METHOD FOR JOINING SILICONE RUBBER USING PLASMA TREATMENT

Abstract

The present invention relates to a method of joining silicone rubber using plasma treatment, and more specifically, it is characterized in that one surface of the silicone rubber is modified to be hydrophilic by plasma treatment, and the silicone rubber is joined to each other using the surface-modified portion.

Claims

1. A method for surface modification of silicone rubber, comprising: a step of plasma treating one surface of silicone rubber, wherein the plasma treatment is performed at a plasma temperature of less than 300 at 1 atm.

2. The method of claim 1, wherein the silicone rubber is in the form of a sheet, and the thickness of the silicone rubber sheet is 0.1 um to 150 mm.

3. The method of claim 1, wherein the gas used in the plasma treatment is air or carbon dioxide (CO.sup.2).

4. The method of claim 3, wherein when air is used in the plasma treatment, the supply flow rate of the air is 1 L/Wh to 10 L/Wh, and when carbon dioxide (CO.sup.2) is used, the supply flow rate of carbon dioxide (CO.sup.2) is 1 L/Wh to 3 L/Wh.

5. The method of claim 3, wherein when air is used in the plasma treatment, the output of the plasma is 0.05 WATT/mm.sup.2 to 0.8 WATT/mm, and when carbon dioxide (CO.sup.2) is used, the output of the plasma is 0.15 WATT/mm or 0.5 WATT/mm.sup.2.

6. The method of claim 1, wherein the discharge frequency of the plasma is 1 khz to 27.12 Mhz.

7. The method of claim 1, wherein the plasma treatment energy is 0.05 WATT/mm.sup.2 to 0.8 WATT/mm.sup.2.

8. The method of claim 1, wherein the plasma treatment interval is 1 mm to 50 mm.

9. The method of claim 1, wherein the surface energy of the surface-modified silicone rubber against water is 10 mN/m to 60 mN/m higher than the surface energy before surface treatment.

10. A joining method of silicone rubber, comprising: a step of compressing and joining silicone rubber, one surface of which has been surface-modified through the method of claim 1, with another silicone rubber.

11. The method of claim 10, wherein the compression is performed for 1 to 60 seconds at a pressure of 0.1 kg/cm.sup.2 to 10 kg/cm.sup.2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG. 1 is a schematic diagram showing the surface modification of the silicone rubber according to one embodiment of the present invention and an adhesive process thereof.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] Hereinafter, the present invention will be described in more detail. However, the present invention may be implemented in various different forms, the present invention is not limited to the embodiments described herein, and the present invention is only defined by the claims to be described later.

[0033] Additionally, the terms used in the present invention are only used to describe specific embodiments and are not intended to limit the present invention. Singular expressions include a plurality of expressions unless the context clearly dictates otherwise. In the entire specification of the present invention, including a certain element means that other elements may be further included rather than excluding other elements, unless specifically stated to the contrary.

[0034] A first aspect of the present application provides a surface modification method of silicone rubber, comprising a step of plasma treating one surface of silicone rubber, wherein the plasma treatment is performed at atmospheric pressure and room temperature. Or may be performed at a plasma temperature of less than 300 C. at 1 atm.

[0035] Hereinafter, the surface modification method of silicone rubber according to the first aspect of the present application will be described in detail.

[0036] In one embodiment of the present application, the silicone rubber may be in the form of a sheet. That is, as shown in FIG. 1, it may have a certain thickness and length, and the thickness of the silicone rubber sheet may be about 0.1 T to 5 T, and according to one embodiment of the present invention, it may be about 1 T.

[0037] Meanwhile, the length of the silicone rubber sheet is not greatly limited, and may be used by adopting a length appropriate for the field to be applied. Additionally, the material of the silicone rubber is not particularly limited, and commonly used silicone rubber sheets may be used.

[0038] In one embodiment of the present application, the plasma treatment may be performed by blowing a constant reaction gas under the application of voltage using a low-temperature/atmospheric pressure plasma surface treatment device capable of surface treatment at the peripheral temperature of the room temperature.

[0039] In one embodiment of the present application, the surface modification method of silicone rubber may include a step of plasma treating one surface of the silicone rubber. In other words, joining to another silicone rubber may be performed using one surface of the plasma-treated silicone rubber. However, the silicone rubber should not be interpreted as limited to plasma treatment of only one surface, and when silicone rubber must be joined to both surfaces as necessary, it should be understood that the other surface is also plasma treated.

[0040] In one embodiment of the present application, gas used in the plasma treatment may be air or carbon dioxide (CO.sup.2). At this time, the air may mean atmospheric air containing oxygen. Meanwhile, the air or carbon dioxide may be a high-purity gas with a purity of 99% or more, and preferably may have a purity of about 99.9%.

[0041] In one embodiment of the present application, when air is used in the plasma treatment, the supply flow rate of the air may be 1 L/Wh to 10 L/Wh, preferably 3 L/Wh to 5 L/Wh according to one embodiment of the present invention. Meanwhile, when the supply flow of the air is less than 1 L/Wh, the surface modification of the silicone rubber may not be performed smoothly because the content of the air supplied is low, and when it is more than 10 L/Wh, it may be non-economical because it exceeds the content of the air required for surface modification.

[0042] In one embodiment of the present application, when air is used in the plasma treatment, the output of the plasma (applied voltage when generating the plasma) may be 0.05 WATT/mm.sup.2 to 0.8 WATT/mm.sup.2, and the best range may be 0.25 WATT/mm.sup.2 to 0.4 WATT/mm.sup.2.

[0043] Meanwhile, according to one embodiment of the present invention, when air is used for the plasma treatment, the output of the plasma may be 0.25 WATT/mm.sup.2 to 0.4 WATT/mm. When the output of the plasma is less than 0.05 WATT/mm.sup.2, the applied voltage may not be performed smoothly, so that the plasma processing may not be performed smoothly, and when it is over 0.8 WATT/mm.sup.2, it may be non-economical because it has already exceeded the required voltage. On the other hand, as the applied voltage when generating the plasma increases, the discharge density may increase and the development of the active functional group on the surface of the silicone rubber increases, so that the adhesive force may be improved.

[0044] In one embodiment of the present application, when carbon dioxide (CO.sup.2) is used in the plasma treatment, the supply flow rate of carbon dioxide (CO.sup.2) may be 1 L/Wh to 3 L/Wh, and the best range is 2 L/Wh to 3 L/Wh, and according to one embodiment of the present invention, it may be 2 L/Wh to 2.5 L/Wh.

[0045] On the other hand, when the supply flow rate of carbon dioxide (CO.sup.2) is less than 1 L/Wh, the surface modification of silicone rubber may not be performed smoothly because the content of carbon dioxide supplied is small, and when it is more than 3 L/Wh, it may be non-economical because it exceeds the content of carbon dioxide required for surface modification.

[0046] In one embodiment of the present application, when carbon dioxide (CO.sup.2) is used in the plasma treatment, the output of the plasma (applied voltage when generating plasma) may be 0.15 WATT/mm.sup.2 to 0.5 WATT/mm.sup.2, the best range. may be 0.25 WATT/mm or 0.4 WATT/mm.

[0047] Meanwhile, according to one embodiment of the present invention, when carbon dioxide is used in the plasma treatment, the output of the plasma may be 0.25 WATT/mm.sup.2 to 0.4 WATT/mm. When the output of the plasma is less than 0.1 WATT/mm.sup.2, the applied voltage may not be performed smoothly and the plasma treatment may not be performed smoothly. When the output of the plasma is more than 0.5 WATT/mm.sup.2, it may be uneconomical because the required applied voltage has already been exceeded. Meanwhile, as the applied voltage when generating the plasma increases, the degree of discharge extinction increases, and the adhesion may be improved as the development of active functional groups on the surface of the silicone rubber increases.

[0048] In one embodiment of the present application, the discharge frequency of the plasma may be 1 khz to 27.12 Mhz. Specifically, the discharge frequency refers to the frequency of the low-temperature/atmospheric pressure plasma surface treatment device, and RF frequency may be applied. At this time, the discharge frequency of the plasma may be about 30 khz to 60 khz according to an embodiment of the present invention. Meanwhile, the transformer of the plasma surface treatment device may also use RF power.

[0049] In one embodiment of the present application, the plasma treatment energy may be 0.05 WATT/mm.sup.2 to 0.8 WATT/mm. The best range may be 0.25 WATT/mm.sup.2 to 0.4 WATT/mm.sup.2. According to one embodiment of the present invention, it may be about 0.4 WATT/mm.sup.2. Meanwhile, it may be desirable to perform the plasma treatment once within the above speed range. When the plasma treatment energy is less than 0.05 WATT/mm.sup.2, the energy is too low and surface modification may not be performed smoothly, and when it is more than 0.8 WATT/mm.sup.2, it may be inefficient.

[0050] In one embodiment of the present application, the plasma treatment interval may be 1 mm to 50 mm, preferably 1 mm to 20 mm, and according to an embodiment of the present invention, may be about 10 mm. At this time, the plasma treatment interval may mean the interval between one surface of the silicone rubber and the reaction gas that is the plasma source. Meanwhile, when the plasma treatment interval is less than 1 mm or more than 50 mm, the interval between one surface of the silicone rubber and the reaction gas, which is the plasma source, is too narrow or too far, causing the problem that surface modification of the silicone rubber due to plasma is not performed smoothly.

[0051] In one embodiment of the present application, the surface energy of the surface-modified silicone rubber with respect to water may be increased by more than 10 mN/m compared to the surface energy before surface treatment.

[0052] At this time, the surface contact angle may specifically mean the contact angle on one surface of the surface-modified silicone rubber.

[0053] That is, the surface of silicone rubber is originally composed of silicon (Si) and hydrocarbons, so it has hydrophobic properties, or radicals are generated in silicon (Si) or hydrocarbons (CH.sub.2, etc.) when performing plasma treatment on the surface, and the radicals recombine with oxygen groups to introduce polar groups such as hydroxy groups (OH) or carbonyl groups (CO), so it has hydrophilic properties.

[0054] Therefore, one surface of the surface-modified silicone rubber, which has hydrophilic properties, may have a low contact angle with water as described above.

[0055] The second aspect of the present application, provides a method of joining silicone rubber, including a step of compressing and joining silicone rubber, one surface of which has been surface-modified, with another silicone rubber through the method according to the first aspect of the present application.

[0056] Detailed description of parts overlapping with the first aspect of the present application has been omitted, but the content described in the first aspect of the present application may be applied equally even if the description is omitted in the second aspect.

[0057] Hereinafter, the joining method of the silicone rubber according to the second aspect of the present application will be described in detail.

[0058] In one embodiment of the present application, the joining of the silicone rubber may be joining two or more silicone rubbers. In this case, each surface of the silicone rubber to be joined may have been surface-modified through the method according to the first aspect of the present application, or only one of the silicone rubber surfaces may have been surface-modified. That is, FIG. 1 only shows the process of joining two silicone rubbers, but it should be understood that other silicone rubbers may be joined to other surfaces as well, and in this case, it should be understood that at least one of each surface has been surface-modified according to the first aspect of the present application.

[0059] In one embodiment of the present application, the compression may be performed at a pressure of 0.1 kg/cm.sup.2 to 10 kg/cm.sup.2, and preferably may be performed at a pressure of 0.1 kg/cm.sup.2 to 5 kg/cm.sup.2, of the present invention, and according to one embodiment of the present invention, it may be performed at a pressure of about 1 kg/cm.sup.2. Meanwhile, when the compression is performed at a pressure of less than 0.1 kg/cm.sup.2, the joining between the silicone rubbers may not be performed smoothly because the pressure is too small, and when the compression is performed at a pressure of more than 10 kg/cm.sup.2, the problem of deforming the silicone rubber may occur because the pressure is too large.

[0060] In one embodiment of the present application, the compression may be performed for 1 second to 60 seconds, preferably for 1 second to 20 seconds, and more preferably for 1 second to 10 seconds. Meanwhile, according to one embodiment of the present invention, it may be performed for about 5 seconds. When the compression is performed for less than 1 second, the joining between silicone rubber may not be achieved smoothly because the compression time is too short, and when it is performed for more than 60 seconds, it is inefficient because the time for joining has already been exceeded.

[0061] In one embodiment of the present application, the silicone rubber joined through the joining method of the silicone rubber may have a cutting strength of about 300 times or more compared to the cutting strength of the silicone rubber before joining.

[0062] More specifically, the cutting strength of the silicone rubber before joining may be less than about 0.5 kgf/cm.sup.2, but as shown in FIG. 1, when two pieces of silicone rubber are joined, the cutting strength of the joined silicone rubber may be about 30 kgf/cm.sup.2 or more.

[0063] Therefore, due to the excellent physical properties of the silicone rubber joined by the above method, it may be applied in a variety of silicone rubber joining fields, such as joining coating of exterior parts in automobiles, joining of clothing and shoes, manufacturing of electric wires, manufacturing of medical devices, protective film for telephone poles, and manufacturing of consumer goods.

[0064] Hereinafter, embodiments of the present invention will be described in detail so that those skilled with ordinary knowledge in the technical field to which the present invention pertains may easily practice it. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein.

Manufacturing Example 1. Surface Modification of Silicone Rubber Using Air (Output: 500 W)

[0065] A regular silicone sheet with a size of 50 mm50 mm and a thickness of 1 T was prepared.

[0066] Plasma treatment was performed on one surface of the prepared silicon sheet under the following conditions. [0067] Ambient temperature: room temperature [0068] Plasma temperature: less than 60 C. [0069] Used gas:air (clean dry air, CDA) [0070] Gas supply flow rate: 4 L/Wh5.5 L/Wh [0071] Plasma method: Atmospheric pressure plasma [0072] Discharge frequency: 30 khz to 27.12 Mhz [0073] Output: 500 W [0074] Plasma energy: 0.25 WATT/mm.sup.2 [0075] Plasma treatment interval: 10 mm

Manufacturing Example 2. Surface Modification of Silicone Rubber Using Air (Output: 1,000 W)

[0076] Surface modification of silicone rubber was performed in the same manner as in Manufacturing Example 1, except that the output was set to 1,000 W.

Manufacturing Example 3. Surface Modification of Silicone Rubber Using Carbon Dioxide (Output: 550 W)

[0077] Surface modification of silicone rubber was performed in the same manner as in Manufacturing Example 1, except that carbon dioxide (CO.sup.2) was used as the gas, the gas supply flow rate was set to 1 L/Wh to 2 L/Wh, and the output was set to 550 W.

Manufacturing Example 4. Surface Modification of Silicone Rubber Using Carbon Dioxide (Output: 800 W)

[0078] Surface modification of silicone rubber was performed in the same manner as in Manufacturing Example 3, except that the output was set to 800 W.

Embodiment. Joining of Silicone Rubber Sheets

[0079] The surface-modified silicone rubber sheets in Manufacturing Examples 1 to 4 were joined to each other. That is, for example, the silicone rubber sheet surface-modified in Manufacturing Example 1 was joined to the silicone rubber sheet surface-modified in the same method (method of Manufacturing Example 1), and each silicone rubber surface-modified according to Manufacturing Examples 2 to 4 was also joined in the same way.

[0080] At this time, the compression pressure between the silicone rubbers was 1 kg/cm.sup.2, the compression time was 5 seconds, and after compression, it was left in atmospheric pressure conditions for 60 seconds.

Experimental Example 1. Contact Angle Measurement Experiment

[0081] The contact angle with water was measured for each surface of the silicone rubber surface-modified in Manufacturing Examples 1 to 4, and is shown in Table 1 below.

TABLE-US-00001 TABLE 1 Contact angle after plasma treatment Division ( ) (degrees) Manufacturing 94, 93, less than 5 Example 1 86 (not measurable) Manufacturing less than 5 Example 2 (not measurable) Manufacturing less than 5 Example 3 (not measurable) Manufacturing 40 61 29 Example 4

[0082] As shown in Table 1 above, the contact angle of the silicon sheet before plasma treatment was measured at about 90 degrees as a result of three measurements, confirming that it has hydrophobic properties. However, in the case of Manufacturing Examples 1 to 3, the contact angle after plasma treatment was measured to be less than 5 degrees, confirming that the surface was modified with excellent hydrophilic properties, and in the case of Manufacturing Example 4, the contact angle was measured to be less than about 60 degrees as a result of three measurements, confirming that the surface was modified to have same hydrophilic properties.

Experimental Example 2. Cutting Strength Measurement Test

[0083] The cutting strength of the silicone rubber sheet before joining and the cutting strength of the joined silicone rubber sheet according to the above example were measured and shown in Table 2 below.

TABLE-US-00002 TABLE 2 cutting strength of the silicone cutting strength of the joined rubber sheet before joining silicone rubber sheet Division (kgf/cm.sup.2) (kgf/cm.sup.2) Example less than 0.5 30 or more (not measurable)

[0084] As shown in Table 2, the cutting strength of the silicone sheet before joining showed a low strength value of less than 0.5 kgf/cm.sup.2, while the cutting strength of the joined silicone sheet according to the embodiment of the present invention was a high strength of 30 kgf/cm.sup.2 or more. By showing the values, it was confirmed that it had excellent cutting strength. Therefore, it was confirmed that when the silicone rubber sheet surface-modified according to the present invention is joined, it has excellent physical properties and may be usefully used in various industrial fields.

[0085] Above, the present invention has been described in detail along with preferred embodiments with reference to the drawings, but the scope of the technical idea of the present invention is not limited to these drawings and examples. Accordingly, various modifications or equivalent embodiments may exist within the scope of the technical idea of the present invention. Therefore, the scope of rights of the technical idea according to the present invention should be interpreted in accordance with the claims, and technical ideas that are equivalent or within the equivalent scope should be interpreted as falling within the scope of the rights of the present invention.