JP2006233393A - Method for producing compact interlaced nonwoven fabric - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an interlaced nonwoven fabric which is suitable for producing a leather-like sheet substrate having both good bent wrinkles and natural leather-like stiff flexibility by treating with water without a chemical agent or the like. <P>SOLUTION: This method for producing the compact interlaced nonwoven fabric comprising ultra fine fiber-forming multi-component fibers containing a water-soluble thermoplastic polyvinyl alcohol-based resin as one component is characterized by imparting water in an amount of ≥5 mass% of the water-soluble resin component to an interlaced nonwoven fabric obtained by interlacing the multi-component fibers and then thermally treating the water-imparted interlaced nonwoven fabric in an atmosphere of a relative humidity of ≥75% to shrink the nonwoven fabric to give a nonwoven fabric area shrinkage factor of ≥15%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a dense entangled nonwoven fabric comprising ultrafine fiber-generating multicomponent fibers, each comprising a water-soluble thermoplastic polyvinyl alcohol resin, and a method for producing a leather-like sheet substrate using the entangled nonwoven fabric. About.

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 that 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 substrate for leather-like sheets, but the products on the market are actually made of fibers with a regular thickness of 0.5 dtex or more of artificial leather with a silver tone. Artificial leather using ultrafine fibers has not been put on the market yet. This is due to the difficulty in obtaining a long-fiber entangled sheet with a stable basis weight, the handleability of the production of ultrafine fiber-generating multicomponent fibers, and the unevenness of products due to unevenness and distortion of the ultrafine fiber-generating multicomponent 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, ultrafine fibers obtained by treating ultrafine fiber-generating multicomponent long fiber nonwoven fabrics obtained by melt spinning water-soluble thermoplastic polyvinyl alcohol and thermoplastic polymers with simple water without using chemicals. There has been proposed a method for obtaining a leather-like sheet substrate by impregnating an elastic polymer into a fiber nonwoven fabric (see, for example, Patent Document 3), but the leather-like sheet is treated with water without using chemicals. Assuming that a substrate is obtained, when an aqueous emulsion binder resin is impregnated and solidified to obtain a leather-like sheet substrate, the binder resin adheres to the ultrafine fibers and the texture is likely to be cured, and good folding is achieved. In order to obtain wrinkles, it is necessary to add a large amount of resin, and as a result, it has good folded wrinkles and natural leather-like waist. It is difficult to achieve both the umbrella.

JP 2000-273769 A (pages 3 to 5) JP-A 64-20368 (1-2 pages) JP 2003-328276 A (2-3 pages)

  An object of the present invention is to enable the production of a leather-like sheet substrate having both a good folding fold and a natural leather-like softness by treating with water without using chemicals or the like. is there. When using a non-woven fabric made of ultrafine fiber-generating multicomponent fibers with water-soluble resin as one component for treatment with water, the amount of polymer elastic body used is reduced and flexible. In order to impart properties, the nonwoven fabric needs to be shrunk and densified. However, after the nonwoven fabric is impregnated with a polymer elastic body, the nonwoven fabric cannot be shrunk, and the shrinking treatment must be carried out at the nonwoven fabric stage. When used, the water-soluble resin melts and the ultrafine fiber and the impregnated polymer elastic body adhere to each other and the texture is cured. Therefore, the water-soluble resin is a fiber until the polymer elastic body is impregnated and solidified. It needs to remain inside. From the above, it is necessary to perform shrinkage treatment at the stage of the nonwoven fabric. However, since the method of shrinking treatment in normal water cannot be used because the water-soluble resin is dissolved, the present invention is not limited to hot water or hot water. A method other than the method of shrinking the nonwoven fabric by dipping in the fabric is provided.

As a result of intensive studies conducted by the present inventors to achieve the above-mentioned problems, the present invention has been achieved. That is, the present invention is obtained by entanglement of the fibers in a method for producing a dense entangled nonwoven fabric composed of ultrafine fiber-generating multicomponent fibers containing a water-soluble thermoplastic polyvinyl alcohol resin as one component. The entangled nonwoven fabric is provided with 5% by mass or more of water of the water-soluble resin component, and is heat-treated in an atmosphere with a relative humidity of 75% or more so that the area shrinkage rate of the nonwoven fabric becomes 15% or more. A dense entangled nonwoven fabric produced by impregnating a water-based emulsion binder resin into the dense nonwoven fabric obtained by the above-described method and solidifying the water-soluble heat This is a method for producing a leather-like sheet substrate by extracting and removing a plastic polyvinyl alcohol resin.
And, preferably, the entangled nonwoven fabric is a long-fiber nonwoven fabric, and the water-soluble thermoplastic polyvinyl alcohol-based resin has an average polymerization degree of 200 to 500, a saponification degree of 90 to 99.99 mol%, and In this case, the melting point is 160 ° C to 230 ° C.

  According to the method for producing a dense entangled nonwoven fabric comprising ultrafine fiber-generating multicomponent fibers containing a water-soluble thermoplastic polyvinyl alcohol resin as one component of the present invention, ultrafine fibers suitable for a base of a leather-like sheet A generation type multicomponent fiber entangled sheet can be obtained, and the inside of the ultrafine fiber generation type multicomponent fiber nonwoven fabric is impregnated with a water-based emulsion binder resin, so that it is treated only with water without using chemicals. A leather-like sheet substrate can be produced by the method. In addition, by treating with simple water without using chemicals, etc., an ultra-fine fiber-generating multicomponent fiber-entangled nonwoven fabric sheet suitable as a leather-like sheet substrate can be obtained. It can be said that it is a sheet. Furthermore, the method for shrinking an entangled nonwoven fabric according to the present invention provides an ultrafine fiber long fiber entangled nonwoven fabric that is most suitable for the production of a leather-like sheet substrate that achieves both good folding folds and natural leather-like softness. .

Examples of specific means for achieving the present invention will be described below.
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. The entanglement process is performed to obtain a long fiber entangled sheet.

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, there is used a method in which 5% by mass or more of the water-soluble 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. Moreover, although there is no limitation in particular about the upper limit of the water to provide, it is generally 50 mass% or less of the PVA component for preventing the dissolved PVA from contaminating the process and for drying efficiency. The amount of water referred to in the present invention is a value based on the weight of the nonwoven fabric after leaving the nonwoven fabric in a standard state (23 ° C., 65% RH).
Specific methods for applying water include a method of spraying water on the nonwoven fabric, a method of applying water vapor or mist-like water droplets to the nonwoven fabric, a method of applying water to the nonwoven fabric surface, and the like. A method of imparting water droplets to the nonwoven fabric is preferred. In this case, as the temperature of water to be applied, a temperature at which PVA does not substantially dissolve is employed. 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 nonwoven fabric, or moisture may be simultaneously applied during the heat treatment. The shrinkage treatment is achieved by leaving the nonwoven fabric in the above atmosphere with as little force as possible. 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.

  At this time, the area shrinkage rate by the shrinkage treatment is preferably 15% or more for use as a leather-like sheet substrate. More preferably, it is 30% or more. When the area shrinkage rate is less than 15%, the apparent density of the obtained composite fiber entangled sheet is not sufficiently high, and it is difficult to maintain the form of the sheet. In addition to inconvenience in terms of handling or process passability, sufficient strength as a leather-like sheet substrate cannot be obtained, and a large amount of binder resin is required to improve shape retention, and natural leather-like waists are required. It becomes difficult to obtain softness with 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. By shrinking the nonwoven fabric in a state in which the PVA constituting the composite fiber is left by the shrinkage method, a high-density composite fiber entangled sheet is obtained. In the present invention, by using a high-density composite fiber entangled sheet, irregular wrinkles derived from long fibers and large irregularities generated on the surface are suppressed, and a good folded wrinkle is obtained, and a nonwoven fabric with less binder resin It is possible to keep the shape of the material 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.

In general, when manufacturing a leather-like sheet using a sea-island long fiber nonwoven fabric, it is difficult to suppress movement due to fiber expansion and contraction at high temperatures such as a sea component removal process, a dyeing process, and irregular wrinkles on the entire sheet surface, There are many cases where irregularities are generated on the surface, but by using the method of the present invention, the occurrence of irregular wrinkles and surface irregularities can be reduced, but if irregular wrinkles and irregularities on the surface still occur In a state where the remaining PVA in the present invention is plasticized or melted, the surface may be smoothed by performing a treatment such as pressing by a known method to reduce wrinkles and improve surface irregularities. .

In order to produce a leather-like sheet substrate by a method of treating only with water without using chemicals, which is one of the objects of the present invention, finally, an aqueous emulsion binder resin is impregnated and coagulated. PVA, which is one component of long fibers made of ultrafine fiber-generating multicomponent fibers, is dissolved and removed by water treatment, and ultrafine fibers are formed to form a leather-like sheet substrate. Here, in the method of impregnating and imparting a binder resin dissolved in an organic solvent into a fibrous sheet and treating it with a non-solvent to wet coagulate, the binder resin forms a continuous foamed state, and a small amount of binder is formed. Although it was possible to give form stabilization and natural leather-like texture with the resin, in the case of using the water-based emulsion binder resin without using chemicals, which is a preferred method of the present invention, the binder resin In order to obtain a continuous structure, a large amount of resin is required, and as a result, the texture tends to be hardened. Therefore, when the shrinkage method of the present invention is not applied, that is, one component of long fibers made of multi-component fibers that generate ultrafine fibers at the time of shrinkage treatment by performing shrinkage in hot water that is generally performed In the state where the PVA is dropped, the water-based emulsion binder resin is impregnated and solidified to obtain a leather-like sheet substrate, since the portion where the binder resin and the ultrafine fiber are bonded is cured. It is difficult to achieve both good folding folds and the softness of natural leather-like waist. However, in the present invention, since the water-based emulsion binder resin is contained in a state in which PVA, which is one component of long fibers, remains, the binder in the leather-like sheet substrate after dissolving and removing PVA, which is one component of long fibers, is used. Appropriate voids are formed between the resin and the ultrafine fibers, allowing the ultrafine fibers to move flexibly. Therefore, both good folding folds and softness with a natural leather-like waist are achieved. A leather-like sheet is obtained. Moreover, in the present invention, since the nonwoven fabric impregnated with the water-based emulsion binder resin has already been shrunk and densified, 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 leather-like sheet substrate thus obtained becomes a suede-like artificial leather by brushing and dyeing the surface by a known method. In addition, the surface of the leather-like sheet substrate is coated with a finishing elastic polymer added with a pigment to form a silver surface coating layer, or the surface is melted by heat to form a smooth surface. It is possible to use 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 are easy to develop shrinkage by heat treatment, and are particularly desirable from the viewpoint of texture and practical performance of processed products. 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. The mass ratio in the ultrafine fiber generation type multicomponent fiber before dissolving and removing the PVA resin is preferably 5 to 70% by mass. 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 melted and kneaded by separate extruders, and the molten resin flow is guided to the spinning head through the composite nozzle and discharged from the nozzle hole. After the fibers are cooled by a cooling device, they are pulled and thinned by high-speed airflow 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 a long fiber web can be produced by depositing on a movable collecting surface and partially pressing as required. 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 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 greater than 15%, so that the nonwoven fabric has 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 . Incidentally, the apparent density of the nonwoven fabric is calculated using the thickness value measured under a load of 1 cm ² per 0.7 g.

  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 obtained leather-like sheet substrate, the densified non-woven fabric obtained by the above method is subjected to surface smoothing with a calender roll as necessary, and an aqueous emulsion binder is contained therein. A leather-like sheet substrate can be manufactured through a step of impregnating and solidifying a resin, and a step of extracting and removing a water-soluble thermoplastic polyvinyl alcohol-based resin with hot water to make ultrafine fiber-generating multicomponent fibers 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 leather-like sheet substrate 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.
The average fineness of the fibers is the density of the resin used for fiber formation and the area of the cross section of the fibers constituting the sheet, observed at a magnification of about several hundred to several thousand times using a scanning electron microscope. Is calculated from 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) with 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 the above washing operation was repeated 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 the polymerization, a methanol solution of polyvinyl acetate obtained by precipitation in n-hexane and reprecipitation purification by dissolving with acetone was performed three times, followed by drying at 80 ° C. under reduced pressure 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.

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 4500 m / min, and long fibers having an average fineness of 2.0 dtex were collected by a net to obtain a 30 g / m ² long fiber web.

Equivalent parts of the above-mentioned eight long fiber webs were overlapped by cross wrapping and sprayed with an oil breakage preventing oil. Next, using a 1-barb needle with a distance of 5 mm from the needle tip to a barb, 3600 P / cm ² of needle punching is alternately performed from both sides at a needle depth of 10 mm, the long-fiber web is entangled, Obtained. The area shrinkage due to the needle punching treatment was 42%, and the delamination strength of the long fiber entangled nonwoven fabric after the needle punching treatment was 7 kg / 2.5 cm.

30% by mass of water is applied to the above-mentioned long fiber entangled nonwoven fabric with respect to the PVA, and it is left to stand under no tension for 3 minutes in an atmosphere of relative humidity of 95% and 70 ° C. And the apparent fiber density of the nonwoven fabric was improved to obtain a densified nonwoven fabric. The area shrinkage due to this densification treatment was 45%, the basis weight of the nonwoven fabric was 750 g / m ² , and the apparent density was 0.46 g / cm ³ . Subsequently, the densified nonwoven sheet 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 R A resin-containing nonwoven fabric sheet with / F = 18/82 was obtained. Subsequently, PVA was dissolved and removed in hot water at 95 ° C. to obtain an ultrafine fiber entangled sheet (leather-like sheet substrate) made of ultrafine fibers. The single fineness of the ultrafine fibers constituting the leather-like sheet substrate was 0.1 dtex. A 50 μm thick polyurethane film prepared on release paper was adhered to the obtained leather-like sheet substrate using a two-component urethane adhesive, and after drying and crosslinking reactions were sufficiently performed, the release paper was peeled off. A toned artificial leather with silver was obtained. The resulting silver-tone artificial leather was a flexible sheet having a good folding fold and a natural leather-like fulfillment.

  In Example 1, 10% by mass of water is applied to PVA, and the high pressure steam at 120 ° C. is directly ejected from the spray nozzle to the nonwoven fabric, except that the shrinkage is applied in 1 minute. An ultra-fine long fiber entangled nonwoven fabric was produced under the same conditions. The area shrinkage after heat shrinkage was 43%. A leather-like sheet was produced from the obtained high-density long fiber entangled sheet by the same process as in Example 1. As a result, the sheet was a flexible sheet having a good folding fold and a natural leather-like fulfillment.

Comparative Example 1
In Example 1, an ultra-thin fiber entangled nonwoven fabric was produced under the same conditions as Example 1 except that water was not applied. The area shrinkage after heat shrinkage was 13%. A leather-like sheet was produced from the obtained high-density long fiber entangled sheet by the same process as in Example 1, but although the texture was good, it was easy to bend and wrinkle and lacked a sense of fulfillment. The material for the sheet was not suitable.

Comparative Example 2
In Example 1, an ultra-thin fiber entangled nonwoven fabric was produced under the same conditions as Example 1 except that dry heat shrinkage was performed in a 70 ° C. atmosphere without applying water. The area shrinkage after heat shrinkage was 10%. A leather-like sheet was produced from the high-density long-fiber entangled non-woven fabric by the same process as in Example 1. Although the texture was good, it was easy to fold and wrinkle and lacked a sense of fulfillment. As unqualified.

According to the method for producing a dense entangled nonwoven fabric comprising ultrafine fiber-generating multicomponent fibers containing a water-soluble thermoplastic polyvinyl alcohol resin as one component of the present invention, ultrafine fibers suitable for a base of a leather-like sheet A dense entangled nonwoven fabric composed of generation type multicomponent fibers can be obtained, and by impregnating the inside of the entangled nonwoven fabric with a water-based emulsion binder resin, it is a method of treating only with water without using chemicals etc. A leather-like sheet substrate can be produced. In addition, a composite fiber entangled sheet as a leather-like substrate can be obtained by simply treating with water without using chemicals, so it can be said that it is an environment-friendly leather-like sheet substrate. The method for shrinking an entangled nonwoven fabric according to the present invention stabilizes the production of a long fiber entangled nonwoven fabric that is optimal for the production of a leather-like sheet substrate having both a good folding fold and a natural leather-like waist softness. It is possible to provide a method for shrinking an entangled nonwoven fabric for improving quality. The leather-like sheet 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 (4)

  In a method for producing a dense entangled nonwoven fabric composed of ultrafine fiber-generating multicomponent fibers comprising a water-soluble thermoplastic polyvinyl alcohol resin as a component, the entangled nonwoven fabric obtained by entanglement of the fibers, 5% by mass or more of water of the water-soluble resin component is applied, and heat treatment is performed in an atmosphere with a relative humidity of 75% or more, and the nonwoven fabric is contracted so that the area shrinkage rate is 15% or more. A method for producing a dense entangled nonwoven fabric.   The manufacturing method according to claim 1, wherein the entangled nonwoven fabric is a long-fiber nonwoven fabric.   The production method according to claim 1 or 2, wherein the water-soluble thermoplastic polyvinyl alcohol resin has an average polymerization degree of 200 to 500, a saponification degree of 90 to 99.99 mol%, and a melting point of 160 to 230 ° C. Production of a leather-like sheet substrate in which a dense nonwoven fabric obtained by the method according to any one of claims 1 to 3 is impregnated with a water-based emulsion binder resin and solidified to extract and remove the water-soluble thermoplastic polyvinyl alcohol-based resin. Method.