EP1456275A1 - Reacted pur binding agents for coil coating lacquers - Google Patents

Abstract

The invention relates to reacted lacquer binding agents and to their production and use in polyurethane single-component stoving lacquers, in particular for the coil coating process.

Description

Reacted PUR binders for coil coating varnishes

The invention relates to reacted lacquer binders, their production and use in one-component polyurethane stoving lacquers, in particular for the coil

Coating Nerfahren.

It is state of the art to produce so-called one-component and storage-stable binders for PUR stoving enamels by mixing blocked polyisocyanates with OH-containing polycondensates or polymers (polyesters or polyacrylates) (e.g. EP-A 125438, EP-A 50284). EP-A 50 284 discloses partially blocked polyisocyanates which, however, still have free ΝCO groups, and their use for the production of powder coatings.

As is known, the blocking agent fulfills two in these one-component paints

Tasks: On the one hand it prevents the ΝCO groups blocked with them from reacting prematurely with the OH component and on the other hand it regulates the curing of the paints in a certain temperature range due to its specific deblocking properties. In addition to these desired properties, the individual blocking agents also bring undesired properties, e.g.

Crystallization or yellowing tendency, poor economy and critical physiological effects. To illustrate this, butanone oxime and 3,5-dimethylpyrazole may be mentioned as examples. Both blocking agents are well compatible with the known lacquer polyisocyanates and deblock at around 30 "(min.) / 130-140 ° C. On the other hand, butanone oxime tends to non-yellowing of the stoved lacquer and it is suspected to be carcinogenic. Dimethylpyrazole is complex to produce from acetylacetone and hydrazine hydrate and gives coatings an unpleasant smell.

The object of the invention was therefore to limit the content of blocking agents in PUR stoving enamels to a minimum. This problem could be solved with the PUR binders according to the invention for one-component PUR stoving enamels.

The invention relates to one-component PU binders containing

A) 100 equivalent% of an aliphatic and / or cycloaliphatic lacquer polyisocyanate,

B) 60-90 equivalent% of a blocking agent for isocyanate groups, CI) 80-95 equivalent% of a polymeric OH component and

C2) 5-20 equivalent% of an OH-functional hydrazide compound

and

if necessary, other additives,

characterized in that the mixture of A + B + Cl + C2 has no free but only blocked NCO groups and the equivalent ratio of A: [CI + C2] is 1: 1 to 1: 1.1.

In the binder mixtures according to the invention, the NCO component A) is not completely, but is only partially blocked, and the unblocked NCO groups of the component of A) have reacted with the OH components (CI + C2).

In addition to the four components mentioned essential to the invention, the binders according to the invention can also contain other additives such as fillers, application aids, stabilizing additives, such as. B. HALS amines, solvents and / or diluents, as well as conventional additives, pigments, etc. For component A), the known polyurets, isocyanurate, allophanate, iminooxadiazinedione (asymmetric trimers), urethane and / or uretdione groups contain lacquer polyisocyanates based on (cyclo) aliphatic diisocyanates with an NCO Content from 12 to 25% by weight. Examples of aliphatic or cycloaliphatic diisocyanates are 1,6-diisocyanatohexane

(HDI), 1-isocyanato-3, 3, 5-trimethyl-5-isocyanatomethyl-cyclohexane (isophorone diisocyanate, IPDI), bis (4-isocyanatocyclohexyl) methane (H ₂ MDI or Desmodur W ^® / Bayer AG ), 2,6 or. 2,5-bis-isocyanato-norbornane or 1,4-bis-isocyanatomethyl-cyclohexane and 1,3- or 1,4-tetramethyl-xylene diisocyanate. Preference is given predominantly to polyisocyanates based on isocyanurate groups

1,6-diisocyanatohexane, IPDI and Desmodur ^® W.

Preferred blocking agents B) for the binders according to the invention are oximes, such as, for. B. butanone oxime, secondary aliphatic amines, e.g. Diisopropylamine, CH-acidic compounds, such as. B. Malon or acetoacetic ester, NH-acidic heterocycles, such as. B. 1,2,4-triazole, imidazole or 3,5-dimethylpyrazole, lactams, such as. B. ε-caprolactam, alcohols, such as. B. methanol, ethanol or n-propanol or mixtures of these blocking agents. Ε-Caprolactam, diisopropylamine, 1,2,4-triazole or mixtures thereof are particularly preferred.

Polyesters, polyethers, polycarbonates or polyacrylates in the OH number range from 50 to 500 are used as the polymeric OH component CI). Branched polyesters with OH numbers from 60 to 140 are preferred. The building blocks for these hydroxyl polyesters are 1, 2-propanediol, neopentyl glycol, 1,6-hexanediol or trimethylolpropane, on the one hand, and maleic anhydride, adipic acid, isophthalic acid or phthalic anhydride, on the one hand.

The stabilizing component against thermal yellowing C2) is preferably the addition product of hydrazine hydrate to 2 mol of propylene carbonate of the formula (I), for example known from EP-A 0829 500: CH, OO CH,

I ³ II II I ³

HO - HC - H ₂ COC - NH - NH - C - O - CH ₂ - CH - OH

(Molecular weight 236)

Another object of the invention is a process for the production of the PUR binders according to the invention, characterized in that the lacquer polyisocyanate A) is initially introduced and reacted with the blocking agent B) at 70-100 ° C. up to the calculated NCO content , then with a solvent inert to NCO groups, e.g. B. Solventnaphta 100 or l-methoxy-2-propyl acetate is diluted and the total amount of OH components (CI + C2) is quickly added at approx. 60 ° C and stirred at approx. 60 ° C until no NCO- Groups are more detectable by IR spectroscopy.

The ready-to-use binder according to the invention is thus obtained in dissolved form.

The OH components (CI + C2) are added so rapidly over a period of up to 45 min, preferably 1 to 30 min, that the temperature of about 60 ° C. is maintained.

The advantages of the PUR binders according to the invention are summarized as follows:

• They have a lower content of blocking agents than comparable fully blocked binders and

• are significantly more reactive.

Another object of the invention is the use of the invention

PUR binder for one-component PUR stoving enamels. These can be used to coat substrates made of metal, ceramics, glass, plastics and wood.

The one-component PUR binders according to the invention are preferred for

Coating used in the coil coating process. Examples

Solvessa ^® , Solventnaphtha: aromatic paint solvents, Exxon Chemicals, Houston, USA

Example 1 (according to the invention)

One-component PUR binders

72.7 equivalent% of the blocking agent B) (here diisopropylamine) are used per 100 equivalent% of the polyisocyanate component A), the difference to 100% equivalent% coming from the OH components (CI + C2).

Approach:

192.5 g (0.55 eq) of an isocyanurate-containing lacquer polyisocyanate based on l-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-. methyl-cyclohexane (IPDI), 70% dissolved in Solventnaphta 100, with an NCO content of 12.0% and a functionality of approx.3.2

107.8 g (0.55 Val) of an isocyanurate-containing lacquer polyisocyanate based on 1,6-diisocyanatohexane (HDI) with an NCO content of 21.4%, a viscosity at 23 ° C of approx. 3000 mPas and a functionality of about 3.5

80.8 g (0.8 val) diisopropylamine (DIPA)

500.0 g (1.0 val) Desmophen ^® 670 (slightly branched hydroxyl polyester, 80% dissolved in butyl acetate, OH content of the delivery form 3.4%, Bayer AG) 11.8 g (0.1 val) addition product of 2 mol Propylene carbonate and 1 mol

Hydrazine hydrate, M = 236 g / mol

166.1 g l-methoxy-2-propyl acetate 166.1 g solvent naphta 100

1225.1 g one-component PUR binder Solids content: Ber. 60%

Viscosity at 23 ° C: approx. 1260 mPas

execution

The two polyisocyanates and the solvents are introduced and heated to 40 ° C. DIPA is added in portions. After the DIPA addition has ended, the mixture is stirred at 60 ° C. for 1 hour. An NCO content of 1.75% was found, calculated 1.76%. The hydrazide adduct and the polyester are added rapidly and the mixture is reacted for about 5 hours at 60 ° C. until NCO groups can no longer be detected by IR spectroscopy. A pale yellow solution of a binder with the above characteristics is obtained.

Example 2 (according to the invention ^')

One-component PUR binder with a mixed block consisting of 1,2,4-triazole and diisopropylamine. For every 100 equivalent% of the polyisocyanate component A) there are 72.7 equivalent% of blocking agents B) and the difference to 100 equivalent% comes from the OH components (C 1 + C2).

Approach:

385.0 g (1.1 eq) of an isocyanurate-containing polyisocyanate based on

IPDI (see example 2)

27.6 g (0.4 val) 1,2,4-triazole

40.4 g (0.4 val) diisopropylamine (DIPA)

807.5 g (0.95 Val) Alkynol ^® VP LS 2013 (slightly branched hydroxyl polyester, 75% dissolved in Solventnaphta 100, OH content as supplied 2%, 1 OH equivalent = 850 g, Bayer AG) 17.7 g (0.15 eq) addition product of 2 mol propylene carbonate and 1 mol

Hydrazine hydrate, M = 236 g / mol 5.0 g Tinuvin ^® 770 DF (HALS amine, Ciba special chemicals) 163.2 g 1-methoxypropyl acetate

163.2 g solvent naphta 100

1609.6 g one-component PUR binder

Solids content: Ber. 60%

, Viscosity at 23 ° C: approx. 1100 mPas

execution

The polyisocyanate, 1-methoxy-propyl acetate and 1,2,4-triazole are introduced and heated to 100 ° C. with stirring. After a reaction time of approximately 1 hour at 100 ° C., the NCO content has dropped to the calculated NCO content of 5.1%. Solventnaphta 100 is added, the mixture is allowed to cool to 60 ° C. and DIPA is added in portions. After stirring for 1 hour at 60 ° C., the calculated NCO content of 1.6% is determined. The polyester and the hydrazide adduct are quickly added and the mixture is reacted for about 5 hours at 60 ° C. until no NCO group can be detected by IR spectroscopy. An almost colorless binder solution with the characteristics indicated above is obtained.

Example 3 (comparison)

The binder according to Example 1 is divided into a fully blocked polyisocyanate and the OH components. Approach:

192.5 g (0.55 eq) of the IPDI trimer according to Example 1 107.8 g (0.55 eq) of the HDI trimer according to Example 1 111.1 g (1.1 eq) diisopropylamine

166.1 g of 1-methoxy propyl acetate

166.1 g solvent naphta 100

743.6 g (1.1 Nal) blocked polyisocyanate crosslinker 500.0 g (1.0 Nal) Desmophen ^® 670 (see Example 1)

11.8 g (0.1 Nal) addition compound from 2 mol propylene carbonate and

1 mol hydrazine hydrate (after distilling off the hydrate water, a colorless oil with M = 236 g / mol remains)

1255.4 one-component PUR binder

In contrast to the binder according to Example 1, this has not partially reacted here. Although it contains the same building blocks, it consists of a mixture of fully blocked polyisocyanate and OH components.

Example 4 (comparison)

The binder according to Example 2 is divided into the corresponding fully blocked

Polyisocyanate and the OH component. Otherwise all blocks are identical.

Approach:

385.0 g (1.1 Nal) IPDI trimer according to Example 2

38.0 g (0.55 Nal) 1,2,4-triazole

55.5 g (0.55 Nal) diisopropylamine 163.2 g l-methoxy-2-propyl acetate

163.2 g solvent naphta 100

804.9 g (1.1 Nal) blocked polyisocyanate

5.0 g Tinuvin ^® 770 DF 807.5 g (0.95 Nal) of Alkynol ^® VP LS 2013 (see Example 2) 17.7 g (0.15 Val) of addition compound from 2 mol of propylene carbonate and

1 mol of hydrazine hydrate with M 236 g / mol, water of hydrate was distilled off 1635.1 g of one-component PUR binder

This binder is produced analogously to the method described in Example 2, in that the completely blocked polyisocyanate component is first prepared and then the OH components and HALS amine are mixed in.

Example 4 (paint results)

The binders of Examples 1-4 are processed with subsequent additives in the Scandex mixer to form lacquer batches (data in% by weight).

Binder of Examples 1 to 4 48.7

Kronos 2160, titanium dioxide, from Kronos 29.2

Acronal 4F, leveling agent and defoamer from BASF 1.5

Cellulose Acetobutyrar CAB-531-1, 10% in solvent naphtha 200S /

7.3

Butyl diglycol (2: 1), leveling agent from Eastman, USA

Dibutyltin dilaurate, 10% in Solvesso ^® 200 S, catalyst of

0.9

Air Products, USA

Solvesso ^® 200 S, solvent naphta 200 S Ϊ2

100.0

The result is 4 paint batches with a processing viscosity of approx. 70 sec. DIΝ 4/23 ° C. These paints are doctored onto chromated aluminum sheets (1 mm) with a dry layer thickness of approx. 20 μm and baked in the Aalborg oven on the turntable at 350 ° C. The following paint properties were measured.

1) ECCA = European Coil Coating Association

In addition to the above tests, other paint tests, such as Micro hardness determination, impact test (ECCA-T5),. Adhesive strength at 6 mm Erichsen depth in cross-cut (ECCA-T 6), T-bend test, (ECCA-T 7) tear strength 30 minutes at 100 ° C. Here the results for the binders according to the invention and the comparison binders were equally good.

These results show that the binders according to the invention achieve slightly better whiteness values than their respective comparison lacquers. It is essential, however, that the PUR binders according to the invention (lacquer 1 and 2) are fully crosslinked already at a PMT of 199 ° C., whereas the comparative lacquers show this degree of crosslinking, as can be seen from the 100 double strokes in the MEK wipe test, only at 204 ° C achieve what is a great application and processing advantage for the binders according to the invention.

Claims

claims 1. Containing one-component PUR binders A) 100 equivalent% of an aliphatic and / or cycloaliphatic lacquer polyisocyanate, B) 60-90 equivalent% of a blocking agent for isocyanate groups, CI) 80-95 equivalent% of a polymeric OH component and C2) 5-20 equivalent% of an OH-functional hydrazide compound and if necessary, other additives, characterized in that the mixture of A + B + CI +, C2 has no free, but only blocked NCO groups, and the equivalent ratio of A: [CI + C2] is 1: 1 to 1: 1.1. 2. One-component binder according to claim 1, characterized in that the OH-functional hydrazide compound as the component C2) Formula (I) CH, O O CH, I ³ II II I ³ (I), HO - CH - CH - O - C - NH - NH - C - O - CH ₂ - CH - OH is used. 3. Binder according to claim 1, characterized in that the blocking agents B) are ε-caprolactam, 1,2,4-triazole or diisopropylamine or mixtures of these blocking agents. 4. One-component PUR binders according to claim 1, characterized in that they contain stabilizing additives. 5. A process for the preparation of the PUR binder according to claim 1, characterized in that the lacquer polyisocyanate A) is initially introduced and reacted with the blocking agent B) at 70-100 ° C. up to the calculated NCO content, then with a NCO groups inert solvent is diluted and the total amount of OH components (CI + C2) is quickly added at about 60 ° C and stirred at about 60 ° C until no more NCO groups can be detected by IR spectroscopy , 6. Use of the PUR binder according to claim 1 for one-component PUR stoving lacquers. 7. Use of the binders according to claim 1 for coil coating coatings.