CS255019B1 - Fiexible air-drying alkyd resins - Google Patents

Abstract

The purpose of the solution is to increase the flexibility of alkyd resins based on reaction products of drying and/or semi-drying oils or acyclic monocarboxylic acids, oleyl alcohols and aromatic carboxylic acids, which are the basic components of air-drying paint compositions. This is achieved by modifying the resins with vinyl compounds so that the resulting product contains 2 to 14 wt. chemically bonded segments composed of vinyl acetate units and/or acrylic acid and its derivatives, especially esters.

Description

The invention relates to air-drying alkyd resins, which provide coatings with increased flexibility after drying. These resins can be used for the production of coatings drying by the oxypolymerization mechanism.

In available monographs (J. Mleživa et al.: Polyesters, their production and processing, 2nd edition, SNTL, Prague 1978) and in numerous descriptions of inventions and literary sources (e.g. Czechoslovak Pat. No. 146,600, Czechoslovak AO No. 195,782, Polymere Paint Colour Journal 14. No. 4,057, pp. 70, 72-80, 92 (1981)) many advantageous properties of air-drying alkyds are mentioned, in particular easy preparation, excellent pigmentability, excellent film-forming properties or good drying of coatings. Some properties can be further improved by chemical or physical modification. For example, maleinization accelerates the preparation (Austrian patent no. 407 538, German patent no. 2 441 935)* cyclopentadienization and styrenization accelerate drying (Belgian patent no. 832 962, German patent no. 1 520 174, French patent no. 1 518 562). Recently, fast-drying alkyds, referred to as acrylated alkyds, have also been described. However, upon closer study, it can be found that these are mostly styrene-acrylate or

255 819 about _alkyds in which methyl methacrylate is always present as the predominant acrylate component. The proportion of the modifying component is high and constitutes up to 45% by weight in the dry resin (pat. NSR No. 2 123 177, pat. USA δ. 2 227 870, Czechoslovak pat. No.

138 573, Czechoslovak Pat. No. 138 826). With simple oil alkyds themselves, the coatings become brittle during drying and later during progressive polymerization during aging, which leads to easy destruction of the coatings, especially in weather conditions. This tendency is even greater with known chemical modifications, so that, for example, styrenated alkyds with excellent drying are not suitable for surface protection intended for outdoor applications. At the same time, consumers are increasingly demanding that air-drying coatings also withstand rapid deformations, that they show resistance in indentation, impact, bending tests, etc. A certain solution is the addition of plasticizers (Czech Republic AO No. 245 608), but a larger number of components complicates the production of coatings and, in addition, the effectiveness of plasticizers gradually decreases and can also bring other problems, such as sticking, etc.

The above-mentioned shortcomings are eliminated by the present invention, the subject of which are flexible air-drying alkyd resins based on reaction products of drying and/or semi-drying oils and acyclic monocarboxylic acids, polyalcohols and aromatic carboxylic acids chemically modified with vinyl compounds, with an oil distance of 45 to 65. The essence of the invention lies in the fact that these alkyd resins contain 2 to 14% by weight of chemically bonded segments composed of vinyl acetate units and/or acrylic acid and its derivatives, especially esters.

These new types of alkyd resins have maintained the drying speed and pigmentability compared to pure oil alkyds, while significantly improving the elasticity of the coatings. They maintain this improvement for a long time and

255 819 therefore have an increased service life even in outdoor weather conditions.

Compared to known types of styrene and styrene-acrylate alkyds, they do not have a shortened drying time, but they are well soluble in the most common solvents (in white spirit) and after curing they produce coatings that are incomparably more flexible than the previously known types of modified alkyds.

The production of flexibilized alkyd resins according to the present invention includes generally known processes for preparing alkyds. It is possible to start from semi-drying and/or drying natural oils or from acyclic monocarboxylic acids isolated mainly from these natural oils. Modification with vinyl acetate, acrylic acid and its esters can be carried out at any stage of the preparation of alkyds. It is possible to vinylize either the starting oils or acyclic acids, or the product of transesterification or even the oil alkyd. The vinylization is carried out in the presence of initiators at temperatures of 70 to 150 °C, preferably in the presence of solvents. It is possible to prepare a copolymer of acrylic acid and their specified esters in advance _; and then incorporate it by esterification by reaction with hydroxy esters of acyclic acids. In the first process, the final alkyd contains, for example, segments of the type

If - 00C. (CH ₂ ) ₇ CH - CH ₂ CH ₂ CH = CH - CH^CH =

P = CH - CH ₂ CH ₃ , where Ak is the residue of alkyds and P represents a segment composed of vinyl acetate units, acrylic acid and its derivatives. It is evident that it is bound in a chain of unsaturated acyclic acids. It flexibilizes the macromolecule, firstly by its own character (longer flexible chain), then by distancing the alkyd chains and thus increasing their mobility, and finally by drawing unsaturated acids from the chain

255 Θ19 one double bond, thus regulating the density of the network. It also has a positive effect on the light resistance of the coating. In the second method, segments are created, as shown in the example

Ak - C00 - P or Ak - 00C - P, where the ester groups mediating the connection of vinyl acetate or polyacrylate segments with alkyd are introduced either as carboxyl groups of acrylic acid units, or as hydroxyl groups formed "in situ" by transesterification of vinyl acetate units.

For the preparation of alkyd resins according to the invention, volatile or semi-drying oils can be used, in particular, linseed, soybean, safflower, dehydrated castor, wood, pernite and rapeseed oil of low erucic type. As acyclic monocarboxylic acids, in particular, acids obtained by cleavage of these oils and tall oil acid are used. As polyalcohols, pentaerythritol, glycerol and trimethylolpropane have proven themselves, and from lower alcohols, ethylene glycol, propylene glycol and neopentyl glycol. From carboxylic aromatic acids, all isomers of phthalic acid and their derivatives, endomethylenetetrahydrophthalic acid, and as an addition also benzoic acid or p-tert.butylbenzoic acid. As vinylic starting monomers, vinyl acetate and acrylic acid and its derivatives can be used. Of these, alkyl derivatives of the general formula are particularly suitable

H _O C = C - C - OX, ² 1 ti

R 0 where R and X are hydrogen or alkyl groups with 1 to 8 carbon atoms, whereby R and X may be the same or different.

Examples include acrylic acid, metha5 acid

255 819 acrylic acid, methyl methacrylic acid ester, butyl acrylic acid ester, 2-ethylhexyl acrylic acid ester, butyl acrylate ester, 2-hydroxyethyl methacrylic acid ester, etc.

Design examples

In the following embodiments, polymer components containing carboxyl or ester functional groups, prepared by radical copolymerization of monomer components, are used. Their basic characteristics are given in the following table:

Representation of monomers in the reaction mixture (molar ratio) Polymer component WM Μ» MB WM»«»1M« X MMMMw» MM»—» — — — II XXX acrylic acid butyl ester 1 - 1 Acrylic acid 2-ethylhexyl ester — 1 - methacrylic acid methyl ester 0.147 — - acrylic acid 0.031 0.053 - vinyl acetate “· 0.167 initiator used di-tert.butylperoxide • dicumyl peroxide - di-tert.butyl peroxide % wt. in reaction mixture 1.5 1.5 1.0 reaction temperature (°C) 110 - 135 120 - 135 100 - 135 viscosity of a 50% solution in xylene (mPa.s/20 C) 24.0 19.5 26.0 number average molecular weight 2,500 2,700 3,200 acid number (mg KOH/g) 5.8 7,θ w.

Example 1 255 βιβ

First, an oil-modified alkyd resin is prepared, which is flexibilized by reaction with acrylic acid and vinyl acetate in the presence of tert-butyl peroxide. The oil length of the modified resin is 45 and the content of the acrylic acid and vinyl acetate segment is 2% by weight.

The preparation is done as follows:

422 parts by weight of linseed oil are introduced into the reactor,

200.8 parts by weight of pentaerythritol and 0.08 parts by weight of PbO and at a temperature of 240 to 245 °C, an equilibrium mixture of hydroxyesters is prepared by alcoholysis in a nitrogen environment, which is esterified at a temperature of 200 to 230 °C after the addition of 256.5 parts by weight of phthalic anhydride, 93.3 parts by weight of benzoic acid and 8.2 parts by weight of dehydrated castor oil acids. The esterification is terminated when the acid number drops below 10 mg KQH g" ^1. At a temperature of 140 °C, the alkyd is diluted with 20 parts by weight of xylene and at 140 °C the alkyd is flexibilized by the addition of a mixture of 9.55 parts by weight of acrylic acid, 9.55 parts by weight of vinyl acetate and 0.29 parts by weight of di-tert-butyl peroxide. The above mixture of monomers and of the initiator is added evenly over a period of 1 h, after which the reaction mixture is further heated to reflux until the acid number of a sample of the distilling solvent mixture drops below 0.5 mg ^KOH.g1 .

The finished flexibilized alkyd is diluted with a mixture of white spirit and xylene (mass ratio 1:1) to a 50% solution with a viscosity of 850 to 1,900 mPa s at 20 °C. Enamel film during siccation with the addition of 0.04% mass Co, 0.03% mass

Pb and 0.15% by weight Ca (based on the resin content) dries to level 1 in 1/2 h, to level 4 in 24 h. The resistance of the coating film to pitting is better than 8, when bending 3 mm.

Example 2 255 βιβ

First, an alcoholyzate of oil and polyalcohol is prepared, which is esterified in the first stage with a polymeric acid and in the second stage with phthalic anhydride. The resulting alkyd resin has an oil length of 55 and the content of the segment formed by vinyl compounds is 4% by weight. The preparation is carried out in the following way:

533.2 parts by weight of soybean oil, 179.6 parts by weight of trimethylolpropane and 0.11 parts by weight of PbO are weighed into the reactor. At a temperature of 240 to 250 °C, an alcoholyzate is prepared in an inert atmosphere (nitrogen). After reaching equilibrium, the temperature is reduced below 150 °C and 77.6 parts by weight of a 50% xylene solution of polymer component I is added to the reactor, which is azeotropically esterified at a temperature of

210 to 230 °C. The esterification in several stages is terminated after the acid number of the reaction mixture reaches 0.2 mg KOH/g.

After cooling to 160 °C, 248.4 parts by weight of phthalic anhydride are added to the reaction mixture, which is esterified in the 2nd stage at a temperature of 200 to 235 °C to an acid number below 15 mg KOH.g ¹ .

The finished alkyd is diluted with white spirit to a 50% solution with a viscosity of 500 to 900 mPa s at 20 °C. The varnish film sicculated by the addition of a mixed siccative (0.04% by weight Co, 0.03% by weight Pb and 0.15% by weight Ca, based on the resin content) dries to stage 1 in 3 hours, to stage 2 in 6 to 8 hours and to stage 4 in 3 days. The enamel film has a resistance to indentation of 8 to 9 mm, to bending of 3 mm and to impact of 90 to 100 cm.

Example 3

First, a hydroxyester is prepared by reacting polyalcohols and polymer component II, which is esterified in the second stage with a mixture of soybean oil acids and phthalic anhydride. The flexibilized alkyd resin has a linear length of 50 and contains 6% by weight of a segment composed of vinylic-

of components. 255 ei9

Alkyd resin is prepared as follows:

112.6 parts by weight of a 50% xylene solution of polymer component II, 12<á>7 parts by weight of trimethylolpropane and 104.8 parts by weight of glycerol are weighed into the reactor and in the first stage, a hydroxyester of the polymer acid is prepared at a temperature of 220 to 240 °C, which is esterified in the second stage at a temperature of up to 235 °C with a mixture of 448.6 parts by weight of soybean oil acids and 263.6 parts by weight of phthalic anhydride. Esterification in the first stage is terminated when an acid number of 0.2 to 0.3 mg KOH . g”^ is reached, in the second stage when the acid number drops to 8 to 10 mg KOH . g“ ¹ .

The finished alkyd is diluted with white spirit to a 50% solution with a viscosity of 800 to 1,500 mPa s at 20 °C. A paint film of an alkyd binder sicculated with the addition of 0.06% by weight of Co (based on the alkyd content) dries to stage 1 in 2 1/2 h, to stage 2 in 6 to 8 h and to stage 4 in 3 days. This film has an impact resistance of 100 cm after 30 days after application to the substrate.

Example 4

By reacting oil and polyalcohol under PbO catalysis, an equilibrium mixture of hydroxyesters is prepared, in the presence of which a flexibilizing prepolymer is prepared by reacting butyl acrylic acid ester, methyl methacrylic acid ester, acrylic acid and dehydrated castor oil acids with initiation of di-tert.butyl peroxide, which in the next stage is esterified with isophthalic acid by hydroxyl groups of the hydroxyester. The preparation of a flexibilized alkyd binder, whose oil length is 65 and the content of the segment composed of vinyl compounds is 14% by weight, is as follows:

255,819

572.1 parts by weight of soybean oil, 89.4 parts by weight of pentaerythritol and 0.11 parts by weight of PbO are weighed into the reactor and hydroxyesters are prepared at a temperature of 245 to 250 °C with the exclusion of atmospheric oxygen. After cooling to 140 °C, 47.5 parts by weight of dehydrated castor oil acids and 35 parts by weight of xylene are added to the reaction mixture and after heating to 140 °C, a homogenized mixture of 115.3 parts by weight of butyl acrylate, 16.4 parts by weight of methyl methacrylate, 2 parts by weight of acrylic acid and 2 parts by weight of di-tert-butyl peroxide is evenly added over 2 h. After the dropwise addition of the monomer mixture with the initiator is complete, the reaction mixture is heated to reflux for another 3 h to complete the reaction. 157.2 parts by weight of isophthalic acid are then weighed into the reactor and the temperature is gradually increased up to 235 °C with continuous distillation of the reaction water. The esterification is terminated when the acid number of the reaction mixture drops below 10 mg KOH . g”^ .

A 50% resin solution in white spirit has a viscosity of 400 to 1,000 mPa.s at 20 °C and after siccation of 0.06% by weight Co (based on the resin content) the paint film dries to level 1 in 3.5 hours, to level 2 in 48 hours and to level 4 in 5 days. The hardness of the paint film with pencils corresponds to No. 6, the indentation resistance is greater than 12 mm, the impact resistance after 30 days from application is 100 cm.

Example 5

By reacting the oil and polymer component III with pentaerythritol, an equilibrium mixture of modified hydroxyesters is prepared, which in the second stage of preparation are esterified with phthalic anhydride with the addition of ethylene glycol to form an alkyd binder with an oil length of 55 and a content of 10% by weight of a modifying segment composed of vinyl compounds.

295,819

409.8 parts by weight of linseed oil, 149.0 parts by weight of 90% xylene solution of polymer component III, 98.4 parts by weight of pentaerythritol and 0.06 parts by weight of PbO are weighed into the reactor. An equilibrium mixture of vinyl-modified hydroxyesters is prepared by reaction at 240 °C, which are subsequently esterified after addition of 174.2 parts by weight of phthalic acid anhydrides and 14.3 parts by weight of ethylene glycol. The esterification is terminated when the acid number drops below 10 mg KOH . g* ¹ .

The finished alkyd is diluted with white spirit to a 90% solution with a viscosity of 700 to 1,200 mPa s at 20 °C. The alkyd paint film, when dried with a mixed siccative (0.04% by weight Co, 0.03% by weight Pb and 0.19% by weight Ca, based on the resin content), dries to stage 1 in 2 hours, to stage 2 in 7 to 24 hours and to stage 4 in 9 to 7 days. The paint film has a resistance to indentation of 10 mm, to bending of less than 3 mm and to impact on sheet metal and paint of 100 cm.

Claims (1)

SUBJECT OF THE INVENTION Flexible air-drying alkyd resins based on the reaction products of drying and / or semi-drying oils and acyclic monocarboxylic acids, polyalcohols and aromatic carboxylic acids, chemically modified with vinyl compounds, β oil length 49 to 69, characterized in that they contain 2 to 14% by weight · chemically bonded segments composed of vinyl acetate and / or acrylic acid units and derivatives thereof, in particular esters Printed by Moravian printing works, center. 1] 100, cl. People's Militia 3, Olomouc Price: 2,40 Kčs