Copolymers of vinyl alcohol and itaconic acid for use in paper coatings
View Patent ↗The present invention is a composition useful for coating the surface of paper wherein the coating composition is an aqueous solution comprising less than 40 wt % water and consisting essentially of a polyvinyl alcohol copolymer that is at least about 95% hydrolyzed, and a process for preparing the same.
1. A method for preparing a high solids paper coating composition having an aqueous phase, said aqueous phase comprising a copolymer comprising units of vinyl alcohol, alkyl acrylate, itaconic acid and optionally vinyl acetate, said copolymer comprising i) less than about 5 mol % vinyl acetate units; (ii) about 1 mol % to about 9 mol % itaconic acid units; (iii) at least about 90 mol % vinyl alcohol units and (iv) about 1 mol % to about 9 mol % alkyl acrylate units wherein said copolymer is completely dissolved in said aqueous phase of the coating composition and the amount of water present in said aqueous phase is such that the concentration of water in the paper coating composition is less than 40% by weight, based on the total weight of the paper coating composition, the method comprising the steps of: providing a first aqueous composition and adding said copolymer as a dry solid component to said first aqueous composition.
2. A method of claim 1 wherein the alkyl acrylate units of the copolymer are present in the form of lactones.
3. A method of claim 1 wherein said first aqueous composition is a solution.
4. A method of claim 1 wherein said first aqueous composition is an aqueous mixture.
5. A method of claim 4 wherein said aqueous mixture is selected from the group consisting of aqueous slurries, aqueous dispersions and aqueous suspensions.
6. A method of claim 1 wherein the alkyl groups of said alkyl acrylate units have from 1 to 10 carbon atoms.
7. A method of claim 6 wherein the alkyl groups have from 1 to 3 carbon atoms.
8. A method of claim 7 wherein the alkyl groups have 1 carbon atom.
9. A method of claim 1 wherein the copolymer comprises less than about 3 mol % vinyl acetate units.
10. A method of claim 9 wherein the copolymer comprises less than about 1 mol % vinyl acetate units.
11. A method of claim 1 wherein the paper coating composition is prepared at a temperature of less than 30° C.
12. A method of claim 1 wherein the copolymer is soluble in the aqueous phase at a temperature of less than or equal to 25° C.
13. A method of claim 1 wherein the copolymer is at least about 95% hydrolyzed.