Method for producing breathable leather laminate

Abstract

To provide a method for producing a breathable leather laminate that can easily ensure stable breathability together with sufficient waterproofness and can remarkably reduce defective products regarding breathability.SOLUTION: The method for producing a breathable leather laminate according to the present invention sequentially includes a laser irradiation step of forming through holes by irradiating a leather sheet with a laser to produce a breathable leather sheet, an adhesive application step of applying an adhesive around the through holes of the breathable leather sheet to form an adhesive-coated surface so that the adhesive is not applied to the through holes, and a laminate forming step of bonding a waterproof sheet to the adhesive-coated surface of the breathable leather sheet to form a leather laminate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a breathable leather laminate, and more specifically to a method for manufacturing a breathable leather laminate that is easy to ensure sufficient waterproofness and stable breathability, and that significantly reduces the occurrence of defective products in terms of breathability. [Background technology]

[0002] Generally, when shoes are made from leather (natural leather, artificial leather, etc.), the breathability of the leather is very low or non-existent. Therefore, when a user wears the shoes, the humidity inside the shoes remains extremely high, causing them to become stuffy and ultimately becoming a breeding ground for bacterial growth.

[0003] To address this issue, breathable materials are selected or fine through-holes are formed in the leather. As a method for forming minute through-holes in leather, for example, Patent Document 1 discloses that a laser in the infrared region (such as a carbon dioxide laser or a YAG laser) is used to form through-holes in artificial leather, thereby imparting high breathability to the artificial leather.

[0004] On the other hand, once shoes made of leather, especially natural leather, absorb water due to rain or other reasons, the water penetrates deep into the shoes, making them difficult to dry and, in some cases, causing mold, unpleasant odors, etc. For this reason, leather laminates, in which a waterproof sheet is laminated on the surface of the leather via an adhesive to improve waterproofing, are also used as shoe materials. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-248644 Summary of the Invention [Problem to be solved by the invention]

[0006] However, it is not easy to achieve both breathability (breathability) and waterproofness in artificial leather. In other words, if through-holes are formed in leather to improve breathability, when exposed to water, as mentioned above, water will penetrate deep into the leather, and water will easily enter the through-holes, making it difficult to dry.

[0007] On the other hand, if waterproof sheets are applied to improve waterproofing, this will naturally result in a significant loss of breathability (breathability).

[0008] Furthermore, the inventors of the present invention discovered that even if a leather sheet and a waterproof sheet are bonded together with an adhesive to form a laminate, and countless through-holes are formed in the laminate using a laser, there are still uneven breathability in different areas.

[0009] Therefore, after extensive research, the inventors have found that these problems can be solved by manufacturing a breathable leather laminate by irradiating a leather sheet with a laser to form through-holes, applying adhesive around the through-holes so that the adhesive does not get into the through-holes, and then laminating a waterproof sheet to form a laminate.

[0010] That is, the object of the present invention is to provide a method for manufacturing a breathable leather laminate that can easily ensure sufficient waterproofness and stable breathability, and can significantly reduce the occurrence of defective products in terms of breathability. [Means for solving the problem]

[0011] The method for producing a breathable leather laminate according to the present invention includes a laser irradiation step of irradiating a leather sheet with a laser to form through-holes to produce a breathable leather sheet; an adhesive application step of applying adhesive to the breathable leather sheet around the through holes so that the adhesive is not applied to the through holes, thereby forming an adhesive-applied surface; and a laminate forming step of laminating a waterproof sheet to the adhesive-coated surface of the breathable leather sheet to form a leather laminate. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram illustrating a method for producing a breathable leather laminate according to the present invention. [Figure 2] 2(A) and 2(B) are diagrams showing a leather sheet and a breathable leather sheet obtained by forming through-holes in a leather sheet by irradiating the leather sheet with a laser, respectively. [Figure 3] FIG. 3 is a diagram showing an example of a laser irradiation device used in the laser irradiation step. [Figure 4] FIG. 4 is a diagram illustrating one embodiment of the adhesive-coated region (R1) and the adhesive-uncoated region (R2) on the adhesive-coated surface of the breathable leather sheet. [Figure 5] FIG. 5 is a diagram illustrating another embodiment of the adhesive-coated region (R1) and the adhesive-uncoated region (R2) on the adhesive-coated surface of the breathable leather sheet. [Figure 6] FIG. 6 is a diagram showing the shape of the roller surface of the coating device (roll coater). [Figure 7] FIG. 7 is a cross-sectional view and an enlarged view showing the leather laminate obtained in the laminate formation step. [Figure 8] FIG. 8 is a diagram illustrating a conventional breathable leather laminate. [Figure 9] FIG. 9 shows an apparatus for evaluating the breathability of the test laminate used in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, the method for producing the breathable leather laminate according to the present invention will be described in detail with reference to the drawings as appropriate.

[0014] The breathable leather laminate of the present invention is characterized by the essential steps of laser irradiation (S1), adhesive application (S2), and laminate formation (S3) being carried out in sequence, as shown in S1 to S3 in Figure 1, and other steps may be carried out as necessary.

[0015] First, the first of the essential steps, the laser irradiation step (perforation step), is a step in which a laser is irradiated onto a leather sheet X1 to form through-holes to produce a breathable leather sheet X2, as shown in Figure 2.

[0016] Here, the type of laser is not particularly limited, but examples include CO2 laser, YAG laser, fiber laser, and semiconductor laser.

[0017] Furthermore, it is desirable that the laser emitter be cooled by a cooling unit during laser irradiation, as indicated by reference numeral 40 in Fig. 3. Here, the cooling unit is not particularly limited as long as it is a device that cools the laser emitter, and examples thereof include a water-cooled chiller and a cold air chiller.

[0018] The laser irradiation speed from the laser emitter and the conveying speed of the roller feeder are not particularly limited and can be adjusted appropriately taking into consideration the density of the through holes, etc. The through holes generally have a diameter of 0.01 mm to 0.5 mm, and the density of the through holes is generally 20 to 100 per square centimeter.

[0019] Here, the leather sheet refers to a sheet of natural leather or artificial leather, and may be used alone or in a laminated form. The natural leather is not particularly limited as long as it is obtained by tanning the hides of animals such as cows, horses, and pigs.

[0020] There are no particular limitations on the artificial leather, but examples include those made of a nonwoven fabric layer made of synthetic fibers (e.g., nylon fibers or polyester fibers) soaked in polyurethane resin and a surface resin layer made of polyurethane resin, etc. More specific examples include celluloid leather, PVC leather (vinyl chloride leather), and PU leather (polyurethane leather). The leather sheet used in the present invention may be made of natural leather or artificial leather with a waterproof layer or the like laminated thereon, if necessary.

[0021] The adhesive application process, which is the next process after the laser irradiation process, is a process in which adhesive is applied to the breathable leather sheet around the through holes so that the adhesive is not applied to the through holes, thereby forming an adhesive-coated surface.

[0022] The adhesive used in this step is not particularly limited as long as it is a typical leather adhesive, but examples include styrene-butadiene rubber adhesives, nitrile rubber adhesives, vinyl acetate adhesives, and thermoplastic hot melt adhesives such as ethylene vinyl acetate.

[0023] The number X in Figure 4(A) indicates the state of the breathable leather sheet X3 coated with adhesive obtained by the adhesive coating process. That is, in the adhesive coating process, an adhesive-coated surface is formed on the leather sheet so that there are adhesive-coated areas where adhesive is applied and adhesive-free areas where adhesive is not applied in the perforated areas formed by the laser.

[0024] More specifically, as shown in (B), an enlarged view of Fig. 4(A), in the leather sheet X3 having an adhesive-coated surface, there are an adhesive-coated region R1 where the adhesive is coated and an adhesive-free region R2 where the adhesive is not coated, in the adhesive coating process. Here, the adhesive-free region R2 has perforations P formed by a laser.

[0025] Here, in FIG. 4, the adhesive application regions R1 are formed in a dot pattern, but the shapes of the adhesive application regions R1 and the adhesive non-application regions R2 are not particularly limited.

[0026] As shown in FIGS. 5(A) to (C), the non-adhesive-application region R2 may be rectangular (FIG. 4(A)), circular (FIG. 4(B)), or diamond-shaped (FIG. 4(C)), and the adhesive-application region R1 may be formed on the periphery of each non-adhesive-application region R2.

[0027] Furthermore, the method for forming the adhesive application region R1 is not particularly limited, and examples include application using a jet dispenser or a roller with an uneven surface (application device (roll coater)). Figure 6(A) shows the shape of the roller surface of an application device (roll coater) used when applying with a roller. Figure 6(B) is an enlarged photograph of the roller surface of this device. Here, non-adhesive application regions are formed in the gaps on the surface, while adhesive application regions are formed around them.

[0028] The final essential step is the laminate formation step, which involves laminating a waterproof sheet to the adhesive-coated surface of the breathable leather sheet to form a leather laminate. As shown in Figure 7(A), the leather laminate is made up of a leather sheet X, an adhesive layer Y, and a waterproof sheet Z. As shown in the enlarged view of Figure 7(B), the adhesive layer Y has voids (i.e., areas where no adhesive is present) in the adhesive-free areas.

[0029] Here, the method for bonding the leather sheet and the waterproof sheet is not particularly limited, but they can be easily bonded by using a roller feeder as shown in Figure 3.

[0030] Waterproof sheets are not particularly limited, but examples include plastic films such as polyvinyl chloride sheets and olefin sheets, fabrics with surface treatments such as water repellency, and GORE-TEX (registered trademark) films.

[0031] The roller feeder is not particularly limited as long as it conveys the leather sheet with adhesive surface formed and the waterproof sheet by the roller and bonds them together by the pressure of the roller. As shown in Figure 3, as indicated by the reference numeral 20, it generally consists of a feed reel 22 rotated by a motor or the like, and an upper roll (free roller) that sandwiches the leather between the feed reel 22 and enables transport.

[0032] 7, the breathable leather laminate obtained by carrying out the laminate formation step is composed of a leather sheet X, an adhesive layer Y, and a waterproof sheet Z laminated together, and as shown in the enlarged view of FIG. 8(B), through holes P are formed by a laser irradiation device in the adhesive-free areas. Thus, the manufacturing method according to the present invention makes it possible to obtain a breathable leather laminate that is sufficiently waterproof, easily ensures stable breathability, and significantly reduces the occurrence of defective products in terms of breathability.

[0033] In contrast, in conventional breathable leather laminates, through-holes are formed by laser after the leather laminate is formed as shown in Figure 8. Here, it is extremely difficult to avoid the adhesive-coated areas and advance to the non-adhesive-coated areas, which can lead to problems such as difficulty in ensuring stable breathability along with sufficient waterproofing, and the likelihood of producing defective products with poor breathability. [Example]

[0034] The method for producing the breathable leather laminate of the present invention will be described in more detail below with reference to examples, but the technical scope of the present invention is not limited thereto.

[0035] [Example 1] A laser irradiation device (KH866A laser micro-hole processing line manufactured by Wenzhou Kanghong Machinery Co., Ltd., laser: CO2 laser) was prepared.

[0036] The leather sheet was placed in a laser irradiation device, and was continuously irradiated with laser light in the laser irradiation section while being cooled in a water-cooled cooling section, to form through-holes.

[0037] Furthermore, using a roller coater equipped with a roller having countless square meshes on its surface and hot melt adhesive that had been heated to a liquid state, an adhesive-coated surface was formed on the surface of the leather sheet, consisting of square adhesive-free areas at the through holes and adhesive-coated areas around them.

[0038] Next, the leather sheet with the adhesive-coated surface formed thereon and a waterproof sheet (polypropylene sheet) were fed into a roller feeder and stuck together to produce a breathable leather laminate.

[0039] The obtained breathable leather laminate was cut and molded into a square shape (20 cm on a side) to prepare test leather laminate 1, which was then subjected to evaluation test 1 (breathability test). The evaluation results are shown in Table 1.

[0040] [Evaluation test] 1. Evaluation test 1 (breathability test) A breathability tester was prepared as shown in Figure 9. Here, the breathability tester is composed of a bottom syringe T2 with only the top side open and a top syringe T1 with both bottom sides open. The bottom syringe T2 is connected to an air blower B via a rubber tube, and air is sent to the bottom syringe T2 by compressing the air blower B.

[0041] The test leather laminate obtained in the example or comparative example was sandwiched between the lower syringe T2 and the upper syringe T1 as shown by the number L in Figure 9, and the lower syringe T2 and the upper syringe T1 were tightly attached to each other with a clamp.

[0042] Furthermore, after water was poured into the upper syringe T1, air was sent to the lower syringe T2 using a blower B. At this time, the state of air bubbles in the water of the upper syringe T1 was observed through the test leather L, and evaluated based on the following evaluation criteria.

[0043] [Evaluation criteria] ◯: Uniform fine bubbles were generated (excellent breathability). △: Uneven bubbles were generated (breathability was uneven). ×: No bubbles were generated (no breathability).

[0044] [Comparative Example 1] A test leather laminate 2 was prepared in the same manner as in Example 1, except that the hot melt adhesive, which had been heated to a liquid state, was applied to the entire surface of the leather sheet using a roller coater to form an adhesive-coated surface (i.e., there were no areas where the adhesive was not applied, and the adhesive was applied even to the through-holes), and was subjected to Evaluation Test 1 (breathability test). The evaluation results are shown in Table 1.

[0045] [Table 1]

[0046] As shown in Table 1, it was confirmed that uniform fine air bubbles were generated in the test leather laminate 1 during the test, and the results of the breathability test were good.

[0047] On the other hand, in the test leather laminate 2, air bubbles were generated, which indicates that the laminate is breathable, but the size of the air bubbles varied (non-uniform air bubbles were generated), which indicates that the breathability varied. [Explanation of symbols]

[0048] 10: Leather laminate 20: Roller feeder 21: Upper roll 22: Feed roll 30: Laser irradiation unit 31: Laser 40: Cooling section 50:Through hole X1: Leather seats X2: Breathable leather seats X3: Breathable leather sheet with adhesive surface Y: Adhesive layer Z: Tarpaulin P: Through hole R1: Adhesive application area R2: Area without adhesive S1: Laser irradiation process S2: Adhesive application process S3: Laminate formation process T1: Top syringe T2: Lower syringe W:Water B: Air blower L: Test laminate

Claims

[Claim 1] a laser irradiation step of irradiating a leather sheet with a laser to form through-holes to create a breathable leather sheet; an adhesive application step of applying adhesive to the breathable leather sheet around the through holes so that the adhesive is not applied to the through holes, thereby forming an adhesive-applied surface; a laminate forming step of laminating a waterproof sheet to the adhesive-coated surface of the breathable leather sheet to form a leather laminate.

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