KR20010084070A - Method for bonding sole by plasma surface treatment - Google Patents

Abstract

PURPOSE: A method for adhering a sole by plasma surface treatment is provided, to improve the adhering power between soles and an adhesive by an automatic single process without using an organic solvent. CONSTITUTION: The method comprises the steps of burping the midsole and outsole mechanically and inserting them into a low temperature plasma apparatus; inserting an inert gas into the apparatus under vacuum to wash the midsole and outsole; modifying the both sides of the midsole and the one side of the outsole by plasma treatment; and pasting an aqueous adhesive onto the soles and adhering them together. Preferably the washing process is carried out by inserting 40-200 sccm of Ar at a pressure of 150-600 mTorr, and the midsole is made of ethylene acetic acid vinyl copolymer or polyurethane, and the outsole is made of rubber. The modification of soles is carried out by inserting an inert gas and a reactive gas at a pressure of 150-650 mTorr, in the range of 20-100 kHz and 20-275 V or 13.56 MHz and 60-500 V. Preferably the inert gas is argon gas and the reactive gas is hydrogen, oxygen, nitrogen, ammonia or their mixtures.

Description

Method for bonding sole by plasma surface treatment {Method for bonding sole by plasma surface treatment}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of bonding a surface of a sole to a plasma and bonding the surface of the sole, and more particularly, by injecting inert and reactive gases in a plasma atmosphere using a low temperature plasma apparatus. The present invention relates to a method for bonding environmental and human-friendly soles as a single automated process that can combine the activation and chemical bonding effects to promote adhesion between the sole and the adhesive, and can be universally performed on all kinds of soles and adhesives.

In the 2000s, a high-tech society is expected to lead all industries. With the development of these technologies, inevitably the deterioration of human biological function and immunity, depletion of global resources, environmental pollution, etc. must be solved. Therefore, processes using environmentally friendly and human-friendly new materials will replace existing materials and processes.

The shoe industry is a representative handicraft industry, most of the manufacturing process is carried out by human hands, and because it uses a lot of organic solvents that are toxic to the living body, it is not only harmful to the human body at the time of manual work, but also causes problems with environmental pollution. In addition, the manufacturing process of shoes is complicated, and the operation process is not free and the labor and time are required for production, and the reproducibility is bad due to the lack of automation, so the manufacturing cost is high and it is very difficult to produce products of uniform quality. to be.

As a prior art related to shoes, Korean Patent Registration No. 70232 provides a method for bonding soles and midsoles to sneakers and the like, and the device used in the above bonding method, which provides excellent adhesion between soles and midsoles of shoes, and The adhesion state is good so that no defect rate occurs according to the adhesion state. In addition, Korean Laid-Open Patent Publication No. 95-23346 discloses a method of adhering an upper of a shoe by vacuum pressure. In adhering, a midsole bonding structure using a far-infrared emitting material in which a far infrared ray emitting powder is mixed with the adhesive in a range of 7: 3 to 8: 2 and bonded between the sole and the midsole with the adhesive is disclosed.

However, these patents are only one effort to improve the adhesion between the midsole and the outsole of the shoe, and do not solve the fundamental problem caused by the organic solvent generated in the bonding process. In addition, although the new material can be used to improve the pretreatment process, adhesive type, adhesive application method and surface treatment method according to the material and molding process of the shoe sole or sole, the existing process uses a large amount of organic solvent. Since it is difficult to replace the adhesive, a new type of advanced shoe manufacturing process is required regardless of the material or molding process of the shoe.

Shoe manufacturing consists of sole manufacturing, upper manufacturing and assembly, and the sole manufacturing process is composed of sole manufacturing, midsole manufacturing and bonding. After the sole and the midsole is molded, the finished window of the shoe is generally manufactured through a detailed process of buffing washing, solvent treatment, and bonding, and these detailed processes are shown in FIG. 1. Pretreatment process for adhesion promotion in the detailed process shown in Figure 1 is an important process to determine the quality of the manufactured shoes, even when manufacturing shoes for a new use beyond the concept of existing shoes with environmental and human-friendly new materials in the future Processes will remain a key part of the shoe manufacturing process.

As can be seen in the pretreatment process for shoe adhesion shown in Figure 1, the conventional shoe adhesion process uses an organic solvent harmful to the human body during the cleaning and pretreatment process, the majority of the manufacturing process is carried out by hand and consume a lot of manpower and time It is difficult to replace the existing adhesive pretreatment process even if new materials are used because the efficiency of the process is very low because there is no mutual compatibility due to poor reproducibility and subsequent process of the adhesive pretreatment process depending on the material and molding process of the sole. In addition, the manufacturing process is complicated, and mass production is impossible due to automation, and thus, manufacturing efficiency is remarkably low.

In view of the above problems, the present invention could simplify the intermediate process of adhesion pretreatment between the sole manufacturing process and the adhesion process in a single process by replacing the conventional complex pretreatment of the sole with a surface modification process by plasma. Completed on this basis.

Accordingly, an object of the present invention is to inject the sole by the activated gas ions by the plasma by injecting Ar and inert gas O ₂ , N ₂ , H ₂ , NH ₃ and mixtures thereof using a low temperature plasma apparatus The present invention provides an environmentally friendly and human-friendly method for adhering soles by modifying the surface of the sole.

Another object of the present invention is to provide an economical shoe sole bonding method having a low process cost through mass production, improved manufacturing efficiency, excellent reproducibility, and cost reduction by advanced process simplification and automation.

Another object of the present invention is to combine the material of the sole and the adhesive by combining the adhesion enhancement effect by the sputter etching effect, the adhesion enhancement effect by physical etching, the adhesion activation effect by chemical activation and chemical bonding. As a homogenization and generalization process irrespective of the molding process, it is to provide a shoe sole bonding method that can modify all kinds of sole surface by low temperature plasma device.

Adhesive method of the present invention for achieving the above object is the step of mechanically buffing the sole and the sole of the shoe, and then injecting into the low-temperature plasma apparatus; Cleaning the midsole and the sole of the shoe by injecting a fluorinated gas while maintaining the device in a vacuum; Modifying the surface of the sole by treating both sides of the midsole and one surface of the sole with plasma; And applying a water soluble adhesive to the surface of the sole, and then integrally bonding the midsole and the sole.

1 is a schematic view showing a pretreatment process for bonding the midsole and the sole of a shoe in the prior art.

Figure 2 is a schematic diagram showing a process for bonding the sole and the sole of the shoe in accordance with the present invention.

3 is an infrared spectrometer spectrum of a shoe midsole made using ethylene vinyl acetate copolymer polymer.

4A is an X-ray photoelectron analyzer spectrum of a shoe sole manufactured by a compression molding method using a material of an ethylene vinyl acetate copolymer polymer without plasma surface treatment.

4B is an X-ray photoelectron analyzer spectrum of a shoe sole manufactured by a compression molding method using a material of a plasma-treated ethylene vinyl acetate copolymer polymer according to the present invention.

FIG. 5A is a SEM (scanning electron microscope) microstructure photograph of a shoe sole surface prepared by a compression molding method using a material of an ethylene vinyl acetate copolymer polymer not subjected to plasma surface treatment.

Figure 5b is a SEM (scanning electron microscope) microstructure photograph of the surface of the shoe midsole manufactured by the compression molding method using the material of the plasma surface treated ethylene vinyl acetate copolymer polymer according to the present invention.

Figure 6a is a surface scanning electron micrograph of the shoe midsole without plasma surface treatment.

6B is a surface scanning electron micrograph of a mechanical buffed shoe midsole.

Figure 6c is a surface scanning electron micrograph of the shoe midsole plasma treated in accordance with the present invention.

7a to c are X-ray photoelectron analyzer spectra of shoe soles made by injection molding using a material of ethylene vinyl acetate copolymer polymer.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

Referring to FIG. 2, the present invention may be divided into a shoe midsole and a sole pretreatment process (or a mechanical buffing process), a plasma surface treatment process, and an adhesion process. In other words, in the case of the ethylene vinyl acetate copolymer polymer (EVA) prepared by injection molding as a pretreatment step for plasma surface treatment, the surface of the adherend is dense and hard, and thus, primarily buffing treatment (scraper treatment, sand treatment, and / or After washing with water), the process is charged to a plasma apparatus through a washing process. In the case of EVA manufactured by the compression molding process, only the washing process is carried out, the adherend is charged into the plasma apparatus, and the adherend is then transferred to a low temperature plasma surface treatment apparatus. After charging, the vacuum and cleaning process, the plasma surface treatment process, and the bonding process are continuously performed.

Vacuum and Cleaning Process

The adherend loaded into the plasma apparatus is repeatedly injected with gas about several times by injecting Ar of about 40 to 200 sccm while maintaining a vacuum degree of 150 to 600 mTorr.

Plasma surface treatment process

Power supply within the DC voltage range of 60 to 500 V using the 20 to 275 V range using the MF power supply with a frequency range of 20 to 100 kHz and 13.56 MHz frequency band when using the RF power supply. After turning on, inert gas and reactive gas are injected to maximize ion current density while maintaining a vacuum degree of 150-650 mTorr.

For example, in the case of injection molded EVA substrate, the sputter etching and physical etching processes are performed for 20 to 60 seconds while maintaining the NH ₃ to Ar gas composition ratio (sccm) of 20 to 40:60 to 80, followed by continuous mixing. Plasma surface treatment is performed for 1 to 15 minutes so that the gas composition ratio is maintained at 50 to 90:50 to 10 so that chemical activation and chemical bonding effects of the adherend occur. In addition, in the case of the compression-molded EVA adherend, the sputter etching and physical etching processes were performed for 20 to 60 seconds while maintaining the O ₂ to Ar gas composition ratio (sccm) of 40 to 70:30, followed by continuous 20 to 200 sccm Plasma surface treatment is performed for 30 seconds to 10 minutes using only O ₂ gas to generate chemical activation and chemical bonding effects of the adherend. Then, the gas is washed with Ar gas, and then the adherend of the shoe sole is taken out of the low temperature plasma apparatus to proceed with the bonding process.

Bonding process

After the surface modification of the shoe sole by the plasma surface treatment apparatus as described above, a water-soluble adhesive, for example, a polyurethane-based adhesive, an epoxy-based adhesive or a graft chloroprene-based adhesive is applied to adhere the rubber to the sole of the shoe.

On the other hand, the present invention can improve the adhesion of the sole and the adhesive by modifying the surface of the sole by combining the excellent properties of sputter etching, physical etching, chemical activation and chemical bonds using a low temperature plasma device. The device is a device capable of automation and mass production, and is configured to maximize product functionality, reproducibility, uniformity and economy. The three effects of surface modification obtained by this apparatus are explained in detail as follows.

First, when the surface modification process using a low temperature plasma apparatus has a sputter etching effect to remove the surface impurities present on the sole surface, the surface compound produced by the fillers, foaming agents and release agents used in the shoe sole manufacturing In addition, the surface cleaning effect to remove surface impurities caused by exposure to the atmosphere enhances the adhesion between the sole and the adhesive.

The shoe sole is made of ethylene vinyl acetate copolymer (EVA), polyurethane (PU), etc., and it is suitable for blowing, filling, releasing agent and natural or synthetic rubber during press or injection molding. Add. The FT-IR (Infrared Spectroscopy) spectrum of the ethylene vinyl acetate copolymer polymer, which is a material used most as a midsole, is shown in FIG. 3, and as shown in FIG. 3, it is composed of a copolymer of ethylene and vinyl acetate, Depending on the type and amount of additives as well as the manufacturing method of the shoe changes the characteristics of the shoe midsole. The midsole manufactured by such a molding method exhibits a property of adsorbent compounds or impurities adsorbed from the atmosphere due to deterioration of adhesive strength with the adhesive. The surface impurities must be removed to improve the adhesive strength.

4 is a plasma surface treatment as a result of XPS (X-ray photoelectron analyzer) spectrum analysis before and after plasma treatment on the surface of the shoe midsole manufactured by the compression or injection molding method using the material of the ethylene vinyl acetate copolymer polymer by the plasma apparatus in the prior case of using, as well as oxides such as Si, Al, Mg, Zn formed by the additive addition. However, there are a carbon and oxygen impurity contamination in the atmosphere, using NH ₃ / Ar mixed gas plasma surface treatment, the additive It can be seen that there are almost no surface impurities due to and that surface impurities formed upon exposure to the atmosphere have been removed. As such, sputter etching of the surface by the plasma device produces a surface cleaning effect that removes only impurities present on the surface without changing the bulk properties of the sole, thereby improving the adhesion between the shoe midsole and the adhesive. . This characteristic is a phenomenon occurring early in the surface modification process by the plasma treatment, the higher the ratio of the inert / reactive gas and the ion current density can maximize the surface cleaning effect.

Secondly, when performing surface modification process using low temperature plasma device, it has buffing property to physically etch the sole surface, which not only increases the adhesion area of the sole surface but also shows the effect of anchoring, and it is mechanically effective when applying the adhesive. The interlocking and elastic tightening effect increases the adhesion between the sole and the adhesive. In addition, when using plasma surface modification process compared to general buffing such as rubber or leather, it is uniformly buffed regardless of the shape to proper depth of surface, and chemical bonding between functional groups on sole surface by reactive gas injected at the same time as buffing Because of this, the reinforcing effect on the buffing surface eliminates the need for rebuffing even after a long time. In addition, by cutting the polymer chain present on the surface of the sole by physical etching to convert to a low molecular weight material, by increasing the fluidity of the polymer chain by these to facilitate the mutual diffusion to increase the adhesion.

FIG. 5 is a SEM (scanning electron microscope) microstructure photograph of a shoe midsole surface manufactured by a compression molding method using a material of an ethylene vinyl acetate copolymer polymer before and after plasma surface treatment. It is shown against. As observed in the microstructure photograph of FIG. 5, when the plasma surface treatment process is performed, the sole surface is physically etched to have a buffing effect. FIG. 6 is a scanning electron microscope microstructure photograph of a shoe midsole surface manufactured by an injection molding method using an ethylene vinyl acetate material. Before the plasma surface treatment (FIG. 6A), only the buffing treatment (FIG. 6B), the buffing treatment is performed. It was shown for each of the post-plasma surface treatment (FIG. 6C). When the microstructure photographs of FIG. 5 and FIG. 6 are compared to each other, the surface of the shoe sole manufactured by the injection molding method is dense and hard compared to the surface prepared by the compression molding method. The surface layer may be subjected to mechanical buffing (scraper treatment, sand treatment, water washing treatment) first and then physical etching by plasma surface treatment to maximize the buffing effect. That is, as can be seen in the microstructure photograph of FIG. 6, it can be seen that the combination of mechanical buffing and plasma surface treatment is superior in the buffing effect compared to the mechanical buffing alone.

The buffing characteristic by physical etching is a phenomenon that occurs early in the surface modification process by plasma treatment, and occurs almost simultaneously with the sputter etching phenomenon, and the higher the ionic current density and the mixed gas composition ratio of the inert gas and the reactive gas, the higher the buffing effect. It can be maximized.

Third, in the case of performing the surface modification process using a low temperature plasma apparatus, the polymer surface of the adherend is chemically activated by the activated inert and reactive gas ions to improve the affinity, and the hydroxy (OH) group and the carboxyl group. New functional groups such as (COOH) group, carbonyl (C = O) group, amine (NH) group, and nitrile (CN) group are formed on the surface of the adherend. Strong covalent bonds are generated, surface free energy increases due to the formation of polar groups, and the wettability of the surface of the polymer is improved, and the weak boundary layer (WBL) of the surface is cross-linked with low molecular materials by plasma treatment to strengthen WBL. These effects can then be combined to enhance the adhesion between the sole and the adhesive.

In addition, the plasma surface modification method is sole bonding process independent of sole material, molding manufacturing process, and adhesive material, so that the affinity state of the adherend surface or new functional groups can be generated when the sole and adhesive material and molding process are determined. The adhesion between the sole and the adhesive can be improved by selecting inert and reactive gases suitable for the control of plasma surface treatment process parameters such as frequency band, voltage, treatment time and gas composition ratio.

In addition, it is possible to process the plasma uniformly regardless of shoe type, and it is an environmentally and human-friendly advanced process that can enhance adhesion by injecting only harmless gases without using any organic solvents harmful to human body.

7 is an X-ray photoelectron spectrum of a shoe midsole manufactured using an injection molding method using an ethylene vinyl acetate copolymer polymer material before plasma surface treatment and plasma surface treatment using NH ₃ / Ar mixed gas. The chemical bonding and activation states of the C, N and O components for each case are shown. As observed in FIG. 7A, in the case of carbon, CH and CC chemical bonds dominate irrespective of plasma surface treatment, and the concentration of carbon decreases by performing plasma surface treatment. Many functional groups are created on the surface to chemically activate the surface of the sole to improve affinity. Among the functional groups formed on the surface of the adherend, hydroxyl groups and carboxyl groups form strong covalent bonds by chemical reaction with -NCO functional groups of the polyurethane-based adhesive to enhance adhesion.

In the case of nitrogen, it is shown in FIG. 7B. As can be seen from the X-ray photoelectron spectrometer spectrum, the concentration of nitrogen is increased by performing plasma surface treatment, and the area of the binding energy peak is widened, thereby chemically activating the surface of the sole and affinity. Improve. Among the functional groups produced on the surface of the adherend, amine groups and nitrile groups form strong hydrogen bonds and covalent bonds with the -NCO reactor of the adhesive to promote adhesion.

In the case of Figure 7c shows the X-ray photoelectron spectrum of the oxygen, before the plasma surface treatment shows the COC and C = O chemical bond form of the metal oxides and ethylene vinyl acetate copolymer polymer component by the additive, In the case of plasma surface treatment using NH ₃ / Ar mixed gas, the concentration of surface oxygen is decreased and the amount of metal oxides that decrease adhesion is decreased as compared to before plasma surface treatment, and the functional group of hydroxyl group on the surface of the adherend. Are formed to form a strong chemical bond with the -NCO reactor of the polyurethane-based adhesive to promote adhesion. In the case of Figure 7c to the surface modification of the shoe sole of the ethylene vinyl acetate copolymer polymer prepared by the injection molding method, the chemical state of the surface of the adherend is a carbon / oxygen ratio of about 3: 1 and contains a lot of metal additives When the polyurethane adhesive is used to bond with the shoe sole, it can be seen that the adhesion enhancement effect is very large by plasma treatment using NH ₃ / Ar mixed gas.

In addition, when the chemical state of the shoe midsole of the ethylene vinyl acetate copolymer polymer manufactured by the compression molding method, which is widely used for mass production, is observed by X-ray photoelectron analyzer, the surface of the adherend is carbon compared to the shoe midsole manufactured by the injection molding method. Oxygen concentration ratio is about 5: 1, low oxygen concentration and low metal additives. In order to apply and adhere a polyurethane-based adhesive to the surface of the adherend, plasma surface treatment is performed using oxygen gas, rather than injection of nitrogen and hydrogen gas during plasma treatment, so that the surface of the adherend is described as shown in FIG. 7C. Adhesion can be enhanced by forming and affinity for new functional groups.

Therefore, the surface modification method of the sole by the plasma surface treatment of the present invention is a state-of-the-art adhesion process irrespective of the sole material, the molding manufacturing process and the adhesive material, the adhesion enhancement effect by sputter etching, the adhesion enhancement effect by physical etching, It is a one-step environmental and human-friendly shoe manufacturing process that can maximize the adhesion between the sole and the adhesive by adjusting the inert gas and reactive gases to adjust the adhesion effect by chemical activation and chemical bonding.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to the following examples.

Example 1

Midsole Compression EVA

Compression EVA was used as the sole of the shoe, and rubber was used as the sole. The midsole is washed with air to deposit the adherend into the plasma apparatus. In the adherend loaded into the plasma apparatus, 100 sccm of Ar was injected while maintaining a vacuum degree of 210 mTorr, and gas washing was repeated several times. MF after the power is turned on at the DC voltage of the 22kHz frequency and 80V using a power supply, O ₂ vs. Ar gas composition ratio (sccm) 70: by keeping it at 30 subjected to sputter etching and physical etching process for about 30 seconds, Subsequently, plasma surface treatment was performed for about 5 minutes to continuously generate chemical activation and chemical bonding effects of the adherend using only 80 sccm of O ₂ gas. After surface modification, gas was washed with Ar gas, and the adherend of the shoe sole was taken out of the low temperature plasma apparatus, and the polyurethane-based adhesive was applied to bond the rubber with the sole of the shoe.

Example 2

Midsole is injection EVA

First, buffing treatment (scraper treatment, sand treatment, and water washing treatment) is carried out, followed by washing with air, and charged into a plasma apparatus. In the adherend loaded in the plasma apparatus, 100 sccm of Ar was injected while maintaining a vacuum of 590 mTorr, and gas washing was repeated several times. After turning on the power at 13.56MHz frequency band and DC voltage of 340V by using RF power supply, sputter etching and physical etching process were performed for about 30 seconds by maintaining NH ₃ to Ar gas composition ratio (sccm) of 50: 50 In addition, the plasma surface treatment process was performed for about 4 minutes so that the mixed gas composition ratio was continuously maintained at 80:20 to generate chemical activation and chemical bonding effects of the adherend. The following steps were carried out in the same manner as in Example 1.

Adhesive strengths of the soles and the adhesives according to Examples 1 and 2 are shown in Tables 1 and 2, respectively.

Kinds Untreated shoe sole Buffed shoe sole Plasma Treated Shoe Existing product standard Adhesive Strength (kg / cm) 〈0.1 〈0.1 3.3 to 5.5 depending on measurement area 2.5 to 3.0

Kinds Untreated shoe sole Buffed shoe sole Plasma Treated Shoe Buffing and plasma treated sole Existing product standard Adhesive Strength (kg / cm) 〈0.1 〈0.1 4.5 to 5.5 depending on measurement area 5.5 to 6.5 depending on measurement area 2.5 to 3.0

As can be seen from the results of Table 1 and Table 2, regardless of the molding manufacturing method, the adhesive strength of the shoe sole subjected to the plasma surface treatment was measured to be higher than the standard value of the existing product, and it can be confirmed that the adhesion was improved to the extent that it can be put to practical use. . In addition, the EVA sole manufactured by injection and compression molding method is surface-modified by plasma surface treatment, and then a polyurethane-based adhesive is applied to the sole of the shoe to bond with the rubber, and then these windows are mechanically separated to break the form of the sole. As a result, regardless of the molding manufacturing method, the fracture form of the shoe sole subjected to the plasma surface treatment shows the material fracture, which shows the most ideal fracture mode. Therefore, it can be seen that the surface modification is made by the plasma surface treatment of the shoe sole is improved adhesion between the sole and the adhesive.

Plasma surface treatment technology as described above is a homogenizing and generalizing process that can improve the adhesion between the sole and the adhesive by modifying the surface of all kinds of sole by the low temperature plasma device regardless of the material of the sole and the adhesive and the molding manufacturing process. Manufacturing process. In addition, the conventional shoe manufacturing process uses organic solvents that are harmful to the human body in the cleaning and pretreatment process, whereas the plasma surface treatment process does not use any organic solvents and uses only inert and reactive gases that are harmless to the human environment. And human friendly shoe manufacturing process. In addition, the present invention simplifies the existing complex shoe adhesion pretreatment manufacturing process into a single process of plasma surface modification, and replaces the existing complex manual processes with the surface modification process by automated and mass production, which is much lower than the conventional process. Economical shoe manufacturing process with process cost.

Claims (9)

Mechanically buffing the midsole and the sole of the shoe and then injecting it into the cold plasma apparatus; Cleaning the midsole and the sole of the shoe by injecting a fluorinated gas while maintaining the device in a vacuum; Modifying the surface of the sole by treating both sides of the midsole and one surface of the sole with plasma; And And applying the water-soluble adhesive on the surface of the sole, and then adhering the midsole and the sole integrally. The method of claim 1, wherein the buffing step is a scraper treatment, sand treatment and / or water washing treatment. The method of claim 1, wherein the cleaning step is performed by injecting Ar at 40 to 200 sccm while maintaining a vacuum degree of 150 to 600 mTorr. The method of claim 1, wherein the midsole is made of ethylene vinyl acetate copolymer polymer or polyurethane, and the sole is made of rubber. The method of claim 1, wherein the modification of the midsole and the sole is injected with an inert gas and a reactive gas within the frequency range of 20 to 100kHz and 20 to 275V, or the 13.56MHz frequency range and 60 to 500V DC voltage range. How to bond the shoe sole by plasma surface treatment, characterized in that carried out while maintaining a vacuum degree of 150 ~ 650mTorr. The method of claim 5, wherein the inert gas is Ar, and the reactive gas is H ₂ , N ₂ , O ₂ , NH _3, and a mixture thereof. 6. The method of claim 5, wherein when the midsole is an injection-molded ethylene vinyl acetate copolymer polymer, the NH ₃ to Ar gas composition ratio (sccm) is maintained at 20 to 40: 60 to 80, and the sputter etching and physical etching processes are performed at 20 to 20. After 60 seconds, the plasma surface treatment was performed for 1 to 15 minutes to continuously maintain the mixed gas composition ratio of 50 to 90:50 to 10 so as to generate chemical activation and chemical bonding effects of the adherend. How to attach the sole. The method of claim 5, wherein the midsole is a compression molded ethylene vinyl acetate copolymer polymer, the sputter etching and physical etching process for 20 to 60 seconds by maintaining the O ₂ to Ar gas composition ratio (sccm) of 40 to 70: 30 And then performing plasma surface treatment for 30 seconds to 10 minutes to continuously maintain only O ₂ gas at 20 to 200 sccm to generate chemical activation and chemical bonding effects of the adherend. The method of claim 1, wherein the water-soluble adhesive is a polyurethane adhesive, an epoxy adhesive, or a graft chloroprene adhesive.