JP4647295B2 - Method for producing flame-retardant sheet - Google Patents

Description

  The present invention relates to a method for producing a flame retardant sheet material useful as a leather-like sheet substrate.

Conventionally, synthetic fibers, particularly polyester fibers, polyamide fibers, and the like have been indispensable as materials for clothing, interiors, and the like in terms of their excellent dimensional stability, weather resistance, mechanical properties, and durability. However, depending on the application, it is desired to give further special functions. For example, it is extremely important to provide flame retardancy in the interior field, in particular, in the field of artificial leather used as a covering material for railcar seats, automobile seats, aircraft seats and the like.
For imparting flame retardant performance, methods using halogen-based flame retardants, typically brominated flame retardants, have been generally used, but problems such as high toxicity during combustion and high environmental impact Therefore, substitution with non-halogen flame retardants is progressing.
In general, non-halogen flame retardants typified by phosphorus flame retardants are inferior to halogen flame retardants in the amount of addition, so a large amount of flame retardants must be prescribed for imparting flame retardancy, and artificial leather When it is applied to applications that require texture and softness, there is a problem that texture hardening occurs.

  The present inventors have previously disclosed a method for producing artificial leather using phosphorus-modified polyester in order to maintain the texture and achieve flame resistance in a halogen-free manner (see Patent Document 1). . This method makes it possible to produce a sheet-like material having a certain level of flame retardancy, but there is a problem that the physical properties of the fiber deteriorate due to phosphorus modification, and it is used for applications that require high strength properties and wear resistance. It was impossible.

  In the conventional method for producing artificial leather, short fibers have been mainly used as the nonwoven fabric base, but if long fibers are used instead of the short fibers as the nonwoven fabric base, compared to a nonwoven fabric made of short fibers, The sheet physical property improvement resulting from the continuity of the fiber can be expected. Moreover, there is an advantage that a series of large-scale facilities such as a raw cotton supply device, a fiber opening device, and a card machine are not required as the manufacturing method.

  Attempts have been made to use long fibers as a nonwoven fabric base material for leather-like sheets, but products that are actually on the market are regular fibers of 0.5 decitex or more as the base material for artificial leather with silver. Artificial leather using ultrafine fibers has not been put on the market yet. This is presumably caused by the difficulty in obtaining a long-fiber entangled sheet with a stable basis weight, the handleability of the production of ultra-fine fiber-generating composite spun fibers, and product unevenness due to unevenness and distortion of the composite long fibers. . 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 (see, for example, Patent Document 2) can be considered. There are cases where the contribution to the strong physical properties due to the connected fibers is reduced and the characteristics of the long fibers cannot be fully utilized. In addition, a method of introducing a reinforcing fabric such as a woven or knitted fabric to suppress fiber shape change (see, for example, Patent Document 3) is conceivable. However, simply introducing a reinforcing fabric does not cause the fibers to fall off due to friction or the like. Even if it is effective for the prevention effect, it may not resist the strain relaxation of the fiber and may cause a wrinkle defect.

JP 2002-115183 A Japanese Patent No. 3176492 JP-A 64-20368

  An object of the present invention is to provide a method for producing a flame-retardant sheet material having both flame retardancy and strength properties by utilizing an ultra-thin fiber entangled sheet that has been difficult to use as a nonwoven fabric substrate of a leather-like sheet. It is to provide.

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 difficult to entangle, shrink, and process ultrafine fibers of a long fiber web composed of ultrafine fiber-generating fibers composed of a water-soluble thermoplastic polyvinyl alcohol resin and a phosphorus-modified polyester resin. When making a flammable sheet,
I. The delamination strength after the entanglement treatment is 2 kg / 2.5 cm or more,
II. The area shrinkage rate by the shrinkage treatment after the entanglement treatment is 35% or more,
III. It ultrafine fiber is a fiber composed of phosphorus-modified polyester resin by the following average phosphorus concentration of 3 000 ppm or more 20000 ppm,
Is a method for producing a flame-retardant sheet.
And it is preferable that this entanglement process is a needle punch process, and it is preferable that a contraction process is a hot water contraction process. Further, the water-soluble thermoplastic polyvinyl alcohol resin preferably has a viscosity 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.

  Further, the present invention is a method for producing a flame retardant leather-like sheet substrate comprising a step of impregnating a polymer elastic body into a flame retardant sheet material obtained by any of the above methods, It is a flame-retardant leather-like sheet substrate obtained by a method for producing a heat-resistant leather-like sheet substrate.

  According to the method for producing a flame retardant sheet material of the present invention, a flame retardant sheet material suitable for a base of a flame retardant leather-like sheet can be obtained, and a polymer is formed inside the flame retardant sheet material. By impregnating the elastic body, a flame-retardant leather-like sheet substrate can be produced. Further, a suede-like or nubuck-like leather-like sheet is obtained by fluffing the surface of the leather-like sheet substrate, and the surface of the leather-like sheet substrate is coated with a resin or melted with heat or a solvent. By using as a resin layer, a leather-like sheet having a silver surface can be obtained. These leather-like sheets are excellent in flame retardancy and mechanical performance, have a natural leather-like fineness and texture, and are excellent in softness and aesthetics.

  An example of a specific means for achieving the present invention is that the single yarn fineness after ultrafinening using a water-soluble thermoplastic polyvinyl alcohol resin (hereinafter sometimes abbreviated as PVA) and a phosphorus-modified polyester resin. A long fiber entangled sheet is formed using a filament composed of sea-island type composite fibers capable of forming ultrafine fiber long fibers of 0.0003 to 0.5 dtex, and this long fiber entangled sheet is used as necessary. A long fiber entangled sheet that is laminated by a method such as cross wrapping and is entangled three-dimensionally so that the delamination strength is at least 2 kg / 2.5 cm by entanglement treatment, thereby improving the apparent fiber density of the sheet. And Next, by shrinking the sheet by 35% or more by shrinking treatment, the apparent fiber density of the sheet is further improved, and the PVA component is removed to express ultrafine fibers. It is made into a sheet-like material. Here, the long fiber entangled sheet constituting the flame retardant sheet is not necessarily composed of the phosphorus-modified polyester alone, and is a mixture or laminate of the phosphorus-modified polyester and the unmodified polyester. In other words, it is necessary that the phosphorus concentration in the entire long fiber entangled sheet constituting the flame retardant sheet-like material, that is, the average phosphorus concentration of the ultrafine fibers is 3000 ppm or more and 20000 ppm or less.

  The obtained flame-retardant sheet can be used as it is as a flame-retardant sheet, but preferably has a stable form-retaining property by impregnating a polymer elastic body as a binder. It is possible to make a leather-like sheet substrate, and the surface of the flame-retardant leather-like sheet substrate thus obtained is ground in the same manner as described above, and then subjected to a dyeing treatment to make it difficult to suede. A flame-retardant leather-like sheet can be obtained, and it is also possible to form a flame-retardant leather-like sheet with a silver tone by forming a skin on the surface.

In the present invention, the ultrafine fiber generation type fiber for obtaining the long fiber entangled sheet composed of the ultrafine fiber generation type fiber is not particularly limited, and the sea-island type obtained by using a method represented by a mixed spinning method or a composite spinning method. Long fibers made of ultrafine fiber-generating fibers having a water-soluble thermoplastic polyvinyl alcohol-based resin as a sea component and a polyester-based resin as an island component are preferable.
Polyester resins such as polyethylene terephthalate (hereinafter also referred to as PET), polytrimethylene terephthalate, polybutylene terephthalate (hereinafter also referred to as PBT), and polyester elastomer are used as the polyester resin. Although not particularly limited, phosphorus-modified polyester resins are mainly used from the viewpoint of imparting flame retardancy. Further, the phosphorus-modified resin and the unmodified resin may be separately used as a composite fiber with a PVA resin.
Further, these polymers preferably have a melting point of 160 ° C. or higher. When the temperature is lower than 160 ° C., the form stability is inferior, which is not preferable from the viewpoint of practicality. The melting point was raised to 250 ° C. at a temperature rising rate of 10 ° C./min in nitrogen using a differential scanning calorimeter (hereinafter referred to as DSC), cooled to room temperature, and again heated to 10 ° C. The temperature at the peak top of the endothermic peak indicating the melting point of the polymer when the temperature is raised to 250 ° C. per minute is employed.

  In the present invention, a water-soluble thermoplastic polyvinyl alcohol-based resin is used as the sea component of the ultrafine fiber-generating fiber, but the use of the resin was selected in consideration of environmental pollution, shrinkage characteristics during dissolution and removal, and the like. Is. That is, when such a polyvinyl alcohol-based resin is used for dissolution and removal, large shrinkage occurs, and the densification of the ultrafine fiber entangled sheet constituting the flame-retardant sheet is achieved, and the leather-like sheet The draping and texture when done are very similar to natural leather. As a mass ratio which occupies in the ultra fine fiber generation type | mold fiber before polyvinyl alcohol-type resin melt | dissolution removal, 5-70 mass% is preferable. More preferably, it is 10-60 mass%, Most preferably, it is 15-50 mass%. A preferred embodiment of the water-soluble thermoplastic polyvinyl alcohol resin itself will be described later.

In the present invention, the long fiber web composed of ultrafine fiber-generating fibers can be efficiently produced by a method of producing a so-called spunbond nonwoven fabric directly connected to melt spinning, and includes a water-soluble thermoplastic polyvinyl alcohol resin and a water-insoluble thermoplastic. The resin is melted and kneaded with separate extruders, the melted resin flow is guided to the spinning head through the composite nozzle and discharged from the nozzle hole, and the discharged composite fiber is cooled by a cooling device, and then an air jet nozzle, etc. It is necessary to use a suction device to make it fine with a high-speed air stream 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 and deposit it on the mobile collection surface. Depending on the case, it can be manufactured by partial pressure bonding. The fineness of the ultrafine fiber-generating long fibers 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. In addition, it is possible to set the number of islands of sea-island fibers so that the single fiber fineness after forming ultrafine fibers is in the range of 0.0003 to 0.5 dtex. It is preferable in terms of excellent flexibility and appearance quality when formed into a sheet.

The long fiber web obtained as described above is overlaid using a cross wrapper or the like as needed, an oil agent is applied, and an entanglement process is performed by a known method. Further, it is preferable to perform the needle punching process from the viewpoint of three-dimensionally entanglement and easy improvement of the apparent density of the sheet. The number of overlaps and the basis weight can be appropriately set depending on the target thickness of the leather-like sheet, but the total basis weight after the overlap is preferably in the range of 100 to 1000 g / m ² from the viewpoint of process handling. Here, it is possible to superimpose a long fiber web composed of a composite fiber of a phosphorus-modified polyester resin and a PVA resin and a long fiber web composed of a composite fiber of an unmodified polyester resin and a PVA resin. It is necessary to set the concentration of the phosphorus-modified resin, the mixing rate, or the web lamination rate so that the average phosphorus concentration in the flame-retardant sheet material is 3000 ppm or more and 20000 ppm or less after removing the fiber and removing ultrafine fibers. is there.

  In the needle punching process, it is necessary to entangle the long fiber web so that the delamination strength of the long fiber entangled sheet after needle punching is 2 kg / 2.5 cm or more. The delamination strength is a measure of the degree of three-dimensional entanglement. When the delamination strength is less than 2 kg / 2.5 cm, the entanglement is insufficient, and the density is high due to the shrinkage treatment process such as hot water shrinkage. When a leather-like sheet is obtained through the process, sufficient strong physical properties cannot be obtained, and wrinkle defects are caused due to the fact that the fibers are easily displaced.

There are no particular limitations on so-called needle conditions such as the oil agent, the needle shape, the needle depth, the number of punches, etc. for satisfying such conditions, and it can be appropriately selected from known methods. For example, the needle shape is more efficient when the number of barbs is larger, but can be selected from 1 to 9 barbs within a range where needle breakage does not occur, and the depth is such that the needle needle barbs penetrate to the nonwoven fabric surface. In addition, it can be set within a range where the needle mark does not appear strongly. The necessary number of punches varies depending on the selection of needle type, oil agent, etc., but 500 to 5000 punches / cm ² is preferable. In any case, it is necessary to entangle so that the delamination strength is 2 kg / 2.5 cm or more.

  Next, it is necessary to shrink the long fiber entangled sheet after the entanglement process such as a needle punch. Although the shrinkage treatment method can be performed by a known method, the long fiber entangled sheet after the entanglement treatment by hot water treatment is used in that the shrinkage treatment and PVA are dissolved and removed at the same time. It is preferable to contract. By the above treatment, it is possible to continuously develop ultrafine fibers and obtain an ultrafine fiber entangled sheet. At this time, the area shrinkage rate by the shrinkage treatment is required to be 35% or more for use as a leather-like sheet substrate. When the area shrinkage rate is less than 35%, the apparent density of the obtained ultrafine fiber entangled sheet is not sufficiently high, and it becomes difficult to maintain the form of the sheet. In addition to inconvenience in terms of the upper or processability, sufficient strength as a leather-like sheet substrate cannot be obtained. As the conditions for the shrinkage treatment, the first stage is preferably 80 ° C. or lower, more preferably 75 ° C. or lower after being immersed in warm water for 3 to 60 seconds, and the second stage is preferably 85 ° C. or higher, more preferably 90 ° C. Immerse in the warm water. By the above two-stage dipping method, a flame-retardant sheet-like material comprising ultrafine fibers obtained by further converting ultrafine fiber-generating fibers into ultrafine fibers can be obtained with an area shrinkage of 35% or more. Further, the upper limit of the area shrinkage rate is not particularly set, but it is preferably 80% or less in consideration of the physical shrinkage limit and the texture. Here, the area shrinkage rate means a ratio obtained by dividing a value obtained by subtracting an area after shrinkage from an area before shrinkage by an area before shrinkage.

  The obtained flame-retardant sheet-like material has a feeling of fulfillment that is unmatched as a nonwoven fabric made of a single fiber, and can be used as it is as a base for flame-retardant silvered or suede-like leather-like sheets. However, it is preferable to impregnate a polymer elastic body as a binder to obtain a flame-retardant leather-like sheet substrate having more stable form retention. In addition, a woven fabric, a knitted fabric or the like can be laminated and integrated by a known method within a range that does not impair the object and effect of the present invention.

  Examples of the polymer elastic body that can be used in the present invention include polyurethane, SBR, NBR, polyamino acid, acrylic adhesive, and the like, and any polymer having rubber-like elasticity can be used. Of these, polyurethane is preferably used because of its good texture and physical properties when used as a leather-like sheet. There are various application methods, such as a method of wet coagulation after impregnating a solution of a polymer elastic body or an aqueous emulsion resin, or a method of impregnating and drying and fixing a solution of a polymer elastic body or an aqueous emulsion resin. The method can be used. The use of an aqueous emulsion type resin is a preferred example because it does not use an organic solvent and has a low environmental impact. Further, if necessary, when the polymer elastic body is applied to the fabric or after that, it may be applied to the surface to form a silver-tone layer. The amount of the polymer elastic body to be applied is preferably 15% by mass or less, particularly preferably 1 to 10% by mass, based on the mass of the leather-like sheet substrate to be obtained. If it exceeds 15% by mass, the flame retardancy of the entire sheet may not be maintained, and the texture is not flexible.

  The flame-retardant leather-like sheet substrate thus obtained can be made into a suede-like leather-like sheet by fluffing the surface, softening treatment, and dyeing treatment. As a method for fluffing, buffing using sandpaper or a needle cloth can be used. Moreover, it can also be set as a leather-like sheet with a silver tone or semi-silver tone by a process such as surface forming, embossing, softening treatment, and dyeing under desired conditions by a known method. These leather-like sheets are excellent in flame retardancy and mechanical properties, have no wrinkles, have a natural leather-like fullness, and draping properties derived from long fibers, and require flame retardance such as car seats and interiors. It is suitable as a material for product use such as for shoes and gloves as well as for use.

  In general, when a leather-like sheet is manufactured using a sea-island type 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 and a dyeing process, resulting in irregular wrinkles on the entire sheet surface. There are many cases. This tendency is particularly noticeable when the ratio of the binder resin is low, but the remaining components in the fiberization and entanglement steps are removed by removing the component to be removed (sea component) before applying the binder resin as in the present invention. In addition to alleviating the distortion that occurs in the island component) and increasing the apparent density of the resulting sheet by sufficient entanglement and large shrinkage, it makes it difficult for fibers to expand and contract and is made of a flame-retardant sheet made of ultrafine fibers As a result, it is possible to suppress the occurrence of wrinkles when producing a flame-retardant leather-like sheet substrate or a flame-retardant leather-like sheet. Moreover, since it can be set as a flame-retardant leather-like sheet | seat by providing a comparatively small amount of polymeric elastic bodies, it has the advantage that it is not necessary to make a polymeric elastic body flame-retardant.

  Next, PVA suitably used in the present invention will be described in detail. As PVA used as one component of the ultrafine fiber generating fiber of the present invention, those having a viscosity average degree of polymerization (hereinafter simply referred to as polymerization degree) of 200 to 500 are preferable, and a range of 230 to 470 is particularly preferable. 250 to 450 is particularly 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 an advantage that the dissolution rate is increased when dissolving with hot water.

The polymerization degree (P) of PVA here is 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 range of 200 to 500, the object of the present invention can be achieved more suitably.

  The saponification degree of the PVA of the present invention is preferably 90 to 99.99 mol%, more preferably 93 to 99.98 mol%, further preferably 94 to 99.97 mol%, and 96 to 99.96 mol%. % Is particularly preferred. 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 kind of the polymerization monomer, the water solubility of PVA is lowered, and the composite fiber of the present invention may not be obtained. On the other hand, PVA having a saponification degree larger than 99.99 mol% cannot be produced stably.

  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 further more 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 250 ° C. in nitrogen at a heating rate of 10 ° C./min, cooled to room temperature, and then heated again to 250 ° 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.

  PVA can be obtained by saponifying a resin mainly containing 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 homo-resin 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. The types of comonomer include ethylene, propylene, 1-butene, and isobutene having 4 or less α-olefins, methyl vinyl ether, and ethyl vinyl ether from the viewpoints of copolymerizability, melt spinnability, and water solubility of the fiber. , Vinyl ethers such as n-propyl vinyl ether, i-propyl vinyl ether and n-butyl vinyl ether are preferred. The unit derived from α-olefins having 4 or less carbon atoms and / or vinyl ethers is preferably present in PVA in an amount of 1 to 20 mol%, more preferably 4 to 15 mol%, and 6 to 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, n-propyl peroxycarbonate, and the like. And known initiators such as azo initiators and peroxide initiators. Although there is no restriction | limiting in particular about superposition | polymerization temperature, The range of 0-150 degreeC is suitable.

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 fiber is the density of the resin used for fiber formation and the area of the cross section of the fiber constituting the sheet observed at a magnification of 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 determined by using a DSC (TA3000, manufactured by Mettler) measuring instrument in nitrogen at a heating rate of 10 ° C./min to 250 ° C., then cooling 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 250 ° C. was adopted.
The flame retardancy is determined by the combustion test of the flammability test method for organic materials for automotive interior according to JIS D1201.
Flammability: Combustion rate exceeding 100 mm / min Slow flammability: Combustion rate being 100 mm / min or less Self-extinguishing property: Classified as flame extinguished within 50 mm and within 60 seconds from the marked line.
Moreover, the average phosphorus concentration in the sheet | seat in an Example was calculated | required by measuring phosphorus atom concentration with the ICP emission-analysis apparatus IRISAP made from a jarrel ash company.

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 (Mettler, TA3000).

Using a known polyester polymerization method, a phosphorus-based reactive flame retardant M-Ester (manufactured by Sanko Co., Ltd., molecular weight 434, phosphorus content 7% by mass) was added during the polymerization, and phosphorus-modified polyethylene terephthalate having a phosphorus concentration of 6000 ppm. A polyester was obtained. Using the resin as an island component, using the water-soluble thermoplastic polyvinyl alcohol resin obtained in Production Example 1 as a sea component, and using a melt compound spinning die having 25 islands per fiber. The mixture was discharged from the base at 260 ° C. so that the mass ratio of sea component / island component was 30/70. Spinning speed is The ejector pressure was adjusted so that 4500 m / min, a long fiber having an average fineness of 2.0 dtex were collected on the net, to obtain a spunbonded sheet of 30 g / ^{m 2.}

Six spunbond sheets were laminated by cross wrapping so that the total basis weight was 180 g / m ² , and a needle breakage preventing oil was sprayed. Then, the distance from the needle tip to barb with the 5 mm 1 barb needle, alternately from both sides at the needle depth 10mm perform needle punching 3600P / cm ^2, was allowed entangled long fiber-entangled sheet. The area shrinkage due to this needle punching treatment was 47%, the basis weight of the long fiber entangled sheet after needle punching was 330 g / m ² , and the delamination strength was 7.8 kg / 2.5 cm.

This long fiber entangled sheet is immersed in hot water at 70 ° C. to cause area shrinkage due to relaxation of island components, and then PVA is dissolved and removed in hot water at 95 ° C. to form a flame-retardant sheet made of ultrafine fibers. I got a thing. The area shrinkage rate measured after drying was 52%, the basis weight of the sheet was 480 g / m ² , the apparent specific gravity was 0.55, and the single fineness of the ultra-fine long fiber was 0.1 dtex.

  The obtained flame-retardant sheet is impregnated with Evaphanol AP-12 (manufactured by Nikka Chemical Co., Ltd.) as a water-based polyurethane emulsion, dried and cured, and has a resin fiber ratio of R / F = 8/92. A flammable leather-like sheet substrate was obtained. When the surface of the obtained substrate was fluffed by buffing and dyed with a disperse dye, it became a flame-retardant suede-like leather-like sheet having a natural leather-like fullness without any wrinkle defects. The flammability was determined to be self-extinguishing, and had strong physical properties suitable for uses such as interiors and car seats.

Comparative Example 1
In Example 1, a flame-retardant sheet was produced under the same conditions as Example 1 except that the number of needle punches was 120 P / cm ² . The delamination strength of the long fiber entangled sheet after needle punching was 0.78 kg / 2.5 cm. When the obtained long fiber entangled sheet was subjected to shrinkage ultrafine treatment by the same process as in Example 1, the area shrinkage rate was as high as 51%, but the strength of the flame retardant sheet was not sufficient. The feeling was insufficient, and it was not suitable as a material for flame-retardant leather-like sheets.

Comparative Example 2
In Example 1, a long fiber entangled sheet was produced by the same process as Example 1 up to the needle punch, and subjected to a dry heat treatment at 170 ° C. for 20 minutes to alleviate the distortion of the island components. Next, the treated long fiber entangled sheet is immersed in hot water at 70 ° C. to cause area shrinkage, and then PVA is dissolved and removed in hot water at 95 ° C. to obtain a flame-retardant sheet made of ultrafine fibers. Obtained. The area shrinkage rate measured after drying was 12%, and the obtained flame-retardant sheet was unsuitable for use as a material for a leather-like sheet.

Comparative Example 3
In Example 1, a flame-retardant suede-like leather-like sheet was prepared under the same conditions as in Example 1 except that the phosphorus concentration of the phosphorus-modified polyethylene terephthalate fiber was 1000 ppm. The leather-like sheet was good in appearance and mechanical properties, but flammability was flammable and could not be used for applications requiring flame retardancy.

According to the method for producing a flame retardant sheet material of the present invention, a flame retardant sheet material having both flame retardancy and strength properties can be obtained, and a polymer elastic body is provided inside the flame retardant sheet material. By impregnating, flame retardant leather-like sheet substrate can be produced. The flame-retardant leather-like sheet obtained using the flame-retardant leather-like sheet substrate can be applied not only to uses that require flame retardancy such as car seats and interiors, but also to products such as shoes and gloves.

Claims (6)

A long-fiber web comprising ultrafine fiber-generating fibers composed of a water-soluble thermoplastic polyvinyl alcohol resin and a phosphorus-modified polyester resin is entangled, shrunk, and made into an ultrafine fiber; When doing
I. The delamination strength after the entanglement treatment is 2 kg / 2.5 cm or more,
II. The area shrinkage rate by the shrinkage treatment after the entanglement treatment is 35% or more,
III. It ultrafine fiber is a fiber composed of phosphorus-modified the polyester resin by the following average phosphorus concentration of 3 000 ppm or more 20000 ppm,
A method for producing a flame retardant sheet material characterized by satisfying The method for producing a flame-retardant sheet according to claim 1, wherein the entanglement process is a needle punch process. The method for producing a flame-retardant sheet according to claim 1 or 2, wherein the shrinkage treatment is a hot water shrinkage treatment. The flame retardant according to any one of claims 1 to 3, wherein the water-soluble thermoplastic polyvinyl alcohol resin has a viscosity 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. Manufacturing method of sheet-like material. A method for producing a flame-retardant leather-like sheet substrate, comprising a step of impregnating a polymer elastic body into the flame-retardant sheet-like material obtained by the method according to claim 1. A flame-retardant leather-like sheet substrate obtained by the production method according to claim 5.