United States Patent (19) 11) 4,338,237 Sulzbach et al. 45 Jul. 6, 1982 (54) PROCESS FOR THE PREPARATION OF 57 ABSTRACT AQUEOUS, COLLOIDAL DISPERSIONS OF COPOLYMERS OF THE An improved process for the preparation of aqueous, TETRAFLUOROETHYLENE/ETHYLENE colloidal dispersions of copolymers comprising at most TYPE 60 mole % of units of tetrafluoroethylene, 60 to 40 mole % of units of ethylene and 0 to 15 mole % of units of at 75 Inventors: Reinhard A. Sulzbach; Robert least one other a-olefinic monomer, which can be copo Hartwimmer, both of Burghausen, lymerized with tetrafluoroethylene and ethylene, in the Fed. Rep. of Germany presence of manganese compounds as the catalyst is 73 Assignee: Hoechst Aktiengesellschaft, described. In this process, the emulsion polymerization Frankfurt, Fed. Rep. of Germany is carried out in an aqueous phase in the presence (a) of 21 Appl. No.: 275,881 a chain transfer agent of the formula X-CH2-COOR (X = Cl, Br, COOH, COOR, COCH5, CH3, C2H5 or 22 Filed: Jun. 22, 1981 C3H7; and R = C1-C4-alkyl), and (b) of a compound 30 Foreign Application Priority Data which stabilizes the dispersion and has the formula Jun. 28, 1980 IDE Fed. Rep. of Germany ....... 3O24450 NH-O-C-Y 51 Int. Cl. ................................................ C08K 5/32 52 U.S. C. ...................................... 524/777; 526/91; O 526/211; 526/255; 524/767 58 Field of Search ..................... 260/29.6 N, 29.6 T, (Y-COONH4, COOH, CH3, CH2OH, CH2COOH or 260/29.6 F; 526/91, 255, 211 CH2COONH4). (b) can additionally contain an ammo nium salt of an inorganic non-metal acid, for example 56 References Cited ammonium chloride or fluoride, Terpolymers or quater U.S. PATENT DOCUMENTS polymers containing, in addition to tetrafluoroethylene 3,704,285 11/1972 Porter ............................ 260/87.5 A and ethylene, preferably hexafluoropropylene and/or a 3,707,519 12/1972 Hahn ............... ... 260/29.6 F "bulky" vinyl monomer as the third and/or fourth co 3,859,262 l/1975 Hartwimmer .................... 260/80.77 monomer are preferably prepared. The copolymer dis 4,016,345 4/1977 Holmes ........... ... 526/2O6 persions thus prepared have very low coagulate con 4,078,134 3/1978 Kuhls et al. ......... ... 526/204 tents and are very stable and the copolymers have melt 4,098,975 7/1978 Shimuzo et al. ... ... 52.6/73 flow indices most appropriate to the processing opera 4,123,602 10/1978 Ukinashi et al. .................... 526/206 tions. They can be processed to coatings and shaped Primary Examiner-Joseph L. Schofer articles. Assistant Examiner-Bernard Lipman Attorney, Agent, or Firm-Connolly and Hutz 4 Claims, No Drawings 4,338,237 2 other monomers) which have too high a molecular PROCESS FOR THE PREPARATION OF weight, and, as a result, too high a melt viscosity (or too AQUEOUS, COLLOIDAL DISPERSIONS OF low a melt flow index), for processing of the copolymer COPOLYMERS OF THE by thermoplastic shaping processes are obtained by this TETRAFLUOROETHYLENE/ETHYLENE TYPE 5 known procedure. As a further disadvantage, the aque ous, colloidal dispersions prepared by this known pro The invention relates to a process for the preparation cess have an unsatisfactory dispersion stability, that is to of stable, aqueous, colloidal dispersions of copolymers say they tend to coagulate, and coagulate completely if of the tetrafluoroethylene type in the presence of chain the copolymer solids content exceeds 15% by weight transfer agents. 10 during the preparation. Copolymers of tetrafluoroethylene and ethylene units There was thus the object of improving the process are known. They have an excellent stability to changes for the preparation of aqueous, colloidal dispersions of in temperature and to chemicals and can be processed copolymers of the tetrafluoroethylene/ethylene type in from the melt by thermoplastic shaping processes. the presence of manganese acids or salts thereof as cata However, the copolymers consisting exclusively of 15 lysts, to the effect that the mean molecular weight of the tetrafluoroethylene and ethylene units are somewhat colloidally dispersed copolymers is reduced and the brittle in the temperature range between 150 C. and melt viscosity of these copolymers is thus adjusted to 200 C. An improvement is achieved by incorporating within the range necessary for the processing operation, into the chains of these copolymers units of other vinyl and, at the same time, the stability of the copolymer monomers in an amount of up to 15 mole %. dispersions formed is increased such that colloidal dis Such copolymers comprising tetrafluoroethylene, persions of tetrafluoroethylene/ethylene copolymers ethylene and, if appropriate, other monomers are usu with a solids content of more than 15% by weight can ally prepared by polymerization in organic solvents, be prepared directly by copolymerization in the purely fluoroalkanes and fluorochloroalkanes having proved aqueous phase without substantial formation of coagul to be advantageous solvents. This type of copolymer 25 late and without the addition of organic solvents. ization in organic solvents gives a suspension of the To achieve this object, the present invention provides copolymer particles with a mean particle diameter of a process for preparing a stable, aqueous, colloidal dis > 10 um in the solvent. The fluoroalkanes or fluoro persion of a copolymer containing as comonomers in chloralkanes employed for this purpose are expensive copolymerized form at most 60 mole percent of tetraflu substances which must as far as possible be recovered. 30 oroethylene, from 60 to 40 mole percent of ethylene, Attempts have therefore already been made to carry and from 0 to 15 mole percent of at least one additional out the copolymerization of tetrafluoroethylene and a-olefinic comonomer copolymerizable with tetrafluor ethylene in mixtures of water and an organic solvent or oethylene and ethylene, by copolymerization of said in a purely aqueous reaction medium. The use of fluoro comonomers in an aqueous medium having dissolved chloroalkanes in a mixture with water is described in 35 therein a fluorinated emulsifying agent and a catalyst Japanese Allowed Patent Specification No. 49-011,746 selected from the group of acids of manganese, their and in Japanese Laid-Open Patent Application No. salts, and manganese compounds capable of being con 49-024,295. A process in which 10 to 150% by weight of verted into said manganese acids or salts thereof under a fluorochloralkane is added to the aqueous reaction copolymerization conditions, which comprises copoly medium as a reaction accelerator is known from Ger 40 merizing in the presence of man Offenlegungsschrift No. 2,444,516. Mixtures of (a) a chain transfer agent of the general formula tert.-butyl alcohol and water are recommended as the X-CH2-COOR wherein X is Cl, Br, COOH, COOR, reaction medium in U.S. Pat. No. 2,468,664 and U.S. COCH3, CH3, C2Hs, or C3H7; and R is an alkyl group Pat. No. 3,401,155. However, stable aqueous disper having of from 1 to 4 carbon atoms; or a mixture sions comprising colloidal particles of copolymers of 45 thereof, and the tetrafluoroethylene/ethylene type cannot be pre (b) a dispersion-stabilizing compound of the general pared by these processes mentioned. It is also not possi formula ble to prepare stable aqueous, colloidal dispersions of such tetrafluoroethylene/ethylene copolymers under conditions such as are customary for the preparation of 50 NH-O-C-Y aqueous, colloidal dispersions of polytetrafluoroethyl O ene, that is to say in the presence of perfluorinated emulsifiers and watersoluble peroxidic compounds or wherein Y is COONH4, COOH, CH, CH2OH, redox systems as catalysts. Under these conditions, ei CH2COOH, or CH2COONH4, including hydrates and ther no reaction takes place or the dispersions already 55 mixtures of said compounds, said dispersion-stabilizing coagulate at a very low solids content, unless additional compound being present in an amount of at least 0.001 organic solvents, such as, for example, trifluorotri mole/l aqueous medium. chloroethane, are used as stabilizing additives (Italian It is indeed known to carry out the polymerization of Pat. No. 874,129). fluoroolefins in the presence of chain transfer agents, The preparation of colloidal dispersions in a purely 60 and a large number of classes of compounds have al aqueous phase became possible when it was found that ready been proposed for this purpose. The copolymer aqueous dispersions of tetrafluoroethylene/ethylene ization of tetrafluoroethylene and ethylene (and, if ap copolymers with a solids content of up to about 15% by propriate, other additional monomers) in organic sol weight can be obtained using manganese acids or salts vents has also already been carried out in the presence thereofas catalysts in the presence of customary emulsi 65 of chain transfer agents, for example in the presence of fiers. This is described in U.S. Pat. No. 3,859,262. How acetone or cyclohexane, in isolated cases. However, ever, aqueous, colloidal dispersions of copolymers of when the copolymerization of tetrafluoroethylene and tetrafluoroethylene and ethylene (and, if appropriate, ethylene and, if appropriate, other monomers is carried 4,338,237 3 4. out in a purely aqueous phase, these chain transfer aqueous medium during the copolymerization, that is to agents have one, several or all of the disadvantages say at pH values from 6 to 1, preferably from 4 to 2. mentioned in the following text: the molecular weight These ammonium salts of inorganic non-metal acids regulating action is insufficient, the rate of polymeriza which are additionally employed are added in an tion is too greatly reduced, the dispersion stability is amount of 0 to 0.1 mole/l of aqueous polymerization drastically reduced, or the properties of the pulverulent medium. copolymers formed by coagulation are considerably Both the compounds (b) which stabilize the disper impaired, which is manifested, for example, by blister sion and the ammonium salts of inorganic non-metal ing, discoloration or poorer mechanical properties of acids which are additionally added, if appropriate, can shaped articles produced therefrom.