Water-resistant alkaline corrugating adhesive composition

Claim 2

In a process for preparing a crosslinking additive for imparting water resistance to starch-based corrugating adhesive compositions wherein acetone and formaldehyde are reacted in a molar ratio of 1 mole of acetone to about 2 to 5.5 moles of formaldehyde under aqueous alkaline conditions at about 20°-80° C. to obtain a water-soluble acetone-formaldehyde condensate containing about 1-10% unreacted formaldehyde, the improvement which comprises adding to said water-soluble acetone-formaldehyde condensate at least an effective amount of dihydroxyethylene urea to react with the unreacted formaldehyde present therein and allowing the reaction to proceed at about 20°-80° C. until the unreacted formaldehyde remaining is reduced to about 0.1-2% by weight.

Claim 3

The process of claim 1 further comprising adding dimethylol dihydroxyethylene urea to said crosslinking additive.

Claim 4

The process of claim 1 wherein the reaction with dihydroxyethylene urea proceeds at about 30°-60° C. until the unreacted formaldehyde remaining is 0.1 to 1.5%.

Claim 5

The process of claim 1 wherein the reaction of acetone and formaldehyde proceeds at about 30°-50° C. at pH 8-12, and the molar ratio is 1 mole acetone to about 3 to 5 moles formaldehyde.

Claim 6

The process of claim 1 further comprising neutralizing said crosslinking additive after it is prepared.

Claim 7

The crosslinking additive produced by the process of claim 1.

Claim 8

The crosslinking additive produced by the process of claim 2.

Claim 9

A water-resistant alkaline curing, starch-based corrugating adhesive composition comprising: A. from about 10 to 40%, based on total weight of the adhesive, of starch, this including the ungelatinized as well as the gelatinized portions of the starch; B. from about 0.3 to 5%, based on total weight of the starch, of an alkali; C. from about 54 to 89%, based on total weight of the adhesive, of water; and D. from about 0.3 to 10%, based on total weight of the starch, dry basis, of a crosslinking additive prepared by reacting acetone and formaldehyde in a molar ratio of 1 mole of acetone to about 2 to 5.5 moles of formaldehyde under aqueous alkaline conditions at about 20°-80° C. to obtain a water-soluble acetone-formaldehyde condensate containing about 1-10% unreacted formaldehyde; adding to the condensate at least an effective amount of dihydroxyethylene urea to react with the unreacted formaldehyde present therein; and allowing the reaction to proceed at about 20°-80° C. until the unreacted formaldehyde remaining is reduced to about 0.1-2% by weight.

Claim 10

A water-resistant alkaline curing, starch-based corrugating adhesive composition comprising: A. from about 10 to 40%, based on total weight of the adhesive, of starch, this including the ungelatinized as well as the gelatinized portions of the starch; B. from about 0.3 to 5%, based on total weight of the starch, of an alkali; C. from about 54 to 89%, based on total weight of the adhesive, of water; and D. from about 0.3 to 10%, based on total weight of the starch, dry basis, of a crosslinking additive prepared by reacting acetone and formaldehyde in a molar ratio of 1 mole of acetone to about 2 to 5.5 moles of formaldehyde under aqueous alkaline conditions at about 20°-80° C. to obtain a water-soluble acetone-formaldehyde condensate containing about 1-10% unreacted formaldehyde; adding to the condensate at least an effective amount of dihydroxyethylene urea to react with the unreacted formaldehyde present therein; and allowing the reaction to proceed at about 20°-80° C. until the unreacted formaldehyde remaining is reduced to about 0.1-2% by weight.

Claim 11

The adhesive of claim 8 further comprising up to 5%, based on total weight of the starch, of borax.

Claim 12

The adhesive composition of claim 8 comprising 18-35% starch, 1-4% alkali, 60-81% water and 1-5% crosslinking additive.

Claim 13

The adhesive composition of claim 8 wherein dimethylol dihydroxyethylene urea is added to the crosslinking additive after preparation thereof.