JP2565517B2 - Fiber reinforced hydraulic molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a polyvinyl alcohol-based synthetic fiber (hereinafter referred to as PVA) having a flat cross section and a large crystal length / width ratio.
The present invention relates to a fiber-reinforced hydraulic molded product (hereinafter abbreviated as FRC) having a reinforcing material of (a type fiber).

<Prior art> Asbestos has been most commonly used as a reinforcing material for FRC, but as the carcinogenicity of asbestos has been revealed in recent years and its use is being regulated, it is used as an alternative material.
Various synthetic fibers such as PVA-based fibers and acrylic fibers, and inorganic fibers such as steel fibers and glass fibers have been proposed,
Among them, PVA fibers are preferably used because they have good alkali resistance and relatively excellent mechanical properties.

However, even with such excellent PVA-based fiber, the performance required for the reinforcing fiber as shown below has not been sufficiently satisfied, and therefore FR using this as a reinforcing material is used.
C was also unsatisfactory.

The performance required of the reinforcing fiber is said to be firstly high strength and high elasticity. When the fibers do not have sufficient strength and elasticity, the resulting fiber-reinforced molded product naturally does not have toughness.

Secondly, the performance required is that the reinforcing fiber has excellent adhesiveness to a hydraulic substance represented by cement. If the adhesion between the reinforcing fiber and the hydraulic material is insufficient,
In the fiber-reinforced molded product, the strength and elasticity of the reinforcing fiber are not sufficiently utilized against external stress, and cracking or breakage occurs without the reinforcing effect being obtained. It is effective to increase the surface area of the fiber in order to improve the adhesion between the fiber and the hydraulic substance, and specifically, there are methods such as flattening, deforming, and fine denier of the cross section of the fiber.

The most typical method for producing PVA-based fibers is PVA
It is a method in which an aqueous solution is wet-spun in a coagulation bath at room temperature containing salts having a dehydrating ability, drawn, heat-treated, and optionally acetalized. PVA fiber obtained by this method,
As is well known, it has a relatively large surface area with a cocoon-shaped cross section having a two-layer structure of skin and core, but it can be stretched only to a total stretching ratio of about 8 times and its strength is about 7 g / d.
It is not satisfactory as a reinforcing fiber from the viewpoint of dust and strength.

Further, as a method for obtaining a PVA-based fiber having higher strength, Japanese Patent Publication No. 48-32623, Japanese Patent Publication No. 53-1368, and Japanese Patent Publication No. 60-126312.
And Japanese Patent Laid-Open No. 61-108712. However, the fibers obtained by these methods are
Although the strength and elasticity are greatly improved, it is very homogeneous and has a cross section close to a circle and a small surface area. In general, as the strength of the reinforcing fiber increases, the limit fiber length becomes longer, so that the fiber tends to come off when stress is applied. Since such fibers also have a long critical fiber length and a small surface area, a reinforcing effect cannot be obtained as expected for the strength of the fibers.

On the other hand, as a means to intentionally increase the surface area of the fiber, there is a method in which the cross-section is modified by spinning using a modified nozzle, but the fiber obtained by this method is inferior in mechanical physical properties.
Not as satisfactory as C. Further, by decreasing the denier of the fiber, the surface area per unit amount can be increased, but in this case, the dispersibility in the cement slurry is deteriorated and the mechanical properties of FRC are not improved.

As described above, conventional fibers are required to be reinforcing fibers.
It does not combine the two performances, and the mechanical properties of the FRC obtained accordingly cannot be fully satisfied.

<Problems to be Solved by the Invention> The present invention aims to provide an FRC having excellent mechanical properties.

<Means for Solving Problems> As a result of examining the reinforcing effect of various PVA-based fibers in order to develop an FRC having excellent mechanical properties, the present inventors found that the reinforcing effect is the strength of the reinforcing fiber.・ Rather than elastic modulus
I do not know why, but the ratio of the length (L) to the width (W) of the fiber crystals (hereinafter abbreviated as L / W) is more closely related and L / W is sufficient to obtain a sufficient reinforcing effect. The present invention has been found out that it is essential that W is 2.1 or more and the cross-sectional solidity is 65% or less, preferably L / W is 2.3 or more and the cross-sectional solidity is 60% or less. The length L of the crystal of the fiber has little correlation with the mechanical properties of the fiber and the reinforcing effect, and L / W
For the first time, a strong correlation appears.

Effective manufacturing method of the PVA fiber used in the present invention,
A PVA aqueous solution containing boric acid or borate is used as a spinning dope, and wet spinning is performed in an alkaline coagulation bath at 55 to 95 ° C containing salts having a dehydrating ability, and the obtained spinning dope is drawn at a draw ratio of 17 times or more. Is the way to do it. Such a method is conventionally 20-
Compared to the coagulation bath temperature of 50 ° C, this is 55
It is characterized by raising the temperature to ~ 95 ° C. The obtained fiber has a flat cross section, and the L / W of the fiber increases, so that the mechanical properties of the fiber are significantly improved. Although the reason is not well understood, it is considered that the solidification mechanism is completely different from the conventional spinning method.

Hereinafter, one example of the method for producing the PVA fiber used in the present invention will be described in detail.

The degree of polymerization of the PVA used is 1500 or more, preferably 2000 or more, and more preferably 3000 or more.

The spinning solution is an aqueous solution having a concentration of 5 to 30% by weight of the PVA, containing 0.5 to 5% by weight of boric acid or borate with respect to the PVA, and the concentration of PVA is preferably 6 to 25% by weight, It is preferably from 7 to 18% by weight, and it is preferable to adjust it appropriately according to the degree of polymerization of PVA.

The spinning dope temperature is 85 to 125 ° C., preferably 95 to 120 ° C. If it is too low, the drawability is hindered, and if it is too high, the stock solution boils. To stabilize the spinning condition, an appropriate amount of an organic acid such as acetic acid or an inorganic acid such as nitric acid can be added to the spinning solution.

The temperature of the coagulation bath is 55 to 95 ° C, preferably 60 to 80 ° C. Below 55 ° C, the fiber cross section does not become flat and L / W does not increase. On the other hand, if the temperature is 95 ° C or higher, it is not preferable because boiling of the coagulating bath and sticking between the single fibers occur.

A caustic alkali such as sodium hydroxide or potassium hydroxide is used as the alkali component of the coagulation bath, and the concentration thereof is 2 to 200 g /, preferably 5 to 50 g /. As the salt component of the coagulation bath, a salt having a dehydrating ability such as sodium sulfate and sodium carbonate is used, and the concentration is 100 g / ~
It is a saturated concentration, and it is preferable that the concentration is close to saturation.

As the spinning nozzle, an ordinary circular nozzle or a nozzle having a shape similar to that is used. For the fiber after spinning, neutralization of alcal, wet heat drawing, washing with water, drying, drawing and heat treatment may be carried out in accordance with a usual method, but at least 17 It is necessary to perform stretching at least twice, preferably at least 20 times. The larger the draw ratio, the larger the L / W.
If it is less than 7 times, the L / W will not reach 2.1.

The PVA fiber excellent in the reinforcing property can be used in any form depending on the manufacturing method or the construction method of the molded product. For example, a single fiber or a chopped strand that has been cut and cut may be used, or filament yarns or bundled filament yarns may be used in the form of long fibers, or may be used in so-called fiber rods. Further non-woven fabric,
It can also be used as a mat-like material, a mesh-like material, a knit-like material, a two-dimensional or three-dimensional fabric, and the like. PV that takes again
A fiber can be used in combination with rebar, glass fiber,
It can also be used as a hybrid with steel fibers, acrylic fibers and the like.

On the other hand, it is not necessary to use any special method for producing the molded product, and a general FRC production method may be used. For example, in the case of a thin plate, a typical production method is a wet papermaking method, and a typical example is the hachiek method.

In the case of mortar, concrete, etc., there are casting, spray molding, injection molding, etc. as the on-site molding method. Further, in factory molding, there are vibration molding, centrifugal molding, extrusion molding and the like.

The addition ratio of the PVA fiber in the hydraulic molded product of the present invention is 0.2 to 20% by weight, preferably 1 to 5% by weight. Also, when used as short fibers, the ASPECT ratio is 50 to 2000,
It is preferably 150 to 600.

As the hydraulic material of the present invention, cement is a typical one, and Portland cement is a typical one, but blast furnace cement, fly tattoo cement, alumina cement and the like can also be used, and, You may mix and use these. Further, these cements can be mixed with sand or gravel to be used as mortar or concrete. Other hydraulic materials include Setsukou,
There are setucous rug, magnesia, etc., but any material can be used as long as it is a hydraulic substance.

Further, auxiliary agents such as mica, sepiolite and attapulgite can be used.

<Effects of the Invention> The FRC of the present invention is reinforced by PVA-based fibers having a large surface area with a flat cross section such that the L / W is large and the cross-section solidity is 65% or less as compared with the conventional FRC, It has excellent mechanical properties and is used for all cements, concrete moldings such as slate boards, pipes, blocks, wall panels, floor panels, roofing materials, partitions, road paving, tunnel linings, slope protection, etc. It can be used for the next product.

Hereinafter, the present invention will be described more specifically with reference to Examples. The cross-sectional solidity (the degree of flatness of the cross-section, the smaller the numerical value is flatness), the ratio of the length of the crystal to the width (L / W), the mechanical properties of the fiber and the cement specified in the present invention. The bending strength of the molded body (slate plate) is measured by the following method.

○ enlarged depict cross-sectional photograph of a cross section adequacy fibers about 100 mm ² cross-sectional area F
Ask for.

 Next, the widest width B in the cross section was obtained and calculated by the following formula.

In addition, this value is obtained for 20 single fibers arbitrarily taken out from one multifilament yarn, and the average value thereof is defined as the cross-sectional integrity of the fibers constituting the multifilament yarn.

○ Ratio of crystal length to width (L / W) It was measured under the following conditions by a known wide-angle X-ray diffraction method.

Wide-angle X-ray (1) Rigaku Denki Co., Ltd. rotating anticathode type X-ray diffractometer (Type RAD-rA) with 40kV, 100mA CuKα (Graphite Monochromator) scintillation counter (2) Goniometer slit system: DS 1 / 2 °, SS 1/2 °, RS 0.15mm Scanning speed: 2θ = 1/2 ° / min (3) Sample (fiber of 125 mg arranged in parallel with 2.5 cm in length and 1.5 cm in width) The sample was mounted on a sample table, and the diffraction curves of surface indices (020) and (100) were measured by the transmission method to obtain the half-value width B (hkl) of each curve.

Ratio of crystal size (L / w) Calculate each crystal size from Scherrer's formula from the value of half-value width B (hkl) of peaks of plane index (020) and (100) obtained by the above transmission method. did.

D (hkl) = Kλ / Bo (hkl) COSθ (hkl) where K = 0.9 λ = 1.5418 (Å) The spread of the diffraction curve after correction of the slit by the method of Bo: Jones (radian) θ (hkl): Bragg angle (Deg.) L / W = D (020) / D (100).

○ Dry rupture strength / elongation, initial elastic modulus (1) Sample …… Multifilament yarn (2) Dry rupture strength / elongation, initial elasticity …… Temperature of 20 ℃ and relative humidity of 65% In accordance with the test, a test length of 20 cm and a pulling speed of 10 cm / min were measured with an Instron tester, and the initial elastic modulus was determined from its elongation-load curve.

Bending strength of slate plate Measured with an Instron tester according to JIS K6911.

Examples 1 and 2, Comparative Example 1 Fully saponified PVA having a degree of polymerization of 3500 was dissolved in water to a concentration of 9% by weight, and boric acid was added to the PVA at 3.5% by weight to prepare a spinning dope. Next, this spinning solution is heated to 105 ° C.,
A base having a 1000-hole circular nozzle in a coagulation bath consisting of 15 g of sodium hydroxide / 350 g of sodium sulfate / 60 ° C. (Example 1), 70 ° C. (Example 2) and 30 ° C. (Comparative Example 1). Was spun through, and the bath was allowed to separate at a speed of 6 m / min. Subsequently, roller drawing, neutralization, wet heat drawing, washing with water and drying were carried out, and then dry drawing was carried out at 230 ° C. to obtain a 1800 d / 1000 f multifilament yarn. The total draw ratio was 22.5 (Example 1), 26.8 (Example 2), and 14.6 (Comparative Example 1).

Each fiber is cut into a length of 6 mm, wet-machined with a Hachiekku machine by mixing 2 parts of the fiber, 4 parts of the pulp, and 94 parts of Portland cement, and after 5 days of natural curing, a thickness of 5 mm.
The slate board of was produced.

 Table 1 shows the physical properties of each fiber and the slate plate.

As can be seen from this example, the FRC of the present invention has outstanding mechanical properties.

Comparative Example 2 Spinning was carried out in the same manner as in Example 2 until drying, and the dry-wet draw ratio was reduced to a draw ratio of 16 times, the cross-sectional solidity was 36%, L / W 2.
0, single yarn denier 1.8d, breaking strength 12.8g / d, elastic modulus 280g / d
Fibers were obtained. This was cut into a length of 6 mm, and a slate plate was produced by the above method. The bending strength of this slate plate was 290 kg / cm ² as shown in Table 1, which was far inferior to that of Example 2.

Comparative Example 3 A fully saponified PVA having a degree of polymerization of 3500 was dissolved in dimethylsulfoxide at a concentration of 10% by weight to prepare a spinning stock solution, which was dry-wet spun from a 50-hole nozzle into a methanol coagulation bath at 10 ° C. The obtained spun raw yarn was subjected to 6-fold wet drawing while being desolvated and dried. Next, dry heat drawing was carried out at 240 ° C., and the total draw ratio was 24 times. The denier of the obtained fiber was 1.8, and its cross-section solidity was 92%, which was very high and was almost circular. The L / W is 2.6, which is a strength of 21.0 g / d and elastic modulus of 530.
It was g / d. This fiber was cut into a length of 6 mm, and a slate plate was produced by the above method.

The bending strength of this slate plate is as shown in Table 1 above.
At 350 kg / cm ² , the mechanical properties were inferior for the strength of the reinforcing fiber.

Further, for all the FRCs of Examples 1 and 2 and Comparative Examples 1 to 3, when the fracture surface of the sample after bending strength measurement was observed with an electron microscope, it was found that the reinforcing fibers were not cut in Comparative Examples 1 and 3. Although withdrawal occurred, Comparative Example 3 was more noticeable.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideki Hojo 1-2-1 Kaigandori, Okayama City, Okayama Prefecture Kuraray Co., Ltd. Examiner Masahiro Inoue

Claims (1)

(57) [Claims] 1. A fiber-reinforced hydraulically-molded article comprising a polyvinyl alcohol-based synthetic fiber as a reinforcing material, which has a cross-sectional solidity of 65% or less and a crystal length / width ratio of 2.1 or more.