NO117392B - - Google Patents

Description

Process for the production of condensation polymers.

The invention relates to condensation polymers and in particular to polymers suitable for use as coating compositions, particularly water-dilutable compositions, which can be applied by standard methods and then fired. An essential embodiment of the invention relates to the production of coating mixtures which can be applied by means of electrodeposition methods.

Patent no. 112,037 mentions the production of condensation copolymers by condensing a glycidyl polyether of a dihydric phenol with a) at least one monobasic fatty acid which can be saturated or unsaturated, or a mixture of saturated or unsaturated acids, and b) at least one fatty acid which in the molecule contains at least two carboxyl groups, of which at least one is bound to a polymethylene group containing at least 4 carbon atoms, or the anhydride of such a fatty acid,

so that the individual amounts of a and b do not exceed the chemical equivalence of the glycidyl polyether.

The invention therefore relates to a process for the production of condensation polymers suitable for use in water-dilutable coating mixtures by condensing a glycidyl polyether of dibasic phenol with a dibasic or tribasic carboxylic acid, of which at least one carboxyl group is linked to a polymethylene group, containing 4-10 carbon atoms or an anhydride or partial ester of such an acid, and the method is characterized by more than 1 and up to 2 chemical equivalents of said acid, anhydride or ester being used per equivalent polyether in the case of dibasic acids, and more than 1 and up to 3 chemical equivalents of the mentioned feyr, anhydride or ester are used per equivalent polyester when it comes to tribasic acids.

The glycidyl polyether of a polyhydric phenol used according to the invention is the condensation product of epichlorohydrin and a dihydric phenol. Examples of suitable phenols are diphenylol-propane, hydroquinone and resorcinol. Such condensation products are also known as epoxy resins and for reasons of simplicity they will be referred to as such in the following. It is well known that a number of epoxy resins are commercially available, e.g. those sold under the trademark "Epikote".

The polybasic fatty acid can be a long-chain dicarboxylic acid such as adipic acid or sebacic acid or it can be a dimerized fatty acid (otherwise known as a dimer acid) or mixture thereof, e.g. dimerized soybean oil fatty acid. Dicarboxylic acids such as phthalic acid or terephthalic acid are excluded. Tribasic fatty acids can also be used, e.g. the commercially available acids and mixtures having the general formula: where R is a pentyl or hexyl group, and R' is.

Esters, especially the methyl esters, of the specified acids

can also be used.

The method according to the invention can be carried out by heating the two reaction participants to a high temperature, e.g.

I4O<0>to 200°C. Water is formed by condensation and should be removed or rendered harmless as it forms. The ratio between the chemical equivalents of the acid and the epoxy resin is greater than 1:1, but the chemical equivalent of the acid used per equivalent epoxy resin should preferably not be higher than the basicity of the acid. Thus, for a dibasic acid the ratio should preferably not exceed 2:1 and for a tribasic acid it should preferably not exceed 3:1-

For the production of coating mixtures, the resin condensate is mixed with a solvent which can be water or organic solvent and a neutralizing agent such as an alkali. For mixtures to be applied by common methods such as brushing or spraying, the neutralizing agent must be volatile. Suitable neutralizing agents for these purposes are diethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, morpholine, dimethylaminoethanol, diethylaminoethanol, ammonia and monoisopropanolamine. For electrodeposition, a volatile or non-volatile neutralizing agent such as caustic soda can be used.

The resin can be dissolved with water alone. When an organic solvent is used, it must be an amphiphatic solvent, i.e. a compound containing one or more polar groups segregated from a relatively large non-polar group; such a solvent helps to dissolve or disperse the resin in water. Certain solvents such as butyl alcohols in conjunction with a small excess of an alkali will dissolve the resins to form substantially clear solutions, while others form solutions showing varying degrees of opalescence and still others lead to the formation of emulsions. Aqueous solutions of amphiphatic solvents can also be used. Although all of these solvent and emulsion types can be used for coating compositions, it is preferred to use clear solutions, which are capable of being infinitely diluted with water as a paint base.

The resin solutions and emulsions which can be pigmented if desired can be applied as coating compositions by any of the known methods, e.g. by dipping or applying with a brush. They can also be applied by electrodeposition by immersing the article to be coated and one electrode in a bath of the resin and passing an electric current through the bath by means of a suitable cathode, e.g. the container used for the resin.

In the following, the invention will be explained in more detail with the help of some examples.

Example 1.

130 g (1 g equiv.) of "Epikote 1001" (an epichlorohydrin-diphenylol propane product) and 600 g (2 g equiv.) of dimerized linolenic fatty acids sold under the name "Diraac S" were heated in a flask equipped with a Dean and Stark apparatus and the mixture was heated to 195° ti! 200°C for 2 hours, as the water that was formed was eventually evaporated. The product was solubilized by forming a mixture as follows:

The resulting liquid was a 50% by weight non-volatile, clear solution which could withstand infinite dilution with water.

The solution, diluted with water to 10% non-volatile by weight, was used to electrodeposit a steel panel which was made the anode in a cell with a voltage difference of 60 volts, applied for 1 minute. The panel received a coating which, after heating for 30 minutes at 190°C, was very hard and tough.

A further amount of the resin was dissolved without the use of any amphiphatic solvent in the following manner:

The result was a clear, soap-like solution that could withstand infinite dilution with water. It could also be used for electrodeposition for 1 minute at a voltage difference of 80 volts of a coating which was heated to a hard tough adherent film within 30 minutes at 190°C.

Example 2.

130 g (1 g equivalent) ay "Epikote 1001", 375 g

(3 g equivalents) of "Admerginate A" (a tribasic fatty acid) and 56 g xylol were heated together to 14-0°C over 3 1/2 hours and this temperature was held for 1/2 hour. The mixture is diluted with butyloxytol to 70% by weight solid and neutralized with 280 g of 50% by weight aqueous diethylamine. The mixture was then diluted to 50% solids by weight with water to give a clear solution. The final acid number was 210 compared to the theoretical value of 222.

For coating purposes, the resin solution was diluted with water to 10% solids by weight; the solution which still remained clear had a pH value of 10.55°6 and a conductivity of 4»5x 10^ mMhos. The solution was electrodeposited at 20 volts and the resulting film, after firing at 160°C for 1/2 hour, was pale, clear and hard. Example 3.

130 g (1 g equivalent) "Epikote 1001", 250 g

(2 g equivalent) of "Admerginate A" and 42 g xylol were heated together to 145°C over 80 minutes and this temperature was held for 30 minutes. The mixture was diluted to 70 wt.% solids with butyloxytol and solubilized with 178 g of 50 wt.% aqueous diethylamine; the mixture was then diluted to 50% solids by weight to give a clear solution. The final acid number was l80 compared to the theoretical value of I96.

The resin solution was diluted with water to 10% solids by weight to give a clear solution pH = 8.5 and conductivity 3>6 x 10 ^ mMhos. The solution was electrodeposited at 20 volts and the film, after firing at 160°C for 30 minutes, was pale, clear and hard.

Example 4.

This example shows the use of the methyl ester moiety, "Admerginate E" instead of the acid, "Admerginate A". A mixture of 131 g of "Admerginate E" and 58 g of "Epikote 1001" (1:1 in chemical equivalents) was heated with stirring, and maintained for 1/4 hour at 155 - 160°C, after which a test pellet when cooled to room temperature was clear, hard and tough, and had an acid number of 60.7" Sample pellets taken out earlier became softer and not permanently clear when cold.

A solution of 27 g of caustic soda in 393 S of water was then added. The product was a heterogeneous mixture which, however, when maintained for 3 hours at about 90°C with the addition of 320 g of butyloxytol, became a partial solution.

A portion diluted with 9 parts by weight of water was pressed through a finely washed tissue and used to coat steel panels by anodic electrodeposition at 20 volts. The deposits that formed became continuous and coherent, and when fired for 1/2 hour at 65°C they became hard, adherent and tough. A deposit burned for 1/2 hour at 150°C was very hard. and had an eggshell skin.

Most of the xylene used in Examples 2 and 3 remains associated with the resin condensate, but has no significant effect on the coating compositions produced from the condensate.

Claims (1)

Process for the preparation of condensation polymers suitable for use in water-dilutable coating compositions by condensation of a glycidyl polyether of a dihydric phenol with a dibasic or tribasic carboxylic acid, of which at least one carboxyl group is linked to a polymethylene group, containing 4-10 carbon atoms, or an anhydride or partial ester of such an acid, characterized in that more than 1 and up to 2 chemical equivalents of said acid, anhydride or ester are used per equivalent polyether in the case of dibasic acids, and that more than 1 and up to 3 chemical equivalents of said acid, anhydride or ester are used per equivalent polyether in the case of tribasic acids.