CS231383B1 - A method of preparing a low viscosity copolymer polyvinyl acetate dispersion - Google Patents

Abstract

The invention relates to the preparation of a low-viscosity copolymer polyvinyl acetate dispersion intended primarily for use as a binder for pigment coatings of paper, where the polyvinyl acetate dispersions used so far do not meet the specified requirements for processing and quality. This problem is solved by the present invention describing a method for preparing a low-viscosity copolymer polyvinyl acetate dispersion based on a mixture of vinyl acetate/n-butyl acrylate in the presence of alkyl polyglycol ether, alkaline salts of phosphoric acid with alkyl polyglycol ethers and alkaline salts of phosphoric acid and/or carbonic acid using a peroxybisulphate initiation system. In order to achieve high mechanical stability of the dispersion as well as other specific properties of the dispersion and the polymer film prepared from it, it is modified during its preparation and/or at the end of its preparation by adding an ethylene oxide-propylene oxide copolymer. The proposed method can be used to prepare a dispersion that, in terms of quality, meets the requirements for the use of dispersions in paper finishing.

Description

1,231,383

The invention is. relates to a process for preparing a low viscosity vinylate acetate / n-butyl acrylate based polyvinyl acetate dispersion suitable for use as a pigment for paper coating.

The funkyia of the binder in the coating composition is that. binds a. the particles of pigments to each other and simultaneously to the fibers of the substrate provided that:. pigments are kept in a stable suspension during the coating process.

In the preparation of the coating composition, a combination of natural or synthetic materials and combinations thereof may be used. In practice, the use of polymeric acrylate, styrene acrylate, butadiene styrene and vinyl acetate water dispersions as a binder for the preparation of pigmented pigments is widespread.

Of paints for paper, cardboard and cardboard. The presence of the dispersion in the paint affects the processing properties of which the most important are flow behavior, water retention capacity and resistance to mechanical and thermal stress. * Binder dispersion is also a significant part of the formation of the paper surface quality properties.

Of cardboard or cardboard treated with pigment coating compositions.

Pigment coating compositions prepared using medium-viscosity and high viscosity polyvinyl acetate dispersions containing protective cryoids (e.g. cellulose derivatives, polyvinyl alcohol and the like, exhibit undesirable high apparent, dynamic viscosity even at relatively low solids content, as well as undesirable dilatant flow and large thixotropy.

Certain improvements have been made by CS No. 191563, which allows the use of a protective colloid-free emulsion system to prepare a low viscosity copolymer polyvinyl acetate dispersion allowing the control of selected mechanical properties of the film formed by drying the dispersion and allowing the preparation of pigment coating compositions with satisfactory lower medium content properties. solids / max. In particular, the fact that the higher solids content (in the range of 50-60% w / w) in the pigment coating composition, the steep increase in the viscosity, worsens its flow properties, thus satisfying the requirements, is mainly due to the 50% w / w of this solution. violet has been shown to show the inhomogeneity of the blend indicative of low dispersion stability to higher alkaline pH values in the use of satin white in the pigment coating of the coating composition at high pH values required by the pigment. The more ambitious improvement is provided by A-A-11647, which, by defining the composition of the emulsifying system, makes it possible to prepare a low viscosity polymer polyvinyl acetate dispersion suitable for preparation of coating compositions with satisfactory flow properties! A disadvantage of this solution is mainly the fact that the copolymer polyvinylate acetate dispersion of the pigment coating composition prepared by its use exhibits a reduction in the mechanical stress stability especially pronounced at higher temperatures, which does not allow them to be processed in fast-flowing processes. coating equipment. the lesser drawback of this method is the low wear resistance of the film prepared from the dispersion and its wetting, which will be similar to the modified surfaces obtained by the application of the dispersion »

These drawbacks are remedied by the low viscosity copolymer / vinyl vinylate dispersion prepared by the present invention, which, unlike other polyvinyl acetate dispersions, makes it possible to prepare pigment coating compositions and a high solids content (up to 63% by weight) even in the bleached bleach composition. having the necessary stability to higher alkalinity and which at the same time provides sufficient high stability to both mechanical stress and thermal stress, high film and paint resistance upon wetting to abrasion 231 383, while retaining other desired functional properties of the paper, cardboard or cardboard surfaces treated therewith .

The process of preparing the low viscosity copolymer polyvinyl acetate dispersion of the present invention consists in emulsifying copolymerization of vinyl acetate with n-butyl acrylate using an aqueous phase containing a mixture of alkali metal salts of phosphoric esters with an alkyl polyglycol ether and an alkyl polyglycol ether in the presence of an alkaline salt of phosphoric acid. or carbonic, by the peroxodisulfate initiation system, wherein the polymerization system is dosed and / or dosed during and / or after dosing. monomers that last for 200 to 280 minutes; with continuous mixing, a total of 0.1 to 1.2% by weight of the propylene oxide-ethylene oxide copolymer relative to the dispersion in question is added, the monomer mixture, which is determined by the ratio of 3 to 7 in favor of vinyl acetate, is added to the aqueous phase at temperatures of 63 ° C and temperature the reactive mixture does not exceed 82 ° C throughout the preparation.

The eisperiae of the present invention exhibit the following properties: viscosity 10 to 120 mPa.s, non-volatile content of 50 to 56%, unreacted monoer content of max. 0.9%, pH of 2.5 to 6.5, particle size in the range of 120 to 240 nm, mechanical stability, at 3,000 rpm is at least 10 minutes, resistance to elevated temperature is min. 5 cycles at plus 60®C and wet film resistance is at least 15 minutes.

Pigment paint mixture prepared after. the use of said dispersion exhibits the desired pseudoplastic flux and low low rutixotropy. The prepared coating compositions show satisfactory values of apparent viscosity even at higher solids content. The mixture is stable and retains its properties even in the alkaline range at pH 10-12 in the presence of satin white. The pigment mixture is stable and excellent to be applied to high-speed wiping devices, while at the same time increasing mechanical and; tepnomnamáhaní.

The examples which follow illustrate the invention but do not limit it in any way. - 4 - 231 383 Example 1

966.5 kg of steam condensate is pumped into the polymerization reactor, and 390 l of a 10% by weight sodium poly (ethylene glycol glycol ether phosphate / trade name Slovafos.RTM.) And 2940 l of 8.5% alkylpolyethylene glycol ether / commercial binder are added. Next, 315 l of an aqueous solution containing 9 kg of primary potassium phosphate, 5.5 kg, was added to the reactor. NaOH and 11 kg of sodium bicarbonate

During the addition of the components, the polymer content of the reactor was tempered to 68 ° C. Upon reaching this temperature, 300 l of 5% sodium persulfate solution are added. Immediately thereafter, at a temperature of 66 ° C, a batch of 5000 kg of a mixture of 80% by weight monomer mixture is continuously fed into the reactor. vinylacetate and 20% n-butyl acrylate, which lasts for 240 minutes. As a result of the reaction, the temperature in the reactor starts to rise and is cooled at a polymerization value of 75 - 1 ° C. while maintaining the cooling at 80 ° C for 45 minutes. Thereafter, with stirring, 400 µl of a 7.5% aqueous solution of propylene oxide-ethylene oxide / commercial grade Salvanik PV 370 was added to the reactor. After cooling the reactor contents to 40 ° C, it is dispersed in the containers.

The properties of the prepared dispersion are as follows: viscosity 25 mPa.s, non-volatile content 51.5 wt%, free vinyl acetate 0.6 wt%, value. The pH is 5.2, the particle size is 185 nm, the mechanical stability is 25 min, the elevated temperature resistance is 6 cycles at plus 60 ° C and the wet film resistance is 45 min.

The preparation as in Example 1 except that 400 µl of a 7.5% propylene oxide-ethylene oxide copolymer solution was used and 170 kg of a 70% propylene oxide-ethylene oxide copolymer paste were added to the polymerization reactor feed prior to the beginning of dosing 5,000 kg of monomer mixture, which consists of 87.5 wt% vinyl acetate and 12.5 wt%. n-butyl acrylate. 231 383

The properties of the prepared dispersion are as follows: viscosity is 115 mPa.s, non-volatile content is 55.8 wt%, free vinyl acetate content is 0.85 wt%, pH value is 3.8, particle size 215 nm, mechanical stability is 15 min, elevated temperature resistance is 8 cycles at plus 60 ° C, and wet film resistance is 25 min Example 3, Preparation Example 1, with the difference that the © 400 1 7, Of a 5% propylene oxide-ethylene oxide copolymer solution, 30 l of a 35% strength solution of propylene oxide-ethylene oxide copolymer are added to the polymerization reactor and the half-dose of a total of 5,000 kg of blend monomers consisting of 75 wt. % vinyl acetate and 25 wt. n-butyl acrylate.

The properties of the prepared dispersion are as follows: viscosity is 75 mPa.s, the non-volatile content is 53.1 wt.%, The free vinyl acetate content is 0.55 wt. The pH is 6.1, the particle size is 125 nm, the mechanical stability is 11 min, the elevated temperature resistance is 5 cycles at plus 60 ° C and the wet film abrasion resistance is 15 minutes.

The qualitative indicators of the copolymerized polyvinyl acetate dispersions obtained correspond to the current highest requirements for the use of the present dispersions by the papermaking industry, in particular as a binder in the preparation of pigment coating compositions with a high dry matter content of about 60%, which are processed on high-speed coating equipment for production high quality graphic paper, wallpaper and cardboard. The prepared dispersions are also suitable for textile auxiliaries and raw materials for the preparation of dispersion adhesives for use in red.

Claims (1)

SUMMARY OF THE INVENTION 231,383 The preparation of a low viscosity copolymer polyvinylation dispersion by copolymerization of a monomeric vinylacetate / n-butyl acrylate mixture in an aqueous phase medium comprising a mixture of alkyl polyglycol ethers and alkali metal salts of phosphoric esters with alkyl polyglycol ethers in the functionality of emulsifiers. the presence of alkaline salts of phosphoric acid and / or carbon by the action of the peroxodisulfate initiation system, characterized in that the d polymerization system is added before and / or after the addition of a / b or after the completion of the monomer feed, it takes from 200 to 280 minutes, with a total of 0.1 to 1.2% by weight of propylene oxide-ethylene oxide copolymers pertaining to the dispersion being added, with stirring, the monomer mixture being represented by the ratio of 3 to 7 relative to the vinyl acetate, the aqueous phase is then added thereto by heating 63 ° C and the temperature of the reaction mixture does not exceed 82 ° C throughout the preparation. Printed by Moravian Printing Works, Price: 2,40 Kčs operation 12, tř.Lidových milicí 3, Olomouc