CS239773B1 - Auxiliary desiccant based on barium carboxylic acid salts - Google Patents

Abstract

An auxiliary drier based on barium salts, in which at least 2.8 moles of carboxylic acid per mole of barium, preferably 3.0 to 3.1 moles, and an acid with 6 to 18 carbon atoms with a branched chain or with a five to six-membered ring is used as the carboxylic acid. The carboxylic acid is preferably 2-ethylhexanoic or 2,2-dimethyloctanoic or naphthenic acid with a molecular weight of 190 to 220 or a mixture thereof. The drying agent according to the invention is soluble in white spirit and oil, oil-resin or alkyd binders. Increases the effect of cobalt and manganese driers.

Description

The invention relates to an auxiliary drying agent based on barium salts, used together with active drying agents, for example based on cobalt or manganese salts, to accelerate the film formation of coatings drying under the influence of atmospheric oxygen.

The process of forming a paint film of air-drying paints is significantly accelerated by the presence of salts of certain metals, which act catalytically on the oxidation and polymerization reactions taking place during film formation.

These substances are called desiccants or siccatives. The importance of lead compounds, formed by dissolving lead oxide in linseed oil at elevated temperatures, was pointed out by Justus Liebig at the beginning of the last century, and at the end of the century the first types of soluble desiccants appeared on the market.

These were compounds of lead and manganese with fatty acids of linseed oil and with resin acids /A. C. ELM, Ind. Eng. Chem. 26, 386/1934//. An important milestone was the discovery of the siccative effect of the cobalt salt of linseed fatty acids at the beginning of this century /Η. T. Vulte, H. W. Gibson, J. Am. Chem. Soc. 24, 215 /1902//.

This discovery stimulated the study of the properties of compounds of other metals, such as uranium, vanadium, but also compounds of alkali and rare earths. In the period before World War II, in addition to fatty and resin acids, naphthenic acids were also used to produce desiccants.

In the 1950s, the use of synthetically produced 2-ethylhexanoic acid began to expand. The range of salts of various organic acids used today, referred to as desiccants, is wide.

For example, the American standard for liquid paint driers /ASTM D 600-80 Standard specification for liquid paint driers/ includes compounds of the elements Ca, Ce, Co, Fe, Mn, Ni, Pb, Zn and Zr as well as salts of rare earth mixtures.

However, it does not include Ba compounds, although their use is common in the plastics industry. The reason is that the barium salts of the acids most commonly used in the production of drying agents, such as naphthenic or 2-ethylhexanoic, are not sufficiently soluble in the hydrocarbon solvents used in the formulation of oil, oleoresin or alkyd paints, nor in these binders.

At the beginning of the seventies, the Borchers company in the Federal Republic of Germany introduced a mixed desiccant onto the market, containing not only Co and Zn but also Ba, but not the barium desiccant itself, and the combined type did not particularly catch on either.

However, according to our findings, barium compounds can be prepared that can be used excellently as auxiliary drying agents and have all the required properties, such as solubility, miscibility, storage stability, and a favorable effect on drying and other properties of coatings.

For this purpose, instead of the usual salts, where one mole of barium contains two moles of carboxylic acid, it is necessary to prepare salts in which one mole of barium contains at least 2.8 moles, but preferably 3.0 to 3.1 moles of the respective acid.

The subject of this invention is an auxiliary drying agent based on barium salts, characterized in that per mole of barium there are at least 2.8 moles, preferably 3.0 to 3.1 moles of a carboxylic acid with six to eighteen carbon atoms, with a branched chain or with a five or six-membered ring in the chain.

The composition and properties of such a desiccant are best illustrated by the following examples. The percentages in the following examples are by weight.

Example

424 g /1 mol/ stoichiometric barium salt of 2-ethylhexanoic acid, containing 32.2%

Ba /theory 32.41%/ and 0.2% moisture are mixed with 939 g of white spirit according to Csn 65 6541. Even prolonged mixing or heating does not lead to the formation of a usable solution.

Example 2

The amount of Ba salt given in Example 1 is mixed with 142 g of 2-ethylhexanoic acid (1 mol) and 797 g of white spirit. Further mixing produces a clear solution containing 10% Ba. This solution can be further diluted with white spirit without restriction. The solution complies with the miscibility test with linseed oil according to ASTM D 564-47.

Example3

The amount of Ba salt mentioned in Example 1 is mixed with 170 g of 2-ethylhexanoic acid (1.2 mol) and 769 g of white spirit. Stirring again produces a clear solution, which is freely miscible with white spirit and which passes the miscibility test with linseed oil.

Example 4

The amount of Ba salt mentioned in Example 1 is mixed with 114 g of 2-ethylhexanoic acid (0.8 mol) and 825 g of white spirit. Stirring produces a slightly cloudy solution containing 10% barium, similar to Examples 2 and 3.

Higher additions of 2-ethylhexanoic acid than those given in Example 3 also produce solutions miscible with white spirit, which pass the miscibility test with linseed oil. However, the use of such a higher addition of acid is technically impractical or undesirable.

The use of lower additions leads to a deterioration of solubility and to a deterioration of miscibility with linseed oil. Similar results as were obtained with 2-ethylhexanoic acid were obtained with 2,2-dimethyloctanoic acid, which is also available as a commercial product, and also with naphthenic acid with a molecular weight of 190 to 220, if the same molar ratios were observed. Similar results were also obtained when using mixtures of the mentioned acids.

Stoichiometric barium soaps can be dissolved into clear solutions in polar solvents, such as alcohols, but such solutions are not clearly miscible with linseed oil or other oil or alkyd binders of air-drying paints and therefore cannot be used as auxiliary drying agents.

The auxiliary barium driers prepared according to this invention can be combined without difficulty with all soluble driers, such as naphthenates of Co, Mn, Pb, 2-ethylhexoates of these metals, etc. They can be successfully applied to almost all air-drying coatings.

They can replace a significant part of lead-based desiccants. In combination with cobalt-based desiccants, they increase their effect. An example of the achieved results is given in the following table.

Vehicle A

B

C

D drying time of binders for Siccation I II 'l2

8 4

2.5 3 glasses, hours III IV

9

6

2.5 3

2.5

Binders: And raw linseed oil

B linseed oil, concentrated

C linseed oil copolymer with cyclopentadiene

D pentaerythritol alkyd, 65% linseed oil fatty acids

Siccation: I 0.02% WHAT II 0.02% Mn III 0.02% Co + 0.1% Ba IV 0.02% Mn + 0.1% Ba

The drying time was determined according to the methodology used in testing linen varnish according to ČSN 67 3201, II. degree, at a temperature of 20 °C and a relative humidity of 50%. The table shows the beneficial effect of the addition of barium desiccant. This desiccant itself does not affect the drying process of the tested binders. '

Claims (1)

SUBJECT OF THE INVENTION Auxiliary drier based on carboxylic acid barium salts selected from the group consisting of 2-ethylhexanoic acid, 2,2-dimethyloctanoic acid and naphthenic acid having a molecular weight of 190 to 220 and a mixture thereof, characterized in that at least 2.8, preferably 3.0 to 3.1 mol of carboxylic acid.