Method for producing moisture-permeable leather laminate

Abstract

To provide a method for producing a moisture-permeable leather laminate having sufficient waterproofness and stable gas permeability, and capable of significantly reducing generation of a defect product concerning gas permeability.SOLUTION: A method for producing a moisture-permeable leather laminate includes: an adhesive coating process of coating a leather sheet X with an adhesive so as to obtain an adhesive-coated region R1 coated with an adhesive and an adhesive-non-coated region R2 coated with no adhesive; a laminate-forming process of laminating the leather sheet formed with an adhesive layer and a waterproof sheet Z to form a leather laminate; and a laser-irradiating process of irradiating with laser so as to penetrate the adhesive-non-coated region R2 of the leather laminate to form open holes P.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a moisture-permeable leather laminate, and more specifically to a method for manufacturing a moisture-permeable leather laminate that is easy to ensure sufficient waterproofness and stable breathability, and that can significantly reduce 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, moisture-permeable 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 (moisture permeability) 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, breathability (moisture permeability) will naturally be significantly reduced.

[0008] Furthermore, the inventors of the present invention discovered that even if leather 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 will be uneven breathability in different areas.

[0009] Therefore, after extensive research, the inventors have found that this problem can be solved by applying adhesive to leather so that there are adhesive-applied areas and non-adhesive-applied areas, attaching a waterproof sheet to form a leather laminate, and then irradiating a laser so that it penetrates the non-adhesive-applied areas of the leather laminate to form through-holes.

[0010] That is, the present invention aims to provide a method for producing a moisture-permeable 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 manufacturing the moisture-permeable leather laminate of the present invention includes the steps of: applying an adhesive to a leather sheet to form an adhesive-coated surface on the leather sheet so that there are an adhesive-coated area (R1) where the adhesive is coated and an adhesive-free area (R2) where the adhesive is not coated; a laminate forming step of laminating a leather sheet having an adhesive layer formed thereon and a waterproof sheet to form a leather laminate; and a laser irradiation step of irradiating a laser so as to penetrate the adhesive-free region (R2) of the leather laminate to form through-holes. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram illustrating a method for producing a moisture-permeable leather laminate according to the present invention. [Figure 2] FIG. 2 is a diagram illustrating the adhesive application surface of the leather sheet. [Figure 3] FIG. 3 is a diagram illustrating one embodiment of an adhesive-coated region (R1) and an adhesive-uncoated region (R2) on the adhesive-coated surface of a leather sheet. [Figure 4] FIG. 4 is a diagram for explaining another embodiment of the adhesive-coated region (R1) and the adhesive-uncoated region (R2) on the adhesive-coated surface of the leather sheet. [Figure 5] FIG. 5 is a diagram showing the shape of the roller surface of the coating device (roll coater). [Figure 6] FIG. 6 is a cross-sectional view and an enlarged view showing the leather laminate obtained in the laminate formation step. [Figure 7] FIG. 7 is a diagram showing an example of a laser irradiation device used in the laser irradiation step. [Figure 8] FIG. 8 is a cross-sectional view and an enlarged view showing the breathable leather laminate obtained by the laser irradiation step. [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 adhesive application step (S1), laminate formation step (S2), and laser irradiation step (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 step, the adhesive application step, is a step of applying adhesive to a leather sheet to form an adhesive application surface on the leather sheet so that there are adhesive application areas (R1) where the adhesive is applied and adhesive non-application areas (R2) where the adhesive is not applied.

[0016] 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.

[0017] 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).

[0018] 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.

[0019] 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.

[0020] Furthermore, the number X in Fig. 2(A) indicates the state of the leather sheet before the adhesive application process is performed, and the number X' in Fig. 2(B) indicates the state of the leather sheet after the adhesive application process is performed. That is, in the adhesive application process, an adhesive-coated surface is formed on the leather sheet so that there are adhesive-coated areas where adhesive is applied and adhesive-uncoated areas where adhesive is not applied.

[0021] More specifically, as shown in Figure 3(A) and (B), which is an enlarged view of (A), in the leather sheet X' on which an adhesive application surface is formed, in the adhesive application process, there are an adhesive application area R1 where the adhesive is applied and an adhesive non-application area R2 where the adhesive is not applied.

[0022] Here, in FIG. 3, 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.

[0023] As shown in FIGS. 4(A) to 4(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.

[0024] The method for forming the adhesive application region R1 is not particularly limited, and examples thereof include application using a jet dispenser or a roller with an uneven surface (applicator (roll coater)). Figure 5(A) shows the shape of the roller surface of an applicator (roll coater) used when applying with a roller.

[0025] Figure 5(B) is an enlarged photograph of the roller surface of this device. Here, the gaps on the surface form areas where no adhesive is applied, while the surrounding areas form areas where adhesive is applied.

[0026] The laminate formation process is a process of laminating a leather sheet with an adhesive-coated surface and a waterproof sheet to form a leather laminate. As shown in Fig. 6(A), the leather laminate is formed by laminating a leather sheet X, an adhesive layer Y, and a waterproof sheet Z. As shown in Fig. 6(B), which is an enlarged view, the adhesive layer Y has voids (i.e., areas where no adhesive exists) in the adhesive-free areas.

[0027] 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 7.

[0028] 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.

[0029] 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 7, 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.

[0030] Of the essential steps, the final step, the laser irradiation step (perforation step), is a step in which a laser is irradiated so as to penetrate the adhesive-free regions (R2) of the leather laminate to form through-holes.

[0031] Here, in order to be able to use a laser irradiation device to penetrate the non-adhesive application area R2, a positioning device may be used to determine the location of the non-adhesive application area R2 from the surface of the leather laminate, or the location of the non-adhesive application area R2 may be marked during the previous adhesive application process or leather laminate formation process.

[0032] The type of laser is not particularly limited, but examples include CO2 laser, YAG laser, fiber laser, and semiconductor laser.

[0033] Furthermore, as shown by reference numeral 40 in Fig. 7, it is desirable that the laser be cooled by a cooling unit of the laser output device during laser irradiation. Here, the cooling unit is not particularly limited as long as it is a device that cools the laser output device, and examples thereof include a water-cooled chiller and a cold air chiller.

[0034] 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.

[0035] As shown in Figure 8, the breathable leather laminate obtained by carrying out the laser irradiation process (perforation process) 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 Figure 8(B), through holes P are formed by the laser irradiation device in the non-adhesive application area.

[0036] Thus, the manufacturing method of the present invention can provide a moisture-permeable leather laminate that is easy to ensure has sufficient waterproofness as well as stable breathability, and can significantly reduce the occurrence of defective products in terms of breathability. [Example]

[0037] 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.

[0038] [Example 1] A laser irradiation device (KH866A laser micro-hole processing line manufactured by Wenzhou Kanghong Machinery Co., Ltd., laser: CO2 laser) was prepared.

[0039] 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 non-adhesive-coated areas and adhesive-coated areas around them.

[0040] Next, the leather sheet with the adhesive-coated surface and the waterproof sheet () were fed into a roller feeder and bonded together to form a leather laminate.Furthermore, while cooling in a water-cooled cooling section, the laminate was continuously irradiated with a laser in a laser irradiation section to form through-holes, thereby producing a breathable leather laminate.

[0041] 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.

[0042] [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.

[0043] 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.

[0044] 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.

[0045] [Evaluation criteria] ◯: Uniform fine bubbles were generated (excellent breathability). △: Uneven bubbles were generated (breathability was uneven). ×: No bubbles were generated (no breathability).

[0046] [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 was subjected to Evaluation Test 1 (breathability test). The evaluation results are shown in Table 1.

[0047] [Table 1]

[0048] 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.

[0049] 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]

[0050] 10: Leather laminate 20: Roller feeder 21: Upper roll 22: Feed roll 30: Laser irradiation unit 31: Laser 40: Cooling section 50:Through hole X: Leather seats X': Leather sheet with adhesive applied surface Y: Adhesive layer Z: Tarpaulin P: Through hole R1: Adhesive application area R2: Area without adhesive S1: Adhesive application process S2: Laminate formation process S3: Laser irradiation process T1: Top syringe T2: Lower syringe W:Water B: Air blower L: Test laminate

Claims

[Claim 1] an adhesive application step of applying an adhesive to the leather sheet to form an adhesive-applied surface on the leather sheet so that there are an adhesive-applied area (R1) where the adhesive is applied and an adhesive-unapplied area (R2) where the adhesive is not applied; a laminate forming step of laminating a leather sheet having an adhesive layer formed thereon and a waterproof sheet to form a leather laminate; and a laser irradiation step of irradiating a laser so as to penetrate the adhesive-free region (R2) of the leather laminate to form through-holes.

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