JP6638510B2 - Composite fiber and reinforcing material for hydraulic material using the same - Google Patents

Description

  The present invention relates to a conjugate fiber and a reinforcing material for hydraulic material using the same, and more particularly, at least on the fiber surface, a conjugate fiber in which a poorly water-soluble resin and a water-soluble resin have a sea-island structure; The present invention relates to a reinforcing material for hydraulic material, comprising:

  Conventionally, concrete obtained by mixing and hardening a hydraulic material, for example, cement, aggregate, water, and an admixture, has excellent compression resistance and is robust even when a large load is applied from the top, so that high-rise building It is widely used for huge buildings such as roads, expressways, harbors and dams. However, hydraulic materials are excellent in compression resistance, but are weak in tensile force.Therefore, they can be installed with concrete bars or steel frames in concrete, or synthetic fibers, steel fibers, carbon fibers, glass fibers, etc. can be used in concrete. Reinforcement is performed by mixing in the form of short fibers.

  As such a short fiber for reinforcing concrete, for example, vinylon fiber has been proposed (see Patent Document 1). However, since vinylon fibers are difficult to disperse uniformly in the concrete composition, there is a problem that the strength of the resulting concrete body is uneven, and it is difficult to obtain a sufficient reinforcing effect as a whole.

  Therefore, as a short fiber having a better dispersibility in the concrete composition, a fiber composed of a saponified ethylene-vinyl ester copolymer (hereinafter abbreviated as “EVOH”) having a larger proportion of hydroxyl groups than vinylon fiber is used. Its use has been proposed (see Patent Document 2).

JP-A-11-350246 JP 2003-261371 A

  However, the EVOH fiber has a good affinity for water and is more easily dispersed in the concrete composition than the vinylon fiber, but the surface of the fiber is smooth, so that the adhesive strength to concrete is low and the tensile strength to concrete is strong. When a shift or distortion occurs due to a force, there is a problem that the fiber surface is detached from the concrete and the reinforcing effect on the concrete is weakened.

  The present invention has been made in view of such circumstances, and can be suitably used as a reinforcing material for concrete and the like, has a good dispersibility in an aqueous material and a high adhesive strength to a partner that contains and disperses the same. It is an object of the present invention to provide a conjugate fiber that can be exerted, and to provide a reinforcing material for hydraulic material using such a conjugate fiber.

  In order to solve the above-mentioned problems, the inventors of the present invention did not use EVOH alone, but used EVOH and a water-soluble resin such as a polyvinyl alcohol (hereinafter abbreviated as “PVA”) resin in the course of intensive research to solve the above-mentioned problems. If the fiber surface becomes uneven by dissolving and removing the water-soluble resin in an aqueous material, it is possible to increase the adhesive strength between the partner to be reinforced and the fiber by using a composite fiber obtained by combining I got the idea of whether or not.

  Then, taking as an example a composite fiber having a sea-island type structure in which the present applicant has already filed an application, wherein EVOH is a sea component and a specific PVA-based resin is an island component (see Japanese Patent Application Laid-Open No. 2010-189829). As a result of repeated studies as to whether or not those having both dispersibility and adhesiveness as described above are obtained, the composite fiber described in JP-A-2010-189829 simply has a sea-island structure in a fiber cross section. It was found that there was room for further improvement in terms of adhesiveness. Therefore, as a result of further studies, it is important to provide a sea-island structure in which EVOH is a sea component, PVA is an island component and the island component has a large aspect ratio of 10 or less on the fiber surface during melt spinning. And arrived at the present invention.

  In the conjugate fiber described in JP-A-2010-189829, since the viscosity of EVOH and the specific PVA-based resin is almost equal, the surface of the fiber obtained by melt-spinning is an island due to shear force during spinning. The component (PVA-based resin) is stretched in a streak along the spinning direction, and a sea-island structure having many island components having an aspect ratio of 10 or less on the fiber surface as in the present invention cannot be obtained.

<Summary of the Invention>
That is, the present invention is a composite fiber containing EVOH (A) and a water-soluble resin (B), wherein the saponified ethylene-vinyl ester copolymer (A) is a sea component at least on the fiber surface, A composite in which the water-soluble resin (B) has a sea-island structure as an island component, and the ratio of the area of the island component having an aspect ratio of 10 or less on the fiber surface to the total area of the island component on the fiber surface is 50% or more. The fibers are the first gist.

In addition, the present invention has a logarithmic ratio (B / A) of melt viscosity of the EVOH (A) and the water-soluble resin (B) at a shear rate of 912 sec ⁻¹ and 210 ° C. of 1.10 to 10.10. A composite fiber having a ratio of 1.50 is defined as a second gist.

  Furthermore, the present invention particularly provides a conjugated fiber in which the water-soluble resin (B) is a PVA-based resin having a 1,2-diol structural unit represented by the following general formula (1): In particular, a conjugate fiber in which the average degree of polymerization of the PVA-based resin is 600 to 1500 is referred to as a fourth summary.

[Wherein, R ¹ , R ² and R ³ each independently represent a hydrogen atom or an organic group,
X represents a single bond or a bond chain, and R ⁴ , R ⁵ and R ⁶ each independently represent a hydrogen atom or an organic group. ]

  In addition, the present invention particularly relates to a composite fiber in which the content ratio (weight ratio, A / B) between EVOH (A) and water-soluble resin (B) is 95/5 to 65/35. The summary is 5.

  A sixth aspect of the present invention is a hydraulic material reinforcing material using the composite fiber according to any one of the first to fifth aspects.

  In the conjugate fiber of the present invention, EVOH (A) is a sea component and water-soluble resin (B) is an island component on at least the fiber surface, and the aspect ratio of the fiber surface is 10 or less with respect to the total area of the island component on the fiber surface. Has a special sea-island structure in which the ratio of the area of the island component is 50% or more. According to this configuration, by dissolving and removing the water-soluble resin (B) from the fiber surface, it is possible to obtain a fiber having a unique texture having a complex uneven shape due to the EVOH (A).

  And, since the above-mentioned uneven shape exerts an anchor effect and exhibits high adhesive strength in concrete, resin and rubber, it can be used as an excellent fiber reinforcing material. In particular, when used in combination with a hydraulic material, for example, a concrete material containing water, the water dissolves and removes the water-soluble resin (B) from the water. It is not necessary to carry out, and it can be suitably used.

In addition, among the present invention, the logarithmic ratio (B / A) of the melt viscosity of the EVOH (A) and the water-soluble resin (B) at a shear rate of 912 sec ⁻¹ and 210 ° C. is 1.10 to 1.0. The composite fiber having a viscosity of 50 is preferable because a sea-island structure having a special structure in which the EVOH (A) is a sea component and the water-soluble resin (B) is an island component is easily formed on at least the fiber surface due to its viscosity characteristics. It is.

  Further, among the present invention, particularly, the conjugate fiber in which the water-soluble resin (B) is a specific PVA-based resin having a 1,2-diol structural unit represented by the general formula (1), On the fiber surface, a sea-island structure having a special configuration in which EVOH (A) is a sea component and water-soluble resin (B) is an island component is likely to be formed. Then, complex irregularities are likely to be formed on the fiber surface after the water-soluble resin (B) is dissolved and removed, and exhibit high adhesive strength to other substances (such as objects to be reinforced by the composite fiber), which is preferable. .

  Further, among the above specific PVA-based resins, in particular, the conjugate fiber having an average degree of polymerization of 600 to 1500 has a relatively high viscosity of the PVA-based resin. The water-soluble resin (B) has a sea-island structure in which island components composed of a PVA-based resin are dispersed in particles with respect to the water-soluble resin (B). This is preferable because the particles are dispersed in a granular form and can exhibit higher adhesive strength.

  Furthermore, among the present invention, particularly, the composite fiber in which the content ratio (weight ratio) A / B of the EVOH (A) and the water-soluble resin (B) is 95/5 to 65/35 is a required dispersion. Both properties and adhesive strength exhibit particularly excellent performance, which is preferable.

  The reinforcing material for a hydraulic material using the composite fiber according to any one of the first to fifth aspects is hardened in a state of being uniformly dispersed in the hydraulic material, and furthermore, to the hardened hydraulic material. On the other hand, since they are joined and integrated with high adhesive strength, an excellent reinforcing effect can be exhibited.

It is explanatory drawing which shows the sea-island structure in the composite fiber of this invention typically. It is explanatory drawing which shows the sea-island structure different from this invention typically. It is an enlarged photograph by SEM of the product of Example 1. It is an enlarged photograph by SEM of the comparative example 1. It is an enlarged photograph by SEM of the product of Comparative Example 2.

The conjugate fiber of the present invention contains EVOH (A) and a water-soluble resin (B).
In the present invention, at least on the fiber surface, the EVOH (A) has a sea-island structure in which the sea component is the sea component and the water-soluble resin (B) is the island component. The greatest feature is that the ratio of the area of the island component having an aspect ratio of 10 or less is 50% or more.

  That is, when the fiber surface of the conjugate fiber of the present invention is schematically shown, as shown in FIG. 1, a sea-island structure having EVOH (A) as a sea component 1 and a water-soluble resin (B) as an island component 2 is obtained. ing. The island component 2 tends to extend in the length direction of the fiber during the spinning process. The sea-island structure according to the present invention divides such an island component 2 into a relatively round island component 2a having an aspect ratio of 10 or less and an elongated elongated island component 2b having an aspect ratio exceeding 10; The area (total area, the same applies hereinafter) of the island components 2a having a ratio of 10 or less accounts for 50% or more of the total area of the island components 2 on the fiber surface.

  According to this configuration, when the water-soluble resin (B) as the island component 2 is dissolved and removed on the fiber surface, a complicated uneven shape due to the EVOH (A) as the sea component 1 is given, and thus a unique shape is provided. A textured fiber can be obtained. In addition, since the uneven shape exerts an anchor effect and exhibits high adhesive strength in concrete, resin and rubber, it can be used as an excellent fiber reinforcing material. In particular, a remarkable anchor effect is obtained in a concave portion having an aspect ratio of 10 or less and derived from a relatively round island component 2a.

  Incidentally, if the relatively round island component 2a having an aspect ratio of 10 or less and deviating from the sea-island structure of the present invention is less than 50% of the total area of the island component 2, as shown in FIG. Since the streak-like island component 2b extending in the length direction occupies most of the island component 2, the uneven shape obtained by dissolving and removing the water-soluble resin (B) has a poor anchor effect.

  In the present invention, the ratio P of the area of the island component 2a having the aspect ratio of 10 or less to the total area of the island component 2 is 50% or more as described above, and particularly, 60% or more. It is more preferably at least 70%.

The ratio P of the area of the island component 2a having the aspect ratio of 10 or less to the entire area of the island component 2 can be obtained by the following method.
[How to determine the ratio P occupied by the area of the island components having an aspect ratio of 10 or less]
For example, the aspect ratio can be determined by measuring the major axis and the minor axis of the island component in an SEM image obtained by observing the fiber surface at 2000 times, and dividing the major axis by the minor axis. A value calculated by dividing the area of the island component having the aspect ratio of 10 or less by the area of all the island components is defined as a ratio P occupied by the area of the island component having the aspect ratio of 10 or less.

The details of the composite fiber of the present invention will be described in order.
First, the EVOH (A) will be described.

EVOH (A) is a resin obtained by copolymerizing ethylene and a vinyl ester monomer and then saponifying it, and is a water-insoluble thermoplastic resin. As the polymerization method, any known polymerization method, for example, solution polymerization, suspension polymerization, or emulsion polymerization can be used. In general, solution polymerization using a lower alcohol such as methanol as a solvent is used. Saponification of the obtained ethylene-vinyl ester copolymer can also be performed by a known method.
That is, EVOH (A) mainly contains an ethylene structural unit and a vinyl alcohol structural unit, and may include a small amount of a vinyl ester structural unit which remains without being saponified.

  As the vinyl ester-based monomer, vinyl acetate is typically used from the viewpoint of availability on the market and high efficiency of impurity treatment during production. In addition, aliphatic vinyl esters such as vinyl formate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl versatate, and benzoic acid Examples thereof include aromatic vinyl esters such as vinyl, and are usually aliphatic vinyl esters having 3 to 20 carbon atoms, preferably 4 to 10 carbon atoms, and particularly preferably 4 to 7 carbon atoms. These are usually used alone, but if necessary, a plurality of types may be used in combination.

  The EVOH (A) used in the present invention has an ethylene content of usually 20 to 60 mol%, particularly preferably 25 to 50 mol%, more preferably 28 to 45 mol%, as measured on the basis of ISO14663. preferable. If the ethylene content is too large, the compatibility with the water-soluble resin (B) described below is reduced, and the yarn breakage tends to occur frequently during composite spinning. On the other hand, if the ethylene content is too small, the melting point will be high, and thus there will be a tendency for thermal degradation during melt spinning.

  The MFR (melt flow rate) of EVOH (A) is usually 3 to 50 g / 10 min (210 ° C., 2160 g), particularly preferably 5 to 40 g / 10 min (210 ° C., 2160 g), and further preferably 8 to 20 g / min. 10 minutes (210 ° C., 2160 g) is preferred. If the MFR is too large, the tension during melt spinning is weak, and stable melt spinning tends to be difficult. On the other hand, if it is too small, the melt viscosity tends to be too high, so that fibers having a small fiber diameter cannot be spun.

  The degree of saponification of EVOH (A) (measured according to JIS K6726, where the EVOH resin is a solution uniformly dissolved in a water / methanol solution) is usually 99 mol% or more, particularly 99.5 mol%. The above is preferred. If the saponification degree is too low, an unpleasant odor tends to be generated due to thermal deterioration during melt spinning, and the fiber tends to be easily colored.

Further, the EVOH (A) in the present invention may further contain a structural unit derived from the following comonomer within a range that does not inhibit the effects of the present invention (for example, 10 mol% or less).
Examples of the comonomer include olefins such as propylene, 1-butene and isobutene, 3-buten-1-ol, 3-butene-1,2-diol, 4-penten-1-ol, 5-hexene-1, Hydroxy group-containing α-olefins such as 2-diol, derivatives thereof such as esterified products and acylated products, acrylic acid, methacrylic acid, crotonic acid, (anhydrous) phthalic acid, (anhydrous) maleic acid, (anhydrous) itaconic acid, etc. Unsaturated acids or salts thereof, or mono- or dialkyl esters having 1 to 18 carbon atoms, acrylamide, N-alkylacrylamide having 1 to 18 carbon atoms, N, N-dimethylacrylamide, 2-acrylamidopropanesulfonic acid or a salt thereof, Acrylamide propyldimethylamine or an acid salt or a quaternary salt thereof Amides, methacrylamides, N-alkyl methacrylamides having 1 to 18 carbon atoms, N, N-dimethylmethacrylamide, 2-methacrylamidopropanesulfonic acid or salts thereof, methacrylamidopropyldimethylamine or salts thereof or quaternary thereof N-vinylamides such as methacrylamides such as salts, N-vinylpyrrolidone, N-vinylformamide and N-vinylacetamide; vinyl cyanides such as acrylonitrile and methacrylonitrile; alkyl vinyl ethers having 1 to 18 carbon atoms; Vinyl ethers such as alkyl vinyl ether and alkoxyalkyl vinyl ether, vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, and vinyl bromide, and trimethoxyvinylsilane Allyl halides such as vinylsilanes, allyl acetate, allyl chloride, allyl alcohols such as allyl alcohol and dimethoxy allyl alcohol, trimethyl- (3-acrylamido-3-dimethylpropyl) -ammonium chloride, acrylamido-2-methyl Comonomers such as propanesulfonic acid can be mentioned. These may be used alone or in combination of two or more.

Furthermore, "post-modified" EVOH such as urethanation, acetalization, cyanoethylation, oxyalkyleneation and the like can also be used.
In particular, EVOH obtained by copolymerizing a hydroxy group-containing α-olefin is preferable in that the secondary moldability is improved, and EVOH having a 1,2-diol structure in a side chain is particularly preferable.

  In the EVOH (A) used in the present invention, compounding agents generally mixed with the EVOH, for example, a heat stabilizer, an antioxidant, an antistatic agent, a coloring agent, and an ultraviolet absorber as long as the effects of the present invention are not impaired. Agents, lubricants, plasticizers, light stabilizers, surfactants, antibacterial agents, desiccants, antiblocking agents, flame retardants, crosslinking agents, curing agents, foaming agents, crystal nucleating agents, antifogging agents, additives for biodegradation , A silane coupling agent, an oxygen absorber and the like.

  Examples of the water-soluble resin (B) used in the present invention include starch, cellulose, polyvinylpyrrolidone, polyethylene glycol, PVA-based resin, water-soluble nylon, polyacrylamide and the like. These may be used alone or in combination of two or more. Among them, a PVA-based resin is preferred because of its excellent compatibility with EVOH, and a PVA-based resin having a 1,2-diol structural unit represented by the following general formula (1) is excellent in hot-melt moldability. Therefore, it is preferable.

[Wherein, R ¹ , R ² and R ³ each independently represent a hydrogen atom or an organic group,
X represents a single bond or a bond chain, and R ⁴ , R ⁵ and R ⁶ each independently represent a hydrogen atom or an organic group. ]

In addition, it is desirable that all of R ^{1 to} R ³ and R ^{4 to} R ⁶ in the 1,2-diol structural unit represented by the general formula (1) are hydrogen atoms, and in the following general formula (1 ′) A PVA-based resin having the structural unit represented is preferably used.

Further, R ^{1 to} R ³ and R ^{4 to} R ⁶ in the 1,2-diol structural unit represented by the general formula (1) may be an organic group as long as the resin properties are not significantly impaired. The organic group may be, but is not particularly limited to, an organic group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a tert-butyl group. Alkyl groups are preferable, and these alkyl groups may have a substituent such as a halogen group, a hydroxyl group, an ester group, a carboxylic acid group, or a sulfonic acid group, if necessary.

Furthermore, X in the 1,2-diol structural unit represented by the general formula (1) is most preferably a single bond because it is easy to form a sea-island structure with the EVOH (A) described above. A binding chain may be used as long as the effect of the present invention is not impaired. Such a bond chain is not particularly limited, but may be a hydrocarbon group such as alkylene, alkenylene, alkynylene, phenylene, naphthylene (these hydrocarbon groups may have a halogen such as fluorine, chlorine, bromine and the like). _{, -O -, - (CH 2} O) m -, - (OCH 2) -, - (CH 2 O) mCH 2 -, - CO -, - COCO -, - CO (CH 2) mCO -, - CO _{(C 6 H 4) CO -} , - S -, - CS -, - SO -, - SO 2 -, - NR -, - CONR -, - NRCO -, - CSNR -, - NRCS -, - NRNR-, _{-HPO 4 -, - Si (OR} ) 2 -, - OSi (OR) 2 -, - OSi (OR) 2 O -, - Ti (OR) 2 -, - OTi (OR) 2 -, - OTi (OR _{) 2 O -, - Al (} OR) -, - OAl (OR) -, - Al (OR) O-like (R is an optional substituent each independently, a hydrogen atom, an alkyl group is preferred, m is a natural number) and the like. Among them, an alkylene group having 6 or less carbon atoms, particularly a methylene group, or —CH ₂ OCH ₂ — is preferable from the viewpoint of stability during production or use.

  Examples of the method for producing the PVA-based resin having the 1,2-diol structural unit include (i) a method of saponifying a copolymer of a vinyl ester-based monomer and a compound represented by the following general formula (2), , (Ii) a method of saponifying and decarboxylating a copolymer of a vinyl ester monomer and a compound represented by the following general formula (3), or (iii) a method wherein a vinyl ester monomer is represented by the following general formula (4): The method of saponifying and deketalizing the copolymer with the compound to be used is preferably used. Among them, the method (i) is particularly preferable. As the methods (i), (ii), and (iii), for example, the method described in JP-A-2006-95825 can be adopted.

Note that R ¹ , R ² , R ³ , X, R ⁴ , R ⁵ , and R ⁶ in the general formulas (2), (3), and (4) are the same as those in the general formula (1). It is. R ⁷ and R ⁸ are each independently a hydrogen atom or R ⁹ —CO— (wherein R ⁹ is an alkyl group). R ¹⁰ and R ¹¹ are each independently a hydrogen atom or the same organic group as R ^{1 to} R ⁶ .

In particular, in the above general formula (2), R ^{1 to} R ⁶ are hydrogen, X is a single bond, and R ^{7 to} R ⁸ are R ^{9 in} view of excellent copolymerization reactivity and industrial handling. 3,4-diasiloxy-1-butene, which is —CO—, and R ⁹ is an alkyl group, among which 3,4-diacetoxy-1-butene, in which R ⁹ is a methyl group, is particularly preferable. Used.

  Examples of the vinyl ester monomers include, for example, vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate And vinyl versatate, vinyl trifluoroacetate and the like. Of these, vinyl acetate is particularly preferred from the viewpoint of economy.

  In addition to the above-mentioned monomers [vinyl ester-based monomers, compounds represented by general formulas (2), (3) and (4)], copolymer components may be used as long as they do not significantly affect the resin properties. For example, α-olefins such as ethylene and propylene; hydroxy-containing α-olefins such as 3-buten-1-ol, 4-penten-1-ol, 5-hexene-1,2-diol, and the like. Derivatives such as acylated products; unsaturated acids such as itaconic acid, maleic acid and acrylic acid or salts thereof or mono- or dialkyl esters; nitriles such as acrylonitrile; amides such as methacrylamide and diacetone acrylamide; ethylenesulfonic acid and allyl Sulfonic acid, methallylsulfonic acid, AMPS (2-acrylamido-2-methylpropanesulfone Compounds such as olefin sulfonic acids such as acid) or salts thereof may be copolymerized.

  The PVA-based resin suitably used in the present invention contains the 1,2-diol structural unit represented by the general formula (1) in an amount of usually 0.1 to 20 mol%, preferably 1 to 10 mol%, more preferably 1 to 10 mol%. Contains 3 to 8 mol%. Even if the molar fraction of the 1,2-diol structural unit represented by the general formula (1) is excessively increased, the improvement in melt spinnability and water solubility reaches a plateau, and a PVA-based resin having a predetermined polymerization degree can be obtained. Tends to be difficult to be performed. On the other hand, if the molar fraction is too low, the melting temperature will be high, so the molding temperature must be increased, and the melt spinnability tends to decrease, and insolubles due to thermal degradation tend to be generated. In addition, the water solubility of the PVA-based resin decreases, and it tends to take a long time to elute from the conjugate fiber or not to elute completely.

In the PVA-based resin, the content (molar fraction) of the 1,2-diol structural unit represented by the general formula (1) is determined by the ¹ H-NMR spectrum of a completely saponified PVA-based resin. Solvent: DMSO-d6, internal standard: tetramethylsilane), specifically, hydroxyl proton, methine proton, and methylene proton in the 1,2-diol unit, methylene proton in the main chain, and methylene proton in the main chain. It can be calculated from the peak area derived from the protons of the connecting hydroxyl group.

  Further, the degree of saponification of the PVA-based resin (measured according to JIS K6726) is usually 70 to 100 mol%, particularly preferably 75 to 99.9 mol%, and more preferably 80 to 99.5 mol%. In particular, the PVA-based resin used in the present invention has a high degree of saponification, the crystal size is controlled by the 1,2-diol structure of the side chain, the rise in melting point is suppressed, and good melt moldability is obtained. In addition, there is little problem of thermal deterioration. If the saponification degree is too low, the thermal stability at the time of melt spinning tends to decrease, and the acetic acid odor tends to occur.

  The average degree of polymerization of the PVA-based resin (measured according to JIS K6726) is usually 600 to 1500, particularly preferably 800 to 1400, and more preferably 1000 to 1300. If the average polymerization degree is too high, the melt viscosity tends to be high, and spinning tends to be difficult. On the other hand, if the average degree of polymerization is too low, the PVA-based resin easily flows along the spinning direction without resistance during kneading with the EVOH (A) and melt spinning. There is a tendency that a sea-island structure in which the conductive resin (B) is an island component is hardly formed.

  The MFR (melt flow rate) of the PVA-based resin is usually 0.05 to 6 g / 10 minutes (230 ° C., 2160 g), particularly preferably 0.05 to 4 g / 10 minutes (230 ° C., 2160 g), Further, it is preferably 0.08 to 2 g / 10 minutes (230 ° C., 2160 g). If the MFR is too large, the tension during melt spinning is weak, and stable melt spinning tends to be difficult. On the other hand, if it is too small, the melt viscosity tends to be too high, making spinning difficult.

  The conjugate fiber of the present invention can be produced by mixing and spinning the EVOH (A) and the water-soluble resin (B). In the mixed spinning, for example, the EVOH (A) and the water-soluble resin (B) are melt-kneaded in one extruder, and subsequently discharged from the same spinning nozzle to be wound and fiberized. Alternatively, the EVOH (A) and the water-soluble resin (B) are melt-kneaded in a single extruder, pelletized, and then charged into a spinning machine, discharged from a nozzle of the spinning machine and wound up. It may be. The production conditions such as the temperature of the spinneret at the time of spinning and the shear rate at the time of passing through the nozzle depend on the content ratio of the EVOH (A) and the water-soluble resin (B) of the composite fiber to be produced, the cross-sectional shape of the composite fiber, and the like. It is set appropriately.

  In the present invention, one or more additives may be added to the EVOH (A) and / or the water-soluble resin (B), if necessary, or the EVOH (A) And water-soluble resin (B). Such additives include, for example, polyvalent resins such as glycerin, sorbitol, and polyethylene glycol as plasticizers for improving melt fluidity, suppressing thermal decomposition in the fiberizing step, and obtaining good plasticization and spinnability. An alcohol or an alkylene oxide adduct thereof can be blended. Further, a lubricant such as ethylene bisstearyl amide or an antioxidant may be blended.

In the present invention, the EVOH (A) and the water-soluble resin (B) used in the present invention have a logarithmic ratio (B / A) of melt viscosity at 210 ° C. of 912 sec ⁻¹ and 1.10 to 1.10. A ratio of 1.50 is preferred for forming the special sea-island structure of the present invention on the fiber surface.

  A more preferred range of the logarithmic ratio (B / A) of the melt viscosity is 1.15 to 1.40, particularly 1.15 to 1.30. If the logarithmic ratio (B / A) of the melt viscosity is too large, melt spinning tends to be difficult, while if too small, a sea-island structure tends to be hardly formed on the fiber surface.

To satisfy the logarithmic ratio (B / A) of the melt viscosity at 210 ° C. and the shear rate of 912 sec ^{−1 of} the EVOH (A) and the water-soluble resin (B) within a predetermined range, for example, the following method is appropriately used. It becomes possible by combining them.

<Method of adjusting melt viscosity of EVOH (A)>
(1) The degree of polymerization, ethylene composition, and degree of saponification are adjusted in the reaction step.
(2) Two or more types of EVOH having different degrees of polymerization, ethylene composition and saponification degree are melt-blended to adjust the apparent melt viscosity.
(3) One or more additives having a large effect on the melt viscosity are adjusted by using a small amount. Such additives include, for example, (1) a polyamide resin which is a reactive resin for the EVOH resin, (2) a polyolefin, polyester, polystyrene, polycarbonate which is a non-reactive resin for the EVOH resin, and a combination thereof. Examples include polymers, (3) fillers, inorganic substances such as glass fibers, and (4) higher fatty acid metal salts such as higher fatty acid zinc salts. The higher fatty acid salt used in the higher fatty acid zinc salt refers to a fatty acid having 8 or more carbon atoms (preferably having 12 to 30 carbon atoms, more preferably having 12 to 20 carbon atoms), and specifically, lauric acid, tridecyl acid, Examples include myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, oleic acid, capric acid, behenic acid, linoleic acid, and the like. Among these, stearic acid, oleic acid, and lauric acid are preferably used.

<Method of adjusting melt viscosity of water-soluble resin (B)>
(1) In the manufacturing process, the degree of polymerization (or molecular weight) is adjusted.
Among them, in the case of PVA resin, there is a method of adjusting not only the degree of polymerization but also the degree of saponification and modification.
(2) Two or more water-soluble resins having different degrees of polymerization are melt-blended to adjust the apparent degree of polymerization.
(3) One or more additives having a large effect on the melt viscosity are adjusted by using a small amount. Examples of such additives include (1) fillers, inorganic substances such as glass fibers, (2) acid anhydrides, isocyanate-based crosslinking agents, amine-based crosslinking agents, aldehyde-based crosslinking agents, epoxy-based crosslinking agents, and melamine-based crosslinking agents. And a crosslinking agent such as a metal chelate crosslinking agent. Among these, boric acid, methylol melamine, ferric chloride, titanium lactate, titanium diisopropoxybis (triethanolaminate), ammonium zirconium carbonate, zirconium oxychloride, etc. may be used as the crosslinking agent for the PVA resin. it can. (3) Polyhydric alcohols such as glycerin, sorbitol and polyethylene glycol, or plasticizers such as alkylene oxide adducts thereof can also be used.

  In particular, by using the water-soluble resin (B) whose degree of polymerization is adjusted by melt blending in the reaction step or the subsequent step, the logarithm (B / A) of the target melt viscosity is within a predetermined range. It is preferred that

  In the present invention, the content ratio (A / B) of the EVOH (A) and the water-soluble resin (B) is preferably 95/5 to 65/35 by weight, and more preferably , 90/10 to 75/25. If the EVOH (A) is too large relative to the water-soluble resin (B), a sea-island structure in which the EVOH (A) is a sea component and the water-soluble resin (B) is an island component is not sufficiently obtained on the fiber surface, and There is a possibility that the adhesive strength to the hard material is reduced. Conversely, if the EVOH (A) is too small relative to the water-soluble resin (B), the fiber strength tends to decrease.

  The cross-sectional shape of the conjugate fiber of the present invention may be any shape such as a perfect circular shape, a hollow shape, and an irregular cross-sectional shape, but the conjugate fiber is used as a reinforcing material for hydraulic material such as concrete. In this case, the larger the contact area between the fiber and the partner to be reinforced, the higher the bonding strength at the interface, so that it is preferable that the fiber has an irregular cross-sectional shape. However, the shape may be a perfect circle in consideration of the efficiency of the manufacturing process.

  Further, the conjugate fiber of the present invention may contain one or more other thermoplastic resins in addition to the above-mentioned essential components, EVOH (A) and water-soluble resin (B). Other thermoplastic resins include, for example, polypropylene resins, polyethylene resins (LLDPE, LDPE, VLDPE, etc.), polyester resins (PET, PBT, etc.), polyamide resins (nylon 6, nylon 6/66, nylon 12). And the like, and polyester resins are particularly preferred in terms of improving fiber properties such as strength.

  When such another thermoplastic resin is contained, it is necessary that the portion composed of the composite resin containing the EVOH (A) and the water-soluble resin (B) is exposed to the fiber surface. . For example, in a side-by-side or core-sheath type composite fiber, another thermoplastic resin is disposed inside the fiber, and a composite resin containing EVOH (A) and a water-soluble resin (B) is disposed outside the fiber. It is important to

  In the present invention, spun yarn spun using the above-mentioned conjugate fiber is also conceptually included in the conjugate fiber of the present invention. As such a spun yarn, a spun yarn using a staple fiber composed of a conjugate fiber having a sea-island structure in which EVOH (A) is a sea component and a water-soluble resin (B) is an island component, or this staple fiber and another staple fiber are used. Spun yarns composed of fibers are given. Examples of other short fibers include short fibers made of the above-mentioned other thermoplastic resins (eg, polyester resin and polyamide resin) and natural fibers (eg, cotton, hemp, silk).

  The spun or spun conjugate fiber may be subjected to drawing or heat treatment as necessary. The heat treatment can be performed simultaneously with the stretching or in a separate step from the stretching. When the conjugate fiber is used for reinforcing a hydraulic material such as concrete, in order to suppress shrinkage that occurs when the water-soluble resin (B) is dissolved and removed, the conjugate fiber itself is subjected to a degree of thermal shrinkage in advance. The heat treatment may be performed up to.

  In the composite fiber of the present invention, at least on the fiber surface, EVOH (A) is a sea component, and the water-soluble resin (B) is an island component, and the aspect ratio of the fiber surface to the total area of the island component on the fiber surface is 10 or less. Has a special sea-island structure in which the ratio of the area of the island components is 50% or more (see FIG. 1). Therefore, by dissolving and removing the water-soluble resin (B) from the surface of the fiber having the special sea-island structure, it is possible to obtain a fiber provided with a complex uneven shape by EVOH (A).

  Therefore, if this composite fiber is mixed into concrete, resin, rubber, or the like, the irregular shape of the fiber surface exhibits an anchor effect, and exhibits excellent adhesive strength. For this reason, the composite fiber can be used as an excellent reinforcing material for various materials. When the conjugate fiber of the present invention is used as a reinforcing material for a hydraulic material such as concrete, the dispersibility is good even when short fibers are incorporated into the material as it is, and the fibers are uniformly dispersed, which is convenient. Of course, not only short fibers but also yarns, woven fabrics, knitted fabrics, and nonwoven fabrics can be used as the reinforcing material.

  As described above, when used as a reinforcing material such as concrete, resin, rubber, or the like, conjugate fibers (including various types of fiber products using conjugate fibers) are immersed in water or hot water in advance to obtain a water-soluble resin. (B) may be used after dissolving and removing it. However, when the partner to be used as the reinforcing material contains water such as a hydraulic material such as a concrete material, the water-soluble resin (B) of the conjugate fiber is used in advance. Even if it is not removed, the water-soluble resin (B) of the conjugate fiber dissolves and forms irregularities on at least the fiber surface only by mixing and mixing with the hydraulic material, so that high adhesive strength with the hydraulic material is obtained. And an excellent reinforcing effect can be imparted. Therefore, the conjugate fiber of the present invention is optimally used as a reinforcing material for hydraulic materials.

  In addition, when the conjugate fiber of the present invention is used as a reinforcing material for hydraulic material as short fibers, the fineness of the conjugate fiber is preferably 0.01 to 3000 dtex, more preferably 1 to 300 dtex. It is suitable for obtaining a reinforcing effect. The short fiber preferably has a length of 1 to 100 mm, more preferably 3 to 40 mm, in order to obtain a reinforcing effect.

  In the conjugate fiber of the present invention, in the case where the water-soluble resin (B) is dissolved and removed in advance to form at least the fiber surface with irregularities, the temperature of water or hot water used for that purpose is usually 5 to 95 ° C, preferably 20 to 95 ° C. ８０80 ° C. If the temperature of the water is too high, the other component, EVOH (A), may be softened and clear irregularities may not be easily formed. On the other hand, if the temperature of the water is too low, it may take a long time to dissolve and remove the water-soluble resin (B), or the removal may be incomplete, so that clear irregularities may not be easily formed. However, the dissolution and removal of the water-soluble resin (B) need not be completely performed on the entire conjugate fiber, but the water-soluble resin (B) is removed at least on the fiber surface, and the EVOH (A) becomes a sea component and a water-soluble resin. In the sea-island structure in which the conductive resin (B) is an island component, it is sufficient that the EVOH (A) portion remains as a convex portion and irregularities are formed on the fiber surface.

  The treatment method for previously dissolving and removing the water-soluble resin (B) from the conjugate fiber is not particularly limited, and a method of immersing the conjugate fiber in water such as hot water or hot water, or spraying water on the conjugate fiber by spraying or the like. And the like. The water used for the treatment may contain additives such as a surfactant.

  Hereinafter, examples of the present invention will be specifically described together with comparative examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In the following description, “%” and “part” mean on a weight basis.

〔material〕
Details of the materials used in Example 1 and Comparative Examples 1 and 2 are shown below.
・ EVOH1:
Ethylene content 32 mol%, MFR 12 g / 10 min (2160 g, 210 ° C.),
Degree of saponification of 99.5 mol% or more Water-soluble resin 1 (modified PVA1 having 1,2-diol structural unit in side chain):
1,2-diol structural unit content 6 mol%, polymerization degree 1200,
MFR 0.1 g / 10 min (2160 g, 230 ° C.), degree of saponification 99 mol%
Water-soluble resin 2 (modified PVA2 having 1,2-diol structural unit in side chain):
1,2-diol structural unit content 6 mol%, polymerization degree 450,
MFR 8g / 10min (2160g, 230 ° C), degree of saponification 99mol%

[Method for producing water-soluble resin 1 (modified PVA1)]
In a reaction vessel equipped with a reflux condenser, a dropping funnel, and a stirrer, 1000 parts of vinyl acetate, 120 parts of methanol, and 87.6 parts of 3,4-diacetoxy-1-butene (73% of the total charged amount, 6 mol% based on the total charged amount) (Vinyl acetate charged) and 0.07 mol% of azobisisobutyronitrile (vs. vinyl acetate charged) were added, and the temperature was increased under a nitrogen stream with stirring to initiate polymerization. Further, 32.4 parts of 3,4-diacetoxy-1-butene (27% of the total charged amount) was dropped at a constant speed over 7 hours. When the polymerization rate of vinyl acetate reached 72%, m-dinitrobenzene was added as a polymerization inhibitor to terminate the polymerization. Subsequently, unreacted vinyl acetate monomer was removed from the system by a method of blowing methanol vapor to obtain a methanol solution of a PVA-based resin.

  Then, the solution was diluted with methanol to adjust the concentration to 45%, and charged into a kneader. While maintaining the solution temperature at 35 ° C., a 2% methanol solution of sodium hydroxide was added to the vinyl acetate structural unit in the PVA-based resin and Saponification was carried out by adding 12 mmol to the total amount of 1 mol of 3,4-diacetoxy-1-butene structural unit. As the saponification progresses, the saponified product precipitates and separates into solids and liquids at the time when the particles are formed, washed well with methanol, and dried in a hot air drier at 70 ° C. for 12 hours to obtain a modified PVA-based resin. Thus, a water-soluble resin 1 was obtained.

The degree of saponification of the obtained water-soluble resin 1 was 99 mol% as analyzed by alkali consumption required for hydrolysis of residual vinyl acetate and residual 3,4-diacetoxy-1-butene. The degree was 1200 when analyzed according to JIS K6726. The introduction amount of the side chain containing a 1,2-diol structure was 6 mol% as measured by ¹ H-NMR spectrum (solvent: DMSO-d6, internal standard: tetramethylsilane). .

[Production method of water-soluble resin 2 (modified PVA2)]
In a reaction vessel equipped with a reflux condenser, a dropping funnel, and a stirrer, 400 parts of vinyl acetate (40% of the total charged amount), 74 g of methanol, 48 parts of 3,4-diacetoxy-1-butene (40% of the total charged amount) , 6 mol% based on the charged vinyl acetate) and 0.068 mol% azobisisobutyronitrile (based on the charged vinyl acetate), and the temperature was increased under a nitrogen stream with stirring to initiate polymerization. Further, the remaining amounts of vinyl acetate and 3,4-diacetoxy-1-butene were dropped at a constant rate over 13.5 hours. When the polymerization rate of vinyl acetate reached 91%, m-dinitrobenzene was added as a polymerization inhibitor to terminate the polymerization. Other than that, the water-soluble resin 2 which was the modified PVA-based resin 2 was obtained in the same manner as in the above-mentioned production method.

The degree of saponification of the obtained water-soluble resin 2 was 99 mol% when analyzed by alkali consumption required for hydrolysis of residual vinyl acetate and residual 3,4-diacetoxy-1-butene. The degree was 450 when analyzed according to JIS K6726. The introduction amount of the side chain containing a 1,2-diol structure was 6 mol% as measured by ¹ H-NMR spectrum (solvent: DMSO-d6, internal standard: tetramethylsilane). .

[Example 1]
The EVOH1 pellets and the powder of the water-soluble resin 1 were dry-blended at a mass ratio of 80/20, and were melt-kneaded with a twin-screw extruder (KZW15-60 manufactured by Technovel Corp.) in the following temperature pattern to obtain EVOH1. / An alloy pellet of water-soluble resin 1 was obtained.
<Temperature pattern>
C1: 130 ° C, C2: 210 ° C, C3: 230 ° C, C4: 230 ° C,
C5: 230 ° C, C6: 230 ° C, C7: 230 ° C, C8: 220 ° C,
D: 220 ° C

The obtained alloy pellets are melt-spun using a melt spinning tester (MST-CII, manufactured by Fuji Filter Industries Co., Ltd.) in the following temperature pattern to produce the desired conjugate fiber (fiber diameter 350 μm: 1160 dtex). (The same applies to the following examples).
<Temperature pattern>
C1: 200 ° C, C2: 210 ° C, D: 210 ° C

[Comparative Example 1]
EVOH fibers were produced in the same manner as in Example 1 using only the EVOH1 pellets.

[Comparative Example 2]
The pellets of EVOH1 and the powder of water-soluble resin 2 are dry-blended at a mass ratio of 80/20, and are melt-kneaded by a twin-screw extruder (KZW15-60, manufactured by Technovel) in the same temperature pattern as in Example 1. Thus, an alloy pellet of EVOH / water-soluble resin 2 was obtained. Using this alloy pellet, melt spinning was performed in the same manner as in Example 1 to obtain a target conjugate fiber.

  The characteristics of the obtained Example 1 product and Comparative Examples 1 and 2 are summarized in Table 1 below.

  In Example 1 and Comparative Example 2, the melt viscosity ratio of the resin materials to be combined before melt spinning the conjugate fiber was determined according to the following method. In Example 1 and Comparative Examples 1 and 2, the state of the surface of each fiber was observed and subjected to sensory evaluation according to the following method. The ratio P of the surface island components to the total area was determined according to the method described above. Further, in Example 1 and Comparative Examples 1 and 2, the adhesive strength to cement was measured according to the method described below. The results are shown in Table 2 below.

(Melting viscosity ratio)
The melt viscosity of each resin at 210 ° C. and a shear rate of 912 sec ⁻¹ was measured using a capillograph (1B PMD-C, manufactured by Toyo Seiki Seisaku-sho, Ltd.). The value obtained by dividing the logarithm of the viscosity of the water-soluble resin by the logarithm of the viscosity of EVOH1 was defined as a melt viscosity ratio. The larger this value is, the larger the difference in viscosity between them is.

(Fiber surface observation)
Each fiber (fiber diameter 350 μm) was immersed in warm water at 60 ° C., subjected to ultrasonic treatment for 3 hours to dissolve the water-soluble resin on the fiber surface, and then dried. Then, the surface of the treated fiber was observed with a SEM (JSM-6060LA, manufactured by JEOL Ltd.). FIG. 3 is an enlarged photograph (magnification: 2000 times) of Example 1 by the SEM. FIG. 4 is an enlarged photograph of the comparative example 1 (magnification: 2000 times), and FIG. 5 is an enlarged photograph of the comparative example 2 (magnification: 2000 times).

(Adhesion strength measurement with cement)
A cement slurry was prepared by mixing cement powder (Ube Mitsubishi Cement Co., oil well cement) and water at a mass ratio of 75/25. Then, after adding the above cement slurry to a sample tube having a tube diameter of 1 cm and a length of 3 cm so as to have a depth of 2 cm, one fiber (fiber diameter of 350 μm) of Example 1, Comparative Examples 1 and 2 was added, respectively. It was inserted vertically into the sample tube, immersed in cement slurry (the cement / fiber contact length was 2 cm), and allowed to stand at room temperature 23 ° C. for 4 days to solidify the cement. Then, a sample tube was fixed to a lower chuck of an autograph (manufactured by Shimadzu Corporation, AG-IS), and a fiber was fixed to an upper chuck, and a tensile test was performed at a speed of 5 mm / min. The maximum value of the force detected up to the displacement of 2 mm was defined as the adhesive strength between the cement and the fiber.

  From the above results, the product of Example 1 has a complex uneven shape derived from an island component having an aspect ratio of 10 or less formed on the fiber surface, and a composite fiber capable of forming such a fiber surface is reinforced for concrete. It can be seen that when used as a material, it exhibits high adhesive strength to concrete. In contrast, the product of Comparative Example 1 had no irregularities formed on the fiber surface. Therefore, when used as a reinforcing material for concrete, the adhesive strength to concrete is inferior to that of the product of Example 1. Also, in Comparative Example 2, most of the recesses on the fiber surface derived from the island component had a shape extending in a streak shape in the length direction of the fiber (shape having an aspect ratio exceeding 10), and the unevenness was shallow. It seems that the anchor effect due to the unevenness cannot be expected. The adhesive strength is also higher than that of the product of Comparative Example 1, but also inferior to that of the product of Example 1.

  INDUSTRIAL APPLICABILITY The present invention is widely used as a conjugate fiber capable of exhibiting good dispersibility in an aqueous material and high adhesive strength to a partner that disperses and contains the same, and as a reinforcing material for a hydraulic material using the conjugate fiber. can do.

Claims (6)

  A composite fiber containing a saponified ethylene-vinyl ester copolymer (A) and a water-soluble resin (B), wherein the saponified ethylene-vinyl ester copolymer (A) is present on at least the fiber surface. The sea component has a sea-island structure in which the water-soluble resin (B) is an island component, and the ratio of the area of the island component having an aspect ratio of 10 or less on the fiber surface to the total area of the island component on the fiber surface is 50% or more. A conjugate fiber characterized by the following. The logarithmic ratio (B / A) of the melt viscosity of the saponified ethylene-vinyl ester copolymer (A) and the water-soluble resin (B) at 210 ° C. and 912 sec ⁻¹ is 1.10 to 1.50. The composite fiber according to claim 1, wherein The conjugate fiber according to claim 1 or 2, wherein the water-soluble resin (B) is a polyvinyl alcohol-based resin having a 1,2-diol structural unit represented by the following general formula (1).

[Wherein, R ¹ , R ² and R ³ each independently represent a hydrogen atom or an organic group,
X represents a single bond or a bond chain, and R ⁴ , R ⁵ and R ⁶ each independently represent a hydrogen atom or an organic group. ]
  The composite fiber according to claim 3, wherein the average degree of polymerization of the polyvinyl alcohol-based resin is from 600 to 1500.   The content ratio (weight ratio, A / B) of the saponified ethylene-vinyl ester copolymer (A) and the water-soluble resin (B) is 95/5 to 65/35. 5. The conjugate fiber according to any one of items 4 to 4.   A reinforcing material for hydraulic material, comprising the conjugate fiber according to any one of claims 1 to 5.