CA2186089A1 - Blocked aliphatic diisocyanates or diisocyanate adducts - Google Patents
Blocked aliphatic diisocyanates or diisocyanate adductsInfo
- Publication number
- CA2186089A1 CA2186089A1 CA 2186089 CA2186089A CA2186089A1 CA 2186089 A1 CA2186089 A1 CA 2186089A1 CA 2186089 CA2186089 CA 2186089 CA 2186089 A CA2186089 A CA 2186089A CA 2186089 A1 CA2186089 A1 CA 2186089A1
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- Canada
- Prior art keywords
- diisocyanate
- group
- weight
- blocked
- parts
- Prior art date
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- Abandoned
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
- C08G18/72—Polyisocyanates or polyisothiocyanates
- C08G18/80—Masked polyisocyanates
- C08G18/8061—Masked polyisocyanates masked with compounds having only one group containing active hydrogen
- C08G18/807—Masked polyisocyanates masked with compounds having only one group containing active hydrogen with nitrogen containing compounds
- C08G18/808—Monoamines
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- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Paints Or Removers (AREA)
- Polyurethanes Or Polyureas (AREA)
Abstract
Blocked Aliphatic Diisocyanates or Diisocyanate Adducts Disclosed is a blocked aliphatic diisocyanate or diisocyanate adduct, which is obtainable by reacting:
A) at least one member selected from the group consisting of:
(1) an aliphatic diisocyanate of the general formula:
OCN-R-NCO (I) (in which R is a C4-C12-alkylene radical which may contain one to three methyl or ethyl groups or, instead of 4 CH2 groups, a cyclohexane radical), and (2) an adduct of the aliphatic diisocyanate of the formula (I) which contains an isocyanurate group, biuret group or urethane group and which has free isocyanate groups, with B) a sterically hindered secondary amine having a boiling point of at least 160°C and being represented by the general formula:
(see fig. II) (in which R1 and R2 are identical or different and are each independently hydrogen, alkyl, cycloalkyl or aralkyl or two of R1 or two of R2 together with the carbon atom to which they are attached or R1 and R2 together with the HN
group and the two carbon atoms to which they are attached form a ring which may be substituted by one to four alkyl groups or, instead of a CH2 group, may contain an oxygen atom or a -NH group), wherein the sterically hindered secondary amine is employed in an amount of 0.5 - 1 mol per mole of isocyanate groups in the aliphatic diisocyanate or the adduct. The blocked diisocyanate or adduct thereof is useful as a hardener in a polyurethane powder coating composition.
A) at least one member selected from the group consisting of:
(1) an aliphatic diisocyanate of the general formula:
OCN-R-NCO (I) (in which R is a C4-C12-alkylene radical which may contain one to three methyl or ethyl groups or, instead of 4 CH2 groups, a cyclohexane radical), and (2) an adduct of the aliphatic diisocyanate of the formula (I) which contains an isocyanurate group, biuret group or urethane group and which has free isocyanate groups, with B) a sterically hindered secondary amine having a boiling point of at least 160°C and being represented by the general formula:
(see fig. II) (in which R1 and R2 are identical or different and are each independently hydrogen, alkyl, cycloalkyl or aralkyl or two of R1 or two of R2 together with the carbon atom to which they are attached or R1 and R2 together with the HN
group and the two carbon atoms to which they are attached form a ring which may be substituted by one to four alkyl groups or, instead of a CH2 group, may contain an oxygen atom or a -NH group), wherein the sterically hindered secondary amine is employed in an amount of 0.5 - 1 mol per mole of isocyanate groups in the aliphatic diisocyanate or the adduct. The blocked diisocyanate or adduct thereof is useful as a hardener in a polyurethane powder coating composition.
Description
Blocked Aliphatic Diisocyanates or Diisocyanate Adducts The present invention relates to novel blocked aliphatic diisocyanates or diisocyanate adducts and to polyurethane powder coatings prepared therefrom.
Polyurethane (PU) powders, whose rapid development commenced at the beginning of the 1970s, usually consist of ~-caprolactam-blocked polyisocyanates in combination with hydroxyl-containing polyester resins. This combination produces powder coatings which virtually attain the flow properties of liquid coating systems and are equivalent in their other properties.
From the large number of polyisocyanates, the only ones suitable for preparing weather-resistant polyurethane coatings are the ~-caprolactam adducts of isophorone diisocyanate (IPDI). ~-Caprolactam-blocked IPDI melts at 53 - 55C. As a result of the low melting point, the powders prepared from this blocked IPDI undergo caking on storage. To raise the melting pointr IPDI is "subjected", before ~-caprolactam blocking, to chain extension with a polyol (NCO:OH = 2:1). In German Patent Publication (DE-A) 21 05 777, the chain extenders mentioned for IPDI are polyols such as trimethylolpropane r 2,2,4-trimethylhexane-1,6-diol and diethylene glycol in DE-A 25 42 191, they are mixtures of di-and trifunctional polyols. In DE-A 31 43 060, chain extension of the IPDI is carried out with aliphatic diamines. DE-As 27 35 497 and 28 42 641 describe reactive PU powders which comprise as hardener an ~-caprolactam-blocked, isocyanurate-containing IPDI adduct.
O.Z. 5013 The preparation of PU powders on the basis of ~-cap-rolactam-blocked aliphatic diisocyanates and/or their adducts containing isocyanurate groups, biuret groups and urethane groups was not hitherto possible, since these compounds are either not solids, and therefore cannot be milled, or are in fact solids - as is the case with ~-caprolactam-blocked hexamethylene diisocyanate - but show inadequate stability when stored as a mixture with the hydroxyl-containing polyester.
An object of the invention, therefore, is to provide novel hardeners for PU powder coatings based on blocked aliphatic diisocyanates or their adducts.
It has surprisingly been found that hardeners based on aliphatic diisocyanates or their adducts have the advantageous properties, for PU powder coatings, of the hardeners described in the above mentioned German patent publications if sterically hindered secondary amines are employed instead of ~-caprolactam as blocking agent.
The invention provides blocked aliphatic diisocyanates or diisocyanate adducts, which are obtainable by reacting:
A) 1. aliphatic diisocyanates of the general formula:
OCN-R-NCO (I) (in which R is a C4-C12-alkylene radical which may contain one to three methyl or ethyl groups or, instead of 4 CH2 groups, a cyclohexane radical), and/or 2. adducts or the aliphatic diisocyanates which contain isocyanurate groups, biuret groups or urethane groups 2 1 ~6089 and which have free isocyanate groups, with B) sterically hindered secondary amines having a boiling point of 160C or more of the general formula:
: R 1 HN
\ CR 3 (II) (in which R1 and R2 are identical or different and are each independently hydrogen, alkyl, cycloalkyl or aralkyl, two of R together with the carbon atom to which they are attached, two of R2 to which they are attached or R1 and R2 together with the HN group and the two carbon atoms to which they are attached form a ring which may be substituted by one to four alkyl groups or, instead of a CH2 group, may contain an oxygen atom or a -NH group), wherein the sterically hindered secondary amines are employed in amounts of 0.5 - 1 mol, preferahly 0.8 - 1 mol, per mol of isocyanate groups of the aliphatic diisocyanates or the adducts.
Sterically hindered secondary amines which are suitable for preparing the compounds according to the invention are only those having a boiling point of at least 160C. For example, owing to its low boiling point, diisopropylamine is unsuitable for preparing PU powder hardeners since the volatile diisopropylamine liberated in the course of hardening leads to the formation of foam in the coating film.
Suitable aliphatic diisocyanates of the formula (I) in the context of the present invention are pentamethylene 2 ~ 86089 1,5-diisocyanate, hexamethylene 1,6-diisocyanate, hexamethylene 1,5-diisocyanate, 2-methylpentamethylene 1,5-diisocyanate, 2-ethyltetramethylene 1,4-diisocyanate and any desired mixture of these two isomers, p- and m-hexahydroxylylene diisocyanate, 5-methylnonamethylene 1,9-diisocyanate, 1,8-diisocyanato-2,4-dimethyloctane and dodecamethylene 1,12-diisocyanate.
For preparing the hardeners according to the invention, the aliphatic diisocyanates are reacted with the secondary sterically hindered amines generally without prior molecular enlargement. In some cases, however, it can be entirely advantageous to subject the aliphatic diisocyanate, prior to blocking, to a molecular enlargement reaction with the chain extenders which are common in isocyanate chemistry, as is described for the chain extension with polyols (which form urethane groups) in DE-As 19 57 483, 21 05 777, 25 42 191, 30 04 876 (in part), for the molecular enlargement of the aliphatic diisocyanates by trimerization (which form isocyanurate groups) in DE-As 28 39 133, 29 01 479 and 31 51 855, and for the molecular enlargement by biuretization (which forms biuret groups) in DE-As 22 61 065 and 30 07 670.
The alkyl groups for R and R are preferably linear or branched alkyl groups of 1 to 6 carbon atoms. The cyclo-alkyl groups for R1 and R2 preferably have 5 or 6 carbon atoms (i.e. cyclopentyl and cyclohexyl), and may have one to four methyl substituents. The aralkyl groups for R1 and R2 are preferably a benzyl group. When two of R or two of R
together with the carbon atom to which they are attached form a ring, the ring is preferably piperidinyl, morpholinyl, cyclopentyl or cyclohexyl and may have one to four methyl substituents. When Rl and R2 together with the HN group and the two carbon atoms to which they are attached form a ring, the ring is preferably piperidine or morpholine, each of which may have one to four methyl substituents. More preferably, the groups CR13 and CR23 are each independently a branched alkyl of 4 to 6 carbon atoms (e.g., t-butyl), cyclopentyl (optionally having one to four methyl substituents), cyclohexyl (optionally having one to four methyl substituents) or piperidinyl (optionally having one to four methyl substituents). Also more preferably the secondary amines are piperidine (having two to four methyl substituents, at least in the 2-and 6-positions) or morpholine (having two to four methyl substituents, at least in the 3- and 5-positions).
Examples of preferred secondary amines of the formula (II) in the context of the invention include dicyclohexylamine, t-butylcyclohexylamine, di(3,5,5-trimethyl) cyclohexylamine, dicyclopentylamine, 2,6-dimethylpiperidine, 3,5-dimethylmorpholine and di(2,2,6,6-tetramethylpiperidinyl) amine. A most preferred blocking agent employed is di(2,2,6,6-tetramethylpiperidinyl)amine, since on baking it remains predominantly within the coating film and therefore contributes to the UV stabilization of the coatings. It is also possible in accordance with the invention to employ mixtures of the abovementioned secondary amines.
The reaction of the aliphatic diisocyanates and/or their adducts (prepared by molecular enlargement) with the sterically hindered secondary amines may be carried out either in solution or in bulk. If solvent-free operation is chosen, then the secondary amine is added to the diisocyanate, heated at 70 - 140C, at a rate such that the temperature of the reaction mixture does not exceed 190C. Following the end of the addition of blocking agent, preferably the reaction mixture is maintained in the melt for about one hour more in order to complete the reaction. As already mentioned, blocking can also be carried out in solvents. Suitable solvents for this reaction are of course only those which do not react with isocyanates. Examples, of such solvents include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, etc., aromatics such as toluene and nitrobenzene, cyclic ethers such as tetrahydrofuran, and polar aprotic solvents such as dimethylformamide, dimethylacetamide, dimethyl sulfoxide, etc.
The compounds according to the invention which are obtainable in this way are generally compounds with molecular weights ranging from 300 - 1600, preferably 350 - 1000. Many of them have a melting range of 50 - 180C, preferably 70 -120C. The aliphatic diisocyanate or diisocyanate adduct blocked with the secondary amines may be additionally characterized by a content of blocked terminal isocyanate groups (calculated as NC0 (42)) of 6 - 22% by weight, preferably 8 - 17% by weight.
The products are particularly suitable as hardeners for compounds of relatively high functionality containing Zerewitinoff active hydrogen atoms. In combination with compounds of this type containing Zerewitinoff active hydrogen atoms, the process products lead above 120C, preferably 130 -170C, to systems which can be cured to give high-grade plastics. The most important field of application for the compounds according to the invention is as hardeners for light-resistant polyurethane powder coatings.
The present invention, accordingly, also provides storage-stable heat-curable polyurethane powder coating compositions based on the blocked aliphatic diisocyanates or diisocyanate adducts according to the invention and on OH-containing polymers and having the following composition (a) 100 parts by weight (pbw) of OH-containing polymers, (b) 10 - 90 pbw of the blocked aliphatic poly-isocyanate or corresponding adducts, (c) 0 - 160 pbw of pigments, (d) o - 200 pbw of customary fillers, (e) 0 - 5 pbw of catalysts, and (f) 0.5 - 5 pbw of leveling agents.
Constituent (a) may in principle by any polymer containing at least two OH groups which has a melting temperature of at least 70C. These include polyether polyols, polyester amide polyols, polyurethane polyols, hydroxylate~ acrylic resins, etc., whose OH groups are intended for crosslinking with the blocked aliphatic diisocyanates according to the invention. In the context of - 6a -the invention, among the many possibilities for hydroxyl-containing polymers particular preference is given to polyester polyols. Such polyester polyols often have a molecular weight between 1000 and 3000, preferably between 1500 and 2500, and an OH number of 30 - 240. Examples of such polyester polyols are described in DE-As 19 57 483, 25 42 191, 30 04 876 and 31 43 060.
In order to increase the gel rate of the heat-curable powder coatings it is possible to add catalysts.
Catalysts used are often organotin compounds such as dibutyltin dilaurate, Sn(II) octoate, dibutyltin maleate, etc.
The amount of catalyst added is preferably 0.1 - 5 parts by weight per 100 parts by weight of the hydroxyl-containing polyester.
For the preparation of polyurethane (PU~ powder coatings, the isocyanate component is mixed with the appropriate hydroxyl-containing polymer and, if desired, with catalysts and pigments and customary auxiliaries, such as fillers and leveling agents, for example silicone oil, acrylate resins, and the mixture is homogenized in the melt.
This can be carried out in appropriate equipment, for example heatable kneading apparatus, but preferably by extrusion, in the course of which upper temperature limits of 130 to 140C
should not be exceeded. After cooling to room temperature and appropriate comminution, the extruded composition is ground to give the ready-to-spray powder. The application of this ready-to-spray powder to appropriate substrates can be carried out in accordance with the known methods, for example by - 6b -- 2 ~ 86Q89 electrostatic powder spraying or (electrostatic) fluidized-bed sintering. Following application of the powder, the coated workpieces are cured by heating at a temperature of 150 to 220C for from 4 to 60 minutes, preferably at 160 - 200C for 6 - 30 minutes.
The PU powder coatings according to the invention are distinguished by outstanding weathering resistance and very good color stability.
A Preparation of the blocked polyisocyanates Example 1 362 parts by weight of dicyclohexylamine were added dropwise at 100C to 210 parts by weight of 2,2,4(2,4,4)-trimethylhexamethylene diisocyanate (TMDI) at a rate such that the temperature of the reaction mixture did not rise above 120C. After the dicyclohexylamine had been added, heating was continued at 120C for about 1 hour more in order to complete the reaction. The resulting reaction product has a melting range of 76 - 84C and a blocked NC0 content of 14.6%;
the amine content was below 0.1%.
- 6c -~ 2186089o z 5013 Example 2 530 parts by weight of di(3,5,5-trimethyl)cyclohexylamine were added dropwise at 100C to 210 parts by weight of TMDI over the course of about 3 hours. After the amine had been added, the reaction mixture was heated further at 110C for 1 hour more. The reaction mixture had a melting range of 63 - 70C and a blocked NCO content of 11.3%.
Example 3 530 parts by weight of di(3,5,5-trimethyl)cyclohexylamine were added dropwise at 100C to 168 parts by weight of 2-methylpentamethylene diisocyanate at a rate such that the temperature did not rise above 120C. After the amine had been added, the reaction mixture was heated further for about 1 hour more. The reaction product had a melting range of 56 - 65C and a blocked NCO content of 12.0%.
Example 4 Following the procedure of Example 3, 168 parts by weight of 2-methylpentamethylene diisocyanate were reacted with 226 parts by weight of 2,6-dimethylpiperidine. The reaction product had a melting range of 48 - 53C and a blocked NCO content of 21.3%.
Example S
181 parts by weight of dicyclohexylamine and 265 parts by weight of di(3,5,5-trimethyl)cyclohexylamine were added dropwise at 110C to 168 parts by weight of hexamethylene diisocyanate at a rate such that the temperature of the reaction mixture did not rise above 120C. After the amine had been added, heating was continued at 120C for about 1 hour more. The reaction product had a melting range of 78 - 84C and a blocked NCO content of 13.6%.
_ 82 1 8 6 0 8 9 -Z. 5013 Example 6 Following the procedure of Example 5, 168 parts by weight of hexamethylene diisocyanate were reacted with 530 parts by weight of di(3,5,5-trimethyl)cyclohexylamine. The reaction product had a melting range of 60 - 68C and a blocked NC0 content of 12.0%.
Example 7 Following the procedure of Example 5, 168 parts by weight of hexamethylene diisocyanate were reacted with 226 parts by weight of 2,6-dimethylpiperidine. The reaction product had a melting range of 51 - 59C and a blocked NC0 content of 21.3%.
Example 8 362 parts by weight of dicyclohexylamine were added dropwise at 130C to 168 parts by weight of 2-methyl-pentamethylene diisocyanate at a rate such that during the dicyclohexylamine addition the temperature of the reaction mixture rose to 190C. The reaction mixture was held at this temperature for about 5 minutes and then cooled to room temperature. The reaction product had a melting range of 170 - 180C and a blocked NC0 content of 15.8%; the amine content was below 0.1%.
Example 9 Following the procedure of Example 8, 224 parts by weight of an isomer mixture of about 90% 5-methylnonamethylene diisocyanate and 10% 2,4-dimethyloctamethylene diisocyan-ate were reacted with 362 parts by weight of dicyclo-hexylamine. The reaction product had a melting range of 156 - 164C and a blocked NC0 content of 14.3~; the amine content was below 0.1%.
Example 10 530 parts by weight of di(3,5,5-trimethyl)cyclohexylamine - 9 - O.Z. 5013 were added dropwise at 100C to 224 parts by weight of an isomer mixture of about 90~ 5-methylnonamethylene diiso-cyanate and 10% 2,4-dimethyloctamethylene diisocyanate at a rate such that the temperature of the reaction mixture did not rise above 120C. After the amine had been added, the reaction mixture was heated further at 120C for about 0.5 h more in order to complete the reaction. The resulting reaction product had a melting range of 54 -61C and a blocked NCO content of 11.1%.
Example 11 With intense stirring and under a nitrogen blanket, 181 parts by weight of dicyclohexylamine were added dropwise at 110C to 186.6 parts by weight of a commer-cially available (as DESMODUR N 3200) biuret of hexa-methylene diisocyanate at a rate such that the tempera-ture of the reaction mixture did not rise above 130C.
After the dicyclohexylamine had been added, the reaction mixture was heated further at 130C for about 0.5 h more in order to complete the reaction. The resulting reaction product had a melting range of 91 - 95C and a blocked NCO content of 11.5%; the basic amine content was below O . 1% .
Example 12 240 parts by weight of an isocyanatoisocyanurate of 2,2,4(2,4,4)-trimethylhexamethylene diisocyanate, pre-pared according to the teaching of DE-A 27 12 931, Example 10, with a NCO content of 17.5% were reacted under the reaction conditions described in Example 11 with 181 parts by weight of dicyclohexylamine. The reaction product had a melting range of 107 - 112C and a blocked NCO content of 9.9%.
Example 13 212.1 parts by weight of an isocyanatoisocyanurate prepared according to the teaching of DE-A 31 51 855, Example 1, from 2-methylpentamethylene diisocyanate, and Trade-mark 2 1 8 6f)89 - 10 - O.Z. 5013 with a NCO content of 19.8%, were reacted under the reaction conditions described in Example 11 with 181 parts by weight of dicyclohexylamine. The melting range of the reaction product was 99 - 103C and the S blocked NCO content was 10.6%.
Example 14 190.9 parts by weight of a commercially available (as DESMODUR N 3300) isocyanurate of hexamethylene diisocyan-ate were reacted under the reaction conditions described in Example 11 with 181 parts by weight of dicyclohexyl-amine. The reaction product had a melting range of 9S -98C and a blocked NCO content of 11.2%; the basic N
content was below 0.1%.
Example 15 195.3 parts by weight of a reaction product of 4 mol of 2,2,4-trimethylhexamethylene diisocyanate and 1 mol of trimethylolpropane, with a NCO content of 21.5%, were reacted under the reaction conditions indicated in Example 11 with 181 parts by weight of dicyclohexylamine.
The reaction product had a melting range of 84 - 87C and a blocked NCO content of 11.0%.
Example 16 0.5 part by weight of the commercially available quaternary ammonium salt DabcoR*TMR was added at 80C to 500 parts by weight of hexamethylene diisocyanate. The temperature of the reaction mixture rose to 145C over the course of about S minutes; in the same period the NCO
content fell from 50 to 36.5%. The reaction mixture was then cooled to 80C and reacted under the reaction conditions described in Example 11 with 786 parts by weight of dicyclohexylamine. The reaction product had a melting range of 55 - 63C and a blocked NCO content of 14.1%.
Example 17 Trade-mark 23443-583 2 1 ~6U89 - 11 - O.Z. 5013 190.9 parts by weight of a commercially available (as DESMODUR* N 3200) biuret of hexamethylene diisocyanate were reacted under the reaction conditions described in Example 11 with 135.7 parts by weight of dicyclohexyl-amine. The reaction product had a melting range of 85 -93C and a blocked NCO content of 9.6% with a free NCO
content of 3.4%.
Example 18 186.6 parts by weight of a commercially available (as DESMODUR N 3200) biuret of hexamethylene diisocyanate were reacted under the reaction conditions described in Example 11 with 144.8 parts by weight of dicyclohexyl-amine. The reaction product had a melting range of 85 -89C and a blocked NCO content of 10.1% with a free NCO
content of 2.5%.
Example 19 210 parts by weight of trimethylhexamethylene diisocyan-ate were reacted with 326 parts by weight of dicyclo-hexylamine under the reaction conditions described in Example 11. The reaction product had a melting range of 59 - 63C, a blocked NCO content of 14.1% and a free NCO
content of 1.5%.
Example 20 When carrying out blocking with di(2,2,6,6-tetramethyl-piperidyl)amine it has proven expedient to carry out the procedure in the inverse sequence (relative to Examples 1 - 19)-295 parts by weight of di(2,2,6,6-tetramethylpiperidyl)-amine were heated to 120C. With intense stirring, 84 parts by weight of hexamethylene diisocyanate were added dropwise at a rate such that the temperature of the reaction mixture did not rise above 130C. After the hexamethylene diisocyanate had been added, the reaction product was heated at 120C for about 1 hour more.
21 8608~
- 12 - O.Z. 5013 The melting range of the reaction product was 90 - 97C;
the blocked NCO content was 11%; the amine content was 5.2 mmol/g.
Example 21 In analogy to Example 20, 295 parts by weight of di-(2~2~6~6-tetramethylpiperidyl)amine were reacted with 193 parts by weight of the isocyanurate of hexamethylene diisocyanate (Desmodur N 3300).
The reaction product had the following characteristics:
Melting range C: 104 - 110 % NCO (blocked): 8.6 NH, mmol/g : 4.1 B Polyol component General preparation procedure The starting components - terephthalic acid (TA), dimethyl terephthalate (DMT), 1,6-hexanediol (HD), neopentyl glycol (NPG), 1,4-dimethylolcyclohexane (DMC) and trimethylolpropane (TMP) - are placed in a reactor and heated with the aid of an oil bath. After the major-ity of the substances have melted, 0.05% by weight of di-n-butyltin oxide is added as catalyst at a temperature of 160C. Initial elimination of methanol takes place at a temperature of about 170C. The temperature is raised to 220 - 230C over the course of from 6 to 8 hours and the reaction is brought to an end over the course of a further 12 to lS hours. The polyester is cooled to 200C
and largely freed from volatile fractions by applying a vacuum (1 mm Hg) over the course of 30 to 45 minutes.
Throughout the reaction period, the bottom product is stirred and a gentle stream of N~ is passed through the reaction mixture.
The following table shows the polyester compositions and the corresponding physical and chemical characteristics.
- 13 - O.Z. 5013 Table l: Polyesters Ex- Starting components Chemical and physical characteristics ample TA DMT HD NPG DMC TMP OH Acid m.p. DTA Viscosity [mol] tmol] ~mol] lmol] ~mol] lmol] number number [C] [C] at 160C
[mg of [mg of [mPa-s]
KOH/g ] KOH/g ]
l lOlO 6.25 lO.S 2 2.9 55-60 3-4 about about= 25,000 2 CRY~COA~ 2 0 from UCB = 50 < lO lO0 ' 8 55 + 8 3 9 9 3 13 3 l 50-56 3-4 about about= 10,000 ~0 50 ~;o o ~O
2 1 ~6089 -- 14 - O.Z. 5013 C Polyurethane powder coatin~s General preparation procedure The ground products - diisocyanate, polyester and level-ing agent masterbatch - are intimately mixed in an edge runner mill, together if desired with the white pigment and fillers, and the mixture is then homogenized in an extruder at from 80 to 110C. After cooling, the extrud-ate is fractionated and ground using a pinned-disk mill to a particle size of < 100 ~m. The powder thus prepared is applied using an electrostatic powder spraying unit at 60 kV to degreased, optionally pretreated iron panels which are then baked in a convection oven at temperatures between 150 and 180C for between 35 and 10 minutes.
Leveling agent masterbatch 10% by weight of the leveling agent - a commercial copolymer of butyl acrylate and 2-ethylhexyl acrylate -is homogenized in the melt in the corresponding polyester and comminuted after solidification.
The abbreviations in the tables below have the following 20 meanings:
CT = coat thickness in ~m EI = Erichsen indentation in mm (DIN 53 156) CH = cross-hatch test (DIN 53 151) GG 60~ = Gardner gloss measurement (ASTM-D 523) 25 Imp. rev. = impact reverse in g-m 21 86~89 ~ ~ ~ o o.
N ~ U~ In rl O rl I COD
' ^ ' ^ ' r ~n --' O u .n _a~ r U~
r ~ ~ o o -' ~O'' ~ _ , U~ o ~,, o ~ O
^ o ~ a` ~O
r ~r ~ `~ r ~
r ~ O "~ r ~O O a`, ~D O c~
r r ~~ N o O r o -- o O r ~O ~
_I ~ ~ -- ~ o _ ~, ~ O O r ,.~ O O~ _ ~~, ~ O U~ r ~-1 0 ~ r U
N ~ O ~ o o ~, O ~o U r ~ ~ o ~ ~ ~
-- o o l ~o o ~ o t~ r _ O o t~
3 -- v ~ ~ ~ v t, ,, U ~ V
3 ~ c ~ ~ l v o ~ ~ tu V _ C E~ v
Polyurethane (PU) powders, whose rapid development commenced at the beginning of the 1970s, usually consist of ~-caprolactam-blocked polyisocyanates in combination with hydroxyl-containing polyester resins. This combination produces powder coatings which virtually attain the flow properties of liquid coating systems and are equivalent in their other properties.
From the large number of polyisocyanates, the only ones suitable for preparing weather-resistant polyurethane coatings are the ~-caprolactam adducts of isophorone diisocyanate (IPDI). ~-Caprolactam-blocked IPDI melts at 53 - 55C. As a result of the low melting point, the powders prepared from this blocked IPDI undergo caking on storage. To raise the melting pointr IPDI is "subjected", before ~-caprolactam blocking, to chain extension with a polyol (NCO:OH = 2:1). In German Patent Publication (DE-A) 21 05 777, the chain extenders mentioned for IPDI are polyols such as trimethylolpropane r 2,2,4-trimethylhexane-1,6-diol and diethylene glycol in DE-A 25 42 191, they are mixtures of di-and trifunctional polyols. In DE-A 31 43 060, chain extension of the IPDI is carried out with aliphatic diamines. DE-As 27 35 497 and 28 42 641 describe reactive PU powders which comprise as hardener an ~-caprolactam-blocked, isocyanurate-containing IPDI adduct.
O.Z. 5013 The preparation of PU powders on the basis of ~-cap-rolactam-blocked aliphatic diisocyanates and/or their adducts containing isocyanurate groups, biuret groups and urethane groups was not hitherto possible, since these compounds are either not solids, and therefore cannot be milled, or are in fact solids - as is the case with ~-caprolactam-blocked hexamethylene diisocyanate - but show inadequate stability when stored as a mixture with the hydroxyl-containing polyester.
An object of the invention, therefore, is to provide novel hardeners for PU powder coatings based on blocked aliphatic diisocyanates or their adducts.
It has surprisingly been found that hardeners based on aliphatic diisocyanates or their adducts have the advantageous properties, for PU powder coatings, of the hardeners described in the above mentioned German patent publications if sterically hindered secondary amines are employed instead of ~-caprolactam as blocking agent.
The invention provides blocked aliphatic diisocyanates or diisocyanate adducts, which are obtainable by reacting:
A) 1. aliphatic diisocyanates of the general formula:
OCN-R-NCO (I) (in which R is a C4-C12-alkylene radical which may contain one to three methyl or ethyl groups or, instead of 4 CH2 groups, a cyclohexane radical), and/or 2. adducts or the aliphatic diisocyanates which contain isocyanurate groups, biuret groups or urethane groups 2 1 ~6089 and which have free isocyanate groups, with B) sterically hindered secondary amines having a boiling point of 160C or more of the general formula:
: R 1 HN
\ CR 3 (II) (in which R1 and R2 are identical or different and are each independently hydrogen, alkyl, cycloalkyl or aralkyl, two of R together with the carbon atom to which they are attached, two of R2 to which they are attached or R1 and R2 together with the HN group and the two carbon atoms to which they are attached form a ring which may be substituted by one to four alkyl groups or, instead of a CH2 group, may contain an oxygen atom or a -NH group), wherein the sterically hindered secondary amines are employed in amounts of 0.5 - 1 mol, preferahly 0.8 - 1 mol, per mol of isocyanate groups of the aliphatic diisocyanates or the adducts.
Sterically hindered secondary amines which are suitable for preparing the compounds according to the invention are only those having a boiling point of at least 160C. For example, owing to its low boiling point, diisopropylamine is unsuitable for preparing PU powder hardeners since the volatile diisopropylamine liberated in the course of hardening leads to the formation of foam in the coating film.
Suitable aliphatic diisocyanates of the formula (I) in the context of the present invention are pentamethylene 2 ~ 86089 1,5-diisocyanate, hexamethylene 1,6-diisocyanate, hexamethylene 1,5-diisocyanate, 2-methylpentamethylene 1,5-diisocyanate, 2-ethyltetramethylene 1,4-diisocyanate and any desired mixture of these two isomers, p- and m-hexahydroxylylene diisocyanate, 5-methylnonamethylene 1,9-diisocyanate, 1,8-diisocyanato-2,4-dimethyloctane and dodecamethylene 1,12-diisocyanate.
For preparing the hardeners according to the invention, the aliphatic diisocyanates are reacted with the secondary sterically hindered amines generally without prior molecular enlargement. In some cases, however, it can be entirely advantageous to subject the aliphatic diisocyanate, prior to blocking, to a molecular enlargement reaction with the chain extenders which are common in isocyanate chemistry, as is described for the chain extension with polyols (which form urethane groups) in DE-As 19 57 483, 21 05 777, 25 42 191, 30 04 876 (in part), for the molecular enlargement of the aliphatic diisocyanates by trimerization (which form isocyanurate groups) in DE-As 28 39 133, 29 01 479 and 31 51 855, and for the molecular enlargement by biuretization (which forms biuret groups) in DE-As 22 61 065 and 30 07 670.
The alkyl groups for R and R are preferably linear or branched alkyl groups of 1 to 6 carbon atoms. The cyclo-alkyl groups for R1 and R2 preferably have 5 or 6 carbon atoms (i.e. cyclopentyl and cyclohexyl), and may have one to four methyl substituents. The aralkyl groups for R1 and R2 are preferably a benzyl group. When two of R or two of R
together with the carbon atom to which they are attached form a ring, the ring is preferably piperidinyl, morpholinyl, cyclopentyl or cyclohexyl and may have one to four methyl substituents. When Rl and R2 together with the HN group and the two carbon atoms to which they are attached form a ring, the ring is preferably piperidine or morpholine, each of which may have one to four methyl substituents. More preferably, the groups CR13 and CR23 are each independently a branched alkyl of 4 to 6 carbon atoms (e.g., t-butyl), cyclopentyl (optionally having one to four methyl substituents), cyclohexyl (optionally having one to four methyl substituents) or piperidinyl (optionally having one to four methyl substituents). Also more preferably the secondary amines are piperidine (having two to four methyl substituents, at least in the 2-and 6-positions) or morpholine (having two to four methyl substituents, at least in the 3- and 5-positions).
Examples of preferred secondary amines of the formula (II) in the context of the invention include dicyclohexylamine, t-butylcyclohexylamine, di(3,5,5-trimethyl) cyclohexylamine, dicyclopentylamine, 2,6-dimethylpiperidine, 3,5-dimethylmorpholine and di(2,2,6,6-tetramethylpiperidinyl) amine. A most preferred blocking agent employed is di(2,2,6,6-tetramethylpiperidinyl)amine, since on baking it remains predominantly within the coating film and therefore contributes to the UV stabilization of the coatings. It is also possible in accordance with the invention to employ mixtures of the abovementioned secondary amines.
The reaction of the aliphatic diisocyanates and/or their adducts (prepared by molecular enlargement) with the sterically hindered secondary amines may be carried out either in solution or in bulk. If solvent-free operation is chosen, then the secondary amine is added to the diisocyanate, heated at 70 - 140C, at a rate such that the temperature of the reaction mixture does not exceed 190C. Following the end of the addition of blocking agent, preferably the reaction mixture is maintained in the melt for about one hour more in order to complete the reaction. As already mentioned, blocking can also be carried out in solvents. Suitable solvents for this reaction are of course only those which do not react with isocyanates. Examples, of such solvents include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, etc., aromatics such as toluene and nitrobenzene, cyclic ethers such as tetrahydrofuran, and polar aprotic solvents such as dimethylformamide, dimethylacetamide, dimethyl sulfoxide, etc.
The compounds according to the invention which are obtainable in this way are generally compounds with molecular weights ranging from 300 - 1600, preferably 350 - 1000. Many of them have a melting range of 50 - 180C, preferably 70 -120C. The aliphatic diisocyanate or diisocyanate adduct blocked with the secondary amines may be additionally characterized by a content of blocked terminal isocyanate groups (calculated as NC0 (42)) of 6 - 22% by weight, preferably 8 - 17% by weight.
The products are particularly suitable as hardeners for compounds of relatively high functionality containing Zerewitinoff active hydrogen atoms. In combination with compounds of this type containing Zerewitinoff active hydrogen atoms, the process products lead above 120C, preferably 130 -170C, to systems which can be cured to give high-grade plastics. The most important field of application for the compounds according to the invention is as hardeners for light-resistant polyurethane powder coatings.
The present invention, accordingly, also provides storage-stable heat-curable polyurethane powder coating compositions based on the blocked aliphatic diisocyanates or diisocyanate adducts according to the invention and on OH-containing polymers and having the following composition (a) 100 parts by weight (pbw) of OH-containing polymers, (b) 10 - 90 pbw of the blocked aliphatic poly-isocyanate or corresponding adducts, (c) 0 - 160 pbw of pigments, (d) o - 200 pbw of customary fillers, (e) 0 - 5 pbw of catalysts, and (f) 0.5 - 5 pbw of leveling agents.
Constituent (a) may in principle by any polymer containing at least two OH groups which has a melting temperature of at least 70C. These include polyether polyols, polyester amide polyols, polyurethane polyols, hydroxylate~ acrylic resins, etc., whose OH groups are intended for crosslinking with the blocked aliphatic diisocyanates according to the invention. In the context of - 6a -the invention, among the many possibilities for hydroxyl-containing polymers particular preference is given to polyester polyols. Such polyester polyols often have a molecular weight between 1000 and 3000, preferably between 1500 and 2500, and an OH number of 30 - 240. Examples of such polyester polyols are described in DE-As 19 57 483, 25 42 191, 30 04 876 and 31 43 060.
In order to increase the gel rate of the heat-curable powder coatings it is possible to add catalysts.
Catalysts used are often organotin compounds such as dibutyltin dilaurate, Sn(II) octoate, dibutyltin maleate, etc.
The amount of catalyst added is preferably 0.1 - 5 parts by weight per 100 parts by weight of the hydroxyl-containing polyester.
For the preparation of polyurethane (PU~ powder coatings, the isocyanate component is mixed with the appropriate hydroxyl-containing polymer and, if desired, with catalysts and pigments and customary auxiliaries, such as fillers and leveling agents, for example silicone oil, acrylate resins, and the mixture is homogenized in the melt.
This can be carried out in appropriate equipment, for example heatable kneading apparatus, but preferably by extrusion, in the course of which upper temperature limits of 130 to 140C
should not be exceeded. After cooling to room temperature and appropriate comminution, the extruded composition is ground to give the ready-to-spray powder. The application of this ready-to-spray powder to appropriate substrates can be carried out in accordance with the known methods, for example by - 6b -- 2 ~ 86Q89 electrostatic powder spraying or (electrostatic) fluidized-bed sintering. Following application of the powder, the coated workpieces are cured by heating at a temperature of 150 to 220C for from 4 to 60 minutes, preferably at 160 - 200C for 6 - 30 minutes.
The PU powder coatings according to the invention are distinguished by outstanding weathering resistance and very good color stability.
A Preparation of the blocked polyisocyanates Example 1 362 parts by weight of dicyclohexylamine were added dropwise at 100C to 210 parts by weight of 2,2,4(2,4,4)-trimethylhexamethylene diisocyanate (TMDI) at a rate such that the temperature of the reaction mixture did not rise above 120C. After the dicyclohexylamine had been added, heating was continued at 120C for about 1 hour more in order to complete the reaction. The resulting reaction product has a melting range of 76 - 84C and a blocked NC0 content of 14.6%;
the amine content was below 0.1%.
- 6c -~ 2186089o z 5013 Example 2 530 parts by weight of di(3,5,5-trimethyl)cyclohexylamine were added dropwise at 100C to 210 parts by weight of TMDI over the course of about 3 hours. After the amine had been added, the reaction mixture was heated further at 110C for 1 hour more. The reaction mixture had a melting range of 63 - 70C and a blocked NCO content of 11.3%.
Example 3 530 parts by weight of di(3,5,5-trimethyl)cyclohexylamine were added dropwise at 100C to 168 parts by weight of 2-methylpentamethylene diisocyanate at a rate such that the temperature did not rise above 120C. After the amine had been added, the reaction mixture was heated further for about 1 hour more. The reaction product had a melting range of 56 - 65C and a blocked NCO content of 12.0%.
Example 4 Following the procedure of Example 3, 168 parts by weight of 2-methylpentamethylene diisocyanate were reacted with 226 parts by weight of 2,6-dimethylpiperidine. The reaction product had a melting range of 48 - 53C and a blocked NCO content of 21.3%.
Example S
181 parts by weight of dicyclohexylamine and 265 parts by weight of di(3,5,5-trimethyl)cyclohexylamine were added dropwise at 110C to 168 parts by weight of hexamethylene diisocyanate at a rate such that the temperature of the reaction mixture did not rise above 120C. After the amine had been added, heating was continued at 120C for about 1 hour more. The reaction product had a melting range of 78 - 84C and a blocked NCO content of 13.6%.
_ 82 1 8 6 0 8 9 -Z. 5013 Example 6 Following the procedure of Example 5, 168 parts by weight of hexamethylene diisocyanate were reacted with 530 parts by weight of di(3,5,5-trimethyl)cyclohexylamine. The reaction product had a melting range of 60 - 68C and a blocked NC0 content of 12.0%.
Example 7 Following the procedure of Example 5, 168 parts by weight of hexamethylene diisocyanate were reacted with 226 parts by weight of 2,6-dimethylpiperidine. The reaction product had a melting range of 51 - 59C and a blocked NC0 content of 21.3%.
Example 8 362 parts by weight of dicyclohexylamine were added dropwise at 130C to 168 parts by weight of 2-methyl-pentamethylene diisocyanate at a rate such that during the dicyclohexylamine addition the temperature of the reaction mixture rose to 190C. The reaction mixture was held at this temperature for about 5 minutes and then cooled to room temperature. The reaction product had a melting range of 170 - 180C and a blocked NC0 content of 15.8%; the amine content was below 0.1%.
Example 9 Following the procedure of Example 8, 224 parts by weight of an isomer mixture of about 90% 5-methylnonamethylene diisocyanate and 10% 2,4-dimethyloctamethylene diisocyan-ate were reacted with 362 parts by weight of dicyclo-hexylamine. The reaction product had a melting range of 156 - 164C and a blocked NC0 content of 14.3~; the amine content was below 0.1%.
Example 10 530 parts by weight of di(3,5,5-trimethyl)cyclohexylamine - 9 - O.Z. 5013 were added dropwise at 100C to 224 parts by weight of an isomer mixture of about 90~ 5-methylnonamethylene diiso-cyanate and 10% 2,4-dimethyloctamethylene diisocyanate at a rate such that the temperature of the reaction mixture did not rise above 120C. After the amine had been added, the reaction mixture was heated further at 120C for about 0.5 h more in order to complete the reaction. The resulting reaction product had a melting range of 54 -61C and a blocked NCO content of 11.1%.
Example 11 With intense stirring and under a nitrogen blanket, 181 parts by weight of dicyclohexylamine were added dropwise at 110C to 186.6 parts by weight of a commer-cially available (as DESMODUR N 3200) biuret of hexa-methylene diisocyanate at a rate such that the tempera-ture of the reaction mixture did not rise above 130C.
After the dicyclohexylamine had been added, the reaction mixture was heated further at 130C for about 0.5 h more in order to complete the reaction. The resulting reaction product had a melting range of 91 - 95C and a blocked NCO content of 11.5%; the basic amine content was below O . 1% .
Example 12 240 parts by weight of an isocyanatoisocyanurate of 2,2,4(2,4,4)-trimethylhexamethylene diisocyanate, pre-pared according to the teaching of DE-A 27 12 931, Example 10, with a NCO content of 17.5% were reacted under the reaction conditions described in Example 11 with 181 parts by weight of dicyclohexylamine. The reaction product had a melting range of 107 - 112C and a blocked NCO content of 9.9%.
Example 13 212.1 parts by weight of an isocyanatoisocyanurate prepared according to the teaching of DE-A 31 51 855, Example 1, from 2-methylpentamethylene diisocyanate, and Trade-mark 2 1 8 6f)89 - 10 - O.Z. 5013 with a NCO content of 19.8%, were reacted under the reaction conditions described in Example 11 with 181 parts by weight of dicyclohexylamine. The melting range of the reaction product was 99 - 103C and the S blocked NCO content was 10.6%.
Example 14 190.9 parts by weight of a commercially available (as DESMODUR N 3300) isocyanurate of hexamethylene diisocyan-ate were reacted under the reaction conditions described in Example 11 with 181 parts by weight of dicyclohexyl-amine. The reaction product had a melting range of 9S -98C and a blocked NCO content of 11.2%; the basic N
content was below 0.1%.
Example 15 195.3 parts by weight of a reaction product of 4 mol of 2,2,4-trimethylhexamethylene diisocyanate and 1 mol of trimethylolpropane, with a NCO content of 21.5%, were reacted under the reaction conditions indicated in Example 11 with 181 parts by weight of dicyclohexylamine.
The reaction product had a melting range of 84 - 87C and a blocked NCO content of 11.0%.
Example 16 0.5 part by weight of the commercially available quaternary ammonium salt DabcoR*TMR was added at 80C to 500 parts by weight of hexamethylene diisocyanate. The temperature of the reaction mixture rose to 145C over the course of about S minutes; in the same period the NCO
content fell from 50 to 36.5%. The reaction mixture was then cooled to 80C and reacted under the reaction conditions described in Example 11 with 786 parts by weight of dicyclohexylamine. The reaction product had a melting range of 55 - 63C and a blocked NCO content of 14.1%.
Example 17 Trade-mark 23443-583 2 1 ~6U89 - 11 - O.Z. 5013 190.9 parts by weight of a commercially available (as DESMODUR* N 3200) biuret of hexamethylene diisocyanate were reacted under the reaction conditions described in Example 11 with 135.7 parts by weight of dicyclohexyl-amine. The reaction product had a melting range of 85 -93C and a blocked NCO content of 9.6% with a free NCO
content of 3.4%.
Example 18 186.6 parts by weight of a commercially available (as DESMODUR N 3200) biuret of hexamethylene diisocyanate were reacted under the reaction conditions described in Example 11 with 144.8 parts by weight of dicyclohexyl-amine. The reaction product had a melting range of 85 -89C and a blocked NCO content of 10.1% with a free NCO
content of 2.5%.
Example 19 210 parts by weight of trimethylhexamethylene diisocyan-ate were reacted with 326 parts by weight of dicyclo-hexylamine under the reaction conditions described in Example 11. The reaction product had a melting range of 59 - 63C, a blocked NCO content of 14.1% and a free NCO
content of 1.5%.
Example 20 When carrying out blocking with di(2,2,6,6-tetramethyl-piperidyl)amine it has proven expedient to carry out the procedure in the inverse sequence (relative to Examples 1 - 19)-295 parts by weight of di(2,2,6,6-tetramethylpiperidyl)-amine were heated to 120C. With intense stirring, 84 parts by weight of hexamethylene diisocyanate were added dropwise at a rate such that the temperature of the reaction mixture did not rise above 130C. After the hexamethylene diisocyanate had been added, the reaction product was heated at 120C for about 1 hour more.
21 8608~
- 12 - O.Z. 5013 The melting range of the reaction product was 90 - 97C;
the blocked NCO content was 11%; the amine content was 5.2 mmol/g.
Example 21 In analogy to Example 20, 295 parts by weight of di-(2~2~6~6-tetramethylpiperidyl)amine were reacted with 193 parts by weight of the isocyanurate of hexamethylene diisocyanate (Desmodur N 3300).
The reaction product had the following characteristics:
Melting range C: 104 - 110 % NCO (blocked): 8.6 NH, mmol/g : 4.1 B Polyol component General preparation procedure The starting components - terephthalic acid (TA), dimethyl terephthalate (DMT), 1,6-hexanediol (HD), neopentyl glycol (NPG), 1,4-dimethylolcyclohexane (DMC) and trimethylolpropane (TMP) - are placed in a reactor and heated with the aid of an oil bath. After the major-ity of the substances have melted, 0.05% by weight of di-n-butyltin oxide is added as catalyst at a temperature of 160C. Initial elimination of methanol takes place at a temperature of about 170C. The temperature is raised to 220 - 230C over the course of from 6 to 8 hours and the reaction is brought to an end over the course of a further 12 to lS hours. The polyester is cooled to 200C
and largely freed from volatile fractions by applying a vacuum (1 mm Hg) over the course of 30 to 45 minutes.
Throughout the reaction period, the bottom product is stirred and a gentle stream of N~ is passed through the reaction mixture.
The following table shows the polyester compositions and the corresponding physical and chemical characteristics.
- 13 - O.Z. 5013 Table l: Polyesters Ex- Starting components Chemical and physical characteristics ample TA DMT HD NPG DMC TMP OH Acid m.p. DTA Viscosity [mol] tmol] ~mol] lmol] ~mol] lmol] number number [C] [C] at 160C
[mg of [mg of [mPa-s]
KOH/g ] KOH/g ]
l lOlO 6.25 lO.S 2 2.9 55-60 3-4 about about= 25,000 2 CRY~COA~ 2 0 from UCB = 50 < lO lO0 ' 8 55 + 8 3 9 9 3 13 3 l 50-56 3-4 about about= 10,000 ~0 50 ~;o o ~O
2 1 ~6089 -- 14 - O.Z. 5013 C Polyurethane powder coatin~s General preparation procedure The ground products - diisocyanate, polyester and level-ing agent masterbatch - are intimately mixed in an edge runner mill, together if desired with the white pigment and fillers, and the mixture is then homogenized in an extruder at from 80 to 110C. After cooling, the extrud-ate is fractionated and ground using a pinned-disk mill to a particle size of < 100 ~m. The powder thus prepared is applied using an electrostatic powder spraying unit at 60 kV to degreased, optionally pretreated iron panels which are then baked in a convection oven at temperatures between 150 and 180C for between 35 and 10 minutes.
Leveling agent masterbatch 10% by weight of the leveling agent - a commercial copolymer of butyl acrylate and 2-ethylhexyl acrylate -is homogenized in the melt in the corresponding polyester and comminuted after solidification.
The abbreviations in the tables below have the following 20 meanings:
CT = coat thickness in ~m EI = Erichsen indentation in mm (DIN 53 156) CH = cross-hatch test (DIN 53 151) GG 60~ = Gardner gloss measurement (ASTM-D 523) 25 Imp. rev. = impact reverse in g-m 21 86~89 ~ ~ ~ o o.
N ~ U~ In rl O rl I COD
' ^ ' ^ ' r ~n --' O u .n _a~ r U~
r ~ ~ o o -' ~O'' ~ _ , U~ o ~,, o ~ O
^ o ~ a` ~O
r ~r ~ `~ r ~
r ~ O "~ r ~O O a`, ~D O c~
r r ~~ N o O r o -- o O r ~O ~
_I ~ ~ -- ~ o _ ~, ~ O O r ,.~ O O~ _ ~~, ~ O U~ r ~-1 0 ~ r U
N ~ O ~ o o ~, O ~o U r ~ ~ o ~ ~ ~
-- o o l ~o o ~ o t~ r _ O o t~
3 -- v ~ ~ ~ v t, ,, U ~ V
3 ~ c ~ ~ l v o ~ ~ tu V _ C E~ v
Claims (11)
1. A blocked aliphatic diisocyanate or diisocyanate adduct, which is obtainable by reacting:
A) at least one member selected from the group consisting of:
(1) an aliphatic diisocyanate of the general formula:
OCN-R-NCO (I) (in which R is a C4-C12-alkylene radical which may contain one to three methyl or ethyl groups or, instead of 4 CH2 groups, a cyclohexane radical), and (2) an adduct of the aliphatic diisocyanate of the formula (I) which contains an isocyanurate group, biuret group or urethane group and which has free isocyanate groups, with B) a sterically hindered secondary amine having a boiling point of at least 160°C and being represented by the general formula:
(II) (in which R1 and R are identical or different and are each independently hydrogen, alkyl, cycloalkyl or aralkyl or two of R1 or two of R together with the carbon atom to which they are attached or R1 and R together with the HN
group and the two carbon atoms to which they are attached form a ring which may be substituted by one to four alkyl groups or, instead of a CH2 group, may contain an oxygen atom or a -NH group), wherein the sterically hindered secondary amine is employed in an amount of 0.5 - 1 mol per mole of isocyanate groups in the aliphatic diisocyanate or the adduct.
A) at least one member selected from the group consisting of:
(1) an aliphatic diisocyanate of the general formula:
OCN-R-NCO (I) (in which R is a C4-C12-alkylene radical which may contain one to three methyl or ethyl groups or, instead of 4 CH2 groups, a cyclohexane radical), and (2) an adduct of the aliphatic diisocyanate of the formula (I) which contains an isocyanurate group, biuret group or urethane group and which has free isocyanate groups, with B) a sterically hindered secondary amine having a boiling point of at least 160°C and being represented by the general formula:
(II) (in which R1 and R are identical or different and are each independently hydrogen, alkyl, cycloalkyl or aralkyl or two of R1 or two of R together with the carbon atom to which they are attached or R1 and R together with the HN
group and the two carbon atoms to which they are attached form a ring which may be substituted by one to four alkyl groups or, instead of a CH2 group, may contain an oxygen atom or a -NH group), wherein the sterically hindered secondary amine is employed in an amount of 0.5 - 1 mol per mole of isocyanate groups in the aliphatic diisocyanate or the adduct.
2. A blocked aliphatic diisocyanate as claimed in claim 1, wherein in the formula (II), R1 and R2 are identical or different and are each independently hydrogen, alkyl having 1 to 6 carbon atoms, cycloalkyl having 5 or 6 carbon atoms or benzyl or two of R1 or two of R2 together with the carbon atom to which they are attached form a ring which is selected from the group consisting of piperidinyl, morpholinyl, cyclopentyl and cyclohexyl and which may have one to four methyl substituents or R1 and R2 together with the HN group and the two carbon atoms to which they are attached form a ring which is selected from the group consisting of piperdine or morpholino and which may have one to four methyl substituents.
3. A blocked aliphatic diisocyanate as claimed in claim 1 or 2, wherein 0.8 - 1 mol of the secondary amine is employed per mole of isocyanate groups in the member A).
4. A blocked aliphatic diisocyanate as claimed in any one of claim 1 to 3 wherein the diisocyanate of the formula (I) is selected from the group consisting of pentamethylene diisocyanate, hexamethylene 1,6-diisocyanate, hexamethylene 1,5-diisocyanate, 2-methylpentamethylene 1,5-diisocyanate, 2-ethyltetramethylene 1,4-diisocyanate and any desired mixtures of these two isomers, p- and m-hexahydroxylylene diisocyanate,
5-methylnona-methylene diisocyanate, 1,8-diisocyanato-2, 4-dimethyloctane and dodecamethylene diisocyanate.
5. A blocked aliphatic diisocyanate as claimed in any one of claims 1 to 4, wherein the secondary amine is selected from the group consisting of dicyclohexylamine, t-butylcyclohexylamine, di(3,5,5-trimethyl)-cyclohexylamine, dicyclopentylamine, 2,6-dimethylpiperidine, 3,5-dimethylmorpholine and di(2,2,6,6,-tetramethylpiperidinyl) amine.
5. A blocked aliphatic diisocyanate as claimed in any one of claims 1 to 4, wherein the secondary amine is selected from the group consisting of dicyclohexylamine, t-butylcyclohexylamine, di(3,5,5-trimethyl)-cyclohexylamine, dicyclopentylamine, 2,6-dimethylpiperidine, 3,5-dimethylmorpholine and di(2,2,6,6,-tetramethylpiperidinyl) amine.
6. A blocked aliphatic diisocyanate as claimed in any one of claims 1 to 4, wherein the secondary amine is di(2,2,6,6-tetramethylpiperidinyl)amine.
7. A blocked aliphatic diisocyanate as claimed in any one of claims 1 to 6, wherein the member A) is the adduct (2).
8. A blocked aliphatic diisocyanate as claimed in any one of claims 1 to 6, wherein the member A) is not the adduct (2) but is the diisocyanate (1) of the formula (I).
9. A blocked aliphatic diisocyanate as claimed in any of claims 1 to 8, which has a molecular weight of from 300 to 1600 and a melting point in the range from 50 to 180°C.
10. A blocked aliphatic diisocyanate as claimed in any one of claims 1 to 9, which has a blocked terminal NCO group content of from 6 to 22% by weight.
11. A storage-stable heat-curable polyurethane powder coating, and having the following composition:
(a) 100 parts by weight of an OH- containing polymer which contains at least two OH groups and has a melting temperature of at least 70°C, (b) 10 - 90 parts by weight of the blocked aliphatic polyisocyanate or corresponding adduct according to any one of claims 1 to 10, (c) 0 - 160 parts by weight of a pigment, (d) 0 - 200 parts by weight of a filler, (e) 0 - 5 parts by weight of a catalyst, and (f) 0.5 - 5 parts by weight of a leveling agent.
(a) 100 parts by weight of an OH- containing polymer which contains at least two OH groups and has a melting temperature of at least 70°C, (b) 10 - 90 parts by weight of the blocked aliphatic polyisocyanate or corresponding adduct according to any one of claims 1 to 10, (c) 0 - 160 parts by weight of a pigment, (d) 0 - 200 parts by weight of a filler, (e) 0 - 5 parts by weight of a catalyst, and (f) 0.5 - 5 parts by weight of a leveling agent.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE1996103389 DE19603389A1 (en) | 1996-01-31 | 1996-01-31 | Blocked aliphatic diisocyanates or diisocyanate adducts |
| DE19603389.6 | 1996-01-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2186089A1 true CA2186089A1 (en) | 1997-08-01 |
Family
ID=7784110
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2186089 Abandoned CA2186089A1 (en) | 1996-01-31 | 1996-09-20 | Blocked aliphatic diisocyanates or diisocyanate adducts |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0787754A2 (en) |
| JP (1) | JPH09249731A (en) |
| CA (1) | CA2186089A1 (en) |
| DE (1) | DE19603389A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7176254B2 (en) | 2002-06-17 | 2007-02-13 | Bayer Aktiengesellschaft | Sizing composition |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE10322911A1 (en) * | 2003-05-21 | 2004-12-16 | Bayer Materialscience Ag | Solidified stable blocked polyisocyanates |
| DE10348380A1 (en) * | 2003-10-17 | 2005-06-02 | Bayer Materialscience Ag | Polyisocyanates with biuret structure blocked with secondary amines |
| JP5562267B2 (en) * | 2010-02-08 | 2014-07-30 | 旭化成ケミカルズ株式会社 | Block polyisocyanate composition and coating composition containing the same |
| KR101450985B1 (en) * | 2010-02-08 | 2014-10-15 | 아사히 가세이 케미칼즈 가부시키가이샤 | Block polyisocyanate composition and coating composition containing same |
| JP5562271B2 (en) * | 2010-06-04 | 2014-07-30 | 旭化成ケミカルズ株式会社 | Method for producing block polyisocyanate composition |
| JP6034726B2 (en) * | 2013-03-06 | 2016-11-30 | 三井化学株式会社 | Block isocyanate, coating composition, and method for producing blocked isocyanate |
| JP2014172941A (en) * | 2013-03-06 | 2014-09-22 | Mitsui Chemicals Inc | Block isocyanate and coating composition |
| EP3568423A1 (en) | 2017-01-13 | 2019-11-20 | Covestro Deutschland AG | Low-solvent coating systems for textiles |
Family Cites Families (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE758924A (en) | 1969-11-15 | 1971-05-13 | Bayer Ag | PULVERULENT COATING AGENTS |
| DE2105777C3 (en) | 1971-02-08 | 1976-02-05 | Veba Chemie Ag | Powder coating composition |
| DE2261065C2 (en) | 1972-12-14 | 1982-04-01 | Basf Ag, 6700 Ludwigshafen | Process for the preparation of stable polyisocyanates containing biuret groups |
| GB1465286A (en) | 1974-09-23 | 1977-02-23 | Ucb Sa | High reactivity masked diisocyanates and thermosetting pulverulent compositions containing them |
| DE2712931A1 (en) | 1977-03-24 | 1978-09-28 | Veba Chemie Ag | ISOCYANURATE GROUPS - AND FINALLY BLOCKED ISOCYANATE GROUPS - CONTAINING COMPOUNDS |
| DE2735497A1 (en) | 1977-08-06 | 1979-02-15 | Veba Chemie Ag | POWDERED POLYURETHANE PAINTS |
| DE2842641A1 (en) | 1978-09-29 | 1980-04-10 | Bayer Ag | Poly-isocyanate used as hardener for polyurethane lacquer - prepd. from 1-isocyanato-3,3,5-tri:methyl-5-isocyanato:methyl-cyclohexane and contg. trimerised, blocked and free isocyanate gps. |
| DE2901479A1 (en) | 1979-01-16 | 1980-07-24 | Bayer Ag | NEW ISOCYANATO ISOCYANURATE, A METHOD FOR THE PRODUCTION THEREOF AND THEIR USE AS ISOCYANATE COMPONENT IN POLYURETHANE LACQUER |
| DE3004876A1 (en) | 1980-02-09 | 1981-08-20 | Chemische Werke Hüls AG, 4370 Marl | Reactive blocked poly:isocyanate(s) - comprise reaction prod. of caprolactam with adduct of poly:ol and isophorone di:isocyanate esp. used for polyurethane powder coatings |
| DE3007670A1 (en) | 1980-02-29 | 1981-09-17 | Aquanort Ingenieur Skirde + Co, 2110 Buchholz | Detergent-free laundering of textiles - using aq. soln. of bromide or bromic acid and ozone |
| DE3143060A1 (en) | 1981-10-30 | 1983-05-11 | Chemische Werke Hüls AG, 4370 Marl | Powder coatings based on blocked isophorone diisocyanate adducts |
| DE3151855C2 (en) | 1981-12-30 | 1993-11-04 | Huels Chemische Werke Ag | ISOCYANATO-ISOCYANURATE AND A METHOD FOR THE PRODUCTION THEREOF |
-
1996
- 1996-01-31 DE DE1996103389 patent/DE19603389A1/en not_active Withdrawn
- 1996-09-20 CA CA 2186089 patent/CA2186089A1/en not_active Abandoned
- 1996-11-26 EP EP96118883A patent/EP0787754A2/en not_active Withdrawn
-
1997
- 1997-01-30 JP JP9017107A patent/JPH09249731A/en not_active Withdrawn
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7176254B2 (en) | 2002-06-17 | 2007-02-13 | Bayer Aktiengesellschaft | Sizing composition |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH09249731A (en) | 1997-09-22 |
| DE19603389A1 (en) | 1997-08-07 |
| EP0787754A2 (en) | 1997-08-06 |
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