Water-soluble label adhesive formula

[formula]

Polyvinyl alcohol (7-99 type)

5~10

Formaldehyde (36%~37%)

20~40

corn starch

3~8

hydrochloric acid

Adjust the pH to 2 or so

Sodium hydroxide

Adjust the pH to 7~8

Urea

Proper amount

Defoamer

Proper amount

preservative

Proper amount

Tap water

Add to 100

[Preparation method]

Add 3/4 formula water to the jacketed stainless steel reactor, raise the temperature to about 70°C, start the mixer, add polyvinyl alcohol, continue heating to 90~95°C to completely dissolve.

The temperature of the solution in the reactor was lowered to 80-85°C, and salt was added to adjust the pH to about 2 with stirring, and then the formaldehyde solution was added for condensation reaction for 40-60 minutes.

The remaining 1/4 formula water is used to mix the corn starch into a slurry, and the mixture is added into the reaction kettle to mix with the aforesaid glue under stirring. The temperature in the reaction vessel is maintained at 75-80° C., and the agitated corn starch is continuously gelatinized into a transparent state. It is fully dispersed in and crosslinked with polyvinyl formal glue.

The temperature of the glue in the reactor was reduced to below 50°C. The pH was adjusted to 7-8 with sodium hydroxide solution, and the amount of urea was increased to eliminate free formaldehyde.

Source: 21st Century Fine Chemicals Network