JP2012188774A - Nonwoven fabric and method for manufacturing nonwoven fabric - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonwoven fabric having a specific three-dimensional structure.SOLUTION: The present invention provides a nonwoven fabric comprising, between filaments, a bridge of microfiber of a polyolefin resin extending in a vertical direction in a cross-section thereof, and a method for manufacturing the nonwoven fabric. Thus, a fabric having little fluff, high tensile strength and high breaking elongation may be obtained.

Description

  The present invention relates to a nonwoven fabric.

  Conventional non-woven fabrics include non-fibrillated fibers and wet non-woven fabrics containing fibrillated fibers (for example, see Patent Documents 1 and 2), spunbond nonwoven fabrics, melt-blown non-woven fabrics, electrospun nonwoven fabrics (electrospun nonwoven fabrics), etc. There is. The wet nonwoven fabrics of Patent Documents 1 and 2 are produced by a normal wet papermaking method and do not have a specific three-dimensional structure. Nonwoven fabrics having a specific three-dimensional structure are disclosed in which fibers are split or fibrillated by applying a high-pressure water stream and three-dimensionally entangled (see, for example, Patent Documents 3, 4, and 5). The inventor impregnates a porous substrate such as a wet non-woven fabric with a polymer solution, precipitates a network polymer by a microphase separation method, and is integrated with the porous substrate (for example, (See Patent Document 6).

JP 2003-129392 A JP 2002-266281 A JP-A-11-107149 JP 2003-55873 A JP-A-9-31817 International Publication No. 2008/153117 Pamphlet

  An object of the present invention is to provide a non-woven fabric having a unique three-dimensional structure that has not existed before.

  In order to solve the above-mentioned problems, the present inventor has conducted intensive research on a method for producing a non-woven fabric containing a polyolefin resin, the fiber diameter of fibers constituting the non-woven fabric, the melting point of the polyolefin resin and the hot-pressure treatment conditions. The present inventors have found a non-woven fabric characterized by having a bridge made of polyolefin resin superfine yarns in the vertical direction between fibers.

  The nonwoven fabric of the present invention has a bridge made of polyolefin resin superfine yarns in the vertical direction when viewed from the cross section, and is less fuzzy and has a higher tensile strength than a nonwoven fabric without a bridge. The effect that the elongation at break is large is obtained.

An example of the electron micrograph (1500 magnification) of the cross section of the nonwoven fabric produced in Example 4 of this invention is shown. An example of the electron micrograph (1500 magnification) of the cross section of the nonwoven fabric produced in Example 5 of this invention is shown. An example of the electron micrograph (2000 magnification) of the cross section of the nonwoven fabric produced in Example 12 of this invention is shown. An example of the electron micrograph (2000 magnification) of the surface of the nonwoven fabric produced in Example 12 of this invention is shown. An example of the electron micrograph (2000 magnification) of the cross section of the nonwoven fabric produced in Example 14 of this invention is shown. An example of the electron micrograph (1500 magnification) of the cross section of the nonwoven fabric produced in Example 25 of this invention is shown. An example of the electron micrograph (2000 magnification) of the cross section of the nonwoven fabric produced in Example 39 of this invention is shown. An example of the electron micrograph (1000 magnification) of the cross section of the nonwoven fabric produced in Example 40 of this invention is shown. An example of the electron micrograph (1000 magnification) of the cross section of the nonwoven fabric produced in the comparative example 2 of this invention is shown. An example of the electron micrograph (2000 magnification) of the cross section of the nonwoven fabric produced in the comparative example 10 of this invention is shown. An example of the electron micrograph (1000 magnifications) of the surface of the nonwoven fabric produced by the comparative example 10 of this invention is shown. An example of the electron micrograph (2000 magnification) of the cross section of the nonwoven fabric produced in the comparative example 11 of this invention is shown. An example of the electron micrograph (1000 magnifications) of the surface of the nonwoven fabric produced by the comparative example 11 of this invention is shown. It is the electron micrograph of the cross section of a nonwoven fabric, and is explanatory drawing which described "length", "cross-sectional thickness", and "depth" in the case of measuring the number of bridges.

  The super fine yarn of polyolefin resin in the present invention refers to a yarn having the thinnest part having a thickness of 1 μm or less, and is formed in the process of producing a nonwoven fabric. The term “bridge” in the present invention means that both ends of the polyolefin resin superfine yarn are bonded to separate fibers and are connected to each other. The thing which only the fiber is entangled is not called adhesion. The bridge of the present invention is formed between arbitrary fibers inside the nonwoven fabric, and is characterized in that it is formed in the vertical direction when viewed from the cross section. For bridging, it is only necessary to connect fibers in a vertical positional relationship, and there is no regulation for the bonding angle between the fibers and the ultrafine yarn. The bridge may be formed not only between two fibers but also across one or more fibers. When the bridge is formed between two fibers, it is not necessarily formed at the shortest distance between the two fibers. The length of the ultrafine yarn tends to be formed in the range of 0.01 to several hundred μm. The bridge of the present invention may be formed in the plane direction on the surface and inside of the nonwoven fabric.

  In the present invention, the cross-section of the nonwoven fabric is observed with an electron microscope, the number of bridges present per continuous length of 200 μm × cross-sectional thickness × depth of 5 μm is measured, and the number divided by four, that is, the length The average number of bridges per 50 μm × cross-sectional thickness × depth of 5 μm is preferably 5 or more, and more preferably 10 or more. The location of the cross section is arbitrary. FIG. 14 is an electron micrograph of a cross section of the nonwoven fabric. The continuous “length” means a linear distance of a side perpendicular to the thickness when viewed from the cross section of the nonwoven fabric. “Cross-sectional thickness” corresponds to the thickness of the nonwoven fabric. “Depth” means the direction that goes horizontally from the cross section. If the average number of bridges existing in the same range is less than 5, it means that there are few or uneven bridges as a whole. If the average number of bridges is less than 5, the effect of the bridge may not appear in the physical properties of the nonwoven fabric. In the present invention, the thinnest part of the super fine yarn may have a thickness exceeding 1 μm.

  Examples of the polyolefin resin in the present invention include polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, and derivatives thereof. Polyethylene includes low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, ultra low density polyethylene, ultra high density polyethylene, ethylene propylene copolymer, a mixture of polyethylene and other polyolefins, and polypropylene. , Homopropylene (propylene homopolymer), or a random copolymer of propylene and an α-olefin such as ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene or 1-decene A polymer or a block copolymer is mentioned.

  The shape of the polyolefin resin before forming the ultrafine yarn is preferably spherical or substantially spherical. The polyolefin resin may be a powder or an aqueous dispersion, but an aqueous dispersion is preferred from the viewpoint of ease of handling. Examples of the particle diameter of the polyolefin resin include a general-purpose type having a particle size distribution and a monodispersed type in which the particle diameters are almost uniform. However, a monodispersed type is preferable because a highly uniform ultrafine yarn can be obtained. The general-purpose particle size can be confirmed by measuring with a laser diffraction particle size distribution measuring device, and the monodisperse particle size can be confirmed with a laser diffraction particle size distribution measuring device or electron microscope observation. When the general-purpose type is measured with a laser diffraction particle size distribution analyzer, the particle diameter when the mass ratio is 50%, that is, D50 is preferably 0.1 to 10 μm, more preferably 1 to 8 μm. If D50 is less than 0.1 μm, it may be too small to obtain the effect of adding the polyolefin resin, and if it is more than 10 μm, the distribution of the polyolefin resin in the nonwoven fabric may be uneven. The average particle diameter of the monodispersed type is preferably from 0.1 to 10 μm, and more preferably from 1 to 8 μm. If the average particle size of the monodisperse type is less than 0.1 μm, the effect of the polyolefin resin may be difficult to obtain because it is too small. If it is greater than 10 μm, the distribution of the polyolefin resin in the nonwoven fabric may be uneven.

  The softening point of the polyolefin resin in the present invention is preferably 150 ° C. or lower, more preferably 135 ° C. or lower, and further preferably 80 ° C. or lower. The melting point is preferably 170 ° C. or lower, more preferably 150 ° C. or lower, and even more preferably 110 ° C. or lower. The lower the softening point and melting point, the easier it is to form a bridge made of superfine yarn. The softening point means the Vicat softening point of JIS K6760 or the ring and ball softening point of JIS K2207. The melting point can be measured by differential thermal analysis defined in JIS K7121.

The nonwoven fabric of the present invention is
1) A method of wet papermaking a slurry containing an aggregate of polyolefin resin particles and fibers and drying at a temperature of the melting point of the polyolefin resin to the melting point + 80 ° C.,
2) A method in which the non-woven fabric produced by the method 1) is further subjected to hot-pressure treatment at a temperature of room temperature to melting point + 80 ° C.,
3) A method of wet-making a slurry containing an aggregate of polyolefin resin particles and fibers, drying at a temperature lower than the melting point of the polyolefin resin, and then hot-pressing at a temperature between the melting point of the polyolefin resin and the melting point + 80 ° C.,
4) A method of impregnating or applying a polyolefin resin to a non-woven fabric not containing a polyolefin resin and then drying at a temperature of the melting point of the polyolefin resin to the melting point + 80 ° C.,
5) A method in which the non-woven fabric produced by the method 4) is further subjected to hot-pressure treatment at a temperature ranging from room temperature to the melting point of the polyolefin resin + 80 ° C.,
6) After impregnating or coating a polyolefin resin on a non-woven fabric containing no polyolefin resin, drying at a temperature lower than the melting point of the polyolefin resin, and then hot pressing at a temperature between the melting point of the polyolefin resin and the melting point + 80 ° C. Can be manufactured.

  Among these production methods, the polyolefin resin is uniformly supported in the nonwoven fabric, and the bridge is easily formed on the entire nonwoven fabric. Therefore, the method 1) or 2) is preferable, and the generation of fluff is suppressed, and the tensile strength and puncture strength are reduced. The method 2) is more preferable because In the methods 2) and 5), the hot-pressure treatment temperature is more preferably the melting point of the polyolefin resin to the melting point + 80 ° C. Accordingly, the most preferable production method is to wet-paper the slurry containing the agglomerates of polyolefin resin particles and fibers, dry at a temperature of the melting point of the polyolefin resin to the melting point + 80 ° C., and then the melting point of the polyolefin resin to the melting point + 80 ° C. It is a hot-pressure process. Since the methods 3) and 6) are dried at a temperature lower than the melting point of the polyolefin resin, the drying efficiency is lower than the methods 1), 2), 4) and 5), and the polyolefin resin is unevenly distributed on the nonwoven fabric surface. There is a case.

  In the methods 4), 5), and 6), when the pores of the nonwoven fabric are smaller than the polyolefin resin particles, the polyolefin resin particles are deposited on the nonwoven fabric surface, so that some or all of the fibers on the nonwoven fabric surface are coated with the polyolefin resin. In some cases, a large portion of the fiber gap is closed, or the polyolefin resin is melted by hot-pressure treatment to form a non-porous film and cover a large portion of the nonwoven fabric surface. When the coating amount is small, the polyolefin resin is unevenly distributed on the nonwoven fabric surface, and there is a case where it is difficult to form a bridge. When the pores of the nonwoven fabric are larger than the polyolefin resin particles, the polyolefin resin particles enter between the fibers and remain in the shape of the particles, or when they melt by hot pressure treatment and block most of the voids in the nonwoven fabric There is.

  In order to form an aggregate of polyolefin resin particles and fibers, a slurry in which polyolefin resin particles and fibers are separately dispersed in a medium is prepared, and both slurries are mixed and stirred. For dispersion of the fiber, a dispersion aid or an antifoaming agent may be added as necessary. The medium is preferably water, but an organic solvent such as alcohols may be mixed. In order to confirm whether or not the particles are aggregated, it is only necessary to visually confirm whether or not aggregates are formed and whether or not the slurry is cloudy. When the slurry is cloudy, it means that there are many polyolefin resin particles that are not aggregated. If aggregation is difficult by simply mixing the polyolefin resin particles and fibers, a flocculant is added. After forming the agglomerates, chemicals such as a thickener, a paper strength enhancer, an antifoaming agent, and a release agent are added as necessary, and diluted to a predetermined solid content concentration to prepare a raw material slurry. The raw material slurry is wet-made with a paper machine. Drying after wet papermaking may be performed using a Yankee dryer, a cylinder dryer, an air dryer, an infrared heater, a far-infrared heater or the like alone or in combination.

  In order to impregnate the nonwoven fabric with the polyolefin resin, for example, an impregnation machine such as a dip coater can be used. In order to apply the polyolefin resin to the nonwoven fabric, for example, a coating machine such as a transfer roll coater, a reverse roll coater, a blade coater, an air doctor coater, a rod coater, a gravure coater, a die coater, or a notch bar coater can be used. Drying after impregnation or coating may be performed using a Yankee dryer, a cylinder dryer, an air dryer, an infrared heater, a far-infrared heater or the like alone or in combination.

  The linear pressure for the hot press treatment is preferably 50 to 2500 N / cm, more preferably 100 to 2000 N / cm. Examples of the hot pressure treatment method include a method in which a non-woven fabric is pressed between rolls heated to a predetermined temperature, and a method in which a pressure treatment is performed for a predetermined time with a hot press machine heated to a predetermined temperature. When the polyolefin resin distributed on the surface and inside of the nonwoven fabric melts and flows when in the hot-pressed state, they contact each other and are released from the hot-pressed state and cooled down to form superfine fibers of the polyolefin resin. It is considered that a bridge is formed between the resin and the polyolefin resin. The roll used for the hot press treatment may be any of metal-metal and metal-elastic combinations. When the heat treatment temperature is lower than the melting point of the polyolefin resin, the polyolefin resin is not completely melted, so that a bridge composed of superfine fibers of the polyolefin resin is not easily formed, and the fluff of the wet nonwoven fabric tends to be severe. If the melting point exceeds + 80 ° C., there may be a case where a polyolefin resin is stuck to a roll or a hot press machine during the hot-pressure treatment and uniform hot-pressure treatment cannot be performed.

  1-40 mass% is preferable and, as for the content rate of the polyolefin resin in the nonwoven fabric of this invention, 5-30 mass% is more preferable. If the amount is less than 1% by mass, the formation of the bridge may be insufficient. If the amount is more than 40% by mass, the voids of the nonwoven fabric may be blocked.

  The “fiber” in the present invention includes both non-fibrillated fibers and fibrillated fibers. The nonwoven fabric of the present invention preferably contains non-fibrillated fibers. Non-fibrillated fibers have the effect of increasing the tensile strength and breaking elongation of the nonwoven fabric and improving the handleability.

  Non-fibrillated fibers include natural fibers, regenerated fibers, synthetic fibers, and inorganic fibers. Examples of natural fibers include cellulose fibers derived from wood, cellulose fibers derived from non-wood such as hemp, cotton, and sugarcane, biocellulose fibers, wool, and silk. Examples of regenerated fibers include solvent-spun cellulose fibers and cupra fibers. Synthetic fibers include polypropylene, polyethylene, polymethylpentene, polyester, polyester derivatives, acrylic polymers, polyvinyl acetate, ethylene-vinyl acetate copolymers, polyvinyl chloride, polyvinylidene chloride, polyvinyl ether, polyvinyl ketone, poly Ether, polyvinyl alcohol, aliphatic polyamide, aromatic polyamide, wholly aromatic polyamide, wholly aromatic polyester, polyamideimide, polyimide, polyetheretherketone, polyphenylene sulfide, polybenzimidazole, poly-p-phenylenebenzobisthiazole, poly Examples include -p-phenylenebenzobisoxazole, polytetrafluoroethylene, single fibers made of these derivatives, and composite fibers made by combining two or more of these resins.

  The acrylic polymer in the present invention is a polymer composed of 100% acrylonitrile, (meth) acrylic acid derivatives such as acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester, vinyl acetate, etc. with respect to acrylonitrile. Refers to a copolymer of Polyamide refers to aliphatic polyamide, semi-aromatic polyamide, and wholly aromatic polyamide. The aromatic polyamide refers to an aromatic polyamide having a fatty chain or the like in a part of the main chain.

  Examples of the inorganic fiber in the present invention include silica / alumina fiber, alumina fiber, glass fiber, micro glass fiber, zirconia fiber, silicon nitride fiber, silicon carbide fiber and the like.

  Examples of the composite fiber include a core-sheath type, an eccentric type, a side-by-side type, a sea-island type, an orange type, a multiple bimetal type, and a split type. Examples of the split type composite fiber include a fiber in which resins made of different components are adjacent to each other and a sea-island type fiber. The former is mechanically divided by a method of stirring with a pulper or a mixer or a method of applying a high-pressure water flow, and the latter is chemically divided by a method of eluting a resin as a sea component with a chemical to obtain ultrafine fibers. Examples of the cross-sectional shape of the former split type composite fiber include a radial type, a layered type, a comb type, and a grid type. The average fiber diameter of the split composite fibers is preferably 3.0 to 18.0 μm, more preferably 6.0 to 16.0 μm. If it is less than 3.0 μm, it may be difficult to divide, and if it is thicker than 18.0 μm, the long axis of the cross section of the ultrafine fiber after division becomes long, so that the void of the nonwoven fabric may be blocked.

  The average fiber diameter of each non-fibrillated fiber is preferably 0.1 to 12.0 μm or less, and more preferably 0.5 to 10.0 μm or less. If it is thicker than 12.0 μm, it may be difficult to reduce the thickness of the nonwoven fabric. If it is less than 0.1 μm, stable production of fibers becomes difficult. Furthermore, it is preferable that the nonwoven fabric of the present invention contains non-fibrillated fibers having an average fiber diameter of 5.0 μm or less. Non-fibrillated fibers having a size of 5.0 μm or less are preferable because they easily form aggregates with polyolefin resin particles. An average fiber diameter refers to the value which converted the area of the fiber cross section into the diameter of the same area of a perfect circle. The fiber length of the non-fibrillated fiber is preferably 0.1 to 10 mm, and more preferably 0.3 to 6 mm. When the fiber length is less than 0.1 mm, the strength of the nonwoven fabric may be insufficient. When the fiber length is longer than 10 mm, the fibers may be twisted to form formation spots or thickness spots.

  In the present invention, it is preferable to contain non-fibrillated fibers having a theoretical flatness of 1.0 to 5.0. The theoretical flatness means a value obtained by dividing the maximum length of the major axis of the fiber cross section by the minor axis length. A non-fibrillated fiber having a theoretical flatness of 1.0 to 5.0 is obtained by dividing a flat fiber obtained by spinning from a flat spinning nozzle or a split type composite fiber having a flat cross section after splitting. Means flat fibers. In the case of flat fibers obtained by direct spinning, the theoretical flatness can be calculated from the flatness of the spinneret. In the case of a split type composite fiber, the theoretical flatness can be calculated from the fiber diameter and the number of splits of the split type composite fiber before splitting. When the theoretical flatness is larger than 5.0, the voids of the nonwoven fabric may be blocked. The minor axis length of the cross section of the non-fibrillated fiber having a theoretical flatness of 1.0 to 5.0 is preferably 1.0 to 5.0 μm, and more preferably 1.0 to 3.0 μm. . If it is less than 1.0 μm, the theoretical flatness of the cross section becomes too large, and the voids of the nonwoven fabric may be blocked. If it exceeds 5.0 μm, it may be difficult to reduce the thickness of the nonwoven fabric. The minor axis length means the maximum length in the minor axis direction of the flat fiber cross section. The theoretical flatness of the flat fibers is more preferably 1.5 to 3.0.

  5-95 mass% is preferable, as for the content rate of the non-fibrillated fiber in the nonwoven fabric of this invention, 10-90 mass% is more preferable, and 15-80 mass% is further more preferable. If it is less than 5% by mass, the tensile strength may be weakened or may be easily broken, and if it exceeds 95% by mass, it may be easily fuzzed.

  The total content of non-fibrillated fibers having an average fiber diameter of 5.0 μm or less and non-fibrillated fibers having a theoretical flatness of 1.0 to 5.0 is 25 to 100 mass with respect to the entire non-fibrillated fibers in the nonwoven fabric of the present invention. % Is preferable, and 50 to 100% by mass is more preferable. If it is less than 25% by mass, it may be difficult to form a bridge made of a superfine fiber of polyolefin resin.

  The nonwoven fabric of the present invention preferably contains fibrillated fibers. When the non-woven fabric contains fibrillated fibers and does not contain non-fibrillated fibers, the thickness can be reduced and the density can be increased. In the present invention, when the non-woven fabric contains both non-fibrillated fibers and fibrillated fibers, the fibrillated fibers are wound around the non-fibrillated fibers, and further, a synergistic effect with a bridge made of polyolefin resin superfine fibers. Thus, it was found that fluff is less likely to occur than when no fibrillated fiber is contained. Examples of the fibrillated fibers used in the present invention include fibers formed by fibrillating natural fibers, regenerated fibers, and synthetic fibers, and bacterial cellulose fibers. As the degree of fibrillation of the fibrillated fiber, the Canadian standard freeness specified in JIS P8121 is preferably 0 to 600 ml, and more preferably 0 to 400 ml. When the Canadian standard freeness is larger than 600 ml, the fiber diameter distribution becomes wide, and there may be formation unevenness or thickness unevenness of the nonwoven fabric.

  When the degree of fibrillation exceeds a certain level, fibrillated fibers pass through the holes in the sieve plate used to measure Canadian standard freeness, resulting in abnormally high freeness and inaccurate freeness measurement. . In that case, modified freeness is adopted in the present invention. The modified freeness in the present invention is measured in accordance with JIS P811, except that an 80 mesh wire net having a wire diameter of 0.14 mm and an aperture of 0.18 mm is used as a sieve plate, and the sample concentration is 0.1% by mass. Freeness. The modified freeness of the fibrillated fiber used in the present invention is preferably 0 to 400 ml, more preferably 0 to 300 ml. If it exceeds 400 ml, the ratio of the thick fiber diameter increases, so that there may be formation unevenness or thickness unevenness of the nonwoven fabric. In the present invention, only one type of fibrillated fiber may be used, or two or more types may be used in combination. When two or more types are used in combination, fibrillated fibers whose Canadian freeness or modified freeness is not a preferable value may be used as long as they do not cause unevenness or thickness unevenness of the nonwoven fabric.

  Therefore, the fibrillated fiber in the present invention is preferably used if the Canadian standard freeness is in the range of 0 to 600 ml or the modified freeness is in the range of 0 to 400 ml. In general, the modified freeness value is larger than the Canadian standard freeness value. For example, in the fibrillated fibers shown in Table 2, F7 shows a larger value for the Canadian standard freeness than for the modified freeness. This means that the fiber length of the fibrillated fiber is short and slips through the sieve plate of Canadian standard freeness, so that it does not show accurate Canadian standard freeness.

  As the fibrillated fiber in the present invention, a fibrillated fiber made of wholly aromatic polyamide or wholly aromatic polyester is preferable because of its excellent ability to aggregate with polyolefin resin particles.

  5-70 mass% is preferable and, as for the content rate of the fibrillated fiber in the nonwoven fabric of this invention, 10-60 mass% is more preferable. If it is less than 5% by mass, the ability to form aggregates with the polyolefin resin particles may be insufficient, and if it exceeds 70% by mass, the tensile strength may be weakened.

  The nonwoven fabric of the present invention may contain inorganic fillers such as metal oxides, metal hydroxides, metal nitrides, metal borides, metal carbides, metal carbonates, metals, and carbon compounds. Inorganic filler is a non-woven fabric with thermal conductivity, electrical conductivity, insulation, gas adsorption, ion adsorption, moisture adsorption, ion exchange, deodorization, heat exchange, heat dissipation, antibacterial, heat resistance, etc. Since a function can be provided, it is preferable. 1-50 mass% is preferable and, as for the content rate of the inorganic filler in the nonwoven fabric of this invention, 5-30 mass% is more preferable. If it is less than 1% by mass, the effect of adding an inorganic filler may be difficult to appear. When it is more than 50% by mass, the tensile strength of the nonwoven fabric may be weakened.

  As the flocculant used in the present invention, organic flocculants such as polyamine, polyacrylamide, sodium alginate, dicyanamide, sulfate band, ferric sulfate, polyferric sulfate, calcium sulfate, ferric chloride, polychlorinated Examples include inorganic flocculants such as aluminum, and organic flocculants alone or inorganic flocculants alone may be used, and organic and inorganic flocculants may be used in combination. The organic flocculant may contain a salt such as sodium salt or potassium salt. The pH of the slurry may be adjusted to increase the acting force of the flocculant. pH adjusters include sodium hydroxide, potassium hydroxide, lithium hydroxide, magnesium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, carbon dioxide, ammonia, citric acid, gluconic acid, succinic acid, lactic acid, fumaric acid Etc. The addition amount of the flocculant is preferably 0.1 to 30% by mass and more preferably 0.4 to 20% by mass with respect to the solid content of the slurry in terms of solid content. If the addition amount of the flocculant is less than 0.1% by mass in terms of solid content, the raw material slurry may be insufficiently agglomerated, and even if added more than 30% by mass, the agglomeration effect may not change. is there.

  Examples of the thickener used in the present invention include alginic acid, sodium alginate, albumin, casein, starch, polysaccharide, agar, sodium carboxymethylcellulose, calcium carboxymethylcellulose, polyacrylic acid, sodium polyacrylate, acrylic acid / alkyl acrylate. Examples include copolymers, acrylamide / acrylic acid copolymers, carboxyvinyl polymers, dimethyl distearyl ammonium hectorite, vinyl compounds, vinylidene compounds, polyester compounds, polyether compounds, and polyglycol compounds. As addition amount of a thickener, 0.1-10 mass% is preferable with respect to the total solid of raw material slurry in conversion to solid content, and 0.3-5 mass% is more preferable. When the addition amount of the thickener is less than 0.1% by mass in terms of solid content, the bonds between the aggregates may be weak. When the amount exceeds 10% by mass, the aggregates become too large, The formation may be uneven.

  Examples of the paper strength enhancer used in the present invention include anionic polyacrylamide, cationic polyacrylamide, amphoteric polyacrylamide, and epoxy-modified polyamide. The paper strength enhancer is preferably 1 to 10% by mass based on the solid content of the slurry. If it is less than 1% by mass, the effect of adding a paper strength enhancer may not appear, and even if it is added more than 10% by mass, the strength of the nonwoven fabric may be saturated.

  The nonwoven fabric in the present invention may be a single layer or multiple layers. Multi-layer means that two or more layers having the same constituent material, blending ratio, basis weight, etc. are laminated, and two or more layers having different conditions such as constituent material, blending ratio, basis weight, etc. are laminated. Refers to things. To make a multilayer nonwoven fabric, a combination paper machine consisting of a circular paper machine, a long paper machine, a short paper machine, a slanted paper machine, or a slanted short paper machine and the same or different types of paper machines. A method of making a multilayer paper using, a method of laminating non-woven fabrics and bonding them by hot pressing, and a method of placing hot-melt materials between the non-woven fabrics and bonding them by hot pressing. In the case of wet papermaking, multi-layer papermaking may be used in which slurries are supplied to the papermaking net of a slanted paper machine or a slanted short paper machine. In the present invention, after wet papermaking or multi-layering, calendering, thermal calendering, heat treatment and the like may be performed as necessary.

  1 to 3 and 5 to 8 are examples of electron micrographs of cross sections of the nonwoven fabrics produced in the examples of the present invention. A bridge made of superfine fibers of polyolefin resin is formed, and in the cross section of the nonwoven fabric, 10 to several tens of fibers can be confirmed per length of 50 μm × section thickness × depth of 5 μm. Moreover, in the nonwoven fabric cross section, it can be seen that the occupation ratio of the polyolefin resin is low, and voids between the fibers remain. FIG. 4 is an example of an electron micrograph of the surface of the nonwoven fabric produced in the example of the present invention. A bridge made of superfine fibers of polyolefin resin is formed. In the present invention, it is not essential to bridge the nonwoven fabric surface as shown in FIG.

  FIG. 9 is an example of an electron micrograph of a cross section of a non-woven fabric outside the present invention. Since it is produced by a normal wet papermaking method and does not contain a polyolefin resin, there is no bridge made of superfine fibers of polyolefin resin. 10 and 12 are examples of electron micrographs of a cross section of a nonwoven fabric outside the present invention. The polyolefin resin particles are applied, dried at a temperature below the melting point of the polyolefin resin, and then hot-pressed at a temperature below the melting point of the polyolefin resin, and there is no bridge made of super fine fibers of the polyolefin resin. I understand. 11 and 13 are examples of electron micrographs of the surface of the nonwoven fabric outside the present invention. 11 is the surface of the nonwoven fabric of FIG. 10, and FIG. 13 is the surface of the nonwoven fabric of FIG. In both cases, it can be seen that the polyolefin resin in the form of particles remains in the gaps between the fibers, and the polyolefin resin covers the fibers and closes most of the fiber gaps.

5-500 micrometers is preferable and, as for the thickness of the nonwoven fabric of this invention, 10-100 micrometers is more preferable. If it exceeds 500 μm, the thickness unevenness may increase. If it is less than 5 μm, the strength may be insufficient. Density of the nonwoven fabric of the present invention is preferably 0.250~0.800g / cm ^3, more preferably 0.300~0.750g / cm ^3, more preferably 0.400~0.700g / cm ^3.

  The tensile strength of the nonwoven fabric of the present invention is preferably 400 N / m or more, more preferably 500 N / m or more, and still more preferably 600 N / m or more. The breaking elongation is preferably 3% or more, more preferably 4% or more, and further preferably 5% or more. If the tensile strength is less than 400 N / m, it may be easily cut during handling. If the elongation at break is less than 3%, it may be easy to cut during handling.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a present Example. Table 1 shows the polyolefin resins used in the examples of the present invention. In Table 1, P1 to P3 are ethylene / α-olefin copolymer particles, P4 and P6 are low density polyethylene particles, and P5 is high density polyethylene particles. The aqueous dispersions of P1 to P4 were used by stirring with a mixer immediately before wet papermaking to uniformly disperse the polyolefin resin.

  Table 2 shows the fibrillated fibers and non-fibrillated fibers used in Examples and Comparative Examples of the present invention. In Table 2, “PET” means polyethylene terephthalate, “EVOH” means ethylene-vinyl alcohol copolymer, “PP” means polypropylene, and “PE” means high density polyethylene. “Modified PET” means a polyester derivative and has a lower melting point than polyethylene terephthalate. In “Cross-sectional shape” in N15 to N19 in Table 2, the left side is the cross-sectional shape before division, and the right side is the cross-sectional shape after division. Table 3 shows the blending ratio of the raw material slurry of the nonwoven fabric produced in the examples of the present invention. “M1” in Table 3 means magnesium oxide having an average particle diameter of 0.6 μm as an inorganic filler. Table 4 shows the blending ratio of the raw material slurry of the nonwoven fabric produced in the examples and comparative examples of the present invention. The symbols used in the “raw materials” in Tables 3 and 4 correspond to the symbols in Tables 1 and 2. The blending ratio of the polyolefin resin in Table 3 and Table 4 means the amount of solid content. “−” In the heat treatment temperature and the heat treatment linear pressure in Table 5 means that heating and pressurization were not performed, respectively.

Example 1
P1, N1, N2, N3, and N5 were weighed so that the blending ratio of slurry 1 was obtained. After N1, N2, N3, and N5 are dispersed in water with a pulper, the aqueous dispersion of P1 is mixed and stirred to form an aggregate of polyolefin resin particles and non-fibrillated fibers, thereby preparing slurry 1 did. A dispersion aid and an antifoaming agent were used for dispersing the non-fibrillated fiber. Slurry 1 was fed to an inclined paper machine, wet-made, and dried at a Yankee dryer temperature of 120 ° C. Subsequently, the nonwoven fabric of Example 1 was produced by heat-pressure treatment at 110 ° C. and a linear pressure of 400 N / cm.

(Example 2)
P1, N3, and N15 were weighed so that the blending ratio of slurry 2 was obtained. After N3 and N15 were dispersed together in water with a pulper, the aqueous dispersion of P1 was mixed and stirred to form aggregates of polyolefin resin particles and non-fibrillated fibers, whereby slurry 2 was prepared. A dispersion aid and an antifoaming agent were used for dispersing the non-fibrillated fiber. It was confirmed that the split composite fiber of N15 was almost split. The slurry 2 was fed to a slanted paper machine, wet-made, and dried at a Yankee dryer temperature of 130 ° C., followed by hot-pressure treatment according to the heat treatment temperature and heat treatment linear pressure conditions shown in Table 5. 2 nonwoven fabrics were produced.

(Examples 3 to 7)
After making wet papermaking and drying using the slurry 2 in the same manner as in Example 2, heat treatment was performed according to the heat treatment temperature and heat treatment linear pressure conditions shown in Table 5 to produce nonwoven fabrics of Examples 3 to 7.

(Example 8)
The slurry 2 was fed to an inclined paper machine, wet-made, and dried at an air dryer temperature of 70 ° C., and then subjected to hot-pressure treatment according to the conditions of heat treatment temperature and heat treatment linear pressure shown in Table 5. 8 nonwoven fabrics were produced.

Example 9
P2, N8, and N12 were weighed so that the blending ratio of slurry 3 was obtained. N8 and N12 were dispersed together in water with a pulper, and then the P2 aqueous dispersion was mixed and stirred to form aggregates of polyolefin resin particles and non-fibrillated fibers, whereby slurry 3 was prepared. A dispersion aid and an antifoaming agent were used for dispersing the non-fibrillated fiber. Slurry 3 was fed to a circular net type paper machine, wet-made, and dried at a Yankee dryer temperature of 120 ° C. Next, heat treatment was performed according to the heat treatment temperature and the heat treatment linear pressure shown in Table 5, and the nonwoven fabric of Example 9 was produced.

(Example 10)
P2, N3, and N16 were weighed so that the blending ratio of slurry 4 was obtained. N3 and N16 were dispersed together in water with a pulper, and then the P2 aqueous dispersion was mixed and stirred to form aggregates of polyolefin resin particles and non-fibrillated fibers, whereby slurry 4 was prepared. A dispersion aid and an antifoaming agent were used for dispersing the non-fibrillated fiber. It was confirmed that the split composite fiber of N16 was almost split. After wet papermaking and drying using the slurry 4 in the same manner as in Example 2, heat treatment was performed according to the heat treatment temperature and heat treatment linear pressure conditions shown in Table 5 to produce the nonwoven fabric of Example 10.

(Examples 11 and 12)
Slurries 5 and 6 were prepared in the same manner as slurry 3. After wet papermaking and drying in the same manner as in Example 9 using Slurries 5 and 6, heat-pressure treatment was performed according to the conditions of the hot-pressure treatment temperature and the hot-pressure treatment linear pressure shown in Table 5, and Examples 11 and 12 were used. A non-woven fabric was prepared.

(Examples 13 to 15)
P3 and N3 were weighed so that the blending ratio of slurry 7 was obtained. After N3 was dispersed in water with a pulper, the aqueous dispersion of P3 was mixed and stirred to form an aggregate of polyolefin resin particles and non-fibrillated fibers, whereby slurry 7 was prepared. A dispersion aid and an antifoaming agent were used for dispersing the non-fibrillated fiber. Wet papermaking and drying were carried out using slurry 7 in the same manner as in Example 9, and then heat-pressed according to the conditions of heat treatment temperature and heat treatment linear pressure shown in Table 5 to produce nonwoven fabrics of Examples 13-15.

(Examples 16 to 18)
P4, N8, and N16 were weighed so that the blending ratio of slurry 8 was obtained. After N8 and N16 were dispersed together in water using a pulper, the P4 aqueous dispersion was mixed and stirred to form aggregates of polyolefin resin particles and non-fibrillated fibers, whereby slurry 8 was prepared. A dispersion aid and an antifoaming agent were used for dispersing the non-fibrillated fiber. It was confirmed that the split composite fiber of N16 was almost split. After wet papermaking and drying using slurry 8 in the same manner as in Example 2, thermal pressing was performed according to the heat treatment temperature and heat treatment linear pressure conditions shown in Table 5 to produce nonwoven fabrics of Examples 16-18.

(Example 19)
P1, F1, N3, and N15 were weighed so that the blending ratio of the slurry 9 was obtained. After F1 was dispersed in water with a pulper, the P1 aqueous dispersion was mixed and stirred to prepare a slurry in which an aggregate of polyolefin resin particles and fibrillated fibers was formed. To this, N3 and N15 dispersed in water with a pulper were mixed and stirred to prepare slurry 9. A dispersion aid and an antifoaming agent were used for dispersing the non-fibrillated fiber. It was confirmed that the split composite fiber of N15 was almost split. Slurry 9 is fed to a combination paper machine of inclined type paper machine and circular paper machine, wet papermaking, dried at a Yankee dryer temperature of 120 ° C., and then subjected to the heat treatment temperature and heat treatment linear pressure shown in Table 5. The nonwoven fabric of Example 19 was produced by heat-pressure treatment according to the above conditions.

(Examples 20, 22, 24-26, 29, 31-33)
Slurries 10, 12, 14, 15, 17, 19-21 were prepared in the same manner as slurry 9. In any of the slurries, it was confirmed that the split type composite fibers were almost split. Using slurry 10, 12, 14, 15, 17, 19-21, wet papermaking and drying were carried out in the same manner as in Example 19, followed by heat pressure treatment according to the conditions of heat treatment temperature and heat treatment linear pressure shown in Table 5. And the nonwoven fabric of Examples 20, 22, 24-26, 29, 31-33 was produced.

(Example 21)
P1, F8, and N7 were weighed so that the blending ratio of the slurry 11 was obtained. After dispersing F8 in water with a pulper, the aqueous dispersion of P1 was mixed and stirred to prepare a slurry in which an aggregate of polyolefin resin particles and fibrillated fibers was formed. To this, N7 dispersed in water with a pulper was mixed and stirred to prepare slurry 11. A dispersion aid and an antifoaming agent were used for dispersing the non-fibrillated fiber. The slurry 11 is fed to a combination paper machine of an inclined paper machine and a circular paper machine, wet-made, and dried at a Yankee dryer temperature of 110 ° C. Then, the heat treatment temperature and heat treatment linear pressure shown in Table 5 are set. The nonwoven fabric of Example 21 was produced by heat and pressure treatment according to the conditions.

(Examples 23, 27, 28, 30)
Slurries 13, 16, and 18 were prepared in the same manner as slurry 11. The slurry 13, 16, 18 was used for wet papermaking and drying in the same manner as in Example 21, followed by heat pressure treatment according to the heat treatment temperature and heat treatment linear pressure conditions shown in Table 5, and Examples 23, 27, 28 and 30 nonwoven fabrics were produced.

(Example 34)
P1, F3, N3, and N15 were weighed so that the blending ratio of the slurry 22 was obtained. After dispersing F3 in water with a pulper, the aqueous dispersion of P1 was mixed and stirred to prepare a slurry in which an aggregate of polyolefin resin and fibrillated fibers was formed. To this, N3 and N15 dispersed in water with a pulper were mixed and stirred to prepare slurry 22. A dispersion aid and an antifoaming agent were used for dispersing the non-fibrillated fiber. It was confirmed that the split composite fiber of N15 was almost split. Slurry 22 is fed to a combination paper machine of an inclined paper machine and a circular paper machine, wet paper is made, dried at a Yankee dryer temperature of 120 ° C., and calendered at a linear pressure of 400 N / cm. The nonwoven fabric of Example 34 was produced.

(Example 35)
After wet papermaking and drying in the same manner as in Example 34, heat treatment was performed in accordance with the heat treatment temperature and heat treatment linear pressure conditions shown in Table 5 to produce the nonwoven fabric of Example 35.

(Example 36)
P3 and F3 were weighed so that the mixing ratio of the slurry 23 was obtained. After F3 was dispersed in water with a pulper, the aqueous dispersion of P3 was mixed and stirred to prepare slurry 23 in which an aggregate of polyolefin resin and fibrillated fibers was formed. The slurry 23 is fed to a combination paper machine of a circular paper machine and a slanted paper machine, wet-made, and dried at a Yankee dryer temperature of 120 ° C. Then, the heat treatment temperature and heat treatment linear pressure shown in Table 5 are set. The nonwoven fabric of Example 36 was produced by heat and pressure treatment according to the conditions.

(Example 37)
P4 and F9 were weighed so that the mixing ratio of the slurry 24 was obtained. After F9 was dispersed in water with a pulper, the P4 aqueous dispersion was mixed and stirred to prepare slurry 24 in which an aggregate of polyolefin resin and fibrillated fibers was formed. The slurry 24 is fed to a combination paper machine of a circular paper machine and a slanted paper machine, wet-made, and dried at an air dryer temperature of 90 ° C. Then, the heat treatment temperature and heat treatment linear pressure shown in Table 5 are set. The nonwoven fabric of Example 37 was produced by heat and pressure treatment according to the conditions.

(Example 38)
P1, F2, N3, and M1 were weighed so that the blending ratio of the slurry 25 was obtained. After F2 was dispersed in water with a pulper, the aqueous dispersion of P1 and M1 were mixed and stirred to prepare a slurry in which an aggregate of polyolefin resin, inorganic filler, and fibrillated fiber was formed. To this, N3 dispersed in water with a pulper was mixed and stirred to prepare slurry 25. The wet papermaking and drying were performed in the same manner as in Example 19 using the slurry 25, and then subjected to hot pressing according to the conditions of the heat treatment temperature and the heat treatment linear pressure shown in Table 5 to produce the nonwoven fabric of Example 38.

(Example 39)
N3, N4, and N13 were weighed so that the blending ratio of the slurry 26 was obtained. N3, N4, and N13 were dispersed together in water with a pulper to prepare slurry 26. A dispersion aid and an antifoaming agent were used for dispersing the non-fibrillated fiber. Slurry 26 was fed to a circular paper machine and wet-made, and dried at a Yankee dryer temperature of 130 ° C. Subsequently, it was subjected to hot-pressure treatment at 200 ° C. and a linear pressure of 500 N / cm to produce a nonwoven fabric having a thickness of 15 μm and a density of 0.666 g / cm ³ . An aqueous dispersion with a P1 solid content concentration of 8% by mass was coated on a single-sided nonwoven fabric with a thickness of 15 μm with a rod coater, dried at an air dryer temperature of 70 ° C., and then subjected to the heat treatment temperatures and heat treatments shown in Table 5. The nonwoven fabric of Example 39 was produced by heat-pressure treatment according to the linear pressure conditions. The coating amount of the polyolefin resin was 3.2% by mass with respect to the mass of the nonwoven fabric before coating.

(Example 40)
A nonwoven fabric having a thickness of 30 μm and a density of 0.693 g / cm ³ was produced in the same manner as in Example 39 using the slurry 26. A non-woven fabric of Example 40 was prepared by coating one side of a 30 μm-thick non-woven fabric with a P1 solid content concentration of 8 mass% using a rod coater and drying at an air dryer temperature of 120 ° C. The coating amount of the polyolefin resin was 12.6% by mass relative to the mass of the nonwoven fabric before coating.

(Example 41)
In the same manner as in Example 40, a P1 aqueous dispersion was coated on one side of a nonwoven fabric having a thickness of 30 μm and a density of 0.693 g / cm ³ with a rod coater and dried at an air dryer temperature of 120 ° C. A non-woven fabric of Example 41 was produced by heat-pressure treatment according to the conditions of the heat treatment temperature and the heat treatment linear pressure shown in FIG. The coating amount of the polyolefin resin was 12.0% by mass relative to the mass of the nonwoven fabric before coating.

(Example 42)
The nonwoven fabric having a thickness of 30 μm and a density of 0.693 g / cm ³ produced in Example 40 was coated on one side with an aqueous dispersion of P1 with a rod coater and dried at an air dryer temperature of 120 ° C. The nonwoven fabric of Example 42 was produced by heat-pressure treatment according to the conditions of the indicated heat treatment temperature and heat treatment linear pressure. The coating amount of the polyolefin resin was 11.1% by mass relative to the mass of the nonwoven fabric before coating.

(Example 43)
The nonwoven fabric having a thickness of 30 μm and a density of 0.693 g / cm ³ produced in Example 40 was coated on one side with an aqueous dispersion of P1 with a rod coater and dried at an air dryer temperature of 120 ° C. A non-woven fabric of Example 43 was produced by heat-pressure treatment according to the conditions of the indicated heat treatment temperature and linear heat treatment pressure. The coating amount of the polyolefin resin was 8.9% by mass relative to the mass of the nonwoven fabric before coating.

(Comparative Examples 1 and 2)
The slurry 26 was fed to a circular paper machine and wet-made, and after drying at a Yankee dryer temperature of 130 ° C., heat treatment was performed at 200 ° C. and a linear pressure of 500 N / cm. A nonwoven fabric was prepared. The nonwoven fabrics of Comparative Examples 1 and 2 have different thicknesses.

(Comparative Example 3)
Slurry 27 was prepared in the same manner as slurry 26. Using the slurry 27, wet papermaking and calendering were performed in the same manner as in Comparative Example 1 to prepare a nonwoven fabric of Comparative Example 3.

(Comparative Example 4)
F3, N4, N6, and N13 were weighed so that the blending ratio of the slurry 28 was obtained. N4, N6, and N13 were dispersed together in water with a pulper, and then F3 was mixed and stirred to prepare slurry 28. A dispersion aid and an antifoaming agent were used for dispersing the non-fibrillated fiber. The slurry 28 was fed to a circular paper machine and wet-made, and dried at a Yankee dryer temperature of 130 ° C. to prepare a wet nonwoven fabric. Subsequently, the wet roll nonwoven fabric was heated at 200 ° C. by contacting the front and back surfaces of the wet nonwoven fabric at a speed of 20 m / min and heat-treated, thereby producing a nonwoven fabric of Comparative Example 4.

(Comparative Example 5)
F2, F9, and N3 were weighed so that the blending ratio of the slurry 29 was obtained. F2 and F9 were dispersed together in water with a pulper, and then N3 was mixed and stirred to prepare slurry 29. Slurry 29 was fed to an inclined paper machine, wet-made, and dried at a Yankee dryer temperature of 130 ° C. to produce a nonwoven fabric of Comparative Example 5.

(Comparative Example 6)
P5 and F2 were weighed so that the mixing ratio of the slurry 30 was obtained. After F2 was dispersed in water with a pulper, P5 was mixed and stirred to prepare slurry 30 in which aggregates of polyolefin resin particles and fibrillated fibers were formed. The slurry 30 was transferred to a combination paper machine of a circular net paper machine-an inclined short net paper machine-a circular net paper machine, wet-made, and dried at a Yankee dryer temperature of 110 ° C. Next, the thickness was adjusted by passing through with a linear pressure of 44 N / cm, and a nonwoven fabric of Comparative Example 6 was produced. As a result of observation with an electron microscope, it was confirmed that the polyolefin resin and the fibrillated fiber were not thermally fused.

(Comparative Example 7)
N8 and N10 were weighed so that the mixing ratio of the slurry 31 was obtained. A slurry 31 was prepared by dispersing N8 and N10 together in a water with a pulper. A dispersion aid and an antifoaming agent were used for dispersing the non-fibrillated fiber. The slurry 31 was fed to a circular paper machine and wet-made, and dried at a Yankee dryer temperature of 110 ° C. to produce a nonwoven fabric having a thickness of 40 μm and a density of 0.375 g / cm ³ . After the P4 aqueous dispersion was coated on the nonwoven fabric with a rod coater, a nonwoven fabric having a thickness of 40 μm and a density of 0.375 g / cm ³ was further laminated thereon and dried at 80 ° C. to form a three-layer structure. A nonwoven fabric of Comparative Example 7 was prepared. The coating amount of the polyolefin resin was 14.2% by mass relative to the mass of one nonwoven fabric before coating.

(Comparative Example 8)
N12 and N19 were weighed so that the mixing ratio of the slurry 32 was obtained. A slurry 32 was prepared by dispersing N12 and N19 together in a water with a pulper. A dispersion aid and an antifoaming agent were used for dispersing the non-fibrillated fiber. It was confirmed that the split type composite fiber of N19 was almost split. The slurry 32 was fed to a combination paper machine of a circular paper machine and a short paper machine, wet papermaking, and dried at a cylinder dryer temperature of 135 ° C. to produce a nonwoven fabric. Next, the nonwoven fabric was exposed to a mixed gas of fluorine: oxygen: nitrogen = 1: 73: 26 for 1 minute in a volume ratio. Thereafter, it was washed with hot water at 60 ° C. and dried at an air dryer temperature of 70 ° C. The nonwoven fabric is sprayed with 100% by mass of moisture and passed through a pair of metal rolls heated to 130 ° C. at a linear pressure of 500 N / cm at a speed of 3.3 m / min to form an ethylene-vinyl alcohol copolymer into a gel film. A nonwoven fabric of Comparative Example 8 was produced. As a result of observation with an electron microscope, it was confirmed that a gel film of ethylene-vinyl alcohol resin was formed on the surface and inside of the nonwoven fabric.

(Comparative Example 9)
N9 and N14 were weighed so that the mixing ratio of the slurry 33 was obtained. N9 and N14 were dispersed in water with a pulper to prepare slurry 33. A dispersion aid and an antifoaming agent were used for dispersing the non-fibrillated fiber. The slurry 33 was fed to an inclined paper machine, wet-made, and dried at a Yankee dryer temperature of 130 ° C. Subsequently, it was heat-treated by passing it between metal rolls heated to 130 ° C. at a linear pressure of 400 N / cm, to produce a nonwoven fabric having a thickness of 30 μm and a density of 0.500 g / cm ³ . This was impregnated with an aqueous dispersion in which the solid content concentration of P6 was 5% by mass, passed through a rubber roll to remove excess liquid, and dried at an air dryer temperature of 90 ° C. Then, the nonwoven fabric of the comparative example 9 was produced by passing through the metal roll heated at 130 degreeC with the linear pressure of 400 N / cm, and heat-pressing. The adhesion amount of the polyolefin resin was 8.7% by mass.

(Comparative Example 10)
The non-woven fabric with a thickness of 15 μm and a density of 0.666 g / cm ³ produced in Example 39 was coated on one side with an aqueous dispersion of P1 used in Example 39 with a rod coater and dried at an air dryer temperature of 80 ° C. After that, heat treatment was performed according to the heat treatment temperature and heat treatment linear pressure conditions shown in Table 5 to produce a nonwoven fabric of Comparative Example 10. The coating amount of the polyolefin resin was 4.3% by mass with respect to the mass of the nonwoven fabric before coating.

(Comparative Example 11)
A non-woven fabric having a thickness of 15 μm and a density of 0.666 g / cm ³ produced in Example 39 was coated on one side with a rod coater with an aqueous dispersion having a solid content concentration of P4 of 8% by mass, and the air dryer temperature was set to 80 ° C. After drying, the hot-pressure treatment was performed in accordance with the heat treatment temperature and heat treatment linear pressure conditions shown in Table 5 to produce a nonwoven fabric of Comparative Example 11. The coating amount of the polyolefin resin was 6.9% by mass relative to the mass of the nonwoven fabric before coating.

[Evaluation]
The following evaluation was performed about the nonwoven fabric of the Example and the comparative example, and the result was shown in Table 5.

<Thickness>
The thickness was measured according to JIS P8118 and the average value was shown.

<Density>
The basis weight of the nonwoven fabric was measured according to JIS P8124, and the basis weight was divided by the thickness to obtain a value and density obtained by multiplying by 100.

<Hot pressure treatment>
In producing the nonwoven fabric, the state of the nonwoven fabric was observed when the nonwoven fabric was hot-pressed. No shrinkage or slight shrinkage, but ◯ when the nonwoven fabric was not cut smoothly and heat treatment was successful. The case where the partial sticking occurred was “Δ”, the case where the nonwoven fabric was severely shrunk and the nonwoven fabric was cut, or the case where it stuck to the roll and delaminated and could not be subjected to uniform hot-pressure treatment was indicated as “X”. “-” Means that no hot-pressure treatment was performed.

<Bridge>
The cross section of the nonwoven fabric was observed with an electron microscope, and “Yes” was given when there was a bridge made of polyolefin resin superfine yarn, and “None” was given when there was no bridge. The super extra fine thread means a filamentous polyolefin resin having a thickness of 1 μm or less at the thinnest part.

<Average number of bridges>
The cross section of the nonwoven fabric was observed with an electron microscope, and the number N of bridges per continuous length of 200 μm × cross section thickness × depth of 5 μm was measured. By dividing N by 4, the average number of bridges per 50 μm length × cross-sectional thickness × depth of 5 μm was calculated.

<Fuzzy>
The fluffiness when the surface of the nonwoven fabric was rubbed with a finger was examined. The case where there was almost no fluffing and no fibers were dropped was indicated as “◯”, the case where fluffing was present but slight fiber dropping was indicated as “Δ”, and the case where fluffing was severe and the fibers were largely dropped was indicated as “X”.

<Tensile strength>
The nonwoven fabric was cut into a width of 50 mm and a length of 250 mm to prepare a strip-shaped test piece. The 250 mm length was taken as the flow direction of the nonwoven fabric. The upper and lower sides of the test piece are fixed to a chuck of a tabletop material testing machine (trade name: STA-1150, manufactured by Orientec Co., Ltd.) at intervals of 100 mm and pulled up at a constant speed of 100 mm / min until the test piece breaks. The maximum load at that time. Five or more test pieces were measured for each nonwoven fabric, and the average value was multiplied by 20 to obtain a value per 1 m width.

<Elongation at break>
Tested according to the <Tensile Strength> test method, the elongation was shown when the test piece broke. Five or more test pieces were measured for each nonwoven fabric, and the average value was obtained.

<Coating area>
Each area of 500 μm square on the front and back surfaces of the nonwoven fabric was observed with an electron microscope, and the coated area of the polyolefin resin was examined. Covering means a state in which a polyolefin resin covers a plurality of fibers in a film form. A region where the polyolefin resin is present only on the fiber and does not block the fiber gap is not considered as a coating. The case where the covering area of the surface having the larger covering area is 60% or more is “large”, the case where it is 30% or more and less than 60% is “medium”, and the case where it is less than 30% is “small”. In the present invention, the smaller the coating area, the better.

The nonwoven fabrics of Examples 1 to 43 are: 1) wet paper making of a slurry containing an aggregate of polyolefin resin particles and fibers, and drying at a temperature of the melting point of the polyolefin resin to the melting point + 80 ° C.,
2) A method in which the non-woven fabric produced by the method 1) is further subjected to hot-pressure treatment at a temperature of room temperature to melting point + 80 ° C.,
3) A method of wet-making a slurry containing an aggregate of polyolefin resin particles and fibers, drying at a temperature lower than the melting point of the polyolefin resin, and then hot-pressing at a temperature between the melting point of the polyolefin resin and the melting point + 80 ° C.,
4) A method of impregnating or applying a polyolefin resin to a non-woven fabric not containing a polyolefin resin and then drying at a temperature of the melting point of the polyolefin resin to the melting point + 80 ° C.,
5) A method in which the non-woven fabric produced by the method 4) is further subjected to hot-pressure treatment at a temperature ranging from room temperature to the melting point of the polyolefin resin + 80 ° C.,
6) Any of the methods of impregnating or applying a polyolefin resin to a nonwoven fabric not containing a polyolefin resin, drying at a temperature lower than the melting point of the polyolefin resin, and then performing a hot-pressure treatment at a temperature between the melting point of the polyolefin resin and the melting point + 80 ° C. Therefore, a bridge made of a superfine fiber of polyolefin resin was provided between the fibers in the vertical direction when viewed from the cross section.

  The nonwoven fabrics of Examples 1, 3 to 7, 9 to 33, 35, and 36 are wet-paper-made slurry containing aggregates of polyolefin resin particles and fibers, and dried at a temperature of the melting point of the polyolefin resin to the melting point + 80 ° C. Since the polyolefin resin was hot-pressed at a temperature ranging from the melting point to the melting point + 80 ° C., the average number of bridges was large and fluff was difficult to occur. The nonwoven fabric of Example 8 was prepared by wet papermaking a slurry containing an aggregate of polyolefin resin particles and fibers, dried at a temperature below the melting point of the polyolefin resin, and then heated at a temperature between the melting point of the polyolefin resin and the melting point + 80 ° C. Because of the pressure treatment, the average number of bridges was large, and fluff was difficult to occur. Since the nonwoven fabrics of Examples 2 and 16 are hot-pressed at a temperature lower than the melting point of the polyolefin resin, generation of fluff is produced as compared with the nonwoven fabrics of Examples 1, 3 to 15, 17 to 33, and 35 to 37. There were many. Since the nonwoven fabrics of Examples 39 to 43 were produced by applying a polyolefin resin, the average number of bridges was large and fluff was difficult to occur.

  Since the nonwoven fabrics of Examples 1 to 38 are prepared by a wet papermaking method using a slurry containing an aggregate of polyolefin resin particles and fibers, the polyolefin resin covers most of the nonwoven fabric surface (60% or more). It never happened. Since the nonwoven fabric of Examples 40-43 is produced by the method of apply | coating polyolefin resin to the nonwoven fabric which does not contain polyolefin resin, most nonwoven fabric surfaces (60% or more) were coat | covered with polyolefin resin.

  The nonwoven fabric of Example 7 contains a non-fibrillated fiber and a polyolefin resin, and has a bridge made of super fine yarn made of polyolefin resin. However, since the hot-pressure treatment temperature exceeded the melting point of the polyolefin resin + 80 ° C., the roll There was a slight problem with the production stability of the hot-pressure treatment.

  Since the nonwoven fabric of Example 34 was not heat-pressed, the average number of bridges was small and fluff was frequently generated. When the non-woven fabrics of Examples 34 and 35 were compared, the non-woven fabric of Example 35 that had been hot-pressed had higher tensile strength and elongation at break.

  When the nonwoven fabric of Example 39 and Comparative Example 1 were compared, the nonwoven fabric of Example 39 having a bridge made of a superfine fiber of polyolefin resin had a higher tensile strength and a higher elongation at break. Similarly, when the nonwoven fabrics of Examples 40 to 43 and the nonwoven fabric of Comparative Example 2 are compared, the nonwoven fabrics of Examples 40 to 43 having a bridge made of polyolefin resin superfine yarn have higher tensile strength and elongation at break. The degree was great.

  On the other hand, the nonwoven fabrics of Comparative Examples 1 and 2 were composed only of non-fibrillated fibers and did not have bridges made of polyolefin resin superfine yarns, and therefore fluff was frequently generated.

  The nonwoven fabric of Comparative Example 3 was composed only of non-fibrillated fibers and did not have bridges made of polyolefin resin superfine yarns, so that there were many fluffs and low elongation at break.

  The nonwoven fabrics of Comparative Examples 4 and 5 were composed of non-fibrillated fibers and fibrillated fibers, and did not have bridges made of polyolefin resin superfine yarns, and therefore fluff was frequently generated. The nonwoven fabric of Comparative Example 5 had low tensile strength and small elongation at break.

  The nonwoven fabric of Comparative Example 6 is composed of fibrillated fibers and polyolefin resin, but both are not heat-sealed and do not have a bridge made of polyolefin resin superfine yarn, so the tensile strength is weak. The elongation at break was small. Moreover, although fluff was hard to generate | occur | produce, the coating area of the nonwoven fabric surface was large.

  The nonwoven fabric of Comparative Example 7 is composed of non-fibrillated fibers and polyolefin resin, but has only been dried at a temperature lower than the melting point of the polyolefin resin, and thus has a bridge made of polyolefin resin superfine yarn. In addition, the occurrence of fluff was large, the tensile strength was weak, and the elongation at break was small. Further, the surface of the nonwoven fabric was not coated with polyolefin resin, but the intermediate layer made of polyolefin resin was coated almost entirely in the form of particles.

  The nonwoven fabric of Comparative Example 8 was composed of non-fibrillated fibers, and the ethylene-vinyl alcohol copolymer formed a gel film, so that fluff was hardly generated and the tensile strength was strong. A bridge made of ultra-fine yarn was not formed. Further, in the heat treatment for forming the gel film, the heat treatment could not be stably performed by sticking to a roll. Moreover, the coating area of the gel film on the nonwoven fabric surface was large.

  The nonwoven fabric of Comparative Example 9 was composed of non-fibrillated fibers and polyolefin resin, and did not have a bridge made of superfine yarn, but fluff was difficult to occur. This is because the surface of the non-woven fabric is coated with a polyolefin resin, and the covering area is 60% or more, which closes the fiber gap.

  The nonwoven fabrics of Comparative Examples 10 and 11 contain non-fibrillated fibers and a polyolefin resin. After coating the polyolefin resin, the nonwoven fabric is dried at a temperature lower than the melting point of the polyolefin resin, and further subjected to hot-pressure treatment at a temperature lower than the melting point of the polyolefin resin. As a result, the polyolefin resin was not completely melted and remained as particles, and a bridge made of super fine yarn was not formed. Fluff was hardly generated by the remaining particles. However, the coated area of the nonwoven fabric surface was large, and the fibers were clogged with particles.

  The nonwoven fabric of the present invention is suitable for liquid filters, blood filtration filters, air filters, wipers, drug solution holding substrates, biological tissue culture substrates, and the like.

Claims (12)

  A non-woven fabric characterized by having a bridge made of polyolefin resin superfine yarn between fibers in the vertical direction when viewed from a cross section.   2. The nonwoven fabric according to claim 1, wherein in the nonwoven fabric section, the average number of bridges per length of 50 μm × cross-sectional thickness × depth of 5 μm is 5 or more.   The nonwoven fabric of Claim 1 or 2 containing a non-fibrillated fiber as a fiber.   The nonwoven fabric of Claim 1 or 2 containing a fibrillated fiber as a fiber.   The nonwoven fabric according to claim 4, wherein the fibrillated fiber is one of a fibrillated para-type wholly aromatic polyamide fiber and a fibrillated wholly aromatic polyester fiber.   A method for producing a nonwoven fabric, comprising wet-making paper containing a slurry containing an aggregate of polyolefin resin particles and fibers and drying at a temperature of a melting point of the polyolefin resin to a melting point + 80 ° C.   Wet paper making a slurry containing an aggregate of polyolefin resin particles and fibers, drying at a temperature of the melting point of the polyolefin resin ~ melting point + 80 ℃, and then hot pressing at a temperature of room temperature to melting point + 80 ℃, A method for producing a non-woven fabric having a bridge made of superfine fibers of polyolefin resin between fibers in the vertical direction when viewed from a cross section.   The slurry containing the agglomerates of polyolefin resin particles and fibers is wet-papered, dried at a temperature lower than the melting point of the polyolefin resin, and then hot-pressed at a temperature between the melting point of the polyolefin resin and the melting point + 80 ° C. The manufacturing method of the nonwoven fabric which has the bridge | crosslinking which consists of a superfine fiber of polyolefin resin in an up-down direction seeing from a cross section between fibers.   After impregnating or applying a polyolefin resin to a non-woven fabric containing no polyolefin resin, the polyolefin resin is dried at a temperature ranging from the melting point of the polyolefin resin to the melting point + 80 ° C. A method for producing a non-woven fabric having a bridge formed of fibers between fibers.   After impregnating or coating a polyolefin resin on a non-woven fabric containing no polyolefin resin, it is dried at a temperature between the melting point of the polyolefin resin and the melting point + 80 ° C., and further subjected to hot-pressure treatment at a temperature between room temperature and the melting point of the polyolefin resin + 80 ° C. The manufacturing method of the nonwoven fabric which has the bridge | crosslinking which consists of a superfine fiber of polyolefin resin in an up-down direction seeing from a cross section between fibers.   After impregnating or coating a polyolefin resin on a non-woven fabric containing no polyolefin resin, drying at a temperature lower than the melting point of the polyolefin resin, and then hot pressing at a temperature between the melting point of the polyolefin resin and the melting point + 80 ° C. The manufacturing method of the nonwoven fabric which has the bridge | crosslinking which consists of a superfine fiber of polyolefin resin in an up-down direction seeing from a cross section between fibers.   The method for producing a nonwoven fabric according to claim 7 or 10, wherein the temperature in the hot-press treatment is the melting point of the polyolefin resin to the melting point + 80 ° C.