JP6134293B2 - Sealing material - Google Patents

Description

  The present invention relates to a sealing material obtained by molding a composition for a sealing material containing fluororubber as a rubber component.

Fluoro rubber has heat resistance, chemical resistance, non-adhesiveness, low friction characteristics, and the like. In particular, fluororubbers mainly composed of perfluoropolymer are widely used in O-rings for semiconductor manufacturing equipment (Patent Documents 1 and 2).
On the other hand, a method for producing a regenerated fluoropolymer characterized by melting and kneading the molded fluoropolymer in a kneader including a reforming treatment region in which a gas containing oxygen and water are present is known. (Patent Document 3).
However, the above-mentioned method for producing a regenerated fluoropolymer requires a specific kneader, and the perfluoro fluororubber cannot be used industrially at low cost.

JP 2000-154369 A JP-A-6-302527 JP 2003-82106 A

The present invention has been made in order to cope with such problems, and is a composition for a sealing material comprising a perfluoro fluororubber as a rubber component, which is impaired in industrial use because it is expensive by a simple method. It aims at providing the sealing material formed by shape | molding .

The encapsulant of the present invention is an encapsulant formed by molding a composition for encapsulant obtained by blending fluororubber, a crosslinking agent and carbon black, and the fluororubber comprises perfluoroolefin and perfluoroolefin. A fluororubber composed of an uncrosslinked perfluoropolymer composed only of a copolymer of a repeating unit derived from a fluoroalkyl vinyl ether and an iodine or bromine-containing vinyl monomer, and a treated perfluoropolymer. ,
The treated perfluoropolymer is a perfluoropolymer obtained by decomposing crosslinking points by heat-treating the residual perfluoropolymer discharged in the molding process of the sealing material composition,
The fluororubber is a fluororubber formed by blending less than 40 parts by mass of the treated perfluoropolymer with respect to 100 parts by mass of the uncrosslinked perfluoropolymer . In particular, the sealing material is an O-ring for a semiconductor manufacturing apparatus.

  In the present invention, the remaining perfluoropolymer discharged in the molding process is heat-treated to form a perfluoropolymer whose crosslinking points are decomposed, so that the unpercrosslinked perfluoropolymer can be recovered without discarding the remaining perfluoropolymer. Since it is kneaded with the coalesce and reused, waste can be reduced and a fluororubber excellent in environmental resistance can be obtained. The sealing material obtained by molding the composition for sealing material containing the fluororubber and the crosslinking agent of the present invention has the same characteristics as the sealing material obtained from the uncrosslinked perfluoropolymer.

The perfluoropolymer that can be used in the present invention contains repeating units each derived from a fluoroolefin and a perfluoroalkyl vinyl ether.
The fluoroolefin is represented by the following formula (I).

ここで、Ｒ₁、Ｒ₂、Ｒ₃またはＲ₄は、フッ素、フッ化アルキル基、フッ化アルコキシル基の中から選ばれ、少なくともフッ素またはフッ化アルキル基の一つを含む。これらのなかでＲ₁、Ｒ₂、Ｒ₃およびＲ₄が全てフッ素であるテトラフルオロエチレンが封止材としての物性を維持するのに好ましい。

Here, R ₁ , R ₂ , R ₃ or R ₄ is selected from fluorine, a fluorinated alkyl group, and a fluorinated alkoxyl group, and includes at least one of fluorine and a fluorinated alkyl group. Among these, tetrafluoroethylene in which R ₁ , R ₂ , R ₃ and R ₄ are all fluorine is preferable for maintaining the physical properties as a sealing material.

ここで、Ｒ₅は、炭素数１〜６のパーフルオロアルキル基、アルキル基、パーフルオロアルキルエーテル基、シアノパーフルオロアルキル基である。
なお、フルオロオレフィンとパーフルオロアルキルビニルエーテルとの重合比は、フルオロオレフィンが５０〜９５モル％、パーフルオロアルキルビニルエーテルが５〜５０モル％であることが好ましい。また、ゴム弾性体であればよい。 Perfluoroalkyl vinyl ether is represented by the following formula (II).

Here, R ₅ is a C 1-6 perfluoroalkyl group, alkyl group, perfluoroalkyl ether group, or cyanoperfluoroalkyl group.
The polymerization ratio between the fluoroolefin and the perfluoroalkyl vinyl ether is preferably 50 to 95 mol% for the fluoroolefin and 5 to 50 mol% for the perfluoroalkyl vinyl ether. Any rubber elastic body may be used.

これらの中で、架橋部分として、分子末端に臭素原子を有する構造である−Ｃ（またはＳｉ）−Ｂｒ、または分子末端にヨウ素原子を有する構造である−Ｃ（またはＳｉ）−Ｉの構造を単独または併用して所定量含み、いわゆる過酸化物架橋ができる共重合体であることが好ましい。また、他のキュアーサイトの導入であってもよい。特に、ビニル基またはアリール基を２個以上有する多官能化合物で架橋できるパーフルオロゴムであることが過酸化物架橋ができるとの理由で好ましい。 Specific combinations of monomer units constituting the perfluoropolymer are exemplified below.

Among these, as a bridging moiety, a structure of —C (or Si) —Br having a bromine atom at the molecular end or —C (or Si) —I having a structure having an iodine atom at the molecular end is used. A copolymer containing a predetermined amount alone or in combination and capable of so-called peroxide crosslinking is preferred. Also, other cure sites may be introduced. In particular, a perfluoro rubber that can be crosslinked with a polyfunctional compound having two or more vinyl groups or aryl groups is preferred because peroxide crosslinking is possible.

Illustrative examples of fluororubbers that can be used in combination with perfluoropolymers include fluoropolymers, tetrafluoroethylene-propylene copolymers, hexafluoropropylene-ethylene copolymers containing 5 to 80 mol% of —CH ₂ CF ₂ — units. polymers, fluoroalkyl group-substituted silicone polymer, graft or block segments containing thermoplastic fluoropolymer, -CF (CF ₃₎ polymers having a repeating unit represented CF ₂ O-in, -CF ₂ CF ₂ CF ₂ A polymer having a repeating unit represented by O—, a fluorine-based polymer having a segment composed of —CF ₂ CF ₂ — and —CH (OR ¹ ) CH ₂ — (R ¹ is an alkyl having 1 to 4 carbon atoms, represents a halogenated alkyl _{group), -. CF 2 CF 2} - and -CH (CH ₃₎ CH ₂ - consisting, -CH ₂ CH ₂ - and -CF ₂ C CF ₃₎ multi-copolymer composed of F- may be exemplified. These fluoropolymers can be used alone or as a mixture with the perfluoropolymer.

The fluororubber of the present invention is preferably 100% by mass of a perfluoropolymer which is a copolymer of perfluoroolefin, perfluoromethyl vinyl ether and iodine or bromine-containing vinyl monomer.
That is, the fluororubber is preferably composed only of a copolymer of perfluoroolefin, perfluoromethyl vinyl ether, and iodine or bromine-containing vinyl monomer.

  The residual perfluoropolymer that can be used in the present invention is a perfluoropolymer that is discharged without forming a product when the fluororubber comprising the perfluoropolymer is molded. In the processing step of molding fluoro rubber into a sealing material, a rubber compounding agent such as a crosslinking agent, a filler, a plasticizer, a reinforcing agent, an anti-aging agent, and a coloring agent is added to the raw uncrosslinked raw perfluoropolymer. A molded product that has been kneaded and cross-linked under predetermined conditions is post-processed to obtain a final product. For example, when cross-linking molding is performed using a mold, semi-crosslinked perfluoropolymer composition waste discharged from the abutting surface of the mold, and burrs generated on the surface of the product are removed by post-processing. There are burrs and the like of the crosslinked perfluoropolymer composition that sometimes occurs. In the present invention, any of the residual perfluoropolymer generated without becoming a product at each processing stage can be used.

A treated perfluoropolymer is obtained by heat-treating the remaining cross-linked or semi-crosslinked perfluoro polymer generated in the molding process to decompose the cross-linking points.
The heat treatment conditions are a temperature and a time exceeding normal crosslinking conditions, and it is preferable that the above-mentioned crosslinked or semi-crosslinked perfluoropolymer is heat-treated at least at a temperature and a time at which a crosslinking point starts to decompose. As heat processing conditions, 290-310 degreeC and 70-100 hours are preferable. By heat-treating under these conditions, the crosslinking points are dissociated even in the crosslinked perfluoropolymer composition. The heat treatment is preferably performed under normal pressure.
When the heat treatment temperature exceeds 310 ° C., thermal decomposition of the perfluoropolymer main chain starts, and when the heat treatment temperature is less than 290 ° C., the crosslinking points cannot be efficiently decomposed. The presence or absence of crosslinking point decomposition can be judged by the fact that the crosslinked perfluoropolymer composition that is elastically deformed loses elasticity and undergoes plastic deformation due to the dissociation of crosslinking points. Specifically, a treated perfluoropolymer is one which can be plastically deformed by pulling both ends of a molded body made of the perfluoropolymer composition after decomposition at the crosslinking point.

  The fluororubber of the present invention is blended with less than 40 parts by mass, preferably 30 parts by mass or less of the treated perfluoropolymer with respect to 100 parts by mass of the uncrosslinked raw perfluoropolymer. When blended in an amount of 40 parts by mass or more, characteristics such as compression set of the sealing material after crosslinking are lowered.

The composition for sealing material of this invention mix | blends the fluororubber which mix | blended less than 40 mass parts of the said processing perfluoropolymer with respect to 100 mass parts of uncrosslinked raw perfluoropolymer, and a crosslinking agent. can get.
The crosslinking agent is preferably an organic peroxide that easily generates a peroxy radical in the presence of heat or a redox system. In addition, organic peroxides such as dicumyl peroxide and benzoyl peroxide can be used as a crosslinking aid, and polyaryl compounds such as triallyl isocyanurate and polyvalent vinyl compounds can also be used as a crosslinking agent. This method is a preferred crosslinking agent particularly when the hardness of the sealing material is required.

  Examples of organic peroxides include 1,1-bis (t-butylperoxy) -3,5,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-dihydroperoxide, di-t-butylperoxide. Oxide, 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, 2,5-dimethyl-2,5-di (benzoylper) Examples thereof include oxy) hexane, t-butylperoxymaleic acid, t-butylperoxyisopropyl carbonate, and the like.

  In the case of a peroxide crosslinking system, it is preferable to use a crosslinking accelerator. Examples of the crosslinking accelerator include triallyl cyanurate, triallyl isocyanurate, triallyl formal, triallyl trimellitate, N, N′-m-phenylenebismaleimide, dipropanegyl terephthalate, diallyl phthalate, tetraallyl terephthalate amide And triallyl phosphate. The blending amount is 0.05 to 10 parts by mass, preferably 1.0 to 5 parts by mass, and 0.1 to 10 parts by mass, preferably 0.1 to 10 parts by mass, based on 100 parts by mass of the fluororubber. 0.5 to 5 parts by mass.

  In the case of crosslinking using a polyvalent aryl compound, the polyvalent aryl compound is a compound containing diaryl, triaryl or tetraaryl group, and the polyvalent vinyl compound is a compound containing divinyl, trivinyl or tetravinyl group, Further, a fluorine-substituted compound in which a hydrogen atom is substituted with fluorine may be used. These polyvalent aryl compounds or polyvalent vinyl compounds can be used alone or in combination. Of these, those that are particularly halogen-substituted to improve heat resistance are preferred. By blending a polyvalent aryl compound or a polyvalent vinyl compound, heat-resistant cross-linking by heat and peroxide or addition reaction of the branched olefin part of the polymer is facilitated. A compounding quantity is 1-5 mass parts with respect to 100 mass parts of fluororubbers, Preferably it is 2-4 mass parts.

The composition for sealing materials of this invention can mix | blend a filler. Examples of the filler include inorganic fillers such as carbon black, silicon oxide, titanium oxide, and alumina, and organic fillers such as polytetrafluoroethylene powder and polyimide powder. The polytetrafluoroethylene powder is a fine powder obtained by pulverizing Teflon under the trade name of DuPont or a fluororesin having a similar structure, and the average particle diameter is preferably 0.2 to 50 μm.
The blending amount of the filler is 100 parts by mass or less, preferably 1 to 50 parts by mass with respect to 100 parts by mass of the fluororubber.

The composition for a sealing material is blended in an amount of 0 to 40 parts by mass, preferably 0 to 30 parts by mass with respect to 100 parts by mass of the fluororubber.
When the filler exceeds 40 parts by mass, kneading with the perfluoropolymer becomes difficult. As the kneading method, for example, roll kneading, kneader kneading and the like can be adopted, and the molding method can be a molding method such as a compression molding method, an injection molding method, an extrusion molding method, or a transfer molding method.

  As the crosslinking conditions at the time of molding, a crosslinking time of 5 to 30 minutes at a crosslinking temperature of 150 to 170 ° C. for primary crosslinking and a crosslinking time of 4 to 48 hours at a crosslinking temperature of 170 to 250 ° C. for secondary crosslinking are suitable. . In particular, from the viewpoint of energy saving, 2 to 5 hours are preferable at a crosslinking temperature of 170 to 200 ° C.

  The composition for a sealing material of the present invention can be applied to an O-ring used in a dry etching apparatus. The dry etching apparatus can be suitably used for a plasma etching apparatus, a reactive ion etching apparatus, a reactive ion beam etching apparatus, a sputter etching apparatus, an ion beam etching apparatus, and the like.

  The sealing material of the present invention is formed by molding the above-mentioned composition for a sealing material, and in particular, seals a gate valve seal and a plasma channel pipe joint that can be used in a plasma etching apparatus, an ion etching apparatus, and the like. It can be suitably used for peripheral seals such as O-rings that stop. In addition, examples of the shape include an O-ring shape, a square ring shape, a different diameter ring shape, a seal packing shape, and a lip seal shape.

Example 1
The remaining perfluoropolymer, which is a semi-crosslinked and crosslinked perfluoropolymer composition generated in the process of producing O-rings, was heat-treated at 300 ° C. for 70 hours to obtain a treated perfluoropolymer. This treated perfluoropolymer is in a solid state at first glance, but when subjected to stress such as pulling by hand, it is plastically deformed and is in a high-viscosity fluid state.
A perfluoropolymer containing a repeating unit derived from a fluoroolefin and perfluoromethyl vinyl ether and containing peroxide perhexa 2.5B and triallyl isocyanurate and capable of crosslinking with a peroxide, manufactured by Daikin Industries, Ltd. Trade name GA-55 (expressed as perfluoropolymer in Table 1) 100 parts by weight, 30 parts by weight of the treated perfluoropolymer and 15 parts by weight of MT carbon powder were weighed and mixed using a rubber roll mill. did. This perfluoropolymer composition was placed in a crosslinking mold and subjected to primary crosslinking at 160 ° C. for 10 minutes and secondary crosslinking at 180 ° C. for 4 hours to obtain an inner diameter of 25.7 mm, an outer diameter of 32.7 mm, A 3.5 mm O-ring (JIS B2401 P-26) was produced. Further, a large test piece (JIS K6262) was prepared for permanent compression strain measurement.

The initial characteristics of the obtained O-rings and the characteristics after thermal degradation at a temperature of 200 ° C. for 70 hours were measured by the following methods.
Rubber hardness was measured at 25 ° C. with an Asker microhardness meter. The initial value and the tensile strength, elongation, and tensile stress at 100% after thermal degradation were measured by the method of JIS B2401. The change in rubber hardness after heat deterioration is (value after heat deterioration−initial value), and the rate of change in tensile strength and the rate of change in elongation are [((value after heat deterioration−initial value) / initial value) × 100]. It is. The specific gravity was measured by the method of JIS K6268. The compression set is [((initial thickness−thickness after test) / (initial thickness−spacer thickness)) × 100]. The measurement results are shown in Table 1.

Comparative Example 1
In Example 1, O-ring P-26 and a sample for measuring permanent compression strain were prepared in the same manner as in Example 1 except that 30 parts by mass of the treated perfluoropolymer and 15 parts by mass of the MT carbon powder were not blended. The results evaluated in the same manner as in Example 1 are shown in Table 1.

Comparative Example 2
In Example 1, O-ring P-26 and a sample for measuring permanent compression strain were prepared in the same manner as in Example 1 except that 30 parts by mass of the treated perfluoropolymer was not blended. The results evaluated in the same manner as in Example 1 are shown in Table 1.

Comparative Example 3
In Example 1, O-ring P-26 and a sample for measuring permanent compression strain were prepared in the same manner as in Example 1 except that 40 parts by mass of the treated perfluoropolymer and 25 parts by mass of the MT carbon powder were blended. The results evaluated in the same manner as in Example 1 are shown in Table 1.

  The fluororubber of the present invention makes it possible to effectively use perfluoropolymers whose industrial use is impaired due to high product prices.

Claims (2)

A sealing material formed by molding a composition for a sealing material comprising a fluororubber, a crosslinking agent and carbon black ,
The fluororubber is an uncrosslinked perfluoropolymer composed only of a copolymer of a repeating unit derived from perfluoroolefin and perfluoroalkyl vinyl ether and an iodine or bromine-containing vinyl monomer, and a treated perfluoropolymer. Is a fluororubber compounded with
The treated perfluoropolymer is a perfluoropolymer obtained by decomposing crosslinking points by heat-treating the residual perfluoropolymer discharged in the molding process of the sealing material composition ,
The sealing material, wherein the fluororubber is a fluororubber formed by blending less than 40 parts by mass of the treated perfluoropolymer with respect to 100 parts by mass of the uncrosslinked perfluoropolymer.   The sealing material according to claim 1, wherein the sealing material is an O-ring for a semiconductor manufacturing apparatus.