WO1993005095A1 - Unsaturated oligoesters containing alkadienyl groups - Google Patents

Abstract

Oligoesters containing alkadienylether groups useful as air-drying paint binders are disclosed. These oligoesters are produced (A) by reacting polyols with conjugated dienes in the presence of palladium catalysts, phosphines and if necessary water and aliphatic monoalcohols; (B) by reacting the free hydroxyl groups of the polyol partial ethers with polycarboxylic acids or their derivatives; and (C) by almost completely esterifying the carboxyl groups of the product obtained from step B with polyols.

Description

 "Unsaturated Oligoesters Containing Alkadienyl Groups"

The invention relates to unsaturated esters containing alkadienyl groups, which due to their low viscosity are used as air-drying lacquer binders, and to a process for producing the unsaturated polyesters containing alkadienyl groups.

Varnishes are usually applied by spraying, brushing or dipping. A certain viscosity must not be exceeded in order to ensure good flow and complete wetting on the materials to be coated. So far, the person skilled in the art has set the correct viscosity by adding organic solvents or diluents, which, however, from today's perspective are to be limited at least in terms of the amount. In order to achieve this, attempts have been made to produce new paint binders which have a lower viscosity, so that no or only small amounts of organic solvents are necessary to adjust the viscosity. For oven-drying lacquers, this task has been achieved, for example, by the low-viscosity and relatively low-molecular-weight polyesters based on fatty acids, polyols and polyfunctional carboxylic acids described in American Patent 4,049,599. Unfortunately, the solutions for oven drying systems cannot be easily transferred to air drying systems. Air drying of alkyd resins, which are condensation products of unsaturated mono- and dicarboxylic acids and polyols, is a comparatively slow cross-linking reaction that leads to hard coatings the faster the higher the starting molecular weight of the alkyd resin. However, the viscosity of the alkyd resins and therefore the amount of organic solvents or diluents required also increase with increasing molecular weight. In order to remedy this deficiency, the European patent specification 167962 proposes unsaturated, low-viscosity polyesters modified with monofunctional alcohols from olefinically unsaturated monofunctional alcohols and di- and / or tricarboxylic acids and polyols with a functionality of more than 2 as air-drying paint binders to use. Such unsaturated polyesters lead to hard coatings more quickly, but the unsaturated onofunctional alcohol is difficult to produce.

It was an object of the present invention to provide air-drying paint compositions which, on the one hand, are low-viscosity and, on the other hand, show a good drying speed and can be produced from easily prepared starting materials.

The subject of the present invention are thus

Oligoesters containing alkadienyl groups, obtainable by a) partially reacting polyols with 2 to 6 hydroxyl groups with conjugated dienes in the presence of palladium catalysts, phosphines and optionally water and aliphatic monoalkanols, and b) free diol groups of the polyol partial ethers with di-, Tricarboxylic acids and / or their derivatives in a molar ratio of hydroxyl group: carboxylic acid group of 1: 2 to 1: 3 and c) the free carboxyl groups of the polyol ether partial esters are practically completely esterified with polyols with 2 to 6 hydroxyl groups.

Polyols are understood to mean compounds which have at least 2 hydroxyl groups. Suitable diols are those with 2 to 25 carbon atoms, preferably saturated aliphatic diols and in particular the alpha, omega diols thereof. Examples of these diols are ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol with average molecular weights from 300 to 15,000, propylene glycol, polypropylene glycols with average molecular weights from 300 to 15,000, 1,3-propanediol, 1,6-hexanediol, 1,12 -Dodecanediol, 1,16-hexanedecanediol and / or 1,18-octadecandiol. Of the polyols, preference is given to aliphatic polyols having 3 to 6 hydroxyl groups and having 3 to 12 carbon atoms and in particular those selected from the group consisting of triethylolpropane, glycerol, pentaerythritol, diglycerin, dipentaerythritol, sorbitol, glucose, methylglucoside and sucrose. Of the polyols, the aliphatic, saturated, alpha.omega-diols having 2 to 25 carbon atoms are very particularly preferred.

The reaction of the polyols with conjugated dienes in the presence of palladium catalysts, phosphines and optionally water and aliphatic alcohols is the telomerization known per se, which is described in detail in international application WO 90/13531. In the telomerization, free hydroxyl groups of the polyols are etherified by the assembly of 2 molecules of conjugated dienes to form an alkadienyl group. Accordingly, the molar ratio between the hydroxyl groups of the polyols and the conjugated dienes is decisive for the number of alkadienyl groups which the polyols carry etherified. For the purposes of the invention, the polyols should now only be partially reacted with the conjugated dienes, as a result of which polyol partial ethers are formed. This means that the hydroxyl groups of the polyols are only partially etherified with alkadienyl groups and at least one hydroxyl group remains free. For the purposes of the invention, preferably only one hydroxyl group of the polyols is etherified by reaction with conjugated dienes to form an alkadienyl group. Since the telerization according to process step a) involves equilibrium reactions, it can happen that polyols completely etherified with alkadienyl groups are also obtained. As long as the quantities involved are small, preferably less than 15% by weight, based on the reaction mixture obtained after process step a), this is justifiable in the sense of the invention. With higher amounts of completely etherified polyols, separation is recommended, preferably by distillation. A measure of the control of sufficient free hydroxyl groups in the statistical average is the hydroxyl number, which can be determined in accordance with DIN 53240. According to the equation hydroxyl number = 56 110: molecular weight, the person skilled in the art can easily determine which hydroxyl number he must have at least so that he can use a statistical average with a free hydroxyl group. A comparison with the hydroxyl number determined in accordance with DIN 53240 shows the person skilled in the art whether it is necessary to work up the reaction mixture obtained after process step a). For example, the telomerization products of 1,6-hexanediol and butadiene with hydroxyl numbers in the range from 230 to 250 and / or the telomerization products of glycerol and butadiene with hydroxyl numbers in the range from 172 to 560 are suitable.

In principle, the reaction between the polyols and the conjugated dienes is carried out in such proportions that 1 to 10 mol conjugated dienes, preferably 2 to 4 and in particular 2 to 3 mol conjugated dienes, are used per hydroxyl group to be etherified.

The conjugated dienes are to be understood as aliphatic and / or cycloaliphatic hydrocarbon compounds which have 4 to 20 C atoms and two double bonds which are conjugated to one another. Suitable dienes are 1,3-butadiene, dimethylbutadiene, isoprene, 1,3-pentadiene, 1,3- or 2,4-hexadiene and 1,3-cyclooctadiene. 1,3-Butadiene is particularly preferred as the conjugated diene. The telomerization in process step a) expediently takes place in the presence of 0.001 to 1% by weight, based on the polyol, of palladium catalysts, palladium preferably being in the oxidation state 0 and / or 2 in the form of a compound. Suitable palladium catalysts are palladium (II) acetylacetonate, bis (allyl) palladium (II), bis (cyclooctadiene) palladium (II), palladium (II) chloride, palladium (II) acetate and / or allyl palladium (II) chloride. The telomerization is expediently carried out in the presence of 0.001 to 1% by weight, based on the polyol, of palladium (II) acetylacetonate. Alkylated and / or arylated phosphines in combination with the palladium catalysts are present as cocatalysts during the telomerization. The reaction is advantageously carried out in the presence of 0.001 to 1% by weight, based on polyol, and in particular in the presence of 0.001 to 1% by weight of triphenylphosphine. If desired, the reaction can also take place in the presence of aliphatic monoalcohols and water. Secondary and / or tertiary alcohols and in particular isopropanol are preferably used as monoalcohols. The amounts of monoalcohols can be between 10 and 50% by weight, based on the reaction mixture. The amount of water in the molar ratio to polyols can be in the range from 1: 1 to 10: 1. The reaction is expediently carried out at temperatures in the range from 40 to 100 ° C., preferably 60 to 80 ° C.

The free hydroxyl groups of the polyol partial ethers are esterified with di-, tricarboxylic acids and / or their derivatives. Unsaturated aliphatic and / or cycloaliphatic di- and / or tricarboxylic acids with 4 to 10 carbon atoms such as maleic acid, fumaric acid, tetrahydrophthalic acid and / or substituted tetrahydrophthalic acids are preferred. Of these, preference is given to those which form cyclic anhydrides, since their more reactive derivatives, such as anhydrides, esters or acid chlorides, are preferably used instead of the acids. The polyol partial ethers with the free hydroxyl groups are in a molar ratio with the di- and / or tricarboxylic acids of hydroxyl group: carboxylic acid group from 1: 2 to 1: 3, that is, polyol ether partial esters with free carboxyl groups are formed.

The free carboxyl groups of the polyol ether partial esters are then reacted with such amounts of polyols with 2 to 6 hydroxyl groups that oligoesters containing practically completely esterified alkadienyl groups are formed. For the esterification of the free carboxyl groups of the polyether partial esters, preference is given to using polyols having 3 to 6 hydroxyl groups and having 3 to 12 C atoms, which were already described in process step a) during the telomerization. Of these, polyols with 3 hydroxyl groups such as glycerol and trimethylolpropane and / or polyols with 4 hydroxyl groups such as pentaerythritol, diglycerols and sorbitol and / or polyols with 6 hydroxyl groups such as dipentaerythritol are particularly suitable. The term practically complete esterification is understood to mean that the esterification is carried out so long that the oligoesters containing alkadienyl groups on statistical average no longer carry any free hydroxyl group in the molecule. Complete esterification is of course desirable, but in practice this is often difficult to achieve, so low residual acid numbers are permitted. Amounts of polyols are preferably used in process step c) such that a molar ratio of hydroxyl group: carboxyl group of 1: 1 to 1: 0.8 is present.

The present invention further provides a process for the preparation of oligoesters containing alkadienyl groups, characterized in that a) partially conjugated polyols with 2 to 6 hydroxyl groups in the presence of palladium catalysts, phosphines and optionally water and aliphatic monoalkanols Serves and b) the free hydroxyl groups of the polyol partial ethers with di-, tricarboxylic acids and / or their derivatives in a molar ratio of hydroxyl group: carboxylic acid group of 1: 2 to 1: 3 and c) the free carboxyl groups of the polyol ether partial esters are almost completely esterified with polyols having 2 to 6 hydroxyl groups.

Another object of the present invention is the use of the oligoesters of the type described containing alkadienyl groups as air-drying paint binders. The unsaturated oligoesters according to the invention are preferably used for the production of air-drying alkyd resin lacquers. For this purpose, they are mixed with the usual auxiliaries such as siccatives, fillers, pigments, skin-preventing agents, pigment dispersants and the like. If desired, organic solvents can of course also be used.

B e s p i e l e

I) Preparation of 1,4-butanediol monooctadienyl ether

63.6 g (750 mmol) of 1,4-butanediol, 0.0076 g (0.025 mmol) of palladium (II) acetylacetonate, 0.0132 g (0.05 mmol) of triphenylphosphine and 30 ml of isopropyl alcohol were placed in a steel autoclave . The autoclave was evacuated a total of three times and flushed with argon. Subsequently, 27.1 g (500 mmol) of 1,3-butadiene were transferred into the reactor using a lifter. The autoclave was sealed and kept at 70 ° C for 12 hours. After cooling and relaxing, a colorless to pale yellow liquid was obtained, from which isopropyl alcohol and the octatriene formed as a by-product were freed above 50 ° C. and 0.5 bar using a rotary evaporator. The reaction mixture thus obtained has a hydroxyl number of 293.05 and an iodine number (determined according to DGF CV, 11 b) of 249.3 and an acid number of 0.3.

II)

191.2 g of the reaction mixture prepared according to Example 1 were reacted together with 152.0 g of tetrahydrophthalic anhydride at 110 to 120 ° C. for 3 hours under reflux in an esterification apparatus provided with a water separator and nitrogen inlet. Subsequently, 68.8 g of dimethyl methyl propane, 1.0 g of a tin-based esterification catalyst (Swedcat ^R 3, from Swedstab) and 75 ml of xylene were added and esterified at temperatures between 190 to 200 ° C. Water was continuously separated off azeotropically (17 g). The xylene was then distilled off. A low-viscosity polyester (3500 mPas with ICI cone and plate viscometer) with an acid number (DIN 53402) of 7 was obtained. III) Example of use

A clear lacquer was produced from 50 g of the polyester prepared according to Example II, 0.25 g of cobalt naphtenate with 6% by weight of cobalt, 1.25 g of zirconium naphtenate with a zirconium content of 6% by weight and 1.0 g of methyl - ethyl ketone oxime. A film of this clear lacquer with a gap width of 100 μ was drawn on a glass plate and the pendulum hardness was measured according to König (DIN 53157).

Claims

P atentan sp u c h e I. Oladoesters containing alkadienyl groups, obtainable by a) partially reacting polyols with 2 to 6 hydroxyl groups with conjugated dienes in the presence of palladium catalysts, phosphines and optionally water and aliphatic monoalkanols, and b) free hydroxyl groups of the polyol partial ethers with di-, Tricarbonic acids and / or their derivatives in a molar ratio of hydroxyl group: carboxylic acid group of 1: 2 to 1: 3 and c) the free carboxyl groups of the polyol ether partial esters with polyols. practically completely esterified with 2 to 6 hydroxyl groups. 2. Oligoester according to claim 1, characterized in that 1,3-butadiene is used as the conjugated diene. 3. Oligoester according to claim 1 or 2, characterized in that polyols are selected from diols with 2 to 25 C atoms and aliphatic polyols with 3 to 6 hydroxyl groups and with 3 to 12 C atoms. 4. Oligoester according to one of claims 1 to 3, characterized in that the polyols are reacted with conjugated dienes in a molar ratio of hydroxyl groups: conjugated dienes from 1: 1 to 1:10. 5. Oligoester according to one of claims 1 to 4, characterized in that the - polyols in the presence of 0.001 to 1 wt .-% - based on polyol - Palladium (II) acetylacetonate. 6. Oligoester according to one of claims 1 to 5, characterized in that the polyols are reacted in the presence of 0.001 to 1% by weight, based on polyol, of triphenylphosphine. 7. Oligoester according to one of claims 1 to 6, characterized in that the free hydroxyl groups of the polyol partial ethers are reacted with unsaturated aliphatic and / or cycloaliphatic di- and / or tri-carboxylic acids having 4 to 10 carbon atoms. 8. Oligoester according to one of claims 1 to 7, characterized in that the free carboxyl groups of the polyol ether partial esters with polyols with 3 to 6 hydroxyl groups and with 3 to 12 carbon atoms practically completely esterified. 9. A process for the preparation of oligoesters containing alkadienyl groups, characterized in that a) polyols having 2 to 6 hydroxyl groups in the presence of Palladiu catalysts, phosphines and optionally water and aliphatic monoalkanols are partially reacted with conjugated dienes and b) the free ones Hydroxyl groups of the polyol partial ethers with di-, tricarboxylic acids and / or their derivatives in a molar ratio of hydroxyl group: carboxylic acid group of 1: 2 to 1: 3 and c) the free carboxyl groups of the polyol ether partial esters with polyols with 2 to 6 hydroxyl groups practically completely esterified. 10. Use of the oligoesters containing alkadienyl groups according to claim 1, as an air-drying paint binder.