Coating liquid, gas-barrier multilayer structure and gas-barrier shaped article therefrom, and process for producing gas-barrier multilayer structure

1. A coating liquid (A) consisting essentially of a solvent mixture of water and an organic solvent and a polycarboxylic acid polymer partially neutralized with a polyvalent metal wherein the polymer is both dissolved and dispersed as particles in the solvent mixture and wherein the particles dispersed account for 5 to 80 wt % of 100 wt % of the polycarboxylic acid polymer partially neutralized with a polyvalent metal.

2. The coating liquid (A) according to claim 1 , wherein the particles dispersed have an average particle diameter of 500 to 4000 nm.

3. The coating liquid (A) according to claim 1 , wherein the coating liquid (A) has a contact angle of not more than 70° with respect to a polypropylene resin (an unstretched polypropylene homopolymer film having a melting point of 158 to 162° C. and a density of 0.88 to 0.92 g/cm3) as measured by a θ/2 method.

4. The coating liquid (A) according to claim 1 , wherein the polycarboxylic acid polymer partially neutralized with a polyvalent metal is a reaction product of a polycarboxylic acid polymer with 0.05 to 0.30 chemical equivalent of a polyvalent metal compound based on the carboxyl groups in the polycarboxylic acid polymer.

5. The coating liquid (A) according to claim 1 , wherein the polycarboxylic acid polymer partially neutralized with a polyvalent metal is a reaction product of a polycarboxylic acid polymer with 0.01 to 0.35 chemical equivalent of an alkali metal compound based on the carboxyl groups in the polycarboxylic acid polymer and 0.05 to 0.75 chemical equivalent of a polyvalent metal compound based on the carboxyl groups in the polycarboxylic acid polymer (wherein the total of the alkali metal compound and the polyvalent metal compound does not exceed 1.00 chemical equivalent).

6. The coating liquid (A) according to claim 4 , wherein the polycarboxylic acid polymer is a (co)polymer of at least one polymerizable monomer selected from acrylic acid, maleic acid, methacrylic acid and itaconic acid, or a mixture of such (co)polymers.

7. The coating liquid (A) according to claim 4 , wherein the polyvalent metal compound is a calcium compound or a zinc compound.

8. The coating liquid (A) according to claim 5 , wherein the alkali metal compound is a potassium compound or a sodium compound, and the polyvalent metal compound is a calcium compound or a zinc compound.

9. The coating liquid (A) according to claim 1 , wherein the organic solvent is at least one organic solvent selected from the group consisting of C1-5lower alcohols and C3-5lower ketones, and the solvent mixture contains water at 20 to 95 wt % and the organic solvent at 80 to 5 wt % (wherein the total of water and the organic solvent is 100 wt %).

10. A gas-barrier multilayer structure comprising a support and a gas-barrier layer (a) on at least one surface of the support wherein the gas-barrier layer (a) is formed from a coating liquid (A) consisting essentially of a solvent mixture of water and an organic solvent and a polycarboxylic acid polymer partially neutralized with a polyvalent metal wherein the polymer is both dissolved and dispersed as particles in the solvent mixture and wherein the particles dispersed account for 5 to 80 wt % of 100 wt % of the polycarboxylic acid polymer partially neutralized with a polyvalent metal.

11. A gas-barrier multilayer structure comprising a support and a laminate unit on at least one surface of the support wherein the laminate unit comprises a gas-barrier layer (a) formed from a coating liquid (A) consisting essentially of a solvent mixture of water and an organic solvent and a polycarboxylic acid polymer partially neutralized with a polyvalent metal wherein the polymer is both dissolved and dispersed as particles in the solvent mixture and wherein the particles dispersed account for 5 to 80 wt % of 100 wt % of the polycarboxylic acid polymer partially neutralized with a polyvalent metal and a polyvalent metal compound-containing layer (b) in contact with each other.

12. The gas-barrier multilayer structure according to claim 11 , wherein the polyvalent metal compound-containing layer (b) is formed from a coating liquid (B) containing a polyvalent metal compound.

13. A gas-barrier shaped article comprising the gas-barrier multilayer structure of claim 10 , wherein said gas-barrier shaped article has a shape selected from the group consisting of films, sheets, bottles, cups and trays.

14. A process for producing gas-barrier multilayer structures, which process comprises applying a coating liquid (A) consisting essentially of a solvent mixture of water and an organic solvent and a polycarboxylic acid polymer partially neutralized with a polyvalent metal wherein the polymer is both dissolved and dispersed as particles in the solvent mixture and wherein the particles dispersed account for 5 to 80 wt % of 100 wt % of the polycarboxylic acid polymer partially neutralized with a polyvalent metal on at least one surface of a support and drying the liquid to form a gas-barrier layer (a).

15. A process for producing gas-barrier multilayer structures, which process comprises applying a coating liquid (A) consisting essentially of a solvent mixture of water and an organic solvent and a polycarboxylic acid polymer partially neutralized with a polyvalent metal wherein the polymer is both dissolved and dispersed as particles in the solvent mixture and wherein the particles dispersed account for 5 to 80 wt % of 100 wt % of the polycarboxylic acid polymer partially neutralized with a polyvalent metal on at least one surface of a support; drying the liquid to form a gas-barrier layer (a); applying a coating liquid (B) containing a polyvalent metal compound on the gas-barrier layer (a); and drying the liquid to form a polyvalent metal compound-containing layer (b) on the gas-barrier layer (a).