JP7043841B2 - Sheet-like material - Google Patents

Description

The present invention relates to a sheet-like material, particularly a fluffy leather-like sheet-like material.

A suede or nubuck-like fluffy leather-like sheet can be obtained by fluffing the surface of a sheet-like material obtained by impregnating a base material such as a non-woven fabric made of fibers with polyurethane resin using sandpaper or the like. Is widely known. The characteristics of the desired napped leather-like sheet-like material can be arbitrarily and widely designed by the combination of the base material made of fibers and the polyurethane resin.

For example, by using a polycarbonate-based polyurethane resin obtained by reacting a polycarbonate polyol having a specific structure with an aromatic polyisocyanate, the flexibility of the polycarbonate-based polyurethane resin is improved, and the grindability by sandpaper or the like is improved. It has been proposed that an artificial leather having a preferable nap length of ultrafine fibers developed thereby, an graceful appearance due to the naps, a supple surface touch and a soft texture can be obtained (see Patent Document 1).

The fluffy leather-like sheet has an appearance and surface very similar to that of natural leather, and has advantages such as uniformity and dyeing fastness that natural leather does not have. It is expanding its use for a long period of time, such as the skin of furniture and the skin of automobile seats. Above all, in clothing applications, artificial leather that has both excellent flexibility and breakage resistance is required.

In the above proposal, it is proposed that flexible artificial leather can be obtained by making the polycarbonate polyol constituting the polyurethane resin having a specific structure with respect to the hardness of the polycarbonate-based polyurethane resin, which has been a problem in the past. Has been done. However, in applications where a flexible texture is required, such as clothing applications, the flexibility is still insufficient.

Further, it has been proposed that a synthetic leather contributing to excellent low temperature flexibility and reduction of environmental load can be obtained by having a polyurethane resin using a plant-derived polycarbonate polyol (see Patent Document 2). However, in this proposal, while synthetic leather consisting of a non-porous polyurethane resin layer having various molecular weights and a fiber cloth is examined in detail, a napped artificial leather having a soft texture and breakage resistance is examined in detail. No consideration was given to leather.

Further, by adding a specific coagulation conditioner to the polyurethane resin to form a porous layer having fine pores and fluffing it by grinding, a suede-like leather-like sheet having an elegant appearance whose color tone does not change is obtained. (See Patent Document 3). However, in this proposal, a good texture is achieved by adjusting the pore diameter between the non-porous polyurethane resin layer having various molecular weights and the portion close to the surface layer and the fiber substrate layer, but the flexibility is achieved. No studies have been made on the point of achieving both the bending resistance and the wrinkle resistance, and the flexibility is impaired due to the presence of the porous polyurethane resin layer.

Separately, by including holes with a diameter of 10 to 200 μm inside the water-dispersed polyurethane resin, the polyurethane resin has good grindability, and by grinding with sandpaper or the like, it has a graceful appearance with fluff. A method for obtaining a sheet-like material has been proposed (see Patent Document 4). However, in this proposal, when the pores inside the polyurethane resin layer are coarse pores exceeding 20 μm, the pore film of the polyurethane resin layer between the pores becomes thicker, which has the effect and flexibility of improving the grindability of the polyurethane resin. It has been difficult to obtain sufficient flexibility in applications such as clothing applications where it is required to flexibly deform along a complicated shape. Moreover, it was difficult to obtain fine and uniform holes.

Further, it has been proposed to obtain a leather-like base material having a lightweight and supple texture, which is composed of a porous polymer elastic body having a specific pore diameter and a porous hollow fiber non-woven fabric (see Patent Document 5). However, in this proposal, it is difficult to achieve both flexibility and crease resistance because the porous structure gives a flexible texture and uniform creases remain.

As described above, it has been extremely difficult to stably obtain a fluffy leather-like sheet-like material having excellent flexibility and wrinkle resistance with the conventional technique.

WO2005 / 095706 Japanese Unexamined Patent Publication No. 2014-1475 Japanese Unexamined Patent Publication No. 2000-303368 Japanese Unexamined Patent Publication No. 2011-214210 Japanese Unexamined Patent Publication No. 2012-214944

Therefore, an object of the present invention is to provide a fluffy leather-like sheet-like material having a texture having excellent flexibility and a high crease resistance while being flexible, in view of the background of the above-mentioned prior art. It is in.

The present invention is intended to solve the above problems, and the sheet-like material of the present invention is a non-woven fabric made of ultrafine fibers having an average single fiber diameter of 0.3 to 7 μm and a sheet-like material made of an elastic resin. The surface of the sheet-like material has fluff, and the elastic resin has a porous structure. The fine pores having a pore diameter of 0.1 to 20 μm occupying all the pores of the porous structure. It is a sheet-like material having a ratio of 60% or more.

According to a preferred embodiment of the sheet-like material of the present invention, the elastic resin is present in the internal space of the nonwoven fabric.

According to a preferred embodiment of the sheet-like material of the present invention, the elastic resin is a polycarbonate-based polyurethane resin.

According to a preferred embodiment of the sheet-like material of the present invention, the weight average molecular weight of the polyurethane resin is 30,000 to 150,000.

According to a preferred embodiment of the sheet-like material of the present invention, the number of holes per unit cross-sectional area in the porous structure in the elastic resin is 50 or more / 1600 μm ² .

According to the present invention, it is possible to obtain a napped leather-like sheet-like material having both a highly flexible texture and breakage resistance. Specifically, according to the present invention, it is possible to obtain a fluffy leather-like sheet-like material having a graceful appearance due to fluffing and also having excellent flexibility and crease resistance. Here, the highly flexible texture means that, for clothing applications, the sheet-like material can be finished into a complicated three-dimensional shape, and further, it can be deformed according to the movement of the body to provide good comfort. In applications such as furniture and automobile interior materials, it is possible to form and process sheet-like objects along complex three-dimensional shapes, and it flexibly follows deformations such as when a person sits and is used well. It refers to being able to provide a feeling. Further, the crease resistance is excellent in crease recovery, and even when a load-bearing wrinkle occurs due to the above-mentioned deformation during use, the wrinkle leaves a mark after being released from the load. Refers to recovery without wrinkles. In order to develop crease resistance, it is necessary to impart appropriate elasticity to the sheet-like material, which is a property that contradicts flexibility, so it was difficult to achieve both flexibility and crease resistance. ..

The sheet-like material of the present invention is a sheet-like material made of a non-woven fabric made of ultrafine fibers having an average single fiber diameter of 0.3 to 7 μm and an elastic resin, and has fluff on the surface of the sheet-like material. The elastic resin has a porous structure, and is a sheet-like material in which the ratio of fine pores having a pore diameter of 0.1 to 20 μm to all the pores of the porous structure is 60% or more.

As described above, the sheet-like material of the present invention is made of a non-woven fabric made of ultrafine fibers and an elastic resin.

As the material of the ultrafine fibers constituting the non-woven fabric used in the present invention, polyesters such as polyethylene terephthalate, polybutylene terephthalate and polytrimethylene terephthalate, and polyamides such as 6-nylon and 66-nylon can be melt-spun. A plastic resin can be used. Among them, polyester is preferably used from the viewpoint of strength, dimensional stability and light resistance. Further, the non-woven fabric can be mixed with ultrafine fibers made of different other materials.

The cross-sectional shape of the single fiber constituting the nonwoven fabric may be a round cross-sectional shape, but polygonal shapes such as ellipse, flat and triangular, and irregular cross-sectional shapes such as fan-shaped and cross-shaped can be adopted.

It is important that the average single fiber diameter of the ultrafine fibers constituting the non-woven fabric is 7 μm or less from the viewpoint of the flexibility of the sheet-like material and the nap quality. The average single fiber diameter is more preferably 6 μm or less, still more preferably 5 μm or less. On the other hand, it is important that the average single fiber diameter is 0.3 μm or more from the viewpoints of color development after dyeing, dispersibility of bundled fibers during buffing treatment, and ease of handling. The average single fiber diameter is more preferably 0.7 μm or more, still more preferably 1 μm or more.

For the average single fiber diameter referred to here, the cross section of the obtained sheet-like material cut in the thickness direction is observed with a scanning electron microscope (SEM), and the fiber diameters of any 50 ultrafine fibers are measured at three points. Therefore, it is obtained by calculating the average value of the fiber diameters of a total of 150 fibers.

As a means for obtaining the ultrafine fibers used in the present invention, it is a preferable embodiment to use ultrafine fiber generation type fibers. The ultrafine fiber generation type fiber uses two components of thermoplastic resin with different solubility in the solvent as the sea component and the island component, and the island component is made into the ultrafine fiber by dissolving and removing only the sea component with a solvent or the like. A sea-island type composite fiber that enables it, and a peelable composite fiber that enables splitting into ultrafine fibers by alternately arranging two components of thermoplastic resin in a radial or layered manner in the fiber cross section and separating and dividing each component. And multi-layered composite fibers can be used.

As the non-woven fabric, a non-woven fabric made by entwining single fibers of ultrafine fibers or a non-woven fabric made by entwining fiber bundles of ultrafine fibers can be used, but a non-woven fabric made by entwining fiber bundles of ultrafine fibers can be used. , It is preferably used from the viewpoint of the strength and texture of the sheet-like material. Further, from the viewpoint of flexibility and texture, a non-woven fabric having appropriate voids between the ultrafine fibers inside the fiber bundle is particularly preferable. As described above, the nonwoven fabric in which the fiber bundles of the ultrafine fibers are entangled can be obtained by entwining the ultrafine fiber generation type fibers in advance and then generating the ultrafine fibers. In addition, those having appropriate voids between the ultrafine fibers inside the fiber bundle can provide appropriate voids between the island components, that is, between the ultrafine fibers inside the fiber bundle by removing the sea component. It can be obtained by using a type composite fiber.

As the non-woven fabric, either a short-fiber non-woven fabric or a long-fiber non-woven fabric can be used, but the short-fiber non-woven fabric is preferably used from the viewpoint of texture and quality.

The fiber length of the staple fibers in the staple fiber nonwoven fabric is preferably 25 to 90 mm. By setting the fiber length to 25 mm or more, a sheet-like material having excellent wear resistance can be obtained by entanglement. Further, by setting the fiber length to 90 mm or less, a sheet-like material having more excellent texture and quality can be obtained. The fiber length is more preferably 35 to 80 mm, and particularly preferably 40 to 70 mm.

When the ultrafine fiber or the fiber bundle thereof constitutes the non-woven fabric, the woven fabric or the knitted fabric can be inserted into the non-woven fabric for the purpose of improving the strength or the like. The average single fiber diameter of the fibers constituting the woven fabric or knitted fabric used is preferably about 0.3 to 10 μm.

The elastic resin used in the present invention has a porous structure, and the ratio of fine pores having a pore diameter of 0.1 to 20 μm to all the pores of the porous structure is 60% or more. The ratio of the fine pores is more preferably 70% or more, still more preferably 80% or more. Further, as the porous structure, communication holes and closed cells can also be adopted. As described above, by having the fine pores in the elastic resin at a certain ratio or more, the flexibility of the elastic resin can be enhanced, and the sheet-like material can be made to have a highly flexible texture. In order to form the elastic resin into a porous structure having such fine pores, it is preferable to use the wet solidification described later as a method for fixing the elastic resin to the non-woven fabric.

Furthermore, by making the elastic resin a porous structure having fine pores, when the sheet-like material is bent and deformed, the force of deformation can be dispersed and received not as a part of the elastic resin but as a whole. The occurrence of creases accompanied by buckling of the elastic resin is suppressed, and a sheet-like material having excellent crease resistance can be obtained.

Further, it is important that the pore diameter of 60% or more of the total pores of the porous structure of the elastic resin is 0.1 μm or more. It is preferably 0.5 μm or more, and more preferably 1 μm or more. By setting the pore diameter to 0.1 μm or more, the flexibility of the elastic resin can be enhanced and the cushioning property against deformation can be enhanced. On the other hand, it is also important that the pore diameter of 60% or more of the total pores of the porous structure of the elastic resin is 20 μm or less. It is preferably 15 μm or less, and more preferably 10 μm or less. By setting the pore diameter to 20 μm or less, the pore density of the porous structure can be increased, both flexibility and appropriate strength can be achieved, and the entire elastic resin can be subjected to the force of deformation. It can be a sheet-like material having excellent flexibility and breakage resistance.

Further, the number of holes per unit area in the porous structure of the elastic resin is 50 pieces / 1600 μm ² or more, preferably 70 pieces / 1600 μm ² or more, and more preferably 100 pieces / 1600 μm ² or more. .. On the other hand, the number of pores in the porous structure per unit area is preferably 1000 pieces / 1600 μm ² or less, and more preferably 800 pieces / 1600 μm ² or less.

By setting the number of holes per unit area to 50/1600 μm ² or more, the porous structure can be made to have a flexible texture, and the multiple holes can be received by the bending deformation force of the sheet, resulting in excellent bending resistance. Wrinkles can be imparted. If the number of holes per unit area is too small, the force of deformation concentrates on a specific hole and buckles, resulting in poor breakage wrinkle recovery. Further, if the number of holes per unit area is too large, the room for deformation of the holes becomes too small, the force of deformation cannot be dispersed, and the crease recovery property becomes inferior.

The elastic resin used in the present invention preferably grips the ultrafine fibers in the sheet-like material and is present in the internal space of the nonwoven fabric from the viewpoint of having fluff on at least one side of the sheet-like material. Is.

As the elastic resin used in the present invention, a polyurethane resin is preferably used in that it has uniform micropores in a sheet-like material. Further, as the polyurethane resin, a polyurethane resin obtained by reacting a polymer diol with an organic diisocyanate is preferably used.

As the polymer diol, for example, polycarbonate-based, polyester-based, polyether-based, silicone-based, and fluorine-based polymer diols can be adopted, and a copolymer obtained by combining these can also be used.

Appropriate rigidity can be imparted to the polyurethane resin, and by forming a porous structure having fine pores, excellent flexibility can be exhibited, and the polyurethane resin does not buckle and has high bending resistance and wrinkle resistance. Therefore, a polycarbonate-based polymer diol is preferably used.

The polycarbonate-based diol can be produced by a transesterification reaction between an alkylene glycol and a carbonic acid ester, a reaction between a phosgen or a chloraterate and an alkylene glycol, or the like.

Examples of the alkylene glycol include ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, and 1,10-decanediol. Chained alkylene glycols, branched alkylene glycols such as neopentyl glycol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-methyl-1,8-octanediol, 1 , Alicyclic diols such as 4-cyclohexanediol, aromatic diols such as bisphenol A, glycerin, trimethylolpropane, and pentaerythritol. Either a polycarbonate-based diol obtained from each of the single alkylene glycols or a copolymerized polycarbonate-based diol obtained from two or more types of alkylene glycols can be used.

Examples of the polyester-based diol include polyester diols obtained by condensing various low molecular weight polyols with polybasic acids.

Examples of the low molecular weight polyol include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, and 2,2-dimethyl-1,3-propane. Diol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,8-octanediol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, cyclohexane-1,4-diol, and One or more selected from cyclohexane-1,4-dimethanol can be used. Further, as a low molecular weight polyol, an adduct obtained by adding various alkylene oxides to bisphenol A can also be used.

Examples of the polybasic acid include succinic acid, maleic acid, adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecandicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, and hexahydro. One or more selected from isophthalic acid can be mentioned.

Examples of the polyether diol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and a copolymer diol in which they are combined.

The number average molecular weight of the polymer diol is preferably 500 to 5000. By setting the number average molecular weight to 500 or more, more preferably 1500 or more, it is possible to prevent the texture from becoming hard. Further, by setting the number average molecular weight to 5000 or less, more preferably 4000 or less, the strength of the polyurethane resin can be maintained.

Examples of the organic diisocyanate used for synthesizing a polyurethane resin include aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, paraphenylenediisocyanate, 1,5-naphthalenedisocyanate, paraxamethylene isocyanate, and methaxamethylene diisocyanate, 4,4'. Examples thereof include alicyclic diisocyanis such as dicyclohexamethylene diisocyanate and isophorone diisocyanate, and aliphatic diisocyanis such as 1,6-hexamethylene diisocyanate. Among them, aromatic diisocyanates, particularly 4,4'-diphenylmethane diisocyanates, are preferably used from the viewpoint of durability such as strength and heat resistance of the obtained polyurethane resin.

As the chain extender used for synthesizing the polyurethane resin, an organic diol, an organic diamine, a hydrazine derivative and the like can be used.

Examples of organic diols include ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, methylpentanediol, 1,6-hexanediol, 1,7-heptanediol, 1 , 8-octanediol, 1,9-nonanediol, aliphatic diols such as 1,10-decanediol, 1,4-cyclohexanediol, and alicyclic diols such as hydrogenated xylylene glycol, aromatics such as xylene glycol. Group diols can be mentioned.

Examples of organic diamines include ethylenediamine, isophoronediamine, xylenediamine, phenyldiamine, and 4,4'-diaminodiphenylmethane.

Examples of hydrazine derivatives include hydrazine, adipic acid dihydrazide, isophthalic acid hydrazide and the like.

A cross-linking agent can be used in combination with the polyurethane resin for the purpose of improving water resistance, abrasion resistance, hydrolysis resistance and the like. The cross-linking agent may be an external cross-linking agent added as a third component to polyurethane, or an internal cross-linking agent that introduces a reaction point having a cross-linked structure in advance in the polyurethane molecular structure can also be used.

For the synthesis of the polyurethane resin, for example, amines such as triethylamine and tetramethylbutanediamine, metal compounds such as potassium acetate, zinc stearate, and tin octylate can be used as the catalyst.

The weight average molecular weight (Mw) of the polyurethane resin used in the present invention is preferably 30,000 to 150,000, more preferably 50,000 to 130,000. By setting the weight average molecular weight (Mw) to 30,000 or more, the strength of the obtained sheet-like material can be maintained, and the generation of fluffy fluff and pills can be prevented. Further, by setting the weight average molecular weight (Mw) to 150,000 or less, the polyurethane resin in the sheet-like material can have uniform fine pores. By setting the weight average molecular weight (Mw) of the polyurethane resin in such a range, the polyurethane resin is fixed to the non-woven fabric by wet coagulation described later, and then a sheet containing an insoluble solvent, for example, water is dried by heating. In the commonly used manufacturing process, a uniform and fine porous structure is formed starting from the temporary softening of the polyurethane resin by heating and the evaporation of the soluble solvent and insoluble solvent contained in the polyurethane resin after wet solidification. You will be able to get it.

Further, the elastic resin may contain an elastomer resin such as polyester, polyamide and polyolefin, an acrylic resin, an ethylene-vinyl acetate resin and the like as long as the performance and texture are not impaired. In addition, various additives such as pigments such as carbon black, flame retardants such as phosphorus, halogen and inorganic, antioxidants such as phenol, sulfur and phosphorus, benzotriazole and benzophenone, Ultraviolet absorbers such as salicylate, cyanoacrylate and oxalic acidanilide, light stabilizers such as hindered amines and benzoates, hydrolysis resistant stabilizers such as polycarbodiimide, plasticizers, antistatic agents, and surfactants. , Coagulation modifiers, dyes and the like can be contained.

In the sheet-like material of the present invention, the ratio of the elastic resin to the sheet-like material is preferably 10 to 50% by mass, more preferably 15 to 35% by mass. By setting the ratio of the elastic resin to 10% by mass or more, the strength of the sheet-like material can be obtained and the fibers can be prevented from falling off. Further, by setting the ratio of the elastic resin to 50% by mass or less, it is possible to prevent the texture from becoming hard, and it is possible to obtain the desired good nap quality.

Further, as a method of fixing the elastic resin to the nonwoven fabric, there is a method of impregnating the nonwoven fabric with a solution of the elastic resin and performing wet coagulation or dry coagulation, but from the viewpoint of obtaining a uniform and fine porous structure as in the present invention. Therefore, wet solidification is preferably used. As the elastic resin, N, N'-dimethylformamide, dimethyl sulfoxide, or the like can be used as the solvent used when applying the polyurethane resin. Specifically, the nonwoven fabric can be imparted to the nonwoven fabric by immersing the nonwoven fabric in an elastic resin solution dissolved in a solvent, and can be solidified by immersing the nonwoven fabric in an insoluble solvent. It can also be coagulated by immersing it in a mixture of a soluble solvent and an insoluble solvent.

The sheet-like material of the present invention can also be obtained by dividing it into halves or several sheets in the thickness direction of the sheet-like material before performing the fluff treatment.

Further, it is preferable to apply an antistatic agent before the fluff treatment because the grinding powder generated from the sheet-like material by grinding tends to be difficult to deposit on the sandpaper.

Finally, the sheet-like material of the present invention can be suitably used as a fluffy leather-like sheet-like material in which ultrafine fibers are fluffed on at least one surface thereof, and the fluff treatment can be performed by using sandpaper, roll sander, or the like. It can be applied by a method of grinding using the method. In order to obtain fibrous fluff on a good surface, it is a preferred embodiment to apply a lubricant such as a silicone emulsion prior to the fluff treatment.

Finally, the sheet-like material of the present invention can be suitably used as a fluffy leather-like sheet-like material in which ultrafine fibers are fluffed on at least one surface thereof.

The sheet-like material of the present invention is used as a skin material for seats, ceilings, interiors, etc. in the vehicle interior of furniture, chairs, walls, automobiles, trains, aircraft, etc., and also has a very elegant appearance in clothing. Can be suitably used as.

Hereinafter, the sheet-like material of the present invention will be described in more detail with reference to Examples.

[Evaluation methods]
(1) Average single fiber diameter:
A cross section perpendicular to the thickness of the non-woven fabric containing the fibers of the sheet-like material was observed at a magnification of 3000 using a scanning electron microscope (VE-7800 type manufactured by SEM KEYENCE), and was randomly selected within a field of view of 30 μm × 30 μm. The diameters of the 50 single fibers extracted in 1 were measured in μm units up to the first fraction. However, this was done at three places, the diameters of a total of 150 single fibers were measured, and the average value was calculated up to the first decimal place. When fibers having a fiber diameter of more than 50 μm are mixed, the fibers are excluded from the measurement target of the average fiber diameter because they do not correspond to ultrafine fibers. Further, when the ultrafine fiber has an irregular cross section, the diameter of the single fiber was obtained by first measuring the cross-sectional area of the single fiber and calculating the diameter when the cross section was regarded as a circle. The average value using this as the population was calculated and used as the average single fiber diameter.

(2) Pore diameter of the porous structure of the elastic resin and the ratio of fine pores having a pore diameter of 0.1 to 20 μm to all the pores of the porous structure:
A cross section perpendicular to the thickness of the non-woven fabric containing the elastic resin of the sheet-like material was observed at 2000 times using a scanning electron microscope (VE-7800 type manufactured by SEM KEYENCE), and within a field of view of 40 μm × 40 μm. The pore diameters (diameters) of the holes in the 50 randomly selected elastic resin were measured in μm units up to the first fraction. However, this is done at three locations, the hole diameters of a total of 150 holes are measured, the ratio of the number of holes with a hole diameter of 0.1 to 20 μm to the 150 holes is calculated, and 0.1 to 20 μm to the porous structure. The ratio of micropores in. Further, when the hole in the elastic resin is a deformed hole, the hole diameter (diameter) of the hole was obtained by first measuring the cross-sectional area of the hole and calculating the diameter when the cross section is regarded as a circle.

(3) Number of holes in the porous structure of elastic resin per unit area:
A cross section perpendicular to the thickness of the non-woven fabric containing the elastic resin of the sheet-like material was observed at 2000 times using a scanning electron microscope (VE-7800 type manufactured by SEM KEYENCE), and within a field of view of 40 μm × 40 μm. The number of holes in the elastic resin was measured. However, this was done at three locations, and the arithmetic mean value of the number of holes was taken as the number per unit area of the holes in the porous structure. When the elastic resin containing the porous structure is smaller than the field of view of 40 μm × 40 μm, the number of holes in the field of view divided by the effective area of the elastic resin is converted into the number of holes per 1600 μm ² . The number was defined as the number of holes in the porous structure per unit area. When the pore diameter was larger than the field of view of 40 μm × 40 μm, the number of pores in the porous structure per unit area was set to 1.

(4) Weight average molecular weight of polyurethane resin:
A polyurethane resin was extracted from the obtained sheet-like material using N, N'-dimethylformamide (hereinafter, may be referred to as DMF), and the polyurethane resin concentration was adjusted to 1% by mass. The weight average molecular weight of the polyurethane resin was determined by gel permeation chromatography (GPC) under the following conditions. ・ Equipment: GPC measuring machine HLC-8020 (manufactured by Tosoh Corporation)
-Column: TSK gel GMH-XL (manufactured by Tosoh Corporation)
-Solvent: N, N-dimethylformamide (hereinafter abbreviated as DMF)
・ Standard sample: Polystyrene (TSK standard foam; manufactured by Tosoh Corporation)
・ Temperature: 40 ℃
-Flow rate: 1.0 ml / min.

(5) Flexibility:
Based on the A method (45 ° cantilever method) described in 8.21.1 of 8.21 "Stiffness and softness" of JIS L 1096: 2010 "Fabric test method for woven fabrics and knitted fabrics", in the vertical and horizontal directions. Create 5 test pieces of 2 x 15 cm each, place them on a horizontal table with a slope at an angle of 45 °, slide the test pieces, and read the scale when the center point of one end of the test piece touches the slope. The average value of 5 sheets was calculated. The flexibility was good at 45 mm or less.

(6) Breaking wrinkle resistance:
Based on the description of JIS L 1059-1: 2009 "Wrinkle resistance test method for textile products-Part 1: Measurement of recovery of horizontally folded wrinkles (Monsanto method)", a test piece 5 using a 10N load device. The wrinkle recovery angle of each sheet was measured, and the bending wrinkle resistance was calculated by the formula of the wrinkle prevention rate described in 10 "Calculation of wrinkle recovery angle and wrinkle prevention rate", and the average value of 5 sheets was obtained. The crease resistance was good at 90% or more.

[Notation of chemical substances]
The meanings of the abbreviations of chemical substances used in Examples and Comparative Examples are as follows.
-PU: Polyurethane-DMF: N, N-dimethylformamide.

(Example 1)
A sea-island type composite fiber using polystyrene as a sea component and polyethylene terephthalate as an island component was stretched, crimped, and cut to obtain a non-woven raw cotton. The raw cotton thus obtained was made into a fiber web using a cloth wrapper, and a non-woven fabric was made by needle punching.

The non-woven fabric made of the sea-island type composite fiber thus obtained is impregnated with a polyvinyl alcohol aqueous solution and then dried. Then, polystyrene, which is a sea component, is extracted and removed in trichlorethylene, and dried to obtain an average single fiber. A non-woven fabric made of ultrafine fibers having a diameter of 2.0 μm was obtained.

The non-woven fabric made of the ultrafine fibers thus obtained was immersed in a resin solution in which the concentration of the DMF solution of the polycarbonate-based polyurethane resin was adjusted to 11%, and the amount of the polyurethane (PU) resin solution adhered was adjusted by a drawing roll. After that, the PU resin was solidified in an aqueous solution having a DMF concentration of 30%, and then polyvinyl alcohol and DMF were removed with hot water and dried to obtain a sheet having a PU resin content of 17% by mass. One side of the sheet-like material thus obtained was fluffed with 180 mesh endless sandpaper, and then dyed with a disperse dye to obtain a fluffy leather-like sheet-like material.

When the cross section of the inside of the obtained leather-like sheet-like material in the thickness direction was observed with a scanning electron microscope (SEM), the polyurethane resin was present only inside the non-woven fabric, and the polyurethane resin had a porous structure having fine pores. The ratio of micropores having a pore diameter of 0.1 to 20 μm to all the pores in the porous structure was 85%, and the number of pores in the porous structure per unit area was 247/1600 μm. The weight average molecular weight of the polyurethane resin extracted and measured from the fluffy leather-like sheet was 110,000.

The obtained fluffy leather-like sheet-like material had good fluff length and dispersibility of fibers, and had excellent flexibility and crease resistance. The results are shown in Table 1.

(Examples 2 to 7, Comparative Examples 1 to 5)
Similar to Example 1, a fluffy leather-like sheet is formed, except that the average single fiber diameter of the ultrafine fibers, the type of polyurethane resin, and the weight average molecular weight of the polyurethane resin are changed to those shown in Table 1, respectively. I made a thing.

When the cross section in the thickness direction of the inside of the leather-like sheet-like material in each example and the comparative example was observed by a scanning electron microscope (SEM), the polyurethane resin had a porous structure having fine pores, and the polyurethane resin was inside the non-woven fabric. It existed only in.

Table 1 shows the average single fiber diameter of the ultrafine fibers of each example and the comparative example, the type of polyurethane resin, the weight average molecular weight of the polyurethane resin, the average pore size of the porous structure of polyurethane in the obtained sheet-like material, and the total of the porous structures. The ratio of micropores having a pore diameter of 0.1 to 20 μm in the pores, flexibility, and breakage resistance were shown.

In any of the raised leather-like sheet-like materials of Examples 1 to 7, the polyurethane resin forms a porous structure having fine pores, and the weight average molecular weight of the polyurethane resin is adjusted to average the pores in the porous structure. By adjusting the diameter and the ratio of micropores of 0.1 to 20 μm to the total pores of the porous structure and the number of pores in the porous structure per unit area, both excellent flexibility and breakage resistance are achieved. ing. On the other hand, in the sheet-like materials of Comparative Examples 1 to 5, a porous structure is formed in the polyurethane resin as the weight average molecular weight of the polyurethane resin increases, but the pores become coarse and non-uniform, and the pore film becomes thick. As a result, the flexibility is reduced, and the non-uniform pore diameter makes it impossible for the entire polyurethane resin to undergo bending deformation, resulting in inferior bending and wrinkle resistance.

Claims (4)

It is a sheet-like material made of a non-woven fabric made of ultrafine fibers having an average single fiber diameter of 0.3 to 7 μm and an elastic resin, and has fluff on the surface of the sheet-like material, and the elastic resin is a polyurethane resin. The weight average molecular weight of the polyurethane resin is 30,000 to 150,000, and the elastic resin has a porous structure, and the pore diameter occupying all the pores of the porous structure is 0.1 to 20 μm. A sheet-like material characterized by having a ratio of fine pores of 60% or more. The sheet-like material according to claim 1, wherein the elastic resin is present in the internal space of the nonwoven fabric. The sheet-like material according to claim 1 or 2, wherein the elastic resin is a polycarbonate-based polyurethane resin. The sheet-like material according to any one of claims 1 to 3 , wherein the number of holes per unit cross-sectional area in the porous structure in the elastic resin is 50 or more / 1600 μm ² .