WO1994006837A1

WO1994006837A1 - Fluorochemical polymer systems

Info

Publication number: WO1994006837A1
Application number: PCT/US1993/008746
Authority: WO
Inventors: Yvan A. Bogaert; Robert R. Smolders
Original assignee: Minnesota Mining And Manufacturing Company
Priority date: 1992-09-18
Filing date: 1993-09-16
Publication date: 1994-03-31
Also published as: JPH08501585A; EP0660849A1

Abstract

The invention relates to compositions comprising fluorocarbon elastomers and non-fluorinated acrylate or vinyl polymers, combined in a dispersion or suspension polymerization using a special stabilizer to make the polymers compatible. Coatings made with the composition of the invention are clear and have the inherent advantages of the fluorocarbon elastomers as well as good adhesion to many substrates.

Description

FLUOROCHEMICAL POLYMER SYSTEMS

Field of the Invention

The present invention relates to compatible polymeric systems comprising fluorocarbon elastomers and non-fluorinated vinyl polymers, a method of making the compatible systems, and materials such as films, sealants, membranes, and adhesives made therefrom.

Background of the Invention

Fluoropolymers which include fluoroelastomers and plastics are known in the art. Fluoropolymers exhibit high temperature performance, good weatherability, solvent resistance, and acid resistance. Fluoropolymers can be effectively used as surface modifiers of various polymeric substrates because they bloom to the surface giving a low energy surface (i.e., oil and water repellant surface which is useful for low adhesion backsizes in tapes). Fluoropolymers are incompatible with most other polymers, resulting in cloudy or hazy coatings upon blending, which is not acceptable in many applications. Another disadvantage is that fluoropolymers exhibit low wettability and poor adhesion to many substrates.

A need thus exists for a fluoropolymer containing composition having the advantages inherent to fluoropolymers but which also yield clear coatings and which possess good adhesion to many substrates. We have found such a composition.

Brief Description of the Invention The composition of the invention comprises a dispersion comprising the reaction product of:

(A) about 10 to about 80 parts by weight of a combination of components comprising:

(i) about 90 to about 10 percent by weight fluorocarbon elastomer; and

(ii) about 10 to about 90 percent by weight of a monomer charge wherein the monomer charge comprises about 50 to about 100 percent by weight of (meth)acrylic acid ester monomers(s) comprising about C_j to about C_jg alcohol esters of (meth)acrylic acid and about 0 to about 50 percent by weight ethylenically unsaturated monomer selected from the group consisting of acrylic acid, acrylonitrile, vinyl acetate, N-vinylpyrrolidone, methacryloyloxy propyltrimethoxy silane, and mixtures thereof; wherein the weight percentages of (i) and (ii) are based upon the total weight of (A);

(B) about 2 to about 20 percent by weight of a stabilizer based upon the weight of (A) wherein the stabilizer is selected from the group consisting of:

(i) a homopolymer having a weight average molecular weight ranging from about 20,000 to about 200,000 comprising amide containing monomers;

(ii) a copolymer having a weight average molecular weight ranging from about 20,000 to about 200,000, wherein the copolymer comprises: (a) about 10 to about 90 parts by weight of monomer selected from the group consisting of amide-containing monomers and mixtures thereof; and

(b) about 90 to about 10 parts by weight of monomer selected from the group consisting of vinyl esters, alkyl acrylates, alkyl methacrylates, and mixtures thereof;

(iii) a homopolymer macromonomer having a weight average molecular weight ranging from about 3,000 to about 80,000, wherein the homopolymer macromonomer comprises:

(a) amide-containing monomer; and (b) a vinyl-reactive endcapping agent selected from the group consisting of isocyanatoethyl methacrylate, alpha,alpha-dimethyl-meta-isopropenyl benzylisocyanate, parachloromethylstyrene, glycidyl methacrylate, vinyl azlactone, and mixtures thereof; (iv) a copolymer macromonomer having a weight average molecular weight ranging from about 3,000 to about 80,000, wherein the copolymer macromonomer comprises:

(a) about 10 to about 90 parts by weight of monomer selected from the group consisting of amide-containing monomers and mixtures thereof; (b) about 90 to about 10 parts by weight of monomer selected from the group consisting of vinyl esters, alkyl acrylates, alkyl methacrylates, and mixtures thereof; and

(c) a vinyl-reactive endcapping agent selected from the group consisting of isocyanatoethyl methacrylate, alpha.alpha-dimethyl-meta-isopropenyl benzylisocyanate, parachloromethylstyrene, glycidyl methacrylate, vinyl azlactone, and mixtures thereof; wherein the sum of (iv)(a) plus (iv)(b) equals 100 parts by weight total; and

(v) mixtures thereof; (C) about 20 to about 90 parts by weight of a solvent capable of dissolving the fluoroelastomer, the (meth)acrylic acid ester monomer(s), the optional ethylenically unsaturated monomer and the stabilizer; and (D) about 0.01 to about 0.5 percent by weight of an initiator, wherein the weight percent of the initiator is based upon the total weight of the (meth)acrylic acid ester monomer and the ethylenically unsaturated monomer(s), if used, in the combination of components (A); wherein the weight of (A) plus (C) equals 100 parts by weight total.

The invention also provides the composition comprising the reaction product of the monomers, fluorocarbon elastomer, stabilizer and initiator.

The invention also provides powders and polymer beads comprising the reaction product.

The invention also provides films prepared from the compositions of the invention.

Detailed Description of the Invention

Fluorocarbon Elastomers

The term "fluoroelastomer" as used herein refers to fluorinated elastomers. Fluorinated elastomers are a class of synthetic elastomers that are designed for demanding service applications in environments where combinations of extreme temperature ranges, chemicals, fluids, and/or fuels exist. The three basic fluorinated elastomer types are fluorocarbons, fluorosilicones, and fluoroalkoxy phosphazines. This invention involves the use of fluorocarbon elastomers.

Fluorocarbon elastomers are based primarily on vinylidene fluoride (CH₂=CF₂) and hexafluoropropylene (C₃F₆). The Fluorel™ Brand fluorocarbon elastomers, which are useful in the present invention (available from 3M Company) are produced using approximately a 4 to 1 (vinylidene fluoride to hexafluoropropylene) ratio of the monomers. The VITON™ fluorocarbon elastomers, which are also useful according to the present invention, (available from duPont) are available in similar composition or with increased fluorine content via use of tetrafluoroethylene (C2F ) for improved fluid resistance or with perfluoromethylvinyl ether (C2F4OCF3) for better low temperature properties. The raw fluorocarbon elastomers have a density of 1.80 to 1.86 g/cm³. The Kirk-Othmer Encyclopedia of Chemical Technology. Vol. 8, pp. 500-515, Table 1, 3rd Edition, John Wiley & Sons, 1981), lists examples of useful commercially available fluorocarbon elastomers which include those selected from the group consisting of poly(vinylidene fluoride-co-hexafluoropropylene) available under the tradenames Fluorel from 3M, Viton A from duPont, Tecnoflon from Montedison, and Dai-El from

Daikin ; poly (vinylidene fluoride-co-hexafluoropropylene-co-tetrafluorethylene) available under the tradenames Viton B from duPont, and Dai-El G-501 from Daikin; poly(vinylidene fluoride-co-hexafluoropropylene-co-tetrafluorethylene) plus cure site monomer available under the tradename Viton G (peroxide curable) from duPont; poly(vinylidene fluoride-co-tertrafluoroethylene-co- perfluoromethyl vinyl ether) plus cure site monomer available under the tradename Viton GLT (peroxide curable) from duPont; poly(tetrafluoroethylene- co-perfluoromethyl vinyl ether) plus cure site monomer available under the trade name Kalrez from duPont; poly(tetrafluoroethylene-co-propylene) available under the trade name Aflas 100 and 150 from Asahi; poly(vinylidene fluoride-co-chlorotrifluoroethylene) available under the trade name Kel-F 3700 from 3M; poly(vinylidene fluoride-co-1-hydropentafluoropropylene) available under the trade name Tecnoflon SL from Montedison; and poly(vinylidene fluoride-co- 1 -hydropentafluoropropylene-co-tetrafluoroethylene) available under the trade name Tecnoflon T from Montedison.

The following U.S. Patents describe useful fluorocarbon elastomers for the purpose of this invention: U.S. Patent No. 3,051,677 (assigned to E.I. duPont de Nemours & Co., Inc.); U.S. Patent No. 2,968,649 (assigned to E.I. duPont de Nemours & Co., Inc.); U.S. Patent No. 3,331,823 (assigned to Montedison); U.S. Patent Nσ.3,335,106 (assigned to Montedison); U.S. Patent No. 3,712,877 (assigned to 3M); U.S. Patent No. 4,866,118 (assigned to 3M); and U.S. Patent No. 4,956,419 (assigned to 3M).

Preferably, the fluorocarbon elastomers used according to the invention comprise monomers selected from the group consisting of vinylidene fluoride, hexafluoropropylene, tetrafluoroethylene, chlorotrifluoroethylene, 2-chloropentafluoropropene, pentafluoropropene, dichlorodifluoroethylene, trifluoroethylene, 1 , 1-chlorofluoroethylene, l-bromo-2,2-difluoroethylene, perfluoromethylvinyl ether and mixtures thereof, and optionally, in addition, fluoromonomer cure site monomers such as those selected from the group consisting of 3-iodoperfluoropropene, 4-iodoperfluoropentene, bromotrifluoroethylene, bromodifluoroethylene and mixtures thereof, for reasons of commercial availability.

The most preferred fluorocarbon elastomer comprises vinylidene fluoride-hexafluoropropylene copolymer having a Mooney viscosity of about 10 to about 120, preferably about 37. The fluorocarbon elastomers selected preferably have a weight average molecular weight between about 15,000 and about 120,000, most preferably about 25,000 to about 80,000, calculated from the corresponding Mooney viscosity.

(Meth. Acrylic Acid Ester Monomer

Useful (meth)acrylic acid ester monomers include monofunctional ethylenically-unsaturated esters of (meth)acrylic acid and/or substituted (meth)acrylic acid and alcohols comprising about 1 to about 18 carbon atoms, preferably about 1 to about 8 carbon atoms. Useful monomers include but are not limited to those selected from the group consisting of methyl acrylate, butyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, 2-methylbutyl methacrylate, isooctyl acrylate, dimethylaminoethyl methacrylate, butyl methacrylate, 2-ethylhexyl acrylate, hydroxyethyl acrylate, glycidyl methacrylate, tetrahydrofurfuryl acrylate, and mixtures thereof.

Preferred (meth)acrylic acid ester monomers include those selected from the group consisting of isooctyl acrylate, methyl methacrylate, methyl acrylate, ethyl acrylate, 2-methyl butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, and mixtures thereof.

Most preferred (meth)acrylic acid ester monomers include those selected from the group consisting of isooctyl acrylate, methyl methacrylate, and mixtures thereof.

Optional Ethylenicallv-Unsaturated Monomers

The composition of the invention may optionally further comprise other ethylenically-unsaturated monomers in admixture with the above-noted (meth)acrylic acid ester monomers. These additional monomers include those selected from the group consisting of acrylic acid, acrylonitrile, vinyl acetate, N-vinylpyrrolidone, methacryloyloxy propyltrimethoxy silane, and mixtures thereof.

The monomer acrylonitrile is a particularly useful monomer to include. It increases stability due to the strong interaction with the stabilizer and helps provide a more homogeneous coating. Acrylonitrile must be included as a comonomer when a long-chain (meth)acrylic acid ester monomer is used (i.e., greater than about 6 carbon atoms in the chain).

The amount of optional ethylenically unsaturated monomer added depends on the (meth)acrylic acid ester monomer(s) and optional ethylenically unsaturated monomers selected. If ethylenically unsaturated monomer is used, the dispersion typically comprises about 0.1 to about 50 percent of ethylenically unsaturated monomer, preferably if added about 20 to about 40 percent, most preferably if added about 25 to about 30 percent, based upon the total weight of (meth)acrylic acid ester and ethylenically unsaturated monomer. The monomer is used in an amount which will give or maintain a stable dispersion if solution or suspension polymerization is employed.

Stabilizer A third component of the present invention is a stabilizer for the dispersion. The stabilizer can take on a number of forms, all of which are characterized as homopolymers or copolymers comprising at least one amide-containing monomer. Suitable amide-containing monomers include but are not limited to those selected from the group consisting of N-vinylpyrrolidone, N-vinylcaprolactam, acrylamide, N,N-dimethylacrylamide, and mixtures thereof. Preferably, the amide-containing monomer is selected from the group consisting of N-vinylpyrrolidone, acrylamide, and mixtures thereof.

Suitable ethylenically-unsaturated co-monomers from which copolymeric stabilizers are obtained via copolymerization with amide containing monomers include but are not limited to those selected from the group consisting of vinyl esters of C to Cg monocarboxylic acids and C_j to C_jg aliphatic alcohol esters of (meth)acrylic acid, and mixtures thereof. Preferred co-monomers are selected from the group consisting of vinyl acetate, vinyl propionate, methyl acrylate, methyl methacrylate, and mixtures thereof.

Homopolymeric stabilizers comprise homopolymers having a weight average molecular weight of from about 20,000 to about 200,000, as determined by GPC using polystyrene standards.

Copolymeric stabilizers comprise copolymers of amide-containing monomer(s) and ethylenically-unsaturated co-monomer(s) wherein the copolymer has a weight average molecular weight of from about 20,000 to about 200,000. The copolymer comprises from about 10 to about 90 parts by weight of the amide-containing monomer(s) and from about 90 to about 10 parts by weight of the ethylenically-unsaturated co-monomer(s) based upon 100 parts by weight total of the monomer. Preferably, the copolymer comprises from about 40 to about 60 parts by weight of the amide-containing monomer(s) and from about 60 to about 40 parts by weight of the ethylenically-unsaturated co-monomer(s).

The homopolymeric or copolymeric stabilizer may be reacted with a vinyl-reactive endcapping agent to form a macromonomer, the endcapping agent being selected from the group consisting of isocyanatoethyl methacrylate (IEM), alpha, alpha-dimethyl-meta-isopropenyl benzylisocyanate (TMI), parachlorodimethylstyrene, glycidyl methacrylate, vinyl azlactone, and mixtures thereof. Preferably, the endcapping agent is selected from the group consisting of IEM and TMI. Endcapping introduces ethylenically-unsaturated, free-radically polymerizable functional groups into the homopolymer or copolymer stabilizer such that the end-capped macromonomer can be copolymerized with the (meth)acrylic acid ester monomer(s) and optional ethylenically unsaturated monomer of the present invention.

Preferably, the stabilizer comprises a vinyl acetate N-vinylpyrrolidone copolymer endcapped with isocyanatoethyl methacrylate due to its ease of synthesis and the facility with which it is copolymerized with the (meth)acrylic acid ester monomer(s) and optional ethylenically unsaturated monomers. The weight average molecular weight range of the macromenstabilizer is from about 3,000 to about 80,000, preferably about 10,000 to about 70,000. If the molecular weight is too high, the dispersion is too viscous to coat. If the molecular weight is too low, the dispersion is not stable. The stabilizer is an essential part of the formulation of the present invention. The stabilizer is typically present at from about 2 percent to about 20 percent, preferably from about 4 percent to about 8 percent, based on the total weight of the (meth)acrylic acid ester monomer(s) plus fluorocarbon elastomer plus optional ethylenically unsaturated monomers. The copolymer stabilizer can be prepared by combining the desired monomers, initiator (such as those discussed below), a conventional chain transfer agent such as those selected from the group consisting of mercaptans, alcohols, and carbon tetrabromide. Examples of specific chain transfer agents include those selected from the group consisting of mercaptoethanol, mercapto acetic acid, isooctyl thioglycolate, and carbon tetrabromide, and a conventional organic solvent such as ethyl acetate (and/or those discussed below) in a reaction vessel. Typically about 20 to about 50 parts by weight of monomer is used. Typically about 0.5 to about 5 percent of chain transfer agent is used based on the weight of the monomer charge. Typically about 80 to about 50 parts by weight of solvent is used. Polymerization is conducted under inert atmospheric conditions, with agitation, for about 10 to 24 hours.

A macromonomer stabilizer can be prepared by reacting the copolymer with end-capping agent in the presence of a catalytic amount of a catalyst such as those selected from the group consisting of dibutyl tin dilaurate (DBTL) and tin octoate. Preferably about 0.03 to about 0.15 percent of catalyst is used based on the monomer charge. Also about 0.01 to about 0.1 percent of a conventional antioxidant such as Irganox™ 1010 antioxidant (available from Ciba-Geigy) based on the monomer charge is included. The reaction preferably is conducted under inert atmospheric conditions with agitation for about 1 to about 5 hours.

Initiators

Examples of useful free-radical initiators according to the present invention are detailed in Chapters 20 and 21 of Macromolecules. Vol.2, 2nd Ed., H. G. Elias, Plenum Press, 1984, New York. Useful thermal initiators for use in the present invention include, but are not limited to, the following: azo compounds such as 2,2'-azobis-(isobutyronitrile), dimethyl-2,-2'- azo-bis-isobuytrate, azo-bis-(diphenyl methane), 4,4'-azo-bis-(4-cyanopentanoic acid); peroxides such as benzoyl peroxide, cumyl peroxide, tert-butyl peroxide, cyclohexanone peroxide, glutaric acid peroxide, lauroyl peroxide, methyl ethyl ketone peroxide and hydrogen peroxide; hydroperoxides such as tert-butyl hydroperoxide and cumene hydroperoxide; peracids such as peracetic acid and perbenzoic acid; potassium persulfate; and peresters such as diisopropyl percarbonate. Certain of these initiators (in particular the peroxides, hydroperoxides, peracids, and peresters) can be induced to decompose by addition of a suitable catalyst rather than thermally. This redox method of initiation is described in Elias. Chapter 20.

, It is theorized that photochemical initiators would also be useful in the compositions of the present invention. Examples of photochemical initiators include but are not limited to those selected from the group consisting of benzoin ethers such as diethoxyacetophenone, oximino-ketones, acylphosphine oxides, diaryl ketones such as benzophenone and 2-isopropyl thioxanthone, benzil and quinone derivates, and 3-ketocumarines as described by S.P. Pappas, J. Rad. Cur.. July 1987.

Preferably, the initiator used comprises a thermally decomposed azo or peroxide compound for solubility reasons and in order to control the reaction rate. Most preferably, the initiator used comprises 2,2'-azobis-(iso- butyronitrile) for reasons of cost and appropriate decomposition temperature.

Splyent

The use of a solvent is required in the solution polymerization process of the present invention. The solvent is utilized in order to decrease the viscosity during the reaction to allow for efficient stirring and heat transfer. Suitable solvents include but are not limited to those selected from the group consisting of C_j to Cg alcohol esters of acetic acid such as ethyl acetate and butyl acetate; ketones such as methyl ethyl ketone, methyl isobutyl ketone, methyl propyl ketone, and acetone; alcohols such as methanol, ethanol, and isopropanol; phthalates such as diooctyl phthalate; propylene glycol ethers, tetrahydro furan; and mixtures thereof. The amount of solvent is generally about 20 to about 90 parts by weight, preferably about 40 to about 80 parts by weight, most preferably about 30 to about 70 parts by weight.

Crosslinking Agent

The composition of the invention can further comprise about 0.1 percent to about 5 percent by weight of a crosslinker based upon the percent solids (i.e., total weight of fluorocarbon elastomer, monomer, initiator, and stabilizer). Examples of useful crosslinkers include but are not limited to thermally-activated, moisture-activated, and ultraviolet radiation (UV) activated crosslinkers. Examples of thermally-activated crosslinkers include but are not limited to those selected from the group consisting of bisamides such as N,N'-bis-l,2-propyleneterephthalamide, metal complexes such as aluminum acetylacetonate, and isocyanates such as H-12MDI (4,4'-methylene-bis- [cyclohexylisocyanate]). Examples of moisture-activated crosslinkers include but are not limited to those selected from the group consisting of silanes such as trimethoxysilylpropyl methacrylate (Tris), amino silane, epoxy silane, and mixtures thereof. Examples of UV-activated crosslinkers include but are not limited to those selected from the group consisting of chromophore-substituted triazines as described in U.S. Patent No. 4,330,590 (Vesley, 3M) and U.S. Patent No. 4,329,384 (Vesley et al., 3M), such as 2,4-bis(trichloro- methyl)-6-(4-methoxyphenyl)-s-triazine, 2 ,4-bis(trichloromethyl)-6- (3-methoxyphenyl-s-triazine, 2,4-bis(trichloromethyl)-6-(3,4- dimethoxyphenyl)-s-triazine, 2,4-bis(trichloromethyl)-6-(3,4,5- trimethoxyphenyl)-s-triazine, 2,4-bis(trichloromethyl)-6-(3,4-methylene- dioxyphenyl)-s-triazine, and 2,4-bis(trichloromethyl)-6-(4-methoxy- naphthyl)-s-triazine, and U.S. Patent No. 4,181,752 (Martens, 3M), e.g., 2,4- bis(trichloromethyl)-6-(4-methoxystyryl)-s-triazine, and copolymerizable aromatic ketone monomers as described in U.S. Patent No. 4,737,559 and U.S. Patent No. 4,847,137 (Kellen et al., 3M), such as acryloxybenzophenone.

Methods of Polymerization

The homolytic decomposition of the initiator used in the present invention to form free radicals can be induced by heat energy (thermolysis), light energy (photolysis), or the addition of a suitable catalyst. The decomposition rate of the initiator during thermolysis depends upon the chemical nature of the initiator, the reaction temperature, and the solvent (if any) used. The decomposition rate of the initiator during photolysis depends mainly upon the chemical nature of the initiator and the intensity and wavelength of the radiation utilized. Light energy can be supplied to induce the homolytic decomposition of the initiator by means of visible or ultraviolet sources including low intensity fluorescent black light lamps, medium pressure mercury arc lamps, and germicidal mercury lamps. The selection of a preferred light energy source will depend upon the chosen photoinitiator.

The decomposition of the initiator can also be accomplished by using a suitable catalyst. Catalyst induced initiator decomposition involves an electron transfer mechanism resulting in a reduction-oxidation (redox) reaction. Initiators such as peroxides and hydroperoxides are more susceptible to this kind of decomposition. Catalysts useful in inducing the homolytic decomposition of the initiator include, but are not limited to, amines and metal ions used in combination with peroxide or hydroperoxide initiators and bisulfite or mercapto compounds used in combination with persulphate initiators.

The preferred method of initiation is thermolysis which can be readily employed in standard reactors. Thermolysis also provides for ease of control of the reaction rate and exotherm.

In addition to the solution polymerization herein described, the copolymerization may be carried out by other well known techniques such as suspension, dispersion, and bulk polymerization. Suspension polymerization is a well-known method of polymerization which results in the formation of polymer beads.

For solution polymerization the free-radically polymerizable monomers, the initiator, the stabilizer, the fluorocarbon elastomer and solvent employed are charged into an appropriate reaction vessel. Typically, fluorocarbon elastomer is added to and dissolved in a monomer/solvent mixture. Previously prepared stabilizer and initiator is added, following which polymerization is initiated. If photolysis is conducted to decompose the initiator, the reactants and the solvent employed are charged into an energy source transparent vessel and therein subjected to the energy source. If the energy source is ultraviolet light radiation, a suitable ultraviolet light-transparent vessel would be utilized.

If thermolysis is used to decompose the initiator, the reactants and the solvent employed are charged into a suitable glass or metal reactor, and therein subjected to the thermal energy source. If catalysis is used to decompose the initiator, a glass or metal reactor can also be utilized.

The reaction is preferably conducted in a vessel with agitation to permit uniform exposure of the reactants to the energy source. While most of the reactions have been conducted by employing a batch process, it is possible to utilize the same technology in a continuous polymerization operation.

For suspension polymerization a first solution is typically formed comprising fluorocarbon elastomer, chain transfer agent, and monomers by dissolving the fluorocarbon elastomer in the monomer, at room temperature with agitation, following which the chain transfer agent and initiator is added. Typically about 0.5 to about 5 percent by weight of chain transfer agent is used based on the weight of the monomer charge.

A second solution is formed comprising stabilizer, deionized water and a suspension agent such as sodium hypophosphite.

Suspending agents are those conventionally used in suspension polymerization processes. They may be minimally water-soluble inorganic salts such as tribasic calcium phosphate, calcium carbonate, calcium sulfate, barium sulfate, barium phosphate, hydrophilic silicas, and tribasic calcium phosphate. Water-soluble organic suspending agents may also be used, e.g., polyvinyl alcohol, poly-N-vinyl pyrrolidone, polyacrylic acid, polyacrylamide and hydroxyalkl cellulose. The suspending agent is present in amounts ranging from about 0.01 part to about 5 parts based on 100 parts total monomer content.

The two solutions are then combined to form a suspension and are polymerized with agitation for about 2 to 5 hours at a temperature of about 65 to about 85°C, preferably about 70 to about 75°C, to give a suspension which contains the copolymer bead. The beads are then washed and separated from the water by means such as gravity filtration. The filtered product also generally comprises about 15-30 percent water.

The compositions of the invention can be used to prepare a film by conventional methods. The composition can be coated on a substrate such as a polyester substrate and dried to produce a film. It is proposed that the compositions of the invention may also be used to prepare sealants, membranes and adhesives.

Test Methods

Molecular Weight Determination

The characterization of the molecular weight distribution of the polymers described herein can be by conventional gel permeation chromatography (GPC). GPC analysis is done on the samples, using a Perkin Elmer

Series 400 pump autosamples from Polymer Laboratories. The columns (30 cm-0.46 cm) are packed with PL gel (polystyrene crosslinked with divinylbenzene), particle size: 10 micron. The eluens used is THF. Flow rate: 1 ml/min. The calibration is done with Polystyrene standards having molecular weight between 1,200 and 2,950,000. The flow rate marker is toluene. The molecular weight is calculated with a PL GPC datastation version 3.0. Detection is done with a PE LC25 refractive index detector. GPC test methods are further explained in "Modern Size Exclusion Liquid Chromatography," Practice of Gel Permeation Chromatography. John Wiley, New York, 1979.

The following abbreviations and tradenames are used herein:

GLOSSARY Irganox 1010: pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4- hydroxyphenyl)proprionate], from Ciba Geigy

Fluorel™ 2230: vinylidene fluoride - hexafluoropropylene copolymer, fro 3M

AR 174: Methacryloxy trimethoxy silane, from Union Carbide rpm: revolutions per minute THF: tetrahydrofuran VAZO™ 64: 2,2'-azobis(isobutyronitrile), from duPont

Examples The following non-limiting examples further illustrate the present invention. All parts, percentages, ratios, etc. in the examples and the rest of the specification are by weight unless otherwise indicated.

Example 1 - Synthesis of Macromonomer Stabilizer with IEM Endcap

A solution of 14.0 g N-vinylpyrrolidone, 10.84 g vinyl acetate, 0.8 g mercaptoethanol and 12 g of a 1 percent ethyl acetate solution of VAZO™ 64 (duPont) in 29.4 g ethyl acetate was purged with N₂ and sealed in a reaction bottle, then heated to 55°C for 17 hours. The copolymer mixture was cooled and treated with 1.2 g isocyanatoethyl methacrylate (IEM), 1 drop dibutyltin dilaurate and 0.05 g Irganox 1010, resealed and reacted at 55°C for an additional 3 hours. Completion of the reaction was monitored by disappearance of the isocyanate band at 2250 cm^"* in the infrared spectrum. A 39.3 percent solids solution of macromonomer was obtained. Mn = 7,351, Mw = 12,127, Mz = 17,702.

Example 2 - Synthesis of Macromonomer Stabilizer with TMI Endcap The procedure of Example 1 was followed, except for the substitution of 2.06 g alpha, alpha-dimethyl-meta-isopropenyl benzylisocyanate (TMI) for the IEM endcapper and the use of a reaction temperature of 65 °C.

Example 3 - Synthesis of Copolymer Stabilizer

The procedure of Example 1 was followed, except that only 0.2 g of mercapto ethanol was used. In addition, the reaction was stopped at the end of the initial reaction period. The resultant material was not reacted with IEM.

Example 4 - Synthesis of Macromonomer Stabilizer with TMI Endcap

A solution of 129 g N-vinylpyrrolidone and 11 g vinyl acetate in

168 g ethyl acetate was treated with 4.84 g mercaptoethanol and 42 g of a 1 percent solution of VAZO™ 64 in ethyl acetate, then heated at 55 °C under nitrogen for 12 hours. To this copolymer mixture was added 25 g dimethylformamide, 15.7 g TMI, 3 drops dibutyltin dilaurate and 0.05 g

Irganox™ 1010. Reaction was resumed at 65 °C for 17 hours, after which the isocyanate band in the IR spectrum had disappeared.

Example 5 - Preparation of Fluoroelastomer Composition A with a

Macromonomer Stabilizer

A solution of 10 g Fluorel™ 2230 and 30 g methyl methacrylate in 40 g methanol was treated with 4 g of the stabilizer from Example 1 and 0.12 g VAZO™ 64, then heated at 55°C for 20 hours. The resultant milky white dispersion was coated on a polyester substrate, dried 15 minutes at 65 °C, resulting in a clear coating.

An identical milky white dispersion sample was allowed to dry at room temperature for 24 hours, with occasional stirring to prevent the formation of lumps. The methanol solvent evaporated, thus yielding a white powdery material.

Comparative Example 5 - Preparation of Fluoroelastomer Composition A in Absence of a Stabilizer The procedure of Example 5 was followed, except that no stabilizer was added. The product thus obtained was a coagulated white polymer which could not be coated or converted into a useable dry polymer. Example 6 - Preparation of Fluoroelastomer Composition B

A solution of 12 g Fluorel™ 2230, 6 g 2-ethylhexyl methacrylate, 2 g acrylonitrile, 0.06 g VAZO™ 64 and 4 g of stabilizer from Example 2 was dissolved in 40 g methanol. Polymerization took place over 14 hours at 55 °C under N₂. The resulting white dispersion was coated at 65°C and dried according to the procedure of Example 5 which yielded a tough, clear film. The solvent was evaporated from an identical sample according to the procedure of Example 5 yielding a white powdery material.

Comparative Example 6 - Preparation of Fluoroelastomer Composition B without Acrylonitrile

The procedure of Example 6 was followed except that the acrylonitrile component was omitted. The resulting dispersion settled over time, and gave a nonuniform opaque film when coated and dried according to the procedure of Example 5. This comparative example demonstrates the importance of acrylonitrile as a comonomer when long-chain (meth)acrylic acid esters are used.

Example 7 - Preparation of Crosslinked Fluoroelastomer Composition C A solution of 12 g Fluorel™ 2230, 5 g methyl methacrylate, 2 g acrylonitrile, 1 g methacryloxy trimethoxysilane (AR 174), 2 g stabilizer from Example 2 and 0.06 g VAZO™ 64 in 20 g methanol was heated under N₂ at 55 °C for 17 hours. The resulting stable dispersion was coated and dried following the procedure of Example 5 to give a transparent film.

Example 8 - Suspension Polymerization of Fluoroelastomer Composition D

A solution of 10 g stabilizer from Example 4 and 0.8 g sodium hypophosphite in 420 g deionized water was stirred at 550 rpm under nitrogen and heated to 70°C. To the aqueous solution was slowly added a solution of 60 g Fluorel™ 2230, 0.4 g isooctylthioglycolate and 0.4 g VAZO™ 64 in 140 g methyl methacrylate. The reaction mixture was stirred and heated at 70-75 °C for 3 hours. The resultant polymer beads were collected on cheesecloth, washed thoroughly with deionized water and dried.

Example 9 - Preparation of Fluoroelastomer Composition E

A solution of 10 g of Fluorel™ 2230 and 30 g MMA in 60 g of methanol was treated with 8 g of stabilizer from Example 3. 0.12 g of VAZO™ 64 was added following which the mixture was heated at 55 °C for 20 hours. The resultant milky white dispersion was dried to obtain a white powdery material.

While this invention has been described in connection with specific embodiments, it should be understood that it is capable of further modification. The claims herein are intended to cover those variations which one skilled in the art would recognize as the chemical equivalent of what has been described here.

Claims

What is claimed:

1. A composition comprising: a dispersion comprising the reaction product of: (A) about 10 to about 80 parts by weight of a combination of components comprising:

(i) about 90 to about 10 percent by weight fluorocarbon elastomer;

(ii) about 10 to about 90 percent by weight of a monomer charge wherein the monomer charge comprises about 50 to about 100 percent of weight of (meth)acrylic acid ester monomer(s) of alcohols comprising about C_j to about C_jg alcohol esters of (meth)acrylic acid and about 0 to about 50 percent by weight of ethylenically unsaturated monomer selected from the group consisting of acrylic acid, acrylonitrile, vinyl acetate, N-vinylpyrrolidone, methacryloyloxy propyltrimethoxy silane, and mixtures thereof; wherein the weight percentages of (i) and (ii) are based upon the total weight of (A);

(i) a homopolymer having a weight average molecular weight ranging from about 20,000 to about 200,000 comprising amide containing monomers; (ii) a copolymer having a weight average molecular weight ranging from about 20,000 to about 200,000, wherein the copolymer comprises:

(a) about 10 to about 90 parts by weight of monomer selected from the group consisting of amide-containing monomers and mixtures thereof; and

(b) about 90 to about 10 parts by weight of monomer selected from the group consisting of vinyl esters, alkyl acrylates, alkyl methacrylates, and mixtures thereof; wherein the sum of (ii)(a) plus (ii)(b) equals 100 parts by weight total; (iii) a homopolymer macromonomer having a weight average molecular weight ranging from about 3,000 to about 80,000, wherein the homopolymer macromonomer comprises:

(a) amide-containing monomer and (b) a vinyl-reactive endcapping agent selected from the group consisting of isocyanatoethyl methacrylate, alpha,alpha-dimethyl-meta-isopropenyl benzylisocyanate, parachloromethylstyrene, glycidyl methacrylate, vinyl azlactone, and mixtures thereof; (iv) a copolymer macromonomer having a weight average molecular weight ranging from about 3,000 to about 80,000, wherein the copolymer macromonomer comprises:

(a) about 10 to about 90 parts by weight of monomer selected from the group consisting of amide-containing monomers and mixtures thereof;

(b) about 90 to about 10 parts by weight of monomer selected from the group consisting of vinyl esters, alkyl acrylates, alkyl methacrylates, and mixtures thereof; and

(c) a vinyl-reactive endcapping agent selected from the group consisting of isocyanatoethyl methacrylate, alpha,alpha-dimethyl-meta-isopropenyl benzylisocyanate, parachloromethylstyrene, glycidyl methacrylate, vinyl azlactone, and mixtures thereof; wherein the sum of (iv)(a) plus (iv)(b) equals 100 parts by weight total; and

(v) mixtures thereof; (C) about 20 to about 90 parts by weight of a solvent capable of dissolving the fluoroelastomer, the (meth)acrylic acid ester monomer(s), the optional ethylenically unsaturated monomer, and the stabilizer; and (D) about 0.01 to about 0.5 percent by weight of an initiator, wherein said weight percent of the initiator is based upon the total weight of the (meth)acrylic acid ester monomer(s) and the ethylenically unsaturated monomer(s), if used, in the combination of components (A); wherein tb weight of (A) plus (C) equals 100 parts by weight total.

2. The composition of Claim 1 wherein said (meth)acrylic acid ester monomer is selected from the group consisting of methyl acrylate, butyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, 2-methylbutyl methacrylate, isooctyl acrylate, dimethylaminoethyl methacrylate, butyl methacrylate, 2-ethylhexyl acrylate, hydroxyethyl acrylate, glycidyl methacrylate, tetrahydrofurfuryl acrylate, and mixtures thereof.

3. The composition of Claim 1 wherein said solvent is selected from the group consisting of alcohols, ketones, propylene glycol ethers, C_j to Cg esters of acetic acid, phthalates, tetrahydrofuran, and mixtures thereof.

4. The composition of claim 1 wherein the stabilizer comprises a vinyl acetate/N-vinyl pyrrolidone copolymer endcapped with an endcapping monomer selected from the group consisting of isocyanatoethyl methacrylate and alpha, alpha-dimethyl-meta-isopropenyl benzylisocyanate.

5. The composition of claim 1 which further comprises about 0.1 to about 5 percent by weight of a crosslinking agent based upon the total weight of (A) plus (B) plus (D), wherein said crosslinking agent is selected from the group consisting of bisamindes, metal complexes, isocyanates, silanes, and mixtures thereof.

6. The composition of claim 1 wherein said fluorocarbon elastomer comprises vinylidene fludride-hexafluoropropylene copolymer having a Mooney viscosity about 10 to about 120.

7. A composition comprising the reaction product of:

(i) about 90 to about 10 percent by weight fluorocarbon elastomer;

(ii) about 10 to about 90 percent by weight of a monomer charge, wherein the monomer charge comprises about 0 to about 100 percent by weight of (meth)acrylic acid ester monomer(s) comprising about C_j to about C_j alcohol esters of (meth)acrylic acid and about 0 to about 50 weight percent by weight of ethylenically unsaturated monomer selected from the group consisting of acrylic acid, acrylonitrile, vinyl acetate, N-vinylpyrrolidone, methacryloyloxy propyltrimethoxy silane, and mixtures thereof; wherein the weight percentages of (i) and (ii) are based upon the total weight of (A); (B) about 2 to about 20 percent by weight of a stabilizer based upon the weight of (A) wherein the stabilizer is selected from the group consisting of:

(ii) a copolymer having a weight average molecular weight ranging from about 20,000 to about 200,000, wherein the copolymer comprises:

(b) about 90 to about 10 parts by weight of monomer selected from the group consisting of vinyl esters, alkyl acrylates, alkyl methacrylates, and mixtures thereof; wherein the sum of (ii)(a) plus (ii)(b) equals 100 parts by weight total;

(iii) a homopolymer macromonomer having a weight average molecular weight ranging from about 3,000 to about 80,000, wherein the homopolymer macromonomer comprises: (a) amide-containing monomer and

(b) a vinyl-reactive endcapping agent selected from the group consisting of isocyanatoethyl methacrylate, alpha,alpha-dimethyl-meta-isopropenyl benzylisocyanate, parachloromethylstyrene, glycidyl methacrylate, vinyl azlactone, and mixtures thereof;

(iv) a copolymer macromonomer having a weight average molecular weight ranging from about 3,000 to about 80,000, wherein the copolymer macromonomer comprises:

(c) a vinyl-reactive endcapping agent selected from the group consisting of isocyanatoethyl methacrylate, alpha,alpha-dimethyl-meta-isopropenyl benzylisocyanate, parachloromethylstyrene, glycidyl methacrylate, vinyl azlactone, and mixtures thereof; wherein the sum of (iv)(a) plus (iv)(b) equals 100 parts by weight total; (v) mixtures thereof; and

(C) about 0.01 to about 0.5 percent by weight of an initiator, wherein said weight percent of the initiator is based upon the total weight of the (meth)acrylic acid ester monomer(s) and the ethylenically unsaturated monomer(s), if used, in the combination of components (A).

8. The composition of claim 7 fabricated into an article selected from the group consisting of polymer beads, polymer powders, and polymer films.

9. A method for the suspension polymerization of a polymer bead comprising the steps of:

(a) forming a first solution comprising:

(A) about 10 to about 80 parts by weight of a combination of components comprising: (i) about 90 to about 10 percent by weight fluorocarbon elastomer;

(ii) about 10 to about 90 percent by weight of a monomer charge wherein the monomer charge comprises about 50 to about 100 percent of weight of (meth)acrylic acid ester monomer(s) comprising about C_j to about C_jg alcohol esters of (meth)acrylic acid and about 0 to about 50 percent by weight of ethylenically unsaturated monomer selected from the group consisting of acrylic acid, acrylonitrile, vinyl acetate,

N-vinylpyrrolidone, methacryloyloxy propyltrimethoxy silane, and mixtures thereof; wherein the weight percentages of (i) and (ii) are based upon the total weight of (A); and

(B) about 0.5 to about 5 percent by weight of a chain transfer agent based upon the weight of the combination of the fluorocarbon elastomer and the monomer charge;

(C) about 0.01 to about 0.5 percent by weight of an initiator, wherein said weight percent of the initiator is based upon the total weight of the (meth)acrylic acid ester monomer(s) and the ethylenically unsaturated monomer(s), if used;

(b) forming a second solution comprising:

(A) about 4 to about 20 percent by weight of a stabilizer based upon the weight of the combination of the fluorocarbon elastomer and the monomer charge wherein the stabilizer is selected from the group consisting of:

(a) amide-containing monomer and (b) a vinyl-reactive endcap selected from the group consisting of isocyanatoethyl methacrylate, alpha,alpha-dimethyl-meta-isopropenyl benzylisocyanate, parachloromethylstyrene, glycidyl methacrylate, vinyl azlactone, and mixtures thereof; (iv) a copolymer macromonomer having a weight average molecular weight ranging from about 3,000 to about 80,000, wherein the copolymer macromonomer comprises: (a) about 10 to about 90 parts by weight of monomer selected from the group consisting of amide-containing monomers and mixtures thereof;

(v) mixtures thereof; (B) about 20 to about 90 parts by weight of deionized water; wherein the sum of the weight of the deionized water and the fluorocarbon elastomer and the monomer charge equals 100 parts by weight total;

(C) about 0.01 to about 5 parts by weight suspending agent based upon 100 parts by weight of said monomer charge;

(c) combining said first solution with said second solution to form a suspension; (d) concurrently agitating said suspension and permitting polymerization of said monomer(s) until polymer beads are formed; and (e) collecting said polymer beads.

10. A polymer bead made by the process of claim 9.