JP4748125B2 - Fluorine rubber crosslinking composition - Google Patents

Description

  The present invention relates to a fluororubber crosslinking composition that provides a novel crosslinking system. ADVANTAGE OF THE INVENTION According to this invention, the fluorine-containing crosslinked rubber molded product excellent in mechanical characteristics, especially compression set and heat resistance can be provided.

  Fluorine-containing elastomers, especially perfluoroelastomers centered on tetrafluoroethylene (TFE) units, exhibit excellent chemical resistance, solvent resistance, and heat resistance, so they are widely used as sealing materials in harsh environments. Has been.

  However, as the technology advances, the required characteristics become more severe, and the sealing performance in a high temperature environment of 300 ° C. or higher is required in the aerospace field, semiconductor manufacturing equipment field, and chemical plant field.

  In response to such demands, attempts have been proposed to improve the heat resistance by devising a crosslinking system. As one of those directions, a triazine crosslinking system that uses a fluorine-containing elastomer introduced with a nitrile group as a crosslinking point and forms a triazine ring with an organotin compound (see, for example, Patent Document 1), also introduces a nitrile group as a crosslinking point. An oxazole crosslinking system that forms an oxazole ring with bisaminophenol (for example, see Patent Document 2) and an imidazole crosslinking system that forms an imidazole ring with a bisdiaminophenyl compound (for example, see Patent Document 2) A thiazole cross-linking system in which a thiazole ring is formed by bisaminothiophenol is known (for example, see Patent Document 3).

  A series of PCT patent applications (Patent Document 4, Patent Document 5, Patent Document 6 and Patent Document 7) of US DuPont have improved the crosslinking rate in the peroxide crosslinking system in addition to the triazine crosslinking system and the oxazole crosslinking system. For this purpose, it has been proposed that the end of the nitrile group-containing fluorine-containing elastomer is a carbonyl-containing end group.

  However, the crosslinked rubber obtained by the crosslinking systems described in Patent Document 1, Patent Document 2 and Patent Document 3 has a mechanical strength because the crosslinkable functional group exists only in the branched chain derived from the cure site monomer. Insufficient compression set at high temperatures.

  In addition, the invention described in the specification of the series of DuPont applications has an essential purpose of reducing sulfonic acid end groups that can cause crosslinking inhibition. Trying to. That is, instead of trying to improve the crosslinking rate using the carbonyl-containing group as a crosslinking point, the crosslinking rate is improved by reducing the sulfonic acid group. This can also be seen from the fact that it is preferred that ionized or ionizable carbonyl-containing end groups increase the viscosity of the elastomer, so that it is preferable to heat and decarboxylate to lower the viscosity. Carboxyl groups, carboxylates and carboxyamide groups are listed as carbonyl-containing end groups, but they were coagulated and isolated because metal salts were used for coagulation of the resulting emulsion polymer. The carbonyl-containing terminal group of the elastomer subjected to crosslinking is substantially a carboxylic acid metal salt or a carboxyamide group, and it is considered that these salts cause an increase in the viscosity of the elastomer. Further, this decarboxylation treatment of the terminal carbonyl-containing group indicates that the terminal group is not used for crosslinking.

  Further, in the invention of DuPont, the mechanical strength and the compression set at high temperature of the cross-linked product obtained by a cross-linking system using a nitrile group-containing fluorine-containing elastomer having a carbonyl-containing group as a terminal group are not improved.

JP 58-152041 A JP 59-109546 A JP-A-8-104789 WO97 / 19982 pamphlet WO98 / 23653 pamphlet WO98 / 23654 pamphlet WO98 / 23655 pamphlet

  An object of the present invention is to provide a novel crosslinking system of a fluorine-containing elastomer that gives a crosslinked product with particularly improved mechanical strength and compression set at high temperature.

  That is, the present invention relates to a fluororubber crosslinking composition containing a fluorine-containing elastomer having a carboxyl group and / or an alkoxycarbonyl group as a crosslinkable group at the end of the main chain and / or a branched chain, and the fluororubber crosslinking composition. Fluorine-containing crosslinked rubber molded product obtained in particular, a fluorine-containing rubber-crosslinking composition comprising a fluorine-containing elastomer having a carboxyl group as a crosslinkable group at the end of the main chain and / or a branched chain, particularly at the end, and the fluorine rubber The present invention relates to a fluorine-containing crosslinked rubber molded product obtained by crosslinking a composition for use.

  In addition, after polymerization of the fluorine-containing monomer using a compound that gives a carboxyl group and / or alkoxycarbonyl group to the main chain and / or branched chain as one of the polymerization initiator and / or monomer, the polymerization product is treated with an acid. The present invention also relates to a method for producing a fluorine-containing elastomer.

As this fluorine-containing elastomer, the formula (I):
^{X 1 - [A- (Y)} p] q -X 2 (I)
Or formula (II):
^{X 1 - [A- (Y 1} ) p] q - [B- (Y 2) r] s -X 2 (II)
(In the formula, X ¹ and X ² are the same or different, all are carboxyl group, alkoxycarbonyl group, iodine atom, bromine atom or sulfonic acid group, Y, Y ¹ and Y ² are the same or different, both are side Divalent organic group having a carboxyl group, alkoxycarbonyl group, iodine atom, bromine atom or nitrile group in the chain, A is an elastomeric fluoropolymer chain segment (hereinafter referred to as “elastomeric segment A”, B is non-elastomeric Fluoropolymer chain segment (hereinafter referred to as “non-elastomeric segment B”), p is an integer of 0 to 10, q is an integer of 1 to 5, r is an integer of 0 to 10, and s is an integer of 1 to 3. there, however any one of ^{X 1, X 2, Y,} Y 1 or Y ² is carboxyl group or alkoxycarbonyl group, Y, Y ¹ Oyo Y ² is represented by A or may contain randomly in the segments of B), crosslinkable novel having a carboxyl group and / or alkoxycarbonyl group at the terminal and / or branched chain of the main chain as a crosslinkable group A fluorine-containing elastomer is preferred.

  Moreover, as an elastomeric fluorine-containing polymer chain segment, what has 90 mol% or more of perhaloolefin units as a structural unit is preferable.

The present invention also provides a compound of formula (Ia):
^{X 1 - [A- (Y)} p] q -X 2 (Ia)
Or formula (IIa):
^{X 1 - [A- (Y 1} ) p] q - [B- (Y 2) r] s -X 2 (IIa)
(In the formula, X ¹ and X ² are the same or different, all are carboxyl group, alkoxycarbonyl group, iodine atom, bromine atom or sulfonic acid group, Y, Y ¹ and Y ² are the same or different, both are side Divalent organic group having a carboxyl group, alkoxycarbonyl group, iodine atom, bromine atom or nitrile group in the chain, A is an elastomeric fluoropolymer chain segment, B is a non-elastomeric fluoropolymer chain segment, p is 0 to 0 An integer of 10, q is an integer of 1 to 5, r is an integer of 0 to 10, s is an integer of 1 to 3, provided that either X ¹ or X ² is a carboxyl group, and Y, Y ¹ and Y ² may be randomly included in the segment of A or B) and have a carboxyl group as a crosslinkable group at the end of the main chain About.

  In the formulas (I), (II), (Ia) and (IIa), the alkoxyl group of the alkoxycarbonyl group includes, for example, a linear or branched alkoxyl group having 1 to 10 carbon atoms, a hydrogen atom May be substituted with a fluorine atom.

Further, the fluorine-containing elastomer of the present invention has a relational expression (1):
(Sco / Scf) × (D / Dp) × (F / Fp) ≧ 0.01 (1)
Those having a carboxyl group content satisfying (characters in the formula will be described later) are preferable.

  According to the present invention, a novel fluorine-containing elastomer to which a new crosslinking system can be applied, and mechanical strength and compression set obtained by crosslinking the elastomer, particularly compression set at a high temperature can be greatly improved. it can.

  First, the crosslinkable fluorine-containing elastomer of the present invention will be described.

The fluorine-containing elastomer used in the present invention has the formula (I):
^{X 1 - [A- (Y)} p] q -X 2 (I)
Or an elastomer having a main chain of an elastomeric segment A represented by formula (II):
^{X 1 - [A- (Y 1} ) p] q - [B- (Y 2) r] s -X 2 (II)
Is a fluorine-containing multi-segmented elastomer having a main chain composed of an elastomeric segment A and a non-elastomeric segment B (in formulas (I) and (II), X ¹ , X ² , Y, Y ¹ Y ² , A, B, p, q, r and s are the same as above. Among these, a fluorine-containing elastomer having a carboxyl group represented by the formula (Ia) or (IIa) at the end of the main chain (that is, at least one of X ¹ or X ² is a carboxyl group) is a novel elastomer. .

  As the elastomeric segment A, for example, the formula (1):

(Wherein m is 95 to 50, n is 5 to 50, and R _f is a C 1-8 perfluoroalkyl group) or a copolymer rubber represented by formula (2):

(Wherein, l is 95 to 35, m is 0 to 30, n is 5 to 35, and _Rf is a perfluoroalkyl group having 1 to 8 carbon atoms). Segment or formula (3):

(Wherein, m is 85-60, n is 15-40),
Formula (4):

(Wherein l is 85 to 20, m is 0 to 40, and n is 15 to 40),
Formula (5):

(In the formula, l is 95 to 45, m is 0 to 10, n is 5 to 45, Z ¹ , Z ² and Z ³ are each independently a fluorine atom or a hydrogen atom, and R _f is 1 to 8 carbon atoms. A terpolymer rubber represented by a perfluoroalkyl group), or

A non-perfluoroelastomer segment such as 1 is 1 to 80, m is 0 to 80, n is 10 to 50, and R _f is the same as described above.

Examples of Y, Y ¹ and Y ² for introducing a crosslinking point into the branched chain include CX ₂ = CX-R _f ¹ CHRI (where X is H, F or CH ₃ , and R _f ¹ is 1). A linear or branched fluoro- or perfluoroalkylene group, or a fluoro- or perfluorooxyalkylene group, a fluoropolyoxyalkylene group or a perfluoropolyoxy, which may have at least one ether type oxygen atom An alkylene group, R is H or CH ₃ ), an iodine-containing monomer, a bromine-containing monomer,

Nitrile group-containing monomers, carboxyl group-containing monomers, alkoxycarbonyl group-containing monomers, and the like, usually iodine-containing monomers, nitrile group-containing monomers, carboxyl group-containing monomers Etc. are suitable.

  As the iodine-containing monomer, a perfluorovinyl ether compound is preferable because of its copolymerizability. For example, perfluoro (6,6dihydro-6-iodo-3-oxa-1-hexene), perfluoro (5-iodo-3-oxa-1-pentene) and the like are preferable.

  Other general formulas described in JP-B-5-63482:

(Wherein Y ³ is a trifluoromethyl group, and n is 0 to 2).

Also, CF ₂ = CHI can be suitably used.

Among these, when at least one of the terminal groups X ¹ or X ² is a carboxyl group or an alkoxycarbonyl group, a unit containing a nitrile group or a carboxyl group is preferred from the viewpoint of crosslinking reactivity.

  The non-elastomeric segment B is not basically limited as long as it contains fluorine atoms and does not have the above-mentioned elastomeric properties. To select. Of these, a crystalline polymer chain segment having a crystalline melting point of 150 ° C. or higher is preferable in order to impart mechanical properties.

Among the monomers that can constitute the non-elastomeric segment B, examples of the fluorine-containing monomer include TFE, chlorotrifluoroethylene (CTFE), perfluoro (alkyl vinyl ether) (PAVE), hexafluoropropylene (HFP), CF ₂ = CF (CF ₂ ) _p X (p is an integer of 1 to 10, X is F or Cl), perhaloolefins such as perfluoro-2-butene; vinylidene fluoride, vinyl fluoride, trifluoroethylene ,

(X ⁴ and X ⁵ are H or F, q is an integer of 1 to 10), and one or more of partially fluorinated olefins such as CH ₂ ═C (CF ₃ ) ₂ can be used. Monomers that can be copolymerized therewith, for example, one or more of ethylene, propylene, vinyl chloride, vinyl ethers, carboxylic acid vinyl esters, and acrylics can also be used as the copolymerization component.

  Of these, from the viewpoint of chemical resistance and heat resistance, the monomer used as the main component is preferably a fluorine-containing olefin alone or a combination of fluorine-containing olefins, a combination of ethylene and TFE, and a combination of ethylene and CTFE. A perhaloolefin alone or a combination of perhaloolefins is preferred.

In particular,
(1) VdF / TFE (0-100 / 100-0), especially VdF / TFE (70-99 / 30-1), PTFE or PVdF;
(2) Ethylene / TFE / HFP (6-60 / 40-81 / 1-30), 3,3,3-trifluoropropylene-1,2-trifluoromethyl-3,3,3-trifluoropropylene- 1 / PAVE (40-60 / 60-40);
(3) TFE / CF ₂ = CF—R _f ³ (composition range showing non-elastomeric properties, ie, CF ₂ = CF—R _f ³ is 15 mol% or less. R _f ³ is one or more ether type oxygen atoms. A linear or branched fluoro- or perfluoroalkyl group, or a fluoro- or perfluorooxyalkyl group, which may have
(4) VdF / TFE / CTFE (50 to 99/30 to 0/20 to 1);
(5) VdF / TFE / HFP (60 to 99/30 to 0/10 to 1);
(6) Ethylene / TFE (30-60 / 70-40);
(7) polychlorotrifluoroethylene (PCTFE);
(8) Ethylene / CTFE (30-60 / 70-40)
Etc. Of these, non-elastomeric copolymers of PTFE and TFE / CF ₂ = CF—R _f ³ (R _f ³ is the same as described above) are particularly preferred from the viewpoint of chemical resistance and heat resistance.

Further, as the monomer that can constitute the non-elastomeric segment B, the unit Y ² that gives the above-mentioned cured site for various cross-linkings may be introduced in an amount of 5 mol% or less, preferably 2 mol% or less.

  The block copolymerization of the non-elastomeric segment B can be performed, for example, by changing the monomer for the non-elastomeric segment B following the emulsion polymerization of the elastomeric segment A.

  The number average molecular weight of the non-elastomeric segment B can be adjusted in a wide range of 1,000 to 1,200,000, preferably 3,000 to 400,000.

  Further, when 90 mol% or more, particularly 95 mol% or more of the structural unit of the elastomeric segment A is a perhaloolefin unit, the non-elastomeric segment B can be surely block copolymerized with the elastomeric segment A, and the non-elastomer The molecular weight (degree of polymerization) of the sex segment B can be increased.

As described above, X ¹ and X ² which are end groups of the elastomer are a carboxyl group, an alkoxycarbonyl group, an iodine atom, a bromine atom or a sulfonic acid group. Examples of a method for introducing these functional groups into the terminal group include an acid treatment method described later.

A feature of the present invention is to use a fluorine-containing elastomer in which at least one of X ¹ , X ² , Y, Y ¹ , and Y ² that can serve as a crosslinking point is a carboxyl group or an alkoxycarbonyl group. As described above, among these, the fluorine-containing elastomer having a carboxyl group represented by the formula (Ia) or (IIa) at the end of the main chain (that is, at least one of X ¹ or X ² is a carboxyl group) is novel An elastomer.

  The DuPont application specification describes a fluorine-containing elastomer having a carbonyl-containing end group, and examples of the carbonyl group-containing group include a carboxyl group, a carboxylate salt and a carboxyamide group. However, in this specification, these are collectively treated as carbonyl group-containing groups without distinction, and it is unclear whether the carboxyl group actually exists at the end of the main chain. According to the knowledge of the present inventors, the terminal group is substantially a carboxyl group metal salt or ammonium under the polymerization conditions and coagulation conditions described in these international publications, particularly at pH 3.5 to 7.0. It is considered that there is almost no free carboxyl group as well as an alkoxycarbonyl group.

  Another feature of the present invention is that the fluorine-containing elastomer of the present invention is not a polymerization product itself but a fluorine-containing elastomer in a state isolated from a polymerization reaction mixture. Therefore, if a crosslinking agent is added or high energy rays are irradiated, it is in a so-called mass state that can be crosslinked.

  As described above, a polymerization product (elastomer) after polymerization represented by emulsion polymerization is usually coagulated and isolated from a polymerization reaction mixture with a metal salt and then crosslinked. Therefore, even if the polymerization product has a carboxyl group, it becomes a carboxylate at this salting out stage, and a fluorine-containing elastomer containing a free carboxyl group has not been actually obtained. This has hindered improvement of the mechanical strength and compression set of the crosslinked product.

  Thus, the fluorine-containing elastomers represented by the above formulas (Ia) and (IIa) as well as the fluorine-containing elastomers represented by the above formulas (I) and (II) have not conventionally existed in a state where they are subjected to crosslinking. It was.

The content of the carboxyl group in the novel fluorine-containing elastomer represented by the above formulas (Ia) and (IIa) of the present invention is the relational formula (1):
(Sco / Scf) × (D / Dp) × (F / Fp) ≧ 0.01
It is preferable from the viewpoint of securing a crosslinking point, increasing heat resistance, and improving compression set.

  Next, the characters in relational expression (1) will be described.

In the formula, Sco, Scf, D, Dp, F, and Fp are the following values of the target fluorine-containing elastomer of the present invention and the standard perfluoroelastomer described later, respectively.
Sco: Total area absorbance of absorption based on the carbonyl group of an associated and non-associated carboxyl group having an absorption peak at 1680 to 1830 cm ⁻¹ when the target elastomer is measured by FT-IR. For example, in TFE / perfluoro (methyl vinyl ether) (PMVE) / CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ X (X is CN or COOH), the absorption based on the associated carbonyl group is 1800. At ˜1820 cm ⁻¹ , absorption based on non-association appears at 1760-1780 cm ⁻¹ .
Scf: Area absorbance of absorption based on harmonics of C—F bonds having an absorption peak at 2220 to 2840 cm ⁻¹ when the target elastomer is measured by FT-IR. However, if the nitrile groups present subtracting the area absorbance of absorption based on the nitrile group with a peak of absorption in 2220～2300Cm ^-1 from the total area absorbance of all absorption having a peak absorption in 2220～2840Cm ^-1 Value. This correction is for eliminating the influence of absorption because an absorption peak appears at 2220 to 2300 cm ⁻¹ when a nitrile group is present.
D: Specific gravity at 20 ° C. of the target elastomer.
Dp: Specific gravity (measured value: 2.03) at 20 ° C. of a standard perfluoroelastomer (copolymer having a molar ratio of TFE / PMVE of 58/42, measured by ¹⁹ F-NMR). The reason why a copolymer having a molar ratio of TFE / PMVE of 58/42 is a standard perfluoroelastomer is that it is easily available.
F: Fluorine content (% by weight) of the target elastomer obtained by elemental analysis.
Fp: Fluorine content of the standard perfluoroelastomer obtained by elemental analysis (measured value: 71.6% by weight).

  Next, the meaning of the relational expression (1) will be described.

The Sco / Scf term is the ratio of the carbonyl group in the fluorine-containing elastomer (the carbonyl group of the carboxyl group; hereinafter the same in this description) to the C—F bond. When the fluorine-containing elastomer of the present invention is a perfluoroelastomer, only this term is necessary. That is, Sco / Scfp ≧ 0.01
(Scfp may be the area absorbance of the C—F bond of the perfluoroelastomer).

  The D / Dp term and the F / Fp term are correction terms when the fluorine-containing elastomer of the present invention is copolymerized with a non-perfluoroelastomer such as vinylidene fluoride. That is, when a non-perfluoromonomer such as vinylidene fluoride is copolymerized, the amount of C—F bonds in the elastomer is relatively reduced, and when measured by transmission IR, the area absorbance of C—F bonds is relatively reduced.

  In general, when measured by transmission IR, the area absorbance of C—F is proportional to the number of moles of fluorine atoms per unit volume of the elastomer (the value obtained by dividing the weight of fluorine atoms by the atomic weight of fluorine 19). Then, the weight of the volume V perfluoroelastomer is V × Dp (Dp is the specific gravity of the perfluoroelastomer), and the weight of fluorine in this perfluoroelastomer is V × Dp × Fp / 100 (Fp is the fluorine of the perfluoroelastomer). Content (Fp wt%)) and the number of moles of fluorine is V × Dp × Fp / 1900. Similarly, the number of moles of fluorine in the non-perfluoroelastomer having a volume V is V × D × F / 1900 (D and F are specific gravity and fluorine content of the non-perfluoroelastomer, respectively).

  Here, if the area absorbance of the CF bond of the perfluoroelastomer is Scfp and the area absorbance of the CF bond of the non-perfluoroelastomer is Scf, the area absorbance of the CF bond and the number of moles are proportional. / Scf = VDpFp / VDF, and Scfp = (DpFp / DF) × Scf. By substituting this equation into the relational expression in the case of perfluoroelastomer: Sco / Scfp ≧ 0.01, the relational expression (1) is obtained.

The measurement in relational expression (1) uses the following method and apparatus.
(FT-IR measurement)
Measuring: Perkin Elmer FT-IR spectrometer 1760X Type Sample: thickness of approximately 0.1mm films measurement conditions: Resolution 2 cm ^-1, measured interval 1 cm ^-1, measured by transmission method

(Elemental analysis)
Measuring instrument: Microprocessor manufactured by Orion Research Ionizer 901 type Measuring method: Add a small amount of Na ₂ O ₂ (combustor) to samples 1.4 to 1.9 mg and burn in a combustion flask containing 25 ml of pure water. . After leaving for 30 minutes, 10 ml is taken out, and 10 ml of tissab liquid (500 ml of acetic acid, 500 g of sodium chloride, 5 g of trisodium citrate dihydrate and 320 g of sodium hydroxide to which pure water is added to make 10 liters) is added and F is added. Measure the amount of F ions with an ion meter.

(specific gravity)
Measuring machine: Automatic Densimeter D-1 type manufactured by Toyo Seiki Seisakusho Co., Ltd. Measuring condition: 20 ° C

  The relational expression (1) means that the fluorine-containing elastomer of the present invention has a carboxyl group of 1 mmol or more per kg of the polymer regardless of whether it is a perfluoroelastomer or a non-perfluoroelastomer. Is preferred. Moreover, when it is what copolymerized the carboxyl group-containing monomer, it is preferable that the copolymerization composition ratio is 0.3-2 mol% especially.

Moreover, as the bonding position, the ends X ¹ and X ^{2 of the} main chain are preferable from the viewpoint of further improving the physical properties of the obtained crosslinked product.

  The fluorine-containing elastomer of the present invention can be produced by a polymerization method such as an emulsion polymerization method, a suspension polymerization method, or a solution polymerization method.

As the polymerization initiator, a carboxyl group or a group capable of forming a carboxyl group (for example, acid fluoride, acid chloride, CF ₂ OH. These all generate a carboxyl group in the presence of water) is preferably present at the end of the elastomer. What you get is used. Specific examples include ammonium persulfate (APS) and potassium persulfate (KPS).

  In addition, a chain transfer agent usually used for adjusting the molecular weight may be used, but it is better not to use it as much as possible because the ratio of the group capable of forming a carboxyl group or an alkoxycarbonyl group introduced at the terminal decreases. . However, this does not apply as long as the chain transfer agent can cause the group to exist at the end of the elastomer. When no chain transfer agent is used, the molecular weight may be adjusted by carrying out the polymerization at a low pressure, for example, less than 2 MPa · G, preferably 1 MPa · G or less. Other polymerization conditions are not particularly limited, but in order to obtain a polymerization product having a carboxyl group at the terminal and / or branched chain without the acid treatment described later, the pH of the polymerization system is set to 3 or less strongly acidic. It is preferable to do this.

  Some of the polymerization products thus obtained do not contain free carboxyl groups depending on the polymerization conditions, but they can also be converted to free carboxyl groups by the following acid treatment.

  One of the important features of the present invention is that a group such as a metal salt or ammonium salt of carboxylic acid present in the polymerization product is converted into a carboxyl group by acid treatment of the polymerization product. As the acid treatment method, for example, washing with hydrochloric acid, sulfuric acid, nitric acid or the like, or a method of bringing the mixture system after polymerization reaction with these acids to pH 3 or less is suitable.

  This acid treatment is preferably applied as a coagulation means when the polymerization product is isolated from the polymerization reaction mixture by coagulation, from the viewpoint of simplification of the process. Alternatively, the polymerization mixture may be acid-treated, and then the polymerization product may be isolated by means such as lyophilization. Furthermore, methods such as coagulation by ultrasonic waves and coagulation by mechanical force can be employed.

  Moreover, a fluorine-containing elastomer containing iodine or bromine can be oxidized with fuming nitric acid to introduce a carboxyl group.

  The present invention further provides a fluorine-containing elastomer having a carboxyl group and / or an alkoxycarbonyl group as a crosslinkable group at the end of the main chain and / or a branched chain, particularly the fluorine-containing elastomer represented by the above formulas (I) and (II). The present invention relates to a fluororubber composition containing

  The fluorine-containing rubber composition of the present invention can be crosslinked by a crosslinking method that does not use a crosslinking agent, for example, a high energy beam irradiation method such as an electron beam irradiation method, a radiation irradiation method, or an ultraviolet irradiation method. A crosslinking agent capable of reacting with an alkoxycarbonyl group, particularly a crosslinking agent used for an oxazole crosslinking system, an imidazole crosslinking system, or a thiazole crosslinking system is blended.

  Examples of the crosslinking agent used in the oxazole crosslinking system, imidazole crosslinking system, and thiazole crosslinking system include, for example, formula (III):

(Wherein R ³ is —SO ₂ —, —O—, —CO—, an alkylene group having 1 to 6 carbon atoms, a perfluoroalkylene group having 1 to 10 carbon atoms, or a single bond, and R ¹ and R ² is a bisdiaminophenyl-based cross-linking agent represented by the following formula: ₂ is —NH ₂ and the other is —NH ₂ , —OH or —SH, preferably both R ¹ and R ² are —NH ₂ -Based crosslinking agent, bisaminothiophenol-based crosslinking agent, formula (IV):

A bisamidrazone crosslinking agent represented by formula (V) or (VI):

(Wherein R _f ³ is a C 1-10 perfluoroalkylene group),

(Wherein n is an integer of 1 to 10), and the like. These bisaminophenol-based crosslinking agents, bisaminothiophenol-based crosslinking agents, bisdiaminophenyl-based crosslinking agents and the like have been conventionally used for crosslinking systems having a nitrile group as a crosslinking point. It reacts with the carboxyl group and alkoxycarbonyl group of the elastomer to form an oxazole ring, a thiazole ring and an imidazole ring to give a crosslinked product.

  Particularly preferred crosslinking agents include a plurality of 3-amino-4-hydroxyphenyl groups, 3-amino-4-mercaptophenyl groups or the formula:

(Wherein R ³ is the same as described above, R ⁴ and R ⁵ are both amino groups), and a compound having a 3,4-diaminophenyl group is mentioned. (3-amino-4-hydroxyphenyl) hexafluoropropane (generic name: bis (aminophenol) AF), 2,2-bis (3-amino-4-mercaptophenyl) hexafluoropropane, tetraaminobenzene, bis- 3,4-diaminophenylmethane, bis-3,4-diaminophenyl ether, 2,2-bis (3,4-diaminophenyl) hexafluoropropane, and the like.

  The amount of the crosslinking agent is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the elastomer.

  In the composition of the present invention, usual additives blended in the fluorine-containing elastomer composition, for example, fillers, processing aids, plasticizers, colorants and the like can be blended as necessary. May contain one or more different conventional crosslinking agents and crosslinking accelerators. Moreover, you may mix a well-known fluororubber in the range which does not impair the effect of this invention.

  The composition of the present invention can be prepared by mixing each of the above components using a normal rubber processing machine, for example, an open roll, a Banbury mixer, a kneader or the like. In addition, it can be prepared by a method using a closed mixer or a method of co-coagulation from emulsion mixing.

  A method for obtaining a preform from the above composition may be an ordinary method, and may be performed by a known method such as a method of heat-compressing with a mold, a method of press-fitting into a heated mold, or a method of extruding with an extruder. it can. In the case of an extruded product such as a hose or an electric wire, the shape can be maintained even after extrusion, so that a preform that has been extruded without using a crosslinking agent can be used as it is. Of course, it is also possible to use a preform that has been heat-crosslinked with steam using a crosslinking agent. Further, when it is difficult to maintain the shape even after release in a non-crosslinked state with a molded product such as an O-ring, it can be carried out by using a preform that has been previously crosslinked using a crosslinking agent.

  In the present invention, when oxazole crosslinking is performed using a crosslinking agent such as bisaminophenol, it can be performed under the usual crosslinking conditions of fluororubber. For example, press crosslinking is performed by placing in a mold and holding at 120-250 ° C. under pressure for 1-60 minutes, followed by oven crosslinking by holding in a 120-320 ° C. oven for 0-48 hours. When performed, a crosslinked rubber can be obtained. Further, bis (aminophenol) AF or the like may be added to a known fluororubber crosslinking method, for example, polyamine crosslinking, polyol crosslinking, or peroxide crosslinking, and the crosslinking may be performed in combination.

  Further, imidazole crosslinking in which a carboxyl group is crosslinked with a bisdiaminophenyl-based crosslinking agent is most suitable for a carboxyl-containing polymer having a carboxyl group other than the terminal, and has a relatively low crosslinking temperature (for example, 150 to 230 ° C., preferably 170 to 200). )) To give a crosslinked product having good physical properties.

  The present invention also relates to the cross-linked product thus obtained. Since the cross-linked product of the present invention can be cross-linked using the terminal group of the fluorine-containing elastomer as a cross-linking point, it gives high mechanical strength that has not been obtained in the past. In addition, surprisingly, the compression set, which is a criterion for evaluating the sealing performance, which is indispensable particularly as a sealing material, is greatly reduced, and the compression set at high temperatures is also reduced.

  The crosslinked product of the present invention is useful as various molded articles in the fields shown in the following Tables 1, 2 and 3.

Specifically, it can be used by being incorporated in the following semiconductor manufacturing apparatus.
(1) Etching device Dry etching device Plasma etching device Reactive ion etching device Reactive ion beam etching device Sputter etching device Ion beam etching device Wet etching device Ashing device (2) Cleaning device Dry etching cleaning device UV / O ₃ cleaning device Ion Beam cleaning equipment Laser beam cleaning equipment Plasma cleaning equipment Gas etching cleaning equipment Extraction cleaning equipment Soxhlet extraction cleaning equipment High-temperature high-pressure extraction cleaning equipment Microwave extraction cleaning equipment Supercritical extraction cleaning equipment (3) Exposure equipment Stepper Coater / Developer (4) Polishing equipment CMP apparatus (5) Film forming apparatus CVD apparatus Sputtering apparatus (6) Diffusion / ion implantation apparatus Oxidation diffusion apparatus Ion implantation apparatus

  Next, the present invention will be described with reference to examples, but the present invention is not limited to such examples.

Example 1
In a stainless steel autoclave with an internal volume of 3 liters and no ignition source, 1 liter of pure water and emulsifier

10 g, charged with 0.09 g of disodium hydrogen phosphate and 12 hydrate as a pH adjuster, thoroughly purged the system with nitrogen gas, degassed, heated to 50 ° C. while stirring at 600 rpm, A mixed gas (TFE / PMVE = 25/75 molar ratio) of fluoroethylene (TFE) and perfluoro (methyl vinyl ether) (PMVE) was charged so that the internal pressure was 0.78 MPa · G. Next, 10 ml of an aqueous solution of ammonium persulfate (APS) having a concentration of 527 mg / ml was injected under nitrogen pressure to initiate the reaction.

When the internal pressure dropped to 0.69 MPa · G due to the progress of the polymerization, 3 g of CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ CN (CNVE) was injected under nitrogen pressure. Next, 4.7 g of TFE and 5.3 g of PMVE were respectively injected under their own pressure so that the pressure became 0.78 MPa · G. Thereafter, as the reaction proceeds, TFE and PMVE are similarly injected, and the pressure is increased and decreased repeatedly between 0.69 and 0.78 MPa · G, and the total amount of TFE and PMVE is 70 g, 130 g, 190 g, and 250 g. At that time, 3 g of CNVE was injected under nitrogen pressure.

  19 hours after the start of the polymerization reaction, when the total amount of TFE and PMVE reached 300 g, the autoclave was cooled to release unreacted monomers, and 1330 g of an aqueous dispersion having a solid content concentration of 21.2% by weight. Got.

  1196 g of this aqueous dispersion was diluted with 3588 g of water and slowly added to 2800 g of 3.5 wt% aqueous hydrochloric acid with stirring. After stirring for 5 minutes after the addition, the coagulated product was filtered off, and the obtained polymer was further poured into 2 kg of HCFC-141b, stirred for 5 minutes, and filtered again. Thereafter, washing with HCFC-141b and filtration were repeated four more times, followed by vacuum drying at 60 ° C. for 72 hours to obtain 240 g of a polymer (nitrile group-containing elastomer).

As a result of ¹⁹ F-NMR analysis, the monomer unit composition of this polymer was TFE / PMVE / CNVE = 56.6 / 42.3 / 1.1 mol%. When measured by infrared spectroscopic analysis, the chart shown in FIG. 1 was obtained.

In the chart of FIG. 1, characteristic absorption of carboxyl group 1774.9Cm ^-1, around 1808.6Cm ^-1, characteristic absorption of OH group is observed near 3557.5Cm ^-1 and 3095.2cm ^-1. (Sco / Scf) × (D / Dp) × (F / Fp) = 0.040.

For reference, an IR analysis of the elastomer obtained by coagulating the product with magnesium chloride and ethanol revealed no absorption based on carboxyl groups, and the magnesium salt of carboxylic acid was found at 1729 cm ⁻¹ . Absorption was observed.

Furthermore, coagulation was carried out by freeze coagulation (pH 3.5 to 7.0), and the obtained elastomer was also subjected to IR analysis. As a result, there was no absorption based on carboxyl groups, and 1651 cm ^-1 Absorption of ammonium salt (—COONH ₄ ) was observed.

  The obtained fluorine-containing elastomer of the present invention (nitrile group-containing elastomer having a carboxyl group at the terminal) and 2,2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane [bis (aminophenol) as a crosslinking agent AF] and carbon black as a filler (Thermax N-990 manufactured by Cancarb) were mixed at a weight ratio of 100/2/20, and kneaded with an open roll to prepare a crosslinkable fluororubber composition.

  The fluororubber composition was pressed at 180 ° C. for 10 minutes for crosslinking, and further subjected to two-stage oven crosslinking in an oven under the conditions shown in Table 4 to obtain a crosslinked product having a thickness of 2 mm and an O-ring ( A test sample of AS-568A-214) was prepared. Table 4 shows the results of measurement of the crosslinkability, normal physical properties, and compression set of this crosslinked product.

(Crosslinking)
For each cross-linking composition, a vulcanization curve was obtained at the temperatures shown in Table 4 using a JSR type curlastometer type II, and the lowest viscosity (νmin), the highest viscosity (νmax), the induction time (T ₁₀ ), and the optimum addition Find the sulfur time (T ₉₀ )

(Normal characteristics)
According to JIS K6301, 100% modulus, tensile strength, tensile elongation and hardness (JIS A hardness) in a normal state (25 ° C.) of a crosslinked product having a thickness of 2 mm are measured.

(Compression set)
According to JIS K6301, the compression set of an O-ring (AS-568A-214) after 70 hours at 200 ° C., 168 hours at 200 ° C., 70 hours at 230 ° C. and 168 hours at 230 ° C. is measured.

Example 2
In a stainless steel autoclave with an internal volume of 3 liters and no ignition source, 1 liter of pure water and emulsifier

10 g, charged with 0.09 g of disodium hydrogen phosphate and 12 hydrate as a pH adjuster, thoroughly purged the system with nitrogen gas, degassed, heated to 50 ° C. while stirring at 600 rpm, A mixed gas (TFE / PMVE = 25/75 molar ratio) of fluoroethylene (TFE) and perfluoro (methyl vinyl ether) (PMVE) was charged so that the internal pressure was 0.78 MPa · G. Next, 10 ml of an aqueous solution of ammonium persulfate (APS) having a concentration of 527 mg / ml was injected under nitrogen pressure to initiate the reaction.

When the internal pressure dropped to 0.69 MPa · G due to the progress of the polymerization, 3.78 g of CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ COOH (CBVE) was injected under nitrogen pressure. Next, 4.7 g of TFE and 5.3 g of PMVE were respectively injected under their own pressure so that the pressure became 0.78 MPa · G. Thereafter, TFE and PMVE were injected in the same manner as the reaction proceeded, and the pressure increase and decrease were repeated between 0.69 and 0.78 MPa · G. After 4.2 hours from the start of the polymerization reaction, when the total amount of TFE and PMVE reached 80 g, the autoclave was cooled to release unreacted monomers, and an aqueous dispersion having a solid content concentration of 7.5% by weight 1091 g was obtained.

  1000 g of this aqueous dispersion was diluted with 3000 g of water and slowly added to 2800 g of 3.5 wt% aqueous hydrochloric acid with stirring. After the addition, the mixture was stirred for 5 minutes, and then the coagulated product was filtered off. The obtained polymer was further poured into 800 g of HCFC-141b, stirred for 5 minutes, and filtered again. Thereafter, washing with HCFC-141b and filtration were repeated four more times, followed by vacuum drying at 120 ° C. for 72 hours to obtain 72 g of a polymer.

As a result of ¹⁹ F-NMR analysis, the monomer unit composition of this polymer was TFE / PMVE / CBVE = 57.3 / 41.8 / 0.9 mol%. When measured by infrared spectroscopic analysis, the chart shown in FIG. 2 was obtained.

In the chart of FIG. 2, a characteristic absorption of carboxyl group in the vicinity of 1774.4Cm ^-1, characteristic absorption of OH group is observed in the vicinity of 3557.0Cm ^-1 and 3087.7cm ^-1. It was (Sco / Scf) × (D / Dp) × (F / Fp) = 0.53.

  Obtained fluorine-containing elastomer (carboxyl group-containing elastomer), 2,2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane [bis (aminophenol) AF] as a crosslinking agent, and carbon black as a filler (Thermax N-990 manufactured by Cancarb) was mixed at a weight ratio of 100/2/20, and kneaded with an open roll to prepare a crosslinkable fluororubber composition.

  The fluororubber composition was pressed at 180 ° C. for 10 minutes for crosslinking, and further subjected to two-stage oven crosslinking in an oven under the conditions shown in Table 4 to obtain a crosslinked product having a thickness of 2 mm and an O-ring ( A test sample of AS-568A-214) was prepared. Table 4 shows the results of measurement of the crosslinkability, normal physical properties, and compression set of this crosslinked product.

Example 3
In Example 2, instead of bis (aminophenol) AF as a crosslinking agent, the formula:

で示されるビスジアミノフェニル化合物を用いたほかは同様にして架橋可能なフッ素ゴム組成物を調製し、表４に示す架橋条件（実施例１と同じ条件）で架橋を行ない、得られた架橋物の架橋性、常態物性および圧縮永久歪みを実施例１と同様にして測定した。結果を表４に示す。

A cross-linked fluororubber composition was prepared in the same manner except that the bisdiaminophenyl compound represented by the formula (1) was used, and cross-linking was performed under the cross-linking conditions shown in Table 4 (the same conditions as in Example 1). The crosslinkability, normal physical properties, and compression set were measured in the same manner as in Example 1. The results are shown in Table 4.

Example 4 (triazine crosslinking system)
100 parts by weight of the nitrile group-containing elastomer having a carboxyl group at the end obtained in Example 1 was mixed with 3 parts by weight of tetraphenyltin instead of bisaminophenol AF as a crosslinking agent, and 10 parts by weight of SRF carbon black as carbon black. Except for blending, it was crosslinked in the same manner as in Example 1 under the conditions shown in Table 4 to obtain a crosslinked product. About this crosslinked material, it carried out similarly to Example 1, and measured crosslinking | crosslinked property and each physical property. The results are shown in Table 4.

  As shown in Table 4, a nitrile group-containing polymer having a carboxyl group at its terminal (Example 1) is a crosslinked product excellent in normal physical properties and compression set at a low crosslinking temperature. In Example 2, a crosslinked product having excellent normal physical properties is obtained. Moreover, in the imidazole bridge | crosslinking (Example 3) of a carboxyl group-containing polymer, the crosslinked material in which the compression set was especially improved with the low crosslinking temperature (180 degreeC) was obtained. Further, even when a nitrile group-containing polymer having a carboxyl group at the terminal is crosslinked with tetraphenyltin (Example 4), the minimum viscosity at the time of crosslinking is low, and good processability is exhibited.

2 is a chart of infrared spectroscopic analysis of the fluorine-containing elastomer of the present invention obtained in Example 1. FIG. 2 is a chart of infrared spectroscopic analysis of the fluorine-containing elastomer of the present invention obtained in Example 2. FIG.

Claims (6)

A perfluoroelastomer having a carboxyl group and / or alkoxycarbonyl group as a crosslinkable group at both ends of the main chain, and capable of reacting with the carboxyl group or alkoxycarbonyl group and used in an oxazole crosslinking system, imidazole crosslinking system or thiazole crosslinking system A composition for crosslinking a fluororubber comprising a crosslinking agent. 2. The fluororubber crosslinking composition according to claim 1, wherein the perfluoroelastomer is a perfluoroelastomer having carboxyl groups at both ends of the main chain as crosslinkable groups. A crosslinking agent capable of reacting with a carboxyl group or an alkoxycarbonyl group is of formula (III):

(In the formula, ^one of R ¹ and R ² is —NH ₂ and the other is —NH ₂ , —OH or —SH, and R ³ is —SO ₂ —, —O—, —CO—, carbon number A bisdiaminophenyl crosslinking agent, a bisaminophenol crosslinking agent, a bisaminothiophenol crosslinking agent represented by a 1-6 alkylene group, a C1-C10 perfluoroalkylene group or a single bond),
Formula (IV):

A bisamidrazone crosslinking agent represented by
Formula (V) or (VI):

(Wherein R _f ³ is a C 1-10 perfluoroalkylene group),

The composition for crosslinking a fluororubber according to claim 1 or 2, which is a bisamidoxime-based crosslinking agent represented by (wherein n is an integer of 1 to 10). 100 parts by weight of perfluoroelastomer and formula (III):

(In the formula, ^one of R ¹ and R ² is —NH ₂ and the other is —NH ₂ , —OH or —SH, and R ³ is —SO ₂ —, —O—, —CO—, carbon number 1 to 6 alkylene group, a C 1-10 perfluoroalkylene group or a single bond), and 0.5 to 5.0 parts by weight of a crosslinking agent. The composition for crosslinking a fluororubber as described. The fluororubber crosslinking composition according to claim 4, wherein a bisaminophenyl crosslinking agent in which R ¹ and R ² are both —NH ₂ in the formula (III) is used. Perfluoroelastomer is represented by the formula (I):
^{X 1 - [A- (Y)} p] q -X 2 (I)
Or formula (II):
^{X 1 - [A- (Y 1} ) p] q - [B- (Y 2) r] s -X 2 (II)
(Wherein X ¹ and X ² are the same or different, both are carboxyl groups or alkoxycarbonyl groups, Y, Y ¹ and Y ² are the same or different, and all are carboxyl groups, alkoxycarbonyl groups, iodines in the side chain) A divalent organic group having an atom, bromine atom or nitrile group, A is an elastomeric perfluoropolymer chain segment, B is a non-elastomeric perfluoropolymer chain segment, p is an integer of 0 to 10, q is 1 to 5 An integer, r is an integer of 0 to 10, s is an integer of 1 to 3, provided that Y, Y ¹ and Y ² may be randomly contained in the segment of A or B) It is an elastomer, The fluororubber crosslinking composition in any one of Claims 1-5.

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