WO2018135243A1

WO2018135243A1 - Sheet-like object

Info

Publication number: WO2018135243A1
Application number: PCT/JP2017/046354
Authority: WO
Inventors: 孝宜古井; 隆司宿利; 現小出
Original assignee: 東レ株式会社
Priority date: 2017-01-23
Filing date: 2017-12-25
Publication date: 2018-07-26
Also published as: CN110191987B; JPWO2018135243A1; KR20190104536A; EP3572580A4; EP3572580A1; EP3572580B1; TW201833406A; JP7043841B2; CN110191987A; US20190368124A1

Abstract

The present invention provides a sheet-like object having an excellent flexible texture, and further, having high resistance to creases and wrinkles while being flexible. The sheet-like object according to the present invention comprises an elastic resin and a nonwoven fabric made of ultrafine fibers having an average monofilament diameter of 0.3-7 μm, wherein the surface of the sheet-like object has erected hairs formed therein, the elastic resin has a porous structure, and micropores each having a pore diameter of 0.1-20 μm account for at least 60% of all the pores in the porous structure.

Description

Sheet

The present invention relates to a sheet-like material, particularly a sheet-like material such as napped leather.

To obtain suede or nubuck-like napped leather-like sheet-like material by raising the surface of the sheet-like material impregnated with polyurethane resin into a non-woven fabric base material using sandpaper etc. Is widely known. The desired properties of the raised leather-like sheet-like material can be designed in a wide variety of ways depending on the combination of the substrate 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 and an aromatic polyisocyanate, the flexibility of the polycarbonate-based polyurethane resin is improved, and the grindability with sandpaper is improved. It has been proposed that an artificial leather having a raised length of a preferable ultrafine fiber, an elegant appearance by the raised hair, a supple surface touch and a flexible texture can be obtained (see Patent Document 1).

Napped leather-like sheet-like material has an appearance and surface very similar to natural leather, and has advantages such as uniformity and dyeing fastness that are not found in natural leather. It is spreading to applications that are used for a long time, such as furniture skins of automobiles and seat skins for automobiles. In particular, for apparel applications, artificial leather that achieves both excellent flexibility and crease resistance is required.

In the above proposal, it is proposed that a flexible artificial leather can be obtained by making the polycarbonate polyol constituting the polyurethane resin have a specific structure with respect to the hardness of the polycarbonate-based polyurethane resin, which has been regarded as a conventional problem. Has been. However, in applications that require a soft texture such as clothing, the flexibility is still not sufficient.

In addition, it has been proposed that synthetic leather contributing to excellent low-temperature flexibility and environmental load reduction can be obtained by having a polyurethane resin using plant-derived polycarbonate polyol (see Patent Document 2). However, in this proposal, a synthetic leather composed of a non-porous polyurethane resin layer having various molecular weights and a fiber fabric has been studied in detail, while an artificial nail-like material having a soft texture and a crease-resistant wrinkle resistance. No consideration was given to leather.

In addition, a specific coagulation regulator is added to polyurethane resin to form a porous layer having fine pores, and by fuzzing it by grinding, a suede-like leather-like sheet having an elegant appearance that does not change color tone is obtained. Has been proposed (see Patent Document 3). However, in this proposal, a fine texture is achieved by adjusting the pore diameter between the nonporous polyurethane resin layer having various molecular weights and the surface layer and the portion close to the fiber substrate layer. No consideration has been given to the compatibility between crease resistance and crease resistance, and flexibility has been impaired because of the porous polyurethane resin layer.

In addition, by including pores with a diameter of 10 to 200 μm inside the water-dispersible polyurethane resin, the polyurethane resin has good grindability, and has an elegant appearance with napping by grinding with sandpaper or the like. 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 thick, and the effect and flexibility of improving the grindability of the polyurethane resin. It is difficult to achieve sufficient flexibility in applications that require flexible deformation along complicated shapes such as clothing applications. In addition, it was difficult to obtain fine and uniform holes.

Furthermore, it has been proposed that a leather-like substrate having a light and supple texture composed of a porous polymer elastic body having a specific pore size and a porous hollow fiber nonwoven fabric is obtained (see Patent Document 5). However, in this proposal, since it has a soft texture due to the porous structure, and it is uniform but creases remain, it is difficult to achieve both flexibility and crease resistance.

As described above, with the conventional technology, it is extremely difficult to stably obtain a raised leather-like sheet-like material excellent in both flexibility and folding resistance.

WO2005 / 095706 JP 2014-1475 A JP 2000-303368 A JP 2011-214210 A JP 2012-214944 A

Therefore, in view of the background of the above-described conventional technology, an object of the present invention is to provide a napped leather-like sheet-like material that has a texture excellent in flexibility, and further has a soft and high crease resistance. It is in.

The present invention is to solve the above-mentioned problems, and the sheet-like material of the present invention is a sheet-like material comprising a nonwoven fabric composed of ultrafine fibers having an average single fiber diameter of 0.3 to 7 μm and an elastic resin. The surface of the sheet-like material has napping, and the elastic resin has a porous structure, and micropores having a pore diameter of 0.1 to 20 μm occupying all the pores of the porous structure. It is a sheet-like material with a ratio of 60% or more.

According to a preferred aspect 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 polyurethane resin has a weight average molecular weight of 30,000 to 150,000.

According to a preferred aspect of the sheet-like material of the present invention, the number of pores 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 which has both a high texture rich in flexibility and crease resistance. Specifically, according to the present invention, it is possible to obtain a napped leather-like sheet-like material having an elegant appearance by napping and having excellent flexibility and crease resistance. Here, the high texture that is rich in flexibility means that if it is used for clothing, the sheet can be finished into a complex three-dimensional shape, and can be deformed following the movement of the body to provide good comfort In applications such as furniture and automobile interior materials, it enables the formation and processing of sheet-like objects along complex three-dimensional shapes, and it can be used flexibly following deformation such as sitting down. It means being able to provide a feeling. In addition, the crease resistance means that the crease is excellent in recovery from crease, and even when wrinkles that are loaded due to deformation during use are generated, the wrinkles leave marks after being released from the load. It means to recover without it. Appropriate elasticity must be imparted to the sheet-like material in order to exhibit folding resistance, and it is difficult to achieve both flexibility and resistance to bending because it is incompatible with flexibility. .

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 a nap on the surface of the sheet-like material. The elastic resin has a porous structure, and the ratio of fine pores having a pore diameter of 0.1 to 20 μm occupying all pores of the porous structure is a sheet-like material of 60% or more.

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

The material of the ultrafine fibers constituting the nonwoven fabric used in the present invention includes heat-spinnable heat such as polyesters such as polyethylene terephthalate, polybutylene terephthalate and polytrimethylene terephthalate, and polyamides such as 6-nylon and 66-nylon. A plastic resin can be used. Of these, polyester is preferably used from the viewpoints of strength, dimensional stability and light resistance. The nonwoven fabric can be mixed with ultrafine fibers of different materials.

As the cross-sectional shape of the single fiber constituting the nonwoven fabric, a round cross-section may be used, but a polygonal shape such as an ellipse, a flat shape and a triangle, or a deformed cross-sectional shape such as a sector shape and a cross shape may be employed.

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

The average single fiber diameter here refers to a cross section obtained by cutting the obtained sheet-like material in the thickness direction with a scanning electron microscope (SEM), and the fiber diameter of any 50 ultrafine fibers is measured at three locations. Thus, the average value of the diameters of a total of 150 fibers is calculated.

As a means for obtaining ultrafine fibers used in the present invention, it is preferable to use ultrafine fiber generating fibers. The ultrafine fiber generation type fiber uses two component thermoplastic resins with different solubility in solvent as sea component and island component, and dissolves and removes only sea component with solvent etc. to make island component as ultrafine fiber. Sea-island type composite fibers that can be made, and peelable composite fibers that allow two-component thermoplastic resins to be alternately arranged in a fiber cross-section radial or layered form and split into ultrafine fibers by separating and separating each component Or multilayer type composite fibers can be used.

The non-woven fabric can be a non-woven fabric formed by entanglement of single fibers of ultrafine fibers or a non-woven fabric formed by entanglement of fiber bundles of ultrafine fibers. From the viewpoint of the strength and texture of the sheet-like material, it is preferably used. Further, from the viewpoint of flexibility and texture, a nonwoven fabric having an appropriate gap between ultrafine fibers inside the fiber bundle is particularly preferably used. Thus, the nonwoven fabric in which the fiber bundles of ultrafine fibers are entangled can be obtained by generating ultrafine fibers after entanglement of the ultrafine fiber generating fibers in advance. Moreover, what has an appropriate space | gap between the ultrafine fibers inside a fiber bundle is a sea island which can give an appropriate space | gap between island components by removing a sea component, ie, an ultrafine fiber inside a fiber bundle. It can be obtained by using a mold composite fiber.

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

The fiber length of the short fiber in the short 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 abrasion resistance can be obtained by entanglement. In addition, when the fiber length is 90 mm or less, it is possible to obtain a sheet-like product having a better texture and quality. The fiber length is more preferably 35 to 80 mm, particularly preferably 40 to 70 mm.

When the ultrafine fiber or its fiber bundle constitutes a nonwoven fabric, a woven fabric or a knitted fabric can be inserted for the purpose of improving the strength. 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 proportion of fine pores having a pore diameter of 0.1 to 20 μm in all pores of the porous structure is 60% or more. The proportion of the fine holes is more preferably 70% or more, and further preferably 80% or more. The porous structure can also employ communication holes and closed cells. Thus, by having a micropore in a certain ratio or more in the elastic resin, the flexibility of the elastic resin can be increased, and the sheet-like material can have a soft texture. In order to make the elastic resin have a porous structure having such fine pores, it is preferable to use wet coagulation described later as a method of fixing the elastic resin to the nonwoven fabric.

Furthermore, since the elastic resin has a porous structure having fine pores, when bending deformation is applied to a sheet-like material, the deformation force can be distributed and received not as a part of the elastic resin. Further, the occurrence of folding wrinkles accompanied by buckling of the elastic resin is suppressed, and a sheet-like product having excellent folding wrinkle resistance can be obtained.

Also, it is important that the diameter of 60% or more of all the pores of the porous structure of the elastic resin is 0.1 μm or more. Preferably it is 0.5 micrometer or more, More preferably, it is 1 micrometer or more. By setting the hole 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 hole diameter of 60% or more of all the holes of the porous structure of the elastic resin is 20 μm or less. Preferably it is 15 micrometers or less, More preferably, it is 10 micrometers 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 deformation force can be received by the entire elastic resin. Thus, a sheet-like material having excellent flexibility and crease resistance can be obtained.

Further, the number of pores per unit area in the porous structure of the elastic resin is 50/600 μm ² or more, preferably 70/1600 μm ² or more, more preferably 100/1600 μm ² or more. . On the other hand, the number of pores in the porous structure per unit area is preferably 1000/1600 μm ² or less, and more preferably 800/1600 μm ² or less.

By setting the number of holes per unit area to 50/1600 μm ² or more, the porous structure can have a flexible texture, and can be received by the force of bending deformation of the sheet through a plurality of holes, and has excellent folding resistance. Wrinkle properties can be imparted. If the number of holes per unit area is too small, the deformation force concentrates on a specific hole and buckles, resulting in poor crease recovery. Moreover, when there are too many holes per unit area, the deformation | transformation space of a hole will become too small, it will become impossible to disperse | distribute the force of a deformation | transformation, and it will be inferior to a wrinkle recovery property.

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

As the elastic resin used in the present invention, a polyurethane resin is preferably used in that it has uniform fine pores in the sheet-like material. Moreover, as a polyurethane resin, the polyurethane resin obtained by reaction of polymer diol and organic diisocyanate is used preferably.

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

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

Polycarbonate-based diol can be produced by transesterification of alkylene glycol and carbonate, or reaction of phosgene or chloroformate with alkylene glycol.

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

Examples of the polyester diol include polyester diols obtained by condensing various low molecular weight polyols and 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.

Polybasic acids include, for example, succinic acid, maleic acid, adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, and hexahydro One kind or two or more kinds selected from isophthalic acid can be mentioned.

Examples of polyether diols include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and copolymer diols combining them.

The number average molecular weight of the polymer diol is preferably 500 to 5,000. 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. Moreover, the intensity | strength as a polyurethane resin is maintainable by making a number average molecular weight into 5000 or less, More preferably, 4000 or less.

Examples of the organic diisocyanate used in the synthesis of the polyurethane resin include aromatic diisocyanates such as 4,4′-diphenylmethane diisocyanate, paraphenylene diisocyanate, 1,5-naphthalene diisocyanate, paraxylene diisocyanate, metaxylene diisocyanate, and 4,4 ′. -Alicyclic diisocyanates such as dicyclohexylmethane diisocyanate, isophorone diisocyanate and aliphatic diisocyanates such as 1,6-hexamethylene diisocyanate. Of these, aromatic diisocyanates, particularly 4,4'-diphenylmethane diisocyanate, is preferably used from the viewpoint of durability such as strength and heat resistance of the resulting polyurethane resin.

As the chain extender used for the synthesis of the polyurethane resin, organic diols, organic diamines, hydrazine derivatives, 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, Aliphatic diols such as 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,4-cyclohexanediol, and alicyclic diols such as hydrogenated xylylene glycol, and aromatics such as xylene glycol Group diols can be mentioned.

Examples of organic diamines include ethylene diamine, isophorone diamine, xylene diamine, phenyl diamine, and 4,4'-diaminodiphenyl methane.

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

In the polyurethane resin, a crosslinking agent can be used in combination 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 the polyurethane, or an internal cross-linking agent that introduces a reaction point that becomes a cross-linked structure in advance in the polyurethane molecular structure may be used.

For the synthesis of 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 catalysts.

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, it is possible to maintain the strength of the obtained sheet-like material and to prevent the occurrence of nap and pills. Moreover, 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, after fixing the polyurethane resin to the nonwoven fabric by wet coagulation described later, a sheet-like material containing an insoluble solvent, such as water, is dried by heating. In the normally used manufacturing process, a uniform and fine porous structure starts with the temporary softening of the polyurethane resin by heating and the evaporation of the soluble and non-soluble solvents contained in the polyurethane resin after wet coagulation. Be able to get.

In addition, the elastic resin can contain polyester-based, polyamide-based, polyolefin-based elastomer resins, acrylic resins, ethylene-vinyl acetate resins, and the like as long as performance and texture are not impaired. Further, various additives, e.g., pigments such as carbon black, a phosphorus flame retardant such as halogen-based and inorganic-based, phenol-based, oxidation prevention agent such as sulfur-based and phosphorus-based, benzotriazole-based, benzophenone-based, UV absorbers such as salicylates, cyanoacrylates and oxalic acid anilides, light stabilizers such as hindered amines and benzoates, hydrolysis stabilizers such as polycarbodiimides, plasticizers, antistatic agents, surfactants , A coagulation adjusting agent, and a dye.

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, and 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. Moreover, 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 to obtain a desired good napped quality.

Further, as a method of fixing the elastic resin to the nonwoven fabric, there is a method of impregnating the elastic resin solution into the nonwoven fabric 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 coagulation is preferably used. As the elastic resin, N, N′-dimethylformamide, dimethyl sulfoxide, or the like can be used as a solvent used when applying a polyurethane resin. Specifically, the elastic resin can be solidified by applying the elastic resin to the non-woven fabric by immersing the non-woven fabric in an elastic resin solution dissolved in a solvent, and immersing it in an insoluble solvent. It can also be solidified by dipping 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 into half or several sheets in the thickness direction of the sheet-like material before performing the napping treatment.

Also, applying an antistatic agent before the napping treatment can be preferably used 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 napped leather-like sheet-like material in which ultrafine fibers are raised on at least one surface, and the napping treatment is performed using sandpaper, roll sander, or the like. It can be applied by a grinding method. In order to obtain good surface fiber napping, it is a preferable embodiment to apply a lubricant such as a silicone emulsion before napping treatment.

The sheet-like material of the present invention can be suitably used as a nap-finished leather-like sheet-like material in which ultrafine fibers are finally raised on at least one surface thereof.

The sheet-like material of the present invention is a skin material having a very graceful appearance in clothing, such as furniture, chairs, wall coverings, seats, ceilings, and interiors in vehicle interiors such as automobiles, trains, and aircraft. Can be suitably used.

Hereinafter, the sheet-like material of the present invention will be described more specifically using examples.

[Evaluation methods]
(1) Average single fiber diameter:
A cross section perpendicular to the thickness direction of the nonwoven fabric containing the fibers of the sheet-like material was observed with a scanning electron microscope (VE-7800 manufactured by SEM KEYENCE) at a magnification of 3000 times, and randomly within a 30 μm × 30 μm field of view. The diameters of 50 single fibers extracted in (1) were measured to the first decimal place in units of μm. However, this was performed at three locations, the diameter of a total of 150 single fibers was measured, and the average value was calculated 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 as not corresponding to the ultrafine fibers. When the ultrafine fiber has an irregular cross section, first, the cross-sectional area of the single fiber was measured, and the diameter of the single fiber was calculated by calculating the diameter when the cross section was assumed to be circular. An average value of this as a population was calculated and used as the average single fiber diameter.

(2) The pore size of the porous structure of the elastic resin and the proportion of fine pores having a pore size of 0.1 to 20 μm in the total pores of the porous structure:
A cross section perpendicular to the thickness direction of the nonwoven fabric containing the elastic resin of the sheet-like material was observed at a magnification of 2000 using a scanning electron microscope (VE-7800 manufactured by SEM KEYENCE), and within a field of view of 40 μm × 40 μm. The pore diameter (diameter) of 50 randomly selected elastic resins was measured to the first decimal place in μm. However, this is performed at three locations, the diameters of a total of 150 holes are measured, the ratio of the number of holes having a diameter of 0.1 to 20 μm in 150 holes is calculated, and the ratio of 0.1 to 20 μm in the porous structure is calculated. The percentage of fine pores. When the hole in the elastic resin is an irregular hole, the cross-sectional area of the hole was first measured, and the diameter when the cross-section was assumed to be circular was calculated to obtain the hole diameter (diameter).

(3) Number of pores per unit area in the porous structure of the elastic resin:
A cross section perpendicular to the thickness direction of the nonwoven fabric containing the elastic resin of the sheet-like material was observed at a magnification of 2000 using a scanning electron microscope (VE-7800 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 performed at three locations, and the arithmetic average value of the number of holes was defined as the number per unit area of the holes in the porous structure. When the elastic resin containing a 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 to the number of holes per 1600 μm ^2. The number per unit area of pores in the porous structure was used. When the pore diameter was larger than the field of view of 40 μm × 40 μm, the number of pores per unit area in the porous structure was 1.

(4) Weight average molecular weight of polyurethane resin:
From the obtained sheet-like material, a polyurethane resin was extracted using N, N′-dimethylformamide (hereinafter sometimes 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) and measured under the following conditions: Instrument: GPC measuring instrument 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 polystyrene; manufactured by Tosoh Corporation)
・ Temperature: 40 ℃
-Flow rate: 1.0 ml / min.

(5) Flexibility:
Based on method A (45 ° cantilever method) described in 8.21.1 of 8.21 “Bending softness” of JIS L 1096: 2010 “Testing method for fabrics and knitted fabrics”. Make 5 test pieces of 2 x 15 cm each, place them on a horizontal platform with a slope of 45 °, slide the test piece, 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) Folding resistance:
Based on the description of JIS L 1059-1: 2009 “Testing method for wrinkle resistance of textile products—Part 1: Measurement of horizontal folding wrinkle recovery (Monsanto method)”, test piece 5 The wrinkle recovery angle on the sheet was measured, and the crease resistance was calculated by the formula of wrinkle prevention rate described in 10 “Calculation of wrinkle recovery angle and wrinkle prevention rate”, and the average value of 5 sheets was obtained. Folding resistance of 90% or more was considered good.

[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 composite fiber using polystyrene as the sea component and polyethylene terephthalate as the island component was drawn, crimped, and cut to obtain a nonwoven raw cotton. Subsequently, the obtained raw cotton was made into a fiber web using a cross wrapper, and was made into a nonwoven fabric by needle punching.

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

The nonwoven fabric composed of the ultrafine fibers thus obtained was dipped in a resin solution in which the concentration of the polycarbonate-based polyurethane resin in DMF was adjusted to 11%, and the amount of polyurethane (PU) resin solution deposited was adjusted by a squeeze roll. Thereafter, the PU resin was coagulated in an aqueous solution having a DMF concentration of 30%, subsequently polyvinyl alcohol and DMF were removed by hot water, and dried to obtain a sheet-like material having a PU resin content of 17% by mass. One side of the sheet-like material thus obtained was napped using a 180 mesh endless sandpaper, and then dyed with a disperse dye to obtain a napped leather-like sheet-like material.

When the cross section in the thickness direction inside the obtained leather-like sheet was observed with a scanning electron microscope (SEM), the polyurethane resin was present only inside the nonwoven fabric, and the polyurethane resin had a porous structure with fine pores. The proportion of fine pores having a pore diameter of 0.1 to 20 μm in the total pores of the porous structure was 85%, and the number of pores in the porous structure per unit area was 247/1600 μm. Moreover, the weight average molecular weight of the polyurethane resin measured by extracting from the napped-toned leather-like sheet was 110,000.

The obtained napped-leather-like sheet-like material had good nap 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)
A napped-toned leather-like sheet-like shape in the same manner as in Example 1 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 were changed to those shown in Table 1, respectively. A product was made.

When the cross section in the thickness direction inside the leather-like sheet material in each Example and Comparative Example was observed with a scanning electron microscope (SEM), the polyurethane resin had a porous structure with fine pores, and the polyurethane resin was inside the nonwoven fabric. Was only present.

Table 1 shows the average single fiber diameter of the ultrafine fibers of each Example and Comparative Example, the type of polyurethane resin, the weight average molecular weight of the polyurethane resin, the average pore diameter of the porous structure of the polyurethane in the obtained sheet-like material, and the total porous structure The proportion of fine pores with a pore diameter of 0.1 to 20 μm in the pores, flexibility, and crease resistance were shown.

In any napped leather-like sheet-like material 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 obtain an average of the pores in the porous structure. By adjusting the diameter and the proportion of fine pores of 0.1 to 20 μm in the total pores of the porous structure and the number of pores per unit area in the porous structure, both excellent flexibility and crease resistance are achieved. ing. In contrast, the sheet-like materials of Comparative Examples 1 to 5 form a porous structure in the polyurethane resin as the weight average molecular weight of the polyurethane resin increases, but the pores are coarse and uneven, and the pore film is thick. As a result, the flexibility is lowered, and the non-uniform pore diameter prevents the entire polyurethane resin from undergoing bending deformation, resulting in poor crease resistance.

Claims

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 the surface of the sheet-like material has nappings, and the elastic resin has a porous structure. And a sheet-like material characterized in that the proportion of fine pores having a pore diameter of 0.1 to 20 μm in all the pores of the porous structure is 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.
3. The sheet-like material according to claim 1, wherein the elastic resin is a polycarbonate-based polyurethane resin.
The sheet-like material according to claim 3, wherein the polyurethane resin has a weight average molecular weight of 30,000 to 150,000.
5. The sheet-like material according to claim 1, wherein the number of pores per unit cross-sectional area in the porous structure in the elastic resin is 50 or more / 1600 μm 2 .