JP2000314067A - Thermoplastic polyvinylalcohol-based melt blown non- woven fabric and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a water degradable PVA-based melt blown non-woven fabric showing strong affinities to water such as a water dissolution property, water-absorbing property, water-swelling property, etc. SOLUTION: This non-woven fabric consists of a polyvinyl alcohol (A) having 200-500 viscosity-average degree of polymerization, 90-99.99 mole % saponification degree, 66-99.9 mole % central hydroxyl group in 3 successive hydroxyl groups in a triad expression for its vinyl alcohol units and 160-230 deg.C melting point, and also is characterized by containing 0.0003-1 pt.wt. alkali metal ion (B) based on 100 pts.wt. (A).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic polyvinyl alcohol-based melt blown nonwoven fabric having a specific composition and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, polyvinyl alcohol (hereinafter referred to as P
VA may be abbreviated). Examples of the fibers include: 1) a fiber obtained by wet spinning of a stock solution and a solidification bath, both of which are aqueous; 2) a fiber obtained by dry spinning of a stock solution of water; 3) any of a stock solvent and a solidification bath. Fibers formed by wet spinning (gel spinning) using a solvent system are known.

[0003] These PVA-based water-soluble fibers are used as staples or shortcut fibers in papermaking, dry nonwoven fabrics, spinning, and the like, and as multifilaments in woven fabrics and knitted fabrics. In particular, shortcut fibers soluble in hot water at 80 ° C. to 90 ° C. occupy an important position in the papermaking industry as fibrous binders, and multifilaments are also often used as base fabrics for chemical lace.
In recent years, biodegradable fibers have attracted attention due to environmental problems.

On the other hand, in the nonwoven fabric manufacturing technique, a so-called melt-blown nonwoven fabric manufacturing technique uses a conventional dry nonwoven fabric in which a nonwoven fabric is formed directly from a raw material polymer, and is then formed into fibers and then formed in a separate process. It is known as an extremely rational method for producing a nonwoven fabric as compared with the production technology for wet and nonwoven fabrics. Furthermore, since this melt blown nonwoven fabric is basically manufactured using a melt spinning method, unlike a nonwoven fabric composed of conventional PVA fibers obtained by a wet spinning method using an organic solvent, There is no problem that a trace amount of the organic solvent remains in the nonwoven fabric.

[0005] In a so-called dry nonwoven fabric manufacturing technique in which a fiber is once manufactured and the fiber is carded into a nonwoven fabric, various processes are required in the fiber manufacture and carding for forming a nonwoven web is required. It is essential to attach an oil agent to the fiber surface during the production of the fiber, and the oil agent is usually treated with an aqueous treatment liquid. However,
Water-based treatment liquids cannot be used to produce fibers that exhibit strong affinity for water, such as water solubility, water absorption, and water swelling properties. Equipment measures were necessary. As a result, there has been a great limitation in producing such a nonwoven fabric using fibers as a raw material while ensuring desired quality.

[0006] Attempts to apply such a rational melt-spinning nonwoven fabric manufacturing technique to PVA-based fiber nonwoven fabrics have been conventionally studied in the so-called spunbond method.

For example, as an example of converting PVA into a nonwoven fabric by a direct method, Japanese Patent Application Laid-Open No. 51-112980 discloses an average degree of polymerization of 50 to 300 and a residual acetic acid group of 15 to 80.
Disclosed is a method for producing a polyvinyl alcohol yarn synthetic fiber nonwoven fabric, wherein a filament obtained by melt-extruding mol% of anhydrous polyvinyl alcohol is taken up by a suction jet and sprayed and deposited on a forming surface by a jet stream. Average degree of polymerization of 50 to 300 and residual acetic acid groups of 15
In the case of PVA of up to 80 mol%, a nonwoven fabric cannot be obtained if it is used for an extremely short time, but a deacetic acid reaction occurs during heating and melting, and the working environment is poor due to the generated acetic acid gas. In addition, gelation occurs due to cross-linking due to intermolecular deacetic acid, which causes problems such as an increase in melt viscosity, gel mixing into the spun polymer stream, cutting of the polymer stream, and filter clogging. , Not at the level of industrial production.

A melt blown nonwoven fabric made of PVA is disclosed in a paper by Maureen Dever, Ph.D., "Development and Evaluation of Water Soluble Blown Melt Blown".
Non-Woovens "(Development and Evaluation of
Water Soluble Melt Blown Nonwovens), TAPPI P
Although disclosed in Roceedings, Nonwovens Conference, pp 99-110, 1993, in this paper melt blowns are made to ensure good cold water solubility and biodegradability, especially using a PVA resin with a saponification degree of less than 90%. ing.

A paper by AYAKhan et al., "Melt Blown Processing and Characterization of Cellulose Acetate and Polyvinyl Alcohol"
erization of Cellulose Acetate and Polyvinyl A
lcohol), TAPPI Proceedings, Nonwovens Conference, p
p111-113, 1993 discloses a melt blown nonwoven fabric using PVA, but the resin used here is MI = 26-
No. 30 is disclosed, and no specific resin composition is disclosed. Further, Japanese Unexamined Patent Application Publication No.
No. 3 discloses a cloth made of a PVA homopolymer that is water-soluble at a temperature of 50 ° C. or higher, and discloses a melt blown nonwoven fabric as an example of the cloth.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyvinyl alcohol melt blown nonwoven fabric having excellent water disintegration properties and an appropriate barrier property by a melt blown method.

[0011]

That is, according to the present invention, the viscosity average degree of polymerization is from 200 to 500 and the degree of saponification is from 90 to 99.
99 mol%, the molar fraction of the central hydroxyl group of three hydroxyl groups in the triad notation with respect to the vinyl alcohol unit is 66 to 99.9 mol%, and the melting point is 160 ° C. to 23.
A polyvinyl alcohol (A) at 0 ° C.,
(A) 100 parts by weight of alkali metal ion (B)
Is a melt blown nonwoven fabric comprising polyvinyl alcohol containing 0.0003 to 1 part by weight,
Viscosity average degree of polymerization of 200 to 500, saponification degree of 90 to 9
9.99 mol%, the molar fraction of the central hydroxyl group of three hydroxyl groups in the triad representation with respect to the vinyl alcohol unit is 66 to 99.9 mol%, and the melting point (Tm) is 16
A polyvinyl alcohol having a temperature of 0 ° C to 230 ° C,
(A) 100 parts by weight of alkali metal ion (B)
(Tm + 10) ° C. to (Tm +
80) ° C, 0.01 to 2.0 Nm ³ / min / c as hot air flow
This is a method for producing a polyvinyl alcohol-based melt-blown nonwoven fabric, characterized in that an ultrafine fiber web is obtained by spinning under conditions of m and spraying onto a collecting device within 50 cm of a spinning nozzle.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The polyvinyl alcohol in the polyvinyl alcohol-based melt-blown nonwoven fabric of the present invention includes a homopolymer of polyvinyl alcohol and a modified polyvinyl alcohol having a functional group introduced by copolymerization, terminal modification and post-reaction.

The viscosity-average degree of polymerization (hereinafter, abbreviated as degree of polymerization) of PVA used in the present invention is from 200 to 500, preferably from 230 to 470, particularly preferably from 250 to 450. When the degree of polymerization exceeds 500, the melt viscosity is high, so that the average fiber diameter of the melt blown nonwoven fabric becomes large, and fibers in which a partially coiled or ball-like mass is mixed are mixed and roughened. The resulting nonwoven fabric becomes soft to the touch, and the characteristics of the meltblown nonwoven fabric cannot be utilized. If the degree of polymerization is further increased, the polymer cannot be discharged from the nozzle.

The degree of polymerization (P) of PVA is determined according to JIS-K
It is measured according to 6726. That is, PVA is re-soaped
Intrinsic viscosity measured in water at 30 ° C after purification and purification
Is obtained from [η] (dl / g) by the following equation.
You. P = ([η] × 10³/8.29)^{(1 / 0.62)}  When the degree of polymerization is in the above range, the object of the present invention is more suitably
Can be reached.

The degree of saponification of the PVA used in the present invention is 90
９９99.99 mol%, 92-99.9
8 mol% is preferable, 93 to 99.97 mol% is more preferable, and 94 to 99.96 mol% is particularly preferable. When the saponification degree is less than 90 mol%, the thermal stability of PVA is poor, and not only melt blown spinning cannot be performed satisfactorily due to thermal decomposition or gelation, but also an aqueous solution of PVA depending on the type of copolymerizable monomer described below. In some cases, the water-disintegrable nonwoven fabric intended in 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 fiberization cannot be stabilized.

In the present invention, the central hydroxyl group of the triad of the triad is defined as d6-DMS of PVA.
500 MHz proton NMR (JEOLG
X-500) Peak (I) that reflects the triad tacticity of hydroxyl protons measured at 65 ° C.
Means Peak (I) is a triad-represented isotacticity sequence of the hydroxyl group of PVA (4.54 pp).
m), the sum of the heterotacticity chain (4.36 ppm) and the syndiotacticity chain (4.13 ppm), and the peak (II) derived from the hydroxyl group in all vinyl alcohol units has a chemical shift of 4.0.
Since it appears in the region of 5 ppm to 4.70 ppm,
The molar fraction of the center hydroxyl group of the three-chain hydroxyl group by the triad display with respect to the vinyl alcohol unit of the present invention is:
It is represented by 100 × (I) / (II).

In the present invention, by controlling the amount of the central hydroxyl group of the three hydroxyl groups required above, various physical properties relating to water such as water solubility, hygroscopicity and water resistance of PVA, strength, etc. can be obtained.
We have found that various properties related to fiber such as elongation and elastic modulus, and various properties related to melt molding such as melting point, melt viscosity and melt viscosity can be controlled. This is presumably because the central hydroxyl group of the triad of triads is rich in crystallinity, thereby exhibiting the characteristics of PVA.

In the nonwoven fabric of the present invention, the content of the central hydroxyl group of three hydroxyl groups by the triad display of PVA is 6
6 to 99.9 mol%, preferably 70 to 99 mol%, more preferably 74 to 97 mol%, further preferably 75 to 96 mol%, and particularly preferably 76 to 95 mol%. When the content of the central hydroxyl group of three hydroxyl groups in the triad display of PVA is less than 66 mol%, the crystallinity of the polymer is reduced, the spinnability at the time of melt spinning is poor, and the melt blown nonwoven fabric aimed at by the present invention is not obtained. I am not satisfied. In addition, a water-disintegrable nonwoven fabric may not be obtained. P
When the content of the central hydroxyl group of three hydroxyl groups in the triad display of VA is more than 99.9 mol%, the melting point of the polymer must be increased because the melting point of the polymer is high. Poor thermal stability,
Troubles such as decomposition, gelation and coloring occur.

The melting point of PVA used in the present invention is 160
To 230 ° C, preferably 170 to 227 ° C, 17
5 to 224 ° C is more preferable, and 180 to 220 ° C is particularly preferable. If the melting point is lower than 160 ° C., the crystallinity of the PVA is reduced, so that fibers having sufficient strength cannot be obtained. Are mixed together, resulting in a web that cannot maintain the performance as a so-called melt blown nonwoven fabric, and furthermore, it may not be possible to form a web.
On the other hand, if the melting point exceeds 230 ° C., the blown temperature rises, and the blown temperature approaches the decomposition temperature of PVA.
VA meltblown nonwoven fabric cannot be manufactured stably.

The melting point of PVA is raised to 250 ° C. at a rate of 10 ° C./min in nitrogen, cooled to room temperature, and then raised again to 250 ° C. at a rate of 10 ° C./min in nitrogen using DSC. Means the temperature at the peak top of the endothermic peak indicating the melting point of PVA in this case.

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

The PVA constituting the nonwoven fabric of the present invention preferably contains a monomer unit other than a vinyl alcohol unit and a vinyl ester unit. Examples of such a unit include α-olefins such as ethylene, propylene, 1-butene, isobutene and 1-hexene, acrylic acid and salts thereof, methyl acrylate, ethyl acrylate, n-propyl acrylate, and i-acrylate. Acrylates such as -propyl, methacrylic acid and salts thereof, methyl methacrylate, ethyl methacrylate, methacrylic acid n
-Propyl, methacrylic acid esters such as i-propyl methacrylate, acrylamide, N-methyl methacrylamide, methacrylamide derivatives such as n-ethyl methacrylamide, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, vinyl ethers such as n-butyl vinyl ether, ethylene glycol vinyl ether, 1,3-
Propanediol vinyl ether, hydroxy group-containing vinyl ethers such as 1,4-butanediol vinyl ether, allyl acetate, propyl allyl ether,
Allyl ethers such as butyl allyl ether and hexyl allyl ether, monomers having an oxyalkylene group,
Vinylsilanes such as vinyltrimethoxysilane, isopropenyl acetate, 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, 7-octen-1-ol, 9-decene-1 -All 3-methyl-
A carboxyl group derived from hydroxy group-containing α-olefins such as 3-buten-1-ol, fumaric acid, maleic acid, itaconic acid, maleic anhydride, phthalic anhydride, trimellitic anhydride or itaconic anhydride; Monomer having a sulfonic acid group derived from ethylenesulfonic acid, allylsulfonic acid, methallylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, etc .; vinyloxyethyltrimethylammonium chloride, vinyloxy Methyl diethylamine, N-acrylamidomethyltrimethylammonium chloride, N-
Monomers having a cationic group derived from acrylamidodimethylamine, allyltrimethylammonium chloride, methallyltrimethylammonium chloride, dimethylallylamine, allylethylamine and the like can be mentioned. The content of these monomers is usually 25 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, i -Propyl vinyl ether, vinyl ethers such as n-butyl vinyl ether, hydroxy group-containing vinyl ethers such as ethylene glycol vinyl ether, 1,3-propanediol vinyl ether, 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, 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.

Among them, ethylene, propylene, and ethylene are preferred from the viewpoint of water disintegration showing excellent affinity for water such as copolymerizability, spinnability at the time of blown, water solubility of water, water absorption, and water swellability. Α-olefins having 4 or less carbon atoms, such as butene and 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 are more preferable. Units derived from α-olefins and / or vinyl ethers having 4 or less carbon atoms are represented by P
Preferably, 0.1 to 25 mol% is present in VA, more preferably 4 to 15 mol%, and particularly preferably 6 to 13 mol%. Furthermore, when the α-olefin is ethylene, the spinnability at the time of blown becomes good, and blown fibers having an average fiber diameter of 20 μm or less are stably formed. It is more preferable to use a modified PVA in which 6 to 13 mol% is introduced.

The polymerization method of PVA used in the present invention includes solution polymerization, bulk polymerization, pearl polymerization, emulsion polymerization and the like. 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 ′
Azo initiators or peroxide initiators such as -azobisisobutyronitrile, 2,2'-azobis (2,4-dimethyl-valeronitrile), benzoyl peroxide, n-propylperoxydicarbonate, etc. Known initiators. The polymerization temperature is not particularly limited,
A range from 0 ° C to 150 ° C is appropriate.

The content of the alkali metal ion (B) in the PVA used in the present invention is 0.0003 to 1 part by weight with respect to 100 parts by weight of the PVA (A).
03-0.8 parts by weight, preferably 0.0005-0.6 parts by weight
Part by weight is more preferable, and 0.0005 to 0.5 part by weight is particularly preferable. Alkali metal ion content of 0.0
When the amount is less than 003 parts by weight, not only is it easy to gel during blown, it is difficult to form a fiber, but also sufficient water solubility is not obtained 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 at the time of blown are remarkable, and fiber 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 a compound containing an alkali metal ion after once obtaining PVA, When saponifying the coalesced solvent in a solvent, the use of an alkaline substance containing an alkali ion as a saponification catalyst can reduce PV
A method of mixing alkali metal ions in A and washing the PVA obtained by saponification with a washing liquid to control the alkali metal ions contained in 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.

As the alkaline substance used as the saponification catalyst, potassium hydroxide or sodium hydroxide can be mentioned. The molar ratio of the alkaline substance used for the saponification catalyst is
0.004-0.5 is preferable with respect to a vinyl acetate unit, and 0.005-0.05 is especially preferable. 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, dimethyl 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, ethyl acetate, hexane, and water, and among them, methanol, methyl acetate, and water alone or a mixed liquid are more preferable. The amount of the washing liquid is set so as to satisfy the content ratio of the alkali metal ion (B), but usually 300 to 5,000 parts by weight based on 100 parts by weight of PVA. The washing temperature is preferably from 5 to 80 ° C, and from 20 to 80 ° C.
70 ° C. is more preferred. Washing time is 20 minutes to 1
0 hours is preferable, and 1 hour to 6 hours is more preferable.

Furthermore, the PVA used in the present invention includes:
A plasticizer may be added to lower the melt viscosity or to impart flexibility to the nonwoven fabric. The plasticizer is not particularly limited as long as it can reduce the glass transition point and melt viscosity of PVA. Examples of the plasticizer include water, ethylene glycol and its oligomers, polyethylene glycol, propylene glycol, and its oligomers, and polyglycerin. Glycerin derivatives such as ethylene oxide, propylene oxide, etc. added to glycerin, sorbitol,
Pentaerythritol and the like. Among them, polyhydric alcohols such as glycerin, ethylene glycol, propylene glycol, sorbitol, and pentaerythrol and derivatives thereof are preferably used. The amount of the plasticizer is not limited, but is 0.01 to 1 part by weight based on 100 parts by weight of PVA.
It is preferable to add a plasticizer in the range of 0 parts by weight.

In addition, stabilizers such as copper compounds, coloring agents, ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, flame retardants, and the like, as long as the objects and effects of the present invention are not impaired.
A plasticizer, a lubricant, and a crystallization rate retarder 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.

Further, if necessary, the average particle size is 500
Fine particles having a size of not more than nm can be added in an amount of 0.1 to 5% by weight during the polymerization reaction or in a subsequent step. The type of the fine particles is not particularly limited. For example, silica gel (colloidal silica), dry silica, dry silica containing aluminum oxide, dry silica having an alkyl group on the particle surface and silanol groups blocked on the particle surface, Inert fine particles such as alumina sol (colloidal alumina), titanium oxide, calcium carbonate and its sol (colloidal calcium carbonate); and internally precipitated fine particles obtained by reacting and depositing a phosphorus compound and a metal compound in a PVA polymerization reaction system. it can. Particularly, silica having an average particle diameter of 15 to 70 nm is preferable, and the melt blown spinnability is improved.

The production of the melt blown nonwoven fabric comprising the polyvinyl alcohol of the present invention is described in, for example, Industrial and Engineering Chemistry, 48
Vol. 8, No. 134 (p1342-p1346), 1956
Can be manufactured using a known melt blown apparatus. That is, the PVA pellets are melt-kneaded by a melt extruder, the melted polymer is weighed by a gear pump, guided to a melt blown spinning nozzle, discharged, blown off by a heated air stream, and spun. It is obtained by depositing on a nonwoven fabric and winding it up. In addition, if necessary, by blowing a cold air of about 40 ° C. or less into the melt blown fiber stream immediately below the nozzle, the degree of fiber adhesion in the nonwoven fabric can be minimized, and the resulting nonwoven fabric can be made more flexible. can do.

However, as a condition for forming a melt blown nonwoven fabric in the present invention, it is important to perform melt blown spinning at a blown temperature of (Tm + 10 ° C.) to (Tm + 80 ° C.) with respect to the melting point Tm of the polymer. If the blown temperature is lower than (Tm + 10 ° C.), the melt viscosity of the polymer is too high, and the resin cannot be thinned by high-speed blown air, resulting in a very coarse nonwoven fabric. Also, (Tm + 80
C.), thermal decomposition of PVA occurs and stable spinning cannot be performed.

In the present invention, the melting point Tm of PVA is a peak temperature of a main endothermic peak observed by a differential scanning calorimeter (DSC: for example, TA3000 manufactured by Mettler).

In the melt blown nonwoven fabric of the present invention, if necessary, some or all of the fibers may be subjected to thermocompression bonding to improve the adhesive force between the fibers and to improve the strength of the nonwoven fabric. Since the fibers constituting the melt blown nonwoven fabric of the present invention have a low degree of adhesion between the fibers when the web is formed, the fibers may be broken in a form in which the fibers of the web are pulled out. Therefore, the web strength can be improved and the practicality can be improved by thermocompression bonding and fixing the fibers partially or over the entire surface by, for example, hot embossing or heat calendering. The temperature, pressure, processing speed, embossing roll pattern, etc. of the heating roll in the thermocompression bonding can be appropriately selected depending on the purpose. The PVA-based long fiber constituting the nonwoven fabric of the present invention is active against water, and its apparent melting point decreases in the presence of water. It is possible to reduce the temperature of the heating roll.

The thus obtained thermoplastic PVA-based melt blown nonwoven fabric of the present invention can be made into a nonwoven fabric having various air permeability depending on the application.
A nonwoven fabric having an air permeability of about 400 cc / cm ² / sec can be obtained. In this case, if the average fiber diameter of the fibers constituting the nonwoven fabric exceeds 20 μm, it becomes difficult to achieve the air permeability in such a range, so the average fiber diameter is preferably 20 μm or less. Further, the nonwoven fabric of the present invention is a water-disintegrable nonwoven fabric showing a strong affinity for water, such as water solubility, water absorption, and water swellability, and has good water disintegratability even in cold water of 5 ° C. It can be made into a nonwoven fabric exhibiting properties, and can be treated with water in a normal environmental temperature range of 5 ° C to 30 ° C.

Here, the water-disintegrability of the nonwoven fabric means that the nonwoven fabric does not remain in the original sheet form.
Typically, the non-woven fabric is dissolved by water, the fibers constituting the non-woven fabric are disconnected from each other, and the shape of the sheet is not maintained.In some cases, due to water absorption, swelling, etc., shrinkage, bending, distortion such as wrinkles etc. Indicates that it will be clumped.

The melt-blown non-woven fabric thus obtained is a non-woven fabric having water disintegration properties as it is,
When it is necessary to exhibit water disintegration at a higher temperature, the nonwoven fabric can be adjusted by heat treatment. This is because the heat treatment promotes crystallization of the resin forming the fibers. The heat treatment itself may be performed during the melt blown nonwoven fabric manufacturing process, or may be performed by a method of once winding and then performing a heat treatment again. When the heat treatment is performed in this manner, the nonwoven fabric of the present invention does not exhibit water disintegration at a temperature lower than 50 ° C. when the weight retention of PVA constituting the nonwoven fabric is 99% or more,
Further, when the temperature is further increased, for example, the polymer dissolves rapidly under the condition of 70 ° C. or higher, and exhibits water disintegration controlled at a temperature.

It is important that the non-woven fabric is heat-treated at a temperature of 40 ° C. to Tm-5 ° C. In this case, if the treatment temperature is lower than 40 ° C., sufficiently crystallized fibers cannot be obtained, and the effect of improving the water collapse temperature of the nonwoven fabric cannot be obtained. On the other hand, if the treatment temperature is higher than Tm-5 ° C., the fibers adhere to each other due to heat, and the surface of the nonwoven fabric becomes rough, and the texture becomes undesirably hard.

The method of heat treatment may be any method other than directly exposing the nonwoven fabric to water, such as a water bath.
Although it can be performed by a heat roller or the like, a method of performing treatment using a heat roller which is industrially easy to perform continuous processing is preferable. When this heat roller is used, a method is used in which the nonwoven fabric touches the heat roller. This heat treatment
Heat treatment may be applied to only one side of the nonwoven fabric, or both sides may be treated. If necessary, not only heat but also pressure may be applied simultaneously. The dissolving temperature of the nonwoven fabric in water is determined by the boiling temperature of the nonwoven fabric dissolved in cold water depending on the blown conditions such as the blown temperature and the amount of blown air, and the heat history such as the heat treatment temperature or the heat treatment time after the nonwoven fabric, in addition to the specifications of the raw polymer. Until the non-woven fabric finally dissolves in water,
You can change it freely.

In addition, the water temperature when the nonwoven fabric is subjected to the dissolution treatment may be appropriately adjusted according to the purpose. The higher the treatment temperature, the shorter the treatment time. When dissolving with hot water, the treatment is preferably performed at 50 ° C. or higher, more preferably 60 ° C. or higher, particularly preferably 70 ° C. or higher, and most preferably 80 ° C. or higher. Further, the melting treatment of the melt blown nonwoven fabric made of PVA may involve decomposition of the fiber.

The fibers constituting the PVA meltblown nonwoven fabric of the present invention have biodegradability, and are decomposed into water and carbon dioxide when treated with activated sludge or buried in soil. When the fibers are continuously treated with activated sludge, they are almost completely decomposed in about two days to one month. From the viewpoint of biodegradability, the saponification degree of the fiber is preferably 90 to 99.99 mol%,
-99.98 mol% is more preferable, and 93-99.97.
Molar% is particularly preferred. Further, the content of 1,2-glycol bond in the modified PVA constituting the nonwoven fabric is from 1.2 to 1.2.
2.0 mol% is preferable, 1.25 to 1.95 mol% is more preferable, and 1.3 to 1.9 mol% is particularly preferable.
When the content of the 1,2-glycol bond in the PVA is 2.0 mol% or more, the thermal stability of the PVA deteriorates, and the melt blown spinnability may decrease. 1, in PVA
The 2-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 under reduced pressure at 90 ° C. for 2 days. PVA was dissolved in d6-DMSO, and a few drops of trifluoroacetic acid were added. Using proton NMR of 500 MHz (JEOL GX-500), 80 ° C.
Measure with The peak derived from the methine group of the vinyl alcohol unit is 3.2 to 4.0 ppm (integral value A), and the peak derived from one methine group of the 1,2-glycol bond is 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%) = B (100
−Δ) / A

Such a PVA meltblown nonwoven fabric of the present invention can be imparted with water solubility or disintegration depending on the intended use by selecting PVA and changing the setting of conditions during the production of the nonwoven fabric. PVA meltblown nonwovens can be used alone or in various products by laminating with other nonwovens (e.g., spunbond, dry nonwovens, wet nonwovens, etc.), fabrics, knits, nets, films, etc., depending on other purposes. Can, for example, detergents, bath agents, bactericides, deodorants, pharmaceuticals, drugs such as agricultural chemicals, seeds, food,
Packaging materials for packing baits, etc., various products, products, parts, wrapping materials such as powder, disposable warmer bags, diaper liners, disposable diapers, sanitary products, sanitary materials such as incontinence pads, surgical gowns, surgical tapes, masks Medical-related products such as sheets, bandages, gauze, clean cotton, first aid base cloth, pulp base cloth, wound dressing material, embroidery lace, splicing tape, hot melt sheets (including temporary fixing sheets), interlining , Vegetation sheet, agricultural covering material, root wrap sheet, masking tape, cap, filter, wiping cloth, abrasive cloth, towel, towel, makeup puff, makeup pack material, apron, gloves, table cloth, toilet seat For applications such as breathable re-wet adhesives, water-soluble toys, etc. used as various types of covers such as covers, wallpaper, backing paste for wallpapers, etc. It is possible to have. In addition, the nonwoven fabric of the present invention can be used as an intermediate material by using a part of the nonwoven fabric during the production stage of the product and dissolving and removing the final product, and the nonwoven fabric of the present invention can be used as a laminated product. It is considered that the use of a single layer allows stepwise control of the water disintegration timing of the entire product. Furthermore, the nonwoven fabric of the present invention can be used as a substitute for a highly water-absorbent resin or a highly water-absorbent fiber nonwoven fabric by preparing the nonwoven fabric of the present invention with a modified PVA that swells in normal temperature water.

[0044]

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

The method for analyzing the PVA and the method for measuring the proportion of the three-chain hydroxyl groups and the melting point of the PVA by the triad display of the PVA are as described above.

[Water disintegration property] The disintegration of the PVA-based melt blown nonwoven fabric of the present invention in water means that a square nonwoven fabric sample of about 0.1 g is collected, weighed, and adjusted to a predetermined temperature.
Pour into 000 cc of distilled water and leave for about 30 minutes, stirring occasionally. Thereafter, the state of the nonwoven fabric sample is observed, and if the shape of the nonwoven fabric sheet is not maintained, it is defined as collapsed. Thereafter, the state of the nonwoven fabric sample is observed, and if the shape of the nonwoven fabric sheet is not maintained, it is defined as collapsed. When the nonwoven fabric sample becomes clumpy due to shrinkage, swelling, curvature, etc., and it cannot be visually determined whether or not the shape of the nonwoven fabric sheet is retained, the sample piece is taken out, weighed after drying, and compared with before water injection, If the weight retention was 70% or less, it was considered collapsed.

[Weight Retention] The weight retention of the PVA meltblown nonwoven fabric was determined based on the weight of the untreated nonwoven fabric (25 ° C., 60%
R. H. Immersed in water at 50 ° C. for 30 minutes (after standing for 24 hours in water) and dried, and then dried at 25 ° C. and 60% R.F. H.
And the weight percentage after standing for 24 hours.

[Strength and elongation of non-woven fabric] JIS L1085
The measurement was performed in accordance with the “Nonwoven Interlining Test Method”.

[Measurement of air permeability] JIS L1096
The measurement was performed with a Frazier tester in accordance with the method A of “General fabric test method”.

[Measurement of Average Fiber Diameter] A photograph of the surface of the nonwoven fabric was magnified 1000 times by using a scanning electron microscope (2 diagonal lines were drawn on the photograph, The value obtained by converting the thickness into a magnification was used.
The average value of 100 fibers was used as the average fiber diameter. However, when the diameter of one fiber could not be measured because the corresponding fiber was unclear or a plurality of fibers were overlapped, it was excluded from the measurement target.

Example 1 29.0 kV of vinyl acetate was placed in a 100 L pressurized reaction tank equipped with a stirrer, a nitrogen inlet, an ethylene inlet, and an initiator inlet.
g and 31.0 kg of methanol were charged, the temperature was raised to 60 ° C., and 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 . 2,2 'as initiator
-Azobis (4-methoxy-2,4-dimethylvaleronitrile) (AMV) dissolved in methanol at a concentration of 2.8.
The g / L solution was adjusted, and nitrogen replacement was performed 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 increase the reaction tank pressure to 5.9 k.
g / cm ² , the polymerization temperature was maintained at 60 ° C., and AMV was continuously added at 610 ml / hr using the above initiator solution to carry out polymerization. After 10 hours, when the polymerization rate reached 70%, the polymerization was stopped by cooling. After the reactor was released and ethylene was removed, nitrogen gas was bubbled through to completely remove ethylene. Then, the reaction vinyl acetate monomer was removed under reduced pressure to obtain a methanol solution of polyvinyl acetate. Methanol was added to the obtained polyvinyl acetate solution to adjust the concentration to 50% by adding 200 g of methanol solution of polyvinyl acetate (molar ratio (MR) to vinyl acetate unit in solution: 0.10). Alkaline solution (N
(10% methanol solution of aOH) was added for saponification. Approximately 2 minutes after the addition of the alkali, the gelled system was pulverized with a pulverizer, left at 60 ° C. for 1 hour to allow saponification to proceed, and then 1000 g of methyl acetate was added to neutralize the remaining alkali. did. After confirming the completion of neutralization using a phenolphthalein indicator, the white solid PV obtained by filtration was obtained.
A, 1000 g of methanol was added to A, and it was left and washed at room temperature for 3 hours. After repeating the above washing operation three times, the PVA obtained by centrifugal dewatering was left in a dryer at 70 ° C. for 2 days to obtain dry PVA.

The resulting ethylene-modified PVA had a degree of saponification of 9
It was 8.4 mol%. After the modified PVA was ashed, 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 was added to n-hexane, and the precipitated polyvinyl acetate was collected.Then, the polyvinyl acetate was dissolved in acetone. After reprecipitation purification by adding to n-hexane again and precipitating three times, drying under reduced pressure at 80 ° C. for 3 days was performed to obtain purified polyvinyl acetate. The polyvinyl acetate was dissolved in d6-DMSO, and 500 MHz proton NM was added.
The content of ethylene was 10 mol% as measured at 80 ° C. using an R (JEOL GX-500) apparatus. After saponifying the above methanol solution of polyvinyl acetate at an alkali molar ratio of 0.5, the pulverized product was treated at 60 ° C. for 5 hours.
After allowing the saponification to proceed for a period of time, methanol soxhlet was carried out for 3 days, and then dried under reduced pressure at 80 ° C. for 3 days to obtain purified ethylene-modified PVA. The PVA
The average degree of polymerization was 330 according to a standard method of JIS K6726. The amount of 1,2-glycol bond and the content of hydroxyl group of three hydroxyl groups of the purified PVA were determined by 500 MHz proton NMR (JEOL GX-50).
0) It was 1.50 mol% and 83 mol%, respectively, as determined from the measurement by the apparatus as described above. Further, a 5% aqueous solution of the purified modified PVA was prepared to prepare a cast film having a thickness of 10 μm. After the film was dried under reduced pressure at 80 ° C. for 1 day, the film was dried using DSC (Mettler, TA3000) according to the method described above.
The melting point of VA was 206 ° C. (Table 1)

[0053]

[Table 1]

The PVA obtained above was melt-kneaded at 250 ° C. using a melt extruder, and the melted polymer stream was guided to a melt blow die head, weighed by a gear pump, and holes having a diameter of 0.3 mmφ were formed at a pitch of 0.75 mm. The fibers were discharged from the melt blown nozzles arranged in a line, and at the same time, hot air of 250 ° C. was sprayed on the resin, and the discharged fibers were collected on a molding conveyor to obtain a melt blown nonwoven fabric having a basis weight of 50 g / m ² . At this time, the single-hole discharge amount of the resin was 0.2 g / min / hole, the hot air flow was 0.15 Nm ³ / min / cm width,
The distance between the nozzle and the collection conveyor was 15 cm. Also, at this time, an air flow of 15 ° C. was blown into the melt blown fiber stream at a flow rate of 1 m ³ / min / cm width using equipment provided with a secondary air blowing device immediately below the nozzle of the melt blown device.

The obtained melt blown nonwoven fabric became a nonwoven fabric having a fiber diameter of 9.6 μm and an air permeability of 140 cc / cm ² / sec. When it was put into cold water at 5 ° C., it dissolved without remaining the original nonwoven fabric form. Similarly, even when poured into warm water of 50 ° C., the nonwoven fabric did not remain in the original nonwoven fabric form but dissolved. In addition, the evaluation results of the blown state, the state of the obtained nonwoven fabric, and the water disintegrability in hot water at 98 ° C. are summarized in Table 2. Table 3 shows the physical properties of this nonwoven fabric. The meanings of the symbols in the table are as follows. ：: extremely good ○: good △: slightly difficult ×: poor

[0056]

[Table 2]

Examples 2 to 16 The PVA shown in Table 1 was used in place of the PVA used in Example 1, and a PVA meltblown nonwoven fabric was obtained under the same conditions as in Example 1 except for the spinning temperature shown in Table 2. Was. The evaluation results of the blown state, the state of the obtained nonwoven fabric, the water disintegration property, and the like are summarized in Table 2.

Example 17 The PVA melt blown nonwoven fabric obtained in Example 1 was subjected to thermocompression embossing between a metal engraving roll having a round convex portion having a compression area ratio of 20% and a flat metal roll, thereby embossing the embossed nonwoven fabric. Obtained. The surface temperature of the roll at this time was 100 ° C. for both the engraving roll and the flat roll, and the linear pressure was 3
The speed was 5 kg / cmL and the speed was 5 m / min. Table 3 shows the physical properties of this nonwoven fabric. It is presumed that the reason why the strength of the nonwoven fabric is improved by the embossing is that the fibers in the nonwoven fabric are fixed by the embossing, and the frequency of the fibers slipping through is reduced.

Examples 18 to 22 The PVA meltblown nonwoven fabric obtained in Example 1 was run while being in contact with a metal flat roll rotating at a surface speed of 5 m / min. Heat treatment was performed by bringing the opposite surfaces into contact. At this time, the time during which the roll and the nonwoven fabric were in contact was about 8 seconds for both the front and back sides. At this time, in order to clarify the change in water disintegration of the nonwoven fabric due to the difference in the heat treatment temperature, samples were collected by changing the treatment temperature at several points. Tables 3 and 4 show the results obtained by investigating the morphology, physical properties, and water disintegration properties of these samples. Further, in relation to water disintegration, the weight retention and appearance after immersion in warm water at 50 ° C. were also investigated and are shown in Table 4. All of these nonwoven fabrics swelled in water, but the higher the heat treatment temperature, the higher the weight retention, and the heat-treated products at 180 ° C. and 200 ° C. had a weight retention of 99% or more and little change in appearance. . In particular, in the nonwoven fabrics of Examples 18 to 20, the appearance of the nonwoven fabric after immersion in water at 50 ° C. was distorted due to swelling and the shape of the fibers constituting the nonwoven fabric was lost, and the film was formed. Further, although the nonwoven fabric of Example 18 had a weight retention of 30%, the swelling of the fiber morphology was remarkable.

[0060]

[Table 3]

[0061]

[Table 4]

Example 23 In order to clarify the effect of increasing the heat treatment time,
The above Examples 18 to 2 were repeated except that the heat treatment for 8 seconds on each of the front and back sides was repeated 5 times by connecting 10 heat treatment rolls.
A sample was obtained by performing heat treatment under the same conditions as in Example 2. Tables 3 and 4 show the results of investigation of the form, physical properties and water disintegration of the nonwoven fabric.

Example 24 In order to improve the strength of the nonwoven fabric when swollen, the P obtained in Example 21 was used.
The VA melt blown nonwoven fabric was subjected to thermocompression embossing between a metal engraving roll having a round convex portion having a compression area ratio of 20% and a flat metal roll. The surface temperature of the roll at this time was 120 ° C. for both the engraving roll and the flat roll.
And the contact pressure was 35 kg / cmL and the speed was 5 m / min.

Example 25 The same embossing as in Example 24 was performed except that the PVA meltblown nonwoven fabric obtained in Example 22 was used.
Regarding the nonwoven fabrics obtained in Examples 23 to 25, the morphology, physical properties, water-disintegration, and water-disintegration-related weight retention after immersion in 50 ° C warm water and appearance are shown in Table 3 and The results are shown in Table 4. Examples 24 and 25
In the nonwoven fabric, the strong elongation of the nonwoven fabric was improved by the embossing treatment as compared with the nonwoven fabric before the treatment.

Comparative Examples 1 to 5 PVA shown in Table 1 was used in place of the PVA used in Example 1, and a PVA melt blown nonwoven fabric was obtained under exactly the same conditions as in Example 1 except for the blown temperature shown in Table 2. Was. Table 2 shows the spinnability, the state of the obtained nonwoven fabric, the water disintegration property, and the overall evaluation results. When the PVA shown in Comparative Example 1 was used, the melt viscosity was too high, so that stable ejection from the spinning hole could not be performed, and a nonwoven web could not be formed. Increasing the blown temperature to 270 ° C. reduced the apparent melt viscosity but caused degradation and gelation, further exacerbating the situation. In the case where the PVA of Comparative Example 2 was used, the melt viscosity was too low, so that the drip-shaped discharge was mixed and stable fiber formation could not be performed, and the nonwoven web could not be formed. In Comparative Example 3, yarn breakage occurred frequently due to the generation of gas containing acetic acid due to the thermal decomposition of PVA and gelation, and countless granular resins were scattered all over the surface, so that a so-called nonwoven web was not formed. In Comparative Example 4, at a blown temperature of 250 ° C., the melt viscosity was too high because the temperature was close to the polymer melting point. Therefore, when the blown temperature was increased to 270 ° C., the apparent melt viscosity was reduced, but decomposition and gelation occurred, and the situation was further deteriorated. In Comparative Example 5, it was presumed that the crystallinity of PVA was reduced, but the formed nonwoven fabric was stuck to the collector net and could not be wound.

Comparative Example 6 When manufacturing the PVA used in Example 1, the same methanol washing as in Example 1 was performed four times, and then washing was performed three times with a mixed solution of methanol / water = 90/10. PV with the sodium ion content of 0.0001 parts by weight
Using A, spinning was attempted in the same manner as in Example 1. As a result, countless granular resins were scattered on one side, and did not reach the point where the nonwoven fabric was wound. It is considered that the increase in the melt viscosity was due to the generation of a gel-like substance in the melt system.

COMPARATIVE EXAMPLE 7 When producing PVA used in Example 1, the melt blown was carried out in the same manner as in Example 1 except that the methanol was not washed and PVA having a sodium ion content of 1.4 parts by weight was used. But it could not be stably blown due to thermal decomposition.

Comparative Examples 8 to 12 In place of the PVA used in Example 1, PVA shown in Table 1 was used. Except for the blown temperature shown in Table 2, the PVA was composed of ultrafine fibers under the same conditions as in Example 1. A non-woven fabric was used.
Table 2 shows the spinnability and the evaluation results of the obtained nonwoven fabric.
When the PVA shown in Comparative Example 8 was used, the PVA
It was gelled and had poor blown spinnability, and did not reach the point where the nonwoven fabric was wound. In Comparative Example 9, the blown temperature was 200
At 0 ° C, spinnability was poor and fiberization was not possible, and nonwoven web formation was not possible. By setting the blown temperature to 240 ° C., the apparent melt viscosity was reduced, but decomposition and gelation occurred, yarn breakage occurred frequently, countless granular resins were scattered all over the surface, and a nonwoven web could not be formed. . In Comparative Example 10 and Comparative Example 11, the spinnability was good and the state of the nonwoven fabric was good, but the water disintegrability, which is the object of the present invention, was insufficient and was unsuitable. In Comparative Example 12, PVA having a low degree of polymerization and a low degree of saponification similar to those conventionally studied was used. Spinning temperature 2
Melt blown was attempted at 20 ° C., but pyrolysis and gelation occurred from the beginning, and did not lead to fiberization.

Claims (10)

[Claims] 1. A viscosity-average degree of polymerization of 200 to 500, 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 66 to 99.9 mol%. A polyvinyl alcohol (A) having a melting point of 160 ° C. to 230 ° C., wherein the alkali metal ion (B) is contained in an amount of 0.0003 to 1 part by weight per 100 parts by weight of (A) Melt blown nonwoven fabric. 2. The nonwoven fabric according to claim 1, wherein the polyvinyl alcohol is a modified polyvinyl alcohol containing 0.1 to 25 mol% of α-olefin units and / or vinyl ether units having 4 or less carbon atoms. 3. The nonwoven fabric according to claim 2, wherein the polyvinyl alcohol is a modified polyvinyl alcohol containing 3 to 20 mol% of ethylene units. 4. The content of 1,2-glycol bond is 1.
The nonwoven fabric according to any one of claims 1 to 3, which is 2 to 2.0 mol%. 5. Disintegration by water at 5 ° C. or higher.
5. The nonwoven fabric according to any one of the above items 4. 6. The nonwoven fabric according to claim 5, which disintegrates with water at 5 ° C. to 30 ° C. 7. Disintegration by water at 70 ° C. or higher, and 50
The nonwoven fabric according to any one of claims 1 to 4, which has a weight retention of 99% or more with respect to water at a temperature of not more than 0C. 8. The fiber constituting the nonwoven fabric has an average fiber diameter of 2
The nonwoven fabric according to any one of claims 1 to 7, wherein the nonwoven fabric has a pore size of 0 µm or less and an air permeability of 1 to 400 cc / cm ² / sec. 9. A viscosity average degree of polymerization of 200 to 500, 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 is 66 to 99.9 mol%. Is the melting point
Polyvinyl alcohol having a (Tm) of 160 to 230 ° C. and containing 0.0003 to 1 part by weight of an alkali metal ion (B) with respect to 100 parts by weight of (A), a spinning nozzle temperature As (Tm + 1
0) ° C. to (Tm + 80) ° C., 0.01 to 2.
Spinning under the condition of 0 Nm ³ / min / cm, and 5 spun from the spinning nozzle.
A method for producing a polyvinyl alcohol-based melt-blown nonwoven fabric, characterized in that an ultrafine fiber web is obtained by spraying onto a collection device separated by 0 cm or less. 10. The nonwoven fabric is subjected to a heat treatment at an arbitrary stage after the formation of the ultrafine fiber web.
3. The method for producing a nonwoven fabric according to item 1.