DD151456A1 - METHOD FOR PRODUCING CARBOXYLATED ELASTOMERLATICES FOR COATING APPLICATIONS - Google Patents

Abstract

The invention relates to a process for the preparation of carboxylated elastomer latices by emulsion polymerization of butadiene, styrene and / or acrylonitrile and aethylenisch ungesettigten carboxylic acids. With these latices coatings with a smooth surface can be produced. According to the invention, at least one monocarboxylic acid and at least one dicarboxylic acid are initially introduced in 60 to 80% or 70 to 100% neutralized form before the start of the polymerization known per se, and then the polymerization is continued until a conversion of 98% of all monomers is obtained. Preferably, the neutralization is carried out with bases or carbonates. The carboxy latices according to the process of the invention are mechanically stable and free of microcoagulum.

Description

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Title of the invention

Process for the preparation of carboxylated elastomer latices for coating purposes

Areas of application of the invention

The invention relates to a process for the preparation of carboxylated elastomer latices, preferably of butadiene copolymer latices with styrene and / or acrylonitrile, which are particularly suitable as binders in coating compositions in which gelatin is also processed and which give a smooth surface.

Characteristics of the known technical solutions ·

The preparation of carboxylated latices has been widely described in the literature. Different advantages are highlighted.

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However, it is surprising that seemingly identical formulations in different patents give products with different properties. This proves that not only the raw materials used exert a significant influence on the final properties, but also the reaction or process technology.

It is obvious that in the advancing technology of the processing of latexes for paper coatings, for the consolidation of nonwoven materials and for carpet back coating, as described in DE-OS 23 18 4-19 described, use schneilauf-end machines, the tendency of Emulsionspolymerisatlatices, stable foams to be countered by new developments.

A substantial reduction in the amount of emulsifier causes a significant loss of mechanical stability, which in turn is required in high-speed processing machinery.

Although improvement of the mechanical stability can be achieved by the incorporation of carboxyl groups, so far the problem of microcoagulum formation has not yet been solved. In many cases this does not have a disturbing effect, there are certain applications, in particular those, for example, where lustrous surfaces are required and little or no pigments are used, and in which this microsolating the microsurfactant disturbs the surface and thereby inhibits the use of carboxyl-containing latexes many other desirable properties prevented.

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Object of the invention

The aim of the invention is to produce mechanically stable Carboxyllatices without Mikrokoagulatbildung, which can be used in coating compositions with smooth surface formation and processed on high-speed machines.

Presentation of the invention

The invention has for its object to develop a process for the preparation of carborylated Elastomeriatices with improved utility properties by a suitable driving regime of the known emulsion polymerization, wherein the above requirements are met.

The object is achieved in that in the known per se methods for emulsion copolymerization of conjugated dienes with styrene and / or acrylonitrile and ethylenically unsaturated carboxylic acids in the aqueous phase prior to the reaction at least one monocarboxylic acid in 50 to 80 % neutralized form and at least a dicarboxylic acid in 70 to 100 % neutralized form, after which the reaction is started and the polymerization is continued to at least 98 % conversion of all monomers.

To neutralize the ethylenically unsaturated carboxylic acids used, bases, metals, metal oxides and carbonates may be used, but preferably bases or carbonates. The amount of neutralizing agent to be used for a certain amount of carboxylic acid is of course dependent on the nature and can be very easily determined by titration by the skilled artisan 7 ^ _o & earth

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Since heat is released in the neutralization process according to the neutralization enthalpy, it is advantageous to use this heat in addition to achieving the polymerization temperature, which is preferably between 321 and 353 K. So this method is also still energy efficient.

As bases, the inorganic bases are preferred, in particular the hydroxides of the alkali metals, since they are very soluble in water. Under certain conditions, it is advantageous to use sodium bicarbonate for neutralization. Here, however, the volatility of the hydrogen carbonate should be taken into account during processing. It is z. For example, it is necessary to start from the same starting temperature of the neutralization with the same formulation, otherwise different degrees of neutralization will be achieved «

As ethylenically unsaturated carboxylic acids are those having 3 to 5 carbon atoms, such as. For example, the monocarboxylic acids acrylic acid and methacrylic acid or the dicarboxylic acids fumaric acid, itaconic acid or maleic acid are preferred. ,

The polymerization is carried out in the presence of alkylaryl sulfonates having from 3 to 20 and in particular from 4 to 12 carbon atoms in the alkyl radical. Suitable alkylarylsulfonates which may be mentioned are the sulfonates of alkylbenzene and alkylnaphthalene in the form of their water-soluble alkali metal and ammonium salts. Also suitable are alkylaryl sulfates, for example sodium lauryl sulfate. It is possible to use a portion of the anionogenic Bmulgators by nonionic surfactants

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to replace, such as ζ. B. by the reaction products of 10 "to 30 moles of ethylene oxide with 1 mole of alkyl-substituted phenols having 4" to 12 carbon atoms in the alkyl radical.

Suitable initiators for the polymerization are the customary initiators, in particular the customary water-soluble per compounds, preference being given to persulfates.

Preferred initiators are ammonium, sodium, potassium peroxydisulfate, optionally in combination with sodium bisulfite or other conventional reducing agents.

Further, molecular weight regulators, for. B. mercaptans, such as tert. Dodecylmercaptan or Diisopropylxanthogendisulfid and similar known molecular weight regulators are used.

A preferred known procedure is to provide all raw materials except for about 85% of the major monomers and, after reaching the reaction temperature, gradually add the remaining amount of the main monomers while maintaining the reaction. After the end of the addition, the reaction is continued as far as possible until complete conversion of the monomers, but in any case to at least 98 % conversion. The reaction is complete after about 16 to 20 hours.

Ausfüh rungsbe ispiel

The invention will be explained in more detail below with reference to examples. The stated amounts (T) are by weight unless otherwise stated.

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The mechanical stability of the latexes is tested by a modified Allan stability test as follows:

200 ml of the latex to be tested are filtered through a metal mesh of 80 mesh. Then in the cup of a Hamilton Beach Mixer (# 30 Drink Master) exactly 150 g of latex are weighed. In a water bath, the beaker is heated to 50 ⁰ O and the contents are stirred for 5 minutes at a rate of 12000 to 15000 revolutions per minute. Upon completion of stirring, the contents of the beaker are filtered under light vacuum over a tared 80 mesh metal screen (approximately 900 mesh / cm). Rinse all the polymer particles that are attached to the "/ and carefully onto the screen. Finally, the coagulate is so long rinsed with water until all latex removed. The metal screen with the coagulate is dried in an oven at 105 ⁰ O to constant weight (30 to 60 minutes) and weighed after cooling in a desiccator.

The amount of coagulum formed on stirring is expressed as a percentage of the total solids content of the latex according to the following formula; % Coagulum = 10,000 χ Χ

GxF

where X = weight of the coagulum in g G = weight of the weighed amount of latex in g F = total solids content of the latex in %

example 1

In a polymerization vessel of about 900 1 are presented:

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310 T of distilled water

5 T of potassium persulphate a solution of:

20 T distilled water, 1.67 T sodium bicarbonate and 1.15 T fumaric acid 0.4 T sodium lauryl sulfate a solution of: 20 T distilled water 1.33 T sodium bicarbonate and 1.9 T acrylic acid 3.8 T carbon tetrachloride and 38.2 T styrene

After evacuation twice 24.6 T butadiene are added.

The original is heated to 345 K and held at this temperature for 30 minutes.

While maintaining the reaction, a mixture of 185 T styrene and 134 T butadiene is gradually added in 9 hours.

At the end of the addition, the reaction is continued at about 348 K for about 6 hours.

The latex adjusted to pH 8.5 with ammonium hydroxide had a total solids content of 51.6 %.

The latex was free of microcoagulum and coarse coagulum.

The mechanical stability was determined according to the test method described and gave only 0.0011 % coagulum.

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Example 2

In a polymerization kettle are placed: 3980 T of distilled water

84 T sodium benzene sulphonate a solution of 200 T distilled water 11.6 T NaOH 25 T methacrylic acid and a solution consisting of: 200 T distilled water 4.82 T KaOH and;

10 T fumaric acid

5 T potassium persulfate 120 T acrylonitrile

After two evacuations are still 280 T butadiene

added "

The original is heated to 323 K and held at this temperature for 60 minutes.

After that, a mixture of about 12 hours is; 712 T acrylonitrile

1627 I butadiene and

21 T tert-Bodecy! Mercaptan

added.

After the end of the addition, the temperature is increased to 338 K; after another 4 hours, the reaction is complete. After adjusting the pH to 8.5 with NaOH, a latex is obtained having a total solids content of 45.2 % . He is free of any coagulum. The mechanical stability test results in a coagulum amount of less than 0.001%.

- % - 2 2 60 % Degree of neutralization ! T 9.17 100 % Example 1 1 the acids used 80% acrylic acid Example 2: fumaric acid methacrylic acid

Fumaric acid 70%

Example 3 (not according to the invention, for comparison with the prior art)

According to DE-OS 23 18 419 - Example 3 - a latex was prepared

 In this case, 60 S sodium hydroxide 80 Ϊ methacrylic acid and 80 T acrylic acid were submitted.

Based on the assumption that the sodium hydroxide neutralizes both acids to the same extent, the following degrees of neutralization were achieved: methacrylic acid 98.8% acrylic acid 98.8 %.

Here, both monocarboxylic acids were almost completely neutralized.

After adjusting the pH to 8.7 with semi-concentrated ammonia, a latex having a solids content of 51.8% was obtained. The coagulum content was 0.2%.

The mechanical stability test gave a coagulum amount of 0.008 % and was thus significantly higher than in the latices prepared according to the invention.

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Claims (1)

-1Q- 22 19 17 Claim for invention A process for the preparation of οarboxylated elastomer latices for feed purposes by emulsion polymerization of butadiene, styrene and / or acrylonitrile and ethylenically unsaturated carboxylic acids, characterized in that in the aqueous phase prior to the beginning of the reaction at least one unsaturated monooarboxylic acid in 60 to 80% neutralized form and at least one unsaturated dicarboxylic acid in 70 to 100 % neutralized form, after which the reaction is started and the polymerization is carried out to at least 98% conversion of the total monomers.