CS268437B1 - Aqueous dispersions of synthetic polymers with increased frost resistance - Google Patents

Abstract

Increasing the frost resistance of aqueous dispersions of synthetic polymers to - 18 °C up to - 35 °C is achieved by using copolymers of vinyl chloride or styrene and acrylic acid esters, which in the polymer chain contain 3 to 20% by weight of acrylic acid or methacrylic acid in the form of ammonium salts derived from amines selected from the group containing acyclic and acyclic alkylamines or acyclic alkanolamines and mixtures thereof. Aqueous dispersions of polymers containing these ammonium salts have, in comparison with the original dispersions, higher viscosity, higher frost resistance, higher resistance to water and atmospheric influences, higher ductility and elasticity and a reduced minimum film-forming temperature.

Description

The invention relates to increasing the frost resistance of aqueous dispersions of synthetic polymers (hereinafter aqueous dispersions) containing in the polymer chain 3 to 20% by weight of acrylic acid and / or methacrylic acid in the form of ammonium salts derived from amines selected from the group consisting of acyclic and / or alicyclic alkylamines, and / or acyclic alkanolamines, singly or in combination with each other.

Aqueous dispersions of synthetic polymers are thermodynamically unstable due to the large interfacial surface and tend to coagulate. Important temperatures promoting coagulation include low temperatures. During the crystallization of water, the aqueous dispersion coagulates due to the mutual compression of the particles and the increasing concentration of electrolytes outside the crystals of the freezing water. Coagulation is an irreversible process and coagulated dispersions can no longer be used. The frost resistance of dispersions is partially increased by the incorporation of · polar hydroxyl groups into the polymer chain, which act in a dissociated state, i.e. at pH above 6. Some polymers, especially softer types - coagulate more easily than hard (NADIUS H., KING AP: J. Polym Sci., C 27, 311 (1969). , glycols, various surfactants, etc. (SLROKOVA GA et al., J. Pr. The disadvantage of these methods is the altered properties of films formed from aqueous polymer dispersions, such as higher absorbency, lower mechanical strength and turbidity of the film. at temperatures above 15 ° C. Processing of polymer dispersions is then only possible above this temperature and still depending on the minimum film-forming temperature (MFT).

The invention relates to aqueous dispersions of synthetic polymers which contain in the chain 3 to 20% by weight of acrylic acid and / or methacrylic acid in the form of ammonium salts derived from amines selected from the group consisting of acyclic and / or alicyclic alkylamines and / or acyclic alkanolamines, respectively. or in combination with each other. It has been shown experimentally that the steric arrangement of the individual comonomers, in particular alternating copolymers, gives stable salts (hydroxyalkyl-substituted salts) of polymers only at a content of at least 3% by weight of acyclic unsaturated monocarboxylic acid in the polymer chain, based on polymer dry weight. Suitable acids are acrylic acid and / or methacrylic acid. Suitable amines are mono-, di- and triethylamine, cyclohexylamine, dicyclohexylamine, morpholine and its derivatives, as well as alkanolamines monodi- and triethanolamine, diethylaminoethanol, alone or in combination with one another.

Dispersions containing the above-mentioned ammonium salts of polymers are characterized by a higher viscosity, high frost resistance, which is higher than -15 ° C for all salts and higher than -30 ° C in some types compared to the original dispersion. The aqueous dispersion retains these properties even in combination with various fillers and other modifying components to modify the properties of the final mass. Simultaneously with the increase in the frost resistance of the dispersion composition and the aqueous polymer dispersion, the minimum film-forming temperature (MFT) also decreases, thus expanding the application range of the use of aqueous polymer dispersions and compositions based on them. Films formed from alkyl- or alkanolmonium salts of aqueous dispersions of polymers according to the invention are soft, flexible and stretchable, have increased water resistance and are sufficiently weather-resistant. Alkanolammonium salts of carboxylated aqueous polymer dispersions give the corresponding amides at temperatures above 150 ° C, which are spatially crosslinked and form films with very good adhesion to substrates, are rigid, tough, have high mechanical strength, are water and weather resistant, and many organic solvents and thinners. Films from untreated dispersions at these temperatures are already beginning to show signs of degradation.

2. 268 437 01

Example 1

To 100.0 parts by weight of an aqueous styrene-butyl acrylate-acrylic acid dispersion with a weight of individual comonomers of 45: 52: 3, based on the dry weight of the polymer, 3.6 parts of diethylaminoethanol are gradually added with constant stirring. Neutralization takes place at 20 ° C for 30 min. After perfect homogenization: the dispersion has a viscosity of 520 mPas / 20 ° C against 320 mPas of the original dispersion, frost resistance 23 ° C against +6 ° C, MFT +5 ° C against +15 ° C, water absorption (24 h) 12.7 \ against 24.9% by weight, and elongation 780% against 490%.

Example 2

To 100.0 parts by weight of an aqueous dispersion of vinyl chloride-ethyl acrylate-methacrylic acid with a weight of individual comonomers of 22: 63:15, based on the dry weight of the polymer, 1.5 parts by weight of monoethanolamine and 4.0 parts by weight are added as in Example 1. parts of triethylamine. Neutralization takes place at 20 ° C for 14 minutes, at 10 ° C for 21 minutes. and at 30 ° C for 8 min. An aqueous dispersion with a viscosity of 680 mPas against 85 mPas of the original dispersion is formed, frost resistance -29 ° C against +8 ° C, MFT 6 ° C against 33 ° C, water absorption (24 h) 3.8% by weight, against 20.2 % by weight, and elongation 2,850% versus 1,630%.

Example 3

To 100.0 parts by weight of an aqueous dispersion of styrene-2-ethyl-hexyl acrylate-acrylic acid having a weight ratio of 45: 50: 5 of individual comonomers, 8.0 parts by weight of triethanolamine are added in a manner similar to Example 1. The treated dispersion has a viscosity of 480 mPas against 135, frost resistance -34 ° C against +11 ° C, MFT o ° C against +16 ° C, water absorption 2.6% by weight, against 14.8 and elongation 2,130% against 1 350%.

Example 4

To 100.0 parts by weight of an aqueous dispersion of butyl acrylate-ethyl acrylate-methacrylic acid with a weight ratio of 57:33:10 by weight of individual comonomers, based on the dry weight of the polymer, 5.0 parts of morpholine and 3.6 parts of dicyclohexylamine are added. The resulting product has a viscosity of 480 mPas against 210, frost resistance -37 ° C against + 8 ° C, MFT 0 ° C against + 9 ° C, water absorption (24 h) 1.9% by weight, against 11.8 and ductility 570 % vs. 310%.

The aqueous dispersions with increased frost resistance according to the invention can be used as conventional dispersions for the preparation of paints, for waterproofing materials, for sealants, for polymer-cement mixtures and especially where higher flexibility, ductility and toughness of the binder component are required.

Claims (3)

Aqueous dispersions of synthetic polymers with increased frost resistance based on comonomers of vinyl chloride or styrene and esters of acrylic acid, preferably ethyl, butyl or 2-ethylhexyl acrylate, characterized in that they contain 3 to 20% by weight of acrylic acid in the synthetic polymer chain and and / or methacrylic acid in the form of ammonium salts derived from amines selected from the group consisting of acyclic and / or alicyclic alkylamines and / or acyclic alkanolamines and mixtures thereof. 2. Aqueous dispersions according to claim 1, characterized in that the acyclic and / or alicyclic alkylamines are mono-, di-, triethylamine, morpholine and its derivatives, cyclohexylamine or dicyclohexylamine, alone or in combination with one another. 268 437 Bl 3. Aqueous dispersions according to claim 1, characterized in that the acyclic alkanolamines are mono-, di-, triethanolamine or diethylaminoethanol, alone or in combination with one another.