JP4648755B2 - Binder fiber for wet papermaking - Google Patents

Description

The present invention relates to a wet paper product prepared using the binder fibers and the binder fibers for wet papermaking. More particularly, the present invention was prepared using the binder fibers and the binder fibers for wet papermaking that the specific thermoplastic polyvinyl alcohol polymer and certain other thermoplastic polymer is complexed or mixed It relates to wet papermaking. The binder fiber for wet papermaking of the present invention can be easily manufactured by melt spinning without using wet spinning, and has excellent binder properties even under wet conditions. By using it as a binder fiber in carrying out, a wet paper product excellent in water resistance, mechanical strength and formation can be produced.

  Polyvinyl alcohol fiber has been conventionally used as a binder fiber when manufacturing a wet sheet or the like. Polyvinyl alcohol fibers have a high affinity with water due to a large number of hydroxyl groups present in the molecule, and are sufficiently dispersed in an aqueous papermaking raw material. In addition, the fiber swells in a water-containing state, and when heat is applied in the swollen state, the resin dissolves and further crystallizes again by drying to form a network structure, thereby exhibiting a binder effect.

  Polyvinyl alcohol fibers are generally subjected to wet-stretching after spinning a spinning solution in which polyvinyl alcohol is dissolved into a gel-like fiber structure by spinning into a coagulation bath made of an aqueous salt solution having a solidifying ability for the polymer. Manufactured by a wet gel spinning method of drying by heating.

  However, in the case of the wet gel spinning method, the production apparatus becomes very large, and it is necessary to strictly control the temperature and composition of the stock solution and coagulation bath, and it is difficult to operate stably. Many and high production techniques are required. In addition, since the coagulation treatment in wet gel spinning is basically performed in one step, it is difficult to employ a coagulation bath composition capable of coagulating two or more types of polymers having different coagulation performances simultaneously. It is difficult to produce composite fibers and mixed fibers made of polymer components. Further, even if two or more kinds of polymer components can be coagulated simultaneously in one coagulation bath, in order to realize the production of a composite fiber composed of two or more kinds of polymer components, it is necessary to combine them. It is difficult to produce core-sheath type composite fibers and sea-island type composite fibers that can be manufactured relatively easily by melt spinning by wet gel spinning. It is in.

  On the other hand, in composite spun fibers and mixed spun fibers manufactured by melt spinning, for example, in core-sheath type composite spun fibers and mixed spun fibers, the sheath component is formed from a low melting point polymer that functions as an adhesive component, and the core It is widely practiced to form a component from a high-melting polymer to impart reinforcing action and dyeability to the fiber. Examples include a core-sheath type composite spun fiber using a low melting point polyethylene as the sheath component, a high melting point polypropylene or polyester as the core component, a low melting point isophthalic acid-modified polyester as the sheath component, and the core component. Core-sheath type composite spun fiber using normal polyester with higher melting point, sea-island type composite spun fiber and mixed spinning using low melting point polyethylene for sea component and high melting point polypropylene or polyester for island component Sea-island composite spun fibers and mixed spun fibers are known in which low-melting isophthalic acid-modified polyester or the like is used for fibers and sea components, and normal polyester having a higher melting point is used for island components.

In recent years, in the polyvinyl alcohol polymer, an ethylene-modified polyvinyl alcohol polymer introduced by copolymerizing ethylene units has been developed for the purpose of obtaining a polyvinyl alcohol polymer that can be melt-spun and melt-molded. Production of composite spun fibers and mixed spun fibers by melt spinning using the ethylene-modified polyvinyl alcohol polymer and other thermoplastic polymers has already been performed (see Patent Documents 1 and 2).
However, when conventional composite spun fiber or mixed spun fiber using ethylene-modified polyvinyl alcohol polymer is used as a binder fiber for wet papermaking, the fiber is dispersed in an aqueous papermaking raw material. The ethylene-modified polyvinyl alcohol polymer constituting the polymer was dissolved in water, and the yield was not easily exhibited without sufficiently exerting the binder action, and the practical value as a binder fiber was not obtained. In addition, even when the binder effect is exhibited to some extent, the mechanical strength and water resistance of wet papermaking products such as wet papermaking paper tend to be insufficient, especially when exposed to water, the strength is likely to drop significantly. Met.

JP 2000-239926 A JP 2001-214329 A

An object of the present invention is to provide a plurality of heats that can be easily and smoothly produced with good fiberization process properties by melt spinning, without using wet gel spinning, and that are excellent in binder properties, water resistance, mechanical properties, and the like. It is to provide a binder fiber made of a plastic polymer.
In particular, the object of the present invention is to disperse well in an aqueous papermaking raw material when producing a wet papermaking such as paper, sheet, and non-woven fabric by wet papermaking, yet exhibiting a high binder effect, strength and It is an object of the present invention to provide a binder fiber that is excellent in water resistance and can provide a wet paper product having a good texture.
And the objective of this invention is providing the manufacturing method of the binder fiber which has the above-mentioned outstanding characteristic.
Furthermore, the objective of this invention is providing the wet papermaking which is excellent in intensity | strength and water resistance, and has a favorable formation which uses the binder fiber which has the above-mentioned outstanding characteristic.

In order to achieve the above object, the present inventors have repeatedly studied, as a result, thermoplastic polyvinyl alcohol polymers having a specific melting point, degree of polymerization, degree of saponification and alkali metal ion content, and other A melt composite spinning or melt mixing spinning is performed using a thermoplastic polymer in a specific ratio, and a fiber having a specific fineness (a composite spun fiber or a fiber having a thermoplastic polyvinyl alcohol polymer exposed on a fiber surface in a specific ratio). When mixed spinning fiber) is stretched or stretched / heat treated under specific conditions, the thermoplastic polyvinyl alcohol polymer exposed on the fiber surface has extremely low solubility in water and is moderate to water. It has been found that a binder fiber having excellent swelling performance can be obtained smoothly with good fiber forming process properties without causing troubles such as yarn breakage during melt spinning.
And when the present inventors manufactured a wet papermaking using the binder fiber obtained thereby, they had high strength both in drying and in wetness and had good hydrophilicity. In addition, the present inventors have found that a wet papermaking product having excellent water resistance and free from spots and having a uniform texture can be obtained, and the present invention has been completed based on these findings.

That is, the present invention
(1) <a> a thermoplastic polymer comprising a thermoplastic polyvinyl alcohol polymer (A) having a melting point of 160 to 230 ° C., and a polyolefin polymer and a polyamide polymer having a melting point of 240 ° C. or less. (B) is a binder fiber for wet papermaking formed by composite or mixing,
<B> The thermoplastic polyvinyl alcohol polymer (A) and the thermoplastic polymer (B) are combined or mixed in the form of sea-island type or bonded type in the cross section of the fiber;
<C> The thermoplastic polyvinyl alcohol polymer (A) constituting the binder fiber has a viscosity average polymerization degree of 200 to 500, a saponification degree of 90 to 99.9 mol%, and an alkali metal ion converted to sodium ion. Is a thermoplastic polyvinyl alcohol polymer having a content of 3 to 10000 ppm;
<D> The mass ratio of the thermoplastic polyvinyl alcohol-based polymer (A) to the thermoplastic polymer (B) in the binder fiber is 10:90 to 90:10;
Exposure rate of the thermoplastic polyvinyl alcohol polymer in the <e> fiber surface (A) is located at least 30%;
Single fiber fineness of <f> binder fiber be 0.1～15Dtex;
Single fiber fineness of each of the thermoplastic polymer (B) component in the <g> binder fiber in the be 0.001～4Dtex;
<H> Thermoplastic polyvinyl alcohol polymer in water elution amount of (A) is located at 10 wt% or less; and,
<I> The degree of swelling in water is 70 to 300%;
This is a binder fiber for wet papermaking .
Here, the “binder paper for wet papermaking” in the present invention is added to the main fiber in order to perform adhesion between the fibers when producing the wet papermaking by wet papermaking using the main fiber. Refers to the fiber used. The binder fiber for wet papermaking of the present invention is generally used by being added to and mixed with an aqueous papermaking raw material in which main fibers are dispersed.

And this invention,
(2) The thermoplastic modified polyvinyl alcohol polymer (A) has a structural unit derived from an olefin having 4 or less carbon atoms and / or a structural unit derived from vinyl ether in a proportion of 1 to 20 mol%. It is a binder fiber for wet papermaking according to (1), which is an alcohol polymer .

The present invention also provides:
(3) Heat having a melting point of 160 to 230 ° C., a viscosity average polymerization degree of 200 to 500, a saponification degree of 90 to 99.9 mol%, and a content of alkali metal ions converted to sodium ions of 3 to 1000 ppm. A mass of 10:90 to 90:10 of a thermoplastic polyvinyl alcohol polymer (A) and a thermoplastic polymer (B) comprising at least one of a polyolefin polymer having a melting point of 240 ° C. or less and a polyamide polymer. Used in the ratio, melt composite spinning or melt mixing spinning to obtain a composite spun fiber or mixed spun fiber having a sea-island-type or bonded-type composite form or mixed form in the cross section of the fiber, and under dry conditions, 110 to The moisture according to claim 1, which is produced by stretching at a temperature of 200 ° C for 0.5 to 1800 seconds or by performing stretching and heat treatment. It is a binder fiber for formula papermaking.

And this invention,
(4) A wet papermaking product produced using at least one binder fiber for wet papermaking according to any one of (1) to (3).

The binder fiber for wet papermaking of the present invention (hereinafter, “binder fiber for wet papermaking” may be simply referred to as “binder fiber”) exhibits excellent binder characteristics in the presence of moisture. Therefore, when the binder fiber of the present invention is used to produce a wet papermaking product such as paper, sheet, and nonwoven fabric by wet papermaking, it is dispersed uniformly and uniformly in the aqueous papermaking raw material, In addition, it is possible to produce a wet papermaking that is excellent in water resistance, flat and has a good texture.
The binder fiber of the present invention can be produced smoothly and easily with good fiberization processability by melt spinning such as melt composite spinning and melt mixing spinning.
If according to the present invention, the binder fibers having the above-mentioned excellent properties can be produced smoothly. In particular, in the present invention , the melt-spun binder fiber yarn is stretched and / or heat-treated under specific conditions, so that the elution amount of the thermoplastic polyvinyl alcohol polymer (A) in water is 10% by mass. The binder fiber of the present invention having a swelling degree in water of 70 to 300% can be obtained smoothly.

The binder fiber of the present invention is a fiber in which a thermoplastic polyvinyl alcohol polymer (A) “hereinafter referred to as“ thermoplastic PVA polymer (A) ”) and another thermoplastic polymer (B) are combined or mixed. (Ie composite spun fibers or mixed spun fibers).
The thermoplastic PVA polymer (A) constituting the binder fiber of the present invention has a melting point of 160 to 230 ° C., a viscosity average polymerization degree of 200 to 500, a saponification degree of 90 to 99.9 mol%, and sodium ions. Is a thermoplastic polyvinyl alcohol polymer (PVA polymer) having an alkali metal ion content of 3 to 10000 ppm.

The thermoplastic PVA-based polymer (A) has a viscosity average polymerization degree of 200 to 500, so that the fiberization processability when the binder fiber of the present invention is produced by melt spinning is improved. If the viscosity average polymerization degree of the thermoplastic PVA polymer (A) is too low, sufficient spinnability cannot be obtained, while if it is too high, the melt viscosity is too high and it is difficult to discharge the polymer from the spinning nozzle. become. The viscosity average degree of polymerization of the thermoplastic PVA polymer (A) is preferably 230 to 480, and more preferably 250 to 450.
Here, the viscosity average degree of polymerization of the thermoplastic PVA polymer (A) in the present specification means a viscosity average degree of polymerization measured according to JIS K6726. That is, after re-saponifying and purifying the thermoplastic PVA polymer (A), from the intrinsic viscosity [η] measured in water at 30 ° C., the formula: P = ([η] × 10 ³ /8.29) ^The degree of polymerization P determined from ^{(1 / 0.62)} (hereinafter, the viscosity average degree of polymerization may be simply referred to as “degree of polymerization”).

When the thermoplastic PVA polymer (A) constituting the binder fiber of the present invention has a saponification degree of 90 to 99.9 mol%, the binder fiber of the present invention can be smoothly melt-spun with good thermal stability. Can be manufactured. If the saponification degree of the vinyl alcohol polymer is less than 90 mol%, the thermal stability is poor, and the polymer is thermally decomposed or gelled during melt spinning, so that melt spinning cannot be performed smoothly. On the other hand, a vinyl alcohol polymer in which the degree of saponification of the vinyl alcohol polymer is higher than 99.99 mol% cannot be produced stably, and it is difficult to stably fiberize the polymer itself. It is.
The saponification degree of the thermoplastic PVA polymer (A) is preferably 96 to 99.98 mol%, more preferably 97 to 99.97 mol%, and 97.5 to 99.96 mol. % Is more preferable.

The thermoplastic PVA polymer (A) constituting the binder fiber of the present invention has a melting point of 160 to 230 ° C., so that the binder of the present invention is excellent in fiber strength while maintaining good thermal stability during melt spinning. Fiber can be produced. When the melting point of the PVA polymer is lower than 160 ° C., the crystallinity of the PVA polymer is lowered, the strength of the obtained fiber is lowered, and the thermal stability of the PVA polymer is lowered, so that melt spinning is performed. It may be difficult to fiberize. On the other hand, when the melting point of the PVA polymer is higher than 230 ° C., it is necessary to perform melt spinning at a temperature close to the decomposition temperature of the PVA polymer, and accordingly, the PVA polymer is decomposed during melt spinning. As a result, the binder fiber cannot be manufactured stably.
The melting point of the thermoplastic PVA polymer (A) is preferably 170 to 227 ° C, and more preferably 180 to 220 ° C.
The melting point of the PVA polymer referred to in this specification is determined by using DSC (differential scanning calorimeter), raising the temperature to 250 ° C. in nitrogen at a heating rate of 10 ° C./min, cooling to room temperature, and increasing again. This means the temperature required as the peak top of the endothermic peak when the temperature is raised to 250 ° C. at a temperature rate of 10 ° C./min, and the detailed measurement method is as described in the following examples.

The thermoplastic PVA polymer (A) constituting the binder fiber of the present invention has an alkali metal ion in terms of sodium ion of 3 to 10,000 ppm [thermoplastic PVA with respect to the mass of the thermoplastic PVA polymer (A). Content of 0.0003 to 1 part by mass relative to 100 parts by mass of the polymer (A)], decomposition and gelation do not occur during melt spinning, and the affinity of the resulting fiber for water Can be kept high.
When the content of alkali metal ions in the PVA polymer is less than 3 ppm as described above, the affinity of the resulting fiber for water becomes insufficient. On the other hand, when the content is more than 10,000 ppm, Decomposition and gelation occur, resulting in poor fiberization processability.
The alkali metal ion content in the thermoplastic PVA polymer (A) is preferably 3 to 8000 ppm, more preferably 5 to 6000 ppm, and even more preferably 5 to 5000 ppm in terms of sodium ions. .
Examples of the alkali metal ion include potassium ion and / or sodium ion, and among them, sodium ion is preferable.
The content of alkali metal ions in the PVA polymer referred to in the present specification means a value determined by an atomic absorption method, and details thereof are as described in the following examples.

  The thermoplastic PVA polymer (A) may be a PVA homopolymer consisting of only vinyl alcohol units, or may be a copolymerizable monomer with vinyl alcohol units as long as it has the above-mentioned properties. It may be a modified PVA polymer having a derived structural unit (copolymerization unit). Among these, a modified PVA polymer having a copolymer unit is preferable from the viewpoints of melt spinnability, affinity with water, physical properties of the obtained fiber, and the like.

Examples of the copolymerizable monomer forming the copolymer unit in the thermoplastic PVA polymer (A) (modified PVA polymer) include α such as ethylene, propylene, 1-butene, isobutene, and 1-hexene. -(Meth) acrylic such as olefins, (meth) acrylic acid, salts thereof, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate Acid esters, (meth) acrylamide derivatives such as (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n- Vinyl ethers such as butyl vinyl ether, ethylene glycol vinyl Hydroxy group-containing vinyl ethers such as ether, 1,3-propanediol vinyl ether and 1,4-butanediol vinyl ether, allyl ethers such as allyl acetate, propyl allyl ether, butyl allyl ether and hexyl allyl ether, having an oxyalkylene group Monomers, vinylsilyls such as vinyltrimethoxysilane, isopropenyl acetate, 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, 7-octen-1-ol, 9 -Hydroxyl group-containing α-olefins such as decene-1-ol and 3-methyl-3-buten-1-ol, carboxyl groups such as fumaric acid, maleic acid, itaconic acid, maleic anhydride, itaconic anhydride (anhydrous Monomer having carboxylic acid group), ethylene Monomers having sulfonic acid groups such as sulfonic acid, allylsulfonic acid, methallylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, vinyloxyethyltrimethylammonium chloride, vinyloxybutyltrimethylammonium chloride, vinyloxyethyl Cationic groups such as dimethylamine, vinyloxymethyldiethylamine, N-acrylamidomethyltrimethylammonium chloride, N-acrylamidoethyltrimethylammonium chloride, N-acrylamidodimethylamine, allyltrimethylammonium chloride, methallyltrimethylammonium chloride, dimethylallylamine, allylethylamine And the like.
The thermoplastic PVA polymer (A) can have a structural unit (copolymerization unit) derived from one or more of the above-described copolymerizable monomers.
The content ratio of the copolymer unit derived from the copolymerizable monomer in the thermoplastic PVA polymer (A) is preferably 25 mol% or less, more preferably 20 mol% or less, More preferably, it is 15 mol% or less.

  Among them, the thermoplastic PVA polymer (A) includes, as copolymer units, α-olefins such as ethylene, propylene, 1-butene, isobutene, and 1-hexene, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, Hydroxy group-containing vinyl ethers such as i-propyl vinyl ether and n-butyl vinyl ether, ethylene glycol vinyl ether, 1,3-propanediol vinyl ether, 1,4-butanediol vinyl ether, allyl acetate, propyl allyl ether, butyl allyl Ethers, 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 It has a copolymer unit derived from hydroxy group-containing α-olefins such as octen-1-ol, 9-decen-1-ol, and 3-methyl-3-buten-1-ol. From the viewpoint of easy availability of a modified vinyl alcohol polymer having various copolymer units.

In particular, from the viewpoint of easy availability of the modified vinyl alcohol polymer and melt spinnability, the thermoplastic PVA polymer (A) is a carbon composed of ethylene, propylene, 1-butene or isobutene as a copolymer unit. It is preferable to have a structural unit (copolymerization unit) derived from vinyl ethers such as α-olefins having a number of 4 or less, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, and n-butyl vinyl ether. In this case, the proportion of structural units (copolymerized units) derived from α-olefins having 4 or less carbon atoms and / or vinyl ethers (the total proportion when having two or more copolymerized units) is 0. It is preferably 1 to 20 mol%, more preferably 4 to 15 mol%, and still more preferably 6 to 13 mol%.
When the thermoplastic PVA polymer (A) has an ethylene unit as a copolymer unit, the proportion of the ethylene unit is preferably 4 to 15 mol%, particularly 6 to 13 mol%, since the fiber physical properties become high. .

  The method for producing the thermoplastic PVA polymer (A) constituting the binder fiber of the present invention is not particularly limited. For example, a vinyl ester compound is used together with one or more of the above-described copolymerizable monomers as necessary, and known methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization are used. The polymerization is carried out by a method, preferably a bulk polymerization method or a solution polymerization method, to produce a vinyl ester compound homopolymer or a copolymer of a vinyl ester compound and a copolymerizable monomer, and then the vinyl in the polymer. It can be produced by saponifying an ester bond derived from an ester compound into a hydroxyl group.

  In the production of a polymer of a vinyl ester compound that is a precursor of a PVA polymer, examples of the vinyl ester compound include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, Examples thereof include vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl persate, etc. Among them, vinyl acetate is preferably used.

As a solvent for solution polymerization using a vinyl ester compound, lower alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol are preferably used.
Moreover, as a polymerization initiator used for manufacture of the homopolymer or copolymer of a vinyl ester compound, for example, α, α′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethyl- Azo polymerization initiators such as valeronitrile) and peroxide polymerization initiators such as benzoyl peroxide and n-propyl peroxycarbonate.
The polymerization temperature is not particularly limited, but is generally in the range of 0 ° C to 150 ° C.

  Saponification treatment of the ester group derived from the vinyl ester compound in the vinyl ester compound obtained above or an alkali substance containing alkali metal ions, particularly potassium hydroxide or sodium hydroxide. Then, the vinyl alcohol polymer produced thereby is washed with a washing liquid, and the content of alkali metal ions in the vinyl alcohol polymer is adjusted to 3 to 10000 ppm, whereby the alkali used in the binder fiber of the present invention is used. A thermoplastic PVA polymer (A) having a metal ion content of 3 to 10,000 ppm can be obtained.

In the saponification of a homopolymer or copolymer of a vinyl ester compound, an alkaline substance (potassium hydroxide or sodium hydroxide) is generally added to 1 mol of a structural unit derived from the vinyl ester compound in the polymer. It is preferably used in a ratio of 0.004 to 0.5 mol, particularly 0.005 to 0.5 mol. The alkaline substance may be added all at once in the initial stage of the saponification reaction, or may be added sequentially during the saponification reaction.
The saponification reaction is preferably performed in an organic solvent such as methanol, methyl acetate, diethyl sulfoxide, or dimethylformamide, and among them, it is preferable to perform in methanol. In carrying out the saponification reaction in methanol, it is necessary to use methanol having a water content of 0.001 to 1% by mass, more preferably 0.003 to 0.9% by mass, and particularly 0.005 to 0.8% by mass. preferable.

  The saponified polymer is washed using a washing solution such as methanol, acetone, methyl acetate, ethyl acetate, hexane, water or the like. Among these, it is preferable to wash using methanol, methyl acetate and water alone or using a mixture of these two or three kinds. By adjusting the usage-amount of a washing | cleaning liquid, content of the alkali metal ion in the thermoplastic PVA-type polymer (A) finally obtained can be adjusted to 3-10000 ppm. In general, it is preferable to perform the cleaning treatment using 300 to 10,000 parts by mass, particularly 500 to 5000 parts by mass of the cleaning liquid with respect to 100 parts by mass of the vinyl alcohol polymer. The washing temperature is generally preferably 5 to 80 ° C., particularly preferably 20 to 70 ° C., and the washing time is preferably 20 minutes to 10 hours, particularly 1 to 6 hours.

  In order to make the content of alkali metal ions in the thermoplastic PVA polymer (A) 3 to 10,000 ppm as described above, in addition to the method described above, a vinyl alcohol polymer having a content of alkali metal ions less than 3 ppm is used. A method of manufacturing in advance or obtaining separately and adding a necessary amount of alkali metal ions may be adopted.

  The thermoplastic PVA polymer (A) constituting the binder fiber of the present invention is a colorant, a heat stabilizer, an ultraviolet absorber, and a light stabilizer as necessary, as long as the object and effect of the present invention are not impaired. Antioxidants, antistatic agents, flame retardants, plasticizers, lubricants, crystallization rate retarders, and the like can be added and contained during the polymerization reaction or in subsequent steps. In particular, the thermoplastic PVA polymer (A) contains, as a heat stabilizer, an organic stabilizer such as hindered phenol, a copper halide compound such as copper iodide, and an alkali metal halide compound such as potassium iodide. In this case, even when exposed to the melting temperature for a relatively long time during melt spinning, the stability is maintained well.

  Furthermore, the thermoplastic PVA polymer (A) constituting the binder fiber of the present invention contains fine particles having an average particle diameter of 0.01 to 5 μm in a proportion of 0.05 to 10% by mass as necessary. It may be. The fine particles can be added in the polymerization step or in subsequent steps. The kind of fine particles is not particularly limited, and examples thereof include silica, alumina, titanium oxide, calcium carbonate, barium sulfate, and the like, and one or more of these can be contained. In particular, when inorganic fine particles having an average particle size of 0.02 to 1 μm are contained in the thermoplastic PVA polymer (A), spinnability and stretchability are improved.

Melting point of the thermoplastic polymer constituting the binder fiber of the present invention (B) is 240 ° C. or less. When the melting point of the thermoplastic polymer (B) is higher than 240 ° C., it is necessary to perform melt spinning for producing binder fibers at a temperature of 240 ° C. or higher. In this case, the melt spinning temperature is thermoplastic. The decomposition temperature of the PVA polymer (A) is very close to or exceeds the decomposition temperature, causing the thermoplastic PVA polymer (A) to decompose during melt spinning and smoothly producing the desired binder fiber. become unable.
The melting point of the thermoplastic polymer (B) is preferably 80 to 240 ° C, more preferably 80 to 200 ° C.
The melting point of the thermoplastic polymer (B) in this specification is determined by using DSC (Differential Scanning Calorimeter) to raise the temperature to 300 ° C. in nitrogen at a heating rate of 10 ° C./min, and then cooling to room temperature. It means the temperature required as the peak top of the endothermic peak when the temperature is raised again to 300 ° C. at a rate of temperature increase of 10 ° C./min, and the detailed measurement method is as described in the following examples.
Inder fibers can be obtained smoothly.

Examples of the thermoplastic polymer having a melting point of 240 ° C. or lower include polyolefin polymers, polyamide polymers, modified polyvinyl alcohol (for example, polyvinyl alcohol having 25 to 70 mol% of ethylene units), and thermoplastic elastomers (styrene and diene). , Chlorine-based, olefin-based, polyester-based, polyurethane-based, polyamide-based, and fluorine-based thermoplastic elastomers) . In the present invention, the thermoplastic polymer (B) is the above-described thermoplastic polymer. Of these, polyolefin polymers and polyamide polymers having a melting point of 240 ° C. or lower are used. Among them, as the thermoplastic polymer (B), at least one of a fiber-forming polyolefin polymer and a polyamide polymer is preferably used.

  Examples of the polyolefin polymer having a melting point of 240 ° C. or lower include a homopolymer such as polypropylene, polyethylene, polybutene, and polymethylpentene, or a structure derived from one or more of propylene, ethylene, butene, and methylpentene. Examples thereof include a copolymer having a unit.

  When the thermoplastic polymer (B) is a polyamide polymer, for example, nylon 6, nylon 10, nylon 12, nylon 6-12 and the like can be mentioned.

  The thermoplastic polymer (B) that constitutes the binder fiber of the present invention comprises, if necessary, inorganic fine particles, fluorescent brightener, thermal stabilizer, antioxidant, ultraviolet absorber, hydrolysis inhibitor, antistatic agent. In addition, one or more of flame retardants, colorants and other additives may be contained.

The binder fiber of the present invention contains the thermoplastic PVA polymer (A) and the thermoplastic polymer (B) in a mass ratio of 10:90 to 90:10 based on the mass of the binder fiber.
When the content of the thermoplastic PVA polymer (A) is less than 10% by mass in the binder fiber [when the content of the thermoplastic polymer (B) exceeds 90% by mass], when used for wet papermaking In addition, the binder fiber does not sufficiently disperse and swell in the aqueous papermaking raw material, and accordingly, the binder function cannot be exhibited sufficiently, and the strength of the resulting wet papermaking product is lowered. On the other hand, when the content ratio of the thermoplastic PVA polymer (A) exceeds 90% by mass [when the content ratio of the thermoplastic polymer (B) is less than 10% by mass), the heat having the reinforcing action of the binder fiber. When the proportion of the plastic polymer (B) is lowered and the fiber strength is lowered, the strength of the wet paper product is lowered when used as a binder fiber.
The content ratio of the thermoplastic PVA polymer (A) and the thermoplastic polymer (B) in the binder fiber of the present invention is a mass ratio of 20:80 to 80:20, particularly a mass ratio of 25:75 to 75:25. It is preferable that

  In the binder fiber of the present invention, the exposure ratio of the thermoplastic PVA polymer (A) on the fiber surface needs to be 30% or more, preferably 50% or more, and preferably 70% or more. More preferably, it is still more preferably 80 to 100%. When the exposure rate of the thermoplastic PVA polymer (A) on the fiber surface of the binder fiber is less than 30%, when used for wet papermaking, the affinity for water is low and the aqueous papermaking raw material is Thus, the binder fibers are not uniformly dispersed, and it becomes difficult to obtain a wet paper product having a good flat texture. In addition, the binder fiber does not swell sufficiently, and accordingly, the binder function cannot be exhibited sufficiently, and the strength of the resulting wet paper product is lowered.

  The binder fiber of the present invention is generally a composite spun fiber in which the thermoplastic PVA polymer (A) and the thermoplastic polymer (B) are combined with each other, or the thermoplastic PVA polymer (A) and the thermoplastic. It is a mixed spun fiber in which the polymers (B) are mixed with each other in an incompatible state.

As is well known, a composite spun fiber is a single fiber (composite fiber) in which two or more polymers are joined together in a continuous state in the fiber length direction without interruption. In general, the composite form is divided into the core-sheath type, sea-island type, bonded type (side-by-side type, layered-divided type, radial-divided type), or a mixed type thereof, as seen from the cross-sectional shape of the fiber. It is done.
The mixed spun fiber is a fiber formed by mixing and spinning two or more kinds of polymers that do not mix uniformly with each other before spinning from the spinneret, and the two or more kinds of polymers. 1 type or 2 types or more are fibers that are joined together to form one fiber while being interrupted in the length direction of the fiber, and the cross section of the fiber generally has a sea-island structure. In many cases, it may have a bonded structure.

In the binder fiber of the present invention, the content ratio of the thermoplastic PVA polymer (A) and the thermoplastic polymer (B) in the fiber is 10:90 to 90:10, and the thermoplastic PVA system on the fiber surface. exposure rate of the polymer (a) is 30% or more, the complex form or mixed form, as long as the exposure ratio of the thermoplastic PVA polymer in the fiber surface (a) is 30% or more, the sea islands , A bonding type (side-by-side type, layered division type, radial division type), or a mixed type thereof may be used.

Among them, the binder fiber of the present invention, thermoplastic PVA based polymer (A) as a sea component, the thermoplastic polymer (B) in the case of a composite spun fiber or mixed spun fibers sea-island to island component things, exposure rate of the thermoplastic PVA polymer (a) is increased in the fiber surface Bas Indah fibers, high affinity with water, water-dispersible and highly water-swellable, yet having excellent binder effect It becomes.

When the binder fiber of the present invention is a sea-island type composite spun fiber or mixed spun fiber having the thermoplastic PVA polymer (A) as a sea component and the thermoplastic polymer (B) as an island component, The component may be formed from one type of thermoplastic polymer (B), or may be formed from two or more types of thermoplastic polymers (B). When the island component is formed from two or more kinds of thermoplastic polymers (B), a plurality of islands may be formed separately from different types of thermoplastic polymers (for example, a specific island is heated). is formed from thermoplastic polymer B _1, if the other islands that are formed from a thermoplastic polymer B ₂ of different types from that), has a plurality of islands are formed from a mixture of two or more thermoplastic polymers (For example, when all of the islands are formed from a mixture of thermoplastic polymers B ₁ and B ₂ ).
However, when the binder fiber of the present invention is a sea-island type mixed spun fiber, depending on the viscosity balance of the thermoplastic PVA polymer (A) and the thermoplastic polymer (B) and the use ratio of both polymers. Since the sea and islands are reversed, the thermoplastic PVA polymer (A) may become an island component, so that the thermoplastic PVA polymer (A) becomes a sea component, the viscosity balance and It is necessary to adjust the use ratio of both polymers.

  The cross-sectional shape of the binder fiber of the present invention is not particularly limited, and may be any cross-sectional shape such as a round shape, a flat shape, a saddle shape, a hollow shape, a T shape, a triangular shape, a multileaf shape, and a V shape. Also good.

The binder fiber of the present invention needs to have a single fiber fineness of 0.1 to 15 dtex, preferably 0.5 to 13 dtex, and more preferably 1 to 9 dtex.
When the single fiber fineness of the binder fiber is less than 0.1 dtex, it becomes difficult to produce the binder fiber with high productivity. On the other hand, when it exceeds 15 dtex, the fiber becomes thick and has a large adhesion point when used as a binder. And the function as a binder fiber is not fully exhibited.

In the binder fiber of the present invention, the single fiber fineness of each thermoplastic polymer (B) component in the binder fiber [in the case where the thermoplastic polymer (B) is present in the binder fiber in the form of island components , The single fiber fineness of each island, and the single fiber fineness of the individual thermoplastic polymer (B) portion forming the bonded structure in the bonded composite spun fiber, etc., must be 0.001 to 4 dtex. 0.01 to 1 dtex is preferable, and 0.04 to 0.2 dtex is more preferable.
When the single fiber fineness of the individual thermoplastic polymer (B) component in the binder fiber is less than 0.001 dtex, the fineness is too small and the reinforcing action of the fiber by the thermoplastic polymer (B) component is not exhibited. In addition, the strength of the binder fiber is lowered, and as a result, the strength of the wet paper product obtained using the binder fiber is lowered. On the other hand, if the single fiber fineness of the individual thermoplastic polymer (B) component in the binder fiber exceeds 4 dtex, the unevenness in the wet papermaking becomes large when used in wet papermaking, resulting in a smooth and uniform texture. It becomes difficult to obtain a wet papermaking product.

Furthermore, the binder fiber of the present invention needs to have an elution amount of the thermoplastic PVA polymer (A) in water of 10% by mass or less and a degree of swelling in water of 70 to 300%.
When the amount of the thermoplastic PVA polymer (A) in the binder fiber eluted in water exceeds 10% by mass, the thermoplastic PVA system constituting the binder fiber when wet papermaking is performed using the binder fiber. The proportion of the polymer that dissolves in the aqueous papermaking stock solution increases, so that a sufficient binder effect is not exhibited, and the strength of the resulting wet papermaking product is lowered. In the binder fiber of this invention, it is preferable that the elution amount of the thermoplastic PVA-type polymer in water is 8 mass% or less.
The “elution amount of the PVA polymer in water in the binder fiber” in the present specification means the elution amount of the PVA polymer when the binder fiber is immersed in water at 30 ° C. for 20 hours. The measuring method is as described in the following examples.

Further, if the degree of swelling of the binder fiber in water is less than 70%, the binder fiber does not swell sufficiently, so that the adhesive effect is not sufficiently exhibited when used in wet papermaking, etc. Reduces strength. On the other hand, if the swelling degree of the binder fiber in water exceeds 300%, the solubility of the thermoplastic PVA polymer in the binder fiber is increased in water, and the PVA forming the binder fiber when used for wet papermaking or the like. When the polymer is dissolved in water and lost, it does not exhibit a sufficient binder effect, and the strength of the resulting wet paper product decreases. In the binder fiber of the present invention, the degree of swelling in water is preferably 90 to 200%, and more preferably 100 to 180%.
In this specification, “the degree of swelling of the binder fiber in water” refers to the degree of swelling of the fiber when the binder fiber is immersed in water at 30 ° C. for 30 minutes, and the detailed measurement method is described in the following examples. It is as follows.

  The binder fiber of the present invention has a melting point of 160 to 230 ° C., a viscosity average polymerization degree of 200 to 500, a saponification degree of 90 to 99.9 mol%, and a content of alkali metal ions converted to sodium ions of 3 to 10,000 ppm. The above-described thermoplastic PVA polymer (A) and a thermoplastic polymer (B) having a melting point of 240 ° C. or less are used at a mass ratio of 10:90 to 90:10, and melt spinning (melt compound spinning) Or melt-mixed spinning), or stretching or heat-treating, the exposure ratio of the thermoplastic PVA polymer (A) on the fiber surface is 30% or more, the single fiber fineness is 0.1 to 15 dtex, and A binder fiber having a single fiber fineness of 0.001 to 4 dtex of each thermoplastic polymer (B) component in the fiber is produced, and at that time, melt spinning (melt compound spinning or melting) The fibers spun by (spinning) are dried at 110 to 200 ° C. for 0.5 to 1800 seconds under the drying conditions in the above-described drawing step, in the heat treatment step, or in both the drawing step and the heat treatment step. It can obtain smoothly by the manufacturing method of this invention heated over (total heating time in 110-200 degreeC).

In the production method of the present invention described above, the melt spinning (melt composite spinning or melt mixed spinning) is the same melt spinning apparatus as conventionally employed for producing composite spun fibers or mixed spun fibers by melt spinning. And adopting the method.
In melt spinning, in order to prevent thermal decomposition of the thermoplastic PVA polymer (A), it is preferable to employ a temperature ranging from the melting point of the thermoplastic PVA polymer (A) to the melting point + 30 ° C. Is preferably employed at a melting temperature of 200 to 250 ° C.
At the time of melt spinning, the spinning amount of the polymer is the single fiber fineness of the binder fiber to be produced, the number of spinning holes in the spinneret, and the composite form of the thermoplastic PVA polymer (A) and the thermoplastic polymer (B) in the binder fiber. It can be adjusted according to the mixing mode, the take-up speed, etc.
In addition, it is preferable that the spinning yarn obtained by spinning from the spinneret is generally drawn at a draw ratio of 2 to 6 times. Stretching may be performed subsequent to spinning, or may be performed while winding the spun yarn and then rewinding it.

  The thermoplastic PVA polymer having a melting point of 160 to 230 ° C. used in the binder fiber of the present invention has a relatively small molecular weight of 200 to 500 in order to lower the melting point and enable melt spinning. Is modified by a copolymerization component or the like to further lower its melting point. Therefore, when a binder fiber is produced using such a thermoplastic PVA polymer, the crystal on the fiber surface has a sufficient size even if normal stretching orientation is performed to promote crystallization during fiberization. As a result, the degree of swelling of the fiber in water becomes too high, the solubility in water becomes high, and when used as a binder fiber in wet papermaking, the thermoplastic PVA polymer is dissolved in water and lost. The binder effect is not sufficiently exhibited.

The present inventors use a thermoplastic PVA polymer having a relatively low melting point of 160 to 230 ° C., which can smoothly perform melt spinning, and has low solubility in water and high degree of swelling in water. In order to develop a binder fiber that is in an appropriate range and has an excellent binder effect, the inventors have repeatedly studied. As a result, when producing the binder fiber by performing melt spinning (melt compound spinning or melt mixed spinning) using the thermoplastic PVA polymer (A) and the thermoplastic polymer (B), melt spinning is performed. By heating the spun fiber in the subsequent drawing step, in the heat treatment step, or in both the drawing step and the heat treatment step, under the above-mentioned specific conditions, the solubility in water is 10%. The binder fiber of the present invention having an excellent binder effect was obtained with an appropriate degree of swelling in water of 70 to 300%.
Heating under drying conditions in the stretching step and / or heat treatment step after melt spinning is preferably performed at a temperature of 120 to 180 ° C. for 0.7 to 1200 seconds, and at a temperature of 135 to 160 ° C. More preferably, it is carried out for 5 to 600 seconds.

If the heating temperature after melt spinning is out of the range of the present invention described above and is less than 110 ° C., the solubility of the fiber in water and the degree of swelling in water are too large to obtain the binder fiber of the present invention. In addition, when the heating temperature after melt spinning exceeds 200 ° C., the crystal size on the fiber surface becomes too large, the degree of swelling in water becomes excessively small, the fiber is thermally decomposed, etc., and has a binder effect. Fiber cannot be obtained.
Further, even when heating at 110 to 200 ° C. under drying, if the heating time is out of the range in the present invention and is too short, the growth of crystal size becomes insufficient, while the heating time is in the present invention. If it is too long outside the range, the crystal size becomes excessively large, and further, thermal decomposition of the fiber occurs. In each case, the solubility in water is 10% or less and the degree of swelling in water is 70 to 300%. Certain binder fibers of the present invention cannot be obtained.

In carrying out the manufacturing method of the present invention described above, as a method for heating the melt-spun fiber,
(I) The melt-spun fiber has a moisture content of 70% or less, preferably 50% or less, more preferably 20% or less, and the inside temperature of the furnace in the above-described range of 110 to 200 ° C. A method in which the fiber stays in the furnace for 0.5 to 1800 seconds as described above and is drawn while being continuously passed and then taken out from the heating furnace;
(Ii) The melt-spun fiber is passed through a dry room having a moisture content of 70% or less, preferably 50% or less, and more preferably 20% or less. A method of bringing the heating plate into contact with the drawing roller or heating plate so that the contact time is 0.5 to 1800 seconds as described above, and then drawing out from the chamber;
Etc. can be adopted.
Among them, the above method (i) is preferably employed from the viewpoint that the heat treatment time can be sufficiently and sufficiently taken and the productivity is improved.

The binder fiber of the present invention can be effectively used as a binder fiber for producing wet paper products such as paper, sheet, and non-woven fabric by wet paper making, and as a binder fiber for wet-drying by dry entanglement of a dry non-woven fabric. it can.
Among them, the binder fiber of the present invention is suitable as a binder fiber for producing a wet paper product. By producing a wet paper product using the binder fiber of the present invention, the strength, water resistance, and texture are improved. An excellent wet paper product can be obtained.

In producing a wet paper product using the binder fiber of the present invention, for example, the binder fiber of the present invention is generally cut into short fibers of about 2 to 15 mm, and the short fiber is dispersed in water based on a main fiber. After adding and mixing to the papermaking raw material and making it with a papermaking machine, it is usually heated at 80 ° C or higher, preferably 90 to 120 ° C, so that the main fibers are well bonded with the binder fiber of the present invention. In addition, a paper product having good adhesion between the binder fiber and the main fiber of the present invention can be obtained.
In that case, it is preferable that the addition ratio of the binder fiber of this invention is 5-40 mass% with respect to the mass of a main fiber, especially 10-25 mass%.

The type of the main fiber in producing the wet papermaking is not particularly limited, and suitable fibers can be used according to the use of the wet papermaking, for example, various natural pulps, cellulose fibers, polyvinyl alcohol fibers. , Polyamide fiber, polyester fiber, vinyl chloride-vinyl acetate copolymer fiber, ethylene-vinyl acetate copolymer fiber, polypropylene fiber, polyethylene fiber, polyacrylonitrile fiber, polyvinylidene chloride fiber, wholly aromatic polyester fiber, all An aromatic polyamide fiber etc. can be mentioned.
The solid content concentration in the aqueous papermaking raw material is not particularly limited, and may be adjusted according to a conventionally known papermaking technique. Moreover, what is necessary is just to employ | adopt the papermaking apparatus, papermaking conditions, etc. suitable for each condition.

  Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the following production examples, comparative production examples, examples, and comparative examples, various physical properties were measured and evaluated as follows.

(1) Melting point of thermoplastic PVA polymer:
(I) A thermoplastic PVA polymer obtained in the following production examples or comparative production examples is dissolved in water to prepare a 5% aqueous solution, which is cast on a substrate to obtain a cast film (thickness before drying). 10 μm), and the cast film was dried at 80 ° C. under reduced pressure for 24 hours to prepare a dried thermoplastic PVA polymer film.
(Ii) Using the dried thermoplastic PVA polymer film obtained in (i) above, using DSC (Differential Scanning Calorimeter) (“TA3000” manufactured by METTLER) in a nitrogen gas atmosphere The temperature was raised to 250 ° C. at a rate of temperature increase of 10 ° C./min, cooled to room temperature, and then again raised to 250 ° C. at a rate of temperature increase of 10 ° C./min. The melting point (° C.) of the system polymer was used.

(2) Viscosity average polymerization degree of thermoplastic PVA polymer:
The viscosity average polymerization degree of the thermoplastic PVA polymer obtained in the following production examples or comparative production examples was measured according to JIS K6726.

(3) Degree of saponification of thermoplastic PVA polymer:
The saponification degree of the thermoplastic PVA polymer obtained in the following production examples or comparative production examples was measured according to JIS K6726.

(4) Content of sodium ion in thermoplastic PVA polymer:
A part of the thermoplastic PVA polymer obtained in the following production examples or comparative production examples is collected, completely ashed, and the ashed sample is dissolved in nitric acid. The content of sodium ion was measured using an absorptiometer (“Z-5300” manufactured by Hitachi, Ltd.).

(5) Copolymerization ratio (modification ratio) of ethylene or ethyl vinyl ether in the thermoplastic PVA polymer:
In the following production examples or comparative production examples, an ethylene / vinyl acetate copolymer or an ethyl vinyl ether / vinyl acetate copolymer (vinyl acetate copolymer before saponification to a vinyl alcohol copolymer) obtained in the middle of the synthesis. A sample for measurement, and ¹ H-NMR (“JEOL GX-500” manufactured by JEOL Ltd., 500 MHz) is used to measure the sample under conditions of 80 ° C. The copolymerization ratio (modification ratio) (mol%) of ethylene or ethyl vinyl ether was determined. Since the copolymerization ratio of ethylene or ethyl vinyl ether does not change between the vinyl acetate copolymer obtained in the middle of the synthesis and the PVA polymer finally obtained by saponifying it, the vinyl acetate copolymer The copolymerization ratio of ethylene or ethyl vinyl ether in the thermoplastic PVA polymer finally obtained in each production example or comparative production example was taken as the copolymerization ratio of ethylene or ethyl vinyl ether.

(6) Melting point of thermoplastic polymer (B):
Using thermoplastic polymer (B) (polypropylene, isophthalic acid-modified polyethylene terephthalate, nylon 6 or polyethylene terephthalate) (pellet form), using DSC (differential scanning calorimeter) ("TA3000" manufactured by PerkinElmer) In a nitrogen gas atmosphere, the temperature was raised to 300 ° C. at a rate of temperature increase of 10 ° C./min, then cooled to room temperature, again raised to 300 ° C. at a rate of temperature increase of 10 ° C./min, and the endothermic peak at that time The peak top was taken as the melting point (° C.) of the thermoplastic polymer (B).

(7) Spinning processability:
In the spinning steps in the following production examples, comparative production examples, examples and comparative examples, the number of yarn breaks that occurred when 100 kg of fibers were continuously produced by spinning was counted, and it was good when the number of yarn breaks was within 3 times ( (Circle)) When the frequency | count of a thread breakage was 4-7 times, it evaluated as a defect ((triangle | delta)) somewhat, and when the frequency | count of a thread breakage was 8 times or more, it evaluated as a defect (x).

(8) Exposed degree of thermoplastic PVA polymer on binder fiber surface:
(I) In the binder fiber in which the surface state of the fiber is point-symmetric, such as the core-sheath type, sea-island type, and radial split type composite spun fiber, photographs are taken with an electron microscope at five locations on any side of the fiber. About each photograph, the area ratio (%) which a thermoplastic PVA polymer occupies was calculated | required, the average value of five places was taken, and it was set as the exposure degree (%) of the thermoplastic PVA polymer in the binder fiber surface.
(Ii) When the surface state of the fiber is not point-symmetric, such as a side-by-side type composite fiber, the cross section of the fiber is photographed, and the ratio of the thermoplastic PVA polymer to the circumference of the fiber (in the circumference The length ratio) was defined as the degree of exposure (%) of the thermoplastic PVA polymer on the binder fiber surface.
(Iii) In the case of a fiber having an asymmetric fiber surface state and a non-uniform polymer distribution state, such as a modified cross-section fiber, 20 locations on any side of the fiber are photographed with an electron microscope. The area ratio (%) occupied by the thermoplastic PVA polymer was determined, and the average value of 20 locations was taken as the exposure degree (%) of the thermoplastic PVA polymer on the binder fiber surface.

(9) Single fiber fineness of each thermoplastic polymer (B) component in the binder fiber:
It calculated | required in conversion from the fiber diameter of each thermoplastic polymer (B) component (a polypropylene, an isophthalic acid modified polyethylene terephthalate, nylon 6 or polyethylene terephthalate) in a binder fiber.

(10) Elution amount of thermoplastic PVA polymer in water in binder fiber:
(I) From the binder fiber obtained in the following examples or comparative examples, weigh out the binder fiber in such an amount that the mass of the thermoplastic PVA polymer in the binder fiber is 1 g, and put it in 100 ml of water at 30 ° C. The solution was completely immersed in the solution and kept at a temperature of 30 ° C. for 20 hours. Next, the undissolved fiber is separated and removed, and 50 ml of the supernatant is collected, placed in an evaporating dish and left at 95 ° C. for 5 hours to evaporate and dry the water, and then the whole dish is heated with a hot air dryer (Inabaya cold heat). And dried at 95 ° C. for 5 hours, and the amount of residue W ₁ (g) remaining in the dish after drying was measured.
(Ii) Since the residue (i) contains an inorganic substance other than the PVA polymer, the residue obtained in (i) is put in a baking apparatus at 600 ° C. to reduce the mass. Baking completely until it no longer occurs, the amount W ₂ (g) of the residue after firing was measured, and the elution amount S (mass%) of the thermoplastic PVA polymer in water was determined by the following mathematical formula. .
Elution amount S (mass%) = {(W ₁ −W ₂ ) × 100/50} × 100

(11) Swelling degree of binder fiber in water:
(I) From the binder fiber obtained in the following examples or comparative examples, weigh out the binder fiber in such an amount that the mass of the thermoplastic PVA polymer in the binder fiber is 1 g, and put it in 100 ml of water at 30 ° C. The solution was completely immersed in the solution and kept at 30 ° C. for 30 minutes. Next, the fiber content is collected by filtration, and the fiber content is put on the center of a square cotton cloth of size = 10 cm × 10 cm, wrapped at the four corners, and wrapped in a centrifugal dehydrator (manufactured by Kokusan Co., Ltd.) with a rotation speed of 3000 rpm. Then, after removing water adhering to the surface of the fiber by removing the water from the cotton cloth, the fiber content was taken out from the cotton cloth and its weight Wa (g) was measured.
(Ii) The fiber part whose weight Wa was measured in the above (i) was put into a 100 ° C. hot air dryer (Inabaya Cold Heat Industrial Co., Ltd.) and dried for 4 hours, and the weight Wb (g) at that time was measured. The degree of swelling (%) in water of the binder fiber was determined from the following formula.
Swelling degree of binder fiber in water (%) = {(Wa−Wb) / Wb} × 100

(12) Dry tear length (DB) and wet tear length (WB) of wet papermaking sheet:
(I) Dry fracture length (DB):
The wet papermaking sheets obtained in the following examples or comparative examples were allowed to stand for 24 hours in a temperature-controlled humidity chamber at a temperature of 23 ° C. and a humidity of 50% RH, and then wet from the central portion in the width direction of the wet papermaking sheets. Immediately cut an elongated test piece of 170 mm along the length direction of the papermaking sheet (the sheet transfer direction during wet papermaking) and 15 mm in the width direction. Using a tensile tester (“Autograph” manufactured by Shimadzu Corporation), the distance between the two gripping tools (initially 100 mm) is gradually increased at a pulling speed of 50 mm / min. The force (strength) DS (N) applied to the test piece when the test piece was cut was read, and the following formula was calculated from the strong DS (N) and the basis weight W (g / m ² ) of the wet papermaking sheet. The dry tear length of the wet papermaking sheet ( B) was determined.
Dry tear length of wet papermaking sheet (DB) (N · m / g) = {DS / (15 × W)} × 1000

(Ii) Wetting crack length (WB):
The wet papermaking sheets obtained in the following examples or comparative examples were immersed in water at a temperature of 20 ° C. and allowed to absorb water for 24 hours, and from the central portion in the width direction of the wet papermaking sheet, the lengthwise direction of the wet papermaking sheet Along with (the sheet transfer direction during wet papermaking), a 170 mm long and 15 mm wide test piece is immediately cut out in the width direction, and both ends in the length direction of the test piece are gripped at 100 mm using two gripping tools. A grip test is performed at a tensile speed of 50 mm / min as in (i) above, and the force (strong) WS (N) applied to the test piece when the test piece is cut is read, and the strong WS From (N) and the basis weight W (g / m ² ) of the wet papermaking sheet, the wet breaking length (WB) of the wet papermaking sheet was determined by the following formula.
Wet paper breaking sheet wet tear length (WB) (N · m / g) = {WS / (15 × W)} × 1000

(13) Formation of wet papermaking sheet:
The wet papermaking sheet obtained in the following examples or comparative examples is held over a white fluorescent lamp (40 type, 36 W), and the wet papermaking sheet is visually observed from the side opposite to the white fluorescent lamp to form a wet papermaking sheet. It was evaluated as good (◯) when the presence of spots was not substantially observed, slightly poor (Δ) when spots were slightly observed, and poor (×) when spots were conspicuous.

<< Production Example 1 >> [Production of ethylene-modified PVA polymer and single fiber of the polymer]
(1) Into a 100 liter pressurized reactor equipped with a stirrer, nitrogen gas inlet, ethylene inlet and polymerization initiator addition port, 29.0 kg of vinyl acetate and 31.0 kg of methanol were charged, and the temperature was raised to 60 ° C. Then, the inside of the system was purged with nitrogen by bubbling with nitrogen gas for 30 minutes, and then ethylene was introduced so that the pressure in the reaction tank was 5.9 kg / cm ² .
(2) 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) (AMV) (polymerization initiator) dissolved in methanol (initiator concentration 2.8 g / liter) was prepared, Nitrogen gas was bubbled to replace the nitrogen.
(3) After adjusting the internal temperature of the reaction tank of (1) above to 60 ° C., 170 ml of the polymerization initiator solution prepared in (2) above was poured into the reaction tank to initiate polymerization. During the polymerization, ethylene was introduced to maintain the pressure in the reaction vessel at 5.9 kg / cm ² , the internal temperature of the reaction vessel was maintained at 60 ° C., and the initiator solution prepared in (2) above was added to 610 ml / Polymerization was carried out by continuously adding to the reaction vessel at a rate of hr. Since the polymerization rate reached 70% after 10 hours, the reaction vessel was cooled and the polymerization was stopped.

(4) After the reaction vessel was opened and deethylene removed, nitrogen gas was bubbled to completely remove ethylene, and then unreacted vinyl acetate was removed under reduced pressure to remove ethylene-modified polyvinyl acetate methanol. A solution was obtained.
(5) Collect a part of the methanol solution of ethylene-modified polyvinyl acetate obtained in (4) above, add n-hexane to the solution to precipitate ethylene-modified polyvinyl acetate, and dissolve the precipitate with acetone. After performing reprecipitation purification three times, it was dried under reduced pressure at 80 ° C. for 3 days to obtain purified ethylene-modified polyvinyl acetate. When this purified ethylene-modified polyvinyl acetate was dissolved in DMSO-d6 and the copolymerization ratio of ethylene was measured by the method described above, the copolymerization ratio of ethylene was 8.6 mol%.

(6) To 200 g of the ethylene-modified polyvinyl acetate solution obtained in the above (4) (100 g of ethylene-modified polyvinyl acetate in the solution), 46.5 g of a 10% methanol solution of sodium hydroxide (in ethylene-modified polyvinyl acetate) Saponification was performed by adding a molar ratio of sodium hydroxide to a structural unit derived from vinyl acetate = 0.10).
(7) About 2 minutes after the addition of the sodium hydroxide methanol solution, a gelled product was formed. The gelled product was pulverized with a pulverizer while still in the solution, and then left at 60 ° C. for 1 hour. Then, 1000 g of methyl acetate was added to neutralize the remaining alkali.
(8) After confirming the completion of neutralization using a phenolphthalein indicator, a white solid ethylene-modified PVA polymer was recovered by filtration, and 1000 g of methanol was added to it and allowed to stand at room temperature for 3 hours for washing. did. After repeating this washing operation three times, centrifugal dehydration was performed to recover the ethylene-modified PVA polymer, which was left in a dryer at 70 ° C. for 2 days to obtain a dried ethylene-modified PVA polymer. .

(9) The melting point, viscosity average degree of polymerization, degree of saponification, and sodium ion content of the dried ethylene-modified PVA polymer obtained in (8) above were measured by the methods described above. It was as shown.
(10) To 100 parts by mass of the ethylene-modified PVA polymer obtained in (8) above, 5 parts by mass of a plasticizer (a compound obtained by adding 2 mol of ethylene oxide to 1 mol of sorbitol) is added and melted at 230 ° C. A modified PVA polymer composition was prepared by mixing. Using this composition alone, it was melt-spun at 240 ° C. using a spinning device, and the spinning yarn was subsequently stretched three times by a roller plate method at a temperature of 130 ° C. and then wound at a speed of 100 m / min. 70 dtex / 24f of modified PVA polymer multifilament was produced. The spinning process at that time was evaluated by the method described above. As a result, the number of yarn breaks that occurred when 100 kg of multifilament was continuously produced by spinning was 0, and the spinning process, continuous running, and stretchability were good. There was no problem at all.

<< Production Examples 2-3 >> [Production of ethylene-modified PVA polymer and single fiber of the polymer]
(1) Using vinyl acetate and ethylene as raw material monomers, the same steps as in Production Examples 1 (1) to (8) were performed, and the melting point, viscosity average polymerization degree, and saponification shown in Table 1 below. An ethylene-modified PVA polymer having a sodium ion content was prepared.
(2) Using each ethylene-modified PVA polymer obtained in (1) above, the same operation as in (10) of Production Example 1 was carried out to obtain a multifilament (70 dtex) consisting of an ethylene-modified PVA polymer alone. / 24f) was produced, and the number of yarn breaks that occurred when 100 kg of multifilaments were continuously produced by spinning was 0, and the spinning processability, continuous running properties, and stretchability were good, and there were no problems. There wasn't.

<< Production Example 4 >> [Production of PVA polymer and production of single fiber of the polymer]
(1) Using only vinyl acetate as a raw material monomer, the same operations as in Production Examples 1 (1) to (8) were performed, and the melting point, viscosity average polymerization degree, and saponification degree shown in Table 1 below. A PVA polymer having a sodium ion content was produced.
(2) Using the PVA polymer obtained in (1) above, the same operation as in Production Example 1 (10) was performed to produce multifilaments (70 dtex / 24f) each consisting of a PVA polymer alone. As a result, the number of yarn breaks that occurred when 100 kg of multifilaments were continuously produced by spinning was zero, and the spinning processability, continuous running properties, and stretchability were good, and there were no problems.

<< Production Example 5 >> [Production of Ethyl Vinyl Ether-Modified PVA Polymer and Single Fiber of the Polymer]
(1) Using vinyl acetate and ethyl vinyl ether as raw material monomers, the same operations as in (1) to (8) of Production Example 1 were performed, and the melting point, viscosity average polymerization degree, and Ken shown in Table 1 below. An ethyl vinyl ether-modified PVA polymer having a degree of conversion and a sodium ion content was produced.
(2) Using the ethyl vinyl ether-modified PVA polymer obtained in (1) above, the same operation as in (10) of Production Example 1 was carried out to obtain a multifilament (70 dtex) consisting of the ethyl vinyl ether-modified PVA polymer alone. / 24f) was produced, the number of yarn breaks that occurred when 100 kg of multifilaments were continuously produced by spinning was 0, and the spinning processability, continuous running properties, and stretchability were good, and there were no problems.

<< Comparative Production Examples 1 to 6 >> [Production of ethylene-modified PVA polymer and single fiber of the polymer]
(1) Using vinyl acetate and ethylene as raw material monomers, the same operations as in Production Examples 1 (1) to (8) were performed, and the melting points, viscosity average polymerization degrees, and saponifications shown in Table 1 below were performed. An ethylene-modified PVA polymer having a sodium ion content was prepared.
(2) Using each ethylene-modified PVA polymer obtained in the above (2), the same operation as in (10) of Production Example 1 was carried out to obtain a multifilament (70 dtex) consisting of an ethylene plastic PVA polymer alone. / 24f) was produced respectively.
As a result, as shown in Table 1 below, when 100 kg of multifilament was continuously produced, in Comparative Production Examples 1 and 2, the viscosity average polymer of the ethylene-modified PVA polymer was out of the range of 200 to 500. In Comparative Production Example 3, since the degree of saponification of the ethylene average PVA polymer is less than 90 mol%, 6 times of yarn breakage occurred, and Comparative Production Example 5 occurred. In No. 6 and No. 6, since the sodium ion content in the ethylene-modified PVA polymer is out of the range of 3 to 10,000 ppm, the yarn breakage occurred 8 times or more.
In Comparative Production Example 4, since the melting point of the modified PVA polymer was as low as 156 ° C., the spun multifilaments were unsatisfactory and could not be stretched.

<< Example 1 >> [Production of Binder Fiber]
(1) Using the ethylene-modified PVA polymer produced in Production Example 1 as a sea component, using polypropylene (“Y-2005GP” manufactured by Idemitsu Kosan Co., Ltd., melting point 161 ° C.) as an island component, the number of islands is 16 Using the melt compound spinning die as described above, the ethylene-modified PVA polymer: polypropylene = 50: 50 was supplied at a mass ratio of 50:50 and spun from the die at 240 ° C. (total spinning amount from the die) 24 g / min), following spinning, the spinning yarn was led to a first stage hot air furnace (length 3 m, furnace temperature 90 ° C.) and drawn three times (yarn in the first stage hot air furnace) 6 seconds), and then led to a second stage hot air furnace (length 3 m, furnace temperature 140 ° C., furnace humidity 0%) provided adjacent to the first stage hot air furnace 140 ° C. (Yarn staying time 2.6 seconds in the second stage hot air furnace) and winding at 70 m / min A sea-island type composite spun fiber (binder fiber; multifilament; 72 dtex / 24f) having a circular cross section in which 16 islands made of polypropylene are present in a sea component made of an ethylene-modified PVA polymer. Manufactured. The number of yarn breaks that occurred during the continuous production of 100 kg of sea-island type composite spun fiber (binder fiber; multifilament) by this melt compound spinning was zero, and the spinning processability, continuous running property and stretchability were good. There was no problem at all.
(2) About the composite spinning fiber (binder fiber) obtained in the above (1), the exposed ratio of the ethylene-modified PVA polymer on the fiber surface, and individual islands made of polypropylene in the composite spinning fiber (binder fiber) The single fiber fineness, the elution amount of the modified PVA polymer in water, and the degree of swelling in water were calculated by the methods described above, and as shown in Table 2 below.

Example 2 [Production of binder fiber]
(1) An ethylene-modified PVA polymer was obtained in the same manner as in Example 1 except that nylon 6 (“1011FK” manufactured by Ube Industries, Ltd., melting point 220 ° C.) was used instead of polypropylene as the island component. A sea-island type composite spun fiber (binder fiber; multifilament; 72 dtex / 24f) having a circular cross section in which 16 islands of nylon 6 are present in the sea component is produced. The number of yarn breaks that occurred during the continuous production of 100 kg of sea-island type composite spun fiber (binder fiber; multifilament) by this melt compound spinning was zero, and the spinning processability, continuous running property and stretchability were good. There was no problem at all.
(2) About the composite spinning fiber (binder fiber) obtained by said (1), the result of having measured the fiber physical property etc. similarly to (2) of Example 1 is shown in following Table 2.

Example 3 [Production of binder fiber]
(1) Ethylene-modified PVA polymer produced in Production Example 1 and the same polypropylene as used in Example 1, using a layered 11-split type composite spinning die, : Polypropylene = 50: 50 by mass ratio, and after spinning from the die at 240 ° C. (total spinning amount from the die of 24 g / min), following spinning, the same drawing and stretching as in Example 1 6 layers including both surface layers are subjected to heat treatment, and 6 layers including an ethylene-modified PVA polymer, and the remaining 5 layers are made of polypropylene. A spun fiber (binder fiber; multifilament; 72 dtex / 24f) was produced. The number of yarn breaks that occurred during the continuous production of 100 kg of composite spun fibers (binder fibers; multifilaments) by this melt composite spinning was zero, and the spinning processability, continuous running properties and stretchability were good, and there were no problems. There wasn't.
(2) About the composite spinning fiber (binder fiber) obtained by said (1), the result of having measured the fiber physical property etc. similarly to (2) of Example 1 is shown in following Table 2.

Example 4 [Production of binder fiber]
(1) Ethylene-modified PVA polymer produced in Production Example 1 and the same polypropylene as used in Example 1, using a radial 18-split composite spinning die. : Polypropylene = 50: 50 by mass ratio, and after spinning from the die at 240 ° C. (total spinning amount from the die of 24 g / min), following spinning, the same drawing and stretching as in Example 1 A heat-treated, layer-bonded composite spun fiber (binder fiber; multifilament; 72 dtex / 24f) having a circular cross section, in which ethylene-modified PVA polymer and polypropylene are alternately bonded radially in 18 layers Manufactured. The number of yarn breaks that occurred during the continuous production of 100 kg of composite spun fibers (binder fibers; multifilaments) by this melt composite spinning was zero, and the spinning processability, continuous running properties and stretchability were good, and there were no problems. There wasn't.
(2) About the composite spinning fiber (binder fiber) obtained by said (1), the result of having measured the fiber physical property etc. similarly to (2) of Example 1 is shown in following Table 2.

Example 5 [Production of binder fiber]
(1) Except that the single fiber fineness of the composite spun fiber is 12.0 dtex, the same method as in Example 1 is adopted, and the sea component made of ethylene-modified PVA polymer is made of polypropylene. A sea-island type composite spun fiber (binder fiber; multifilament; 288 dtex / 24f) having a circular cross section with a single island was produced. The number of yarn breaks that occurred during the continuous production of 100 kg of sea-island type composite spun fiber (binder fiber; multifilament) by this melt compound spinning was zero, and the spinning processability, continuous running property and stretchability were good. There was no problem at all.
(2) About the composite spinning fiber (binder fiber) obtained by said (1), the result of having measured the fiber physical property etc. similarly to (2) of Example 1 is shown in following Table 2.

<< Example 6 >> [Production of Binder Fiber]
(1) Except that the single fiber fineness of the composite spun fiber is 0.7 dtex, the same method as in Example 1 is adopted, and the sea component made of ethylene-modified PVA polymer is made of polypropylene. A sea-island type composite spun fiber (binder fiber; multifilament; 17 dtex / 24f) having a circular cross section with a single island was produced. The number of yarn breaks that occurred during the continuous production of 100 kg of sea-island type composite spun fiber (binder fiber; multifilament) by this melt compound spinning was zero, and the spinning processability, continuous running property and stretchability were good. There was no problem at all.
(2) About the composite spinning fiber (binder fiber) obtained by said (1), the result of having measured the fiber physical property etc. similarly to (2) of Example 1 is shown in following Table 2.

<< Examples 7 and 8 >> [Production of Binder Fiber]
(1) Implemented except that the mass ratio of sea component (ethylene-modified PVA polymer): island component (polypropylene) was changed from 50:50 to 70:30 (Example 9) or 30:70 (Example 10). By performing the same operation as in Example 1, sea island type composite spun fiber (binder fiber; having a circular cross section) in which 16 islands made of polypropylene are present in the sea component made of ethylene-modified PVA polymer. Multifilament; 72 dtex / 24f) was produced. The number of yarn breaks that occurred when 100 kg of sea-island type composite spun fiber (binder fiber; multifilament) was continuously produced by this melt compound spinning was 0 in all examples, and the spinning processability, continuous running property, The drawability was good and there was no problem at all.
(2) For each composite spun fiber (binder fiber) obtained in (1) above, the results of measuring the fiber properties and the like in the same manner as in (2) of Example 1 are shown in Table 2 below.

Example 9 [Production of binder fiber]
(1) Instead of the ethylene-modified PVA polymer obtained in Production Example 1 as the sea component, the ethylene-modified PVA polymer obtained in Production Example 2 was used, and the furnace temperature in the second stage hot air furnace The sea island having a circular cross section in which 16 islands made of polypropylene are present in the sea component made of ethylene-modified PVA polymer except that the temperature is changed to 125 ° C. A type of composite spun fiber (binder fiber; multifilament; 72 dtex / 24f) was produced. The number of yarn breaks that occurred during the continuous production of 100 kg of sea-island type composite spun fiber (binder fiber; multifilament) by this melt compound spinning was zero, and the spinning processability, continuous running property and stretchability were good. There was no problem at all.
(2) About the composite spinning fiber (binder fiber) obtained by said (1), the result of having measured the fiber physical property etc. similarly to (2) of Example 1 is shown in following Table 2.

<< Comparative Examples 1 and 2 >> [Production of Binder Fiber]
(1) Except for changing the mass ratio of sea component (ethylene-modified PVA polymer): island component (polypropylene) from 50:50 to 95: 5 (Comparative Example 1) or 5:95 (Comparative Example 2). A sea island type composite spun fiber (binder fiber) having a circular cross section in which 16 islands made of polypropylene are present in the sea component made of ethylene-modified PVA polymer by performing the same operation as in Example 1. Multifilament; 72 dtex / 24f). The number of yarn breaks that occurred when 100 kg of sea-island type composite spun fiber (binder fiber; multifilament) was continuously produced by this melt compound spinning was zero in all comparative examples, and the spinning processability, continuous running property, The drawability was good.
(2) For each composite spun fiber (binder fiber) obtained in (1) above, the results of measuring the fiber properties and the like in the same manner as in (2) of Example 1 are shown in Table 2 below.

<< Comparative Examples 3 and 4 >> [Production of Binder Fiber]
(1) The same operation as in Example 1 was carried out except that the temperature inside the second stage hot stove was changed to 30 ° C. (Comparative Example 3) or 215 ° C. (Comparative Example 4). A sea-island type composite spun fiber (binder fiber; multifilament; 72 dtex / 24f) having a circular cross section in which 16 islands made of polypropylene exist in the sea component made of coalescence was produced. The number of yarn breaks that occurred when 100 kg of sea-island type composite spun fiber (binder fiber; multifilament) was continuously produced by this melt compound spinning was 0 in all comparative examples, and the spinning processability, continuous running property and The drawability was good.
(2) For each composite spun fiber (binder fiber) obtained in (1) above, the results of measuring the fiber properties and the like in the same manner as in (2) of Example 1 are shown in Table 2 below.

<< Comparative Example 5 >> [Manufacture of Binder Fiber]
As the island component, polyethylene terephthalate (manufactured by Kuraray Co., Ltd., melting point 254 ° C.) is used instead of polypropylene, and the melt composite spinning temperature is 295 ° C. As a result of the production, thermal decomposition of the ethylene-modified PVA polymer occurred during spinning, and a composite spun fiber could not be produced.

<< Comparative Example 6 >> [Manufacture of Binder Fiber]
(1) Except for producing a core-sheath type composite spun fiber having a single fiber fineness of 10 dtex, the same operation as in Example 4 was performed, and an ethylene-modified PVA polymer was used as a sheath component and polypropylene was used as a core component. A core-sheath type composite spun fiber (binder fiber; multifilament; 240 dtex / 24f) having a cross section of The number of yarn breaks that occurred when 100 kg of sea-island composite spun fiber (binder fiber; multifilament) was continuously produced by this melt compound spinning was zero, and the spinning processability, continuous running property, and stretchability were good. there were.
(2) For each composite spun fiber (binder fiber) obtained in (1) above, the results of measuring the fiber properties and the like in the same manner as in (2) of Example 1 are shown in Table 2 below.

<< Comparative Example 7 >> [Manufacture of Binder Fiber]
(1) The number of islands was changed to 100, the mass ratio of sea component (modified PVA polymer): island component (polypropylene) was changed to 85:15, and the single fiber fineness of the resulting composite spun fiber was set to 0.00. Except for changing to 5 dtex, the same operation as in Example 1 was performed, and in the sea component made of an ethylene-modified PVA polymer, 100 islands made of polypropylene were present, and a sea-island type having a circular cross section A composite spun fiber (binder fiber; multifilament; 12 dtex / 24f) was produced. The number of yarn breaks that occurred when 100 kg of sea-island composite spun fiber (binder fiber; multifilament) was continuously produced by this melt compound spinning was zero, and the spinning processability, continuous running property, and stretchability were good. there were.
(2) For each composite spun fiber (binder fiber) obtained in (1) above, the results of measuring the fiber properties and the like in the same manner as in (2) of Example 1 are shown in Table 2 below.

<< Comparative Example 8 >> [Manufacture of Binder Fiber]
The single fiber fineness of the resulting composite spun fiber was set to 0.09 dtex, and other than that, an operation similar to that in Example 1 was adopted to produce a sea-island type composite spun fiber. However, the fiber was stably wound. Could not be taken, and the fiber could not be produced substantially.

<< Comparative Example 9 >> [Manufacture of Binder Fiber]
(1) The same operation as in Example 1 was performed except that the single fiber fineness of the obtained composite spun fiber was 16.0 dtex, and the sea component made of ethylene-modified PVA polymer was made of polypropylene. A sea-island type composite spun fiber (binder fiber; multifilament; 384 dtex / 24f) having a circular cross section and having 16 islands was produced. The number of yarn breaks that occurred during the continuous production of 100 kg of sea-island type composite spun fiber (binder fiber; multifilament) by this melt compound spinning was zero, and the spinning processability, continuous running property and stretchability were good. there were.
(2) For each composite spun fiber (binder fiber) obtained in (1) above, the results of measuring the fiber properties and the like in the same manner as in (2) of Example 1 are shown in Table 2 below.

<< Comparative Example 10 >> [Manufacture of Binder Fiber]
(1) Except having changed the mass ratio of ethylene-modified PVA polymer: polypropylene to 30:70, the same operation as in Example 5 was carried out to have an ethylene-modified PVA polymer layer on both surfaces. A split type composite spun fiber (binder fiber; multifilament; 72 dtex / 24f) was produced. The number of yarn breaks that occurred during the continuous production of 100 kg of sea-island type composite spun fiber (binder fiber; multifilament) by this melt compound spinning was zero, and the spinning processability, continuous running property and stretchability were good. there were.
(2) For each composite spun fiber (binder fiber) obtained in (1) above, the results of measuring the fiber properties and the like in the same manner as in (2) of Example 1 are shown in Table 2 below.

<< Example 10 >> [Production of wet papermaking sheet]
(1) The binder fiber (composite spun fiber) obtained in Example 1 is cut into a fiber length of 3 mm to make a short fiber, and 10 parts by mass of the short fiber is made of PVA fiber (made by Kuraray Co., Ltd.). 90 parts by mass (VPB103 ", single fiber fineness 1.2 dtex, fiber length 5 mm, water insoluble) are mixed, and the mixed fibers are uniformly dispersed in water to prepare an aqueous slurry having a solid content concentration of 0.2% by mass. did.
(2) Using the aqueous slurry prepared in (1) above, wet-making is performed using a TAPPI-type wet paper-making device (manufactured by Kumagai Riki Co., Ltd.), and then dried using a 90 ° C. drum-type drying device. Thus, a wet papermaking sheet having a basis weight of 10 g / m ² was produced.
(3) The dry tear length (DS) and wet tear length (WS) of the wet papermaking sheet obtained in (2) above are measured by the method described above, and the wet tear length (WS) and dry tear length ( When the ratio of DS (WS / DS) was calculated, it was as shown in Table 3 below.
Moreover, when the formation of the wet papermaking sheet obtained in the above (2) was evaluated by the method described above, it was as shown in Table 3 below.

<< Examples 11 to 18 and Comparative Examples 11 to 18 >> [Production of wet papermaking sheet]
(1) Instead of the binder fiber obtained in Example 1, what was obtained by cutting the binder fiber obtained in Examples 2 to 9 , Comparative Examples 1 to 4, 6 to 7 and 9 to 10 to a fiber length of 3 mm A wet papermaking sheet having a basis weight of 10 g / m ² was produced in the same manner as in Example 12 except that each was used.
(2) The dry tear length (DS) and wet tear length (WS) of each wet papermaking sheet obtained in (2) above are measured by the method described above, and the wet tear length (WS) and dry tear length are determined. When the ratio of length (DS) (WS / DS) was calculated, it was as shown in Table 3 below.
Moreover, when the formation of each wet papermaking sheet | seat obtained by said (2) was evaluated by the above-mentioned method, it was as showing in following Table 3.

As seen in the results of Tables 1 to 3 above, particularly the results of Tables 2 and 3, Examples 10 to 18 obtained using the binder fibers of Examples 1 to 9 satisfying all the requirements in the present invention. The wet papermaking sheet has a high dry fracture length (DS) and wet fracture length (WS), is excellent in strength and moisture resistance, and is flat and excellent in formation.
In contrast, the binder fibers of Comparative Examples 1 and 2 have a mass ratio of thermoplastic PVA polymer (A): thermoplastic polymer (B) that is out of the range of 10:90 to 90:10. The wet papermaking sheets of Comparative Example 11 and Comparative Example 12 produced using the binder fibers of Comparative Examples 1 and 2 had values of dry fracture length (DS) and wet fracture length (WS) of Examples 10 to 18. Compared with the wet papermaking sheet obtained in the above, the wet papermaking sheet is low in strength and inferior in moisture resistance, and the binder fibers of Comparative Examples 1 and 2 do not exhibit a sufficient binder action.

Further, the binder fiber of Comparative Example 3 has a binder fiber of Comparative Example 3 because the elution amount of the thermoplastic PVA polymer (A) in water exceeds 10% by mass and the degree of swelling in water exceeds 300%. wet papermaking sheet of Comparative example 13 prepared with the fibers, dry breaking length (DS) and humidity breaking length (WS) value significantly compared to wet papermaking sheets obtained in examples 10 to 18 lower the The wet papermaking sheet is low in strength and inferior in moisture resistance, and the binder fiber of Comparative Example 3 is not suitable as a binder fiber.
Since the binder fiber of Comparative Example 4 has a degree of swelling in water of less than 70%, the wet papermaking sheet of Comparative Example 14 produced using the binder fiber of Comparative Example 4 has a dry tear length (DS) and a wet tear length. The value of the length (WS) is significantly lower than the wet papermaking sheets obtained in Examples 10 to 18 , the wet papermaking sheet has low strength and is inferior in moisture resistance. The binder fiber of Comparative Example 4 is Not suitable as a binder fiber.

In Comparative Example 5, since the thermoplastic polymer (B) having a melting point exceeding 240 ° C. was used, thermal decomposition of the thermoplastic PVA polymer (A) occurred during melt compound spinning, and production of a binder fiber (composite fiber) I was not able to.
Since the binder fiber of Comparative Example 6 has a single fiber fineness of the sheath component exceeding 4 dtex, the wet papermaking sheet of Comparative Example 15 produced using the binder fiber of Comparative Example 6 has large irregularities, Inferior.
Since the binder fiber of Comparative Example 7 has a sea component single fiber fineness of less than 0.001 dtex, the wet papermaking sheet of Comparative Example 16 produced using the binder fiber of Comparative Example 7 has a dry tear length (DS). And the value of wet tear length (WS) is significantly lower than the wet papermaking sheets obtained in Examples 10 to 18 , and the wet papermaking sheet has low strength and is inferior in moisture resistance.

In Comparative Example 8, since it was attempted to produce a binder fiber (composite spun fiber) having a single fiber fineness of less than 0.1 dtex, the fiber could not be stably wound and the binder fiber could not be substantially produced. .
Since the single fiber fineness of the binder fiber of Comparative Example 9 exceeds 15 dtex, the wet papermaking sheet of Comparative Example 17 produced using the binder fiber of Comparative Example 9 has large irregularities and is inferior in formation. .
Since the binder fiber of Comparative Example 10 has an exposure ratio of the thermoplastic PVA polymer (A) on the fiber surface of less than 30%, the wet papermaking of Comparative Example 18 produced using the binder fiber of Comparative Example 10 The sheet has significantly lower dry tear length (DS) and wet tear length (WS) values than the wet paper sheets obtained in Examples 10 to 18 , and the wet paper sheets have low strength and moisture resistance. It is inferior to.

Since the binder fiber of the present invention exhibits excellent binder properties in the presence of moisture, it can be effectively used as a binder fiber when producing a wet papermaking product such as paper, sheet or nonwoven fabric by wet papermaking.
By producing a wet paper product using the binder fiber of the present invention, a wet paper product having excellent strength, water resistance and formation can be provided.

Claims (4)

<a> Thermoplastic polyvinyl alcohol polymer (A) having a melting point of 160 to 230 ° C., and a thermoplastic polymer (B) comprising at least one of a polyolefin polymer and a polyamide polymer having a melting point of 240 ° C. or less. Is a binder fiber for wet papermaking made of composite or mixed,
<B> The thermoplastic polyvinyl alcohol polymer (A) and the thermoplastic polymer (B) are combined or mixed in the form of a sea-island type or a bonded type in the cross section of the fiber;
<C> The thermoplastic polyvinyl alcohol polymer (A) constituting the binder fiber has a viscosity average polymerization degree of 200 to 500, a saponification degree of 90 to 99.9 mol%, and an alkali metal ion converted to sodium ion. Is a thermoplastic polyvinyl alcohol polymer having a content of 3 to 10000 ppm;
<D> The mass ratio of the thermoplastic polyvinyl alcohol-based polymer (A) to the thermoplastic polymer (B) in the binder fiber is 10:90 to 90:10;
Exposure rate of the thermoplastic polyvinyl alcohol polymer in the <e> fiber surface (A) is located at least 30%;
Single fiber fineness of <f> binder fiber be 0.1～15Dtex;
Single fiber fineness of each of the thermoplastic polymer (B) component in the <g> binder fiber in the be 0.001～4Dtex;
<H> Thermoplastic polyvinyl alcohol polymer in water elution amount of (A) is located at 10 wt% or less; and,
<I> The degree of swelling in water is 70 to 300%;
A binder fiber for wet papermaking characterized by the above. The thermoplastic polyvinyl alcohol polymer (A) has a structural unit derived from an olefin having 4 or less carbon atoms and / or a structural unit derived from vinyl ether in a proportion of 1 to 20 mol%. The binder fiber for wet papermaking according to claim 1, which is a coalescence. Thermoplastic polyvinyl alcohol having a melting point of 160 to 230 ° C., a viscosity average polymerization degree of 200 to 500, a saponification degree of 90 to 99.9 mol%, and an alkali metal ion content of 3 to 1000 ppm converted to sodium ions A thermoplastic polymer (B) composed of at least one of a polymer based polymer (A) and a polyolefin polymer having a melting point of 240 ° C. or less and a polyamide polymer is used at a mass ratio of 10:90 to 90:10 Then, a composite composite fiber or a mixed spun fiber having a sea-island-type or bonded-type composite form or mixed form in the cross section of the fiber is formed by melt composite spinning or melt-mixing spinning, and then dried at 110 to 200 ° C. under dry conditions. The wet papermaking according to claim 1, wherein the wet papermaking is made by stretching at a temperature for 0.5 to 1800 seconds or by performing stretching and heat treatment. Binder fiber of use. Wet paper product prepared using at least one binder fibers for wet papermaking according to any one of claims 1-3.