SK281409B6 - Process of preparation of a copolymer dispersion, based on vinylester of versatic acid, vinylacetate and acrylate esters - Google Patents

Abstract

A copolymeric aqueous dispersion based on vinylic acid, vinyl acetate and acrylate esters is prepared by emulsion copolymerization by dispensing into the aqueous phase components of an emulsion system consisting of a protective colloid and a non-ionic emulsifier, electrolyte and the necessary amount of water. After heating the aqueous phase to a temperature of about 70 ° C, an initial batch of monomer mixture is added to the aqueous weight and the polymerization reaction is initiated by adding a determined amount of potassium, sodium or ammonium persulphate. Upon polymerization of the initial batch of monomer mixture, an increasing amount of the monomer mixture is added to the reaction system. At the end of the dosing, the dispersion is maintained at 79-80 ° C for 30-45 minutes and cooled.

Description

The present invention relates to a process for the preparation of an aqueous copolymer dispersion, emulsion copolymerization of versatic acid ester, vinyl acetate and acrylate esters using potassium, sodium or ammonium persulphate, wherein the polymer is characterized by properties that allow its use in outdoor (outdoor) conditions, especially in various applications. in the construction industry, and for the preparation of anticorrosive primers.

BACKGROUND OF THE INVENTION

Emulsion polymerization and copolymerization of vinyl acetate, vinylesters of versatic acid and acrylate esters, either alone or as copolymers and terpolymers with various other monomers and with each other, are used to prepare polymer dispersions for both traditional and special applications.

One of the areas of application of aqueous polymer dispersions is the construction industry, where polymer dispersions are used in both exterior and interior applications, especially in paints, as an additive to polymer cement mortars, concrete, renderings, screeds, sealants and building adhesives .

Aqueous copolymer dispersions also find application in the preparation of basic anticorrosive paints.

The use of aqueous copolymer dispersions in exterior façade paints as well as in anticorrosive coatings imposes high quality requirements on the dispersion and the polymer contained therein. In the past, mainly solvent coating systems have been used in these applications, which are still in use today. At present, however, the most widely used method of protection against external influences, including corrosion, is the application of organic coatings. The development and application of new, constantly improved surface protection systems today is influenced by a number of factors, the most important of which are the environmental and economics of surface treatments. From this point of view, an organic coating must meet the requirements for physiological harmlessness, low or no organic solvent content, no toxic pigments, and applicability independent of environmental influences.

The environmental aspect has been gaining importance in recent years and is a limiting factor in many countries. In the past, attention has been directed primarily to the volatile organic compounds contained in the paints. Combating organic solvent emissions has greatly reduced both manufacturers and processors of conventional paints. Paints based on organic solvents are therefore replaced by water-borne, powdered and high-solid paints.

Building paints form a significant group of water-based paints. They are used for painting plasters, concrete, ceramic, fibreboard or wood walls and drywall. Both types of paints for construction - exterior and interior - are highly filled paints in which the volume concentration of pigments and fillers (OKP) is 50 to 80%. Thus, they are filled to a higher or equal concentration than the critical pigment volume concentration (KOKP) value in the system. The content of the binder (aqueous dispersion) is in the range of 5 to 25% by weight. The specific amount of binder is dependent on the ability of the binder to bind pigment and filler particles.

Dispersion paints contain a variety of ingredients which affect the properties of both the paint itself and the film formed after it has dried. The chemical composition affects the Tg (glass transition temperature), MFT (minimum film forming temperature) values, which have a significant effect on the applicability of the prepared paint. The polymer composition also affects the physico-mechanical properties of dry films such as ductility, thermal expansion, flexibility, etc. The resulting film properties may also be affected by the initiation system used. Likewise, the protective colloid or surfactant can affect the absorbency of the dispersion film to some extent. The choice of a suitable dispersion for the coating formulation must be selected with respect to the chemical composition of the dispersion, the initiator system used and the protective colloid or surfactant.

In addition to the above-mentioned requirements for the aqueous polymer dispersion used for the preparation of building (facade) paints, it must contain a polymer which provides the facade paint with desired gloss, adhesion and hardness, low diffusion resistance and water absorption, good washability and high abrasion resistance. UV resistance is a very important criterion.

Aqueous polymer dispersion suitable for formulating anticorrosive primers should contain a polymer from which the protective film formed after the paint has dried must fulfill a protective function under the action of water and moisture, polluted atmosphere (SO ₂ , CK), oxygen, elevated temperature and UV radiation ( for the top layers of the system).

Aqueous polymer dispersions belong to a group of substances which fully meet the requirements for the formulation of building and anticorrosive primers from an environmental point of view. It has been shown that by the appropriate composition of the monomer mixture and the polymerization process, the conditions under which the resulting polymer particles and their distribution, as well as the polymer structure, favorably affect the homogeneity of the polymer film formed from the dispersion and hence its application properties in the desired direction. The prepared aqueous copolymer dispersion with its properties as well as the properties of the polymer contained therein is suitable for the preparation of exterior (facade) and interior building paints, as well as for the preparation of basic anticorrosive paints.

The present invention provides a process for preparing such an aqueous polymer dispersion.

SUMMARY OF THE INVENTION

Process for preparing an aqueous copolymer dispersion based on vinyl ester versatic acid, vinyl acetate and acrylate esters, by emulsion copolymerization in an aqueous phase medium containing polyvinyl alcohol as a protective colloid, alkylpolyethylene glycol ether as a non-ionic emulsifier and an electrolyte system according to the invention, having a composition of 20-40 wt. vinyl acetate, 40-55 wt. % vinyl ester of versatic acid, 15 - 25 wt. % methyl methacrylate and up to 15 wt. 2-ethylhexyl acrylate is added to the aqueous phase at temperatures above 67 ° C, the temperature of the reaction mixture does not exceed 80 ° C throughout the preparation, with the monomer mixture added at a constant rate for 140 minutes and then uniformly reduced to 0, 85 to 0.45 wt. parts per minute, based on the total batch, at a dosing time of 270 to 300 minutes, or dosed at a constant rate of 235 to 245 minutes, adding to 3 to 10 times 2.3 wt. parts by weight of potassium, sodium or ammonium persulfate, all based on 1000 wt. parts of the polymerization batch.

SK 281409-6

DETAILED DESCRIPTION OF THE INVENTION

Example 1

18% by weight of the aqueous phase components are gradually fed into the polymerization reactor. parts by weight of polyvinyl alcohol having a molecular weight given by a K-value of 45-55, calculated according to Fickentscher, with a residual acetate content of 10-15% by weight; and specific electrical conductivity max. 200 pS.cm ^-1 (commercial name Duvioi SP-1), 18 wt. parts by weight of an alkylpolyethylene glycol ether, characterized by a content of ethalene oxide of 87-93 wt. and a relative number expressing the hydrophilic lipophilic balance (HLB) of 16-20 (trade name Slovasol 2430), 1.5 wt. parts of NaHCO ₃ and enough water to not exceed a total amount of 478.5 wt. parts.

The aqueous phase thus prepared is heated to 69-70 ° C with stirring and 23.8 wt. % of the monomer mixture, which is 5 wt. of its total. The monomer mixture has a composition of - 20 wt. % vinyl acetate, 45 wt. % vinyl ester of versatic acid (trademark VeoVa 10), 20 wt. % methyl methacrylate and 15 wt. 2-ethylhexyl acrylate. After 5 to 10 minutes of emulsification, a first initiator dose of 1.5 wt. parts of potassium sulfate peroxide. After addition of the initiator, the temperature of the reaction mixture started to rise due to the reaction. After reaching a temperature of 72-73 ° C, the remaining 452.9 wt. parts of the monomer mixture. Within 140 minutes, the mixture was dosed at a uniform rate of 1.95 wt. parts per minute. Starting from the 140th minute, the feed rate is uniformly reduced, so that in the last 10 minutes the monomer mixture is dosed at a rate of 0.85 to 0.45 wt. parts per minute. The dosing of the monomer mixture takes a total of 270 to 300 minutes.

The temperature of the reaction mixture was maintained at 74-76 ° C throughout the dosing period. At the 120-minute feed rate of the monomer mixture, a second batch of initiator is added to the polymerization batch in an amount of 0.4 wt. parts of potassium persulfate, additional portions are added at 150 minutes in an amount of 0.1 wt. parts and then at 180, 210, 240 and 270 minutes, each in an amount of 0.075 wt. parts of potassium persulphate.

After the monomer mixture is dosed, the polymerization batch is maintained at 78-80 ° C for 30-45 minutes. During this time, the free monomers have reacted and then the reactor contents are cooled to 30-35 ° C. parts of ethylene glycol.

The amounts of the individual components, expressed in wt. parts are based on 1000 wt. parts of the polymerization batch.

The dispersion prepared as described above has the following quality:

- Content of non-volatile matter - min. % 50 wt. - Viscosity (Rheotest) - 2 - 3 Pa.s. - Particle size - 120 - 150 nm ~ pH -4-5 - Minimum film-forming temperature (MFT) -4 ° C - Absorption of polymer film in water - 10 - 30 wt. - Degree of alkaline hydrolysis movie - 0 wt. - Film abrasion -> 45 minutes - Ductility of the film -800- 1500%

The dispersion facade coating has the following properties:

- Adhesion to the substrate -1. degree - Diffusion resistance - 65 - 80 - Absorbency -0.02 - 0.06 kg / m ² - Hardness -19-25% - Wet wipes - approx. 5000 cycles

- After 1000 hours of exposure to alternating UV rays, water rinsing, -20 and + 50 ° C exposure, there was no change in gloss, hue, adhesion and weight from the original values.

Example 2

Preparation procedure as in Example 1 except that a mixture of monomers having a composition of 40 wt. % vinyl acetate, 40 wt. % vinyl ester of versatic acid (VeoVa 10), 15 wt. % methyl methacrylate and 5 wt. 2-ethylhexyl acrylate. The monomer mixture is metered in at a constant rate of 1.89 wt. parts per minute, dosing lasting 235 to 245 minutes. The peroxodisulphate initiator is added to 3x, the first dose being 1.5 wt. parts. An additional portion is added in the 120th minute of dosing in an amount of 0.5 wt. parts and the last in an amount of 0.3 wt. parts are added after the dosing of the monomer mixture is complete.

The prepared dispersion and the facade paint formulated therefrom have similar properties to those described in Example 1.

Example 3

The preparation process and the amounts of the individual components of the polymerization system as in Examples 1 and 2, except that the composition of the monomer mixture is 20% by weight. % vinyl acetate, 55 wt. % vinyl ester of versatic acid (VeoVa 10) and 25 wt. methyl methacrylate.

The prepared dispersion and the façade paint of the formulated base have similar properties as in Example 1.

Example 4

The preparation process and the amounts of the individual components of the polymerization system as in Examples 1 and 2, except that the composition of the monomer mixture is 20% by weight. % vinyl acetate, 50 wt. % vinyl ester of versatic acid (VeoVa 10), 25 wt. % methyl methacrylate and 5 wt. 2-ethylhexyl acrylate.

The prepared dispersion has similar properties to that of Example 1, and the base anticorrosive paint formulated thereon, in addition to the basic properties, meets the requirements of the accelerated NaCl and SO ₂ atmospheric exposure tests.

Industrial usability

Polymer dispersions prepared on the basis of vinyl ester of versatic acid, vinyl acetate and acrylate esters prepared according to the invention extend the possibilities of preparing polymeric aqueous dispersions and are useful in the paint industry and in the construction industry.

Claims (2)

A process for the preparation of an aqueous copolymer dispersion based on vinyl ester versatic acid, vinyl acetate and acrylate esters, by emulsion copolymerization in an aqueous phase medium containing polyvinyl alcohol and alkylpolyethylene glycol ether, by peroxydisulfate initiator system, characterized in that the mixture has a monomer mixture of 20% by weight. % vinyl acetate, 40-55 wt. % vinyl ester of versatic acid, 15 - 25 wt. % methyl methacrylate and up to 15 wt. The 2-ethylhexyl acrylate is added to the aqueous phase at temperatures above 67 ° C, while the temperature of the reaction mixture does not exceed 80 ° C throughout the preparation, the monomer mixture is added at a constant rate for 140 minutes and then the rate of addition is uniformly reduced to 0.85 to 0.45 wt. parts per minute, based on the total batch, at a dosing time of 270, resp. 300 minutes, or dosed at a constant intensity over 235 to 245 minutes, adding 2.3 to 2.3 times by weight. parts by weight of potassium, sodium or ammonium persulfate per 1000 wt. parts of the total polymerization batch.