JPH07118929A - Polyvinyl alcohol fiber having water resistance and thermocompression bonding character - Google Patents

Abstract

PURPOSE:To obtain a polyvinyl alcohol fiber having a water resistance, thermocompression bonding character and a high strength, especially having the ordinary handleability of a fiber in a common use and having little dimensional change in a thermocompression-bonding treatment to enable thermocompression bonding. CONSTITUTION:This fiber is obtained by blending a polyvinyl alcohol polymer having high melting point and a water-resistant polymer having a low melting point in a specific range of the ratio and subjecting to low-temperature blended spinning in such a manner that the fiber is solidified evenly in the direction of the cross section. This is a strong fiber and has a sea-island configuration composed of a sea component consisting of a polyvinyl alcohol polymer having a high melting point and an island component consisting of a water resistant polymer having a low melting point, wherein the plenty number of island components preferably distribute within 1 p depth from the outermost surface of the fiber. Further, this fiber has the characteristic fiber function of the high-melting polyvinyl alcohol of the matrix phase in a common use but when pressure is applied at a high temperature during thermocompression bonding treatment the low melting polymer of the island component is extruded on the fiber surface to enable the thermocompression bonding of fibers with each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to water-resistant and thermocompression-bonding polyvinyl alcohol (hereinafter abbreviated as PVA-based) fibers. The present invention relates to a PVA-based fiber that enables high strength and has a small dimensional change of the fiber during thermocompression bonding, a method for producing the same, and a nonwoven fabric using the same.

[0002]

2. Description of the Related Art For melt-spinnable polyethylene, polyester, etc., heat-bondable fibers are commercially available. Recently, a core-sheath composite fiber having a core as a high-melting polymer and a sheath as a low-melting polymer has been developed, which makes it possible to suppress shrinkage during heat bonding. Utilizing the merits of simplicity, high speed, and no pollution, the application is expanding more and more.

However, these thermo-adhesive binder fibers have a low adhesive effect to hydrophilic fibers such as PVA type and cellulose type, and cannot be used in applications requiring high strength. Therefore, polymers such as acrylic type, melamine type, and PVA type polymers are used alone or in combination as a chemical adhesive in order to obtain a high strength. For example, a dry non-woven fabric made of water resistant vinylon, acrylic, melamine,
A method of applying or impregnating an emulsion or an organic solvent solution of a polymer adhesive such as a PVA system or impregnating it with a composite and drying it is generally carried out, but in the case of an emulsion, it takes time to dry the polymer. Therefore, it can only be produced at low speeds, and there is also the problem that the adhesive and its alterations stick to the rollers. In the case of the organic solvent solution, there is a problem that the volatilized organic solvent impairs human health. If hydrophilic P
If heat-adhesive and water-resistant fibers can be developed for VA fibers, hydrophilic nonwoven fabrics can be produced at high speed. It also enables high-speed production of hydrophilic cellulose nonwoven fabric, which is important as a base cloth for wet wipers.

However, conventional heat-adhesive fibers are based on a melt-spinnable hydrophobic polymer, and have fibers having both heat-adhesiveness to hydrophilic fibers and water resistance, and other fiber properties that are practically usable. unknown. PVA-based polymers and cellulosic-based polymers, which are typical examples of hydrophilic polymers, have strong intermolecular interactions due to hydroxyl groups in the molecule, have a melting point close to the thermal decomposition temperature, and can usually be melted without thermal decomposition. No heat-bondable fibers can be obtained.

Against this background, even in PVA-based polymers, the melting point and softening point are lowered to enable melt molding by internal plasticization due to copolymerization modification or post-reaction modification and external plasticization due to mixing of a plasticizer, or hot melt. Proposals for use as an adhesive have been made. For example, JP-A-51-87
No. 542, JP-A-51-96831, JP-A-53-5.
Each of the publications of No. 0239 discloses a water-soluble and hot-melt PVA-based adhesive, but if it is attempted to fiberize only these hot-melt PVA-based polymers, the viscosity at the time of hot-melt is lowered. In order to increase the adhesiveness, the degree of polymerization of PVA is as low as 600 or less, so that not only low-strength fiber can be obtained, but when it is used as a heat-adhesive fiber, molecules that are oriented during fiberization Melts and relaxes during heat-bonding, so the fiber shrinks greatly,
It is difficult to use practically.

Japanese Patent Publication No. 47-29579 and Japanese Patent Publication No. 47-
In each publication of No. 42050, a fiber obtained by adding an ethylene-vinyl acetate copolymer emulsion to a PVA solution and performing wet spinning has heat sealability and can be used as a binder fiber or a main fiber of paper or a nonwoven fabric. Has been described. However, the fiber production methods of these publications are dehydration coagulation methods using an aqueous solution of Glauber's salt, and are non-uniform coagulated spinning in which a skin core is formed, and therefore cannot be made into high-strength fibers.

Further, Japanese Patent Publication No. 41-6605 and Japanese Patent Publication No. 47-31376 describe that a fiber which can be easily fibrillated is prepared by mixing and spinning a completely saponified PVA and a partially saponified PVA. There is. However, these techniques are aimed at easily fibrillated fibers, and there is no description of thermal adhesiveness. Further, the fiber production methods of these publications are dehydration coagulation methods using an aqueous solution of Glauber's salt, and since they are heterogeneous coagulated spinning in which a skin core is formed, high strength fibers cannot be obtained.

Further, Japanese Patent Publication No. 51-28729 discloses that
PVA, polyacrylonitrile, and acrylonitrile graft polymerization PVA is dissolved in dimethylsulfoxide (hereinafter abbreviated as DMSO), which is a common solvent, and a gel yarn obtained by wet spinning is drawn and beaten to describe a self-adhesive synthetic pulp. However, since it is difficult to heat melt PVA and polyacrylonitrile without decomposition, a heat-adhesive fiber cannot be obtained.

Further, in JP-A-52-5318, a low polymerization degree and a low saponification degree PVA and a polymer having a fiber-forming ability are mixed or composite-spun and washed with water to obtain a low polymerization degree and a low saponification degree. It has been proposed to produce ultrafine fibers by removing the degree of conversion of PVA, but the purpose is completely different from the present invention, and water-resistant heat-bondable fibers cannot be obtained.

Further, Japanese Patent Laid-Open No. 1-260017 discloses that
A high-strength water-disintegrating PVA-based composite fiber has been proposed which uses a PVA polymer having a saponification degree of 80 to 95 mol% as a core component and a PVA polymer having a saponification degree of 96 mol% or more as a sheath component. With this conjugate fiber, the purpose is different from that of the fiber of the present invention, and a water-resistant heat-bondable fiber cannot be obtained.

[0011]

As described above, it has been strongly desired to develop a PVA-based fiber having both high heat-adhesiveness and water resistance and high strength, but it has not been obtained by the conventional technique.
Therefore, an object of the present invention is to obtain a high-strength PVA-based fiber having water resistance and thermal adhesiveness. Moreover, it is providing the manufacturing method of the nonwoven fabric and fiber using it.

[0012]

[Means for Solving the Problems] The present inventors have completed the present invention as a result of intensive studies on the above problems. That is, the present invention has a sea-island structure in which a PVA-based polymer having a melting point of 220 ° C. or higher is a sea component, and a water-resistant polymer having a melting point or a fusion temperature of less than 210 ° C. is an island component, and a blend of both polymers. A high-strength, water-resistant and thermocompression-bondable PVA-based fiber having a ratio of 98/2 to 55/45 and a strength of 7 g / dr or more.

The fiber of the present invention is a multi-component fiber having a sea-island structure, and the PVA polymer having a melting point of 220 ° C. or higher is the sea component. When the melting point of the sea component PVA-based polymer that becomes the matrix is less than 220 ° C., the heat resistance of the fiber of the present invention
The water resistance is insufficient and it is not possible to obtain fibers that can be used practically. Also, high strength fibers cannot be obtained. More preferably, the melting point of the sea component PVA-based polymer is 225 ° C. or higher. There is no particular limitation on the upper limit of the melting point of the sea component polymer, but PVA having a melting point of 260 ° C. or higher is not common.

Specific examples of the sea component PVA-based polymer include a polymerization degree of 500 to 24,000 and a saponification degree of 99 to.
Highly saponified PVA of 100 mol%. Polymerization degree is 15
It is more preferable that the saponification degree is from 00 to 4000 and the saponification degree is from 99.5 to 100 mol% from the viewpoint of water resistance and thermocompression bonding. In addition, ethylene, allyl alcohol, itaconic acid, acrylic acid, maleic anhydride and ring-opened products thereof, arylsulfonic acid, fatty acid vinyl esters having 4 or more carbon atoms such as vinyl pivalate, vinylpyrrolidone and a part of the above ionic groups. In addition, PVA modified with a modification unit such as a neutralized product is also included. The amount of modifying unit is less than 1 mol%, preferably 0.5 mol% or less. The method of introducing the modifying unit is not particularly limited, whether it is copolymerization or a post reaction.
The distribution of the denaturing unit is not limited to random or block. When distributed in blocks, the crystallization-inhibiting effect is small, and the high melting point can be maintained even if it is modified more than randomly.
By using a high melting point PVA-based polymer having a high degree of saponification as a continuous phase, it is possible to obtain a performance close to that of a single fiber having a high melting point, and by using a high melting point polymer as the outermost layer of the fiber, it becomes It is possible to prevent wearing.

As the island component of the sea-island fiber of the present invention, a water resistant polymer having a melting point or a fusion temperature of less than 210 ° C. is used. If the melting point is 210 ° C. or higher, the thermocompression bonding temperature becomes too high, and the orientation and crystallinity of the PVA-based polymer of the sea component are easily destroyed during thermocompression bonding, which is not preferable. Even if the water-resistant amorphous polymer does not have a melting point, the minimum temperature at which the amorphous polymer chips fuse to each other when the amorphous polymer chips are heated to a predetermined temperature and a pressure of 0.1 kg / cm ² is applied for 10 minutes. When the temperature is the fusion temperature, the water resistant amorphous polymer having a fusion temperature of less than 210 ° C. is included in the water resistant polymer of the present invention and can be effectively used as the island component water resistant polymer. The island component water-resistant polymer preferably has a melting point or a fusion temperature (hereinafter, this temperature is also included in the term "melting point") of 200 ° C or lower, and more preferably 190 ° C or lower. Furthermore, it is preferable that the difference in melting point between the sea component and the island component is 15 ° C. or more because the fiber dimensional change during thermocompression bonding becomes small. The melting point difference is more preferably 30 ° C. or higher, and 50 ° C.
It is more preferable that it is above. Since the water-resistant polymer having a melting point of less than 210 ° C. has low orientation and low crystallinity, it is disadvantageous when it is used for the sea component which is the matrix of the fiber because it has low strength and low heat resistance. Further, when the low melting point polymer is present on the outermost surface of the fiber, it is easy to harden in the fiber manufacturing process, and from this point as well, it is necessary to use the low melting point polymer as an island component.

Specific examples of the water resistant polymer having a melting point of less than 210 ° C. in the present invention include ethylene / vinyl alcohol copolymer (molar composition ratio = 50/50 to 20/80),
Ethylene / vinyl acetate copolymer (molar composition ratio = 92/8 to 2
0/80), polyvinyl butyral, polyvinyl formal, PVA modified with vinyl ester of fatty acid having 3 to 20 carbon atoms, modified acrylic resin, hydrocarbon elastomer such as polyisoprene, polyurethane elastomer and the like. Above all, cellulosic fibers and P
The ethylene / vinyl alcohol copolymer (molar composition ratio = 50/50 to 20/8) is excellent in thermal adhesion to hydrophilic fibers such as VA-based fibers, performance reproducibility (stability), and cost.
0), ethylene / vinyl acetate copolymer (molar composition ratio = 92 /
8-20 / 80) PVA-based polymer is useful as an island component of the fiber of the present invention. There is no particular limitation on the degree of polymerization of the island component polymer, but it is important that the island component does not contribute to the fiber strength but to the adhesiveness. ~ 1000 is preferred.

The sea component / island component blend ratio of the sea-island fiber of the present invention is in the range of 98/2 to 55/45 by weight. If the content of the high melting point PVA polymer of the sea component is less than 55%, high strength fibers cannot be obtained. The high melting point PVA-based polymer is less than 55%, and the low melting point water resistant polymer is 4%.
When it is more than 5%, the low melting point water resistant polymer tends to become a sea component, which is not preferable in terms of hardening. On the other hand, if the low-melting-point water resistant polymer is less than 2%, the thermocompression bonding performance that can be practically used cannot be obtained. From the balance of strength and thermocompression bonding property, the sea / island blend ratio is more preferably 95/5 to 60/40, and further preferably 92/8 to 70/30.

In the fiber of the present invention, the low melting point polymer of the island component is not preferably present in the outermost surface layer of the fiber, but is preferably present in the vicinity of the outermost surface layer. The minimum thickness of the sea component (closest distance to the fiber outermost surface of the low melting point polymer of the island component) near the outermost layer is that the high melting point PVA polymer of the outermost layer breaks during thermocompression bonding, and the low melting point water resistance of the island component It is important for the polymer to be extruded on the surface and for adhesion.
It is preferable that at least a part of the island component is present within 0.01 to 2 μm from the outermost layer. The island component may be uniformly distributed in the fiber cross-sectional direction, but it is preferable to distribute it more concentratedly on the surface side. Further, the island component may be continuous in the fiber axis direction, but is not necessarily continuous, and may be spherical or intermittent long and thin rod-like or rugby ball-like.

The fiber of the present invention has a strength of 7 g / dr or more. When the strength is less than 7 g / dr, for example, when it is used as a main fiber of a heat-sealable wet non-woven fabric, which is one of the applications of the fiber of the present invention, if the strength of the single fiber is weak, only low strength paper can be obtained. In the dry non-woven fabric capable of thermocompression bonding, which is one of the other applications, if it is a high-strength fiber,
It is possible to reduce the basis weight, and the nonwoven fabric becomes flexible,
The handling property and drapeability are improved, but it is difficult to reduce the basis weight when the fiber strength is low. Further, as the fiber strength increases and the nonwoven fabric becomes stronger, the production speed of the nonwoven fabric also improves. Even when the fiber of the present invention is blended with a hydrophilic cellulosic substrate as a base cloth for wet wipers, there is a great merit that the blending amount can be reduced if the fiber strength is high. The fiber of the present invention exerts its function by thermocompression bonding. It is important to have sufficient strength even if the strength is slightly lowered by thermocompression bonding, and for this purpose, the strength before thermocompression bonding is required to be high. The fiber of the present invention has a strength of 8 g.
/ D or more is more preferable, and even more preferably 10 g / d.

As described above, in the fiber of the present invention, in contrast to the core-sheath composite heat-adhesive fiber in the conventional hydrophobic polymer in which the core is the high melting point polymer and the sheath is the low melting point polymer, the sea component is High melting point polymer, island component low melting point polymer, usually high orientation, high crystallinity high melting point PVA
Excellent polymer performance due to the base polymer, the high melting point PVA polymer phase of the fiber outermost layer is broken during thermocompression bonding (high temperature and high pressure application), forming islands near the surface layer. The polymer is extruded on the surface of the fiber and adheres to the water resistant polymer of the island component of another fiber, or to the high melting point polymer of the sea component to ensure thermocompression bonding. Highly oriented and highly crystallized high melting point PVA polymer forms a matrix phase, so even if the island component is low oriented and low crystalline low melting point water resistant polymer, it has excellent strength and dimensional stability, and thermocompression bonding Since the matrix phase is not greatly affected by the time, the dimensional change during thermocompression bonding is small and high strength can be obtained even after thermocompression bonding.

In the present invention, the thermocompression bonding means that the fibers are bonded by applying a linear pressure of 1 kg / cm or more or a surface pressure of ² kg / cm ² or more at a temperature of 80 ° C. or more. When the temperature is less than 80 ° C., the linear pressure is less than 1 kg / cm, or the surface pressure is less than 2 kg / cm ² , the high melting point PVA polymer phase of the outermost layer is not broken, and the low melting point water resistant polymer of the island component is extruded on the fiber surface. Since it does not come, the adhesive strength is low. By heating the high melting point polymer of the outermost layer and applying pressure in a softened state, the polymer phase of the outermost layer is broken, and the low melting point polymer of the adhesive component near the surface layer can be extruded and adhered. If the thermocompression bonding temperature is too high, the molecular orientation of sea components and even crystals may be broken.
Should not be above 0 ° C. The appropriate pressure bonding temperature varies depending on the sea / island polymer specifications, distribution state, applied pressure, etc., but is preferably 100 to 210 ° C., more preferably 120 to 200 ° C., and further preferably 130 to 190 ° C. If the applied pressure is too high, the fiber structure of the sea component will be broken, and the fiber strength after thermocompression bonding will be reduced, which is not preferable. The linear pressure applied by a thermal calendar roller or the like is preferably 500 kg / cm or less. Linear pressure is 200k
More preferably g / cm or less, 100 kg / c
It is more preferably m or less. The surface pressure by hot pressing or the like is preferably 1000 kg / cm ² or less. Surface pressure is 40
More preferably 0 kg / cm ² or less, 200 k
It is more preferably g / cm ² or less. Usually 5-5
Linear pressure of 0 kg / cm or 10 to 100 kg / cm ²
Surface pressure is used. The thermocompression bonding time can be as short as 0.01 to 10 seconds or so. The ability to bond in a short time is a very important property of the thermocompression bonding method. In the case of the fiber of the present invention, if the thermocompression bonding time is set to 10 minutes or longer, the adhesive force tends to decrease rather. The cause is unknown,
It is assumed to be related to the crystallization of the polymer. For this reason,
The linear pressure application type thermal calender roll method, which has a shorter treatment time, is more preferable than the surface pressure application type heat press method, which has a longer treatment time, and can be preferably used for thermocompression bonding.

Next, a method for producing the fiber of the present invention will be described. The above-mentioned high melting point PVA-based polymer and low melting point water resistant polymer are dissolved in a solvent at a ratio of 98/2 to 55/45 to obtain a spinning dope. The solvent mentioned here must be a solvent that dissolves at least the high melting point PVA polymer. A common solvent that also dissolves the low-melting point water-resistant polymer is more preferable, but it is not always necessary to use it, but it can be used if it can be pulverized and dispersed so as to be dispersed in a high-melting point PVA-based polymer solution to 10 μm or less. . Dispersed particle size is 5
It is preferably μ or less, more preferably 1 μ or less. Even if dissolved in a common solvent for both polymers, a homogeneous transparent solution cannot be obtained depending on the compatibility of both polymers. Rather, it is a polymer blend solution in which the high melting point PVA polymer is finely dispersed in the matrix (sea) phase and the low melting point water resistant polymer droplets are finely dispersed in the island phase in the spinning stock solution state, resulting in a turbid homogeneous finely dispersed phase separation liquid. It is preferable that Of course, when the compatibility of both polymers is good, it becomes a uniform transparent solution,
The fiber of the present invention can be produced if the undiluted solution and the spinning conditions are set so that the high-melting point polymer becomes the sea component during fiberization.

Specific examples of the solvent used in the method for producing the fiber of the present invention include dimethyl sulfoxide (hereinafter abbreviated as DMSO), dimethylacetamide, N-methylpyrrolidone,
Examples thereof include polar solvents such as dimethylimidazolidinone, polyhydric alcohols such as glycerin and ethylene glycol, strong acids such as nitric acid and sulfuric acid, concentrated aqueous solutions such as rhodan salts and zinc chloride, and mixed solutions of these solvents. DMSO is particularly preferable in terms of low-temperature solubility, low toxicity, low corrosion and the like. Add both polymers to the solvent and stir to dissolve, or strongly stir to finely disperse when dissolving, especially when it becomes a phase-separated liquid, and also perform low-speed stirring to the extent that bubbles do not bite so as not to coagulate and settle while leaving degassing. Consideration such as continuing is preferable.

Next, although the viscosity of the spinning dope varies depending on the spinning method, it is 5 to 500 at the temperature near the nozzle during spinning.
0 poise is preferred. For example, in dry spinning, 500 to 50
The polymer concentration and the undiluted solution temperature are adjusted so as to be 00 poise, 80-800 poise for dry-wet spinning, and 5-200 poise for wet spinning. In addition to both polymers, a compatibilizer, a phase separation accelerator, etc. may be appropriately added for controlling the sea-island structure of both polymers in the spinning stock solution state and the fiber state. Various additives may be added to the stock solution for other specific purposes. For example, with antioxidants, light stabilizers, UV absorbers for preventing polymer deterioration, pigments and dyes for fiber coloring, surfactants for controlling interfacial tension, acids or alkalis for pH adjustment, etc. is there.

Next, the obtained stock solution is subjected to dry spinning, dry wet spinning or wet spinning. In dry spinning, the high melting point polymer is a matrix (sea component) while the solvent evaporates.
Select the spinning and drawing conditions so that the low melting point polymer becomes islands,
The obtained fiber is wound up. In dry-wet spinning, the stock solution is once discharged from a nozzle into an inert gas layer (for example, an air layer), then passed through a solidification solution, solidification and extraction of the stock solution solvent are performed, wet drawing and dry heat drawing are performed, and the film is wound up. . Or in wet spinning, the stock solution is directly discharged from the nozzle to the solidifying solution,
After solidification and extraction, wet stretching and dry heat stretching are applied and wound up. In either spinning method, it is necessary to consider the stock solution and spinning conditions so that the high melting point polymer becomes the sea component and the low melting point polymer becomes the island component. Specifically, it is effective to increase the blending ratio of the high melting point polymer to be the sea component. In addition, it is effective to set the stock solution and the spinning conditions so as to facilitate phase separation.

Further, in the present invention, since the strength is 7 g / d or more, a uniform solidified yarn is obtained in the solidifying process. To confirm that uniform solidification was performed, the cross section of the fiber after stretching was observed with an optical microscope, and when a fiber having a substantially circular cross section was obtained, it can be determined that uniform solidification was performed. Conventionally, when a concentrated Glauber's salt aqueous solution generally used for spinning PVA is used in the solidifying bath, the solidification becomes nonuniform, resulting in a cocoon-shaped cross section and insufficient stretch orientation.
/ D or more cannot be obtained. In addition, when boric acid is added to the stock solution and solidified in an alkaline dehydration salt bath, compared to the case where a concentrated aqueous solution of Glauber's salt is used in the solidification bath, the solidification approaches uniform solidification, resulting in a flat cross section, but not a circular shape. Is insufficient. On the other hand, alcohols such as methanol and ethanol, ketones such as acetone and methyl ethyl ketone, aliphatic esters such as methyl acetate and ethyl acetate,
Also, when an organic solvent having a solidifying ability for the high melting point PVA-based polymer, which is a sea component such as a mixed solvent of these and a stock solution solvent, is used in the solidifying bath, uniform solidification occurs, so that the cross section becomes substantially circular, Sufficient oriented crystallization can be performed by subsequent wet stretching and dry heat stretching, and strength of 7 g / dr or more can be achieved. The cross-sectional shape of the fiber referred to in the present invention can be observed by using an ordinary optical microscope. In order to obtain a more uniform gel yarn, it is preferable to set the temperature of the solidifying bath to a low temperature of 0 to 10 ° C. It should be noted that these solidifying baths do not necessarily have to have solidifying ability with respect to the low-melting point water-resistant polymer that is the island component. Extremely low melting polymers can be spun even if they are soluble in the setting bath. In this case, however, if the blending ratio of the high melting point polymer / low melting point polymer is more than 6/4, the amount of the low melting point polymer is too large, it will be eluted in the solidifying bath and the fibers will be hardened, which is not preferable. 7
It is more preferable that the low melting point polymer is less than / 3. When the low-melting point polymer is soluble in the solidifying bath, the low-melting point polymer tends to move in the surface direction of the solidified thread with the stock solution solvent during solidification, and tends to be distributed more in the surface layer than in the central part of the fiber. It has been found that an unexpected preferable tendency is that the decrease in the thermocompression bonding property, which is the object of the present invention, is small even if the blending amount of the melting point polymer is small. If the blending amount of the low melting point polymer is small, there is also an advantage that high strength fibers can be obtained.

Next, the use of the fiber of the present invention will be described.
The fibers of the present invention can be effectively used for fabrics for industrial materials such as tents and cold chillers, sewing threads, and non-woven fabrics. As a typical example, non-woven fabrics will be described. A dry nonwoven fabric or a wet nonwoven fabric containing at least 10% of the fiber of the present invention has a linear pressure of 1 kg / cm or more or a surface pressure of 2 at a temperature of 80 to 230 ° C.
It is a nonwoven fabric that can be heat-bonded by thermocompression bonding under the condition of kg / cm ² or more. The nonwoven fabric containing less than 10% of the fiber of the present invention cannot obtain practical thermocompression bonding under the above thermocompression bonding conditions. In order to further enhance the thermal adhesive force when the nonwoven fabric of the present invention is thermocompression bonded, the content of the fiber of the present invention is preferably 20% or more, and more preferably 30% or more. When the nonwoven fabric of the present invention is composed of the fibers of the present invention alone or the fibers of the present invention and other water resistant fibers such as water resistant vinylon, a water resistant and thermocompression-bondable nonwoven fabric is obtained. This non-woven fabric can be bonded by thermocompression bonding when it is formed into a three-dimensional structure such as a bag or a pot. Compared with the conventional molding process using chemical adhesive, it is faster, simpler, and pollution-free.
Since the molding process can be performed in a safe process, it is possible to greatly reduce the molding cost. The nonwoven fabric of the present invention is characterized in that a water-resistant three-dimensional structure can be produced by molding by thermocompression bonding. Therefore, it can be effectively used, for example, in tea bags, drainage bags, wet wipers, paper pots and the like.

In addition, hydrophilic vinylon fibers and rayon,
The non-woven fabric of the present invention, which is obtained by adding 10% or more of the present fiber to cellulose fiber such as cupra, polynosic, solvent-based cellulose fiber, and cotton, can be thermocompression-bonded, and when it is processed into a three-dimensional structure, conventional chemical adhesion is used. It is possible to apply the thermocompression bonding method having the above advantages as compared with the case of using the agent. The thermocompression-bonded three-dimensional structure has sufficient strength even when it comes into contact with water or hot water. Particularly, the island component polymer of the fiber of the present invention is PVA represented by ethylene / vinyl alcohol copolymer or ethylene / vinyl acetate copolymer. When it is a polymer, it is characterized in that it exhibits extremely excellent adhesive strength to vinylon fibers and cellulosic fibers. Therefore, it becomes possible to secure the heat-sealing property of a cellulose-based or vinylon-based non-woven fabric, which has been difficult in the past. Cellulose fibers are attracting attention as natural-disintegrating, earth-friendly fibers, but when molding non-woven fabric containing cellulose fibers into a three-dimensional structure, conventionally, chemical adhesives have been used to prepare adhesives → Although a complicated process such as quantitative application → drying / curing is performed, or the heat-bonding method is used to bond the hydrophobic heat-bondable fibers, the hydrophobic heat-bondable fibers have low adhesion to the cellulose fibers. Therefore, only a low-strength nonwoven fabric can be obtained. When the nonwoven fabric of the present invention is used, it can be molded by a thermocompression bonding method (heat sealing method) and can be easily incorporated into an automated line at high speed, with ease and without pollution, and can be manufactured. Moreover, the fiber of the present invention is
Since it is a hydrophilic fiber, when the vinylon fiber or the cellulose fiber is made into a nonwoven fabric by a wet method, it has excellent uniform dispersibility with the vinylon fiber or the cellulose fiber, so that a nonwoven fabric having uniform performance can be obtained. Become.

The method for producing the nonwoven fabric of the present invention is not limited. The staple obtained by crimp-cutting the fiber of the present invention alone or mixed with the above water-resistant vinylon staple or rayon, cellulose fiber staple such as polynosic, is subjected to card or random webber, and the obtained web is needle punched. Method, a chemical bonding method, a heat bonding method, or the like, and bonded or entangled to form a nonwoven fabric by a dry method. Further, the fiber of the present invention is 1 to 10 m.
Shortcut to m, if necessary, pulp, rayon,
A wet process non-woven fabric (including paper) can be prepared by mixing with vinylon or the like. The obtained non-woven fabric is characterized by having thermocompression bonding properties (heat sealing properties). The fiber of the present invention has a fusing temperature in water of 100 ° C. or higher and can be used as a main fiber, and heat-sealable vinylon paper or heat-sealable cellulose paper can be obtained by making paper using a conventional vinylon binder or thermocompression-bonding type binder. can get. The dry method or the wet method should be appropriately selected depending on the performance required for the application. However, the preferred method for producing the nonwoven fabric of the present invention utilizes the thermocompression bonding property of the fibers of the present invention, a web containing 10% or more of the fibers of the present invention at a temperature of 80 to 230 ° C. and a linear pressure of 1 kg / cm or more or a surface pressure. This is a method for producing a non-woven fabric, which comprises thermocompression bonding under a condition of ² kg / cm ² or more. The temperature and pressure which are the thermocompression bonding conditions in the present invention are the temperatures and pressures actually applied to the web, not the set temperature and the set pressure.
The actual temperature and pressure can be measured by a thermo label or a pressure indicator. If the pressure bonding temperature is less than 80 ° C., or if the linear pressure is less than 1 kg / cm or the surface pressure is less than 2 kg / cm ² , the adhesive strength by thermocompression bonding is low and it cannot be put to practical use. When the pressure bonding temperature exceeds 230 ° C., the melting point of the PVA-based polymer of the sea component forming the matrix becomes close to, and the fiber structure that is oriented and crystallized is broken,
The fiber strength is reduced or the fiber shrinks. From the viewpoint of adhesiveness by thermocompression bonding, fiber strength after compression bonding, and dimensional stability, the temperature is 100 to 210 ° C., the linear pressure is 2 to 200 kg / cm,
Alternatively, the surface pressure is more preferably 5 to 400 kg / cm ² , the temperature is 130 to 190 ° C., and the linear pressure is 5 to 50 kg / cm ^2.
It is more preferable that the cm or the surface pressure is 10 to 100 kg / cm ² .

The non-woven fabric produced by the thermocompression bonding method of the web of the present invention alone or a web obtained by mixing the conventional water-resistant vinylon with 10% or more of the present fiber is water-resistant and is extremely hydrophilic as a hydrophilic non-woven fabric. It is useful. In the conventional production of hydrophilic non-woven fabric, a step of applying an adhesive during the production step and a drying or curing step for expressing the adhesive strength are indispensable, and moreover, it takes 1 minute or more for the drying or curing to be expensive. In addition to the need for capital investment, the line speed must be suppressed to ensure quality, making high-speed manufacturing difficult. In addition, during the adhesive application step-drying / curing step, the adhesive or its denatured material adheres to the equipment, which causes defects in the nonwoven fabric,
It is necessary to stop the operation of the equipment to remove adhered substances and wash them. On the other hand, when a hydrophilic nonwoven fabric is manufactured using the nonwoven fabric manufacturing method of the present invention, since the bonding step is a thermocompression bonding method, bonding can be performed within 3 seconds only by passing it through a thermal calendar roller, and high-speed and simple manufacturing is possible. . Further, since no adhesive is used, the adhesive and its degenerated substances do not adhere to the equipment, so that no defect occurs in the nonwoven fabric, and therefore it is not necessary to stop the operation of the equipment for washing and removing the adhered material. The use of the fiber of the present invention makes it possible for the first time to produce a hydrophilic and water-resistant non-woven fabric by a thermocompression bonding method, and it has become possible to produce it at high speed, simply and without pollution.

The definition of the parameters and the measuring method thereof in the present invention are as follows. 1. Melting point In the case of a crystalline polymer, a differential scanning calorimeter (DSC-20) manufactured by METTLER CORPORATION was used, and the sample polymer was placed under nitrogen at 20
When the temperature is raised at a rate of ° C / min, the temperature showing an endothermic peak is measured.

2. Fusing temperature In the case of an amorphous polymer, when the polymer chips are placed in a hot air dryer at a specified temperature and a pressure of 0.1 kg / cm ² is applied for 10 minutes, the chips melt to the extent that the boundaries between the chips cannot be determined. Measure the lowest temperature to wear.

3. Fiber strength In accordance with JIS L-1015, the single fiber strength is 20m.
m, tensile rate 50% / min.

[0034]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the examples,% is a value based on weight unless otherwise specified. Example 1 Polymerization degree 1750, saponification degree 99.9 mol%, melting point 23
PVA at 3 ° C., ethylene / vinyl alcohol copolymer = 32/68 (molar ratio), polymerization degree 870, melting point 18
EVAL-F manufactured by Kuraray Co., Ltd. at 6 ° C. was mixed and stirred in DMSO at 90 ° C. under nitrogen so as to be 15% and 5% respectively, and dissolved. The high melting point PVA-based polymer / low melting point water resistant polymer blend ratio was 75/25. The obtained blend solution was a semi-turbid solution having a good spinnability and did not tend to separate into two phases even when left at 90 ° C. for 8 hours, and was a stable dispersion solution.

This spinning dope was prepared with a pore diameter of 0.08 mm and a pore number of 5
00 nozzle, methanol 70% and DMSO30
Wet spinning in a solidification solution of 3% at 3 ° C. The obtained solidified itinose was cloudy, and it was estimated that both PVAs were phase-separated. At this time, no special turbidity was generated in the solidified liquid. This solidified yarn is subjected to 5.0 times wet drawing,
DMSO in the solidified silkworm was extracted and washed by immersion in a methanol solution, a mineral oil-based oil agent was added, and the mixture was dried at 100 ° C. and then dry-heat stretched at 225 ° C. so that the total stretching ratio was 15 times. The obtained filament of 1000 dr / 500f had no sticking, the melting temperature in water was 125 ° C, and the water resistance was good. The single yarn strength was 12.3 g / dr. In addition, from the cross-sectional observation, it is a circular cross-section, PVA with a high melting point is a sea component, and EVAL-F with a low melting point is an island component, and the number of islands is at least 100. It was found that many island components exist within 1 μm.

This fiber is stapled, and a web having a basis weight of 30 g / m ² is made on a card, and a temperature of 190 is applied to the web.
A thermocalender roll treatment was performed under thermocompression bonding conditions of a temperature of 60 ° C., a linear pressure of 60 kg / cm, and a treatment time of 1 second or less. There was not much dimensional change due to calendering. The obtained non-woven fabric is well adhered, and even if it is rubbed with force by hand, the single yarn does not come apart, and the length is 6.8 km and the width is 2.2 km.
Showed a breaking length of. Further, even if the non-woven fabric after thermocompression bonding was put into boiling water, no special change was observed and the water resistance was good.

Comparative Example 1 Only PVA having a polymerization degree of 1700 and a saponification degree of 99.9 mol%, which is the high melting point PVA of Example 1, was dissolved in DMSO in the same manner as in Example 1 so as to be 16%. The obtained solution was a uniform transparent liquid. This spinning stock solution was subjected to spinning and drawing in the same manner as in Example 1. The solidified Ishino is almost transparent, and Example 1
No white turbid phase separation was observed. When the cross section of the obtained fiber was observed, it was uniform and no sea-island structure was observed. This fiber was stapled in the same manner as in Example 1,
A card was applied to make a web, and the web was thermocompression bonded. The obtained non-woven fabric seemed to be adhered at first glance, but when it was rubbed by hand, the single yarn was peeled off, and only the breaking length of 0.4 km in length and 0.1 km in width was obtained, and only a weak non-woven fabric was obtained.

Comparative Example 2 Only EVAL-F, which is the low melting point component of Example 1, was added to DMS.
It was dissolved in O in the same manner as in Example 1 so as to be 26%. The resulting solution was clear. An attempt was made to spin this spinning dope in the same manner as in Example 1, but the solidifying solution was methanol / DM.
When SO = 70/30, it did not solidify and could not be spun. Even if the solidified liquid was 100% methanol, it did not solidify and could not be spun. Spinning was possible by changing the solidifying liquid to 100% acetone and changing the wet drawing bath and the extraction bath to acetone. When wet drawing was performed 4.5 times and dried at 80 ° C., fibers with almost no sticking were obtained. The solidified Ishino was almost transparent, the cross section of the obtained fiber was uniform, and the sea-island structure could not be observed. This fiber was stapled in the same manner as in Example 1, carded, a web was formed, and thermocompression bonding was performed. The size of the web shrank by more than half during thermocompression bonding, and the obtained product had good adhesion, but it was coarse and hard and could not be said to be a non-woven fabric.

Comparative Example 3 Spinning and drawing were carried out in the same manner as in Example 1 except that the blending ratio of PVA and EVAL-F was 99/1. The obtained fiber had a circular cross-section without sticking and had a high strength of 15.4 g / d. This was stapled in the same manner as in Example 1, hung on a card to make a web, and subjected to thermocompression bonding. The obtained non-woven fabric seemed to be adhered at first glance, but it was easily peeled off by rubbing with a hand, and the non-woven fabric strength was low. When the amount of the low melting point component is small like the fiber of this comparative example, the effect of improving the thermocompression bonding property is insufficient.

Comparative Example 4 Spinning and drawing were attempted in the same manner as in Example 1 except that the blending ratio of PVA and EVAL-F was 50/50. However, after drying, the thread was severely stuck and the cross section was deformed, and a normal thread could not be obtained. Turbidity was observed in the solidified liquid. It is presumed that EVAL-F did not form a complete island component but formed a part of the sea component phase.

Example 2 Polymerization degree 1750, saponification degree 99.3 mol%, melting point 23
PVA at 3 ° C., ethylene / vinyl alcohol copolymer = 47/53 (molar ratio), polymerization degree 750, melting point 16
Blending ratio with Kuraray EVAL-G at 3 ℃ is 80/2
The mixture was mixed so that the total PVA concentration was 25%, and the mixture was heated and dissolved in DMSO at 90 ° C under nitrogen under stirring. The obtained blended solution was considerably turbid, but it was a stable dispersion without showing a tendency to aggregate and separate into two phases when left standing for 8 hours. The spinning solution was dry-wet spun into the same solidifying solution as in Example 1 through an air gap of 12 mm from a nozzle having a hole diameter of 0.12φ and a hole number of 80. The obtained solidified itinose was cloudy, and it was estimated that both PVAs were phase-separated. At this time, no special turbidity was generated in the solidified liquid. The solidified itoshino was wet-stretched, extracted, oiled, and dried in the same manner as in Example 1. Then, at 225 ° C., the total draw ratio is 12.
It was subjected to dry heat drawing so as to have a draw ratio of 5 to obtain a filament of 240 d / 80 f. This fiber has no sticking, has a water fusion temperature of 124 ° C. in water and has good water resistance, and has a single yarn strength of 13.
It was 1 g / dr. In addition, from cross-section observation, it is a circular cross-section, PVA with a high melting point is a sea component, and EVAL-G with a low melting point.
It was found that the island component was dispersed to 100 or more, and a large number of island components were present within 1 μm from the outermost surface.

This fiber was stapled to give a web having a basis weight of 30 g / m ² on a card, and a temperature of 190
A thermocalender roll treatment was performed under thermocompression bonding conditions of a temperature of 60 ° C., a linear pressure of 60 kg / cm, and a treatment time of 1 second or less. There was not much dimensional change due to calendering. The obtained non-woven fabric was well adhered, and even if it was rubbed by hand, the single yarn was not distorted, and showed a breaking length of 7.1 km in length and 1.4 km in width. Further, even if the non-woven fabric after thermocompression bonding was put into boiling water, no special change was observed and the water resistance was good.

This fiber was cut into 3 mm, and Kuraray papermaking vinylon VPB-105 (binder fiber) was mixed and dispersed in water, paper-made by a tappy paper making machine, dehydrated and drum-dried. A paper having a basis weight of 30/10/105 and a basis weight of 30 g / m ² was obtained. The paper was heat-sealed on both sides with a Fuji Impulse policyr. The adhesive strength of the seal portion was VPB-102 (main fiber of vinylon for commercial Kuraray papermaking) / VPB-105 = 90/10, which was clearly superior to the paper similarly subjected to papermaking, drying and heat sealing. It was estimated that the sealing temperature at this time was 210 ° C. and the pressure was 2 kg / cm.

Example 3 While stirring DMSO, the degree of polymerization was 2400 and the degree of saponification was 9
PVA with a melting point of 235 ° C. and a polymerization degree of 9
40, ethylene / vinyl acetate = 32 / with a fusion temperature of 50 ° C or less
A 68% (molar ratio) copolymer of 35% methanol solution was added, the atmosphere was replaced with nitrogen, and the mixture was heated and dissolved at 90 ° C. PVA /
The ethylene-vinyl acetate copolymer was mixed so that the blending ratio was 9/1, and dissolved so that the total polymer concentration was 20%. The obtained solution was cloudy, but there was no tendency for aggregated phase separation. This spinning dope was wet spun in the same manner as in Example 2 and subjected to dry heat drawing at 220 ° C. so that the total draw ratio was 14 times, to obtain a filament of 2500 d / 1000 f. This fiber does not have sticking and its fusing temperature in water is 128.
C., and the single yarn strength was 15.7 g / dr. Further, from the cross-sectional observation, it was found that the ethylene / vinyl acetate = 32/68 (molar ratio) copolymer was an island component, and many island components were present within 1 μm from the outermost surface.

This fiber was stapled, and a web having a weight per unit area of 30 g / m ² was formed on a card, and a temperature of 160 g was applied to the web.
A heat calender roll treatment was performed under thermocompression bonding conditions of a temperature of 20 ° C., a linear pressure of 20 kg / cm, and a treatment time of 1 second or less. There is not much dimensional change due to calendering, the obtained non-woven fabric is well adhered, the single yarn does not break even if it is rubbed by hand, and shows a breaking length of 6.6 km in length and 1.6 km in width,
The strength was sufficient for practical use. In addition, no change was observed when the non-woven fabric after thermocompression bonding was added to hot water at 100 ° C., and good water resistance was exhibited. When two non-woven fabrics are stacked and heat-sealed on three sides with a Fuji Impulse policyr, they can be processed into a bag shape and have an adhesive force that does not easily peel off even if peeled by hand. Was obtained only by the thermocompression bonding method.

Example 4 30% of the staple of the present invention obtained in Example 3 and 70% of 2d vinylon staple were mixed, and 40 g of a basis weight was applied to a card.
/ M ² web, temperature 180 ℃, linear pressure 2
The heat calendar roll treatment was performed under the thermocompression bonding conditions of 0 kg / cm and a treatment time of 1 second or less. There was not much dimensional change due to calendering, the obtained non-woven fabric was well adhered, and even if it was rubbed by hand, the single yarn did not come apart.

[0047]

According to the present invention, a high melting point PVA polymer is mixed with a high melting point PVA polymer and a low melting point water-resistant polymer at a predetermined blending ratio and subjected to uniform low temperature solidification spinning to obtain a high melting point PVA polymer. The low melting point water resistant polymer is used as an island component, and the low melting point water resistant polymer is not present on the outermost surface of the fiber, but is allowed to exist very close to the surface layer and has high strength. By using such fibers,
A high-strength hydrophilic fiber having thermocompression bonding properties, which was difficult in the past, was obtained.
In particular, the fiber of the present invention has a high melting point and a high saponification degree PVA as a matrix and is present in the sea component to be highly oriented and highly crystallized, and the dimension is stable even under wet conditions. However, upon thermocompression bonding, the matrix phase on the outermost surface is broken, the low melting point polymer of the island component is extruded onto the fiber surface, and the fibers are bonded together. Since the high melting point PVA polymer phase of the matrix phase does not melt during thermocompression bonding, there is almost no dimensional change and high strength can be maintained even after thermocompression bonding. As described above, the fiber of the present invention is a PVA fiber having both water resistance, thermocompression bonding property, and high strength, and when used in the field of non-woven fabrics, fabrics for industrial materials, etc., hydrophilicity, high strength, which are characteristics of PVA fiber, Bonding by thermocompression bonding is possible while maintaining high Young's modulus, high weather resistance, and high chemical resistance, so high-speed production without pollution is possible with a simple process. Further, since the non-woven fabric obtained by the dry method and the wet method has thermocompression bonding property,
When molding into a three-dimensional structure (eg, bag, pot, box) or the like, a thermocompression bonding method can be used, and heat sealing can be performed, so that the molding can be efficiently performed at high speed. Further, when it is mixed with a hydrophilic material such as vinylon or rayon to form a non-woven fabric, it can be bonded by thermocompression bonding, and a high-strength non-woven fabric can be produced only with the hydrophilic material.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Shunpei Naramura, 1621 Sakazu, Kurashiki, Okayama Prefecture, Kuraray Co., Ltd. (72) Inventor Satoru Kobayashi, 1621, Satsuki, Kurashiki, Okayama, Kuraray Co., Ltd. (72) Inventor Yosuke Sekiya 1-1239 Umeda, Kita-ku, Osaka City Kuraray Co., Ltd.

Claims (5)

[Claims] 1. A sea-island structure fiber in which a polyvinyl alcohol-based polymer having a melting point of 220 ° C. or higher is a sea component, and a water-resistant polymer having a melting point or a fusion temperature of less than 210 ° C. is an island component, both polymers Blend ratio of 98
/ 2 to 55/45, and strength is 7 g / dr
The polyvinyl alcohol fiber having high strength, water resistance, and thermocompression bonding characteristics as described above. 2. A sea-island structure fiber in which a polyvinyl alcohol-based polymer having a melting point of 220 ° C. or higher is a sea component, and a water-resistant polymer having a melting point or a fusion temperature of less than 210 ° C. is an island component, both polymers Blend ratio of 98
/ 2 to 55/45, at least a part of the island component is within 2 μm from the outermost surface of the fiber, and the strength is 7
A polyvinyl alcohol fiber having high strength, water resistance, and thermocompression bonding, which is characterized by having g / dr or more. 3. A polyvinyl alcohol polymer having a melting point of 220 ° C. or higher and a water resistant polymer having a melting point or a fusion temperature of less than 210 ° C. in the range of 98/2 to 55/45 and a melting point of 220 ° C. or higher. A polyvinyl alcohol-based polymer having a melting point of 220 ° C. or higher is a sea component, and a mixed solution or a mixed dispersion obtained by mixing and dissolving the polyvinyl alcohol-based polymer in a solvent is water-resistant, and the melting point or the fusion temperature is less than 210 ° C. Of high-strength, water-resistant and thermocompression-bonding polyvinyl alcohol fiber characterized by performing solution spinning so that the water-soluble polymer becomes an island component, uniform solidification spinning, and wet stretching and dry heat stretching . 4. A dry non-woven fabric or wet non-woven fabric containing at least 10% of the fiber according to claim 1, having a temperature of 80.
~ 230 ° C, linear pressure 1kg / cm or more or surface pressure 2kg /
A non-woven fabric characterized by being able to be crimped by thermocompression bonding with a cm ² or more. 5. A web containing at least 10% of the fiber of claim 1 is applied at a pressure of 80 to 230 ° C. and a linear pressure of 1 k.
A method for producing a non-woven fabric, which comprises thermocompression-bonding under a condition of g / cm 2 or more or a surface pressure of 2 kg / cm ² or more.