JP2002525411A - Fluorinated rubber compounds containing fluorinated rubber that rapidly crosslinks - Google Patents

Abstract

  (57) [Summary] The present invention relates to a fluorinated rubber mixture containing at least one fluorinated rubber having exclusively hydrogen, alkyl and / or alkoxy groups other than vinyl end groups. The invention also relates to the use of the mixture in the production of all types of shaped bodies.

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a fluorinated rubber compound containing at least one fluorinated rubber having exclusively hydrogen, alkyl and / or alkoxy end groups other than vinyl end groups and to the production of various molded articles. Regarding its use.

[0002] Fluorinated rubbers are the polymers of choice for high temperature applications, such as O-rings and seals, that must prevent leakage even after prolonged deformation under pressure. Injection molding technology is used more and more widely to mass produce these parts. This technique has lower manufacturing costs, shorter cycle times, higher degree of automation, and a lower incidence of uneven tolerances in the dimensions of individual parts as compared to compression molding techniques.

[0003] Many conventional fluorinated rubbers are manufactured by injection molding techniques based on their inadequate scorch resistance or because of their premature crosslinking at high temperatures and / or under high shear loads. Can not be used. As a result, fluorinated rubbers crosslinked with bisphenol are advantageously used in injection molding technology. This is because the crosslinking system combines better scorch resistance with a rapid and flexible crosslinking reaction. In addition, parts crosslinked in this way show an improvement in compression set compared to parts crosslinked with peroxide or amine (S. Bowers in: Ka.
utschuk Gummi Kunststoffe, 9/1997, p. 618 et seq.).

[0004] Decreasing the molecular weight of the fluorinated rubber results in a decrease in its viscosity, which allows for shorter cycle times and lower pressures when using injection molding methods, but this is generally the case. The result is that the parts produced by the method exhibit significantly poorer compression set.

[0005] Bisphenol crosslinking requires a certain minimum molecular weight of the fluorinated rubber polymer to ensure at least two bisphenol crosslinking points per fluorinated rubber chain. Unfortunately, the flowability of fluorinated rubbers having a molecular weight of 25,000 g / mol or more is very limited.

In the rubber industry, better processability of the rubber used is generally desired. This is particularly relevant for liquidity. The lower the viscosity of the crude rubber, the easier the processing technique is, the higher the processability and the lower the amount of waste. These aspects are particularly relevant for fluorinated rubbers. These are expensive rubbers that cannot always be produced by injection molding equipment used by the rubber industry.

[0007] According to the prior art, fluoroelastomers are advantageously prepared by aqueous emulsion or suspension polymerization (Ullmann's Encyclopedia of Industrial Chemistry, Vol. A).
-11, VHC Verlagsgesellschaft, Weinheim 1988, p. 417 et seq.). Water-soluble inorganic peroxides, such as persulfates, are generally used in such preparations as initiators and as emulsifiers or suspension stabilizers. To obtain the desired molecular weight, the addition of chain transfer agents such as tetrachloromethane, acetone, diethyl malonate and methanol is customary. In this way, ionic or polar end groups, for example -COF, -COOH, -COOR or OH groups are introduced into the polymer chain. These groups firstly impart, during the production, the behavior of the rubber compound due to the increase in viscosity based on intermolecular interactions and, secondly, onium salts as catalysts (see, for example, US Pat. No. 4,524,197 (Khan)). Inhibition of crosslinking by bis-nucleophiles in the presence of

The problem is therefore to provide fluorinated rubber compounds which do not exhibit at least some of the disadvantages mentioned above.

The present invention relates to an ionic crosslinker system comprising a fluorinated rubber having exclusively hydrogen, alkyl and / or alkoxy end groups other than vinyl end groups and comprising at least one organic polyhydroxy compound, an onium salt And a fluorinated rubber compound containing at least one acid acceptor.

The fluorinated rubber which can be used according to the invention comprises at least one fluorinated rubber in at least one inert fluorine-containing solvent in the presence of an organic peroxide as initiator and in the absence of water and a molecular weight regulator. The fluoromonomer can be prepared by a process characterized by selecting a solvent in which the monomer is dissolved, but the polymer having a molecular weight higher than 25 kg / mol is no longer soluble.

Organic or fluorinated organic dialkyl peroxides, diacyl peroxides,
Dialkyl peroxydicarbonates, alkyl peresters and / or perketals, such as t-butylperoxypivalate, t-butylperoxy-
2-ethyl - hexanoate used, dicyclohexyl peroxydicarbonate, as bis (trifluoroacetyl peroxide) or hexafluoropropene oxide dimer _{{CF 3 CF 2 CF 2 OCF} (CF 2) COO} 2 of peroxide initiator I do.

The inert fluorinated solvents which can be used in the above-mentioned process do not enter into a significant chain transfer reaction under the reaction conditions, and no longer homogeneously dissolve the rubber obtained, whose molecular weight exceeds 25 kg / mol. And has no ozone damage ability. Specific fluorocarbon compounds or fluorohydrocarbons or fluorocarbon compounds having heteroatoms, such as 1,1,1,3,3-pentafluoropropane, perfluorobutanesulfofluoride or 1,1,1,2 , 3,3-Hexafluoropropane is suitable as an inert fluorine-containing solvent.

The following can be used as monomers for the fluorinated rubber used according to the invention: optionally substituted and, apart from fluorine, hydrogen and / or
Or fluorinated ethylene optionally containing chlorine, such as vinylidene fluoride,
Tetrafluoroethylene and chlorotrifluoroethylene, for example fluorinated 1-alkenes having 2 to 8 carbon atoms, for example hexafluoropropene, 3,
3,3-trifluoropropene, chloropentafluoropropene and hexafluoroisobutene and / or formula: CF ₂ CF—OX, where XＸC ₁ -C ₃ -perfluoroalkyl or — (CF ₂ —CFY -O
) And _n -R _F, this time, n = 1 to 4, a Y = F or CF _3, and _R F ₌ C 1 _{~C 3} - perfluorinated vinyl ether of a perfluoroalkyl.

The combination of vinylidene fluoride and hexafluoropropene and optionally tetrafluoroethylene and / or a perfluorinated vinyl ether such as perfluoro (methyl vinyl ether) is advantageous.

The following compositions are particularly advantageous for the fluorinated rubbers that can be used according to the invention: 40 to 90 mol% of vinylidene fluoride, 10 to 15 mol% of hexafluoropropylene, 0 to 25 of tetrafluoroethylene mol%, wherein _{CF 2 = CF-O-X} [ wherein, _{X =} C 1 ~C ₃ - perfluoroalkyl or _- (CF 2 -CFY-O
) And _n -R _F, this time, n = 1~4, Y = F or CF _3, and _R F ₌ C 1 _{~C 3} - vinyl perfluorinated of perfluoroalkyl] 0
25 mol%.

For the fluorinated rubbers which can be used according to the invention, the terminal groups, other than the vinyl terminal groups, are exclusively hydrogen, alkyl or alkoxy groups and, advantageously, depending on the organic peroxide used, A methyl group in addition to the alkyl group
What is important is the -ethyl-pentyl or isobutyl group as well as the t-butoxy group.

The fluorinated rubbers which can be used according to the invention advantageously do not contain chlorine, bromine or iodine and contain carbonyl-(— COF, —COOH, —COOR,
-COR) have neither a terminal group nor a hydroxyl terminal group.

The vinyl end groups are preferably —CH ＝ CF ₂ .

The number average molecular weight of the fluorinated rubber that can be used according to the present invention is 25 to 10
It is in the range from 0 kg / mol, preferably from 40 to 80 kg / mol, and the molecular weight distribution defined by _Mw / _Mn is from 1.5 to 3.5. The Mooney viscosity ML _{1 + 10 at} 120 ° C. is in the range from 1 to 40, preferably from 4 to 20. Mooney viscosity is D
It is defined by IN53523.

Organic polyhydroxy compounds are used as auxiliary crosslinking agents in the fluorinated rubber compounds according to the invention. Organic polyhydroxy compounds are known in the art, for example US-4.
No. 259463 (Moggi et al.), US Pat. No. 4,912,171 (Grootaert et al.
), US-5384374 (Guerra et al.) Or US-5654375 (Jing et al.). Suitable substances within the scope of the present invention are aromatic polyhydroxy compounds, for example 2,2-bis (4-hydroxyphenyl) -hexafluoropropane (bisphenol AF), 4,4'-dihydroxydiphenylsulfone or fluoroaliphatic diols. For example, 1,1,6,6-tetrahydrooctafluorohexanediol and US Pat. No. 4,259,463, US Pat.
2171, U.S. Pat. No. 5,384,374 or U.S. Pat. No. 5,654,375. Bisphenol is preferred.

The organic polyhydroxy compound is 0.1 to 15 phr, preferably 0.3 to 10 phr
Used in amounts in the range of r. Of course, it is also possible to use mixtures of various organic polyhydroxy compounds.

Onium salts act as catalysts or promoters for crosslinking and are known in principle. Suitable onium salts are quaternary phosphonium, ammonium, aminophosphonium, sulfonium arsenic or antimony compounds, which are substituted by alkyl and / or aryl groups, where the alkyl and / or aryl groups are optionally hetero- It may contain atoms such as O, N, Si and the like. Suitable examples are benzyltriphenylphosphonium chloride, benzyltributylphosphonium chloride, bis- (benzyldiphenylphosphine) iminium chloride and US Pat. No. 4,259,463, US Pat. No. 4,912,171, U.S. Pat.
Other compounds described in S-5384374 or U.S. Pat. No. 5,654,375. Benzyltributylphosphonium chloride is preferred.

The onium salt is added in an amount ranging from 0.1 to 15 phr, preferably 0.1 to 8 phr.

The auxiliary crosslinking agent and the accelerator can of course be added individually or as a mixture. It is also possible to condense the polyol and the onium salt before adding it to the fluorinated rubber compound, for example, to form phosphonium phenolate. See U.S. Pat. No. 4,912,171.

Acid acceptors that can be used are metal oxides or hydroxides, such as Ca (
OH) ₂ , CaO, MgO, ZnO, and basic salts with organic acids, such as sodium stearate or magnesium oxalate. These are US-490
No. 2171 is described in detail. Acid acceptor 1-10, preferably 2-8 ph
Used in amounts in the range of r.

The fluorinated rubber compounds according to the invention can be compounded and crosslinked in a customary manner. For example, Ullmann's Encyclopedia of Industrial Che
See mistry, 5th Edition, 1993, Vol. A23, Chapter 2.6, p. 265-p. 269.

[0027] A continuous screw device, kneader or twin-roll mixing apparatus can be advantageously used for compounding.

Before the fluorinated rubber according to the invention is processed to produce a more flexible rubber molding, fillers, processing aids, other accelerators and other modifiers are added to the fluorinated rubber according to the invention. It can be added and mixed.

Due to the low Mooney viscosity of the rubber, the rubber compound is suitable for further processing to form flexible moldings by particularly advantageous extrusion or injection molding techniques. In such a production method, a vulcanizable rubber compound is injected into a mold at 160 to 230 ° C. in a commercially available injection molding apparatus for thermoplastics, and the vulcanizable rubber compound is injected into the mold depending on the composition of the rubber compound and the molding temperature. 30 to 30
Hold for 0 seconds and thereby vulcanize.

The fluorinated rubber compounds according to the invention are very suitable for the production of moldings of all types, in particular seals, hoses and profiles.

[0031]

[Table 1]

Example 1 620 ml of fluorobutanesulphofluoride (PFBSF) were charged into a 4.1 l autoclave. The closed autoclave was evacuated twice while cooling, followed by applying a nitrogen pressure of 3 bar and stirring slowly for 10 minutes each time. 440 g of vinylidene fluoride (VDF) and hexafluoropropene (HF
880 g of P) were added into a vacuum autoclave and the reaction mixture was heated to 60 ° C. with stirring. After reaching this temperature, the internal pressure of the autoclave is reduced to 2
7 bar. TBPPI-75-AL dissolved in 20 g of PFBSF (=
T-butyl peroxypivalate as a 75% solution in aliphatic compounds, Peroxi
d Polymerization was initiated by addition of 4.25 g of a commercial product from Chemie GmbH, peroxide content 47.1%). The polymerization is initiated within a few minutes, as evidenced by the pressure starting to drop. During the polymerization, a monomer mixture consisting of 60% by weight of vinylidene fluoride and 40% by weight of hexafluoropropene was fed under pressure and the internal pressure of the autoclave was kept constant at 26.8 ± 0.2 bar. Thus, a total of 300 g of vinylidene fluoride and 200 g of hexafluoropropene were subsequently added over a reaction time of 14 hours. After the end of the polymerization, the reaction mixture was cooled and the unreacted monomer mixture was removed from the reactor by depressurization and vacuum treatment. The remaining reactor contents were heated to 80 ° C. with stirring. Fifteen minutes after the stirrer was switched off, the reactor contents were drained via a bottom outlet valve to a second pressure vessel located below.

The product was separated from PFBSF and dried, yielding 450 g of a rubber-like copolymer.

The following copolymer composition was confirmed by ¹⁹ F NMR analysis (solvent: acetone; standard: CFCl ₃ ): 20.5 mol% of hexafluoropropene, 79.5 mol% of vinylidene fluoride.

The number average molecular weight (membrane permeation) was 68900 g / mol. M _w / M _n is GPC
It was 2.3 as measured by inspection.

With regard to the Mooney viscosity ML _{1 + 10} at 120 ° C., a value of 16 was confirmed (Table 1).

Example 2 To produce a crosslinkable rubber compound, carbon black MT N 9 was used.
90 30 parts, calcium hydroxide 6 parts, magnesium oxide (Maglite D) 3 parts,
Mixture of bisphenol AF and Viton A ^{(R) (50/50} parts by weight) 4 parts, and benzyl triphenylphosphonium chloride and Viton A mixture of ^(R) (
33/66 parts by mass) 2 parts of fluorinated rubber 1 of Example 1 in a fully cooled mixing device
00 parts by mass.

To clarify the crosslinking behavior, the rubber compound produced in this way was
Monsanto Rheometer Type Tested at 170 ° C. (measurement time 30 minutes) in MDR 2000 E.

The compound was pressed under pressure at 170 ° C. and 200 bar for 30 minutes, 1 × 10
It was vulcanized in a mold for a × 10 mm plate and a 6 × 70 mm cylinder and subsequently post-vulcanized in a circulating air oven (1 hour at 160 ° C., 1 hour at 170 ° C., 1 hour).
2 hours at 80 ° C and 20 hours at 230 ° C). The tensile and elongation properties and the compression set properties (cylinder, 70 hours at 200 ° C.) of the vulcanized moldings were measured before and after hot air aging (275 hours at 275 ° C.). The results are shown in Table 3.

Example 3 The polymerization was carried out as in Example 1, except that PFBSF was replaced by 1,1,1,3.
, 3-pentafluoropropane and 2.5 g of t-butyl-per-2-ethylhexanoate as initiator instead of TBPPI-75-AL, the polymerization temperature was raised to 78 ° C., and The initial pressure was 33.6 bar, depending on.

After a running time of 15 hours, 541 g of rubber were isolated. The results of the analysis are shown in Table 1.

Example 4 A crosslinkable rubber compound was prepared analogously to Example 2 from the product from Example 3 (Table 3).

Example 5 The polymerization was carried out as in Example 1, except that 620 ml of 1,1,1,3,3-pentafluoropropane were used as polymerization medium instead of PFBSF and the initial amount of HFP was Was increased to 1026 g. The initial pressure was accordingly 29 bar.

After a running time of 25 hours, 518 g of rubber were isolated (Table 1).

Example 6 The fluorinated rubber from Example 5 was further processed as in Example 2 to produce a crosslinkable rubber compound, which was tested. The results are shown in Table 3.

Comparative Example 1 25.2 kg of deionized water, lithium perfluorooctyl sulfonate 30.2
g and 29.3 g of oxalic acid dihydrate were charged into a 36 liter autoclave, whereby the aqueous starting mixture had a total pH of 3. The closed autoclave was evacuated four times, each time continuously applying a nitrogen pressure of 3 bar and the contents were slowly stirred for 10 minutes. 269 g of vinylidene fluoride and 366 g of hexafluoropropene were added to the evacuated autoclave and the reaction mixture was heated to 35 ° C. with stirring. After reaching this temperature, the pressure inside the autoclave was 10.5 bar. The polymerization was initiated by the addition of 53 ml of an aqueous solution containing 20 g / l of potassium permanganate. Immediately after the first addition, the solution was metered in continuously at a rate of 39 ml / h. After 20 minutes, the polymerization started, which was evident by the start of the pressure drop. During the polymerization, vinylidene fluoride 60
The monomer mixture consisting of 40% by weight of hexafluoropropene and 40% by weight of hexafluoropropene was fed under pressure and the internal pressure of the autoclave was kept constant at 10.3 ± 0.2 bar. After 250 g of the monomer has reacted, a total of 80 ml of diethyl malonate are added to 20 ml.
It was metered in at a rate of ml / h.

Thus, a total of 4641 g of vinylidene fluoride and hexafluoropropene 3
078 g was added over a reaction time of 7.9 hours. To stop the polymerization, the addition of the permanganate compound was stopped, the unreacted monomer mixture was removed from the reactor by depressurization and vacuum treatment, and the remaining reactor contents were cooled. The latex obtained is precipitated by dropwise addition to a well-stirred receiver liquid consisting of 8000 ml of a 2% solution of CaCl ₂ and subsequently washed with deionized water and in a vacuum drying cabinet at 60 ° C. for 24 hours. Let dry. 7.5 kg of a rubber-like copolymer were isolated in this way.

The following copolymer composition was confirmed by ¹⁹ F NMR analysis: 21.4 mol% of hexafluoropropene, 78.6 mol% of vinylidene fluoride.

The number average molecular weight was 79,800 g / mol. _Mw / _Mn was 1.97 as measured by GPC inspection.

A value of 34 was confirmed for the Mooney viscosity ML _{1 + 10} at 120 ° C. (Table 2).

Comparative Example 2 The crude rubber from Comparative Example 1 was further processed in the same manner as in Example 2 to produce a crosslinkable rubber compound, which was tested. The results are shown in Table 3.

Comparative Example 3 Vi produced by emulsion polymerization and sold by Du Pont Dow Elastomers
ton A 200 ^{(R) (its} properties is that described in Table 2) was processed in the same way as in Example 2, to produce a crosslinkable rubber compounds were tested it. The results are likewise set forth in Table 3.

[0053]

[Table 2]

[0054]

[Table 3]

[0055]

[Table 4]

All examples and comparative examples have a similar VDF content (mol%), do not have chlorine, bromine or iodine end groups and also have OH end groups. Absent. Besides the vinyl end groups, the fluorinated rubbers according to the invention had exclusively H, alkyl and alkoxy end groups. Comparative Example 2 also had only H and alkyl end groups, but no vinyl end groups, while Comparative Example 1 had only carbonyl end groups. The advantages of the fluorinated rubber compounds according to the invention are evident from Table 3.

The minimum viscosities (S′min) of the vulcanized compounds of Examples 2 and 4 and 6 are much lower than those of Comparative Examples 2 and 3, respectively. In the fluorinated rubber compounds according to the invention, the crosslinking takes place more rapidly (t ₉₀ and t ₉₀ -t _s1 ), whereby the rubber compounds according to the invention have a comparable scorch resistance (t _s1 ) and a comparative compound. It has comparable or slightly better tensile / elongation properties and hot air aging properties to the compound.

[Procedure amendment]

[Submission date] March 29, 2001 (2001.3.29)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

1. A non-vinyl end groups exclusively hydrogen, alkyl and / or contains fluorine rubber having an alkoxy end groups, and comprising at least one organic polyhydroxy compound ionic crosslinker system, onium salts and at least A fluorinated rubber compound containing one type of acid acceptor.

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Claims (9)

[Claims] 1. An ionic crosslinker system comprising a fluorinated rubber having exclusively hydrogen, alkyl and / or alkoxy end groups other than vinyl end groups and comprising at least one organic polyhydroxy compound, an onium salt and at least one A fluorinated rubber compound containing one type of acid acceptor. 2. The fluorinated rubber compound according to claim 1, wherein the Mooney viscosity ML1 + 10 measured at 120 ° C. is in the range of 1 to 40. 3. The fluorinated rubber compound according to claim 1, wherein bisphenol is used as the organic polyhydroxyl compound. 4. The fluorinated rubber compound according to claim 1, wherein the organic polyhydroxyl compound is used in an amount of 0.1 to 10 phr. 5. The fluorinated rubber compound according to claim 1, wherein benzyltriphenylphosphonium chloride is used as the onium salt. 6. The fluorinated rubber compound according to claim 1, wherein CaO and / or MgO are used as the acid acceptor. 7. The method according to claim 1, wherein the material is manufactured by an injection molding or extrusion molding technique.
Use of the fluorinated rubber compound described. 8. An injection molded article produced from the fluorinated rubber compound according to claim 1. 9. Use of the fluorinated rubber compound according to claim 1 for producing all kinds of moldings.