JP7562465B2 - Rubber products and their manufacturing method - Google Patents

Description

The present invention relates to an uncrosslinked rubber composition, a rubber product produced using the same, and a method for producing the same.

In the field of semiconductor processing equipment, etc., it is known to use sealing materials made of fluororubber (for example, Patent Documents 1 to 5).

Patent No. 4381087 Patent No. 4628814 Patent No. 4778782 Patent No. 6134391 JP 2001-348462 A

In the preparation of an uncrosslinked rubber composition for producing rubber products such as fluororubber seals, when an organic peroxide and a crosslinking aid are added to the fluororubber of the rubber component and kneaded with a roll, the organic peroxide and the crosslinking aid become liquid, and since the compatibility of the organic peroxide and the crosslinking aid with the fluororubber is low, if the addition rate of these is not slowed down, those that are not absorbed by the fluororubber will adhere to the roll surface and function as a lubricant, causing slippage and preventing smooth kneading. In addition, since the fluororubber becomes brittle by absorbing the liquid organic peroxide and crosslinking aid, it becomes difficult to keep the uncrosslinked rubber composition wound around the roll, and the uncrosslinked rubber composition may fall off the roll and kneading may be interrupted. Therefore, in the preparation of an uncrosslinked rubber composition for producing a fluororubber rubber product, there is a problem of poor kneading processability.

The objective of the present invention is to provide an uncrosslinked rubber composition that has excellent kneading processability.

The uncrosslinked rubber composition of the present invention contains a hydrogen-containing fluororubber other than polyvinylidene fluoride as the main rubber component, and also contains an organic peroxide, a crosslinking aid, polyvinylidene fluoride, and a hydrogen site protector which is a compound that bonds to a carbon radical generated by breaking a carbon-hydrogen bond in the rubber component when irradiated with radiation, the content of the organic peroxide is 0.5 parts by mass or more and 2.0 parts by mass or less per 100 parts by mass of the rubber component, the content of the crosslinking aid is 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the rubber component, the polyvinylidene fluoride is in powder form, the content of the polyvinylidene fluoride is 5 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the rubber component, and the content of the hydrogen site protector is 1 part by mass or more and 20 parts by mass or less per 100 parts by mass of the rubber component.

The rubber product of the present invention is formed by crosslinking the rubber component in the uncrosslinked rubber composition of the present invention, and is formed from a rubber composition in which the hydrogen site protectant is bonded to the carbon of the rubber component.

The method for producing a rubber product of the present invention involves heating the uncrosslinked rubber composition of the present invention to a predetermined temperature to crosslink the rubber component with the organic peroxide, and then irradiating the heated product with radiation.

The uncrosslinked rubber composition of the present invention contains polyvinylidene fluoride, which has relatively high compatibility with organic peroxides and crosslinking aids. This allows the polyvinylidene fluoride to absorb the organic peroxides and crosslinking aids and be smoothly kneaded with the rubber components, while the polyvinylidene fluoride suppresses embrittlement and provides reinforcement, resulting in excellent kneading processability.

The following describes the embodiments in detail.

The uncrosslinked rubber composition according to the embodiment contains a hydrogen-containing fluororubber other than polyvinylidene fluoride (hereinafter referred to as "PVDF") as the main rubber component, and also contains an organic peroxide, a crosslinking aid, and PVDF. The uncrosslinked rubber composition according to the embodiment is suitable for use in the manufacture of rubber products, particularly sealing materials such as O-rings used in semiconductor processing equipment that uses plasma, such as semiconductor etching equipment and plasma CVD equipment.

The uncrosslinked rubber composition according to the embodiment contains PVDF, which has a relatively high compatibility with organic peroxides and crosslinking aids. This allows the PVDF to absorb the organic peroxides and crosslinking aids and be smoothly kneaded with the rubber components. At the same time, the PVDF suppresses embrittlement and reinforces the rubber components, resulting in excellent kneading processability.

Here, the rubber component mainly contains hydrogen-containing fluororubber other than PVDF. In this application, "hydrogen-containing fluororubber" refers to a fluororubber containing carbon with hydrogen bonded to the main chain of the polymer. The content of hydrogen-containing fluororubber other than PVDF in the rubber component is more than 50 mass%, and from the viewpoint of obtaining excellent physical properties, is preferably 80 mass% or more, more preferably 90 mass% or more, and even more preferably 100 mass%. In addition to hydrogen-containing fluororubber other than PVDF, the rubber component may contain hydrogen-free fluororubber such as tetrafluoroethylene (TFE) polymer (PTFE) and silicone rubber.

Examples of hydrogen-containing fluororubbers other than PVDF include copolymers of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) (binary FKM), copolymers of vinylidene fluoride (VDF), hexafluoropropylene (HFP), and tetrafluoroethylene (TFE) (ternary FKM), copolymers of tetrafluoroethylene (TFE) and propylene (Pr) (FEP), copolymers of vinylidene fluoride (VDF), propylene (Pr), and tetrafluoroethylene ( Examples of the copolymer include copolymers of ethylene (E) and tetrafluoroethylene (TFE), copolymers of ethylene (E) and tetrafluoroethylene (TFE) (ETFE), copolymers of ethylene (E), tetrafluoroethylene (TFE) and perfluoromethylvinylether (PMVE), copolymers of vinylidene fluoride (VDF), tetrafluoroethylene (TFE) and perfluoromethylvinylether (PMVE), copolymers of vinylidene fluoride (VDF) and perfluoromethylvinylether (PMVE), and the like. As the hydrogen-containing fluororubber other than PVDF, it is preferable to use one or more of these, and from the viewpoint of obtaining excellent physical properties, it is more preferable to use one containing vinylidene fluoride (VDF) as a monomer, and it is even more preferable to use a ternary FKM. As the hydrogen-containing fluororubber other than PVDF, it is preferable to have iodine or bromine in the molecule from the viewpoint of obtaining excellent physical properties.

Organic peroxides are thermal crosslinking agents that crosslink rubber components when heated to a certain temperature. Examples of organic peroxides include 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-dihydroperoxide, di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, α,α-bis(t-butylperoxy)-p-diisopropylbenzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)-hexyne-3, benzoyl peroxide, t-butylperoxybenzene, t-butylperoxymaleic acid, t-butylperoxyisopropylcarbonate, and t-butylperoxybenzoate. It is preferable to use one or more of these organic peroxides, and from the viewpoint of obtaining excellent physical properties, it is more preferable to use 2,5-dimethyl-2,5-di(t-butylperoxy)hexane.

From the viewpoint of obtaining excellent physical properties, the content of the organic peroxide (A) is preferably 0.5 parts by mass or more and 2.5 parts by mass or less, and more preferably 0.5 parts by mass or more and 2.0 parts by mass or less, per 100 parts by mass of the rubber component.

A crosslinking aid is a compound that bonds between the molecules of rubber components when the rubber components are crosslinked by organic peroxides. Examples of crosslinking aids include triallyl cyanurate, trimethallyl isocyanurate, triallyl isocyanurate, triacrylformal, triallyl trimellitate, N,N'-m-phenylene bismaleimide, dipropargyl terephthalate, diallyl phthalate, tetraallyl terephthalate amide, triallyl phosphate, bismaleimide, fluorinated triallyl isocyanurate (1,3,5-tris(2,3,3-trifluoro-2-propenyl)-1,3,5-triazine, etc. -2,4,6-trione), tris(diallylamine)-S-triazine, triallyl phosphite, N,N-diallylacrylamide, 1,6-divinyldodecafluorohexane, hexaallyl phosphoramide, N,N,N',N'-tetraallylphthalamide, N,N,N',N'-tetraallylmalonamide, trivinyl isocyanurate, 2,4,6-trivinylmethyltrisiloxane, tri(5-norbornene-2-methylene) cyanurate, triallyl phosphite, etc. are included. It is preferable to use one or more of these crosslinking aids, and from the viewpoint of obtaining excellent physical properties, it is more preferable to use triallyl isocyanurate.

The content of the crosslinking aid (B) is preferably 1 part by mass or more and 10 parts by mass or less, more preferably 2 parts by mass or more and 5 parts by mass or less, per 100 parts by mass of the rubber component, from the viewpoint of obtaining excellent physical properties. The content of the crosslinking aid (B) is preferably greater than the content of the organic peroxide (A), from the viewpoint of obtaining excellent physical properties. The ratio (B/A) of the content of the crosslinking aid (B) to the content of the organic peroxide (A) is preferably 1.0 or more and 4.0 or less, more preferably 2.0 or more and 3.0 or less, from the viewpoint of reacting the crosslinking aid without excess or deficiency and obtaining excellent physical properties.

PVDF may be contained so as to constitute a part of the rubber component, but from the viewpoint of improving the absorbency of organic peroxides and processing aids to obtain excellent kneading processability, and improving the tear strength of rubber products using the uncrosslinked rubber composition according to the embodiment to obtain excellent crush resistance, it is preferable that PVDF is in powder form and dispersed in the rubber component.

For example, in a fluororubber sealant used in semiconductor processing equipment, when the rubber component deteriorates due to use in a plasma atmosphere, the powder-like material with high plasma resistance that was dispersed there remains, and the particles are released and contaminate the inside of the equipment. However, since PVDF has plasma resistance equivalent to that of hydrogen-containing fluororubber other than PVDF in the rubber component, even if powdered PVDF is dispersed in the rubber component, the generation of such particles can be suppressed. The average particle size of the powdered PVDF is preferably 1 μm or more and 100 μm or less from the viewpoint of obtaining excellent crush resistance of the rubber product.

The PVDF content (C) is 3 parts by mass or more and 9.8 parts by mass or less, preferably 5 parts by mass or more and 9.7 parts by mass or less, per 100 parts by mass of the rubber component, from the viewpoint of obtaining excellent kneading processability and suppressing sink marks and obtaining excellent physical properties in a rubber product using the uncrosslinked rubber composition according to the embodiment. From the viewpoint of obtaining excellent kneading processability, the PVDF content (C) is preferably equal to or more than the sum of the organic peroxide content (A) and the crosslinking auxiliary content (B). The ratio (C/(A+B)) of the PVDF content (C) to the sum of the organic peroxide content (A) and the crosslinking auxiliary content (B) is preferably 0.5 to 6, more preferably 0.9 to 2.

The uncrosslinked rubber composition according to the embodiment may further contain a hydrogen site protecting agent. The hydrogen site protecting agent is a compound that bonds to a carbon radical generated when the carbon-hydrogen bond of the rubber component is broken when the rubber product is irradiated with radiation during production.

The hydrogen site protector preferably contains a perfluoro-skeleton compound having an alkenyl group in the molecule that bonds to the carbon radical of the rubber component, and/or a siloxane-skeleton compound having an alkenyl group in the molecule that bonds to the carbon radical of the rubber component. Examples of the alkenyl group include vinyl, allyl, butenyl, pentenyl, hexenyl, and heptenyl groups. Of these, the vinyl group is preferred as the alkenyl group.

Examples of perfluoro skeleton compounds having an alkenyl group in the molecule include compounds having a perfluoropolyether structure and compounds having a perfluoroalkylene structure. Examples of siloxane skeleton compounds having an alkenyl group in the molecule include polymers of methylvinylsiloxane, polymers of dimethylsiloxane, copolymers of dimethylsiloxane and methylvinylsiloxane, copolymers of dimethylsiloxane, methylvinylsiloxane and methylphenylsiloxane, etc. Other examples include organopolysiloxanes containing alkenyl groups in the molecule, which are liquid silicone rubbers produced by addition polymerization. It is preferable to use one or more of these as the hydrogen site protection agent.

From the viewpoint of improving plasma resistance, the content of the hydrogen site protectant is preferably 1 part by mass or more and 20 parts by mass or less, and more preferably 5 parts by mass or more and 15 parts by mass or less, per 100 parts by mass of the rubber component.

Depending on the rubber product to be manufactured, the uncrosslinked rubber composition according to the embodiment may contain reinforcing materials such as carbon black and silica, plasticizers, processing aids, vulcanization accelerators, anti-aging agents, etc. However, when used in the manufacture of rubber products in which particle generation in a plasma atmosphere is a problem, the content of powdery inorganic fillers such as carbon black, silica, metal oxides, etc. is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and most preferably 0 parts by mass, per 100 parts by mass of the hydrogen-containing fluororubber.

The uncrosslinked rubber composition according to the embodiment can be prepared using an open-type rubber kneader such as an open roll, or an enclosed-type rubber kneader such as a kneader. Among these, particularly in an open-type rubber kneader such as an open roll, excellent kneading processability can be obtained.

Next, a method for producing a rubber product using the uncrosslinked rubber composition according to the embodiment will be described.

In the method for manufacturing a rubber product, first, a predetermined amount of the uncrosslinked rubber composition according to the embodiment is filled into the cavity of a preheated mold, and then the mold is closed and maintained in that state for a predetermined molding time at a predetermined molding temperature and a predetermined molding pressure. At this time, the uncrosslinked rubber composition according to the embodiment is molded into the shape of the cavity, and the rubber component is crosslinked by the organic peroxide and loses plasticity. This molding may be press molding or injection molding. The molding temperature is, for example, 150°C or higher and 180°C or lower. The molding pressure is, for example, 0.1 MPa or higher and 25 MPa or lower. The molding time is, for example, 3 minutes or higher and 20 minutes or lower. Then, the mold is opened, the molded product is removed from the inside and cooled to obtain a rubber product. The molded product removed from the mold may be further subjected to a heat treatment at a heating temperature of 150°C or higher and 250°C or lower and for a heating time of 2 hours to 6 hours.

When powdered PVDF is added to the uncrosslinked rubber composition according to the embodiment, excellent crush resistance is exhibited, and from the viewpoint of suppressing cracking in a plasma atmosphere when manufacturing a rubber product to be used in a plasma atmosphere, it is preferable to irradiate the molded product after heating. In this case, the irradiation with radiation causes crosslinking at the interface between the rubber component and the PVDF, which are the starting point of cracking, and they are integrated, thereby inhibiting the growth of the crack.

Examples of radiation include alpha rays, beta rays, gamma rays, electron beams, ions, etc. Of these, it is preferable to use electron beams or gamma rays as the radiation. From the viewpoint of suppressing particle generation, the radiation exposure dose is preferably 10 kGy or more and 200 kGy or less, more preferably 20 kGy or more and 80 kGy or less.

(Mixing of Uncrosslinked Rubber Composition and Preparation of Crosslinked Rubber Sheet)
In each of the following Examples 1 to 6, Comparative Examples, and Reference Examples, an uncrosslinked rubber composition was kneaded and a crosslinked rubber sheet was prepared using the kneaded composition. The composition of each example is also shown in Table 1.

Example 1
Using an 8-inch open roll, ternary FKM (Daiel G912, Daikin Industries, Ltd.) of the rubber component was mixed with 1.5 parts by mass of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (Perhexa 25B, Nippon Oil & Fats Co., Ltd.) of the organic peroxide, 4 parts by mass of triallyl isocyanurate (Taiku, Nippon Kasei Co., Ltd.) of the crosslinking aid, 5 parts by mass of powdered PVDF (Daikin Industries, Ltd., average particle size: 7 μm), and 10 parts by mass of a perfluoro skeleton compound having a vinyl group in the molecule of the hydrogen site protective agent (I) (SIFEL3590-N, Shin-Etsu Chemical Co., Ltd.) to prepare an uncrosslinked rubber composition. The kneading time required to obtain 4 kg of a uniform uncrosslinked rubber composition was 2.0 hours.

Next, this uncrosslinked rubber composition was press molded at a molding temperature of 165°C, a molding pressure of 5 MPa, and a molding time of 15 minutes, and then heat-treated at a heating temperature of 200°C and a heating time of 4 hours to obtain a sheet-shaped rubber composition.

Then, this sheet-like rubber composition was irradiated with gamma rays at a dose of 30 kGy to obtain a crosslinked rubber sheet.

Example 2
The same operation as in Example 1 was carried out, except that the irradiation with gamma rays was not carried out and the sheet-shaped rubber composition obtained by heat treatment was made into a crosslinked rubber sheet. The kneading time required to obtain 4 kg of a uniform uncrosslinked rubber composition was 2.0 hours.

Example 3
The same operation as in Example 1 was carried out, except that the amount of powdered PVDF added was 10 parts by mass per 100 parts by mass of the rubber component. The kneading time required to obtain 4 kg of a uniform uncrosslinked rubber composition was 1.5 hours.

Example 4
The same operation as in Example 1 was carried out, except that the amount of powdered PVDF added was 30 parts by mass per 100 parts by mass of the rubber component. The kneading time required to obtain 4 kg of a uniform uncrosslinked rubber composition was 1.0 hour.

Example 5: Reference Example
The rubber component was a blend rubber containing 90% by mass of ternary FKM and 10% by mass of PVDF (manufactured by Daikin Industries, Ltd.), i.e., PVDF was contained so as to constitute a part of the rubber component, but the same operation as in Example 1 was performed. The kneading time required to obtain 4 kg of a uniform uncrosslinked rubber composition was 2.5 hours.

Example 6
The same operation as in Example 1 was carried out, except that a siloxane skeleton compound having a vinyl group in the molecule of the hydrogen site protecting agent (II) (KE-1830, manufactured by Shin-Etsu Chemical Co., Ltd.) was added instead of the hydrogen site protecting agent (I). The kneading time required to obtain 4 kg of a uniform uncrosslinked rubber composition was 2.0 hours.

Comparative Example
The same procedure as in Example 1 was carried out, except that no powdery PVDF was added. The kneading time required to obtain 4 kg of a uniform uncrosslinked rubber composition was 5.0 hours.

<Reference Example>
The same operation as in Example 1 was carried out, except that powdered PTFE (manufactured by Daikin Industries, Ltd., average particle size: 27 μm) was added instead of powdered PVDF. The kneading time required to obtain 4 kg of a uniform uncrosslinked rubber composition was 2.0 hours.

(Test Method)
<Plasma resistance>
For the crosslinked rubber sheets prepared in each of Examples 1 to 6, Comparative Examples, and Reference Examples, an _O2 plasma irradiation test and a _CF4 plasma irradiation test were performed using a microwave plasma generator with an elongation rate of 10%, and mass loss, the presence or absence of cracks, and the presence or absence of particle generation were examined. In the tests, _O2 and _CF4 were used as reaction gases, and the flow rate ratio of these was 50:1 in the _O2 plasma irradiation test and 1:50 in the _CF4 plasma irradiation test. The reaction pressure was 100 Pa and the plasma irradiation time was 60 minutes.

<Tensile properties>
For each of the crosslinked rubber sheets prepared in Examples 1 to 6, Comparative Examples, and Reference Examples, a tensile test was carried out based on JIS K6251 to measure the 100% modulus ( _M100 : tensile stress at 100% elongation), tensile strength (TB), and elongation at break (EB).

<Compression set>
For each of the crosslinked rubber sheets prepared in Examples 1 to 6, Comparative Example, and Reference Example, compression set was measured in accordance with JIS K6262:2013 at a test time of 72 hours and a test temperature of 200°C.

<40% crushing crack>
The crosslinked rubber sheets prepared in each of Examples 1 to 6, Comparative Example, and Reference Example were subjected to a heat treatment at 150° C. for 24 hours, and then compressed by 40% to visually check for the presence or absence of cracks.

(Test Results)
The test results are shown in Table 1.

According to Table 1, in Examples 1 to 6 in which PVDF was added, the kneading time of the uncrosslinked rubber composition was less than half that of the Comparative Example in which PVDF was not added, and therefore the kneading processability was superior.

Comparing Examples 1 and 2, it is found that Example 1, which was irradiated with gamma rays after hot molding, has better _O2 plasma resistance and crush resistance than Example 2, which was not irradiated with gamma rays. This is presumably because gamma ray irradiation causes crosslinking at the interface between the ternary FKM and PVDF rubber components, which are the starting points for crack generation, and these are integrated, thereby inhibiting the growth of cracks.

Comparing Examples 1, 3, and 4, it is found that as the content of powdered PVDF increases, the _O2 plasma resistance tends to decrease and the compression set tends to increase.

Comparing Examples 3 and 5, it can be seen that Example 3, in which powdered PVDF was added, has better kneading processability and crush resistance due to the shorter kneading time than Example 5, in which PVDF was included to constitute part of the rubber component.

Comparing Examples 1 and 6, it can be seen that the addition of either hydrogen site protection agent (I) or hydrogen site protection agent (II) has no effect on kneading processability, plasma resistance, physical properties, and crushing resistance, and shows excellent performance.

In the reference example in which powdered PTFE was added, it was found that excellent kneading processability was obtained, but plasma resistance and crush resistance were low. This is presumably because PTFE has higher plasma resistance than the rubber component ternary FKM, and therefore when the ternary FKM deteriorates, only the powdered PTFE remains, and even when irradiated with gamma rays, no crosslinking occurs between the rubber component ternary FKM and PTFE that does not contain hydrogen atoms bonded to carbon atoms.

The present invention is useful in the technical fields of uncrosslinked rubber compositions, rubber products manufactured using the same, and methods for manufacturing the same.

Claims (4)

A rubber product formed from a rubber composition in which an uncrosslinked rubber composition contains a hydrogen-containing fluororubber other than polyvinylidene fluoride as a rubber component, an organic peroxide, a crosslinking aid, powdered polyvinylidene fluoride dispersed in the rubber component , and a perfluoro-skeleton compound having an alkenyl group in its molecule, or a siloxane-skeleton compound having an alkenyl group in its molecule , is heated to a predetermined temperature to crosslink the rubber component with the organic peroxide, and then is irradiated with radiation to break carbon-hydrogen bonds in the rubber component to generate carbon radicals to which the alkenyl group of the perfluoro-skeleton compound or the alkenyl group of the siloxane-skeleton compound is bonded,
In the uncrosslinked rubber composition,
a content of the organic peroxide is 0.5 parts by mass or more and 2.5 parts by mass or less based on 100 parts by mass of the rubber component,
the content of the crosslinking aid is 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the rubber component,
an amount of the powdered polyvinylidene fluoride per 100 parts by mass of the rubber component is 5 parts by mass or more and 30 parts by mass or less;
a ratio of the content of the powdered polyvinylidene fluoride to the sum of the content of the organic peroxide and the content of the crosslinking aid is 0.9 or more and 2 or less;
The rubber product has a content of the perfluoro skeleton compound or the siloxane skeleton compound in a range of 1 part by mass to 20 parts by mass per 100 parts by mass of the rubber component. The rubber product according to claim 1,
The powdered polyvinylidene fluoride has an average particle size of 1 μm or more and 100 μm or less. The rubber product according to claim 1 or 2 ,
The rubber product is a sealing material. The method for producing a rubber product according to any one of claims 1 to 3 ,
The uncrosslinked rubber composition is heated to a predetermined temperature to crosslink the rubber component with the organic peroxide, and the heated composition is irradiated with radiation to break carbon-hydrogen bonds in the rubber component to generate carbon radicals to which an alkenyl group of the perfluoro skeleton compound or an alkenyl group of the siloxane skeleton compound is bonded to form the rubber composition .