Patent Application
20110224459
The invention relates to new β-hydroxyalkylamides, to a method for production of same and to the use of same.
β-Hydroxyalkylamides are valuable intermediate products in organic syntheses.
For ten years, β-hydroxyalkylamides have found technical applications as curing agents (also known as cross-linking agents) in powder lacquers.
β-Hydroxyalkylamides as well as methods for production of same are known from the following patent documents: DE 2509237, DE19823925, EP 0473380, EP 0960878, WO 2000050384, WO 200055266.
Powder lacquers based on triglycidyl isocyanurate (TGIC) as cross-linking agent (curing agent) and acid-functional polyesters yield corrosion-resistant and weatherproof powder coatings. However, TGIC is classified as mutagenic and toxic.
β-Hydroxyalkylamides are toxicologically safe and also more reactive as cross-linking agents. In U.S. Pat. Nos. 4,076,917 and 4,101,606, powder lacquers are obtained by combining β-hydroxyalkylamides with polymers containing at least one carboxylate or anhydride function, especially with polyacrylates. EP 0322834 describes thermally curing powder lacquers composed of polyesters containing acid groups and of β-hydroxyalkylamides.
Coating systems imparting a uniformly level and matte surface to a substrate command particular interest. The reason is of predominantly practical nature. Glossy surfaces require much more intensive cleaning than do matte surfaces. Furthermore, safety considerations may make it desirable to avoid highly reflective surfaces. Broad sectors of the powder-lacquer industry, such as the architecture, automobile and metal-furniture sectors, are seeing a rising demand for matte (10-30 units) and semi-matte (30-50 units) surfaces, measured as reflectometer values according to DIN 67530/ISO 2813 at an angle of incidence of 60°.
The simplest principle by which a matte surface can be obtained is to admix fillers such as chalk, finely divided silicon dioxide or barium sulfate with the powder lacquer in lower or higher proportions, depending on the desired matte effect. However, such additives lead to deterioration of the lacquer-specific properties, such as adhesion, flexibility, impact resistance and chemical resistance.
The addition of substances incompatible with the lacquer, such as waxes or cellulose derivatives, indeed achieves distinct matting. However, slight changes during extrusion lead to fluctuations in surface gloss and to fade-out in dark color tones. Reproducibility of the matte effect is not guaranteed.
EP 0698645 describes the creation of matte powder coatings by means of dry mixing (dry blend) of at least two separately manufactured hydroxyalkylamide powder lacquers.
For semi-matte and matte (<50 gloss units) powder coatings containing hydroxyalkyamides, therefore, dry blends represent the state of the art. In other words, two hydroxyalkylamide powder lacquers having different acid numbers in the binder components must be separately produced then added as a dry mixture to the grinding process. This imposes considerable extra time and effort and, if any binder component suffers from deviations, leads to gloss deviations, which require considerable additional time and effort to correct. Furthermore, these dry mixtures separate even in the possession of the end customer, with a resulting shift in gloss, if the powder lacquer is scheduled to be recycled in the usual way.
The object of the present invention was to find new 3-hydroxyalkylamides that can be used as intermediate products and curing agents. In particular, the object of the invention was to find new β-hydroxyalkylamides that lead to matte surfaces in powder lacquers after curing and that do not require any dry mixture for production of the powder lacquers.
The object was achieved by the inventive new β-hydroxyalkylamides.
Subject matter of the invention are β-hydroxyalkylamides having two or three or four β-hydroxyalkylamide groups per molecule of formula I
where
R1, R2: independently of one another denote the same or different radicals, selected from alkyl radicals, cycloalkyl radicals, aryl radicals, aralkyl radicals or alkenyl radicals having 1-24 carbon atoms, wherein the radicals may also contain heteroatoms and/or functional groups and wherein
R1 may also be hydrogen,
and wherein R2 may also be
where R3: independently of one another denote the same or different radicals, selected from hydrogen, alkyl radicals, cycloalkyl radicals, aryl radicals, aralkyl radicals or alkenyl radicals having 1-24 carbon atoms, wherein the radicals may also contain heteroatoms and/or functional groups and wherein two or more R3 substituents may be linked to one another to form rings; wherein the β-hydroxyalkylamides exist in solid form below 150° C.
Surprisingly, it has been found that β-hydroxyalkylamides having a cyclohexane ring in the skeleton, with the proviso that the β-hydroxyalkylamides exist in solid form below 150° C., lead to matte surfaces after curing in powder lacquers. Moreover, the inventive β-hydroxyalkylamides represent new intermediate products.
The β-hydroxyalkylamides can be produced from various starting materials. A known method is the reaction of β-hydroxyalkylamines with esters of carboxylic acids, the latter generating the basic skeleton (A). Depending on the choice of starting materials, the inventive β-hydroxyalkylamides can be produced in this way.
Alternative but less preferred methods are based on other carboxylic acid derivatives, such as carboxylic acids, carboxylic acid chlorides, carboxylic acid anhydrides or other activated carboxylic acid derivatives as starting materials, which are reacted with β-hydroxyalkylamines. Suitable β-hydroxyalkylamines are such containing alkyl groups having at least 2 to 10 carbon atoms in the hydrocarbon skeleton. The alkyl groups may be linear, branched or even cyclic. Likewise, the alkyl groups may be substituted with hetero atoms, preferably oxygen and nitrogen. Furthermore, these alkyl groups may also contain functional groups, preferably carbonyl groups, carboxyl groups, amino groups, amide groups and urethane groups, and may have an additional alkyl radical on the nitrogen.
In this invention the β-hydroxyalkylamides are preferably produced from N-alkyl-1,2-alkanolamines and/or from N,N-bis-2-hydroxyalkylamines and esters of cyclohexanedicarboxylic acids.
Particularly preferably, there are used β-hydroxyalkylamines of formulas II and/or III:
where
R1 denotes hydrogen, methyl, ethyl, propyl,
R2 denotes methyl;
where R1 denotes hydrogen, methyl, ethyl, propyl, either simultaneously or independently of one another.
According to the invention, the following compounds are used particularly preferably as starting materials for production of the β-hydroxyalkylamides: diethanolamine (DEA), diisopropanolamine (DIPA), di-sec-butanolamine, N-methylethanolamine, N-methyl-isopropanolamine.
1,2-Substituted, 1,3-substituted and 1,4-substituted cyclohexanedicarboxylic acid derivatives, especially cyclohexanedicarboxylic acid dialkyl esters, are suitable as starting compounds for substituents A in the inventive β-hydroxyalkylamides. These starting compounds may have any desired cis/trans content.
Preferably there are used compounds of formula IV,
where R4 denotes methyl, ethyl, propyl, butyl simultaneously or independently of one another. Particularly preferably there are used 1,4-substituted cyclohexanedicarboxylic acid esters, most particularly preferably dimethyl-1,4-cyclohexyl dicarboxylate.
Those β-hydroxyalkylemides of dialkyl-1,4-cyclohexyldicarboxylates, preferably of dimethyl-1,4-cyclohexyldicarboxylate, which are particularly preferred according to the invention have a trans content, relative to the position of the carboxyl groups on the cyclohexyl ring, of greater than or equal to 70 mol %, preferably greater than 80 mol % and particularly preferably greater than 85 mol %. In this connection, dialkyl-1,4-cyclohexyldicarboxylates having any desired trans content may be used.
The inventive β-hydroxyalkylamides (I) exist in solid form below 150° C., preferably below 170° C., particularly preferably below 180° C.
As secondary products, the p-hydroxyalkylamides also contain small amounts of dimers, trimers, oligomers and other condensation products of the target product.
Particularly preferred inventive β-hydroxyalkylamides have the following formulas:
where
R2: methyl,
or
or
where R1A denotes methyl, ethyl, propyl and R1B denotes hydrogen;
and
A: 1,4-disubstituted cyclohexane ring of the formula
wherein the trans content of A is ≧70 mol %;
and wherein the β-hydroxyalkylamides exist in solid form below 150° C.
That β-hydroxyalkylamide of dimethyl-1,4-cyclohexyldicarboxylate and diethanolamine which is particularly preferred according to the invention and has four β-hydroxyalkylamide groups per molecule according to formula XII
has a trans content on the cyclohexyl ring of greater than or equal to 70 mol %, preferably greater than 80 mol % and particularly preferably greater than 85 mol %.
In principle, the inventive β-hydroxyalkylamides may be produced by known methods, for example according to DE 2509237, DE19823925, EP 473380, EP 960878, WO 2000050384, WO 200055266. The method may be carried out continuously, semicontinuously or discontinuously, as in the batch method, for example.
Preferably, however, the continuous method described in detail hereinafter will be used for production of the β-hydroxyalkylamides from dialkyl-1,4-cyclohexyl dicarboxylates.
The invention also relates to a method for solvent-free, continuous production of the preferred inventive β-hydroxyalkylamides from dialkyl-1,4-cyclohexyl dicarboxylates, especially from dimethyl-1,4-cyclohexyl dicarboxylate, having a trans content on the cyclohexyl ring of greater than or equal to 70 mol %, preferably greater than 80 mol % and particularly preferably greater than 85 mol %, and existing in solid form below 150° C., in an extruder, intensive kneader, intensive mixer or static mixer.
Surprisingly, it has been found that enrichment of the trans form to 70 mol % trans or more on the 1,4-disubstituted cyclohexane ring takes place very easily during production of the β-hydroxyalkylamides by means of a continuous method in an extruder, intensive kneader, intensive mixer or static mixer. For this purpose it is possible to use dialkyl-1,4-cyclohexyl dicarboxylates that have any desired trans content.
In the dialkyl-1,4-cyclohexyl dicarboxylate starting product used according to the invention, the trans configuration is usually between 15 and 35 mol %, depending on raw-material source. However, any desired isomeric composition may be used.
Subject matter of the invention is therefore a method for solvent-free and continuous production of β-hydroxyalkylamides having at least two or three or four β-hydroxyalkylamide groups per molecule of formula I
where
R1, R2: independently of one another denote the same or different radicals, selected from alkyl radicals, cycloalkyl radicals, aryl radicals, aralkyl radicals or alkenyl radicals having 1-24 carbon atoms, wherein the radicals may also contain heteroatoms and/or functional groups and wherein
R1 may also be hydrogen
and wherein R2 may also be
and
A: 1,4-disubstituted cyclohexane ring of the formula
wherein the trans content of A is ≧70 mol %;
and
wherein the β-hydroxyalkylamides (I) exist in solid form below 150° C., in an extruder, intensive kneader, intensive mixer or static mixer.
The principle of the method is that the conversion of the feed substances takes place continuously in an extruder, intensive kneader, intensive mixer or static mixer by intensive intermixing and short-time reaction, preferably with heat input.
Temperatures of 50 to 325° C. may be used in the method, the temperatures varying according to the product, as shown in the examples.
Intensive intermixing and short-time reaction with heat input means that the dwell time of the feed substances in the aforesaid machines usually ranges from 3 seconds to 15 minutes, preferably 3 seconds to 5 minutes, particularly preferably 5 to 180 seconds. In the process, the reactants are made to react within a short time with heat input at temperatures of 50° C. to 325° C., preferably 50 to 225° C., most particularly preferably 70 to 200° C. Depending on the nature of the feed substances and of the end products, however, these values of dwell time and temperature may also fall within other preferred ranges.
If necessary, the process is followed by a continuous after-reaction. Completeness of the reaction is ensured by removal of the alcohols formed during amidation. This removal is preferably achieved by evacuating the alcohols by means of vacuum via apertures in the housings of the extruder or intensive kneader or intensive mixer or static mixer and/or by passing a gas stream over the intensively mixed reaction mixture, thus entraining the more volatile alcohols in the gas stream.
The reaction may be accelerated by catalysts. Suitable catalysts are hydroxides and/or alcoholates of alkali metals, such as sodium or potassium hydroxide, sodium or potassium methanolate, quaternary ammonium hydroxides, alkoxides and/or other strong bases. The concentration is 0.01 to 5%, preferably 0.1 to 3% relative to the total mass used.
The arrangement of vacuum domes or gas-passage stations may be variable, and will depend on the nature of the starting materials and of the resulting alcohols. A station for removal of residual amounts of alcohol may also be added downstream from the actual reaction part.
The end product can then be obtained by subsequent rapid cooling.
Extruders such as single-screw or multi-screw extruders, especially twin-screw extruders, planetary rolling extruders or ring extruders (flow tube, intensive kneader, intensive mixer or static mixer) are particularly suitable as machines for the inventive method and are preferably used. Particularly preferable are twin-screw or multi-screw extruders, especially twin-screw extruders.
It was surprising that the conversion, which in the discontinuous method needs several hours, goes to completion in a few seconds in the said machines, and in this connection that transformation of the cis to the trans form also takes place with suitable catalysis. It is a basic principle that short-time thermal treatment in interaction with the mixing effect of the intensive kneader should be sufficient to convert the reaction partners completely or very extensively. By virtue of appropriately equipped mixing chambers or appropriately assembled screw geometries, the intensive kneaders permit intensive rapid intermixing with simultaneous intensive heat exchange. In addition, steady through-flow in longitudinal direction with the most uniform dwell time possible is also assured. Moreover, different temperature regulation must be possible in the individual machine housings or sections.
The starting products are usually metered into the machines in separate product streams. In the case of more than two product streams, these may also be fed in bundled form. It is also possible to include additional catalysts and/or additives, such as leveling agents, stabilizers or adhesion promoters to this product stream. The substance streams may also be split and in this way fed to the machines in different proportions at various stations. In this way concentration gradients are selectively established, helping to achieve completeness of the reaction. The inlet station for the product streams in the sequence may be variable and manipulated so as to shift in time.
Several machines may also be combined to achieve pre-reaction and/or completion of the reaction.
The machines used for the reaction are equipped with vacuum domes, in order to remove the alcohols formed during the reaction (depending on the carboxylic acid esters used) while the reaction is still proceeding. This helps to complete the reaction by shifting the chemical equilibrium toward the desired β-hydroxyalkylamide.
Product quality may be improved by storing the product at temperatures above 40° C. for between 1 hour and four weeks, and/or by recrystallizing it.
Depending on the viscosity of the product leaving the machine or the after-reaction zone, finishing is first brought to a suitable temperature by further cooling by means of suitable equipment. This is followed by pelletization or else by size reduction to a desired particle size by means of roll-type crusher, hammer mill, cutting mill, air separation ball mill, pinned disk mill, flaking roller mill or the like.
Subject matter of the invention is also the use of the β-hydroxyalkylamides having two or three or four β-hydroxyalkylamide groups per molecule of formula I
where
and wherein R2 may also be
where R3: independently of one another denote the same or different radicals, selected from hydrogen, alkyl radicals, cycloalkyl radicals, aryl radicals, aralkyl radicals or alkenyl radicals having 1-24 carbon atoms, wherein the radicals may also contain heteroatoms and/or functional groups and wherein two or more R3 substituents may be linked to one another to form rings; wherein the β-hydroxyalkylamides exist in solid form below 150° C.,
as cross-linking agents for carboxyl-group-containing polymers, preferably for carboxyl-group-containing polyesters.
Subject matter of the invention is also the use of the inventive β-hydroxyalkylamides in powder lacquers, preferably for carboxyl-group-containing polyester powder lacquers.
Subject matter of the invention is also the use of the inventive β-hydroxyalkylamides in powder lacquers exhibiting matte surfaces after curing (<50 gloss units, measured as reflectometer values according to DIN 67530/ISO 2813 at an angle of incidence of 60°).
The subject matter of the invention will be explained hereinafter on the basis of examples.
Three substance streams were used:
Stream 1 comprised DMCD
Stream 2 comprised DEA
Stream 3 comprised the catalyst, in the form of methanolic sodium methylate solution.
The substance streams were metered in such a way that the molar ratio between dimethyl-1,4-cyclohexyl dicarboxylate and diethanolamine was 1:1.95.
The total amount of catalyst (sodium methylate only, calculated as solvent-free) relative to the total formulation was 0.50 to 3.0%.
Stream 1 was fed at a rate of 10.0 kg/h into the first housing of a twin-screw extruder (ZSK 30, 32 d) (temperature of the substance stream 80 to 130° C.).
Stream 2 was fed at a rate of 9.9 kg/h (temperature of the substance stream 65 to 145° C.).
Stream 3 was atomized into stream 2 (0.5 to 2.0 kg/h) upstream from the inlet into the extruder.
The extruder used comprised 8 housings, each capable of being separately heated and cooled. Housings 1-5: 160° C., housings 6-8: 120-160° C.
Housings 3, 5 and 8 were equipped with a vacuum dome (100 to 600 mbar).
The extruder screws were equipped with conveyor elements. Kneader blocks were installed upstream from the vacuum domes.
All temperatures represented target temperatures. They were regulated by electrical heating and water cooling. The extruder head was also heated electrically (100-160° C.).
The screw speed was 300 rpm. The reaction product was discharged from the extruder via a gear pump. The total throughput rate was 20 kg/h.
The end product was cooled via a length of pipe or via an extruder, passed onto a cooling belt and further cooled. The product was then recrystallized at 100° C. in demineralized water and cooled to room temperature. The mother liquor was filtered off, after which the filter cake was washed three times in methanol at room temperature and then dried in the vacuum drying oven at approximately 20 mbar and 50° C. Thereafter it was ground.
1Analytical values by GC
The trans-N,N,N′,N′-tetrakis-(2-hydroxyethyl)cyclohexyl-1,4-diamide (formula XII) produced was characterized by the NMR spectra in
Using the inventive β-hydroxyalkylamide (matte curing agent) from Example 1, the powder lacquer was produced in the molten state by coextrusion of all components according to Table 2 at a temperature (housing) of 90° C. (charge temperature approximately 130° C.). The composition of the raw materials is listed in Table 2. The ratio of acid groups of the polyester to OH groups of the curing agent was 1:1.
The extrudate is then cooled, ground and sieved to a grain size of <100 μm. The powder lacquer produced in this way was applied with an electrostatic powder-spraying machine at 60 kV onto degreased steel sheets (deep-drawn steel of the KrUppel Co., 210×70×0.8 mm) and/or aluminum sheets (Q-panel AL-36 5005 H 14/08 0.8 mm) and baked between 160 and 220° C. in a circulating-air drying oven. The cured lacquer films exhibited a layer thickness of approximately 55 to 65 μm. The data in the examples relate to a baking time of 20 minutes at 200° C.
Feed substances:
1) Cross-linking agents:
2) Amorphous polyesters:
3) Further formulation components:
Properties of the coating:
Baking conditions: 20 minutes at 200° C.
Gloss: 33 scale divisions at 60° angle
Gloss: 42 scale divisions at 85° angle
Erichsen indentation: >8 mm
Ball impact (direct): >80 in·lb
Specular gloss: DIN 67530/ISO 2813
Erichsen indentation: DIN ISO 1520
Ball impact: DIN EN ISO 6272
| Number | Date | Country | Kind |
|---|---|---|---|
| 102010002783.9 | Mar 2010 | DE | national |
