A GLASS-FIBER-REINFORCED CEMENT PANEL AND A PROCESS FOR ITS MANUFACTURE

Abstract: Disclosed are a glass-fiber-reinforced cement panel and a process for its manufacturing, according to which a cement slurry devoid of asbestos fiber consisting of 0.5-­ 3.0% by weight of glass fiber or glass fiber and polyvinyl alcohol fiber in combination, and pulp in an amount 2-2.5 times the total amount of glass fiber and polyvinyl alcohol fiber, balance cement, is prepared; then, the cement slurry, with 0.005-0.6% by weight of a cement flocculant added in the midway as it is transferred from the chest to the bats, is subjected to the Hatschek sheetmaking process, thereby forming the glass-fiber-reinforced cement panel.

Description: Description Title of the Invention: A Glass-Fiber-Reinforced Cement Panel and a Process for its Manufacture. Technical Field of the Invention: The present invention relates to a glass-fiberreinforced cement panel manufactured by way of sheetmaking with a cement slurry, accordmg to claim 10 cd 11, and the manufacturing process thereof, according to clams 1 to 9. Prior Art: The process for manufacturing asbestos cement panels by way of sheet-making with cement slurries prepared by adding asbestos fiber to cement has heretofore been employed, and as a representative manufacturing process, the Hatschek sheet-making process shown in an accompanying drawing is known. According to this sheet-making process1 at the pulper (1), cement, asbestos and water are mixed to produce a slurry, and this slurry is transferred to the chest (2). The slurry in the chest (2) is continuously fed to the bats (3); and the slurry in the bat is taken on the sheetmaking cylinder (4) in a sheet form. Then, the sheet on the sheet-making cylinder (4) is transferred to the felt belt (5) running in contact with this cylinder (4), and the sheet on the felt belt (5) is, in turn, taken up by the making roll (6). As the sheet is taken up on this making roll to the predetermined thickness, the taken-up sheet is cut, and stripped off the making roll (6). it is, then, expanded flat, and after being passed through a press, is cured in a high temperature, high pressure steam, yielding a set cement panel. Recently, this process has encountered some problems, including scanty supply of asbestos fiber, rising costs, and in addition, problems of work-site environment where asbestos fiber is handled, involving the adverse effect on human body of asbestos fiber scattered from weathered asbestos cement panels. To overcome such difficulties, search is now going on for other fibers to replace asbestos. Disclosure of the Invention The present inventors pursued investigations on the use of glass fiber in place of asbestos fiber. Replacement of asbestos fiber with glass fiber, however, involves various problems. The glass fiber gives only slight dis persionin slurry, has smaller cement capturing capacity than asbestos fiber, and shows low sheet-making ability, since with glass fiber only, the cement particles in the slurry penetrate through the sheet-making cylinder, badly affecting the sheet-making with cement solids on the sheetmaking cylinder. In order to explore a suitable manufacturing method of the glass-fiber-reinforced cement panels, the present inventors have carried out studies on the possibility of sheet-making with cement slurries containing glass fiber by conducting the following experiments: Experiment 1. In the mixed material of glass fiber which would be opened into mono-filaments in water, pulp and cement, the mixing rate of glass fiber was widely varied over 0.1 by weight1 and that of pulp over 0.1 - 10% weight. Forty liters (40 2) of water was added to 2,000 g of this mixed material. This mixture was stirred for 150 seconds, and the dispersed state of glass fiber after the stirring was observed. The result revealed that if the amount of pulp is twice as large as the amount of glass fiber or more, the glass fiber may be adequately dispersed. It also turned out, however, that the settling and separation of glass fiber with passage of time is appreciably rapid, giving rise to a difficulty causing glass fiber to be dispersed in slurry in stable state merely by addition of pulp. Experiment 2. In order to achieve an improvement on the settling and separation of glass fiber, a strong anionic floccuant is added to the mixed material of the aforementioned Experiment 1; then1 water was added similarly as in Experiment 1, followed by stirring, and after this stirring, the settling and separating state of glass fiber was observed. The result suggested that if the addition of the flocculant is more than 0.005to by weight of cement, the settling and separation of glass fiber may be adequately hindered. The reason is because the viscosity of the slurry is increased by the addition of the flocculant. Experiment 3. The slurry after being stirred in Experiment 2 was filtered through a 60 mesh wire-netting, and the percentage of the cement solids in the slurry made into sheet on the wire-netting was measured. The result evidently showed that while the sheetmaking efficiency is higher than 70%, with the addition of the flocculant more than 0.005% by weight1 it runs below 50 < 0 without addition of the flocculant. Thus, it has been confirmed by the above-described experiments that the problem in the dispersion of glass fiber may be solved by the addition of pulp and cement flocculant to the slurry, and that the problem in the sheet-making efficiency of cement solids may be eliminated by the addition of the cement flocculant above-mentioned. That the impact resistance of the cement panel may be improved by the addition of polyvinyl alcohol fiber, together with glass fiber, into the cement slurry has hitherto been known. However, polyvinyl alcohol fiber, like glass fiber1 is inferior in giving dispersion and in the sheetmaking ability, having smaller cement solids capturing capacity than asbestos fiber. According to this invention, by the use of polyvinyl alcohol fiber and glass fiber in admixture, and through the addition of pulp and a certain cement flocculant, it is possible to improve the dispersion in the cement slurry and the cement capturing capacity, and to manufacture glassfiber-reinforced cement panels having excellent impact resistance. As the cement flocculant is added to the cement slurry, the cement particles are agglomerated, and become more easily captured by the pulp fiber and the cement fiber groups, giving rise to an improvement in the sheet-making ability. However, the effect of improving the sheet-making ability is largely dependent on in what step of the manufacturing process the flocculant is added. Although the grounds are not certain, the agglomeration of cement particles caused by the addition of the flocculant is believed to result from the active parts of the cement particles and the active branches of the flocculant being bridged, and thereby chemically bonded. When such a cement slurry is violently stirred, the bridged molecules are served, to be turned into low molecular weight compounds. The object of this invention is to provide a glassfiber-reinforced cement panel having nearly equivalent strength to that of asbestos-fiber-reinforced cement panels, manufactured by use of a material prepared by mixing cement1 glass fiber, pulp and cement flocculant, without employing asbestos fiber, and the manufacturing process thereof. Another object of this invention is to provide a glassfiber-reinforced cement panel manufactured by use of a cement material containing glass fiber and polyvinyl alcohol fiber, without employing asbestos fiber, and the manufacturing process thereof. Further object is to offer an improvement in the sheetmaking property of the cement slurry by making the addition of the cement flocculant in the midway as the cement slurry is transferred from the chest to the bats. Figure 1 presents an explanatory diagram of a Hatschek model sheet-making system employed for exercising the process of this invention, showing the position for making the addition of the cement flocculant by an arrow A. According to the Hatschek sheet-making process of this invention, a mixed material of 0.5 - 3.0% by weight of glass fiber and pulp in an amount 2 - 2.5 times the amount of glass fiber, balance cement1 is charged into the pulper (1), and formed into a cement slurry through the chest (2). Then, in the midway, as indicated by the arrow A, as this cement slurry is transferred from the chest (2) to the bats (3), 0.005 - 0.620 by weight, preferably 0.01 - 0.06 by weight, of the cement flocculant, on the basis of the amount of cement, is continuously added. The slurry in the bat (3) is taken in a sheet form on the sheet-making cylinder (4) as well-known, and this sheet goes through the felt belt (5), and is taken up on the making roll (6). As it is taken up on the making roll (6) to the predetermined thickness, the taken-up sheet is cut, and stripped off the making roll (6). Then, it is extended, passed through the press, and cured, yielding a set cement panel. For the mixed material of the cement slurry, the total amount of glass fiber and polyvinyl alcohol fiber running up to 0.5 - 3,0% by weight, and the amount of pulp 2 - 2.5 times the total amount of glass fiber and polyvinyl alcohol fiber, balance cement, are used. The cement slurry prepared from this mixed material, to which 0.005 - 0.6% by weight of a cement flocculant, based on cement, is added at the midpoint between the chest and the bats, is made into a sheet. In that way, a glass-fiber-reinforced cement panel containing polyvinyl alcohol fiber can be manufactured. The glass fiber confers the bending strength on the panel. An addition of glass fiber in the range of 0.5 3.0% by weight enables achieving a bending strength equivalent to that of the conventional asbestos-fiber reinforced cement panels, being 150 - 300 kg/cm2. For the glass fiber employed in the process of this invention, strands formed by collecting and setting monofilaments by use of a water soluble collector-setter and, then, chopped, are used. The chopped strand has a length of 3 - 19 mm. The longer the glass fiber, the better effect may be achieved on improving the bending strength of panels, 3 mm or less being disadvantageous from panel bending strength standpoint. With longer glass fibers, however, they have difficulty being homogenously disperse-d, and it becomes hard to cut the taken-up sheet which has been taken in a sheet form on the making roll. The compromise length of the glass fiber may be limited to 19 mm. The polyvinyl alcohol fiber provides the panel with improved shock resistance. Its preferred amount of addition should be less than 1/3 times that of the glass fiber. The polyvinyl alcohol fiber employed in the process of this invention has n higher than 9 g/dr tensile strength, 5 - 74/4 elongation, and 15 - 25 dr fiber diameter, such fibers commercially available including Vinylon Fiber (trade name for a polyvinyl alcohol fiber manufactured by Kuraray Company, Product No. VPM 1502). The length of the polyvinyl alcohol fiber is nearly equal to that of the aforementioned glass fiber. Pulp contributes to the improvements in the dispersion of glass fiber and polyvinyl alcohol fiber and in the cement solids capturing capacity. With regard to the amount of pulp added, pulp has no effect on improving the dispersion of glass fiber and polyvinyl alcohol fiber, when the amount is less than twice the amount of glass fiber or the total amount of glass fiber and polyvinylalcohol, if the polyvinyl alcohol fiber is mixed in, and it detracts from the strength and the resistance to moisture absorption of the panels, when its amount exceeds 2.5 times. The cement flocculant provides an effective means for improving the sheet-making property of cement. Dut if its addition is less than 0.005%, both the aforementioned prevention of settling and separation of glass fiber and polyvinyl alcohol fiber and ensuring higher than 70% sheetmaking efficiency of cement solids can not adequately be attained, and if it is more than 0.6%, the bonding strength of the cement matrix after being formed into a panel is reduced, and consequently, reduction in the panels strength is brought about. For the cement flocculants for the process of this invention either the anionics or the cationics are usable, but those of strong anionic type having molecular weights of 106 - 107 are most effective. Of the flocculants of strong anionic type, by aid of which the cement particles are supposed to be flocculated due principally to the bridge forming and adsorbing effects, those having larger molecular weights are believed to be advantageous. Particularly desirable for use are polyacrylamides. Such polyacrylamides employed in the process of this invention have molecular weights ranging from 3 - 13 millions. Polyacrylamides of this invention are polyacrylamides on which Na substitution is made as represented by the following formula: EMI10.1 m Those with (degree of anionization) found in the range m+n of 0.03 - 0.2 have been confirmed to give high effect of flocculation. The above-mentioned products of strong anionic flocculants commercially available include Flocculant EXP No.4 manufactured by Modern Chemical Industry Co., Ltd. (Kindai Kagaku Kogyo K. K.), Diaflock AP-335, Diaflock AP825, and Sumiflock FA-50. The flocculation by the aid of cationic flocculants is believed to result from the electrical bonding of the cations of the flocculant and the anions of the cement particles. Commercially available products representing intcrmediately, cationic flocculants include Diaflock XP-156A, and commercially available weakly cationic flocculants Diaflock KP-102. In exercising the process of this invention1 cement panels were manufactured, with the amount of pulp used varied in the range from 0 - 7.0% by weight, the amount of glass fiber from 0.5 - 3.0% by weight, and the amount of the flocculant added from 0.0002 - 0.06 by weight. The results of the measurements of the bending strength, flexure (80 cm span) and the Charpy impact resistance of each panel are shown in Table l. Referring, now; to Table 1, in the Experiment Nos. 9 16, and 25 - 32, glass fiber (chopped strands of glass 6 mm long formed by collecting, and setting by the aid of a water soluble ollector-setter, 300 monofilaments 13 Mm in fiber diameter), pulp and cement (Portland cement as specified by JIS-R-5210) were mixed with 5,000 kg of water in a pulper (capacity 7 m3, rotation of stirring paddle 700 rpm) for 3 minutes. This mixture was transferred to the chest. Then, while continuously feeding the slurry in the chest into the bats, a strongly anionic flocculant (EXP No.4 manufactured by Modern Chemical Industry Co., Ltd.) was continuously added to the slurry in the predetermined ratio thereto at the midpoint between the chest and the bats. The slurry in the bat was taken in a sheet form on the sheet-making cylinder (at 30 m/min circumferential rotational speed) formed of a 60 mesh round wire-netting. This sheet thus produced was fed to the making roll through a felt shape belt, and as the sheet was taken up on this roll to 5 mm thickness, the taken-up sheet was cut, and stripped off the making roll. The stock board stripped off the making roll was extended to a flat plate. This board was, then, prssured for 10 minutes a surface pressure of 80 kg/cm2, and for the following seven days, it was cured by leaving intact outdoors. In the Experiment Nos. 33 - 34, as the slurry materials, 2.56o by weight of glass fiber and 0.5% by weight of Vinylon (trade name for a polyvinyl alcohol fiber1 VPN 1502, manufactured by Kuraray Co., Ltd.; tensile strength lOg/dr, fiber diameter 20 dr, and fiber length 6 mm) were utilized. Other conditions were the same as in Experiment Nos. 25 - 32. Experiment Nos. 1 - 8 and 17 - 24 are controls in which no inclusion of pulp was made, other conditions being identical with those in Experiment Nos. 9 - 16 and 25 - 32. Table 1. EMI13.1 <tb> <SEP> Amount <SEP> of <SEP> Glass <tb> puip <SEP> bending <SEP> Onarpy <SEP> impact <tb> Experiment <SEP> flocculant <SEP> fiber <SEP> Flexure <tb> (% <SEP> by <SEP> strength <SEP> resistance <tb> No. <SEP> (% <SEP> by <SEP> (% <SEP> by <SEP> (mm) <tb> weight) <SEP> (kg/cm2) <SEP> (kg.cm/cm2) <tb> weight) <SEP> weight) <tb> 1 <SEP> 0.0002 <SEP> 0.5 <SEP> 0 <SEP> 162.0 <SEP> 6.0 <SEP> 2.80 <tb> <SEP> 2 <SEP> 0.0006 <SEP> 0.5 <SEP> 0 <SEP> 163.0 <SEP> 5.4 <SEP> 2.83 <tb> 3 <SEP> 0.001 <SEP> 0.5 <SEP> 0 <SEP> 164.0 <SEP> 5.8 <SEP> 2.93 <tb> <SEP> 4 <SEP> 0.003 <SEP> 0.5 <SEP> 0 <SEP> 164.2 <SEP> 5.4 <SEP> 2.86 <tb> <SEP> 5 <SEP> 0.006 <SEP> 0.5 <SEP> 0 <SEP> 159.0 <SEP> 5.6 <SEP> 2.76 <tb> <SEP> 6 <SEP> 0.01 <SEP> 0.5 <SEP> 0 <SEP> 160.0 <SEP> 5.5 <SEP> 2.80 <tb> <SEP> 7 <SEP> 0.03 <SEP> 0.5 <SEP> 0 <SEP> 158.0 <SEP> 5.5 <SEP> 2.96 <tb> <SEP> 8 <SEP> 0.06 <SEP> 0.5 <SEP> 0 <SEP> 154.0 <SEP> 5.3 <SEP> 2.74 <tb> <SEP> 9 <SEP> 0.0002 <SEP> 0.5 <SEP> 1.2 <SEP> 180.0 <SEP> | <SEP> 12.0 <SEP> 3.10 <tb> <SEP> 10 <SEP> 0.0006 <SEP> 0.5 <SEP> 1.2 <SEP> 181.0 <SEP> | <SEP> 1 <SEP> 11.4 <SEP> 3.14 <tb> <SEP> 11 <SEP> 0.001 <SEP> 0.5 <SEP> 1.2 <SEP> 183.0 <SEP> 11.8 <SEP> 3.10 <tb> <SEP> 12 <SEP> 0.003 <SEP> 0.5 <SEP> 1.2 <SEP> 182.0 <SEP> 12.0 <SEP> 3.02 <tb> <SEP> 13 <SEP> 0.006 <SEP> 0.5 <SEP> 1.2 <SEP> 180.0 <SEP> 12.0 <SEP> 3.10 <tb> <SEP> 14 <SEP> | <SEP> 0.01 <SEP> 0.5 <SEP> 1.2 <SEP> 176.0 <SEP> 11.8 <SEP> 3.17 <tb> <SEP> 15 <SEP> 0.03 <SEP> 0.5 <SEP> 1.2 <SEP> 178.0 <SEP> 11.7 <SEP> 3.13 <tb> <SEP> 16 <SEP> 0.06 <SEP> 0.5 <SEP> 1.2 <SEP> 172.0 <SEP> 11.9 <SEP> 3.09 <tb> <SEP> 17 <SEP> 0.0002 <SEP> 3.0 <SEP> o <SEP> 250.0 <SEP> 31.0 <SEP> 6.4 <tb> <SEP> 18 <SEP> 0.0006 <SEP> 3.0 <SEP> o <SEP> 242.0 <SEP> 32.4 <SEP> 6.5 <tb> <SEP> 19 <SEP> 0.001 <SEP> 3.0 <SEP> o <SEP> 244.0 <SEP> 30.4 <SEP> 6.3 <tb> <SEP> 20 <SEP> 0.003 <SEP> 3.0 <SEP> 0 <SEP> 251.0 <SEP> 31.8 <SEP> 6.5 <tb> <SEP> 21 <SEP> 0.006 <SEP> 3.0 <SEP> 0 <SEP> 246.0 <SEP> 30.7 <SEP> 6.4 <tb> <SEP> 22 <SEP> 0.01 <SEP> 3.0 <SEP> 0 <SEP> 249.0 <SEP> 29.8 <SEP> 6.2 <tb> <SEP> 23 <SEP> 0.03 <SEP> 3.0 <SEP> 0 <SEP> 251.0 <SEP> 26.0 <SEP> 6.3 <tb> <SEP> 24 <SEP> 0.06 <SEP> 3.0 <SEP> 0 <SEP> 250.0 <SEP> 28.2 <SEP> 6.4 <tb> EMI14.1 <tb> <SEP> $ <SEP> Anount <SEP> of <SEP> @ <SEP> Glass <tb> puip <SEP> denoing <SEP> Onarpy <SEP> impaco <tb> Experiment <SEP> flocculant <SEP> fiber <SEP> Flexure <tb> <SEP> (% <SEP> by <SEP> strength <SEP> rosistance <tb> No. <SEP> (% <SEP> by <SEP> (% <SEP> by <SEP> (mm) <tb> <SEP> weight <SEP> (kg.cm/cm2) <tb> weight <SEP> weight <SEP> (kg/cm2) <tb> 25 <SEP> 0.0002 <SEP> 3.0 <SEP> 7.0 <SEP> 320.0 <SEP> 40.2 <SEP> 8.2 <tb> 26 <SEP> 0.0006 <SEP> 3.0 <SEP> 7.0 <SEP> 321.0 <SEP> 41.0 <SEP> 8.0 <tb> 27 <SEP> 0.001 <SEP> 3.0 <SEP> 7.0 <SEP> 314.0 <SEP> 38.0 <SEP> 8.1 <tb> 28 <SEP> 0.003 <SEP> 3.0 <SEP> 7.0 <SEP> 31.0 <SEP> 37.0 <SEP> 8.2 <tb> 29 <SEP> 0.006 <SEP> 3.0 <SEP> 7.0 <SEP> 318.0 <SEP> 38.6 <SEP> 7.9 <tb> <SEP> 30 <SEP> 0.01 <SEP> 3.0 <SEP> 7.0 <SEP> 316.0 <SEP> 39.6 <SEP> 7.9 <tb> <SEP> 31 <SEP> 0.03 <SEP> 3.0 <SEP> , <SEP> 7.0 <SEP> 314.0 <SEP> 39.2 <SEP> 8.3 <tb> <SEP> 32 <SEP> 0.06 <SEP> 3.0 <SEP> 7.0 <SEP> 312.0 <SEP> 41.0 <SEP> 8.2 <tb> Glass <tb> <SEP> fiber <tb> 2.3 <tb> <SEP> 33 <SEP> 0.0008 <SEP> Polyvinyl <SEP> 7.0 <SEP> 310.0 <SEP> 42.2 <SEP> 9.8 <tb> <SEP> alochol <tb> <SEP> fiber <tb> <SEP> 0.15 <tb> <SEP> 34 <SEP> 0.0006 <SEP> ditto <SEP> . <SEP> 7.0 <SEP> .308.0 <SEP> 40.2 <SEP> 9.3 <tb> <SEP> 35 <SEP> 0.001 <SEP> ditto <SEP> 7.0 <SEP> , <SEP> 311.0 <SEP> 41.8 <SEP> 9.6 <tb> 36 <SEP> 0.003 <SEP> ditto <SEP> 7.0 <SEP> 312.0 <SEP> 42.4 <SEP> 9.4 <tb> 37 <SEP> 0.006 <SEP> ditto <SEP> 7.0 <SEP> 312.0 <SEP> 41.4 <SEP> 8.9 <tb> 38 <SEP> 0.01 <SEP> ditto <SEP> 7.0 <SEP> 308.0 <SEP> 48.0 <SEP> 9.2 <tb> <SEP> 39 <SEP> 0.03 <SEP> ditto <SEP> 7.0 <SEP> 307.0 <SEP> 41.8 <SEP> 9.5 <tb> 40 <SEP> 0.06 <SEP> ditto <SEP> 7.0 <SEP> 307.0 <SEP> 41.1 <SEP> 9.4 <tb> The above-listed experiments showed evident results that the glass-fiber-reinforced cement panels manufactured by the process of this invention all had higher mechanical strengths, as compared with the controls containing no pulp, and that the improvement in the dispersion of glass fiber realized by the addition of pulp and flocculant was remarkable.

Claims: CLAIMS: 1. A process for manufacturing a fiber-reinforced cement panel by way of sheet-making with a cement slurry comprising the step of forming a slurry consisting of 0.5 - 3.0 ,0 by weight of glass fiber1 with pulp added in an amount 2 - 2.5 times the amount of the aforementioned glass fiber, balance cement, the step of adding, to this cement slurry, 0.005 0.60/-ó by weight of a cement flocculant, based on cement, and the step of sheet-making with the flocculant-added cement slurry above-mentioned. 2. The process for manufacturing a fiDer-reinforced cement panel1 as specified in Claim 1, wherein the addition of the cement flocculant is made in the midway as the slurry, after being stirred, is fed from the chest to the bats. 3, The process for manufacturing a fiber-reinforced cement panel, as specified in Claim 2, wherein the flocculant is polyacrylamide. 4. The process for manufacturing a fiber-reinfcrced-cement panel by way of sheet-making with a cement slurry comprising the step of forming a cement slurry devoid of asbestos fiber prepared by adding, to cement, a total amount of 0.5 - 3.0 O by weight of glass fiber and polyvinyl aocohol fiber, and pulp in an amount 2 - 2.5 times the total amount of the aforementioned glass fiber and polyvinyl alcohol fiber, the step of adding, to the cement slurry, 0.005 - o.600 by weight of a cement flocculant based on the amount of cement, and the step of sheet-making with the aforementioned flocculant-added cement slurry. 5 The process for manufacturing a fiber-reinforced cement panel1 as specified in Claim 4, wherein the amount of polyvinyl alcohol fiber is less than 1/3 times the amount of glass fiber. 6. The process for manufacturing a fiber-reinforced cement panel, as specified in Claim 11, wherein the glass fiber is produced by chopping the strand formed by collecting and setting monofilaments by the aid of a water soluble collector-setter, the chopped strand having a length of 3 19 mm. 7. The process for manufacturing a fiber-reinforced cement panel, as specified in 1 or ll, ruhcrcin the addition of the flocculant is made in the midway as the cement slurry, after being stirred in the pulper, is being fed from the chest to the bats. 8. The process for manufacturing a fiber-reinforced cement panel wherein the flocculant is polyacrylamide. 9. The process for manufacturin@ a fiber-r@infprc@d c@ment panel wherein for the polyacrylamide, a Na substituted polyacrylamide having a molecular weight of 3 - 13 million and represented by the undermentioned formula is employed; EMI18.1 where m and n are integers, holding a relation of mm+n = 0.03 0.2. 10. A fiber-reinforced cement panel formed by sheet-making with a material slurry consisting of 0.5 - 3.0% by weight of glass fiber, and pulp in an amount 2 - 2.5 times the amount of glass fiber1 balance cement1 with 0.005 - 0.6% by weight of a cement flocculant based on the amount of cement added. 11. A fiber-reinforced cement panel formed by way of sheetmaking with a material slurry consisting of 0.5 - 3.0 S by weight of glass fiber and polyvinyl alcohol fiber, and pulp in an amount 2 - 2.5 times the total amount of the aforementioned glass fiber and polyvinyl alcohol fiber, balance cement, with 0.005 - 0.5% by weight of a cement flocculant based on the amount of cement added.

Inventors: INUI, NOBUO, TERAMOTO, HIROSHI
Applicants: KUBOTA LTD.
Application year: 1980
Main classification: C04B31
IPC codes: C04B28, C04B24