JP2003096257A - Fluororubber composition for hard disk drive gasket and vulcanized gasket - Google Patents

Abstract

(57) An object of the present invention is to provide a fluororubber composition for a hard disk drive (HDD) gasket which is inexpensive and generates a small amount of gas, and an HDD gasket using the same. A composition comprising (a) fluororubber, (b) an ethylene-propylene-nonconjugated diene copolymer and (c) an organic peroxide, wherein (a) component, (b) component and ( c) Component is a content ratio of 1 to 300 parts of (b) component and 0.3 to 10 parts of (c) component with respect to 100 parts of (a) component, and (b) anti-aging agent for component The amount of gas generated when a vulcanized product obtained by vulcanizing the composition is heated at 100 ° C. for 10 minutes is 5 μg / cm ² or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluororubber composition for hard disk drive gaskets that produces a small amount of gas and a hard disk drive gasket obtained by vulcanizing the composition.

[0002]

2. Description of the Related Art Fluorine rubber is particularly hard disk drive (hereinafter referred to as HD
Called D. ) Is useful as a gasket and has been put to practical use. However, the HDD gasket obtained from fluororubber has an amount of gas generated from the vulcanizate of 5 μg / cm.
Although excellent as ² or less, the problem was that the price was relatively high.

As a means for solving these problems, a composition in which fluororubber and a rubber other than fluororubber are blended has been proposed.

JP-A-5-1276 discloses a blend of a vinylidene fluoride / 4-fluorinated ethylene / 6-propylene propylene terpolymer and an ethylene-propylene-non-conjugated diene copolymer (hereinafter referred to as EPDM). ). However, the composition obtained by mixing the fluororubber composition and the EPDM rubber composition has E
Since the antioxidant for PDM is mixed, the vulcanized product obtained by vulcanization produces a very large amount of gas.

Japanese Unexamined Patent Publication No. 2000-344987 discloses a composition of fluororubber and acrylic rubber.
There is no description or suggestion of the amount of gas generated from the vulcanizate obtained from the composition of fluororubber and EPDM.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fluororubber composition that provides an HDD gasket that is inexpensive and produces less gas, and an HDD gasket obtained by vulcanizing the same.

[0007]

The present invention is a composition containing (a) fluororubber, (b) EPDM, and (c) organic peroxide, which comprises (a) component, (b) component and ( c) component is 1 to 3 parts of (b) component for 100 parts of (a) component
The content of the vulcanizate is 00 parts and the content of the component (c) is 0.3 to 10 parts, and the vulcanizate obtained by vulcanizing the composition without the antioxidant for the component (b) is 10 at 100 ° C. Provided is a fluororubber composition for an HDD gasket, which has an amount of gas generated of 5 μg / cm ² or less when heated for a minute.

The present invention also provides an HDD gasket obtained by vulcanizing the fluororubber composition.

In the present specification, "part" means "part by mass".

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION As the component (a) in the present invention, a fluororubber produced by copolymerization of two or more kinds of fluoromonomers or copolymerization of fluoromonomers and hydrocarbon comonomers is preferable. In the latter case, the fluorine-based monomer and the hydrocarbon-based comonomer may be used alone or in combination of two or more kinds.

As the fluorine-based monomer, tetrafluoroethylene (hereinafter referred to as TFE), vinylidene fluoride (hereinafter referred to as VdF), ethylene trifluoride chloride,
Vinyl fluoride, hexafluoropropylene (hereinafter HF
It is called P. ), Fluorinated olefinic monomers such as pentafluoropropylene, perfluoro (methyl vinyl ether) (hereinafter referred to as PMVE), TFE-perfluoro (propyl vinyl ether) (hereinafter referred to as PPVE).
Say. ), Perfluoro (3,6-dioxa-5-methyl-1-decene) (hereinafter referred to as PHVE), and the like, and the like. Further, as the hydrocarbon-based comonomer, hydrocarbon-based olefin-based monomers such as ethylene, propylene (hereinafter referred to as P) and butene, ethyl vinyl ether (hereinafter referred to as EVE), and alkyl vinyl ether-based monomers such as butyl vinyl ether, etc. Can be mentioned. Copolymerization between the fluorine-based monomers and between the fluorine-based monomers and the hydrocarbon-based comonomers is carried out at an arbitrary ratio depending on the physical properties required for the vulcanized product.

Specific examples of the component (a) include TFE-P copolymer, TFE-P-VdF copolymer and VdF-HFP.
Copolymer, VdF-HFP-TFE copolymer, VdF-
TFE-EVE copolymer, TFE-P-VdF-EVE
Copolymer, VdF-PHVE Copolymer, VdF-TFE
-PHVE copolymer, ethylene-PHVE copolymer, T
FE-PMVE copolymer, TFE-PPVE-VdF copolymer, etc. are mentioned. These may be used alone or in combination of two or more.

The component (a) is preferably a TFE-P copolymer, a TFE-P-VdF copolymer, a VdF-HFP copolymer or a VdF-HFP-TFE copolymer,
A TFE-P copolymer or a TFE-P-VdF copolymer is more preferable.

In order to accelerate the vulcanization of the fluororubber composition of the present invention, it is also preferable to use a fluororubber having a small amount of bromine atom, iodine atom or double bond in the molecule as the component (a). Such a fluororubber may be added with a chain transfer agent or a monomer having a bromine atom, an iodine atom or a double bond at the time of polymerizing the above-mentioned fluoromonomer, or may be subjected to a post-treatment such as a heat treatment or an alkali treatment after the copolymerization. Manufactured by doing.

Specific examples of the chain transfer agent include perfluoro (1,4-diiodobutane), perfluoro (1-bromo-4-iodobutane), perfluoro (1,6-diiodohexane) and perfluoro (1 , 8-diiodooctane) and the like.

Specific examples of the monomer include perfluoro (3-iodo-1-propene), perfluoro (4-iodo-1-butene) and perfluoro (4-bromo-1-).
Butene), perfluoro (5-bromo-3-oxa-1)
-Pentene), perfluoro (6-iodo-1-hexene) and the like.

The polymerization method for producing the component (a) is as follows:
Methods such as bulk polymerization, suspension polymerization, emulsion polymerization and solution polymerization can be adopted. In addition, when classified by the type of initiation reaction, radical polymerization method using organic peroxide initiator or azo initiator, polymerization method using redox catalyst, polymerization method using ionizing radiation, polymerization method initiated by heat or light, etc. Is preferred.

The molecular weight of fluororubber is usually 2000-5.
The range of 00000 is preferred.

The component (b) in the present invention is EPDM. As the non-conjugated diene, a non-conjugated diene which usually does not have a fluorine atom is preferable, and ethylidene norbornene (hereinafter referred to as ENB) or dicyclopentadiene (hereinafter referred to as DCPD) is more preferable.

The component (b) has a molecular weight of 2000 to 500.
At 000, liquid to solid EPDM is preferred.

The amount of the component (b) used is 10 times that of the component (a).
It is 1 to 300 parts with respect to 0 parts. When the amount is less than 1 part, the cost improvement is not sufficient, and when the amount is more than 300 parts, the amount of gas generated from the vulcanized product increases. It is more preferably 10 to 100 parts.

In the present invention, the TEF-P copolymer or the TEF-P-VdF copolymer has excellent compatibility with EPDM, and the vulcanizing agent and vulcanization aid are well dispersed, so that kneading and molding are easy. .

The component (c) in the present invention is an organic peroxide. The component (c) acts as a vulcanizing agent for the components (a) and (b).

Specific examples of the organic peroxide include peroxyketal, dialkyl peroxide, diacyl peroxide, peroxy ester, hydroperoxide and the like. Specific examples include benzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-bis (tert.
-Butylperoxy) hexane, 2,5-dimethyl-
2,5-bis (t-butylperoxy) hexyne-3,
α, α'-bis (tert-butylperoxy) -p-
Examples include diisopropylbenzene and 1,1-bis (tert-butylperoxy) -3,3,5-trimethylcyclohexane.

The amount of component (c) used is 10 parts of component (a).
It is 0.3 to 10 parts with respect to 0 parts. If it is less than 0.3 part, the vulcanization will be insufficient. If it is more than 10 parts, the vulcanizate loses its elasticity. More preferably 0.5
~ 3 parts.

The fluororubber composition of the present invention does not contain an antiaging agent for EPDM. It is not preferable to include an antiaging agent for EPDM because the amount of gas generated in the vulcanized product increases. EP
Examples of the anti-aging agent for DM include amine type, quinoline type, hydroquinone derivative, phenol type, phosphite type and the like. As a specific example, 4,4 ′-(α, α
-Dimethylbenzyl) diphenylamine, 2,2,4-
Polymer of trimethyl-1,2-dihydroquinone, 2,5
-Di-tert-butylhydroquinone, 2,6-di-t
ert-butyl-4-methylphenol, 2,2′-methylene-bis (4-methyl-6-tert-butylphenol), 4,4′-thiobis (6-tert-butyl-3-methylphenol), diphenyliso Examples include decyl phosphite, 2-mercaptobenzimidazole and the like.

In the present invention, it is also preferable that the component (a) contains a vulcanization aid, a vulcanization accelerator, an acid acceptor and the like in addition to the components (b) and (c).

Examples of the vulcanization aid include unsaturated polyfunctional compounds, and specific examples thereof include unsaturated bonds in the molecules of triallyl isocyanurate, triallyl cyanurate, trimethylolpropane trimethacrylate, polybutadiene and the like. An organic compound having a plurality of The preferred blending amount of the vulcanization aid is 0.1 to 20 parts, and more preferably 0.5 to 10 parts, relative to 100 parts of the component (a).

As the vulcanization accelerator, organic onium compounds such as organic quaternary ammonium salts and organic quaternary phosphonium salts, nitrogen-containing organic compounds such as amines and imines, and organic phosphorus compounds such as phosphines and phosphites are preferably used. To be

Specific examples of vulcanization accelerators include tetrabutylammonium hydrogen sulfate, tetrabutylammonium bromide, 8-benzyl-1,8-diazabicyclo [5.
4.0] undeca-7-enium chloride, p-toluenesulfonic acid 1,8-diazabicyclo [5.4.0] undec-7-enium, tetrabutylphosphonium chloride, trioctylmethylphosphonium chloride, triphenylbenzylphosphonium Chloride, 1,8-diazabicyclo [5.4.0] undecene-7, pyridine,
Examples thereof include tributylamine, triphenylphosphine, tributylphosphite and the like. The preferred amount of the vulcanization accelerator is 0.05 to 1 with respect to 100 parts of the component (a).
It is 0 part, and more preferably 0.1 to 5 parts.

As the acid acceptor used in combination with the vulcanization accelerator, a divalent metal oxide or hydroxide is used. Specific examples include hydroxides and oxides of magnesium, calcium, lead, zinc and the like. The amount of the acid acceptor to be blended is preferably 1 to 50 parts, more preferably 1 to 30 parts, relative to 100 parts of the component (a).

The fluororubber composition of the present invention contains EPDM
Except the antiaging agent for use, various compounds conventionally used in the production of vulcanized rubber can be further compounded.

Specific examples include fillers such as carbon black, silica, clay, talc and glass fiber, pigments such as titanium oxide and red iron oxide, processing aids such as fatty acids and fatty acid salts, component (a) and component (b). Examples include resins and rubbers other than the components.

The fluororubber composition of the present invention can be easily produced by uniformly mixing the above components in a rubber mixing device such as a roll, a kneader, a Banbury mixer or an extruder.

The fluororubber composition of the present invention is usually vulcanized at the same time as molding, like press vulcanization, but it may be vulcanized after molding.

As the molding method, compression molding, injection molding, extrusion molding, calender molding, dipping by dissolving in a solvent, coating, etc. are adopted.

Various vulcanizing conditions are adopted in consideration of the molding method and the shape of the vulcanized product, but usually 100 to 400.
The range of several seconds to 24 hours at 0 ° C is preferably adopted. Secondary vulcanization is preferably adopted for the purpose of improving mechanical properties and compression set of the vulcanizate and stabilizing other properties.
The secondary vulcanization conditions are 100 to 300 ° C. and 30 minutes to 4
About 8 hours is preferable.

The amount of gas generated when the vulcanized product obtained by vulcanizing the fluororubber composition of the present invention is heated at 100 ° C. for 10 minutes is 5 μg / cm ² or less. The amount of generated gas is measured in detail by the method described later and has a thickness of 0.2 cm and a length of 0.5 c.
It is a value calculated by converting the amount of organic gas generated from a vulcanized product having m and a width of 0.5 cm per unit surface area (cm ² ). Amount of gas generated, as small, preferably as HDD gaskets, more preferably 10 [mu] g / cm ² or less, 0.6 [mu] g / cm ² or less is most preferable.

The present invention provides an HDD gasket obtained by vulcanizing the above fluororubber composition.

The hardness of the HDD gasket obtained by vulcanizing the fluororubber composition of the present invention is preferably 50 to 70. It is more preferably 55 to 65, and most preferably 58 to
63.

The vulcanized product of the present invention is particularly suitable for HDD gaskets because it contains a small amount of organic gas. Further, it is preferably applied to applications such as connectors and dampers in the electronic field.

[0042]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. Examples 1 to 4 are examples, and Examples 5 to 7 are comparative examples. The following methods were used to measure the physical properties of the vulcanizate and the amount of evolved gas.

[Measurement of Physical Properties of Vulcanized Product] Each component was uniformly mixed in a blending amount (unit: part) shown in Table 1 with a two-roll mill to obtain a fluororubber composition. 180% of this fluororubber composition
After press vulcanization at 10 ° C. for 10 minutes, secondary vulcanization was performed at 180 ° C. for 4 hours. Using the obtained sheet of vulcanizate, JIS
Tensile strength (unit: MPa) and elongation at break (unit:%) were measured according to K6251. In addition, JIS K62
The hardness (unit: JISA) was measured according to 53. The abbreviations listed in Table 1 are as follows.

A: TFE-P copolymer (Aflas 150P manufactured by Asahi Glass Co., Ltd.), B: TFE-P-VdF copolymer (Aflas SP manufactured by Asahi Glass Co., Ltd.), C: VdF-HFP-TFE
Copolymer (Daiel G902 manufactured by Daikin Industries, Ltd.).

D: E-P-ENB copolymer (E polymerized units / P polymerized units = 50/50 (molar ratio), containing ENB polymerized units in an amount of 10 mol% based on the total of E polymerized units and P polymerized units) , Sumitomo Chemical Co., Ltd. Esplen 505).

E: MT carbon, F: magnesium oxide (Kyowamag # 150 manufactured by Kyowa Chemical Industry Co., Ltd.), G: calcium hydroxide (calbit manufactured by Omi Chemical Co., Ltd.).

H: triallyl isocyanurate, I:
α, α'-bis (tert-butylperoxy) -p-
Diisopropylbenzene (Perkadox 14 manufactured by Kayaku Akzo Co., Ltd.), J: 2,5-dimethyl-2,5-bis (te
rt-Butylperoxy) hexane (Perhexa 25B manufactured by NOF CORPORATION).

K: sodium stearate, L: zinc oxide No. 3, M: zinc stearate, N: anti-aging agent for EPDM 2-mercaptobenzimidazole.

[Measurement of amount of gas generated from vulcanized product] From the sheet of the vulcanized product obtained above, a thickness of 0.2 cm and a length of 0.5
cm, 0.5 cm in width, a test piece was cut out, and the amount of gas generated was measured by the thermal desorption (hereinafter, TD) method using an infrared heating furnace (hereinafter, IR furnace). The measurement was performed. The test piece was placed in a platinum container and heated in an IR furnace, and the generated gas was collected in a glass tube adsorption tube (adsorbent: tenax GR) at room temperature.
A gas chromatograph (hereinafter referred to as CG) was measured by thermally desorbing the adsorption tube by the TD method. For the quantitative determination of the generated gas amount, 0.5% pentadecane solution was used as a standard, blank measurement was first performed, and the converted value was calculated by subtracting from the total peak area of each sample. The measurement conditions are as follows.

(1) Heating conditions Heating conditions: The temperature was raised from room temperature to 100 ° C. in 2 minutes and kept for 10 minutes. (2) Adsorption condition Carrier gas: Helium, flow rate 100 ml / min. Adsorbent: tenax GR Collection temperature of generated gas: room temperature. (3) CG condition column: BD-5, 0.20.5 cmφ × 30 m. Film thickness: 0.25 μm. Oven heating temperature: held at 35 ° C. for 5 minutes, then heated at 10 ° C./minute, and held at 280 ° C. for 10 minutes.

[0051]

[Table 1]

[0052]

[Table 2]

[0053]

INDUSTRIAL APPLICABILITY The fluororubber composition of the present invention is an HDD with a low total organic gas generation amount, a low hardness, and a low price.
Provide gasket.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 3J040 FA07                 4J002 BB15X BD12W BD14W BD15W                       BD16W BE04W EK016 EK036                       EK046 GJ02

Claims (3)

[Claims] 1. A composition containing (a) a fluororubber, (b) an ethylene-propylene-non-conjugated diene copolymer, and (c) an organic peroxide, comprising (a) component, (b) component and The component (c) has a content ratio of 1 to 300 parts of the component (b) and 0.3 to 10 parts of the component (c) with respect to 100 parts of the component (a), and the aging prevention for the component (b). A fluororubber composition for a hard disk drive gasket, characterized in that the amount of gas generated is 5 μg / cm ² or less when the vulcanized product obtained by vulcanizing the composition is heated at 100 ° C. for 10 minutes without containing an agent. object. 2. The fluororubber composition according to claim 1, wherein the fluororubber (a) is a tetrafluoroethylene / propylene copolymer or a tetrafluoroethylene / propylene / vinylidene fluoride copolymer. 3. A hard disk drive gasket obtained by vulcanizing the fluororubber composition according to claim 1.