JP2011058107A - Base material of artificial leather, and method of producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a base material of artificial leather constituted of a dense nonwoven fabric structure comprising bundles of ultrafine fibers and of an elastomer permeating the nonwoven fabric structure, with the elastomer uniformly distributed in the thickness direction of the nonwoven fabric structure. <P>SOLUTION: The highly dense nonwoven fabric structure is impregnated with a solution of an elastomer or an aqueous dispersion thereof from both sides, and is subsequently subjected to roll-nipping at a deformation rate in the thickness direction thereof of 25 to 45%, and thereafter the elastomer is coagulated. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a nonwoven fabric structure comprising ultrafine fiber bundles, a base material for artificial leather comprising a polymer elastic body impregnated in the nonwoven fabric structure, and a method for producing the same. More specifically, for artificial leather comprising a dense nonwoven fabric structure composed of ultrafine fiber bundles and a polymer elastic body contained in the nonwoven fabric structure, and the distribution of the polymer elastic body in the thickness direction of the nonwoven fabric structure is uniform The present invention relates to a substrate and a method for producing the same.

  Artificial leather has been recognized by consumers as being lighter and easier to handle than natural leather, and is widely used in clothing, general materials, sports products, and the like. The conventional general artificial leather base material is generally formed by stapling ultrafine fiber-generating fibers composed of two types of polymers having different solubility, and is formed into a web using a card, a cross wrapper, a random weber, etc. After entanglement of ultrafine fiber generation fibers with a needle punch or the like to form a nonwoven fabric, a polymer elastic body such as polyurethane dissolved in a solvent is applied, and one component in the ultrafine fiber generation fibers is removed. Manufactured by ultra-thinning method.

  In order to achieve the properties required for artificial leather, such as good texture, high wear resistance, and high strength, it is common practice to impregnate a nonwoven fabric with a certain amount of polymer elastic body such as polyurethane. ing. In order to improve quality, stabilize and reduce manufacturing costs, it is important to control the amount of polymer elastic material impregnated in the nonwoven fabric and the distribution of polymer elastic material in the thickness direction of the nonwoven fabric. Has been proposed.

Patent Document 1 proposes to control the distribution of the rubber-like elastic polymer by utilizing the migration phenomenon of the glue (a phenomenon in which the glue migrates to the front and back surfaces). First, before applying the rubbery elastic polymer, the fiber sheet is impregnated with a paste solution (polyvinyl alcohol aqueous solution, etc.), and the paste is migrated to the surface layer and the back layer by drying. A fiber sheet in which a small amount of glue is distributed in the intermediate layer is obtained, and then the rubber sheet is impregnated with a rubber-like elastic polymer solution and solidified, so that the rubber-like elastic polymer becomes an intermediate layer. A fiber sheet distributed in large numbers is obtained.
However, in this method, migration control is difficult for a high-density nonwoven fabric of 0.34 g / cm ³ or more.

In Patent Document 2, a high-density layer and a low-density layer are formed by impregnating a polymer material from one side of the nonwoven fabric or by slicing the nonwoven fabric perpendicularly in the thickness direction after impregnating the polymer material from both sides of the nonwoven fabric. Napped fiber sheet is obtained.
However, when the polymer material solution is impregnated from only one side of the nonwoven fabric, the impregnation distribution varies significantly depending on the solution viscosity, and it is difficult to control the penetration depth in the thickness direction of the nonwoven fabric, which tends to cause quality variations. The same problem occurs when slicing after impregnating from both sides of the nonwoven fabric.

In Patent Document 3, the polymer elastic body B is filled in the voids of the ultrafine fibers constituting the three-dimensional entangled sheet, and the polymer elastic body C is unevenly distributed near the three-dimensional entangled sea surface portion. A sheet-like material in which fibers are bonded is disclosed. This sheet-like material is obtained by impregnating a polymer elastic body B in a void portion of a sheet obtained by three-dimensionally entanglement of ultrafine fibers and wet coagulating it, and then grinding and raising the surface of the sheet. Manufactured by applying C and dry-solidifying.
However, this method requires two stages of polymer elastic body impregnation and solidification processes, which complicates the process and increases manufacturing costs. In addition, nothing is described or studied about intentionally controlling the distribution of the polymer elastic body, particularly the polymer elastic body B.

Patent Document 4 discloses a fiber sheet-like composite in which there is no migration and a water-based urethane resin filled between fibers forms a uniform microporous layer. The fiber sheet composite is (A) an aqueous urethane resin containing a carboxyl group and a nonionic hydrophilic group, and / or an aqueous urethane obtained by forcibly dispersing a urethane resin containing a carboxyl group in the molecule with a nonionic emulsifier. It is manufactured by impregnating or applying a water-based resin composition comprising a resin, (B) an inorganic salt, and (C) a nonionic surfactant having a cloud point to a fiber material substrate and thermally coagulating it with steam.
However, this method requires an aqueous resin composition having a complicated composition, and the production method is complicated. Furthermore, it is difficult for the water-based urethane resin to exist in the intended distribution state in the thickness direction of the high density nonwoven fabric of 0.34 g / cm ³ or more by this method.

Patent Document 5 discloses an artificial leather substrate in which the apparent density A of the elastic polymer constituting the front surface side and the apparent density B of the elastic polymer constituting the back surface side satisfy 0.07 + B ≧ A ≧ 0.01 + B. Disclosure. As a method of impregnating the base layer with the polyurethane resin, a polyurethane resin constituting the surface side from the top surface, a method of infiltrating the polyurethane resin constituting the back side from the bottom surface, filling the back surface side polyurethane resin on the base back side, A method of applying a surface-side polyurethane resin to the substrate surface side and infiltrating the polyurethane resin into the inside of the substrate surface, a method of filling the entire nonwoven fabric with the back-side polyurethane resin, and then applying the back-side polyurethane resin to infiltrate the substrate Is described. In any method, it is described that excess polyurethane resin on the surface of the substrate is scraped off with a knife or the like.
In this method, it is necessary to perform a polyurethane resin impregnation operation on each of the front and back surfaces, and the manufacturing process is complicated. Moreover, when using a high density nonwoven fabric of 0.34 g / cm ³ or more, it is difficult to sufficiently scrape the polymer elastic body in the vicinity of the surface with a knife, the squeezing becomes insufficient, and the surface becomes uneven and the quality It is easy to produce variation.

Japanese Patent Laid-Open No. 05-079886 Japanese Patent Publication No. 48-32302 Japanese Patent Laid-Open No. 06-330473 JP 11-335975 A JP-A-2005-97763

  As described above, a simple method is known in which a polymer elastic body is present in a non-woven fabric composed of ultrafine fibers, particularly a high-density non-woven fabric, in an intended distribution state in the thickness direction, for example, in a uniform distribution state in the thickness direction. However, a base material for artificial leather in which a polymer elastic body is uniformly distributed in the thickness direction of the nonwoven fabric has not been provided. An object of the present invention is to provide a base material for artificial leather having a uniform distribution in the thickness direction of the nonwoven fabric of a polymer elastic body and a method for easily producing such a base material for artificial leather.

  As a result of intensive research, the inventors of the present invention conducted a roll-nip treatment on the nonwoven fabric structure at a specific deformation ratio immediately after impregnating the nonwoven fabric structure with the polymer elastic body solution or dispersion liquid. The present invention was completed by finding that the distribution of the nonwoven fabric structure in the thickness direction can be made uniform.

That is, the present invention comprises a dense nonwoven fabric structure comprising ultrafine fiber bundles, and a polymer elastic body contained in the nonwoven fabric structure, and the thickness direction uneven distribution degree of the polymer elastic body represented by the following formula: The present invention relates to a base material for artificial leather in which X is −10 to + 10%.
Uneven distribution X = AB
In the formula, A represents an average area ratio (%) of the polymer elastic body in the surface layer, B represents an average area ratio (%) of the polymer elastic body in the intermediate layer, and each of the average area ratios represents artificial leather. A scanning electron micrograph of an arbitrary cross section parallel to the thickness direction of the substrate for image processing was subjected to image processing, and then obtained from a thickness direction distribution chart of the polymer elastic body obtained by image analysis.

Furthermore, the present invention provides the following steps (a) to (e):
(A) a step of converting sea-island fibers in which the sea component is a water-soluble polymer and the island component is a heat-shrinkable polymer into a fiber web;
(B) entanglement treatment of the fiber web to obtain a nonwoven fabric structure;
(C) a step of wet-heat-treating the nonwoven fabric structure to obtain a densified nonwoven fabric structure having a density of 0.34 g / cm ³ or more;
(D) The densified nonwoven structure is impregnated with a solution or aqueous dispersion of a polymer elastic body from both sides, and roll-nip treatment is performed at a deformation rate in the thickness direction of the nonwoven fabric structure of 25 to 45%. A step of solidifying the elastic body to obtain a non-woven structure containing a polymer elastic body, and (e) a sea component extracted from the sea-island fiber constituting the non-woven structure containing the polymer elastic body with water or an aqueous solution, A process of obtaining a base material for artificial leather by transforming a mold fiber into an ultrafine fiber bundle,
Alternatively, the following steps (a) to (c), (f) and (g):
(A) a step of converting sea-island fibers in which the sea component is a water-soluble polymer and the island component is a heat-shrinkable polymer into a fiber web;
(B) entanglement treatment of the fiber web to obtain a nonwoven fabric structure;
(C) a step of wet-heat-treating the nonwoven fabric structure to obtain a densified nonwoven fabric structure having a density of 0.34 g / cm ³ or more;
(F) a step of extracting and removing sea components from the sea-island fibers constituting the densified nonwoven structure with water or an aqueous solution, and transforming the sea-island fibers into ultrafine fiber bundles to obtain an ultrafine nonwoven structure.
(G) The ultrafine nonwoven fabric structure is impregnated with a polymer elastic body solution or aqueous dispersion from both sides, and roll-nip treatment is performed at a deformation rate in the thickness direction of the nonwoven fabric structure of 25 to 45%, and then the polymer The present invention relates to a method for manufacturing a base material for artificial leather including a step of solidifying an elastic body to obtain a base material for artificial leather.

  According to the present invention, a base material for artificial leather having a uniform distribution of the elastic polymer in the thickness direction can be produced by a simple method.

It is the schematic which shows the process of carrying out the roll nip process of the nonwoven fabric structure impregnated with the polymer elastic body solution. It is a graph which shows the thickness direction distribution of the polymeric elastic body in the cross section of the base material for artificial leather.

  The base material for artificial leather of the present invention comprises a non-woven fabric composed of ultrafine fibers and a polymer elastic body impregnated in the non-woven fabric, and can be obtained, for example, by sequentially performing the following steps (a) to (e). .

Step (a)
A heat-shrinkable polymer is used for the island component and a water-soluble polymer is used for the sea component. The sea component polymer and the island component polymer are extruded from a composite spinning die, and the sea-island long fibers are melt-spun.
The spinneret for composite spinning has a structure in which multiple rows of nozzle holes arranged in a straight line are arranged in parallel to form a cross-sectional state in which 8 to 70 island component polymers are dispersed in a sea component polymer. Those are preferred.
The relative supply amount or supply pressure of the sea component polymer and the island component polymer is adjusted so that the area ratio (that is, the polymer volume ratio) in the cross section of the obtained fiber is the ratio of sea / island = 5/95 to 60/40. The molten polymer is discharged from the die at a die temperature of 180 to 350 ° C.
The cross-sectional area of the obtained sea-island long fibers is preferably 70 to 350 μm ² , and the single fiber fineness is, for example, when the island component polymer is polyethylene terephthalate and the sea component polymer is water-soluble thermoplastic polyvinyl alcohol, the ratio of the composite polymer However, it is preferably 0.9 to 4.9 dtex, more preferably 1.9 to 3.9 dtex.
The melt-spun sea-island long fibers are accumulated in a collection surface such as a net in a random orientation state without being cut, or cut into short fibers and used with cards, cross wrappers, random webbers, etc. A fiber web having a desired basis weight, preferably 10 to 1000 g / m ² , is produced.

Step (b)
The fiber web is overlapped with a plurality of layers in the thickness direction using a cross wrapper or the like, if necessary, and at least 6 barbs of needles are used, and at least one barb of the needles penetrates. The sea-island fibers are extremely dense, with needle-punching from both sides simultaneously or alternately to three-dimensionally entangle the fibers, and the sea-island fibers are present at a density of 400 to 2000 / mm ² in a cross section parallel to the thickness direction. To obtain a non-woven structure. The fiber web has an oil agent that has an antistatic effect at any stage after its manufacture and until the entanglement process, an oil agent for controlling the friction resistance with the needle, an oil agent for controlling the friction resistance between the fibers, etc. You may give single or multiple types.

Step (c)
The nonwoven fabric structure obtained by the step (b) is wet-heat treated under conditions such that the sea component polymer is plasticized and the island component polymer is contracted, and a hot press treatment is added as necessary. Thus, in the cross section parallel to the thickness direction, densification is performed until the density of existence of the cross section of the sea-island fibers substantially orthogonal to the cross section becomes 1000 to 3500 pieces / mm ² . As the wet heat treatment, a method of introducing saturated water vapor into an atmosphere in which continuous supply is performed, a water amount sufficient to swell and plasticize the sea component polymer to a desired level is applied to the nonwoven fabric structure, and then heated air And a method of heating moisture in the nonwoven fabric structure by electromagnetic waves such as infrared rays or a combination thereof. In addition to the effect of densifying the fiber structure, the heat press treatment can be expected to have an effect of fixing the form of the nonwoven fabric structure or an effect of smoothing the surface.
For example, if the island component polymer is polyethylene terephthalate and the sea component polymer is water-soluble thermoplastic polyvinyl alcohol, the average apparent density of the densified nonwoven structure obtained by the step (c) is preferably 0.34 g / cm ³ or more. Is 0.34 to 0.85 g / cm ³ , more preferably 0.45 to 0.65 g / cm ³ . The average apparent density can be obtained by a method that does not apply a compressive load, for example, a method by cross-sectional observation with an electron microscope or the like. The basis weight of the densified nonwoven structure is preferably 100 to 2000 g / m ² .

Step (d)
The densified nonwoven structure is impregnated with an aqueous solution or dispersion of a polymer elastic body from both sides, and roll-nip treatment is performed at a deformation rate of 25 to 45% in the thickness direction of the nonwoven structure. By solidifying, a non-woven structure containing a polymer elastic body is obtained.

Step (e)
The sea component polymer is extracted and removed from the sea-island fibers constituting the elastic body-containing nonwoven fabric structure with water or an aqueous solution, and the sea-island fibers are transformed into ultrafine fiber bundles to obtain a base material for artificial leather.

  Further, the order of the steps (d) and (e) may be reversed so that the following steps (f) and (g) are performed.

Step (f)
The sea components are extracted and removed from the sea-island fibers constituting the densified nonwoven structure obtained in the step (c) with water or an aqueous solution, and the sea-island fibers are transformed into ultrafine fiber bundles to obtain ultrafine nonwoven structures.

Step (g)
The ultrafine nonwoven fabric structure is impregnated with a solution or aqueous dispersion of a polymer elastic body from both sides, and roll / nip treatment is performed at a deformation rate of 25 to 45% in the thickness direction of the nonwoven fabric structure. Solidify to obtain a base material for artificial leather.

Hereinafter, the present invention will be described in more detail.
The sea-island fiber constituting the nonwoven fabric structure of the present invention is a multicomponent composite fiber composed of at least two types of polymers, and in the sea component polymer mainly constituting the fiber outer peripheral portion in the fiber cross section, It is a fiber having a cross-sectional shape in which different types of island component polymers are distributed. The island component polymer of the present invention is distributed in a substantially circular cross-sectional shape by suitably selecting the effect of surface tension and the ratio of the sea component polymer and the island component polymer. In addition, the substantially circular shape here means a shape that is literally close to a circle, and is a circular shape or a polygonal shape or an elliptical shape close to it. This sea-island type fiber is made up of the remaining island-component polymer by extracting or decomposing and removing the sea-component polymer at an appropriate stage before or after the step of impregnating and solidifying the polymer elastic body. It is possible to produce a fiber bundle in which a plurality of fibers thinner than the fibers are bundled. Such a sea-island type fiber can be obtained by using a spinning method of a multicomponent composite fiber represented by a conventionally known chip blend (mixed spinning) method or a composite spinning method. The sea-island fiber is composed mainly of the outer periphery of the fiber component in the fiber cross section, compared to the split split type composite fiber such as a petal shape or a superimposed shape in which a plurality of components are alternately configured on the outer periphery of the fiber. In addition, fiber damage such as cracking, bending, and cutting during the fiber entanglement process typified by needle punching can be extremely reduced, that is, the degree of densification due to entanglement can be further increased. In addition, the sea-island fiber has less anisotropy in the in-plane direction perpendicular to the fiber axis than the split split-type composite fiber, and the fineness of the individual ultrafine fibers, that is, the fineness of the cross-sectional area is high. Since a fiber bundle can be obtained, a very large number of fiber bundles can be assembled in a non-woven structure with an unprecedented density. Therefore, the non-woven fabric structure of the present invention is manufactured using sea-island fibers in order to obtain these effects that cannot be obtained with peeled split composite fibers such as petals and superposed shapes.

  It is important that the polymer constituting the island component of the sea-island fiber is a heat-shrinkable polymer. For example, a polyester resin such as polyethylene terephthalate (hereinafter abbreviated as PET), polytrimethylene terephthalate (hereinafter abbreviated as PTT), polybutylene terephthalate (hereinafter abbreviated as PBT), polyester elastomer, or the like Various heat-shrinkable polymers having a conventionally known fiber forming ability, such as modified products, heat-shrinkable polyamide resins or modified products thereof, heat-shrinkable polyolefin resins or modified products thereof, are suitable. Among these, by using a polyester-based resin such as PET, PTT, PBT, or modified polyester thereof, an artificial structure comprising a nonwoven fabric structure in which ultrafine fiber bundles as intended by the present invention are densely assembled by heat shrinkage. A leather base material can be obtained, and features such as fine surface feeling and solid texture, and practical performance such as wear resistance, light resistance, and form stability are good. It is particularly preferable in that it can be an artificial leather product. The island component polymer preferably has a melting point (hereinafter abbreviated as Tm) of 160 ° C. or higher, and more preferably a fiber-forming crystalline resin having a Tm of 180 to 330 ° C. When the Tm of the island component polymer is less than 160 ° C., the shape stability of the obtained ultrafine fibers cannot reach the target level of the present invention, particularly from the point of practical performance of the artificial leather product. It is not preferable. In the present invention, Tm is raised from room temperature to 300 to 350 ° C. according to the type of polymer at a heating rate of 10 ° C./min in a nitrogen atmosphere using a differential scanning calorimeter (hereinafter abbreviated as DSC). Thereafter, the temperature was immediately cooled to room temperature, and the peak top temperature of the endothermic peak observed when the temperature was immediately increased again to 300 to 350 ° C. at a temperature increase rate of 10 ° C./min was adopted. In the present invention, a colorant, an ultraviolet absorber, a heat stabilizer, a deodorant, a fungicide, an antibacterial agent, and other various stabilizers may be added to the polymer constituting the ultrafine fiber at the spinning stage.

  It is important that the polymer constituting the sea component of the sea-island fiber is a water-soluble polymer. And since it is necessary to transform the sea-island type fibers into ultrafine fiber bundles, it is necessary to make the solubility or decomposability to the solvent or decomposing agent different from the adopted island component polymer, and the island component from the viewpoint of spinning stability. The polymer is preferably a polymer having a low affinity and having a melt viscosity smaller than the island component polymer under the spinning conditions, or a polymer having a surface tension smaller than the island component polymer. Specific examples include water-soluble polymers such as modified polyesters and polyethylene oxides that are copolymerized with polyvinyl alcohol, polyethylene glycol, or compounds containing alkali metal sulfonates. Polyvinyl alcohol homopolymers, polyvinyl alcohol copolymers A polyvinyl alcohol resin such as coalescence (hereinafter collectively referred to as PVA) is optimal. Here, the water-soluble polymer refers to a polymer that can be dissolved or removed by heating, pressurizing, or the like with water or an aqueous solution such as an alkaline aqueous solution or an acidic aqueous solution. By using these water-soluble polymers as the sea component, the sea component polymer instantly swells and plasticizes when the nonwoven fabric structure is subjected to wet heat treatment, and the present invention has almost no inhibition of the shrinkage of the island component polymer. It is possible to obtain a base material for artificial leather consisting of a non-woven fabric structure in which ultrafine fiber bundles are gathered densely as desired, featuring features such as a dense surface feeling and a rich texture, and abrasion resistance. This is particularly preferable in that an artificial leather product having good practical performance such as wear, light resistance, and form stability can be obtained.

  The PVA can be obtained by saponifying a polymer having a vinyl ester unit as a main constituent unit. Vinyl compound monomers for forming vinyl ester units include vinyl formate, vinyl acetate, vinyl propionate, vinyl valenate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate and Examples include vinyl versatate, and among these, vinyl acetate is preferable from the viewpoint of easily obtaining PVA.

  The PVA may be a homo PVA or a modified PVA into which copolymer units are introduced, but it is preferable to use a modified PVA from the viewpoint of melt spinnability, water solubility, and fiber properties. By appropriately selecting the type of copolymerization monomer used for modification, it is possible to stably produce sea-island fibers without reducing the water solubility of PVA. Examples of the comonomer include α-olefins having 4 or less carbon atoms such as ethylene, propylene, 1-butene, and isobutene from the viewpoints of copolymerizability, melt spinnability, and water solubility of fibers; and methyl vinyl ether Vinyl ethers such as ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether and n-butyl vinyl ether are preferred. 1-20 mol% is preferable, as for copolymer unit content in PVA, 4-15 mol% is more preferable, and 6-13 mol% is further more preferable. Furthermore, when the copolymer unit is ethylene, the fiber physical properties become high, and thus ethylene-modified PVA is particularly preferable. The ethylene unit content in the ethylene-modified PVA is preferably 4 to 15 mol%, more preferably 6 to 13 mol%.

  The PVA is produced by a known method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, or an emulsion polymerization method. Among them, a bulk polymerization method or a solution polymerization method in which polymerization is performed without solvent or in a solvent such as alcohol is usually employed. Examples of the alcohol used as the solvent for the solution polymerization include lower alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol. For copolymerization, azo initiators such as a, a′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethyl-valeronitrile), benzoyl peroxide, n-propyl peroxycarbonate, etc. Alternatively, a known initiator such as a peroxide-based initiator is used. Although there is no restriction | limiting in particular about superposition | polymerization temperature, The range of 0 to 150 degreeC is suitable.

200-500 are preferable, as for the viscosity average polymerization degree (henceforth abbreviated polymerization degree) of the said PVA, 250-470 are more preferable, 300-450 are further more preferable. When the degree of polymerization is 200 or more, the melt viscosity shows a sufficiently high value for stable complexation, and when the degree of polymerization is 500 or less, the melt viscosity shows a sufficiently low value for easy ejection from the spinning nozzle. . Further, by using so-called low polymerization degree PVA having a polymerization degree of 500 or less, there is an advantage that the dissolution rate when removing with water or an aqueous solution is increased. The polymerization degree of PVA is calculated | required by following Formula according to JIS-K6726.
P = ([η] × 10 ³ /8.29) ^{(1 / 0.62)}
(P is the viscosity average polymerization degree, and [η] is the intrinsic viscosity measured in water at 30 ° C. after re-saponification and purification of PVA.)

  The saponification degree of the PVA is preferably 90 to 99.99 mol%, more preferably 93 to 99.77 mol%, further preferably 95 to 99.55 mol%, and particularly preferably 97 to 99.33 mol%. . When the degree of saponification is 90 mol% or more, the thermal stability is good, and it becomes difficult to undergo thermal decomposition or gelation during melt spinning. When the degree of saponification is 99.99 mol% or less, PVA is stable. It is possible to manufacture.

  The Tm of the PVA is preferably 160 ° C. or more, more preferably 170 to 230 ° C., further preferably 175 to 225 ° C., and particularly preferably 180 to 220 ° C. in view of spinnability. When the Tm is 160 ° C. or higher, a decrease in fiber strength of PVA due to a decrease in crystallinity can be avoided. Moreover, the thermal stability of PVA is good and the fiber forming property is good. When Tm is 230 ° C. or lower, the melt spinning temperature can be made sufficiently lower than the decomposition temperature of PVA, and ultrafine fiber bundle-forming fibers (sea-island type fibers) can be stably produced.

  The ratio of the sea component polymer in the sea-island fibers is preferably 5 to 60%, more preferably 10 to 50% in terms of the area ratio in the fiber cross section. When the ratio of the sea component polymer in the sea-island fiber is smaller than 5%, the spinning stability of the sea-island fiber is lowered, so that the industrial productivity is inferior. In addition, when the sea-island fiber is wet-heat-shrinked due to the small amount of sea components, the effect of reducing friction and interference between island components is insufficient, and the intended shrinkage state, densification cannot be obtained, The nonwoven fabric structure is impregnated with a polymer elastic body solution or water dispersion and solidified, and then the sea component is removed, and then the gap formed between the ultrafine fiber bundle and the polymer elastic body is insufficient. To do. As a result, it is difficult to obtain the intended effects of the present invention such as a feeling of swelling, a feeling of fullness, and a fine surface feeling. On the other hand, when the ratio of the sea component polymer exceeds 60%, the shape and distribution of the island component in the cross section of the sea-island fiber becomes irregular, and the quality stability is inferior. In some cases, the island component having shrinkage ability is relatively insufficient, so that the desired shrinkage state and densification cannot be obtained. As a result, it is difficult to obtain the intended effect of the present invention. In addition, the higher the ratio of the sea component polymer, the smaller the amount of ultrafine fibers in the base material for artificial leather, so the amount of the elastic polymer necessary for imparting shape stability tends to increase significantly. Moreover, not only the load on industrial production increases in terms of energy and cost required for recovering the removed sea component polymer, but also the load on the global environment naturally increases. Therefore, it is preferable to lower the ratio of the sea component polymer within a range where the effects of the present invention can be obtained.

  In the present invention, the sea-island fiber may be either a long fiber or a short fiber, but it is preferable to use a long fiber in order to obtain the effects of the present invention more reliably. The long fiber is a fiber that is not intentionally cut, such as a short fiber (fiber length: 10 to 50 mm). Although the fiber length of the long fiber cannot be specified in general, the fiber length of the sea-island type long fiber is preferably 100 mm or more in order to achieve the effects of the present invention, and can be technically manufactured, and As long as it is not physically cut, the fiber length may be several meters, several hundred meters, several kilometers, or more.

  A composite spinning die is used for spinning the sea-island type fibers. In the composite spinning base, a plurality of nozzle holes are arranged in parallel or concentric circles at equal intervals. 8 to 70 island component polymer channels are uniformly arranged in each nozzle hole, and a sea component polymer channel is provided so as to surround the island component polymer channels. A molten sea-island type composite fiber composed of a sea component polymer and an island component polymer is continuously discharged from each nozzle hole. While substantially cooling and solidifying with cooling air at any stage from directly below the nozzle hole to the suction device described later, a high-speed air current is applied using a suction device such as an air jet nozzle, and the composite fiber is the target. It is drawn and thinned uniformly to achieve fineness. The high-speed air current is applied so that the average spinning speed corresponding to the mechanical take-up speed in normal spinning is 1000 to 6000 m / min. Furthermore, while sucking from the opposite surface side of the net on the collecting surface of a conveyor belt-like mobile net, etc., while opening the composite fiber with a collision plate or airflow according to the texture of the obtained fiber web The fiber web is formed by collecting and depositing.

  When the compound spinning base is concentrically arranged, one nozzle-like suction device is generally used for one base. For this reason, a large number of sea-island fibers converge at the center point of the concentric circles during suction. Generally, since a plurality of bases are arranged in a straight line to obtain a desired spinning amount, there are almost no fibers between the bundles of sea-island fibers discharged from two adjacent bases. Therefore, in order to make the texture of the fiber web uniform, it is important to open the fiber web. If the composite spinning bases are arranged in parallel, a linear slit-like suction device facing the base is used. For this reason, since the sea-island type fibers from between the rows arranged in parallel are concentrated at the time of suction, a fiber web having a more uniform texture can be obtained as compared with the case where the concentric bases are employed. In this respect, the parallel arrangement is more preferable than the concentric arrangement.

  It is also preferable that the obtained fiber web is subsequently pressure-bonded while being partially heated or cooled by pressing, embossing or the like, depending on the degree of form stability required in the subsequent step. When the melt viscosity of the sea component polymer is smaller than the island component polymer, the sea island type fiber constituting the fiber web is formed by heating or cooling at a temperature of about 60 to 120 ° C. without applying a high temperature up to the melting temperature. Without significantly impairing the cross-sectional shape, the texture of the fibrous web can be sufficiently maintained in the subsequent steps. Furthermore, it is also possible to improve the shape stability of the fiber web to a level that allows handling such as winding.

  According to the production method of the present invention, it is possible to use a fiber having a very thin fiber diameter, and further, it is not necessary to impart crimps, and the fiber itself does not become bulky. , An extremely dense state can be stably obtained from a conventional nonwoven fabric structure, and by combining the methods described later, an extremely high-quality artificial leather that could not be realized with conventional artificial leather can be obtained. is there.

In the production method of the present invention, even a very thin sea-island fiber having a cross-sectional area of 100 μm ² or less can be used. However, in order to obtain a dense non-woven structure intended by the present invention, the cross-sectional area is 70 ˜350 μm ² is preferable, and 80 to 300 μm ² is more preferable in view of form stability and handleability in the subsequent process. By using the sea-island fiber having such a cross-sectional area, the obtained fiber web has a cross-section of the sea-island fiber that is substantially orthogonal to the cross-section in an arbitrary cross-section parallel to the thickness direction. A dense fiber structure of the present invention is finally obtained by entanglement, shrinkage, etc. in the subsequent process, where a fiber distribution state existing at a density of 600 / mm ² , more preferably 150-500 / mm ² is obtained. Can be obtained.

In the present invention, the density of the nonwoven fabric structure constituting the base material for artificial leather to be obtained is important, and it is particularly necessary to improve the density of the nonwoven fabric structure constituting the surface layer portion of the base material for artificial leather. For this reason, the cross-sectional area of the ultrafine fiber bundle obtained by removing the sea component polymer from the sea-island fiber is preferably 700 μm ² or less. The cross-sectional area of 700 μm ² or less of the ultrafine fiber bundle corresponds to the fineness of the ultrafine fiber bundle being about 10 dtex or less, for example, when the polymer constituting the ultrafine fiber is polyethylene terephthalate. In order to make an artificial leather base material from which extremely high-grade napped-toned artificial leather or fine-folded silver-like artificial leather can be obtained, a non-woven structure obtained by a fiber bundle of such a thickness The denseness of the is necessary. Especially when the microfine fiber napped like nubuck is intended for artificial leather having a dense surface feeling short, the cross-sectional area of the microfine fiber bundle is preferably 500 [mu] m ² or less, more preferably 400 [mu] m ² or less. The lower limit value of the cross-sectional area of the ultrafine fiber bundle does not affect the properties of the base material for artificial leather as much as the upper limit value described above, but if it is too thin, the strength and surface friction durability of the artificial leather will be significantly reduced. In some cases, the cross-sectional area of the ultrafine fiber bundle is preferably 170 μm ² or more, more preferably 180 μm ² or more, and even more preferably 190 μm ² or more because of restrictions on the manufacturing process of artificial leather.

  In the present invention, the number of ultrafine fibers constituting one ultrafine fiber bundle is such that the ultrafine fiber bundle is easily bendable, that is, easily entangled within the nonwoven fabric structure and finally obtained easily bent base material for artificial leather. The number of fibers is 8 or more from the viewpoint of the property, etc., and 70 or less from the viewpoint of the flexibility of the ultrafine fiber bundle, the deformability in the cross-sectional shape, and the color developability of the finally obtained artificial leather substrate. Further, the number of ultrafine fibers is more preferably 10 to 60, and further preferably 12 to 45. If the number of ultrafine fibers is 7 or less, not only is the flexibility of the ultrafine fiber bundle inferior, but the restraint rate, that is, the ratio of the number of ultrafine fibers located on the outer periphery of the fiber bundle to the total number of ultrafine fibers in the ultrafine fiber bundle increases. Therefore, the flexibility of the ultrafine fiber bundle is easily hindered by the polymer elastic body, and the texture is easily cured even with a small amount of the polymer elastic body. Accordingly, since the spots of the polymer elastic body are easily manifested as texture spots of the artificial leather base material, the value as an industrial product is lowered. On the other hand, if the number of ultrafine fibers exceeds 70, the bendability of each ultrafine fiber is excellent, but the contact area between the ultrafine fibers in the ultrafine fiber bundle increases, and the ultrafine fiber bundle easily bends. It tends to be rather inferior. Further, the ultrafine fiber bundle is easily flattened by the compressive force from the direction perpendicular to the fiber axis, and the interval between the ultrafine fibers is widened to increase the bulk of the fiber bundle, thereby restricting the densification of the nonwoven fabric structure. Such bulkiness is the same for the sea-island type fibers. If the sea-island type fibers are easily flattened, the filling rate of the sea-island type fibers in the nonwoven fabric structure is lowered, and the densification targeted by the present invention cannot be obtained. .

  For these reasons, the number of ultrafine fibers in the fiber bundle is preferably 70 or less so that the ultrafine fiber bundle is difficult to flatten. The flatness of the ultrafine fiber bundle in the finally obtained artificial leather substrate is preferably 4.0 or less, more preferably 3.0 or less. Further, the adverse effects caused by the flattening of the ultrafine fiber bundle are particularly remarkable on the surface of the artificial leather base material, and the width of the ultrafine fiber bundle when viewed from the surface, that is, the projected size of the ultrafine fiber bundle is 10 to 60 μm. It is preferably 15 to 45 μm. When the projected size of the ultrafine fiber bundle exceeds 60 μm, the fiber bundle is not sufficiently densified, and especially when it is made into a napped artificial leather, the number of ultrafine fiber bundles that can form napped is reduced, and the raised surface has a high appearance quality. It becomes difficult to obtain. On the other hand, if the projected size of the ultrafine fiber bundle is less than 10 μm, the ultrafine fiber bundle is very easy to be densified, but even if the ultrafine fiber bundle is too thin and not flattened at all, the ultrafine fiber bundle is cut by the raising process. Frequently occurs, it is difficult to obtain a good napped appearance, and the surface wear resistance is inferior.

By forming an ultrafine fiber bundle having the characteristics as described above, in any cross section parallel to the thickness direction, the cross section of the ultra fine fiber bundle substantially orthogonal to the cross section exists at a high density of 1500 to 3000 pieces / mm ² Thus, an extremely dense non-woven structure that has never been obtained can be obtained. When the number is less than 1500 / mm ^2, the existence density of the ultrafine fiber bundle is small, and a space in which the ultrafine fiber bundle does not exist is generated. When the existence density is low, the ultrafine fiber bundle is not uniformly dispersed and tends to exist by being divided into a dense region and a sparse region that hardly exist. Further, when the space between the ultrafine fiber bundles is increased, the surface appearance and surface properties are inferior due to extremely large density spots. When it exceeds 3000 pieces / mm ² , a denser nonwoven fabric structure can be obtained. However, a structure in which the nonwoven fabric structure is forcibly compressed in the thickness direction by hot pressing or the like, or shrinkage bonded to the nonwoven fabric structure It is similar to the structure that is forced to compress in the length direction and width direction by the shrinkage force of natural woven and knitted fabrics, etc., and the physical properties deteriorate because the ultrafine fiber bundle is flattened in the compressed direction And the texture becomes stiff. Preferably, a 2000 to 2700 pieces / mm ^2.

In a conventional nonwoven fabric structure for manufacturing a base material for artificial leather, a thick ultrafine fiber bundle-forming fiber having a cross-sectional area of about 300 to 600 μm ² when transformed into an ultrafine fiber bundle is used. Therefore, densification of the nonwoven fabric structure before the ultrafine treatment is insufficient, and the existence density of the ultrafine fiber bundle cross section in the cross section of the nonwoven fabric structure after the ultrafine treatment is at most about 200 to 600 pieces / mm ² , at most. It was about 750 / mm ² . Temporarily, when trying to obtain a nonwoven fabric structure in which the existing density of the cross section of the ultrafine fiber bundle exceeds 750 pieces / mm ² in the conventional technique, an excessive needle punching process, a forced compression process by a hot press, etc. are necessary. is there. However, excessive needle punching treatment damages the fiber bundle, compression treatment greatly deforms the cross-sectional shape of the ultrafine fiber bundle, and only such a process can obtain a structure with large gaps between the ultrafine fiber bundles, The base material for artificial leather intended in the present invention cannot be obtained. Further, in the conventional nonwoven fabric structure in which the density of the cross section of the ultrafine fiber bundle is at most about 200 to 600 pieces / mm ² , the gap between the ultrafine fiber bundles is large. The body forms a thick continuous film. Accordingly, not only the texture of the nonwoven fabric structure becomes harder than necessary, but also a region where the microfiber bundles or polymer elastic bodies are densely gathered and a region where there are almost no ultrafine fiber bundles or polymer elastic bodies. It becomes a structure with very large rough spots scattered in various places. On the other hand, the nonwoven fabric structure of the present invention has an ultra-dense structure in which ultrafine fiber bundles are gathered extremely densely and uniformly, so that a thin continuous film of a polymer elastic body is formed between the ultrafine fiber bundles. In addition, since the cells surrounded by the polymer elastic body are smaller and uniformly distributed, it is possible to suppress the occurrence of remarkable coarse and dense spots inside the artificial leather substrate.

  In the present invention, the fiber diameter of the ultrafine fibers is not particularly limited as long as the nonwoven fabric structure is constituted by the ultrafine fiber bundles that satisfy the above-described requirements. In order to form a raised surface having an elegant appearance and touch intended by the present invention, the fiber diameter of the ultrafine fibers at least at the raised portion is preferably 0.8 to 15 μm, more preferably 1. It is 0-13 micrometers, More preferably, it is 1.2-10 micrometers, and it is most preferable that it is 1.5-8.5 micrometers. If the fiber diameter of the ultrafine fiber exceeds 15 μm, it is preferable because it may adversely affect the appearance quality of the napped-toned artificial leather, for example, spots may occur on the napped color of the surface or the smoothness of the touch may be hindered. Absent. On the other hand, when the fiber diameter of the ultrafine fiber is less than 1.0 μm, the napped feel becomes fine when it is made into napped artificial leather, but the total appearance quality and surface properties are adversely affected. For example, the napped color of the surface may become whitish or the wear resistance of the surface such as pilling resistance may deteriorate.

  If the resulting fabric web is insufficient in fabric weight or thickness, it is wrapped so as to have the desired fabric weight and thickness (one fiber web is fed from the direction perpendicular to the flow direction of the process, It is adjusted by folding in the width direction or by folding the web supplied from the direction parallel to the flow direction of the process in the length direction) and stacking (stacking a plurality of fiber webs). Needle punch method, etc., when the shape stability of the nonwoven fabric structure composed of sea-island fibers and the denseness of the fibers are insufficient, or when the orientation of the sea-island fibers in the thickness direction of the nonwoven fabric structure is adjusted A mechanical entanglement process is performed by a known method. As a result, the fibers constituting the fiber web, in particular, the fibers in adjacent layers of the layered fiber webs that have been wrapped or stacked, are three-dimensionally entangled. When entanglement processing is performed by the needle punch method, the type of needle (needle shape and count, barb shape and depth, the number and position of barbs, etc.), the number of needle punches (the number of needles implanted on the needle board) Needle punch processing density per unit area multiplied by the density and the number of strokes that cause the board to act per unit area of the fiber web), punch depth of the needle (depth at which the needle acts on the fiber web), etc. Processing conditions are selected as appropriate.

  As for the type of needle, the same one as used in conventional artificial leather production can be used as appropriate, but in order to obtain the effects of the present invention, the needle count, the depth of the barbs, and the number of barbs are particularly It is important to use mainly the types of needles described below.

  The needle count is a factor that affects the density and surface quality obtained after processing, and at least the size of the blade portion (the portion where the barb at the tip of the needle is formed) is No. 30 (the cross-sectional shape is an equilateral triangle) If it is circular, the diameter is preferably smaller (thin) if it is circular, and the diameter is preferably about 0.73 to 0.75 mm, more preferably 32 (about 0.68 to 0.70 mm) to 46 ( 0.33 to 0.35 mm), more preferably 36 (height 0.58 to 0.60 mm) to 43 (height 0.38 to 0.40 mm). A needle with a blade size larger than 30 (thick) has a high degree of freedom in the shape and depth of the barb and is preferable in terms of the strength and durability of the needle. Therefore, it is difficult to obtain a dense fiber assembly state and surface quality intended by the present invention. Moreover, since the frictional resistance between the fibers in the fiber web and the needle becomes too large, it is not preferable because it is necessary to apply an excessive amount of oil for needle punching. On the other hand, a needle having a blade size smaller than No. 46 is not only suitable for industrial production in terms of strength and durability, but also makes it difficult to set a barb having a suitable depth in the present invention. The cross-sectional shape of the blade portion is preferably an equilateral triangle from the standpoints of easy fiber catching and low frictional resistance.

  The barb depth is the height from the deepest part of the barb to the tip of the barb. In general-shaped barbs, the height to the tip of the barb protruding outward from the side of the needle (sometimes referred to as kick-up) and the depth to the deepest part of the barb formed inside the needle side (throat depth) It also refers to the combined height. The barb depth is at least equal to or greater than the diameter of the sea-island fiber, and preferably 120 μm or less. If the barb depth is less than the diameter of the sea-island fiber, it is not preferable because the sea-island fiber becomes very difficult to be caught by the barb. On the other hand, when the barb depth exceeds 120 μm, the fibers are very easily caught, but a needle punch mark having a large hole diameter tends to remain on the surface of the nonwoven fabric structure, and the dense fiber aggregation state and surface quality intended by the present invention are obtained. It becomes difficult. Further, the barb depth is preferably 1.7 to 10.2 times, more preferably 2.0 to 7.0 times the diameter of the sea-island fiber. When the barb depth is less than 1.7 times, the sea-island type fiber is not easily caught by the barb, so even if the number of punches is increased, the entanglement effect commensurate with it may not be obtained. On the other hand, even if it exceeds 10.2 times, rather than improving the ease of catching sea-island fibers, the tendency to increase damages such as cutting and cracking of sea-island fibers is increased, which is not preferable.

  The number of barbs may be appropriately selected so that a desired entanglement effect is obtained in the range of 1 to 9, but in order to obtain the dense nonwoven fabric structure of the present invention, the needle punch entanglement process is performed. It is preferable that the number of barbs of a needle mainly used, that is, a needle used for punching of 50% or more of the number of punches described later is six. In the present invention, the number of needle barbs used in the needle punching process need not be one, for example, 1 and 6, 3 and 6, 6 and 9, 1 and 6 And needles with different numbers of barbs such as 9 may be combined as appropriate and used in any order. In the case of having a plurality of barbs, the positions of the respective barbs may be different from each other from the needle tip side or may be the same. Examples of the latter needle include a needle having a regular triangular cross-sectional shape and one barb at each of the three apex angles at the same distance from the tip. In the present invention, the former needle is used as the needle mainly used for the entanglement treatment. This is because a needle having a plurality of barbs at the same distance has an effect that the blade portion of the needle is apparently thick and the depth of the barb is large, so that the entanglement effect is high, while the blade portion is This is because the inconvenience seen when the barb is too thick and the barb is too deep appears. Furthermore, if the needle punching process using the latter needle is performed excessively, many places of dozens to dozens of fibers are bundled at one place and many places are oriented in the thickness direction of the nonwoven fabric structure. Therefore, there is a tendency that it is difficult to obtain a dense structure as intended by the present invention. That is, in an arbitrary cross section parallel to the thickness direction of the nonwoven fabric structure, there are a large number of fibers oriented substantially parallel to the cross section, and the density of the fibers substantially orthogonal to the cross section tends to extremely decrease. However, since a strong entanglement effect can be obtained even with a small number of punches, it is also preferable to use the latter needle as part of the entanglement process. For example, at any stage from the initial stage to the middle stage of the entanglement process, the latter needle is entangled to an extent that does not hinder the target dense structure, and then the former needle is used to obtain the target dense structure. The method is mentioned as one of the preferred embodiments. In the present invention, the number of barbs is 6 is the total number of barbs that penetrate the nonwoven fabric structure at the needle tip and barbs that substantially act on the nonwoven fabric structure without penetrating the nonwoven fabric structure. Does not include inactive barbs. For example, even if the number of barbs formed on the needle is nine, the number of barbs is six in the case of the entanglement processing condition in which three barbs remain outside the nonwoven fabric structure when the needle is deeply stabbed. It is a piece.

The total number of punches of the needle is preferably 800 to 4000 punch / cm ² , more preferably 1000 to 3500 punch / cm ² . The number of punches in the needle punch process using the needles having a plurality of barbs at the same distance is about 300 punch / cm ² or less, preferably about 10 to 250 punch / cm ² . When a needle punching process exceeding 300 punches / cm ² is performed using a needle having a plurality of barbs at the same distance, fibers are oriented in the thickness direction, so that a needle using another needle is used thereafter. Even if a punching process, a heat shrink process, a press process, or the like is performed, it tends to be difficult to increase the density of the nonwoven fabric structure. When the total number of needle punches is less than 800 punches / cm ² , not only the densification is insufficient, but the integration of the nonwoven fabric structure due to the entanglement of the fibers of different fiber webs is insufficient, whereas the 4000 punches / Cm ² , although depending on the shape of the needle, damage to the sea-island fiber such as cutting and cracking is conspicuous, and when the damage to the sea-island fiber is particularly severe, the shape stability of the nonwoven structure is In addition to a significant decrease, the denseness may decrease.

From the viewpoint of the mechanical properties of the nonwoven fabric structure and artificial leather base material obtained, such as form stability and tear strength, and fiber orientation in the thickness direction, the barb of the needle is formed over the entire thickness of the fiber web. Is more effective. Therefore, it is preferable to set the punch depth of the needle to such a depth that at least the barb on the most distal side of the needle penetrates the fiber web. In particular, when using a needle with six barbs, it is preferable not to allow all barbs to penetrate in order to maximize the entanglement effect as intended by the present invention. That is, it is preferable to operate the needle with a punch depth such that the barb farthest from the tip stays in the fiber web. When all the barbs are penetrated, all the fibers caught by the six barbs are protruded from the fiber web, so that a precise structure as intended by the present invention cannot be obtained. The number of barbs not penetrating the fibrous web is preferably 2 to 5 out of 6 barbs, more preferably 3 or 4. Also, in order to realize an unprecedented dense structure, the punching of 50% or more of the number of punches is preferably set to a punch depth at which the barb at the needle tip penetrates the fiber web, and is 70% or more. It is more preferable that the punching is performed at a punch depth at which the barb at the tip of the needle penetrates the fiber web. However, if the punch depth is increased too much, not only a fine structure cannot be obtained as described above in the case of a needle with six barbs, but also one, two, three, four, and barbs. In the case of needles, 5, or 7, 8, 9, or even 10 or more needles, that is, regardless of the number of barbs, fiber damage due to barbs becomes significant. Since the fiber is cut and a punching mark may remain on the surface of the nonwoven fabric structure, the needle conditions are set in consideration of these points. In an arbitrary cross section parallel to the thickness direction of the nonwoven fabric structure obtained by the entanglement treatment by the needle punch, the cross section of the sea-island fiber that is substantially orthogonal to the cross section is preferably 300 to 1000 pieces / mm ² , more preferably 400. ˜800 pieces / mm ² and a density higher than the density in the fiber web.

  In order to suppress damage and cutting of the fiber due to the needle punching process and to suppress charging and heat generation caused by strong friction between the needle and the fiber, at any stage after the fiber web manufacturing process and before the entanglement processing process It is preferable to apply an oil agent. As a method for imparting, a known coating method such as a spray coating method, a reverse roll coating method, a kiss roll coating method, a lip coating method, etc. can be adopted, and among them, the spray coating method is non-contact with the fiber web, And since the low-viscosity oil agent which permeates into a fiber web for a short time can be used, it is the most preferable. The term “after the fiber web manufacturing process” here refers to the stage after the stage in which sea-island fibers are melt-spun and collected and deposited on a collection surface such as a movable net. In the present invention, the oil agent to be applied before the entanglement treatment may be an oil agent composed of one type of component, but a plurality of types of oil agents having different effects may be used by mixing them or applying them sequentially. The oil agent used in the present invention is an oil agent having a high sliding effect that relieves friction between the needle and the fiber, that is, friction between the metal and the polymer. Specifically, a mineral oil-based oil agent or a polysiloxane-based oil agent is used. In the latter case, an oil mainly composed of dimethylsiloxane is more preferable. When using an oil agent with a high sliding effect in a polysiloxane system, the sliding effect is too strong, and the entanglement effect due to catching on the barb is locally reduced significantly, especially the friction coefficient between fibers is remarkable. It is also preferable to use an oil agent having a high friction effect, for example, a mineral oil-based oil agent, for the purpose of preventing the maintenance of the entangled state from becoming difficult. However, in the present invention, a water-soluble polymer is used as the sea component of the sea-island fiber, and water or an aqueous solution is used to transform the sea-island fiber into an ultrafine fiber bundle. In particular, polysiloxane oils are transformed into ultrafine fiber bundles. It is not removed at the time, and much remains on the surface of the ultrafine fiber or the surface of the polymer elastic body in the base material for artificial leather. Therefore, when the obtained artificial leather base material is made into a suede-like artificial leather, the processing agent, for example, the dyeing state may become patchy due to the remaining oil when the treatment in the water bath such as the dyeing treatment is performed. . Alternatively, if it remains without being completely removed even after finishing treatment such as in-bath treatment, the fixed state of the napped fibers may be weakened, which may cause problems such as pilling. Therefore, it is necessary to pay particular attention to the use of polysiloxane oils. In addition to the combined use of a mineral oil-based oil and a polysiloxane-based oil, it is also preferable to use a surfactant, for example, a polyoxyalkylene-based surfactant as an antistatic agent when charging due to friction is significant.

The density of the sea-island fibers in the densified nonwoven structure before the ultrathinning treatment (the number per unit area of the cross section of the sea-island fibers in an arbitrary cross section parallel to the thickness direction substantially orthogonal to the cross section) is 1000 ~ 3500 / mm ² is preferable, more preferably 1100 to 3000 / mm ² , still more preferably 1200 to 2500 / mm ² , and more than the density of the nonwoven fabric structure obtained by the entanglement treatment high. In order to obtain a dense structure having such a density, a wet heat shrinkage treatment with hot air, hot water, steam or the like is used after an entanglement treatment such as a needle punch treatment. By combining one or more of these treatments, it is possible to finally obtain a dense structure intended by the present invention. Of course, it is also preferable to perform a press treatment in addition to the entanglement treatment and the wet heat shrinkage treatment. When the press process is used in combination with the entanglement process, the entanglement process may be performed before or after the entanglement process, or the press process may be performed. Further, when used together with the wet heat shrinkage treatment, it may be performed before or after the wet heat shrinkage treatment. However, a method of performing the wet heat shrinkage treatment while performing the press treatment is not preferable because the shrinkage state becomes non-uniform.

The wet heat treatment performed after the needle punching process is a process of thermally shrinking the nonwoven fabric structure after the needle punching process so as to have a desired density in a high temperature and high humidity atmosphere. For example, if the density of sea-island fibers to obtain a fineness of 800-1100 pieces / mm ² of about nonwoven structure, first by needle punching process after densified up to about 350 to 750 pieces / mm ^2, the target It is preferable to perform heat shrink treatment so that For heat shrink treatment, the nonwoven fabric structure must be formed of sea-island fibers containing heat-shrinkable components, and the nonwoven fabric structure manufactured by using shrinkable fibers other than sea-island fibers It is also preferable to stack the shrinkable webs manufactured separately. In order to obtain a heat-shrinkable sea-island type fiber, it is only necessary to use a heat-shrinkable polymer for spinning in either or both of the sea component polymer and the island component polymer. The heat-shrinkable polymer described above is used as the component polymer. Conditions for the wet heat shrinkage treatment are not particularly limited as long as at least the island component polymer is sufficiently shrunk and the sea component polymer swells and plasticizes but does not elute, and the heat shrink treatment method and treatment to be employed are not particularly limited. What is necessary is just to set suitably according to the processing amount etc. of a target object. For example, a method of introducing a saturated water vapor into an atmosphere controlled at a temperature of 65 to 100 ° C. and a relative humidity of 70 to 100% by continuously supplying water vapor, and a sea component polymer swells and plasticizes in a nonwoven fabric structure. A preferred example is a method in which a non-woven structure is heated by one of the following methods to shrink the island component polymer and swell and plasticize the sea component polymer after or while applying a sufficient amount of water. As mentioned. As a method of heating the nonwoven fabric structure to which moisture has been applied, a method of introducing it into an atmosphere controlled to a desired temperature, a method of causing air at a desired temperature to act directly on the nonwoven fabric structure, or an electromagnetic wave such as infrared rays is applied to the nonwoven fabric A preferred example is a method in which the nonwoven fabric structure is heated to a desired temperature by acting on the structure. When the area of the nonwoven fabric structure is increased, spots are likely to occur in the heat-shrinked state due to the influence of the weight of the nonwoven fabric structure itself. For the purpose of controlling the shrinkage start point and shrinkage speed, the length of the sheet-like nonwoven fabric structure It is also a preferable aspect to control the temperature different depending on the position in the vertical direction and the width direction.

In addition to the above-described entanglement treatment by needle punching and heat shrinkage treatment, it is necessary prior to the impregnation treatment of the polymer elastic body to be described later in order to make the nonwoven fabric structure made of sea-island fibers a desired density. Accordingly, it is also preferable to employ a press process. For example, when the density of sea-island fibers is targeted at a density of about 1000 to 1200 pieces / mm ² , the target is first densified to about 600 to 900 pieces / mm ² until the heat shrink treatment. What is necessary is just to press-process so that it may become detailed. Specific examples of adopting the press treatment include a method of pressing the wet state after the wet heat shrinkage treatment as it is, a method of pressing the wet heat shrinkage treatment and drying it, and a method without completely drying. The method of pressing in the state where the part moisture remains is mentioned. The temperature for the press treatment is a method in which the softening component is solidified at a temperature lower than the surface temperature of the nonwoven fabric structure before the temperature of the wet heat shrinkage treatment or the drying treatment is lowered, and the temperature is higher than the surface temperature of the nonwoven fabric structure. Examples thereof include a method of pressing one component while softening one component and evaporating contained water. By adopting such a processing method, since densification by press processing in addition to heat shrink processing proceeds almost simultaneously, it is possible to obtain a uniform densified state rather than simply performing press processing, It is also possible to obtain excellent production efficiency. When a sea-island type fiber is used in which the softening temperature of the sea component polymer is preferably 20 ° C. or more, more preferably 30 ° C. or less, lower than the softening temperature of the island component polymer, the press treatment in combination with the heat shrink treatment is more effective for densification. In this case, only the sea component polymer in the sea-island fiber is heated by heating to a temperature range near the softening temperature of the sea component polymer to a temperature lower than the softening temperature of the island component polymer and higher than the shrinkage temperature of the island component polymer. When it becomes soft or close to it, the contraction of the shrinkable island component polymer becomes weak and shrinks. After the shrinkage has sufficiently progressed, when the nonwoven fabric structure is pressed at a temperature equal to or higher than the softening temperature of the sea component polymer, the nonwoven fabric structure is compressed into a more dense state. A nonwoven fabric structure fixed in a state can be obtained. Advantages other than the densification of the press treatment include an effect that the surface of the nonwoven fabric structure can be fixed in a more smooth state. By smoothing, it is possible to more effectively obtain a very dense aggregate state of the ultrafine fiber bundles, which is the greatest feature of the base material for artificial leather of the present invention. That is, since the surface of the base material for artificial leather can be made smoother, it becomes possible to reduce the amount of grinding in the napping formation processing such as buffing in the production of napped-tone artificial leather. In the production of the artificial leather, it is possible to stably form an extremely thin silver surface layer having a smooth surface and a thickness of 50 μm or less without subjecting the surface of the substrate to hot pressing or buffing.

The existence density of the sea-island fibers thus obtained is 1000 to 3500 pieces / mm ² , and the density is 0.34 g / cm ³ or more, preferably 0.34 to 0.85 g / cm ³ , more preferably. A densified non-woven structure having a thickness of 0.45 to 0.65 g / cm ³ is immersed in an aqueous solution or dispersion of a polymer elastic body at room temperature before or after the ultrathinning treatment, Impregnated with an aqueous solution or dispersion. The solid content concentration of the aqueous solution or dispersion of the polymer elastic body is preferably 5 to 40% by mass, and since the environmental load is small, it is preferable to use a water-dispersed emulsion.

  As the polymer elastic body to be contained in the nonwoven fabric structure, any of those conventionally used for base materials for artificial leather can be employed. Specific examples include polyurethane elastomers, acrylonitrile elastomers, olefin elastomers, polyester elastomers, An acrylic elastomer is mentioned, Preferably it is a polyurethane elastomer and an acrylic elastomer.

  Examples of the polyurethane elastomer include at least one polymer polyol having an average molecular weight of 500 to 3000 selected from polyester diol, polyether diol, polyether ester diol, polycarbonate diol, 4,4′-diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene. At least one polyisocyanate selected from aromatic, alicyclic, and aliphatic diisocyanates such as diisocyanate, and at least one active hydrogen atom having two or more active hydrogen atoms such as ethylene glycol and ethylenediamine. Examples include various polyurethane elastomers obtained by polymerizing a low molecular weight compound at a predetermined molar ratio by a one-step or multi-step melt polymerization method, bulk polymerization method, solution polymerization method, etc. . The content of the polymer polyol component in the polyurethane elastomer is preferably 15 to 90% by mass.

As the acrylic elastomer, the homopolymer has a glass transition temperature in the range of −90 to −5 ° C., and preferably a non-crosslinkable monomer such as methyl acrylate, n-butyl acrylate, isobutyl acrylate, The glass transition temperature of at least one soft component selected from isopropyl acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like is in the range of 50 to 250 ° C. A monomer which is preferably non-crosslinkable, for example, at least one hard component selected from methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, (meth) acrylic acid, etc. Monofunctional or polyfunctional ethylenic unsaturation that can form structures Compound or compound capable of reacting with ethylenically unsaturated monomer unit introduced into polymer chain to form crosslinked structure, for example, ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol Examples thereof include various acrylic elastomers obtained by polymerizing at least one crosslinkable and ethylenically unsaturated monomer selected from di (meth) acrylate and 1,4-butanediol di (meth) acrylate.

  The base material for artificial leather obtained by adopting a polymer elastic body mainly composed of polyurethane elastomer is excellent in balance of texture and mechanical properties, and also in balance including durability. preferable. In addition, the base material for artificial leather obtained by adopting acrylic elastomer has low adhesiveness to ultrafine fiber bundles compared to polyurethane elastomer and acrylic fiber has poor nap fixing effect at the time of napping. Although it is unsuitable for forming an artificial leather, it is particularly preferred when forming a silver-tone artificial leather because the degree of curing of the texture with respect to the content is low. Different polymer elastic bodies may be mixed and contained, or different polymer elastic bodies may be included separately in multiple times. In addition to the main polymer elastic bodies, synthetic rubber, You may make it contain as a polymeric elastic body composition which added polymeric elastic bodies, such as a polyester elastomer, as needed.

  The content of the polymer elastic body in the aqueous solution or aqueous dispersion of the polymer elastic body is preferably 0.1 to 60% by mass. In aqueous solutions or dispersions of polymer elastic bodies, colorants such as dyes and pigments, coagulation regulators, antioxidants, UV absorbers are used as long as they do not impair the properties of the final artificial leather substrate. , Fluorescent agents, antifungal agents, penetrants, antifoaming agents, lubricants, water repellents, oil repellents, thickeners, extenders, curing accelerators, foaming agents, water-soluble polymer compounds such as polyvinyl alcohol and carboxymethyl cellulose Various additives to be blended in the elastic polymer body fluid to be contained in the conventional artificial leather base material such as the above may be blended as appropriate. The amount of the elastic polymer contained in the nonwoven structure may be appropriately adjusted according to the mechanical properties, durability, texture, etc. required for the intended use. When the basis weight is 100, 1 to 80% by mass is preferable, 2 to 60% by mass is more preferable, and 5 to 40% by mass is further preferable. When the content of the polymer elastic body is less than 1% by mass, it is difficult to uniformly contain the polymer elastic body. Quality as a base material for leather is difficult to stabilize. On the other hand, when the content of the polymer elastic body exceeds 80% by mass, the nonwoven fabric structure is extremely dense, so that the texture of the artificial leather base material is remarkably cured and the rubber feeling is also strong. Absent.

The nonwoven fabric structure impregnated with an aqueous solution or dispersion of a polymeric elastomer is then roll nip processed. By this treatment, an aqueous solution or an aqueous dispersion of a polymer elastic body adhering excessively to the surface layer portion is squeezed. For example, as shown in FIG. 1, the roll / nip treatment is performed by allowing the nonwoven fabric structure 1 to pass through the gap between the press roll 2 and the backup roll 3. The roll gap between the press roll 2 and the backup roll 3 is adjusted by the air cylinder 4 to deform the nonwoven fabric structure in the thickness direction at a deformation rate of 25 to 45%, preferably 30 to 40%. The deformation rate is [1- (roll gap / thickness of non-woven fabric structure before treatment)] × 100
It is represented by The conveyance speed of the nonwoven fabric structure when passing through the gap is preferably 4 to 10 m / min. The material of the nip roll is not particularly limited as long as the gap is easily controlled and does not bend, but the press roll / backup roll is preferably a rubber roll / metal roll or a metal roll / metal roll. By this roll-nip treatment, a structure in which the impregnated and solidified polymer elastic body exists uniformly in the thickness direction of the nonwoven fabric structure is obtained.

  The aqueous solution or aqueous dispersion of the polymer elastic body impregnated in the nonwoven fabric structure is solidified by a conventionally known dry method or wet method after the roll / nip treatment to fix the polymer elastic body in the nonwoven fabric structure. The dry method herein refers to all methods for fixing a polymer elastic body in a nonwoven fabric structure by removing a solvent or a dispersion medium by drying or the like. In addition, the wet method means that a non-woven structure impregnated with an aqueous solution or dispersion of a polymer elastic body is treated with a non-solvent or coagulant of the polymer elastic body, or a polymer elastic body with a heat-sensitive gelling agent added. Temporarily or completely fix the polymer elastic body in the nonwoven fabric structure before removing the solvent or dispersion medium by heat-treating the nonwoven fabric structure impregnated with the aqueous solution or aqueous dispersion of the body Refers to all methods. Solidification by the dry method is performed, for example, by treating the nonwoven fabric structure with a heating device such as an infrared heater at a nonwoven fabric surface temperature of 70 to 100 ° C. for 60 to 300 seconds. Solidification by a wet method is performed by, for example, processing for 20 to 300 seconds in a non-woven fabric surface temperature of 60 to 90 ° C. in a humidified and warm air atmosphere with a wet bulb temperature of 70 to 100 ° C. In order to completely fix the solidified polymer elastic body, it is also preferable to perform a curing treatment such as a heat treatment after removing the solvent or the dispersion medium.

As a method for removing the sea component polymer from the sea-island type fibers constituting the nonwoven fabric structure before or after the inclusion of the polymer elastic body, a non-solvent or non-decomposing agent for the island component polymer is used. A method of treating a nonwoven fabric structure with a liquid that is also a non-solvent or non-decomposing agent for a macromolecular elastic body and a liquid that is a solvent or decomposing agent for a sea component polymer when the body is removed after being incorporated Is employed in the present invention. For example, when a water-soluble polymer such as polyvinyl alcohol as described above is used as the sea component polymer, it may be removed with warm water at a temperature at which the polymer is soluble. When using a readily alkali-degradable modified polyester copolymerized with a compound containing such an alkali metal salt of sulfonic acid, the temperature at which the sea component polymer dissolves using an aqueous solution that is an alkaline decomposing agent such as an aqueous sodium hydroxide solution Can be removed. By such sea component polymer removal treatment, the sea-island fiber is transformed into an ultrafine fiber bundle made of the island component polymer, whereby the artificial leather substrate of the present invention is obtained. The fineness of the ultrafine fiber bundle is preferably 0.9 to 4.9 dtex, and the fineness of the ultrafine fiber is preferably 0.001 to 0.6 dtex. The basis weight of the base material for artificial leather of the present invention thus obtained is preferably 120 to 1600 g / m ^{2 and} more preferably 200 to 1200 g / m ^{2 in} terms of texture and fullness. Although the thickness of the base material for artificial leather is suitably selected according to a use and is not specifically limited, Preferably it is 0.3-4 mm, More preferably, it is 0.5-3 mm.

The base material for artificial leather of the present invention obtained as described above comprises a dense nonwoven fabric structure composed of ultrafine fiber bundles and a polymer elastic body contained in the nonwoven fabric structure. In an arbitrary cross section parallel to the thickness direction of the nonwoven fabric structure, the cross section of the ultrafine fiber bundle substantially orthogonal to the cross section exists at a high density of 1500 to 3000 pieces / mm ² . The ratio (mass ratio) of the nonwoven fabric structure and the polymer elastic body is preferably 90/10 to 50/50, and the polymer elastic body is uniformly in the thickness direction of the nonwoven structure (artificial leather substrate). Distributed. In the present invention, the following formula is used as an index representing a uniform distribution:
Uneven distribution X = AB
(In the formula, A represents the average area ratio (%) of the polymer elastic body in the surface layer, and B represents the average area ratio (%) of the polymer elastic body in the intermediate layer)
Is used. In the base material for artificial leather of the present invention, the degree of uneven distribution is −10 to + 10%, preferably −5 to + 5%.

  The degree of uneven distribution is (1) selective dyeing of a polymer elastic body (select a dye that does not dye the fiber), (2) scanning electron micrograph of a sample cross section, (3) image processing of a scanning electron micrograph (2 (Gradation), (4) Distribution chart of polymer elastic body by image analysis, (5) Calculation of area ratio of polymer elastic body of surface layer and intermediate layer, (6) Calculation of uneven distribution . Each step will be described below, but the present invention is not limited to the following method as long as a chart accurately showing the distribution of the elastic polymer is obtained.

(1) Dyeing of polymeric elastic body The operation of alternately washing a sample having a thickness of about 2.5 mm with hot water and then with cold water is repeated three times, and the washed sample is immersed in the dyeing solution at room temperature for 2 to 3 minutes. During this time, it is preferable to repeat the nip operation about three times so that the elastic polymer inside the sample is also dyed. As the dye, the red metal-containing dye has a high contrast between the dyed portion (polymer elastic body) and the non-dyed portion (extra fine fiber bundle and void), and subsequent image processing can be performed successfully. Examples of red metal-containing dyes include “PM Red531” manufactured by Taoka Chemical Industry Co., Ltd. The dye concentration of the dyeing solution is preferably about 2% by mass. After dyeing, the sample is treated with an aqueous detergent solution of 10 g / L. Use it, wash it at room temperature about 3 times, and then dry it thoroughly with a dryer at 100-150 ° C.

(2) Photographing of sample cross section A stained sample is cut along the thickness direction at an arbitrary position, and the obtained cross section is photographed with a scanning electron microscope (50 to 100 times).

(3) Image processing of scanning electron micrographs (2 gradations)
A scanning electron micrograph of a cross-section is processed using image processing software (for example, Imagepro Plus manufactured by Medhia Cybernetios), and two gradations are expressed in which the elastic polymer is black, the ultrafine fibers, and the voids are white. Create an image.

(4) Creation of a distribution chart of a polymer elastic body The obtained two-tone image is processed using image analysis software (for example, Popping of Digital Being Kids Co., Ltd.) to obtain a polymer elastic body. A chart showing the distribution in the thickness direction is created (see FIG. 2).

(5) Calculation of the area ratio of the polymer elastic body between the surface layer and the intermediate layer As shown in FIG. The 5 mm portion is defined as the intermediate layer. The average area ratio A (%) of the elastic polymer is obtained by integrating the distribution curve of the surface layer. Similarly, the average area ratio B (%) of the polymer elastic body is obtained.

(6) Calculation of uneven distribution degree Using the obtained average area ratio A and average area ratio B, the uneven distribution degree X is calculated according to the above formula: uneven distribution degree X = A−B. The degree of uneven distribution calculated from the chart shown in FIG. 2 is -4.2%.

When a base material for artificial leather is manufactured using long fibers without cutting the sea-island type fibers, in addition to the above-mentioned advantages, there are characteristics not found in conventional base materials for artificial leather, for example, between ultrafine fiber bundles. The size of the void formed is preferably not more than 70 μm, more preferably not more than 60 μm, and is extremely small, uniform, and small in size. this is,
(1) A long-fiber web obtained directly from sea-island type long fibers having a cross-sectional area of about 350 μm ² or less (fiber diameter of about 21 μm or less) and having a number of islands that are difficult to flatten is unlikely to be bulky in the following production process. Forming a nonwoven structure,
(2) Since the long fiber web is composed of continuous long fibers randomly arranged, a needle punching process for three-dimensionally entanglement of the long fiber web is performed through the barb in the thickness direction using a 6 barb needle. When performed under such conditions, densification and three-dimensional entanglement proceed in a very good balance, and a nonwoven fabric structure having a cross-section in which long fibers are closely gathered at a sufficiently high existence density can be obtained,
(3) Since a water-soluble polymer is used as the sea component and a heat-shrinkable polymer is used as the island component, when the heat shrink treatment is performed in a humid heat environment, the sea component instantly swells and plasticizes and the island component shrinks. It becomes easy, the island component shrinks and the fiber diameter increases to a desirable level, so that the sea-island long fibers are easily shrunk along the fiber axis, and moreover, like the conventional sea-island type fiber, the sea-island type The fibers move randomly and do not exclude adjacent sea-island fibers,
(4) When removing the sea component, water having a molecular size smaller than that of the conventional organic solvent and having polarity is used as the solvent, so that the diffusion rate of the solvent molecules in the sea component polymer is relatively high, The process from swelling to dissolution occurs stably. Therefore, it is not necessary to apply hydraulic pressure or mechanical stress to sequentially remove the sea component polymer from the sea-island fiber. Therefore, even in a non-woven fabric structure that is extremely dense compared to conventional ones, it is possible to easily dissolve and remove sea components without increasing the gap size between the ultrafine fiber bundles,
It is thought that this is the result of compounding such factors.

  Manufacture a base material for artificial leather that is suitable for manufacturing napped-toned artificial leather with finer appearance quality and fine-grained silver-tone artificial leather with a more uniform gap size between ultrafine fiber bundles Therefore, it is also preferable to solidify the easily extractable polymer by applying a solution, aqueous dispersion or melt of the easily extractable polymer to the surface of the artificial leather base material which is the front side of the artificial leather product. In the present invention, an aqueous dispersion of a polymer elastic body is applied to the surface of the artificial leather product for the purpose of obtaining a smoother and more uniform raised surface in the buffing process as a post-process, and the polymer elastic body After solidifying, if an easily extractable polymer has been previously applied, it is removed by dissolution or the like. Next, by grinding while pressing the surface to which the polymer elastic body is applied, not only the region from the original surface to a depth of about 20 to 200 μm is ground, but also from the surface after the grinding treatment, about 100 to The nonwoven fabric structure in the region up to a depth of about 300 μm can be further densified. Prior to the application of the polymer elastic body to the surface, the surface and the back surface of the artificial leather base material may be smoothed by buffing treatment, calendar treatment, or the like. The obtained base material for artificial leather not only has a smooth surface by grinding treatment, but also has an average gap size between 10 to 40 μm between the ultrafine fiber bundles existing in the range from the surface to 200 μm. It is in a uniform and dense state.

  Examples of the easily extractable polymer include polyvinyl alcohol, polyurethane elastomer, acrylic elastomer, polyethylene glycol, paraffin wax, polyethylene wax and the like. Examples of the polymer elastic body include those similar to the polymer elastic body to be contained in the nonwoven fabric structure, such as polyurethane elastomer and acrylic elastomer. Examples of coating methods for easily extractable polymers and polymer elastic bodies include known coating methods such as gravure roll coating, rotary screen coating, spray coating, and reverse roll coating. The roll coating method is preferable in view of the balance between the liquid viscosity to be applied and the coating amount. An example of grinding treatment is buffing with sandpaper. The pressure level on the sandpaper evaluates the surface state of the artificial leather substrate while evaluating the cross-sectional state of the artificial leather substrate after treatment. The optimum value may be set by adjusting as appropriate.

  The base material for artificial leather thus obtained is sliced into multiple pieces parallel to the surface as necessary, and the thickness is adjusted by grinding the back surface, etc., as required in conventional artificial leather manufacturing. Alternatively, the surface to be the back surface or the surface to be the front surface is treated with a liquid containing a polymer elastic body or a solvent for the ultrafine fiber bundle. Thereafter, at least the surface to be the surface is raised by a method such as buffing to form a raised surface mainly composed of ultrafine fibers, thereby obtaining a raised artificial leather such as suede or nubuck. Moreover, a silver-tone artificial leather can be obtained by forming a coating layer made of a polymer elastic body on the surface to be the surface.

  For the formation of the fiber raised surface, any known method such as buffing with sandpaper or knitted cloth or brushing can be used. In addition, before or after the raising treatment, a solvent capable of dissolving or swelling the polymer elastic body or the ultrafine fiber bundle, for example, dimethylformamide (DMF) is used if the polymer elastic body is a polyurethane elastomer. If the treatment liquid or the ultrafine fiber bundle is a polyamide resin, a treatment liquid containing a phenol compound such as resorcin may be applied to the surface to be raised. Thereby, it is possible to finely adjust the restraint state of the ultrafine fiber bundle by adhesion of the polymer elastic body or the ultrafine fiber bundle, the ultrafine fiber napping length of the napped-tone artificial leather, the surface friction durability, and the like.

  For the formation of a coating layer made of a polymer elastic body, a liquid containing the polymer elastic body is directly applied to the surface of the artificial leather base material, or once the liquid is applied onto a support base material such as a release paper. Any known method such as a method of bonding to a base material for artificial leather can be used. The polymer elastic body used for the coating layer to be formed is the same as the polymer elastic body for inclusion in the non-woven fabric structure described above, and is known as a polymer elasticity known as a coating layer for conventional silver-tone artificial leather Any body can be used. If the thickness of the coating layer to be formed is about 300 μm or less, there is no particular limitation because it is possible to produce a silver-tone artificial leather having a well balanced texture with the artificial leather substrate of the present invention. In the case of producing a silver-tone artificial leather having a very smooth and uniform surface layer obtained by a dense aggregate state of ultrafine fiber bundles, which is the greatest feature of the base material for artificial leather of the present invention, the thickness is 100 μm. It is better to form a coating layer in the range of about the following, preferably about 80 μm or less, more preferably about 3 to 50 μm. By forming the coating layer with such a thickness, an extremely fine natural leather-like crease and wrinkle can be formed. It is also possible to obtain a silver-tone artificial leather.

  The base material for artificial leather of the present invention may be dyed at any stage after the sea-island type fibers are transformed into ultrafine fiber bundles. Conventional padders, jiggers, circulars, wins, etc. using dyes mainly composed of disperse dyes, reactive dyes, acid dyes, metal complex dyes, sulfur dyes, sulfur vat dyes, etc. Any dyeing method using a known dyeing machine usually used for dyeing artificial leather can be employed. In addition to dyeing, if necessary, mechanical padding treatment in a dry state, relaxation treatment in a wet state using a dyeing machine or a washing machine, softening agent treatment, flame retardant, antibacterial agent, deodorant Resins other than those mentioned above, such as water and oil repellents, functional treatments such as silicone resins and silk protein-containing treatments, grip modifiers such as gripping resins, colorants and enamel coating resins It is also preferable to perform a finishing process such as a design imparting process to be applied. Since the base material for artificial leather of the present invention has a structure in which very fine fiber bundles are gathered very densely, relaxing treatment and softening agent treatment in a wet state remarkably improve the texture. This treatment is preferably employed in artificial leather. For example, if the treatment is relaxed, it can be treated in water that contains a surfactant in the temperature range of about 60 to 140 ° C., so that it has a feeling of flexibility and swelling that is not inferior to natural leather, but has a dense structure. It is also possible to obtain an artificial leather that is intact.

  Next, embodiments of the present invention will be described with specific examples, but the present invention is not limited to these examples. In the examples, “part” and “%” relate to mass unless otherwise specified.

(1) Average fineness Measure the cross-sectional area of sea-island fibers (20 fibers) or ultrafine fibers (20 fibers) forming a nonwoven fabric structure with a scanning electron microscope (magnification: several hundred to several thousand times). The average cross-sectional area was determined. The average fineness was calculated from the average cross-sectional area and the density of the polymer forming the fiber.

(2) Presence density With respect to an arbitrary cross section parallel to the thickness direction of the sample, using a scanning electron microscope (about 100 to 300 times), the observation area is about 0.3 to 0.5 mm ^{2 in} total. A continuous cross-sectional area was observed. In the observation field of view, the number of each section of sea-island type fibers or ultrafine fiber bundles oriented almost perpendicular to the cross section is counted, and the total number is divided by the observation area to obtain sea islands per 1 mm ² of the sample cross section. The number of cross sections of the mold fiber or ultrafine fiber bundle was determined. Such observation was performed on at least five places for one type of sample, and the smallest value was defined as the existence density of the sample.

(3) Density A sample was cut into a length of 10 cm and a width of 10 cm, and the weight was measured to two decimal places. Next, using a thickness measuring instrument with a load of 50 g / m ² , the average of the five thicknesses was calculated to obtain the density (g / cm ³ ).

Production Example Production of Water-Soluble Thermoplastic Polyvinyl Alcohol Resin 29.0 kg of vinyl acetate and 31.0 kg of methanol were charged into a 100 L pressurized reaction vessel equipped with a stirrer, nitrogen inlet, ethylene inlet and initiator addition port. After raising the temperature to 0 ° C., the system was purged with nitrogen by nitrogen bubbling for 30 minutes. Next, ethylene was introduced so that the reactor pressure was 5.9 kgf / cm ² . 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) (initiator) was dissolved in methanol to prepare an initiator solution having a concentration of 2.8 g / L, and bubbling with nitrogen gas was performed. Replaced with nitrogen. After adjusting the polymerization tank internal temperature to 60 ° C., 170 mL of the initiator solution was injected to initiate polymerization. During the polymerization, ethylene was introduced to maintain the reactor pressure at 5.9 kgf / cm ² , the polymerization temperature at 60 ° C., and the above initiator solution was continuously added at 610 mL / hr. After 10 hours, when the polymerization rate reached 70%, the polymerization was stopped by cooling. After the reaction vessel was opened to remove ethylene, nitrogen gas was bubbled to completely remove ethylene.
Subsequently, the unreacted vinyl acetate monomer was removed under reduced pressure to obtain a methanol solution of ethylene-modified polyvinyl acetate (modified PVAc). Saponification was performed by adding 46.5 g of a 10% methanol solution of NaOH to 200 g of a 50% methanol solution of modified PVAc prepared by adding methanol to the solution (NaOH / vinyl acetate unit = 0.10 / 1 ( Molar ratio)). The system gelled about 2 minutes after the addition of NaOH. The gelled product was pulverized with a pulverizer and allowed to stand at 60 ° C. for 1 hour to further promote saponification, and then 1000 g of methyl acetate was added to neutralize the remaining NaOH. After confirming neutralization with a phenolphthalein indicator, the mixture was filtered to give a white solid. 1000 g of methanol was added to the white solid, and the mixture was left to wash at room temperature for 3 hours. The above washing operation was repeated three times, and then the solution was centrifuged and left standing in a dryer at 70 ° C. for 2 days to obtain ethylene-modified polyvinyl alcohol (modified PVA). The degree of saponification of the obtained modified PVA was 98.4 mol%. Further, after the modified PVA was incinerated, a sample obtained by dissolving in acid was analyzed by an atomic absorption photometer. The content of sodium was 0.03 parts by mass with respect to 100 parts by mass of the modified PVA.

  In addition, n-hexane was added to the methanol solution of the modified PVAc, and then the precipitation-dissolution operation of adding acetone was repeated three times, followed by drying under reduced pressure at 80 ° C. for 3 days to obtain purified modified PVAc. When this modified PVAc was dissolved in d6-DMSO and analyzed using a 500 MHz proton NMR (JEOL GX-500) at 80 ° C., the content of ethylene units was 10 mol%. The above modified PVAc was saponified (NaOH / vinyl acetate unit = 0.5 (molar ratio)), pulverized, and allowed to stand at 60 ° C. for 5 hours to further promote saponification. The saponified product was extracted with methanol Soxhlet for 3 days, and the extract was dried under reduced pressure at 80 ° C. for 3 days to obtain purified modified PVA. It was 330 when the average degree of polymerization of this modified PVA was measured according to JIS K6726. The purified modified PVA was analyzed by 5000 MHz proton NMR (JEOL GX-500). As a result, the amount of 1,2-glycol bonds was 1.50 mol% and the content of 3-chain hydroxyl groups was 83%. Further, a cast film having a thickness of 10 μm was prepared from a 5% aqueous solution of the purified modified PVA. The film was dried at 80 ° C. under reduced pressure for 1 day, and then the melting point was measured by the method described above.

Example 1
The ethylene-modified polyvinyl alcohol as the sea component polymer and isophthalic acid-modified polyethylene terephthalate (content of isophthalic acid unit of 6.0 mol%) as the island component polymer were individually melted. The molten polymer is combined with the sea component polymer and the island in the cross section in a composite spinning nozzle having a large number of nozzle holes arranged in parallel, which can form a cross section in which 25 island component polymers of equal cross section are distributed in the sea component polymer It was supplied with a pressure balance such that the average area ratio of the component polymers was sea component / island component = 25/75, and was discharged from the nozzle hole at a die temperature of 250 ° C. The air-jet-nozzle type suction device with the airflow pressure adjusted so that the average spinning speed is 3600 m / min is pulled and thinned to spin about 2.4 dtex sea-island long fibers, which are sucked from the back side. However, it was continuously collected on the net. Adjust the net moving speed to adjust the amount of deposition, and press it with an embossing roll kept at 80 ° C. with a linear pressure of 70 kg / cm, weight per unit area of 30 g / m ² , sea-island long fiber on the cross section parallel to the thickness direction A cross section of about 230 pieces / mm ² was obtained, and a fiber web whose shape was stabilized to such an extent that winding was possible was obtained.
The fiber web was continuously folded using a cross wrapper device to form a 14-layer laminar fiber web. Next, the layered fiber web was three-dimensionally entangled by needle punching to obtain a nonwoven fabric structure in which the density of sea-island long fibers was 500 / mm ² .
Needle punching is needle No. 40, barb depth of 40 μm, one barb needle A with a regular triangular cross section, pre-entangled, that is, folded at the punch depth through which the barb penetrates in the thickness direction from both sides. After entanglement to such an extent that the long fiber web is not displaced, needle No. 42, barb depth of 40 μm, needle B with 6 barbs and equilateral triangle cross section, 3 barbs from both sides are in the thickness direction The sea-island type fibers were entangled in the thickness direction to a desired level at a punch depth penetrating into the surface. Needle punching with the needle B was performed with a total number of punches of 1700 punch / cm ² from both sides.
Next, after water was applied to the nonwoven fabric structure, the nonwoven fabric structure was subjected to wet heat shrinkage treatment in an atmosphere at a temperature of 110 ° C. (dry bulb temperature 110 ° C., wet bulb temperature 73 ° C.) and a relative humidity of 23%, An extremely dense non-woven fabric structure having a weight per unit area of 1900 g / m ² , a density of 0.66 g / cm ³ , and a density of sea-island fibers of 1900 pieces / mm ² in a cross section parallel to the thickness direction. Got the body.
The resulting densified nonwoven structure was impregnated with an aqueous dispersion (solid content concentration 20% by mass) of a polyurethane composition mainly composed of polycarbonate / ether polyurethane, and then press linear pressure 40 kg / cm, deformation rate 35 % (The roll gap was set to 0.65 times the thickness of the densified nonwoven structure) (nip roll: metal roll / metal roll). Next, the polymer elastic body is thermally coagulated by applying an infrared heater for about 1 minute under the condition that the surface temperature of the nonwoven fabric structure is 90 ° C., and then the polymer elastic body is dried and cured. A non-woven structure containing a polymer elastic body present in the voids between sea-island fibers was obtained.
Next, the ethylene-modified polyvinyl alcohol in the sea-island fiber is extracted and removed with hot water at 95 ° C. in a liquid dyeing machine, and then dried to obtain an ultrafine fiber bundle of isophthalic acid-modified polyethylene terephthalate (the average single fiber fineness of the ultrafine fiber). The base material for artificial leather of the present invention having a thickness of about 1.9 mm, in which a polymer elastic body was contained inside a non-woven fabric structure composed of 0.02 dtex) was obtained. In an arbitrary cross section parallel to the thickness direction of the nonwoven fabric structure, the density of the ultrafine fiber bundles was 2600 / mm ² .
When the presence state of the polymer elastic body is confirmed in the cross section of the obtained base material for artificial leather, the ratio of the polyurethane / nonwoven fabric structure (including voids) in the vicinity of the front surface, the central portion and the back surface is approximately 1: 1: 1. The distribution was uneven (degree of uneven distribution: 0%), and the distribution was uniform in the thickness direction. The mass ratio of the nonwoven fabric structure to the polymer elastic body was 88:12.
When the obtained artificial leather base material was finished into a suede-like artificial leather by a known method, there was no fuzz unevenness or dyeing unevenness and excellent uniformity.

  The base material for artificial leather of the present invention should be used for the production of artificial leather such as clothing, shoes, bags, furniture, car seats, gloves, bags, curtains, etc. Can do.

1 Nonwoven Structure 2 Press Roll 3 Backup Roll 4 Air Cylinder

Claims (6)

It consists of a dense nonwoven fabric structure composed of a bundle of ultrafine fibers and a polymer elastic body contained in the nonwoven fabric structure, and the thickness direction unevenness degree X of the polymer elastic body represented by the following formula is −10 % To + 10% of artificial leather base material.
Uneven distribution X = AB
(In the formula, A represents an average area ratio (%) of the polymer elastic body in the surface layer, B represents an average area ratio (%) of the polymer elastic body in the intermediate layer, and each of the average area ratios is an artificial ratio. (A scanning electron micrograph of an arbitrary cross section parallel to the thickness direction of the base material for leather was subjected to image processing, and then obtained from a thickness direction distribution chart of a polymer elastic body obtained by image analysis). The base for artificial leather according to claim 1, wherein in an arbitrary cross section parallel to the thickness direction of the base material for artificial leather, the cross section of the ultrafine fiber bundle oriented almost perpendicularly to the cross section is 1500 to 3000 pieces / mm ^2. Wood. The following steps (a) to (e):
(A) a step of converting sea-island fibers in which the sea component is a water-soluble polymer and the island component is a heat-shrinkable polymer into a fiber web;
(B) entanglement treatment of the fiber web to obtain a nonwoven fabric structure;
(C) a step of wet-heat-treating the nonwoven fabric structure to obtain a densified nonwoven fabric structure having a density of 0.34 g / cm ³ or more;
(D) The densified nonwoven structure is impregnated with a solution or aqueous dispersion of a polymer elastic body from both sides, and roll-nip treatment is performed at a deformation rate in the thickness direction of the nonwoven fabric structure of 25 to 45%. A step of solidifying the elastic body to obtain a polymer elastic body-impregnated nonwoven fabric structure; and (e) a sea component is extracted and removed from the sea-island fiber constituting the polymer elastic body-impregnated nonwoven fabric structure with water or an aqueous solution. A process of obtaining a base material for artificial leather by transforming a mold fiber into an ultrafine fiber bundle,
Alternatively, the following steps (a) to (c), (f) and (g):
(A) a step of converting sea-island fibers in which the sea component is a water-soluble polymer and the island component is a heat-shrinkable polymer into a fiber web;
(B) entanglement treatment of the fiber web to obtain a nonwoven fabric structure;
(C) a step of wet-heat-treating the nonwoven fabric structure to obtain a densified nonwoven fabric structure having a density of 0.34 g / cm ³ or more;
(F) a step of extracting and removing sea components from the sea-island fibers constituting the densified nonwoven structure with water or an aqueous solution, and transforming the sea-island fibers into ultrafine fiber bundles to obtain an ultrafine nonwoven structure.
(G) The ultrafine nonwoven fabric structure is impregnated with a polymer elastic body solution or aqueous dispersion from both sides, and roll-nip treatment is performed at a deformation rate in the thickness direction of the nonwoven fabric structure of 25 to 45%, and then the polymer The manufacturing method of the base material for artificial leather including the process of solidifying an elastic body and obtaining the base material for artificial leather. In any cross-section parallel to the thickness direction of the fiber web, the manufacturing method according to claim 3 in which the cross section of the sea-island fibers oriented substantially perpendicular to the cross section is present in the density of 100 to 600 pieces / mm ² . In an arbitrary cross section parallel to the thickness direction of the nonwoven fabric structure obtained in the step (b), the cross-section of the sea-island fibers oriented almost perpendicular to the cross section is 300 to 1000 pieces / mm ² , and The manufacturing method of Claim 3 or 4 which exists with a presence density higher than the presence density in the said fiber web. In an arbitrary cross section parallel to the thickness direction of the densified nonwoven structure, the density of sea-island fibers oriented almost perpendicular to the cross section is 1000 to 3500 / mm ² , and the step (b) The production method according to any one of claims 3 to 5, wherein the non-woven fabric structure obtained in step 1 is present at a higher density than that in the nonwoven fabric structure.

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