Method for producing sound-absorbing material using piece-cut leather

Abstract

To provide a method for producing a sound absorbing material using scrap leather, which reduces cost by using scrap leather, is not only environmentally friendly but also excellent in sound absorbing effect.SOLUTION: A method for producing a sound-absorbing material using offcut leather includes a first step of pretreating offcut leather, a second step of cutting and pulverizing the offcut leather to produce a pulverized product, a third step of drying the pulverized product, a fourth step of mixing the pulverized product with an aqueous adhesive, latex, and water to produce a mixture, a fifth step of compressing the mixture to produce a molded body, and a sixth step of drying the molded body.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing sound-absorbing material using scrap leather, and more particularly to a method for manufacturing sound-absorbing material using scrap leather that achieves resource circulation by recycling various scrap leather (leftover leather, etc.) obtained from products such as car seats. [Background technology]

[0002] Recently, violent incidents caused by noise clashes between floors have been occurring frequently in apartment complexes and other multi-family housing. In response, the Ministry of Land, Infrastructure, Transport and Tourism announced "Measures to Eliminate Noise Between Floors" in December 2023, stipulating that construction approval will not be granted if noise standards are not met. As a result, demand for sound-absorbing materials is expected to soar in apartment complexes, new schools, and other multi-family housing. Conventional sound-absorbing materials are manufactured by either heating and pressurizing the upper and lower plates or by heating the mold in a boiler and then injecting the material, but this process is complicated, energy inefficient, and requires capital investment. Furthermore, sound-absorbing materials such as sponge, polystyrene foam, rock wool, and glass wool are known to be harmful to the human body, emitting toxic gases in the event of a fire, and rock wool and glass wool are known to cause lung cancer. As a result, efforts are underway to develop cost-effective sound-absorbing materials made from car seat scraps and used leather, which are made from environmentally friendly natural leather scraps. Approximately 4 million tons of car seat scraps and waste leather are generated annually, most of which is disposed of by landfill or incineration. This processing method causes environmental and soil pollution due to increased greenhouse gas emissions from carbon emissions, but currently there is insufficient technology to use scrap leather and waste leather from car seats. To solve these problems, technology is needed to prevent soil and environmental pollution by realizing resource circulation through the recycling of leather scraps and waste leather from automobiles, and to manufacture sound-absorbing materials with excellent sound-absorbing properties. Summary of the Invention [Problem to be solved by the invention]

[0003] The present invention aims to provide a method for producing sound-absorbing material using scrap leather that achieves resource recycling using scrap leather, prevents environmental pollution and soil pollution, and has excellent sound-absorbing properties. [Means for solving the problem]

[0004] To achieve the above object, the method for manufacturing sound-absorbing material using scrap leather according to the present invention includes a first step of pre-treating the scrap leather; a second step of cutting and pulverizing the pre-treated scrap leather to produce pulverized material; a third step of drying the pulverized material; a fourth step of mixing the dried pulverized material with an aqueous adhesive, latex, and water to produce a mixture; a fifth step of compressing the mixture to produce a molded body; and a sixth step of drying the molded body. In the second step, the scrap leather can be cut using a cutter and then crushed using a crusher to a size of 2 to 5 mm. In the third step, the pulverized material can be dried at 45 to 50° C. for 60 to 72 hours, and then allowed to air dry. In the fourth step, the mixture may contain the ground material, the water-based adhesive, the latex, and the water in a weight ratio of 1:0.2-0.4:0.05-0.15:0.005-0.015, where the water-based adhesive may include water-based bond, and the latex may include natural rubber latex. In the fifth step, the dried pulverized material is pressed into a mold and pressed under a pressure of 60 to 100 tons to produce a compact, where the compact is in the form of a pad, and the thickness of the pad may be 2 to 2.5 cm. In the sixth step, the green body may be sequentially dried with cold air, hot air, and air-dried. [Effects of the Invention]

[0005] The method for producing sound-absorbing material using leather scraps according to the present invention reduces incineration costs and production costs, realizes resource recycling, and reduces soil and environmental pollution. Furthermore, the method uses environmentally friendly materials that are harmless to the human body, and provides excellent heat dissipation, dustproofing, and soundproofing effects. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a flowchart showing the manufacturing process of a sound-absorbing material using scrap leather according to an embodiment of the present invention. [Figure 2] FIG. 2 is a photograph showing the scrap leather cut by the pulverization production process of FIG. 1 and the shredded pulverized scrap leather. [Figure 3] FIG. 3 is a photograph showing the scrap leather cut by the pulverization production process of FIG. 1 and the shredded pulverized scrap leather. [Figure 4] FIG. 4 is a photograph showing the process of mixing the ground material of FIG. 3 with a water-based adhesive, latex, and water to produce a mixture. [Figure 5] FIG. 5 is a photograph showing a pad-type sound-absorbing material manufactured by a manufacturing process for a sound-absorbing material using scrap leather according to an embodiment of the present invention. [Figure 6] FIG. 6 is a photograph showing an example of a pad-type sound-absorbing material manufactured by the manufacturing process for a sound-absorbing material using scrap leather according to an embodiment of the present invention, installed on the ceiling of an apartment building. DETAILED DESCRIPTION OF THE INVENTION

[0007] All terms described in this specification are generally used and widely in consideration of the features of the present invention. However, these may differ depending on the intentions, practices, or the emergence of new technologies of those skilled in the art. When the inventor specifies any term in this specification, the meaning of the term will be described in the detailed description of the invention. Therefore, the terms used in this specification should be interpreted based on the substantive meaning of the term and the overall content described in this specification, rather than simply the name of the term. Hereinafter, a method for manufacturing a sound-absorbing material using scrap leather according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a flowchart showing the manufacturing process of a sound-absorbing material using scrap leather according to an embodiment of the present invention. Referring to FIG. 1, a method for manufacturing a sound-absorbing material using scrap leather according to an embodiment of the present invention includes a first step of pre-treating the scrap leather, a second step of cutting and crushing the scrap leather to produce a pulverized material, a third step of drying the pulverized material, a fourth step of mixing the dried pulverized material with a water-based adhesive, latex, and water to produce a mixture, a fifth step of compressing the mixture to produce a molded body, and a sixth step of drying the molded body. [1] First step (pre-treatment of leather scraps) In the first step, leather scraps are pretreated. The leather scraps refer to leather or leather residue remaining after cutting when manufacturing leather products such as car seats. The car seats can be made of natural leather or artificial leather. The natural leather is produced by extracting leather from calves, lambs, kids, etc., while the artificial leather can be produced from at least one plastic resin such as PU, PVC, EVA, PET, etc. In the present invention, car seat scraps (preferably produced by extracting leather from calves) can be selected. The leather scraps can also include discarded car seat sheets produced by extracting leather from calves, etc. The pretreatment step can be carried out by collecting, washing, and drying. Specifically, the pretreatment step can involve collecting the leather scraps and using a strong multi-purpose cleaner to wipe off the contaminants with tissue or cloth, or by using a cleaning mixture. The leather scraps from which the contaminants have been removed can be air-dried at room temperature (21-30°C). The cleaning mixture may contain water, shell powder, and baking soda. For example, the cleaning mixture may be a mixture of 100 parts water, 0.05-0.25 parts shell powder, and 0.03-0.05 parts baking soda by volume. Shell powder can be included in the washing mixture. The shell powder can be produced by the following five steps. In other words, it can be produced by the following steps: (1) preparing and washing shells; (2) drying the washed shells under natural light for 24 to 72 hours; (3) primarily pulverizing the dried shells in a roll mill to an average particle size of 2 to 5 mm; (4) low-temperature firing the primarily pulverized shells at 400 to 500°C for 10 to 20 hours, followed by high-temperature firing at 70 to 1000°C for 5 to 10 hours; and (5) secondary pulverization of the fired shells into fine powder.

[0008] The shells may be selected from, but are not limited to, clam shells, ark shells, seashells, scallop shells, and oyster shells. The clam shells have various patterns, such as stripes and waves, and are composed of 89-99% calcium carbonate and 1-2% calcium phosphate. The ark shells are usually oval-shaped and are composed of 89-99% calcium carbonate and 1-2% calcium phosphate. The shells are circular and are composed of 89-99% calcium carbonate and 1-2% calcium phosphate. The scallop shells are fan-shaped and come in various colors and are composed of 89-99% calcium carbonate and 1-2% calcium phosphate. The oyster shells are composed almost entirely of calcium carbonate, with gypsum and other components. The step (1) of preparing and washing the shells is a step of removing impurities and contaminants from the shells, and is preferably carried out by washing with fresh water. The drying step (2) is a step for removing salt and odor remaining in the washed shells, and the washed shells can be dried for 24 to 27 hours, but is not limited to this. In the primary pulverization step (3), the shells can be pulverized using a roll mill to an average particle size of 2 to 5 mm. If the shells are pulverized to an average particle size of less than 2 mm, they may be pulverized too finely and scatter, and if they are pulverized to an average particle size of more than 5 mm, the firing process described below may not be properly achieved. The calcination step (4) can be performed by performing a low-temperature calcination at 400-500°C for 10-20 hours in an air- and oxygen-free environment, followed by a high-temperature calcination at 700-1000°C for 5-10 hours in air. Therefore, if the calcination temperature and time are below the range, impurities may remain, the calcination reaction may not proceed properly, and it may be difficult to increase the calcium carbonate content. However, if the calcination temperature and time are above the range, the shells may be burned away. This two-stage calcination process can improve the antifungal and antibacterial properties as the calcium carbonate content increases. Leather scraps washed with the mixture can be protected from mold and mildew.

[0009] The secondary crushing step (5) can produce shell powder with an average particle size of 1 to 5 μm. If the average particle size of the secondary crushed shell powder is less than 1 μm, it is difficult for the cleaning mixture to exert its effect, and if it exceeds 5 μm, it may not be mixed properly with other ingredients. Therefore, the shell powder can be mixed in a volume ratio of 0.05 to 0.25 with respect to 100% water in the cleaning mixture. If the volume ratio of the shell powder is less than 0.05, it is difficult to improve the antifungal and antibacterial effects of the sound absorbing material, and if it exceeds 0.25, the content of other components is relatively reduced, making it difficult to obtain an adequate cleaning effect. The baking soda can be included in a cleaning mixture. The baking soda is an environmentally friendly material with excellent cleaning power and is weakly alkaline. The baking soda is weakly alkaline and can neutralize pollutants and oily stains made of fatty acids, turning them water-soluble. Therefore, when using the baking soda and water, pollutants and oily stains can be thoroughly removed without using detergents that cause environmental pollution. The baking soda can also be in the form of powder, granules, liquid, etc. The baking soda may be included in the cleaning mixture in a volume ratio of 0.03 to 0.05 with respect to 100 parts by volume of water. If the volume ratio of baking soda is less than 0.03, the cleaning effect may not be achieved and contaminants may remain on the leather scraps, while if the volume ratio is more than 0.05, it may not be technically significant. Therefore, the pretreated leather scraps are purified of impurities and are useful for producing high-quality antifungal sound-absorbing materials.

[0010] [2] Second stage (production of crushed material) 2 and 3 are photographs showing the scrap leather cut and the shredded scrap leather pulverized material produced by the pulverized material producing step of FIG. Referring to Figures 2 and 3, in the second step, the leather scraps are cut and crushed to produce crushed material. Referring to Figure 2, the leather scraps are classified and grouped by size, and then the leather scraps within the same group can be cut into pieces of 2 cm or less in thickness and 20 to 30 cm in length using a cutter. The cutter is a device for cutting leather scraps, and commonly known devices can be used. Referring to Figure 3, the cut leather scraps can be crushed using a crusher to produce crushed pieces of 2 to 5 mm in size (width, length, and height). The crusher can be, but is not limited to, a leather cutter or the like. If the size of the pulverized particles is less than 2.0 mm, the air gap structure that can absorb sound in the air will be reduced, and the sound absorbing performance against high frequency noise may be reduced. On the other hand, if the size of the pulverized particles is more than 5 mm, the density of the sound absorbing material will be reduced, and the mechanical strength and durability may be reduced due to the non-uniform structure, or the air gaps between the large particles may be large due to insufficient blending, and the sound absorbing performance against low frequency noise may be reduced.

[0011] [3] Third stage (drying of crushed material) In the third step, the pulverized material is dried to produce the sound-absorbing material. This drying step is intended to remove moisture, contaminants, dust, and residue remaining in the pulverized material. Specifically, the pulverized material can be placed in a drying oven and dried at 45-50°C for 60-72 hours, followed by natural drying. In the present invention, natural drying can be performed at room temperature of 21-30°C. A commonly known device can be used as the drying oven. In another embodiment, if mass-production equipment is available, the process of placing the pulverized material in the drying oven and drying it with hot air can be omitted, and only natural drying can be performed. Natural drying can prevent distortion and improve quality compared to hot air drying, while reducing the equipment and operation costs associated with hot air drying. Therefore, if the drying temperature is less than 45°C, not only will the drying time be long and energy efficiency be poor, but moisture may remain due to insufficient drying, and if the drying temperature exceeds 50°C, the pulverized material may burn or become distorted. Furthermore, if the drying time is less than 60 hours, moisture may remain due to insufficient drying, and if it exceeds 72 hours, the longer production time will result in poor energy efficiency and may cause problems in mass production.

[0012] [4] Step 4 (Mixture Formation) FIG. 4 is a photograph showing the process of producing a mixture by mixing the pulverized material of FIG. 3 with a water-based adhesive, latex, and water. Referring to Figure 4, the fourth step of preparing the mixture is the process of adhering the ground material. The mixture can be prepared by mixing the ground material with an aqueous adhesive, latex, and water. The mixture can contain the ground material, aqueous adhesive, latex, and water in a weight ratio of 1:0.2-0.4:0.05-0.15:0.005-0.015. The water-based adhesive is used to bond the ground material, and a water-based bond can be used. This water-based bond can be made of environmentally friendly materials. This water-based bond does not use organic solvents and emits little volatile organic compounds, making it environmentally friendly, quick-drying, and shortens work time. It is also cheaper and more economical than other organic solvent-based adhesives. Here, the water-based bond can contain 20 to 40 parts by weight per 100 parts by weight of ground material. If the water-based bond content is less than 20 parts by weight, it may be difficult to bond the ground material, which may reduce the sound-absorbing effect. Furthermore, if the water-based bond content exceeds 40 parts by weight, the ground material content will be relatively low, which may reduce the strength, durability, sound-absorbing properties, etc. of the sound-absorbing material. The latex is an environmentally friendly material, and natural rubber latex can be used to bond the ground material and improve sound absorption. This natural rubber latex is not only environmentally friendly, but also has excellent durability, adhesion, and sound absorption properties. The natural rubber latex can be contained in an amount of 5 to 15 parts by weight per 100 parts by weight of the pulverized material. If the content of natural rubber latex is less than 5 parts by weight, adhesion and sound absorption effects become difficult to achieve. On the other hand, if the content of natural rubber latex exceeds 15 parts by weight, the sound-absorbing material becomes too flexible, making it difficult to mold into the desired shape, and although the elasticity is improved, the sound-absorbing function is reduced. The water may be included in the mixture to bond the components together. Here, the water content may be 0.5 to 1.5 parts by weight per 100 parts by weight of the pulverized material. If the water content is less than 0.5 parts by weight, it may be difficult to bond the mixture and molding may become difficult. Furthermore, if the water content exceeds 1.5 parts by weight, the sound absorption function may be reduced.

[0013] [5] Fifth step (production of molded body) In the fifth step, the mixture is compressed to produce a compact, which allows the sound-absorbing material to be molded into various custom shapes suitable for buildings such as apartments, condominiums, townhouses, and schools. The molding method for producing the molded body can be selected from sheet molding, extrusion molding, injection molding, press molding, etc. In the present invention, press molding is preferably selected. Press molding is a method for producing a molded body by filling a mold with powder and applying pressure. Depending on the pressing method, there are uniaxial pressing and multiaxial pressing (hydrostatic pressing). The molding method according to the embodiment of the present invention is mainly uniaxial pressing, in which powder is pressed into a mold. Furthermore, the mold into which the powder has been pressed can be pressed at a predetermined pressure to form the mold. For example, a molded body can be produced by press molding, in which the mixture is forced into a mold at room temperature (21-30°C) and a pressure of 60-100 tons. If the pressure used to produce the molded body is less than 60 tons, the density of the molded body will be uneven, air gaps will occur, and adhesion will be weakened, potentially leading to a deterioration in material properties such as strength and sound absorption performance. On the other hand, if the pressure exceeds 100 tons, the density will increase, sound absorption performance will decrease, uniform molding will become difficult, and defects such as fine cracks will occur, reducing the durability of the manufactured sound-absorbing material. The molded body may be in the form of a pad of various shapes, such as a circle or a square. When the molded body is in the form of a pad, the thickness of the pad may be 2 to 2.5 cm. If the thickness of the pad is less than 2 cm, material properties such as sound absorption performance and durability deteriorate. On the other hand, if the thickness of the pad exceeds 2.5 cm, the cost and weight increase while not contributing much to improving sound absorption performance.

[0014] [6] Step 6 (drying the molded body to produce sound-absorbing material) In the sixth step of drying the green body, the green body is dried in the order of cold air drying, hot air drying and natural drying. Cold air drying is a method of drying the compact with low-temperature air without damaging it, and the cold air can absorb moisture from the surface of the compact. Hot air drying is a method of drying the compact dried with cold air with air at a temperature of 100 to 150°C, which allows for uniform drying and continuous drying, making mass production possible. Natural drying allows the compact dried with hot air to be dried at 25 to 30°C. In another embodiment, the compact can be dried only by natural drying. Fig. 5 is a photograph showing a pad-shaped sound-absorbing material manufactured by a sound-absorbing material manufacturing process using scrap leather according to an embodiment of the present invention, and Fig. 6 is a photograph showing an example of the sound-absorbing material of Fig. 5 installed on the ceiling of an apartment building. Referring to Figs. 5 and 6, the manufacturing method of the sound-absorbing material according to the present invention uses scrap leather, thereby realizing resource circulation and preventing soil pollution and environmental pollution, and since it is manufactured using only environmentally friendly materials (scrap leather including cowhide), the manufacturing method is simple and reduces costs, and it has excellent heat dissipation, vibration dissipation, sound absorption and sound insulation properties, so it can be installed in various places that require sound-absorbing equipment, such as schools, apartments and music rooms. Next, Production Examples, Examples, and Comparative Examples will be described in detail. <Production example> [Production Example 1] Shell powder 1 kg of oyster shells were prepared and washed with fresh water, and then dried under natural light for 36 hours. The washed oyster shells were crushed using a roll mill to a primary particle size of 3 mm. The crushed oyster shells were then fired at a low temperature of 450 ° C for 10 hours, and then fired at a high temperature of 900 ° C for 7 hours. The fired oyster shells were then crushed to a secondary particle size of 2 μm. [Example 2] Cleaning mixture (containing shell powder) To prepare a cleaning mixture, water, shell powder prepared according to Preparation Example 1, and baking soda were weighed and mixed in a volume ratio of 100:0.15:0.05. [Comparative Example 3] Cleaning mixture (without shell powder) To prepare the cleaning mixture, water and baking soda were measured and mixed in a volume ratio of 100:0.05 to prepare the cleaning mixture.

[0015] <Examples and Comparative Examples> [Example 1] Leather scraps were collected and washed with the cleaning mixture prepared according to Example 2 to remove contaminants, then air-dried at room temperature. The leather scraps were cut into 1.5 cm thick pieces and 30 cm long pieces using a cutter. The cut leather scraps were then crushed into 3.5 mm pieces using a grinder. The crushed pieces were dried at 45°C for 66 hours. 500 g of the dried crushed pieces were mixed with 150 g of water-based glue, 55 g of natural rubber latex, and 5 g of water to obtain a mixture. This mixture was inserted into a mold and pressed under a pressure of 80 tons to produce a pad-shaped molded body with a thickness of 2 cm. This molded body was then dried using a dryer with cold air, hot air, and air-dried to produce an experimental sound-absorbing material. [Comparative Example 1] In Comparative Example 1, a sound absorbing material was prepared in the same manner as in Example 1, except that the cleaning mixture prepared according to Comparative Preparation Example 3 was used. Table 1 below shows examples and comparative examples with and without shell powder.

[0016] [Table 1] [Example 2] After collecting the leather scraps, they were cleaned by wiping off any contaminants with a cloth using the powerful multi-purpose cleaner NB-1 and then air-dried at room temperature. The leather scraps were cut into 1.5 cm thick and 30 cm long pieces using a cutter. The cut leather scraps were then ground into 2 mm pieces using a grinder. The resulting ground pieces were dried at 45°C for 66 hours. 500 g of the dried ground material was mixed with 150 g of water-based glue, 55 g of natural rubber latex, and 5 g of water to produce a mixture. The mixture was inserted into a mold and pressed under a pressure of 80 tons to produce a pad-shaped molded body with a thickness of 10 mm. The molded body was then dried using a dryer with cold air, hot air, and air-dried to produce the sound-absorbing material of the present invention.

[0017] [Example 3, Comparative Example 2 and Comparative Example 3] In Example 3, a sound-absorbing material of the present invention was produced in the same manner as in Example 2, except that the size of the pulverized material was 5 mm. Sound-absorbing materials were manufactured in the same manner as in Example 2, except that the size of the pulverized material was 1 mm in Comparative Example 2 and 10 mm in Comparative Example 3. Table 2 below shows examples and comparative examples with different pulverized material sizes, mixture component contents, molding pressures, and molded body thicknesses. [Examples 4 to 8, and Comparative Examples 4 and 12] In Example 4, the size of the crushed material was 3.5 mm and the amount of water-based bond was 100 g, and in Example 5, the size of the crushed material was 3.5 mm and the amount of water-based bond was 200 g. Sound-absorbing materials were manufactured in the same manner as in Example 2, except that In Example 6, the size of the pulverized material was 3.5 mm and the amount of natural rubber latex was 25 g, and in Example 7, the size of the pulverized material was 3.5 mm and the amount of natural rubber latex was 75 g. The sound-absorbing materials of the present invention were produced in the same manner as in Example 2, except that in Example 6, the size of the pulverized material was 3.5 mm and the amount of natural rubber latex was 25 g. In Example 8, a sound-absorbing material of the present invention was produced in the same manner as in Example 2, except that the size of the pulverized material was 3.5 mm and the pad thickness was 2.5 cm. In Comparative Example 4, the size of the crushed material was 3.5 mm and the amount of water-based bond was 50 g, and in Comparative Example 5, the size of the crushed material was 3.5 mm and the amount of water-based bond was 250 g. Except for this, sound-absorbing materials were manufactured in the same manner as in Example 2. In Comparative Example 6, the size of the pulverized material was 3.5 mm and the amount of natural rubber latex was 15 g; in Comparative Example 7, the size of the pulverized material was 3.5 mm and the amount of natural rubber latex was 85 g; and in Comparative Example 8, the size of the pulverized material was 3.5 mm, the amount of water-based bond was 50 g, and the amount of natural rubber latex was 15 g. Sound-absorbing materials were manufactured in the same manner as in Example 2. In Comparative Example 9, the pressure during press molding was 50 tons, and in Comparative Example 10, the pressure was 110 tons, but the sound absorbing material was produced in the same manner as in Example 2. In Comparative Example 11, a pad-shaped compact having a crushed material size of 3.5 mm and a thickness of 1 cm was produced, and in Comparative Example 12, a pad-shaped compact having a crushed material size of 3.5 mm and a thickness of 3.5 cm was produced in the same manner as in Example 2. Table 2 shows examples and comparative examples in which the size of the pulverized material, the content of the mixture components, the compacting pressure and the thickness of the compact were varied. [Table 2]

[0018] [Test example] [Experimental Example 1] Washing Antifungal test of cleaned leather scraps Test method: Test specimens suitable for KS J 3201 were prepared, and antifungal tests were carried out using five types of mold strains after the first pretreatment step (collection → washing → drying) of Example 1 and Comparative Example 1. Table 3 shows the antifungal effects of the examples of the present invention and the comparative examples. [Table 3] Test results: Referring to Table 3, it was confirmed that no fungal strains grew in Example 1. On the other hand, it was found that fungal strains grew in Comparative Example 1, which did not contain shell powder. As a result, it was found that the presence or absence of shell powder in the cleaning mixture affects the antifungal effect. [Test Example 2] Sound absorption Test method: Test pieces of sound-absorbing material were prepared according to the examples and comparative examples of the present invention, and their sound absorption characteristics were measured using a sound level meter. The sound level meter displays transmission loss in decibels based on the amount of energy reduction from the noise source, with a maximum measurement frequency of 6.3 kHz. Each test piece was measured five times, and the measured values ​​were averaged. Table 4 shows the results of the sound absorption effects of the examples and comparative examples of the present invention. Test results: See Table 4. Except for Comparative Example 1, which uses a different method for cleaning recycled leather scraps, and Comparative Example 12, which uses a different pad thickness, all examples achieved a maximum noise reduction of 12 dB compared to all other comparative examples, achieving better soundproofing. Specifically, when Example 1 and Comparative Example 1, which differ only in the method of cleaning the scrap leather for collection, were compared, it was found that there was almost no difference in the sound absorbing effect. Furthermore, when comparing Examples 1 to 3 and Comparative Examples 2 and 3 based on the size of the pulverized material, it was found that the transmission loss at frequencies within the range of the present invention was 30 dB or more, and that the sound absorption effect was excellent. On the other hand, in Comparative Example 2, where the size of the pulverized material was 1 mm, it was found that the transmission loss at high frequencies decreased as the frequency increased, and in Comparative Example 3, where the size of the pulverized material was 5 mm, the transmission loss at low frequencies was small, indicating that there is a difference in the sound absorption effect depending on the size of the pulverized material.

[0019] Furthermore, when Examples 4 to 7 were compared with Comparative Examples 4 to 8 according to the content of the mixture, it was found that the Examples within the content range of each mixture component had a larger transmission loss and better sound absorption effect than the Comparative Examples. In particular, Comparative Example 8, which contained less water-based bond and natural rubber latex than the present invention, had the lowest sound absorption effect, while Comparative Example 6, which contained less natural rubber latex, showed a slightly improved sound absorption effect. In Comparative Examples 9 to 11, due to differences in molding pressure and pad thickness, the transmission loss was smaller than in Examples, and it was found that the sound absorption effect was smaller than in Examples. On the other hand, Comparative Example 12, which has a thicker pad, was almost the same as Examples in terms of sound absorption performance, but the increased cost and weight made installation more difficult. Therefore, it was confirmed that sound absorption performance differs depending on the size of the crushed material, the content of each component in the mixture, molding pressure, pad thickness, etc. [Test Example 3] - Tensile strength Test method: Test pieces of the sound-absorbing materials according to the examples and comparative examples of the present invention were prepared, and the tensile strength was measured according to the test method of ASTM D638-03. Table 4 shows the results of the sound-absorbing effect and tensile strength according to the examples and comparative examples of the present invention. Test Results: Referring to Table 4, it was generally found that the Examples were superior to the Comparative Examples. Specifically, all Examples showed a tensile strength of 30 MPa or more. On the other hand, the Comparative Examples showed a difference of up to 7 MPa compared to the Examples. In particular, Comparative Example 11, which had the thinnest pad thickness, also ranked lowest in tensile strength, followed by Comparative Example 8, which contained a small amount of water-based bond and latex. The results showed that the tensile strength was significantly dependent on the pad thickness. In addition to the pad thickness, the effects of molding pressure and latex content on the tensile strength were also confirmed. [Table 4]

[0020] The above-described embodiments are merely illustrative, and various modifications and equivalent embodiments may be made by those skilled in the art. Therefore, the technical scope of the present invention should be determined solely by the technical ideas of the invention as set forth in the claims.

Claims

1. In a method for manufacturing a sound-absorbing material, A first stage of pre-treatment in which the leather scraps are collected and washed with a multi-purpose cleaner or cleaning mixture, then air-dried to remove contaminants; a second step of cutting and grinding the pretreated leather scraps to produce a grind; a third step of drying the ground product; a fourth step of mixing the dried pulverized material, the water-based adhesive, the latex, and water in a weight ratio of 1:0.2-0.4:0.05-0.15:0.005-0.015 to form a mixture; A fifth step of pressing the mixture into a mold at a pressure of 60 to 100 tons to produce a molded body; and A sixth step of drying the molded body; The cleaning mixture comprises water, shell powder, and baking soda in a volume ratio of 100:0.05-0.25:0.03-0.05; The method for manufacturing sound-absorbing material using scrap leather is characterized in that the molded body is pad-shaped and the thickness of the pad is 2 to 2.5 cm.

2. The second stage comprises:

2. A method for manufacturing a sound-absorbing material using scrap leather according to claim 1, characterized in that the scrap leather is cut into pieces having a thickness of 2 cm or less and a length of 20 to 30 cm using a cutting machine, and then crushed into pieces having a size of 2 to 5 mm using a crusher.

3. The third stage is The method for producing a sound-absorbing material using scrap leather according to claim 1, characterized in that the crushed material is dried at 45 to 50°C for 60 to 72 hours and then allowed to dry naturally.

4. The water-based adhesive comprises a water-based bond; 2. The method for manufacturing a sound-absorbing material using scrap leather according to claim 1, wherein the latex contains natural rubber latex.

5. The sixth step is 2. The method for manufacturing a sound-absorbing material using scrap leather according to claim 1, wherein the molded body is subjected to cold air drying, hot air drying and natural drying in that order.

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