CS231384B1 - Alkyd resin - Google Patents

Abstract

Alkyd resins contain ester-bound polymeric carboxylic acids, which are formed by polymeric carboxylic acids with an average molecular weight of 500 to 25,000 and acyclic monocarboxylic saturated and/or unsaturated acids with 6 to 24 carbon atoms, or monocarboxylic aromatic acids and/or polycarboxylic acyclic, alicyclic or aromatic acids with 7 to 12 carbon atoms.

Description

The invention relates to alkyd resins based on reaction products of acyclic polyalcohols with 2 to 6 hydroxyl groups and acyclic and/or cyclic carboxylic acids or substituted and functional derivatives of these starting components.

Among blue synthetic lacquer binders, for example based on polyester, polyurethane, polyimide, polyepoxide and polyacrylic resins, alkyd resins still hold the first place. This is mainly because their starting materials are available, relatively cheap and the production of the resins is also not expensive. In addition, they are easily processed into coatings. They are prepared by reacting polyalcohols with natural oils or their monocarboxylic acids and with polycarboxylic acids or their anhydrides (j. Mleziva et al.: Polyestery, jej proizvoda a právační, 2nd edition, SNTL Praha 1978). Alkyd resins are well pigmented, have excellent film-forming properties and are capable of being strengthened by air drying or baking. However, coatings based on them also have some disadvantageous properties, such as slow drying of films, their softness, stickiness, tendency to yellowing, low resistance to water, alkalis and acids.

To overcome these shortcomings, common types of alkyd resins are chemically or physically modified. Chemical modifications include reactions of alkyds with unsaturated compounds, especially maleinization (Australian patent no. 407,538,

German Patent No. 2,441,935)» styrene (French Patent No.

518,562, British Pat. No. 1,376,194)» acrylics (German Pat. No.

231,384

295,816 and 2,333,384), cyclopentadienization (Belgian Pat. No. 832,962, German Federal Republic Pat. No. 1,520,174), siliconization (USSR AO No.

394,406, US Pat. No. 3 948 827) and urethaneization (NSR Pat. No.

644 750 and 1 644 801), or with other low-molecular and high-molecular substances. Physical modifications include mixtures of alkyd resins with reactive and non-reactive macromolecular substances, e.g. with resins of rosin formaldehyde, melamine formaldehyde (Belgian Pat. δ. 874 241, French Pat. No. 2 192 155, German Federal Republic Pat. δ. 2 710 994), phenol formaldehyde (Belgian Pat. δ. 833 822, European Pat. No. 2 488) and natural (Czech Republic AO δ. 155 002, Japanese Pat. δ.

102,407), vinyl polymers (German Patent No. 1,770,299, US Patent No. 3,468,826) and elastomers (Australian Patent No. 1,770,299).

293 252 and 425 563)· Coating materials based on these modified alkyd resins usually dry faster, the cured coatings are hard, shiny and resistant to chemicals. On the other hand, it is very difficult to prepare homogeneous and stable coating compositions of the said modified alkyd resins. The obtained coating films often show surface defects, are often too hard, brittle and have poor adhesion to metal substrates.

The above-mentioned shortcomings are solved by the present invention describing alkyd resins based on reaction products of acyclic polyalcohols with 2 to 6 hydroxyl groups, acyclic and/or cyclic carboxylic acids or substituted and functional derivatives of these starting components. The essence of the invention lies in the fact that alkyd resins contain from 1 to 70% by weight of the total amount of ester-bound carboxylic acids ₍

polymeric carboxylic acids with an average molecular weight of 500 to 25,000 and 25 to 80% by weight of acyclic monocarboxylic saturated and/or unsaturated acids with 6 to 24 carbon atoms. Optionally, they further contain up to 32% by weight of monocarboxylic aromatic acids and/or polycarboxylic acyclic, alicyclic or aromatic acids with 7 to 12 carbon atoms.

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Alkyd resins according to the present invention have some advantages compared to known conventional and modified alkyds. First of all, they form completely homogeneous and long-term storable products. By choosing different types and amounts of starting carboxylic acids or their derivatives, especially polymeric carboxylic acids, alkyd resins of suitable consistency and other valuable properties are obtained. They are very well compatible with other paint binders, especially with pigments, fillers and other additives. The coating films are cured by air drying and baking at a relatively low temperature. The cured coatings are smooth, flexible, tough, well resistant to weathering and also have excellent adhesion to a wide variety of substrates.

Alkyd resins are reaction products of polyalcohols and carboxylic acids or substituted and functional derivatives of these components. The alcoholic component of the alkyd resin according to the present invention consists of acyclic polyhydric alcohols containing 2 to 6 hydroxyls. They include glycols (ethylene glycol, propylene glycols, butylene glycols, neopentyl glycol, diethylene glycol, dipropylene glycol, triethylene glycol and other polyalkylene glycols), alicyclic diols (1,2- and 1,4-cyclohexanediol, 1,4-bis(hydroxymethyl)cyclohexane), hydrogenated or alkylene-oxidized bisphenols (2,2,**bis(4-hydroxycyclohexyl)propane,

2,2-bis(4-hydroxyethoxyphenyl)propane, 2,2-bis(4-hydroxypropoxyphenyl)propane), trihydric alcohols (glycerol, 1,1,1-trimethylolethane, 1,1,1-trimethylolpropane, 2,3,4-pentanetriol, 1,2,3-trihydroxybutane, 1,2,6-hexanetriol, tris(2-hydroxyethyl)isocyanurate), tetrahydric to hexahydric (pentaerythritol, dipentaerythritol, arabitol, s orbitol, xylitol, mannitol). The above polyalcohols or their derivatives are used individually or in mixtures with each other.

The acid component of the alkyd resins according to this invention is represented by polymeric carboxylic acids and acyclic monocarboxylic acids, optionally also by monocarboxylic acids.

231 384 boxyl aromatic acids and/or acyclic, alicyclic or aromatic polycarboxylic acids, or their functional and substituted derivatives.

The first component is polymeric carboxylic acids based on homopolymers and copolymers of α-unsaturated carboxylic acids or their anhydrides or unsaturated polymers modified therewith with an average molecular weight of 500 to 25,000. The α-unsaturated carboxylic acids include acrylic, methacrylic, maleic, fumaric, citraconic, pyrocinchonic, mesaconic, itaconic acid or their respective anhydrides, especially maleic anhydride and other acyclic unsaturated carboxylic acids and their derivatives. Of the homopolymers of α-unsaturated monocarboxylic acids, polyacrylic and polymethacrylic acid are particularly suitable. The copolymers of the aforementioned unsaturated carboxylic acids and their anhydrides contain acyclic, alicyclic and aromatic monoolefins (ethylene, propylene, butenes, pentenes, hexenes, heptenes, vinyl chloride, vinylidene chloride, vinyl acetate, cyclopentenes, cyclohexenes, indene, methylindenes, coumarone, allylbenzene) and acyclic and alicyclic diolefins (butadiene, isoprene, piperylene, dimethylbutadiene, chloroprene, pentadienes, hexadienes, cyclopentadiene, dicyclopentadiene, cyclohexadiene) For copolymerization with unsaturated acids, either individual monomers with one or two double bonds or their various mixtures can be used. Instead of the mentioned comonomers, their liquid _oligomers , cooligomers or low molecular weight homopolymers and copolymers containing unsaturated double bonds can be used for copolymerization or for the addition of the unsaturated acid component. The proportion of these polymeric carboxylic acids in alkyd resins is 1 to 70% by weight, based on the total content of ester-bound carboxylic acids.

The second acid component includes acyclic monocarboxylic acids, mainly from natural drying oils (linseed, wood, safflower, rapeseed, oiticica, perillum, castor, fish), semi-drying (soybean,

231 384 thallium, sunflower, cottonseed) and non-drying (coconut, castor, olive, peanut). These acids form mixtures of saturated and/or unsaturated monocarboxylic acyclic acids containing 6 to 24 carbon atoms. Of the saturated acids, caproic, caprylic, capric, lauric/myristic, palmitic, stearic, arachidonic, behenic and lignoceric acids are important. Unsaturated acids are represented by oleic, linoleic, linolenic,

¢. - and /J-eleostearic, erucic, ricinoleic and 9,11-ricinenoic acids. In addition to these acids, it is also possible to use synthetic saturated acyclic acids with 7 to 20 carbon atoms (neo acids, Koch acids), as well as 2-ethylhexanoic, pelargonic and others. The synthesis is based on these acyclic carboxylic acids, individual ones, their mutual mixtures, fractionated acids or more often their functional derivatives, especially esters with polyhydric alcohols (glycerides). In alkyd resins, acyclic monocarboxylic acids account for 25 to 80% by weight of the total ester-bound carboxylic acids.

The third acid component consists of monocarboxylic aromatic and or polycarboxylic acyclic, alicyclic or aromatic acids with 7 to 12 carbon atoms. However, these acids or their substitution and functional derivatives do not have to be present in the alkyd resins according to this invention. Monocarboxylic aromatic acids are represented mainly by benzoic acid, p-tert.butylbenzoic acid and m- and p-hydroxybenzoic acid, or resin acids (abietic and levopimaric). Polycarboxylic. acids include acyclic (adipic, azelaic, sebacic, dodecanedioic, maleic, fumaric, itaconic, propanetricarboxylic, butanetetracarboxylic), alicyclic (tetrahydrophthalic, 3,6-endomethylenetetrahydrophthalic, hexachloroendomethylenetetracarboxylic, hexahydrophthalic, cyclopentanetetracarboxylic) and mainly aromatic (orthophthalic, isophthalic, terephthalic, tetrachlorophthalic, tetrabromophthalic, trimellitic, pyromellitic) acids.

231 384 vou), or the corresponding anhydrides, esters and half-esters of these acids. They are again used individually or in mixtures with each other. Their share of the total abundance of ester-bound carboxylic acids in alkyd resins can possibly be up to 32% by weight.

The production of alkyd resins according to the present invention generally includes known one-stage and two-stage processes, which are carried out intermittently (batch) or continuously (continuously). In the batch process, the resins are prepared in a stirred reactor equipped with a jacket for heating and cooling, and, if necessary, also with an azeotropic attachment and a device for measuring viscosity or conductivity. In the continuous process, the reaction mixture is continuously passed through a system of reactors arranged in series or in a cascade or through a tubular reactor. In the one-stage process, a mixture of starting components, i.e. polyalcohol, polymeric carboxylic acid, acyclic monocarboxylic acids and optionally also monocarboxylic aromatic acid and/or polycarboxylic acyclic, alicyclic or aromatic acid or their derivatives, is introduced into a heated reactor with effective mixing and subjected to direct esterification at a temperature of 180 to 250 °C. The reaction takes place without a catalyst or in its presence, either with the addition of a small amount of an azeotropic solvent) or in the melt of the reaction mixture and in an inert gas atmosphere. In the two-stage process, the alcoholysis of the starting natural oil first takes place, i.e. its catalyzed reaction with a polyalcohol at a temperature of 230 to 260 °C. The partial esters formed, in the case of glycerolysis monoglycerides, and the excess polyalcohol are esterified at the same temperature with a polymeric carboxylic acid, or with other cyclic carboxylic acids or their derivatives. The reaction again takes place either in the presence of an organic solvent or in the melt in an inert atmosphere. In both cases, the course of polyesterification is monitored by determining the acid number. The viscosity of the reaction mixture is also measured. The prepared alkyd resins or their solutions in organic solvents, usually in xylene or white spirit, are finally filtered.

The alkyd resins according to the invention are mainly used as binders for paints. Drying alkyds are cured by oxidative polymerization of the unsaturated acyclic carboxylic acids present in the presence of siccatives by air drying. Non-drying alkyds, in combination especially with amino resins, are cured by firing at a temperature of 120 to 160 °C.

The subject matter of the invention is further illustrated by examples.

Example 1

Alkyd resin in which the total content of ester-bound carboxylic acids is 2.5% by weight of polymethacrylic acid with an average molecular weight of = 20,000, 20% by weight of isophthalic acid, 3.5% by weight of benzoic acid and 74% by weight of acyclic unsaturated and saturated soybean oil acids

This alkyd resin is prepared by subjecting 677 g of soybean oil and 121 g of pentaerythritol to alcoholysis at 240 °C for 150 minutes under stirring in an inert atmosphere and catalysis by 0.105 g of PbO. After cooling to 100 °C, 21 g of polymethacrylic acid, 200 g of isophthalic acid and 32.5 g of benzoic acid are added to the alcoholysate. An azeotropic esterification is carried out in the presence of xylene at a temperature of 230 °C until the acid number drops to 10 mg KOH/g. The varnish is prepared by diluting the obtained alkyd with white spirit to a dry matter content of 50% The oil length is 67% and the resin has a viscosity of 550 mPa.s at 20 °C.

Example 2

Alkyd resin in which the total content of ester-bound carboxylic acids constitutes 24% by weight of the polymeric carboxylic acid

231,384 acids prepared by adding 6.7 parts by weight of acrylic acid to 93.3 parts by weight of a copolymer containing 70% by weight of styrene and 30% by weight of butadiene with a molecular weight of 2,000, 6.5% by weight of phthalic acid and 69.4% by weight of acyclic unsaturated and saturated soybean oil acids.

607 g of soybean oil fatty acids, 134 g of pentaerythritol are placed in a flask and 202 g of acrylic acid adduct and styrene-butadiene copolymer are added. The mixture is gradually heated to 200 °C in an inert atmosphere over the course of an hour, then cooled to 150 °C and 69 g of phthalic anhydride are added. Azeotropic esterification is carried out at 230 °C until an acid number of 10 mg KOH/g is reached. Alkyd with an oil length of 60% is dissolved in white spirit to a 50% solution with a viscosity of 400 mPa.js.

Example 3 to 5

Alkyd resins for which the content of ester-bound carboxylic acids is given in Table 1.

ad) Example 3

533 g of linseed oil, 65 g of pentaerythritol, 0.159 g of PbO as catalyst are placed in the flask and alcoholysis is carried out as in Example 1. After cooling to 100 °C, 467 g of polymeric carboxylic acid A are added to the alcoholyzate. Azeotropic esterification is carried out at 200 °C until the acid number drops below 10 mg KOH/g. The product is cooled and diluted with a mixture of white spirit and xylene (4:1) to a 50% solution. The oil length of the alkyd is 53% and the viscosity is 300 mPa.s at 20 °C.

ad) Example 4 In a flask, alcoholysis of 527 g of safflower oil and 81 g of pentaerythritol catalyzed by 0.158 g of PbO is carried out under the conditions given in Example 1. After cooling to 150 °C, the alcohol is added to the

231 384 lysate is added with 310 g of polymeric carboxylic acid B and azeotropic esterification is carried out at 200 °C until the acid number drops below 0.5 mg KOH/g. Then the contents of the flask are cooled again to 150 °C and 99 g of phthalic anhydride are added. Azeotropic esterification is continued until the acid number drops below 10 mg KOH/g. The cooled alkyd is diluted with xylene to a 50% solution. The oil length of the alkyd is 52% and the viscosity is 400 mPa.s at 20 °C.

ad) Example 5

In a flask, alcoholysis of 244 g of soybean oil and 118 g of pentaerythritol is carried out with the addition of 0.089 g of PbO and under conditions as in Example 1. After cooling to 150 °C, 511 g of polymeric carboxylic acid B is added to the alcoholyzate. This is followed by azeotropic esterification at a temperature of 200 °C, which is carried out to an acid number of 0.5 mg KOH/g. After cooling to 150 °C, 70 g of benzoic acid and 85 g of phthalic anhydride are added. Azeotropic esterification continues to an acid number of 10 mg KOH/g. The obtained alkyd is diluted with xylene to a 50% solution. It has an oil length of 24% and a viscosity of 250 mjfy.s at 20 °C.

Table 1

Content of ester-bound carboxylic acids % Example 3 4 5 Acyclic monocarboxylic acids linseed oil 55 — Acyclic monocarboxylic acids safflower oil - 56 - Acyclic monocarboxylic acids soybean oil M - 26 Polymeric carboxylic acids A ^x ^ 45 . - - Polymeric carboxylic acids B ³³ ·^ - 35 59 Phthalic acid - 9 8 Benzoic acid — - 7

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x) A Prepared by adding 15 parts by weight of maleic anhydride to parts by weight of a copolymer of styrene, indene, butadiene, cyclopentadiene, dicyclopentadiene, pentene and hexene.

Average molecular weight 5SL = 600.

n xx) B Prepared by adding 8 parts by weight of fumaric acid to 92 parts by weight of a copolymer of indene, styrene, butadiene, cyclopentadiene, dicyclopentadiene, pentene and hexene. Average molecular weight = 1,600

Claims (1)

OBJECT OF THE INVENTION 231 384 Alkyd resins based on the reaction products of 2 to 6 hydroxyl groups of acyclic polyalcohols and acyclic and / or cyclic carboxylic acids or substitution and functional derivatives of said starting components, characterized in that they comprise from 1 to 70% by weight of the total ester-linked carboxylic acid content. polymeric carboxylic alkyl Selina average molecular weight of 500 to 25,000 and 25 to 80 wt ⁰ Jo. acyclic monocarboxylic saturated and / or unsaturated. % of an acid having 6 to 24 carbon atoms, optionally up to 32 wt. monocarboxylic aromatic acids and / or polycarboxylic acyclic, alicyclic or aromatic acids having 7 to 12 carbon atoms.