JPH083848A - Nonwoven fabric being water soluble at low temperature and production thereof - Google Patents

Abstract

PURPOSE:To obtain a nonwoven fabric being water soluble at a low temperature, having thermally bonding property and heat sealing property and suitable as a hygienic material, a medical material, etc., by using a polyvinyl alcohol- based fiber being water-soluble at a low temperature, having a specific melting point. CONSTITUTION:A polyvinyl alcohol-based fiber which is water-soluble at a low temperature, having 170-220 deg.C melting point is carded to form a web and subjected to thermal pressing treatment at a temperature which is 20-150 deg.C lower than the melting point under 3-100 kg/cm linear pressure to provide the objective nonwoven fabric being water-soluble at a low temperature, in which the water-soluble polyvinyl alcohol-based fiber existing in 3-50% area part of the surface is formed so as to have flat cross sections having 3-30 flat ratio and the tear length is 0.5-5km and a temperature at which it is dissolved in water is 0-40 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-temperature water-soluble non-woven fabric, which has thermo-compression bonding properties and heat-sealing properties, which have hitherto been difficult, and which dissolves in low-temperature water even after thermo-compression bonding, and its production. It is about law.

[0002]

2. Description of the Related Art Polyvinyl alcohol (hereinafter abbreviated as PVA) type fibers are used in large amounts in the field of wet non-woven fabrics as binder fibers for paper because they are capable of producing water-soluble fibers. The PVA binder fiber needs to be dispersed in normal temperature water (white water) and formed into a film when the wet paper is dried. Therefore, the dissolution temperature in water must be 50 to 80 ° C., and the PVA binder fiber is dissolved in water at 40 ° C. or lower. Doing fibers are inconvenient. Further, Japanese Patent Publication No. 54-29638 proposes a non-woven fabric in which an allyl alcohol-modified PVA fiber having a water dissolution temperature of 30 ° C. or lower and a water-soluble PVA-based fiber having a dissolution temperature of 50 ° C. or higher are mixed. Since the PVA-based fiber having a melting temperature of 50 ° C. or higher is used as the base fiber, the water dissolution temperature is 50 ° C. or higher. Many so-called water-decomposable non-woven fabrics that disintegrate and disperse when placed in normal temperature water have been proposed. For example, in JP-A-5-179548, it has been proposed to apply a salt-sensitive binder aqueous solution containing an unsaturated carboxylic acid salt to vinylon fiber or rayon fiber, but these water-decomposable nonwoven fabrics become separated at room temperature water. Although the non-woven fabric shape disappears, most of the fibers remain in water without being dissolved.

On the other hand, recently, various chemicals such as detergents, sizing agents, paints, agricultural chemicals, fertilizers, growth promoters, etc. are hermetically packaged in a water-soluble film in unit amounts, and the user puts the required number in the package into the water. However, a method of dissolving or dispersing the drug in water, that is, a unit packaging method has begun to be widely implemented. This method not only does not require the labor of weighing each time it is used, but it also has the merit that there is no worry of contaminating the user's body or environment such as hands, mouth, eyes, nose with drugs, and it is increasingly used. There is a direction. It goes without saying that the water-soluble film used for this unit packaging must be one that easily dissolves or swells in normal temperature water (seawater in some cases) and loses its form. The film for use must have mechanical strength (in particular, impact strength that can withstand transportation work under low temperature and low humidity), and a PVA-based film is generally used. In order to secure the strength of PVA-based film under low temperature and low humidity, a plasticizer such as glycerin may be added (external plasticization), or a partially saponified product or a copolymer with another monomer may be used (internal plasticization). , The glass transition temperature is lowered to make it soft at low temperature. However, if the glass transition temperature is low, the films stick to each other due to moisture absorption when stored at high temperature and high humidity, and if peeled off, they burst and must be stored in a dehumidifying bag or dehumidifying box. The water-soluble film at room temperature is a two-dimensional product having low crystallinity and low orientation, and it seems difficult to prevent extreme changes in mechanical properties under low temperature and low humidity and high temperature and high humidity.

[0004]

As sanitary materials, wiping materials, medical materials, unit packaging materials, etc.,
Most of it dissolves and disappears in low-temperature water of 40 ° C or lower, and even when the environment changes from low-temperature low-humidity (eg -30 ° C x RH10%) to high-temperature high-humidity (eg 40 ° C x RH90%), compared to water-soluble films. Although there is a great need for a non-woven fabric with significantly less change in physical properties, it has not been obtained by the conventional techniques. An object of the present invention is to provide a nonwoven fabric having the above performance at low cost by an efficient manufacturing process.

[0005]

[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 is a water-soluble PV having a melting point of 170 to 220 ° C.
A non-woven fabric composed of A-based fibers, which has a surface area of 3
The fibers present in an area of ˜50% have a flat cross section with a flatness in cross section of 3 to 30, and a breaking length of 0.5 to 5
It is a low temperature water-soluble nonwoven fabric characterized by having a dissolution temperature in water of 0 to 40 ° C., and as a method for producing the same, a web made of water-soluble PVA-based fibers having a melting point of 170 to 220 ° C. 20 to 150 from the melting point of the fiber by using a hot embossing roller having 3 to 50%.
The method uses thermocompression bonding at a low temperature of 3 ° C. and a linear pressure of 3 to 100 kg / cm.

The nonwoven fabric of the present invention has a melting point of 170 to 220 ° C.
Of water-soluble PVA fiber. Water-soluble fibers other than PVA-based fibers have low strength and cannot be put to practical use.
If the melting point of the PVA-based fiber exceeds 220 ° C., the melting temperature in water exceeds 40 ° C., and the low temperature water-soluble nonwoven fabric object of the present invention cannot be obtained. The melting point of PVA fiber is 170
If the temperature is lower than ℃, the crystallinity is low and a non-woven fabric that can be used practically cannot be obtained. The melting point of the PVA-based fiber is more preferably 190 to 220 ° C., and the melting point of 195 to 215 ° C. is most preferable from the viewpoint of balance between low-temperature water solubility and nonwoven fabric performance. As the PVA-based polymer that can be used for the water-soluble fiber used in the present invention, partially saponified PVA having a polymerization degree of 200 to 4500 and a saponification degree of 70 to 96 mol% is preferable. Further, vinyl compounds such as allyl alcohol, itaconic acid, acrylic acid, maleic anhydride and ring-opened products thereof, arylsulfonic acid, vinylpyrrolidone, ethylene, vinyl bivalate, fatty acid vinyl esters having 4 or more carbon atoms and the above ionic groups. A PVA-based polymer modified with a modification unit such as a neutralized product of a part or the whole amount thereof can also be suitably used.
The amount of the modifying unit is 0.2 to 10 mol%, preferably 1
~ 8 mol%. When the nonwoven fabric of the present invention is used as a packaging material for an alkaline drug or an absorbent for an alkaline liquid,
When partially saponified PVA is used, the portion in contact with alkali may be saponified and the water dissolution temperature may rise to 40 ° C. or higher. Therefore, when used in such applications, PVA-based polymer that is not saponified with alkali For example, allyl alcohol and ionic group copolymerized PVA-based polymers are more preferable. The melting point is set to 170 to 220 ° C. by controlling the degree of orientation and crystallinity of the PVA polymer.

The non-woven fabric of the present invention comprising the low temperature water-soluble PVA fiber thus obtained has a total surface area of 3 to 50%.
Is composed of fibers having a cross-sectional flatness of 3 to 30. If the area where the cross section of the fiber is flat is less than 3%, there are few bonded portions, and when the nonwoven fabric is sheared in the lateral direction, the single fiber comes off and fuzz is formed, which is not preferable in appearance. If the same area exceeds 50%, there are many bonded portions, the texture becomes hard, and the tear strength becomes low. More preferably, the area where the cross section of the fiber is flat is 6 to 40%,
It is more preferably 10 to 30%. When the cross-sectional flatness of the fiber is less than 3, the adhesive effect due to flattening is insufficient, and when the cross-sectional flatness exceeds 30, the strength of the fiber itself is lowered and the strength of the nonwoven fabric is lowered. It is more preferable that the flatness of the cross section is 5 to 20.

The breaking length of the nonwoven fabric of the present invention is 0.5 to 5 km. If the breaking length is less than 0.5 km, the strength is low and unsatisfactory. It is difficult to manufacture a low temperature water-soluble nonwoven fabric having a breaking length of more than 5 km at the current technical level. A major feature of the nonwoven fabric of the present invention is that the melting temperature in water is as low as 0 to 40 ° C. 40
The point of the present invention is to obtain a non-woven fabric that dissolves in water at a temperature of ℃ or below. Fibers with a cross-section flatness of 3 to 30 are 3 to 5
A nonwoven fabric containing 0% and soluble in water at 40 ° C. or lower has not been known. By using a non-woven fabric that is soluble in water at 40 ° C or lower, it can be used for the first time for sanitary materials, medical materials, wiping materials, and unit packaging materials that can replace water-soluble films. . Furthermore, the area shrinkage of the nonwoven fabric when the nonwoven fabric of the present invention is dissolved in water is preferably 40% or less.
A content of 30% or less is more preferable, and a content of 20% or less is most preferable because the nonwoven fabric is dissolved while almost maintaining the dimensions of the nonwoven fabric. If the nonwoven fabric shrinks by more than 40% when dissolved in water, the nonwoven fabric becomes a dango-like lump and the subsequent solubility is impaired, and substantially complete dissolution tends to be difficult. The PVA-based fiber preferably has a fineness of 0.1 to 10 denier.

The non-woven fabric of the present invention comprises the above low temperature water-soluble PVA.
In addition to the fibers, other fibers such as naturally disintegrating cellulosic fibers may be contained within the scope of the present invention. Further, the basis weight of the nonwoven fabric of the present invention is not particularly limited because it varies depending on the use, but when aiming at the above-mentioned use, the needle punching method tends to cause insufficient entanglement and a relatively low basis weight of 100 g / m ² or less is more preferable, and 5 to 40 g. / M ²
Is more preferable. Further, the nonwoven fabric of the present invention has thermocompression-bonding performance in making a final product such as a diaper or a unit packaging bag, that is, if it can be heat-sealed particularly at 160 ° C. or less, the final product can be highly efficiently produced. preferable. The inventors of the present invention have filed Japanese Patent Application No. 5-2581.
No. 17 proposes a water-soluble nonwoven fabric obtained by thermocompression bonding sea-island structure fibers in which a PVA-based polymer having a melting point of 210 ° C. or higher is a sea component and a water-soluble polymer having a melting point or a fusing temperature of less than 210 ° C. is an island component. However, the non-woven fabric is mainly used for chemical lace base fabric, etc., and has a water dissolution temperature of 40 ° C.
However, the nonwoven fabric of the present invention is different in that the essential condition is 40 ° C. or lower.

Next, a method for producing the fibrous nonwoven fabric of the present invention will be described. As described above, as the raw material polymer used in the present invention, partially saponified PVA or various modified PVA-based polymers are used. In the present invention, this polymer is dissolved in an organic solvent having a dissolving ability to prepare a spinning dope. The stock solution solvent used in the present invention is not particularly limited as long as it is an organic solvent having a solvent ability to the polymer, but dimethyl sulfoxide (hereinafter referred to as D
(Abbreviated as MSO), dimethylacetamide, dimethylformamide, polar solvents such as N-methylpyrrolidone, glycerin, ethylene glycol and the like. Particularly, DMSO is most preferable in terms of low temperature solubility, low toxicity and low corrosion. When a low saponification degree PVA-based polymer having a vinyl acetate unit is used in the present invention, if the spinning stock solution is strongly alkaline or acidic, a saponification reaction may occur during dissolution and defoaming, and the dissolution temperature in water may increase. Therefore, it is necessary to avoid adding strong alkaline substances such as caustic soda and strong acidic substances such as sulfuric acid in excess of the limit, but under weak alkaline conditions such as DMSO solution and addition of sodium acetate or under slightly acidic conditions. No saponification reaction occurs. In the case of a polymer having an ionic group such as carboxylic acid or sulfonic acid, the acidity of the spinning dope may be adjusted by adding caustic soda for neutralizing hydrogen ions. The polymer concentration varies depending on the polymer composition, the degree of polymerization, and the solvent, but is generally in the range of 6 to 60%.
It is preferable that the dissolution is carried out by stirring under reduced pressure after substituting with nitrogen, from the viewpoint of preventing oxidation, decomposition, crosslinking reaction and suppressing foaming. When a low melting point PVA polymer is used as in the present invention, addition of a solidifying solvent such as methanol to the stock solution improves the solidification ability of the stock solution and is effective in preventing sticking.

The spinning dope thus obtained is wet- or dry-wet spun in a solidifying bath mainly composed of an organic solvent having a solidifying ability for the polymer, that is, a solidifying solvent. The solidification referred to in the present invention means that the spinning stock solution with fluidity changes to a solid with no fluidity, and both the gelation and the coagulation of the stock solution that solidify without changing the composition of the stock solution change. Include. In the present invention, as the solidifying solvent having a solidifying ability for the polymer spinning dope, alcohols such as methanol, ethanol, propanol, butanol, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl acetate, ethyl acetate, etc. Examples thereof include aliphatic esters, aromatics such as benzene and toluene, and mixtures of one or more of these. It is also possible to mix the stock solution solvent with these solidifying solvents to form a solidifying bath. Among them, a mixture of methanol and a stock solvent is used for a PVA polymer having a low degree of modification, and methanol is not suitable for a PVA polymer having a high degree of modification. It is preferable to use the mixed solution of 1 or the mixed solution of acetone and the stock solution solvent in the solidifying bath. The mixing weight ratio of the solidifying solvent / the stock solution solvent is preferably 95/5 to 40/60. It is more preferably 90/10 to 50/50, and most preferably 85/15 to 55/45. By mixing the stock solution solvent with the solidifying bath, the solidifying ability can be adjusted and the cost for separating and collecting the stock solution solvent and the solidifying solvent can be reduced. The temperature of the solidification bath is not limited,
It is usually carried out between -20 and 30 ° C. From the viewpoint of homogeneous solidification and energy saving, the solidification bath temperature is preferably −10 to 20 ° C., more preferably −5 to 15 ° C., and 0 to 10 ° C.
It tends to be most preferable when the temperature is ° C. The spinning method of the present invention is not particularly limited whether it is wet spinning or dry-wet spinning. Any spinning method can be adopted if the spinning conditions suitable for each spinning method are set, but the wet spinning method is preferable from the viewpoint of suppressing sticking when Nozuru is porous.

The obtained Shinoshino is wet-stretched 2 to 8 times in a wet stretching bath composed of a solidifying solvent or a mixture of a solidifying solvent and a stock solvent. It is important to increase the wet draw ratio within the range where there is no fluff in order to suppress the sticking of Ishino. If the wet drawing is less than 2 times, it sticks hard, and if it exceeds 8 times, fluff tends to appear. In order to increase the wet drawing ratio, it is also effective to raise the temperature of the wet drawing bath to near the boiling point. It is also effective to carry out the wet drawing in two or more stages. After wet drawing, the Shinoshino is contacted with an extraction bath mainly composed of a solidifying solvent to extract and remove the stock solution solvent from the Shinoshino. In this extraction, the pure solidified solvent is continuously flowed in a countercurrent direction with respect to Isono, so that the stock solution solvent content of Isono can be reduced to 1% or less, preferably 0.1% or less in a short residence time. . The contact time is preferably 15 seconds or longer, and more preferably 20 seconds or longer. In order to increase the extraction rate and improve the extraction, the solidifying solvent is preferably heated. Generally, a method of performing wet drawing and then immediately drying without extracting and removing the solvent of the undiluted solution has been used, but in the case of a fiber made of a polymer that easily causes single-yarn hardening as in the present invention. The above-mentioned conventional method alone will cause single-yarn hardening during drying. Therefore, in the present invention, the solvent extraction treatment after wet drawing is an important step. After extraction, the Itoshino is dried in a gas bath at 150 ° C or lower. It is also effective to suppress hard adhesion by adhering a hydrophobic oil agent such as mineral oil-based, silicon-based or fluorine before drying, or by shrinking to reduce shrinkage stress during drying.

The spun raw yarn obtained as described above has a melting point of 1 by subjecting it to a dry heat constant length treatment, a dry heat stretching treatment, a dry heat shrinkage treatment, or a combination thereof.
A low temperature water-soluble PVA fiber having a dissolution temperature in water of 70 to 220 ° C. of 0 to 40 ° C. The heat treatment temperature for obtaining a normal highly oriented and highly crystalline water resistant PVA-based fiber is at least 22.
The temperature is 0 ° C. or higher, preferably 230 to 250 ° C., but the temperature of the heat treatment of the low temperature water-soluble PVA fiber used in the nonwoven fabric of the present invention (including any treatment of constant length, stretching and shrinkage) is at most 200 ° C. Below, preferably 80-180
° C, more preferably 100 to 150 ° C. The high temperature heat treatment raises the melting point of the fiber and raises the melting temperature in water,
Further, it becomes easy to harden. The dry heat draw ratio in the case of applying the dry heat draw treatment is generally 3 to 6 times in the case of ordinary water-resistant PVA fiber, but the low temperature water-soluble PV used in the nonwoven fabric of the present invention.
In the case of A-based fibers, it is preferably 1.0 times (constant length treatment) to 2.5 times. High-magnification stretching increases shrinkage during water dissolution and raises the dissolution temperature.

The melting point thus obtained is 170-220.
The filament tow of low temperature water-soluble PVA fiber at ℃ is opened by the repulsive action by frictional charging, or crimped.
The cut staples are opened with a card or the like to form a web, and the web is formed by using a hot embossing roller having a press-bonding area ratio of 3 to 50% from the melting point of the low temperature water-soluble PVA-based fiber constituting the web. 3 at low temperature of 20-120 ℃
Thermocompression bonding with a linear pressure of -100 kg / cm. When the pressure-bonding ratio of the hot embossing roller is less than 3%, the pressure-bonding area is small and the strength of the non-woven fabric is insufficient. When it exceeds 50%, the pressure-bonding area is large and the texture of the non-woven fabric is hard, resulting in paper-like.
In addition, wrinkles easily occur. The embossing roller crimp ratio is 5
-40% is more preferable, and 10-30% is more preferable in terms of balance between strength and feeling. When the thermocompression bonding temperature is higher than (Tm−20 ° C.) when the melting point of the web-forming PVA-based fiber is Tm, the texture of the nonwoven fabric becomes coarse and hard. Further, the shrinkage of the non-woven fabric during hot embossing is large, which is not preferable. If it is lower than (Tm-150 ° C.), thermocompression bonding becomes insufficient and the nonwoven fabric has low strength. Thermocompression bonding temperature is (Tm-
It is more preferable that it is 50 ° C) to (Tm-130 ° C).
It is preferable that the thermocompression bonding temperature be low when the pressure bonding ratio is high, and high when the pressure bonding ratio is high. The thermocompression bonding temperature here is the temperature of the nonwoven fabric itself, not the embossing roller temperature. When the speed of the embossing roller is low, the temperature of the non-woven fabric and the temperature of the roller are almost the same, but when the embossing roller is rotated at high speed, the heat conduction becomes insufficient and the temperature of the non-woven fabric decreases, so it is necessary to set the temperature of the embossing roller to a higher temperature. is there. If the linear pressure is less than 3 kg / cm, the cross section of the fiber in the thermocompression bonded portion will not be sufficiently flat and the bonded area will not be large, so the strength of the nonwoven fabric will be insufficient. When thermocompression bonding is performed at a linear pressure exceeding 100 kg / cm, the fibers themselves are damaged by the compression bonding, cracks are formed around the embossed points, holes are formed, and the strength is lowered, which is not preferable. Linear pressure is 10
More preferably 80 kg / cm, 15-40 kg
/ Cm is more preferable in terms of the strength of the nonwoven fabric. From the viewpoint of the overall performance of the nonwoven fabric, it is preferable that the linear pressure is high when the pressure-bonding ratio is small or the pressure-bonding temperature is low and the linear pressure is low when the pressure-bonding ratio is low. It is an important property that the nonwoven fabric of the present invention dissolves and disappears in low temperature water of 0 to 40 ° C., but the water dissolution temperature of the nonwoven fabric is not only the dissolution temperature of the PVA fiber used in water but also the bonding temperature, linear pressure, bonding ratio, etc. Note that it is also affected by the thermocompression bonding conditions. For example, if the pressure-bonding temperature is increased or the linear pressure or the pressure-bonding ratio is increased, the dissolution temperature of the nonwoven fabric in water increases. This is because the crystallinity of the PVA-based polymer itself that constitutes the non-woven fabric is increased, and the dissolution temperature of the non-woven fabric in water is essentially increased. At the same time, the adhesiveness is increased, the specific surface area in contact with water is reduced, and the dissolution rate is increased. It is presumed that this is due to the slowing down and apparently higher melting temperature.

The embossed pattern of the nonwoven fabric of the present invention has no special limitation because the required performance varies depending on the use.
For example, when emphasizing the texture such as sanitary materials and wipers, an embossing roller with a small crimping ratio is used, and a non-woven fabric thermocompressed with a deformed square pattern, pinpoint pattern, etc. under low temperature and low linear pressure conditions is preferable. In applications such as the above, it is important that powders of various chemicals in the bag do not spill out of the bag. In this case, a non-woven fabric thermocompression-bonded with a textured pattern having a large pressure-bonding ratio is preferable.

The fibers constituting the present invention have a circular cross-sectional shape and have a uniform structure in the surface layer portion and inside thereof before heat embossing and in a portion which has not been subjected to thermocompression bonding after heat embossing. Preferably. Conventionally, as a general method for producing PVA-based fibers, P
A spinning method in which a spinning stock solution in which a VA polymer is dissolved in water is discharged into a saturated inorganic salt aqueous solution to coagulate is generally carried out. PVA-based fibers obtained by such a method have a cocoon-shaped cross-section. And the fiber surface is a dense skin layer,
The inside of the fiber is a sparse core layer, and the core layer has a so-called skin-core structure non-uniform cross-section that hardly contributes to the tensile strength of the fiber. In the present invention,
PVA-based fibers that do not have such a skin-core structure and have a so-called uniform cross-sectional structure are preferable in terms of tensile strength, and have such a uniform cross-sectional structure and a circular cross-sectional shape. As described above, a certain PVA-based fiber is obtained by wet spinning or dry-wet spinning a spinning dope in which a PVA polymer is dissolved in an organic solvent such as DMSO, and then sufficiently stretching. Whether or not the fiber has a uniform cross-sectional structure can be determined by observing the cross section of the fiber with an optical microscope. That is, in the case of a non-uniform cross-section having a skin-core structure, the skin portion has a large light transmission and looks bright, whereas the core portion looks dark due to light scattering. When the fiber has a uniform cross-sectional structure, there is substantially no difference in brightness between the surface layer and the inside of the fiber.

The parameters used in the present invention are measured as follows. (1) Melting point of PVA-based fiber ... Using a differential scanning calorimeter (DSC-20) manufactured by METTLER CORPORATION, a fiber sample (10 mg) collected from a non-bonded portion of a non-woven fabric was subjected to nitrogen at 20 ° C./min.
The temperature at which the endothermic peak is exhibited when the temperature is raised at the rate of is measured.

(2) Flatness of the fiber cross section: The fiber cross section of the crimped portion of the nonwoven fabric is observed with a scanning electron microscope. When the longer one of the single fiber cross sections is vertical and the shorter one is horizontal, Measurement, vertical / horizontal ratio is measured at n = 30, and the average value is obtained.

(3) Cleavage length: Two kinds of samples were taken in a rectangular shape having a width of 5 cm and a length of 15 cm in each orthogonal direction, and a test length of 10 was measured by a Shimadzu tensile tester autograph.
cm, and the tensile speed is 10 cm / min, and a tensile test is performed to obtain the tensile strength (kg / 5 cm) that shows the maximum stress. The average tensile strength is calculated for two kinds of samples, each n = 10 and orthogonal to each other. Separately, the tensile strength (kg / cm) is divided by the basis weight (g / m ² ) of the non-woven fabric, and the units are combined to obtain the breaking length (km).

(4) Dissolution temperature in water: 2 cm x 2 cm
After immersing the non-woven fabric sample of No. 2 in water at a predetermined temperature for 24 hours, the minimum water temperature at which the non-woven fabric is almost completely dissolved and disappeared is measured.

(5) Area shrinkage of nonwoven fabric when dissolved in water at 20 ° C .... Area shrinkage when a nonwoven fabric sample of 2 cm × 2 cm is immersed in water at 20 ° C. and the entire nonwoven fabric shrinks before dissolution disappears. Measure the rate (vertical x horizontal). When it does not dissolve in water at 20 ° C, the maximum area shrinkage ratio is measured up to 1 hour after immersion in water at 20 ° C.
For example, the area shrinkage ratio when shrinking 30% in the vertical direction and 20% in the horizontal direction is {1- (1-0.3) × (1-0.
2)} × 100 = 44% is calculated.

[0022]

EXAMPLES The present invention will be further described with reference to examples, but the present invention is not limited to these examples. Example 1 A partially saponified PVA having a polymerization degree of 1700 and a saponification degree of 88.0 mol% (PVA-217 manufactured by Kuraray) was dissolved in a mixed solvent of DMSO / methanol = 90/10 at 90 ° C. for 8 hours with stirring to obtain 20% PVA. To obtain a spinning dope. Pass this spinning dope through a nozzle with 2000 holes and 0.08 mmφ
Wet spinning in a solidification bath of methanol / DMSO = 90/10 at 50 ° C., wet heat drawing of 4.5 times in a methanol bath at 50 ° C., DMSO in the Shinoshino is extracted with methanol, and a spinning oil is added. Dried at 80 ° C.,
Dry heat draw ratio of 1.2 times at 20 ° C. (total draw ratio TD = 5.
4T) was dry-heated to obtain a water-soluble PVA-based fiber having a melting point of 202 ° C. and a dissolution temperature in water of 5 ° C. or less. This fiber had a uniform cross-sectional structure without a skin core structure and a circular cross-sectional shape. This fiber is crimped and cut, 2d
The embossing roller with a deformed square pattern having a staple area of × 51 mm, a card, and a crimping area ratio of 15% was set at 130 ° C., and the web was heat-embossed at a linear pressure of 30 kg / cm. At this time, when the actual temperature of the non-woven fabric was measured using a thermo label, it was 120 ° C to 130 ° C.
° C.

The non-woven fabric thus obtained had a basis weight of 30 g / m ² , 15% of the total area of the fibers had a sectional flatness of 15, and the other portions had a circular fiber cross section. The breaking length of this nonwoven fabric was 1.1 km, the texture was soft, and no fluffing was observed. When this non-woven fabric was put into water at 20 ° C., it dissolved and disappeared at a dissolution shrinkage of 10%. The melting temperature of this nonwoven fabric in water was 120 ° C. In addition, this non-woven fabric is a heat sealer FI-600 manufactured by Fuji Impulse.
-2 type, heat-sealed with a scale of 4.5,
It was heat-sealable and could not be easily processed into a bag and the bag could not be sealed.

Comparative Examples 1 to 6 The webs obtained in the examples were heat-embossed under various conditions and their performances were measured.

[Table 1]

Example 2 Partially saponified PVA having a degree of polymerization of 1750 and a degree of saponification of 92.0 mol% was dissolved in a mixed solvent of DMSO / methanol = 95/5 at 90 ° C. for 8 hours with stirring to prepare a spinning solution containing 19% of PVA. Obtained. This spinning dope contains 2000 holes and 0.08 mm hole diameter.
Methanol / DMSO = 7 at 5 ℃ through φ nozzle
Wet spinning in 5/25 solidification bath, 4.5 times wet heat drawing in 50 ° C. methanol bath, extract DMSO in thread Shino with methanol, apply spinning oil, dry at 70 ° C. The obtained dry raw yarn was dry heat drawn under the conditions of 130 ° C dry heat draw ratio of 1.1 times (TD 5.0 times), and the melting point was 215 ° C.
The water-soluble PVA-based fiber of was obtained. This fiber had a uniform cross-sectional structure without a skin-core structure and had a circular cross-sectional shape. This fiber is crimped and cut, 1.5d x 51m
m staple, carded web, 140% embossed roller with texture pattern with 22% crimping area ratio
The web was heat embossed at 40 ° C. and a linear pressure of 40 kg / cm. The non-woven fabric thus obtained had a basis weight of 40 kg / m ² , 22% of the total area of the fibers had a cross-sectional flatness of 20, and the other portions had a circular fiber cross-section. Further, the breaking length of this nonwoven fabric was 1.3 km, and no fluffing was observed. The nonwoven fabric had a dissolution temperature in water of 25 ° C and an area shrinkage ratio in water of 20 ° C of 25%.

Comparative Example 7 Partially saponified PVA having a polymerization degree of 1730 and a saponification degree of 96.0 mol% was dissolved in DMSO with stirring at 90 ° C. for 8 hours to obtain PVA.
A 17% spinning dope was obtained. The number of holes in this spinning solution is 0.08.
Methanol / DMSO at 5 ℃ through mmφ nozzle
= 75/25 in a solidification bath, wet spinning, and wet heat drawing at a temperature of 50 ° C in a methanol bath of 4.0 times, DMSO in the yarn is extracted with methanol, a spinning oil is added, and dried at 80 ° C. Then, the film was dry-heated drawn at 200 ° C. under a total draw ratio of 9 times to obtain a water-soluble PVA fiber having a melting point of 222 ° C. This fiber is crimped and cut to form a staple of 2d × 51 mm, and a card is applied to form a web.
% Deformed square pattern embossing roller at 180 ° C for 60k
Heat embossing was performed with a linear pressure of g / cm. The non-woven fabric thus obtained had a low breaking strength of 0.3 km, and when it was rubbed, the single yarn was easily broken and fluffed. When this non-woven fabric was poured into water at 40 ° C., it greatly shrank, but did not dissolve and disappear.

[0027]

INDUSTRIAL APPLICABILITY The present invention is a low temperature water-soluble PVA having a specific melting point.
By heat embossing a web made of a series of fibers into water, it dissolves and disappears in water at 40 ° C or less when placed in water, and the cross-section flatness of the constituent fibers can be locally greatly adhered to make it easy to tear. Is a non-woven fabric of a practically usable level. Furthermore, it is a non-woven fabric that has little shrinkage when dissolved in water and has a large dissolution disappearance rate. 40 for non-woven fabric with good texture
Nothing was obtained that dissolved and disappeared in water below ℃, especially at room temperature. Since the nonwoven fabric of the present invention has a soft texture and can be disposed of in a toilet, it can be used as a wiping material, a sanitary material such as a diaper or a liner, and a disposable medical material. In addition, compared to the current water-soluble film whose physical properties change drastically with temperature and humidity, the nonwoven fabric of the present invention has a significantly smaller environmental dependency due to temperature and humidity, so that the handling property during storage, transportation, use, etc. is greatly improved. Therefore, it is also useful as a unit packaging material.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location D04H 1/54 D (72) Inventor Shunpei Naramura 1621 Sakata, Kurashiki-shi, Okayama Kuraray Co., Ltd. ( 72) Inventor Tomoyuki Sano 1621 Sakata, Kurashiki City, Okayama Prefecture Kuraray Co., Ltd.

Claims (2)

[Claims] 1. A non-woven fabric composed of water-soluble polyvinyl alcohol fibers having a melting point of 170 to 220 ° C., and the fibers present in an area portion of 3 to 50% of the surface of the non-woven fabric have a cross-section flatness of 3 to. A low-temperature water-soluble nonwoven fabric having a flattened cross section of 30, a breaking length of 0.5 to 5 km, and a dissolution temperature in water of 0 to 40 ° C. 2. A web made of water-soluble polyvinyl alcohol fiber having a melting point of 170 to 220 ° C. and a temperature of 20 to 150 ° C. lower than the melting point of the fiber by using a hot embossing roller having a pressing area ratio of 3 to 50%. 3 to 100 kg
The method for producing a non-woven fabric according to claim 1, wherein thermocompression bonding is performed with a linear pressure of / cm.