JPS6244066B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to polyvinyl alcohol synthetic fibers with roughened surfaces (hereinafter abbreviated as PVA fibers) and a method for producing the same. The fibers of the present invention can be used in various fields by taking advantage of their surface properties, but are particularly useful as fibers for reinforcing and filling inorganic or organic molding materials such as cement, plaster, synthetic resins, and asphalt. Therefore, the present invention will be explained below using fibers for reinforcing cement materials as an example. As is well known, cement molded products have poor bending strength, tensile strength, impact strength, etc., so in order to effectively utilize these cement products, they are reinforced with fibers or the like. Asbestos is a typical reinforcing material for fibers, etc., but in recent years, inorganic reinforcing materials such as steel fiber and glass fiber, and reinforcing materials of organic synthetic fibers such as polypropylene, polyamide, and polyvinyl alcohol have been used alone or in combination. It is often used. Regarding fiber-reinforced cement materials that use PVA fibers as a reinforcing material, methods for manufacturing fiber-reinforced cement boards using a wet papermaking method using a combination of high-strength PVA fibers and asbestos or a combination of PVA fibers and glass fibers have been published. According to the research conducted by the present inventors, it has not been observed that the adhesion between the reinforcing fibers and the matrix is sufficiently high in the known technology.
Therefore, it is considered that the performance of the reinforcing fibers is not fully exhibited. The interfacial bonding force of fibers to the matrix is an extremely important factor in the performance of cement molded products, and various chemical and physical methods have been published. As a chemical method, it is known to use synthetic fiber as a reinforcing material by attaching a substance that is reactive with cement, such as colloidal silica or alumina, to the fiber surface. It does not adhere well to the fiber surface, and the adhered material falls off frequently, making it practically ineffective in adhering to the cement material. It is also known that melt-spun fibers with cement components kneaded into the fibers are used as reinforcing materials to increase the chemical bond with cement. The reinforcing effect is not practically satisfactory. In particular, in such known examples, melt-spun polyamide-based or polyolefin-based fibers are targeted as the fibers used, and since these synthetic fibers are hydrophobic, the fiber itself has poor adhesion to cement and chemical properties. Physical connectivity cannot be expected. In addition, physical methods include creating pulsations in the discharge amount of the stock solution during the spinning stage, applying an external force such as ultrasonic waves during coagulation to give irregularities in fineness, and making both ends of the fiber spherical or irregular in cross-section. Methods that attempt to impart an anchoring effect are known, but these methods are impractical in actual operation, and the degree of deformation of the fibers itself is too large, so that in practice, the reinforcement material and cement material due to deformation are The adhesive effect is not exhibited. The present invention provides reinforcing fibers for cement materials.
Even without using PVA fibers with high strength and high Young's modulus as shown in the above-mentioned known technology, it is possible to exhibit excellent performance as a final cement molded product, that is, it has excellent adhesion with the cement matrix. The present invention provides a high-quality PVA fiber and a method for producing the same. That is, the present invention has a single particle diameter of 10 microns (hereinafter referred to as μ
A PVA fiber containing a particulate solid material obtained by mixing and spinning the following particulate solid material that is insoluble or poorly soluble in water, and the fiber has a surface on which the particulate solid material has been removed. This is a PVA fiber with a roughened surface and many crack-like depressions extending in the direction of the fiber axis. Similar to conventionally known PVA fibers, such surface-roughened PVA fibers can be obtained by a dry spinning method, a dry spinning method, or after a film manufacturing method, but the above two methods are common. The PVA concentration as a spinning stock solution is 8 to 20 in the case of wet spinning.
%, or 25-60% PVA aqueous solution for wet spinning. The particulate solid substance to be added to this aqueous solution must be insoluble or poorly soluble in water with a single particle size of 10μ or less, can be uniformly suspended in the PVA aqueous solution, and is preferably acid-free depending on the spinning method. Alternatively, a substance that is soluble in alkali or that is converted into a soluble substance during the PVA fiber manufacturing process is used. Such solid substances that can be added as a stock solution can be selected from the following: That is, as silicates, clay (kaolin,
hydrated aluminum silicate such as kaolin clay, hard clay clay), calcined clay (aluminum silicate), talc (magnesium talc silicate), Canada mica (potassium magnesium silicate), mica (muscovite, potassium aluminum silicate) Asbestos powder (asbestos powder, hydrated calcium magnesium silicate), wollastonite (wollastonite, calcium metasilicate), vermiculite (Mg.
Fe/Al complex silicate), calcium silicate (calcium silicate, calcium orthosilicate), feldspar powder (composite silicate), acid clay (aluminum silicate), waxite clay (pyrofluorite, silicate) aluminum), sericite (sericite K, Mg,
Al composite silicate), sillimanite (siliconite, aluminum silicate), bentonite (composite silicate), glass flake (E glass, Ca/Al borosilicate), glass powder (A glass, soda lime glass), There are glass beads, slate powder (slate), shirasu (volcanic ash, mineral powder, composite silicate), etc. Carbonates include dry and wet whiting, charcoal, and charcoal.
Precipitated charcoal calc, light charcoal calc called light calc, micro-ultrafine charcoal calc, surface-treated extra-fine charcoal calc, light charcoal calc, heavy charcoal calc called heavy calc, gofun (oyster shell powder), precipitated barium carbonate (carbonic acid) Barium), magnesium carbonate (charcoal mag, hydrous basic magnesium carbonate), dolomite (dolomite, dolomite, composite carbonate), etc. are used. Suitable sulfates include barite powder, branfix (barium sulfate), precipitated calcium sulfate, calcined plaster, and flue gas desulfurization plaster. In addition, slaked lime (calcium hydroxide), magnesium hydroxide, aluminum hydroxide (hydrated alumina), etc. can be used as the hydroxide. Oxides include alumina (aluminum oxide), magnesia (magnesium oxide), copper oxide,
Amorphous silica (fine silicic acid), flint quartz, silica sand, white carbon (hydrated silicic acid),
Diatomaceous earth etc. can be used. Other sulfides include molybdenum sulfide, simple carbon black, graphite, fly ash, sulfur powder, and wood powders such as cellulosin, coconut shell powder,
Walnut shell powder, pulp powder, etc. can be used. These particulate solid substances are 0.5 to PVA
Add 50% by weight, preferably 10% by weight or more.
Uniformly suspend in PVA aqueous solution. At this time, if the particle size exceeds 10 μm, overclogging or nozzle clogging occurs during spinning, and yarn breakage occurs during drawing, which tends to cause operational problems. On the other hand, if the particles are on the order of mμ, they will have almost no effect on the spinning or drawing conditions, but if the particles are extremely small and have a high degree of uniformity of dispersion, such as being dispersed almost in the form of single particles without agglomeration. It is thought that the unevenness of the surface of the PVA fiber obtained becomes small and the degree of roughening becomes minute, and in such a case, the reinforcing effect is not expected to improve much. Therefore, the particulate solid substance used preferably has a single particle diameter of about 5 to 0.1 μm, more preferably about 3 to 0.3 μm. However, even if the particles are on the order of mμ, if the fine particles agglomerate and become particles of about 0.1 to 0.5μ after spinning, the roughening of the fiber surface, which is the object of the present invention, can be achieved. If the particulate solid substance is less than 0.5% by weight based on PVA, the desired roughening of the fiber surface cannot be achieved, and if it exceeds 50% by weight, excessive inhibition of the spinning dope, nozzle clogging, and spinnability may occur. It is difficult to add more than this because it may lead to poor quality or yarn breakage during stretching. Overall, addition is preferably from 10 to 50% by weight, more preferably from 10 to 30% by weight. A spinning dope is prepared under these restrictive conditions, and in the case of dry spinning, the spinning solution is stretched and heated after drying.
After treatment with caustic soda or sulfuric acid aqueous solution, it is washed with water and, if necessary, treated with an oil agent to be used as a reinforcing fiber material for cement molded products. In the dry spinning method, it is actually extremely difficult to discharge the spinning dope from the nozzle and then treat the undried filament with acid, alkali, etc. Therefore, after the dry hot stretching heat treatment is completed, It is preferable to carry out acid or alkali treatment. The wet spinning method involves (1) spinning a PVA aqueous solution into a coagulation bath consisting of a concentrated salt aqueous solution; (2)
There are methods such as spinning a PVA aqueous solution into a coagulation bath consisting of a concentrated alkaline aqueous solution, or (3) adding boric acid to the PVA solution and spinning the yarn into a coagulation bath consisting of an alkaline salt aqueous solution. The particulate solid material may be selected in consideration of the method, so that there is no turbulence in the stock solution and the spinning process.
Any spinning method can be used. Typical examples of each spinning method and solid substances added include (1) and calcium carbonate, calcium silicate, (2) and (3) and magnesium sulfate, aluminum chloride, zinc chloride, colloidal silica, and alumina sol. etc. Manufacturing method (1) is the most popular wet spinning method for PVA and can be produced at low cost.On the other hand, calcium carbonate, calcium silicate, etc. are also extremely inexpensive, and their combination is
This is a great advantage as a method for producing PVA fibers. In the case of this spinning method, the spinning stock solution is spun into a sodium sulfate bath and solidified, followed by wet stretching, drying, hot stretching, and acetalization treatment to obtain fibers, but the fiber surface is roughened with acid or alkali. is preferably carried out after hot stretching. It goes without saying that the roughening treatment is carried out in the acid or alkali bath used only for that purpose, and when the fibers are acetalized, sulfuric acid is added to the acetalization bath as an acetalization aid. Therefore, it is convenient to perform acetalization and acid treatment simultaneously in the acetalization bath. If the stretching ratio of the PVA fiber is less than 6 times, the fiber itself will have poor hot water resistance, and the subsequent surface roughening treatment will not easily generate surface cracks, so it is necessary to stretch the fiber to 6 times or more. . As the treatment agent for the fibers, a mineral acid such as sulfuric acid, hydrochloric acid, nitric acid, or an alkali such as caustic soda or caustic potash is appropriately selected in consideration of the particulate solid substance to be added, the spinning method, etc. Furthermore, in the treatment with the treatment agent, it is important to coexist with a coagulant such as Glauber's Salt or methanol in order to suppress swelling and dissolution of the PVA fibers.
An example of the processing conditions is shown below. For acids: Sulfuric acid: Concentration 100-400g/Hydrochloric acid: 5-100g/In case of alkali: Caustic soda: 5-300g/Granite: Concentration: 100-420g/Temperature: Room temperature - 90℃ Time: 1-60 As shown in the electron micrographs of the fibers in the examples described below, the surface of the PVA fiber obtained by the above manufacturing method has a width ranging from fine crack-like depressions of about 30 to 40 mμ to as large as 9 to 10 μm. The length, including the large crack-like depression, is 5 to 11 mm wide.
This results in a rough surface with many relatively large crack-like depressions extending in the fiber axis direction. As understood from the above explanation, the present invention
By adding a particulate solid substance to the PVA stock solution and mixing and spinning the fibers, the fibers obtained are later treated with a solvent that can remove the particulate solid substances, so that relatively large particles caused by the particulate solid substances are formed on the PVA fiber surface. A large number of cracks are formed, and the surface roughening structure created by the cracks enhances the adhesion effect between the fibers and the cement material. Of course, in the present invention, the particulate solid substance has an affinity for substances such as calcium carbonate and calcium silicate, which react with sulfuric acid to form calcium sulfate (i.e., sulfuric acid) in subsequent acid treatment, that is, cement. If a substance is used, the effect of adhesion of the fibers to the cement is further enhanced by the presence of the substance in the fiber cracks or even partially on the surface of the fibers. When the fibers obtained in this way were embedded in cement and a pullout test was performed, the resistance to pullout from the cement was significantly improved beyond expectations, and the bending strength of molded products made by dispersing the fibers in cement was significantly improved. will be further improved. Although there are many aspects of the hardening mechanism of cement or the mechanism of interfacial bonding force generation with reinforcing materials that are still not fully understood, in the case of the present invention, as mentioned above, by shedding or removal of additive substances or reaction products from fibers, It is thought that the fiber surface is roughened and the cement matrix binds to this surface with a kind of anchoring effect, resulting in a remarkable improvement in the interfacial bonding force. Surprisingly, this is much better than the previously mentioned known examples which aim at chemical or physical adhesion effects. The PVA fibers of the present invention can of course be used alone in cement base materials, but they can also be used in combination with inorganic fibers such as asbestos, glass, and metal fibers to impart heat resistance and fire retardant properties. It is possible, and by mixing and combining fibrillar fibers such as pulp with the fibers, the dispersibility of the fibers can be improved.
Improved performance of cement molded products. The range of application is that it can be applied to all or local parts of cement-containing molded products or structures that require bending strength, and can also be used in combination with reinforcing bars and steel frames to prevent local cracks. Naturally, it is effective, and since the fibers have appropriate elongation, the effect of improving impact resistance is also remarkable. The fiber of the present invention has a roughened fiber surface by forming a large number of crack-like recesses on the fiber surface, thereby significantly increasing the surface area. It goes without saying that it may be a composite fiber with a bellows structure, or it may be a modified fiber with a modified cross section. Furthermore, since the surface area of the fibers is significantly increased, they can be used, for example, as air and/or oil filters or absorbent materials, as aquaculture materials such as glue nets, and as rubber fillers. The present invention will be further explained below with reference to Examples. Example 1 Degree of polymerization 1680, degree of saponification 99.9 mol%, PVA concentration
12.92%, calcium carbonate concentration 2.58%, i.e. PVA
A mixed aqueous solution with a total solid content of 15.5% was used as the spinning stock solution. As the calcium carbonate, Whiten P30 manufactured by Toyo Fine Chemical Co., Ltd. was wet-pulverized using an atritor manufactured by Mitsui Miike Manufacturing Co., Ltd. to obtain an average particle size of 1.8 μm. This stock solution
It was spun into a saturated sulfate solution through a nozzle with a hole diameter of 0.09 mm, solidified, further stretched 3 times in a wet state, dried, and further subjected to hot stretching and heat treatment, with a total stretching ratio of 7.4 times and a 3.4 denier material. Charcoal-containing PVA
Obtained fiber. This fiber has a glauber's salt concentration of 130g/and a sulfuric acid concentration of 280g/
The sample was immersed in a mixed solution of 300 g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g of for 30 minutes at 70°C under tension. When immersed in this liquid, carbon dioxide gas was generated, indicating that calcium carbonate was reacting. Furthermore, to remove sulfuric acid and Glauber's salt, 2g/
It was neutralized by passing it through a caustic soda solution, washed with water, dried, and rolled up. The surface condition of this fiber is shown in an electron micrograph (2400x magnification). In this example, the fiber surface has a width of 30 m.
There are many crack-like recesses extending in the fiber axis direction with a width of μ to 1 μ and a length of 5 to 11 times the width, as well as fine crack-like recesses with a width of about 30 mμ to 40 mμ to large crack-like recesses of about 4 μ. It has a roughened surface that is not seen in regular PVA fibers. Example 2 and Comparative Example 1 The fibers obtained in Example 1 and a stock solution without the addition of calcium carbonate were prepared for comparison, and the fibers were produced under exactly the same conditions as in the example, and treated with the same sodium sulfate and sulfuric acid bath. Table 1 shows the physical properties of both fibers and comparison fibers treated with . It should be noted that the surface of the comparison fiber was not roughened like that of normal PVA fiber.

[Table] Both of the above fibers were embedded in cement using Portland cement with a water-cement ratio of 0.5, and the temperature was 25°C.
After curing in the air for 24 hours, the embedded fibers were pulled out.
The length of pullout from the cement was measured. This is shown in Table-2. Furthermore, both of the above fibers are each 6mm
Using chrysotile asbestos 5R, the remaining part was made into Portland cement, the mixing weight ratio was 2:5:93, and a cement laminate was formed using the papermaking method. It was cured in air at 25℃ for 14 days, and its bending strength was evaluated. Measured and displayed the results along with observation under an electron microscope.
Shown in 2.

[Table] From Table 2, it can be understood that the pulling length from the cement is shorter in the case of the example than in the case of the comparative example, and the amount of cement attached to the fibers in the cement board is large. As can be seen, in the case of the examples using the fibers of the present invention, the adhesion effect between the PVA fibers and the cement was excellent, and the values regarding the bending strength were low despite the low strength and Young's modulus of the fibers themselves. As shown in No. 2, it is extremely excellent. Example 3, Comparative Examples 2 and 3 Colloidal silica (Nissan Chemical Snowtex-C particle size 10 to 20 mμ) was added as solid content to PVA with a degree of polymerization of 1730 and a degree of saponification of 99.9 mol%, (1) 1 weight %, (2) 10% by weight, and (3) 30% by weight, and in each case, dry spinning was carried out so that PVA was 42.5% by weight based on the total weight. After drying, these were hot stretched at a magnification of 11 times and subsequently heat treated while giving 2% shrinkage. The spinning gear pump was adjusted so that the fineness after heat treatment was 6 denier in all cases (Test Nos. 1 to 3). On the other hand, fibers were produced under exactly the same conditions as in the example except that colloidal silica was added in an amount of (4) 0% by weight, (5) 0.3% by weight, and (6) 55% by weight. (Test No.
4-6). However, for No. 6, it was not possible to obtain a sample using the above method due to poor spinnability during spinning. 80g/60 of these 5 types of yarn No. 1 to 5
After immersion in caustic soda aqueous solution at ℃ for 2 hours, 5g/
After neutralizing with sulfuric acid, washing with water, and air drying,
The sample was dried at ℃ for 4 hours and its physical properties were measured as an absolutely dry sample. A series of treatments from alkali treatment to drying were all carried out at a fixed length. When each of the obtained fibers was observed under an electron microscope, test No. 1~
There are many large and small crack-like recesses extending in the fiber axis direction on the fiber surface of test No. 3, especially test No. 2.
The coarsening of the fibers of No. 3 and No. 3 was significant. In test Nos. 4 and 5, crack-like depressions as described above were not observed and the surface was smoothed like normal PVA fiber. In Test No. 7, which will be described later, protrusions and crack-like depressions of added particles were also observed, but the surface was not in a rough state as in Tests Nos. 1 to 3. A 5 mm fiber end of the sample was embedded in a single filament in Portland cement slurry with a water/cement ratio of 0.5, and 24 hours later, it was subjected to a pullout test. These results are summarized in Table 3.
In Table 3, Comparative Example 3 is also shown, which was subjected to heat treatment under the same conditions as Test No. 2 of Example, but was not subjected to alkali treatment.

[Table] As seen from Table 3, the addition rate of solid substances is
If it exceeds 50% by weight, it will cause trouble during spinning and it will be difficult to obtain stable yarn, but if it exceeds 50% by weight,
It is shown below that the higher the addition rate, the better the bonding effect between the fibers and the cement matrix. As seen in the fiber modulus value at the time of drawing, Comparative Example 3 shows an improvement in the effect over Comparative Example 2, but it can be seen that the improvement effect in the Examples of the present invention is even more remarkable. Example 4 Degree of polymerization 1720, degree of saponification 99.9 mol%, PVA concentration
A mixed aqueous solution containing 16.2% calcium carbonate and 20% by weight of PVA was used as a spinning dope. The calcium carbonate used was wet-pulverized with an attritor (manufactured by Mitsui Miike Seisakusho) to an average particle size of 3.2 μm. This stock solution is spun into a saturated sulfate solution through a nozzle with a hole diameter of 80μ, solidified, further stretched 3.5 times in a wet state, dried, and heated to a total stretching ratio of 8.75 times to form fibers. Obtained. The fibers were immersed under tension in a mixed aqueous solution of 420 g/g of mirabilite aqueous solution and 80 g/g of hydrochloric acid at 60° C., and calcium carbonate in the filament was extracted as calcium chloride. Carbon dioxide gas is generated in this immersion liquid,
It was observed that calcium carbonate was reacting. It was washed with water to remove the produced calcium chloride, Glauber's salt and hydrochloric acid, and then dried and rolled up. For comparison, a stock solution containing only calcium carbonate was prepared, and fibers were produced under the same conditions as in the example and subjected to the same sodium sulfate hydrochloric acid bath treatment as a comparative example. When the fiber of Example 4 was observed under an electron microscope, it was confirmed that the fiber surface was roughened like the surface of the fiber of Example 1. On the other hand, the surface of the fiber of Comparative Example 5 was the same as that of ordinary PVA fiber. The physical properties of both fibers are shown in Table 5.

[Table] Each of these fibers was embedded in cement using Portland cement with a water-to-cement ratio of 0.5, and after curing in air at 25°C for 24 hours, the embedded fibers were pulled out and the length of the fibers pulled out from the cement was measured. Separately, each of the above fibers was cut into 6 mm pieces, and the remaining part was made into Portland cement using chrysotile asbestos 5R, with a mixing weight ratio of 2:5:93,
Form a cement laminate using the papermaking method and store it in air at 25℃.
After curing for 14 days, the bending strength was measured. These results are shown in Table 6.

[Table] From the results in Table 6, when comparing the pull-out length from cement, Example 4 is much shorter than Comparative Example 5, and the adhesion effect with cement is improved, and the bending strength is also higher than that of the present invention. This shows that the effect of fibers is large.

[Brief explanation of the drawing]

The photo is an electron micrograph showing the surface condition of PVA fiber, which is an example of the fiber of the present invention (magnification: 2400).
times).

Claims (1)

[Scope of Claims] 1. A polyvinyl alcohol-based synthetic fiber obtained by mixing and spinning a particulate solid substance that is insoluble or poorly soluble in water and has a single particle diameter of 10 microns or less,
A polyvinyl alcohol-based synthetic fiber characterized in that the surface of the fiber is roughened by the presence of a large number of crack-like depressions extending in the fiber axis direction from which the particulate solid substance has been removed. 2 In polyvinyl alcohol aqueous solution, the single particle size
Particulate solid substances that are insoluble or poorly soluble in water with a size of 10 microns or less are added to the polyvinyl alcohol.
Add 0.5 to 50% by weight, mix and spin, and stretch using a conventional method. 1. A method for producing polyvinyl alcohol-based synthetic fibers, which comprises performing heat treatment and then elution treatment with at least a particulate solid substance solvent. 3. The method for producing polyvinyl alcohol-based synthetic fibers according to claim 2, wherein the particle diameter of the solid particulate material is 5 to 0.1 microns. 4. The method for producing polyvinyl alcohol-based synthetic fibers according to claim 2, wherein the amount of the particulate solid substance added is 10 to 50% by weight based on the polyvinyl alcohol. 5. The method for producing polyvinyl alcohol-based synthetic fibers according to claim 2, wherein the particulate solid substance is a substance containing a sulfate group, a carbonate group, or a silicate group on one side of the chemical formula. 6. The method for producing a polyvinyl alcohol synthetic fiber according to claim 2, wherein the stretching ratio is 6 times or more. 7. The polyvinyl alcohol system according to claims 2 to 6, wherein the spinning method is a wet spinning method using a high concentration mirabilite coagulation bath, and the solvent treatment is carried out in the same bath as the acetalization bath. Method of manufacturing synthetic fibers. 8. The method for producing polyvinyl alcohol synthetic fibers according to claims 2 to 7, wherein the particulate solid substance is calcium carbonate. 9. The method for producing polyvinyl alcohol synthetic fibers according to claims 2 to 7, wherein the particulate solid substance is calcium silicate.