JPH0587460B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to cement moldings reinforced with trunk-branch shaped chopped filament type polypropylene (PP) film fibers, in particular 20 mm thick manufactured by papermaking, extrusion or cast molding methods. The present invention relates to the following cement molded products. [Conventional technology] PP fibers are often used as reinforcing fibers for cement moldings that are thinner than before, for example, 20 mm or less, but the PP fibers that have been used so far have circular or round cross sections. It is a fiber with a smooth surface and usually has an aspect ratio of 300 or more (see Japanese Patent Application Laid-Open No. 129861/1983). Since such fibers have a smooth surface, they easily slip off during the formation of a cement molding, and because of their large aspect ratio, it is very difficult to uniformly disperse them in a cement matrix. Fibrillate axially stretched PP films as an alternative to traditional PP fibers.
However, chopped filament type PP film fibers with trunk and branch shapes in which the trunk fibers are cut to appropriate lengths have been reported (see British Patent No. 1130612).
Furthermore, chopped filament type PP film fibers made by subjecting the surface of the above PP film to a corona discharge treatment and further applying a surfactant have been reported (U.S. Pat. Nos. 4,261,754 and 4,261,754).
(See No. 4310475). However, the film fibers described in the above British Patent No. 1130612 do not have sufficient adhesion to the cement matrix, and the film fibers described in U.S. Patent Nos. 4,261,754 and 4,310,475 do not have sufficient adhesion to the cement matrix. Although it has been improved,
All of the film fibers described in these documents have a main fiber fineness of 2 to 35 dtex (1.8 to 31.5 denier) and an aspect ratio of 300 or more. A major feature of such film fibers is the presence of split ends on the sides, and these split ends are highly effective as reinforcing fibers.
Film fibers with such a shape have a fineness of 2 to 2.
35dtex, its aspect ratio is over 300, so it is not easy to uniformly disperse it in the cement matrix, and there are problems with its dispersibility. Without this, it is difficult to fully utilize the features of the film fibers mentioned above. That is, the strengths of cement molded products made using film fibers having such fineness and aspect ratio vary widely, and it is difficult to obtain cement molded products with uniform strength, especially in the case of thin cement molded products. [Problems to be Solved by the Invention] The reinforcing effect of fibers on cement molded articles generally depends on the physical and chemical properties of the fibers themselves (e.g., strength and elongation, elastic modulus, adhesion to cement matrix, and durability). It is known that the fiber content depends greatly on the volume fraction of fibers in the total volume of the cement matrix. However, even the same volume fraction is highly dependent on the uniformity of the fiber dispersion in the cement matrix and on the total surface area of the dispersed fibers. Therefore, in order to strengthen the fiber by increasing the total surface area of the fiber at the same volume fraction, it is generally accepted to increase the aspect ratio of the fiber used.
Over 300 fibers are used. However, the higher the asbestos ratio, the more easily the fibers become entangled, and the easier it is to form lumps or fiber balls during the mixing process with the cement matrix, resulting in uneven dispersion in the cement matrix. Therefore, even if the volume fraction is sufficient, a sufficient strengthening effect on the cement molded product cannot be obtained, and furthermore, there has been a problem that variations in the various strengths of the cement molded product become large. Particularly in thin cement moldings, the formation and presence of fiber balls deteriorates the strength of the cement molding. The purpose of the present invention is to improve the shape, especially the fineness and aspect ratio, of chopped filament type PP film fibers in the trunk and branch shape when reinforcing thin cement moldings with a thickness of 20 mm or less, for example, with film fibers. By controlling the amount within an appropriate range, the above-mentioned dispersibility can be improved and the strength of the cement molded product can be improved. [Means for Solving the Problems] The present invention uses a chopped filament type reinforcing fiber having a trunk and branch shape, which has the following shape characteristics: Average fineness of trunk fiber: 40 to 60 denier Aspect ratio of trunk fiber: 40 to 200 It is a cement molded product made by mixing 0.3 to 5.0% by volume of PP film fibers with cement. In producing the trunk-branch shaped chopped filament type PP film fiber used in the present invention, a PP film is produced by a known method, and the film is highly hot stretched in the axial direction to achieve a thickness of twenty five~
It can be made by taking a 35μ film, tearing it through a porcupine roller, and then cutting. Methods for producing such fibers are themselves described in the UK and US patents mentioned above. According to the present invention, the highly stretched film for making the trunk-branch shaped chopped filament type PP film fiber has the following properties: Cutting strength: 50 Kg/mm2 ^or more Cutting elongation: 8% or less Elastic modulus : It is recommended to use a film with characteristics of 1200Kg/mm ² or more. In the first place, when a load is applied to a cement molded product, the stress is transmitted to the reinforcing fibers through the cement matrix.At this time, if the cutting strength of the PP film fibers is less than 50 kg/ ^mm2 , the cement molded product, especially This is not preferable because the cement molded product may break before it reaches the strength required for a thin cement molded product. Furthermore, even if the cutting strength of the PP film fiber is 50Kg/mm2 or ^more , if the cutting elongation exceeds 8%, the PP film fiber itself will elongate significantly even without cutting, so a low load below the product strength will be applied. This is undesirable because cracks may occur, which may actually lead to the destruction of the cement molded product. Furthermore, even if the cutting strength is 50 Kg/mm ² or more and the cutting elongation is 8% or less, unless the elastic modulus is 1200 Kg/mm ² or more, cracking at the initial stage of loading will not be sufficiently prevented and the breaking strength of the molded product will not improve. According to the present invention, a PP film having the above-mentioned properties and having a thickness of 25 to 35μ is then passed through a porcupine roller to split, split, and cut to obtain an average fineness of main fibers of 40 to 60. Denier Trunk fiber aspect ratio: 40-200 Trunk-branch chopped filament type PP
Make it into film fiber. The length of the above-mentioned PP filament fibers can be set to the most suitable length for the purpose.
9 mm, preferably about 6 mm, usually 3 to 3 mm for extrusion molding
15mm, preferably 9-12mm, 6-18 for cast molding
mm, preferably 12-15 mm are used. For this reason, also in the present invention, it is preferable to use the PP filament fiber whose main fiber length is 3 to 18 mm. Next, regarding the average fineness and aspect ratio of the main fibers, if the fibers have good dispersibility, generally the larger the aspect ratio, the higher the reinforcing performance. However, in reality, the larger the aspect ratio, the worse the dispersibility, and as a result, the desired strength of a cement molded product made using it may not be obtained. For this reason, if the fineness is smaller than 40 denier and the aspect ratio exceeds 200, the fiber length will exceed 20mm and it will not be possible to obtain uniform dispersion through normal mixing. As it becomes smaller, the dispersion improves, but the reinforcing performance of the PP film fiber becomes inferior. Further, when the fineness is greater than 60 denier and the aspect ratio is less than 40, the fiber length becomes 2 mm or less, making it impossible to obtain substantial reinforcing performance. Therefore, in the present invention, the preferable ranges are a fineness of 40 to 60 deniers and an aspect ratio of 40 to 200 in view of the fiber length. According to the present invention, the above-mentioned chopped filament type PP film fibers having a trunk and branch shape are mixed with a cement matrix in the usual manner to form a cement molded product. At this time, the above PP film fiber is 0.3% of the total amount with the cement matrix.
Blend so that the amount is ~5.0% by volume. The compounding method can be carried out by a well-known method. If the above-mentioned blending ratio is less than 0.3% by volume, no substantial reinforcing effect can be obtained, and if it is more than 5.0% by volume, dispersion becomes extremely difficult and the mixing time becomes long, which is not practical. Further, the completed cement molded product becomes porous, which may reduce the bending strength or dimensional stability of the cement molded product, which is undesirable. The PP film fiber used in the present invention is
It is preferable to subject the film before the above-mentioned splitting and fibrillation to a corona discharge treatment according to a conventional method, since this improves the adhesion with the cement matrix. Also
It is preferable to treat the PP film fibers with a surfactant, such as an anionic surfactant such as polyethylene glycol alkyl ester, after forming the PP film fibers, since this improves the dispersibility of the PP film fibers into the cement matrix. According to the present invention, a paper molding method, an extrusion molding method or a casting molding method can be used to produce a cement molding from the above-described mixture of PP film fibers and cement matrix. In addition to the above-mentioned PP film fibers, additives commonly used in the production of cement moldings, such as cellulose fibers such as pulp, methyl cellulose, and sulfurizing agents such as Mighty M-150 (Kao product) may be added. [Function] When the trunk-branch shaped chopped filament type PP film fibers according to the present invention described above are used in a thin cement molding having a thickness of usually 20 mm or less, the PP film fibers are is very easily and uniformly dispersed in the cement matrix in a short period of time. Also, during the mixing process, the PP filament fibers are re-cleaved and the surface area increases. This makes it possible to obtain cement molded products with extremely excellent strength properties. [Example] The present invention will be described below with reference to Examples. Manufacture of chopped filament type PP film fiber with trunk and branch shape for test purposes: General grade PP resin (MI: 3.0) is passed through a ring die of a normal extruder at a temperature of approximately
It was extruded by the inflation method at 220°C and a blow ratio of 1:1, then air cooled, passed through a hot air oven at 180°C, uniaxially stretched 20 times, and then annealed through a hot air oven at 160°C to a thickness of 30 μm.
I made a film of. Next, the surface of the above film was subjected to corona discharge treatment at a high voltage of 12KW, and the needle density was 170.
film/cm ² , and the surface speed is 3 times, 5 times, and 7 times the film speed.The final polyoxyethylene glycol After applying an ester surfactant, the fibers were cut into PP film fibers with trunk fiber lengths of 9 mm, 12 mm, and 15 mm, respectively. The fineness and aspect ratio of each of the PP film fibers thus produced are shown in the table for each example. Incidentally, as the surface speed of the porcupine roller and the number of passes (number of steps) increase, the degree of cleavage becomes finer. Example 1 and Comparative Examples 1 to 3 This Example and Comparative Examples were carried out by a paper forming method. The materials used are shown below.

[Table] Using an experimental pulper with a capacity of approximately 500, which is exactly the same type as the disintegrating machine (pulper) used in normal papermaking and forming methods, under the conditions of rotor/stator: 0.8 mm, rotor rotation speed: 600 rpm. First, 450 kg of water was put into a pulper, 2.7 kg of reinforcing fiber was mixed therein, and the mixture was stirred for 8 minutes. Then, 5.4Kg of asbestos and 1.4Kg of pulp were mixed and continued to be stirred for 7 minutes. lastly
114.7 kg of cement and 10.8 kg of microsilica were added and stirred for an additional 5 minutes. The slurry made in this way was processed into an experimental paper making machine that is exactly the same as the Hachietsu-type paper machine that is normally used, to a thickness of 6 mm and a width of 72 mm.
cm, and the length was 182 cm (flat plate).
At this time, the volume fraction of the reinforcing film fibers to the volume of the molded product was 2%. During this papermaking process,
Slurry was circulated between the pulper and the papermaking tank. After the molded product was naturally cured for 28 days, it was subjected to physical property tests. Table 1 shows the test results for the cement molded product.
In Table 1, Comparative Example 3 used spun general PP fibers with a fiber length of 6 cm.

[Table] Example 2 and Comparative Examples 4 to 6 This example and comparative examples were carried out by extrusion molding. The materials used are shown below.

[Table] Using an experimental omnimixer (manufactured by Chiyoda Giken Kogyo Co., Ltd.) with a capacity of about 30, 15 kg of cement, 4.5 kg of micro silica, 4.5 kg of water, and 0.3 kg of Mighty 150 were first added and kneaded at 300 rpm for 1 minute. then pulp
0.21Kg was added and kneaded for 1 minute. Next, 0.27 kg of reinforcing fiber was added and kneaded for 5 minutes, and the final silica sand #8 was added and kneaded for 2 minutes to form a mortar. Next, the mortar was put into an experimental extruder (manufactured by Miyazaki Iron Works), which is the same type as a commonly used extruder, and was further rolled into a plate shape (flat plate) with a thickness of 10 mm and a width of 316 mm. It was cut into 316mm pieces and left indoors for 24 hours to harden. At this time, the volume fraction of the reinforcing film fibers to the volume of the molded product was 2%. The plates thus formed were naturally cured for 28 days and then subjected to physical property tests. Table 2 shows the test results for the cement molded product.
In Comparative Example 6 in Table 2, spun general PP fibers with a length of 9 cm were used.

[Table] Example 3 and Comparative Examples 7 to 9 This Example and Comparative Examples were made by the casting method. The materials used are shown below.

[Table] Using an experimental omnimixer with a capacity of about 30, first mix 15 kg of cement, 9 kg of silica sand #6, and Mighty.
150 0.15 kg and 6 kg of water were added and kneaded at 300 rpm for 3 minutes and 30 seconds. Next, 0.27 kg of reinforcing fiber was added and kneaded for another 1 minute and 30 seconds. Next, pour the mortar into a 10mm deep, 316mm vertically, 316mm horizontally, and use a vibrator (manufactured by Hayashi Vibrator) to approx.
After vibration molding was performed by applying vibrations of 3000 times/min, the material was left indoors for 24 hours to harden. At this time, the volume fraction of the reinforcing film fibers to the volume of the molded product was 2%.
It was hot. After that, the plate was removed from the mold and left to naturally cure for 28 days.
It was subjected to physical property tests. Table 3 shows the test results for the cement molded product.
Comparative Example 9 is a spun general PP fiber with a length of 12
mm was used.

〔Effect of the invention〕

As is clear from the data of the above Examples and Comparative Examples, the cement molded product according to the present invention has a small number of fiber balls and is excellent in bending strength and impact strength.

Claims (1)

[Scope of Claims] 1. As reinforcing fibers, chopped filament type polypropylene film fibers in a trunk/branch shape having the following shape characteristics: Average fineness of trunk fibers: 40 to 60 denier Aspect ratio of trunk fibers: 40 to 200 0.3 ~5.0 volume%
A cement molded product characterized by being mixed into a cement matrix and molded. 2. The cement molded article according to claim 1, wherein the length of the main fiber of the polypropylene film fiber is 3 to 18 mm. 3 Thickness of polypropylene film fiber is 25~
The cement molded article according to claim 1, which has a diameter of 35μ. 4 Polypropylene film fibers are axially stretched, corona discharge treated and surfactant treated and have the following properties: Cutting strength: 50 Kg/mm ² or more Cutting elongation: 8% or less Elastic modulus: 1200 Kg/mm ² or more A cement molded article according to claim 1, 2 or 3 made from a film. 5. The cement molded product according to any one of claims 1 to 4, wherein the cement molded product has a thickness of 20 mm or less.