 50 g / l at 80 ° C. The fiber thus obtained has a strength of 1
8.3 g / d, gel elastic modulus, degree of acetalization, and elution rate are 13.9 × 10 3 g / cm · d and 24.5 m, respectively.
ol% and 12%. The fiber was cut into a length of 6 mm, and a slate plate was formed in the same manner as in Example 1 and was autoclaved at 170 ° C. for 10 hours. The dimensional stability of the obtained slate plate was 0.07%, and the toughness ratio in a wet state was as excellent as 3.7.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-213510 (JP, A) JP-A-4-104925 (JP, A) JP-A-4-228610 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C04B 16/06 C04B 28/18

Claims (2)

(57) [Claims] (1) containing a polyvinyl alcohol-based synthetic fiber as a reinforcing material in an amount of 0.3 to 10% by weight, and having a dimensional stability of 0.1 to 10%;
An autoclave-cured fiber-reinforced hydraulic molded product having a toughness ratio of 15% or less and a wet toughness ratio of 1.2 or more. 2. A strength of 11 g / d or more and a gel elasticity of 6.0.
× 10 ↑ -3 g / cm · d or more and a dissolution rate of 40% or less, 0.3 to 10% by weight of a hydraulic molding material is compounded as a reinforcing material in a hydraulic molding material.
A method for producing a hydraulic molded product which is autoclaved at 140 ° C. or higher.