Laminate, laminate structure, and automobile interior material

Abstract

The present invention addresses the problem of providing a laminate which does not generate wrinkles or peeling even in a conventional molding machine, more specifically, a laminate obtained by bonding a crosslinked polyolefin resin foam and suede-like artificial leather.　Provided is a laminate in which a skin material and a crosslinked polyolefin resin foam are directly bonded or bonded via a layer having an adhesive function, wherein the skin material is at least one selected from the group consisting of artificial leather, synthetic leather, woven fabric, knitted fabric, nonwoven fabric, and felt, and the heat shrinkage rate when heated at 180°C for 10 minutes is 0.5-10%.

Description

Laminates, laminated structures, and automotive interior materials

[0001] This invention relates to laminates, laminated structures, and automotive interior materials.

[0002] Cross-linked polyolefin resin foams are frequently used in automotive interior materials to improve tactile feel, flexibility, and appearance, and improvements have been made over time. From a tactile perspective, for example, by appropriately adjusting the relationship between strain and stress, cross-linked polyolefin resin foams that feel soft have been developed and are approaching a good level.

[0003] On the other hand, for automotive interior materials where appearance is a priority, foams made by laminating artificial leather and other materials have been proposed. In such technologies, the appearance is improved and flexibility can be maintained to a certain extent. However, in addition to the insufficient improvement in flexibility, the adhesive strength is inadequate, and shrinkage occurs when exposed to high temperatures such as during molding or when driving, and delamination remains a problem. Patent Document 1 attempts to solve these problems, focusing on improving the heat resistance and adhesiveness of the laminate during molding and other processes.

[0004] Furthermore, it is said that when cross-linked polyolefin resin foam is used in automotive interior materials with deep and sharp shapes, appearance defects are likely to occur. As a countermeasure, Patent Document 2 discloses a technique in which a non-foamed surface material is laminated onto the surface of a two-layer laminated foam sheet.

[0005] International Publication No. 2023 / 181789, Japanese Patent Publication No. Sho 62-174131

[0006] However, when the laminate described in Patent Document 1 is used as an interior material for vehicles, the shape and processing conditions of the interior material are restricted in order to maintain the luxurious feel and texture inherent in artificial leather during the molding process, and wrinkles and peeling may occur, leading to a decrease in productivity.

[0007] The technology described in Patent Document 2 requires a two-layer structure for the foamed sheet, and further requires the lamination of adhesive layers and surface materials. As a result, the effort and cost of creating the laminate itself are significant, making it impractical for real-world use.

[0008] Therefore, the present invention aims to provide a laminate that does not produce wrinkles or peeling even with conventional molding machines, more specifically, a laminate formed by bonding a cross-linked polyolefin resin foam with various fabrics, including suede-like artificial leather, as the surface material, and that maintains the luxurious feel and texture of the surface material even after molding.

[0009] The inventors of this invention conducted diligent research and discovered that a laminate that does not produce wrinkles or peeling can be obtained not by the adhesion between the two layers, as focused on in conventional technology, but by adjusting the thermal shrinkage rate when heated to a certain range, thus arriving at the present invention.

[0010] In other words, the present invention is as follows: (1) A laminate comprising a surface material and a crosslinked polyolefin resin foam directly bonded together, or bonded together via an adhesive layer, wherein the surface material is at least one selected from the group consisting of artificial leather, synthetic leather, woven fabric, knitted fabric, nonwoven fabric, and felt, and the heat shrinkage rate when heated at 180°C for 10 minutes is 0.5% or more and 10% or less. (2) The laminate according to (1), wherein the surface material is artificial leather comprising a fiber entanglement body made of ultrafine fibers and a polymer elastic body. (3) The laminate according to (1) or (2), wherein the heat shrinkage rate of the crosslinked polyolefin resin foam when heated at 180°C for 10 minutes is 25% or more and 40% or less. (4) The laminate according to any one of (1) to (3), wherein the amount of change in the heating angle of the crosslinked polyolefin resin foam is 12 degrees or less. (5) A laminate according to any one of (1) to (4), comprising an adhesive between artificial leather and a crosslinked polyolefin resin foam. (6) A laminated structure formed by bonding the laminate according to any one of (1) to (5) with another substrate. (7) An automotive interior material made using the laminated structure according to (6).

[0011] Conceptual diagram showing a basic example of how to cut evaluation samples from a sheet of foam. Conceptual diagram showing an example of how to cut evaluation samples from a 90 cm wide sheet of foam. Example of calculating the average value. An example of cutting 3 sheets of foam lengthwise and 3 sheets widthwise, for a total of 9 sheets. Diagram of the actual evaluation sample. Diagram of the evaluation sample viewed from directly above. Conceptual diagram of an apparatus for manufacturing laminates from surface material and cross-linked polyolefin resin foam.

[0012] The present invention will be described in detail below.

[0013] The laminate of the present invention is formed by directly bonding a surface material such as artificial leather or other fabrics composed of a fiber entanglement body made of ultrafine fibers and a polymeric elastic material to a crosslinked polyolefin resin foam, or by bonding them via an adhesive layer, and has a heat shrinkage rate of 0.5% to 10% when heated at 180°C for 10 minutes. In this invention, the crosslinked polyolefin resin foam may be simply referred to as the foam.

[0014] <Laminate> As described above, the laminate of the present invention is formed by directly bonding a surface material such as artificial leather or various other fabrics, which consists of a fiber entanglement body made of ultrafine fibers and a polymer elastic material, to a crosslinked polyolefin resin foam, or by bonding them via a layer with adhesive function. In the present invention, the layer with adhesive function is not particularly limited as long as it is a film or an adhesive layer having continuity and uniformity. Specifically, the film or adhesive layer having continuity and uniformity is preferably a thermoplastic resin layer, and a thermoplastic resin layer selected from polyacrylic resin, polyester resin, polystyrene resin, polyamide resin, polyurethane resin, polymethacrylimide resin, polyolefin resin, etc., or copolymers and modified versions thereof can be preferably used. These may also be resins blended from two or more types, and polyolefin resin is most preferred.

[0015] Among polyolefin resins, polyethylene resins, particularly linear low-density polyethylene or ethylene-vinyl acetate copolymers, are preferred from the viewpoint of adhesion between the surface material and the cross-linked polyolefin resin foam, bending stress, and tensile strength.

[0016] The adhesive layer is preferably of a thickness that does not significantly affect the physical properties of the laminate, such as mechanical strength and flexibility, and is preferably formed on the surface of the surface material or cross-linked polyolefin resin foam by methods such as film application, melting, or dissolving. Furthermore, the thickness of this adhesive layer is preferably 1 μm or more and 400 μm or less.

[0017] There are no restrictions on the method of directly bonding the surface material and the cross-linked polyolefin resin foam, or bonding them via an adhesive layer. Examples of direct bonding methods include heat fusion, where the bonding surfaces of the surface material and the cross-linked polyolefin resin foam are heated and melted to directly bond them, and placing an adhesive between the surface material and the cross-linked polyolefin resin foam. Examples of bonding via an adhesive layer include placing an adhesive layer between the surface material and the cross-linked polyolefin resin foam. Among these, the method of placing an adhesive or an adhesive layer between the surface material and the cross-linked polyolefin resin foam is preferred in terms of adhesive strength and productivity.

[0018] Methods for applying an adhesive layer or adhesive include, for example, performing electrical discharge machining on the surface of the cross-linked polyolefin resin foam that comes into contact with the adhesive, introducing hydroxyl groups to the surface to improve adhesion, and applying the adhesive to the cross-linked polyolefin resin foam and bonding them together. Combining these methods can further improve adhesion. Examples of adhesives include polyurethane-based reactive hot melt adhesives, polyolefin-based reactive hot melt adhesives, photocurable hot melt adhesives, various resin emulsions, two-component polyurethane adhesives, and polyester-based and urethane-based solvent adhesives.

[0019] The laminate of the present invention may also have an adhesive layer laminated or an adhesive applied to the surface to be bonded to another substrate. By adopting such a configuration, the laminate can be bonded to another base material to manufacture a laminated structure which can be used for furniture, chairs and wall materials, as well as seats, ceilings and interiors in the interiors of vehicles such as automobiles, trains and aircraft.

[0020] The present invention provides a laminate formed by bonding a cross-linked polyolefin resin foam with various surface materials, including suede-like artificial leather. The surface materials used have a high-quality texture and appearance, as well as excellent feel and flexibility. While their use as lining is not out of the question, it is preferable to use them as the outer surface, i.e., as the outer base fabric.

[0021] There are no particular restrictions on the manufacturing process of laminates of cross-linked polyolefin resin foams using a variety of fabrics, including artificial leather, as the surface material. A typical process involves applying an adhesive to the cross-linked polyolefin resin foam and / or to the surface material, and then bonding the two together. Methods for applying the adhesive include spraying it directly onto the target material (cross-linked polyolefin resin foam and / or surface material), or applying it to release paper, attaching the release paper to the target material, and then peeling off the release paper. However, the method using release paper is preferred because it allows for stable work.

[0022] Furthermore, it is preferable to laminate the surface material and the cross-linked polyolefin resin foam in a manner that aligns the MD direction of the surface material with the MD direction of the cross-linked polyolefin resin foam.

[0023] In the laminate of the present invention, the maximum peel strength of the interfacial peel between the surface material and the cross-linked polyolefin resin foam, or the maximum peel strength of material breakage, is preferably 15 N / 25 mm or more in both the MD direction and the TD direction, and more preferably 20 N / 25 mm or more. By setting the maximum peel strength of the interfacial peel or the maximum peel strength of material breakage to 15 N / 25 mm or more, the surface material and the cross-linked polyolefin resin foam are less likely to separate when broken, resulting in a better appearance, and the problem of parts of the surface material and cross-linked polyolefin resin foam scattering is also less likely to occur. In particular, in automotive interior materials equipped with airbags, the surface material and the cross-linked polyolefin resin foam are less likely to separate due to the impact of the airbag breaking the laminate, thus reducing concerns that they may hit the driver or passenger. There is no upper limit to the maximum peel strength between the constituent materials of the laminate or laminated structure of the present invention, but it is preferably 150 N / 25 mm or less, and more preferably 45 N / 25 mm or less. Furthermore, the ratio of the peel strength in the MD direction to the peel strength in the TD direction (MD direction peel strength / TD direction peel strength) is preferably 1.0 to 1.3, and more preferably 1.03 to 1.25, from the viewpoint of morphological stability and dimensional stability. Methods for setting the maximum peel strength of interfacial peeling, the maximum peel strength of material breakage, and the MD direction peel strength / TD direction peel strength to the above range include, for example, adjusting the strength of the crosslinked polyolefin resin foam itself, selecting an adhesive, and selecting a coating method.

[0024] [Heat Shrinkage Rate of Laminate] As described above, the heat shrinkage rate of the laminate of the present invention is 0.5% or more and 10% or less when heated at 180°C for 10 minutes. Here, "the heat shrinkage rate of the laminate is 0.5% or more and 10% or less" means that the heat shrinkage rate is 0.5% or more and 10% or less in both the MD direction and the TD direction of the laminate. If the heat shrinkage rate of the laminate is less than 0.5% or more than 10%, when the laminate is used as an automotive interior material, wrinkles will occur in the adhesion between the laminate and the resin substrate, and reliable adhesion will not be possible. From the viewpoint of further reducing the rate of wrinkle occurrence, the heat shrinkage rate of the laminate is preferably 1% or more, more preferably 2% or more, and most preferably 2.5% or more. Furthermore, the heat shrinkage rate of the laminate is preferably 9% or less, more preferably 8% or less, and most preferably 7.5% or less. Note that the shrinkage rate is often greater in the MD direction than in the TD direction. Therefore, for example, it is permissible to set the heat shrinkage rate in the MD direction higher than the heat shrinkage rate in the TD direction, such as setting the heat shrinkage rate in the MD direction to 1% or more and 10% or less, and the heat shrinkage rate in the TD direction to 0.5% or more and 8% or less.

[0025] Methods for adjusting the heat shrinkage rate of the laminate within the above range include, for example, adjusting it with a cross-linked polyolefin resin foam, adjusting it with a surface material, and adjusting the manufacturing method of the laminate.

[0026] As a method for adjusting the cross-linked polyolefin resin foam, it is preferable to keep the heat shrinkage rate of the cross-linked polyolefin resin foam within a specific range, as will be described later. From a different perspective, it is also preferable to keep the change in heating angle of the cross-linked polyolefin resin foam within a specific range. If the cross-linked polyolefin resin foam falls outside these numerical ranges, it becomes more prone to deformation when heated and molded, which is undesirable.

[0027] Regarding the method of adjusting with surface material, various factors such as the type and weight of the surface material, the elongation rate of the surface material, and the tension during the manufacturing process can cause changes in various properties.

[0028] In addition, there are various methods for manufacturing the laminate, and since there are a number of adjustment items for each manufacturing method, the heat shrinkage rate of the laminate can be appropriately set within a desirable range according to the manufacturing method employed.

[0029] The heat shrinkage rate of the laminate varies depending on at least one of the conditions of the crosslinked polyolefin-based resin foam, the skin material, and the lamination conditions. It can be said that the quality of the formability of the laminate is almost determined by the heat shrinkage rate of the laminate.

[0030] Here, the laminate of the present invention preferably has a heat shrinkage rate of 3% or less, more preferably 2% or less, and most preferably 1.5% or less when heated at 110°C for 120 minutes. By setting the heat shrinkage rate of the laminate when heated at 110°C for 120 minutes within the above range, particularly when the laminate is used as an automotive interior material, the possibility of losing the aesthetic appearance of the interior material using the laminate even when exposed to a high-temperature environment in summer tends to decrease. Examples of methods for setting the heat shrinkage rate of the laminate when heated at 110°C for 120 minutes within the above range include a method of reducing the heat shrinkage rate of the foam, a method of increasing the gel fraction of the foam, and a method of increasing the melting point of the foam or the melting point of the polyolefin-based resin used as the raw material of the foam.

[0031] The heat shrinkage rate when the laminate is heated at 180°C for 10 minutes and the heat shrinkage rate when it is heated at 110°C for 120 minutes are not necessarily correlated. This is considered to be due to the properties of the foam, particularly the resin softening temperature of the foam, the skin material, the adhesive, etc. Even if the heat shrinkage rate when heated at 110°C for 120 minutes is 1% or less, the heat shrinkage rate when heated at 180°C for 10 minutes may exceed 10%. Therefore, when aiming for the highest level of characteristics as an automotive interior material, it is preferable to improve the heat shrinkage rate for 10 minutes at 180°C and then aim to improve the heat shrinkage rate for 120 minutes.

[0032] A laminate in which a plurality of foams are adhered directly or through an adhesive functional layer and further adhered to a skin material, and having a heat shrinkage rate of 0.5% or more and 10% or less at 180°C for 10 minutes also has improved moldability. However, the improvement in moldability by combining a plurality of foams is not so great, and the addition of productivity and cost increases. Therefore, it is preferable to use a single layer of the foam itself.

[0033] <Crosslinked polyolefin resin foam> [Heat shrinkage rate of the foam] In the laminate of the present invention, the heat shrinkage rate of the crosslinked polyolefin resin foam when heated at 180°C for 10 minutes is preferably 25% or more and 40% or less. By setting the heat shrinkage rate of the crosslinked polyolefin resin foam to 25% or more, the heat shrinkage rate of the laminate is likely to be within an appropriate range, and when used as an automotive interior material, the heat resistance becomes better. By setting the heat shrinkage rate of the crosslinked polyolefin resin foam to 40% or less, the heat shrinkage rate of the laminate is likely to be within an appropriate range, and when used as an automotive interior material, the flexibility often becomes higher. The heat shrinkage rate of the crosslinked polyolefin resin foam is more preferably 26% or more, and most preferably 28% or more. On the other hand, the heat shrinkage rate of the crosslinked polyolefin resin foam is more preferably 38% or less, further preferably 35% or less, and most preferably 33% or less.

[0034] As a method for setting the heat shrinkage rate of the crosslinked polyolefin resin foam to the above range when heated at 180°C for 10 minutes, for example, setting of foaming conditions according to the raw materials, particularly optimization of the setting of the foaming rate and the foaming tension of the foaming polyolefin resin sheet, etc. can be mentioned. As an example, in addition to the method of reducing the tension of the sheet during foaming or increasing the foaming time during foam production, methods of adjusting the elongation rate in the MD direction or TD direction at the stage of solidification after foaming, methods of reducing the tension at the stage of solidification after foaming, methods of raising the resin temperature again after solidification to relax the shrinkage, etc. can be mentioned. It should be noted that these adjustments are preferably carried out by setting the foaming conditions according to the selection of the raw material resin and the raw material resin to be used, and appropriately setting the conditions for producing a laminate suitable for molding.

[0035] In the laminate of the present invention, it is preferable that the heat shrinkage rate of the crosslinked polyolefin resin foam when heated at 180°C for 10 minutes is 25% or more and 40% or less, and that the heat shrinkage rate of the crosslinked polyolefin resin foam when heated at 120°C for 60 minutes is 5% or less. By setting the heat shrinkage rate of the crosslinked polyolefin resin foam within the above range, it becomes easier to reduce the heat shrinkage rate of the laminate, especially when heated at 110°C for 120 minutes. As a method for setting the heat shrinkage rate of the crosslinked polyolefin resin foam when heated at 120°C for 60 minutes within the above range, for example, is to appropriately set the foaming speed and the tension of the foamable polyolefin resin sheet during foaming. Furthermore, as mentioned above, in addition to methods such as reducing the tension of the sheet during foaming or increasing the foaming time during foam manufacturing, other methods include reducing the tension during the solidification stage after foaming, and raising the resin temperature again after solidification to mitigate shrinkage. However, when adjusting the heat shrinkage rate at 120°C, the raw material resin has a greater influence than when adjusting it at 180°C, and using a raw material resin with a melting point of around 120°C or below plays an important role.

[0036] In the laminate of the present invention, it is preferable that the heat shrinkage rate of the crosslinked polyolefin resin foam when heated at 180°C for 10 minutes is 25% to 40%, and that the heat shrinkage rate of the crosslinked polyolefin resin foam when heated at 70°C for 60 minutes is 1.5% or less. If the heat shrinkage rate is 1.5% or less, the dimensions of the foam will not change even when the temperature is raised to 70°C, and no problems will occur during the manufacture of automotive interior materials. Furthermore, when installed in a vehicle, it will not undergo dimensional changes even when exposed to sunlight. To further improve this characteristic, the heat shrinkage rate when heated at 70°C for 60 minutes is preferably 1.0% or less, more preferably 0.7% or less. Methods for achieving the above range for the heat shrinkage rate when heated at 70°C for 60 minutes include, for example, adjusting the tension of the foam during foam production, increasing the gel fraction of the foam, and increasing the melting point of the foam.

[0037] [Change in Heating Angle] In the laminate of the present invention, it is preferable that the change in heating angle of the crosslinked polyolefin resin foam is 12 degrees or less. By setting the change in heating angle to 12 degrees or less, productivity is further improved and more stable, and the disorder of the nap direction of the artificial leather is also reduced. The change in heating angle is preferably 10 degrees or less, more preferably 5 degrees or less, and most preferably 3 degrees or less. The method for measuring the change in heating angle is as described below. The change in heating angle is measured at the melting point + 20°C as described below, because the reason is that the melting point + 20°C is close to the molding temperature. In this specification, "change in heating angle of 12 degrees or less" may be expressed as "maximum value of change in heating angle of 12 degrees or less". Both have the same meaning.

[0038] One common application for cross-linked polyolefin resin foams or laminates is in automotive interior instrument panels. In this application, the area around the speedometer has significant irregularities and curved sections, requiring the sheet-like foam to be applied smoothly and efficiently without wrinkles. Increasing the yield of the final product is also essential. Reducing the heating angle change significantly improves wrinkle formation, efficiency, and yield.

[0039] Methods to keep the heating angle change of cross-linked polyolefin resin foam within the above range include, for example, selecting the foaming method, preventing and removing sheet deformation and wrinkles during foaming, adjusting the foaming speed, and selecting foaming conditions according to the raw materials. To explain the selection of foaming methods in more detail, for example, among the salt bath foaming, horizontal hot air foaming method, and vertical hot air foaming method described later, salt bath foaming is generally easier to keep the heating angle change within the above range under a wide range of foaming conditions. In salt bath foaming, by optimizing the foaming conditions according to the raw materials, especially the foaming speed, it is possible to achieve a temperature of 10 degrees or less, 5 degrees or less with further optimization, and 3 degrees or less by maintaining the best value. Even with salt bath foaming, if the removal of sheet deformation that occurs during foaming is neglected, the heating angle change often exceeds 12 degrees even when foaming with the same raw materials and foaming speed, so it is necessary to optimize deformation removal. On the other hand, when using the horizontal or vertical hot air foaming method, the change in the heating angle of the foam often exceeds 12 degrees. However, by optimizing the foaming conditions and foaming speed according to the raw materials, adjusting the stretch ratio in the MD and TD directions at the stage when solidification begins after foaming, and mitigating deformation by reheating the foam after foaming, the change in the heating angle can be reduced to 10 degrees or less.

[0040] In the laminate of the present invention, it is preferable that the difference between the maximum and minimum values ​​of the heating angle change of the cross-linked polyolefin resin foam is 6 degrees or less. By setting the difference between the maximum and minimum values ​​of the heating angle change to 6 degrees or less, productivity is further improved, stability is increased, and surface material disturbance is less likely to occur. More preferably, the difference between the maximum and minimum values ​​of the heating angle change is 3 degrees or less, and most preferably 2 degrees or less.

[0041] One method for ensuring that the difference between the maximum and minimum values ​​of the heating angle change of a cross-linked polyolefin resin foam is 6 degrees or less is to optimize the foaming speed setting using a salt bath foaming method.

[0042] Furthermore, it is preferable that the change in the heating angle of the entire laminate of the present invention is 6 degrees or less. By keeping the change in the heating angle of the entire laminate to 6 degrees or less, productivity is not only improved and stabilized, but the texture of the surface material (mainly artificial leather) is maintained. More preferably, the change in the heating angle of the entire laminate is 3 degrees or less, and most preferably 2 degrees or less.

[0043] Furthermore, it is preferable that the difference between the maximum and minimum values ​​of the heating angle change for the entire laminate is 6 degrees or less. By making the difference between the maximum and minimum values ​​of the heating angle change for the entire laminate 6 degrees or less, productivity can be further improved, and the disorder of the nap direction of the artificial leather can be further reduced.

[0044] [Method for Producing Foam] As for the method for producing the foam in the present invention, there are no particular limitations as described below, but an atmospheric pressure foaming method is preferred, which involves melt-kneading a polyolefin resin composition containing a polyolefin resin, a crosslinking aid, a foaming agent, and a lubricant, combining this with a crosslinking step, and foaming by heating at atmospheric pressure. First, the polyolefin resin, crosslinking aid, foaming agent, and lubricant will be described.

[0045] [Polyolefin Resin] The polyolefin resin used in the present invention is not particularly limited, but it is preferable that the polyolefin resin contains at least one of a polypropylene resin, a polyethylene resin, or a thermoplastic elastomer resin.

[0046] While there are no particular limitations on the composition ratio of the polyolefin resin used in the present invention, if the base resin mainly consists of polyethylene resin and polypropylene resin and does not contain thermoplastic elastomer resin, it is preferable to use a resin mixture consisting of 0% to 50% by mass of polyethylene resin and 50% to 100% by mass of polypropylene resin as the base resin. Furthermore, if the base resin consists of polyethylene resin, polypropylene resin, and polyolefin elastomer resin, it is preferable from the viewpoint of moldability, heat resistance, etc. to use a resin mixture containing 0% to 30% by mass of polyethylene resin, 30% to 80% by mass of polypropylene resin, and 20% to 50% by mass of polyolefin elastomer as the base resin.

[0047] In the present invention, the melting point of the polyolefin resin is preferably 110°C or higher. Furthermore, when two or more types of polyolefin resins are used, it is preferable that the melting point of the polyolefin resin with the highest melting point is 110°C or higher. Having a melting point within the above range makes it easier to reduce the heat shrinkage rate of the crosslinked polyolefin resin foam or laminate made using the polyolefin resin. There is no particular upper limit to the melting point, but it is usually around 165°C. The method for measuring the melting point is described below.

[0048] Examples of polypropylene resins used in the present invention include homopolypropylene, ethylene-propylene random copolymer, and ethylene-propylene block copolymer. Copolymers of propylene monomer and other copolymerizable monomers may also be used as needed. The polypropylene resin in the crosslinked polyolefin resin foam may be a blend of two or more types, rather than just one type. Furthermore, there are no particular restrictions on the polymerization method of these polypropylene resins; high-pressure methods, slurry methods, solution methods, and gas-phase methods may all be used. The polymerization catalyst is also not particularly limited and can be a Ziegler catalyst, metallocene catalyst, etc.

[0049] Examples of polyethylene resins include high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), ethylene-ethyl acrylate copolymer (EEA), and ethylene-butyl acrylate copolymer (EBA). Copolymers of ethylene monomer and other copolymerizable monomers can also be used as needed. These polyethylene resins may be used individually or blended from two or more types. Furthermore, there are no particular restrictions on the polymerization method of these polypropylene resins; high-pressure methods, slurry methods, solution methods, and gas-phase methods are all acceptable, and the polymerization catalyst is not particularly limited, including Ziegler catalysts and metallocene catalysts.

[0050] The thermoplastic elastomer resin may be any of the conventionally known resins, such as polystyrene-based thermoplastic elastomers (SBC, TPS), polyolefin-based thermoplastic elastomers (TPO), vinyl chloride-based thermoplastic elastomers (TPVC), polyurethane-based thermoplastic elastomers (TPU), polyester-based thermoplastic elastomers (TPEE, TPC), polyamide-based thermoplastic elastomers (TPAE, TPA), and polybutadiene-based thermoplastic elastomers.

[0051] [Crosslinking Aid] The crosslinked polyolefin resin foam used in the present invention can be produced using a crosslinking aid and polyolefin resins. A polyfunctional monomer can be used as the crosslinking aid. Examples of polyfunctional monomers that can be used include divinylbenzene, diallylbenzene, divinylnaphthalene, divinylbiphenyl, divinylcarbazole, divinylpyridine and their nuclear-substituted compounds and closely related congeners, acrylic acid compounds such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, butylene glycol diacrylate, and butylene glycol dimethacrylate, or methacrylic acid compounds, and vinyl esters of aliphatic dicarboxylic acids or aromatic dicarboxylic acids.

[0052] [Foaming Agent] The crosslinked polyolefin resin foam used in the present invention is manufactured by mixing a foaming agent capable of generating gas with a polyolefin resin composition. Examples of manufacturing methods include an atmospheric pressure foaming method in which a thermal decomposition type chemical foaming agent is added to a polyolefin resin composition as a foaming agent, melt-kneaded, and foamed under atmospheric pressure heating; an extrusion foaming method in which a thermal decomposition type chemical foaming agent is heated and decomposed in an extruder and foamed while being extruded under high pressure; and a press foaming method in which a thermal decomposition type chemical foaming agent is heated and decomposed in a press die and foamed under reduced pressure. The atmospheric pressure foaming method, in which a thermal decomposition type chemical foaming agent is added to a polyolefin resin composition as a foaming agent, melt-kneaded, combined with a crosslinking process, and foamed under atmospheric pressure heating, is the most preferred.

[0053] The thermal decomposition type chemical blowing agent used here is a chemical blowing agent that decomposes and releases gas when heat is applied, and examples of organic blowing agents include azodicarbonamide, N,N'-dinitrosopentamethylenetetramine, and p,p'-oxybenzenesulfonylhydrazide.

[0054] [Lubricants] Known lubricants used in foam molding can be used as lubricants in cross-linked polyolefin resin foams. Examples include fatty acid amides; fatty acid carboxylic acids and their derivatives such as stearic acid, behenic acid, and 12-hydroxystearic acid; hydrocarbons such as liquid paraffin, paraffin wax, microwax, and polyethylene wax; fatty acid esters such as butyl stearate, monoglyceride stearate, pentaerythritol tetrastearate, hydrogenated castor oil, and stearyl stearate; higher alcohols such as stearyl alcohol; and metal soaps such as calcium stearate, zinc stearate, magnesium stearate, and lead stearate.

[0055] Examples of fatty acid amides include hydroxy fatty acid amides, stearic acid amides, oleic acid amides, erucic acid amides, methylenebisstearic acid amides, ethylenebisstearic acid amides, and ethylenebisstearic acid amides.

[0056] Within the limits that do not impair the features of the present invention, various additives such as foaming agent decomposition accelerators, bubble nucleation modifiers, antioxidants, heat stabilizers, colorants, flame retardants, antistatic agents, and inorganic fillers can be incorporated into the polyolefin resin composition.

[0057] [Foam Manufacturing Process] Next, we will describe an example of the manufacturing process for crosslinked polyolefin resin foam.

[0058] Although there are no particular limitations on the manufacturing process of crosslinked polyolefin resin foam, a preferred method is atmospheric pressure foaming, which involves melt-kneading a polyolefin resin composition containing a polyolefin resin, a crosslinking aid, a thermal decomposition type chemical blowing agent, and a lubricant, combining this with a crosslinking step, and then foaming it by heating at atmospheric pressure. Specifically, in a preferred embodiment, it can be manufactured by a manufacturing process that includes the following steps 1 to 3. Each step is described below.

[0059] • Process 1 This process involves uniformly mixing a polyolefin resin with a pyrolysis-type foaming agent, crosslinking aid, lubricant, etc., necessary for creating a foam, to produce a sheet of uniform thickness. The mixing of the polyolefin resin and the foaming agent can be done using extruders such as single-screw extruders, twin-screw extruders, or tandem extruders, as well as kneader mixers such as mixing rolls or Banbury mixers. Among these, using a twin-screw extruder is preferable because it allows for control of both mixing performance and resin temperature. Furthermore, it is preferable to provide a vacuum vent in the twin-screw extruder to prevent the generation of large air bubbles and to equip it with a gear pump to stabilize the thickness. In addition, by providing a die for forming a sheet shape, such as a T-die, at the tip, it is possible to continuously produce long sheets.

[0060] As mentioned above, azodicarbonamide is preferred as the foaming agent to obtain a flexible foam with a smooth surface. Furthermore, polyfunctional monomers such as divinylbenzene and 1,6-hexanediol dimethacrylate are preferred as crosslinking aids.

[0061] Step 2: This step involves irradiating the polyolefin resin prepared in Step 1 with a predetermined amount of ionizing radiation to crosslink the resin. Examples of ionizing radiation include alpha rays, beta rays, gamma rays, and electron beams. The irradiation dose of ionizing radiation varies depending on the target gel fraction, the shape and thickness of the irradiated object, etc., but the irradiation dose is usually 1 to 20 Mrad, preferably 1 to 10 Mrad. If the irradiation dose is too low, the crosslinking will not proceed sufficiently and the effect will be insufficient, and if it is too high, the resin may decompose, which is undesirable. Among these, electron beams are preferred because the resin can be efficiently crosslinked for irradiated objects of various thicknesses by controlling the electron acceleration voltage. The acceleration voltage is preferably in the range of 200 to 1000 kV. If the acceleration voltage is too low, the gel fraction on the non-irradiated side may be insufficient, and conversely, if the acceleration voltage is too high, the gel fraction on the irradiated side may be insufficient. There are no particular restrictions on the number of irradiations with ionizing radiation.

[0062] In this invention, the degree of crosslinking affects the heat shrinkage rate of the laminate and the heat shrinkage rate of the crosslinked polyolefin resin foam itself. Therefore, in addition to adjusting the irradiation dose of ionizing radiation, it is also necessary to adjust the amount of polyfunctional monomers added, such as divinylbenzene and 1,6-hexanediol dimethacrylate.

[0063] Step 3: This step involves heating the foamable polyolefin resin sheet prepared in Step 2 to obtain a foam. The heating method can be any conventionally known method, such as a vertical or horizontal hot air foaming furnace, a salt bath foaming furnace, or even on a chemical bath.

[0064] In salt bath foaming, two to four components of sodium, potassium, calcium, and magnesium nitrates or nitrites are mixed and heated above the melting point of the resin to create a molten salt, on which the resin is floated and foamed.

[0065] Horizontal or vertical hot air foaming is a method of heating and foaming resin by continuously supplying it into a furnace set to 200-300°C.

[0066] In any foaming method, it is also possible to heat the resin by using an infrared heater or the like in combination.

[0067] In order to optimize and improve the amount of change in the heating angle and the heating shrinkage rate of the foam regardless of the method of heat foaming, it is also preferable to heat-treat the foam itself. As a method of this treatment, it can be carried out in a vertical or horizontal hot air furnace, a hot water bath, etc. Also, it is preferable to perform stable heating and strain treatment on a roller using a roller. It is also possible to improve the amount of change in the heating angle and the heating shrinkage rate of the foam by performing heat treatment immediately after heating and foaming the foamed polyolefin resin sheet, or to add it as an individual process after completing the foaming process and once commercializing the product. As means for improving the strain and shrinkage rate of the foam by devising the foaming process and the heat treatment after the foaming process, there are descriptions in documents such as JP-A-63-47128, JP-A-9-300379, JP-B-7-4828, JP-A-52-123460, and the distortion removal of a foamed sheet by the reheating zone No. 75 of the Patent Office Gazette No. 57(1982)-133

[3347] issued on August 3, 1982.

[0068] [Properties of the Foam] The apparent density of the crosslinked polyolefin resin foam is preferably ３ 20 kg / m ３ or more and ３ 100 kg / m ３ or less. When the apparent density is 20 kg / m ３ or more, the tensile strength of the foam falls within a preferable range for automotive interior materials. When the apparent density is 100 kg / m ３ or less, the foam becomes light and soft, and the compression flexibility falls within a preferable range for automotive interior materials. When used as an automotive interior material, the apparent density of the crosslinked polyolefin resin foam is preferably ３ 30 kg / m ３ or more and ３ 100 kg / m ３ or less, more preferably

[0069] The gel fraction of the crosslinked polyolefin resin foam is preferably in the range of 30% to 70%. When the gel fraction is 30% or more, the processability of the laminate is improved. When the gel fraction is 70% or less, the compressive flexibility of the foam is in a more preferable range. Based on the usage characteristics of the laminate and the foam, the gel fraction of the crosslinked polyolefin resin foam is preferably in the range of 30% to 60%, more preferably 30% to 55%. Methods for achieving the above range for the gel fraction of the crosslinked polyolefin resin foam include, for example, adjusting the amount of crosslinking aid added or the irradiation dose of ionizing radiation.

[0070] The melting point of the cross-linked polyolefin resin foam is preferably 110°C or higher. The upper limit of the melting point is not particularly limited, but it is usually around 165°C. Having the melting point within the above range makes it easier to reduce the heat shrinkage rate of the laminate made using the cross-linked polyolefin resin foam. The method for measuring the melting point is described below. Methods for setting the melting point within the above range include, for example, selecting a polyolefin resin with a high melting point to be used as a raw material for the cross-linked polyolefin resin foam. When using two or more types of polyolefin resins, methods include raising the melting point of the polyolefin resin with the highest melting point.

[0071] Cross-linked polyolefin resin foams preferably have a closed-cell structure. A closed-cell foam allows for sufficient air extraction during vacuum forming, enabling the creation of complex shapes. Furthermore, fine and uniform cells are preferable, as this results in a smooth surface for the foam and molded products. Methods for creating a closed-cell foam include, for example, using a hot-air foaming furnace or a salt-bath foaming furnace. Among these, the salt-bath foaming furnace method is preferred.

[0072] In the present invention, it is preferable that the tensile elongation in the MD direction of the crosslinked polyolefin resin foam is 200% or more. By setting the tensile elongation within the above range, when the laminate of the present invention is attached to another substrate, wrinkles are less likely to occur even if there are extremely sharp parts in the other substrate. The upper limit of the tensile elongation is not particularly limited, but is usually around 500%. The method for measuring the tensile elongation is as described below. Methods for setting the tensile elongation within the above range include, for example, reducing the content of inorganic additives or omitting inorganic additives. Examples of inorganic additives with characteristics such as coloring or property imparting include amorphous carbon, porous ceramics, porous glass, silica, silicate clay, alum, metal oxides, carbon black, activated carbon, zeolite, alumina, zirconia, silica gel, silicon dioxide, potassium aluminum sulfate dodecahydrate, iron alum, aluminum powder, niobium oxide, tantalum oxide, titanium oxide, zirconium oxide, cerium oxide, tin oxide, and antimony oxide.

[0073] The thickness of the cross-linked polyolefin resin foam is preferably between 1 mm and 4 mm. When it is 1 mm or thicker, the flexibility and response to compressive stress are even more favorable when used as an interior material for automobiles. Furthermore, when it is 4 mm or less, the flexibility and response to compressive stress are even more favorable, and it is even more favorable because it allows for a slight increase in interior space.

[0074] <Surface Material> The surface material of the present invention is formed by directly bonding a crosslinked polyolefin resin foam or bonding it via an adhesive layer to form a laminate, and is at least one selected from the group consisting of artificial leather, synthetic leather, woven fabric, knitted fabric, nonwoven fabric, and felt.

[0075] When a laminate is subjected to a molding machine, it is important to adjust the heat shrinkage rate of the laminate to be within a certain range in order to reduce the occurrence of wrinkles and delamination and to achieve high productivity. For this purpose, it is preferable to adjust the heat shrinkage rate and the amount of change in heating angle of the cross-linked polyolefin resin foam. On the other hand, for the surface material, it is preferable to set the elongation rate at room temperature to a predetermined range so that it is easier to adjust the heat shrinkage rate of the laminate to a predetermined range.

[0076] There are various methods for measuring the elongation rate of the surface material, and either JIS L 1096 Method A or Method B may be used, but Method B was used in this invention. In order to set the heat shrinkage rate of the laminate within a desirable range, it is preferable that the elongation rate obtained by Method B be between 5% and 150%, with a lower limit of 15% being more preferable and 25% or more being most preferable. Furthermore, as an upper limit for the elongation rate, 120% is more preferable and 100% or less is most preferable. It is preferable to investigate or measure the elongation rate when selecting the surface material to be used as the material for the laminate, but this is generally determined by the type and structure of the surface material. From this viewpoint and from the perspective of the high-quality feel of the laminate, artificial leather is preferred as the surface material.

[0077] There are no particular restrictions on the method of adjusting the elongation rate of the surface material. When the surface material is artificial leather, it is generally necessary to increase the elongation rate, and there are methods such as creating a structure consisting of ultrafine inelastic fibers and ultrafine elastic fibers, and then dissolving or bonding some of the elastic fibers (for example, described in Japanese Patent Publication No. 1-41742, Japanese Patent Application Publication No. 5-339863, etc.), bonding a shrinkable sheet to one side of the artificial leather, performing a shrinkage treatment, and then removing the shrinkable sheet (for example, described in Japanese Patent Application Publication No. 2003-089983, etc.), a manufacturing method that includes a process of rubbing and shrinking a woven or knitted fabric containing yarn made of side-by-side bonded composite fibers and / or eccentric core-sheath composite fibers (for example, described in Japanese Patent Application Publication No. 2008-261082, etc.), and other methods such as changing the thickness or the structure in the thickness direction. When the surface material is woven fabric, knitted fabric, nonwoven fabric, felt, etc., it is common to adjust it by changing the manufacturing method such as the weaving or knitting method.

[0078] <Artificial Leather> The artificial leather in this invention is made by applying a napping treatment to the surface of an artificial leather substrate or a half-cut artificial leather substrate to give it a suede-like appearance.

[0079] The substrate for artificial leather is composed of a fiber entanglement made of ultrafine fibers and a polymeric elastic material. Details are described below.

[0080] [Fiber Entanglement] As the fibers constituting the fiber entanglement used in the present invention, synthetic fibers are preferably used from the viewpoint of excellent durability, especially mechanical strength, heat resistance and light resistance, and polyester fibers and polyamide fibers are particularly preferably used.

[0081] When polyester fibers are used as synthetic fibers, the dicarboxylic acids and / or ester-forming derivatives thereof that can be used include aliphatic carboxylic acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid (e.g., 2,6-naphthalenedicarboxylic acid), diphenyldicarboxylic acid (e.g., diphenyl-4,4'-dicarboxylic acid), oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanediic acid, and dodecanediic acid, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and aromatic dicarboxylic acids and their ester derivatives such as 5-sulfoisophthalates (lithium 5-sulfoisophthalate, potassium 5-sulfoisophthalate, sodium 5-sulfoisophthalate, etc.).

[0082] In addition, as diols, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, cyclohexanedimethanol, diethylene glycol, 2-methyl-1,3-propanediol, polyoxyalkylene glycols (such as polyethylene glycol) with a molecular weight of 500 to 20000, and bisphenol A-ethylene oxide adducts can be used.

[0083] When using polyamide fibers as synthetic fibers, nylon 6, nylon 66, nylon 56, nylon 610, nylon 11, nylon 12, and copolymerized nylon can be used, but nylon 56, nylon 610, and nylon 11, which contain components derived from biomass resources, are preferably used.

[0084] When synthetic fibers are used as the fibers constituting the fiber entanglement, the polymer forming the fibers can be supplemented with inorganic particles such as titanium dioxide particles, lubricants, pigments, heat stabilizers, ultraviolet absorbers, conductive agents, heat storage agents, and antibacterial agents, depending on the purpose.

[0085] The average single fiber diameter of the ultrafine fibers constituting the fiber entanglement is preferably 1 μm or more and 10 μm or less. By setting the average single fiber diameter to 10 μm or less, a substrate for artificial leather with a dense, soft touch and excellent surface quality can be obtained. On the other hand, by setting the average single fiber diameter to 1 μm or more, excellent color development and colorfastness after dyeing can be achieved. The average single fiber diameter of the ultrafine fibers is more preferably 1 μm or more and 6 μm or less, and even more preferably 1.5 μm or more and 4 μm or less.

[0086] The average single fiber diameter is calculated by taking scanning electron microscope (SEM) images of the cross-section of the artificial leather substrate, randomly selecting 50 circular or nearly circular elliptical fibers, measuring their single fiber diameters, and calculating the arithmetic mean of these 50 fibers. When using ultrafine fibers with irregular cross-sections, the single fiber diameter is determined by first measuring the cross-sectional area of ​​the single fiber and calculating the equivalent diameter.

[0087] Nonwoven fabrics, which are woven fabrics intertwined in a three-dimensional manner, can also be used for fiber entanglement. Using woven fabrics allows for a dense structure and a surface appearance that is of high quality.

[0088] The weight of the fabric used in this invention is 20 to 200 g / m². ２ It is desirable to have a basis weight of 30 to 150 g / m², most preferably 30 to 150 g / m². ２ This involves using fabrics within a specified range. Furthermore, plain weave fabrics are preferred as the basic structure.

[0089] [Polymer Elastic Body] The polymer elastic body that constitutes the substrate for artificial leather is a binder that grips the fibrous entanglement made of ultrafine fibers that make up the substrate for artificial leather. Considering the flexible texture of the substrate for artificial leather, examples of polymer elastic bodies that can be used include polyurethane, SBR, NBR, and acrylic resin. Among these, it is preferable to use polyurethane as the main component. By using polyurethane, it is possible to obtain a substrate for artificial leather that has a substantial feel, a leather-like appearance, and physical properties that can withstand actual use. Furthermore, the term "main component" here means that the mass of polyurethane is greater than 50% by mass of the total mass of the polymer elastic body.

[0090] In the present invention, when polyurethane is used, either an organic solvent-based polyurethane used in a dissolved state in an organic solvent or a water-dispersible polyurethane used in a dispersed state in water can be employed. Furthermore, as the polyurethane, polyurethane obtained by the reaction of a polymer diol, an organic diisocyanate, and a chain extender is preferably used.

[0091] When polyurethane is used as the polymer elastic material, at least one polymer diol can be used, selected from polymer diols such as polyester diols, polyether diols, polycarbonate diols, or polyester polyether diols, with an average molecular weight of 500 to 3000. However, it is preferable to include polycarbonate diol, which has excellent hydrolysis resistance.

[0092] When polyurethane is used as the polymeric elastic material, the isocyanate used may be at least one type of diisocyanate selected from aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate, and aliphatic diisocyanates such as hexamethylene diisocyanate.

[0093] When polyurethane is used as the polymeric elastic material, examples of chain extenders that can be used include water, ethylene glycol, butanediol, ethylenediamine, and at least one low-molecular-weight compound having two or more active hydrogen atoms, such as 4,4'-diaminodiphenylmethane.

[0094] Furthermore, polymeric elastic materials may contain various additives depending on the purpose, such as pigments like carbon black, flame retardants such as phosphorus-based, halogen-based, and inorganic types, antioxidants such as phenol-based, sulfur-based, and phosphorus-based types, ultraviolet absorbers such as benzotriazole-based, benzophenone-based, salicylate-based, cyanoacrylate-based, and oxalic acid anilide-based types, light stabilizers such as hindered amine-based and benzoate-based types, hydrolysis-resistant stabilizers such as polycarbodiimide, plasticizers, antistatic agents, surfactants, coagulation modifiers, and dyes.

[0095] The content of polymeric elastic material in the artificial leather substrate can be appropriately adjusted considering the type of polymeric elastic material used, the manufacturing method of the polymeric elastic material, and the texture and physical properties. The polymeric elastic material content is preferably 10% to 60% by mass relative to the mass of the fiber entanglement, more preferably 15% to 45% by mass, and even more preferably 20% to 40% by mass. If the polymeric elastic material content is less than 10% by mass, the bonding between fibers by the polymeric elastic material becomes weaker, and the abrasion resistance of the artificial leather substrate tends to be poor. Also, if the polymeric elastic material content exceeds 60% by mass, the texture of the artificial leather substrate tends to become harder.

[0096] When using an organic solvent-based polymer elastomer, the polymer elastomer can be extracted and isolated using an organic solvent such as N,N-dimethylformamide. When using a water-dispersible polymer elastomer, methods can be used to remove the fibers using a solvent that dissolves fibers (for polyester, such as 1,1,1,3,3,3-hexafluoro-2-propanol or orthochlorophenol), or to decompose and extract the water-dispersible polymer elastomer using N,N-dimethylformamide heated to 60°C or 100°C.

[0097] [Substrate for artificial leather] It is preferable that the substrate for artificial leather has a fibrous entanglement structure in the form of a nonwoven fabric. By using a nonwoven fabric, a uniform and elegant appearance and texture can be obtained when the surface is napped.

[0098] While both long-fiber and short-fiber nonwoven fabrics can be used as the form of the nonwoven fabric, a short-fiber nonwoven fabric is preferred because it has a large number of raised fibers on the product surface, making it easier to obtain an elegant appearance.

[0099] When using short-fiber nonwoven fabric, the fiber length of the ultrafine fibers is preferably 25 mm to 90 mm. By setting the fiber length to 90 mm or less, good quality and texture are obtained, and by setting the fiber length to 25 mm or more, a substrate for artificial leather with excellent abrasion resistance can be obtained. The fiber length is more preferably 35 mm to 80 mm, and even more preferably 40 mm to 70 mm.

[0100] The basis weight of the fiber entanglement constituting the substrate for artificial leather was measured according to JIS L1913 (2010) 6.2 and was 50 g / m². ２ More than 400g / m ２ The following range is preferred, and more preferably 80 g / m² ２ More than 300g / m ２ The following range applies: The basis weight of the fiber entanglement is 50 g / m². ２ Below this level, the artificial leather base material becomes paper-like and lacks texture. Also, the basis weight of the fiber entanglement material is 400 g / m². ２ Beyond a certain point, the texture of the artificial leather substrate tends to become harder.

[0101] In order to improve strength and dimensional stability, it is also preferable for the artificial leather substrate to have a woven fabric laminated inside or on one side of the entangled fiber structure and entangled and integrated.

[0102] When intertwining and integrating fabrics, various types of fibers can be used to make up the fabric, including filaments, spun yarns, innovative spun yarns, and composite yarns made from a mixture of filaments and spun yarns. However, due to their structure, spun yarns have many fibers on their surface, and when these fibers are detached and exposed on the surface during intertwining with nonwoven fabrics and woven fabrics, this becomes a disadvantage. Therefore, it is more preferable to use filaments, and among filaments, it is preferable to use multifilaments.

[0103] The fiber diameter of the individual fibers constituting the fabric is preferably between 1 μm and 50 μm. By setting the fiber diameter of the individual fibers to 50 μm or less, a substrate for artificial leather with excellent flexibility can be obtained, and by setting the fiber diameter of the individual fibers to 1 μm or more, the morphological stability of the product as a substrate for artificial leather is improved.

[0104] The total fineness of the yarns constituting the fabric is measured according to JIS L1013 (2010) 8.3b (simplified method), and is preferably 30 dtex or more and 170 dtex or less. By setting the fineness to 170 dtex or less, a substrate for artificial leather with excellent flexibility can be obtained, and by setting the total fineness to 30 dtex or more, the morphological stability of the product as an artificial leather substrate is improved. In this case, it is preferable that the total fineness of the warp and weft multifilaments be the same.

[0105] It is preferable that the fiber components constituting the fabric are the same as the components of the fiber entanglement.

[0106] The substrate for artificial leather preferably has a thickness of 0.2 mm or more and 1.2 mm or less, as measured by JIS L1913 (2010) 6.1A method. If the thickness of the substrate for artificial leather is less than 0.2 mm, the processability during manufacturing deteriorates, and if the thickness is greater than 1.2 mm, the flexibility of the substrate for artificial leather tends to be impaired. The thickness of the substrate for artificial leather is more preferably 0.3 mm or more and 1.1 mm or less, and even more preferably 0.4 mm or more and 1 mm or less.

[0107] The substrate for artificial leather preferably has a wet tensile strength measured by JIS L1913 (2010) 6.3.2 method in the range of 10 N / cm to 200 N / cm. If the wet tensile strength of the substrate for artificial leather is 10 N / cm or less, it will have poor durability in actual use and will result in poor processability such as breakage during dyeing, which is undesirable. If it is 200 N / cm or more, it will have poor moldability. The wet tensile strength of the substrate for artificial leather is more preferably 15 N / cm to 180 N / cm, and even more preferably 25 N / cm to 150 N / cm.

[0108] [Form of Artificial Leather] The substrate for artificial leather can also be used as a suede-like artificial leather having a nap on its surface. When using a suede-like artificial leather, the nap may be present on only one side of the artificial leather, or it may be present on both sides. When the surface has a nap, from the viewpoint of design effect, it is preferable that the nap has a length and directional flexibility such that when the nap is traced with a finger, the direction of the nap changes, leaving a mark, a so-called finger mark. More specifically, the length of the nap on the surface is preferably 100 μm or more and 400 μm or less, and more preferably 150 μm or more and 350 μm or less. The length of the nap on the surface is calculated by taking an SEM image of the cross-section of the artificial leather at a magnification of 50x with the nap of the artificial leather raised, measuring the height of the nap portion (layer consisting only of ultrafine fibers) at 10 points, and calculating the average value.

[0109] [Method for manufacturing artificial leather substrates] Next, a method for manufacturing artificial leather substrates will be described.

[0110] In the present invention, it is preferable to use ultrafine fiber-generating fibers as a means of obtaining ultrafine fibers constituting a fiber entanglement body. By first entangling ultrafine fiber-generating fibers to form a nonwoven fabric and then performing ultrafine fiber thinning, a nonwoven fabric in which bundles of ultrafine fibers are entangled can be obtained.

[0111] As a type of ultrafine fiber generating fiber, it is preferable to use a sea-island type composite fiber in which two thermoplastic resins with different solvent solubility (two or three components if the island fibers are core-sheath composite fibers) are used as the sea component and island component, and the sea component is dissolved and removed using a solvent or the like to form the island component into ultrafine fibers. This is preferable from the viewpoint of the texture and surface quality of the artificial leather substrate because when the sea component is removed, appropriate voids can be provided between the island components, i.e., between the ultrafine fibers inside the fiber bundle.

[0112] As for sea-island type composite fibers, a method using a polymer interconnected array that is spun by using a sea-island type composite spindle and interconnecting two components (three components if the island fiber is a core-sheath composite fiber) of sea component and island component is preferred from the viewpoint of obtaining ultrafine fibers with uniform single fiber fineness.

[0113] As the marine component of sea-island type composite fibers, polyethylene, polypropylene, polystyrene, copolymerized polyester obtained by copolymerizing sodium sulfoisophthalic acid or polyethylene glycol, and polylactic acid can be used, but from the viewpoint of spinnability and ease of elution, polystyrene and copolymerized polyester are preferably used.

[0114] Furthermore, the fiber entanglement body preferably takes the form of a nonwoven fabric. As mentioned above, both short-fiber and long-fiber nonwoven fabrics can be used, but a short-fiber nonwoven fabric is preferable because it has more fibers oriented in the thickness direction of the artificial leather substrate compared to a long-fiber nonwoven fabric, and a high level of density can be obtained on the surface of the artificial leather substrate when it is napped.

[0115] When a short-fiber nonwoven fabric is used as the fiber entanglement, the resulting ultrafine fiber-generating fibers are preferably crimped and cut to a predetermined length to obtain raw cotton. Known methods can be used for crimping and cutting.

[0116] Next, the obtained raw cotton is formed into a fiber web using a cross wrapper or the like, and then entangled to obtain a short-fiber nonwoven fabric. Methods such as needle punching or water jet punching can be used to entangle the fiber webs and obtain a short-fiber nonwoven fabric.

[0117] Furthermore, if the substrate for artificial leather includes a woven fabric, the obtained short-fiber nonwoven fabric and the woven fabric are laminated and then intertwined and integrated. To intertwine and integrate the short-fiber nonwoven fabric and the woven fabric, the woven fabric can be laminated to one or both sides of the short-fiber nonwoven fabric, or the woven fabric can be sandwiched between multiple short-fiber nonwoven fabric webs, and then the fibers of the short-fiber nonwoven fabric and the woven fabric can be intertwined by processes such as needle punching or water jet punching.

[0118] The apparent density of a short-fiber nonwoven fabric made of composite fibers (ultrafine fiber-generating fibers) after needle punching or water jet punching is 0.15 g / cm³. ３ 0.45g / cm or more ３ Preferably, the apparent density is 0.15 g / cm³. ３ By doing so, the artificial leather base material can be obtained to have sufficient morphological and dimensional stability. On the other hand, the apparent density is preferably 0.45 g / cm³. ３ By doing the following, it is possible to maintain sufficient space for imparting a polymeric elastic material.

[0119] Next, the aforementioned fiber entanglement can be impregnated with an aqueous solution of a water-soluble resin and dried to impregnate it with the water-soluble resin. By impregnating the fiber entanglement with the water-soluble resin, the fibers are fixed and dimensional stability is improved.

[0120] When using ultrafine fiber-generating fibers, the resulting fiber entanglement is treated with a solvent to generate ultrafine fibers with an average single fiber diameter of 1 μm or more and 10 μm or less.

[0121] When the ultrafine fiber-generating fiber is a sea-island type composite fiber, the solvent used to dissolve and remove the sea component can be an organic solvent such as toluene or trichloroethylene if the sea component is polyethylene, polypropylene, or polystyrene. If the sea component is copolymerized polyester or polylactic acid, an alkaline aqueous solution such as sodium hydroxide can be used. If the sea component is a water-soluble thermoplastic polyvinyl alcohol-based resin, hot water can be used.

[0122] Next, the fiber entanglement is impregnated with a polymer elastic solvent solution and solidified to impart the polymer elasticity, thus creating a substrate for artificial leather. Methods for fixing the polymer elasticity to the fiber entanglement include impregnating the fiber entanglement with a polymer elasticity solution, followed by wet or dry solidification. These methods can be appropriately selected depending on the type of polymer elasticity used.

[0123] From the viewpoint of manufacturing efficiency, it is also preferable for the artificial leather substrate to be cut in half in the thickness direction.

[0124] [Method for Manufacturing Artificial Leather] Artificial leather can be made suede-like by applying a napping treatment to the surface of an artificial leather substrate or a half-cut artificial leather substrate. The napping treatment can be applied by grinding using sandpaper or a roll sander. It is preferable to dye the above-mentioned artificial leather. For this dyeing treatment, for example, immersion dyeing treatments such as liquid flow dyeing treatment using a jigger dyeing machine or liquid flow dyeing machine, thermosol dyeing treatment using a continuous dyeing machine, or printing treatments on the napped surface by roller printing, screen printing, inkjet printing, sublimation printing and vacuum sublimation printing can be used. Among these, it is preferable to use a liquid flow dyeing machine because it can be obtained as a flexible texture. In addition, various resin finishing processes can be applied after dyeing as needed.

[0125] Furthermore, the artificial leather described above can be given decorative finishes to its surface as needed. For example, post-processing treatments such as perforation, embossing, laser processing, pin sonic processing, and printing can be applied.

[0126] Other materials for the surface of the present invention besides artificial leather include at least one selected from the group consisting of woven fabrics, knitted fabrics, nonwoven fabrics, and felt. In the present invention, these may be referred to as fabrics. These fabrics consist of resins such as polyester, polyamide, and polyolefin, or various copolymers containing these, or mixtures of these synthetic resins (hereinafter collectively referred to as chemical fibers), or natural fibers such as cotton, silk, hemp, and wool, mixtures of these natural fibers, regenerated fibers, mixtures of natural fibers and chemical fibers, semi-synthetic fibers, etc.

[0127] Examples of synthetic fiber materials include polyester fibers, polyamide fibers, polyolefin fibers, polyurethane fibers, and acrylic fibers.

[0128] When using polyester fibers, dicarboxylic acids and / or their ester-forming derivatives can be used, including aliphatic carboxylic acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid (e.g., 2,6-naphthalenedicarboxylic acid), diphenyldicarboxylic acid (e.g., diphenyl-4,4'-dicarboxylic acid), oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanediic acid, and dodecanediic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; aromatic dicarboxylic acids and their ester derivatives such as 1,4-cyclohexanedicarboxylic acid and 5-sulfoisophthalates (lithium 5-sulfoisophthalate, potassium 5-sulfoisophthalate, sodium 5-sulfoisophthalate, etc.).

[0129] In addition, as diols, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, cyclohexanedimethanol, diethylene glycol, 2-methyl-1,3-propanediol, polyoxyalkylene glycols (such as polyethylene glycol) with a molecular weight of 500 to 20000, and bisphenol A-ethylene oxide adducts can be used.

[0130] When using polyamide fibers, nylon 6, nylon 66, nylon 56, nylon 610, nylon 11, nylon 12, and copolymerized nylon can be used. When components derived from biomass resources are included, nylon 56, nylon 610, and nylon 11 are preferably used. Furthermore, when aromatic polyamides are included, polyamides containing polyamides such as polyamide 6T, polyamide 6I, polyamide 9T, and polyamide 5MT are preferably used.

[0131] When using polyolefin fibers, polyolefins such as polyethylene, polypropylene, polystyrene, and polyvinyl chloride are preferably used.

[0132] Furthermore, examples include polyurethane resins obtained by combining polyisocyanates such as tolylene diisocyanate and diphenylmethane diisocyanate with polyols such as polypropylene glycol and polytetramethylene ether glycol; polyacrylics such as polymethyl methacrylate, polyethyl methacrylate, polypropyl methacrylate, polybutyl methacrylate, polyethylhexyl methacrylate, polydimethylaminoethyl methacrylate, and polyhydroxyethyl methacrylate; and acrylic resins which are copolymers or mixtures thereof; as well as copolymers or mixtures thereof.

[0133] Furthermore, depending on the purpose, inorganic particles such as titanium dioxide particles, lubricants, pigments, heat stabilizers, ultraviolet absorbers, conductive agents, heat storage agents, and antibacterial agents can be added. Even when inorganic substances are included, they are preferably in particulate form, with a diameter of 5 μm or less, more preferably 3 μm or less, and most preferably 1 μm or less.

[0134] Furthermore, natural fibers include cotton, silk, linen, and wool; regenerated fibers include rayon and cupro; and semi-synthetic fibers include acetate and triacetate. Of course, mixtures of natural fibers and chemical, regenerated, or semi-synthetic fibers can also be used.

[0135] These fibers can be processed into textiles such as woven fabrics, knitted fabrics, nonwoven fabrics, and felt.

[0136] The preferred weave structures include the three basic weaves such as plain weave, twill weave, and satin weave; modified weaves such as modified plain weave, modified twill weave, and modified satin weave; special weaves such as honeycomb weave, gauze weave, and crepe weave; single double weaves such as warp double weave and weft double weave; warp pile weaves such as open weave, bag weave, double velvet, towel, seal, and velour; weft pile weaves such as velveteen, weft velvet, velvet, and corduroy; and leno weaves such as ro, sha, and figured gauze. Furthermore, weaving is preferably carried out using shuttle looms (such as fly shuttle looms) or shuttleless looms (such as rapier looms, gripper looms, water jet looms, and air jet looms).

[0137] The type of knitted fabric may be weft knitted fabric or warp knitted fabric, etc. The knitted fabric structure is preferably plain knit, jersey knit, rib knit, double knit, pearl knit, tuck knit, float knit, single rib knit, lace knit, or flocked knit for weft knitting, and single denby knit, single atlas knit, double cord knit, half tricot knit, loopback knit, or jacquard knit for warp knitting. The woven fabric may be single layer or multi-layered with two or more layers. The knitting is preferably carried out using a circular knitting machine, a flat knitting machine, a cotton type knitting machine, a tricot knitting machine, a Raschel knitting machine, a Milanese knitting machine, etc.

[0138] Common names for each include, for woven fabrics, plain weaves such as taffeta, pongee, poplin, de chine, palace, georgette, and twill weaves such as twill, serge, gabardine, and denim, and satin weaves such as satin and doeskin; and for knitted fabrics, plain knits such as tricot knit, raschel knit, and Milanese knit, as well as weft knits such as rib knit and pearl knit.

[0139] Examples of nonwoven fabrics include dry-laid nonwoven fabrics, wet-laid nonwoven fabrics, spunbond nonwoven fabrics, and burst fiber nonwoven fabrics. Furthermore, both short-fiber and long-fiber nonwoven fabrics are acceptable, and for long-fiber nonwoven fabrics, any of the following methods are acceptable: tow opening, burst fiber method, spunbond method, melt flow method, or flash prevention method.

[0140] Furthermore, synthetic leather manufactured by methods such as impregnating and adhering polymer materials to a base fabric can also be used.

[0141] In addition, by incorporating a resin with adhesive properties into the fabric, the adhesion to the crosslinked polyolefin resin foam can be improved. Specifically, a thermoplastic resin layer is preferred as such a resin, and a thermoplastic resin layer selected from polyacrylic resin, polyester resin, polystyrene resin, polyamide resin, polyurethane resin, polymethacrylimide resin, polyolefin resin, and copolymers and modified versions thereof can be used. These may also be resins blended from two or more types, with polyolefin resin being the most preferred.

[0142] <Formation and Utilization of Lamination of Laminate and Other Substrates> The laminated structure of the present invention is formed by bonding the laminate of the present invention with other substrates. By adopting this configuration, it can be developed into a variety of three-dimensional bodies, such as furniture, chairs and wall materials, and interior materials that have a very elegant appearance as surface materials for seats, ceilings and interiors in the interiors of vehicles such as automobiles, trains and aircraft. Examples of materials that form the other substrate include resin substrates, metals, concrete and glass. More specific examples of laminated structures include a laminate with various fabrics including artificial leather as the surface material, a three-layer laminated structure of cross-linked polyolefin resin foam and resin substrate, a laminate with various fabrics including artificial leather as the surface material, a three-layer laminated structure of cross-linked polyolefin resin foam and metal, and a laminate with various fabrics including artificial leather as the surface material, a three-layer laminated structure of cross-linked polyolefin resin foam and concrete. Of these, a three-layer laminated structure consisting of a laminate with various fabrics such as artificial leather as the surface material, a cross-linked polyolefin resin foam, and a resin base material is preferred for use as an automotive interior material due to its texture, heat resistance, light weight, and airbag deployment properties. In this invention, even if a layer of adhesive is formed in the laminate or laminated structure, the adhesive layer is not counted as one layer.

[0143] Examples of resin substrates include polypropylene resin, ABS resin, polycarbonate resin, and molded composites made by reinforcing these with inorganic fillers such as talc, mica, wollastonite, glass beads, glass fibers, and carbon fibers.

[0144] The laminated structure of the present invention may have a protective layer provided on the surface of the outer material. By providing a protective layer, the outer material that forms the surface of the laminated structure can be protected.

[0145] Methods for manufacturing the laminated structure of the present invention include, for example, a method of attaching the laminate of the present invention to a resin substrate after molding it, and a method of coexisting with the laminate of the present invention when molding the resin substrate. Methods for bonding the laminate to other substrates include, for example, a method using an adhesive and a heat-sealing method. Among these, the method using an adhesive is preferred. There are no particular restrictions on the adhesive used to bond the laminate to the resin substrate. Specific examples of adhesives include "Pandex T-5265" manufactured by Dainippon Ink and Chemicals, Inc. and "Desmocol #500" manufactured by Bayer Co., Ltd.

[0146] The automotive interior material of the present invention is made using the laminate or laminated structure of the present invention. As the automotive interior material, instrument panels, particularly instrument panels laminated with a resin substrate having an airbag storage structure, and door panels are most preferred. Furthermore, by laminating the laminate of the present invention with an impact-absorbing material to form the laminated structure of the present invention, it is also possible to create an impact-absorbing sheet that can be suitably used in electrical and electronic materials.

[0147] <Method for measuring the thickness of the foam> The thickness of the foam was measured according to ISO 1923 (1981) "Method for measuring the line dimensions of foamed plastics and rubber". Specifically, the foam was placed on a flat surface and measured by 10 cm. ２ A dial gauge with a circular measuring probe having an area of ​​10 g / 10 cm² is measured on the surface of the foam. ２ The measurement was taken by applying constant pressure to the contact area.

[0148] <Method for measuring the apparent density of foam> The apparent density of the foam was measured and calculated in accordance with JIS K6767 (1999) "Foamed plastics - Polyethylene - Test methods". Specifically, the thickness and mass of a 10 cm square test piece (foam) were measured, and the apparent density was determined using the following formula.

[0149] Apparent density (g / cm³) ３ ) = Mass of the test specimen (g) / [Test specimen area 100 (cm²) ２ ) × Thickness of the test piece (cm) <Method for measuring the gel fraction of the foam> The gel fraction of the foam was measured as follows: The foam was cut into approximately 0.5 mm squares, and 100 mg was weighed with an accuracy of 0.1 mg. The weighed foam was immersed in 200 mL of tetralin at 140°C for 3 hours, then naturally filtered through a 100 mesh stainless steel wire mesh, and the insoluble matter on the wire mesh was dried in a hot air oven at 120°C for 1 hour. Next, the dried insoluble matter was cooled in a desiccator containing silica gel for 30 minutes, and the mass of this insoluble matter was precisely weighed, and the gel fraction of the foam was calculated as a percentage according to the following formula.

[0150] Gel fraction (%) = [Mass of insoluble matter (mg) / Mass of weighed foam (mg)] × 100 <Method for measuring tensile elongation> The tensile elongation of the foam was measured and calculated in accordance with JIS K6767 (1999) "Foamed plastics - Polyethylene - Test methods". Polyolefin resin foam was measured after being left in an oven adjusted to 23°C for 1 hour.

[0151] <Heat shrinkage rate of foams and laminates> The heat shrinkage rate was measured in accordance with JIS K6767 (1999) "Foamed plastics - Polyethylene - Test method". Specifically, a test piece with 100 mm square markings was placed in a hot air oven adjusted to 180°C for 10 minutes, then cooled in an environment of 23°C for 60 minutes or more. The value was then expressed as a percentage of the decrease in the distance between the markings drawn in the length direction (MD) and width direction (TD) divided by the original distance between markings of 100 mm.

[0152] <Method for measuring the change in heating angle> 1) Sampling of evaluation samples when the cross-linked polyolefin resin foam is in the form of a long sheet Square evaluation samples with sides of 10 cm were cut from a total of three points: both ends in the width direction of the long sheet and the center point. The basic principle was to keep the positions of these three points in the length direction of the long sheet the same. However, if there are scratches, foreign matter, deformation, etc., the position in the length direction will be changed. If scratches or deformation are noticeable at both ends and hinder improvement, move the sample 1 to 3 cm inward and take an evaluation sample. If a normal sample still cannot be obtained, it is also possible to reduce the size of the square by 1 to 3 cm. That is, an evaluation sample of a square with sides of 7 to 9 cm may be used. Also, if the sheet width is less than 30 cm, it is also possible to shift the positions where the evaluation sample is taken at three individual points in the length direction of the long sheet. Each side of the square of the evaluation sample will coincide with the MD direction and TD direction of the long sheet.

[0153] If the sheet width is 50 cm or more, five evaluation samples are collected. Similarly, if the sheet width is 70 cm or more, seven evaluation samples are collected, and if it is 90 cm or more, nine evaluation samples are collected. Thereafter, an odd number of evaluation samples are collected according to the sheet width for every 20 cm increase in sheet width. If the required number of samples cannot be collected due to damage, foreign matter, deformation, etc., and the required number cannot be collected even by shifting the collection position 1 to 3 cm inward or reducing the size of the square by 1 to 3 cm, the number of samples may be reduced, for example, from 9 to 7, or to 5 if still not possible. However, the minimum number of samples to be collected is 3. The odd number of evaluation samples collected in this manner are treated as one group.

[0154] Furthermore, if the length of the elongated sheet is 20 cm or more, two groups of evaluation samples will be collected, corresponding to the sheet width. If the length is 30 cm or more, three groups will be collected. Even if the length is 40 cm or more, the number of samples collected will be limited to three groups. If the required number of groups cannot be collected due to damage, foreign matter, deformation, etc., and the required number of groups cannot be collected even by shifting the collection position 1 to 3 cm inward or by reducing the size of the square by 1 to 3 cm, the number of groups may be reduced. The positions of the evaluation samples from both ends of the elongated sheet will be the same for all groups.

[0155] Figure 1 shows a conceptual diagram illustrating how evaluation samples are cut from a foam sheet with a width of approximately 55 cm, as an example. Figure 2 shows an example of cutting evaluation samples from a foam sheet with a width of 90 cm. As shown in Figure 2, 27 samples were sampled from a 90 cm wide polyolefin resin foam sheet, each a 10 cm square, in the width direction. Nine samples were collected in one group, and three groups were used to confirm experimental reproducibility. In this test, the average value of three samples with the same distance from both ends was used for the change in heating angle.

[0156] When the sheet width significantly exceeds 100 cm, although infrequently, significant distortion may occur at the edges. Therefore, when the sheet width exceeds 100 cm, although the number of evaluation samples corresponding to the sheet width is collected, the two edge samples are not used for measurement, and the remaining evaluation samples are used for measurement.

[0157] 2) Measurement of Heating Angle Change After marking the midpoint connecting line of the collected evaluation samples with an oil-based marker, the evaluation samples were placed in a heating furnace set to the melting point + 20°C for 10 minutes, and then observed and quantified. For quantification, the heating angle change was calculated using a digital protractor (Shinwa Measuring Instruments Co., Ltd.) for the angle of the midpoint connecting line. The following precautions were taken during the test.

[0158] Before heating: The front and back sides of the evaluation sample were kept the same before and after the test. Then, the angle at the intersection of the midpoint connecting lines connecting the midpoints of opposite sides of the square was measured before heating. Measurements were taken and recorded at all four measurement locations. It was confirmed that the angle at the intersection of the connecting lines was 90 degrees before heating.

[0159] Figure 4 shows a physical representation of the evaluation sample, and Figure 5 shows a top-down view of the evaluation sample. As shown in Figures 4 and 5, midpoint connecting lines were drawn with a marker to connect the midpoints of each side of the square sample, creating the sample piece. Each sample was marked to indicate the front and back.

[0160] After heating: If the test specimen was deformed into a convex or concave shape due to heating, and it was difficult to measure the angle with the original sample, a photograph of the sample was taken and the angle was measured. If the sample was tilted, the sample was cut to be horizontal and used for angle measurement.

[0161] The angles at four points along the midpoint connecting line intersection were measured, and the change in heating angle from the pre-heating angle of 90 degrees was calculated for each point. After heating, the angle may be above or below 90 degrees, but the difference from 90 degrees was calculated as an absolute value. The average of these four absolute values ​​was used as the change in heating angle for the evaluated sample.

[0162] When one group of evaluation samples was taken, the change in heating angle was the value measured for each individual evaluation sample. That is, when three evaluation samples were taken, three values ​​were obtained as the change in heating angle, measured for each evaluation sample. Here, "the maximum value of the change in heating angle is 12 degrees or less" means that the largest of the three values ​​is 12 degrees or less. Also, "the difference between the maximum and minimum values ​​of the change in heating angle is 6 degrees or less" means that the difference between the largest and smallest of the three values ​​is 6 degrees or less.

[0163] On the other hand, when multiple evaluation samples are taken, the change in heating angle refers to the average value of the evaluation samples taken from positions at equal distances from the edge of the foam. For example, if three evaluation samples are taken in the width direction and two groups in the length direction from a foam sheet with a width of 30 cm and a length of 20 cm, three average values ​​of the change in heating angle are obtained: the average value of the two samples taken from one end, the average value of the two samples taken from the center, and the average value of the two samples taken from the other end. Similarly, "the maximum value of the change in heating angle is 12 degrees or less" means that the maximum of the three average values ​​is 12 degrees or less. Also, "the difference between the maximum and minimum values ​​of the change in heating angle is 6 degrees or less" means that the difference between the maximum and minimum of the three average values ​​is 6 degrees or less.

[0164] Figure 3 shows an example of calculating the average value of evaluation samples when multiple groups are collected, where a total of nine evaluation samples are cut from the foam: three in the length direction and three in the width direction. The nine numbers from A11 to A33 represent the measured values ​​of the change in heating angle for each evaluation sample. The numbers from A1 to A3 represent the average of three values ​​for each group within the sheet, more specifically, the average of the change in heating angle of three evaluation samples that are equally far from the edge of the sheet (e.g., A11, A12, A13).

[0165] 3) Sampling of evaluation samples when the length and width of the cross-linked polyolefin resin foam are unknown. If the length and width of the foam are unknown, specifically, for example, if the foam is a sign-shaped sheet, the width and length are estimated from the shape of the foam's bubbles. Based on this estimation, an odd number of evaluation samples are taken in the width direction, and the change in heating angle for each evaluation sample is measured. If the length is 20 cm or more and evaluation samples from multiple groups can be taken, the variation in the change in heating angle within each group, and the variation in the change in heating angle between groups for evaluation samples at equal distances from the edge of the foam are evaluated. If the variation in the change in heating angle between groups for evaluation samples at equal distances from the edge of the sheet is clearly larger than the variation in the change in heating angle within each group, it is determined that the estimated width and length directions are incorrect, and the estimated length direction is used as the width direction for recalculation. If necessary, the evaluation samples are resampled and remeasured based on the new width and length directions. If the widthwise and lengthwise orientation of the sheet is unclear based on the data variability, it is possible that the foam is produced by floating a crosslinked polyolefin resin composition, which has been cut into a notebook shape, in a salt bath foaming tank, and then foaming it. In such cases, the initial data should be used.

[0166] <Method for Measuring the Melting Point of Foam> The melting point of the foam was measured in accordance with JIS K7121 (1987). A differential scanning calorimeter (DSC, RDC220-Robot DSC manufactured by Seiko Electronics Industries, Ltd.) was used for the measurement. 5 mg of cross-linked polyolefin resin foam was heated from room temperature to 200°C at a rate of 10°C / min under a nitrogen atmosphere, and then held at 200°C for 5 minutes (1st run). Next, it was cooled to 0°C at a rate of 10°C / min, and then heated again to 200°C at a rate of 10°C / min (2nd run). The melting peak (endothermic peak) was read in the 2nd run. If multiple melting points were observed in this measurement, the highest melting point was taken as the melting point of the foam.

[0167] <Method for Measuring the Peel Strength of Laminates> To measure the peel strength of the laminate, a test piece was prepared by cutting out a section of the laminate so that it was 150 mm in the MD or TD direction and 25 mm in the vertical direction. One end of this test piece was clamped and fixed together with the laminate, and only the film of the laminate was fixed with the other end of the clamp. A peel test was performed using a Tensilon UCT-500 manufactured by Orientec Corporation at a speed of 100 mm / min, a peel angle of 180°, and a tensile force of 30 mm or more. The obtained peel strength was the maximum peel strength value within the peeled range, and the average value obtained from two measurements was taken as the peel strength.

[0168] <Elongation of the surface material> The elongation was evaluated by performing the elongation test described in "8.16.1 Method B" of JIS L1096:2010 "Testing methods for woven and knitted fabrics".

[0169] <Reference Example> [Artificial Leather] (hereinafter referred to as "Artificial Leather A") <Process for manufacturing a fibrous base material> Using polystyrene as the sea component and polyethylene terephthalate with an intrinsic viscosity (IV value) of 0.72 as the island component, a sea-island type composite fiber was obtained with a composite ratio of 20% by mass of sea component and 80% by mass of island component, with 16 islands per filament and an average single fiber diameter of 20 μm. The obtained sea-island type composite fiber was cut to a fiber length of 51 mm to form staples, and a fiber web was formed by passing it through a card and a cross wrapper, and a needle punching process was performed to manufacture a fiber structure.

[0170] <Process for forming ultrafine fibers> The obtained fiber structure was immersed in trichloroethylene and squeezed with a mangle 10 times, thereby obtaining a sheet made of ultrafine fibers from which the marine component of the sea-island type composite fiber had been removed.

[0171] <Process for imparting polymeric elasticity> The sheet made of ultrafine fibers obtained as described above was immersed in a polyurethane N,N-dimethylformamide (DMF) solution, which mainly consists of organic solvent-based polyurethane and has been adjusted to have a solid content concentration of 13% by mass. The polyurethane resin was then solidified in an aqueous solution of DMF with a concentration of 30% by mass. After that, a polyurethane resin-imparted sheet was obtained by drying with hot air at a temperature of 110°C for 10 minutes.

[0172] <Process of cutting and polishing the sheet-like material> The polyurethane resin-coated sheet obtained as described above was cut in half perpendicular to the thickness direction, and the uncut surface was polished with 240-grit endless sandpaper to obtain a sheet-like material with a pile.

[0173] <Process for dyeing the raw material> The sheet-like material with a pile obtained as described above was dyed with a black dye using a liquid jet dyeing machine at a temperature of 120°C, and then dried in a dryer to obtain artificial leather A. The elongation rate of artificial leather A was approximately 80%.

[0174] [Crosslinked Polyolefin Foam] Crosslinked polyolefin sheet S (hereinafter referred to as "sheet S") 80 parts by mass of ethylene-propylene random copolymer as a polypropylene resin and 20 parts by mass of linear low-density polyethylene as a polyethylene resin were first blended. To 100 kg of this resin blend, 7 kg of azodicarbonamide as a foaming agent, 4 kg of 55% divinylbenzene as a crosslinking aid, and 1 kg of antioxidant were added and mixed using a Henschel mixer. Melt extrusion was performed at a temperature of 170°C using a twin-screw extruder, and a polyolefin resin sheet of a predetermined thickness was produced using a T-die. The polyolefin resin sheet obtained in this way was irradiated from one side with an electron beam at an acceleration voltage of 800 kV and a predetermined absorbed dose to obtain a crosslinked sheet.

[0175] - Cross-linked polyolefin foams 1-3 (foaming of "sheet S") "Sheet S" was floated on a salt bath at a temperature of 220°C and heated from above with an infrared heater to induce foaming. The foam was cooled with water at a temperature of 50°C, the surface of the foam was washed with water and dried to obtain cross-linked polyolefin foams.

[0176] Here, three types of foams were obtained by adjusting the foaming time on the salt bath. More specifically, the foam with a long foaming time was cross-linked polyolefin foam 1. The foam with a short foaming time was cross-linked polyolefin foam 3. The foam with an intermediate foaming time was cross-linked polyolefin foam 2. The physical properties of cross-linked polyolefin foams 1 to 3 are shown in Table 1.

[0177] ・Cross-linked polyolefin foam 4 (Foaming of "Sheet S") Sheet S was foamed in a hot air foaming furnace at 300°C to produce cross-linked polyolefin foam 4. The obtained foam was a cross-linked foam having a closed-cell structure, and its physical properties are shown in Table 1. Cross-linked polyolefin foam 4 differed significantly from cross-linked polyolefin foams 1 to 3 in terms of heat shrinkage rate and change in heating angle. There were some differences in other physical properties, but these were judged to be within the range of test variability and not intrinsic differences caused by the foaming equipment, such as heat shrinkage rate and change in heating angle. ・Cross-linked polyolefin foam 5 A cross-linked polyolefin sheet was made in the same manner as Sheet S, except that a mixture of 60 parts by mass of ethylene-propylene random copolymer as the polypropylene resin, 10 parts by mass of linear low-density polyethylene as the polyethylene resin, and 30 parts by mass of polyolefin elastomer was used as the base resin, and it was foamed in the same manner as foam 1. This cross-linked polyolefin foam was referred to as cross-linked polyolefin foam 5 below.

[0178]

[0179] [Example 1] A two-component polyurethane adhesive with adjusted viscosity was applied to the aforementioned cross-linked polyolefin foam 1 using a gravure roll at a rate of 60 g / m². ２The material was coated in this manner and preheated with steam at 80°C. Next, artificial leather A was placed on the surface of the cross-linked polyolefin foam 1 coated with adhesive resin, then nipped with a calender roll at 80°C, and subsequently dried in a dryer at 90°C to obtain a laminate.

[0180] A schematic diagram of the process is shown in Figure 6. The cross-linked polyolefin foam 2, which has been formed into a roll, is drawn out using a control roll 9 and supplied to the adhesive application process 5. In the adhesive application process 5, a two-component polyurethane adhesive supplied from the adhesive tank 6 is applied using a gravure roll. In the preheating process 7, the cross-linked polyolefin foam with the adhesive applied is preheated using 80°C steam. After preheating, the artificial leather 3 supplied from the roll is placed on top of the adhesive-coated surface and dried in the heating process 8, which is heated to 90°C, to obtain a laminate. In this process, the tension of the foam and artificial leather was adjusted using control rolls 11 and 12, as well as other control rolls. Note that in order to simplify the process, other rolls, additives, introduced materials, and waste are not shown in Figure 6.

[0181] [Examples 2 and 3] Two types of laminates were manufactured using cross-linked polyolefin foams 2 and 4, similar to Example 1.

[0182] [Comparative Example 1] A laminate was manufactured using cross-linked polyolefin foam 3 in the same manner as in Example 1. The characteristics of the laminates manufactured in Examples 1 to 3 and Comparative Example 1 are shown in Table 2.

[0183] [Examples 4 and 5] Laminates were manufactured using diagonal weave and tricot as the surface material instead of artificial leather A. The characteristics of the laminates are shown in Table 2.

[0184] [Example 6] A laminate was prepared in the same manner as in Example 1, except that cross-linked polyolefin foam 5 was used instead of foam 1. The properties of the laminate are shown in Table 2.

[0185] [Example 7] A laminate was manufactured using cross-linked polyolefin foam 1 and artificial leather A, similar to Example 1. During manufacturing, the tension of the surface material 3 (artificial leather A in Example 7) supplied from the roll shown in Figure 6 was increased by approximately 20% compared to Example 1. The characteristics of the obtained laminate are shown in Table 2. The moldability evaluation result was 3 points, but compared to Example 3, which also received a moldability evaluation result of 3 points, the surface irregularities of artificial leather A were smaller, and the result was closer to 4 points.

[0186] [Comparative Example 2] Similar to Example 3, a laminate was manufactured using cross-linked polyolefin foam 4 and tricot as the surface material. The characteristics of the laminate are shown in Table 2.

[0187] [Comparative Example 3] Similar to Example 5, a laminate was manufactured using cross-linked polyolefin foam 1 and tricot as the surface material. During manufacturing, the tension of the surface material 3 (tricot in Comparative Example 3) supplied from the roll shown in Figure 6 was increased by approximately 20% compared to Example 5, similar to Example 7. The characteristics of the obtained laminate are shown in Table 2.

[0188] [Molding Evaluation] The moldability was evaluated by attaching a lid-shaped mold, mimicking an automobile instrument panel, to a vacuum forming machine and molding it. Specifically, a polypropylene resin molded body with adhesive applied to its surface was placed in the lid-shaped mold, and a laminate was molded including this polypropylene resin molded body. A cross pattern mimicking a shogi board was drawn on the surface of the laminate to be molded in advance, and the deformation due to molding was observed, as well as the adhesion between the edges of the polypropylene resin and the laminate. Each molded product was scored based on the following criteria to evaluate its applicability to automobile interior material components. 5 points: The parallelism and right angles of the laminate are maintained at a high level in both the center and edges of the molded product. The adhesion at the edges of the molded product is also good. 3 points: Disruption of the parallelism and right angles of the cross is observed in the molded product. And / or, poor adhesion is observed at the edges of the molded product. 1 point: The cross is slanted or the right angles are clearly disrupted in the molded product. Furthermore, the adhesion at the edges of the molded product is poor. 4 points and 2 points represent intermediate scores.

[0189]

[0190] The results shown in Table 2 indicate that the moldability of a laminate is largely determined by its heat shrinkage rate. The heat shrinkage rate of a laminate varies depending on the foam, even when the surface material and lamination conditions are the same. Furthermore, it varies depending on the surface material, even when the foam and lamination conditions are the same.

[0191] 1: Midpoint connecting wire 2: Foam 3: Surface material 4: Laminate 5: Adhesive application process 6: Adhesive tank 7: Preheating process 8: Heating process 9-12: Control roll

Claims

1. A laminate comprising a surface material and a crosslinked polyolefin resin foam directly bonded together, or bonded together via an adhesive layer, wherein the surface material is at least one selected from the group consisting of artificial leather, synthetic leather, woven fabric, knitted fabric, nonwoven fabric, and felt, and the heat shrinkage rate when heated at 180°C for 10 minutes is 0.5% or more and 10% or less.

2. The laminate according to claim 1, wherein the surface material is artificial leather composed of a fiber entanglement body made of ultrafine fibers and a polymer elastic body.

3. The laminate according to claim 1 or 2, wherein the heat shrinkage rate of the crosslinked polyolefin resin foam when heated at 180°C for 10 minutes is 25% or more and 40% or less.

4. The laminate according to any one of claims 1 to 3, wherein the change in heating angle of the cross-linked polyolefin resin foam is 12 degrees or less.

5. The laminate according to any one of claims 1 to 4, comprising an adhesive between the artificial leather and the crosslinked polyolefin resin foam.

6. A laminated structure formed by bonding a laminate according to any one of claims 1 to 5 with another substrate.

7. An automotive interior material comprising the laminated structure described in claim 6.

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