CS269397B1 - Process for preparing flexible alkyd resins - Google Patents

Abstract

The procedure consists first of reacting natural esters derived from glycerol and acyclic monocarboxylic acids of a specified iodine number with acyclic tri- to tetravalent alcohols in the presence of metal compounds of the 1st and 2nd columns of the periodic table, in an inert atmosphere and at a temperature of 220 to 260 °C for 2 to 4 h. The resulting mixture of hydroxyesters is then subjected to polyesterification at a temperature of 220 to 270 °C in the presence of an inert gas and/or in an organic solvent with carboxylic acids or their anhydrides and with a modifier prepared by the addition reaction of a cyclic anhydride with epelin-caprolactam, until the acid number of the product drops below 15 mg KOH.g-·1.

Description

The invention relates to flexible alkyd resins used for the formulation of coatings drying by the oxypolymerization mechanism.

Among modern synthetic medical binders, e.g. based on polyester, polyurethane, polyamide, polyepoxide and polyacrylic resins, alkyd resins still hold the first place. This is mainly because their starting materials are available and relatively cheap. The production of resins themselves is not complicated and the resins are easily processed into coatings. Alkyds are prepared by reacting polyalcohols with vegetable oils or their monocarboxylic acids and with polycarboxylic acids or their anhydrides. 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 film drying, their softness, stickiness, tendency to yellowing, low resistance to water, alkalis and acids. To eliminate these shortcomings, common types of alkyd resins are chemically or physically modified. Chemical modifications include primarily reactions with unsaturated compounds, especially maleinization (Australian patent No. 407,538, German patent No. 2,441,935), cyclopentadienization (Belgian patent No. 832,926, German patent No. 1,520,174), siliconization (SSS copyright certificate No. 394,406, US patent No. 3,948,827) and urethaneization (German patent No. 1,644,750 and 1,644,801). Of the chemical modifications, styrenation (French patent No. 1,518,562, British patent No. 1,376,194, etc.) is particularly important, and more recently, acrylate (US patent No. 3,374,194, British patent No. 957,367). However, it is difficult to prepare homogeneous and long-term stable alkyds with these properties, as well as alkyds for coatings with long-term weather resistance. Physical modifications include mixing alkyd resins with reactive and non-reactive macromolecular substances, e.g. with resins, urea-formaldehyde, melamine-formaldehyde (Belgian patent No. 874 241, French patent No. 2 192 155, German patent No. 2 710 994), phenol-formaldehyde (Belgian patent No. 833 822, European patent No. 2 488) and natural (Czech copyright certificate No. 155 002, Japanese patent No. 74 102 407), as well as vinyl polymers (German patent No. 1 770 299, US patent No. 3 468 826) and elastomers (Australian patent No. 293 252 and 425 563). Recently, an increasingly valued property of alkyds is the high flexibility of the paint films created from them.

It has now been found that flexible alkyd resins can be prepared by the process according to the present invention, the subject of which is a method for preparing flexible alkyd resins based on reaction products of vegetable oils, carboxylic acids, polyalcohols and modifiers. The essence of the invention consists in first reacting at a temperature of 220 to 260 °C, for a period of 2 to 4 h, in the presence of metal compounds of the 1st and 2nd columns of the periodic table and in an inert atmosphere 400 to 650 parts by weight of natural esters of glycerol and acyclic monocarboxylic acids with an iodine number of 90 to 200 g J ₂ /100 gs with 80 to 200 parts by weight of acyclic tri- to tetrahydric alcohols. The obtained mixture of hydroxyesters is then subjected to a polyesterification reaction at a temperature of 220 to 270 °C in the presence of an inert gas and/or in an organic non-reactive solvent with 180 to 280 parts by weight of dicarboxylic acids or their anhydrides and 50 to 360 parts by weight of a modifier, which is an addition product of a cyclic anhydride with epsilon-caprolactam, until the acid number of the reaction product drops below 15 mg KOH.g"\

The production of alkyd resins using the above-described process can be carried out in conventional types of polycondensation reactors. The prepared resins are characterized by faster drying times (in the case of drying types) and higher flexibility of the coatings.

Alkyd resins prepared according to this invention are reaction products of natural oils (triglycerides of acyclic monocarboxylic acids) with polyols, dicarboxylic acids and modifiers. The alcoholic component is polyhydric acyclic alcohols containing 2 to 6 hydroxyl groups. These are glycols (e.g. ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, diethylene glycol, dipropylene glycol and higher polyethylene glycols), alicyclic diols (e.g. 1,2- and 1,4-cyclohexanediol, 1,4-bis(hydroxy

CS 269397 Bl methyl)cyclohexane), hydrogenated or alkylene-oxidized bisphenols (e.g. 2,2-bis(4-hydroxycyclohexyl)propane, 2,2-bis(4-hydroxyethoxyphenyl)propane, 2,2-bis(4-hydroxypropoxyphenyl)propane), from trihydric alcohols in particular glycerol, 1,1,1-trimethylolethane, 1,1,1-trimethylolpropane, 2,3,4-pentanetriol, 1,2,3-trihydroxybutane, 1,2,6-hexanetriol and tris(2-hydroxyethyl)-isocyanurate, from the group of tetra- to hexahydric alcohols pentaerythritol, dipentaerythritol, arabitol, sorbitol, xylitol and mannitol are suitable. These alcohols can be used either individually, but better in mixtures with each other.

The acid components that can participate in the above preparation of alkyds belong to the following groups by their nature: First of all, they are acyclic monocarboxylic acids with a straight chain, containing 4 to 22 carbon atoms, which occur in mixtures of various compositions in vegetable oils in the form of triglycerides. Of the vegetable oils, the following are considered: linseed, soybean, dehydrated, castor, rapeseed, sunflower, cottonseed, safflower, oiticica and some other oils, the iodine number of which falls within the range of 80 to 200 g 0 ₂ /100 g. Another group consists of dicarboxylic acids or their anhydrides, especially phthalic anhydride, 1,2,3,6-tetrahydrophthalic anhydride, hexahydrophthalic anhydride, isophthalic, adipic and sebacic acid. These anhydrides can also be used for the preparation of modifiers by addition reaction with epsilon-caprolactam.

The progress of alkyd preparation is monitored by determining the acid number of the mixture and the viscosity of the alkyd solution in hydrocarbon solvents (white spirit, xylene).

Alkyd resin solutions prepared by the process of this invention are processed into basecoats and enamels. Modifiers, i.e. addition products with epsilon-caprolactam, can be prepared in advance or in situ in the reaction medium of alkyds.

Design examples

The modifiers used in the following examples are prepared by the following procedures:

Modifier A

In a reactor, 148 g of phthalic anhydride are reacted with 114 g of epsilon-caprolactam for 5 h at a temperature of 140 °C. After this time, the reaction product is poured onto a sheet. A solid, light white substance with an acid number of 220 to 225 mg KOH.g"^ is obtained.

Modifier B

Under the same conditions, a product with an acid number of 212 to 220 mg KOH.g"\ is prepared by reacting 152.g of tetrahydrophthalic anhydride and 114 g of epsilon-caprolactam.

Example 1.

430 g of soybean oil (iodine number 126 g 3 ₂ /100 9) < 21θ 9 pentaerythritol and 0.05 g of lead oxide are introduced into the reactor. The reaction mixture is heated to 260 °C under nitrogen supply and alcoholysis is allowed to take place. The process is monitored by measuring the conductivity of the reaction mixture, the reaction is terminated after 1.5 h to 2 h. The reactor contents are cooled to 170 °C and 259 g of phthalic anhydride with 340 g of modifiers A are introduced. 50 q of xylene are added and the mixture is gradually heated to 230 °C while the water released by the reaction is constantly removed. The reaction is terminated when the acid number of the reaction mixture drops below 13 mg KOH.g“\ The obtained resin is cooled to a temperature of 140 °C and is not diluted to a 60% solution with xylene. The viscosity of the product is 250 to 300 mPa.s. '

After siccation, the resin dries to stage 1 in 2 hours, to stage 2 in 16 hours. The dried coatings have the following values: resistance to digging 9 mm, resistance to impact 100 cm, resistance to bending over a mandrel - at 3 mm the coating is intact. Compared to similar resins without modifiers, the properties have improved by 30 to 40%.

Example 2

321 g of linseed oil (iodine number 190 g Jg/100 g), 140 g of pentaerythritol and 15 g of glycerol are introduced into the reactor. After adding 0.1 g of calcium oxide and introducing C0 ₂ into the reactor, the mixture is heated to 240 °C and alcoholysis is allowed to take place, which is completed in 2.5 h. The reaction mixture is cooled to 150 °C and 150 g of tetrahydrophthalic anhydride and 110 g of epsilon-caprolactam are added. The temperature is maintained for 3 h at 140 to 150 °C,

CS 269397 B1 then 194 g of phthalic anhydride and 70 g of xylene are introduced and the temperature is gradually increased to 235 °C while the reaction water is constantly removed. The preparation is terminated when the acid number of the product drops below 10 mg KOH.g ^- ^.

Alkyd resin after siccation dries to stage 1 in 1.5 h, to stage 2 in 6 h and to stage 4 in 24 h. The dried coatings show the following values: pendulum hardness after 3 days 14%, resistance to indentation 8 mm, resistance to bending - at 3 mm intact and impact resistance 80 cm. Compared to a similar resin without modifier, the properties have improved by 35%.

Example 3

500 g of linseed meal, 118 g of low-erucic rapeseed oil (iodine number 95 g 0 ₂ /100 g), 100 g of pentaerythritol, 29 g of trimethylolpropane and 0.6 g of lithium hydroxide are introduced into the reactor. The reaction mixture is heated to a temperature of 225 °C while supplying nitrogen to the reactor and maintained at this temperature until its maximum conductivity is reached; The reaction takes 3.5 to 4 h under the conditions. The reaction mixture is cooled to 170 °C and 210 g of isophthalic acid, 20 g of xylene and 30 g of methyl isobutyl ketone are added and the reaction temperature is gradually increased to 260 °C while constantly distilling off the reaction water. When the acid number of the mixture drops below 30 mg KOH.g"^, the reactor contents are cooled to 160 °C and 60 g of modifier B are added. Esterification is continued until the acid number of the product drops below 15 mg KOH.g"^.

Alkyd resin, after dissolution in white spirit and siccation, dries after application to the substrate in stage 1 to 3 hours and in stage 2 in 12 hours. The dried coating has a pendulum hardness of 14% after 3 days, resistance to digging 7.5 mm, resistance to bending over a mandrel - at 3 mm intact and resistance to impact 90 cm. Compared to a similar type of resin without a modifier, the properties have improved by 15%.

Claims (1)

SUBJECT OF THE INVENTION A method for preparing flexible alkyd resins based on reaction products of vegetable oils, carboxylic acids, polyalcohols and modifiers, characterized in that 400 to 650 parts by weight of natural esters of glycerol and acyclic monocarboxylic acids with an iodine number of 90 to 200 g J ₂ /100 gs are first reacted at a temperature of 220 to 260 °C for 2 to 4 h in the presence of metal compounds of the 1st and 2nd columns of the periodic table and in an inert atmosphere with 80 to 200 parts by weight of acyclic tri- to tetrahydric alcohols and a mixture of hydroxyesters is formed, which is then subjected to a polyesterification reaction at a temperature of 220 to 270 °C in the presence of an inert gas and/or in an organic non-reactive solvent with 180 to 280 parts by weight of dicarboxylic acids or their anhydrides and 50 to 360 parts by weight of of the modifier, which is the addition product of a cyclic anhydride with β-caprolactam, until the acid value of the reaction product drops below 15 mg KOH.g ^-1 .