Laminate and production process thereof

1. A laminate having a layer structure that a carboxyl group-containing polymer layer (A) and a polyvalent metal compound-containing layer (B) are arranged adjacently to each other on at least one side of a polymeric base,

wherein the polyvalent metal compound-containing layer (B) contains particles of a polyvalent metal compound, a binder resin and a surfactant, and

wherein the laminate has an oxygen transmission rate of no more than 1,000 cm 3 (STP)/(m 2 ·day·MPa) as measured at 30° C. and 0% relative humidity as well as at 30° C. and 80% relative humidity.

2. The laminate according to claim 1 , wherein the carboxyl group-containing polymer layer (A) is ionically crosslinked by a polyvalent metal ion migrated from the polyvalent metal compound-containing layer (B).

3. The laminate according to claim 1 , wherein a multi-layer film having a layer structure that the carboxyl group-containing polymer layer (A)/the polyvalent metal compound-containing layer (B), the polyvalent metal compound-containing layer (B)/the carboxyl group-containing polymer layer (A)/the polyvalent metal compound-containing layer (B), or the carboxyl group-containing polymer layer (A)/the polyvalent metal compound-containing layer (B)/the carboxyl group-containing polymer layer (A) are arranged in this order is arranged on at least one side of the polymeric base.

4. The laminate according to claim 1 , wherein at least one another resin layer is further arranged on at least one side of the polymeric base in addition to the multi-layer film having the layer structure.

5. The laminate according to claim 1 , wherein the polymeric base is a plastic film, and the whole laminate is a multi-layer film.

6. The laminate according to claim 1 , wherein a proportion of the polyvalent metal compound particles to the carboxyl group-containing polymer is a proportion that a chemical equivalent of the total (Bt) of the polyvalent metal compound particles to the total (At) of the carboxyl group in the carboxyl group-containing polymer amounts to at least 0.6.

7. The laminate according to claim 1 , wherein the carboxyl group-containing polymer is a homopolymer of a carboxyl group-containing unsaturated monomer, a copolymer of carboxyl group-containing unsaturated monomers, a copolymer of a carboxyl group-containing unsaturated monomer and any other polymerizable monomer, a carboxyl group-containing polysaccharide or a mixture thereof.

8. The laminate according to claim 1 , wherein the carboxyl group-containing unsaturated monomer is at least one α,β-monoethylenically unsaturated carboxylic acid selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid and fumaric acid.

9. The laminate according to claim 1 , wherein the polyvalent metal compound particles are particles having an average particle diameter of 10 nm to 10 μm.

10. The laminate according to claim 1 , wherein the polyvalent metal compound is an oxide, carbonate, organic acid salt or alkoxide of beryllium, magnesium, calcium, copper, cobalt, nickel, zinc, aluminum or zircomum.

11. The laminate according to claim 1 , wherein the polyvalent metal compound particles are particles of a divalent metal compound.

12. The laminate according to claim 1 , wherein the polyvalent metal compound-containing layer (B) contains the polyvalent metal compound particles and the binder resin in a proportion of 99:1 to 1:99 in terms of a mass ratio.

13. The laminate according to claim 1 , wherein the polyvalent metal compound-containing layer (B) contains the polyvalent metal compound particles and the surfactant in a proportion of 99.9:0.1 to 50:50 in terms of a mass ratio.

14. The laminate according to claim 1 wherein the thickness of the carboxyl group-containing polymer layer (A) is 0.001 μm to 1 mm, and the thickness of the polyvalent metal compound-containing layer (B) is 0.00 1 μm to 1 mm.

15. The laminate according to claim 1 , which is obtained by a process comprising forming at least one carboxyl group-containing polymer layer (A) and at least one polyvalent metal compound-containing layer (B) adjacently to each other on the polymeric base by a coating method and then aging the formed layers under an atmosphere of a relative humidity of at least 20% and a temperature of 5° C. to 200° C. to cause the polyvalent metal compound to migrate from the polyvalent metal compound-containing layer (B) into the carboxyl group-containing polymer layer (A), thereby forming a polyvalent metal salt with the carboxyl group in the carboxyl group-containing polymer layer.

16. The laminate according to claim 1 , wherein the carboxyl group-containing polymer layer (A) comprises

a) at least one carboxyl group-containing polymer selected from the group consisting of a homopolymer of an α,β-monoethylenically unsaturated carboxylic acid, a copolymer of α,β-monoethylenically unsaturated carboxylic acids, a copolymer of an α,β-monoethylenically unsaturated carboxylic acid and an ethylenically unsaturated monomer, and a partially neutralized product thereof in which a part of the carboxyl group is neutralized with an alkali hydroxide or a volatile base with a degree of neutralization of at most 20%; and

b) at least one additive component selected from the group consisting of other polymers, softening agents, stabilizers, anti-blocking agents, pressure-sensitive adhesives, inorganic lamellar compounds, colorants and ultraviolet absorbents in the range of at most 1% by weight in terms of the total amount of the additives based on the weight of the carboxyl group-containing polymer.

17. The laminate according to claim 16 , wherein the at least one carboxyl group-containing polymer is a polyacrylic acid or a partially neutralized product of a polyacrylic acid.

18. The laminate according to claim 16 , wherein the carboxyl group-containing polymer layer (A) further comprises a polyhydric alcohol as a crosslinking agent in which a proportion of the carboxyl group-containing polymer to the polyhydric alcohol is 5:95 to 90:10 in terms of a mass ratio.

19. The laminate according to claim 16 , wherein the surfactant is an ester type nonionic surfactant, or an anionic surfactant, or a surfactant having a polymer skeleton.

20. The laminate according to claim 1 , wherein the laminate has an oxygen transmission rate of no more than 500 cm 3 (STP)/(m 2 ·day·MPa) as measured at 30° C. and 0% relative humidity as well as at 30° C. and 80% relative humidity.

21. The laminate according to claim 1 , wherein the laminate has an oxygen transmission rate of no more than 100 cm 3 (STP)/(m 2 ·day·MPa) as measured at 30° C. and 0% relative humidity as well as at 30° C. and 80% relative humidity.