Patent Application
20180215879
The present invention relates to low-VOC, tertiary amines from renewable raw materials for stabilizing aqueous polymer dispersions against electrolytes.
Polymer dispersions have many uses for film formation in emulsion paints and printing inks, adhesives, textile and leather coating and also in paper coating and upgrading. For this purpose, the dispersions have to be stable to environmental influences and also to typical formulation constituents in the end applications.
According to the prior art, polymer dispersions are typically neutralized using alkali metal hydroxides or ammonia.
DE-1956509 teaches polymer dispersions which are stabilized by neutralization with alkanolamines and form homogeneous films even at room temperature.
EP-1177223 teaches aqueous polymer dispersions whose anionic groups have been neutralized with N-methylglucamine.
EP-0614881, U.S. Pat. No. 5,449,770 and U.S. Pat. No. 2,016,962 describe methods for preparing glucamines from glucose.
EP-1676831 describes tertiary N,N-dialkylglucamines such as N,N-diethyl-glucamine and relatively long-chain dialkylamines for use as emulsifier, wetting agent and dispersant for applications in coatings, inks, adhesives, agricultural formulations, shampoos and cleaners and also in oil recovery or in cement processing.
A disadvantage of the neutralizing agents described in the prior art is that they have only limited electrolyte stability.
It was therefore an object of the present invention to increase the stability of polymer dispersions toward electrolytes such as CaCO3, which are customarily used as fillers in paints or adhesives.
It has now surprisingly been found that polymer dispersions whose pH is set by means of N,N-dialkylamines have improved electrolyte stability over a wider temperature range than the comparative examples ammonia and N-methyl-glucamine.
The invention accordingly provides for the use of an amine base for neutralization of a polymer dispersion, wherein the amine base used corresponds to the formula (I)
where R1 is C1-C4-alkyl, CH2CH2OH or CH2CH(CH3)OH.
R1 is preferably methyl or CH2CH2OH.
The polyhydroxy unit is a hexose, preferably the epimer glucose.
The compounds of the formula (I) can be used as pure substances or as aqueous solutions. The tertiary amines such as N,N-dimethylglucamine, N-hydroxyethyl- and N-hydroxypropyl-N-methylglucamine have little susceptibility to formation of nitrosamines and are to be preferred.
The polymer dispersion is a homopolymer or copolymer of olefinically unsaturated monomers. Preferred olefinically unsaturated monomers are, for example,
In a further preferred embodiment, at least one of the olefinically unsaturated monomers contains an anionic group. In a particularly preferred embodiment, the anionic group is an acrylate.
The invention further provides a method of improving the electrolyte stability of polymer dispersions, wherein >0.01%, preferably 0.01-10%, in a particularly preferred embodiment 0.01-5%, of the amine base (I) is added to the polymer dispersion. The addition of the base can be carried out during the polymerization or afterward. The percentages refer to the weight of the compound of the formula (I).
The dispersions according to the invention are suitable for producing coatings of all types. The dispersions according to the invention are particularly suitable for producing paints, printing inks and emulsion paints, emulsion varnishes and also adhesives and sealants.
To determine the electrolyte stability, a 5% strength CaCl2 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 CaCl2 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.
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.
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.
To produce the initiator solution, 2.3 g of potassium peroxodisulfate were dissolved in 74.5 g of deionized water.
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.
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.
To produce the initiator solution, 3.8 g of ammonium peroxodisulfate were dissolved in 98.5 g of deionized water.
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.
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).
It was surprisingly found that dialkylglucamines display better electrolyte stabilities than the comparative examples ammonia and NMG.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2015 213 123.8 | Jul 2015 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2016/063433 | 6/13/2016 | WO | 00 |
