JP2001073267A - Wet wiper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wet wiper having a water-absorbing capacity equal to that of a cellulose fiber-made wet wiper, high in liquid retention rate, and capable of being dissolved or disintegrated in hot water after use. SOLUTION: This wet wiper comprises a thermoplastic polyvinyl alcohol fiber comprising a polyvinyl alcohol (A) having a viscosity average polymerization degree of 200-600, a saponification degree of 90-99.99 mol%, a mole fraction of the central hydroxy group of a three-hydroxy group chain in a vinyl alcohol unit expressed by a triad method of 70-99.9 mol% and a melting point of 160-230 deg.C. Further, the thermoplastic polyvinyl alcohol fiber contains an alkali metal ion (B) in an amount of 0.0003-1 pt.wt. in terms of sodium ion based on 100 pts.wt. of the component (A).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet wiper useful for wiping and cleaning an object such as a body, a plastic product, an optical device, and a painted object. Furthermore, the present invention relates to a wet wiper which is water-soluble in hot water and biodegradable and is environmentally friendly at the time of disposal.

[0002]

2. Description of the Related Art Conventionally, as a wet wiper, a nonwoven fabric of fibers mainly composed of regenerated cellulose fibers has been used from the viewpoints of liquid absorption, moisture absorption and liquid retention. That is,
A non-woven fabric made of regenerated cellulose fiber or a non-woven fabric obtained by fixing the non-woven fabric with a binder resin, a non-woven fabric made by mixing a regenerated cellulose fiber and a thermal binder fiber and heat-fixing the non-woven fabric,
It has been proposed in Japanese Patent Application Laid-Open No. 63-275311, Japanese Utility Model Application Laid-Open No. 62-182691, Japanese Utility Model Application Laid-Open No. 62-182692, etc. .

[0003]

The regenerated cellulose fibers used in conventional wet wipers are characterized by the fact that sulfur compounds, other decomposable substances and volatile substances are used in the production of pulp and regenerated cellulose fibers as raw materials. It remains. When a wet wiper is made while containing these substances, it acts with humectants such as hydroalcohol contained in the non-woven fabric, bactericide, fragrance, etc. Will occur. Preventing or counteracting this unpleasant odor is difficult with the addition of a few processing steps,
As a countermeasure, unpleasant odors are generally suppressed by selecting and increasing the amount of the fragrance. The present invention is a liquid absorption equivalent to a wet wiper made of regenerated cellulose fiber,
An object of the present invention is to provide a wet wiper having a liquid retaining property, having no unpleasant odor, and having water solubility in hot water and biodegradability.

[0004]

That is, according to the present invention, the viscosity average degree of polymerization is from 200 to 600 and the saponification degree is from 90 to 99.
99 mol%, the molar fraction of the central hydroxyl group of three hydroxyl groups in the triad display with respect to the vinyl alcohol unit is 70 to 99.9 mol%, and the melting point is 160 ° C. to 23.
A thermoplastic polyvinyl alcohol (A) having a temperature of 0 ° C., wherein the alkali metal ion (B) is contained in an amount of 0.0003 to 1 part by weight in terms of sodium ion with respect to 100 parts by weight of the component (A). The wet wiper is a wet wiper in which a fiber composed of alcohol is used as a main fiber, and preferably, the single fiber denier of the main fiber is 5 denier or less, and the water retention is 5% or more.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The polyvinyl alcohol in the polyvinyl alcohol fiber used in the present invention means not only a homopolymer of polyvinyl alcohol but also a modified polyvinyl having a functional group introduced by copolymerization, terminal modification and post-reaction. Alcohol is also included. The viscosity average degree of polymerization of PVA used in the present invention (hereinafter simply referred to as degree of polymerization) is 200 to 600,
230 to 470 are preferred, and 250 to 450 are particularly preferred. If the degree of polymerization is less than 200, sufficient spinnability cannot be obtained at the time of spinning, and fiberization cannot be performed. When the degree of polymerization exceeds 600, the melt viscosity is too high, so that the polymer cannot be discharged from the spinning nozzle.

The degree of polymerization (P) of PVA is determined according to JIS-K67.
26 is measured. That is, after PVA is re-saponified and purified, the intrinsic viscosity [η] measured in water at 30 ° C. is determined by the following equation. P = ([η] × 10 ³ /8.29) ^{(1 / 0.62) When the} degree of polymerization is in the above range, the object of the present invention can be more suitably achieved.

The degree of saponification of the PVA of the present invention is 90 to 99.9.
Must be 9 mol%. 93-99.98 mol%
Is preferred, more preferably 94 to 99.97 mol%,
96-99.96 mol% is particularly preferred. 90 degree of saponification
When the amount is less than mol%, not only the thermal stability of PVA is poor and satisfactory melt spinning cannot be performed due to thermal decomposition or gelation, but also the water solubility of PVA decreases depending on the type of a copolymer monomer described later. In some cases, the water-soluble fiber of the present invention cannot be obtained. On the other hand, PVA having a degree of saponification of more than 99.99 mol% cannot be produced stably, and stable fiberization cannot be achieved.

In the present invention, the central hydroxyl group of a triad of three hydroxyl groups is defined as d6-DMS of PVA.
500 MHz 1H-NMR (JEOL GX-500) apparatus with O solution, 65
It means the peak (I) reflecting the tacticity of the triad of the hydroxyl group proton measured by ° C. Peak (I)
Are isotacticity chains (4.54 ppm) and heterotacticity chains (4.36 ppm) of PVA hydroxyl groups.
ppm) and syndiotacticity chain (4.13 ppm). The peak (II) of the hydroxyl group in all vinyl alcohol units has a chemical shift of 4.05 ppm to 4.70 p.
Since it appears in the region of pm, the molar fraction of the central hydroxyl group of three hydroxyl groups in the triad representation with respect to the vinyl alcohol unit of the present invention is represented by 100 × (I) / (II).

In the present invention, by controlling the amount of the central hydroxyl group of the three hydroxyl groups, various physical properties relating to water such as water solubility and hygroscopicity of PVA, various physical properties relating to fiber such as strength, elongation and elastic modulus are obtained. Various properties related to melt spinnability such as melting point and melt viscosity can be controlled. This is because the central hydroxyl group of the triad of the triad is rich in crystallinity and PVA.
It seems that the features of the above are exhibited.

In the fiber of the present invention, the content of the central hydroxyl group of three hydroxyl groups in the triad representation of PVA is 70.
９９99.9% by mole, preferably 72-99% by mole, more preferably 74-97% by mole, further preferably 75-96% by mole, particularly preferably 76-95% by mole. When the content of the central hydroxyl group of three hydroxyl groups in the triad display of PVA is less than 70 mol%, the crystallinity of the polymer is reduced, the fiber strength is reduced, and at the same time, the fibers are stuck together during melt spinning and wound up. It may not be possible to unwind later. In addition, a wet wiper excellent in water retention and wiping properties, which is the object of the present invention, cannot be obtained. PVA
When the content of the central hydroxyl group of the three hydroxyl groups in the triad notation is more than 99.9 mol%, the melting point of the polymer is high and the melt spinning temperature must be increased. Has poor thermal stability, causing decomposition, gelling, and coloring of the polymer.

The melting point (Tm) of PVA used in the present invention is
160-230 ° C, preferably 170-227 ° C, 175-224 ° C
Is more preferable, and 180 to 220 ° C. is particularly preferable. Melting point 16
If the temperature is lower than 0 ° C., the crystallinity of the PVA is reduced and the fiber strength is lowered, and at the same time, the thermal stability of the PVA is deteriorated and the fiber may not be formed into fibers. On the other hand, when the melting point exceeds 230 ° C., the melt spinning temperature becomes high, and the spinning temperature and the decomposition temperature of PVA become close to each other, so that it is impossible to produce PVA fibers stably.

The melting point of PVA is determined by using DSC
After heating to 250 ° C at a heating rate of 10 ° C / min, cool to room temperature,
PVA when heated up to 250 ° C again at a heating rate of 10 ° C / min
Means the temperature at the peak top of the endothermic peak indicating the melting point.

The PVA used in the present invention is obtained by saponifying a vinyl ester unit of a vinyl ester polymer. Vinyl compound monomers for forming vinyl ester units include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate and Examples thereof include vinyl versatate, and among them, vinyl acetate is preferred from the viewpoint of obtaining PVA.

The polymer constituting the polyvinyl alcohol fiber of the present invention may be a homopolymer of polyvinyl alcohol or a modified PVA into which copolymerized units have been introduced. From the viewpoint, it is preferable to use modified polyvinyl alcohol into which copolymerized units have been introduced. Examples of the type of the comonomer include, for example, ethylene, propylene, 1-butene, isobutene,
Α-olefins such as 1-hexene, acrylic acid and its salts, acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate and i-propyl acrylate, methacrylic acid and its salts, methacrylic acid Methyl, ethyl methacrylate, n-propyl methacrylate, methacrylic acid esters such as i-propyl methacrylate, acrylamide, N-methylacrylamide, acrylamide derivatives such as N-ethylacrylamide, methacrylamide, N-methylmethacrylamide,
Methacrylamide derivatives such as N-ethyl methacrylamide, methyl vinyl ether, ethyl vinyl ether, n
Vinyl ethers such as -propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether,
Hydroxy group-containing vinyl ethers such as ethylene glycol vinyl ether, 1,3-propanediol vinyl ether, and 1,4-butanediol vinyl ether;
Allyl acetate, propyl allyl ether, butyl allyl ether, allyl ethers such as hexyl allyl ether, monomers having an oxyalkylene group, vinyl silyls such as vinyltrimethoxysilane, isopropenyl acetate, 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, 7-octen-1-
Hydroxy-containing α-olefins such as all, 9-decene-1-ol, 3-methyl-3-buten-1-ol, fumaric acid, maleic acid, itaconic acid, maleic anhydride, phthalic anhydride, anhydride A monomer having a carboxyl group derived from trimellitic acid or itaconic anhydride; a sulfonic acid group derived from ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, or the like; Monomers having: vinyloxyethyltrimethylammonium chloride, vinyloxybutyltrimethylammonium chloride, vinyloxyethyldimethylamine, vinyloxymethyldiethylamine, N-acrylamidomethyltrimethylammonium chloride, N-acrylamidoethyltrimethylammonium chloride Chloride, N- acrylamide dimethylamine, allyl trimethyl ammonium chloride, methallyl trimethylammonium chloride, dimethyl allyl amine include monomers having a cationic group derived from the allyl ethyl amine. The content of these monomers is usually 20 mol% or less.

Among these monomers, α-olefins such as ethylene, propylene, 1-butene, isobutene and 1-hexene, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, Vinyl ethers such as i-propyl vinyl ether and n-butyl vinyl ether; hydroxy group-containing vinyl ethers such as ethylene glycol vinyl ether, 1,3-propanediol vinyl ether and 1,4-butanediol vinyl ether; allyl acetate, propyl allyl ether and butyl Allyl ether,
Allyl ethers such as hexyl allyl ether, monomers having an oxyalkylene group, 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, 7-octen-1-ol, Monomers derived from hydroxy group-containing α-olefins such as 9-decene-1-ol and 3-methyl-3-buten-1-ol are preferred.

Particularly, from the viewpoints of copolymerizability, melt spinnability and water solubility of the fiber, ethylene, propylene, 1-butene,
More preferred are α-olefins having 4 or less carbon atoms in isobutene, and vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, and n-butyl vinyl ether. Units derived from α-olefins having 4 or less carbon atoms and / or vinyl ethers are 0.1 to 0.1 in PVA.
Preferably, it is present in an amount of 20 mol%,
5 mol% is preferable, and 6 to 13 mol% is particularly preferable.
Furthermore, when the α-olefin is ethylene, it is preferable to use a modified PVA in which ethylene units are introduced in an amount of 4 to 15 mol%, more preferably 6 to 13 mol%, since the fiber properties are increased.

The PVA used in the present invention as described above has biodegradability, and is decomposed into water and carbon dioxide when treated with activated sludge or buried in soil. The PVA
Is almost completely decomposed in 2 days to 1 month when continuously treated with activated sludge in the state of an aqueous solution. From the viewpoint of biodegradability, the saponification degree of the fiber is preferably 90 to 99.99 mol%, and 92 to 9 mol%.
9.98 mol% is more preferable, and 93 to 99.97 mol% is particularly preferable. Further, the 1,2-glycol bond content of the fiber is preferably 1.2 to 2.0 mol%, and
-1.95 mol% is more preferable, and 1.3-1.9 mol% is particularly preferable. When the 1,2-glycol bond amount of PVA is less than 1.2 mol%, not only the biodegradability of PVA is deteriorated, but also the melt viscosity is too high, and the spinnability may be deteriorated. When the 1,2-glycol bond content of PVA is 2.0 mol% or more, the thermal stability of PVA may be deteriorated and spinnability may be reduced. 1,2- of PVA
The glycol bond content can be determined from the NMR peak. After saponification to a degree of saponification of 99.9 mol or more, the sample was thoroughly washed with methanol, and then dried at 90 ° C. under reduced pressure for 2 days. (J
EOL GX-500) at 80 ° C. The peak derived from methine in the vinyl alcohol unit is 3.2 to 4.
The peak derived from methine at 0 ppm (integral value A) and one of the 1,2-glycol bonds is assigned to 3.25 ppm (integral value B), and the 1,2-glycol bond content can be calculated by the following equation. Here, Δ represents the amount of modification (mol%). 1,2-glycol bond content (mol%) = 100B / {100A / (1
00-Δ)}

The PVA used in the present invention includes known methods such as bulk polymerization, solution polymerization, suspension polymerization and emulsion polymerization. Among them, a bulk polymerization method or a solution polymerization method in which polymerization is performed without a solvent or in a solvent such as an alcohol is usually employed. Examples of the alcohol used as a solvent during the solution polymerization include lower alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol. As the initiator used for the copolymerization, α, α′-azobisisobutyronitrile, 2,2′-azobis (2,
4-dimethyl-valeronitrile), benzoyl peroxide,
Known initiators such as an azo initiator such as n-propyl peroxycarbonate and a peroxide initiator are exemplified. The polymerization temperature is not particularly limited.
A range of 50 ° C. is appropriate.

The content of the alkali metal ion (B) in the fiber of the present invention is 0.0003 to 1 part by weight in terms of sodium ion with respect to 100 parts by weight of PVA (A), and 0.0003 to 0.8. Parts by weight are preferred, and 0.00
0.05 to 0.6 parts by weight is more preferable, and 0.0005 to 0.6 parts by weight.
0.5 parts by weight is particularly preferred. When the content ratio of the alkali metal ion is less than 0.0003 parts by weight, the obtained fiber may not show sufficient water solubility and undissolved matter may remain. On the other hand, when the content of the alkali metal ion is more than 1 part by weight, decomposition and gelation during melt spinning are remarkable, and fibers cannot be formed. Examples of the alkali metal ion include a potassium ion and a sodium ion.

In the present invention, the method of adding a specific amount of alkali metal ion (B) to PVA is not particularly limited, and a method of adding an alkali metal ion-containing compound after polymerizing PVA, a method of vinyl ester polymer Is saponified in a solvent, by using an alkaline substance containing an alkali ion as a saponification catalyst,
A method of mixing alkali metal ions in A and washing the PVA obtained by saponification with a washing liquid to control the content of alkali metal ions contained in the PVA can be mentioned, but the latter is more preferable. The content of the alkali metal ion can be determined by an atomic absorption method.

The alkaline substance used as the saponification catalyst includes potassium hydroxide or sodium hydroxide. The molar ratio of the alkaline substance used in the saponification catalyst is preferably from 0.004 to 0.5, more preferably from 0.005 to 0.05, based on the vinyl acetate unit. The saponification catalyst may be added all at once in the early stage of the saponification reaction, or may be additionally added during the saponification reaction. As the solvent for the saponification reaction, methanol, methyl acetate, diethyl sulfoxide,
Dimethylformamide and the like. Among these solvents, methanol is preferable, and the water content is 0.001 to 0.001.
Methanol controlled at 1% by weight is more preferable, methanol controlled at a water content of 0.003 to 0.9% by weight is more preferable, and methanol controlled at a water content of 0.005 to 0.8% by weight is particularly preferable. . Examples of the washing liquid include methanol, acetone, methyl acetate, acetate, hexane, and water. Among them, a single or mixed liquid of methanol, methyl acetate, and water is more preferable. The amount of the washing liquid is set so as to satisfy the content ratio of the alkali metal ion (B), and usually 300 to 10000 parts by weight with respect to 100 parts by weight of PVA,
500 to 5000 parts by weight is more preferred. As washing | cleaning temperature, 5-80 degreeC is preferable and 20-70 degreeC is more preferable. The washing time is preferably from 20 minutes to 10 hours, more preferably from 1 hour to 6 hours.

Further, as long as the objects and effects of the present invention are not impaired, stabilizers such as copper compounds, coloring agents, ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, flame retardants,
Plasticizers, lubricants and crystallization rate retarders can be added during the polymerization reaction or in a subsequent step. In particular, when organic stabilizers such as hindered phenol, copper halides such as copper iodide, and alkali metal halides such as potassium iodide are added as heat stabilizers, the melt retention stability during fiberization is improved. Is preferred.

In the present invention, the fiber cross-sectional shape may be an irregular cross-section other than a round cross-section. For example, a U-shaped, T-shaped, three-lobe, four-lobe, five-lobe, six-lobe, seven-lobe, eight-lobe, or other multi-leaf shape or various cross-sectional shapes are formed by a nozzle having an irregular shape during spinning. May be. Among the irregular cross-sectional shapes, a cross-sectional shape having a concave portion is preferable because moisture is quickly absorbed in the concave portion.

Further, as a fiber cross section, a core-sheath composite structure,
Although a conjugate fiber having a side-by-side structure can be used, in this case, it is preferable that the above-described polyvinyl alcohol component occupies 40% or more, particularly 50% or more of the fiber cross-sectional circumference.

The water absorption performance of the wet wiper of the present invention is as follows:
By setting the single fiber denier to 5 deniers or less, a more excellent water retention rate can be provided. The method of evaluating the water absorption performance will be described in detail later. However, the water retention of the wet wiper has a remarkable performance in a region where the single fiber denier is 5 deniers or less as compared with a nonwoven fabric made of ordinary polyester fibers. Differences appeared and similar results were obtained in the actual wiping test. Although the reason is not clear, it is presumed to be due to a synergistic effect between the hydrophilic property of the polymer itself constituting the wet wiper and the capillary effect as a fiber aggregate.

The method for producing a wet wiper according to the present invention comprises:
A staple fiber is used as the polyvinyl alcohol fiber, and if necessary, another fiber, for example, a fiber selected from a heat binder fiber, a heat-shrinkable fiber, a cellulosic fiber, a water-absorbing polyester, and the like is preferably used in a proportion of 40% by weight or less. It can be produced by mixing cotton, forming a fiber web by a usual dry method or wet method, and performing a fiber entanglement treatment by a needle punch method and / or a water jet method. Alternatively, it can also be obtained by a method in which a fiber web mixed with thermal binder fibers is heat-set by heat treatment. The weight of the wet wiper is preferably in the range of ^{20 to} 100 g / m ² . The wet wiper may be subjected to a finishing process such as embossing or calendering as necessary. The wet wiper is provided with a wetting agent such as hydroalcohol, a bactericide, a fragrance, and a chemical solution containing a preservative, an antifungal agent, and the like as necessary, and is cut into a desired shape or processed into a desired shape. It is said. In addition,
The water absorption performance of the wet wiper of the present invention is 5 g of wiper.
Was immersed in water at room temperature for 5 minutes to absorb water sufficiently, and then subjected to dehydration treatment at 1500 G for 10 minutes with a centrifugal dehydrator. Then, the residual water after the treatment was measured and expressed as a percentage with respect to the fiber weight. According to this evaluation method, the present invention provides a wet wiper having a high water retention of 5% or more, and more preferably 8% or more.

The polyvinyl alcohol constituting the wet wiper of the present invention shows solubility or disintegration by hot water and also has biodegradability. Therefore, after use, the polyvinyl alcohol is treated with hot water of 50 ° C. or more, especially 60 ° C. or more. Can be easily disposed of.

[0028]

EXAMPLES Next, the present invention will be described specifically with reference to Examples.
The present invention is not limited to these examples. In the examples, parts and percentages relate to weight unless otherwise specified.

In the wiping test of the wet wiper, a predetermined amount of water was wiped once on the desk with a normal force by a human hand, and the remaining state of the water on the desk was evaluated.

[Analysis method of PVA] The analysis method of PVA was in accordance with JIS-K6726 unless otherwise specified. The amount of modification was determined using a modified polyvinyl ester or modified PVA at 500 MHz proton NMR (JEOL GX-
500) It was determined from measurement by an apparatus. The content of the alkali metal ion was determined by an atomic absorption method.

The ratio of the amount of hydroxyl groups in the three chains by the triad display of the PVA of the present invention was determined by the following measurement. P
After saponification of VA to a degree of saponification of 99.5 mol% or more, washing with methanol was carried out sufficiently, and then, it was dissolved in d6-DMSO using PVA which was dried at 90 ° C. under reduced pressure for 2 days.
MHz proton NMR (JEOL GX-500)
The measurement was performed at 65 ° C. by the apparatus. The peak derived from the hydroxyl group of the vinyl alcohol unit in PVA is a chemical shift
It appears in the range of 4.05 ppm to 4.70 ppm, and the integrated value is defined as the vinyl alcohol unit amount (II). The center hydroxyl group of the three hydroxyl groups in the triad representation of PVA appears at 4.54 ppm for the isotacticity chain, 4.36 ppm for the heterotacticity chain, and 4.13 ppm for the syndiotacticity chain, respectively. The sum of the three integrated values is defined as the central hydroxyl group amount (I) of three hydroxyl groups in triad display. The molar fraction of the central hydroxyl group of three hydroxyl groups in the PVA of the present invention with respect to the vinyl alcohol unit is represented by 100 × (I) / (II).

[Melting point] The melting point of PVA was determined by using DSC (Mettler, TA3000) in nitrogen at a heating rate of 10 ° C /
After heating to 250 ° C in minutes, cool to room temperature,
The temperature was expressed as a peak-top temperature of an endothermic peak indicating the melting point of PVA when the temperature was raised to 250 ° C. at 0 ° C./min.

Example 1 [Production of ethylene-modified PVA] 29.0 kg of vinyl acetate and methanol 3 were placed in a 100 L pressure reactor equipped with a stirrer, a nitrogen inlet, an ethylene inlet and an initiator inlet.
After 1.0 kg was charged and the temperature was raised to 60 ° C., the inside of the system was replaced with nitrogen by bubbling nitrogen for 30 minutes. Then, ethylene was introduced and charged so that the reaction tank pressure became 5.9 kg / cm ² . A 2.8 g / L solution of 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) (AMV) dissolved in methanol as an initiator was prepared.
Nitrogen was replaced by bubbling with nitrogen gas. After adjusting the internal temperature of the polymerization tank to 60 ° C., 170 ml of the initiator solution was injected to start polymerization. During the polymerization, ethylene was introduced to maintain the reaction vessel pressure at 5.9 kg / cm 2 and the polymerization temperature at 60 ° C.
The polymerization was carried out by continuously adding AMV at a rate of ml / hr. 1
After 0 hour, when the degree of polymerization reached 70%, the polymerization was stopped by cooling. After the reaction vessel was opened to remove ethylene, nitrogen gas was bubbled through to completely remove ethylene. Next, unreacted vinyl acetate monomer was removed under reduced pressure to obtain a methanol solution of polyvinyl acetate. 200 g of a methanol solution of polyvinyl acetate adjusted to a concentration of 50% by adding methanol to the obtained polyvinyl acetate solution.
(100 g of polyvinyl acetate in solution) to 46.5 g
(Molar ratio (MR) 0.10 to vinyl acetate unit in polyvinyl acetate) alkaline solution (10% NaOH)
% Methanol solution) for saponification. After about 2 minutes from the addition of the alkali, the gelled system was pulverized with a pulverizer, left at 60 ° C. for 1 hour to progress saponification, and then 1000 g of methyl acetate was added to neutralize the remaining alkali. After confirming the completion of the neutralization using a phenolphthalein indicator, 1000 g of methanol was added to the white solid PVA obtained by filtration and washed at room temperature for 3 hours. After the above washing operation was repeated three times, P
VA was left in a dryer at 70 ° C. for 2 days to obtain dry PVA.

The degree of saponification of the obtained ethylene-modified PVA is 9
It was 8.4 mol%. After the modified PVA was incinerated, the content of sodium measured by an atomic absorption spectrophotometer using a substance dissolved in an acid was 0.03 parts by weight based on 100 parts by weight of the modified PVA. Further, a methanol solution of polyvinyl acetate obtained by removing unreacted vinyl acetate monomer after polymerization is precipitated in n-hexane, and reprecipitated by dissolving with acetone three times, and then dried under reduced pressure at 80 ° C. for 3 days. To obtain purified polyvinyl acetate. The polyvinyl acetate was dissolved in DMSO-d6, and 500 MHz proton N was dissolved.
When measured at 80 ° C. using MR (JEOL GX-500), the ethylene content was 10 mol%.
After saponifying the above methanol solution of polyvinyl acetate at an alkali molar ratio of 0.5, the pulverized product was left at 60 ° C. for 5 hours to progress saponification, and then methanol soxhlet was carried out for 3 days, and then 80 ° C. And dried under reduced pressure for 3 days to obtain a purified ethylene-modified PVA. The average degree of polymerization of the PVA was 330 as measured according to the conventional method of JIS K6726. The amount of 1,2-glycol bond and the content of hydroxyl groups of three hydroxyl groups of the purified PVA were 50
It was 1.50 mol% and 83%, respectively, as determined from the measurement with a 0 MHz proton NMR (JEOL GX-500) apparatus as described above. Further, a 5% aqueous solution of the purified modified PVA was adjusted to prepare a cast film having a thickness of 10 μm. 80 ° C.
After drying for 1 day under reduced pressure, DSC (Mettler,
The melting point of PVA was measured by the above-mentioned method using TA3000) and found to be 206 ° C. Table 1 shows the polymerization degree, saponification degree, melting point, modified species, modification amount, central hydroxyl group content, sodium ion content and the like of the modified PVA obtained here.

[0035]

[Table 1]

The modified PVA obtained above was melt-kneaded at 240 ° C. using a melt extruder, and the molten polymer stream was guided to a spinning head (240 ° C.), weighed with a gear pump, and measured for a hole diameter of 0.25 mm and a number of holes. The mixture was discharged from a 72 round section spinning nozzle and wound up at a speed of 800 m / min. The obtained spun yarn is drawn on a roller plate at a hot roller temperature of 75 ° C. and a hot plate temperature of 170 ° C. to 2.0 times (corresponding to HDmax × 0.7), and 150d / 72f (single fiber fineness: 2 denier).
Was obtained. The cross-sectional shape of the obtained drawn yarn was a uniform perfect circle.

Next, fifty of the drawn yarns are combined into a bundle of 7500 denier, subjected to mechanical crimping by a press crimping machine, and then cut into a fiber length of 51 mm to form staple fibers. forming a fibrous web through a random webber, performs fiber entangling treatment by applying a high pressure water jet from the nozzle, the average basis weight 45 g / m ^2, an apparent density of 0.16
g / cm ³ of a fiber-entangled nonwoven fabric was obtained. The entangled nonwoven fabric was impregnated with a quaternary ammonium salt cationic activator and an aromatic agent using a hydrous alcohol as a wetting agent, and finished into a wet wiper. The water retention of the wiper was 10.2%, and the wipeability was good. The wiper was sealed in a glass bottle, left in an atmosphere of 40 ° C. for 60 days, and examined for discoloration and change in odor. As a result, no discoloration or change in odor of the nonwoven fabric was observed. Furthermore, although no preservative or fungicide was added, generation of mold was not observed. For comparison, the same test was performed on a wet wiper made using a conventional regenerated cellulose fiber, and as a result, the nonwoven fabric was slightly yellowish and gave off an unpleasant odor.

Examples 2 to 14 Fiberization, production of a nonwoven fabric and preparation of a wet wiper were carried out in the same manner as in Example 1 except that the polyvinyl alcohol shown in Table 1 was used. Was performed. Table 2 shows the evaluation results.

[0039]

[Table 2]

Example 15 Fiberization, production of a non-woven fabric and preparation of a wet wiper were carried out in the same manner as in Example 1 except that a U-shaped spinning nozzle having a slit width of 0.2 mm was used as the spinning nozzle. The sex was evaluated. Table 2 shows the evaluation results.

Example 16 The procedure of Example 1 was repeated, except that a T-shaped spinning nozzle having a slit width of 0.2 mm was used as the spinning nozzle, to carry out fiberization, manufacture of a nonwoven fabric, preparation of a wet wiper, water retention and wiping. The sex was evaluated. Table 2 shows the evaluation results.

Example 17 One pair of the modified PVA and polypropylene used in Example 1 was used.
Using a side-by-side type composite spinning apparatus so as to have a composite ratio of 1, melt spinning from a round cross-section spinning nozzle, Example 1
The drawing was performed in the same manner as described above to obtain a drawn yarn of 150d / 48f (single fiber fineness: 3 denier). A nonwoven fabric and a wet wiper were prepared from the obtained drawn yarn in the same manner as in Example 1, and the water retention and wiping properties were evaluated.
Table 2 shows the evaluation results.

Example 18 A fiber having a single fiber fineness of 1.3 denier (100 d / 7) was prepared by changing the hole diameter of the spinning nozzle to 0.2 mm and changing the discharge amount.
Fiberization in the same manner as in Example 1 except that 2f)
A nonwoven fabric was manufactured and a wet wiper was prepared, and the water retention and wiping properties were evaluated. Table 2 shows the evaluation results.

Example 19 By setting the number of holes in the spinning nozzle to 48 and changing the discharge amount, a fiber having a single fiber fineness of 3.0 denier (150/48
Except for f), fiberization, production of a nonwoven fabric, and preparation of a wet wiper were performed in the same manner as in Example 1, and the water retention and wiping properties were evaluated. Table 2 shows the evaluation results.

Comparative Example 1 Fiberization, production of a nonwoven fabric, preparation of a wet wiper, and evaluation of water retention and wiping properties were performed in the same manner as in Example 1 except that the modified PVA shown in Table 1 was used. However, all had low water retention and poor wiping properties (Table 2).

Comparative Example 2 A nonwoven fabric and a wet wiper were prepared in the same manner as in Example 1 except that the modified PVA fiber used in Example 1 was replaced with polyethylene terephthalate fiber having the same fineness as the fiber constituting the wet wiper. , Was evaluated,
Both the water retention and the wiping properties were extremely poor (Table 2).

Claims (4)

[Claims] 1. A viscosity-average degree of polymerization of 200 to 600, a saponification degree of 90 to 99.99 mol%, and a molar fraction of a central hydroxyl group of three hydroxyl groups in a triad display with respect to a vinyl alcohol unit of 70 to 99.9 mol%. A thermoplastic polyvinyl alcohol (A) having a melting point of 160 ° C. to 230 ° C., wherein alkali metal ion (B) is 0.1% in terms of sodium ion with respect to 100 parts by weight of (A).
A wet wiper composed mainly of fibers of thermoplastic polyvinyl alcohol contained in 0003 to 1 part by weight. 2. The wet wiper according to claim 1, wherein the polyvinyl alcohol is a modified polyvinyl alcohol containing 0.1 to 20 mol% of α-olefin units having 4 or less carbon atoms and / or vinyl ether units. 3. The wet wiper according to claim 2, wherein the polyvinyl alcohol is a modified polyvinyl alcohol containing 4 to 15 mol% of ethylene units. 4. The wet wiper according to claim 1, wherein a single fiber denier of the polyvinyl alcohol fiber is 5 deniers or less, and a water retention rate is 5% or more.