CA1043489A - Fast-setting polyurethane-forming varnishes - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Fast-setting varnishes for coating preferably metallic materials with highly deformable coatings by thermal treatment at temperatures exceeding 175°C., preferably at 180 to 450 C., consisting of a binding agent mixture dissolved in high-boiling varnish solvents and consisting of:
50 - 90 wt.-% of a high-molecular, hydroxyl-group-containing polyester on the basis of mainly aromatic dicarboxylic acids and diols and/or triols having 4 to 12 carbon atoms, and 10 - 50 wt.-% of adducts on the basis of 3-isocyanato-methyl-3,5,5-trimethylcyclohexylisocyanate blocked with .epsilon.-caprolactam, plus, if desired, varnish additives, dyes and/or pigments.

Description

~0~34~39 BACKGROUND

Polyurethane varnishes are superior in a number of characteristics to a great many other varnishes, including reactive varn~shes. In particular they are distinguished by hi~h resistance to chemicals, especially acids, by high elasticity combined with great hardness in some cases, and by good resistance to wear.
The prototype of the polyurethane varnishes is the~
two-component varnish, consisting of synthetic resins con-taining hydroxyl groups (e.g., polyesters, polyethers, polyacrylates) and an NC0 terminal adduct on the basis of diisocyanates. Such a two-component varnish by its very nature has the disadvantage of a lim$ted pot life ranging, 15 as a rule, from 6 to 20 hours. -Another approach to the preparation of polyurethane varnishes is to react resins containing hydroxyl groups (polyesters, polyethers, polyacrylates) with diisocyanates in an 0~ : NC0 ratio of l : 2 or the like, or in any event - with an excess of N00 groups. The resulting prepolymers containing NC0 groups then set under the influence of `~ atmospheric humidity to form films. To all intents and purposes this is a one-component system, but one which ~'~ 25 must be protected against the action of moisture. This :
implies that special precautions must be taken in the ~- manufacture, pigmentation, etc., of these varnishes.
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i In a number of technical applications, as for example ln roller varnishing, where the insensitivity of the system

-2-~ ' ' to surrounding influences, such as air and humidity, and constancy of viscosity over long periods of time are -important, such systems cannot be used. It has hitherto been necessary to get along without the good character-istics of the polyurethane varnishes in such applications.

It is known that there are a number of substances which react with isocyanates to fosm chemically neutral substances, which can in turn be cleaved at elevated tem~-lO perature to form isocyanates again. These blocked prod-ucts would be ideally suited for the composition of the types of varnishes desired for this kind of application.
A number of these products, however, must be re~ected because they tend to yellow from the heat during the setting process. Furthermore, one must distinguish be-tween the aromatic isocyanates and the aliphatic or cyclo-aliphatic isocyanates, since only the latter group of substances assures resistance to light and to weather ` simultaneously.
Now, if -caprolactam is used as the blocking agent, i.e., as the reagentt in order to transform isocyanates ` to a form that is non-reactive at lower temperatures, no --difficulty is encountered in achieving a setting process -that is free of yellowing. This cannot be done in prac-tice, of course, since ~-caprol~tam blocked isocyanates ~
are incompati~le in solvents commonly used in varnishes. -- , -., -1~)43489 THE INVENTION

It has now surprisingly been found that the diffi-culties regarding compatibility will not be encountered in fast-setting varnishes for covering substrates, preferably metallic materials with highly pliant coatings by heat treatment at temperatures exceeding 175C and preferably tempera-tures of 180 to 450C, consisting of a binding agent mix-ture dissolved in high-boilin~ varnish solvents having a boiling point of not less than about 110C, if the said mixture consists of 50 to 90%, by weight, of polyesters of great molecular weight containing hydroxyl groups and prepared on the basis of mainly aromatic di-carboxylic acids and a mixture of diols and triols having 4 to 12 carbon atoms in a ratio of at least 1.5:1, and 10 to 50%, by weight, of ~-caprolactam-blocked adducts of 3-isocyanatomethyl-3,5,5-tri-; methylcyclohexylisocyanate (also called ~isophorone di-isocyanate~ or ~IPDI~), plus, if desired, varnish addi- -tives, dyes and/or pigments, it being often advantageous ` to permit a small percentage, i.e., 0.01 to 5% by weight - 20 of free NCO groups in the blocked isocyanate adduct. It -is additionally to be found that the IPDI is distinguished from other aliphatic diisocyanates by an outstanding thermal stability. ; ~
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Inasmuch as sheet metals coated by a roller coating method, especially the coil coating method, are afterwards sub~ected to deformation in various ways, the elasticity -~
and adhesion of the films must satisfy stringent require-m~nts, and these qualities must be achieved without loss ; 30 of hardness.

50 to 90%, by weight, of the binding agent of the varnishes of the invention consist of polyesters of high .
molecular weight containing hydroxyl groups, whose gen-e~al properties can be described preferably by the f~llo~ing chem-5 ical and physical data:
1. Mainly aromatic dicarboxylic acids are used as the acids, the molar ratio of aromatic to aliphatic or cycloaliphatic dicarboxylic acids being greater than 4 ~
2. The required high flexibilization is achieved through the glycol components. Usable glycols are products having 3 to 8 carbon atoms, and preferably 4 to 6 carbon atoms, in the chain.

3. The branching is achieved in the conventional manner by means of trifunctional or higher functional poly-ols, the molar ratio of glycols to higher functional ~; polyols being greater than 1.5 : 1, preferably 2.5- -~
3.5 : 1. :-:

4. The hydroxyl number of the polyesters used is to be - -. 20 between S0 and 150 mg KOH/g, preferably between 80 and 125 mg KOH/g. -

5. Furthermore, the suitable,hydroxyl-group-containing polyesters are to be described by the glass trans- ~
formation.temperatures which are to be determined by -. means of differential thermoanalysis. The glass trans-formation temperature of the claimed hydroxyl poly-esters is below +20qC, preferably ranging from -20 to +lOqC.

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Suitable aromatic or aliphatic and cycloaliphatic poly-carboxylic acids (the aromatic polycarboxylic acids can be mono- or polynuclear) are, for example, oxalic acid, succinic acid, adipic acid, sebacic acid, terephthalic acid, methylterephthalic acid, 2,5- and 2,6-dimethyltereph-thalic acid, chloroterephthalic acid, 2,5-dichlorotereph-thalic acid, fluoroterephthalic acid, isophthalic acid, trimellitic acid~ naphthalinedicarboxylic acid, especially the 1,4-, 1,5-, 2,6- and 2,7-isomers, phenylenediacetic~
acid, 4-carboxyphenoxyacetic acid, m- and p-terphenyl-4,-4~-dicarboxylic acid, dodecahydrodiphenic acid, hexahydro-terephthalic acid, 4,4'-diphenic acid, 2,2'- and 3,3'-dimethyl-4,4'-diphenic acid, 2,2'-dibromo-4,4'-diphenic acid, bis-(4-carboxyphenyl)-methane, 1,1- and 1,2-bis-(4-carboxyphenyl)-ethane, 2,2-bis-(4-carboxyphenyl)-pro-- pane, 1,2-bis-(4-carboxyphenoxy)-ethane, bis-4-carboxy- ~
phenyleth~r, bis-4-carboxyphenylsulfide, bis-4,carboxy- ~ -phenylketone, bis-4,carboxyphenylsulfoxide, bis-4-carboxy-phenylsulfone, 2,8-dibenzofurandicarboxylic acid, 4,4'-stilbenedicarboxylic acid and octadecahydro-m-terphenyl-4,4~-dicarboxylic acid, etc. Mixtures of the above-named compounds may also be used.
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In the preparation of the hydroxyl-group-containing polyesters, diols are used predominantly as the alcohol component. The partial use of other polyols in the stated molar ratios is possible, such as triols for example.
Examples of suitable compounds are: ethylene glycol, pro- --pylene glycol such as 1,2- and 1,3-propanediol, 2,2-di-30 methylpropanediol-(1,3), butanediols such as butanediol- ;-

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lV43489 (~,4), hexanediols such as hexanediol-(1,6), 2,2,4-tri-methylhexanediol-(1,6), 2,4,4-trimethylhexanediol-(1,6), heptanediol-(1,7), octadecane-9, 10-diol-(1,12), thio-diglycol, octadecanediol-(1,18), 2,4-dimethyl-2-propyl-heptanediol-(1,3), butene- or butinediol-(1,4), diethylene-glycol, triethyleneglycol, cis- or trans-1,4-cyclohexane-dimethanol, 1,4-cyclohexanediols, glycerine, hexanetriol-(1,2,6), l,l,l-trimethylolpropane, l,l,l-trimethylolethane, `pentaerythritol, etc. Mixtures of the above-named com-~10 pounds may also be used.

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In the preparation of the polyester, the polyol is used in such amounts that there will be more than one hydroxylgroup equivalent for each carboxyl group equiv-alent.
The hydroxyl-group-containing polyesters can be pre-pared in a known and conventional manner. Particularly the following two processes are available. -In the first case the starting product is a dicar-boxylic acid free of mineral acid, which is to be refined, if necessary, by recrystallization. The ratio of the equivalents of acid to alcohol depends, of course, on the desired molecule size and on the hydroxyl number that is to be established. Upon the addition of 0.005 to 0.5%, preferably 0.05 to 0.2%, by weight, of a catalyst such as a tin compound, e.g., di-n-butyl tin oxide, di-n-butyl tin diester, etc., or a titanium ester, especially tetra-isopropyltitanate, the reaction components are heated in -a suitable apparatus under a current of an inert gas suc~
as nitrogen, for example- At approximately 180qC the first . ' ' .

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forming of water occurs. The water is removed f~om the reaction mixture by distillation. Over a period of sevèral hours the reaction temperature is raised to 240qC. The reaction medium remains inhomogenous until shortly before the end of the complete esterification. After about 24 hours the reaction is ended.

In the second process the starting substances are dimethyl esters of the dicarboxylic acid ester, and they are esterified under a current of an inert gas such as nitrogen, for example, with the desired alcohol component.
The transesterification catalysts can again be titanium esters, dialkyl tin esters or di-n-butyl t~n oxide in concentrations of O.Q05 to 0.5 wt.-X. After a tempera- -ture of about 120C is reached, the first production of - methanol occurs. Cver a period of several hours the tem- ;
perature is increased to 220-230~C. The transesterifica-`!i, tion is ended after 2 to 24 hours, depending on the mixture !'` Used.
Suitable high-boiling varnish solvents are those whose lower boiling point or limit is llOqC. The upper limit of the solvent depends on the conditions of the baking-on ~ process. For this purpose inert high-boiling compounds i 2S as well as mixtures thereof can be used. The term ~inert~
in this connection is considered to mean that the solvents ~ -beha~e in a chemically neutral manner towards the binding agent components under the conditions of mixing and stor- -age. The following are named as examples of suitable pure compounds: aromatic compounds such as toluene, xylenes, ,........ .

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~)43489 cumene, tetrahydronaphthalene, decahydronaphthalene;

ketones, such as methylisobutylketone, diisobutylketone, isophorone; esters, such as acetic acid-n-butyl ester, acetic acid-n-hexyl ester, acetic acid isoamyl ester, acetic acid cyclohexyl ester, acetic acid-3,3,5-trimethyl-cyclohexyl ester, lactic acid-n-butyl ester, ethylene glycol acetate, butylene glycol acetate, and the like.

The amount of the solvent is not critical. It is de~-sirable first to prepare a highly concentrated solution in which the solid content ranges from 50 to 70%. ~his -concentrated solution can be diluted to the concentration specified for the desired application ~ust prior to use.

Agents for the improvement of leveling and gloss are, for example, polyvinyl butyrals, copolymers of n-butyl acrylate and vinyl isobutyl ether, ketone-aldehyde con- -densation resins, solid silicone resins, silicone oils, or mixtures of zinc soaps of fatty acids and aromatic carboxylic acids.
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Common commercial,sterically impeded, polyvalent phe-nols of high molecular weight have proven valuable as heat stabilizers and antioxidants, but others can also ~ 25 be used.
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The quantity of the additives to be used will depend on the ~ndividual case and on the desired properties of the product. No general pronouncement can be made in this .
regard.
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lV43489 The polyester resin, blocked isocyanate, high-boiling varnish solvent, the described varnish additives, and the desired pigment or dye, if any are to be used, are mixed together by known methods below the cleavage temperature of the blocked isocyanate. If incompletely blocked iso-cyanates are used, it is recommendable to sub~ect the dis-solved resins to a thermal treatment between 80 and 160C
before proceeding with the rest of the varnish formulation.
The time of this treatment will amount to from 3 hours ~o 15 minutes, depending on the established temperature. The solution can be brought to the desired solid content prior to use by the addition of more solvent. -." ` ' ' , . .
The varnishes of the invention find application in coil coating processes for weather-resistant one-coat and two-coat applications. In modified states they can also be used in the spray painting field by the airless or electrostatic spray method, especially for aluminum.

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, ~)43489 The preparation and the application of the varni6hes of the present invention is illustrated by the following Examples:
Example 1 A. PreParation of the Hydroxvl-GrouD_Containina ~olvester In a six-liter glass flask~ 10 moles (1,940 9) o tereph-thalic acid dimethyl ester were sub~ected to transesterifica-tion with 8 moles (1,280 g) of 2,2,4- and 2,4,4-trimethyl-hexanediol-1,6 isomer mixture (approx. 40:60) and 3 molSs (402 g) of l,l,l-trimethylolpropane. 0.05 wt.-% of tetra-isopropyl titanate was used as transesterification catalyst.
The mixture was slowly heated until a uniform melt was obtained, methanol being formed after a temperature of 185qC
was reached. In accordance with the methanol formation, 15 the temperature was increased over a period of 8 hours to -` - a maximum of 215~C^ When virtually no more methanol was being produced, the temperature was reduced to 200~C and the reaction mixture was exposed for about 30 minutes to ` a ~acuum of 1 to 3 mm Hg~ whereupon the volatile content was substantially removed from the melt.
;~ Chemical and ~hvsical characteristics of the Dolvester ` Hydroxyl number 93 - 95 mg KOH/g Acid number Less than 1 mg KOH/g Molecular weight 1,600 to 1,700 Glass transformation temperature -5qC to +8C
B. PreDaration of the ~-CaDrolactam-Blocked Diisocvanates In accordance with the following general specifications, virtually completely capped diisocyanates were produced in a known manner from hexamethylenediisocyanate-1,6 (HDI), z .
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lV434~9 4,4'-diphenylmethanediisocyanate (HMDI) and 3-isocyanato-methyl-3,5,5-trimethylcyclohexylisocyanate (IPDI).

Diisocyanate and ~-caprolactam were mixed in a glass flask in a molar ratio of 1.0 : 2.0 and this mixture was heated to about 80C. At about 80C the very exothermic reaction started. The reaction mixture was kept below 150~C by appropriate cooling. After the temperature had diminished to about 110C the reaction product was kept~
for an additional 2 hours at this temperature to complete the reaction.

The reaction products, -caprolactam-blocked diiso-cyanates, are solid resins whose free NC0 content is less than 0.3% by weight.

! C.
To test the shelf life of these products, stoichio-metric mixtures of the hydroxyl polyester with the various , ,:
-~` 20 ~-caprolactam-blocked diisocyanates were dissolved to form 60 wt.-% solutions in a 2 : 1 (weight-parts) mixture of Solvesso(R) 150 and ethyleneglycol acetate. This procedure was performed preferably with heating at about lOO~C.
(Solvesso(R) 150 is a mixture of aromatics boiling in a ~ -25 range of 180 to 212qC and has a flame point of at least 65C. Supplier: Esso. Recommended as solvent for bake-on 1 varnishes and enamels.) ,, ~ r~
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Composition of the Solutions Solution Polyester HDI+cap. HMDI~cap. IPDI+cap Solvent No.(see above (see under A) above) C 1 45.0% 15% - - 40%
C 2 42.5% - 17.5% - 40%
C 3 43.5% - - 16.5% 40%
(All percentages in this table are percentages by weight.) , .
D. Shelf Life of Solutions C 1~ C 2 and C, 3, Solution State after storage at room temperature for No.
O days 1 day 1 week 1 month 1 year C 1 clear very much solution turbid sedi-solu- ment ` tion .
. 15 C 2 clear clear little much solution solu- sedi- sedi-tion ment ment C 3 clear clear clear clear clear solution solu- solu- solution solution tion tion . .

E. ExamDle of Application Starting with the solution identified as C 3, a pig-mented varnish was formulated as specified below, hardened , under ~coil coating~ conditions and tested. -~- ,, .
Formula: 67.9 wt.-% of Solution C 3 ~ ~
2.0 wt.-% of n-butyleneglycol acetate -:~ -30.0 wt.-% of white pigment (TiO2) 0.1 wt.-% of silicone oil OL leveling agent, mfr.: Bayer AG
1 mm thick aluminum and steel sheet materials were ;~
coated with this varnish and hardened for 75 seconds at * Trade Mark ~043489 - 310 to 320C in a circulating air drying oven. The tests on a 25 micron thick coating showed the following charac- -teristics:
Hardness Pendulum hardness (Konig) DIN 53157 175 sec.
measure- Impression hardness DlN 5315~ 100 (Buchholz) ments Rocker hardness (Sward) 50 Lead pencil hardness 2 H

. _ . . _ . . _ Elasticity Erichsen cupping DIN 53156 ~10 m~m Impact (reverse) >82 in~lb T-bend test .
Gloss Gardner ASTM-D-523 20 95 Gardner ASTM-D-523 45 60 Gardner ASTM-D_523 60 95-100 Adhesion Criss-cross slash test DIN 53151 0 -- ~ .
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ExamDle 2 A. PreDaration of the hYdroxYl-~rouP-containinq PolYester

7 moles of isophthalic acid (1,163 g), 6 moles of hex-anediol-1,6 (709 9) and 2 moles of l,l,l-trimethylolpropane (268 9) were subjected to esterification in a 4-liter glass flask with the addition of 0.1 wt.-% of n-dibutyl tin oxide.
As the temperature increased a homogeneous melt formed and water first began to form at about 195C. Over a period of

8 hours the temperature was increased to 220C and the esterification was carried to completion at this tempera-30 ture for an additional 6 hours. The acid number was then `
-14_ i lV43489 less than 1 mg KOH/g. After the polyester melt had cooled down to about 200C, the volatile components were removed under a vacuum of 20 to 30 mm Hg for 30 to 45 minutes.
During the entire reaction a weak current of nitrogen gas was passed through the reaction system.
Chemical and PhYsical Characteristics OH number 105 mg KOH/g Acid number <1 mg KOH/g Molecular weight 2,400 Glass transformation temp. -12C to ~SC
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B. Pre~aration of the ~_Caprol,ac~,am-Blocked Diisocvanates In accordance with the general specifications (cf.
Example 1), ~-caprolactam-blocked diisocyanates were pre-- 15 pared which, in contrast to the products described in Ex- ~
ample 1, still had a content of free NCO groups after the - --,~ reaction.
- The following list shows the composition of the batches in parts by weight,and the free NCO group contents experimentally determined after the blocking process.
Number Diisocyanate Blocking Agent Free NCO group content ,~
B 1 1000 p. HDI 1211 p. cap. 2.05 weight-percent B 2 1000 p. HMDI 776 p. cap. 2.01 weight-percent B 3 1000 p. IPDI 914 p. cap. 1.98 weight-percent ~ ~
,i 25 '~ " ', 'C. PreDaration of the Varnish Solutions -The polyester described under A and one of the blocked i isocyanate adducts described under B were dissolved in a t' ~tolehlom~tric ratio in a solvent mixture of Solvesso(R) 150 and ethyleneglycol acetate (EGA) in a ratio of 2 : 1 by weight :6~ "
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lV43489 - to form 60 weight-percent solutions, and the free NC0 groups were made to react. For this purpose the solu-tion was heated to lOOqC and held at that temperature for 1 to 2 hours.
Com~osition of the Solutions Solution Polyester Blocked Diisocyanate Solvent (see A) (see B) . . . . . ...
C 1 45.1% 14.9% 40%
C 2 42.4~ 17.6% 40X
lo c 3 43.5% 16.5X 40%

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(All percentages in this table are percentages by weight.) D. Shelf Life Tests ~ 15 Specimens of the solutions described under C were ; stored at temperatures between 5 and 8C and samples were taken at certain intervals for testing for turbid-ity and precipitation.
Solution State after storage at 5 to 8C for ~ O days 1 week 4 weeks 3 months C 1 slightly very sediment turbid turbid ` C 2 clear clear decidedly very turbid turbid -C 3 clear clear clear clear . ~
E. ExamD,le of ADDlication ¦-With the solution described under C 3, a varnish ~`
was prepared according to the following formula:
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~043~89 .;
Formula: 62.5% solution C 3 (see above) 8.0% solvent mixture: . .
Solvesso( ) 150/EGA, 2 : 1 29.5% white pigment (TiO2) 0.1% silicone oil `~ Aluminum and steel sheets 1 m~ thick were coated with this pigmented varnish and hardened for 75 seconds at 310-320C in a circulating air drying oven~ The test-ing of a 25-m~cron thick coating showed the following:
Hardness Pendulum hardness (Konig) DIN 53157 170 sec.
measure- Impression hardness DIN 53153 111 (Buchholz) ments Rocker hardness (Sward) 45-55 Lead pencil hardness H - 2H

Elasti- Erichsen cupping DIN 53156 ~10 mm city Impact (reverse) ~82 inch-lb T-bend test 0 -, . ` :.
3, Adhesion Criss-cross slash test DIN 53151 0 __ . Gloss Gardner ASTM-D-523 20 70-75 -25 . ~`

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~043489 Examples for Purposes of Comparison Exam~le 3 In the polyester described in Example 2, one of the seven moles of isophthalic acid was replaced with adipic acid. The polyester was thus prepared from 6 moles (1000 g) of isophthalic acid, 1 mole (146 9) of adipic acid, 6 moles (709 g) of hexanediol-1,6 and 2 moles (268 g) of l,l,l-trimethylolpropane in the manner described in Ex-ample 2.
Chemical and ~hysical Characteristics OH number 117 mg KOH/g Acid number <1 mg KOH/g Molecular weight 2000 Glass transformation temp. -20 to -15C
`~ On the basis of this polyester and the adduct of 3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate ~` (IPDI) described in Example 1, a pigmented varnish of ` the following formula was prepared and applied:
27.4 wt~-% polyester (see above) 13.4 wt.-% adduct (see Ex. 1) 29.1 wt.-% white pigment (TiO2) 10.0 wt--% ethyleneglycol acetate 20.0 wt.-% Solvesso( 150 0.1 wt.-X silicone oil OL
Evaluation will be given at the end of Example 5.
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1()434~39 Example 4 In the polyester described in Example 1, the tereph-thalic acid was replaced with hexahydroterephthalic acid.
10 moles of hexahydroterephthalic acid dimethyl ester (2000 g), 8 moles (1280 g) of 2,2,4- and 2,4,4-trimethyl-hexanediol-1,6 isomer mixture (appxox. 40:60) and 3 moles (402 g) of l,l,l-trimethylolpropane were transesterified in the manner described in Example 1.
Chemic~ d P)~Ysi-c~al5~i~i~ ~
Hydroxyl number 98 mg KOH/g ~ --Acid number ~1 mg KOH/g Molecular weight 1600 Glass transfoxmation temp. -30C
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With this polyester and the adduct of isophorone-d~isocyanate (IPDI) described in Example 1, a pigmented varnish was prepared in accordance with the following formula and applied to 1 mm steel and aluminum sheets and set for 90 seconds at 300C:
29.0 wt.-% polyestex of Example 4 11.0 wt.-% IPDI adduct (see Example 1) - 30.0 wt.-% white pigment (TiO2) ~
10.0 wt.-% ethyleneglycol acetate .
20.0 wt.-% Solvesso(R) 150 0.1 wt.-% silicone oil OL
See evaluation at end of Example 5.

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1()434~9 Example 5 6 moles (740 g) of phthalic acid anhydride, 3 moles (438 9) of adipic acid, 2 moles (208 ~) of 2,2-dimethyl-propanediol-1,3, 4.5 moles (531 g) of hexanediol-1,6, and 5 2 moles (268 g) of l,l,l-trimethylolpropane were subjected to esterification in the usual manner under the catalytic effect of 0.1 wt.-% of di-n-butyl tin oxide.
Chem~cal and PhYsical Characteristics Hydroxyl number 76 mg KOH/g 10Acid number 3 mg KOH/g Molecular weight 2700 Glass transf. temp. -20 to -15C
A varnish was prepared in accordance with the follow-- ing formula, from this polyester and the adduct of iso-15 phoronediisocyanate described in Example 1, for testing purposes:
27.7 wt.-% polyester (see above) `~ 8.7 wt.-% adduct (cf. Example 1) 27.5 wt.-% white pigment (TiO2) 2012.0 wt.-% ethyleneglycol acetate ~:
24.0 wt.-% Solvesso(R) 150 ~
0.1 wt.-% Silicone oil OL --~..
Comparative Review of the Most ImDortant Test Results ~
2~iObtained with Varnishes from ExamDles 1. 2. 3. 4 and 5 --- Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Pendulum 175 170 140 60 20 -hardness sec. sec. sec. sec. sec. -Lead pen- :
C~1 hardn. 2H H-2H F F-HB B-HB
30 T-bend 1 0 1-2 0-1 0 test ,.

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Example 6 The polyester described in Example 1 was modified by changing the molar ratio of glycol to higher-function alcohols from 2.65 : 1 to 1 : 1.
10 moles (1940 9) of terephthalic acid dimethyl ester, 5.85 moles (785 g) of l,l,l-trimethylolpropane and 5.85 moles (940 9) of 2~2,4- and 2,4,4-trimethylhexanediol-1,6 isomer mixture were subjected, after the addition of 3.7 9 of tetraisopropyltitanate, to transesterification in th~
manner described in Example 1 to form a hydroxyl polyester.
Chemical and PhYsical Characteristics Hydroxyl number 150 mg KOH/g Acid number <1 mg KOH/g Molecular weight 2600 Glass transformation temp. 14 to 28qC
In the following table the most important test results obtained with the varnish described in Example 1 are com-pared with a varnish prepared on the basis of the polyester ~
described in this example and made in accordance with the ' 20 following formula: --; 22.6 wt.-X hyd~oxyl polyester (see abcve) - 13.8 wt.-% adduct (cf. Example 1) 30.2 wt.-% white pigment (TiO2) ll.l wt.-% ethyleneglycol acetate 22.2 wt.-% Solvesso(R) 150 ^ 0~1 wt.-% silicone oil OL
Varnish Pendulum Lead Pencil T-bend Test formula hardness hardness - Example 6 170 sec. 3H 4 _ 5 Example 1 175 sec. 2H

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Claims (5)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE
IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Fast-setting varnishes for coating substrates being settable by thermal treatment at temperatures exceeding 175°C, consisting of a binding agent mixture dissolved in high-boiling varnish solvents having a boiling point of not less than about 110°C and consisting of 50 - 90 wt.-% of a high-molecular, hydroxyl-group-containing polyester derived from aromatic dicarboxylic acids, diols and triols having 4 to 12 carbon atoms the molar ratio of diols to triols being at least 1:5 to 1, and 10 - 50 wt.-% of adducts on the basis of 3-isocyanato-methyl-3,5,5-trimethylcyclohexylisocyanate blocked with .epsilon.-caprolactam.

2. Fast-setting varnishes of Claim 1, characterized in that the adduct blocked with .epsilon.-caprolactam has 0.01 to 5 wt.-% of free isocyanate groups.

3. Fast-setting varnishes as claimed in Claim 1 or 2 which also include varnish additives, dyes and/or pigments.

4. Fast-setting varnishes as claimed in Claim 1 or 2 wherein the thermal treatment is at temperatures between 180-450°C.

5. Fast-setting varnishes as claimed in Claim 1 or 2 wherein the substrate is a metallic material.