Transparent ionomeric films from blends of ionomeric copolymers
The present invention is a film obtained from a blend of chemically distinguishable copolymers, wherein the film has a light transmission of at least 85%, and/or a haze of less than 6%, and wherein the blend comprises a component copolymer has a secant modulus of less than 15,000 when cast independently into a film.
1 . A blend of at least a first copolymer and a second copolymer each of said copolymers being chemically distinguishable and being obtained by copolymerization of ethylene each independently with at least one other comonomer, wherein the at least one other comonomer is independently an ethylenically unsaturated carboxylic acid or derivative thereof, and wherein a film obtained from the blend (a) has a secant modulus of less than about 15,000 psi as measured according to ASTM D882-01 and (b) (i) transmits at least about 85% of incident visible light and/or (ii) has a haze value of equal to or less than about 6% as measured according to ASTM D1003-00.
2 . The blend of claim 1 wherein the at least first and second copolymers are ionomers.
3 . A film obtained from the blend of claim 1 .
4 . The film of claim 3 having a modulus as measured according to ASTM D882-01 which is less than that which would be predicted from a composition weighted average of the moduli of films obtained by producing films individually from the first copolymer and the second copolymer and further optional copolymers alone.
5 . The film of claim 3 that transmits at least about 88% of incident visible light or (ii) has a haze value of equal to or less than about 3% as measured according to ASTM D1003-00.
6 . The film of claim 5 wherein the at least first and second copolymers are ionomers.
7 . The film of claim 6 wherein the at least first and second ionomers are derived from copolymers that each independently comprises from about 8 wt % to about 20 wt % of carboxylic acid monomer, based on the total weight of the copolymer.
8 . The film of claim 7 wherein the at least first and second ionomers are derived from copolymers that each independently comprises from about 12 wt % to about 20 wt % of carboxylic acid monomer, based on the total weight of the copolymer.
9 . The film of claim 8 wherein the at least first and second ionomers are derived from copolymers that each independently comprises from about 14 wt % to about 19 wt % of carboxylic acid monomer, based on the total weight of the copolymer.
10 . The film of claim 9 wherein the first copolymer is present in a range of from about 20 wt % to about 60 wt %, and the second copolymer is present in a range of from about 80 wt % to about 40 wt %, and wherein the first copolymer is an ionomer component having a secant modulus of less than about 15,000 and the second copolymer is an ionomer component having an optical transmission of at least about 87%.
11 . A composition obtained from the melt extrusion of a blend of a first copolymer, a second copolymer and optional further copolymers each of said copolymers being chemically distinguishable and being obtained by copolymerization of ethylene with at least one other comonomer, wherein the at least one other comonomer is an ethylenically unsaturated carboxylic acid or derivative thereof, and wherein a film obtained from the blend (a) has a secant modulus of less than about 15,000 psi as measured according to ASTM D882-01 and (b) (i) transmits at least about 85% of incident visible light or (ii) has a haze value of equal to or less than about 6% as measured according to ASTM D1003-00.
12 . A film obtained from the blend of claim 11 .
13 . A photovoltaic cell module that comprises at least one encapsulant layer comprising an optically transparent film, said film comprising a blend of a first copolymer, a second copolymer and optional further copolymers each of said copolymers being chemically distinguishable and being obtained by copolymerization of ethylene each with at least one other comonomer, wherein the at least one other comonomer is independently an ethylenically unsaturated carboxylic acid or derivative thereof, and wherein the film (a) has a secant modulus of less than about 15,000 psi as measured according to ASTM D882-01 and (b) (i) transmits at least about 85% of incident visible light or (ii) has a haze value of equal to or less than about 6% as measured according to ASTM D1003-00.
14 . A process for preparing an optically transparent film having a modulus of less than about 15,000 psi as measured according to ASTM D882-01 wherein the film (i) transmits at least about 85% of incident visible light or (ii) has a haze value of equal to or less than about 6% as measured according to ASTM D1003-00, the process comprising the step of: blending at least two chemically distinguishable copolymers that are each obtained by copolymerization of ethylene with at least one other comonomer, wherein the at least one other comonomer is an ethylenically unsaturated carboxylic acid.