JP2012211414A - Method for manufacturing suede touch leather-like sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for simply manufacturing a suede touch leather-like sheet which can be used for actual wear in an industrial material application such as a conveyer belt requiring high strength and pilling resistance as a high molecular elastomer is distributed concentrated in a surface layer part in the thickness direction of a nonwoven cloth.SOLUTION: The method comprises: impregnating a nonwoven cloth structure having a definite range of an apparent density with a high molecular elastomer solution or dispersion; immediately thereafter squeezing the liquid by roll-nip treatment so that the nonwoven cloth structure has a definite range of an impregnation magnitude; and drying it.

Description

  The present invention relates to a nonwoven fabric structure comprising ultrafine fiber bundles and a method for producing a suede-like leather-like sheet comprising a polymer elastic body contained in the nonwoven fabric structure. More specifically, it is composed of a dense nonwoven fabric structure composed of ultrafine fiber bundles and a polymer elastic body contained in the nonwoven fabric structure, and the polymer elastic body is distributed unevenly in the surface layer portion in the thickness direction of the nonwoven fabric structure. The present invention relates to a method for producing a suede-like leather-like sheet.

  Artificial leather has been recognized by consumers as being lighter and easier to handle than natural leather, and is widely used in clothing, interiors, and sports products. In particular, suede-like artificial leather with nap on the surface has been accepted by consumers for its elegant appearance, and its sales volume has increased in the market as luxury clothing and luxury interiors. On the other hand, the effectiveness of industrial materials such as conveyor belts is being recognized due to the frictional resistance generated by napping, and the development of materials that can withstand actual use is being promoted.

  Conventional general suede-like artificial leather is generally made of stapled ultra-fine fiber-generating fibers composed of two types of polymers with different solubility properties, and then converted into a web using a card, cross wrapper, random weber, etc. After entanglement of ultrafine fiber generating fibers with a 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 generating fibers is removed to remove ultrafine fibers. Then, the surface is ground with sandpaper or the like to generate napped hair, and is manufactured by a method of coloring to a desired color.

  However, the conventional suede-like artificial leather has a problem in that the surface of the napped surface is rubbed during use, and the fibers are easily pulled out from the inside of the base material, and pilling (fibers entangled with each other) tends to occur. When used as interiors, attempts have been made to extend the useful life. In order to achieve high pilling resistance that can withstand practical use, a non-woven fabric is generally impregnated with a certain amount of a polymer elastic body such as polyurethane. Moreover, in order to suppress the fiber omission by increasing the inter-fiber friction, attempts have been made to strengthen the fiber entanglement and increase the density of the nonwoven fabric. In order to improve pilling resistance in practical use, stabilize quality 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. Until now, the following methods have 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 very high density nonwoven fabric with an apparent density of 0.66 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 surface layer portion of the three-dimensional entangled sheet. 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 an extremely high density nonwoven fabric having an apparent density of 0.66 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.
However, 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 with an apparent density of 0.66 g / cm ³ or more, it is difficult to sufficiently scrape the polymer elastic body in the vicinity of the surface with a knife, resulting in insufficient squeezing, and the surface is in an uneven state. It tends to cause quality variations.

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 non-woven fabric composed of ultrafine fibers, particularly a very high density nonwoven fabric, a polymer elastic body can be present in a distribution state intended in the thickness direction, for example, a distribution state biased in the thickness direction surface layer portion. The method was not known. In the present invention, the polymer elastic body is distributed unevenly in the surface layer in the thickness direction of the nonwoven fabric, so that the suede tone has both pilling resistance and mechanical strength that can withstand practical use even in industrial material applications such as conveyor belts. It aims at providing the method of manufacturing a leather-like sheet | seat simply.

  As a result of intensive research, the present inventors have conducted a roll so that the nonwoven fabric structure has a specific impregnation ratio immediately after impregnating the nonwoven fabric structure having an extremely high apparent density with the polymer elastic body solution or dispersion. -Squeezed by nip treatment, and then dried, the polymer elastic body was found to be distributed unevenly in the thickness direction surface layer portion of the nonwoven fabric structure, and the present invention was completed.

That is, this invention is a manufacturing method of the suede tone leather-like sheet | seat including the following process (a)-(f).
(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 an apparent density of 0.66 g / cm ³ or more and 0.85 g / cm ³ or less,
(D) The densified nonwoven structure is impregnated with a polymer elastic body solution or water dispersion from both sides thereof, and squeezed by roll nip treatment so as to obtain an impregnation ratio W ₁ satisfying the following formula (1). Next, the polymer elastic body is solidified and then dried to obtain a polymer elastic body-impregnated nonwoven fabric structure,
(E) a step of removing a sea component from the sea-island fiber constituting the polymer elastic body-impregnated nonwoven fabric structure with water or an aqueous solution, and transforming the sea-island fiber into an ultrafine fiber bundle to obtain a base material for artificial leather;
And (f) a step of forming napping on at least one surface of the base material for artificial leather.
However,
0.65 ≦ W ₁ / W ₂ ≦ 0.85 (1)
In the formula, W ₁ is the impregnation ratio of the polymer elastic body solution or the aqueous dispersion to the densified nonwoven fabric structure, and can be obtained by the following formula (2).
_{W 1 = (W W -W D} ) / W D (2)
However, W _D: basis weight of the densified nonwoven structure before impregnated with a solution or dispersion of the elastic polymer (g / m ^2),
W _W : The basis weight (g / m ² ) of the densified nonwoven structure after impregnating the polymer elastic body solution or aqueous dispersion, and W ₂ is completely filled with the voids in the densified nonwoven structure This is the impregnation ratio of the polymer elastic body solution or water dispersion to the densified nonwoven fabric structure, and can be obtained by the following equation (3).
W ₂ = D ₂ × [1- (D ₁ / D ₃ )] / D ₁ (3)
However, _{D 1:} Apparent density (g / cm ³⁾ of the densified nonwoven structure,
D ₂ : density of polymer elastic body solution or aqueous dispersion (g / cm ³ ), and D ₃ : density of fibers constituting the densified nonwoven fabric structure (g / cm ³ ).

  According to the present invention, a suede-like leather-like sheet can be produced by a simple method, and a suede-like leather-like sheet distributed unevenly in the surface layer portion in the thickness direction of a nonwoven fabric structure having a high apparent density can be obtained. The sheet has both pilling resistance and mechanical strength, and is suitable for industrial material applications such as a conveyor belt.

  The suede-like leather-like sheet of the present invention is composed of a nonwoven fabric composed of ultrafine fiber bundles and a polymer elastic body impregnated in the nonwoven fabric, and can be obtained by sequentially performing the following steps (a) to (f).

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 on a collection surface such as a net in a randomly oriented state without being cut, or cut into short fibers and used with a card, a cross wrapper, a random weber, etc. A fiber web having a desired basis weight, preferably 10 to 1000 g / m ² , is produced. On the cross section parallel to the thickness direction of the fiber web, the cross section of the sea-island fiber is 100-
It is preferable that 400 / mm ² exist.

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. It becomes dense. 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.
The apparent density of the densified nonwoven fabric structure obtained by the step (c) is in a very high range and needs to be 0.66 to 0.85 g / cm ³ . However, when the apparent density is 0.85 g / cm ³ or more, the voids inside the densified nonwoven fabric structure are reduced, so that the impregnation ratio of the polymer elastic body solution or aqueous dispersion in the next step is sufficiently high. Cannot be secured. On the other hand, when it is less than 0.66 g / cm ³ , mechanical properties such as sufficient breaking strength cannot be obtained, and it cannot be practically used particularly for industrial materials such as a conveyor belt.

Step (d)
The densified non-woven structure is impregnated with a solution of an elastic polymer or an aqueous dispersion from both sides thereof, and roll / nip treatment is performed so as to obtain an impregnation magnification W ₁ (liquid holding amount) satisfying the following formula (1). The polymer elastic body is then solidified to obtain a polymer elastic body-impregnated nonwoven fabric structure.
0.65 ≦ W ₁ / W ₂ ≦ 0.85 (1)
In the formula, W ₁ is an impregnation ratio (measured impregnation ratio) with respect to a densified nonwoven structure of a polymer elastic body solution or an aqueous dispersion, and can be obtained by the following formula (2).
_{W 1 = (W W -W D} ) / W D (2)
However, W _D: basis weight of the densified nonwoven structure before impregnated with a solution or dispersion of the elastic polymer (g / m ²⁾
W _W : The basis weight (g / m ² ) of the densified nonwoven structure after impregnating the polymer elastic body solution or aqueous dispersion, and W ₂ is completely filled with the voids in the densified nonwoven structure This is the impregnation ratio (theoretical impregnation ratio) for the densified nonwoven structure of the polymer elastic body solution or aqueous dispersion, which can be obtained by the following equation (3).
W ₂ = D ₂ × [1- (D ₁ / D ₃ )] / D ₁ (3)
However, D ₁ : Apparent density (g / cm ³ ) of the densified nonwoven structure
D ₂ : density of polymer elastic body solution or aqueous dispersion (g / cm ³ )
D ₃ : Density (g / cm ³ ) of fibers constituting the densified nonwoven fabric structure.
The extensive studies of the present inventors, for having both the pilling resistance and mechanical strength in the suede-finished leather-like sheet as a final product, to control the ratio of the actual impregnation ratio W ₁ and theoretical impregnation ratio W ₂ It turned out to be very important. That is, when the ratio of W ₁ and W ₂ is less than 0.65, the amount of liquid squeezed is too much, so that the amount of the elastic polymer existing in the vicinity of the surface layer of the final product becomes relatively small, and the fibers are gripped. This is not preferable because the force to be reduced is likely to cause pilling during practical use. On the other hand, when it exceeds 0.85, the filled polymer elastic body solution or aqueous dispersion oozes out to the outermost surface of the nonwoven fabric structure in the process of coagulation and drying, and the appearance of the final product is uneven. In addition, the surface frictional resistance is also uneven, which is not preferable because quality stability as an industrial material such as a conveyor belt is lowered.

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.

Step (f)
A suede-like leather-like sheet is obtained by forming nappings by a known method such as grinding at least one side of the base material for artificial leather using sandpaper.

  If necessary, functions such as coloring and water repellency may be imparted to the obtained suede-like leather-like sheet by a known method.

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 the sea component polymer mainly constituting the outer periphery of the fiber is of a different type. It is a fiber having a cross-sectional shape in which island component polymers are dispersed. 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 close to a circle, literally, 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. A fiber bundle in which a plurality of fibers thinner than the mold fiber are converged is generated. 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. In the sea island type fiber, the sea component polymer mainly constitutes the outer periphery of the fiber in the fiber cross section, and therefore, compared to the peeled split type composite fiber such as a petal shape or a superposed shape in which a plurality of components are alternately formed on the outer periphery of the fiber, Fiber damage such as cracking, bending, and cutting during fiber entanglement, which is representative of punching, is extremely small, and the degree of densification due to entanglement can be further increased. In addition, the sea-island fiber has less anisotropy in the plane perpendicular to the fiber axis than the split split-type composite fiber, and the fineness of the individual ultrafine fiber, that is, the uniformity of the cross-sectional area is high. Since a bundle is 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. This is particularly preferable in that a leather base material can be obtained, and an artificial leather product having good mechanical properties such as wear resistance and breaking strength can be obtained. 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 island component polymer, a coloring agent, an ultraviolet absorber, a heat stabilizer, a deodorant, a fungicide, an antibacterial agent, and other various stabilizers may be added at the spinning stage.

  It is important that the polymer constituting the sea component of the sea-island fiber is a water-soluble polymer. Since the sea component is removed and the sea-island fibers are transformed into ultrafine fiber bundles, it is necessary to make the island component polymer different in solubility or decomposability with respect to the solvent or the decomposing agent. The component polymer is preferably a polymer having a low affinity and a polymer 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 comprising a nonwoven fabric structure in which ultrafine fiber bundles are densely assembled as intended, and to make an artificial leather product with good mechanical properties such as wear resistance or breaking strength. It is particularly preferable because it can be performed.

  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 degree of polymerization of PVA is determined by the following formula (4) according to JIS-K6726.
P = ([η] × 10 ³ /8.29) ^{(1 / 0.62)} (4)
(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. 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 energy and production cost required to recover the removed sea component polymer increase, 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.

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 fiber distribution state present at a density of 600 / mm ² , more preferably 150 to 500 / mm ² is obtained, and the suede-like leather sheet of the present invention is finally obtained by entanglement or shrinkage in the post-process. It becomes possible to obtain a dense nonwoven fabric structure for obtaining.

  According to the production method of the present invention, it is possible to use sea-island type fibers having a very small fiber diameter, and further, it is not necessary to impart crimps, and the fibers themselves do not become bulky. From the stage of accumulating, a highly dense state can be stably obtained from the conventional non-woven fabric structure, and by combining the methods described later, an extremely high density suede tone that cannot be realized with conventional artificial leather A leather-like sheet can be obtained.

  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.

  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. Thereby, when the fiber which comprises a fiber web, especially when lapping and stacking, the fibers in an adjacent fiber web are entangled three-dimensionally. Needle punch is the type of needle (needle shape and count, barb shape and depth, number and position of barbs, etc.), needle punch number (the density of needles implanted in the needle board and the fiber web. Various processing conditions such as the needle punching density per unit area multiplied by the number of strokes applied per unit area, and the needle punch depth (depth at which the needle acts on the fiber web) carry out.

  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 count of the needle is a factor that affects the degree of density and entanglement obtained after processing, and at least the size of the blade part (the part where the barb at the tip of the needle is formed) is No. 30 (the cross-sectional shape is correct). If it is a triangle, the height is preferable, and if it is a circle, the diameter is preferably smaller (thin) about 0.73 to 0.75 mm, more preferably 32 (about 0.68 to 0.70 mm) to 46. No. 36 (about 0.33 to 0.35 mm), more preferably No. 36 (height 0.58 to 0.60 mm) to No. 43 (height about 0.38 to 0.40 mm). A needle with a blade size larger than No. 30 (thick) has a high degree of freedom in the shape and depth of the barb and has high needle strength and durability, but there is a needle punch mark with a large hole diameter on the surface of the nonwoven fabric structure. It is difficult to obtain a dense nonwoven fabric structure that is the object of 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 is 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 fiber is 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 it is difficult to obtain a dense nonwoven fabric structure intended by the present invention. Become. 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. If the barb depth is less than 1.7 times the diameter of the sea-island fiber, the sea-island fiber is difficult to be caught by the barb, so even if the number of punches is increased, the entanglement effect corresponding to that may not be obtained. . On the other hand, when the diameter exceeds 10.2 times the diameter of the sea-island fiber, it is preferable because damage to the sea-island fiber is likely to increase rather than the ease of catching of the sea-island fiber increases. Absent.

  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, the number of fibers oriented substantially parallel to the cross section tends to increase, and the number of fibers substantially orthogonal to the cross section tends to decrease extremely. 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 when three barbs remain outside the non-woven fabric structure when the needle penetrates deepest.

The total number of punches of the needle is preferably 800 to 4000 punch / cm ² , more preferably 1000 to 3500 punch / cm ² . When the needles having a plurality of barbs at the same distance are used, the total number of punches 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 also the integration of the nonwoven fabric structure due to the entanglement of fibers in different fiber webs is insufficient. When punch / cm ² is exceeded, depending on the shape of the needle, damage to the sea-island fiber such as cutting or cracking is conspicuous, and when the damage to the sea-island fiber is particularly severe, the morphological stability of the nonwoven structure As a result, the denseness may decrease.

From the viewpoints of the physical properties of the nonwoven fabric structure and artificial leather substrate obtained, such as the mechanical stability such as tear strength, and the orientation of the fiber in the thickness direction, It is preferable that the barb acts more. 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 obtain the maximum entanglement effect as intended by the present invention. That is, the punch depth is preferably such that the barb farthest from the tip remains 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 and more preferably 3 or 4 out of 6 barbs. Further, 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 more than 70%. More preferably, 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 dense structure cannot be obtained as described above in the case of a needle with six barbs, but also one to five barbs, or seven to nine. Even in the case of 10 needles or more than 10 needles, that is, regardless of the number of barbs, fiber damage due to barbs becomes significant, and in extreme cases, the fibers are cut, and the punching marks are non-woven structure. The needle conditions are set with these points in mind as well. 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 “fiber web manufacturing process and later” here refers to the stage after the stage where melt-spun sea-island fibers are 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 significantly reduced locally, especially the friction coefficient between fibers is significantly reduced. In order to suppress the difficulty of maintaining the entangled state, it is also preferable to use an oil agent having a high friction effect, for example, a mineral oil-based oil agent in combination. 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 base material for artificial leather is a suede-like leather-like sheet, the oil agent may remain on the surface. Alternatively, if it remains without being completely removed after finishing treatment such as in-bath treatment, the fixed state of the napped fibers may be weakened, which may cause problems such as easy pilling during practical use. 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 sea-island fibers in the densified non-woven structure before the ultrafine 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 perpendicular 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 is preferred. In order to obtain a dense structure having such a presence density, a moist heat shrinking process using hot air, hot water, steam, or the like is used after an entanglement process such as a needle punch process. 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 pressing process is used in combination with the entanglement process, it can be performed before or after the entanglement process. Further, the entanglement process can be performed while performing the press process. In addition, 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 uneven.

The wet heat treatment is a treatment for thermally shrinking the sea-island type fiber so that the nonwoven fabric structure after the entanglement treatment has 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, by first entangling treatment 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 quantity. For example, a method of introducing a saturated water vapor continuously into an atmosphere controlled at a temperature of 65 to 100 ° C. and a relative humidity of 70 to 100%, and the sea component polymer swells and plasticizes in the nonwoven fabric structure. After or while applying a sufficient amount of water (preferably 5 to 20% by mass of the nonwoven fabric structure), the nonwoven fabric structure is heated by any of the following methods to shrink the island component polymer. A preferred example is a method of swelling and plasticizing the sea component polymer. 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 is increased. It is also a preferable aspect to control the temperature different depending on the position in the vertical direction and the width direction. The atmosphere in the case of wet heat-treating the nonwoven fabric structure to which moisture has been applied is preferably 90 to 130 ° C., and the relative humidity is preferably 15 to 40%. The wet heat treatment time is selected according to the treatment method, but is preferably 20 to 60 seconds.

In addition to the entanglement treatment by the needle punch and the wet heat treatment, a press treatment is performed prior to the impregnation treatment of the polymer elastic body, which will be described later, in order to make the nonwoven fabric structure made of sea-island fibers a desired density. It is necessary to adopt. 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 by wet heat treatment. What is necessary is just to press-process so that it may become dense. Specific examples of the case where the press treatment is adopted include a method of pressing in the wet state after the wet heat treatment, a method of pressing in the wet state after drying, and a partial moisture without being completely dried. For example, a method of pressing in a state where the mark remains is used. As a press treatment method, before the temperature after the wet heat treatment or the drying treatment is lowered, a method in which the component softened at a temperature lower than the surface temperature of the nonwoven fabric structure is solidified and the temperature is higher than the surface temperature of the nonwoven fabric structure. Examples thereof include a method in which one component of the sea-island fiber is softened, and a press treatment is performed while the contained water is evaporated. By adopting such a treatment method, densification by press treatment in addition to wet heat treatment proceeds almost simultaneously, so it is possible to obtain a uniform densified state rather than simply performing wet heat treatment. 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 more lower than the softening temperature of the island component polymer, press treatment in combination with wet heat 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 heat-shrinkable island component polymer becomes less restrained and shrinks. After the shrinkage has sufficiently progressed, pressing the nonwoven fabric structure at a temperature equal to or higher than the softening temperature of the sea component polymer, preferably 125 ° C. or lower, preferably for 0 to 5 seconds, the nonwoven fabric structure is compressed into a denser state, If this is cooled to room temperature, the nonwoven fabric structure fixed in a desired dense state can be obtained. In particular, in order to obtain a nonwoven fabric structure having a high apparent density used in the present invention, it is preferable to keep the press pressure at the time of hot pressing high, generally 30 kg / cm or more, more preferably 45 kg / cm or more, More preferably, a non-woven fabric structure having a desired high apparent density can be obtained by applying a linear pressure of 60 kg / cm or more. 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 also possible to more effectively obtain an extremely dense assembly state of ultrafine fiber bundles, which is the greatest feature of the artificial leather base material for obtaining the suede-like leather-like sheet of the present invention. . That is, since the surface of the artificial leather base material for obtaining the suede-like leather-like sheet can be made smoother, in the production of the suede-like leather-like sheet, the amount of grinding in the napping formation process such as buffing is reduced. It becomes possible to do.

The densified non-woven fabric structure having a density of sea-island fibers thus obtained of 1000 to 3500 pieces / mm ² and an apparent density of 0.66 to 0.85 g / cm ³ is obtained before the ultrafine treatment. Alternatively, it is immersed in a solution or aqueous dispersion of the polymer elastic body at room temperature and impregnated with the solution or water dispersion of the polymer elastic body from both sides. The solvent is not particularly limited as long as it can dissolve or disperse the polymer elastic body to be used, and examples thereof include organic solvents such as methanol, ethanol, acetone, methyl ethyl ketone, toluene, dimethylformamide, and water. The solid content concentration of the polymer elastic body solution or water dispersion is preferably 5 to 20% by mass, and a water dispersion emulsion is preferably used from the viewpoint of low environmental load.

  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 low hydrogen having two or more active hydrogen atoms such as ethylene glycol and ethylenediamine. Examples include various polyurethane elastomers obtained by polymerizing a molecular compound by a one-step or multi-step melt polymerization method, bulk polymerization method, solution polymerization method or the like at a predetermined molar ratio.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, At least one soft component selected from isopropyl acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like, and the glass transition temperature of the homopolymer thereof is in the range of 50 to 250 ° C. A monomer that 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, and the like, Monofunctional or polyfunctional ethylenically unsaturated compounds capable of forming a crosslinked structure A compound or a compound that can react with an ethylenically unsaturated monomer unit introduced into a polymer chain to form a crosslinked structure, for example, ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di Examples include various acrylic elastomers obtained by polymerization reaction of at least one crosslinkable and ethylenically unsaturated monomer selected from (meth) acrylate, 1,4-butanediol di (meth) acrylate and the like.

  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. 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 solution or aqueous dispersion of the polymer elastic body impregnated into the densified nonwoven structure is preferably 5 to 20% by mass. When the content of the polymer elastic body in the polymer elastic body solution or aqueous dispersion is less than 5% by mass, a high impregnation ratio is obtained to ensure the amount of the polymer elastic body remaining in the final product. Although it is necessary to control the squeezed solution, the amount of water that must be removed by drying increases, which is not preferable because productivity decreases. Further, if it exceeds 20% by mass, it is necessary to control the squeezing so that the amount of the elastic polymer remaining in the final product is an appropriate amount so that the impregnation ratio is low, but it is necessary to squeeze with a strong mangle pressure. Therefore, it is difficult to control the stability, and the polymer elastic particles in the liquid are easily formed into a film at the time of gelation or drying in the subsequent process, which makes it difficult to obtain a uniform artificial leather substrate. Absent.

  In the polymer elastic body solution or aqueous dispersion, colorants such as dyes and pigments, coagulation regulators, antioxidants, UV absorbers are used as long as the properties of the finally obtained suede leather-like sheet are not impaired. , 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 nonwoven structure impregnated with the polymer elastic solution or aqueous dispersion is then roll nip treated. By this treatment, a solution or an aqueous dispersion of a polymer elastic body adhering excessively to the surface layer portion is squeezed. The roll nip treatment is performed by passing the nonwoven fabric structure through a gap between nip rolls composed of a press roll and a backup roll. The roll gap between the press roll and the backup roll is adjusted by an air cylinder to deform the nonwoven fabric structure in the thickness direction. 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.

It was hypothesized that the impregnation magnification W ₁ of the polymer elastic body solution or aqueous dispersion with respect to the densified nonwoven structure and the voids in the densified nonwoven structure were completely filled with the polymer elastic body solution or aqueous dispersion. the ratio of the theoretical impregnation ratio W ₂ of a solution or aqueous dispersion of the elastic polymer against densified nonwoven structures case, it is necessary to satisfy the following equation (1).
0.65 ≦ W ₁ / W ₂ ≦ 0.85 (1)
W ₁ can be obtained by the following equation (2).
_{W 1 = (W W -W D} ) / W D (2)
However, W _D is the basis weight of the densified nonwoven structure before impregnated with a solution or dispersion of the elastic polymer ^{(g / m 2), W} W is impregnated with a solution or dispersion of the elastic polymer It is the fabric weight (g / m < ² >) of the subsequent densified nonwoven fabric structure.
W ₂ can be obtained by the following formula (3).
W ₂ = D ₂ × [1- (D ₁ / D ₃ )] / D ₁ (3)
Where D ₁ is the apparent density (g / cm ³ ) of the densified nonwoven structure, D ₂ is the density of the polymer elastic body solution or aqueous dispersion (g / cm ³ ), and D ₃ is the densified nonwoven structure. Is the density (g / cm ³ ) of the fibers constituting the.
The value of W ₁ / W ₂ needs to be 0.65 or more and 0.85 or less, and a preferable range is 0.70 or more and 0.80 or less. When W ₁ / W ₂ is less than 0.65, the amount of the elastic polymer remaining directly under the surface layer of the densified non-woven structure decreases, and as a result, the gripping force of the surface nap in the final product is reduced, which is practical. Sometimes pilling is easily generated, which is not preferable. When W ₁ / W ₂ exceeds 0.85, the surface of the densified nonwoven structure is partially covered with the polymer elastic body, leading to a reduction in surface homogeneity such as fluff spots on the final product. Further, it is not preferable because productivity is lowered due to drying of excessive moisture.

In order to satisfy the above-described formula (1), first, a solution or an aqueous dispersion of a polymer elastic body is immersed so that the impregnation ratio is equal to or higher than the theoretical impregnation ratio W ₂ calculated by the expression (3), and then A method of squeezing the liquid by adjusting the gap between the nip rolls so as to obtain an impregnation magnification W ₁ satisfying the formula (1) is preferably used. Theory impregnation ratio W ₂ or more solutions or aqueous dispersion of elastic polymer so as to impregnate magnification for immersing the will, time of dipping the densified nonwoven structure in the solution or aqueous dispersion of elastic polymer The method of forcibly dipping up to the inside of the densified nonwoven structure by repeating the dipping and squeezing by roll nip treatment a plurality of times, etc. can be adopted, This is preferable because the processing time can be shortened. Then, the theoretical impregnation ratio W ₂ or more impregnation magnification become as elastic polymer solution or aqueous dispersion densified nonwoven structure is immersed such that the impregnation ratio W ₁ satisfying formula (1) Squeeze by adjusting the nip roll gap. A suitable nip roll gap varies depending on the apparent density of the densified nonwoven structure, but generally a value of 65% to 95% of the thickness of the densified nonwoven structure is employed. In actual processing, it is important to measure the impregnation ratio and adjust the nip roll gap. Moreover, when the method of repeating the immersion and squeezing described above is adopted, the impregnation magnification W ₁ satisfying the formula (1) can be obtained by adjusting the nip roll gap when the squeezing process is finally performed. .

  The 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, and the polymer elastic body is fixed 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 a polymer elastic body solution or water dispersion 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. The polymer elastic body is temporarily fixed or completely fixed in the nonwoven fabric structure prior to removing the solvent or dispersion medium by heat-treating the nonwoven fabric structure impregnated with the body solution or aqueous dispersion. 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, it should be removed using an alkaline decomposing agent such as an aqueous sodium hydroxide solution at a temperature at which the sea component polymer is decomposed. That's fine. By such sea component polymer removal treatment, the sea-island type fibers are transformed into ultrafine fiber bundles made of island component polymers, thereby obtaining a base material for artificial leather. 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 thus obtained is preferably 120 to 1600 g / m ^{2 and} more preferably 200 to 1200 g / m ^{2 in} terms of securing mechanical properties such as breaking strength. 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.

In the present invention, the density of the ultrafine fiber nonwoven fabric structure 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 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 obtain a base material for artificial leather from which a suede-like artificial leather having a very uniform raised surface is obtained, the non-woven structure obtained by the fiber bundle having such a thickness needs to be dense. Therefore, when the microfine fiber napped are 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 still 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 is 8 or more from the viewpoint of the property, etc., and 70 or less from the viewpoint of the bendability of the ultrafine fiber bundle and the deformability in the cross-sectional shape. Further, the number of ultrafine fibers is more preferably 10 to 60, and further preferably 12 to 45. When the number of ultrafine fibers is 7 or less, not only the flexibility of the ultrafine fiber bundle is inferior, but also 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 is Therefore, the flexibility of the ultrafine fiber bundle is easily hindered by 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, when the number of ultrafine fibers exceeds 70, the flexibility 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 (major axis / minor axis of the fiber bundle cross section) in the finally obtained artificial leather substrate is preferably 4.0 or less, and 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 when a suede-like artificial leather is used, the number of ultrafine fiber bundles that can form napped fibers is reduced, resulting in a homogeneous and dense napped surface. It becomes difficult to obtain. On the other hand, when the projected size of the ultrafine fiber bundle is less than 10 μm, it is very easy to densify the nonwoven fabric structure. However, even if the ultrafine fiber bundle is too thin and not flattened at all, Cutting frequently occurs, and it becomes difficult to obtain a uniform raised surface, and the surface wear resistance is inferior.

By forming the ultrafine fiber bundle having the characteristics as described above, the cross section of the ultrafine fiber bundle substantially orthogonal to the cross section is 1500 to 3000 / mm ^{2 in} the cross section of an arbitrary nonwoven fabric structure parallel to the thickness direction. Thus, an extremely dense nonwoven fabric structure which is present at a high density and is unprecedented can be obtained. When the cross section of the ultrafine fiber bundle substantially orthogonal to the cross section 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. In addition, when the space between the ultrafine fiber bundles is increased, the surface is inferior to a uniform napped surface or surface properties due to extremely large uneven 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 for obtaining the target suede-like leather-like sheet 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 with excellent pilling resistance, which is the object of the present invention, the fiber diameter of at least the raised fiber is preferably 0.8 to 15 μm, more preferably 1.0 to 13 μm. 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, spots may occur on the nap when used as a suede-like leather-like sheet, or the homogeneity of frictional resistance may be impaired. Industrial materials such as conveyor belts It is not preferable for practical use. On the other hand, when the fiber diameter of the ultrafine fibers is less than 1.0 μm, the napped fibers become dense when the suede-like leather-like sheet is used, but the surface properties are adversely affected. For example, surface wear resistance such as surface pilling resistance may deteriorate.

  The ratio (mass ratio) of the nonwoven fabric structure and the polymer elastic body of the base material for artificial leather obtained as described above is preferably 90/10 to 50/50, and the polymer elastic body is a nonwoven structure ( The surface layer portion in the thickness direction of the base material for artificial leather is distributed (the surface layer contains more polymer elastic body than the intermediate layer). The intermediate layer refers to a portion in which the distance from the center in the thickness direction falls within the range of 10% of the thickness in the cross-sectional direction when the cross section of the artificial leather substrate is observed with a scanning electron microscope. The part from which the distance from the outermost surface enters the range of 10% of the thickness in the cross-sectional direction.

  The base material for artificial leather thus obtained was subjected to raising treatment at least on the surface to be a surface by a known method such as buffing treatment in the same manner as conventional artificial leather production, and a raised surface mainly composed of ultrafine fibers was formed. By forming, the suede-like leather-like sheet of the present invention is obtained. Before or after raising, if necessary, the thickness can be adjusted by slicing into multiple sheets parallel to the surface, grinding the back surface, etc., and the back surface or front surface can be polymer elastic It can also be treated with a liquid containing a solvent for the body and the microfiber bundle.

  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.

  The suede-like leather-like sheet 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. By dyeing the suede-like leather-like sheet, there is an advantage that dirt is less noticeable and the useful life can be extended during actual use in industrial materials such as a conveyor belt. 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 It is also preferable to carry out a function imparting treatment such as a water / oil repellent.

  The suede-like leather-like sheet obtained as described above exhibits moderate and uniform frictional resistance due to the presence of napping having pilling resistance on the surface, and also has mechanical properties such as breaking strength. Therefore, it is suitably used as a material for industrial materials such as a conveyor belt.

  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) Apparent density of densified non-woven structure: D ₁
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, and the apparent density D ₁ (g / cm ³ ) was determined from the obtained weight and thickness values.

(3) Density of polymer elastic body solution or aqueous dispersion: D ₂
The density D ₂ (g / cm ³ ) of the polymer elastic body solution or aqueous dispersion is obtained by measuring the weight of a 100 cm ³ solution or aqueous dispersion measured using a graduated cylinder to two decimal places. It was.

(4) Density of fibers constituting the densified nonwoven structure: D ₃
Using the density (g / cm ³ ) of the polymer used as the raw material for the sea-island fiber and the mixing ratio, the density D ₃ (g / cm ³ ) of the fiber constituting the densified nonwoven fabric structure was calculated by the following equation (5). .
D ₃ = D _A × R _A + D _B × R _B (5)
However, D _A : density of water-soluble polymer used as sea component (g / cm ³ )
R _A : Mixing ratio (weight ratio) of water-soluble polymer used as sea component
D _B : density of heat-shrinkable polymer used as an island component (g / cm ³ )
R _B : Mixing ratio (weight ratio) of heat-shrinkable polymer used as island component
R _A + R _B = 1

(5) Pilling resistance of the surface of the leather-like sheet Evaluated by the “modified Martindale method” described in ISO 12945-2, and visually evaluated the occurrence of pilling at the time of 500 times, 1000 times, 2000 times and 5000 times friction. did.

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. The density of the pellets obtained by melting, defoaming and granulating the purified modified PVA at 230 ° C. was 1.25 g / cm ³ .

Example 1 The above-mentioned ethylene-modified polyvinyl alcohol as sea component polymer and isophthalic acid-modified polyethylene terephthalate (content of isophthalic acid unit: 6.0 mol%, polymer density: 1.34 g / cm ³ ) as island component polymers were melted individually. I let you. 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-sectional area are distributed in the sea component polymer. The polymer was supplied at 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, which adjusts the air pressure so that the average spinning speed is 4000 m / min, is pulled and thinned to spin about 2.2 dtex sea-island long fibers and 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 into an 18-layer laminar fiber web. Next, the layered fiber web was three-dimensionally entangled by needle punching to obtain a nonwoven fabric structure. Needle punching has a needle count of 42, a barb depth of 40 μm, a number of barbs of 6 and equilateral triangle cross-section needles, and a total of 1700 punch depths through which three barbs penetrate in the thickness direction from both sides. The punching was performed with a punch number of punch / cm ² .

Next, 10% by mass of water of the nonwoven fabric structure was sprayed from both sides of the nonwoven fabric structure, and then the nonwoven fabric structure was heated to 110 ° C. (dry bulb temperature 110 ° C., wet bulb temperature 78 ° C.) and relative humidity 28%. Wet heat-shrink treatment in the inside, and further heat until the surface temperature of the nonwoven fabric structure reaches 120 ° C, and then use a metal roll at 120 ° C to take a clearance of 50% of the thickness of the nonwoven fabric structure before pressing to obtain a linear pressure. A heat press treatment was performed at 70 kg / cm to obtain a very dense nonwoven fabric structure having a basis weight of 1250 g / m ² and an apparent density of 0.73 g / cm ³ . Moreover, the density of the fiber which comprises the densified nonwoven fabric structure at this time was 1.32 g / cm < ³ >.

It was previously obtained after preparing an impregnation solution having a solid content concentration of 12.5 mass% by mixing ammonium sulfate (gelation modifier) and a crosslinking agent in an aqueous dispersion of a polyurethane composition mainly composed of polycarbonate / ether polyurethane. The densified nonwoven structure was impregnated. The density of the adjusted impregnation solution was 1.01 g / cm ³ . Subsequently, a clearance of 85% of the thickness of the densified non-woven structure was taken and roll nip treatment was performed. At this time, a 49% impregnation ratio W ₁ of the aqueous dispersion of the polyurethane composition, if this value which voids densification nonwoven structure unit virtually to have completely filled with the aqueous dispersion of the polyurethane composition The numerical value was 78% with respect to the theoretical impregnation magnification W ₂ (63%). The used impregnation solution had a heat-sensitive gelation temperature of 67 ° C., and when the residue which had been heated to 70 ° C. and evaporated to dryness was observed with an optical microscope, an aggregate of granular components having an average particle size of 15 μm I found out that

  Next, the polymer elastic body is thermally coagulated by applying an infrared heater for about 1 minute under conditions such that the internal temperature of the nonwoven fabric structure is 70 ° 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.

  The obtained elastic elastic body-containing non-woven fabric structure was extracted and removed from the sea-island fiber with hot water at 95 ° C. in a liquid dyeing machine, and then dried to obtain ultrafine isophthalic acid-modified polyethylene terephthalate. A base material for artificial leather having a thickness of about 1.8 mm in which a polymer elastic body was contained inside a nonwoven fabric structure composed of fiber bundles (average single fiber fineness of ultrafine fibers: 0.02 dtex) was obtained. When the surface and cross section of the obtained base material for artificial leather were observed with a scanning electron microscope, polyurethane was unevenly distributed in the vicinity of the surface layer of the base material, while polyurethane was found in the central portion in the thickness direction of the base material. It was scattered.

  By grinding both surfaces of the obtained artificial leather base material using a 320th sandpaper, a suede-like leather-like sheet having napped surfaces was obtained. The obtained suede-like leather-like sheet was subjected to a relaxation treatment at 120 ° C. for 60 minutes using a liquid dyeing machine, and had uniform and dense napped surfaces. Using the obtained sheet, a belt having a width of 50 cm and a circumference of 5 m was prepared, and the belt was rotated at a peripheral speed of 20 m / min for 24 hours under a tension of 5.0 kg / cm. Even after 24 hours, the running performance of the belt was good, and the shape change (elongation, strain) of the belt material after use was 0.5% or less. In addition, as a result of performing a pilling resistance test measurement by the ISO method on the surface of the suede leather-like sheet, it was found that pilling was not observed, and that it was a material that could withstand practical use in industrial material applications such as conveyor belts. .

Example 2
In Example 1, the same operation as in Example 1 was performed except that the clearance between rolls at the time of roll / nip treatment was 70% of the thickness of the densified nonwoven structure, and the roll / nip treatment was performed, and suede leather A sheet was obtained. Impregnation ratio _{W 1} is 43%, and a numerical value corresponding to 68% of the theoretical impregnation ratio _W 2 (63%).
This suede-like leather-like sheet also had homogeneous and dense napping on the surface. Using the obtained sheet, a belt was produced in the same manner as in Example 1 and a practical test was performed. The running property of the belt was good even after 24 hours, and the shape change (elongation, elongation) of the belt material after use. Strain) was also 0.5% or less. In addition, as a result of performing a pilling resistance test measurement by the ISO method on the surface of the suede leather-like sheet, it was found that pilling was not observed, and that it was a material that could withstand practical use in industrial materials such as a conveyor belt. .

Comparative Example 1
In Example 1, the same treatment as in Example 1 was performed except that a clearance of 90% of the thickness of the nonwoven fabric structure before pressing was taken and the heating was performed at a linear pressure of 50 kg / cm, and the basis weight was 1130 g / m ² . A dense nonwoven fabric structure having a density of 0.51 g / cm ³ is obtained, impregnated with an impregnation solution having a solid content concentration of 12.5% by mass, and a clearance of 80% of the thickness of the densified nonwoven fabric structure is taken to perform a roll nip treatment. Except that, the same operation as in Example 1 was performed to obtain a suede-like leather-like sheet. The impregnation ratio W ₁ was 77%, which was a numerical value corresponding to 63% with respect to the theoretical impregnation ratio W ₂ (122%).
This suede-like leather-like sheet also had homogeneous and dense napping on the surface. As a result of the pilling resistance test measurement by the ISO method on the surface of the obtained sheet, no pilling was observed. However, when a belt was produced and tested for practical use in the same manner as in Example 1, 10% residual elongation was observed in the circumferential direction after use, and wrinkles were generated in the belt while the belt was running. It could not withstand practical use in industrial materials such as belts.

Comparative Example 2
In Example 1, the same operation as in Example 1 was performed except that the clearance between the rolls during the roll / nip treatment was 60% of the thickness of the densified non-woven structure and the roll / nip treatment was performed. A sheet was obtained. The impregnation ratio W ₁ was 35%, which was a numerical value corresponding to 55% with respect to the theoretical impregnation ratio W ₂ (63%).
This suede-like leather-like sheet also had uniform and dense napping on the surface, but the fluff length was longer than that of Example 1. Using the obtained sheet, a belt was produced in the same manner as in Example 1 and a practical test was performed. The running property of the belt was good even after 24 hours, and the shape change (elongation, elongation) of the belt material after use. Strain) was 0.5% or less, but pilling due to friction with the driving roll was observed. In addition, as a result of the pilling resistance test measurement by the ISO method on the surface of the suede leather-like sheet, the occurrence of pilling was observed from around 2000 times, and it can be practically used in industrial materials such as conveyor belts. It was not.

  The suede-like leather-like sheet obtained by the production method of the present invention can be suitably used for industrial material applications such as conveyor belts that require both physical properties such as pilling resistance and breaking strength.

Claims (4)

A method for producing a suede-like leather-like sheet comprising the following steps (a) to (f):
(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 an apparent density of 0.66 g / cm ³ or more and 0.85 g / cm ³ or less,
(D) The densified non-woven structure is impregnated with a solution of an elastic polymer or an aqueous dispersion from both sides, and the following formula (1):
0.65 ≦ W ₁ / W ₂ ≦ 0.85 (1)
In the formula, W ₁ is the impregnation ratio with respect to the densified nonwoven structure of the polymer elastic body solution or aqueous dispersion, and can be obtained by the following formula (2).
_{W 1 = (W W -W D} ) / W D (2)
However, W _D: basis weight of the densified nonwoven structure before impregnated with a solution or dispersion of the elastic polymer (g / m ²⁾
W _W : The basis weight (g / m ² ) of the densified nonwoven structure after impregnating the polymer elastic body solution or aqueous dispersion, and W ₂ is completely filled with the voids in the densified nonwoven structure This is the impregnation ratio for the densified nonwoven fabric structure of the polymer elastic body solution or aqueous dispersion when assumed, and can be obtained by the following equation (3)
W ₂ = D ₂ × [1- (D ₁ / D ₃ )] / D ₁ (3)
However, D ₁ : Apparent density (g / cm ³ ) of the densified nonwoven structure
D ₂ : density of polymer elastic body solution or aqueous dispersion (g / cm ³ )
D ₃ : Density of fibers constituting the densified nonwoven structure (g / cm ³ )
Squeezing by roll nip treatment so as to satisfy the impregnation ratio W ₁ , then solidifying the polymer elastic body and then drying to obtain a polymer elastic body-impregnated nonwoven fabric structure,
(E) a step of removing a sea component from the sea-island fiber constituting the polymer elastic body-impregnated nonwoven fabric structure with water or an aqueous solution, and transforming the sea-island fiber into an ultrafine fiber bundle to obtain a base material for artificial leather;
And (f) a step of forming napping on at least one surface of the base material for artificial leather. The method for producing a suede-finished leather-like sheet according to claim 1, wherein the sea-island type fibers described in step (a) are long fibers. The method for producing a suede-like leather-like sheet according to claim 1 or 2, wherein a solid content concentration of the polymer elastic body solution or the aqueous dispersion in step (d) is 5 to 20% by mass. The suede tone leather-like sheet | seat obtained by the manufacturing method of any one of Claims 1-3.