JPH0116784B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a molded product having a matrix of a hydraulic material reinforced with polyvinyl alcohol synthetic fibers (hereinafter abbreviated as PVA fibers). It is well known that asbestos is a typical inorganic fiber that is used to mold hydraulic substances such as cement and to provide a reinforcing effect. However, demand for asbestos is dependent on imports, and asbestos is expected to become increasingly difficult to obtain as resources are depleted and resources are depleted worldwide. In addition, from the perspective of health problems, it is better to avoid inhaling asbestos fibers, and there are concerns about environmental health and pollution.
Substitutes for this asbestos are being considered. For example, Cement Concrete Products Volume 16 8
No. 1 Mitsugu (1970) Mr. Oki's ``Development of fibers to replace hot asbestos for slate'', Cement Technology Annual Report 1975 448 Mitsugu, Mr. Kishitani and others conducted experiments.
It has been reported that it will be difficult to obtain fibers to replace asbestos. The present inventors aimed to improve folding strength using PVA fibers, and as a result of intensive research, they arrived at the present invention. DJ Hannant's "FIBRE CEMENTS and
FIBER CONCRETES” (Copyright 1987by
According to John Wiley & Sons, LTD.
If λMR is the rupture coefficient after cracking, the formula of λ _MR =K・(1−lc/2l)λ _fv・Vf (1) is shown from the compound law that is generally said to be the rupture coefficient after cracking. K is a constant including the orientation coefficient, lc is the limiting fiber length, l is the length of the fiber, λfv is the fracture stress of the fully attached fiber, and Vf is the volume fraction of the fiber. Now, from this equation (1), in order to increase λMR, it is necessary to increase λfv and Vf, but when λfv and Vf are kept constant, lc/2l must be minimized. That is, by reducing lc, lc/2l becomes smaller, so it is possible to obtain a larger λMR. lc means the minimum fiber length that can be pulled out when fibers are pulled out from the cement matrix, and is expressed by the following equation based on the balance between adhesive strength and fiber strength. lc=λ _fv・d/2τ (2) Here, τ is the adhesive strength between the fiber and matrix, and d is the diameter of the fiber. Originally, PVA fibers are hydrophilic, so compared to other synthetic fibers and inorganic fibers such as glass and steel, PVA fibers have better adhesion to cement matrices (larger τ) and therefore have a smaller lc. However, it cannot be said that it is sufficient in terms of reinforcing effect. Furthermore, it is necessary to reduce d in order to reduce le, and it has been found that PVA fibers with a small fineness within the range indicated by the present invention can further increase the reinforcing effect. On the other hand, there is a fiber spacing theory as one of the reinforcement theories, and it is said that the smaller the spacing between adjacent fibers, the greater the reinforcing property (References, D, J, above,
Hannant). The fiber spacing is generally expressed by the following formula: where c is a constant, d and V _f are the diameter of the fiber and its volume fraction. If the addition rate (V _f ) is constant, the diameter of the fiber is
The smaller the number (d), the larger the number of fibers that can be inserted, and therefore the smaller the fiber spacing, which is advantageous for the reinforcing effect. As mentioned above, the composite law and the fiber spacing theory, which are typical theories regarding the reinforcing effect of reinforcing brittle materials with fibers, have in common that the smaller the fiber diameter, the greater the reinforcing effect. By the way, the above-mentioned theory is based on the premise that the fibers are uniformly dispersed in the matrix, and if the dispersion is poor, the reinforcing effect will be significantly reduced. Generally, the smaller the fiber thickness, the worse the dispersibility. In fact, in order to improve the quality of glass fibers, the fibers are made into chopped strands and the single fibers are bundled together to make them thicker. Also, synthetic fibers of several deniers or more are only used for fear of deterioration of dispersion, and known literature does not find a region with a small fineness. Furthermore, PVA-based fibers are extremely susceptible to poor dispersion, and only known documents have been found for PVA fibers of 2 deniers or more, and no studies have been made for smaller areas. In other words, it is common knowledge that the reinforcing effect is small if the denier is less than 2 denier. However, since PVA fibers are inherently highly hydrophilic, the present inventors presumed that dispersion would be possible even with a denier of less than 2 deniers, and after conducting studies, a remarkable reinforcing effect was obtained, leading to the present invention. In other words, we have obtained new knowledge that breaks the conventional wisdom that 0.1 to 1.8 deniers have a much greater reinforcing effect than 2 deniers or more. However, although PVA fibers originally have good dispersibility, dispersibility is still a key point in making the reinforcing effect of fibers of 1.8 denier or less more effective. The characteristic that influences its dispersibility is the aspect ratio (hereinafter referred to as AR value = l/d), which is the ratio of the diameter (d) and length (l) of the fiber. One of the conditions for maximizing the reinforcing effect is that l should be longer than in equation (1), and d should be smaller than in equations (1), (2), and (3). That is, it is important to increase the AR value. However, another condition for increasing the reinforcing effect is good dispersibility. As for the dispersibility, it is naturally preferable to reduce the AR value. Therefore, the important features of the present invention are the use of fine denier and the selection of its AR value. The denier is preferably 0.1 to 1.8 denier, more preferably 0.5 to 1.8 denier. If the fiber is less than 0.1 denier, it does not have an AR value that increases the reinforcing effect, and it is difficult to economically manufacture the fiber. Further, if the denier is 1.8 denier or more, the denier becomes too large and the reinforcing effect decreases. 100-1200 for AR value
is preferable, and 200 to 800 is more preferable. If it is less than 100, the dispersibility is good, but the adhesion with the matrix is reduced and the reinforcing effect is small, and if it is more than 1200, the dispersibility is markedly reduced and the reinforcing effect is not sufficient. Due to these restrictions on AR value and fineness, the optimum fiber length is 0.5 to 12 mm to maximize reinforcing properties. The present inventors conducted extensive experiments between these AR values and the fiber length depending on the fiber diameter, and obtained the relationship shown in FIG. 1 in conjunction with the examples described later. A in Figure 1
(100, 1.44), B (100, 0.5), C (150, 0.5), D
A preferable range is within the range surrounded by (1200, 4), E (1200, 12), and F (850, 12). Figure 2 shows the results of extensive experiments between the AR value and the bending strength depending on the fiber diameter.
It can be seen that there is a region where the bending strength is increased around ~400 denier, and as the fiber becomes smaller than 2 denier, the bending strength increases. The addition rate of PVA fiber is preferably 0.05 to 4% (expressed as the weight of fiber in the total weight of the solid content. Hereinafter simply abbreviated as %). If it is less than 0.05%, the effect of adding fiber is On the other hand, if it exceeds 4%, it is meaningless because the dispersibility of the fibers deteriorates. In this way, the fineness is 0.1~1.8 denier and the fiber length is 0.5~
A hydraulic material containing 0.05 to 4% of 12 mm PVA fibers is firmly consolidated with PVA fibers to provide a cement-based hydraulic molded product with a large reinforcing effect. Paper formability, which is important in the wet paper making method, is ensured not only by the good affinity of PVA fibers with the natural cement particles, but also by using a flocculant such as polyacrylamide and by reducing the size of the cylinder mesh. be able to. Furthermore, it is also possible to use asbestos, vegetable fibers, or glass fibers in combination to improve paper formability and reinforcing properties. The required performance of the board material can be changed depending on its compounding ratio, and it can be freely applied as a complete or partial replacement for asbestos in so-called asbestos slate boards, pulp cement boards, flexible boards, asbestos perlite boards, pulp cement perlite boards, etc. . According to equation (1), the higher the strength of the PVA fiber used for reinforcement, the greater the contribution to λMR. Specifically, the range used in the examples described later, that is, 11.2 g per denier or more, has an excellent reinforcing effect. be employed in order to obtain The matrices that make up the molded product include ordinary, early-strength, ultra-early-strength, medium-heat, and sulfate-resistant Portland cement; mixed cements include blast furnace cement, silica cement, fly ash cement,
Furthermore, alumina cement, ultra-fast hardening cement, colloid cement, oil well cement, etc. can be used. Furthermore, semi-hydrated slag, slag-slag type, slag, magnesium carbonate, etc. can also be used. Inorganic fillers include charcoal, clay,
Inorganic fillers such as fired slate powder, serpentine rock, silica, slag, and mica can be used. There is no particular type or grade of asbestos, but chrysotile amosite, blue asbestos, etc. of classes 4 to 7 are generally used. It is also possible to use low-purity mesh asbestos other than the 7 classes called asbestos tailings.
As the glass fiber, alkali-resistant glass fiber containing ZrO, E-glass, glass fiber, rock wool, etc. can also be used. Next, as natural fibers, bleached and unbleached softwood and hardwood pulps can be used, and of course recycled waste paper,
Waste newspapers are also used. In addition to pulp, cotton, manila hemp, jute, mulberry, mitsumata, etc. can also be used. Naturally, it is also possible to use it in combination with organic synthetic fibers. The synthetic fibers used include strands of split yarn made from filament or film materials such as polyolefin polyethylene and polypropylene, polyamide nylon 6 and nylon 66, and other polyacrylonitrile, polyvinyl chloride, polyvinylidene chloride, polyester, and polyimide. Chopped strands such as Kepler, polyamideimide, etc. can also be used in combination. Alternatively, as the synthetic pulp, one obtained by flash spinning polyethylene, polypropylene, or a polymer obtained by mixing these polymers with an inorganic filler can also be used. This will be explained below using examples. Example 1 and Comparative Example 1 A PVA aqueous solution with a polymerization degree of 1680 to which 1.8% boric acid was added was spun into a pseudo-solid bath containing 20 g of caustic soda, 330 g of sodium sulfate, and 1 g of boric acid, and wetted through a neutralization and water washing process. In the process, it was stretched 5 times, dried and rolled up. In order to change the fineness, the discharge amount is changed by changing the flow rate of the PVA aqueous solution,
Dry yarns of various finenesses were obtained. After further hot stretching and heat treatment process, single fiber denier is 0.5, 1.0,
PVA fibers of 1.3, 2.0, 6, and 15 deniers were obtained.
In order to obtain fibers with different AR values, the fibers were cut into the fiber lengths shown in Table 1. Next, we mixed it into the cement matrix and investigated its reinforcing effect. The asbestos was composed of 5% 5R chrysotile asbestos, 2% unbeaten and unbleached kraft pulp, 2% PVA fiber, and the balance normal Portland cement. The molding was performed by laminating 10 plies using the papermaking method, and after being pressurized, it was left to dry in the air, and after 4 weeks, the bending strength and impact strength were measured using the Izod method. As controls for comparing bending strength, 15% asbestos and 2% pulp, and 5% asbestos and 2% pulp without PVA fibers were also shown.

[Table] Bending strength and impact strength are asbestos 15%+
360Kg/cm ² and 2.4 respectively based on pulp 2% + No.20
It is shown as a value normalized to Kg-cm/cm ² as 1.0. Typical examples and comparative examples in Table 1 are shown in FIG. 1 and FIG. 2 by the numbers in Table 1. From Figure 2, as mentioned above, there is a local maximum point where the bending strength of the molded product reaches its maximum around the AR value of 200 to 400, and as the fineness becomes smaller than 2 denier, the bending strength increases. , 2.0 denier, it can be seen that the effect of reducing the denier has not been fully achieved yet. Furthermore, as can be seen from the comparative examples, it is also clear that AR value alone has no effect on bending strength. Example 2 and Comparative Example 2 Single yarn denier 1.0 denier shown in Example 2
Using PVA fiber, 2% of this PVA fiber cut into 3.2 mm (AR value 300), 6, 10, 15% each of waste paper pulp (NUKP) is added, and the remainder is cement. An asbestos board was made using a hatchet machine. Similarly, calcium carbonate and fly ash were added as alkali-resistant glass fibers and inorganic fillers.
A molded product was obtained by paper making with the formulation shown in the table. The paper is cut into 16 plies using a hatchet machine.
It was pressed to 50 kg/cm ² and cured in air for 28 days. For comparison, the same test was conducted using the 6 denier fiber used in Comparative Example 1 cut into 5.2 mm pieces (AR value 200). This is shown in Table 2.

[Table] As for the additives used, the waste paper pulp used was cotton-containing waste paper manufactured by Kuniko Kenzai. The alkali-resistant glass fiber used was Asahi Glass roving cut into 13 mm pieces. The calcium carbonate used was Whiten P-30 manufactured by Shiraishi Kogyo, and the fly ash was Chuden fly ash. Examples Nos. 22 to 24 are samples without asbestos, and there are no problems in papermaking properties, and No. 22 has improved folding strength by 29% compared to Comparative Example No. 30. Furthermore, compared to No. 30 and 22, Comparative Example No. 35 has an improvement in folding strength of 24 compared to No. 30 and No. 22 from the one without PVA fiber.
%, which has dramatically improved to 66%. Asbestos
When pulp is used in combination with glass fiber, examples of combination systems with inorganic filler and combination of glass fiber and inorganic filler are shown in Nos. 25 to 29, and comparative examples of each corresponding system are shown in Nos. 31 to 34. . These results 28~
It was shown to improve by 42%.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between AR value and fiber length using fiber diameter as a parameter, and FIG. 2 is a diagram showing the relationship between AR value and bending strength using fiber diameter as a parameter.

Claims (1)

[Claims] 1. Single yarn fineness is 0.1 to 1.8 denier and length is 0.5 to 1.8 denier.
A fiber-reinforced hydraulic molded product containing 0.05-4% of polyvinyl alcohol synthetic fiber as a reinforcing material, with a diameter of 12 mm, a strength of 11.2 g/denier or more, and an aspect ratio of 100-1200. 2. The fiber-reinforced hydraulic molded product according to claim 1, which contains 0 to 25% asbestos. 3. The fiber-reinforced hydraulic molded product according to claim 1 or 2, which contains 0 to 15% vegetable fiber. 4. The fiber-reinforced hydraulic molded product according to any one of claims 1 to 3, containing 0 to 30% of glass fiber or inorganic filler.