N,N-Dialkyl glucamine for stabilising polymer dispersions

Abstract

The invention relates to the use of an amine base as neutralisation agent for polymer dispersions, characterised in that the amine base used corresponds to the formula (I),

##STR00001##

where R.sup.1 represents C.sub.1-C.sub.4-alkyl, CH.sub.2CH.sub.2OH or CH.sub.2CH(CH.sub.3)OH.

Claims

1. A neutralizing agent for a polymer dispersion comprising an amine base, wherein the amine base corresponds to the formula (I), ##STR00003## where R.sup.1 is C.sub.1-C.sub.4-alkyl, CH.sub.2CH.sub.2OH or CH.sub.2CH(CH.sub.3)OH.

2. The neutralizing agent as claimed in claim 1, wherein R.sup.1 is methyl or CH.sub.2CH.sub.2OH.

3. The neutralizing agent as claimed in claim 1, wherein R.sup.1 is methyl.

4. The neutralizing agent as claimed in claim 1, wherein the concentration of the amine base of the formula (I) is from 0.01 to 10% by weight.

5. The neutralizing agent as claimed in claim 1, wherein the amount of the amine base of the formula (I) is from 0.01 to 5% by weight, based on the weight of the polymer dispersion.

6. The neutralizing agent as claimed in claim 1, wherein the concentration of the amine base of the formula (I) is from 0.01 to 1% by weight, based on the weight of the polymer dispersion.

7. The neutralizing agent as claimed in claim 1, wherein the polymer dispersion contains at least one anionic group.

8. The neutralizing agent as claimed in claim 7, wherein the anionic group in the polymer dispersion is an acrylate group.

9. The neutralizing agent as claimed in claim 1, wherein the pH of the neutralized dispersion is 7.

10. The neutralizing agent as claimed in claim 1, wherein the pH of the neutralized dispersion is >7.

11. A method of increasing the electrolyte stability of polymer dispersions, wherein 0.01% of an amine base of the formula (I) is added to a polymer dispersion, ##STR00004## where R.sup.1 is C.sub.1-C.sub.4-alkyl, CH.sub.2CH.sub.2OH or CH.sub.2CH(CH.sub.3)OH.

12. The method as claimed in claim 11, wherein the amine base of the formula (I) is used in an amount of from 0.01 to 10% by weight, based on the weight of the polymer dispersion.

13. The method as claimed in claim 11, wherein the amine base of the formula (I) is used in an amount of from 0.01 to 5% by weight, based on the weight of the polymer dispersion.

14. The method as claimed in claim 11, wherein R.sup.1 is methyl or CH.sub.2CH.sub.2OH.

15. The method as claimed in claim 11, wherein R.sup.1 is methyl.

16. The method as claimed in claim 12, wherein R.sup.1 is methyl or CH.sub.2CH.sub.2OH.

17. The method as claimed in claim 13, wherein R.sup.1 is methyl or CH.sub.2CH.sub.2OH.

Description

EXAMPLES

Determination of the Electrolyte Stability:

[0026] To determine the electrolyte stability, a 5% strength CaCl.sub.2 solution is stirred into the polymer dispersion (1:1 w/w). The mixture is immediately visually checked for coagulum formation after the addition of the CaCl.sub.2 solution is complete. If the mixture is still homogeneous, the polymer dispersion is introduced into a measuring cylinder, closed so as to be airtight and checked again for homogeneity after 24 hours; if no coagulation is found, the dispersion is heated stepwise and in each case stored for 24 hours at the corresponding temperature.

Determination of the Freeze-Thaw Stability:

[0027] To determine the freeze-thaw stability, the polymer dispersion is frozen at 18 C. for 8 hours. It is subsequently warmed to room temperature and checked visually for coagulum and speck formation.

Determination of the Storage Stability

[0028] To determine the storage stability, the dispersion is stored at 50 C. for 7 days in an oven. The dispersion is subsequently cooled to room temperature (20-25 C.) and assessed visually for phase separation and speck formation.

Preparation of the Pure Acrylate Dispersion:

[0029] To produce the initiator solution, 2.3 g of potassium peroxodisulfate were dissolved in 74.5 g of deionized water.

[0030] To prepare the monomer emulsion, 285 g of deionized water, 22.5 g of Emulsogen EPA 073, 19.0 g of nonionic emulsifier, 6.0 g of sodium hydrogencarbonate, 380 g of n-butyl acrylate, 380 g of methyl methacrylate and 7.6 g of methacrylic acid are combined in succession with vigorous stirring.

[0031] In the reaction vessel, 312 g of deionized water and 11.3 g of Emulsogen EPA 073 are heated to 80 C. while stirring in a nitrogen atmosphere. 19.2 g of the initiator solution and 27.5 g of the monomer emulsion are subsequently added, and after a further 15 minutes the remaining initiator solution and monomer emulsion are added at a uniform rate over a period of 3 hours. After the addition is complete, the mixture is stirred at 80 C. for a further 6 minutes and cooled to room temperature. The reaction mixture is filtered to determine coagulum, divided into three equal parts and neutralized with different bases.

Preparation of the Styrene-Acrylate Dispersion

[0032] To produce the initiator solution, 3.8 g of ammonium peroxodisulfate were dissolved in 98.5 g of deionized water.

[0033] To prepare the monomer emulsion, 284 g of deionized water, 22.5 g of Emulsogen EPA 073, 21.7 g of nonionic emulsifier, 4.0 g of sodium hydrogencarbonate, 342 g of styrene, 418 g of n-butyl acrylate and 7.6 g of methacrylic acid are combined in succession with rigorous stirring. In the reaction vessel, 286 g of deionized water and 11.3 g of Emulsogen EPA 073 are heated to 80 C. while stirring in a nitrogen atmosphere. 25.6 g of the initiator solution and 27.5 g of the monomer emulsion are subsequently added, and after a further 15 minutes the remaining initiator solution and monomer emulsion are added at a uniform rate over a period of 3 hours. After the addition is complete, the mixture is stirred at 80 C. for a further 6 minutes and cooled to room temperature. The reaction mixture is filtered to determine coagulum, divided into three equal parts and neutralized with different bases.

[0034] In a comparative trial, different emulsion polymers were prepared and neutralized to pH 7 using the amine bases ammonia, N-methylglucamine (NMG) and N,N-dimethylglucamine (DMG).

[0035] It was surprisingly found that dialkylglucamines display better electrolyte stabilities than the comparative examples ammonia and NMG.

TABLE-US-00001 Electrolyte stability at room Electrolyte temperature stability after Freeze- Monomer Nonionic Coagulum after 24 h at [ C.] thaw Storage Ex. system emulsifier Base >40 m Immediately 24 h 40 60 80 stability stability 1 (C) Pure Arkopal Ammoniacal solution 2853 ppm stable stable stable stable solid solid stable acrylate N 238 (25% strength) 2 (C) NMG stable stable stable stable solid solid stable 3 DMG stable stable stable stable stable solid stable 4 (C) Pure Emulsogen Ammoniacal solution 5646 ppm stable stable stable stable solid solid stable acrylate LCN 118 (25% strength) 5 (C) NMG stable stable stable stable solid solid stable 6 DMG stable stable stable stable stable solid stable 7 (C) Pure Emulsogen Ammoniacal solution 238 ppm stable stable stable stable solid solid stable acrylate LCN 287 (25% strength) 8 (C) NMG stable stable stable stable solid solid stable 9 DMG stable stable stable stable stable solid stable 10 (C) Styrene- Emulsogen Ammoniacal solution 1327 ppm stable stable stable stable solid solid stable acrylate LCN 287 (25% strength) 11 (C) NMG stable stable stable stable solid solid stable 12 DMG stable stable stable stable stable solid stable