Uncrosslinked rubber composition and rubber molded article using same

Abstract

The uncrosslinked rubber composition contains a base rubber mainly composed of a silicone rubber, a compound having a perfluoro skeleton having an ethylenically unsaturated bond, and a first silica. The mass ratio of the content of the perfluoro skeleton compound to the content of the first silica is less than 5.

Description

Technical Field

[0001] This invention relates to an uncrosslinked rubber composition and rubber molded articles using the uncrosslinked rubber composition. Background Technology

[0002] Silicone rubber compositions are used in many applications due to their excellent electrical insulation, heat resistance, and cold resistance. For example, Patent Document 1 discloses a rubber composition made by mixing a silicone rubber composition with a perfluoropolyether-based fluorinated rubber composition for use in seals, etc. Patent Document 2 discloses a silicone rubber composition containing an alkenyl-containing organopolysiloxane, an alkenyl-containing perfluoropolyether, and an organohydrogen polysiloxane for use in rubber parts for automobiles, etc.

[0003] Existing technical documents Patent documents Patent Document 1: Japanese Patent No. 5083489 Patent Document 2: Japanese Patent Application Publication No. 11-5902 Summary of the Invention The present invention is an uncrosslinked rubber composition comprising a matrix rubber mainly composed of silicone rubber, a compound having a perfluorinated skeleton with ethylene unsaturated bonds, and a first silica, wherein the mass ratio of the content of the perfluorinated skeleton compound to the content of the first silica is less than 5.

[0004] The present invention is a rubber molded article formed by molding the uncrosslinked rubber composition of the present invention into a specified shape and then crosslinking it. Detailed Implementation

[0005] The implementation method will be described in detail below.

[0006] The uncrosslinked rubber composition involved in the embodiments contains a matrix rubber A, mainly composed of silicone rubber, a compound B having a perfluorinated skeleton with vinyl unsaturated bonds, and a first silica C. Furthermore, the mass ratio of the content of the perfluorinated skeleton compound B to the content of the first silica C in the uncrosslinked rubber composition is less than 5.

[0007] According to this embodiment, the uncrosslinked rubber composition can be used to obtain rubber molded articles with excellent plasma resistance.

[0008] Here, "first silica" in this application refers to silica that is added together with compound B of the perfluorinated backbone to the matrix rubber A to form an uncrosslinked rubber composition. Furthermore, "second silica" as described later refers to silica that is pre-added to silicone rubber to form rubber compound X.

[0009] The base rubber A is mainly composed of silicone rubber. Therefore, the silicone rubber content in the base rubber A is greater than 50% by mass, which is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass, from the viewpoint of obtaining a rubber molded article with excellent plasma resistance. It should be noted that the base rubber A may also contain, for example, fluororubber in addition to silicone rubber.

[0010] Examples of silicone rubbers include phenyl vinyl methyl silicone rubber (PVMQ), vinyl methyl silicone rubber (VMQ), fluorosilicone rubber (FVMQ), dimethyl silicone rubber (MQ), and other compoundable silicone rubbers. The silicone rubber preferably contains one or more of the above-mentioned types, and from the viewpoint of obtaining rubber molded articles with excellent plasma resistance and low-temperature flexibility, it is more preferable to include phenyl vinyl methyl silicone rubber (PVMQ).

[0011] The uncrosslinked rubber composition described in the embodiments can also be prepared using rubber compound X, which is formed by pre-adding a second silica to silicone rubber as described above. In rubber compound X, the second silica is dispersed within the silicone rubber. Examples of the second silica include dry-processed silica and wet-processed silica. The content of the second silica in rubber compound X is, for example, 20% by mass or more and 40% by mass or less. Commercially available materials for rubber compound X include, for example, KE-186-U manufactured by Shin-Etsu Chemical Industry Co., Ltd.

[0012] Compound B, which forms the perfluoropolymer backbone, is uniformly mixed with the matrix rubber A. Examples of compounds B that form the perfluoropolymer backbone include compounds with a perfluoropolyether structure and compounds with a perfluoroalkylene structure. From the viewpoint of obtaining rubber molded articles with excellent plasma resistance, compounds B forming the perfluoropolymer backbone preferably include compounds with a perfluoropolyether structure.

[0013] Compound B, as a perfluorinated skeleton, possesses functional groups containing vinyl unsaturated bonds, such as vinyl, allyl, propargyl, butenyl, and ethynyl. From the viewpoint of obtaining rubber molded articles with excellent plasma resistance, the functional groups containing vinyl unsaturated bonds are preferably vinyl. Similarly, from the same viewpoint, compound B of the perfluorinated skeleton preferably contains two or more functional groups containing vinyl unsaturated bonds.

[0014] From the viewpoint of obtaining rubber molded articles with excellent plasma resistance, the perfluorinated skeleton compound B preferably contains a liquid material, and more preferably contains a substance having a viscosity of 350 Pa·s or more and 450 Pa·s or less at 23°C.

[0015] Commercially available materials for compound B with a perfluorinated skeleton include, for example, the SIFEL3000 series manufactured by Shin-Etsu Chemical Co., Ltd. From the viewpoint of obtaining rubber molded articles with excellent plasma resistance, commercially available materials for compound B with a perfluorinated skeleton preferably include a single-liquid material from the SIFEL3000 series, more preferably a material containing a viscosity of 350 Pa·s or more and 450 Pa·s or less at 23°C, and even more preferably containing X-71-369-N.

[0016] When using a rubber compound X composed of silicone rubber and second silica, from the viewpoint of obtaining a rubber molded article with excellent plasma resistance, the content of the perfluorinated skeleton compound B in the uncrosslinked rubber composition according to the embodiments is preferably 3 parts by mass or more and 40 parts by mass or less, more preferably 5 parts by mass or more and 30 parts by mass or less, and even more preferably 10 parts by mass or more and 25 parts by mass or less, relative to 100 parts by mass of rubber compound X.

[0017] The first silica C is dispersed in a uniformly mixed matrix rubber A and a perfluorinated backbone compound B. Examples of the first silica C include dry-processed silica and wet-processed silica. Examples of dry-processed silica include fumed silica. Examples of wet-processed silica include precipitated silica and gel-processed silica. From the viewpoint of obtaining a rubber molded article with excellent plasma resistance, the first silica C preferably contains dry-processed silica, and more preferably contains fumed silica.

[0018] The first silica C may comprise untreated hydrophilic silica. From the viewpoint of obtaining a rubber molded article with excellent plasma resistance, the primary particle size of the hydrophilic silica is preferably 5 nm or more and 20 nm or less, more preferably 10 nm or more and 15 nm or less. From the same viewpoint, the BET specific surface area of ​​the hydrophilic silica is, for example, 150 m². 2 / g or more and 200m 2 / g or less, 175m 2 / g or more and 225m 2 / g or less.

[0019] The first silica C may comprise hydrophobic silica that has been surface-treated with a surface-treatment agent. Examples of surface-treatment agents include dimethyldichlorosilane, hexamethyldisilazane, octylsilane, and silicone oil. From the viewpoint of obtaining a rubber molded article with excellent plasma resistance, the hydrophobic silica is preferably a substance surface-treated with dimethyldichlorosilane as described above. Similarly, from the viewpoint of the first silica, the primary particle size is preferably 10 nm or more and 25 nm or less, more preferably 15 nm or more and 20 nm or less. Similarly, the BET specific surface area of ​​the hydrophobic silica is, for example, 50 m². 2 / g or more and 150m 2 / g or less, 90m 2 / g or more and 130m 2 / g or less.

[0020] When using a rubber compound X composed of silicone rubber and second silica, from the viewpoint of obtaining a rubber molded article with excellent plasma resistance, the content of first silica C in the uncrosslinked rubber composition according to the embodiments is preferably 2 parts by mass or more and 25 parts by mass or less, more preferably 3 parts by mass or more and 15 parts by mass or less, and even more preferably 4 parts by mass or more and 10 parts by mass or less, relative to 100 parts by mass of rubber compound X.

[0021] From the viewpoint of obtaining a rubber molded article with excellent plasma resistance, the mass ratio of the content of the perfluorinated skeleton compound B in the uncrosslinked rubber composition according to the embodiments to the content of the first silica C is preferably 1.5 or more and 4.5 or less, more preferably 2 or more and 4 or less.

[0022] The uncrosslinked rubber composition involved in the embodiments may further contain organic peroxide D as a thermal crosslinking agent. Examples of organic peroxide D include dialkyl peroxides, peroxide ketals, and peroxide esters. Examples of dialkyl peroxides include 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, dicumyl peroxide, and 1,3-di(tert-butylperoxy)diisopropylbenzene. Examples of peroxide ketals include 1,1-di(tert-hexylperoxy)cyclohexane, 1,1-di(tert-butylperoxy)cyclohexane, and n-butyl-4,4-di(tert-butylperoxy)valerate. Examples of peroxide esters include 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, tert-hexylperoxybenzoate, and tert-butylperoxybenzoate. The organic peroxide D preferably contains one or more of the above-mentioned components. From the viewpoint of obtaining a rubber molded article with excellent plasma resistance, it preferably contains a dialkyl peroxide, and more preferably contains 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

[0023] When using a rubber compound X composed of silicone rubber and second silica, from the viewpoint of obtaining a rubber molded article with excellent plasma resistance, the content of the organic peroxide D of the thermal crosslinking agent in the uncrosslinked rubber composition according to the embodiments is preferably 0.5 parts by mass or more and 5 parts by mass or less, more preferably 1 part by mass or more and 3 parts by mass or less, relative to 100 parts by mass of rubber compound X.

[0024] The uncrosslinked rubber composition involved in the embodiments may contain rubber additives such as plasticizers, processing aids, and anti-aging agents, but from the viewpoint of limiting dust generation when exposed to a plasma atmosphere, it is preferable that it does not contain carbon black.

[0025] The uncrosslinked rubber composition described in the embodiments can be prepared by mixing a matrix rubber A, which is mainly composed of silicone rubber, a compound B with a perfluorinated skeleton, and silica C, along with other rubber additives, using a known rubber mixing mill such as a Banbury mixer, a kneader, or an open roll mill. In this case, a rubber compound X composed of silicone rubber and silica can also be used.

[0026] The uncrosslinked rubber composition described in the embodiments can be molded into a rubber article by shaping it into a predetermined shape and then crosslinking it. In this case, the crosslinking of the uncrosslinked rubber composition can be a single crosslinking process, for example, by heating and pressurizing the uncrosslinked rubber composition through stamping. Alternatively, it can be combined with secondary crosslinking, in which the primary crosslinked material is heated for a longer period at a higher temperature than the primary crosslinking process using a girder oven or similar device. Radiation crosslinking by irradiating the secondary crosslinked material with radiation can also be incorporated.

[0027] Examples of rubber molded products include O-rings and other seals. From the viewpoint of achieving excellent plasma resistance, rubber molded products are preferably seals for semiconductor manufacturing equipment.

[0028] The hardness Hs of the rubber composition forming the rubber molded article is preferably A50 or higher and A90 or lower, more preferably A60 or higher and A80 or lower, and even more preferably A70 or higher and A80 or lower. This hardness Hs is measured based on JIS K6253-3:2012 using a type A hardness tester as the instantaneous value at which the pressure plate comes into contact with the test piece.

[0029] The tensile strength Tb of the rubber composition forming the rubber molded article is preferably 7 MPa or more, more preferably 8 MPa or more. The elongation is preferably 150% or more, more preferably 250% or more. The tensile stress S100 at 100% elongation is preferably 1.5 MPa or more and 4 MPa or less, more preferably 2 MPa or more and 2.5 MPa or less. These tensile strengths Tb, elongation Eb, and tensile stress S100 at 100% elongation are measured using dumbbell-shaped No. 3 test pieces based on JIS K6251:2017.

[0030] Example (Uncrosslinked rubber composition) Uncrosslinked rubber compositions of Examples 1-11 and Comparative Examples 1-7 were prepared. Their respective compositions are also shown in Tables 1 and 2.

[0031] <Example 1> An uncrosslinked rubber composition was prepared by adding, relative to 100 parts by mass of a rubber compound X (KE-186-U, manufactured by Shin-Etsu Chemical Industry Co., Ltd.) composed of a matrix rubber A, namely phenyl vinyl methyl silicone rubber (PVMQ-X), and a second silica, 5 parts by mass of a perfluorinated backbone compound B, namely a perfluorinated polyether structure compound (X-71-369-N, manufactured by Shin-Etsu Chemical Industry Co., Ltd., a liquid material, viscosity (23°C): 410 Pa·s), and a first silica C, namely hydrophilic silica (AEROSIL 200, manufactured by Aerosil Corporation of Japan, untreated dry silica, primary particle size: 12 nm, BET specific surface area: 200 m²). 2 The product was obtained by mixing 3 parts by weight of ( / g) and 2 parts by weight of organic peroxide D, namely 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane (C-8, manufactured by Shin-Etsu Chemical Industry Co., Ltd.), and was used as Example 1.

[0032] <Example 2> An uncrosslinked rubber composition with the same structure as in Example 1 was prepared, except that the amount of first silica C, i.e., hydrophilic silica, added was set to 5 parts by weight relative to 100 parts by weight of rubber compound X, and this was used as Example 2.

[0033] <Example 3> An uncrosslinked rubber composition with the same structure as in Example 2 was prepared, except that the amount of compound B with a perfluorinated skeleton, i.e., a perfluorinated polyether structure, added was set to 10 parts by mass relative to 100 parts by mass of rubber compound X. This composition was then used as Example 3.

[0034] <Example 4> An uncrosslinked rubber composition with the same structure as in Example 2 was prepared, except that the amount of compound B with a perfluoro backbone, i.e., a perfluoropolyether structure, added was set to 20 parts by weight relative to 100 parts by weight of rubber compound X. This composition was then used as Example 4.

[0035] <Example 5> An uncrosslinked rubber composition with the same structure as in Example 4 was prepared, except that the amount of first silica C, i.e., hydrophilic silica, added was set to 8 parts by weight relative to 100 parts by weight of rubber compound X, and this was used as Example 5.

[0036] <Example 6> An uncrosslinked rubber composition with the same structure as in Example 4 was prepared, except that the amount of first silica C, i.e., hydrophilic silica, added was set to 15 parts by weight relative to 100 parts by weight of rubber compound X, and this was used as Example 6.

[0037] <Example 7> In addition to C as the primary silica, hydrophobic silica (AEROSIL R972, manufactured by AEROSIL Corporation of Japan, dry-processed silica with surface treatment using dimethyldichlorosilane, primary particle size: 16 nm, BET specific surface area: 130 m²) was added to replace the hydrophilic silica. 2 Except for / g), an uncrosslinked rubber composition with the same composition as in Example 2 is used as Example 7.

[0038] <Example 8> An uncrosslinked rubber composition with the same structure as in Example 7 was prepared, except that the amount of compound B with a perfluorinated skeleton, i.e., a perfluorinated polyether structure, added was set to 10 parts by mass relative to 100 parts by mass of rubber compound X. This composition was then used as Example 8.

[0039] <Example 9> An uncrosslinked rubber composition with the same structure as in Example 7 was prepared, except that the amount of compound B with a perfluorinated skeleton, i.e., a perfluorinated polyether structure, added was set to 20 parts by weight relative to 100 parts by weight of rubber compound X. This composition was then used as Example 9.

[0040] <Example 10> An uncrosslinked rubber composition with the same structure as in Example 2 was prepared, except that rubber compound Y (KE-183-U, manufactured by Shin-Etsu Chemical Industry Co., Ltd.) composed of matrix rubber A, namely phenyl vinyl methyl silicone rubber (PVMQ-Y), and second silica was used instead of rubber compound X. This composition was used as Example 10.

[0041] <Example 11> An uncrosslinked rubber composition with the same structure as in Example 10 was prepared, except that the amount of compound B with a perfluorinated skeleton, i.e., a perfluorinated polyether structure, added was set to 20 parts by weight relative to 100 parts by weight of rubber compound Y. This composition was then used as Example 11.

[0042] <Comparative Example 1> An uncrosslinked rubber composition with the same structure as in Examples 1-9 was prepared, except that compound B and first silica C were not added, and was used as Comparative Example 1.

[0043] <Comparative Example 2> An uncrosslinked rubber composition with the same composition as Comparative Example 1 was prepared, except that the amount of carbon black (Thermax N990, manufactured by Cancarb) added was set to 5 parts by weight relative to 100 parts by weight of rubber compound X, and this composition was used as Comparative Example 2.

[0044] <Comparative Example 3> An uncrosslinked rubber composition with the same structure as Comparative Example 2 was prepared, except that the amount of compound B with a perfluorinated skeleton, i.e., a perfluorinated polyether structure, added was set to 5 parts by mass relative to 100 parts by mass of rubber compound X. This composition was then used as Comparative Example 3.

[0045] <Comparative Example 4> An uncrosslinked rubber composition with the same structure as Comparative Example 3 was prepared, except that the amount of compound B with a perfluorinated skeleton, i.e., a perfluorinated polyether structure, added was set to 10 parts by mass relative to 100 parts by mass of rubber compound X. This composition was used as Comparative Example 4.

[0046] <Comparative Example 5> An uncrosslinked rubber composition with the same structure as Comparative Example 3 was prepared, except that the amount of compound B with a perfluorinated skeleton, i.e., a perfluorinated polyether structure, added was set to 20 parts by mass relative to 100 parts by mass of rubber compound X. This composition was then used as Comparative Example 5.

[0047] <Comparative Example 6> An uncrosslinked rubber composition with the same structure as in Example 2 was prepared, except that the amount of first silica C, i.e., hydrophilic silica, added was set to 1 part by weight relative to 100 parts by weight of rubber compound X, and this composition was used as Comparative Example 6.

[0048] <Comparative Example 7> An uncrosslinked rubber composition with the same structure as in Example 10, except that compound B without the addition of a perfluorinated backbone, was prepared and used as Comparative Example 7.

[0049] [Table 1]

[0050] [Table 2]

[0051] (Experimental methods and results) Test pieces of rubber compositions were prepared by crosslinking the above-mentioned uncrosslinked rubber composition, and the following tests were conducted using them. The results are shown in Tables 1 and 2.

[0052] <Hardness> The uncrosslinked rubber compositions of Examples 1-11 and Comparative Examples 1-7 were subjected to primary and secondary crosslinking to produce sheet-like rubber compositions with a thickness of 2 mm. It should be noted that the primary crosslinking conditions were 5 minutes at 165°C by stamping, and the secondary crosslinking conditions were 4 hours at 200°C by a Gill oven (the same applies below). Then, three sheets of this rubber composition were overlapped to form a test piece. The hardness Hs was measured using a type A hardness tester according to JIS K6253-3:2023 as the instantaneous value at which the pressure plate came into contact with the test piece.

[0053] <Tension Properties> The uncrosslinked rubber compositions of Examples 1-11 and Comparative Examples 1-7 were subjected to primary and secondary crosslinking to produce dumbbell-shaped No. 3 test pieces of the rubber compositions. Then, using the test pieces, the tensile strength Tb, elongation Eb, and tensile stress S100 at 100% elongation were measured based on JIS K6251:2017.

[0054] Plasma Resistance The uncrosslinked rubber compositions of Examples 1-11 and Comparative Examples 1-7 were subjected to primary and secondary crosslinking to produce test pieces of AS-214 O-rings of the rubber compositions. These test pieces were then placed in a plasma exposure apparatus (manufactured by Shinko Seiki Co., Ltd.) and exposed for 30 minutes to plasma generated under conditions of a 2:1 volume ratio of O2 and CF4 gas at a frequency of 2.45 GHz, a pressure of 100 Pa, an output power of 1500 W, and a total gas flow rate of 510 ml / min. The presence or absence of dust was visually confirmed. The mass reduction rate and mass reduction ratio were calculated based on the following formulas. A mass reduction ratio less than 1.1 was rated A, and a mass reduction ratio greater than or equal to 1.1 was rated B. It should be noted that the AS-214 O-ring manufactured by FKM (a ternary system) was used as a standard test piece. This standard test piece was also subjected to plasma exposure under the same conditions as described above, and the mass reduction rate was calculated.

[0055] Mass reduction rate (%) = (Difference in test piece mass before and after exposure / Mass of test piece before exposure) × 100 Mass reduction ratio = Mass reduction rate / Mass reduction rate of standard test piece -Industry Applicability- This invention is useful in the field of uncrosslinked rubber compositions and rubber molded articles using the uncrosslinked rubber compositions.

Claims

1. An uncrosslinked rubber composition, characterized in that: It contains a matrix rubber mainly composed of silicone rubber, a perfluorinated skeleton with ethylene unsaturated bonds, and silica. The mass ratio of the content of the perfluorinated framework compound to the content of the first silica is less than 5.

2. The uncrosslinked rubber composition according to claim 1, characterized in that: The matrix rubber comprises phenyl vinyl methyl silicone rubber.

3. The uncrosslinked rubber composition according to claim 1 or 2, characterized in that: The perfluorinated framework compound comprises a liquid material.

4. The uncrosslinked rubber composition according to claim 3, characterized in that: The compound of the perfluorinated framework, i.e., the liquid material, has a viscosity of 350 Pa·s or higher and 450 Pa·s or lower at 23°C.

5. The uncrosslinked rubber composition according to any one of claims 1 to 4, characterized in that: The first silicon dioxide comprises dry-processed silicon dioxide.

6. The uncrosslinked rubber composition according to any one of claims 1 to 5, characterized in that: The uncrosslinked rubber composition is an uncrosslinked rubber composition prepared using a rubber compound formed by pre-adding a second silica to the silicone rubber.

7. The uncrosslinked rubber composition according to claim 6, characterized in that: The content of the perfluorinated skeleton compound is 3 parts by mass or more and 40 parts by mass or less relative to 100 parts by mass of the rubber compound.

8. The uncrosslinked rubber composition according to claim 6 or 7, characterized in that: The content of the first silica is 2 parts by mass or more and 25 parts by mass or less relative to 100 parts by mass of the rubber compound.

9. The uncrosslinked rubber composition according to any one of claims 1 to 8, characterized in that: The uncrosslinked rubber composition also contains organic peroxides.

10. The uncrosslinked rubber composition according to claim 9, characterized in that: The organic peroxide comprises dialkyl peroxide.

11. A rubber molded article, characterized in that: The rubber molded article is a rubber molded article obtained by molding the uncrosslinked rubber composition according to any one of claims 1 to 10 into a predetermined shape and then crosslinking it.

12. The rubber molded article according to claim 11, characterized in that: The rubber molded product is a sealing component.

13. The rubber molded article according to claim 12, characterized in that: The seal is a seal used in semiconductor manufacturing equipment.

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