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The invention relates to a process for producing a separator comprising the steps of: providing a sheetlike porous substrate, a solvent, ceramic particles and an adhesion promoter; preparing a slip by mixing the solvent, the adhesion promoter and the ceramic particles; coating the substrate with the

The invention relates to a process for producing a separator comprising the steps of: providing a sheetlike porous substrate, a solvent, ceramic particles and an adhesion promoter; preparing a slip by mixing the solvent, the adhesion promoter and the ceramic particles; coating the substrate with the slip and thermally drying the coated substrate to obtain the separator. The problem addressed is that of specifying a process useful for producing separators having a higher ceramic content. The problem is solved when the solvent used is a mixture of water and at least one organic component; the adhesion promoter used is a mixture of silanes and at least one thermally crosslinkable acrylic polymer; the slip is admixed with a carboxylic acid preparation and also with a defoamer component free from silicone oil.

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1. A method for producing a separator, said method comprising: a) preparing a slip, comprising:a solvent comprising water and at least one organic compound;a thermally crosslinkable acrylic polymer;at least one silane selected from the group consisting of 3-aminopropyltriethoxysilane, 2-aminoethyl-3

1. A method for producing a separator, said method comprising: a) preparing a slip, comprising:a solvent comprising water and at least one organic compound;a thermally crosslinkable acrylic polymer;at least one silane selected from the group consisting of 3-aminopropyltriethoxysilane, 2-aminoethyl-3-aminopropyltrimethoxysilane, 3-glycidyloxy-trimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris(2-methoxyethoxy)silane, methyltriethoxysilane, and 3-glycidyloxypropyltriethoxysilane;particles of a ceramic;a carboxylic acid mixture having a melting point below 80° C. comprising carboxylic acids selected from the group consisting of a fatty carboxylic acid, an oily carboxylic acid and a polymeric carboxylic acid; anda silicone oil free defoamer;b) coating a sheetlike porous substrate with the slip; andc) thermally drying the coated substrate to obtain the separator. 2. The method according to claim 1, whereinthermally drying the coated substrate to obtain the separator in c) cures the silanes, crosslinks the acrylic polymer, and is carried out at a temperature below the glass transition temperature TG of the acrylic polymer. 3. The method according to claim 1, whereinthe acrylic polymer swells little or not at all in the solvent and is infusible after crosslinking in c). 4. The method according to claim 1, wherein the slip further comprises a silicate. 5. The method according to claim 1, wherein the silicone oil free defoamer component comprises an organic supporting medium and an organic solid. 6. The method according to claim 1, wherein the organic component of the solvent is an alcohol. 7. The method according to claim 1, wherein the porous substrate is a fibrous nonwoven web. 8. The method according to claim 1, wherein the porous substrate is a fibrous nonwoven web comprising organic fibres selected from the group consisting of polyacrylonitrile, polyester, polyimide, polyamide, polytetrafluoroethylene, polyethylene terephthalate and polyolefin. 9. The method according to claim 1, whereinthe ceramic particles have a non-spherical structure, andthe ceramic is selected from the group consisting of oxides of the metals Al, Zr, Si, Ti and Y. 10. The method according to claim 1, wherein the thermally crosslinkable acrylic polymer is in the form of a dispersion. 11. The method according to claim 10, wherein preparing the slip comprises:a) introducing the carboxylic acid mixture into the solvent;b) dispersing the ceramic particles in the carboxylic acid mixture solvent composition from a) to obtain a dispersion;c) introducing the silanes and the acrylic polymer into the solvent to obtain a sol;d) mixing the dispersion and the sol;e) admixing the silicone oil free defoamer component to the mixed dispersion and sol to obtain the slip. 12. The method according to claim 1, wherein a proportion of the silicone oil free defoamer component in the slip is less than 200 ppm. 13. The method according to claim 1, wherein a proportion of ceramic particles is in the range from 45 to 60 wt % in the slip and more than 90 wt % in the slip dried state. 14. The method according to claim 1, whereina content of the silane is from 25 to 45 wt % based on the weight of the thermally crosslinkable acrylic polymer and the at least one silane. 15. A separator obtained by the process according to claim 1. 16. The separator according to claim 15, wherein a content of the ceramic in the dried cured coating is 80 wt % or less. 17. The separator according to claim 15 wherein a thickness of the separator is from 18 to 25 μm and/or a porosity of the separator is from 30% to 70%. 18. An electric energy store or of an electrochemical cell comprising the separator of claim 15 positioned to insulate an electrode in said energy store or cell. 19. A composition configured for use in producing a separator comprising: a solvent comprising water and an alcohol; a thermally crosslinkable acrylic polymer;at least one silane selected from the group consisting of 3-aminopropyltriethoxysilane, 2-aminoethyl-3-aminopropyltrimethoxysilane, 3-glycidyloxy-trimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris(2-methoxyethoxy)silane, methyltriethoxysilane, and 3-glycidyloxypropyltriethoxysilane;particles of a ceramic;a carboxylic acid mixture having a melting point below 80° C. comprising carboxylic acids selected from the group consisting of a fatty carboxylic acid, an oily carboxylic acid and a polymeric carboxylic acid; and a silicone oil free defoamer.