Paper surface treatment compositions

1. A method of preparing a surface-treated cellulosic substrate, the method comprising:

applying a surface treatment composition to a cellulosic substrate, the composition being prepared by a method comprising the steps of:

(a) introducing (i) a source of boron, (ii) a crosslinking di-aldehyde, and (iii) a blocking agent to form a crosslinking composition;

(b) introducing the crosslinking solution with starch and optionally pigments and/or optionally polymeric particles to form the composition, where the surface treatment composition is characterized by a pH from about 7 to about 9.

2. The method of claim 1 , where the surface treatment composition is characterized by a viscosity of less than 2500 cps.

3. The method of claim 1 , wherein the surface treatment composition is characterized by a solids content of from about 30 to about 80.

4. The method of claim 1 , wherein the starch is selected from the group consisting of modified starches and natural starches.

5. The method of claim 1 , where the starch is selected from the group consisting of ethylated (hydroxylated) starch, peroxide-treated starch (acid modified), and cationized starch.

6. The method of claim 1 , wherein the dialdehyde includes glyoxal.

7. The method of claim 1 , wherein the surface treatment composition includes a pigment selected from the group consisting of kaolin clay, calcium carbonate, titanium dioxide, gypsum, talc, and plastic pigments.

8. The method of claim 1 , wherein the polymer particles are selected from the group consisting of elastomeric particles, styrene acrylates, and polyvinyl acetate particles.

9. The method of claim 1 , wherein the polymer particles include styrene-butadiene latexes and derivatives thereof.

10. The method of claim 1 , wherein the cellulosic substrate includes paper or paper board.

11. The method of claim 1 , where said step of applying forms a coating on at least one surface of the cellulosic substrate, and wherein the wet thickness of the coating is from about 1 to about 30 microns.

12. The method of claim 1 , wherein the source of boron includes a borate.

13. The method of claim 1 , where the surface treatment composition includes calcium carbonate pigment and is characterized by a pH of at least 8.5.

14. The method of claim 1 , where said step of introducing a source of boron and a dialdehyde includes introducing an aqueous borate solution and an aqueous glyoxal solution.

15. The method of claim 1 , where the blocking agent includes a compound that binds chemically to the di-aldehyde and upon a threshold level of dehydration, will allow the di-aldehyde to react and crosslink starch.

16. The method of claim 1 , where the blocking agent includes pentaerythritol, glycerin, lanolin, a mono or oligosaccharide having multiple hydroxyl groups, or a mixture thereof.

17. The method of claim 1 , where the blocking agent includes sorbitol.

18. The method of claim 1 , where the blocking agent includes pentaerythritol.