Patent Application
20130041103
The invention relates to thermosetting powder coating compositions which have a matt surface after the coating is cured, and also to a simple method for their production.
Heat-curable powder coating materials do not emit any organic solvents on application, and therefore clearly possess environmental advantages over liquid paints. Crosslinking under hot conditions takes place via polyaddition reactions or polycondensation reactions between the functional groups present in the binders. Typical binder systems are epoxy resins with curing agents based on amines, amidines, acids, anhydrides; carboxyl polyesters or polyacrylates with curing agents based on epoxides; hydroxyl polyesters or polyacrylates with crosslinkers based on blocked isocyanates; polyacrylates containing epoxide groups with dicarboxylic acids as crosslinkers, carboxyl polyesters or polyacrylates with crosslinkers based on β-hydroxyalkylamides, etc. As well as the technical coatings properties, the various binder systems differ particularly in the stability to outdoor weathering. The pure binder systems lead in general to highly glossy surfaces, with a gloss of >80 scale divisions (DIN 67530/ISO 2813, incident angle 60°), when they are processed in a one-shot process with only one co-reactant, e.g., crosslinker and resin, and are induced to cure.
There is considerable interest in coating systems which endow a substrate with a uniformly even and matt surface. The reason for this is primarily practical. Glossy surfaces require a far higher degree of cleaning than do matt surfaces. Furthermore, it may be desirable on safety grounds to avoid highly reflecting surfaces. In wide areas of application in the powder coatings industry, such as architectural, automotive, and metal-furnishing segments, etc., there is a rise in demand in matt (10-30 units) and semimatt (30-50 units) surfaces, measured as reflectometer values to DIN 67530/ISO 2813 at an incident angle of 60°.
The most simple principle for obtaining a matt surface is to admix the powder coating material with smaller or greater amounts—depending on the extent of the desired matt effect—of fillers, such as chalk, finely divided silicon dioxide or barium sulfate, for example. These additions, though, produce a deterioration in the technical coatings film properties, such as adhesion, flexibility, impact strength, and chemicals resistance.
Although the addition of substances incompatible with the coating material, such as waxes or cellulose derivatives, for example, does produce a distinct matting, slight changes during extrusion lead to fluctuations in the surface gloss and to a “fade-out” effect in dark shades. The reproducibility of the matt effect is not guaranteed. EP 0698645 describes the production of matt powder coatings by dry-blending of at least two separately produced hydroxylalkylamide powder coating materials. U.S. Pat. No. 3,842,035 therefore proposes producing matt powder coatings by dry-blending ready-made powder coating materials having sufficiently different reactivities, i.e., powder coating materials having very short and very long gelling times. The binders used are acrylic resins, alkyd resins, and—preferably—epoxy resins. WO-A-89/06674 describes the production of satin-gloss or matt surfaces by dry blending, in other words physical blends of ready-made powder coating materials, which are composed of different binder systems.
DE 2 324 696 proposes a method for producing matt coatings by using a specialty curing agent reacting with epoxide groups—the salt of cyclic amidines with certain polycarboxylic acids. According to this method, the powder coating material undergoes crosslinking with different reactivity at different temperatures, thus forming, on the surface, microstructures which exhibit a matt surface. The application of this method, however, is confined to epoxide and carboxyl polyester/epoxide powder coating materials, meaning that this method cannot be used to produce coatings with sufficient weathering stability.
EP 366 608 likewise proposes a method for producing powder coatings having matt surfaces. It relates to powder coating materials based on epoxy resins or epoxide compounds, such as triglycidyl isocyanurate (TGIC), for example, with carboxyl-terminated polyester resins and mixtures of di-, tri- or tetrakis(β-carboxyethyl)cyclohexanones or -cyclopentanones. The matt effect here is attributed to the difference in reactivity between the aliphatic carboxylate groups of the crosslinker and the aromatic carboxylate groups of the carboxyl-terminated polyester resin.
Another patent specification, DE 3 232 463, describes powder coatings with matt surfaces by joint extrusion of hydroxyl-terminated polyester resins, epoxide compounds, such as TGIC, for example, and special, reversibly blocked polyisocyanates having free carboxylate groups.
U.S. Pat. No. 4,801,680 (EP 322 834) describes a heat-curable powder coating material which consists of a particulate mixture comprising a polyester containing carboxylate groups and a β-hydroxyalkylamide. Following application to a substrate, this powder coating material leads to glossy film surfaces. According to example 2 of U.S. Pat. No. 4,801,680, the resulting film surfaces exhibit no film-surface deterioration after an accelerated weathering test has been carried out and using UV irradiation EP 520429 describes a resin composition comprising polyesters having different hydroxyl numbers. The resin composition described necessarily comprises a substantially ungelled polyester A, a substantially ungelled polyester B, tetramethoxymethylglycoluril as curing agent, and an organic sulfonic acid as catalyst.
Numerous further publications have appeared concerning the possibilities for matting hydroxyalkylamide powder coatings, examples being R. Franiau, “Advances in β-Hydroxyalkylamide crosslinking chemistry” ECJ, (2002) 10, p 409ff; D. Fink, U. Kubilius, “Optimising the Matting of Powder Coatings”, Powder Coatings Europe 2002, and R. Guida, “A Novel Approach to Produce Reduced Gloss β-Hydroxyl Alkylamide Powder Coatings” Powder Coating 2002 PCI Conference; D. Beccaria et al. “Modeling Gloss Control in Polyester/β-Hydroxyalkylamide Powder Coatings Based on SPM Structure-Property Relationship”, Waterborne, High-Solids and Powder Coatings Symposium, Feb. 26-28, 2003, New Orleans, La., USA.
Laid-open specification KR 10-2009-0111720 (application number 10-2008-0037454), with translated title “CYCLOALKANE DICARBOXAMIDE COMPOUNDS, THEIR PREPARATION AND APPLICATION” (see also J. Korean Ind. Eng. Chem., vol. 20, No. 2, April 2009, 195-200), discloses in particular in example 1 the therein-named compound N1,N1,N4,N4-tetrakis(2-hydroxyethyl)cyclohexane-1,4-dicarboxamide (formula 3). This compound according to
Therefore, for matt and semimatt (<50 gloss units) powder coating compositions with hydroxylalkylamides, state of the art is what are called dry blends; in other words, the separate preparation of two hydroxyalkylamide powder coating materials is required, based on β-hydroxyalkylamides, plus resins (polymers) with different acid numbers, which are then supplied in the form of a dry blend to the grinding operation. This involves considerable extra cost and effort and, in the event of deviation in a binder component, results in gloss deviations which take considerable extra cost and effort to correct. Furthermore, these dry blends undergo separation, including at the premises of the end customer, with a resultant shift in gloss if the powder coating, as is usual, is to be recycled.
It was an object of the invention to find thermosetting powder coating composition which after the coating is cured exhibit a matt surface, and also a simple method for their production.
This object is achieved by the new β-hydroxyalkylamides of the invention as crosslinkers (curing agents), and also by the method of the invention.
The invention provides a powder coating composition substantially comprising
Surprisingly it has been found that through the use of the new β-hydroxyalkylamides of formula I of the invention as crosslinkers it is possible to obtain coatings having matt (10-30 units) and semimatt (30-50 units) surfaces, measured as reflectometer values to DIN 67530/ISO 2813 at an incident angle of 60°.
Surprisingly it has been found that through the method of the invention, in a one-shot operation, in other words by joint extrusion of all of the components, it is possible to obtain the powder coating composition of the invention, based on polymers containing carboxylate groups and β-hydroxyalkylamides of the invention as crosslinkers.
In the context of this invention the terms crosslinker and curing agent are used synonymously.
There is no requirement for costly and involved dry blending of at least two powder coating materials which differ in reactivity, on the basis of β-hydroxyalkylamides as crosslinkers. Furthermore, there is also no need for a polyester mixture or polyacrylate mixture of at least two resins having different reactivities.
Co-reactants contemplated for the β-hydroxyalkylamide compounds used in accordance with the invention for preparing the powder coating composition are polymers A) containing carboxylate groups. Polymers which can be used are addition polymers, polycondensates, and polyaddition compounds. In principle it is possible to use any polymer which contains at least two carboxylate groups and has a glass transition temperature Tg greater than 40° C. Polymers containing carboxylate groups that are suitable for the powder coating materials of the invention are those which have acid numbers of 5-350 mg KOH/g, preferably 15-150 mg KOH/g, with OH numbers <15 mg KOH/g. These polymers preferably have at least two terminal carboxylate groups.
Particularly preferred in the context of the invention are polyacrylates and/or polyesters containing carboxylate groups.
The polyesters A) containing carboxylate groups are preferably polyester polycarboxylic acids prepared from polyols and polycarboxylic acids and/or derivatives thereof. The glass transition temperature Tg of these acidic polyesters is situated in a range from 40 to 80° C., preferably 40 to 70° C.; their acid number varies from 5-250 mg KOH/g, preferably from 10 to 150 mg KOH/g, more preferably 12 to 120 mg KOH/g. The OH numbers are below 15 mg KOH/g. They have an average molecular weight MW of 1000 to 10 000 g/mol, preferably 1500 to 9000 g/mol, more preferably of 2000 to 8000 g/mol.
The polyesters containing carboxylate groups for use in accordance with the invention are prepared using polycarboxylic acids, such as oxalic, succinic, adipic, 2,2,4(2,4,4)-trimethyladipic, azelaic, sebacic, decanedicarboxylic, dodecanedicarboxylic, fumaric, phthalic, isophthalic, terephthalic, trimellitic, pyromellitic acid, for example. For the acidic polyesters, polyols used are, by way of example, the following: ethylene glycol, 1,2- and 1,3-propanediol, 1,2-, 1,3-, 1,4- and 2,3-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 1,12-dodecanediol, 2,2,4(2,4,4)-trimethyl-1,6-hexanediol, trimethylolpropane, glycerol, pentaerythritol, 1,4-bishydroxymethylcyclohexane, cyclohexane-1,4-diol, diethylene glycol, triethylene glycol, and dipropylene glycol. It is of course also possible for hydroxyl-containing polyesters, prepared by known methods from polycarboxylic acids and polyols, to be reacted with polycarboxylic acids and/or polycarboxylic anhydrides to give the polyester polycarboxylic acids.
The polyester resins containing carboxylate groups are prepared by known methods, by esterification or transesterification of dihydric and/or polyhydric linear or branched, aliphatic or cycloaliphatic polyols with polybasic, preferably dibasic or polybasic aliphatic, cycloaliphatic or aromatic carboxylic acids or their anhydrides or esters thereof, in the presence of an esterification or transesterification catalyst at temperatures up to about 250° C. and under reduced pressure toward the end.
Preferred polyols are 2,2-dimethyl-1,3-propanediol (neopentyl glycol), ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-dimethylolcyclohexane, 2,2-[bis(4-hydroxycyclohexyl)]propane, diethylene glycol, dipropylene glycol, glycerol, pentaerythritol etc. The polyol component preferably includes a high fraction of neopentyl glycol in order to obtain very high glass transition temperatures. Preferred polybasic carboxylic acids are terephthalic acid, isophthalic acid, trimellitic acid, adipic acid, and/or 1,4-cyclohanedicarboxylic acid. The functionality of the preferred polyester resins containing carboxylate groups is adjusted via the ratio of dibasic to more-than-dibasic carboxylic acids.
Suitable acrylate polymers containing carboxylate groups possess an acid number of 10-350 mg KOH/g, preferably 20 to 300 mg KOH/g, and a glass transition temperature Tg of greater than 40° C., preferably of 45 to 100° C., prepared by homopolymerization or copolymerization of a monomer mixture.
The polyacrylate comprises carboxylic acid groups and may be a homopolymer or a copolymer.
Monomers which can be used are acrylic acid and/or methacrylic acid, C1-C40 alkyl esters and/or cycloalkyl esters of methacrylic acid and/or acrylic acid, hydroxyalkyl acrylates and/or hydroxyalkyl methacrylates, glycidyl methacrylate, glycidyl acrylate, 1,2-epoxybutyl acrylate, 1,2-epoxybutyl methacrylate, 2,3-epoxycyclopentyl acrylate, 2,3-epoxycyclopentyl methacrylate, and also the analogous amides, where styrene and/or derivatives thereof may also be present.
Preference is given to using butyl acrylate and/or butyl methacrylate, 2-hydroxyethyl acrylate and/or 2-hydroxyethyl methacrylate, methyl methacrylate, styrene (meth)acrylic acid, and, optionally, further unsaturated monomers, with at least one monomer containing carboxylate groups being used.
Further suitable monomers are (cyclo)alkyl esters of acrylic or methacrylic acid having 2 to 18 carbon atoms in the (cyclo)alkyl radical. Examples of suitable and preferentially suitable monomers are ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl methacrylate, neopentyl methacrylate, isobornyl methacrylate, 3,3,5-trimethylcyclohexyl methacrylate, and stearyl methacrylate.
Examples of monomers contemplated include styrene, vinyltoluene, and ethylstyrene. Examples of are acrylic acid and methacrylic acid, which are also used preferably, and also crotonic acid, itaconic acid, fumaric acid, maleic acid, and citaconic acid.
The polyacrylate preferably possesses an OH number of less than 10 mg KOH/g, an acid number of 5 to 350 mg KOH/g, preferably 20 to 300 mg KOH/g, more preferably of 30 to 250 mg KOH/g, a Tg of 40 to 110° C., preferably 45 to 100° C., an Mw of 500 to 50 000 g/mol, preferably 1000 to 30 000 g/mol, more preferably of 1500 to 20 000 g/mol.
As co-crosslinkers it is also possible to use epoxy resins. Those contemplated include, for example, glycidyl ethers and glycidyl esters, aliphatic epoxides, diglycidyl ethers based on bisphenol A, and glycidyl methacrylates. Examples of epoxides of these kinds are triglycidyl isocyanurate (TGIC trade name: e.g., ARALDIT PT 810, Huntsman; TEPIC G, Nissan; Taida TGIC, Anhui Taida), mixtures of diglycidyl terephthalate and triglycidyl trimellitate (trade names, e.g., ARALDIT PT 910 and PT 912, Huntsman), glycidyl esters of Versatic acid (trade name, e.g., CARDURA E10, Shell), 3,4-epoxycyclohexylmethyl 3′,4′-epoxycyclohexanecarboxylate (ECC), diglycidyl ethers based on bisphenol A (trade name, e.g., EPIKOTE 828, Shell), ethylhexyl glycidyl ether, butyl glycidyl ether, pentaerythritol tetraglycidyl ether, (trade name, e.g., POLYPDX R16, UPPC AG), and also other Polypox types having free epoxy groups. Mixtures can also be used. Preference is given to using TEPIC G or ARALDIT PT 910 and 912. Co-crosslinkers of these kinds can be used at up to 50% by weight of the curing agent mixture that is used, composed of β-hydroxyalkylamide of the invention (matt curing agent) and co-crosslinker.
Surprisingly it has been found that β-hydroxyalkylamides having a cyclohexane ring in the framework, the β-hydroxyalkylamides being present in solid form below 150° C., as crosslinkers for carboxyl-containing polymers in powder coating materials, lead to matt surfaces after curing.
The β-hydroxyalkylamides B) may be prepared from various starting materials. A known reaction is that of β-hydroxyalkylamines with esters of carboxylic acids, the latter generating the parent structure (A). Depending on the selection of the starting materials, the β-hydroxyalkylamides of the invention can be generated in this way.
Alternative but less preferred methods are based on other carboxylic acid derivatives, such as carboxylic acids, carbonyl chlorides, carboxylic anhydrides or other activated carboxylic acid derivatives, for example, as starting materials, which are reacted with β-hydroxyalkylamines.
Suitable β-hydroxyalkylamines are those which have alkyl groups having at least 2 to 10 carbon atoms in the hydrocarbon framework. The alkyl groups may be linear, branched or else cyclic. The alkyl groups may likewise be substituted by heteroatoms, preferably oxygen, nitrogen. Furthermore, these alkyl groups may also contain functional groups, preferably carbonyl groups, carboxyl groups, amino groups, amide groups, urethane groups, and may carry an additional alkyl radical on the nitrogen.
Preferably in this invention the β-hydroxyalkylamides are prepared from N-alkyl-1,2-alkanolamines and/or from N,N-bis-2-hydroxyalkylamines and esters of cyclohexanedicarboxylic acids.
Particular preference is given to using β-hydroxyalkylamines of the formulae II and/or III:
where
R1 is hydrogen, methyl, ethyl, propyl,
R2 is methyl;
where radicals R1 simultaneously or independently of one another are hydrogen, methyl, ethyl, propyl.
Particular preference in accordance with the invention is given to using the following compounds as starting materials for preparing β-hydroxyalkylamides: diethanolamine (DEA), di-isopropropanolamine (DIPA), di-sec-butanolamine, N-methylethanolamine, N-methylisopropanolamine.
Suitable starting compounds for the substituent A in the β-hydroxyalkylamides of the invention are 1,2-, 1,3-, and 1-4-cyclohexanedicarboxylic acid derivatives, more particularly dialkyl esters of cyclohexanedicarboxylic acids. These starting compounds may have any desired cis/trans content.
Preference is given to using compounds of the formula IV
where radicals R4 simultaneously or independently of one another are methyl, ethyl, propyl, butyl.
Particular preference is given to using 1,4-substituted cyclohexanedicarboxylic esters, very preferably dimethyl 1,4-cyclohexyldicarboxylate.
The β-hydroxyalkylamides that are particularly preferred in accordance with the invention, formed from dialkyl 1,4-cyclohexyldicarboxylates, preferably from dimethyl 1,4-cyclohexyldicarboxylate, have a trans content, based on the position of the carboxyl groups on the cyclohexyl ring, of greater than or equal to 70 mol %, preferably greater than 80 mol %, more preferably of greater than 85 mol %. For preparing the preferred β-hydroxyalkylamides it is possible in this case to use dialkyl 1,4-cyclohexyldicarboxylates having any desired trans content.
The β-hydroxyalkylamides (I) of the invention are present in solid form below 150° C., preferably below 170° C., more preferably below 180° C.
Particularly preferred β-hydroxyalkylamides of the invention have the following formulae:
where
R2 is methyl,
or
where R1A is hydrogen and R1B is methyl, ethyl, propyl,
or
R1A is methyl, ethyl, propyl and R18 is hydrogen;
and
A is a 1,4-disubstituted cyclohexane ring of the formula
where the trans content of A is ≧70 mol %;
and where the β-hydroxyalkylamides are present in solid form below 150° C.
The β-hydroxyalkylamide that is particularly preferred in accordance with the invention, formed from dimethyl 1,4-cyclohexyldicarboxylate and diethanolamine with four β-hydroxyalkylamide groups per molecule of the formula XII,
has a trans content on the cyclohexyl ring of greater than or equal to 70 mol %, preferably greater than 80 mol %, and more preferably of greater than 85 mol %.
In order to achieve good technical coatings properties for the powder coating composition, the ratio of β-hydroxyalkylamide groups to the carboxylate groups of the polymers containing carboxylate groups is preferably between 0.5 to 1.5:1, more preferably between 0.8 to 1.2:1.
The powder coating composition may be admixed with the auxiliaries and additives C) that are customary in powder coating technology, such as flow control agents, e.g., polysilicones or acrylates, light stabilizers, e.g., sterically hindered amines and/or absorbers, degassing agents (e.g., benzophenone), modified phenolic resins, catalysts and/or other auxiliary agents, as described in EP 669 353, for example, in a total amount of 0.1% to 10% by weight. Fillers and pigments such as titanium dioxide, for example, can be added in an amount of up to 50% by weight of the overall composition.
In quantitative terms the constitution of the powder coating compositions is as follows:
The powder coating compositions of the invention exhibit good storage stability in the storage test customary for powder coating materials, in accordance with DIN EN ISO 8130-8, at temperatures of 30±1 and 40±1° C., and are storable for >30 days.
In the particularly preferred embodiment of the invention, the powder coating compositions of the invention comprise:
The invention provides a method for producing a powder coating composition substantially comprising
The invention also provides a method for producing a powder coating composition, comprising N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide according to formula XIIA as component B)
which has the following parameters:
The invention also provides a method for producing a powder coating composition, comprising N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide according to the formula XIIA as component B)
which has the following parameters:
The powder coating composition of the invention is produced preferably in the melt by joint extrusion of all the components A) to C) at temperatures between 80 to 150° C. The extrudate is subsequently cooled, ground, and sieved off or classified to a particle size of <120 μm, preferably <100 μm. The heat-curable and toxicologically flawless powder coating composition produced in accordance with the invention therefore consists of a matrix obtained by joint extrusion of all the components.
In order to obtain the effect in accordance with the invention, namely the formation of matt surfaces having a gloss to DIN 67530/ISO 2813 of <50 at an incident angle of 60°, it is possible to use numerous polymers containing carboxylate groups, more particularly carboxylate-group-terminated polyesters or polyacrylates, which differ in their functionality and reactivity. The desired gloss can therefore be selected via the selected binder partner (polyester) in conjunction with the hydroxyalkylamide of the invention within a considerable spectrum (examples 1-7), with the formulation being otherwise the same. Example (8) with the polyacrylate deviates from this, since more crosslinker is needed for the increased acid number, and a lower level of pigmentation was selected in view of the anticipated greater brittleness.
The use of and the application of the powder coating materials for producing coatings take place in accordance with methods customary for powder coating materials, preferably by means of an electrostatic powder coating sprayer device in accordance with the triboelectric or corona method or in accordance with the fluid-bed method.
At standard ambient temperatures, the powder coating compositions produced in accordance with the invention possess good storage stability and, after crosslinking between 150 to 220° C., exhibit good technical coatings properties, surfaces which flow out well in optical terms, and the low gloss levels described.
In contrast to the prior art, the coatings obtained with the powder coating compositions of the invention have visually very attractive surfaces with good leveling (PCI evaluation table 8-10), which, however, are matt (10-30 units) and/or semimatt (30-50 units), measured as reflectometer values to DIN 67530/ISO 2813 at an incident angle of 60°, with no need for a dry blend or a polyester mixture or polyacrylate mixture (one-shot blend).
Beyond this variation, the possibility additionally exists of shifting the measured reflectometer value, to DIN 67530/ISO 2813 at an incident angle of 60°, to higher levels, up to the re-acquisition of the high gloss of >80 scale divisions at the 60° angle. This is accomplished by partially replacing the matt curing agent B) of the invention with a standard commercial β-hydroxyalkylamide having two or more than two β-hydroxyalkylamide groups, or mixtures thereof having different functionalities.
The invention provides the use of a powder coating composition substantially comprising
Provided especially preferably by the invention is a powder coating composition which has the compound N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide according to the formula XIIA as component B),
which has the following parameters:
Description of the Particularly Preferred Component B):
Provided more preferably by the invention is a powder coating composition comprising the β-hydroxyalkylamide N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide according to the formula XIIA as component B), having a trans content on the cyclohexyl ring of greater than or equal to 70 mol %, preferably greater than 80 mol %, and more preferably of greater than 85 mol %, based on the total amount of all of the isomers of N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide that are present.
Additionally this β-hydroxyalkylamide of the invention used as component B), N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide according to the formula XIIA, has two endothermic peaks according to DSC analysis (differential scanning calorimetry): first a peak with a maximum (peak 1) of about 160° C., and a further, second peak with a maximum (peak 2) of about 190° C.; see the figures relating to the examples. Preferably, the first peak is situated in the range of 140-170° C. with a maximum of 155-165° C. and the second peak is situated in the range of 170-210° C. with a maximum of 175-207° C.
More preferably, the first peak is situated in the range of 155-170° C. with a maximum of 158-165° C., and the second peak is situated in the range of 170-210° C. with a maximum of 180-205° C.
The ratio of the enthalpies of the endothermic peak 1 (˜160° C.) to the endothermic peak 2 (˜190° C.) may be 1:1 to 1:5, preferably 1:1 to 1:3.
The DSC measurements were carried out in accordance with DIN EN ISO 11357-1 of March 2010. A heat flow difference calorimeter from the manufacturer Mettler-Toledo, model DSC 821, was used. The samples are run once from −30° C. to 250° C. at 10 K/min.
The XRPD measurements on powder samples were carried out in an x-ray diffractometer using Cu Kα radiation (1.541 Å). In accordance with
Especially preferred as component B) is the β-hydroxyalkylamide N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide according to the formula XIIA having a trans content on the cyclohexyl ring of greater than or equal 92 mol %, preferably greater than 94 mol %, and more preferably of greater than 96 mol %, and very preferably of greater than 98 mol %, based on the total amount of all of the isomers of N,N,N′,W-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide that are present.
The β-hydroxyalkylamide of the formula XIIA of the invention that is used as component B) is present in solid form below 175° C., preferably below 180° C., and more preferably of below 185° C.
The β-hydroxyalkylamide of the formula XIIA of the invention that is used as component B), having the features 1. to 4, was investigated by means of x-ray structural analysis of a single crystal. Comprehensive details relating to the measurement are summarized in annex 1. The x-ray structural analysis of a single crystal gave the following result for the structure:
The values within the brackets indicate the measurement accuracy, in each case in plus and minus, for the corresponding last digit or last two digits, respectively.
Provided with very particular preference by the invention is a powder coating composition which comprises the compound N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide according to the formula XIIA as component B)
which has the following parameters:
The particularly preferred N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide according to the formula XIIA which is used as component B) is obtainable by various methods:
First of all, as described precisely earlier on above, the N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide according to the formula XIIA is prepared, preferably solventlessly, in an extruder, intensive compounder, intensive mixer or static mixer, preferably in an extruder. For this preparation, temperatures of 100 to 180° C. are employed. This is followed by recrystallization from a suitable solvent, preferably water. After dissolution at temperatures of 20-100° C. and crystallization, the N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide according to the formula XIIA is obtained with the above-stated parameters. It can then, subsequently, be washed with alcohols, preferably methanol, and dried. Drying takes place preferably at temperatures of 20-90° C., and can also take place under reduced pressure.
Another variant of the preparation takes place as described precisely earlier on above, by the N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide according to the formula XIIA being prepared in an extruder, intensive compounder, intensive mixer or static mixer, preferably in an extruder, preferably solventlessly. In this case temperatures of 100 to 180° C. are employed. This is followed by a thermal conditioning at temperatures of 50-100° C., preferably at temperatures of 70-85° C. The time is more than 6 hours, preferably more than 12 hours. Thermal conditioning may also take place under reduced pressure.
The particularly preferred N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide according to the formula XIIA that is used as component B) may also take place discontinuously in a solvent, in other words in a batch method.
The reaction is carried out in customary reactors. Operation may be unpressurized, using a reflux condenser, or under pressure, with a closed reactor.
The synthesis is carried out in a solvent, preferably in alcohols, preferably methanol. The amount of solvent added is greater than 10% by weight, preferably greater than 15% by weight, based on the total amount of all the reactants (starting materials) used. This operation may take place under reflux, or else at relatively low temperatures, and also relatively high temperatures, under pressure. The preparation takes place at temperatures of 20 to 120° C., preferably at 60 to 90° C., more preferably at 70 to 85° C.
After crystallization has taken place, the N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide according to the formula XIIA is obtained, with the parameters stated above.
Furthermore, the N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide according to the formula XIIA can be prepared in closed apparatus under pressure at temperatures of 60 to 140° C. without addition of solvents.
The N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide according to the formula XIIA prepared in this way in a batch method can be recrystallized from suitable solvents, preferably from water or alcohols, preferably from methanol.
Furthermore, the preparation of the N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide according to the formula XIIA may also take place discontinuously without solvents.
The reaction is carried out in customary reactors. It is possible here to operate using a reflux condenser. The preparation takes place preferably at temperatures of 20 to 140° C., preferably 60 to 90° C., more preferably at 70 to 85° C. The β-hydroxyalkylamide obtained in this way in a batch method is then recrystallized from suitable solvents, preferably from water or alcohols, preferably from methanol. After crystallization has taken place, the N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide according to the formula XIIA is obtained, with the parameters stated above.
The concentration of all of the isomers of N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide in the end product after its preparation is 75% by mass, preferably 80% by mass, and more preferably 85% by mass.
This β-hydroxyalkylamide characterized and described here, N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide of the formula XIIA, produces far-reaching matting in powder coatings, with a gloss of less than 50 scale divisions at the 60° angle, as has been shown in the examples. This product of the formula XIIA therefore differs clearly from the β-hydroxyalkylamide disclosed in accordance with laid-open specification KR 10-2009-0111720 (and from the β-hydroxyalkylamide from Korean Ind. Eng. Chem., vol. 20, No. 2, April 2009, 195-200), as demonstrated there in
The invention also provides the use of a powder coating composition as described above, comprising N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide according to formula XIIA as a component
which has the following parameters:
for producing coatings having matt surfaces with <50 gloss units, measured as reflectometer values to DIN 67530/ISO 2813 with an incident angle of 60°.
The invention also provides the use of a powder coating composition as described above, comprising N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide according to the formula XIIA as component B)
which has the following parameters:
for producing coatings having matt surfaces with <50 gloss units, measured as reactometer values to DIN 67530/ISO 2813 at an incident angle of 60°.
The following examples and tables 1, 2, and 3 characterize the composition of the coating system and the properties of the respective coating after its application and curing.
1Analytical values by GC
The powder coating material was produced first by mixing all of the components as per tables 1 and 2 at room temperature in a MIT mixer at 500 rpm for 120 seconds and then, second, by joint extrusion in the melt at a temperature (barrel) of 90° C. (about 130° C. melt temperature). The stoichiometric ratio of acid groups of the polyester or polyacrylate to OH groups of the β-hydroxyalkylamides (curing agents) was about 1:1. When co-crosslinkers were used, they were taken into account stoichiometrically in respect of the amount of curing agent.
The extrudate was subsequently cooled, ground, and sieved to a particle size of <100 μm. The powder coating material produced in this way was applied using an electrostatic powder spraying unit at 60 KV to degreased steel panels (deep-drawn steel from Krüppel 210×70×0.8 mm) and/or aluminum panels (Q-panel AL-36 5005 H 14/08 0.8 mm) and baked in a forced-air drying oven at between 160 to 220° C. The cured coating films had a film thickness of about 55-65 μm. The example data relate to a baking time of 20 minutes at 200° C.
By replacing the inventive β-hydroxyalkylamide 1a) by a standard commercial β-hydroxyalkylamide, such as VESTAGON HA 320 1b), or else by mixtures with other commercial products with the same and/or different functionality, it is possible to retain the gloss, at low levels of admixture, or, if desired, to shift it to higher values, with increased additivation or replacement. This is shown here in examples 9 to 13 by reference to a polyester.
Formulating examples with inventive β-hydroxyalkylamide 1a (matt curing agent) and different resins, and with commercial β-hydroxyalkylamide 1b)
As co-crosslinkers it is also possible to use epoxy resins. Examples contemplated include glycidyl ethers and glycidyl esters, aliphatic epoxides, diglycidyl ethers based on bisphenol A, and glycidyl methacrylates. Examples of such epoxides are triglycidyl isocyanurate (TGIC trade names, e.g., ARALDIT PT 810, Huntsman; TEPIC G, Nissan; Taida TGIC, Anhui Taida), mixtures of diglycidyl terephthalate and triglycidyl trimellitate (trade names, e.g., ARALDIT PT 910 and PT 912, Huntsman), glycidyl esters of Versatic acid (trade name, e.g., CARDURA E10, Shell), 3,4-epoxycyclohexylmethyl 3′,4′-epoxycyclohexanecarboxylate (ECC), diglycidyl ethers based on bisphenol A (trade name, e.g., EPIKOTE 828, Shell), ethylhexyl glycidyl ether, butyl glycidyl ether, pentaerythritol tetraglycidyl ether, (trade name, e.g., POLYPDX R 16, UPPC AG), and also other Polypox types having free epoxy groups. Mixtures can also be used. Preference is given to using TEPIC G or ARALDIT PT 910 and 912.
Co-crosslinkers of these kinds can be used at up to 50% by weight of the curing agent mixture used, composed of matt curing agent and co-crosslinker.
Formulating examples with inventive β-hydroxyalkylamide 1a (matt curing agent) and co-crosslinker
Examples 3a, b; 4a, b, c, d; 5
The DSC measurements were carried out in accordance with DIN EN ISO 11357-1 of March 2010.
A heat flow difference calorimeter from the manufacturer Mettler-Toledo, model: DSC 821 with serial number 5116131417 was used. The samples are run once from −30° C. to 250° C. at 10 K/min.
The powder sample is pressed into a powder holder and is measured in a Philips PW1800 x-ray diffractometer using Cu Kα radiation (1.541 Å) under the following conditions:
Measuring range: 3°≦2θ≦40°
Step size: 0.1° (2Theta)
Time per step: 20 s
Rotation: ¼ revolution/sec
Receiving slit: coarse
Divergence slit: automatic
A three-neck flask with reflux condenser and glass stirrer is charged with 92.24 g of dimethyl 1,4-cyclohexyldicarboxylate with 96.91 g of diethanolamine, 10.84 g of 30% strength sodium methoxide in methanol, and 52 g of methanol. A homogeneous solution is formed.
The batch is boiled in an oil heating bath under reflux with stirring for six hours (bath temperature 80° C.). The product begins to precipitate after about 0.5 hour.
The reaction mixture is left to cool, during which further product crystallizes out. The precipitated product is subsequently separated from methanol by filtration and then dried. The yield is more than 80% of theory. Table 3a
Obtained accordingly is an N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide according to formula XIIA having two endothermic peaks (1st at about 160° C. and 2nd at about 190° C.) in the DSC as per
The product produced in 3a is dissolved in boiling water, then slowly cooled again and, after crystallization has taken place, briefly washed with methanol. Table 3a This product exhibits the two endothermic peaks, see
1)DEA
1)trans-N,N,N′,N′-Tetrakis(2-hydroxyethyl)cyclohexyl-1,4-
1)cis-N,N,N′,N′-Tetrakis(2-hydroxyethyl)cyclohexyl-1,4-
1)Analytical values by GC GC after silylation with Silyl 991 (BSTFA-TMCS 99: 1) from Macherey and Nagel order
Operation Took Place with Three Streams:
Stream 1 consisted of DMCD
Stream 2 consisted of DEA
Stream 3 consisted of the catalyst, the methanolic sodium methoxide solution.
The streams were metered so that the molar ratio between dimethyl 1,4-cyclohexyldicarboxylate and diethanolamine was 1:1.95.
The total amount of catalyst (only sodium methoxide, calculated on solvent-free basis), based on the total formula, was 0.50% to 3.0%.
Stream 1 was fed at a rate of 10.0 kg/h into the first barrel of a twin-extruder (ZSK 30, 32 d) (stream temperature 80 to 130° C.).
Stream 2 was fed in at a rate of 9.9 kg/h (stream temperature 65 to 145° C.).
Stream 3 was introduced through a nozzle from entry into the extruder into stream 2 (0.5 to 2.0 kg/h).
The extruder used consisted of 8 barrels, which were separately heatable and coolable. Barrels 1-5: 160° C., barrels 6-8: 120-160° C.
Barrels 3, 5, and 8 were provided with a vacuum dome (100 to 600 mbar).
The extruder screws were fitted with conveying elements. Ahead of the vacuum domes, kneading blocks were installed.
All of the temperatures represented setpoint temperatures. Regulation took place via electrical heating or water cooling. The extruder head was likewise heated electrically (100-160° C.).
The screw speed was 300 rpm. The reaction product was conveyed out of the extruder using a gear pump. The total throughput was 20 kg/h.
The end product was cooled via a pipe section or via an extruder and was guided onto a cooling belt, and cooled further.
4a
An N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide with the product data 4a is prepared in the same way as described in example A in an extruder (Werner and Pfleiderer ZSK 30, 32 d). Table 4
4b
This product, described and produced as in example 4a, is recrystallized. For this purpose, the product from example 4a is dissolved in deionized water at boiling and then slowly cooled and crystallized, to convert it back into the solid form. It is subsequently washed with methanol and dried in a vacuum drying oven at 50° C. and about 20 mbar. Table 4
Obtained accordingly is an N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide having two endothermic peaks (1st at about 160° C. and 2nd at about 190° C.) in the DSC. This product with the two peaks in the DSC as per
A noninventive N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide with the DSC as per
This product shows only one endothermic peak in the DSC, at about 190° C., as per
An N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide of the formula XIIA with the product data 4d is prepared in the same way as described in example 1 in an extruder (Werner and Pfleiderer ZSK 30, 32 d). Table 4
This product thus produced is run onto a cooling belt and collected. This material is then conditioned thermally under reduced pressure in a drying cabinet at 80° C. for 24 hours, and the resulting product is subsequently comminuted.
This product produces far-reaching matting in powder coating materials, with a gloss of 40 scale divisions at the 60° angle. Table 4
1)DEA fraction
1)trans-N,N,N′,N′-Tetrakis(2-
1)cis-N,N,N′,N′-Tetrakis(2-
1Analytical values by GC. GC after silylation with Silyl 991 (BSTFA-TMCS 99: 1) from Macherey and Nagel order
1)DEA
1)trans-N,N,N′,N′-tetrakis(2-
1)cis-N,N,N′,N′-tetrakis(2-
A β-hydroxyalkylamide of the formula XIIA was prepared as in example 3a. From it a single crystal was grown. The inventive of the formula XIIA was investigated by x-ray structural analysis of a single crystal. Comprehensive details relating to the measurement are compiled in annex 1.
Analytical method: Single Crystal X-ray Structure Analysis “2012-0573602-06D”
Receipt of sample: 2011-02-22
Report date: 2011-02-25
Objective: Determination of single crystal structure.
Compound: N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide, formula XIIA
Crystallization: by the chemist.
Crystal dimensions: colorless block, 0.50×0.40×0.40 mm3
Code: vesta
Comments: The asymmetric unit comprises half a molecule.
The single crystal structure was determined using an instrument from Oxfor Diffraction which was equipped with a CCD detector (Ruby model), a conventional x-ray tube with CuKα radiation, Osmic mirror as monochromator, and a low-temperature unit of the Cryojet type (T=100 K). Data collection was carried out in phi and omega scans. Data collection and reduction took place using Crysalis (Oxford Diffraction 2007).
Structural resolution and refinement took place using SHELXTL (V. 6.10, Sheldrick, University of Göttingen, 2000). All non-hydrogen atoms were refined anisotropically. The hydrogen atoms were refined as riding groups.
Calculated powder diffractogram based on the single crystal structural determination of N,N,N′,N′-tetrakis(2-hydroxyethyl)cyclohexyl-1,4-diamide (vesta sample)
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2010 002 785.5 | Mar 2010 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2011/053639 | 3/10/2011 | WO | 00 | 9/10/2012 |
