JP4408778B2 - Synthetic leather - Google Patents

Description

  The present invention relates to a synthetic leather in which a dynamically crosslinked thermoplastic polyurethane elastomer foam layer and a thermoplastic polyurethane elastomer non-foam layer are sequentially provided on the surface of a base fabric.

  Synthetic leather used for chairs, vehicle seats, seats of motorcycle saddles, etc. has a sense of volume, is required to be flexible and strong, but conventionally it has been applied to the surface of a base fabric such as woven fabric, knitted fabric or non-woven fabric. In general, a soft polyvinyl chloride foam layer and a soft polyvinyl chloride layer are formed. In recent years, polyolefin resin leathers using random polypropylene, ethylene-vinyl acetate resin, hydrogenated styrene butadiene rubber, etc. have been proposed in place of soft polyvinyl chloride due to recycling problems.

  In addition, synthetic leather having a foam layer using polyurethane as a material is known. Synthetic leather having a foam layer using polyurethane as a material employs a method in which a nonwoven solution is impregnated with a solution-polymerized polyurethane solution and solidified in a poor solvent. In addition, a method has been proposed in which a thermoplastic polyurethane elastomer is formed into a sheet shape by a melt film forming method and laminated on a base fabric (Patent Documents 1 and 2). According to this method, the thermoplastic polyurethane-based elastomer tends to have non-uniform foam cells, and when the foam cells are non-uniform, the strength and volume feeling are insufficient, and the strength and volume feeling are problematic. It was unsuitable for vehicle seats and seats of motorcycle saddles.

In addition, in the method of laminating a polyurethane foam sheet that has been foamed in advance (Patent Document 3), the foamed cells are crushed during lamination or subsequent processing, and the strength and volume are still lacking, and the thermoplasticity is lost. And recyclability is lost.
Japanese Patent Laid-Open No. 9-158056 Japanese Patent Laid-Open No. 48-39602 JP 2003-211612 A

  The present invention relates to a synthetic leather in which a thermoplastic polyurethane-based elastomer foam layer and a thermoplastic polyurethane-based elastomer non-foamed layer are sequentially provided on the surface of the base fabric, the foaming characteristics of the thermoplastic polyurethane-based elastomer foam layer and the non-foamed layer, An object of the present invention is to provide an inexpensive synthetic leather with improved wear resistance.

  In the course of various investigations on an elastomer layer in a synthetic leather provided with a thermoplastic polyurethane-based elastomer foam layer and a thermoplastic polyurethane-based elastomer non-foam layer, the present inventors have added a polyisocyanate as a crosslinking agent to the thermoplastic polyurethane-based elastomer. The conventional cross-linking reaction product that is mixed and heated to cause cross-linking reaction loses its thermoplasticity and cannot be formed into a sheet by calendering. However, this cross-linking reaction is carried out under heat kneading and dynamically cross-linked. The reactants were able to be molded into a sheet for calendering without losing thermoplasticity, and the dynamically crosslinked thermoplastic polyurethane elastomer compounded with a foaming agent was found to have good foaming characteristics, completing the present invention. .

  That is, the present invention is a synthetic leather in which a thermoplastic polyurethane elastomer foam layer and a thermoplastic polyurethane elastomer non-foam layer are sequentially provided on at least one surface of a base fabric, and the thermoplastic polyurethane elastomer foam layer comprises: The thermoplastic polyurethane elastomer is blended with a polyisocyanate and a foaming agent, and heat-kneaded and dynamically cross-linked thermoplastic polyurethane elastomer is molded into a sheet with a calender and then foamed. Synthetic leather. The thermoplastic polyurethane elastomer non-foamed layer is obtained by blending a thermoplastic polyurethane elastomer with a polyisocyanate, and heat-kneading and dynamically crosslinking the thermoplastic polyurethane elastomer into a sheet shape with a calender. preferable. Further, the polyisocyanate is preferably methylene bis (4,1-phenylene) diisocyanate, and its blending amount is preferably 0.1 to 2 parts by mass, particularly 0.1 to 2 parts by mass with respect to 100 parts by mass of the thermoplastic polyurethane elastomer. 1.5 parts by mass is preferred.

  In the present invention, when the synthetic leather is required to have flame retardancy, the base fabric is preferably flame-treated with a nitrogen-phosphorus flame retardant. The nitrogen-phosphorous flame retardant is preferably a flame retardant selected from condensed ammonium phosphate, condensed melamine phosphate, condensed amido ammonium phosphate and carbamate phosphate.

  The synthetic leather of the present invention is superior in foaming characteristics of the foamed layer as compared with a synthetic leather in which a thermoplastic polyurethane elastomer foam layer and a thermoplastic polyurethane elastomer non-foam layer are provided on a conventional base fabric. Furthermore, in the synthetic leather of the present invention, when a non-foamed layer is a dynamically crosslinked thermoplastic polyurethane elastomer, a conventional polyurethane foam is provided with a thermoplastic polyurethane elastomer foam layer and a thermoplastic polyurethane elastomer non-foam layer. Compared to synthetic leather, it has excellent foaming characteristics and wear resistance. In addition, the dynamically cross-linked thermoplastic polyurethane elastomer used in the present invention has thermoplasticity despite being cross-linked, so it can be molded into a sheet by calendering, making synthetic leather easy. And it can be manufactured at low cost. Further, the thermoplastic polyurethane elastomer layer is thermoplastic and has an advantage that it can be separated and recycled from the base fabric.

  The dynamically cross-linked thermoplastic polyurethane elastomer layer that is the material of the synthetic leather of the present invention will be described. The thermoplastic polyurethane elastomer as a raw material for dynamically crosslinking is a polyurethane obtained by reacting a diisocyanate compound with a compound having two or more hydroxyl groups. Among them, a long-chain glycol and a short-chain glycol (short-chain glycol having terminal active hydrogen) are used. A polyurethane-based thermoplastic elastomer (TPU) composed of a so-called soft segment and hard segment obtained by polyaddition reaction of a chain extender) and a diisocyanate can be preferably used. These preferably have a Shore A hardness of 65 to 90 resin hardness, particularly 70 to 80 resin hardness. In addition, the Shore A hardness in this invention is the value (measurement temperature 23 degreeC) measured by ASTMD2240.

  Examples of diisocyanate compounds for synthesizing thermoplastic polyurethane elastomers include tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, tolidine diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated dicyclohexylmethane diisocyanate, isophorone diisoisol. Ianates are used.

  Further, as the long-chain glycol, a polyester polyol which is a condensation reaction product of a dibasic acid such as adipic acid or phthalic acid and a glycol such as ethylene glycol or 1,4-butanediol; a carbonate such as ethylene carbonate; Polycarbonate-based polyols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polyether-based polyols such as polyethylene glycol-polypropylene glycol are used. In the synthetic leather of the present invention, it is preferable to use a polyether polyol because of its physical properties. In addition, a thermoplastic polyurethane using a polyether-based polyol as a raw material is preferable from this viewpoint because it has good aging resistance and calendar processability.

  Examples of chain extenders include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, butane 1,2 diol, butane 1,3 diol, butane 1,4 diol, butane 2,3 diol, hexane diol, and the like. The low molecular weight polyhydric alcohol, diamine, or water is used.

  In order to dynamically crosslink the polyurethane thermoplastic elastomer as a raw material, first, polyisocyanate is blended with the polyurethane thermoplastic elastomer and is mixed uniformly with a blender. As the polyisocyanate, the above-mentioned polyisocyanate is used, and when the dynamic cross-linking reaction is carried out by heating and kneading, an aromatic polyisocyanate is preferable because the cross-linking reaction proceeds at a temperature at which shearing force is applied and kneading efficiency is good. In particular, methylene bis (4,1-phenylene) diisocyanate (MDI) is preferable. Other examples include tolylene diisocyanate (TDI), but there is a problem of transpiration toxicity because the boiling point is 250 ° C., which is close to the processing temperature. Since the aliphatic polyisocyanate needs to have a high crosslinking temperature, the kneading efficiency is lowered, so that the suitability is poor. The polyisocyanate is preferably used as a master batch, that is, a liquid polyisocyanate is blended with a synthetic resin such as polyester and solidified and pelletized. By doing so, it can be uniformly mixed with the raw material polyurethane-based thermoplastic elastomer before the start of crosslinking. The polyisocyanate may be blocked to suppress the reaction, but is not particularly necessary in the present invention because there is no process in which early crosslinking becomes a problem.

  The blending amount of the polyisocyanate with respect to the polyurethane-based thermoplastic elastomer is 0.1 to 2.0 with respect to 100 parts by mass of the thermoplastic polyurethane-based elastomer when methylene bis (4,1-phenylene) diisocyanate (MDI) is used as the polyisocyanate. Mass parts are preferred, and 0.2 to 0.6 parts by mass are particularly preferred from the viewpoints of wear resistance and recyclability. If it is less than 0.1 parts by mass, there is no crosslinking effect, and if it exceeds 2.0 parts by mass, the calender processability is deteriorated. When polyisocyanate other than methylenebis (4,1-phenylene) diisocyanate (MDI) is used, the blending amount is appropriately determined in accordance with the above in consideration of the molecular weight and the number of isocyanate groups.

  A mixture of a polyurethane-based thermoplastic elastomer and a polyisocyanate master batch is heated and kneaded. Although the crosslinking reaction proceeds by heating, the polyurethane-based thermoplastic elastomer is so-called dynamically crosslinked by proceeding with the crosslinking reaction while kneading. In order to carry out the heating and kneading, an apparatus capable of applying a high shear force such as a Banbury or a twin screw type extruder is used. When heating and kneading with high shearing force, for example, Banbury, it is 130 to 200 ° C. for 3 to 10 minutes. Thus, a dynamically crosslinked thermoplastic polyurethane elastomer can be obtained.

  In the present invention, the dynamically crosslinked thermoplastic polyurethane elastomer foam layer is formed by molding a dynamically crosslinked thermoplastic polyurethane elastomer containing a foaming agent into a sheet shape, laminating the sheet on a base fabric, and then foaming treatment. The foaming agent is then fired and formed. Even if it takes about 2 to 3 days from forming into a sheet with a calender to foaming, the state of the foamed cell is not particularly deteriorated. Since the foaming agent needs to be sufficiently kneaded into the dynamically cross-linked thermoplastic polyurethane elastomer, it is preferably blended before the above-mentioned dynamic cross-linking treatment. That is, by blending a raw material thermoplastic polyurethane elastomer with a polyisocyanate as a crosslinking agent and a foaming agent, kneading and dynamically cross-linking, a dynamically crosslinked foamed thermoplastic polyurethane elastomer is obtained. preferable.

  In addition, when molded into a sheet by calendering, the thermoplastic polyurethane elastomer containing a foaming agent that has been heat-kneaded and dynamically cross-linked is reduced in workability when it is cooled and then heated to form a sheet. Therefore, it is preferable to form the sheet as it is without cooling after the dynamic crosslinking reaction. The calendar device to be used is not particularly limited, and an inverted L type, Z type, L type, or the like is used. When a reverse L-shaped four calendar is used, the roll surface temperature is preferably 140 to 160 ° C. The sheet is rolled into a sheet having a thickness of 0.07 to 0.5 mm by a calendar, and then cooled and wound. The use of mixing rolls and warming rolls is optional.

  Examples of the foaming agent include azodicarbonamide (ADCA), p, p'-oxybisbenzenesulfonyl hydrazide (OBSH), paratoluenesulfonyl hydrazide (TSH), dinitropentamethylenetetramine (DPT), and the like. A mixture of two or more of these can also be used. The foaming ratio of the foamed layer is not particularly limited, but about 2 to 6 times the product is good and preferable. Ordinary thermoplastic polyurethane elastomers hardly change in viscosity with temperature change near the foaming temperature. For this reason, since foaming progresses at a stretch from the portion where the foaming temperature has been reached first, uniform foamed cells are not produced, and large cells are produced, resulting in poor strength and volume. On the other hand, the dynamically cross-linked foamed thermoplastic polyurethane elastomer of the present invention remains partially unreacted after calendering. And since the crosslinking reaction occurs near the foaming temperature that is set higher than the calendar temperature, the viscosity of the part that has reached the foaming temperature rises slightly, resulting in the formation of uniform fine foamed cells with high strength. A foamed layer with a sense of volume. The foaming temperature is preferably about 20 ° C. to 50 ° C. higher than the dynamic crosslinking temperature. Below 20 ° C, the amount of foaming agent decomposition in dynamic crosslinking becomes large, and above 50 ° C, the sheet becomes too soft, and the decomposition during processing of the thermoplastic polyurethane-based elastomer proceeds, and further hydrazodicarbonamide If such nitrogen-based flame retardant is used, its decomposition begins. For example, when the dynamic crosslinking temperature is 160 ° C., the foaming temperature is controlled to about 190 ° C. with a foaming aid.

  In the present invention, the thermoplastic polyurethane elastomer of the non-foamed thermoplastic polyurethane elastomer layer laminated on the dynamically crosslinked thermoplastic polyurethane elastomer foam layer is, for example, two or more diisocyanate compounds and hydroxyl groups as described above. Polyurethanes obtained by reacting a compound having a long chain glycol having a terminal active hydrogen, a short chain glycol (short chain extender), and a polyisocyanate comprising a so-called soft segment and hard segment obtained by polyaddition reaction of diisocyanate. Thermoplastic elastomers (TPU) can be used. These preferably have a Shore A hardness of 65 to 90 resin hardness, particularly 70 to 80 resin hardness. In particular, a dynamically crosslinked thermoplastic polyurethane elastomer synthesized as described above using this as a raw material is preferable. These thermoplastic polyurethane-based elastomers are formed into a sheet by calendering and used for lamination.

  Moreover, you may mix | blend an acrylic soft resin with the dynamically-crosslinked thermoplastic polyurethane-type elastomer foam layer and / or thermoplastic polyurethane-type elastomer non-foam layer of the synthetic leather of this invention as needed. The acrylic soft resin is preferably a multilayer structure polymer, that is, a particulate polymer in which two or more kinds of acrylic polymers form a core-shell type multilayer structure, and has a hardness of 50 to 80 in Shore A. Of these, 65 to 75 are preferred. These acrylic soft resins exhibit good flexibility at room temperature, have bending durability, and excellent weather resistance. A preferable blending ratio [dynamically crosslinked thermoplastic polyurethane elastomer: acrylic soft resin] when blending the acrylic soft resin is 80:20 to 70:30 in mass ratio.

  In addition, plasticizers, lubricants, ultraviolet absorbers, light stabilizers, pigments, antibacterial agents and the like that are usually used for blending synthetic resins may be blended. When a plasticizer is blended, the flexibility and feel of the product can be improved. Further, the blending of the plasticizer can lower the processing temperature of the calendering of the resin, and therefore can suppress decomposition during processing of the dynamically crosslinked thermoplastic polyurethane elastomer. The plasticizer is preferably a phosphate ester such as tricresyl phosphate. Some phosphate ester plasticizers have the effect of a flame retardant. In this case, the plasticizer and the flame retardant are used advantageously. The above compounding agent is preferably added and blended together when the polyurethane thermoplastic elastomer and the polyisocyanate master batch are mixed.

  Laminated thermoplastic polyurethane elastomer sheet with dynamically cross-linked foaming agent molded as described above is laminated on the base fabric using urethane adhesive, and then the thermoplastic polyurethane elastomer sheet is laminated. Then, a synthetic leather is manufactured by foaming a foaming agent. Furthermore, an embossing process is performed as needed. Before and after the foaming and embossing treatments, the surface is subjected to marble printing and gloss adjusting agent coating treatment as necessary. As the above-mentioned base fabric, a woven fabric, a knitted fabric or a non-woven fabric is used. The materials of these knitted fabrics are polyamide fiber, polyester fiber, acrylic fiber, polypropylene fiber, cotton, rayon, and blended yarns thereof. Examples of the knitted fabric include a double-sided knitted fabric and a tentacle knitted fabric, and two or more kinds of fibers may be mixed. Examples of the woven fabric include plain woven fabric, twill woven fabric, and satin woven fabric.

  In the synthetic leather of the present invention, flame retardancy is required depending on the application. In that case, it is better to flame retardant the base fabric. The flame retardant processing of the base fabric is preferably performed by adhering a dispersion or solution of a nitrogen-phosphorous flame retardant to the base fabric and then drying by heating to fix the flame retardant to the base fabric. The mixed solution is adhered to the base fabric by dipping, coating, spraying, or the like. As the nitrogen-phosphorus flame retardant, one or more flame retardants selected from condensed ammonium phosphate, condensed melamine phosphate, condensed amido ammonium phosphate and carbamate phosphate are preferably used. In particular, phosphate carbamate has good adhesion to a base fabric, and can perform durable and robust flame-retardant processing without using an emulsion or aqueous solution of a synthetic resin described later. A dispersion or solution is prepared using acetone, isopropyl alcohol, water, or the like.

  In addition, in the above flame retardant processing, a mixed solution of a nitrogen-phosphorus flame retardant and a synthetic resin emulsion or an aqueous solution may be used. The combined use of an emulsion or an aqueous solution of a synthetic resin can promote the durability and fastness of flame retardant processing, but the flame retardancy itself tends to decrease. Synthetic resin emulsions or aqueous solutions include acrylic ester or methacrylic ester polymers, copolymers of these monomers with other vinyl monomers such as acrylic acid, vinyl acetate, etc. A copolymer of a polymer and an olefin monomer such as ethylene, an emulsion or an aqueous solution of polyurethane, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyester, styrene-butadiene rubber, or the like is used. The ratio of the synthetic resin (solid content) and the flame retardant in the mixed solution is 5 to 100 parts by mass of the flame retardant with respect to 100 parts by mass of the synthetic resin.

Examples 1-8, Comparative Examples 1-3
The components in the foamed layer column of each Example and each Comparative Example shown in Table 1 and Table 2 were mixed and heat kneaded at 160 ° C. for 5 minutes using a Banbury to cause a dynamic crosslinking reaction. Next, the kneaded material was stocked on a warming roll so that the temperature did not drop, calendered at a roll temperature of 150 ° C., and formed into a sheet having a thickness of 0.2 mm. The obtained sheet was laminated on a base fabric using an acrylic adhesive to obtain a laminate.
On the other hand, the components in the non-foamed layer column of each of Examples and Comparative Examples shown in Tables 1 and 2 were mixed at room temperature and heated and kneaded at 160 ° C. for 5 minutes using a Banbury to cause a dynamic crosslinking reaction ( However, since the kneaded product of the non-foamed layer of Example 1 and Comparative Examples 1 and 2 does not contain a diisocyanate master batch, no dynamic crosslinking reaction occurs). Next, the kneaded material was stocked on a warming roll so that the temperature did not drop, calendered at a roll temperature of 150 ° C., and formed into a sheet having a thickness of 0.25 mm. This sheet was laminated on the laminate sheet. Next, this laminate was heated to 215 ° C. to foam the foaming agent. Furthermore, the surface was subjected to marble printing, gloss adjusting agent coating treatment, and embossing treatment to obtain a synthetic leather.
The base fabric is a smooth knitted fabric made of 20th blend yarn of 65% rayon and 35% polyester, nonen 109 (manufactured by Maruhishi Oil Chemical Co., Ltd., nitrogen in which a carbamate phosphate is dispersed in a mixture of isopropyl alcohol and water). -Phosphorus flame retardant) was applied to a solid content of 35 g / m ² and dried.

In Table 1, the thermoplastic polyurethane elastomer is DIC Bayer T-8375N (Shore hardness A75), the acrylic soft resin is Kuraray SA1000P (Shore hardness A70), the styrene rubber is Riken Technos 8915X, and the copolymer polyamide is Toray CM-6541X3. (Melting point 133 ° C.) was used. The diisocyanate master batch is a pellet (DIC Bayer Polymer Pandex AC-MASTER) composed of 30% by mass of methylene bis (4,1-phenylene) diisocyanate and 70% by mass of butanediol terephthalate polytetramethylene glycol copolymer. Moreover, Otsuka Chemical KBH-30 was used for hydrazodicarbonamide, Nitto Flour Chemical NS-A for calcium carbonate, and Mitsubishi Rayon Metabrene P-530A for high molecular weight acrylic processing aid.
The obtained synthetic leather was examined for calendar workability, abrasion resistance, flame retardancy, flexibility and foamability. The results are also shown in Table 1.

In Tables 1 and 2, the calendar workability, wear resistance, flame retardancy, flexibility, foaming test method and evaluation method are as follows.
Calendar workability: Each of the foamed layer and the non-foamed layer was tested. What was processed satisfactorily at a roll temperature of 150 ° C. was evaluated as “good”. Those that hardened during kneading in a banbury and could not be calendered were evaluated as “unworkable”.
Abrasion resistance: A No. 6 canvas defined in JIS L3102 (1978) was attached sideways using a Gakushin friction tester specified in JIS K6404-16 (1999). Evaluation was made by the number of times to break at a load of 1 kg. If it is less than 80, when it is used for a seating surface, the service life becomes insufficient.
Flame retardancy: Dependent on JIS D1201 (1998). Pass means that the burning rate is less than 100 mm / min.
Flexibility: The sensory evaluation of the hardness when used as a seating surface of urethane foam.
Foamability: The cross section was observed with a microscope, and the cell uniformity was visually evaluated.
Examples 1 to 7 in Table 1 are suitable for vehicle seat skin materials. In particular, Examples 1 to 3 have good flexibility and are suitable. Further, Example 8 is suitable for the skin material of the seat surface of the saddle of a motorcycle.

Claims (5)

  A synthetic leather in which a thermoplastic polyurethane elastomer foam layer and a thermoplastic polyurethane elastomer non-foam layer are sequentially provided on at least one surface of a base fabric, wherein the thermoplastic polyurethane elastomer foam layer is a thermoplastic polyurethane elastomer. Polyurethane blended with polyisocyanate and foaming agent, heat-kneaded and dynamically crosslinked thermoplastic polyurethane elastomer molded into a sheet shape with a calender, then foamed and foamed with foaming agent Synthetic leather.   2. The thermoplastic polyurethane elastomer non-foamed layer is obtained by molding a thermoplastic polyurethane elastomer obtained by blending a polyisocyanate into a thermoplastic polyurethane elastomer and heating and kneading and dynamically crosslinking it into a sheet shape with a calender. Synthetic leather as described.   The synthetic leather according to claim 1 or 2, wherein methylene bis (4,1-phenylene) diisocyanate is used as the polyisocyanate, and 0.1 to 2 parts by mass is blended with 100 parts by mass of the thermoplastic polyurethane elastomer.   The synthetic leather according to any one of claims 1 to 3, wherein the base fabric is flame-retarded with a nitrogen-phosphorus flame retardant. The synthetic leather according to claim 4, wherein the nitrogen-phosphorus flame retardant is a flame retardant selected from condensed ammonium phosphate, condensed melamine phosphate, condensed ammonium amidophosphate and carbamate phosphate.