DE2950089A1 - Blocked di:isocyanato-methyl tri:cyclo:decane cpds. - blocked with cyclic amidine, their prepn. and use as crosslinker for hydroxylated polymer and epoxide - Google Patents

Abstract

methyl-tricyclo-(5,2,1,0;2.6)- decane cpds. (I)blocked with cyclic amidines having the formula (I) are novel. In (I) B has the formula (II) n is 2 and/or 3. The R gps. independently are H, (cyclo)alkyl or ar(alk)yl). (I) is completely blocked. B is an imidazoline deriv. (n = 2) or tetrahydropyrimidine deriv. (n is 3). (I) is prepd. by reacting 3(4),8(9)-diisocyanatomethyl- tricyclo-(5,2,1,0;2,6)-decane (II) with the cyclic amidine in 1;2 molar ratio at 90-140 (100-120) deg.C. (I) are specified for use as heat-activated crosslinkers for condensates and/or addn. polymers contg. OH gps. for the prodn. of plastics coatings and as powder hardeners for epoxide resins. (I) have a high m.pt. and high Tg.

Description

The present invention relates to new blocked diisocyanates based on 3 (4), 8 (9) -diisocyanatomethyl-tricyclo- [5.2.1.0 [high] 2,6] -decane (TCDI), as well as their production and use.

The production of blocked or masked polyisocyanates is known and is described in Houben-Weyl "Methods of Organic Chemistry" Volume 14, 2, pages 61 to 70.

Such products are also referred to as isocyanate releasers. In contrast to the free diisocyanates, such blocked diisocyanates can be used to produce mixtures with substances containing hydroxyl groups without a reaction taking place. It is therefore possible, with masked polyisocyanates, to produce storage-stable mixtures with products containing hydroxyl groups, such as higher molecular weight polyesters or polyethers, which only give the desired isocyanate reaction at elevated temperature.

All known blocking agents give 3 (4), 8 (9) -diisocyanatomethyl-tricyclo- [5.2.1.0 [high] 2,6] -decane (TCDI) reaction products which are either liquid at room temperature, such as TCDI blocked with ethyl acetoacetate with a viscosity at room temperature of 17,000 mPa.s, or they can be viscous or have a low melting range, as is the case with TCDI capped with epsilon-caprolactam or acetone oxime. TCDI capped in this way is therefore out of the question as a powder hardener for PUR powder coatings.

The object of the invention is to provide blocked TCDI which has a high melting point and glass softening point.

It has now surprisingly been found that this goal can be achieved by using cyclic amidines as blocking agents for TCDI.

The present invention thus relates to 3 (4), 8 (9) -diisocyanatomethyl-tricyclo [5.2.1.0 [high] 2,6] -decane of the general formula blocked with cyclic amidines where B and n is 2 or 3 and R is identical or different substituents from the group H, alkyl, cycloalkyl, aralkyl and aryl radicals. The invention also relates to a process for the preparation of the compounds according to formula I, which is characterized in that 1 mole of TCDI and 2 moles of blocking agent according to formula II are reacted.

Finally, the invention also relates to the use of the compounds according to formula I for the production of polymethane and / or epoxy powder coatings.

Both imidazoline radicals can be used as blocking radicals B in formula I as well as tetrahydropyrimidine residues in question, where R can be identical or different substituents from the group H, alkyl, cycloalkyl, aralkyl and aryl radicals. Accordingly, the following amidines, among others, are suitable for the preparation of compounds according to formula I:

2-phenylimidazoline, 2-benzylimidazoline, 2-methylaminidazoline, 2,4-dimethylimidazoline, 2-methyl-4-ethylimidazoline, 2-phenyl-4-methyl-imidazoline, tetrahydropyrimidine, 2-methyltetrahydropyrimidine, 2-phenyl-tetrahydropyrimidine.

The cyclic amidine derivatives which can be used according to the invention can be prepared by known processes from optionally substituted diamines and aliphatic or aromatic mononitriles in the presence of elemental sulfur as a catalyst.

The reaction of the TCDI with the blocking agent is carried out by adding the blocking agent to the TCDI in portions at 90-140 ° C., preferably 100-120 ° C., in such a way that the temperature of the reaction mixture does not rise above 140 °. In the case of some cyclic amidines, it has proven to be advantageous to proceed in reverse, i.e. to introduce the blocking agent at 90 - 140 ° C and slowly add TCDI. After the addition of the blocking agent or TCDI 'has ended, heating continues at the reaction temperature until the NCO content of the reaction mixture has fallen below 0.7% by weight.

The blocking can, if necessary, also be carried out in inert solvents.

The TCDI masked according to the invention obtained in this way has melting points of 70-130 ° C. and is readily compatible and easy to process with OH-containing polymers such as polyester or polyether.

The compounds according to the invention are outstandingly suitable for the production of reactive PUR powders, the hardening of which takes place at temperatures from 150.degree.

OH-containing polyesters or polyethers whose lower melting point is approximately 70 ° C. and whose lower glass softening point is approximately 40 ° C. are suitable as reactants for the products of the process according to the invention.

The possible polyesters containing OH groups are, for example, reaction products of polyhydric, preferably dibasic and optionally additionally trihydric alcohols with polybasic, preferably dibasic carboxylic acids.

Suitable polyethers containing hydroxyl groups are those of the type known per se and are produced, for example, by polymerizing epoxides, such as, for example, ethylene oxide, propylene oxide, tetrahydrofuran.

The process products are particularly suitable for curing OH-containing compounds if they also have one or more epoxy groups in the molecule, that is to say if they are epoxy resins.

Suitable polyepoxides are, for example, the known reaction products of bisphenol A with epichlorohydrin. Of course, only those epoxy resins that melt between 70-120 ° C, preferably 80-100 ° C, come into question for the production of EP powders. It must be ensured that the melting range of the ready-to-use powder coating binder is at least 10 - 20 ° C below the crosslinking temperature.

While the hardening of OH-containing polyesters or polyethers occurs through the reaction of the NCO groups released during hardening with the OH groups of the resin (equivalent amounts of OH: NCO), the hardening mechanism in the reaction of epoxides with the compounds according to the invention is presumed complex. The low hardener content (catalytic amounts) indicate that the cyclic amidine effects the polymerization of the epoxide groups before or after it is split off from the compounds according to the invention (TCDI blocked with cyclic amidines).

Examples

The pulverulent coating compositions according to the invention and their production and use are further illustrated by the following examples. However, this does not imply any restriction to the compounds mentioned in the examples.

a) Blocking the polyisocyanate

In each example, the blocking of the TCDI with one of the blocking means possible according to the invention is described first.

b) 1,2-epoxy compound

In all examples, a commercially available 1,2-epoxy compound based on an adduct of 2,2-bis- (4-hydroxyphenyl) propane (diane) and epichlorohydrin was used as the epoxy component, which is subjected to HCl cleavage and then with another Dian has been implemented. According to the manufacturer, this product has an epoxy equivalent weight of 900 to 1000, an epoxy value of 0.10 to 0.11 and a melting range of 96 to 104 ° C.

This compound is referred to below as "standard epoxy".

c) Coating agent in powder form containing pigments

The ground products prepared according to a and b and leveling agent masterbatch (= mixture of 90 parts by weight of the standard epoxy and 10 parts by weight of a leveling agent based on polyacrylates, which is commercially available under the name MODAFLOW
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available), are intimately mixed with white pigment (= TiO [deep] 2) in a pan mill and then homogenized in the extruder at 90 to 100 ° C. After cooling, the extrudate was broken up and ground to a grain size of <100μ using a pin mill. The powder produced in this way was applied to degreased iron sheets using an electrostatic powder spraying system at 60 kV and baked in a circulating air drying cabinet at temperatures between 130 or 150, 160 or 180 ° C and 200 ° C.

The lacquer films produced in this way were subjected to the customary investigation methods. When reproducing the results in the respective tables, the following abbreviations were used for the individual characteristic values:

SD = layer thickness (in µ)

HK = hardness according to König (in sec) (according to DIN 53 157)

HB = hardness according to Buchholz (according to DIN 53 153)

ET = Erichsen cupping (in mm) (according to DIN 53 156)

GS = cross-cut test (according to DIN 53 151)

Imp. Rev. = Impact reverse (in inch. Lb) (Gardner ball impact)

GG 60 ° = measurement of the gloss according to Gardner (according to ASTM-D-523)

example 1

a) Blocked polyisocyanate

292 parts by weight of 2-phenylimidazoline were slowly added at room temperature to a mixture of 246 parts by weight of 3 (4), 8 (9) -diisocyanatomethyl-tricyclo- [5.2.1.0 [high] 2,6] -decane (TDCI) and 300 parts by weight of anhydrous acetone dissolved in 400 parts by weight of anhydrous acetone was added dropwise. After the addition of the 2-phenylimidazoline had ended, the mixture was heated at 50 ° C. for one hour. The acetone was then distilled off. The last residues of acetone were removed by drying the reaction product at 60 ° C. in a vacuum drying cabinet.

Melting range: 83-91 ° C

Glass softening temperature (DTA): 49-65 ° C

Splitting temperature: approx. 130 ° C

calc .: C 71.37% H 7.06% N 15.61%

found: C 71.12% H 7.21% N 15.76%

b) Recipes for the powder coating agents 1P [deep] 1, 1P [deep] 2, 1P [deep] 3

1c1. Test results for the paint films of the mixture 1P [deep] 1

Hardening between 180 and 200 ° C

1c2. Test results for the paint films of the mixture 1P [deep] 2

Hardening between 150 and 200 ° C

1c3. Test results for the paint films of the mixture 1P [deep] 3

Hardening between 150 and 200 ° C

Example 2

a) Blocked polyisocyanate

246 parts by weight of TCDI were added dropwise to a melt of 320 parts by weight of 2-phenyl-4-methyl-imidazoline in such a way that the temperature in the reaction flask did not rise above 110.degree. The reaction mixture was kept at 110 ° C. for 2 hours to complete the reaction. These conditions were sufficient for almost complete conversion of the reaction product, so that the residual NCO content was below 0.3% by weight.

Melting range: 85-93 ° C

Glass softening temperature (DTA): 56-68 ° C

Splitting temperature: approx. 130 ° C

calc .: C 72.08% H 7.42% N 14.84%

found: C 71.87% H 7.26% N 14.99%

b) Formulations of the pigmented, powdery coating agents 2P [deep] 1 and 2P [deep] 2

2c1. Test results for the paint films of the mixture 2P [deep] 1

Hardening between 170 and 200 ° C

2c2. Test results for the paint films of the mixture 2P [deep] 2

Hardening between 170 and 200 ° C

The pigmented varnish 2P [deep] 2, which was baked between 170 and 200 ° C, showed a significantly improved elasticity. This improvement was brought about by the approx. 50% increase in the proportion of crosslinker compared to 2P [deep] 1.

Example 3

a) Blocked polyisocyanate

246 parts by weight of TCDI were added dropwise to 196 parts by weight of 2,4-dimethylimidazoline at 100.degree. C. in such a way that the temperature did not rise above 110.degree. After the addition of 2,4-dimethylimidazoline had ended, the mixture was heated at 100 ° C. for a further hour.

Melting range: 80-84 ° C

Glass softening temperature (DTA): 61-75 ° C

Splitting temperature: approx. 150 ° C

calc .: C 65.15% H 8.59% N 19.09%

found: C 64.87% H 8.73% N 18.86%

b) Formulations of the pigmented powder coating agents 3P [deep] 1 and 3P [deep] 2

3c1. Test results for the paint films of the mixture 3P [deep] 1

Hardening between 150 and 200 ° C

3c2. Test results for the paint films of the mixture 3P [deep] 2

Hardening between 130 and 200 ° C

The pigmented powder coating according to Example 3P [deep] 2, which was stoved between 130 and 200 ° C., showed a significantly improved elasticity, caused by a 50% increase in the proportion of crosslinking agent. In addition, the stoving times could be shortened and the stoving temperatures lowered.

Example 4

a) Blocked polyisocyanate

246 parts by weight of TCDI were added dropwise to 338 parts by weight of 2-phenyltetrahydropyrimidine in such a way that the temperature in the reaction flask did not rise above 100.degree. After the addition of 2-phenyltetrahydropyrimidine had ended, the mixture was held at 100 ° C. for a further 2 hours.

Melting range: 65-73 ° C

Glass softening temperature (DTA): 41-54 ° C

Splitting temperature: approx. 130 ° C

calc .: C 72.08% H 7.42% N 14.84%

found: C 71.82% H 7.19% N 15.02% b. Formulation for the pigmented, powdery coating agent 4P

Standard epoxy: 762 parts by weight

Leveling agent masterbatch: 75 parts by weight

Blocked TCDI according to 4 a: 63 parts by weight

White pigment (TiO [deep] 2): 600 parts by weight

c. Test results for the paint films of the mixture 4P

Hardening between 160 and 200 ° C

Claims (6)

1. 3 (4), 8 (9) -diisocyanatomethyl-tricyclo- [5.2.1.0 [high] 2,6] -decane of the general formula blocked with cyclic amidines where B = and n equals 2 and / or 3 and R denotes identical or different substituents from the group H, alkyl, cycloalkyl, aralkyl and aryl radicals. 2. Completely blocked diisocyanates according to claim 1, characterized, that the blocking residue B is an imidazoline derivative where R has the same meaning as in claim 1. 3. Completely blocked diisocyanates according to claim 1, characterized, that the blocking radical B is a tetrahydropyrimidine derivative and R has the same meaning as in claim 1. 4. Process for the preparation of the compounds according to Claim 1, characterized, that 3 (4), 8 (9) -diisocyanatomethyl-tricyclo- [5.2.1.0 [high] 2,6] -decane with the cyclic amidine in a molar ratio of 1: 2 in a conventional manner at 90-140 ° C, preferably at 100-120 ° C. 5. Use of the blocked diisocyanates according to claim 1 as heat-acting crosslinking agents for hydroxyl-containing condensation products and / or addition polymers for the production of plastic coatings. 6. Use of the blocked diisocyanates according to claim 1 as powder hardeners for epoxy resins.