Uncrosslinked rubber composition and rubber molded article using same

Abstract

This uncrosslinked rubber composition comprises: a base rubber containing a silicone rubber as the main component; a compound that has a perfluoro backbone having an ethylenically unsaturated bond; and a first silica. The mass ratio of the contained amount of the compound having the perfluoro backbone to the contained amount of the first silica is less than 5.

Description

Uncrosslinked rubber composition and rubber molded product using the same

[0001] The present invention relates to an uncrosslinked rubber composition and a molded rubber article using the same.

[0002] Silicone rubber compositions are used in many applications due to their excellent electrical insulation properties, heat resistance, cold resistance, etc. For example, Patent Document 1 discloses the use of a rubber composition obtained by mixing a silicone rubber composition with a perfluoropolyether-based fluorine-containing rubber composition in a seal material, etc. Patent Document 2 discloses the use of a silicone rubber composition containing an alkenyl group-containing organopolysiloxane, an alkenyl group-containing perfluoropolyether, and an organohydropolysiloxane in automotive rubber parts, etc.

[0003] Patent No. 5083489 Publication JP-A-11-5902

[0004] The present invention provides an uncrosslinked rubber composition containing a base rubber mainly composed of silicone rubber, a perfluoro skeleton compound having an ethylenically unsaturated bond, and a first silica, wherein the mass ratio of the content of the perfluoro skeleton compound to the content of the first silica is less than 5.

[0005] The present invention is a molded rubber article formed by molding the uncrosslinked rubber composition of the present invention into a predetermined shape and crosslinking it.

[0006] The embodiments will be described in detail below.

[0007] The uncrosslinked rubber composition according to the embodiment contains a base rubber A containing a silicone rubber as a main component, a compound B having a perfluoro skeleton with an ethylenically unsaturated bond, and a first silica C. The mass ratio of the content of the compound B having a perfluoro skeleton to the content of the first silica C in the uncrosslinked rubber composition is less than 5.

[0008] According to the uncrosslinked rubber composition according to this embodiment, a rubber molded article having excellent plasma resistance can be obtained.

[0009] Here, the "first silica" in the present application refers to silica that is blended with the base rubber A together with the perfluoro-skeleton compound B to form the uncrosslinked rubber composition. The "second silica" described below refers to silica that is blended in advance with the silicone rubber to form the rubber compound X.

[0010] The base rubber A is mainly composed of silicone rubber. Therefore, the content of silicone rubber in the base rubber A is more than 50% by mass, and from the viewpoint of obtaining a rubber molded product with excellent plasma resistance, it is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass. In addition to silicone rubber, the base rubber A may also contain, for example, fluororubber.

[0011] Examples of silicone rubbers include millable types such as phenylvinylmethylsilicone rubber (PVMQ), vinylmethylsilicone rubber (VMQ), fluorosilicone rubber (FVMQ), dimethylsilicone rubber (MQ), etc. The silicone rubber preferably contains one or more of these, and more preferably contains phenylvinylmethylsilicone rubber (PVMQ) from the viewpoint of obtaining a rubber molded product having excellent plasma resistance and low-temperature flexibility.

[0012] The uncrosslinked rubber composition according to the embodiment may be prepared using a rubber compound X, which is constructed by blending a second silica into the above-described silicone rubber in advance. In the rubber compound X, the second silica is dispersed in the silicone rubber. Examples of the second silica include dry process silica and wet process silica. The content of the second silica in the rubber compound X is, for example, 20% by mass or more and 40% by mass or less. An example of a commercially available material for the rubber compound X is KE-186-U manufactured by Shin-Etsu Chemical Co., Ltd.

[0013] The perfluoro-skeleton compound B is uniformly mixed with the base rubber A. Examples of the perfluoro-skeleton compound B include a compound having a perfluoropolyether structure and a compound having a perfluoroalkylene structure. From the viewpoint of obtaining a rubber molded product having excellent plasma resistance, it is preferable that the perfluoro-skeleton compound B contains a compound having a perfluoropolyether structure.

[0014] Examples of the functional group containing an ethylenically unsaturated bond contained in the perfluoro-skeleton compound B include a vinyl group, an allyl group, a propargyl group, a butenyl group, and an ethynyl group. From the viewpoint of obtaining a rubber molded article having excellent plasma resistance, the functional group containing an ethylenically unsaturated bond is preferably a vinyl group. From the same viewpoint, the perfluoro-skeleton compound B preferably contains two or more functional groups having an ethylenically unsaturated bond.

[0015] From the viewpoint of obtaining a rubber molded article having excellent plasma resistance, the perfluoro-skeleton compound B preferably contains a one-component material, and more preferably contains one having a viscosity at 23°C of 350 Pa·s or more and 450 Pa·s or less.

[0016] An example of a commercially available material of the perfluoro-skeleton compound B is the SIFEL3000 series manufactured by Shin-Etsu Chemical Co., Ltd. From the viewpoint of obtaining a rubber molded product with excellent plasma resistance, the commercially available material of the perfluoro-skeleton compound B preferably includes a one-component material from the SIFEL3000 series, more preferably one having a viscosity at 23°C of 350 Pa s or more and 450 Pa s or less, and even more preferably X-71-369-N.

[0017] When a rubber compound X composed of silicone rubber and second silica is used, the content of the perfluoro-skeleton compound B in the uncrosslinked rubber composition according to the embodiment is, from the viewpoint of obtaining a rubber molded product having excellent plasma resistance, preferably from 3 parts by mass to 40 parts by mass, more preferably from 5 parts by mass to 30 parts by mass, and even more preferably from 10 parts by mass to 25 parts by mass, per 100 parts by mass of rubber compound X.

[0018] The first silica C is dispersed in the uniformly mixed base rubber A and perfluoro-skeleton compound B. Examples of the first silica C include dry process silica and wet process silica. Examples of the dry process silica include fumed silica. Examples of the wet process silica include precipitated silica and gel process silica. From the viewpoint of obtaining a rubber molded product having excellent plasma resistance, the first silica C preferably contains dry process silica, and more preferably contains fumed silica.

[0019] The first silica C may contain hydrophilic silica that has not been surface-treated. From the viewpoint of obtaining a rubber molded product having excellent plasma resistance, the primary particle diameter 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 m ２ / g or more 200m ２ / g or less, 175m ２ / g or more 225m ２ / g or less.

[0020] The first silica C may contain hydrophobic silica surface-treated with a surface treatment agent. Examples of the surface treatment agent include dimethyldichlorosilane, hexamethyldisilazane, octylsilane, silicone oil, etc. From the viewpoint of obtaining a rubber molded product with excellent plasma resistance, it is preferable that the hydrophobic silica contains one that has been surface-treated with dimethyldichlorosilane. From the same viewpoint, the primary particle diameter of the hydrophobic silica is preferably 10 nm or more and 25 nm or less, more preferably 15 nm or more and 20 nm or less. From the same viewpoint, the BET specific surface area of ​​the hydrophobic silica is, for example, 50 m ２ / g or more 150m ２ / g or less, 90m ２ / g or more 130m ２ / g or less.

[0021] When a rubber compound X composed of silicone rubber and the second silica is used, the content of the first silica C in the uncrosslinked rubber composition according to the embodiment 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, per 100 parts by mass of rubber compound X, from the viewpoint of obtaining a rubber molded product having excellent plasma resistance.

[0022] In the uncrosslinked rubber composition according to the embodiment, the mass ratio of the content of the perfluoro-skeleton compound B 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, from the viewpoint of obtaining a rubber molded product having excellent plasma resistance.

[0023] The uncrosslinked rubber composition according to the embodiment may further contain an organic peroxide D as a thermal crosslinking agent. Examples of organic peroxide D include dialkyl peroxides, peroxyketals, and peroxyesters. Examples of dialkyl peroxides include 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, dicumyl peroxide, and 1,3-di(t-butylperoxy)diisopropylbenzene. Examples of peroxyketals include 1,1-di(t-hexylperoxy)cyclohexane, 1,1-di(t-butylperoxy)cyclohexane, and n-butyl-4,4-di(t-butylperoxy)valerate. Examples of peroxyesters include 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-hexylperoxybenzoate, and t-butylperoxybenzoate. The organic peroxide D preferably contains one or more of these, and from the viewpoint of obtaining a rubber molded article having excellent plasma resistance, it preferably contains a dialkyl peroxide, and more preferably contains 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane.

[0024] When a rubber compound X composed of silicone rubber and second silica is used, the content of the organic peroxide D as the thermal crosslinking agent in the uncrosslinked rubber composition according to the embodiment 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, per 100 parts by mass of rubber compound X, from the viewpoint of obtaining a rubber molded product having excellent plasma resistance.

[0025] The uncrosslinked rubber composition according to the embodiment may contain rubber compounding agents such as a plasticizer, a processing aid, and an antioxidant, but preferably does not contain carbon black from the viewpoint of controlling dust generation when exposed to a plasma atmosphere.

[0026] The uncrosslinked rubber composition according to the embodiment can be prepared by kneading a base rubber A containing silicone rubber as a main component, a perfluoro-skeleton compound B, a first silica C, and other rubber compounding ingredients using a known rubber kneading machine such as a Banbury mixer, a kneader, an open roll, etc. At this time, a rubber compound X composed of silicone rubber and a second silica may be used.

[0027] The uncrosslinked rubber composition according to the embodiment can be molded into a predetermined shape and crosslinked to form a molded rubber product of the rubber composition. In this case, the crosslinking of the uncrosslinked rubber composition may be performed only by primary crosslinking, in which the uncrosslinked rubber composition is heated and pressurized, for example, by press molding. Alternatively, secondary crosslinking, in which the primary crosslinked product is heated at a higher temperature for a longer period of time, for example, by using a gear oven, may be combined. Furthermore, radiation crosslinking, in which the secondary crosslinked product is irradiated with radiation, may be combined.

[0028] Examples of rubber molded products include sealing materials such as O-rings, etc. From the viewpoint of obtaining excellent plasma resistance, rubber molded products are suitable as sealing materials for semiconductor manufacturing equipment.

[0029] The hardness Hs of the rubber composition forming the rubber molded product is preferably A50 or more and A90 or less, more preferably A60 or more and A80 or less, and even more preferably A70 or more and A80 or less. This hardness Hs is measured based on JIS K6253-3:2012 using a type A durometer as the instantaneous value when a pressure plate is brought into contact with a test piece.

[0030] The tensile strength Tb of the rubber composition forming the rubber molded product is preferably 7 MPa or more, more preferably 8 MPa or more. The elongation Eb 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. The tensile strength Tb, elongation Eb, and tensile stress S100 at 100% elongation are measured using a dumbbell-shaped No. 3 test piece in accordance with JIS K6251:2017.

[0031] (Uncrosslinked Rubber Composition) The following uncrosslinked rubber compositions were prepared in Examples 1 to 11 and Comparative Examples 1 to 7. The constitutions of each are also shown in Tables 1 and 2.

[0032] Example 1 A rubber compound X (KE-186-U, manufactured by Shin-Etsu Chemical Co., Ltd.) composed of a base rubber A, phenyl vinyl methyl silicone rubber (PVMQ-X), and a second silica was mixed with 100 parts by mass of the rubber compound X, and 5 parts by mass of a perfluoro-skeleton compound B, a compound having a perfluoropolyether structure (X-71-369-N, manufactured by Shin-Etsu Chemical Co., Ltd., one-component material, viscosity (23°C): 410 Pa s), a hydrophilic silica C, AEROSIL 200, manufactured by Nippon AEROSIL Co., Ltd., a surface-untreated dry-process silica, primary particle diameter: 12 nm, BET specific surface area: 200 m ２ An uncrosslinked rubber composition was prepared by blending and kneading 3 parts by mass of 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane (C-8, manufactured by Shin-Etsu Chemical Co., Ltd.) as organic peroxide D, and the resulting mixture was designated as Example 1.

[0033] Example 2 An uncrosslinked rubber composition having the same composition as Example 1 was prepared, except that the amount of hydrophilic silica in the first silica C was 5 parts by mass relative to 100 parts by mass of the rubber compound X, and this was designated Example 2.

[0034] Example 3 An uncrosslinked rubber composition having the same constitution as in Example 2 was prepared, except that the compounding amount of the perfluoropolyether structure compound B having a perfluoro skeleton was 10 parts by mass relative to 100 parts by mass of the rubber compound X, and this was designated as Example 3.

[0035] Example 4 An uncrosslinked rubber composition having the same constitution as in Example 2 was prepared, except that the compounding amount of the perfluoropolyether structure compound B having a perfluoro skeleton was 20 parts by mass relative to 100 parts by mass of the rubber compound X, and this was designated as Example 4.

[0036] <Example 5> An uncrosslinked rubber composition having the same composition as in Example 4 was prepared, except that the amount of hydrophilic silica in the first silica C was 8 parts by mass relative to 100 parts by mass of the rubber compound X, and this was designated as Example 5.

[0037] Example 6 An uncrosslinked rubber composition having the same composition as Example 4 was prepared, except that the amount of hydrophilic silica in the first silica C was 15 parts by mass relative to 100 parts by mass of the rubber compound X, and this was designated as Example 6.

[0038] Example 7 As the first silica C, instead of hydrophilic silica, hydrophobic silica (Aerosil R972 manufactured by Nippon Aerosil Co., Ltd., dry-process silica surface-treated with dimethyldichlorosilane, primary particle diameter: 16 nm, BET specific surface area: 130 m) was used. ２ An uncrosslinked rubber composition having the same constitution as in Example 2 except that 100g of PEG-100 / g was blended was prepared and designated Example 7.

[0039] Example 8 An uncrosslinked rubber composition having the same constitution as in Example 7 was prepared, except that the compounding amount of the perfluoropolyether structure compound B of the perfluoro skeleton compound was 10 parts by mass relative to 100 parts by mass of the rubber compound X, and this was designated as Example 8.

[0040] Example 9 An uncrosslinked rubber composition having the same constitution as in Example 7 was prepared, except that the compounding amount of the perfluoropolyether structure compound B of the perfluoro skeleton compound was 20 parts by mass relative to 100 parts by mass of the rubber compound X, and this was designated as Example 9.

[0041] Example 10 An uncrosslinked rubber composition having the same composition as in Example 2 was prepared, except that rubber compound Y (KE-183-U manufactured by Shin-Etsu Chemical Co., Ltd.) composed of phenyl vinyl methyl silicone rubber (PVMQ-Y) of base rubber A and second silica was used instead of rubber compound X, and this was designated as Example 10.

[0042] Example 11 An uncrosslinked rubber composition having the same composition as in Example 10 was prepared, except that the compounding amount of the perfluoropolyether structure compound B having a perfluoro skeleton was 20 parts by mass relative to 100 parts by mass of rubber compound Y, and this was designated as Example 11.

[0043] Comparative Example 1 An uncrosslinked rubber composition was prepared having the same constitution as in Examples 1 to 9 except that the perfluoro-skeleton compound B and the first silica C were not compounded. This was designated Comparative Example 1.

[0044] Comparative Example 2 An uncrosslinked rubber composition was prepared having the same constitution as Comparative Example 1, except that 5 parts by mass of carbon black (Thermax N990 manufactured by Cancarb) was blended with 100 parts by mass of rubber compound X. This was designated Comparative Example 2.

[0045] <Comparative Example 3> An uncrosslinked rubber composition having the same constitution as Comparative Example 2 was prepared, except that 5 parts by mass of a compound having a perfluoropolyether structure, which is a perfluoro skeleton compound B, was blended with 100 parts by mass of rubber compound X, and this was designated Comparative Example 3.

[0046] <Comparative Example 4> An uncrosslinked rubber composition having the same constitution as Comparative Example 3 was prepared, except that the compounding amount of the perfluoropolyether structure compound B having a perfluoro skeleton was 10 parts by mass per 100 parts by mass of rubber compound X, and this was designated Comparative Example 4.

[0047] <Comparative Example 5> An uncrosslinked rubber composition having the same constitution as Comparative Example 3 was prepared, except that the compounding amount of the perfluoropolyether structure compound B having a perfluoro skeleton was 20 parts by mass relative to 100 parts by mass of rubber compound X, and this was designated Comparative Example 5.

[0048] <Comparative Example 6> An uncrosslinked rubber composition having the same composition as in Example 2 was prepared, except that the amount of hydrophilic silica in the first silica C was 1 part by mass per 100 parts by mass of the rubber compound X, and this was designated as Comparative Example 6.

[0049] Comparative Example 7 An uncrosslinked rubber composition was prepared having the same constitution as in Example 10 except that the compound B having a perfluoro skeleton was not blended. This was designated Comparative Example 7.

[0050]

[0051]

[0052] (Test Methods and Results) Test pieces of the rubber compositions obtained by crosslinking the uncrosslinked rubber compositions were prepared and used to carry out the following tests. The results are shown in Tables 1 and 2.

[0053] <Hardness> Each of the uncrosslinked rubber compositions of Examples 1 to 11 and Comparative Examples 1 to 7 was subjected to primary crosslinking and secondary crosslinking to prepare a 2 mm thick sheet-shaped rubber composition. The primary crosslinking conditions were press molding at 165°C for 5 minutes, and the secondary crosslinking conditions were a gear oven at 200°C for 4 hours (the same applies below). Three sheets of the sheet-shaped rubber composition were stacked to prepare a test piece, and the hardness Hs was measured using a Type A durometer in accordance with JIS K6253-3:2023 as the instantaneous value when a pressure plate was brought into contact with the test piece.

[0054] <Tensile Properties> Each of the uncrosslinked rubber compositions of Examples 1 to 11 and Comparative Examples 1 to 7 was subjected to primary crosslinking and secondary crosslinking to prepare a dumbbell-shaped No. 3 test piece of the rubber composition. The test piece was then used to measure the tensile strength Tb, elongation Eb, and tensile stress S100 at 100% elongation in accordance with JIS K6251:2017.

[0055] <Plasma Resistance> Each of the uncrosslinked rubber compositions of Examples 1 to 11 and Comparative Examples 1 to 7 was subjected to primary crosslinking and secondary crosslinking to prepare a test piece of the rubber composition AS-214 O-ring. The test piece was then set in a plasma exposure device (manufactured by Shinko Seiki Co., Ltd.) and subjected to plasma exposure. ２ Gas and CF ４ The specimens were exposed to plasma generated for 30 minutes using a mixed gas in a 2:1 volume ratio at a frequency of 2.45 GHz, a pressure of 100 Pa, an output of 1500 W, and a total gas flow rate of 510 ml / min, and the presence or absence of dust generation was visually confirmed. The mass reduction rate and mass reduction ratio were calculated based on the following formula, with a mass reduction ratio of less than 1.1 being rated A and a mass reduction ratio of 1.1 or greater being rated B. An AS-214 O-ring made of ternary FKM was used as the standard test piece. This standard test piece was also exposed to plasma under the same conditions as above, and the mass reduction rate was calculated.

[0056] Mass reduction rate (%) = (difference in mass of test piece before and after exposure / mass of test piece before exposure) x 100 Mass reduction ratio = mass reduction rate / mass reduction rate of standard test piece

[0057] The present invention is useful in the technical fields of uncrosslinked rubber compositions and rubber molded articles using the same.

Claims

1. An uncrosslinked rubber composition is prepared using a rubber compound containing a base rubber mainly composed of silicone rubber, a perfluoro-skeleton compound having an ethylenically unsaturated bond, a first silica, and an organic peroxide, the rubber compound being previously blended with a second silica, the content of the perfluoro skeleton compound is 3 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the rubber compound, an uncrosslinked rubber composition in which the mass ratio of the content of the perfluoro skeleton compound to the content of the first silica is less than 5;

2. The uncrosslinked rubber composition according to claim 1, The uncrosslinked rubber composition wherein the base rubber comprises a phenyl vinyl methyl silicone rubber.

3. The uncrosslinked rubber composition according to claim 1, The uncrosslinked rubber composition includes a one-component material in which the compound having a perfluoro skeleton is present.

4. The uncrosslinked rubber composition according to claim 3, The one-component material, which is a compound having a perfluoro skeleton, has a viscosity at 23°C of 350 Pa·s or more and 450 Pa·s or less.

5. The uncrosslinked rubber composition according to claim 1, The uncrosslinked rubber composition, wherein the first silica comprises dry-process silica.

6. The uncrosslinked rubber composition according to claim 1, The uncrosslinked rubber composition has a content of the first silica of 2 parts by mass or more and 25 parts by mass or less per 100 parts by mass of the rubber compound.

7. The uncrosslinked rubber composition according to claim 1, The uncrosslinked rubber composition, wherein the organic peroxide contains a dialkyl peroxide.

8. A rubber molded article formed by molding the uncrosslinked rubber composition according to claim 1 into a predetermined shape and crosslinking it.

9. The rubber molded product according to claim 8, The rubber molded product is a sealing material.

10. The rubber molded product according to claim 9, The rubber molded product, wherein the sealing material is a sealing material for semiconductor manufacturing equipment.