JP2008265300A - Leather element and its manufacturing process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a leather element which has a touch and a feel of a natural leather shape and a concave-convex pattern, which can express a warm wrinkle expression, does not have disappear of the concave-convex pattern and a mold flow and yet is excellent in wear resistance and heat resistance, and to provide its manufacturing process. <P>SOLUTION: The leather element is characterized in that a foaming layer of thickness of 50 μm to 300 μm having the concave-convex pattern made of polyurethane resin formed by the reaction of a hot-melt urethane polymer and an urethane hardening agent is laminated on the surface of a natural leather having a silver surface layer of thickness of 200 μm to 1,000 μm, further a protecting layer of the thickness of 10 μm to 100 μm is laminated on its surface without vanishing the concave-convex pattern of the foaming layer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is excellent in various properties such as tactile sensation, texture, wrinkle expression, uneven pattern durability, wear resistance, heat resistance and the like, and is suitably used as a member of clothing, bags, shoes, interior materials, vehicle interior materials, etc. The present invention relates to a leather material to be manufactured and a manufacturing method thereof.

  Conventionally, natural leather has been used as a high-quality material in various fields such as clothing, bags, shoes, interior materials, and vehicle interior materials. Natural leather has a soft touch and a soft texture, but has a problem of poor wear resistance. In order to improve this problem, the leather surface is usually covered with a protective layer. Specifically, for example, after buffing the surface of the natural leather silver surface layer, a protective layer is formed by applying polyurethane resin or acrylic resin (usually water-based). As a result, the wrinkles originally present on the surface of the natural leather disappear. Therefore, following the formation of the protective layer, embossing is performed with a roll engraved with a wrinkle-like uneven pattern to give the uneven surface to the leather surface. .

  However, the leather material obtained by the above method has a problem that the resin permeates into the silver layer and the feel and texture of natural leather become coarse. In addition, embossing is a process in which a heated mold is pressed against natural leather, and the natural leather is partially compressed to give a concavo-convex pattern. Therefore, a resin having a high softening temperature is applied to the resin forming the protective layer. If selected, it is necessary to increase the temperature conditions during heating and pressing, and there is a problem that the feel and texture of natural leather become coarser due to heat.On the other hand, if a resin with a low softening temperature is selected, heat resistance is obtained. There was a problem that it was not possible. Thus, it has been difficult to achieve both tactile sensation, texture and heat resistance. Furthermore, the uneven pattern given by embossing has a problem that the concave / convex pattern cannot be maintained gradually due to the restoring force to return to the original thickness of natural leather, and the uneven pattern disappears over time. There was a problem of mold flow that the uneven pattern disappeared when tension was applied to the material.

  On the other hand, as one of the leather materials with high wear resistance, a so-called skin layer is formed on the surface of the floor leather, which is the remaining portion obtained by slicing natural leather and separating the leather portion having the silver layer. Split leather is known (for example, Patent Document 1). Specifically, for example, a polyurethane resin liquid (usually a solvent-based one-part type) is applied to a release paper having a concavo-convex pattern and dried to form a skin layer obtained from a polyurethane resin adhesive (usually a solvent system). It may be produced by bonding to the surface of floor leather that has been subjected to buffing via either one-pack type or two-pack type). Such a split leather can satisfy these physical properties by selecting a resin having high wear resistance and heat resistance as the resin forming the skin layer. However, the feel and texture of the floor leather is inferior to that of natural leather with a silver surface layer, and it is necessary to increase the thickness of the skin layer to some extent in order to eliminate the adverse effects caused by the unevenness of the floor leather surface. However, there was a problem that the adhesive penetrated into the floor leather and the feel and texture became more coarse. In addition, since the silver layer was absent, fine wrinkles peculiar to natural leather were difficult to enter, and wrinkle expression was poor. For this reason, the split leather has a high quality and a low commercial value while using a part of natural leather as a base material.

  Thus, the present condition is that the leather material excellent in all of tactile sensation, texture, wrinkle expression, uneven pattern durability, abrasion resistance, and heat resistance has not been obtained.

JP-A-7-150479

  The present invention has been made in view of such a current situation, has a natural leather-like feel, texture, and uneven pattern, can express fine wrinkles, has no disappearance of uneven pattern or mold flow, and is resistant to damage. It is an object of the present invention to provide a leather material excellent in wear and heat resistance, and a method for producing the same.

The present invention firstly comprises a polyurethane resin formed by a reaction of a hot melt urethane prepolymer and a urethane curing agent on the surface of a natural leather having a silver surface layer having a thickness of 200 to 1000 μm, and has a thickness having an uneven pattern. The leather material is characterized in that a foam layer of 50 to 350 μm is laminated, and a protective layer having a thickness of 10 to 100 μm is laminated on the surface without erasing the uneven pattern of the foam layer.
The softening temperature of the polyurethane resin is preferably 130 to 240 ° C.
The Martens hardness of natural leather is preferably 0.7 to 2.0 N / mm ² , the Martens hardness of the foam layer is preferably 0.5 to 2.5 N / mm ² , and the foam layer The difference between the Martens hardness of the natural leather and the Martens hardness of the natural leather is preferably −0.5 to 0.5 N / mm ² .
The present invention secondly applies a mixture of a hot melt urethane prepolymer and a urethane curing agent to a release substrate having irregularities, and then performs buffing in a state where the mixture is viscous. After bonding to the surface of the natural leather silver surface layer and aging treatment to form a foam layer, the release substrate is peeled off, a resin is applied to the surface of the foam layer, and heat treatment is performed to form a protective layer. This is a method for producing a leather material.

  According to the present invention, a leather material having a natural leather-like tactile sensation, texture, concavo-convex pattern, fine wrinkle expression, no loss of concavo-convex pattern and mold flow, and excellent wear resistance and heat resistance. , And a method for manufacturing the same. The leather material of the present invention can be suitably used as a member of clothing, bags, shoes, interior materials, vehicle interior materials, and the like.

Hereinafter, the present invention will be described in detail.
The leather material of the present invention comprises a polyurethane resin formed by the reaction of a hot melt urethane prepolymer and a urethane curing agent on the surface of natural leather having a silver surface layer having a thickness of 200 to 1000 μm, and has a thickness having an uneven pattern. A foamed layer having a thickness of 50 to 350 μm is laminated, and a protective layer having a thickness of 10 to 100 μm is laminated on the surface of the foamed layer without erasing the uneven pattern of the foamed layer. By using natural leather with a silver surface layer as a base material, the unique texture of natural leather such as touch, texture, and wrinkle expression can be utilized, and a resin layer with excellent wear resistance and heat resistance can be laminated on the surface. By complementing the physical properties that are the weak points of natural leather, and by foaming the resin layer, the unique characteristics of natural leather are highly reproduced to achieve harmony with the natural leather as the base material. And the durability of uneven | corrugated pattern is acquired by laminating | stacking the foaming layer in which the uneven | corrugated pattern was formed previously, and abrasion resistance is further improved by providing a protective layer in the outermost layer.

  Examples of the natural leather used in the present invention include mammal leather such as cow, horse, pig, goat, sheep, deer and kangaroo, bird leather such as ostrich, reptile leather such as sea turtle, monitor lizard, python, crocodile, etc. Men can mention leather. Of these, cowhide having high versatility and a large area is preferable.

  The raw leather of the above-mentioned natural leather usually becomes a semi-finished leather called crust through the steps of wrinkling, re-waxing, neutralization, dyeing, fatting and drying. Next, the surface of the silver layer of the obtained semi-finished leather is buffed. The buffing process is performed to smooth the leather surface by scraping off the surface layer of the silver surface layer, and to remove and equalize the elements that affect the appearance quality such as individual differences, differences in parts, worm-eaten, and scratches. Further, since the fibers on the surface of the silver surface layer are fluffed by buffing, an anchor effect acts on the foamed layer laminated thereon, and there is also an effect of improving wear resistance.

  In the buffing process, it is possible to appropriately set the state of the silver layer by selecting various conditions such as the paper mesh of the sandpaper and the number of contact between the sandpaper and the natural leather. The degree of buffing varies depending on the state of the leather surface such as scratches, but is preferably applied to the extent that the surface layer of the silver layer is scraped by 10 to 100 μm. If the thickness of the silver surface layer to be scraped is less than 10 μm, scratches on the leather surface may affect the appearance quality. If this thickness exceeds 100 μm, the silver layer is greatly destroyed, and there is a possibility that the peculiar characteristics of natural leather such as tactile sensation, texture and wrinkle expression may be impaired. More preferably, the buffing is performed so that the surface layer of the silver surface layer is scraped by 50 to 100 μm.

  The thickness of the silver surface layer after buffing varies depending on the type of natural leather to be used, but it is important that the thickness be 200 to 1000 μm. If the thickness is less than 200 μm, the silver layer is greatly destroyed, and there is a possibility that the peculiar characteristics of natural leather such as touch, texture and wrinkle expression may be impaired. If the thickness exceeds 1000 μm, the feel and texture may become coarse. A preferable thickness range is 200 to 400 μm.

  As long as the thickness of the silver layer is 200 to 1000 μm, the thickness of the whole natural leather is not particularly limited. Although the thickness of the whole natural leather differs depending on the type of natural leather to be used, for example, in the case of adult cowhide, it is usually in the range of 1000 to 1600 μm.

Moreover, it is preferable that the Martens hardness of natural leather is 0.7-2.0 N / mm < ² >, More preferably, it is 0.9-1.3 N / mm < ² >. Here, Martens hardness is a physical property value defined by ISO14577, which is obtained by pushing an indenter into an object to be measured while applying a load, and is highly accurate for a very flexible film or a thin film. In recent years, it has attracted attention because of the fact that measurement values can be obtained. As will be described later, in the present invention, the difference between the foamed layer (thickness: 50 to 350 μm) and the Martens hardness is preferably in a specific range, which is effective for measuring the hardness of such a film. The Martens hardness can be measured using, for example, a commercially available apparatus such as an ultra-micro hardness meter or a Fischer scope PICODETOR HM500 (manufactured by Fisher Instruments Co., Ltd.).

Specifically, the indenter is pushed into the surface of the object to be measured while applying the test load F [N], and the surface area As (h) [mm ² ] into which the indenter has entered is determined from the pushing amount h [mm] and the indenter shape. The Martens hardness HM [N / mm ² ] is obtained by the following formula 1.
[Formula 1]
HM = F / As (h)

In the measurement of the Martens hardness in the present invention, the above PICODETOR HM500 is used, the Vickers indenter is pushed into the surface of the object to be measured so that the maximum load is 1.000 mN over 10 seconds, and the test load is maintained for 5 seconds. Similarly, the condition for reducing the load was adopted. The formula for calculating the surface area when using a Vickers indenter is as follows:
[Formula 2]
As (h) = k × h ²
= 26.43 × h ²
k: Indenter-specific coefficient
h: Pushing amount of indenter Further, natural leather having a desired thickness was used as an object to be measured.

If the Martens hardness is less than 0.7 N / mm ² , the wear resistance may deteriorate. If the Martens hardness exceeds 1.5 N / mm ² , the feel and texture may become coarse and wrinkle expression may be poor.

  The leather material of the present invention comprises a polyurethane resin formed by a reaction of a hot melt urethane prepolymer and a urethane curing agent as the first resin layer on the surface of the silver surface layer of the natural leather, and has a thickness having an uneven pattern. A foamed layer having a thickness of 50 to 350 μm is laminated. By selecting a polyurethane resin excellent in wear resistance and heat resistance, it is possible to impart wear resistance and heat resistance to the leather material. In addition, by setting the thickness of the resin layer within a specific range, the natural leather base material does not impair the unique texture such as touch, texture, and wrinkle expression. Furthermore, by making the resin layer a foamed layer, the rubber elasticity peculiar to the resin is relaxed and the rubbery feel is lost, and the density gradient is close to the silver surface layer of natural leather. The texture, texture, and wrinkle expression can be provided. Thus, the natural leather-like tactile sensation, texture, and wrinkle expression of the leather material of the present invention are achieved by harmonizing the elements of both the natural leather material and the foamed 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 does not soak into the silver surface layer, and the feel and texture of natural leather do not become rough. 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 is obtained at a lower temperature compared to the one-component type, so heat of natural leather The texture does not become hard. Nevertheless, the softening temperature after curing is high and the heat resistance is excellent.

  In the present invention, the foamed layer is formed by appropriately mixing a urethane prepolymer having a hot melt property and a urethane curing agent (hereinafter sometimes referred to as “prepolymer / curing agent mixture”). After applying to the moldable substrate, it is formed by bonding to the surface of the silver surface layer of natural leather and aging treatment.

  As described above, the hot melt urethane prepolymer is obtained by the reaction of a polyol and a polyisocyanate, and the hot melt urethane polyol prepolymer having a hydroxyl group at the molecular end and the isocyanate at the molecular end depending on the ratio of the polyol and the polyisocyanate at the time of production. There are two hot melt urethane polyisocyanate prepolymers with groups. 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. 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, dicyclohexylmethane diisocyanate, tetramethylxylylene diisocyanate and other aliphatic diisocyanates or fats Cyclic diisocyanate and 4,4'-diphenylmethane diisocyanate , And the like polymeric MDI containing dimers and trimers of (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 used in the present invention can be obtained by reacting the above polyol and 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 equivalent ratio exceeds 2.5, when the prepolymer and the urethane curing agent are reacted, an unreacted hydroxyl group remains and the physical properties of the polyurethane resin obtained by curing may be poor.

  On the other hand, the hot melt urethane polyisocyanate prepolymer used in the present invention is obtained by reacting the above polyol and polyisocyanate under the condition that the isocyanate group of the polyisocyanate is excessive with respect to the hydroxyl group of the polyol. Can do. 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. When the equivalence ratio is less than 1.1, hydroxyl groups remain in the prepolymer, and the polyurethane resin obtained by curing is likely to be hydrolyzed, resulting in poor physical properties. 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 touch and texture of natural leather may be cured. In the present specification, the softening temperature was 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, as a urethane curing agent. 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. Contains diisocyanate, naphthalene diisocyanate, phenylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, xylene diisocyanate, tetramethylxylene diisocyanate, norbornene diisocyanate, triphenylmethane triisocyanate, polyphenylpolymethylene polyisocyanate, carbodiimide group Polyisocyanate, alf Polyisocyanates containing sulfonate groups, such as polyisocyanates containing isocyanurate groups can be exemplified, can 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 physical properties of the polyurethane resin obtained by curing may be poor. When the equivalence ratio exceeds 2.0, the curing reaction may proceed so much that the feel and texture may become coarse. At this time, although the usage-amount of the urethane hardening | curing agent with respect to 100 weight part of prepolymers is based also on the molecular weight of a prepolymer or a urethane hardening | curing agent, it is 3-50 weight part normally, Preferably it is 5-40 weight part.

  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. At this time, although the usage-amount of the urethane hardening | curing agent with respect to 100 weight part of prepolymers is based also on the molecular weight of a prepolymer or a urethane hardening | curing agent, it is 3-50 weight part normally, Preferably it is 10-30 weight part.

  In the prepolymer / curing agent mixture, if necessary, a urethanization catalyst, a silane coupling agent, a filler, a thixotropic agent, a tackifier, 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, water repellent Oil agent, hollow foam, crystal water-containing compound, flame retardant, water absorbent, moisture absorbent, deodorant, foam stabilizer, antifoam agent, antifungal agent, antiseptic, algae preventive, pigment dispersant, inert gas , Optional components such as anti-blocking agents and anti-hydrolysis agents can be used singly or in combination of two or more. Among them, it is preferable to use a urethanization catalyst in order to reduce the process load and improve the physical properties of the leather material.

  The hot melt temperature of the hot-melt urethane prepolymer is set to a temperature that is preferably 10 to 80 ° C., more preferably 20 to 60 ° C. higher than the softening temperature. 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 / curing agent mixture 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 / curing agent mixture is preferably 25 to 300 μm, more preferably 50 to 200 μm. By setting the coating thickness within this range, it is possible to obtain a foamed layer having a thickness of 1.1 to 2 times, preferably 1.2 to 1.5 times the coating thickness, preferably 50 to 350 μm, preferably The foamed layer has a thickness of 100 to 200 μm (described later).

  The releasable substrate used in the present invention is not particularly limited, and is a substrate having an uneven pattern and having a releasability with respect to a polyurethane resin, or a substrate subjected to a release treatment. For example, a release paper, 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 can be given.

  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 that is a combination of squares, dotted lines, etc., and by using a releasable substrate having such a concavo-convex pattern, imparting design properties to the surface of the leather material Can do.

  After applying the prepolymer / curing agent mixture 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 natural leather may be deteriorated.

  The concavo-convex pattern in the present invention is different from the concavo-convex pattern by embossing, because the concavo-convex pattern is formed without changing the original shape of natural leather, so the problem of the disappearance of the concavo-convex pattern over time and the mold flow at the time of tensioning There is no risk of occurrence. Further, since the concavo-convex pattern is formed simultaneously with the formation of the foam layer, the process is simple and the productivity is improved. Further, since it is not necessary to heat and press natural leather when forming the uneven pattern, a hot melt urethane prepolymer having a high softening temperature after curing and excellent heat resistance can be selected.

  Next, while the prepolymer / curing agent mixture (a part of which is cured and becomes a polyurethane resin) has a viscous state, it is bonded to the surface of the silver surface layer of natural leather and cooled to room temperature. And by carrying out an aging process, a foaming layer is formed in the silver surface layer surface of natural leather.

  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, there is a possibility that a mold flow may occur when the releasable substrate is peeled off, and physical properties such as wear resistance may deteriorate.

  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. When the softening temperature exceeds 240 ° C., there is a possibility that the feel and texture of natural leather cannot be obtained.

  The thickness of the foam layer is required to be 50 to 350 μm. If the thickness is less than 50 μm, sufficient wear resistance may not be obtained. If the thickness exceeds 350 μm, the natural leather-specific tastes such as touch, texture, and wrinkle created by the natural leather base material may not be transmitted to the surface of the leather material. A preferable thickness range is 100 to 200 μm.

Moreover, Martens hardness of the foam layer is preferably 0.5~2.5N / mm ^2, more preferably 0.7~1.5N / mm ^2. If the Martens hardness is less than 0.5 N / mm ² , the wear resistance may deteriorate. If the Martens hardness exceeds ^2.5 N / mm ² , the feel and texture may become coarse. In addition, the Martens hardness of the foam layer was measured by the same method as the Martens hardness of natural leather. In addition, as the object to be measured, a separately prepared cured film having the same composition as the foam layer was used. Specifically, a prepolymer / curing agent mixture is applied to a desired thickness using a bar coater on a smooth polyester film having a thickness of 100 μm by dial gauge method and not subjected to surface treatment. A cured product was used.

Furthermore, the difference between the Martens hardness of the foam layer and the Martens hardness of the natural leather determined by the following formula 3 is preferably −0.5 to 0.5 N / mm ² , more preferably −0.2 to 0.2 N / mm ² . If this difference is less than −0.5 N / mm ² , the obtained leather material may have poor wear resistance. When this difference exceeds 0.5 N / mm ² , the sense of unity between the foamed layer and natural leather is lacking, and the feel and texture of the entire leather material become coarse, which may impair the unique taste of natural leather.
[Formula 3]
Martens hardness difference = Martens hardness of foam layer-Martens hardness of natural leather

  After the aging treatment, the release substrate is peeled off to obtain a laminate of natural leather and a foam layer. In the leather material of the present invention, a protective layer having a thickness of 10 to 100 μm is further laminated as a second resin layer on the surface of the foamed layer of the laminate without erasing the uneven pattern of the foamed layer. is there. Thereby, abrasion resistance further improves. In the present invention, the protective layer is a general term for resin layers formed on the surface of the foamed layer to protect the foamed layer. The protective layer is composed of at least one resin layer, but two or more resins having the same or different composition. Can consist of layers.

  The resin used for forming the protective layer is not particularly limited, and may be appropriately selected from those generally used for leather. For example, a polyurethane resin, an acrylic resin, a polyvinyl chloride resin, a polyester resin, a polyamide resin, a silicone resin, and the like can be given, and these can be used alone or in combination of two or more. Especially, a polyurethane resin or an acrylic resin is preferable in terms of excellent film strength. The form of the resin may be either solvent-based or solvent-free, but a solvent-free system, particularly a water-based emulsion is preferable from the viewpoint of less environmental burden.

  If necessary, the resin may include one optional component such as a colorant, a matting agent, a smoothing agent, a cross-linking agent, an antifoaming agent, a foam stabilizer, and a dispersing agent, as long as the physical properties of the resin are not impaired. It can be used alone or in combination of two or more. Among these, from the viewpoint of abrasion resistance, it is preferable to use a smoothing agent or a crosslinking agent as an additive in the resin layer that is the outermost layer.

  The protective layer is formed by applying a resin liquid to the surface of the foam layer and then performing a heat treatment. As the coating method, various conventionally known methods can be adopted and are not particularly limited. Examples thereof include a method using a reverse roll coater, spray coater, roll coater, gravure coater, kiss roll coater, knife coater, comma coater, and the like. Especially, application | coating with a spray coater is preferable at the point that formation of a uniform thin film layer is possible and the uneven | corrugated pattern which a foam layer has does not lose | disappear.

In the case of using a cross-linking agent that evaporates the solvent in the resin liquid and dries the resin and causes a cross-linking reaction by the heat treatment, the heat treatment promotes the reaction and forms a film having sufficient strength. Done. In order to prevent excessive moisture evaporation of the natural leather, the heat treatment is preferably performed so that the natural 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 liquid may flow into the concave and convex portions, and the concave and convex patterns may disappear, or the resin may be insufficiently crosslinked and wear resistance may not be obtained. When the heat treatment temperature exceeds 120 ° C., the feel and texture of natural leather may be cured.
Moreover, it is preferable that the heat processing time is 2 to 20 minutes, More preferably, it is 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 natural leather may cause the natural leather to shrink and cause undesirable wrinkles, or the touch and texture may be cured.

  The thickness of the protective layer is required to be 10 to 100 μm. If the thickness is less than 10 μm, it is difficult to form the skin layer uniformly, and there is a possibility that the protective layer is partially lost. When the thickness exceeds 100 μm, there is a possibility that natural leather-like feel, texture and wrinkle expression cannot be obtained. A preferable thickness range is 20 to 50 μm.

Thus, the leather material of the present invention can be obtained.
In forming the protective layer, prior to forming the foam layer on the releasable substrate, a protective layer may be formed by applying a resin to the releasable substrate and heat-treating it. The coating method at this time is not particularly limited, but coating with a knife coater or a comma coater is preferable in that a uniform thin film layer can be formed. 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 natural leather. After that, after applying a prepolymer / curing agent mixture, preferably after heat treatment, it is bonded to the surface of the silver surface layer of natural leather, an aging treatment is performed to form a foam layer, and then the release substrate is peeled off. The leather material of the present invention is obtained.

  The leather material of the present invention is excellent in various characteristics such as tactile sensation, texture, wrinkle expression, uneven pattern durability, abrasion resistance, heat resistance, etc., so that it is a member of clothing, bags, shoes, interior materials, vehicle interior materials, etc. Can be suitably used.

  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. The obtained leather material was evaluated according to the following method.

[Tactile texture]
Sensory evaluation was performed and judged according to the following criteria.
○: Flexible and has a natural leather-like feel Δ: Slightly flexible ×: Hard or flexible but rubber-like feel, not having a natural leather-like feel

[Folding wrinkles]
Sensory evaluation was performed and judged according to the following criteria.
○: Natural leather-like fine wrinkles are seen △: Slightly rough wrinkles are seen ×: Paper-like rough wrinkles are seen

[Abrasion resistance]
One test piece with a width of 70 mm and a length of 300 mm was taken from each of the vertical (head-to-butt direction) and horizontal (back-to-abdominal direction) directions, and the back surface was 70 mm wide, 300 mm long, and 10 mm thick. Attached with a urethane foam with a size of 2 mm, it is fixed to a flat surface wear tester T-TYPE (manufactured by Daiei Scientific Instruments). A test piece is worn by applying a load of 9.8 N to a friction piece covered with a cotton cloth. The frictional wear reciprocates 10,000 times at a speed of 60 reciprocations / minute between 140 mm on the surface of the test piece. The test piece after abrasion was visually observed and judged according to the following criteria.
○: No crack or tear in the protective layer △: A crack occurred in the protective layer ×: A crack occurred in the protective layer

Moreover, paying attention to the uneven pattern, the disappearance degree was determined according to the following criteria.
○: Almost no loss of uneven pattern Δ: Some uneven pattern is lost ×: Most uneven pattern is lost

[Heat-resistant]
Two test pieces each having a size of 10 cm square are collected, and one of the collected test pieces is hung in a drier adjusted to 110 ° C. so as not to come into contact with other objects, and heat-treated for 200 hours. After the treatment, the test piece is taken out and cooled to room temperature. For the initial (unheated test piece) and the treated test piece, the color value at the time of D65 light source irradiation was measured using a spectrophotometer Color i5 (manufactured by GretagMacbeth LLC). ^* Calculate the value. The smaller the Δb ^* value, the better the heat resistance.
[Formula 4]
△ b ^* = b ^* value (after heat treatment)-b ^* value (initial)

Moreover, paying attention to the uneven pattern, the disappearance degree was determined according to the following criteria.
○: Almost no loss of uneven pattern Δ: Some uneven pattern is lost ×: Most uneven pattern is lost

[Type flow of uneven pattern]
One test piece having a width of 100 mm and a length of 200 mm was taken from each of the vertical (head to buttocks) and horizontal (back to belly) directions, and as shown in FIG. The test instrument is placed so that the center is at the apex of the triangle, and 5 kg weights are fixed to both ends of the test piece with clips. In this state, the state of the concavo-convex pattern at the apex portion of the test piece was visually observed and judged according to the following criteria.
○: Almost no loss of uneven pattern Δ: Some uneven pattern is lost ×: Most uneven pattern is lost

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 having a number average molecular weight of 2000, 50 parts of polycarbonate polyol having a number average molecular weight of 2000, and 10 parts of polyether polyol having a number average molecular weight of 1000 After putting in and stirring, 15 parts of 4,4′-diphenylmethane diisocyanate (MDI) was added and stirred at 80 ° C. until the isocyanate group disappeared to obtain a hot melt urethane polyol prepolymer (softening temperature: 40 ° C.).

[Production Example 2]
In a 1 liter four-necked flask kept at 60 ° C., 80 parts of polyester polyol having a number average molecular weight of 1000, 50 parts of polycarbonate polyol having a number average molecular weight of 1000, and 10 parts of polyether polyol having a number average molecular weight of 1000 After putting in and stirring, 30 parts of 4,4′-diphenylmethane diisocyanate (MDI) was added and stirred at 80 ° C. until the isocyanate group disappeared to obtain a hot melt urethane polyol prepolymer (softening temperature: 40 ° C.).

[Production Example 3]
In a 1 liter four-necked flask kept at 60 ° C., 10 parts of polyester polyol having a number average molecular weight of 1000 and 6 parts of 4,4′-diphenylmethane diisocyanate (MDI) were added at 80 ° C. until the polyol group disappeared. The mixture was stirred to obtain a hot melt urethane isocyanate prepolymer (softening temperature: 30 ° C.).

In addition, a commercially available leather resin (both manufactured by Dainippon Ink & Chemicals, Inc.) was used for forming the protective layer. The prescription is as follows.
[Base coat resin]
LCC FF color 100
LCC Filler MK-45 100
LCC Binder S-640K 250
LCC Binder SX-909 100
LCC Binder UB-1450 100
LCC Binder UB-1770 100
LCC Assister RL 30
LCC Fixer UX-10 35
LCC Thickner NA-3 appropriate amount
Water 235
Total about 1050 parts

[Resin for top coat]
LCC WL Mat UM-2509 550
LCC WL Clear UX-2009 150
LCC WL Conditioner SL-5 60
LCC WL Conditioner SL-6 20
LCC WL Fixer UX-10 225
LCC Thickner NA-2 appropriate amount
About 110 water
Total about 1115 parts

[Example 1]
Crust was obtained by using adult cowhide as the raw hide and going through a normal process. The surface of the silver surface layer was scraped by 50 μm by treating the silver surface layer side of the leather twice with a buffing machine equipped with 180 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 natural leather of −4 mm. The thickness of the whole natural leather obtained was 1000 μm, the thickness of the silver layer was 250 μm, and the Martens hardness was 0.9 N / mm ² .

  20 parts of the hot melt urethane polyisocyanate prepolymer of Production Example 3 heated and melted at 40 ° C. as a urethane curing agent to 100 parts of the hot melt urethane polyol prepolymer of Production Example 1 heated and melted to 100 ° C. as a hot melt urethane prepolymer Add 2 parts of carbon black pigment Polyton Black (Dainippon Ink Chemical Co., Ltd.) as a colorant and 1 part of amine catalyst TOYOCAT-DT (Tosoh Corporation) as a urethanization catalyst. After stirring, it was applied to a release paper R-51 (made by Lintec Co., Ltd.) having a grainy uneven pattern with a comma coater in a sheet form so as to have a thickness of 150 μm, and then dried at 130 ° C. for 1 minute. A foam layer was formed by heat treatment.

Next, after the foamed layer has a viscous state, it is bonded to the surface of the natural leather silver surface layer, pressed with a load of 5 kg / m ² with a mangle, and subjected to an aging treatment at room temperature for 1 day. The release paper was peeled off.

  Further, a top coat resin was applied to the surface of the foamed layer with a spray coater so that the thickness after heat treatment was 20 μm, and heat-treated at 100 ° C. for 2 minutes in a dryer to form a protective layer.

The thickness of the foam layer of the obtained leather material was 180 μm, the softening temperature of the polyurethane resin was 200 ° C., and the Martens hardness was 1.1 N / mm ² . As a result, the difference between the Martens hardness of the foam layer and the Martens hardness of the natural leather was 0.2 N / mm ² .

[Comparative Example 1]
The base coat resin was applied to the surface of the silver surface layer of natural leather treated in the same manner as in Example 1 with a roll coater so that the wet weight was 120 g / m ^2, and heat-treated at 80 ° C. for 10 minutes with a dryer. Thus, a base coat layer having a thickness of 40 μm was formed. Next, after embossing was applied on the embossing machine under conditions of 80 ° C., 60 kg / m ² and 5 m / sec, the embossing machine was rubbed for 30 minutes under the conditions of 20 ° C. and 20% RH. Further, a top coat resin is applied on the surface of the base coat layer with a spray coater so that the wet weight is 40 g / m ^2, and heat-treated at 100 ° C. for 2 minutes with a dryer to form a top coat layer having a thickness of 10 μm. Formed.

[Examples 2 to 6 and Comparative Examples 2 to 4]
In producing the leather material, leather materials of Examples 2 to 6 and Comparative Examples 2 to 4 were obtained in the same manner as in Example 1 except that various conditions were set as shown in Table 1.

  Table 2 shows the results of evaluating the performance of the leather materials of the above Examples and Comparative Examples.

As is clear from Table 2, the leather materials of Examples 1 to 6 showed good results in each evaluation item. In particular, the leather material of Examples 1 to 5 in which the difference between the Martens hardness of the foam layer and the Martens hardness of the natural leather is in the range of -0.2 to 0.5 N / mm ² has a high characteristic peculiar to natural leather. It was reproduced. On the other hand, in Comparative Example 1 in which the protective layer was formed by the conventional technique, a mold flow with an uneven pattern was generated. In Comparative Example 2 where the thickness of the foamed layer was large, the tactile sensation and texture were poor, and in Comparative Example 3 where the thickness of the foamed layer was small, fine wrinkle expression and wear resistance were poor. In Comparative Example 4 using a floor leather without a silver layer as a natural leather, the tactile sensation, texture, fine wrinkle expression, and abrasion resistance were poor.

It is the schematic which shows the evaluation method of the type | mold flow of an uneven | corrugated pattern.

Explanation of symbols

A Test piece B Weight C Clip

Claims (4)

  A surface of natural leather having a silver surface layer having a thickness of 200 to 1000 μm is made of a polyurethane resin formed by a reaction of a hot melt urethane prepolymer and a urethane curing agent, and a foam layer having a concavo-convex pattern and having a thickness of 50 to 350 μm. A leather material, characterized in that it is laminated and a protective layer having a thickness of 10 to 100 μm is laminated on the surface thereof without erasing the uneven pattern of the foam layer.   The leather material according to claim 1, wherein the polyurethane resin has a softening temperature of 130 to 240 ° C. Martens hardness of natural leather is 0.7 to 2.0 N / mm ² , Martens hardness of foam layer is 0.5 to 2.5 N / mm ² , and Martens hardness of foam layer and natural leather The leather material according to claim 1 or 2, wherein the difference from the Martens hardness is -0.5 to 0.5 N / mm ² .   After applying a mixture of a hot melt urethane prepolymer and a urethane curing agent to a moldable substrate having irregularities, a silver surface layer of natural leather subjected to buffing while the mixture has a viscosity A leather characterized in that after bonding to the surface and aging treatment to form a foamed layer, the release substrate is peeled off, a resin is applied to the surface of the foamed layer, and heat treatment is performed to form a protective layer. Material manufacturing method.

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