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
  • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
  • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
  • C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used
  • C08G59/4007—Curing agents not provided for by the groups C08G59/42 - C08G59/66
  • C08G59/4014—Nitrogen containing compounds
• • 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
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/40—High-molecular-weight compounds
  • C08G18/58—Epoxy resins
• • 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
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D163/00—Coating compositions based on epoxy resins; Coating compositions based on derivatives of epoxy resins
• • 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
  • C08G2150/00—Compositions for coatings
  • C08G2150/20—Compositions for powder coatings

Definitions

• thermosetting epoxy resin compositions have already been described.
• Dicyandiamide and polycarboxylic acid anhydrides are the most commonly used epoxy resin hardeners. Both the polycarboxylic acid anhydride and the dicyandiamide / epoxy mixtures have an almost unlimited shelf life at room temperature, but they have the disadvantage that too high temperatures or too long curing times are required for their curing.
• DE-OS 22 48 776 it is pointed out as a major technical advance that when imidazoline derivatives are used as hardeners in epoxy resin powder coatings, the required curing temperatures and times are significantly lower or shorter than with common hardeners (such as polycarboxylic acid anhydrides and Dicyandiamide) are formulated powder coating systems.
• the invention relates to powdered coating compositions with high storage stability and a grain size of less than 0.25 mm, preferably between 0.02 and 0.06 mm, based on 1,2-epoxy compounds with more than one 1,2-epoxy group in the molecule and a lower melting point of> 40 ° C, curing agents and conventional paint additives, which are characterized in that the coating agent as a curing agent with cyclic amidines of the general formula contains blocked polyisocyanates in which a 1 or 2, R are identical or different substituents from the group consisting of hydrogen, alkyl, cycloalkyl, aralkyl and aryl and optionally 2 geminal or vicinal R's together form part of an unsubstituted or alkyl-substituted cycloalkyl ring, the curing agent being 2 - 15 wt.%, Based on the amount of solid 1,2-epoxy compound, is present in the coating agent.
• the hardeners according to the invention are extremely compatible with most epoxy resins and, at elevated temperatures, provide homogeneous melts which are very suitable for the production of sinter powders.
• the curable mixtures according to the invention are stable in storage at room temperature; the curing times are within a temperature interval of 140 - 200 ° C within 25 - 5 minutes.
• the hardening mechanism is believed to be complex.
• the homopolymerization of the 1,2-epoxy groups is catalyzed by the basic N of the compounds according to the invention, and on the other hand, during curing, the hardeners are deblocked into the cyclic amidines and the polyisocyanates.
• the released amidine in turn catalyzes the homopolymerization of the 1,2-epoxy groups, while the NCO groups that are liberated coexist with the OH groups of the epoxy resin react an NCO / OH reaction to form urethane bonds.
• the formation of oxazolidinone by reaction of NCO groups with epoxy groups must not be neglected.
• the hardened coatings or coatings are characterized by very good chemical and mechanical properties.
• hydroxyl-containing 1,2-epoxy compounds with more than one 1,2-epoxy group in the molecule and a lower melting point of> 40 ° C. that is to say compounds which correspond to these characteristics, are particularly suitable are polyepoxide compounds which are solid at 40 ° C.
• solid resins those which are solid due to their symmetrical structure or the size of the carbon systems bound to the 1,2-epoxy group and on the other hand, those which have been prepared by reacting liquid 1,2-epoxy compounds with more than one epoxide group per molecule with primary or secondary amines in such an amount that the adduct still contains on average one 1,2-epoxide group per molecule.
• the 1,2-epoxy compounds can be both saturated and unsaturated and aliphatic, oyolialiphatic, aromatic and heterocyclic. They can also contain substituents which do not cause any undesirable side reactions under the mixing and reaction conditions. No side reactions cause alkyl or aryl substituents, ether groups and the like.
• 1,2-epoxy compounds with more than one epoxy group in the molecule are preferred for this application, the epoxy equivalent weight of which is between 500-2,000.
• the solid, polymeric polyglycidyl polyethers of 2,2-bis (4-hydroxyphenyl) propane which are obtained by reacting 2,2-bis (4-hydroxyphenyl) propane with epichlorohydrin in molar ratios of 1: 1.9-1.2 (in the presence of an alkali hydroxide in an aqueous medium).
• Polymeric polyepoxides of this type can also be obtained by reacting a polyglycidyl ether of 2,2-bis (4-hydroxyphenyl) propane with less than the equimolecular amount of dihydric phenol, preferably in the presence of a catalyst such as a tertiary amine, a tertiary phosphine or a quaternary phosphonium salt.
• the polyepoxide can also be a solid epoxidized polyester which has been obtained, for example, by reacting a polyhydric alcohol and / or a polybasic carboxylic acid or its anhydride with a low molecular weight polyepoxide.
• Examples of such low molecular weight polyepoxides are liquid diglycidyl ethers of 2,2-bis (4-hydroxyphenyl) propane, diglycidyl phthalate, diglycidyl adipate, diglycidyl tetrahydrophthalate, diglycidyl hexahydrophthalate, diglycidyl aleate and the 3,4-epoxycyclohexyl acid cyclohexyl methyl ester.
• Solid polyepoxides can also be used, e.g. a mixture of a polyepoxide whose melting point is between 120 and 160 ° C and a polyepoxide with a melting point between 60 and 80 ° C (melting point is determined according to the mercury method of Durrans).
• Suitable mixtures contain between 30 and 50% by weight of a solid polyglycidyl ether of 2,2-bis (4-hydroxyphenyl) propane with an epoxy equivalent weight between 1650 and 2050 and a melting point of 120 to 160 ° C and between 50 and 70% by weight a solid polyglycidyl polyether of 2,2-bis (4-hydroxyphenyl) propane with an epoxy equivalent weight between 450 and 525 and a melting point of 60 to 80 ° C.
• the polyisocyanates blocked with cyclic amidines of the general formula described according to the invention can be prepared by reaction at temperatures of 0-150 ° C., preferably at 80-120 ° C., the polyisocyanates and the cyclic amidines being used in such amounts that 0.5-1.1, preferably 0.8-1.0 mol of cyclic amidine come to an isocyanate group.
• the reaction temperature used should be below the hardening temperature.
• the reaction mixture is expediently kept at the stated temperatures until the NCO content of the mixture has dropped to values below 0.2%.
• the reaction can be carried out either in solvents, in the melt or in excess polyisocyanate.
• Suitable starting compounds which can be used for blocking with the cyclic amidines are, for example, polyisocyanates, in particular diisocyanates, such as aliphatic, cycloaliphatic, araliphatic, ie aryl-substituted aliphatic, and / or aromatic diisocyanates, as described, for example, in Houben-Weyl, methods of organic Chemie, Volume 14/2, pp. 61-70 and the article by W.
• the dimeric and trimeric forms of the polyisocyanates such as uretdiones and isocyanurates, which can be prepared by known methods, can of course also be used as starting materials for blocking with the cyclic amidines, imidazolines and tetrahydropyrimidines described in detail below.
• polyisocyanates are also understood to mean those which, prior to the blooking with the cyclic amidines, are reacted to enlarge the molecules with the so-called chain extenders customary in isocyanate chemistry, such as water, polyols, polyamines, etc.
• chain extenders customary in isocyanate chemistry, such as water, polyols, polyamines, etc.
• the bifunctional or trifunctional chain extender that is to say compounds having groups which are reactive toward isocyanate groups, such as hydroxyl and / or amino groups, are used in such amounts that the resulting new isocyanate bears at least 2 isocyanate groups on average.
• polyisocyanates with one or more urea groups result.
• Suitable polyols are, for example, diols and triols, such as the molecular weight range 60-250, e.g. Ethylene glycol, propylene glycols such as 1,2- and 1,3-propanediol, 2,2-dimethylpropanediol- (1,3), butanediols such as butanediol- (1,4), hexanediols e.g.
• polyamines suitable for chain extension or molecular enlargement for example, 1,2-ethylenediamine, 1,2 and 1,3-propylenediamine, 1,2-1,3 and 1,4-butylenediamine and the hexamethylenediamines, one or can be several C 1 -C 4 alkyl radicals, such as 2,2,4- or 2,4,4-trimethylhexamethylenediamine-1,6 and others, and 3-aminomethyl-3,5,5-trimethyl-cyclohexylamine, which also is referred to as IPD.
• C 1 -C 4 alkyl radicals such as 2,2,4- or 2,4,4-trimethylhexamethylenediamine-1,6 and others
• IPD 3-aminomethyl-3,5,5-trimethyl-cyclohexylamine
• the suitable imidazoline and tetrahydropyrimidine derivatives for the purposes of the present invention which correspond to the general formula described earlier are, for example, those with optionally aryl-substituted alkyl radicals or with optionally alkyl-substituted aryl radicals, such as 2-methylimidazoline, 2,4-dimethylimidazoline, 2-methyl 4- (n-butyl) imidazoline, 2-ethylimidazoline, 2-ethyl-4-methylimidazoline, 2-benzylimidazoline, 2-phenylimidazoline, 2-phenyl-4-methylimidazoline, 2-phenyl 4- (N-morpholinylmethyl) imidazoline, 2- (o-tolyl) imidazoline, 2- (p-tolyl) imidazoline or 2-methyltetrahydropyrimidine, 2,4- (5 or 6), diaethyltetrahydropyrimidine, 2-ethyltetrahydropyrimidine
• imidazoline and tetrahydropyrimidine derivatives which can be used according to the invention can be prepared by known processes from optionally substituted 1,2- or 1,3-diamines and, for example, aliphatic or aromatic mononitriles in the presence of elemental sulfur or sulfuryl chloride as a catalyst.
• the blocking can also be carried out in solvents.
• suitable solvents for this reaction are only those which do not react with the polyisocyanates, for example ketones, such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone among others; Aromatics, such as benzene, toluene, xylenes, chlorobenzene, nitrobenzene and others; cyclic ethers such as tetrahydrofuran, dioxane and others; Esters such as methyl acetate, n-butyl acetate and others; aliphatic chlorinated hydrocarbons, such as chloroform, carbon tetrachloride and others; and aprotic solvents such as dimethylformamide, dimethylacetamide, dimethyl sulfoxide, etc.
• ketones such as acetone, methyl ethyl ketone, methyl isobutyl
• the reaction mixtures are kept at the stated temperatures until the NCO content of the reaction mixture has dropped to values below 0.2% NCO, otherwise until a constant is reached NCO value.
• Blocked polyisocyanates which can be obtained by subsequent reaction of a group of blocked polyisocyanates, namely those in which cyclic amidines have been used in substoichiometric amounts, i.e. the ratio of cyclic amidine to isocyanate groups was ⁇ 1: 1 with the same chain extenders that have previously been described as molecular enlargement agents.
• the reaction also takes place at temperatures in the range from 0-150 ° C., preferably 80-120 ° C., but below the deblocking temperature of the blocked polyisocyanate.
• These blocked polyisocyanates can be used to produce coating compositions which cover practical requirements within very wide limits. This process variant is of particular interest for polyisocyanates with differently reactive NCO groups.
• Blocking diisocyanates extended with divalent chain extenders gives compounds which can be described by the general formula below.
• a and R may have the meaning given above and n 0 or 1, X 0, S or an NH group, R * may be the same or different, optionally alkyl-substituted alkyleny cycloalkylene or arylene radical and R "may be a one or more alkyl radicals, several of which can also be part of a cycloaliphatic ring, substituted, saturated or unsaturated alkylene radical with 2-18 C atoms, which may optionally contain one or more oxygen or sulfur atoms in the hydrocarbon chain, or an optionally alkyl-substituted arylene or cycloalkylene radical.
• the amount of polyisocyanate blocked with a cyclic amidine used as the curing agent can be varied within wide limits. Excellent results are already obtained when using 2-15 parts by weight, preferably 6-12 parts by weight. Hardening agent, based on the amount of solid 1,2-epoxy compound used.
• the coating compositions with blocked polyisocyanate hardeners in which mixed imidazoline-tetrahydropyrimidine derivatives or only tetrahydropyrimidines have been used as blocking agents, have the advantage that they are even more reactive than the first.
• This hardener group can therefore be used with shorter burn-in times, or the hardening can be carried out at somewhat lower temperatures carry out.
• the storage stability at room temperature of the new coating compositions with imidazolines or tetrahydropyrimidines blocked polyisocyanates as hardeners is excellent.
• Ethers such as the polymeric polyethylene and polypropylene glycols, copolymers of n-butyl acrylate and vinyl isobutyl ether, ketone-aldehyde condensation resins, solid silicone resins or mixtures of zinc soaps, fatty acids and aromatic carboxylic acids and the like.
• leveling agents can be present in the batches in amounts of 0.2-5.0% by weight, based on the total amount of the powder coating.
• thermosetting powder coating mixture such as pigments, dyes, fillers, thixotropic agents, UV and oxidation stabilizers, etc. can vary within a wide range, based on the amount of 1,2-epoxy compounds.
• Another object of the invention is the preparation of the powdered coating composition, in which the solid 1,2-epoxy compounds and the curing agents, if appropriate after addition of the paint additives mentioned, mixed in the proportions mentioned and extruded at least 30 ° C. below the splitting temperature of the curing agent and then to a grain size less than 0.25 mm, preferably ⁇ 100 ⁇ , and a grain size maximum between 20 and 60 ⁇ , preferably between 30 and 50 p, grinds and, if necessary, the coarser fraction removed by sieving.
• the application of the powder coating to the bodies to be coated can be carried out by known methods, e.g. electrostatic powder spraying, whirl sintering, electrostatic whirl sintering, etc., happen.
• the powder coating After the powder coating has been applied to the objects to be coated using one of the methods described, they are hardened to temperatures above the splitting temperature of the curing agent, i.e. 130 - 200 ° C, preferably 140 - 180 ° C, heated.
• the resulting coating then has the advantages described.
• the IPDI blocked with 2 - phenylimidazoline is a white powder with a melting range of 98-106 ° C, a softening point (DTA) of 63-80 ° C and a free isocyanate content of ⁇ 0.2% by weight.
• a 1,2-epoxy compound based on an adduct of 2,2-bis (4-hydroxyphenyl) propane (Dian) and epichlorohydrin was used, which was subjected to an HCl elimination and then with further Dian was implemented and which, according to the manufacturer, had an epoxy equivalent weight of 900-1000, an epoxy value of 0.10-0.11, a hydroxyl value of 0.34 and a melting range of 96-104 ° C.
• Powdery coating agent containing pigment 1 c.
• the ground products 1,2-epoxy compound with 2-phenylimidazoline blocked IPDI and leveling agent masterbatch were intimately mixed with the white pigment (Ti0 2 ) in a pan mill and then homogenized in an extruder at 90 - 100 ° C. After cooling, the extrudate was broken and ground with a pin mill to a grain size ⁇ 100 ⁇ .
• the powder thus produced was applied to degreased iron sheets using an electrostatic powder spraying system at 60 kV and baked in a forced-air drying cabinet.
• Example 1b The epoxide according to Example 1b was reacted with varying amounts of the blocked isocyanate component according to Example 1a.
• composition of the powder coating agents :
• the pigmented powder coating according to 1c 1 was cured between 180 ° and 200 ° C.
• the pigmented powder coating agent according to 1c 2 was cured between 150 ° C and 200 ° C.
• the table below shows the values obtained.
• the weight loss was significantly lower than that of films made with ⁇ -caprolactam-blocked diisocyanates because the 2-phenylimidazoline used as a blocking agent still reacted with the 1,2-epoxy groups.
• the pigmented powder coating agent according to 1c 3 was baked between 150 ° C and 200 ° C.
• the table below shows the values obtained.
• IPDI diethylene glycol
• Example 1c two pigmented powder coatings were produced, applied and baked using the following recipes:
• the pigmented powdery coating agent according to Example 2d 1 was cured between 180 ° C and 200 ° C.
• the properties of the paint films obtained are shown in the table below.
• the pigmented powdery coating agent according to Example 2d which was cured between 160 ° C and 200 ° C, showed significantly improved elasticity, caused by a 50% increase in the amount of crosslinker.
• the table below shows the mechanical properties of the coating films.
• the reaction product is a white crystalline powder with a melting range of 95 - 103 ° C, a softening point (DTA) of 65 - 85 ° C and a free NCO content ⁇ 0.1%.
• Example 1c two pigmented powder coatings were produced, applied and baked with the following recipes.
• the pigmented, powdery coating agent according to Example 3c 1 was baked between 170 ° C and 200 ° C.
• the table below shows the specific mechanical properties of the paint films.
• the pigmented lacquer according to FIG. 3c 2 which was baked between 170 and 200 ° C., shows significantly improved elasticity, caused by an approximately 50% increase in the proportion of crosslinking agent.
• a pigmented powder coating was prepared, applied and baked in accordance with Example 1c.
• This pigmented powder coating was then baked between 170 ° C and 200 ° C.
• the table below shows the mechanical values of the paint films obtained.
• IPDI-diethylene glycol adduct blocked with 2-phenyl-4-methyl-imidazoline also achieves greater elasticity while simultaneously reducing the curing temperatures and times.
• Example 1c pigmented powder coatings were produced, applied and baked.
• the pigmented powder coating according to 5c 1 was baked between 150 ° C and 200 ° C.
• the table below shows the values obtained for the lacquer films.
• the pigmented powder coating according to Example 5c 2 which was baked between 130 ° C and 200 ° C, shows a significantly improved elasticity, caused by a 50% increase in the amount of crosslinker. In addition, the burn-in times could be shortened or the temperatures lowered.
• the table below shows the specific mechanical properties of the paint films.
• reaction product is a colorless powder with a melting range of 100 - 107 ° C and a softening point of 60 - 95 ° C.
• Example 1c a pigmented lacquer with the following recipe was produced, applied and baked between 160 and 180.
• the reaction product is a white crystalline powder with a melting range of 90 - 103 ° C, a glass transition temperature (DTA) of 78 - 90 ° C and a splitting temperature of approx. 130 ° C.
• Example 1c a pigmented powder coating was prepared, applied and baked at 160 ° C and 180 ° C.
• the paint films baked at 180 ° C within 12 ' were subjected to the boiling water test and showed no attack after 72 hours.
• the diisocyanate blocked with 2,4-dimethylimidazoline is a white powder with a melting range of 85 - 105 ° C, a glass transition temperature (DTA) of 70 - 91 ° C and a splitting temperature of approx. 150 ° C.
• Example 1c pigmented powder coatings were produced, applied and baked.
• the pigmented powder coating according to 8 c 1 was baked at 160 ° C. and 180 ° C.
• the pigmented powder coating according to Example 8c 2 which was baked between 160 ° C and 180 ° C, shows a significantly improved elasticity.
• Methyl benzoate was added to 3 125 parts by weight. of a mixture of isomers of 1-amino-2-aminomethyl-3.3.5 or -3.5.5-trimethylcyolopentane (TMCPD) is introduced into a reactor, heated to 190 ° C. with stirring and reacted. A pressure of approximately 9 bar was established. The reaction mixture was then held at the temperature of 190 ° C. for 2.5 hours. The pressure was then released and the excess of TMCPD and the cleavage products alcohol and water were distilled off.
• An isomer mixture of various tetrahydropyrimidines of the following structure could be isolated by distillation in an oil pump vacuum (0.5 Torr) in the temperature range from 158 to 170 ° C.
• the product is yellowish and highly viscous.
• the IPDI blocked with the product from FIG. 9a represents a white powder with a melting range of 85-98 ° C., a softening point of 67-75 ° C. determined by differential thermal analysis (-DTA) and a content of free isocyanate of ⁇ 0. 2%.
• the ground products epoxy compound, blocked IPDI corresponding to 9b and leveling agent masterbatch were mixed with the white pigment (TiO 2 ) corresponding to 1c, applied and baked.
• Example 9c The epocide compound according to Example 9c was reacted with varying amounts of the blocked isocyanate component according to Example 9b.
• the pigmented powder coating according to 9 d 2 was cured between 140 ° C and 200 ° C within 14 - 4 minutes. After the various baking conditions, these varnishes showed the following results:
• the paint films baked at 180 ° C within 8 minutes were also subjected to a cooking water test. No traces of an attack could be observed after 24 hours of exposure, the abrasion with the Taber abraser (1000 U, 1000 g, CS 17) was 30 - 45 mg. The weight loss is significantly less than in films made with diisocyanates blocked with ⁇ -caprolactam, since the tetrahydropyrimidine used as a blocking agent reacts with the epoxy groups.
• the paint films which were cured at 180 ° C within 8 minutes, also show excellent boiling water resistance, low abrasion and low weight loss.
• Example 9a 484 parts by weight of compound A (Example 9a) were added in portions to 556 parts by weight of the adduct of 2 mol IPDI and 1 mol diethylene glycol prepared in 2a at 120 ° C. in such a way that the temperature did not rise above 125 ° C. After the addition had ended, the reaction mixture was heated at 120 ° C. for a further 2 hours.
• the reaction product is a pale yellow powder with a melting range of 89-101 ° C, a softening point (DTA) of 75-86 ° C and a free NCO content of 0.2%.
• Example 9d two pigmented powder coatings with the following recipes were produced, applied and baked
• the pigmented powder coating according to Example 10d 2 which was cured between 150 ° C and 200 ° C in the course of 12 to 4 minutes, shows a significantly improved elasticity due to the increase in the cross-linking portion.
• the reaction time was 2.5 hours. After this time the excess diamine was distilled off together with the cleavage products methanol and water. An isomer mixture with a tetrahydropyrimidine structure could be distilled off in a yield of 274 g - 76%, based on the ester, in vacuo at 0.5 torr in a temperature range of 100-119 ° C.
• the viscous, yellow product contains, among other things, compound of the following formula:
• Compound B was 222 parts by weight. IPDI added dropwise so that the temperature in the reaction flask did not exceed 120 ° C. The reaction mixture was kept at 120 ° C. to complete the reaction. These conditions are sufficient for an almost complete implementation.
• the reaction product is a yellowish crystalline powder with a melting range of 95-104 ° C, a softening point (DTA) of 59-74 ° C and a free NCO content ⁇ 0.1%.
• Example 9d a pigmented powder coating was prepared, applied and baked according to the following recipe.
• the pigmented powder coating according to Example 11d was baked between 160 ° and 200 ° C. in the course of 22-8 minutes and achieved the following test results:
• the following examples of powder coatings are particularly suitable for the coating of large pipes and containers made of metal.
• the powder is applied to sandblasted steel substrates, which are heated to a temperature of 240 - 270 ° C, using the electrostatic method.
• the layer thickness of the hardened thermoset coating was 300-350 ⁇ (measured electromagnetically).
• the leveling agent namely polyadrylic acid n-butyl ester with a k-Vert of 30-35
• the proportions of the additives, the preheating temperature before the paint is applied to the pipes and test rods and the dwell time are summarized in the following table, the lower part of which shows the test results.
• Coated test sheets 200 mm long and 8 ma thick were sawn in the middle with a hacksaw.
• the 100 mm long pieces of sheet metal thus obtained were boiled for 28 hours in 10% strength sodium hydroxide solution at 100 ° C.
• Gardner impact resistance 5. Gardner impact resistance
• test was carried out according to the regulations of the DBAFT, British Gas Standard, PS / CW 1.
• mixed-blocked polyisooyanates i.e. blocked both with imidazolines and with tetrahydropyrimidines
• these can be prepared by mixing the individual components or by blocking with mixtures of cyclic amidines.
• mixed-blocked polyisocyanates at least 1% by weight of the second component should be included.

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• 1978
  • 1978-08-22 EP EP78200151A patent/EP0000971B1/fr not_active Expired
  • 1978-08-22 DE DE7878200151T patent/DE2861691D1/de not_active Expired
  • 1978-08-25 JP JP10280078A patent/JPS5460331A/ja active Pending
  • 1978-08-25 IE IE1722/78A patent/IE47157B1/en unknown
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