JPS61167011A - Ultrafine fiber of polyvinyl alcohol and production thereof - Google Patents

Abstract

PURPOSE:PVA is dissolved in aqueous boric acid to prepare an aqueous solution of a specific concentration and the solution is extruded into a coagulation bath under specific conditions, then drawing is effected at a high draw ratio to give flat PVA fibers of fine denier, high strength and high water resistance. CONSTITUTION:PVA of 1,200-3,000 polymerization degree is dissolved in water containing 0.5-5wt% of boric acid or its salt and an acid in such an amount as the solution becomes lower than 5 in pH after dissolution to prepare a polymer solution of 8-14wt%. The solution is used as a spinning dope to extrude the solution through round-nozzles of 0.02-0.04mm diameter into a bath of alkaline high-concentration salt solution with a bath draft ranging from 10 to 60%. Then, drawing is carried out at a ratio over 10 to give the objective fiber of 0.05-0.5 filament denier, higher than 9.0g/d tensile strength, higher than 105 deg.C softening point in water and less than 70% filament circularity.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a flat polyvinyl alcohol fiber that is extremely fine and has excellent strength and water resistance, and a method for producing the same.

B. Prior art and its problems Attempts have been made to produce polyvinyl alcohol (hereinafter abbreviated as PVA)-based ultrafine fibers.

For example, in the method described in Japanese Patent Publication No. 47-31376, fully saponified PVA and low saponified PVA are mixed and spun in a conventional manner, and normal denier fibers are drawn and heat-treated, and then fibers of normal denier are beaten to form ultrafine υ fibrils. The aim is to obtain fibers for use in Since this method uses partially siliconized PVA with large side chains, it is difficult to stretch and crystallization is severely inhibited. Therefore, even before beating, the strength and water resistance are low, but mechanical beating destroys the crystals in which the orientation of molecules and crystals within the amorphous structure is disrupted, so this tendency becomes even more pronounced. It will be encouraged.

Furthermore, Japanese Patent Application Laid-Open No. 54-77720 also discloses a method for producing ultrafine fibers. This is also a method of mixing and spinning high-saponification PVA and low-saponification PVA, and removing the low-saponification PVA by dissolving and removing the resulting normal denier fiber by washing with water.
The aim is to obtain ultrafine fibers of 1/10 to 1/100 of a denier. The difference between the rice grain production method and the former production method is that the method used to make denier into ultra-fine denier is to use the mechanical force of beating to elute low-saponification PVA and fibrillate it, or to significantly swell it by washing with water. However, the physical properties of the fibers, which are low strength and low water resistance, remain the same.

The method described in Japanese Patent Publication No. 58-38526 is also similar, and is characterized by the use of low polymerization degree PVA as the partially saponified PVA, but the resulting fiber properties are the same, low tenacity and low water resistance. . The example of this patent publication exemplifies PVA-based ultrafine fibrils, but it is stated that the shearing rate of normal denier fibers before washing with water is only 3.4 P/dr.

Furthermore, the method described in Japanese Patent Application Laid-Open No. 54-30930,
Although it uses an amorphous water-soluble polymer as a base for low-saponification PVA, it is basically the same. It is a method in which the easily soluble components are eluted and removed by some method from a normal denier PVA fiber made by mixing and spinning a low-crystalline and easily water-soluble polymer, and the fiber is made ultra-fine.
The resulting fibers are expensive because they have low strength and water resistance, require a step of dissolving and removing them, and cause a loss of components to be dissolved and removed.

As described above, PVA-based ultrafine fibers with high strength and high water resistance have not been known until now, but it is no exaggeration to say that the PVA-based fibers, which are flat, are something that could not be imagined. This is because the history of wet-spun PVA fibers has focused on how to improve the circularity and homogenization of cross-sections in order to obtain fibers with high strength and high water resistance. P
The first wet industrial manufacturing method for VA fibers was generally a method in which a conventional PVA aqueous solution was spun in a highly concentrated sodium sulfate bath, and even today, most of the products produced in operation are still produced by this method. The PVA fiber produced by this method has a non-uniform structure having a skin layer with a cross-sectional solidity of about 50 cm and a single core layer, and its strength is about 3 P/dr at the highest, usually 5 to 72 P/dr. It is.

The first attempt to obtain high strength by making such a flat, non-uniform cross section nearly circular was to make the coagulation bath a concentrated alkali (Journal of the Japan Institute of Textile Technology, Vol. 18, 1960, p. 183).

According to this method, the cross-sectional fullness exceeds 70 inches and the skin,
It is possible to obtain a uniform structure without a core and a strength of 10 f/dr or more by increasing the stretching ratio.

Furthermore, a method was invented in which a PVA stock solution containing boric acid was spun into an alkaline coagulation bath (Japanese Patent Publication No. 47-6).
No. 1685, No. 46-11456), the cross-sectional solidity is 7
0% or more, and the strength was improved to 11 f/dr or more. Various other methods have been disclosed, but all of them either involve increasing the cross-sectional solidity of the fibers as a means of obtaining high strength and water resistance, or are methods used to obtain high strength PVA fibers. As a result, the number of concubines has increased. In this historical trend, there is no way that ultra-fine, flat, highly strong, and highly water-resistant PVA fibers would become known.

On the other hand, ultra-thin, flat, and inexpensive PV like this one has excellent performance.
The need for A-type fibers is increasing. A typical example is the reinforcement of brittle materials such as hardened cement and low-strength plastic materials such as plastics. For the reinforcing effect, it is basically important that the strength of the fibers is high, but in addition, the adhesive force with the matrix is also a major factor. Making the fibers thinner and flat will significantly increase the contact area with the matrix, thus greatly improving the adhesive strength.
This increases the reinforcing effect. Furthermore, process passability during molding is significantly improved.

M) Water resistance is also important, especially in the case of IJ Lux hydraulic materials. That is, since the fibers are exposed to relatively high temperature water during molding and setting, the fibers must not swell and as a result their strength will be significantly reduced. Such required properties cannot be satisfied by known PVA-based ultrafine fibers.

A typical example of a product made by reinforcing a hydraulic brittle inorganic material such as cement with fibers is asbestos slate board, which is a composite material whose main components are fibrous asbestos and a hydraulic material such as cement. It is.

The main manufacturing method is to make a 5 to 30% by weight aqueous dispersion (papermaking slurry) of fiber components such as asbestos and hydraulic binding components such as cement together with other additives, and then pour this onto a round net or fourdrinier. A wet papermaking method is used in which the paper is made into paper, dehydrated, molded, hardened, and dried to produce a product. This method is highly productive with simple equipment, and provides a high-strength, inexpensive noncombustible material, and such products are used in large quantities as building materials in a wide range of fields.

The role of asbestos in such hydraulic inorganic paper products is (1)
High productivity imparting effect in the papermaking process) Imparting uniform dispersibility of fibers used together (b) Capturing particulate matter, mainly hydraulic substances, and imparting appropriate reactor water properties (C) Making rolls and Prevention of delamination and water cracking phenomena in forming rolls (dl) Surface smoothness, molding during press molding (dl)
e) Improved green sheet strength (improved handling) (
2) Ensuring product physical properties (reinforcing hydraulic substances) (a) Improving mechanical properties such as bending, tensile, and impact strength (b) Improving dimensional stability (C) Improving cracking resistance and durability It is said. Furthermore, the inherent features of the hydraulic material, such as not impairing its nonflammability, are hardly reduced. In addition, asbestos is a very cheap substance.The role of asbestos in inorganic paper products is extremely important, and it is even said that such inexpensive products with excellent physical properties would not be possible without the presence of asbestos. This is the reason.

The excellent properties of asbestos include the fact that asbestos is a fibrillar material and has a high affinity with hydraulic substances.
High strength, high Young's modulus, and inorganic fibers.
This is due to high water retention.

On the other hand, asbestos generates dust in the air when products containing asbestos are manufactured, processed, and installed. recent years,
It has been pointed out that fine asbestos dust, if inhaled into the human body, may cause lung cancer, etc., and its use is gradually being restricted by laws and regulations, and there are even signs that its use may be banned. Furthermore, asbestos-producing countries are unevenly distributed in certain countries, and there is also the problem of resource depletion. Under these circumstances, there is a strong desire to provide hydraulic inorganic paper products that do not contain asbestos and have the same high productivity and performance as when using asbestos, instead of hydraulic inorganic paper products that contain large amounts of asbestos. There is.

Attempts have been made to replace asbestos with other materials to produce products using wet papermaking methods, but these have not been sufficient and have only been used for very limited purposes. The reason for this is that there is no substitute material that has the excellent properties of asbestos as described above.

In order to enhance the ability to capture hydraulic substances, etc., in addition to the physical requirement that the fibers be thin like asbestos fiber bundles, the chemical requirement is that the fibers have a strong affinity for hydraulic substances. Asbestos is a fiber bundle made up of fine fibrillar substances of 0.02 to 0.03 microns, and its thickness is said to be 0.5 to several microns, although it varies depending on the degree of waste. However, the convergence is not perfect, and the fibers are bundles with fibrillar whiskers, which are very convenient for trapping hydraulic substances. Therefore, the substitute does not simply have to have the same thickness as the asbestos fiber bundle.

In addition, the fiber itself has high tensile strength, which increases reinforcing properties.
It must have excellent adhesive strength with the hydraulic substance after curing, that is, it must have good affinity with the hydraulic substance, the fibers must be as thin as possible, and the spacing between the fibers must be as small as possible to improve crack restraint. That is, it is necessary that the fiber is thin and that the physical properties of the fiber do not change during the molding process or during use. Furthermore, in terms of surface properties and moldability during pressing, the fibers need to have good dispersibility, be thin, and be flexible (thinner is more flexible if the physical properties are the same).

Therefore, fibers that can replace asbestos must be as thin as possible, have a large surface area, be strong, have excellent water resistance and durability, have good affinity with hydraulic substances, have good adhesion, and be dispersible. It means that sex is good.

Natural pulp has been widely studied from the viewpoint of its ability to trap hydraulic substances. In this case, increasing the degree of beating improves the ability to capture hydraulic substances such as cement, but
However, it is still not as good as asbestos.

On the other hand, in terms of reinforcing effect, the pulp, which originally has low strength, is severely damaged by beating, so it has little effect. Furthermore, it is well known that it deteriorates in the cured product. Synthetic pulp is also being considered as an alternative to asbestos. For example, polyethylene-based SWP (manufactured by Mitsui ZEF Bank) is similar to asbestos because it has a fibrillar shape in terms of its ability to capture hydraulic substances, but it is also hydrophobic and is inferior to asbestos. Shi, I'm not satisfied. Furthermore, in terms of reinforcing properties, in addition to the low strength required for reinforcement, swp itself is hydrophobic, so it has poor adhesion to hydraulic substances and has no reinforcing effect. Furthermore, the synthetic pulp itself forms flocs in one step of making the papermaking slurry, resulting in a decrease in papermaking properties and a loss in the appearance quality of the product.

Aramid pulp has also been talked about as an alternative to asbestos, but it cannot be used as an alternative to asbestos, at least not in other fields such as brake shoes, but at least in hydraulic inorganic paper products such as asbestos slate boards. In other words, the trapping ability of hydraulic substances is similar to asbestos in that it is fibrillar, but it is not as good as asbestos, partly because it is hydrophobic. In terms of reinforcing properties, like polyethylene pulp, it is hydrophobic and therefore has poor affinity with hydraulic substances, resulting in poor adhesion.As a result, when a hydraulic inorganic paper product breaks, aramid pulp pulls out, which is inherently As a result, the high strength it possesses is not utilized at all, and the reinforcing effect is hardly exhibited. Another disadvantage is that it is very expensive.

On the other hand, alkali-resistant glass is often studied with an emphasis on its reinforcing effect, but alkali-resistant glass (even though it is called alkali-resistant glass, has problems with durability, and in addition, because it is a thick fiber, it has little ability to trap hydraulic substances. .

Carbon fibers and aramid fibers are being considered as highly strong fibers, but although the fibers themselves have high strength, they have poor adhesion to hydraulic substances and lack reinforcing properties.

Also, like glass fiber, it does not have the ability to trap hydraulic substances and is also very expensive.

Acrylic fibers are also being considered. For example, JP-A-5
According to Japanese Patent No. 1-20222, wet-spun acrylic fibers have many folds on the surface, so they have excellent adhesion to cement, and when they break, the fibers are cut, resulting in a high reinforcing effect.

However, since the strength of the fibers itself is low, even if the fibers break, no significant reinforcing effect can be expected, and furthermore, they do not have the ability to trap cement.

Further, according to British Patent No. 2,075,076, the thickness is 0.1 to 1 dtex (0.09 to 0.9 dr).
, strength 20~80 CN/lex (2,3~6.8
S'/dr) Noacrylic fibers are excellent in their ability to capture hydraulic substances and reinforcing properties, and can be used as a substitute for asbestos.

However, the ability to trap hydraulic substances is not only controlled by the shape of the fibers, but also the affinity with the hydraulic substances is an important factor. Since acrylic fibers are naturally hydrophobic, their affinity is weaker than that of asbestos, and therefore their capture ability is also inferior. More importantly, as shown in Table IVC of the British patent, the strength of the fiber itself is significantly lower than that of asbestos, and therefore the reinforcing effect is inevitably inferior. Also noteworthy in the British patent is the description of PVA-based ultrafine fibers. As mentioned above, known ultra-fine denier PVA
Although all PVA-based fibers have low strength and low water resistance, the British patent states on page 1, lines 44-52 (-In the case of PVA-based fibers,
1 dtex (0,9 dr) or less has low water resistance, partially dissolves in the cement suspension (slurry), and has no reinforcing effect.''

At present, there is no fiber that can satisfactorily replace asbestos and has excellent properties as described above.

C1 Purpose of the Present Invention As a representative example of asbestos replacement, ultrafine, flat PVA-based fibers with high random strength and high water resistance are desired.

Under such circumstances, an object of the present invention is to provide a flat PVA fiber that is ultra-fine, has high strength, and has excellent water resistance, and a method for producing the same at low cost.

D1 Structure of the present invention The PVA-based microfiber with excellent performance of the present invention can be produced not by the known expensive dissolution and removal method, but also by a normal spinning method by adopting specific conditions. This is what led to the present invention.

That is, in the present invention, the single fiber denier is 0.05 to 0.5 dr.
The tensile strength is 9. PV that satisfies Qf/dr or higher, underwater softening point of 105℃ or higher, and cross-sectional solidity of 70% or lower.
The A-based fibers and the method for producing the same, such PVA-based fibers, are obtained through wet spinning under specific conditions, and will be described in detail below.

The PVA used in the present invention has an average degree of polymerization of 1,200 to
3,000, with a saponification degree of 96q6 or more (a degree of saponification that is almost saponified in the alkaline coagulation bath described later), and 0.5 to 5 weight of boric acid to the PVA. Alternatively, it is dissolved in water by a conventional method with a borate and an acid or the like in an amount such that the concentration of the stock solution after dissolution is 5 or less to form a relatively dilute solution of 8 to 14% by weight, which is used as a spinning stock solution. If the concentration is less than 8%, spinning becomes impossible, and if it exceeds 14%, the condition of the metal plate deteriorates significantly and fibers with a flat cross section cannot be obtained. It is discharged into an alkaline high concentration salt bath with a bath draft of 10 to -60 inches from a 04 chicken pore diameter mouthpiece and then spun. The bus draft in the present invention is defined by the following equation.

Note that the above-mentioned speed is the 10th-ra speed.

The pore diameter of a wet spinning nozzle is generally smaller than that for melt spinning and dry spinning, but in the case of wet spinning of a single PVA fiber, conventional wisdom holds that the minimum diameter is 0.05-. Below this, the spinning condition becomes extremely unstable. The present inventors believed that it was necessary to further reduce the diameter of the spinneret hole in order to obtain ultrafine fibers, and conducted various studies on methods for improving the spinning condition. As a result, it is necessary to perform high-level filtration of the stock solution to eliminate foreign substances, but more than that, it is extremely important to keep the bath draft at 10 to -60% in order to ensure stable spinning. I found out. However, when the pore diameter was less than 0.02 m, it was somewhat unstable. The composition of the coagulation bath also has an important influence on the spinning condition and the flattening of the single fiber cross section, and it must be an alkaline high concentration salt bath. What is an alkaline high concentration salt bath?
CI/J or less, containing caustic alkali of 1f/1 or more 25
It means a salt solution having a saturation level of 0-71 or more, and as the salt, sodium sulfate and ammonium sulfate are preferably used. Caustic alkali is 1
If it is less than 2/1, the spinning condition will deteriorate;
When the value exceeds 71, the cross section approaches a circular shape, and the degree of fullness of the cross section becomes 70.
% and the spinning condition is not good.

If the concentration of salts is less than 250,171, the spinning condition will be poor and the single fibers will stick together, which is not preferable.

As will be described later, if the cross-sectional solidity exceeds 70%, the ability to trap cement in the wet papermaking process will deteriorate, which is undesirable.

Furthermore, when used in microfilters, etc., the capture efficiency decreases. In addition, the flexibility of the fibers has a cross-sectional fullness of 70.
If it exceeds 100, it rapidly decreases, which is not preferable for applications where flexibility is required. The cross-sectional fullness of the fiber in the present invention means that obtained as follows. 3X3X1
Make a rectangular parallelepiped of cork with the size of 0 sushi, make a notch in the center,
Insert the fiber bundle into it, then use a safety razor blade to remove the fiber bundle.
,1~0°3. Cut into w-thickness. The thin sections are photographed using a microscope, enlarged to about 100 -, and the cross-sectional area F of each section is determined. Next, draw a circle with a wide width B as the diameter of the middle volume of the drawn cross section, find the area of this circle, and use the following formula to calculate the discharge volume based on the fullness arrow of the cross section.The denier is 0.05.
Adjust so that it becomes ~0.5 dr. If the dr. Problem: It is necessary to cut the material to 1■ or less, but such cutting is industrially impossible and meaningless. Also Q
, if it exceeds 5 dr, the expected effect of fine denier will not be sufficient.

Such spinning ridge fibers are neutralized after roller stretching, then washed with water so that the residual boric acid becomes 0.1 to 0.6%/PVA, and subjected to moist heat stretching in a sodium sulfate bath, or after roller stretching. Neutralize and moist heat stretch to reduce residual boric acid to 0.1-0.6%/
PVA and eggplant. When the residual boric acid is 0.6%/PVA, the stretchability is significantly inhibited in dogs, and the desired strength and water resistance cannot be obtained. Furthermore, in order to make the fiber smaller than 0.1%/PVA, severe washing conditions must be used, resulting in significant swelling of the fibers and a deterioration in quality. The total stretching ratio in the wet area is at least 3 times.

After drying, dry heat stretching is performed so that the total stretching ratio is 10 times or more. Further, if necessary, heat shrinkage and heat treatment are performed to raise the underwater softening point to 105° or more. Unless the film is stretched 10 times or more, a strength of 9.Q f/dr or higher cannot be obtained. If the tensile strength is less than g, QP/dr, the effect as a reinforcing fiber will not be sufficient, and it will also lack suitability as a general industrial material.

The underwater softening point is particularly important when used for reinforcing hydraulic materials such as cement, and if it is lower than 105°C, swelling will occur during the molding process, reducing the original strength and therefore significantly reducing the reinforcing effect. I will do it. In addition, even in general applications, post-processing is often done in aqueous systems, and if the temperature is below 105°C, the fibers will swell during drying after processing, resulting in a decrease in strength, and the surface will partially dissolve, causing problems such as sticking. result. The softening point in water according to the present invention was determined by the following measuring method.

Underwater softening point: Take out the fiber bundle arbitrarily so that the fiber bundle denier is about 1000 dr, align it, attach a weight with a fiber bundle denier of 11500 f to one end, and place 1. Fix it in place.

This is placed vertically in a pressurizable glass tube filled with water and immersed in water. The temperature is raised at a rate of 1"C per minute from room temperature, and the temperature at which the fiber bundle shrinks by 10% or melts.

Only PVA-based fibers obtained under the above combination of conditions have a denier of 0.05 to 0.5 ar and a strength of 9. Q
r/dr or higher, underwater softening point 105℃ or higher, cross-sectional solidity 7
It has excellent physical properties of 0% or less, and in addition, according to the present invention, it can be manufactured using conventional wet manufacturing equipment processes, and the spinning condition is very good, resulting in high productivity. ,
It has the great advantage of being able to produce ultra-fine fibers at the same cost as regular denier PVA fibers.

Next, a hydraulic inorganic paper product, which is a typical use of the ultrafine fiber of the present invention, and a method for producing the same will be described.

The unique feature is that it uses flat, ultra-fine PVA-based fibers with high strength and excellent water resistance as an asbestos replacement fiber.The PVA-based micro-fine fibers can completely replace asbestos and have various properties. This is an epoch-making fact that has been discovered. That is, the denier is 0.05 to 0.5 dr,
By simply using PVA-based ultrafine fibers with a strength of 9.0 f/dr or more, an underwater softening point of 105°C or more, and a cross-sectional solidity of 70 inches or less for asbestos glue in the conventional wet papermaking method, it is equivalent to using asbestos. This made it possible to obtain hydraulic inorganic paper products with high productivity and high performance. A detailed explanation will be given below.

The first and most important role of asbestos is to trap particulate materials such as hydraulic materials. As mentioned above, asbestos is a fiber bundle of 0.5 to several microns and has fibrillar whiskers, so it has excellent physical capture ability, and its chemical structure makes it difficult to interact with hydraulic substances. It is a substance that is easy to capture chemically due to its good affinity. Since PVA fibers originally have hydroxyl groups in their molecules, they have chemically excellent affinity with hydraulic substances such as cement. Therefore, all that is left is to take a form that is physically easy to capture.

Therefore, we created samples of various deniers and examined their ability to trap hydraulic substances using a wet papermaking method.
It has been found that only when the diameter is 2 to 5μ in terms of yen and the cross-sectional solidity is 70% or less, the trapping property is almost the same as that of asbestos. It was insufficient to match the thickness of the PVA fiber to the thickness of the asbestos bundle, which is about several microns, because there was nothing to complement the whiskers of the asbestos bundle. Therefore, I tried to make the sides of the PVA ultra-fine fibers become fibrillated, but although they were fibrillated,
The purpose could not be achieved because tangles occurred and the original strength and water resistance decreased. Next, when we tried to flatten the fibers, we were surprised to find that the cross-sectional fullness was 7.
It has been discovered that when the content is less than 0%, it has a trapping ability almost equal to that of asbestos, without using any pulp at all.

The necessary and sufficient conditions for having a trapping property comparable to that of asbestos are PVA.
The denier of the fiber is 0105 to 0.5 dr,
The degree of fullness of the cross section is 70 inches or less, and if any of the conditions is out of this range, the objective cannot be achieved.

The denier is 0.05 to 0, sar, but preferably 0.2 dr or less. It should be noted that it is difficult to produce fibers with a diameter of 0.05 dr or less, and even if it were possible to produce fibers, it would be necessary to cut the fibers into pieces of 1 m or less from the viewpoint of dispersibility, which is currently industrially impossible and meaningless. However, this is an interesting area if cutting technology is developed.

Further, the cross-sectional solidity must be 70% or less, but the smaller it is within the range of manufacturability, the better.

It has become common knowledge that pulp is used to make wet paper products that do not use asbestos, but according to the present invention, it is possible to obtain the same formability as when using asbestos without using pulp at all. It became.

The second important role of asbestos is to reinforce hydraulic materials.

In order to increase mechanical properties such as tensile strength and bending strength, it is essential that the fibers have high strength, high water resistance, and excellent adhesion to hydraulic cured materials.0 In terms of adhesion, Although PVA fibers have excellent chemical adhesion due to the presence of hydroxyl groups, it is also important to increase the specific surface area to increase the contact area of the cured product with the hydraulic substance. Reducing the denier/JS and flattening it significantly increases the adhesive area and increases the reinforcing effect. At a 0.5 dr or less and a cross-sectional fullness of 70% or less, the reinforcing effect is so great that it seems to be a synergistic effect of both, although the reason is unknown.

Unless the fiber strength is 9.0 P/dr or higher, it is difficult to achieve the reinforcing effect necessary to replace asbestos.

Furthermore, water resistance is an important physical property to prevent changes in physical properties during manufacturing, processing, or use. It must not swell in the papermaking slurry and cause a decrease in strength.
It still has to withstand the temperature rise caused by the heat of hydration during the condensation process. For this purpose, the softening point in water must be at least 10.
Must be at least 5°C.

An important reinforcement effect of asbestos is its crack resistance.
Among the physical properties of asbestos-free hydraulic paper products, this is the one of greatest concern. In order to increase such cracking resistance, the number of fibers is important in addition to the fiber strength, Young's modulus, and adhesion to the hydraulically cured body, and all of these properties must exceed a certain value. Strength9. Qf/dr or more, 0.05
Only ultrafine and flat PVA fibers with ~0.5 dr and a cross-sectional solidity of 70% or less satisfy these characteristics and have the same crack prevention effect as asbestos. In addition, thin and flat fibers improve the surface smoothness of the paper-made product and improve the cleaning properties during pressing. Furthermore, it helps prevent peeling between the eyebrows, wrinkles, and water cracking caused by making rolls and forming rolls.

As mentioned above, strength 9. Qf/dr or higher, underwater softening point 10
5°C or higher, cross-sectional solidity 70L% or less 0.05 to 0.5
Dr's hydraulic inorganic paper products using PVA-based ultrafine fibers are asbestos-free but have almost the same performance as products containing asbestos. Such a hydraulic inorganic paper product can be manufactured simply by using the PVA-based fiber as an asbestos glue using a normal wet paper-making method.

That is, the concentration of PVA-based ultrafine fibers and hydraulic substances is 5 to 30%.
Add water to make a uniform dispersion (slurry) using a pulper.

The amount of PVA fiber added is preferably 0.5 to 5%, more preferably 1 to 2%. If it is less than 0.5%, there is no effect of addition, and if it exceeds 5%, the dispersibility deteriorates, the ability to capture cement, etc. and reinforcing properties decrease, the surface smoothness is impaired, and delamination and water cracking occur. This will cause

Furthermore, the aspect ratio must also be limited based on the balance between dispersibility and reinforcing properties. It is preferably from 100 to 1.500, more preferably from 300 to 800.

If it is less than 100, one fiber bow will fall out, reducing the reinforcing effect, and if it exceeds 1,500, it will result in poor dispersion, which is undesirable.

A product can be obtained by forming a slurry made of PVA fibers and a hydraulic substance into a round net or fourdrinier, and subjecting it to appropriate dehydration, molding, curing, drying, coloring if necessary, and other processing.

Although it is possible to obtain a wet paper-made product with sufficient process passability and physical properties using only the PVA fiber and hydraulic material according to the present invention, it is possible to obtain a wet paper-made product with sufficient process passability and physical properties, but in order to improve the quality, it is also possible to obtain a product with excellent production properties compared to asbestos slate products. If necessary, other substances may be used alone or in combination to provide properties and physical properties.
If you want to improve the quality, you can use a flocculant.

The amount added is preferably 200 ppm or less, and a commercially available flocculant is sufficient. If it is more than 200 ppm, felt stains may occur, and wetability is too good, making it difficult to obtain a uniform green sheet. 0 Improved ability to capture hydraulic substances, dispersibility of PVA-based ultrafine fibers, surface properties, etc. /Merck can also be used in combination to measure. The amount added is 0.2 to 5%, preferably 0.5 to 3%.

If it exceeds 5%, dimensional stability deteriorates and there are concerns about durability. Furthermore, the flammability decreases, causing problems such as difficulty in increasing the bulk specific gravity. Although it is possible to add 0.2- or less, no improvement effect can be expected from this substance. As a nokurupu, natural nokurupu with various degrees of cracking and synthetic nokurupu such as polyethylene, aramid, etc. can be used alone or in combination of two or more types to bring out the effect of zero nokurupu. Voids are filtered by adding PVA fibers to the aqueous dispersion of Norp, but vice versa is not preferred. The effect of improving the valve's ability to capture hydraulic substances and the dispersibility of PVA-based fibers is extremely large (I can't help but think that there is a synergistic effect with the PVA-based ultrafine fibers.

An inorganic molding material having an average particle diameter of 1 x 10-2 to 1 x 10-5 may also be used. The average particle diameter of the inorganic molding material means, in the case of a particulate material, the average of the maximum diameter of the particles, and, in the case of a fibrous material, the average of its fiber lengths. There are various effects of such inorganic molding materials, but they are like seasonings, and due to the delicate synergistic effect with PVA-based ultrafine fibers, hydraulic substances, and other additives, they contribute to stable production and improve physical properties. It makes a significant contribution to improving product value. For example, improving the dispersibility of PVA-based ultrafine fibers, improving the ability to trap hydraulic substances, imparting suitable muddy water properties, improving the lamination properties of paper-made fleece, preventing water from forming on making rolls, preventing wrinkles and cracks, and smoothing the surface. It has the effect of improving properties and imparting moldability during press molding. The amount of such inorganic molding material added is 1 to 20%, preferably 2 to 8%. 2
If it exceeds 0%, the amount added will be too large and will conversely deteriorate the physical properties. On the other hand, if less than 1% is added, there is no problem, but the effect of this substance cannot be expected. The average particle diameter is lX
10-2 to 1 x 10-5 is preferred.

Above 1×10−2 dragon, there is no addition effect, and 1×10−
If the amount is less than 5, the holes in the cylinder during papermaking will become too tight, which is not preferable, and it is also not economical.

Types of inorganic molding materials include natural limestone powder, heavy charcoal,
Alternatively, it is possible to use powders selected from synthetically obtained calcium carbonates, called extremely fine carbonates, and other carbonates such as basic magnesium carbonate dolomite.

Furthermore, silicate compounds represented by clay minerals, such as natural kaolin, clay, pole clay, pyrophyllite, bentonite, montmorillonite, nontronite, sapomate, sericite, zeolite, nephelinsinite, merk plate-shaped or thin plate-shaped objects such as
Furthermore, fibrous or acicular materials such as attapulgite, seviolite, and wollastonite can be used. Furthermore, as synthetic products, synthetic aluminum silicate and synthetic calcium silicate can also be used. As silicic acid, natural product diatomaceous earth,
There are silica powder, etc. In addition, as synthetic products, hydrated fine powder silicic acid,
Anhydrous fine powder silicic acid, something called white carbon, silica dust, silica hneem, and fly ash can also be used as industrial byproducts or wastes.

Mica can also be used in combination in a range of 5 to 30%. Mica is P
In addition to improving the dispersibility of VA-based ultrafine fibers, the synergistic effect with the ultrafine fibers improves the ability to capture particulate matter such as hydraulic substances, and the vat water level is maintained appropriately, resulting in a uniform green sheet. Furthermore, the dimensional stability of the product,
Improves crack resistance and prevents cracking when heated during a fire. The addition rate is 5 to 30%, preferably 8 to 15%. It is okay to add less than 5%, but
Almost no effect of adding mica can be expected.

If it exceeds 30%, the green sheet will lose its flexibility,
It causes various harmful effects. Mica has an aspect ratio of 20 or more (flake diameter/flake thickness) and a particle diameter of 30.
As long as it has a plate-like shape with a diameter of ~5000 μm, it is not subject to the same restrictions depending on chemical composition, crystal form, place of origin, pulverization method, etc. For example, it is appropriately selected from muscovite, phlogopite, biotite, lepidolite, soda mica, synthetic mica, and the like.

Artificial inorganic fibers of 0.5 to 10 inches can also be used in combination.

Such a substance works synergistically with PVA-based ultrafine fibers or other additives to improve the ability to capture solids such as hydraulic particulate matter in the papermaking slurry. It also imparts appropriate hardness to the green sheet and helps prevent cracks that occur when the product is heated.

If it is less than 0.5%, it will not be effective, and if it exceeds 10%, the green sheet will be too hard and will lack old-shape properties, will crack when it is rolled out from a making roll, and will have poor moldability, so it is not preferable. do not have.

The man-made inorganic fibers may be any so-called man-made inorganic fibers, such as glass fibers, shirasu fibers, slag wool, rock wool, and ceramic fibers.

Divalent or trivalent metal hydroxides of up to 10% can also be used in combination. The metal hydroxide can be used if its effectiveness in absorbing heat generated by combustion of organic matter when the product is heated is 6.1% or less.

If it exceeds 10%, the physical properties of the product deteriorate, which is undesirable.

Typical examples of divalent or trivalent metal hydroxides include hydroxides of aluminum, iron, magnesium, and zinc.

The finer the hydroxide particles are, the more preferable they are, and it is particularly preferable that they exist in a colloidal state in the raw material slurry.

Hydraulic inorganic substances used in the present invention include, for example, Portland cement such as ordinary Portland cement, moderate heat Portland cement, ultra-early strength Portland cement, white Portland cement, and sulfate-resistant Portland cement, blast furnace cement, silica cement, and fly ash cement. There are special cements such as mixed cement, alumina cement, super fast hardening cement, colloidal cement, and oil well cement. Furthermore, the material may include hand-watering Ceracola, a mixed hydraulic material of water-containing Ceracola and slag, magnesia, etc., but is not limited thereto, and any hydraulic inorganic material may be used.

Other common fillers can be used. Examples include hollow pearlite, Shirasubarene, and expandable admixtures as lightweight materials.

Combinations with other reinforcing fibers are also possible. In particular, when fire resistance is required, combinations with inorganic fibers such as alkali-resistant glass, carbon fibers, and ceramic fibers are effective. It is also possible to use a combination of normal denier PVA fibers, acrylic fibers, polyamide fibers, and aramid fibers, and a combination of polyolefin fibers and polyamide fibers is particularly effective for improving impact resistance.

This will be explained below using examples.

Examples-1 to 2. Comparative Examples-1-2 Polymerization degree 1,750, saponification Jf 99. OMo#%
OP V A was dissolved together by adding boric acid and acetic acid in an amount of 1.5 and 0.3 parts by weight based on PVA, respectively.
An aqueous solution with a concentration of 13% by weight (viscosity: 8 voids at 90° C., 4.5%) was used as a spinning dope.

The Kono spinning stock solution was prepared with a pore diameter of 0.03 m and a number of pores of 10,000.
50 bucks of soda? /l, mirabilite 300P/
It was discharged into the coagulation bath of J and formed a thread. At this time, the discharge amount was changed to reduce the bath draft by 10% (Example-1)
), -40% (Example-2), +20% (Comparative Example-1)
, -70 inches (Comparative Example-2).

At a stretching speed of 10 gIL/min, it was stretched 2.5 times between rollers, and after neutralization, it was subjected to wet heat stretching 1.8 times, and then washed with water so that the residual boric acid was 0.3%/PVA. Further, a focusing treatment was performed to increase the total stretching ratio to 12.6 times, and heat shrinkage was performed by 2%. The spinning condition was determined by continuous spinning for 8 hours with 10 spindles. Table IK including quality measurement results is shown.

Example-3, Comparative Examples-3 to 4 Degree of polymerization 1,650, '171 carbonization 9.9 mol 1c) PV
A is boric acid, acetic acid is 2.0.0.
3% by weight and dissolved together to make a concentration of 11% by weight (
Example-3), 7% by weight (Comparative Example-3), 16% by weight (
Comparative Example 4) Each aqueous solution (all had a rating of 4.5) was prepared and used as a spinning stock solution. The stock solution has a pore diameter of 0.03+m,
Using a cap with 10,000 holes, 20 f/
J, Glauber's salt was discharged into a coagulation bath of 350 t/l to form a thread. The bus draft was set at -40%, and the speed was set at 10 m/min. This spun fiber was stretched twice with a roller, neutralized, and then washed with water to remove the remaining boric acid by 0.4%/PVA.
The film was treated with a sodium sulfate bath and subjected to wet heat stretching at a stretching ratio of 4.5 times. After further drying, dry heat stretching was carried out to give a total stretching ratio of 12.degree. However, for those that cannot be stretched 12.5 times, the cutting stretching ratio was determined and the stretching ratio was set to 80%. Subsequently, it was subjected to 2% heat shrinkage, washed with sodium sulfate, oiled, dried, and then its quality was measured. The results are shown in Table 2. Examples 4 to 6, Comparative Examples 5 to 6 In Example 2, the concentrations of sodium sulfate and mirabilite in the coagulation bath were 70 f/J and 2701/Ic, respectively. 4), 3
0f/I, 3001/Ic Example-5), 10f! /1
133 (1/J (Example-6), 110 f/l, 23
09/Ic Comparative Example-5), 701/l, .

All examples except 2309/Ic Comparative Example-6)
Table 3 summarizes the results of tests conducted under the same conditions as 2.

Table -1 Table -2 Table -3 As mentioned above, all the examples had good spinning condition, and the cross-sectional fullness was 70.
Compared to the ultrafine fibers with high tenacity and high water resistance of less than 100% obtained, the comparative example has some problems.

Examples-7 to 8, Comparative Example-7 Degree of polymerization 1,800. Care degree 97.51 (7) PVA
was dissolved with boric acid 1.5f/J% (relative to PVA) and acetic acid was added to give %4. O, viscosity 9 voids (90
A spinning stock solution was prepared at ℃).

When spinning the spinning dope through 6,000 holes to form a thread, in order to change the denier and cross-sectional solidity, the dope concentration was 13 to 16%, the bath draft was O to -40%,
The pore diameter was within the range of 0.02 to 0.04, and the concentration of sodium sulfate and sodium sulfate in the coagulation bath was varied. Neutralizes solidified Itoshino,
After the wet heat stretching, the film was washed with water to make the residual boric acid 0.5%/fiber. The total stretching ratio in the wet area was 5.0 times. After that, it is dried and subjected to dry heat stretching (the final stretching ratio is 10 times or more in each case) so that the strength becomes 13.3 f/dr, and heat treated so that the softening point in water becomes 115 ° C or more.
After oiling, it was dried and rolled up.

Fiber denier and cross-sectional fullness are %0.2dr%65
% (Example-7), 0.4 dr, 63% (Example-8)
, 0.2 dr, and 80% (Comparative Example-7). The fibers were cut to have an aspect ratio of 500, and processed using the round net wet papermaking method (Hachinic method) to obtain a concentration of 15% with a solid content of PVA fibers of 2% and the balance of Portland cement.
% slurry was prepared, and a cement board with a thickness of 6 cm was made by diluting it with white water.

Note that during papermaking, a commercially available anionic flocculant of so ppm was used. (Ichikawa Keori's IK Flock T-Comparative Examples-8 to 9 Denny #0,7 dr (Comparative Example-8), t, by the usual method.

dr (Comparative Example-9), strength 13.5/DRS PVA-based fibers with an underwater softening point of 115°C were prepared and used in Examples 7 to 8.
A cement board was made using the same method.

Reference Example 1 An asbestos cement board was prepared in the same manner as in Examples 7 and 8 with a composition of 12% asbestos (grade 6), 1% pulp, and the balance Portland cement. The experimental results of Examples 7 to 8, Comparative Examples 7 to 9, and Reference Example 1 are summarized in Table 4.

Table 4 The bending strengths in Table 4 were corrected for yield in order to compare the true reinforcing properties of the fibers.

Examples 7 and 8 use only 2 inches of the ultrafine fibers of the present invention and do not contain any pulp, and have the same cement retention and reinforcing effect as the conventional asbestos cement board (Reference Example 1). However, it is clear that the comparative example has a low level of fragility. In particular, Comparative Example 7 shows that even if the denier is within the range of the present invention, if the cross-sectional solidity is outside the range, satisfactory results cannot be obtained.

Examples-9 to 10, Comparative Example-10 According to Examples-1 to 2, the total stretching ratio was changed to obtain a strength of 13
．． 0 f/llr (Example-9), l l, Q r/
Table 5 summarizes the results of creating PVA fibers with changes such as dr (Example-10), s, and s f/dr (Comparative Example-10), and looking at the reinforcing effect of the cement board. The denier is 0.2 dr, and the underwater softening point is 113 to 11.
The temperature was approximately the same as 5°C.

Examples-11 to 12, Comparative Example-11 According to Examples 1 and 2, denier 0.15 dr.

Strength 11-11.5 t/dr 0PVA fibers were used to change the W stretching temperature and heat treatment temperature, and the softening point in water was 110° (Example-11), 115° (Example-12), and 100° (
Comparative Example 11) A sample was prepared and the reinforcing effect was examined using a cement board. The results are summarized in Table 5. Table 5 Examples 9 to 12 are based on conventional asbestos cement boards (Reference example
It shows almost the same reinforcing effect as 1), but the comparative example is lower. Incidentally, the cement yield was 91 to 94% in all cases.

Examples-13 to 20' (1) Description of raw materials used PVA-based fibers;
-A/ 0.2 dr, strength 13.59/dr, underwater softening point 116°C, cross-sectional solidity 62% fiber cut into 3 cranes is used. Valve; Canadian freeness, lQQ+d softwood unbleached pulp bentonite; Mica with an average particle diameter of 1.5 x 10-3 m is used as an inorganic molding material. Sozolite mica 40-ZK made by Sori 2 (average aspect ratio 60) Slag wool: with an average diameter of 4 x 1 O-3111I+ After adding the share in advance, sift it to 0.
Use 5-2■.

Aluminum hydroxide; C-303 from Sumitomo Aluminum Co., Ltd.
The flocculant used: IK Flock T-201 (2) by Ichikawa Keori Co., Ltd. The composition is summarized in Table 6.

(8) Cement board manufacturing method Example-13: Put a predetermined amount of PVA fiber, Portland cement, and white water into a slusher-equipped nokuru-no-kuru,
After stirring for a short time, transfer to the chest and make about 1.100 l/l.
slurry for paper making.

This slurry was introduced into a papermaking tank (vat) while adding about so ppm of flocculant and the required amount of water, and
The raw board was formed using a circular mesh screen, wound onto a making roll, and after being cut, the raw board was acid-formed at 20 kp/i.

Curing was performed at 50°C for 24 hours in a humid air, then air-dried for 4 hours.
This was left for a week to obtain a cement board with a thickness of 6wm.

Examples 14 to 20: After each additive was put into a pulper and stirred and dispersed, PVA fibers and Portland cement were added, and the same method as in Example 13 was carried out.

(4) Evaluation method Dispersibility Dispersibility refers to the state of dispersion of a fibrous material in a papermaking slurry. When the papermaking slurry is drawn up into a papermaking slurry, the uneven state on the round screen is observed, and the number of unevenness is A very good dispersion state is marked as ◎, a poor dispersion state with many unevenness is marked as ×, and the two ranks are divided into ◯ and △.

◎: When the water level in the vat is sufficiently uniform and it is possible to make a sheet; ◎: When the water level is almost constant and a uniform sheet cannot be formed; , and the intermediate ranks were qualitatively judged as ○ and Δ.

Cement-capturing ability This refers to the capture rate of solid content in papermaking slurry such as cement and inorganic molding materials, and the slurry concentration before papermaking in the papermaking tank (
wl) and the drainage molding discharged through the round screen, the raw board after the sex-making roll is given a normal corrugated shape,
The appearance of cracks and shrinkage wrinkles were observed, and those with no cracks or wrinkles were marked as ◎, those with severe cracking and shrinkage wrinkles were marked as ×, and those in between were divided into two ranks: ○ and Δ. .

Bending strength was measured according to JISA 1408r Bending Test Method for Architectural Boards, and is shown as the average value in the papermaking direction (vertical direction) and the direction perpendicular to it (horizontal direction). If the capture rate of hydraulic substances, etc. changes, the blended amount of reinforcing fibers will essentially change, so in order to compare the true reinforcing properties, we set the capture rate of solids such as hydraulic substances to 100%. The bending strength is shown with corrections added.

Crack resistance A board left to air dry for one month has a width of 4. Ocm s
-Cut it to a length of ±30 crn, and make a perpendicular cut of ICrn from both sides, leaving a width of 2 crn in the center. Then, drill two holes on each side so that the span is 28, and tighten them with 5mm bolts and nuts to a thickness of 3mm.
fixed to a stainless steel plate. Leave this as it is 2
After being immersed in water at 0°C for 1 day and night, it was air-dried at room temperature for 1 day and night. Furthermore, it was dried in a hot air dryer at 40℃ for 1 day and night, and further dried at 100"C.
Put it in a dryer for 2 hours and observe the rate of cracking during that time. A crack width of 0.05℃m or more is considered a crack, and the total number of test pieces in the vertical and horizontal directions is
It is expressed as a percentage of the number of occurrences. No cracks at all ◎, less than 20% ○, 20-40% △, 40
Those that are more than or equal to Q are marked as ×.

Flame retardancy JISA-1321: ``Flame retardancy test method J for building interior materials and construction methods'' was used to conduct base material tests and surface tests.

(6) Results It is summarized in Table-6.

Example-13 is a cement board made of the PVA-based ultrafine fibers of the present invention and cement, and it can be seen that it has almost the same formability and product physical properties as the conventional asbestos cement board of Reference Example-1, but By adding each of the additives of the present invention, paper forming properties and product physical properties are further improved, and products superior to conventional asbestos t-ment boards can be obtained.

Pulp (Example-14), Bentonite (Example-15)
), the dispersibility of PVA fibers, the capture of solids (mainly cement) in papermaking, the vat water level, the delamination properties,
Improved moldability and surface smoothness. Furthermore, the bending strength was also improved, probably as a result of improved dispersibility.

The addition of mica (Example 16) improved the dispersibility of PVA fibers and the vat water level, resulting in a uniform product and improved surface smoothness. A further characteristic feature is that it is particularly effective in surface tests among flame retardant tests, that is, it is effective in preventing cracks during heating.

The inorganic man-made fiber rock wool of Example 17 has a small effect alone, but can improve paper formability and product properties by combining it with an inorganic molding material or pulp.

Albanium hydroxide is effective for base material testing among flame retardant tests. Example-18 has a large amount of organic components and therefore generates a large amount of heat during combustion, and fails the base material test, but Example-19, in which aluminum hydroxide is added, suppresses heat generation and passes the test.

Example 20 is a formulation example having paper formability and product physical properties equivalent to or better than asbestos cement board.

E1 Effects and Applications of the Present Invention The fiber of the present invention is a flat PVA fiber that is ultra-fine, has high strength, and has excellent water resistance.It can be manufactured at low cost and has a wide range of uses, and can be used in hydraulic materials such as cement. It is possible to make paper such as paper reinforcement, plastic reinforcement, and wet nonwoven fabrics (e.g., high-tension paper, thin paper with excellent texture, etc.), and it is possible to make high-performance filters that take advantage of the characteristics of each paper, fax base paper, bank notes,
It can also be used in applications such as dry-laid nonwoven fabrics, general industrial material applications that take advantage of its high strength and flexibility, and medical applications.

Furthermore, if such ultrafine fibers are used in the field of papermaking for inorganic hydraulic materials, the problem of replacing asbestos in wet papermaking products can be solved, and high-efficiency production can be achieved without asbestos using the same equipment used when using asbestos. It has become possible to obtain paper products that are equivalent to or better than asbestos-containing paper products.

It goes without saying that the asbestos-free hydraulic inorganic paper product obtained by the present invention can be used as a substitute for conventional asbestos-containing products, but it is expected that its use will further expand as it does not contain asbestos. can.

Some examples of applications include corrugated boards that do not contain asbestos, roofing materials such as shingles, flat boards used in buildings and ships, perlite boards, siding materials, curtain walls, fireproof partition walls, exterior panels, etc. There are interior and exterior materials 2 or asbestos-free pipes.

Claims (1)

[Claims] 1. Polyvinyl whose single fibers have a denier of 0.05 to 0.5, a tensile strength of 9.0 g/denier or more, a softening point in water of 105°C or more, and a cross-sectional solidity of the single fibers of 70% or less. Alcohol-based microfiber. 2. Polyvinyl alcohol with an average degree of polymerization of 1,200 to 3,000, with a ratio of 0.5 to the polyvinyl alcohol
To a concentration of 8, dissolve by heating using water containing ~5% by weight of boric acid or a boric acid salt and an acid such that the pH of the solution after dissolution is 5 or less.
An aqueous solution of ~14% by weight is prepared, and this aqueous solution is used as a spinning dope through a round hole nozzle with a diameter of 0.02 to 0.04 mm into a bath consisting of an alkaline high concentration salt aqueous solution within a bath draft range of 10 to -60%. A method for producing polyvinyl alcohol-based ultrafine fibers, which comprises discharging and then stretching 10 times or more.