TEXTILE OR POROUS MATERIAL IMPREGNATED WITH A FLUORINE-CONTAINING COPOLYMER

Abstract: An impregnated material comprising an organic or inorganic material selected from the group consisting of a woven fabric, a non-woven fabric and an open cell porous material which is impregnated with a copolymer which comprises 50 to 95 % by mole of repeating units derived from tetrafluoroethylene and 5 to 50 % by mole of repeating units derived from perfluoroalkyl vinyl ether of the formula: CF₂=CFOR f (I) wherein R f is a C₁-C₆ perfluoroalkyl group or a group of the formula (CF₂CFXO) R f (II) wherein R f is the same as defined above, X is a fluorine atom or a trifluoromethyl group and n is an integer of 1 to 10, which has good chemical, corrosion, solvent and oil resist­ ance as well as water- and oil-repellence.

Description: FIELD OF THE PRESENT INVENTION The present invention relates to a novel impregnated material. More particularly, it relates to a fabric or a porous material impregnated with a specific fluorine-containing elastomeric copolymer. BACKGROUND OF THE INVENTION There is known an impregnated material prepared by impregnating woven fabrics or non-woven fabrics with a solution or dispersion of a vinylidene fluoride/hexafluoropropylene copolymer, a vinylidene fluoride/hexafluoropropylene/tetrafluoroethylene copolymer or a tetrafluoroethylene/propylene copolymer. However, the impregnated material with these fluorine-containing elastomeric copolymer are not necessarily excellent in all of chemical resistance, corrosion resistance and oil resistance, and do not necessarily have good water- and oil-repellency. EP-A-0077998 discloses a fluorine-containing elastomeric copolymer which comprises units of at least one fluorovinyl ether of the formula XO-(CFYCF₂O) n CF=CF₂, where X is a fluoroalkyl group, Y may be inter alia a fluorine atom or a trifluoromethyl group and n is an integer of 1-4. The copolymer also includes units of a copolymerizable fluorine-containing monomer such as tetrafluoroethylene. US-A-4368308 discloses a fluorine containing elastomer essentially based upon ethylene units and fluorovinyl ether units. Other comonomers including tetrafluoroethylene may be present in an amount up to 30 mole%. SUMMARY OF THE INVENTION One object of the present invention is to provide an impregnated material having not only good chemical, corrosion, solvent and oil resistance but also good water-and oil-repellence. Another object of the present invention is to provide an impregnated material with a fluorine-containing elastomeric copolymer gas permeability of which is freely adjusted. According to the present invention, there is provided an impregnated material comprising an organic or inorganic material selected from the group consisting of a woven fabric, a non-woven fabric and an open cell porous material which is impregnated with a crosslinked copolymer which comprises: 50 to 95% by mole of repeating units derived from tetrafluoroethylene; 5 to 50% by mole of repeating units derived from a perfluoroalkyl vinyl ether of the formula: CF₂=CFOR f (I) wherein R f is a C₁-C₆ perfluoroalkyl group or a group of the formula: -(CF₂CFXO) n -R f (II) wherein R f is the same as defined above, X is a fluorine atom or a trifluoromethyl group and n is an integer of 1 to 10; and 0.1 to 20% by mole of repeating units based on the total mole of tetrafluoroethylene and the perfluoroalkyl vinyl ether (I) of a fluorine-containing vinyl ether of the formula: CF₂=CFO-(CF₂CF₂) m -CH₂I (III) wherein m is an integer of 1 to 10. DETAILED DESCRIPTION OF THE INVENTION The fluorine-containing elastomeric copolymer to be impregnated in the material according to the present invention comprises tetrafluoroethylene, the perfluoro-alkyl vinyl ether (I) and the fluorine-containing vinyl ether (III). The preparation of a copolymer containing the first two of these components is described in JP-A-71906/1985, US-A-4,487,903 and EP-A-0077998. The copolymer may further comprise at least one fluorine-containing ethylenically unsaturated comonomer such as vinylidene fluoride, vinyl fluoride, trifluorochloroethylene, trifluoroethylene, hexafluoropropylene, hexafluoroisobutylene, fluoroalkyl vinyl ether and the like. The amount of the fluorine-containing ethylenically unsaturated comonomer to be contained in the copolymer is 0.1 to 20 % by mole based on the total mole of tetrafluoroethylene and the perfluoroalkyl vinyl ether (I). The copolymerization of the comonomer improves vulcanizing characteristics, heat resistance and compression set of the copolymer. In the copolymerization of the copolymer to be used according to the present invention, a chain transfer agent may be added in the polymerization system. Specific examples of the chain transfer agent are C₄-C₆ hydrocarbons, alcohols, ethers and halogenated hydrocarbons (e.g. CCl₄, CBrCl₃, CF₂ClBr, CF₂BrCFBrCF₃ and CF₂I₂). When a fluorocarbon iodide or a fluorocarbon bromide (e.g. CF₂I₂, I(CF₂)₄I, CF₂=CFCF₂CF₂I, CF₂Br₂, BrCF₂CF₂Br and BrCF₂-CFBrCF₃) is used as a chain transfer agent, an iodine or bromine atom is bonded to the chain end of the copolymer and still radically active so that the copolymer is vulcanized with a peroxide as a radical source in the presence of a polyfunctional unsaturated compound such as triallylisocyanurate and triallylcyanurate. The organic or inorganic material to be impregnated according to the present invention includes woven and non-woven fabrics of natural fiber (e.g. cotton, wool and jute), semi-synthetic fiber, synthetic fiber and inorganic fiber (e.g. glass fiber, asbestos fiber, alumina fiber, carbon fiber and other ceramics fiber), paper, open cell porous materials (e.g. open cell plastic foam). The fluorine-containing elastomeric copolymer is impregnated in the form of a solution or dispersion in a suitable solvent. The solid content of the copolymer in the solution or dispersion is at least 5 % by weight. When the solution or dispersion having a low solid content, the impregnation step is repeated till a sufficient amount of the copolymer is carried by the material. When the solid content is large, the permeability of the solution or dispersion in to the matrix of the material is decreased. Preferably, the solid content does not exceed 60 % by weight. The solvent is selected according to a processing temperature from perfluorocompounds such as perfluoro-derivatives of benzene, tertiary amines, ethers, pyrane, alkanes and cycloalkanes having at least 6 carbon atoms. Among them, those having a boiling temperature of 60 to 180°C such as perfluorobenzene, perfluorotriethylamine, perfluorotri-n-butylamine and the like are preferred. For the preparation of the dispersion, a dispersing agent or an emulsifier is used. As a non-aqueous dispersing agent, there exemplified a fluorinated compound such as CCl₂FCClF₂, CClF₂CClF₂, CBrF₂CBrF₂, and a combination of the fluorinated compound and a fluorine-containing surfactant. As an aqueous emulsifier, there exemplified a compound of the formula: R f 'COONH₄ (IV) wherein R f ' is a C₂-C₁₀ fluoroalkyl group, and a compound of the formula: R f ''-(OCFX'CF₂) m -CFX'COONH₄ (V) wherein R f '' is a C₁-C₅ fluoroalkyl group, X' is a fluorine atom or a trifluoromethyl group and m is an integer of 1 to 10. When the copolymer contains a radically active iodine or bromine in the molecule as described in the above, a vulcanizing system such as a combination of a peroxide compound and a polyfunctional unsaturated compound having vinyl, allyl or acryl groups can be used. Since the fluorine-containing elastomeric copolymer and the vulcanizing system are commonly dissolved in only a few solvent, they are preferably used in the form of a dispersion. Preferred examples of the peroxide are 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-dihydroxyperoxide, di-t-butylperoxide, t-butylcumylperoxide, dicumylperoxide, α,α'-bis(t-butylperoxy)-p-diisopropylbenzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, benzoylperoxide, t-butylperoxybenzene, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxymaleic acid, t-butylperoxyisopropylcarbonate and the like. Among them, the dialkyl type compounds are most preferred. The solution or dispersion containing the fluorine-containing elastomeric copolymer optionally contains additives such as pigments and fillers. The impregnation of the solution or dispersion in the material is carried out in various ways. For example, the solution or dispersion is sprayed or coated on the surface of the material, or the material is dipped in the solution or dispersion to penetrate the solution or dispersion into the matrix of the material. Then, the solvent or water is removed by drying. The impregnated material of the invention can be used in an unvulcanized state, although it may be vulcanized by incorporating a vulcanizing system. When the material is vulcanized, it is heated under conditions suitable for employed vulcanizing system. When the peroxide is used, the material is preferably heated and vulcanized in the absence of oxygen. By adjusting the impregnated amount of the fluorine-containing elastomeric copolymer, the impregnated material can be gas permeable or of non-porous. The impregnated material of the invention can find various applications: The permeable impregnated woven and non-woven fabric is used as a filter cloth or a filter by virtue of its porosity and corrosion and solvent resistance. The non-porous impregnated woven and non-woven fabric is used, for example, as a diaphragm valve. The impregnated glass fiber fabric is used as a good liquid resistant element since the copolymer of the invention less suffers from corrosion with dehydrogen fluoride than the conventionally used vinylidene fluoride/hexafluoropropylene copolymer so that the glass fiber fabric is not corroded with hydrogen fluoride. Since the gas permeable impregnated woven fabric has less fuzz, it is used as a material for dust free clothes desirable for the production of LSI or chemical resistant clothes. The impregnated material for these clothes is required to have good washing resistance. The impregnated material of the invention has excellent washing resistance and is suitable for the clothes. Further, the impregnated material may be used as a belt of a belt conveyer used in food or medicine industries, which is required to have good corrosion, solvent, oil, liquid and steam resistance. For the production of an inexpensive impregnated material of the invention, the substrate material is firstly impregnated with a conventional fluorine-containing elastomer as an under layer and then with the fluorine-containing elastomeric copolymer as a top layer according to the present invention. To improve the affinity of the under layer with the top layer, the former may be a blend of the conventional fluorine-containing elastomer and the fluorine-containing elastomeric copolymer of the invention. The weight ratio of the former to the latter may be 10 : 90 to 90 : 10. The present invention will be hereinafter explained further in detail by following examples. Reference Example 1 In a glass-lined 1 ℓ autoclave, pure water (500 ml), I(CF₂)₄I (0.75 g), ICH₂CF₂CF₂OCF=CF₂ (2.2 g), Na₂HPO₄·12H₂O (5 g), C₃F₇-OCF(CF₃)CF₂-OCF(CF₃)COONH₄ (50g) and perfluorovinyl ether (200 g) of the formula: C₃F₇-[OCF(CF₃)CF₂]₂-OCF=CF₂ were charged and the interior of the autoclave was thoroughly purged with nitrogen. Then, tetrafluoroethylene was injected at 30°C with stirring to a pressure of 400 kPa (3 kg/cm²G). Thereafter, an aqueous solution (10.4 g/l) of sodium sulfite 1 ml and an aqueous solution (18.8 g/l) of ammonium persulfate 1 ml were separately injected in the autoclave with tetrafluoroethylene gas as a propellant to initiate polymerization. As the reaction proceeded, the pressure dropped. When the pressured decreased to 300 kPa (2.0 kg/cm²G), tetrafluoroethylene was injected to increase the pressure to 300 kPa (3.0 kg/cm²G). The reaction was continued for 8 hours and 15 minutes with repeating the decrease and increase of the pressure. Then, the unreacted monomers were eliminated to terminate the reaction. The product was an aqueous dispersion containing 20.5 % by weight of a copolymer of tetrafluoroethylene, C₃F₇-[OC(CF₃)CF₂]₂-OCF=CF₂ and ICH₂CF₂CF₂O-CF=CF₂. Example 1 (1) A commercially available Tetoron (trade name) cloth was dipped in the aqueous dispersion prepared in Reference Example 1 for about 20 seconds and dried at 100°C for 10 minutes to prepare a sample cloth. Example 1 (2) A commercially available Tetoron (trade name) cloth was dipped in the aqueous dispersion prepared in Reference Example 1 for about 20 seconds and dried at 100°C for 10 minutes twice. The cloth was again dipped in the same dispersion for about 20 seconds and dried at 100°C for 10 minutes to prepare a sample clothe. Examples 2 (1) and 2 (2) In the same manner as in Examples 1 (1) and 1 (2) but using a Nylon (trade mark) cloth in place of the Tetoron cloth, sample cloths were prepared, respectively. Examples 3 (1) and 3 (2) In the same manner as in Examples 1 (1) and 1 (2) but using a Tetoron/cotton (65 : 35) blended cloth in place of the Tetoron cloth, sample cloths were prepared, respectively. Example 4 In the same manner as in Example 1 (1) but using a cotton cloth in place of the Tetoron cloth, a sample cloth was prepared. Comparative Examples 1-3 In the same manner as in Example 1 but using an aqueous dispersion containing 23 % of a copolymer of vinylidene fluoride/hexafluoropropylene/tetrafluoroethylene (molar ratio = 50 : 30 : 20) in place of the dispersion prepared in Reference Example 1 and one of following cloths, a sample cloth was prepared: Tetoron cloth (Comparative Example 1) Nylon cloth (Comparative Example 2) Tetoron/cotton blended cloth (Comparative Example 3). Comparative Examples 4-6 The same cloths as used in Comparative Examples 1-3 but not impregnated were used as sample cloths, respectively. The properties of the sample cloths prepared in Examples 1-4 and Comparative Examples 1-6 were examined. Water- and oil-repellency of the cloth A contact angle of water or acetone against the cloth was measured at 25°C. Moisture permeability An aluminum made cup containing 21 ml of water was sealed with the cloth and kept in a dry atmosphere at 50°C for 64 hours. The weight loss of water was measured and shown in Table by percentages. Gas permeability By means of a tester used for measuring gas permeability of paper and cardboard, a period of time required for permeating 100 ml of air was measured according to JIS D 8117. The results are shown in Table.

Claims: An impregnated material comprising an organic or inorganic material selected from the group consisting of a woven fabric, a non-woven fabric and an open cell porous material which is impregnated with a crosslinked copolymer which comprises: 50 to 95% by mole of repeating units derived from tetrafluoroethylene; 5 to 50% by mole of repeating units derived from a perfluoroalkyl vinyl ether of the formula: CF₂=CFOR f (I) wherein R f is a C₁-C₆ perfluoroalkyl group or a group of the formula: -(CF₂CFXO) n -R f (II) wherein R f is the same as defined above, X is a fluorine atom or a trifluoromethyl group and n is an integer of 1 to 10; and 0.1 to 20% by mole of repeating units based on the total mole of tetrafluoroethylene and the perfluoroalkyl vinyl ether (I) of a fluorine-containing vinyl ether of the formula: CF₂=CFO-(CF₂CF₂) m -CH₂I (III) wherein m is an integer of 1 to 10.

Inventors: KAWACHI, SHOJI, OKA, MASAHIKO, TOMODA, MASAYUSA, UETA, YUTAKA
Applicants: DAIKIN INDUSTRIES, LIMITED
Application year: 1986
Main classification: D06M15
IPC codes: D06N3, D06M15, D21H19, D06M101, C08J9