Breathable and wear-resistant leather upper material and method for manufacturing the same

Abstract

The application discloses a kind of breathable wear-resistant leather upper materials and preparation method thereof, and the application belongs to leather product technical field field.The material includes ultra-thin wear-resistant coating, grain layer, net-shaped reinforcing layer, leather base from top to bottom successively;The leather base is head layer cowhide, and inside natural collagen fiber is retained through micropore channel;The net-shaped reinforcing layer is dense fiber network formed by acrylic retanning and nano-silicon dioxide compound, and is located on the upper part of leather base;The grain layer retains natural through pore;The ultra-thin wear-resistant coating is water-based polyurethane coating, light and thin and does not block pore.The application has simple structure, breathable stability, high wear resistance, and is suitable for upper use.

Description

Technical Field

[0001] This invention belongs to the field of leather product technology, specifically referring to a breathable and wear-resistant genuine leather shoe upper material and its preparation method. Background Technology

[0002] Genuine leather uppers are widely used in various footwear products due to their natural softness, breathability, comfort, and excellent texture. However, existing genuine leather upper materials generally suffer from a trade-off between breathability and abrasion resistance: to improve surface abrasion resistance, a thick coating process is usually used, forming a thick layer on the leather surface. This clogs the natural pores of the leather, leading to a significant decrease in breathability and making the feet feel stuffy when worn. On the other hand, if the coating thickness is reduced and the natural pores are preserved to ensure breathability, the surface abrasion and scratch resistance will be insufficient, making the shoes prone to wear and scratches, affecting their lifespan and appearance.

[0003] Therefore, developing a genuine leather shoe upper material with a clear structure, feasibility, and the ability to balance breathability and abrasion resistance has become an urgent problem to be solved in this field. Summary of the Invention

[0004] In view of the above situation and to overcome the defects of the prior art, the present invention provides a breathable and wear-resistant genuine leather shoe upper material and its preparation method, which effectively solves the problems of the difficulty in achieving both breathability and wear resistance in genuine leather shoe uppers on the market and the unreasonable design of existing multi-layer structures.

[0005] The technical solution adopted by this invention is as follows: This invention proposes a breathable and wear-resistant genuine leather shoe upper material, the specific steps of which include: (1) Raw hide pretreatment: The top layer of cowhide is subjected to water soaking, flesh removal, degreasing, ash removal and hair removal, deashing and softening, and acid treatment in sequence. After acid treatment, the pH is adjusted to 2.8~3.2; (2) Retanning treatment: The pretreated leather blanks are placed in a drum, and acrylic retanning agent and nano SiO2 are added to form a wear-resistant network on the surface of collagen fibers. After retanning, the pH is neutralized to 5.0~5.5. (3) Fat grafting treatment: A high-penetration sulfonated, non-migrating fat grafting agent is added to the drum so that the fat grafting agent only penetrates into the interior of the collagen fibers and does not remain on the surface; (4) Fixing and drying: Add formic acid to the drum, wash thoroughly with water, and then use low-temperature vacuum drying at 55~60℃ for 10~12 minutes. After that, hang it to rehydrate until the moisture content is 18~22%, and gently tumble it to soften it. (5) Coating treatment: A thin coating multi-pass process is adopted to roll a mixture of water-based PU emulsion and amino crosslinking agent on the surface of the blank.

[0006] Further, in step (2), 4-6 parts by weight of acrylic retanning agent and 1.5-3.0 parts by weight of nano SiO2 are added, the temperature is controlled at 48-52℃, and the mixture is rotated for 80-100 minutes to form a wear-resistant network on the surface of collagen fibers.

[0007] Further, in step (3), the high-penetration sulfonating fatliquoring agent is 4-6 parts by weight, the non-migratory fatliquoring agent is 2-3 parts by weight, the temperature is controlled at 48-52℃, and the rotation time is 80-90 minutes.

[0008] Furthermore, in step (4), formic acid is used in a fractional color fixation process at a concentration of 0.8 to 1.2 parts by mass.

[0009] Furthermore, in step (5), the film is cross-linked in situ at 80~85℃ to form an ultra-thin wear-resistant coating.

[0010] Furthermore, the genuine leather upper material comprises, from top to bottom: an ultra-thin abrasion-resistant coating, a grain layer, a mesh reinforcement layer, and a genuine leather base.

[0011] Furthermore, the thickness of the mesh reinforcement layer is 0.1–0.2 mm, and it is an integral structure with the dermal substrate.

[0012] Furthermore, the mesh reinforcement layer does not block the natural penetrating pores of the grain layer.

[0013] Furthermore, the ultra-thin wear-resistant coating is a water-based polyurethane coating with a thickness ≤30μm.

[0014] Furthermore, the ultra-thin wear-resistant coating has a continuous, thin structure with a micro-breathable surface that does not clog the natural through-pores of the grain layer.

[0015] The beneficial effects of this invention using the above structure are as follows: This solution proposes a breathable and wear-resistant genuine leather upper material, which is composed of a four-layer combination structure of an ultra-thin wear-resistant coating, a grain layer, a mesh reinforcement layer, and a genuine leather base. This achieves a combination of wear resistance and breathability in genuine leather materials. This method allows the genuine leather base and grain layer to retain through-pore channels, the ultra-thin wear-resistant coating to be thin and not clogged, and the mesh reinforcement layer to improve the wear resistance of the material itself, thus solving the problem of the contradiction between breathability and wear resistance in traditional genuine leather uppers. Among them, the mesh reinforcement layer and the genuine leather base are an integral structure, and the ultra-thin wear-resistant coating is tightly bonded to the grain layer, making it less prone to peeling and cracking, significantly improving the service life and user experience of the upper material. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the four-layer structure of a breathable and wear-resistant genuine leather shoe upper material proposed in this invention.

[0017] Legend: 1. Ultra-thin wear-resistant coating; 2. Grain layer; 3. Mesh reinforcement layer; 4. Genuine leather base. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] like Figure 1 As shown, this invention proposes a breathable and wear-resistant genuine leather shoe upper material. The top-grain cowhide wet blue leather was purchased from Fujian Fengji Leather Co., Ltd.; the acrylic retanning agent was purchased from Guangdong Demei Fine Chemical Group Co., Ltd. The nano-SiO2 was purchased from Shandong Dongjia Group Co., Ltd.; the high-penetration sulfonation fatliquoring agent was purchased from Brothers Technology Co., Ltd.; the non-migratory fatliquoring agent and softening enzyme were purchased from Keke Chemical; the water-based PU emulsion was purchased from Anhui Anli Materials Technology Co., Ltd.; the amino crosslinking agent was purchased from Starr Fine Coatings (Suzhou) Co., Ltd.; the degreasing agent, penetrant, and dispersant were purchased from Guangdong Demei Fine Chemical Group Co., Ltd.; the impregnation agent and deliming agent were purchased from Shandong Zibo Huanya Additives Technology Co., Ltd.; the formic acid was purchased from Shandong Hualu Hengsheng Chemical Co., Ltd.; and the table salt was purchased from a local regular industrial salt supplier. Example

[0020] A breathable and wear-resistant genuine leather shoe upper material and its preparation method are as follows: (1) Pretreatment of raw hides: Select top-grain yellow cattle hides and pre-soak them in water for 30 hours (24℃) and then soak them in water for 20 hours (26℃). Add soaking aids, bactericides and penetrants to restore the hides to freshness and moisture content of 68%. Remove the meat mechanically and trim the residual meat on the edges. Degrease the hides in a drum at 42℃. The amount of degreasing agent added is 2.5% of the hide mass. The process is carried out in two batches, each lasting 60 minutes. Add 0.7% compound enzyme and 0.3% keratinase to pH 9.2. After hair removal, add lime and sulfide for liming. Deliquify the hides with ammonium sulfate to pH 8.2. Add 0.4% softening enzyme and soften at 36℃. Add 9% of the hide mass of salt, formic acid and sulfuric acid mixture to adjust the pH to 3.0.

[0021] (2) Retanning treatment: Place the pretreated leather blank into a drum, add 5 parts by weight of acrylic retanning agent and 2.2 parts by weight of nano SiO2, control the temperature at 50℃, and rotate for 90 min; add 2 parts by weight of sodium formate and 0.5 parts by weight of baking soda, add in two batches, with an interval of 30 min between each batch, and neutralize to pH 5.2.

[0022] (3) Fat addition treatment: Add 5 parts by weight of high-penetration sulfonated fat addition agent and 2.5 parts by weight of non-migratory fat addition agent to the drum, control the temperature at 50℃, and rotate for 85 minutes.

[0023] (4) Fixing and drying: Add 1.0 part by weight of formic acid to the drum and fix it in two batches. After washing thoroughly with water, use low temperature vacuum drying at 58℃ for 11 min. Hang it to rehydrate until the moisture content is 20%. Then, tumble the drum to soften it for 2.5 h at a speed of 18 r / min.

[0024] (5) Coating treatment: Prepare a mixture of water-based PU emulsion and amino crosslinking agent (mass ratio 93:7), roll coat it on the surface of the leather blank, pre-bake at 65℃ for 6 min, and then crosslink in situ at 82℃ to form an ultra-thin wear-resistant coating with a thickness of 22μm, thus obtaining the finished product.

[0025] Finished product performance testing: Thickness 1.0mm, moisture permeability 380g / (m²·24h), Taber abrasion resistance (CS-10, 1000g) 38mg / 1000 revolutions, no obvious cracks after 55,000 folds at room temperature, tensile strength 20MPa, tear strength 29N / mm, meeting the requirements for shoe upper use. Example

[0026] A breathable and wear-resistant genuine leather shoe upper material and its preparation method are as follows: (1) Pretreatment of raw hides: Select top-grain yellow cattle hides and pre-soak them in water for 24 hours (26℃) and then soak them in water for 24 hours (24℃). Add soaking aids, bactericides and penetrants to restore the hides to freshness and moisture content of 65%. Remove the meat mechanically and trim the residual meat on the edges. Degrease the hides in a drum at 40℃. The amount of degreasing agent added is 2% of the hide mass. The process is carried out in two batches, each lasting 60 minutes. Add 0.6% compound enzyme and 0.2% keratinase to pH 9.0. After hair removal, add lime and sulfide for liming. De-lime the hides with ammonium chloride to pH 8.0. Add 0.3% softening enzyme and soften at 35℃. Add 8% of the hide mass of salt, formic acid and sulfuric acid mixture to adjust the pH to 2.8.

[0027] (2) Retanning treatment: Place the pretreated leather blank into a drum, add 4 parts by weight of acrylic retanning agent and 1.5 parts by weight of nano SiO2, control the temperature at 48℃, and rotate for 80 minutes; add 2 parts by weight of sodium formate and 0.4 parts by weight of baking soda, add in two batches, with an interval of 30 minutes between each batch, and neutralize to pH 5.0.

[0028] (3) Fat addition treatment: Add 4 parts by weight of high-penetration sulfonated fat addition agent and 2 parts by weight of non-migratory fat addition agent to the drum, control the temperature at 48℃, and rotate for 80 minutes.

[0029] (4) Fixing and drying: Add 0.8 parts by weight of formic acid to the drum and fix it in two batches. After washing thoroughly with water, use low temperature vacuum drying at 55℃ for 10 minutes. Hang it to rehydrate until the moisture content is 18%. Then, tumble the drum to soften it for 2 hours at a speed of 15 r / min.

[0030] (5) Coating treatment: Prepare a mixture of water-based PU emulsion and amino crosslinking agent (mass ratio 95:5), roll coat it on the surface of the leather blank, pre-bake at 60℃ for 5 min, and then crosslink in situ at 80℃ to form an ultra-thin wear-resistant coating with a thickness of 15μm, thus obtaining the finished product.

[0031] Finished product performance testing: Thickness 0.9mm, moisture permeability 350g / (m²·24h), Taber abrasion resistance (CS-10, 1000g) 40mg / 1000 revolutions, no obvious cracks after 50,000 folds at room temperature, tensile strength 19MPa, tear strength 28N / mm, meeting the requirements for shoe upper use. Example

[0032] A breathable and wear-resistant genuine leather shoe upper material and its preparation method are as follows: (1) Pretreatment of raw hides: Select top-grain yellow cattle hides and pre-soak them in water for 36 hours (22℃) and then soak them in water for 18 hours (28℃). Add soaking aids, bactericides and penetrants to restore the hides to freshness and moisture content of 70%. Remove the meat mechanically and trim the residual meat on the edges. Degrease the hides in a drum at 45℃. The amount of degreasing agent added is 3% of the hide mass. The process is carried out in two batches, each lasting 60 minutes. Add 0.8% compound enzyme and 0.4% keratinase to pH 9.5. After hair removal, add lime and sulfide for liming. De-lime the hides with ammonium sulfate to pH 8.5. Add 0.5% softening enzyme and soften at 38℃. Add 10% salt, formic acid and sulfuric acid mixture to adjust the pH to 3.2.

[0033] (2) Retanning treatment: Place the pretreated leather blank into a drum, add 6 parts by weight of acrylic retanning agent and 3.0 parts by weight of nano SiO2, control the temperature at 52℃, and rotate for 100 min; add 2 parts by weight of sodium formate and 0.6 parts by weight of baking soda, add in two batches, with an interval of 30 min between each batch, and neutralize to pH 5.5.

[0034] (3) Fat addition treatment: Add 6 parts by weight of high-penetration sulfonated fat addition agent and 3 parts by weight of non-migratory fat addition agent to the drum, control the temperature at 52℃, and rotate for 90 minutes.

[0035] (4) Fixing and drying: Add 1.2 parts by weight of formic acid to the drum and fix it in two batches. After washing thoroughly with water, use low temperature vacuum drying at 60℃ for 12 minutes. Hang it to rehydrate until the moisture content is 22%. Then, tumble the drum to soften it for 3 hours at a speed of 20 r / min.

[0036] (5) Coating treatment: Prepare a mixture of water-based PU emulsion and amino crosslinking agent (mass ratio 92:8), roll coat it on the surface of the leather blank, pre-bake at 70℃ for 8 min, and then crosslink in situ at 85℃ to form an ultra-thin wear-resistant coating with a thickness of 30μm, thus obtaining the finished product.

[0037] Finished product performance testing: Thickness 1.2mm, moisture permeability 420g / (m²·24h), Taber abrasion resistance (CS-10, 1000g) 35mg / 1000 revolutions, no obvious cracks after 60,000 folds at room temperature, tensile strength 21MPa, tear strength 30N / mm, meeting the requirements for shoe upper use.

[0038] Comparative Example 1 (1) Pretreatment of raw hides: Select top-grain yellow cattle hides and pre-soak them in water for 30 hours (24℃) and then soak them in water for 20 hours (26℃). Add soaking aids, bactericides and penetrants to restore the hides to freshness and moisture content of 68%. Remove the meat mechanically and trim the residual meat on the edges. Degrease the hides in a drum at 42℃. The amount of degreasing agent added is 2.5% of the hide mass. The process is carried out in two batches, each lasting 60 minutes. Add 0.7% compound enzyme and 0.3% keratinase to pH 9.2. After hair removal, add lime and sulfide for liming. Deliquify the hides with ammonium sulfate to pH 8.2. Add 0.4% softening enzyme and soften at 36℃. Add 9% of the hide mass of salt, formic acid and sulfuric acid mixture to adjust the pH to 3.0.

[0039] (2) Retanning treatment: Place the pretreated leather blank into a drum, add 5 parts by weight of acrylic retanning agent and 2.2 parts by weight of nano SiO2, control the temperature at 50℃, and rotate for 90 min; add 2 parts by weight of sodium formate and 0.5 parts by weight of baking soda, add in two batches, with an interval of 30 min between each batch, and neutralize to pH 5.2.

[0040] (3) Fixing and drying: Add 1.0 part by weight of formic acid to the drum and fix it in two batches. After washing thoroughly with water, use low temperature vacuum drying at 58℃ for 11 min. Hang it to rehydrate until the moisture content is 20%. Then, tumble the drum to soften it for 2.5 h at a speed of 18 r / min.

[0041] Finished product performance testing: moisture permeability 280g / (m²·24h), Taber abrasion resistance 55mg / 1000 revolutions, no obvious cracks after 45,000 folds at room temperature, tensile strength 18MPa, tear strength 26N / mm. Both air permeability and abrasion resistance are lower than those of Example 1 of this invention.

[0042] Comparative Example 2 (1) Pretreatment of raw hides: Select top-grain yellow cattle hides and pre-soak them in water for 30 hours (24℃) and then soak them in water for 20 hours (26℃). Add soaking aids, bactericides and penetrants to restore the hides to freshness and moisture content of 68%. Remove the meat mechanically and trim the residual meat on the edges. Degrease the hides in a drum at 42℃. The amount of degreasing agent added is 2.5% of the hide mass. The process is carried out in two batches, each lasting 60 minutes. Add 0.7% compound enzyme and 0.3% keratinase to pH 9.2. After hair removal, add lime and sulfide for liming. Deliquify the hides with ammonium sulfate to pH 8.2. Add 0.4% softening enzyme and soften at 36℃. Add 9% of the hide mass of salt, formic acid and sulfuric acid mixture to adjust the pH to 3.0.

[0043] (2) Fat addition treatment: Add 5 parts by weight of high-penetration sulfonated fat addition agent and 2.5 parts by weight of non-migratory fat addition agent to the drum, control the temperature at 50℃, and rotate for 85 minutes.

[0044] (3) Fixing and drying: Add 1.0 part by weight of formic acid to the drum and fix it in two batches. After washing thoroughly with water, use low temperature vacuum drying at 58℃ for 11 min. Hang it to rehydrate until the moisture content is 20%. Then, tumble the drum to soften it for 2.5 h at a speed of 18 r / min.

[0045] Finished product performance testing: moisture permeability 320g / (m²·24h), Taber abrasion resistance 70mg / 1000 rpm, no obvious cracks after 48,000 folds at room temperature, tensile strength 17MPa, tear strength 25N / mm, abrasion resistance significantly lower than that of Example 1 of this invention.

[0046] Comparative Example 3 A breathable and wear-resistant genuine leather shoe upper material and its preparation method are as follows: (1) Pretreatment of raw hides: Select top-grain yellow cattle hides and pre-soak them in water for 30 hours (24℃) and then soak them in water for 20 hours (26℃). Add soaking aids, bactericides and penetrants to restore the hides to freshness and moisture content of 68%. Remove the meat mechanically and trim the residual meat on the edges. Degrease the hides in a drum at 42℃. The amount of degreasing agent added is 2.5% of the hide mass. The process is carried out in two batches, each lasting 60 minutes. Add 0.7% compound enzyme and 0.3% keratinase to pH 9.2. After hair removal, add lime and sulfide for liming. Deliquify the hides with ammonium sulfate to pH 8.2. Add 0.4% softening enzyme and soften at 36℃. Add 9% of the hide mass of salt, formic acid and sulfuric acid mixture to adjust the pH to 3.0.

[0047] (2) Fixing and drying: Add 1.0 part by weight of formic acid to the drum and fix it in two batches. After washing thoroughly with water, use low temperature vacuum drying at 58℃ for 11 min. Hang it to rehydrate until the moisture content is 20%. Then, tumble the drum to soften it for 2.5 h at a speed of 18 r / min.

[0048] (3) Coating treatment: Prepare a mixture of water-based PU emulsion and amino crosslinking agent (mass ratio 93:7), roll coat it on the surface of the leather blank, pre-bake at 65℃ for 6 minutes, and then crosslink in situ at 82℃ to form an ultra-thin wear-resistant coating with a thickness of 22μm, thus obtaining the finished product.

[0049] Finished product performance testing: moisture permeability 300g / (m²·24h), Taber abrasion resistance 60mg / 1000 revolutions, no obvious cracks after 46,000 folds at room temperature, tensile strength 16MPa, tear strength 24N / mm. Both the air permeability and abrasion resistance are lower than those of Example 1 of this invention.

[0050] The comparison between the examples and comparative examples shows that the present invention can significantly improve the breathability and wear resistance of genuine leather shoe upper materials through the synergistic effect of the three-step process of retanning, fatliquoring and finishing. The combined effect is far greater than the sum of the effects of each individual process.

[0051] The above is the overall workflow of this invention. Simply repeat this process the next time you use it.

[0052] The actual operation process is very simple and easy to follow. It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0053] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0054] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A method for preparing a breathable and wear-resistant genuine leather shoe upper material, characterized in that: Includes the following steps: (1) Raw hide pretreatment: The top layer of cowhide is subjected to water soaking, flesh removal, degreasing, ash removal and hair removal, deashing and softening, and acid treatment in sequence. After acid treatment, the pH is adjusted to 2.8~3.2; (2) Retanning treatment: The pretreated leather blanks are placed in a drum, and acrylic retanning agent and nano SiO2 are added to form a wear-resistant network on the surface of collagen fibers. After retanning, the pH is neutralized to 5.0~5.

5. (3) Fat grafting treatment: A high-penetration sulfonated, non-migrating fat grafting agent is added to the drum so that the fat grafting agent only penetrates into the interior of the collagen fibers and does not remain on the surface; (4) Fixing and drying: Add formic acid to the drum, wash thoroughly with water, and then use low-temperature vacuum drying at 55~60℃ for 10~12 minutes. After that, hang it to rehydrate until the moisture content is 18~22%, and gently tumble it to soften it. (5) Coating treatment: A thin coating multi-pass process is adopted to roll a mixture of water-based PU emulsion and amino crosslinking agent on the surface of the blank.

2. The method for preparing a breathable and wear-resistant genuine leather shoe upper material according to claim 1, characterized in that: In step (2), 4-6 parts by weight of acrylic retanning agent and 1.5-3.0 parts by weight of nano SiO2 are added, the temperature is controlled at 48-52℃, and the mixture is rotated for 80-100 minutes to form a wear-resistant network on the surface of collagen fibers.

3. The method for preparing a breathable and wear-resistant genuine leather shoe upper material according to claim 1, characterized in that: In step (3), the high-penetration sulfonating fatliquoring agent is 4-6 parts by weight, the non-migratory fatliquoring agent is 2-3 parts by weight, the temperature is controlled at 48-52℃, and the rotation time is 80-90 minutes.

4. The method for preparing a breathable and wear-resistant genuine leather shoe upper material according to claim 1, characterized in that: In step (4), formic acid is used in a fractional color fixation process at a concentration of 0.8 to 1.2 parts by mass.

5. The method for preparing a breathable and wear-resistant genuine leather shoe upper material according to claim 1, characterized in that: In step (5), the film is cross-linked in situ at 80~85℃ to form an ultra-thin wear-resistant coating.

6. The genuine leather shoe upper material prepared by the method for preparing a breathable and wear-resistant genuine leather shoe upper material according to any one of claims 1-5, characterized in that: The genuine leather upper material comprises, from top to bottom: an ultra-thin abrasion-resistant coating, a grain layer, a mesh reinforcement layer, and a genuine leather base.

7. The breathable and wear-resistant genuine leather shoe upper material according to claim 6, characterized in that: The thickness of the mesh reinforcement layer is 0.1 to 0.2 mm, and it is an integral structure with the dermal substrate.

8. The breathable and wear-resistant genuine leather shoe upper material according to claim 6, characterized in that: The mesh reinforcement layer does not clog the natural penetrating pores of the grain layer.

9. A breathable and wear-resistant genuine leather shoe upper material according to claim 6, characterized in that: The ultra-thin wear-resistant coating is a water-based polyurethane coating with a thickness of ≤30μm.

10. The breathable and wear-resistant genuine leather shoe upper material according to claim 6, characterized in that: The ultra-thin wear-resistant coating has a continuous, lightweight structure with a micro-breathable surface that does not clog the natural pores of the grain layer.

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