JP5340647B2 - Split leather - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a split leather which shows a sense of togetherness of a split leather and a surface, has an appearance very similar to natural leather with grain, tactile feeling and texture, and has tenacity, particularly tearing strength and tensile strength big enough for usage for industrial material applications. <P>SOLUTION: The split leather has a 0.7 to 1.3 mm thick fresh side split leather (2), a foamed layer (4) of a polyurethane resin made by making a hot-melt urethane prepolymer react with a urethane curing agent and laminated on the surface on the mesh-like layer side of the fresh side split leather, and a protective layer (5) of a polyurethane resin laminated on the surface of the foamed layer. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a so-called split leather in which a skin layer made of polyurethane resin is provided on the surface of a floor leather obtained by removing the silver surface from natural leather, and in particular, it has an excellent sense of unity between the floor leather and the skin layer. Further, the present invention relates to a split leather that can be used in industrial material applications such as interior materials and vehicle interior materials that require high strength, while having a tactile sensation and texture that are very similar to natural leather with a silver surface.

  Conventionally, natural leather with silver has been used in various fields such as clothing, bags, shoes, interior materials, and vehicle interior materials as high-quality materials. However, since natural leather with a silver surface is expensive, a so-called split leather, in which a skin layer made of polyurethane resin is provided on the floor leather surface obtained by removing the silver surface from natural leather, may be used. .

  The floor leather is composed of a reticular layer and a subcutaneous tissue from which the epidermis and nipple layer (collectively referred to as the “silver surface”) is removed from the natural leather consisting of the epidermis, nipple layer, reticular layer, and subcutaneous tissue. . The floor leather composed of the mesh layer and the subcutaneous tissue may be further divided in the thickness direction depending on the application, and the silver side (papillary layer side) floor leather may be used as a grain side. ) Floor leather, flesh side (subcutaneous tissue side) floor leather is referred to as “Fresh Side” floor leather. Of these, grain side floor leather is often used in order to obtain an appearance and texture closer to those of natural leather with a silver surface.

  Grainside floor leather is mainly composed of a mesh layer, but the mesh layer is composed of thick fibers and a coarser density than the nipple layer, and therefore there are irregularities on the floor leather surface. Therefore, when grain side floor leather is used as the base material for split leather, the problem of affecting the appearance and the adhesion between the floor leather and the skin layer are deteriorated, lacking a sense of unity, and the appearance, feel and texture. There is a problem of affecting.

  Moreover, since the density of the fibers in the mesh layer is coarse as described above, there is a problem that the strength, particularly tear strength and tensile strength, of the obtained split leather are inferior. Therefore, it is necessary to increase the thickness of the floor leather in order to obtain sufficient strength for industrial material use, especially tear strength and tensile strength, and the resulting split leather texture becomes hard and strong. There is a problem that it is impossible to balance the texture.

  In order to improve surface smoothness and appearance uniformity in split leather, Patent Document 1 discloses a synthetic resin buffer layer comprising a wet resin microporous layer with an adhesive interposed between floor leather and urethane resin skin. A split leather with a hood has been proposed. According to this document, the resin buffer layer exhibits a buffering action against the delicate unevenness present on the surface of the floor leather, so that the adverse effect of the unevenness on the split leather surface can be eliminated. Moreover, in patent document 2, the surface unevenness of a floor leather is made into split leather by laminating | stacking the skin which consists of polyurethane-type resin through the synthetic resin adhesive layer containing a specific amount of fillers on the floor leather surface. Disclosure of split leather that never appears.

JP 05-345384 A JP 07-242900 A

  However, since the split leather disclosed in Patent Document 1 has an adhesive interposed between the floor leather and the synthetic resin buffer layer and between the synthetic resin buffer layer and the urethane resin skin, There is a problem that a sense of unity is not obtained between the leather and the urethane-based resin skin, and a problem that the appearance, touch and texture of a natural leather-like surface with a silver surface cannot be obtained. Moreover, since the split leather disclosed in Patent Document 2 has a filler added to the synthetic resin adhesive layer, the film strength of the adhesive layer is lowered, and the resulting split leather has a tear strength. There is also a problem that the tensile strength deteriorates. Furthermore, Patent Documents 1 and 2 do not disclose a technique for improving the strength of split leather, and cannot solve these problems.

  In this way, there is no split leather that is excellent in the sense of unity between the floor leather and the skin layer, and that has the appearance, feel and texture similar to those of natural leather with a silver surface, and the strength that can be used for industrial materials. Currently.

  The present invention has been made in view of such a current situation, is excellent in the sense of unity of the floor leather and the skin layer, has an appearance, feel and texture that are very similar to natural leather with a silver surface, and is suitable for industrial material use. An object is to provide a split leather capable of imparting usable strength, in particular, good tear strength and tensile strength.

The split leather according to the present invention comprises a fresh side floor leather having a thickness of 0.7 to 1.3 mm, and a polyurethane resin formed by a reaction of a hot melt urethane prepolymer and a urethane curing agent. A foamed layer laminated on the surface of the network layer, and a protective layer made of a polyurethane resin laminated on the surface of the foamed layer, the foamed layer comprising a hot melt urethane polyol prepolymer as a main agent, and a hot melt It consists of a polyurethane resin formed by a reaction with a urethane curing agent containing a urethane polyisocyanate prepolymer .

  According to the present invention, the floor leather and the skin layer are excellent in unity, have an appearance, touch and texture very similar to those of natural leather with a silver surface, and can be used for industrial materials, in particular, good A split leather having tear strength and tensile strength can be provided.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  FIG. 1 is a cross-sectional view of a split leather (1) according to an embodiment of the present invention. As shown in the figure, split leather (1) has a hot melt urethane prepolymer and urethane as a skin layer (3) on the surface of the mesh layer side of fresh side floor leather (2) having a thickness of 0.7 to 1.3 mm. A foamed layer (4) made of polyurethane resin formed by a reaction of a curing agent and a protective layer (5) made of polyurethane resin are sequentially laminated.

  By using fresh side floor leather (2) having a thickness of 0.7 to 1.3 mm as a base material for split leather in this way, the resulting split leather has a good texture and can be used for industrial material applications. A skin layer (3) in which a foam layer (4) made of a polyurethane resin formed by reaction of a hot melt urethane prepolymer and a urethane curing agent, and a protective layer (5) made of a polyurethane resin are sequentially laminated while being able to obtain strength. ), The adhesion between the floor leather (2) and the skin layer (3) is good and a sense of unity is obtained, and the appearance, feel and texture similar to natural leather with a silver surface are obtained.

  Natural leather used as the material for the floor leather used in the present invention includes cattle, horses, pigs, goats, sheep, deer, kangaroos and other mammal leathers, ostriches and other bird leathers, sea turtles, monitor lizards, pythons, crocodiles and other reptiles. Conventionally known natural leather such as leather can be listed. Among them, cowhide with high versatility, large area, and thickness is preferable.

  The natural leather raw leather is divided in the thickness direction into an epidermis, a nipple layer, a reticular layer, and a subcutaneous tissue to obtain a floor leather composed of the reticular layer and the subcutaneous tissue. The obtained floor leather is further divided in the thickness direction, and includes the upper layer portion of the mesh layer (that is, the upper layer portion in the thickness direction of the mesh layer) on the silver surface side (papillary layer side). Grainside (Grain Side) floor leather, the lower layer part of the mesh layer (that is, the layer part on the lower side in the thickness direction of the mesh layer) and the subcutaneous tissue on the flesh side (subcutaneous tissue side) A fresh side floor leather is obtained.

  In the present invention, it is important to use fresh side floor leather as a base material for split leather. In the fresh side floor leather, the lower part (subcutaneous tissue side) is layered in the cross section in the thickness direction. This is due to the lowermost layer portion of the mesh layer and the traveling direction of the fibers of the subcutaneous tissue being parallel to the leather surface. On the other hand, in the grain side floor leather, fibers are distributed in a lump shape in the cross section in the thickness direction. This is because the fibers are bundled in the upper layer portion of the mesh layer, and these are gently entangled three-dimensionally. Fresh side floor leather, in which fibers run parallel to the floor leather surface to form a layer, has a uniform vertical, horizontal, and diagonal strength. When this is used as a base material, the fibers are agglomerated. Compared to the case where the distributed grain side floor leather is used as a base material, the split leather is excellent in strength, particularly tear strength and tensile strength. By using fresh side floor leather with excellent strength as a base material, split leather with both a feeling of touch, texture, and sufficient strength that can be used for industrial materials is achieved with a relatively thin floor leather described later. Can be obtained.

  In the present invention, the fresh side floor leather has a thickness of 0.7 to 1.3 mm, preferably 0.8 to 1.1 mm. If the thickness is less than 0.7 mm, the strength, particularly tear strength and tensile strength of the obtained split leather may be deteriorated, or the texture may be paper-like. If the thickness exceeds 1.3 mm, the texture may become coarse. The thickness of the fresh side floor leather is the thickness of the center of the 9 sections divided by dividing the floor leather into 3 equal parts in the direction parallel to the back line (vertical) and 3 parts in the vertical direction (horizontal) to the back line. It is obtained by measuring each and calculating the average value.

  The fresh side floor leather usually becomes a semi-finished leather called crust by going through the steps of wrinkling, re-curing, neutralization, dyeing, fatting and drying. Next, buffing is performed on the surface of the net layer side of the obtained fresh side floor leather in a semi-finished product state. The buffing process is performed to smooth the floor leather surface by scraping the surface of the mesh layer, and to remove and uniform the elements that affect the appearance quality such as individual differences, part differences, and scratches.

  In the split leather of the present invention, a foam layer made of a polyurethane resin formed by a reaction of a hot melt urethane prepolymer and a urethane curing agent is laminated as a first skin layer on the surface of the fresh side floor leather on the mesh layer side. It is a thing. By making the resin layer into a foam layer, the rubber elasticity peculiar to the resin is relaxed and there is no rubber-like feel, and the density gradient is close to the silver surface layer of natural leather. (Folded wrinkle expression), tactile sensation, texture can be provided. Thus, the natural leather-like appearance, touch and texture of the split leather of the present invention are achieved by harmonizing the elements of both the floor leather and the skin layer and the foam layer. .

  As is well known, a polyurethane resin is a general term for polymer compounds having a urethane bond (—NHCOO—), and is generally produced by reacting a polyol and a polyisocyanate (crosslinking / curing reaction). In contrast to the one-part type that is provided in a polymerized state (that is, as a polyurethane resin), the two-part curable type reacts the polyol and the polyisocyanate at the time of use. Usually, it consists of two liquids, a urethane prepolymer (main agent) in which the reaction between polyol and polyisocyanate is stopped at an appropriate place, and a urethane curing agent. The polyurethane resin constituting the foam layer is classified into this two-component curable polyurethane resin. In addition, the hot melt property of urethane prepolymers is a property due to the molecular structure, which is solid at room temperature or viscous enough to be applied to a substrate, but melts and becomes liquid when heated. The property that the cohesive force is developed again by cooling.

  Since the hot melt urethane prepolymer used for forming the foamed layer is hot melted, it hardly penetrates into the network layer and the texture of the split leather does not become coarse. In addition, because it is a two-component curable type that reacts with a urethane curing agent to form a polyurethane resin, a viscosity suitable for processing can be obtained at a lower temperature compared to the one-component type, so the floor leather becomes hard due to heat. And the texture of the resulting split leather does not become hard. Nevertheless, the softening temperature after curing is high and the heat resistance is excellent.

  Hereinafter, the hot melt urethane prepolymer, the urethane curing agent, and the polyurethane resin obtained by curing will be described, but it goes without saying that these properties, particularly the properties of the polyurethane resin, are reflected in the properties of the obtained split leather.

  The foamed layer is preferably a releasable base material composed of a composition in which a urethane prepolymer having hot melt properties and a urethane curing agent are appropriately mixed (hereinafter sometimes referred to as “prepolymer composition”). After being applied to the surface, it can be formed by pasting to the surface of the mesh layer side of fresh side floor leather and aging treatment.

  As described above, the hot-melt urethane prepolymer has a urethane bond in the main chain obtained by the reaction between the polyol and the polyisocyanate, and has a hydroxyl group at the molecular terminal depending on the ratio of the polyol and the polyisocyanate at the time of production. There are two types, a hot melt urethane polyol prepolymer and a hot melt urethane polyisocyanate prepolymer having an isocyanate group at the molecular end. The corresponding urethane curing agents are polyisocyanates and polyols.

  The curing reaction between the hot melt urethane prepolymer and the urethane curing agent is shown in the following formula (I). After all, this reaction is shown as a reaction between the hydroxyl group of the polyol and the isocyanate group of the polyisocyanate. Thus, further urethane bonds are formed in the main chain. In addition to the reaction with the hydroxyl group, the isocyanate group reacts with moisture in the atmosphere to produce an amine compound and carbon dioxide (formula (II) below), and further reacts in a chain with the reaction product ( Formulas (III) and (IV) below). A large number of holes are formed in the resin layer by the carbon dioxide gas generated in the formula (II), and a foam layer is formed.

  The polyol that can be used in producing the hot-melt urethane prepolymer is not particularly limited, and examples thereof include polyester polyol, polyether polyol, polycarbonate polyol, acrylic polyol, polyolefin polyol, castor oil polyol, and silicone-modified polyol. These can be used alone or in combination of two or more. Of these, polyether polyol or polycarbonate polyol is preferred from the viewpoint of hydrolysis resistance. Further, polycarbonate polyol is more preferable from the viewpoint of light resistance and heat resistance, and polyether polyol is more preferable from the viewpoint of touch and texture.

  On the other hand, the polyisocyanate that can be used for producing the hot melt urethane prepolymer is not particularly limited, and examples thereof include phenylene diisocyanate, tolylene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), 2 , 4'-diphenylmethane diisocyanate, naphthalene diisocyanate, xylylene diisocyanate and other aromatic diisocyanates, hexamethylene diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate (IPDI), aliphatic such as dicyclohexylmethane diisocyanate, tetramethylxylylene diisocyanate Diisocyanate or alicyclic diisocyanate, and 4,4'-diphenylmethane diisocyanate , And the like polymeric MDI containing dimers and trimers of isocyanate (MDI). Among these, 4,4′-diphenylmethane diisocyanate (MDI) is preferable in that the curing reaction can be easily controlled.

  The hot-melt urethane polyol prepolymer can be obtained by reacting a polyol and a polyisocyanate under conditions where the hydroxyl group of the polyol is excessive with respect to the isocyanate group of the polyisocyanate. Under the present circumstances, it is preferable that the equivalent ratio of a hydroxyl group / isocyanate group is 1.1-2.5, More preferably, it is 1.2-2.0. When the equivalence ratio is less than 1.1, it is difficult to make both ends of the prepolymer into hydroxyl groups, and the isocyanate group remaining in the prepolymer reacts with surrounding moisture, resulting in an increase in molecular weight and an increase in viscosity. There is a possibility that workability may be deteriorated. When the equivalence ratio exceeds 2.5, when the prepolymer and the urethane curing agent are reacted, an unreacted hydroxyl group remains, the polyurethane resin obtained by curing is easily hydrolyzed, and the physical properties related to strength are poor. There is a fear.

  On the other hand, the hot-melt urethane polyisocyanate prepolymer can be obtained by reacting a polyol and a polyisocyanate under conditions where the isocyanate group of the polyisocyanate is excessive with respect to the hydroxyl group of the polyol. At this time, the equivalent ratio of isocyanate group / hydroxyl group is preferably 1.1 to 5.0, more preferably 1.5 to 3.0. If the equivalence ratio is less than 1.1, unreacted hydroxyl groups remain in the prepolymer, and the polyurethane resin obtained by curing is likely to be hydrolyzed, which may result in poor overall physical properties relating to strength. If the equivalence ratio exceeds 5.0, the stability is poor and the curing reaction may not be controlled.

  In order to produce the hot melt urethane prepolymer used in the present invention, various conventionally known methods can be adopted and are not particularly limited. For example, dripping a polyol from which water has been removed into a polyisocyanate, or mixing a polyisocyanate into a polyol from which water has been removed, and then heating and reacting in a batch system, or heating each polyol and polyisocyanate from which water has been removed. In addition, a method in which the reaction is carried out in a continuous extrusion reaction system after being introduced into the extruder at a predetermined ratio can be employed.

  The softening temperature of the hot melt urethane prepolymer thus obtained is preferably 20 to 100 ° C, more preferably 40 to 70 ° C. When the softening temperature is less than 20 ° C., the softening temperature of the polyurethane resin obtained by curing is low, and sufficient heat resistance may not be obtained or the strength may be insufficient. When the softening temperature exceeds 100 ° C., a high temperature is required to obtain a viscosity suitable for processing, workability is deteriorated, and the feel and texture of natural leather may be coarse. In the present specification, the softening temperature is measured by differential scanning calorimetry using a DSC thermal analyzer.

  Next, the urethane curing agent used in the present invention will be described.

  When a hot melt urethane polyol prepolymer is used as a hot melt urethane prepolymer, a polyisocyanate is used as a urethane curing agent. When a hot melt urethane polyisocyanate prepolymer is used as a hot melt urethane prepolymer, a urethane curing agent is used. A polyol is used.

  The urethane curing agent that can be used for the hot melt urethane polyol prepolymer, that is, the polyisocyanate is not particularly limited, and examples thereof include tolylene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), and modified diphenylmethane. Diisocyanate, naphthalene diisocyanate, phenylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate (IPDI), xylene diisocyanate, tetramethylxylene diisocyanate, norbornene diisocyanate, triphenylmethane triisocyanate, polyphenylpolymethylene polyisocyanate, carbodiimide Containing polyisocyanate DOO, polyisocyanates containing allophanate groups, and the like can be illustrated polyisocyanates containing isocyanurate groups may be used in combination thereof singly or two or more. Among them, 4,4′-diphenylmethane diisocyanate (MDI) is preferable in terms of easy control of the curing reaction, and aliphatic polyisocyanate is preferable in terms of less yellowing of the polyurethane resin obtained by curing. Hexamethylene diisocyanate is more preferred.

  Furthermore, as a urethane curing agent, in addition to the above-mentioned polyisocyanate, a compound obtained by reacting a polyol and a polyisocyanate under a condition where an isocyanate group of the polyisocyanate is excessive with respect to a hydroxyl group of the polyol is used. Can do. This compound can be a main component in forming a polyurethane resin as a urethane polyisocyanate prepolymer, and those having hot melt properties can also be used as the hot melt urethane polyisocyanate prepolymer in the present invention. By using such a urethane polyisocyanate prepolymer as a urethane curing agent, in addition to working as a urethane curing agent, an effect as a chain extender can be obtained, so that the flexibility of a polyurethane resin obtained by curing is improved. Can do.

  On the other hand, the urethane curing agent that can be used for the hot melt urethane polyisocyanate prepolymer, that is, the polyol is not particularly limited. For example, polyester polyol, polyether polyol, polycarbonate polyol, acrylic polyol, polyolefin polyol, castor oil polyol And silicone-modified polyols, and the like. These can be used alone or in combination of two or more. Of these, polyether polyol or polycarbonate polyol is preferred from the viewpoint of hydrolysis resistance. Further, polycarbonate polyol is more preferable from the viewpoint of light resistance and heat resistance, and polyether polyol is more preferable from the viewpoint of touch and texture.

  Further, as the urethane curing agent, in addition to the above-mentioned polyol, a compound obtained by reacting a polyol and a polyisocyanate under a condition in which the hydroxyl group of the polyol is excessive with respect to the isocyanate group of the polyisocyanate is used. it can. This compound can be a main component in forming a polyurethane resin as a urethane polyol prepolymer, and those having hot melt properties can also be used as the hot melt urethane polyol prepolymer in the present invention. By using such a urethane polyol prepolymer as a urethane curing agent, the same effect as when a urethane polyisocyanate prepolymer is used as a urethane curing agent for the hot melt urethane polyol prepolymer can be obtained.

  Next, the equivalent ratio when the hot melt urethane prepolymer and the urethane curing agent are reacted will be described.

  When the hot melt urethane polyol prepolymer is used as the hot melt urethane prepolymer and the polyisocyanate is used as the urethane curing agent, the equivalent ratio of isocyanate group / hydroxyl group is preferably 0.95 to 2.0, more preferably. 1.1 to 1.3. If the equivalent ratio is less than 0.95, an unreacted prepolymer remains, and the polyurethane resin obtained by curing is likely to be hydrolyzed, which may result in poor overall physical properties relating to strength. When the equivalence ratio exceeds 2.0, the curing reaction may proceed so much that the feel and texture may become coarse.

  On the other hand, when the hot melt urethane polyisocyanate prepolymer is used as the hot melt urethane prepolymer and the polyol is used as the urethane curing agent, the equivalent ratio of isocyanate group / hydroxyl group is preferably 1.1 to 10, more preferably. 1.2 to 3.0. If the equivalent ratio is less than 1.1, unreacted urethane curing agent remains, and the physical properties of the polyurethane resin obtained by curing may be poor. If the equivalent ratio exceeds 10, the curing reaction may proceed too much and the feel and texture may become coarse.

  In the prepolymer composition, if necessary, within a range that does not impair the physical properties of the polyurethane resin obtained by curing, a urethanization catalyst, a silane coupling agent, a filler, a thixotropic agent, a tackifier, a wax, Heat stabilizer, light resistance stabilizer, fluorescent whitening agent, foaming agent, thermoplastic resin, thermosetting resin, dye, pigment, conductivity imparting agent, antistatic agent, moisture permeability improver, water repellent, oil repellent, Hollow foam, crystal water-containing compound, flame retardant, water-absorbing agent, moisture-absorbing agent, deodorant, foam stabilizer, antifoaming agent, antifungal agent, preservative, algaeproofing agent, pigment dispersant, inert gas, blocking Arbitrary components, such as an inhibitor and a hydrolysis inhibitor, can be used singly or in combination of two or more. Among them, it is preferable to use a urethanization catalyst from the viewpoint of reducing the process load and improving the physical properties of the polyurethane resin.

  Hot melt urethane prepolymer is solid at room temperature or viscous to a degree that is difficult to apply to the base material. To mix with other raw materials and apply to the floor leather, the prepolymer is heated and melted. Need to be liquid. The heating and melting temperature at this time is set to a temperature that is preferably 10 to 80 ° C., more preferably 20 to 60 ° C. higher than the softening temperature of the prepolymer. When the heating and melting temperature is higher than the softening temperature of the prepolymer by less than 10 ° C., the viscosity of the prepolymer is high, and workability at the time of application may be deteriorated. If the heating and melting temperature is higher than the softening temperature of the prepolymer by more than 80 ° C., the curing reaction may not be controlled. The heating and melting temperature is usually set in the range of 30 to 150 ° C, preferably 40 to 120 ° C. The prepolymer is melted by heating in a temperature-controllable raw material tank.

  For mixing the hot-melt urethane prepolymer and the urethane curing agent in a heat-melted state, a mixing head having a structure capable of heating and keeping warm is used, and both are mixed and stirred at a predetermined ratio, and then supplied to a coating apparatus.

  As a method for applying the prepolymer composition to the releasable substrate, various conventionally known methods can be adopted and are not particularly limited. For example, it is applied to the releasable substrate using a roll coater, spray coater, T-die coater, knife coater or comma coater. In particular, coating with a knife coater or a comma coater is preferable because a uniform thin film layer can be formed.

  The coating thickness of the prepolymer composition is preferably 100 to 250 μm, more preferably 150 to 200 μm. By setting the coating thickness within this range, in the obtained split leather, the coating thickness is preferably 0.5 to 2.0 times, more preferably 0.7 to 1.4 times the thickness (minimum thickness) Value), preferably a foamed layer having a thickness (described later) of 100 to 400 μm, more preferably 200 to 350 μm. The prepolymer composition and the fresh side floor leather are bonded together by pressure bonding or thermocompression bonding, and a part of the prepolymer composition penetrates into the fresh side floor leather by the load at this time. Therefore, the thickness of the foam layer finally obtained may be less than the coating thickness.

  The releasable base material used in the present invention is not particularly limited, and may be a base material having releasability with respect to a polyurethane resin or a base material subjected to a release treatment. For example, release paper And a release treatment cloth, a water repellent treatment cloth, an olefin sheet or film made of polyethylene resin or polypropylene resin, a fluororesin sheet or film, a plastic film with release paper, and the like. The releasable base material may have a concavo-convex pattern, and by using such a releasable base material, design properties can be imparted to the surface of the split leather.

  Typical examples of the concavo-convex pattern include a texture pattern, but are not limited thereto. For example, a fabric pattern such as a fabric-like or denim-like pattern, random dots, lines, rounds, triangles, It can be a pattern such as a geometric pattern in which squares, dotted lines, etc. are used alone or in combination.

  After applying the prepolymer composition to the releasable substrate, heat treatment is preferably performed. Since the curing reaction between the hot-melt urethane prepolymer and the urethane curing agent proceeds at room temperature, heat treatment is not necessarily required. However, since the curing reaction is accelerated by the heat treatment, it is preferable to perform the heat treatment in terms of production efficiency. In particular, when a hot-melt urethane polyol prepolymer is used as the hot-melt urethane prepolymer, it is preferable to perform heat treatment since the processing stability is improved by promoting the curing reaction.

  The heat treatment temperature at this time can be appropriately selected depending on the prepolymer and urethane curing agent to be selected, optional additives, coating thickness, etc., but is preferably 90 to 150 ° C., more preferably 100 to 100 ° C. 130 ° C. If the heat treatment temperature is less than 90 ° C., the reaction promoting effect due to the heat treatment may not be sufficiently obtained. If the heat treatment temperature exceeds 150 ° C., the curing reaction cannot be controlled and the processing stability may be lacking.

  The heat treatment time is preferably 30 seconds to 5 minutes, more preferably 1 to 3 minutes. If the heat treatment time is less than 30 seconds, there is a possibility that the reaction promoting effect due to the heat treatment cannot be sufficiently obtained. When the heat treatment time exceeds 5 minutes, the curing reaction proceeds so much that the adhesion to the fresh side floor leather may be deteriorated.

Next, the prepolymer composition (a part of which has undergone a curing reaction and has become a polyurethane resin) is adhered to the surface of the net side of fresh side floor leather by pressure bonding or thermocompression bonding. Match. In this case, the load at the time of bonding is preferably 5~15kg / cm ^2, more preferably 7~13kg / cm ^2. If the load is less than 5 kg / cm ² , sufficient peel strength cannot be obtained, and the sense of unity of the resulting split leather may be impaired. If the load exceeds 15 kg / cm ² , the feel and texture of the resulting split leather may become coarse.

  After bonding, the foamed layer is formed on the surface of the net side of fresh side floor leather by cooling to room temperature and aging treatment.

  The reaction rate between the hot melt urethane prepolymer and the urethane curing agent varies greatly depending on the type and amount of the prepolymer, urethane curing agent, and optional additive (especially urethanization catalyst) to be selected. Although it is necessary to set process conditions suitably, it is normally performed at room temperature for about 1 day to 1 week. In this process, the curing reaction between the prepolymer and the urethane curing agent is completed. If the curing reaction is incomplete, physical properties such as wear resistance may be deteriorated.

  The polyurethane resin layer obtained by curing becomes a foamed layer by carbon dioxide gas generated when a part of the isocyanate group of the hot melt urethane prepolymer or urethane curing agent reacts with moisture in the atmosphere. At this time, the foaming degree of the obtained foamed layer is preferably 1.1 to 2.0 times, more preferably 1.2 to 1.5 times. If the degree of foaming is less than 1.1 times, the irregularities on the floor leather surface may affect the split leather and the appearance may be impaired. When the foaming degree exceeds 2.0 times, the wear resistance may be deteriorated.

Here, the degree of foaming of the foamed layer is determined as follows. In other words, after reading only the foamed layer part of the cross section in the thickness direction of the split leather into a personal computer with a scanner and painting the foamed part white, the foamed part and the non-foamed part are white and black. And binarize and add up the white dot parts by integration. The degree of foaming is obtained using the following formula.
Foaming degree = (Area of foaming part + Area of non-foaming part) / Area of non-foaming part

  The softening temperature of the polyurethane resin obtained by curing is preferably 130 to 240 ° C, more preferably 140 to 200 ° C. If the softening temperature is less than 130 ° C., sufficient heat resistance may not be obtained. If the softening temperature exceeds 240 ° C, the touch and texture may become coarse.

  The thickness of the foamed layer is preferably 100 to 400 μm, more preferably 200 to 350 μm. If the thickness is less than 100 μm, the unevenness of the floor leather surface may affect the split leather and the appearance may be impaired, or the wear resistance may be deteriorated. If the thickness exceeds 400 μm, the feel and texture may become coarse.

  The 100% modulus value of the foamed layer is preferably 1.0 to 10.0 N / 3 cm, more preferably 2.0 to 5.0 N / 3 cm. When the 100% modulus value is less than 1.0 N / 3 cm, the peel strength is lowered and the delamination is likely to occur, the adhesion between the floor leather and the skin layer is impaired and the sense of unity is lacking, and the natural leather with a silver surface There is a possibility that the appearance, touch, and texture of the like cannot be obtained. When the 100% modulus value exceeds 10.0 N / 3 cm, there is a risk that the feel and texture of the resulting split leather will become coarse.

  After the aging treatment, a peelable base material is peeled to obtain a laminate of floor leather and a foam layer.

  The split leather of the present invention is obtained by further laminating a protective layer made of polyurethane resin as a second skin layer on the surface of the foamed layer thus laminated on the surface of the net side layer of the fresh side floor leather. Can be obtained. By providing the protective layer, the abrasion resistance of the split leather is improved. Therefore, the protective layer is a polyurethane resin layer having better wear resistance than the foamed layer, and is usually a non-foamed polyurethane resin layer. In the present invention, the protective layer is a general term for the resin layer as the outermost layer that is formed on the surface of the foamed layer and protects the foamed layer, and is composed of at least one resin layer. It can consist of more than one resin layer.

  The polyurethane resin used for forming the protective layer is not particularly limited, and examples thereof include a polyether-based polyurethane resin, a polyester-based polyurethane resin, a polycarbonate-based polyurethane resin, and the like. It can be used in combination of more than one species. Of these, polycarbonate polyurethane resins are preferable from the viewpoint of durability and light resistance. The form of the polyurethane resin can be used regardless of whether it is solventless (solvent-free), hot-melt, solvent-based, or water-based. And may be appropriately selected depending on the application.

  In the polyurethane resin of the protective layer, if necessary, within a range not impairing the properties of the polyurethane resin, a urethanization catalyst, a silane coupling agent, a filler, a thixotropic agent, a tackifier, a wax, a heat stabilizer, Light stabilizer, fluorescent brightener, thermoplastic resin, thermosetting resin, dye, pigment, flame retardant, conductivity imparting agent, antistatic agent, moisture permeability improver, water repellent, oil repellent, hollow foam, Optional components such as crystallization water-containing compounds, water-absorbing agents, moisture-absorbing agents, foam stabilizers, antifoaming agents, antifungal agents, antiseptics, algae-proofing agents, pigment dispersants, inert gases, antiblocking agents, hydrolysis inhibitors Can be used singly or in combination of two or more.

  The protective layer is formed by applying a polyurethane resin composition to the surface of the foam layer and then performing a heat treatment. As a coating method, various conventionally known methods can be employed, and are not particularly limited. For example, the method using apparatuses, such as a spray coater, a reverse roll coater, a roll coater, a gravure coater, a kiss roll coater, a knife coater, a comma coater, a T-die coater, can be mentioned. Especially, the application | coating by a spray coater is preferable from the point that formation of a uniform thin film layer is possible.

  What is necessary is just to set the application | coating thickness of a polyurethane resin composition suitably according to the thickness (it mentions later) of a protective layer.

  The heat treatment evaporates the solvent in the polyurethane resin composition, dries the resin, and when using a cross-linking agent that causes a cross-linking reaction by the heat treatment, promotes the reaction and forms a film having sufficient strength. Done for. In order to prevent excessive moisture evaporation of the floor leather, the heat treatment is preferably performed so that the floor leather itself does not reach a temperature of 80 ° C. or higher. Therefore, it is preferable that the heat processing temperature is 50-120 degreeC, More preferably, it is 60-100 degreeC. If the heat treatment temperature is less than 50 ° C., the resin may not be sufficiently crosslinked and wear resistance may be deteriorated. If the heat treatment temperature exceeds 120 ° C., the feel and texture of the resulting split leather may become coarse. The heat treatment time is preferably 2 to 20 minutes, more preferably 2 to 10 minutes. When the heat treatment time is less than 2 minutes, there is a possibility that the resin is not sufficiently crosslinked and the wear resistance cannot be obtained. If the heat treatment time exceeds 20 minutes, excessive loss of moisture from the floor leather may result in shrinkage of the floor leather, resulting in undesirable wrinkles, and the feeling and texture may become coarse.

  It is preferable that the thickness of a protective layer is 5-100 micrometers, More preferably, it is 10-50 micrometers. If the thickness is less than 5 μm, it is difficult to form a protective layer uniformly, and the protective layer may be partially lost. If the thickness exceeds 100 μm, the feel and texture of split leather may become coarse. Furthermore, the thickness of the protective layer is preferably 50% or less, more preferably 20% or less of the thickness of the foam layer.

  The 100% modulus value of the protective layer is preferably 0.5 to 10.0 N / 3 cm, more preferably 0.8 to 2.0 N / 3 cm. When the 100% modulus value is less than 0.5 N / 3 cm, the peel strength is lowered and the delamination is likely to occur, the adhesion between the floor leather and the skin layer is impaired and the sense of unity is lacking. There is a possibility that the appearance, touch, and texture of the like cannot be obtained. When the 100% modulus value exceeds 10.0 N / 3 cm, there is a risk that the feel and texture of the resulting split leather will become coarse.

  Thus, the split leather of the present invention can be obtained. In forming the protective layer, prior to forming the foam layer on the releasable substrate, the polyurethane resin composition may be applied to the releasable substrate and heat-treated to form the protective layer. Good. That is, the split leather of the present invention can be produced by applying a prepolymer composition to a releasable substrate and bonding fresh side floor leather to the painted surface. May be applied directly to the releasable substrate, or alternatively, a protective layer may be formed on the releasable substrate and then the prepolymer composition may be applied thereon.

  More specifically, [1] a prepolymer composition obtained by mixing a hot melt urethane prepolymer in a heat-melted state and a urethane curing agent is applied to a releasable substrate, and the prepolymer composition is viscous. The surface of the foam layer is bonded to the surface of the mesh layer of fresh side floor leather, cooled to room temperature, a foamed layer is formed by aging treatment, and then the releasable substrate is peeled off and exposed. The protective layer may be formed by applying a polyurethane resin composition to the substrate and, if necessary, heat treatment or aging treatment. [2] A polyurethane resin composition is applied to a releasable substrate, and if necessary, a protective layer is formed by heat treatment and aging treatment, and then a hot-melt urethane prepolymer in a heated and melted state is formed on the surface of the protective layer. A prepolymer composition obtained by mixing a polymer and a urethane curing agent is applied, and the prepolymer composition is bonded to the surface of a net layer of fresh side leather while the prepolymer composition is viscous, and cooled to room temperature. The foaming layer may be formed by aging treatment, and then the releasable substrate may be peeled off.

  In the production method [2] above, when the polyurethane resin composition is applied to the releasable substrate, the application method is not particularly limited, but a uniform thin film layer can be formed. Application by a knife coater or a comma coater is preferred. Moreover, 50-150 degreeC and 2-20 minutes are employ | adopted as heat processing conditions. This is because there is no restriction to prevent excessive moisture evaporation of the floor leather. After forming the protective layer in this way, after applying the prepolymer composition thereon, preferably after heat treatment, after bonding to the surface of the mesh layer of fresh side floor leather, after aging treatment to form a foam layer The releasable substrate can be peeled off to obtain the split leather of the present invention.

  In the split leather according to the present invention, the thickness (minimum thickness) of the foamed layer remaining on the surface of the fresh leather floor leather after the peel test is preferably 10 to 400 μm, more preferably 100. ˜300 μm. If the thickness is less than 10 μm, the adhesion between the floor leather and the skin layer is impaired and the sense of unity is lacking, and there is a possibility that the appearance, touch and texture of a natural leather with a silver surface may not be obtained. On the other hand, when the thickness exceeds 400 μm, the feel and texture of the resulting split leather may become coarse and the adhesion with the protective layer may be deteriorated. This thickness can be adjusted by the coating thickness of the prepolymer composition forming the foamed layer, the load at the time of bonding the prepolymer composition and the fresh side floor leather, the thickness of the foamed layer, the degree of foaming, etc. .

  The split leather of the present invention has a sense of unity, appearance, touch and texture that is very similar to natural leather with silver, and is excellent in various properties such as tear strength and tensile strength. It can be suitably used as a member such as a vehicle interior material.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example. “Parts” in the examples are based on weight. Moreover, the following methods evaluated the obtained synthetic leather.

[sense of unity]
Sensory evaluation was performed and judged according to the following criteria.
○: Floating wrinkles are not seen, and natural leather-like fine creases are seen △: Natural leather-like unity feeling is observed, but slightly rough wrinkles and floating wrinkles are seen ×: Paper-like rough creases Wrinkles and floating wrinkles are seen

[appearance]
Sensory evaluation was performed and judged according to the following criteria.
○: Unevenness due to floor leather is not seen △: Unevenness due to floor leather is slightly seen ×: Unevenness due to floor leather is seen

[Tactile texture]
Sensory evaluation was performed and judged according to the following criteria.
○: Flexible and has a natural leather-like feel △: Although it has a natural leather-like feel, it is slightly flexible ×: It is hard or flexible but has a rubber-like feel and has a natural leather-like feel Not

[Peel test]
One test piece having a width of 30 mm and a length of 120 mm is taken from each of the vertical (parallel to the back line) and horizontal (perpendicular to the back line), and the skin layer and the floor leather are peeled 40 mm from one end of the test piece. Under conditions of room temperature 20 ± 2 ° C and humidity 65 ± 5% RH, sandwich the skin layer and floor leather with a gripping tool without slack, and use Autograph AG-100A (manufactured by Shimadzu Corporation) The skin layer was peeled off at a width of 30 mm and a gripper moving speed of 200 mm / min.
A cross-sectional photograph of the test piece after the peel test was observed with a microscope, and the thickness of the foam layer remaining on the floor leather (the minimum value of the thickness of the foam layer remaining on the vertical and horizontal floor leather sides) was measured.

[Tear strength]
One test piece having a width of 40 mm and a length of 150 mm is taken from each of the vertical (parallel to the back line) and horizontal (perpendicular to the back line), and a 50 mm long cut is made in the center of the short side of the test piece. . Under the conditions of room temperature 20 ± 2 ° C and humidity 65 ± 5% RH, the notch part of the test piece is pinched with a gripper so that there is no slack, and is gripped using Autograph AG-100A (manufactured by Shimadzu Corporation) The test piece was torn at a width of 30 mm, a grip interval of 25 mm, and a gripper moving speed of 200 mm / min. The maximum load when the test piece was cut was measured and judged according to the following criteria.
○: Vertical and horizontal measured values of 50N or more Δ: Vertical and horizontal measured values of 15N or more and less than 50N ×: Vertical and horizontal measured values of less than 15N

[Tensile strength]
One test piece having a width of 30 mm and a length of 150 mm is sampled from each of the vertical (parallel to the back line) and horizontal (perpendicular to the back line). Under conditions of room temperature 20 ± 2 ° C and humidity 65 ± 5% RH, hold both ends of the test piece with a gripper so that there is no slack, and use autograph AG-100A (manufactured by Shimadzu Corporation) The test piece was broken at 30 mm, a grip interval of 100 mm, and a gripper moving speed of 200 mm / min. The maximum load when the test piece broke was measured and judged according to the following criteria.
○: Vertical and horizontal measured values of 500N or more Δ: Vertical and horizontal measured values of 245N or more and less than 500N
×: Vertical and horizontal measured values are less than 245N

[100% modulus]
Using a bar coater on a smooth polyester film with a thickness of 100 μm by the dial gauge method and not subjected to surface treatment, a film with a thickness of 300 μm foam layer and a protective layer of 50 μm can be obtained. A film was formed by applying the composition. Three test pieces each having a width of 30 mm and a length of 150 mm were collected from the film. Under conditions of room temperature 20 ± 2 ° C and humidity 65 ± 5% RH, hold both ends of the test piece with a gripper so that there is no slack, and use autograph AG-100A (manufactured by Shimadzu Corporation) Pulling was performed at 30 mm, a grip interval of 25 mm, and a gripping tool moving speed of 200 mm / min, and the load when the stroke distance became 25 mm was measured for each of three points to determine the minimum value of the load at the time of cutting.

Moreover, the hot-melt urethane prepolymer was produced as follows.
[Production Example 1]
In a 1-liter four-necked flask kept at 60 ° C., 80 parts of polyester polyol (Kuraray polyol P2012, manufactured by Kuraray Co., Ltd.) having a number average molecular weight of 2000 and polycarbonate polyol (Kuraray polyol C2090, stock) having a number average molecular weight of 2000 10 parts polyether polyol (PTMG1000, manufactured by Sanyo Chemical Industries, Ltd.) having a number average molecular weight of 1000 is added and stirred, and then 15 parts of 4,4′-diphenylmethane diisocyanate (MDI) is added. The mixture was stirred at 80 ° C. until the isocyanate group disappeared (equivalent ratio (hydroxyl group / isocyanate group) was 1.25) to obtain a hot melt urethane polyol prepolymer (softening temperature: 40 ° C.).

[Production Example 2]
10 parts of polyester polyol (Kuraray polyol P1012, manufactured by Kuraray Co., Ltd.) having a number average molecular weight of 1000 and 6 parts of 4,4′-diphenylmethane diisocyanate (MDI) are placed in a 1-liter four-necked flask kept at 60 ° C. The mixture was stirred at 80 ° C. until the hydroxyl group disappeared (equivalent ratio (isocyanate group / hydroxyl group) was 2.4) to obtain a hot melt urethane isocyanate prepolymer (softening temperature: 30 ° C.).

[Production Example 3]
Polyether polyol (PTMG1000, Sanyo Kasei Co., Ltd.) having 60 parts of polycarbonate polyol (Kuraray polyol C2090, manufactured by Kuraray Co., Ltd.) having a number average molecular weight of 2000 in a 1 liter four-necked flask kept at 60 ° C. Kogyo Co., Ltd.) was added and stirred, and then 10 parts of isophorone diisocyanate (IPDI) was added and stirred at 80 ° C. until the isocyanate group disappeared (equivalent ratio (hydroxyl group / isocyanate group) was 1.33). A hot melt urethane polyol prepolymer (softening temperature: 30 ° C.) was obtained.

[Production Example 4]
10 parts of polyester polyol (Kuraray polyol P1012, manufactured by Kuraray Co., Ltd.) having a number average molecular weight of 1000 and 10 parts of isophorone diisocyanate (IPDI) are put into a 1 liter four-necked flask kept at 60 ° C. to eliminate hydroxyl groups. (Equivalent ratio (isocyanate group / hydroxyl group) is 4.5) until a hot melt urethane isocyanate prepolymer (softening temperature: 20 ° C.) was obtained.

For the formation of the protective layer, a commercially available polyurethane resin composition for leather (Dainippon Ink Chemical Co., Ltd.) was used. The prescription is as follows.
[Resin formulation for protective layer]
LCC WL Mat UM-2507 600 parts LCC WL Clear UX-2007 100 parts LCC WL Conditioner SL-5 60 parts LCC WL Fixer UX-10 170 parts LCC Thickner NA-2 Appropriate water About 100 parts TOTAL 1 part

[Example 1]
An adult cowhide from which the silver surface layer was removed was used as the raw leather, and this was divided in the thickness direction, and further subjected to a normal process such as wrinkle to obtain a fresh side floor leather. The fluff was scraped off by treating the front and back surfaces of the floor leather twice with a buffing machine equipped with 600 mesh sandpaper. At this time, buffing was performed by setting the rotation speed of the sandpaper to 1000 rpm, the speed to 5 m / min, and the clearance to the total thickness of the floor leather minus 1 mm. The thickness of the obtained floor leather was 1.0 mm.

  As a hot melt urethane prepolymer, 7 parts of the hot melt urethane polyisocyanate prepolymer of Production Example 2 heated to 40 ° C. as a urethane curing agent was added to 100 parts of the hot melt urethane polyol prepolymer of Production Example 1 which was heated and melted to 100 ° C. And 5 parts of 4,4′-diphenylmethane diisocyanate (MDI) (equivalent ratio (isocyanate group of urethane curing agent / hydroxyl group of prepolymer) is 1.3), carbon black pigment Polyton Black (Dainippon Ink Chemical Co., Ltd.) as a colorant A prepolymer composition prepared by adding 1.5 parts of an amine catalyst TOYOCAT-DT (manufactured by TOSOH Co., Ltd.) as a urethane catalyst and stirring with a stirrer Release paper R-51 (textured uneven pattern on the coater) Subjected coated into a sheet so that the thickness in Ntekku Co., Ltd.) is 200 [mu] m, and heat treated for 1 minute at 120 ° C. in a drier.

Next, while the prepolymer composition is in a viscous state, it is bonded to the net layer side of fresh side floor leather, pressed with a load of 10 kg / cm ² with a mangle, and aged at room temperature for 1 day. After the treatment to form the foam layer, the release paper was peeled off.

  Further, the polyurethane resin composition of the above formulation is applied to the surface of the foam layer with a spray coater so that the thickness after heat treatment is 20 μm, and heat-treated at 100 ° C. for 2 minutes with a dryer to form a protective layer. The split leather of Example 1 was obtained.

[Example 2]
A split leather of Example 2 was obtained in the same manner as Example 1 except that the thickness of the fresh side floor leather was 0.8 mm.

[Example 3]
A split leather of Example 3 was obtained in the same manner as Example 1 except that the thickness of the fresh side floor leather was 1.1 mm.

[Example 4]
A split leather of Example 4 was obtained in the same manner as in Example 1 except that the thickness of the fresh side floor leather was 0.7 mm.

[Example 5]
A split leather of Example 5 was obtained in the same manner as in Example 1 except that the thickness of the fresh side floor leather was 1.3 mm.

[Example 6]
Example 6 was carried out in the same manner as in Example 1 except that the coating thickness of the prepolymer composition was 250 μm, and the load at the time of bonding the prepolymer composition to the mesh layer side of fresh side floor leather was 13 kg / cm ^2. Got split leather.

[Example 7]
Example 7 was carried out in the same manner as in Example 1 except that the coating thickness of the prepolymer composition was 170 μm, and the load at the time of bonding the prepolymer composition to the mesh layer side of fresh side floor leather was 7 kg / cm ^2. Got split leather.

[Example 8]
Example 8 was carried out in the same manner as in Example 1 except that the coating thickness of the prepolymer composition was 300 μm, and the load when adhering the prepolymer composition to the mesh layer side of fresh side floor leather was 15 kg / cm ^2. Got split leather.

[Example 9]
Example 9 was carried out in the same manner as in Example 1 except that the coating thickness of the prepolymer composition was 100 μm, and the load when the prepolymer composition was bonded to the mesh layer side of fresh side floor leather was 5 kg / cm ^2. Got split leather.

[Example 10]
The thickness of the fresh side floor leather was 1.3 mm, the coating thickness of the prepolymer composition was 300 μm, and the load when the prepolymer composition was bonded to the net layer side of the fresh side floor leather was 15 kg / cm ² . A split leather of Example 10 was obtained in the same manner as Example 1 except for the above.

[Example 11]
The load when the prepolymer composition is bonded to the net side of the fresh side floor leather, the thickness of the fresh side floor leather is 0.7 mm, the coating thickness of the prepolymer composition is 100 μm, the heat treatment time is 2 minutes. A split leather of Example 11 was obtained in the same manner as in Example 1 except that was 5 kg / cm ² .

[Example 12]
7 parts of the hot melt urethane polyisocyanate prepolymer of Production Example 2 heated to 40 ° C. as a urethane curing agent and 2 parts of 4,4′-diphenylmethane diisocyanate (MDI) (equivalent ratio (isocyanate group / prepolymer of urethane curing agent) The split leather of Example 12 was obtained in the same manner as in Example 1 except that 1.1) was used and the coating thickness of the prepolymer composition was 180 μm.

[Example 13]
7 parts of the hot melt urethane polyisocyanate prepolymer of Production Example 2 heated to 40 ° C. as a urethane curing agent and 14 parts of 4,4′-diphenylmethane diisocyanate (MDI) (equivalent ratio (isocyanate group / prepolymer of urethane curing agent) The split leather of Example 13 was obtained in the same manner as in Example 1 except that 2.0) was used and the coating thickness of the prepolymer composition was 300 μm.

[Example 14]
7 parts of the hot melt urethane polyisocyanate prepolymer of Production Example 2 heated to 40 ° C. as a urethane curing agent (equivalent ratio (isocyanate group of urethane curing agent / hydroxyl group of prepolymer) is 0.96), prepolymer composition A split leather of Example 14 was obtained in the same manner as in Example 1 except that the coating thickness of the product was 150 μm.

[Example 15]
As a hot melt urethane prepolymer, 100 parts of the hot melt urethane polyol prepolymer of Production Example 3 melted by heating at 100 ° C., and 20 parts of the hot melt urethane polyisocyanate prepolymer of Production Example 4 heated to 40 ° C. as a urethane curing agent (Equivalent ratio (isocyanate group of urethane curing agent / hydroxyl group of prepolymer) is 1.29), 2 parts of carbon black pigment Polyton black (Dainippon Ink Chemical Co., Ltd.) as a colorant, amine as a urethanization catalyst A prepolymer composition was prepared by adding 3 parts of a system catalyst TOYOCAT-DT (manufactured by TOSOH Corporation) and stirring with a stirrer. Thereafter, the split leather of Example 15 was obtained in the same manner as Example 1.

[Comparative Example 1]
Split leather was obtained in the same manner as in Example 1 except that the thickness of the fresh side floor leather was 1.4 mm.

[Comparative Example 2]
Split leather was obtained in the same manner as in Example 1 except that the thickness of the fresh side floor leather was 0.6 mm.

[Comparative Example 3]
Split leather was obtained in the same manner as in Example 1 except that 1.0 mm thick grain side floor leather was used instead of fresh side floor leather.

[Comparative Example 4]
Split leather was obtained in the same manner as in Example 1 except that 2.5 mm thick floor leather that had not been divided was used instead of fresh side floor leather.

  Tables 1 and 2 show the details of the split leathers of the examples and comparative examples, and the results of performance evaluation.

  As shown in Tables 1 and 2, the split leather according to the example was excellent in the sense of unity between the floor leather and the skin layer, and had the appearance, feel and texture of natural leather with a silver surface. Moreover, it had good tear strength and tensile strength that can be used for industrial materials. In particular, in the case of the split leathers of Examples 1 to 3, 6 to 9, 12, 14 and 15, excellent effects were obtained in the tear strength and tensile strength as well as the above-mentioned sense of unity, appearance, touch and texture.

  On the other hand, in the comparative example, it is impossible to achieve both strength and texture. In particular, in Comparative Example 3 in which grain side floor leather is used as a base material, it is excellent in terms of a natural leather-like texture and a sense of unity with silver. Although it was, it was inferior in strength. Moreover, in the comparative example 4 using the whole floor leather, it was inferior to the tactile feeling.

It is sectional drawing of the split leather which concerns on one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Split leather, 2 ... Fresh side floor leather, 3 ... Skin layer, 4 ... Foam layer, 5 ... Protective layer

Claims (4)

Fresh side floor leather with a thickness of 0.7-1.3mm,
A foamed layer made of a polyurethane resin formed by a reaction of a hot melt urethane prepolymer and a urethane curing agent, and laminated on the surface of the mesh layer side of the fresh side floor leather,
A protective layer made of polyurethane resin laminated on the surface of the foam layer;
Equipped with a,
The foam layer comprises a polyurethane resin formed by a reaction between a hot melt urethane polyol prepolymer as a main agent and a urethane curing agent containing a hot melt urethane polyisocyanate prepolymer.
Split leather.   The fresh side floor leather is obtained by dividing a floor leather composed of a reticulated layer obtained by removing the silver surface from natural leather and a subcutaneous tissue in the thickness direction. The split leather according to claim 1, which is floor leather.   The split leather according to claim 1 or 2, wherein a thickness of the foam layer remaining on the surface of the fresh side floor leather after the peel test of the split leather is 10 to 400 µm.   The split leather according to any one of claims 1 to 3, wherein the fresh side floor leather has a thickness of 0.8 to 1.1 mm.

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