WO2001038435A1

WO2001038435A1 - Fluoropolymer compositions containing organo-onium and blocked silylether compounds

Info

Publication number: WO2001038435A1
Application number: PCT/US2000/008155
Authority: WO
Inventors: Naiyong Jing; Brant U. Kolb; Robert E. Kolb
Original assignee: 3M Innovative Properties Company
Priority date: 1999-11-24
Filing date: 2000-03-28
Publication date: 2001-05-31

Abstract

The invention provides fluoropolymer compositions containing silylether-blocked compounds, fluorine-containing polymer, and an organo-onium compound. The invention also provides silylether-blocked compounds, articles made from said fluoropolymer compositions, and methods of making said articles.

Description

FLUOROPOLYMER COMPOSITIONS CONTAINING ORGANO-ONIUM AND BLOCKED SILYLETHER COMPOUNDS

This invention relates to curing agents for fluorocarbon elastomers, also called fluoropolymers, and to curable fluoropolymer compositions

Fluorocarbon elastomers are synthetic elastomeric polymers with a high fluorine content — see, for example, W.M. Grootaert et al., Fluorinated Elastomers, 8 KIRK-OTHMER ENCYCLOPEDIA OF CHEMICAL TECHNOLOGY 990-1005 (4th ed. 1993). Fluorocarbon elastomers, particularly the copolymers of vinylidene fluoride with other ethylenically unsaturated halogenated monomers such as hexafluoropropene (C3F5) have become the polymers of choice for high temperature applications, such as seals, gaskets, and linings. These fluoropolymers exhibit favorable properties against the exposure to aggressive environments such as solvents, lubricants, and oxidizing or reducing agents.

Additionally, these polymers can be compounded and cured to have high tensile strength, good tear resistance, and low compression set.

Presently used curing agents for fluoropolymers include aromatic polyhydroxy compounds, such as polyphenols, used in combination with certain vulcanization accelerators such as ammonium, phosphonium, or sulfonium compounds. U.S. Pat. Nos.

4,882,390 (Grootaert et al.); 4,912,171 (Grootaert et al.); and 5.086,123 (Guenthner et al.), for example, describe these compounds.

In accordance with conventional curing processes, desired amounts of compounding ingredients and other conventional adjuvants or ingredients are added to unvulcanized fluorocarbon elastomer stock and intimately admixed or compounded therewith by employing any of the usual rubber mixing devices such as Branbury mixers, roll mills, or other convenient mixing devices. The components and adjuvants are distributed throughout the fluorocarbon gum during milling, during which period the temperature of the mixture typically will not rise above about 120 °C. The curing process typically comprises either injecting (injection molding) the compounded mixture into a hot mold or pressing (compression molding) the compounded mixture in a mold, for example, a cavity or a transfer mold, followed subsequently by an oven-cure (post cure). In a another method, also known as a "two stage cure." a latent crosslinking agent is required; that is, a crosslinking agent that is dormant at the molding stage and activated only at the post-cure stage. Such a crosslinking agent is particularly desirable for use in molding products having complicated shapes. In one aspect, the present invention provides curable fluoropolymer compositions comprising the reaction product of: (a) a fluorine-containing polymer or blend of fluorine- containing polymers each comprising interpolymerized units derived from one or more fluorine-containing ethylenically unsaturated monomers; (b) one or more organo-onium compounds; (c) one or more silylether-blocked crosslinking agents; and (d) optionally one or more crosslinking agents selected from the group consisting of polyhydroxy compounds, fluorinated ether diols, carbonate-blocked compounds, and combinations thereof.

The fluoropolymer compositions of the invention are particularly suitable for those processes which require that the fluoropolymeric composition obtain a low degree of crosslinking after press cure so to provide for increased elongation and hot tear resistance in order to de-mold products having complicated shapes.

In another aspect, the invention provides a silylether-blocked compound having the formula:

wherein Z¹ is an aryl or polyaryl group; n and n' each is independently selected as 0 or 1 with the proviso that when either n or n' is 0, its corresponding portion of the Z¹ moiety is terminated by hydrogen (that is, its corresponding terminal portion is -Z-OH) or is terminated by a metal or nonmetal cation; and each R group is independently selected as a substituted or unsubstituted aryl group or alkyl groups (including linear, branched, substituted or unsubstituted) having from 2 to 20 carbon atoms. In another aspect, the invention provides a method making an article comprising the steps of: (1) forming an article from a curable fluoropolymer composition comprising a mixture of (a) fluorine-containing polymer or blend of fluorine-containing polymers each comprising interpolymerized units derived from one or more fluorine-containing ethylenically unsaturated monomers, (b) organo-onium compound, and (c) alkyl or aryl silylether-blocked compound as a crosslinking agent, and (d) optionally one or more crosslinking agents selected from the group consisting of polyhydroxy compounds, fluorinated ether diols, carbonate-blocked compounds, and combinations thereof.; and (2) curing said fluoropolymer composition. In yet another aspect, the invention provides articles made from cured fluoropolymer compositions of the invention.

The combinations of an organo-onium compound and the latent cure silylether curing agents, and optionally other crosslinking agents, of the present invention provide increased processing control in the curing of fluoropolymer compositions, and in the formation of articles derived therefrom, without adversely affecting the physical properties of those cured compositions and articles. The silylether curing agents of the present invention can be utilized to manufacture fluoropolymer parts through providing low crosslink density cured articles at the press cure stage. The silylether curing agents become activated at the post cure stage to provide fluoropolymer articles having a high crosslink density.

Among the polymers that may be compounded in accordance with this invention are generally the copolymers whose interpolymerized units are derived from one or more of the following fluoromonomers: vinylidene fluoride, vinyl fluoride, hexafluoropropene, chlorotrifluoroethylene, 2-chloropentafluoropropene, fluorinated vinyl ethers, fluorinated allyl ethers, tetrafluoroethylene, 1-hydropentafluoropropene, dichlorodifluoroethylene, trifluoroethylene, and mixtures thereof. Said fluoromonomers may also be copolymerized with other compounds such as with other cure-site monomers (for example, bromine- containing monomers or perfluorinated monomers such as perfluorobenzyl vinyl ether) or with non-fluorinated alpha-olefin co-monomers (for example, ethylene or propylene). Preferred fluoropolymers are copolymers of vinylidene fluoride and at least one terminally ethylenically-unsaturated hydrocarbon-or fluorocarbon-monomer containing at least one fluorine atom substituent on each double-bonded carbon atom, each carbon atom of said fluoromonomer being substituted only with fluorine and optionally with chlorine, hydrogen, a lower fluoroalkyl radical, or a lower fluoroalkoxy radical.

Fluoropolymer copolymers according to the type described above are available commercially as copolymer gumstock under, for example, the "THV" and "Fluorel" trademarks by Dyneon LLC of Saint Paul, MN. Suitable products of this line include THV™ 200, Fluorel™ FC-2230, FC-2145, FC-2178, and FC-2211. Other commercially available products include fluoropolymers sold under the "Viton" trademark.

The organo-onium compound which is admixed with the fluorine-containing polymer is capable of functioning as a vulcanization accelerator. As is known in the art, an organo-onium is the conjugate acid of a Lewis base (for example, phosphine, amine, ether, and sulfide) and can be formed by reacting said Lewis base with a suitable alkylating agent (for example, an alkyl halide or acyl halide) resulting in an expansion of the valence of the electron donating atom of the Lewis base and a positive charge on the organo-onium compound. Many of the organo-onium compounds useful in the present invention contain at least one heteroatom, that is, a non-carbon atom such as N, P, S, O, bonded to organic or inorganic moieties. One class of quaternary organo-onium compounds particularly useful in the present invention broadly comprises relatively positive and relatively negative ions wherein a phosphorus, arsenic, antimony, or nitrogen generally comprises the central atom of the positive ion, and the negative ion may be an organic or inorganic anion (for example, halide, sulfate, acetate, phosphate, phosphonate, hydroxide, alkoxide, phenoxide, bisphenoxide, etc.).

Many of the organo-onium compounds useful in this invention are described and known in the art. See, for example, U.S. Pat. Nos. 4,233,421 (Worm); 4,912,171 (Grootaert et al.); 5,086,123 (Guenthner et al.); and 5,262,490 (Kolb et al.).

Representative examples include the following individually listed compounds and mixtures thereof: triphenylbenzyl phosphonium chloride tributylallyl phosphonium chloride tributylbenzyl ammonium chloride tetrabutyl ammonium bromide triaryl sulfonium chloride

8-benzyl-l,8-diazabicyclo [5,4,0]-7-undecenium chloride benzyl tris(dimethylamino) phosphonium chloride benzyl(diethylamino)diphenylphosphonium chloride

Another class of organo-oniums finding utility in the practice of this invention include acid-functional oniums that are represented by Formula I below.

( I )

wherein: Q is a nitrogen, phosphorus, arsenic, or antimony;

Z² may be a substituted or unsubstituted, cyclic or acyclic alkyl group having from 4 to 20 carbon atoms that is terminated with a group of the formula - COOA where A is a hydrogen atom or is a metal cation or Z is a group of the formula CY2-COOR' where Y is a hydrogen or halogen atom, or is a substituted or unsubstituted alkyl or aryl group having from 1 to 6 carbon atoms that may optionally contain one or more catenary heteroatoms and where R' is a hydrogen atom, a metal cation, an alkyl group, or is an acyclic anhydride, for example, a group of the formula — COR where R is an alkyl group or is a group that itself contains organo-onium (that is, giving a bis organo-onium); preferably, R' is hydrogen; Z may also be a substituted, or unsubstituted, cyclic or acyclic alkyl group having from 4 to 20 carbon atoms that is terminated with a group of the formula -COOA where A is a hydrogen atom or is a metal cation;

R1, R2, and R^ are each independently an alkyl, aryl, alkenyl, or any combination thereof; each R , R2, and R^ can be substituted with chlorine, fluorine, bromine, cyano, — OR" or — COOR" where R" is a C\ to C20 alkyl, aryl, aralkyl, or alkenyl, and any pair of the Rl, R^, and R^ groups can be connected with each other and with Q to form a heterocyclic ring; one or more of the R 1 , R^, and R^ groups may also be group of the formula Z² where Z² is as defined above; X is an organic or inorganic anion (for example, halide, sulfate, acetate, phosphate, phosphonate, hydroxide, alkoxide, phenoxide, or bisphenoxide); and n is a number equal to the valence of the anion X.

Another class of useful organo-onium compounds include those having one or more pendent fluorinated alkyl groups. Generally, the most useful such fluorinated onium compounds are disclosed in U.S. Pat. No. 5,591,804 (Grootaert et al.). Representative of this useful class of onium compounds are the following:

( H )

C₇F₁₅CH₂O— (CH₂λ i—Bu

( m )

CH₂CH₂CH2CH3)₂

( IV )

Useful silylether blocked compounds used as crosslinking agents in accordance with the present invention have the formula:

( V )

wherein Z rl i :s. an aryl or polyaryl group, and is preferably a polyphenyl group of the formula:

wherein A is a difunctional aliphatic, cycloaliphatic, or aromatic radical of 1 to 13 carbon atoms, or a thio, oxy, carbonyl, or sulfonyl radical, A is optionally substituted with at least one chlorine or fluorine atom, q is 0 or 1 ; R is an aryl group, an alkyl group, or a substituted alkyl group; and n and n' each is independently selected as 0 or 1 with the proviso that when either n or «' is 0, its corresponding portion of the Z moiety is terminated by hydrogen (that is, its corresponding terminal portion is -Z-OH) or is terminated by a metal or nonmetal cation. Preferably, A is a difunctional aliphatic radical or a difunctional perfluoroaliphatic radical. Silylether-blocked compounds useful in the formulations described above wherein each depicted -R group is independently selected as a substituted or unsubstituted aryl group such as those aryl substituent groups according to Formula VI below.

( VI )

where p is a number between 1 and 4 inclusive and where R' is hydrogen, a halogen atom, or is an acyl, aryl, polyaryl (fused to or separated from the aromatic ring) or alkyl radical substituent (or any combination thereof), the latter three of which may be fluorinated but are preferably non-fluorinated and may be straight-chained, branched, cyclic. The -R' group may optionally contain one or more catenary heteroatoms, that is, a non-carbon atom such as nitrogen or oxygen. It will be understood from the above formula that the constituent -R' group can be attached in any position in the ring relative to the bond attaching it to the silylether group depicted in Formula V. Currently preferred aryl R groups for the silylether-blocked crosslinking agents of the present invention include phenyl.

Useful alkyl groups (R in the above formula V) include alkyl groups having from 2 to 20 carbon atoms. The alkyl groups may be cyclic or acyclic, linear or branched, fluorinated or non-fluorinated, may be un-substituted or may be substituted with an aryl or one or more functional groups, and may contain one or more catenary heteroatoms. Preferred alkyl and substituted alkyl groups include ethyl, propyl, isopropyl, and butyl, for example, tert.-butyl.

It will be understood that the silylether-blocked compounds may be oligomerized silylethers. The oligomerized silylethers are the reaction product of a di-chlorosilane with a polyhydroxy compound. Oligomeric silylethers, so formed, are also useful in the practice of the invention and are considered within the scope thereof. It will be further understood that the above-depicted silylether-blocked crosslinking agents may have only one silylether substituent and where more than one silylether substituent is present, that substituent may be the same or may be different in structure than the other substituent or substituents present. It will also be understood that the compositions of the invention may contain one or more silylether-blocked compounds or may contain a mixture of one or more silylether-blocked compounds and one or more other crosslinking agents.

One type of conventional crosslinking agent for a fluorocarbon elastomer gum which may be used in combination with an silylether-blocked crosslinking agent of the invention is a polyhydroxy compound. The polyhydroxy compound may be used in its free or non-salt form or as the anionic portion of the chosen organo-onium accelerator. The crosslinking agent may be any of those polyhydroxy compound known in the art to function as a crosslinking agent or co-curative for fluoropolymers, such as those polyhydroxy compounds disclosed in U.S. Pat. Nos. 3,876,654 (Pattison) and 4,233,421 (Worm). Representative aromatic polyhydroxy compounds include any one of the following: di-, tri-, and tetrahydroxybenzenes, naphthalenes, and anthracenes, and bisphenols of the following formula:

( vπ)

wherein A is a difunctional aliphatic, cycloaliphatic, or aromatic radical of 1 to 13 carbon atoms, or a thio, oxy, carbonyl, or sulfonyl radical, A is optionally substituted with at least one chlorine or fluorine atom, q is 0 or 1 , r is 1 or 2, and any aromatic ring of the polyhydroxy compound is optionally substituted with at least one atom of chlorine, fluorine, bromine, or with a carboxyl or an acyl radical (for example, -COR where R is H or a Ci to Cg alkyl, aryl, or cycloalkyl group) or alkyl radical with, for example, 1 to 8 carbon atoms. It will be understood from the above bisphenol formula that the -OH groups can be attached in any position (other than number one) in either ring. Blends of two or more of these compounds are also used. One of the most useful and commonly employed aromatic polyphenols of the above formula is 4,4'-hexafluoroisopropylidenyl bisphenol, known more commonly as bisphenol AF. The compounds 4,4'-dihydroxydiphenyl sulfone (also known as Bisphenol S) and 4,4 -isopropylidenyl bisphenol (also known as bisphenol A) are also widely used in practice.

Another class of crosslinking compounds that find utility in the practice of the invention comprise generally those with a fluorinated ether diol or a fluorinated aliphatic diol structure. Classes of fluorinated ether crosslinking agents are described, for example, by U.S. Pat. Nos. 4,810,760 and 4,894,418, both to Strepparola et al., and by U.S. Pat. Nos. 5,266,650 and 5,384,374, both to Guerra et al. This general class of crosslinking compounds include the following individual representative difunctional fluorinated ether compounds:

HOCH2-CF2OCF2CF2OCF2-CH2OH, HOCH2-CF₂O(CF₂CF2θCF2CF2θCF2θ)_nCF2-CH2θH, H2NCH2-CF₂O(CF2CF2O)_nCF2-CH2NH₂, and HOCH2-CF2CF2OCF2CF2-CH2OH.

Difunctional ether crosslinking agents may be used alone or in combination with other crosslinking agents or along with monofunctional ether compositions. One or more mono- or difunctional fluorinated ether salts, including salts of the above-depicted representative compounds may also be employed, fluorinated ether salts possessing an added advantage of easy incorporation into a fluoropolymer gum.

Another class of useful crosslinking agents for use in the compositions of the invention are the carbonate-blocked compounds described in U.S. Pat. No. 5,728,773 (Jing et al).

Fluoroahphatic sulfonamides can also be added to the compositions of the invention, including those of the formula RfSO2NHR", where R" is an alkyl radical having, for example, from 1 to 20 carbon atoms, preferably from 1 to 12 carbon atoms, Rf is a fluoroaliphatic radical such as a perfluoroalkyl, for example, C_nF2_n+l where n is 1 to

20, or perfluorocycloalkyl, for example, C_nF2_n-l where n is 3 to 20, such compounds being described, for example, in U.S. Pat. No. 5,086,123 (Guenther et al.). The fluoroahphatic sulfonamide is preferably a perfluoroalkylsulfonamide and may be added as a separate compound, or as the anion of the organo-onium compound.

Fillers can be mixed with the fluoropolymer gum to improve molding characteristics and other properties. When a filler is employed, it can be added to the vulcanization recipe in amounts of up to 100 parts per hundred parts by weight of gum, preferably between 15 to 50 parts per hundred parts by weight of the gum. Examples of fillers which may be used are reinforcing thermal or furnace grade carbon blacks or non- black pigments of relatively low reinforcement characteristics such as clays and barytes. The cure accelerators and crosslinking agent or agents can be added to the uncured polymer gum in the form of finely divided solids or as solutions in alcohol or ketone solvents by mixing the materials into the polymer gum stock. Thus mixed, the gum stock can generally be stored at room temperature for extended periods of time.

Prior to curing, an acid acceptor is mixed into the gum stock, after which storage life of the stock is more limited. Acid acceptors can be inorganic or blends of inorganic and organic. Examples of inorganic acceptors include magnesium oxide, lead oxide, calcium oxide, calcium hydroxide, dibasic lead phosphite, zinc oxide, barium carbonate, strontium hydroxide, calcium carbonate, etc. Organic acceptors include epoxies, sodium stearate, and magnesium oxalate. The preferred acid acceptors are magnesium oxide and calcium hydroxide. The acid acceptors can be used singly or in combination, and preferably are used in amounts ranging from about 2 to 25 parts per 100 parts by weight of the polymer gum stock. All of the components of the curing system may be admixed prior to their incorporation into the polymer gum stock without departing from the scope of the invention.

The relative amounts of the crosslinking agent or agents (that is, the chosen total amount of aryl, or alkyl silylether along with conventional crosslinking agents, if any) and onium salt are present in the composition in such amounts as to provide the desired cure and/or mold release of the composition when mixed with acid acceptor. Representative proportions of components of the curing system are as follows: Acid acceptor: 0.5 to 40 phr Onium salt : 0.2 to 5 mmhr

Crosslinker : 0.3 to 12 mmhr All amounts are given in parts per 100 parts polymer gum stock (abbreviated "phr") or in millimoles per hundred parts polymer gum stock (abbreviated "mmhr"). It will be understood that these proportions are general ranges; the particular amount for each particular cure time and temperature will be apparent to one of ordinary skill in the art. In accordance with this invention, the desired amounts of compounding ingredients and other conventional adjuvants or ingredients are added to the unvulcanized fluorocarbon gum stock and intimately admixed or compounded therewith by employing any of the usual rubber mixing devices such as internal mixers, (for example, Banbury mixers), roll mills, or any other convenient mixing device. For best results, the temperature of the mixture on the mill typically should not rise above about 120 °C.

During milling, it is preferable to distribute the components and adjuvants uniformly throughout the gum for effective cure.

The mixture is then processed and shaped, for example, by extrusion (for example, in the shape of a hose or hose lining) or molding (for example, in the form of an O-ring seal). The shaped article can then be heated to cure the gum composition and form a cured elastomer article.

Pressing of the compounded mixture (that is, press cure) is usually conducted at a temperature between about 95 °C and about 230 °C, preferably between about 150 °C and about 205 °C, for a period of from 1 minute to 15 hours, typically from 5 minutes to 30 minutes. A pressure of between about 700 kPa and about 20,600 kPa is usually imposed on the compounded mixture in the mold. The molds first may be coated with a release agent and prebaked. The molded vulcanizate is then usually post-cured (for example, oven-cured) at a temperature usually between about 150 °C and about 275 °C, typically at about 232 °C, for a period of from about 2 hours to 50 hours or more depending on the cross-sectional thickness of the article. For thick sections, the temperature during the post cure is usually raised gradually from the lower limit of the range to the desired maximum temperature. The maximum temperature used is preferably about 260 °C, and is held at this value for about 4 hours or more. The compositions of this invention can be used to form seals, O-rings, gaskets, etc. EXAMPLES

All of the reagents used in the examples below are available from Aldrich Chemicals, Milwaukee, WI, unless otherwise indicated.

Test Methods

In the following examples, indicated results were obtained using the following test methods:

Cure Rheology Tests were run on uncured, compounded admixture using a Monsanto Moving Die Rheometer (MDR) Model 2000 in accordance with ASTM D 5289- 93a at 150 °C, 177 °C, and 200 °C, no preheat, for the indicated time (60, 12, or 6 minutes), and a 0.5° arc. Minimum torque (M^) and Maximum torque (Mff), that is, highest torque attained during specified period of time when no plateau or maximum torque is obtained, were reported. Also reported were TS2 (time for torque to increase 2 units above M^, T50 [time for torque to reach M^ + 0.5(M -M^)], and T90 [time for torque to reach M^ + 0.9(M -M^)]).

Tensile Strength at Break, Elongation at Break, and Modulus at 100 percent

Elongation were determined using ASTM D 412-92^ε on samples cut from the press-cure or post-cure sheet with ASTM Die D. Units reported in Mega Pascals (M Pa).

Compression set determined by ASTM 395-89 Method B with 0.139 in. (3.5 mm.) After post-curing, the O-rings were compressed for 70 hours at 200 °C. Results are reported as percent.

Example 1 (Silylether A)

Synthesis of triethylsilylether of bisphenol AF Triethylsilyl chloride (17.0 grams, 0.11 mol) was slowly added to a solution of

Bisphenol-AF (17.0 grams, 0.05 mol) in pyridine (80 mL), with stirring, producing a mildly exothermic reaction. Subsequent to the addition of the triethylsilyl chloride, the reaction mixture was stirred overnight at 35 °C. The reaction solution was poured into ice- water (150 mL), and extracted with methylene chloride (1X100 mL). The methylene chloride phase separated, washed with 0.1N HC1 (IX 100 mL), water (2 X 100 mL), and dried over MgSO4 for approximately 2 to 3 hours. Removal of the methylene chloride on a rotary evaporator produced a white semi-solid that was dried under vacuum to produce

27.5 grams (97 % yield) of the indicated product. ^}HNMR(400 MHz, CDC1 ), 7,21(d, J =

36 Hz, 4 H), 6.80(d, J = 36 Hz, 4 H), 0.82 (t, J = 28 Hz, 18 H), 0.4 ppm (q, J = 28 Hz, 12 H). FNMR (376 MHz, CDC13), -64.63 ppm(s, 6F).

Example 2 (Silylether B)

Synthesis of trimethylsilylether of bisphenol AF The trimethylsilylether of bisphenol AF was prepared substantially according to the procedure described in Example 1 except that chlorotrimethylsilane (12.0 grams, 0.11 mol) was substituted for triethylsilyl chloride. The indicated product was obtained as a white solid (22.8 grams (95 %). HNMR (400 MHz, CDCI3), 7.23(d, J = 36 Hz, 4 H), 6.80(d, J =

36 Hz, 4H), 0.24 (s, 18 H). FNMR (376 MHz, CDCI3), -64.88 ppm (s, 6F).

Example 3 (Silylether C)

Synthesis of t-butyldimethylsilylether of bisphenol AF The t-butyldimethylsilylether of bisphenol AF was prepared substantially according to the procedure described in Example 1 except that triethylamine (14 mL) was added to the reaction mixture and chloro-t-butyldimethylsilane (16.6 grams, 0.11 mol) was substituted for triethylsilyl chloride. The indicated product was obtained as a white solid

(28.6 grams) (90 %). HNMR (400 MHz, CDCI3), 7.22(d, J = 36 Hz, 4 H), 6.79(d. J = 36

Hz, 4 H), 1.0 (s, 18 H), 0.21(s, 12 H). FNMR (376 MHz, CDCI3), -64.65 ppm(s, 6F).

Example 4 (Silylether D) Synthesis of bis-triphenylsilyether of Bisphenol AF

Chlorotriphenylsilane (12.37 grams, 41.92 mmole) and dichloroethane (24 grams) were charged into a reaction flask under a dry nitrogen blanket. A solution of Bisphenol AF (7.01 grams, 20.96 mmole) and 2,4,6-collidine (5.11 grams, 41.92 mmole) in dichloroethane (25 grams) were subsequently added to the flask with stirring, over a period of approximately 40 min, producing a mild exotherm (to 32 °C). The reaction was stirred overnight at ambient temperature, the solids removed by filtration, and the solvent removed on a rotary evaporator. Dichlorethane (50 grams) was added to the resulting semisolid residue, the resulting solution washed with water (2 X 30 mL), 0.25M HC1 (2 X 30 mL) and water (2 X 30 mL). The dichloethane solution was dried over MgSO4 and the solvent removed on a rotary evaporator, producing the indicated product (15.24 grams

(85.47 % yield). ²HNMR (400 MHz, CDCI3) 7.65 (d-d, J=8 Hz, J=1.46 Hz 13.7 H), 7.5-

7.3 (m, 20.5 H), 7.09 (d, 4 H), 6.8 (d, 4 H). ¹⁹FNMR (376 MHz, CDCI3), -64.72 (s, 6 F).

Example 5 (Silylether E) Synthesis of oligomers of diphenylsilylether of bisphenol AF

Dichlorodiphenyl silane (6.83 grams) and dichloroethane (20 grams) were charged to a reaction flask. A solution of Bisphenol AF (10.05 grams) and 2,4,6-collidine (6.52 grams) in dichloroethane (40 grams) was added to the reaction mixture, with stirring, over a period of approximately 1.5 h and the resulting mixture stirred overnight at ambient temperature. The white precipitate that formed during the reaction was removed by filtration and the filtrate washed with water (2X 30 mL), 0.25M HC1 (2X 30 mL), water (2X 30 mL) and then dried over MgSO4. The solvent was removed under vacuum producing a white solid. 1HNMR (400 MHz, CDCI3), 7.9-6.8 (several multiplets, 8 H).

!9FNMR (376 MHz, CDCI3) -64.72 (broad, 6 F).

Example 6 (Silylether F)

Synthesis of bis-dimethlvoctylsilylether of BISPHENOL AF Chlorodimethyloctylsilane (8.05 grams, 38.68 mmole) and dichloroethane (20 grams) were charged to a reaction flask under a dry nitrogen atmosphere. A solution of Bisphenol AF (6.47 grams, 19.34 mmole) and triethylamine (3.92 grams, 38.68 mmole) in dichloroethane (37 grams) was added to the reaction mixture, with stirring, over a period of 2 hours, during which time an exotherm to 30 °C was observed and a white precipitate formed. The mixture was stirred at ambient temperature overnight, the solids removed by filtration, and hexane (100 grams) added to the filtrate. The resulting solution was washed with water (2 X 200 mL), 0.25 M HCl (4 X 200 mL), and water (4 X 100 mL), after which it was dried over MgSO4 and the solvent removed on a rotary evaporator, producing the indicated product 10.56 grams (80.9 % yield). iHNMR (400 MHz, CDC1₃), 7.25 (d, 4 H),

6.8 (d. 4 H), 1.4-1.2 (m, 27.4 H), 0.9 (t, 7.4 H), 0.85 (t, 4 H), 0.25 (s, 12 H). ¹⁹FNMR (376 MHz, CDCI3) -64.7 (s, 6 F).

Example 7 (Silylether G)

Synthesis of bis-triisopropylsilylether of Bisphenol AF Triispropylchlorosilane (97 % purity, 10.09 grams, 50.8 mmole) and dichloroethane (20.23 grams) were charged to a reaction flask. A solution of Bisphenol

AF (8.04 grams, 24.13 mmole) and triethylamine (5.95 grams, 48.26 mmole) in dichloroethane (30 grams) was added to the reaction mixture, with stirring, over a period of 15 minutes, producing a mild exotherm to 35 °C and formation of a white precipitate. The mixture was stirred at ambient temperature for 62 hours, the precipitate removed by filtration and hexane (100 grams) added to the filtrate. The resulting solution was washed with water (100 mL), 0.25 M HCl (100 mL), water (lOOmL), and then dried over MgSO4_

The solvent was removed under vacuum to give the product in the form of a viscous oil

(12.54 grams, 80.5 % yield). ^NMR (500 MHz, CDCI3), 7.22 (d, J=8.79 Hz, 4 H), 6.68

(d, J=9.03 Hz, 4 H), 1.22 (septet, J=8 Hz, 6 H), 1.10 ppm (d, J=7.5 Hz, 38 H); ¹⁹FNMR - 64.70 ppm (s, 6 F).

Onium Catalysts

Onium A is tributyl(2-methoxy)propylphosphonium chloride prepared as described in U.S. Pat. No. 4,882,390 (Grootaert et al.).

Fluoropolymer Gum Type

Commercially available fluoropolymer gums were compounded with the compounds described above and various other ingredients as indicated in Table 1 and cured at 177 °C for 60 minutes. The cure rheology, determined according to ASTM 5289- 93a and physical properties of the cured composition are reported in Table 2. Gum A was a copolymer which, except as otherwise indicated, has a Mooney Viscosity of 38 and nominal weight percents of interpolymerized units derived from 60 weight percent vinylidene fluoride and 40 weight percent hexafluoropropene. Some additives, such as curatives for example, are listed in quantities of millimoles per hundred parts of gum (mmhr). Other additives are listed in grams. Percentages are in weight percent unless otherwise specified.

Examples 8-16

The compositions of Examples 8-16 and Comparative Examples 1 and 2 are shown below in Table 1.

TABLE 1

The rheology data in Table 2 shows the cure kinetics and physical properties for the compositions in Table 1.

TABLE 2

Various modifications and alterations of this invention will become apparent to those skilled in the art without departing from the scope and spirit of the present invention, and it should be understood that this invention is not to be unduly limited to the illustrative embodiments set forth hereinabove.

Claims

What is Claimed is:

1. A curable fluoropolymer composition comprising a mixture of:

(a) fluorine-containing polymer or blend of fluorine-containing polymers each comprising interpolymerized units derived from one or more fluorine- containing ethylenically unsaturated monomers;

(b) organo-onium compound;

(c) alkyl or aryl silylether-blocked compound as a crosslinking agent; and (d) optionally one or more crosslinking agents selected from the group consisting of polyhydroxy compounds, fluorinated ether diols, carbonate-blocked compounds, and combinations thereof.

2. A curable fluoropolymer composition according to claim 1 wherein the organo-onium compound is selected from the group consisting of sulfonium, phosphonium, ammonium, and combinations thereof.

3. A curable fluoropolymer composition according to claim 1 wherein the fluorine-containing polymer comprises a copolymer of vinylidine fluoride and at least one terminally ethylenically-unsaturated hydrocarbon- or fluorocarbon-monomer other than vinylidine fluoride.

4. A curable fluoropolymer composition according to claim 1 wherein one or more of the fluorine-containing polymers comprise a copolymer of vinylidine fluoride and hexafluoropropene.

5. A curable fluoropolymer composition according to claim 1 wherein one or more of the fluorine-containing polymers comprise a terpolymer of vinylidine fluoride, hexafluoropropene, and tetrafluoroethylene.

6. A curable fluoropolymer composition according to claim 1 wherein said silyl ether-blocked compound is an oligomer.

7. A curable fluoropolymer composition according to claim 1 wherein one or more of the fluorine-containing polymers comprise either a copolymer of vinylidine fluoride and hexafluoropropene or a terpolymer of vinylidine fluoride, hexafluoropropene, and tetrafluoroethylene and said organo-onium compound is selected from the group consisting of tributyl(2-methoxy)propylphosphonium chloride, carboxyethyltributylphosphonium chloride, and combinations thereof.

8. A curable fluoropolymer composition according to claim 1 wherein said silyl ether-blocked compound has the formula:

wherein Z¹ is an aryl or polyaryl; each R group is independently selected as a substituted or unsubstituted aryl group or an alkyl groups having from 2 to 20 carbon atoms; and n and n' are independently 0 or 1.

9. A curable fluoropolymer composition according to claim 8 wherein each R group is independently ethyl, propyl, isopropyl, butyl, t-butyl, or a combination thereof.

10. A composition of matter comprising a silyl ether-blocked compound having the formula:

wherein Z is an aryl or polyaryl group; each R group is independently selected as a substituted or unsubstituted aryl group or an alkyl groups having from 2 to 20 carbon atoms; and n and n' are independently 0 or 1.

11. A composition of matter according the claim 10 wherein Z is a polyphenyl group having the formula:

wherein:

A is a difunctional aliphatic, cycloaliphatic, or aromatic radical of 1 to 13 carbon atoms, or a thio, oxy, carbonyl, or sulfonyl radical, A is optionally substituted with at least one chlorine or fluorine atom, and q is 0 or 1.

12. A composition of matter according the claim 11 wherein A is a difunctional aliphatic radical.

13. A composition of matter according to claim 12 wherein each R is independently phenyl, substituted phenyl, or an alkyl or substituted alkyl group having from 2 to 20 carbon atoms.

14. A composition of matter according to claim 12 wherein said difunctional aliphatic radical is substituted with at least one fluorine atom.

15. A composition of matter according to claim 13 wherein said alkyl or substituted alkyl group is methyl, ethyl, propyl, isopropyl, t-butyl, or butyl.

16. A composition of matter comprising a silyl ether-blocked compound having the formula:

wherein Z¹ is an aryl or polyaryl group;

R is a methyl group, a methyl group, and a tert-butyl group; and n and n' are independently 0 or 1.

17. A composition of matter according to claim 16 wherein Z¹ is a polyphenyl group having the formula:

wherein:

18. A composition of matter according to claim 17 wherein A is a difunctional aliphatic radical.

19. A composition of matter according to claim 17 wherein said difunctional aliphatic radical is substituted with at least one fluorine atom.

20. An article comprising a shaped article comprising a cured composition comprising the reaction product of the curable fluoropolymer composition of claim 1.

21. A method of making an article comprising the steps of:

(1) forming an article from a curable fluoropolymer composition of claim 1 ; and

(2) curing said fluoropolymer composition.

22. The method of claim 22 wherein the curable fluoropolymer composition is cured by heating said composition at a temperature of about 150 to about 275 °C for a sufficient time to crosslink said fluoropolymer.

23. A method of curing a fluoropolymer composition comprising the steps of: (1) providing a curable fluoropolymer composition of claim 1; and (2) heating the curable fluoropolymer composition at a temperature of about 150 to about 275 °C for a sufficient time to crosslink said fluoropolymer.