JP2011202311A - Base material for artificial leather and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base material for artificial leather originated from a compacting entangled nonwoven fabric in which the unit weight unevenness R in the width direction is reduced, and a method for producing the same.SOLUTION: The base material for artificial leather is produced by impregnating a compacting entangled nonwoven fabric which consists of ultrafine fiber occurrence-form multicomponent system fiber which uses a water-soluble thermoplastic polyvinyl alcohol system resin as one component with an aqueous emulsion binder resin, and after solidifying, carrying out extraction removing of this water-soluble thermoplastic polyvinyl alcohol system resin, where this compacting entangled nonwoven fabric has a unit weight unevenness R in the width direction expressed by the following formula of 5% or less. Unit weight unevenness R(%)=[maximum unit weight(g/m)-minimum unit weight(g/m)]×100/average unit weight(g/m) (wherein, the maximum unit weight is the maximum value when a sample with a length of 50 cm is extracted at intervals of 5 cm in the width direction of the compacting entangled nonwoven fabric and the unit weight is measured, the minimum unit weight is the minimum value when the unit weight is measured in the same way, and the average unit weight is an average value of all samples).

Description

  The present invention relates to a base material for artificial leather derived from a dense entangled nonwoven fabric composed of ultrafine fiber-generating multicomponent fibers containing a water-soluble thermoplastic polyvinyl alcohol resin as one component, and a method for producing the same.

In recent years, artificial leather has been recognized by consumers for features such as lightness and ease of handling, and has been widely used in clothing, general materials, sports fields and the like. A conventional method for producing a general artificial leather is roughly as follows. That is, ultrafine fiber generation type multi-component fibers composed of two types of polymers with different solubility are stapled, formed into a web using a card, a cross wrapper, a random weber, etc., and the fibers are entangled with each other by a needle punch or the like. A method of removing one component in the multi-component fiber of the ultrafine fiber generation after forming a entangled nonwoven fabric, solidifying by applying a solution or emulsion solution of a polymer elastic body represented by polyurethane, or a polymer In this method, the step of impregnating and coagulating the solution or emulsion of the elastic body and the step of removing one component in the ultrafine fiber generating multicomponent fiber are performed in the reverse order. By these methods, the fiber can be made ultrafine and a flexible artificial leather can be obtained.
In the field of artificial leather, a high quality product that satisfies all of the sensibility aspects such as appearance and texture and physical properties such as dimensional stability is required. Specifically, in order to obtain an artificial leather with excellent appearance, texture, etc., as described above, a method of removing one component in an ultrafine fiber-generating multicomponent fiber and making the fiber ultrafine is generally used. It has been.
The above method uses short fibers as the fibers, but when using long fibers instead of short fibers, as compared with the case of non-woven fabric made of short fibers, the raw cotton supplying device, fiber opening device, There is an advantage that a series of large-scale equipment such as a card machine and a crosslay machine is not required, and the strength is higher than that of the short fiber nonwoven fabric because it is made of long fibers.

As a method for producing an ultrafine long-fiber nonwoven fabric, the multicomponent fiber constituting the ultrafine fiber-generating multicomponent long-fiber nonwoven fabric composed of two or more incompatible polymers is divided in the length direction to form a polymer. The method of peeling off at the interface and making it ultrafine is mainly applied. However, in this case, there is a limit to the uniform division of the fiber by the separation method, and it is difficult to obtain ultrafine fibers that can be applied to suede-like artificial leather. On the other hand, in order to obtain an ultrafine long fiber nonwoven fabric composed of only one component, one polymer must be removed from the ultrafine fiber generation type multicomponent long fiber nonwoven fabric composed of two or more incompatible polymers. Had to use chemicals. For example, when removing polyester, caustic soda or the like is used as a chemical, formic acid or the like is used for polyamide, and trichlorethylene or toluene or the like is used for polystyrene.
However, such a method requires special extraction and removal equipment from the viewpoint of handling chemicals and environmental pollution, and is not fully satisfactory in terms of safety and health of workers and manufacturing costs. . In addition, the component other than the component to be removed is undesirably affected by the removal treatment, so the combination of components constituting the ultrafine fiber-generating multicomponent fiber is limited, or the component to be removed cannot be sufficiently removed. In some cases, satisfactory quality nonwoven fabric and artificial leather could not be obtained.

  On the other hand, polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) is a water-soluble polymer, and its basic skeleton, molecular structure, form, and various modifications can change the degree of water-solubility, and melt spinnability. It is known that it is possible to provide It has also been confirmed that PVA is biodegradable. From these facts, PVA and PVA fibers having such basic performance are attracting much attention nowadays, which is a big issue on how to harmonize the synthetic material with the natural world in the global environment.

  Attempts have been made to use long fibers as a non-woven fabric base material for leather, but the products on the market are actually artificial fibers with silver-like fibers having a regular thickness of 0.5 decitex or more. Artificial leather using ultrafine fibers has not been put on the market yet. This is because it is difficult to obtain a long-fiber entangled nonwoven fabric with a stable basis weight, handleability in the production of ultrafine fiber-generating multicomponent fibers, and product unevenness due to unevenness and distortion of ultrafine fiber-generating multicomponent long fibers. It is assumed that this is the cause. In fact, when the same manufacturing method as that when short fibers are used is applied to the ultra-fine long-fiber nonwoven fabric, wrinkle defects occur in the sheet in the ultra-fine fiber forming process, the dyeing process, etc., and it is difficult to produce a stable product.

  As a method of eliminating such unevenness, a method of partially cutting long fibers and partially eliminating strain has been proposed (for example, see Patent Document 1). The contribution to the strong physical properties due to the continuous nature of the fibers is reduced, and the characteristics of the long fibers cannot be fully utilized. In addition, a method of suppressing a fiber shape change by introducing a reinforcing fabric such as a woven or knitted fabric (for example, refer to Patent Document 2) has been proposed. Even if it is effective for preventing the dropout, it cannot resist the strain relaxation of the fiber and may cause a wrinkle defect. In any of the above methods, on the premise of treating with water without using chemicals or the like, in the method of obtaining a leather-like sheet substrate by impregnating and solidifying an aqueous emulsion binder resin, a good folding crease is obtained. In order to obtain it, it is necessary to add a large amount of resin, and as a result, it becomes difficult to obtain a softness with a natural leather-like waist.

  In addition, it can be obtained by treating ultrafine fiber-generating multicomponent long-fiber nonwoven fabrics with water by a method obtained by melt spinning water-soluble thermoplastic polyvinyl alcohol and a thermoplastic polymer without using chemicals. A method for obtaining a leather-like sheet substrate by impregnating an elastic polymer inside an ultra-thin fiber non-woven fabric (for example, see Patent Document 3) has been proposed, but it is treated with water without using chemicals. On the premise of obtaining a leather-like sheet substrate, when an aqueous emulsion binder resin is impregnated and solidified to obtain a leather-like sheet substrate, the texture of the binder tends to harden due to adhesion of the binder resin to the ultrafine fibers, and In order to obtain a good folding fold, it is necessary to add a large amount of resin, and as a result, a good folding fold and a natural leather-like waist It is difficult to achieve both Ruyawaraka of.

On the other hand, in the case of using a nonwoven fabric composed of ultrafine fiber-generating multicomponent fibers containing a water-soluble resin as a component as a substrate for artificial leather, the amount of polymer elastic body used is reduced to provide flexibility. In addition, the nonwoven fabric must be shrunk and densified. However, the nonwoven fabric cannot be shrunk after the nonwoven fabric is impregnated with the polymer elastic body, and the shrinkage treatment needs to be performed at the nonwoven fabric stage. However, in the case of using a method of shrinking in normal water, the water-soluble resin is melted and becomes ultrafine fibers, so that the impregnated polymer elastic body adheres and the texture is cured. . For this reason, it is necessary that the water-soluble resin remains in the fiber until the time when the polymer elastic body is impregnated and solidified.
Therefore, the applicant of the present invention is a method for producing a densified entangled nonwoven fabric composed of ultrafine fiber-generating multicomponent fibers containing a water-soluble thermoplastic polyvinyl alcohol resin as a component, and the entanglement obtained by entanglement of the fibers. Applying 5% by mass or more water of the water-soluble resin component to the composite nonwoven fabric, and heat-treating it in an atmosphere with a relative humidity of 75% or more to shrink the nonwoven fabric so that the area shrinkage ratio is 15% or more. A characteristic manufacturing method was proposed (Patent Document 4).

JP 2000-273769 A JP-A 64-20368 JP 2003-328276 A JP 2006-233393 A

However, even in the method for producing a dense entangled nonwoven fabric described in Patent Document 4, when the same amount of water is uniformly applied in the width direction, the shrinkage rate is higher at the end than at the center, and after shrinkage, the end There was a problem in that the weight of the toner was higher than that of the central portion and did not become a uniform weight in the width direction, that is, there was unevenness in the weight in the width direction.
An object of this invention is to provide the base material for artificial leather originating in the densified entangled nonwoven fabric with few fabric weight unevenness of the width direction, and its manufacturing method.

  As a result of intensive research, the inventors have given water so as to reduce the amount of water to be applied to the end portion from the center portion in the width direction of the entangled nonwoven fabric, and then contracted by heat treatment. The present invention was completed by discovering that the substrate for artificial leather with less unevenness R in the width direction can be obtained.

That is, the present invention provides the following (1) to (8).
(1) A water-soluble thermoplastic polyvinyl polyvinyl alcohol resin is impregnated with a water-based emulsion binder resin on a densified entangled nonwoven fabric composed of ultra-fine fiber-generating multi-component fibers containing a water-soluble thermoplastic polyvinyl alcohol resin as one component. It is a base material for artificial leather from which alcohol resin is extracted and removed,
The densified entangled nonwoven fabric is a base material for artificial leather having a fabric weight unevenness R in the width direction represented by the following formula of 5% or less.
Unevenness of basis weight R (%) = [maximum basis weight (g / m ² ) −minimum basis weight (g / m ² )] × 100 / average basis weight (g / m ² )
(In the formula, the maximum basis weight is the maximum value when a sample having a length of 50 cm is taken at intervals of 5 cm in the width direction of the densified entangled nonwoven fabric, and the basis weight is determined. The minimum basis weight is the same as the basis weight. (The average weight is the average value of all samples.)
(2) The following steps (a) to (e):
(A) a step of forming an ultrafine fiber-generating multicomponent fiber having a water-soluble thermoplastic polyvinyl alcohol resin as one component into a fiber web;
(B) a step of entanglement treatment of the fiber web to obtain an entangled nonwoven fabric;
(C) End portion (A) and end portion (A ′), and the remaining portion of the entangled nonwoven fabric in a proportion of 5 to 20% with respect to the length of the entire width from both ends, each having the same width Is divided into three parts, A / B / A ′, with the central part (B)
Water of 5% by mass or more of the water-soluble thermoplastic polyvinyl alcohol resin component,
The mass ratio of water applied to the both ends and the center is 20 to 30/50/20 to 30 in the end (A) / center (B) / end (A ′), and the end (A). / End (A ′) = 1/1,
A step of obtaining a densified entangled nonwoven fabric having a density of 0.34 g / cm ³ or more by heat-treating in an atmosphere having a relative humidity of 75% or more to shrink the nonwoven fabric so that the area shrinkage ratio is 15% or more;
(D) impregnating and imparting an aqueous emulsion binder resin to the densified entangled nonwoven fabric, and then coagulating the aqueous emulsion binder resin to obtain an aqueous emulsion binder resin impregnated nonwoven fabric; and (e) the aqueous emulsion binder resin impregnated nonwoven fabric. Extracting and removing the water-soluble resin component with water or an aqueous solution from the ultrafine fiber-generating multicomponent fiber constituting the ultrafine fiber generating multicomponent fiber, and transforming the ultrafine fiber generating multicomponent fiber into an ultrafine fiber bundle,
Alternatively, the following steps (a) to (b), (f) and (d) to (e):
(A) a step of forming an ultrafine fiber-generating multicomponent fiber having a water-soluble thermoplastic polyvinyl alcohol resin as one component into a fiber web;
(B) a step of entanglement treatment of the fiber web to obtain an entangled nonwoven fabric;
(F) In the entangled nonwoven fabric, the end portion (C), the end portion (C ′), the intermediate portion (D), the intermediate portion (D ′), and the central portion (E) on both sides in the width direction are C It is divided into five so as to be / D / E / D '/ C',
The width of the central part (E) is 30 to 50% of the full width, the width of each end part (C, C ′) is 5 to 15% of the full width, and the width of each intermediate part (D, D ′) is 10 to 10% of the full width. 30%, the ends (C, C ′) and the intermediate portions (D, D ′) are divided into the same width, and the ends (C, C ′) The middle parts (D, D ′) are divided into the same width,
Water of 5% by mass or more of the water-soluble thermoplastic polyvinyl alcohol resin component,
The mass ratio of the end (C) / center (E) and the end (C ′) / center (E) is applied to be 40 to 60/100,
The mass ratio of the intermediate part (D) / central part (E) and the intermediate part (D ′) / central part (E) is 70 to 90/100, and the mass of the end part (C) / end part (C ′). The ratio and the mass ratio of the intermediate part (D) / intermediate part (D ′) are respectively given to be 1/1,
A step of obtaining a densified entangled nonwoven fabric having a density of 0.34 g / cm ³ or more by heat-treating in an atmosphere having a relative humidity of 75% or more to shrink the nonwoven fabric so that the area shrinkage ratio is 15% or more;
(D) impregnating the densified entangled nonwoven fabric with a solution of an aqueous emulsion binder resin and then coagulating the aqueous emulsion binder resin to obtain a binder resin impregnated nonwoven fabric; and (e) the aqueous emulsion binder resin impregnated nonwoven fabric. The water-soluble thermoplastic polyvinyl alcohol resin component is extracted and removed with water or an aqueous solution from the ultrafine fiber-generating multicomponent fiber constituting the base, and the ultrafine fiber-generating multicomponent fiber is transformed into an ultrafine fiber bundle to form a base for artificial leather Obtaining a material,
The manufacturing method of the base material for artificial leather containing this.
(3) The manufacturing method as described in said (2) whose entangled nonwoven fabric is a long-fiber nonwoven fabric.
(4) Silver-tone artificial leather obtained by forming a silver layer on the surface of the artificial leather substrate according to (1).
(5) Suede-like artificial leather obtained by raising the surface of the base material for artificial leather according to (1).

The base material for artificial leather of the present invention has a fabric weight unevenness in the width direction as small as 5% or less, so that the resulting artificial leather also has quality defects in the width direction such as strength unevenness, dyeing unevenness, bending wrinkle unevenness, and tactile sensation. It is possible to obtain artificial leather of uniform quality in the width direction, which is compatible with both good folding folds and natural leather-like softness.
In addition, the method for manufacturing a base material for artificial leather according to the present invention is characterized by adjusting the amount of moisture to be given by dividing in the width direction in the densification entanglement process step, so that the shrinkage of the end portion is suppressed. Therefore, it is possible to provide a method for manufacturing a base material for artificial leather that can be achieved with a relatively simple device without requiring an end gripping means or a special device.
Furthermore, in the base material for artificial leather and the method for producing the same according to the present invention, the ultrafine fiber is passed through a dense entangled nonwoven fabric composed of ultrafine fiber-generating multicomponent fibers containing a water-soluble thermoplastic polyvinyl alcohol resin as one component. By impregnating the generation type multicomponent fiber nonwoven fabric with an aqueous emulsion binder resin, it can be obtained by a method of treating only with water without using chemicals. Moreover, since the base material for artificial leather can be obtained by simply treating with water without using chemicals, an environment-friendly base material for artificial leather can be provided.

Examples of specific means for achieving the present invention will be described below.
In the present invention, the ultrafine fiber-generating multicomponent 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 effect 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.
Hereinafter, the case where the ultrafine fiber generation type multicomponent fiber is a long fiber will be described.
First, an ultrafine fiber having a single yarn fineness of 0.0003 to 0.5 dtex is formed after forming an ultrafine fiber using a water-soluble thermoplastic polyvinyl alcohol resin (hereinafter sometimes abbreviated as PVA) as one component. It is represented by needle punching treatment by forming a long fiber web using filaments composed of multi-component fibers that can generate ultrafine fibers, and laminating the long fiber web by a method such as cross wrapping as necessary. To make a long fiber entangled nonwoven fabric.

Next, the nonwoven fabric needs to be densified by shrinking the long fiber nonwoven fabric after the entanglement treatment such as needle punching. In the present invention, a method is used in which 5% by mass or more of the water-soluble thermoplastic polyvinyl alcohol-based resin (PVA) component is applied to the long-fiber nonwoven fabric and heat-treated in an atmosphere having a relative humidity of 75% or more. . Preferably, it is a case where 10% by mass or more of water of the PVA component is applied to the long-fiber nonwoven fabric in an atmosphere having a relative humidity of 90% or more. And, as the shrinkage treatment temperature, shrinking under the condition of the atmospheric temperature of 60 ° C. or more is preferable in terms of easy management on equipment and imparting high shrinkage to the long fiber nonwoven fabric. At this time, if the amount of moisture applied to the long-fiber nonwoven fabric is less than 5% by mass, the water-soluble resin component of the ultrafine fiber-generating multicomponent fiber is insufficiently plasticized, and tends to prevent the filament from shrinking. Therefore, a sufficient shrinkage rate cannot be obtained. On the other hand, when the relative humidity is less than 75%, the applied water quickly dries, so that the water-soluble resin is cured, and sufficient shrinkage cannot be obtained. The upper limit value of the water to be applied is not particularly limited, but it is generally 50% by mass or less of the PVA component for preventing the dissolved PVA from contaminating the process and for the drying efficiency. . The amount of water applied in the present invention is a value based on the mass of the nonwoven fabric after the nonwoven fabric is left in a standard state (23 ° C., 65% RH).
In addition, the calculation method about the application | coating amount of the water which provides 5 mass% or more of water of a PVA component is the PVA component which occupies for the fabric weight of a fine fiber generation type | mold multicomponent fiber which comprises the fabric weight of an entangled nonwoven fabric, and this entangled nonwoven fabric previously From this, it is possible to easily calculate, and according to this calculation method, necessary moisture is added.

  As a method for applying water, in order to make the fabric weight in the width direction uniform and the fabric weight unevenness R to be 5% or less, it is preferable that both ends (A, A ′) and A / B / A ′ of the remaining central portion (B), and the basis weight [end (A) and end ( In order to make the difference between the average value of the basis weight of A ′) and the basis weight (average value of the basis weight of the central portion (B)) in the remaining central portion (B) within 3%, The non-woven fabric is divided into three parts, A / B / A ′ at both ends (A, A ′) having a width of at least 5 to 20% of the total width and A / B / A ′ at the remaining central part (B), and water-soluble thermoplastic polyvinyl alcohol system The mass ratio of water which gives 5% by mass or more of the resin component to both ends and the center is 40 to 60/100 at both ends / center. Sea urchin to grant. Specifically, a method of spraying water on the entangled nonwoven fabric at a predetermined ratio as described above, A / B / A ′, and water vapor or mist-like water droplets on the entangled nonwoven fabric. The method of providing, the method of apply | coating water to the surface of an entangled nonwoven fabric, etc. are mentioned, Especially the method of providing water vapor | steam or a mist-like water droplet to an entangled nonwoven fabric is preferable.

In the present invention, both end portions, both intermediate portions, and the central portion as sections mean zones each having a length divided in the width direction, and the end portion (A) or the end portion (C) The end (A ′) or the end (C ′) is the center in the width direction of the entangled nonwoven fabric [the center of the center (B) or (E). When the two ends corresponding to each other are referred to as the same width dimension with respect to the longitudinal center line passing through the A, A ′), both end portions (C, C ′), each end portion (A, A ′), and each portion (C, C ′).
The same applies to the intermediate part (D) and the intermediate part (D ′), which are located at the line target position with respect to the longitudinal center line passing through the center of the central part (E), and the intermediate parts are the same. When the two corresponding intermediate portions are collectively referred to, both end portions (C, C ′), both intermediate portions (D, D ′), or each end portion (C, C ′) These are called intermediate portions (D, D ′).

Further, in order to make the fabric weight in the width direction uniform and make the fabric weight unevenness R 5% or less, preferably in the densified entangled nonwoven fabric, at least both ends (A, A ′) having a width of 5 to 20% of the total width and the remainder Is divided into three parts of A / B / A ′ of the central part (B), and the basis weight of the end part (A) or the end part (A ′) [the basis weight of the end part (A) and the end part (A ′) In the second aspect of the water application method of the present invention, the difference between the basis weight (average value of the basis weight of the central portion (B)) in the remaining central portion (B) is within 3%. The entangled nonwoven fabric is divided into five in the width direction so as to be C / D / E / D ′ / C ′ in both end portions (C, C ′), both intermediate portions (D, D ′) and the central portion (E). Divided into
The width of the central part (E) is 30 to 50% of the full width, the width of each end part (C, C ′) is 5 to 15% of the full width, and the width of each intermediate part (D, D ′) is 10 to 10% of the full width. 30%,
Water of 5% by mass or more of the water-soluble thermoplastic polyvinyl alcohol resin component,
The end portion (C) / center portion (E) and the end portion (C ′) / center portion (E) are given a mass ratio of 40 to 60/100, and the intermediate portion (D) / center portion (E ) And the intermediate part (D ′) / center part (E) so as to have a mass ratio of 70 to 90/100, and each end part (C, C ′) and each intermediate part (D, D ′). ) Are given so as to have the same mass. In this case, a temperature at which PVA does not substantially dissolve is employed as the temperature of water to be applied.

  Moreover, as a specific water application sequence, heat treatment may be performed in an atmosphere with a relative humidity of 75% or more after water is applied to the entangled nonwoven fabric, or moisture may be simultaneously applied during the heat treatment. . The shrinkage treatment is achieved by leaving the entangled nonwoven fabric in the above atmosphere in a state where as little force as possible is applied. The time required for the shrinkage treatment is preferably 1 to 5 minutes from the viewpoint of productivity and from the viewpoint that sufficient shrinkage can be imparted.

Furthermore, as a method of changing the mass of water to be applied to at least both ends and the center, in the first and second aspects described above, stepwise for each segment so that the same mass is imparted in the same segment. To change. In this case, for example, a predetermined spray amount may be supplied for each section in the width direction from a spray nozzle or the like corresponding to the length of the section. In addition, as a method of changing the amount of water continuously in the width direction instead of stepwise, for example, a spray capable of making the speed of the spray nozzle that reciprocates in the width direction faster than the center at both ends. If the traverse device is employed, both ends are smaller than the central portion, and the moisture adhesion amount in the width direction is set to a predetermined profile, so that unevenness in the width direction can be reduced.
As a method for controlling the spray traverse, for example, a method of controlling the rotational speed of the AC servo motor by the control means to increase the moving speed of the nozzles at both end portions from the central portion in the width direction can be exemplified.

At this time, it is preferable to use it as an artificial leather base material by shrinking so that the area shrinkage rate by shrinkage treatment is 15% or more to obtain a densified entangled nonwoven fabric having a density of 0.34 g / cm ³ or more. . More preferably, the area shrinkage rate is 30% or more. When the area shrinkage rate is less than 15%, the apparent density of the densified entangled nonwoven fabric obtained is not sufficiently high, and it is difficult to maintain the shape of the nonwoven fabric. In terms of handling and process passability, it is not possible to obtain sufficient strength as a base material for artificial leather, and a large amount of binder resin is required to improve the shape retention, and natural leather-like It becomes difficult to obtain the softness of the waist. Furthermore, when the area shrinkage rate is less than 15%, irregular wrinkles that the nonwoven fabric has derived from long fibers and large irregularities generated on the surface remain after shrinkage, and a large amount for improvement. Binder resin is required, which adversely affects the texture. The shrinkage of the nonwoven fabric is expressed in the state where the PVA constituting the composite fiber is left by the shrinkage method, and a high-density composite fiber-entangled nonwoven fabric, so-called densified entangled nonwoven fabric is obtained. In the present invention, by using a high-density composite fiber entangled nonwoven fabric, irregular wrinkles derived from long fibers and large irregularities generated on the surface are suppressed, and a good folded wrinkle is obtained, and with a small amount of binder resin It is possible to keep the shape of the nonwoven fabric well, and as a result, it is possible to obtain a softness with a natural leather-like waist. The upper limit of the degree of shrinkage is about 60% in terms of area shrinkage in terms of uniformity when shrinkage is manifested.

The average apparent density of the densified entangled nonwoven fabric is, for example, 0.34 g / cm ³ or more, preferably 0.34 to ³ when the island component polymer is polyethylene terephthalate and the sea component polymer is water-soluble thermoplastic polyvinyl alcohol. 0.85 g / cm ^3, more preferably 0.40~0.65g / cm ^3. The average apparent density can be obtained by a method that does not apply a compressive load, for example, a method by cross-sectional observation with an electron microscope or the like. The basis weight of the densified entangled nonwoven fabric is preferably 500 to 2000 g / m ² .

The basis weight unevenness R in the width direction of the densified entangled nonwoven fabric obtained in this way must be 5% or less. The basis weight unevenness R is obtained by the following formula.
(Formula); basis weight unevenness R (%) = [maximum basis weight (g / m ² ) −minimum basis weight (g / m ² )]
× 100 / average basis weight (g / m ² )
(In the formula, the maximum basis weight is the maximum value when samples having a length of 50 cm are taken at intervals of 5 cm in the width direction of the densified entangled nonwoven fabric, and the basis weight is obtained. (The average weight is the average value of all samples.)
The basis weight unevenness R in the width direction of the densified entangled nonwoven fabric is preferably 5% or less, more preferably 3% or less from the viewpoint of obtaining a base material for artificial leather that is homogeneous in the width direction.
If the fabric weight unevenness R in the width direction is 5% or less, an artificial leather with little quality variation in the width direction can be obtained from the base material for artificial leather.
And preferably in a densified entangled non-woven fabric, it is divided into three parts of A / B / A ′ of at least both ends (A, A ′) of the width of 5 to 20% of the total width and the remaining central part (B). , The basis weight [average value of the basis weight of the end portion (A) and the end portion (A ′)] in the end portion (A) or the end portion (A ′) and the basis weight [center portion (B If the difference in the average value of the weight per unit area] is within 3%, an artificial leather with less quality unevenness in the width direction can be obtained.

  In general, when manufacturing a base material for artificial leather using a sea-island long-fiber non-woven fabric, it is difficult to suppress movement due to fiber expansion and contraction at high temperatures such as the sea component removal process and the dyeing process, and the entire surface of the base material for artificial leather There are many cases where irregular wrinkles and irregularities occur on the surface, but by using the method of the present invention, the occurrence of irregular wrinkles and irregularities on the surface can be reduced. In the case where the occurrence occurs, the remaining PVA in the present invention is plasticized or melted and subjected to a treatment such as pressing by a known method to smooth the surface, reduce wrinkles, and reduce the surface roughness. Improvements may be made.

In order to produce a substrate for artificial leather by a method of treating only with water without using chemicals, which is one of the objects of the present invention, finally, impregnation with a water-based emulsion binder resin, solidification treatment, PVA, which is one component of long fibers made of ultrafine fiber-generating multicomponent fibers, is dissolved and removed by hot water treatment, and ultrafine fiber processing is performed to obtain a base material for artificial leather. Here, in a method of impregnating a densified entangled nonwoven fabric dissolved in a conventional organic solvent and treating it with a non-solvent of the binder resin to wet coagulate, the binder resin forms a continuous foamed state, Although it was possible to give form stabilization and natural leather-like texture with a small amount of binder resin, in the case of using an aqueous emulsion binder resin without using chemicals, which is a preferred method of the present invention. In order to obtain a continuous structure of the binder resin, a large amount of resin is required, and as a result, the texture tends to be cured. Therefore, when the shrinkage method for densification according to the present invention is not applied, that is, the shrinkage in hot water which is generally performed is performed, and the ultrafine fiber generation type multicomponent fiber is formed during the shrinkage treatment. In the state where PVA, which is one component of long fibers, is dropped, it is impregnated with water-based emulsion binder resin and solidified to obtain a base material for artificial leather, and the binder resin and the ultrafine fiber are bonded. Since the part hardens, it is difficult to achieve both good folding folds and the softness of natural leather-like waist. However, in the present invention, since the PVA which is one component of the long fiber is left to be contained in the aqueous emulsion binder resin, the base material for artificial leather after dissolving and removing the PVA which is one component of the long fiber is used. Appropriate voids are formed between the binder resin and the ultra-fine fibers, allowing the ultra-fine fibers to move flexibly, so that both good folding folds and softness with a natural leather-like waist are achieved. Thus, a base material for artificial leather is obtained. Moreover, in the present invention, the densified entangled nonwoven fabric impregnated with the water-based emulsion binder resin has already been contracted and densified, so that the amount of binder resin to be applied can be relatively reduced.
In the present invention, the amount of the aqueous emulsion binder resin to be applied is preferably 2 to 40% by mass in terms of solid content with respect to the mass of the nonwoven fabric after PVA extraction and removal. If the amount is less than this range, the fixing of the ultrafine fibers becomes insufficient, resulting in poor bending wrinkles, form stability, and surface smoothness. More preferably, it is 5-25 mass%.

  The base material for artificial leather thus obtained becomes a suede-like artificial leather by brushing and dyeing the surface by a known method. Also, by applying an elastic polymer for finishing with a pigment added to the surface of such a base material for artificial leather and forming a silver surface coating layer, or by melting the surface with heat to make a smooth surface, silver It is also possible to use a toned artificial leather.

  In the present invention, the ultrafine fiber generation type multicomponent fiber for obtaining a nonwoven fabric composed of the ultrafine fiber generation type multicomponent fiber is not particularly limited, and a method represented by a chip blend (mixed spinning) method or a composite spinning method. Can be appropriately selected from sea-island cross-sectional fibers, multilayer laminated cross-sectional fibers, radial laminated cross-sectional fibers, etc. obtained by using water-soluble thermoplastic polyvinyl alcohol resins as sea components and water-insoluble thermoplastic resins. The sea-island cross-section ultrafine fiber generation type multicomponent fiber as an island component is preferable in terms of less fiber damage during needle punching and the uniformity of the ultrafine fiber. The water-insoluble thermoplastic resin is not particularly limited, but is polyester such as polyethylene terephthalate (hereinafter referred to as PET), polytrimethylene terephthalate, polybutylene terephthalate (hereinafter referred to as PBT), polyester elastomer, nylon 6 and the like. Nylon 66, nylon 610, nylon 12, polyamides such as aromatic polyamides and polyamide elastomers, polyurethanes, polyolefins and other polymers having fiber forming ability are suitable. Among these, polyester resins such as PET and PBT, especially modified PET, are easy to develop shrinkage by heat treatment, and are particularly desirable from the viewpoint of the texture and practical performance of the processed product. These polymers preferably have a melting point of 160 ° C. or higher. When the temperature is lower than 160 ° C., the shape stability is inferior, which is not preferable from the viewpoint of practicality. More preferably, it is a fiber-forming crystalline resin having a melting point of 180 to 250 ° C. In the present invention, the melting point is raised to 300 ° C. at a heating rate of 10 ° C./min in nitrogen using a differential scanning calorimeter (hereinafter referred to as DSC), cooled to room temperature, and then raised again. The temperature at the peak top of the endothermic peak indicating the melting point of the polymer when the temperature is raised to 300 ° C. at a rate of 10 ° C./min is employed. In addition, colorants such as dyes and pigments, ultraviolet absorbers, heat stabilizers, deodorants, fungicides, and various stabilizers may be added to the resin constituting the ultrafine fibers.

  In the present invention, a water-soluble thermoplastic PVA resin is used as the matrix component of the ultrafine fiber-generating multicomponent fiber. The use of the resin comprehensively improves the spinnability, environmental pollution, easiness of dissolution and removal of the composite fiber. It was selected in consideration of the situation. That is, the composite fiber nonwoven fabric using such a PVA resin as one component is heat-treated in a state of being plasticized with water, so that the density of the nonwoven fabric can be increased and the water-based emulsion binder resin is applied, By removing by dissolution, voids are created between the ultrafine fibers and the binder resin, and the densification and texture of the artificial leather are very similar to those of natural leather. Become. As a mass ratio which occupies in the ultrafine fiber generation type | mold multicomponent fiber before PVA-type resin melt | dissolution removal, 5-70 mass% is preferable. More preferably, it is 10-60 mass%, Most preferably, it is 15-50 mass%. If the ratio of the PVA resin in the ultrafine fiber-generating multicomponent fiber decreases, the spinning stability of the composite fiber decreases, and the flexibility of the artificial leather decreases, which is not preferable. As the amount increases, the amount of moisture applied to the entangled nonwoven fabric during shrinkage increases and the excess moisture is dried, resulting in a decrease in productivity and a large amount of binder resin for stabilizing the form of artificial leather. It becomes necessary and is not preferable. A preferred embodiment of the water-soluble thermoplastic PVA resin itself will be described later.

In the present invention, the form of the fiber and the nonwoven fabric is preferably a long-fiber nonwoven fabric composed of ultrafine fiber-generating multicomponent long fibers as described above. Such a long-fiber nonwoven fabric is a so-called spunbond directly connected to melt spinning. It can be efficiently produced by the method for producing a nonwoven fabric. That is, the water-soluble thermoplastic PVA resin and the water-insoluble thermoplastic resin are melt-kneaded by separate extruders, and the melted resin stream is guided to the spinning head through the composite nozzle and discharged from the nozzle hole. After the composite fiber is cooled by a cooling device, it is pulled by a high-speed air current at a speed corresponding to the take-up speed of the composite fiber of 1000 to 6000 m / min so as to achieve the desired fineness using a suction device such as an air jet nozzle. And can be deposited on a movable collection surface and partially crimped as necessary to produce a long fiber web. The fineness of the resulting ultrafine fiber-generating multicomponent fiber is preferably in the range of 1.0 to 5.0 dtex, and the basis weight of the long fiber web is preferably in the range of ^{20 to} 500 g / m ² from the viewpoint of process handleability. Moreover, it is preferable to set the cross-sectional shape of the ultrafine fiber-generating multicomponent fiber so that the single fiber fineness after the ultrafine fiber is in the range of 0.0003 to 0.5 dtex. If it is less than 0.0003 dtex, it is not preferable because the dyeability is difficult when it is made into a suede-like artificial leather. If it exceeds 0.5 dtex, it becomes inferior in flexibility and appearance quality when it is made into artificial leather. It is not preferable. More preferably, it is in the range of 0.2 to 0.01 dtex.

In some cases, a plurality of fiber webs deposited on the collecting surface are overlapped and needle punched to make a nonwoven fabric, but there are no particular restrictions on so-called needle conditions such as oil agent, needle shape, needle depth, number of punches, etc. And can be appropriately selected from known methods. For example, the needle shape is more efficient when the number of barbs is larger, but it can be selected from 1 to 9 barbs as long as needle breakage does not occur, and the depth is such that the needle needle barbs penetrate to the back of the nonwoven fabric. In addition, the needle mark can be set within a range that is not strong. The apparent density of the nonwoven fabric after needle punching is preferably 0.10 g / cm ³ or more. When the apparent density of the nonwoven fabric after needle punching is less than 0.10 g / cm ³ , the area shrinkage obtained by heat-treating the nonwoven fabric needs to be larger than 15%, and the nonwoven fabric should have a uniform and dense structure. It becomes difficult. More preferably, the apparent density is in the range of 0.13 to 0.20 g / cm ³ . The apparent density of the nonwoven fabric is calculated using the thickness value measured with a load of 0.7 g per 1 cm ² .

  Next, PVA used for the nonwoven fabric of this invention is explained in full detail. As PVA used for the ultrafine fiber generating multicomponent fiber constituting the nonwoven fabric of the present invention, those having an average degree of polymerization (hereinafter simply referred to as degree of polymerization) of 200 to 500 are preferable, and in particular, a range of 230 to 470. The thing of 250-450 is preferable and the thing of 250-450 is especially preferable. When the degree of polymerization is less than 200, the melt viscosity is too low and it is difficult to obtain a stable composite. When the degree of polymerization exceeds 500, the melt viscosity is too high, and it becomes difficult to discharge the resin from the spinning nozzle. By using so-called low polymerization degree PVA having a polymerization degree of 500 or less, there is also an advantage that the dissolution rate is increased when dissolving with hot water.

The average degree of polymerization (P) of PVA here is a value measured according to JIS-K6726. That is, after re-saponifying and purifying PVA, it is obtained by the following equation from the intrinsic viscosity [η] measured in water at 30 ° C.
P = ([η] 10 ³ /8.29) ^{(1 / 0.62)}
When the degree of polymerization is in the above range, the object of the present invention can be achieved more suitably.

  The saponification degree of the PVA used in the present invention is preferably in the range of 90 to 99.99 mol%, more preferably in the range of 93 to 99.98 mol%, and further in the range of 94 to 99.97 mol%. The range of 96 to 99.96 mol% is particularly preferable. When the degree of saponification is less than 90 mol%, the thermal stability of PVA is poor, and not only satisfactory melt spinning cannot be performed by thermal decomposition or gelation, but also biodegradability is reduced. Depending on the type of copolymerization monomer, the water-solubility of PVA decreases, and the composite fiber of the present invention may not be obtained. On the other hand, it is difficult to stably produce PVA having a saponification degree larger than 99.99 mol%.

  The PVA used in the present invention has biodegradability, and is decomposed into water and carbon dioxide when treated with activated sludge or buried in soil. The activated sludge method is preferable for the treatment of the PVA-containing waste liquid after dissolving the PVA. When the PVA aqueous solution is continuously treated with activated sludge, it is decomposed in 2 days to 1 month. Moreover, since PVA used for this invention has low combustion heat and the load with respect to an incinerator is small, you may incinerate PVA by drying the waste_water | drain which melt | dissolved PVA.

  160-230 degreeC is preferable, as for melting | fusing point (Tm) of PVA used for this invention, 170-227 degreeC is more preferable, 175-224 degreeC is especially preferable, and 180-220 degreeC is especially preferable. When the melting point is less than 160 ° C., the crystallinity of PVA is lowered and the fiber strength is lowered. On the other hand, when the melting point exceeds 230 ° C., the melt spinning temperature becomes high, and the spinning temperature and the decomposition temperature of PVA are close to each other, so that PVA fibers cannot be stably produced.

  The melting point of PVA is that when DSC is used, the temperature is raised to 300 ° C. in nitrogen at a heating rate of 10 ° C./min, cooled to room temperature, and then heated again to 300 ° C. at a heating rate of 10 ° C./min. It means the temperature at the peak top of the endothermic peak indicating the melting point of PVA.

  The PVA used in the present invention can be obtained by saponifying a resin mainly composed of vinyl ester units. 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 used in the present invention may be a homopolymer or a modified PVA into which copolymer units are introduced. However, from the viewpoint of melt spinnability, water solubility, and fiber properties, copolymer units are introduced. It is preferable to use modified PVA. As the kind of the comonomer, α-olefins having 4 or less carbon atoms such as ethylene, propylene, 1-butene and isobutene, methyl vinyl ether, Vinyl ethers such as ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether and n-butyl vinyl ether are preferred. Units derived from α-olefins having 4 or less carbon atoms and / or vinyl ethers are preferably present in PVA in an amount of 1 to 20 mol%, more preferably 4 to 15 mol% of PVA constituent units. ˜13 mol% is particularly preferred. Further, when the α-olefin is ethylene, the fiber physical properties are high, and therefore, this is a case where a modified PVA into which ethylene units are introduced in an amount of 4 to 15 mol%, more preferably 6 to 13 mol% is used. .

  Examples of the PVA used in the present invention include known methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. 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 alcohol used as a solvent during solution polymerization include lower alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol. Examples of the initiator used for copolymerization include a, a′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethyl-valeronitrile), benzoyl peroxide, and n-propyl peroxycarbonate. And known initiators such as azo initiators or peroxide initiators. Although there is no restriction | limiting in particular about superposition | polymerization temperature, The range of 0 to 150 degreeC is suitable.

In order to improve the surface smoothness of the base material for artificial leather, the densified entangled nonwoven fabric obtained by the above method is subjected to surface smoothing with a calender roll as necessary, and an aqueous emulsion binder resin is provided inside. The base material for artificial leather can be manufactured through the steps of impregnating and solidifying, and by extracting and removing the water-soluble thermoplastic polyvinyl alcohol resin with hot water to make the ultrafine fiber-generating multicomponent fiber ultrafine. . Here, it is preferable from the viewpoint of artificial leather that the water-based emulsion binder resin solution to be impregnated is subjected to thermal gelation treatment or thickening treatment to suppress migration during solidification and drying.
Examples of the resin constituting the water-based emulsion binder resin to be impregnated include polyvinyl chloride, polyamide, polyester, polyester ether copolymer, polyacrylate copolymer, polyurethane, neoprene, styrene butadiene copolymer, silicone resin, polyamino acid, and polyamino acid polyurethane. A synthetic resin such as a copolymer or a natural polymer resin, or a mixture thereof can be used. If necessary, pigments, dyes, crosslinking agents, fillers, plasticizers, various stabilizers, and the like may be added. Among them, polyurethane or a material obtained by adding other resin to the polyurethane is preferably used as a polymer elastic body because a soft texture can be obtained. The resin concentration in the aqueous emulsion binder resin solution is preferably 3 to 40% by mass.
The PVA component of the ultrafine fiber-generating multicomponent fiber constituting the nonwoven fabric is extracted and removed from the nonwoven fabric after impregnating, coagulating and drying the emulsion. As a method of extracting and removing, a dyeing machine such as a liquid dyeing machine and a jigger, and a scouring machine such as an open soaper can be used, but the method is not particularly limited thereto. The water temperature of the extraction bath to be used is preferably 80 to 95 ° C. As a preferable operation method, the operation of squeezing the nonwoven fabric after immersing the nonwoven fabric in the extraction bath is repeated a plurality of times, so that most or all of the PVA components are removed. Extract and remove. At this time, the nonwoven fabric may shrink due to the water temperature, which may result in a more dense feeling and a sense of fulfillment.

  The base material for artificial leather thus obtained can be made into a suede-like artificial leather by fluffing the surface, and further, if necessary, softening treatment and dyeing treatment. As a method for fluffing, buffing using sandpaper or a needle cloth can be used. In addition, by applying a resin for the surface coating layer under the desired conditions by a known method, and further performing processes such as embossing, softening treatment, and dyeing, the surface is heated and melted to smooth the surface. By doing it, it can also be set as the artificial leather of a tone with silver, or a tone with semi-silver. These artificial leathers are free of wrinkles, have a natural leather-like richness, and have a drape characteristic derived from long fibers. For clothing, shoes, gloves, bags, baseball gloves, belts, balls It is suitable as a material for product use such as for interior use such as a sofa or a sofa.

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.
In addition, the average fineness of the fiber is the density of the resin used for fiber formation and is observed at a magnification of about several hundred to several thousand times using a scanning electron microscope. It is calculated from the area of the cross section. Further, the parts and% described in the examples relate to the mass unless otherwise specified.
The melting point of the resin was measured using a DSC (TA3000, manufactured by Mettler) measuring device in nitrogen at a heating rate of 10 ° C./min to 300 ° C., then cooled to room temperature, and again a heating rate of 10 ° C./min. The temperature at the peak top of the endothermic peak indicating the melting point of the resin when the temperature was raised to 300 ° C. was adopted.

Production Example 1
[Production of water-soluble thermoplastic polyvinyl alcohol resin]
A 100-liter pressurized reactor equipped with a stirrer, nitrogen inlet, ethylene inlet and initiator addition port was charged with 29.0 kg of vinyl acetate and 31.0 kg of methanol, heated to 60 ° C., and then bubbled for 30 minutes with nitrogen bubbling. Was replaced with nitrogen. Next, ethylene was introduced and charged so that the reactor pressure was 5.9 kg / cm ² . A solution of 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) (hereinafter sometimes abbreviated as AMV) as an initiator in a concentration of 2.8 g / L in methanol was prepared, and nitrogen was added. Nitrogen substitution was performed by bubbling with gas. After adjusting the temperature inside the polymerization tank to 60 ° C., 170 ml of the initiator solution was injected to start polymerization. During the polymerization, ethylene was introduced to maintain the reactor pressure at 5.9 kg / cm, the polymerization temperature at 60 ° C., and AMV was continuously added at 610 ml / hr using the above initiator solution. . 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. Next, unreacted vinyl acetate monomer was removed under reduced pressure to obtain a methanol solution of polyvinyl acetate. 46.5 g (polyvinyl acetate in acetic acid of polyvinyl acetate) was added to 200 g of polyvinyl acetate in methanol (100 g of polyvinyl acetate in the solution) adjusted to a concentration of 50% by adding methanol to the obtained polyvinyl acetate solution. Saponification was performed by adding an alkaline solution (NaOH in 10% methanol) having a molar ratio (MR) of 0.10 to the vinyl unit. About 2 minutes after the addition of alkali, the gelled system was pulverized with a pulverizer and allowed to stand at 60 ° C. for 1 hour to proceed with saponification, and then 1000 g of methyl acetate was added to neutralize the remaining alkali. . After confirming the end of neutralization using a phenolphthalein indicator, 1000 g of methanol was added to the white solid PVA obtained by filtration, and the mixture was left to wash at room temperature for 3 hours. After repeating the above washing operation three times, the PVA obtained by centrifugal drainage was left in a dryer at 70 ° C. for 2 days to obtain dry PVA.

  The saponification degree of the obtained ethylene-modified PVA was 98.4 mol%. Further, after the modified PVA was incinerated, the content of sodium measured by an atomic absorption photometer using a material dissolved in an acid was 0.03 parts by mass with respect to 100 parts by mass of the modified PVA. In addition, after removing the unreacted vinyl acetate monomer after polymerization, a methanol solution of polyvinyl acetate obtained by precipitation in n-hexane and reprecipitation purification by dissolving with acetone was performed three times, and then dried under reduced pressure at 80 ° C. for 3 days. To obtain purified polyvinyl acetate. When the polyvinyl acetate was dissolved in d6-DMSO and measured at 80 ° C. using 500 MHz proton NMR (JEOL GX-500), the ethylene content was 10 mol%. After saponifying the above methanol solution of polyvinyl acetate at an alkali molar ratio of 0.5, the pulverized product was allowed to stand at 60 ° C. for 5 hours to proceed saponification, followed by methanol soxhlet for 3 days, Ethylene-modified PVA purified by drying under reduced pressure at 80 ° C. for 3 days was obtained. It was 330 when the average degree of polymerization of this PVA was measured according to JIS K6726 of the usual method. The amount of 1,2-glycol bond and the content of hydroxyl group of three-chain hydroxyl group in the purified PVA were determined as described above from the measurement with a 5000 MHz proton NMR (JEOL GX-500) apparatus, and found to be 1.50 mol% and 83%, respectively. Met. Further, a cast film having a thickness of 10 microns was prepared by preparing a 5% aqueous solution of the purified modified PVA. The film was dried under reduced pressure at 80 ° C. for 1 day, and then the melting point was measured by the above-described method using DSC.

Example 1
The water-soluble thermoplastic PVA is used as a sea component, polyethylene terephthalate having an isophthalic acid modification degree of 6 mol% is used as an island component, and the number of islands per ultrafine fiber-generating multicomponent fiber is 25 islands. Using a melt compound spinning die, the mixture was discharged from the die at 260 ° C. so that the mass ratio of sea component / island component was 30/70. The ejector pressure was adjusted so that the spinning speed was 3500 m / min, and long fibers having an average fineness of 2.0 dtex were collected by a net to obtain a 36 g / m ² long fiber web.

A portion corresponding to the 18 long fiber webs was overlapped by cross wrapping and sprayed with an oil breakage preventing oil. Next, using a 6 barb needle with a distance of 3 mm from the tip of the needle to the barb, the needle depth was gradually decreased from 10 mm, and needle punching of 3600 P / cm ² was alternately performed from both sides to form a long fiber web. Entanglement was performed to obtain a long fiber nonwoven fabric having a width of 200 cm and a basis weight of 771 g / m ² . The area shrinkage due to this needle punching treatment was 16%, and the delamination strength of the long fiber entangled nonwoven fabric after the needle punching treatment was 9 kg / 2.5 cm.

20 cm (end C, C ′) from the end to the long fiber entangled nonwoven fabric having a width of 200 cm is provided with 15% by mass of water relative to the PVA, and the range of 20 to 60 cm from the end (intermediate part) D, D ′) gives 25% by weight of water to the PVA, and the remaining central part (center (E)) gives 30% by weight of water to the PVA. The total amount of water applied was 25% by mass relative to the PVA.
Under an atmosphere of relative humidity of 95% and 70 ° C., heat treatment was performed for 3 minutes to cause shrinkage, and the apparent fiber density of the nonwoven fabric was improved. By this densification treatment, the width becomes 150 cm, the maximum value of the basis weight of 30 samples measured at intervals of 5 cm in the width direction (length direction 50 cm) of the nonwoven fabric is 1420 g / m ² , the minimum value is 1380 g / m ² , and the average The basis weight is 1400 g / m ² , the ratio of the maximum value to the minimum value in the width direction with respect to the average basis weight value, that is, the basis weight unevenness R is 2.9%, and both end portions from the end of the densified entangled nonwoven fabric to 20 cm (A, A ′) and A / B / A ′ of the remaining central part (B), and the basis weight (from the end to the A part or A ′ from the end to the A part or from the end to the A ′ part) A densified entangled nonwoven fabric having a difference between the basis weight (average value of basis weight) and the basis weight (average value of the basis weight of the central portion excluding A and A ′) in the remaining part B was 1.6%.

  Next, the densified entangled nonwoven fabric is dry-heated and roll-pressed, impregnated with Superflex E-4800 (Daiichi Kogyo Seiyaku Co., Ltd.) as an aqueous polyurethane emulsion, dried and cured at 150 ° C., and the resin fiber ratio A resin-containing nonwoven fabric sheet having R / F = 18/82 was obtained. Subsequently, PVA was dissolved and removed in hot water at 95 ° C. to obtain an ultrafine fiber entangled sheet (base material for artificial leather) made of ultrafine fibers. The single fineness of the ultrafine fibers constituting the base material for artificial leather was 0.1 dtex. After a polyurethane film having a thickness of 50 μm prepared on a release paper is bonded to the obtained artificial leather substrate using a two-component urethane adhesive, and after sufficient drying and crosslinking reaction, the release paper The artificial leather with silver tone was obtained. The obtained silver-tone artificial leather was a flexible sheet having a uniform folding fold and a natural leather-like fulfillment uniformly throughout the width direction.

Comparative Example 1
In Example 1, a densified non-woven fabric was formed under the same conditions as in Example 1 except that water in an amount of 30% by mass was uniformly applied to the PVA in the width direction of the long fiber entangled non-woven fabric after needle punching. Furthermore, a silver-finished artificial leather was obtained from the densified nonwoven fabric.
The maximum weight of the densified nonwoven fabric measured at an interval of 5 cm in the width direction (length direction: 50 cm) is 1470 g / m ² at the extreme end, 1330 g / m ^{2 at} the center, and the average weight is 1400 g / m ² . m ² , the ratio of the maximum value-minimum value of the fabric weight in the width direction with respect to the average fabric weight, that is, the fabric unevenness R was 10.0%. Further, the obtained silver-tone artificial leather had a texture that became harder as the central part in the width direction became more flexible and became an end, and had a non-uniform texture in the width direction.

Since the base material for artificial leather of the present invention has a basis weight unevenness R of a densified entangled nonwoven fabric composed of ultrafine fiber-generating multicomponent fibers containing a water-soluble thermoplastic polyvinyl alcohol resin as one component, it is 5% or less. It can be effectively used as a base material for artificial leather with a soft silver tone, which has a uniform folding fold and a natural leather-like sense of uniformity across the entire width direction.
The method for producing a base material for artificial leather according to the present invention obtains a densely entangled nonwoven fabric having a small amount of unevenness in the width direction made of an ultrafine fiber-generating multicomponent fiber that is suitable for a base material for artificial leather. By impregnating the water-based emulsion binder resin inside the synthetic nonwoven fabric, it is possible to produce a base material for artificial leather by a method that uses only water without using chemicals. It can be used as a method for manufacturing a material.
The method for producing a silver-tone or suede-like artificial leather according to the present invention is to stabilize the production while improving the quality while reducing the fabric weight unevenness in the width direction of the long-fiber entangled nonwoven fabric that is optimal for the base material for artificial leather. Through the entangled nonwoven fabric densification treatment, it can be used as a method for producing a silver-tone or suede-like artificial leather having both a good crease and a natural leather-like softness.
The silver-tone or suede-like artificial leather obtained by the present invention can be applied to leather products represented by shoes, balls, furniture, vehicle seats, clothing, gloves, baseball gloves, bags, belts or bags.

Claims (5)

A water-soluble thermoplastic polyvinyl alcohol resin is impregnated with a water-based emulsion binder resin in a densified entangled nonwoven fabric composed of ultrafine fiber-generating multi-component fibers containing a water-soluble thermoplastic polyvinyl alcohol resin as one component, and then solidified. A base material for artificial leather from which
The densified entangled nonwoven fabric is a base material for artificial leather having a fabric weight unevenness R in the width direction represented by the following formula of 5% or less.
Unevenness of basis weight R (%) = [maximum basis weight (g / m ² ) −minimum basis weight (g / m ² )] × 100 / average basis weight (g / m ² )
(In the formula, the maximum basis weight is the maximum value when a sample having a length of 50 cm is taken at intervals of 5 cm in the width direction of the densified entangled nonwoven fabric, and the basis weight is determined. The minimum basis weight is the same as the basis weight. (The average weight is the average value of all samples.) The following steps (a) to (e):
(A) a step of forming an ultrafine fiber-generating multicomponent fiber having a water-soluble thermoplastic polyvinyl alcohol resin as one component into a fiber web;
(B) a step of entanglement treatment of the fiber web to obtain an entangled nonwoven fabric;
(C) End portion (A) and end portion (A ′), and the remaining portion of the entangled nonwoven fabric in a proportion of 5 to 20% with respect to the length of the entire width from both ends, each having the same width Is divided into three parts, A / B / A ′, with the central part (B)
Water of 5% by mass or more of the water-soluble thermoplastic polyvinyl alcohol resin component,
The mass ratio of water applied to the both ends and the center is 20 to 30/50/20 to 30 in the end (A) / center (B) / end (A ′), and the end (A). / End (A ′) = 1/1,
A step of obtaining a densified entangled nonwoven fabric having a density of 0.34 g / cm ³ or more by heat-treating in an atmosphere having a relative humidity of 75% or more to shrink the nonwoven fabric so that the area shrinkage ratio is 15% or more;
(D) impregnating and imparting an aqueous emulsion binder resin to the densified entangled nonwoven fabric, and then coagulating the aqueous emulsion binder resin to obtain an aqueous emulsion binder resin impregnated nonwoven fabric; and (e) the aqueous emulsion binder resin impregnated nonwoven fabric. The water-soluble thermoplastic polyvinyl alcohol resin component is extracted and removed with water or an aqueous solution from the ultrafine fiber-generating multicomponent fiber constituting the base, and the ultrafine fiber-generating multicomponent fiber is transformed into an ultrafine fiber bundle to form a base for artificial leather Obtaining a material,
Alternatively, the following steps (a) to (b), (f) and (d) to (e):
(A) a step of forming an ultrafine fiber-generating multicomponent fiber having a water-soluble thermoplastic polyvinyl alcohol resin as one component into a fiber web;
(B) a step of entanglement treatment of the fiber web to obtain an entangled nonwoven fabric;
(F) In the entangled nonwoven fabric, the end portion (C), the end portion (C ′), the intermediate portion (D), the intermediate portion (D ′), and the central portion (E) on both sides in the width direction are C It is divided into five so as to be / D / E / D '/ C',
The width of the central part (E) is 30 to 50% of the full width, the width of each end part (C, C ′) is 5 to 15% of the full width, and the width of each intermediate part (D, D ′) is 10 to 10% of the full width. 30%, and the end portions (C, C ′) and the intermediate portions (D, D ′) are divided into the same width,
Water of 5% by mass or more of the water-soluble thermoplastic polyvinyl alcohol resin component,
The mass ratio of the end (C) / center (E) and the end (C ′) / center (E) is applied to be 40 to 60/100,
The mass ratio of the intermediate part (D) / central part (E) and the intermediate part (D ′) / central part (E) is 70 to 90/100, and the mass of the end part (C) / end part (C ′). The ratio and the mass ratio of the intermediate part (D) / intermediate part (D ′) are respectively given to be 1/1,
A step of obtaining a densified entangled nonwoven fabric having a density of 0.34 g / cm ³ or more by heat-treating in an atmosphere having a relative humidity of 75% or more to shrink the nonwoven fabric so that the area shrinkage ratio is 15% or more;
(D) impregnating and imparting an aqueous emulsion binder resin to the densified entangled nonwoven fabric, and then coagulating the aqueous emulsion binder resin to obtain an aqueous emulsion binder resin impregnated nonwoven fabric; and (e) the aqueous emulsion binder resin impregnated nonwoven fabric. The water-soluble thermoplastic polyvinyl alcohol resin component is extracted and removed with water or an aqueous solution from the ultrafine fiber-generating multicomponent fiber constituting the base, and the ultrafine fiber-generating multicomponent fiber is transformed into an ultrafine fiber bundle to form a base for artificial leather Obtaining a material,
The manufacturing method of the base material for artificial leather containing this.   The manufacturing method according to claim 2, wherein the entangled nonwoven fabric is a long-fiber nonwoven fabric.   A silver-finished artificial leather obtained by forming a silver coating layer on the surface of the base material for artificial leather according to claim 1.   A suede-like artificial leather obtained by raising a surface of the base material for artificial leather according to claim 1.