DE3004902A1 - Epoxy! resin coating and moulding compsn. - with good storage stability and contg. imidazoline blocked di:isocyanate hardener and curing catalyst - Google Patents

Abstract

A moulding and coating compsn. comprise a 1,2-epoxy cpd. (I) contg. more than one epoxy gp. cyclic amidine blocked diisocyanates of formula (II). m is 0 or 1, R is (CH2)n. CH2C(CH3)2CH2CH(CH3)CH2CH2, CH2CH2OCH2CH2 or CH2CH2OCH2CH2- OCH2CH2; n is 2-12, R1-3 are H, (cyclo)alkyl or aralkyl and R4 is a (cyclo)aliphatic hydrocarbon gp. and a hardening catalyst (III). (II) is used in amt. of 2-15, pref. 6-12 wt.% (w.r.t. the compsn.) and (III) in an amt. of 0.05- 10 wt.% (w.r.t. (I)). The compsn. has good storage stability at room temp. and hardens rapidly at elevated temp. The compsn. can be used for press mouldings and single component stoving lacquers esp. for large dia. pipes and metal containers. The coatings are resistant to hot water, heat and alkali, does not form pores and has good adhesion.

Description

Moldings and coating compositions

There is great interest in epoxy hardeners and their epoxy mixtures are storage-stable at room temperature and cure quickly at higher temperatures.

Dicyandiamide and polycarboxylic anhydrides are the most commonly used Epoxy resin hardener. Both the polycarboxylic anhydride and the dicyandiamide / epoxy mixtures are almost indefinitely stable in storage at room temperature; however, they have Disadvantage that too high temperatures or

too long curing times are required. In DE-OS 22 48 776 was found as a significant technical advance that when using imidazoline derivatives as a hardener in epoxy resin powder coatings, the required curing temperatures and - times are significantly lower or shorter than with conventional hardeners formulated powder coating systems. Unfortunately, these imidazoline / epoxy mixtures have only limited storage stability at room temperature. This is achieved with epoxy resin / hardener mixtures both very good storage stability at room temperature and rapid curing at higher temperatures if aromatic polyisocyanates are used as hardeners, whose NCO groups are blocked with phenol. The disadvantage of these mixtures is that when they harden, the highly odorous phenol is released. By the phenol released when these mixtures cure is also their field of application limited to thin coatings.

It has now been found that cyclic amidines blocked aliphatic Polyisocyanates in surprising journey the most important beneficial properties combine the hardening agents listed above without having their disadvantages.

The invention thus relates to moldings and coating compositions which are composed of a) 1,2-epoid compounds with more than one epoxy group in the molecule b) diisocyanates of the general formula blocked with cyclic amidines m - 0.1; n 1 2 - 12; R = (CH2) n; -CH2-CH2-O-CH2-CH2- or CH2-CH2-O-CH2-CH2-O-CH2-CH2-R1, R2, R3 = identical or different, H, alkyl, aralkyl, cycloalkyl R '= aliphatic or cycloaliphatic hydrocarbon radical and c) curing catalysts, where b), based on the total mass in amounts of 2-15% by weight, preferably 6-12% by weight, and c), based on a), in amounts of 0 , 05-10% by weight is present.

Part of the diisocyanate blocked with cyclic amidines can you can also use other known epoxy resin hardeners from the group of polysmines, polyamides, Replace aminoamides, polyaminoamides and dicyandiamide.

The invention further relates to a process for the production of moldings and coating compositions, characterized in that a) 1,2-epoxide compounds with more than one epoxide group in the molecule b) diisocyanates of the general formula blocked with cyclic amidines m = 0.1 I n - 2 - 12; R = (CH2) n; CH2-CH2-O-CH2-CH2-O-CH2-CH2-R1, R2, R3 s identical or different, H, alkyl, aralkyl, cycloalkyl R '. aliphatic or cycloaliphatic hydrocarbon radical and c) curing catalysts are reacted, where b), based on the total mass in amounts of 2-15% by weight, preferably 6-12% by weight and c) based on a) in amounts of 0, 05-10% by weight can be used.

Blocked the use of the above with cyclic amidines In addition to improved storage stability, diisocyanate has other advantages. For example, hardening (at higher temperatures) does not produce gaseous substances Fission products. Furthermore, the compositions according to the invention result in the cured Condition Moldings and coatings with very good heat resistance.

Also show those from the inventive with cyclic amidines blocked diisocyanate / epoxide mixtures are excellent in the production of films Course.

The hardener / epoxy mixtures according to the invention are therefore very suitable for the production of storage-stable, heat-curable molding compounds and one-component stoving enamels.

They are particularly suitable for coating large pipes and metallic containers. The hardenable ones previously used for coating large pipes Epoxy resin compounds have the disadvantage that they are not heat resistant and when damaged the coating is exposed to warm alkaline solutions or hot water or superheated steam Loss of adhesion at the steel / epoxy resin coating interface due to infiltration the shift leads. This sensitivity to alkalis is also common in construction projects, where there is always lime, cement, etc. are present. In addition, the Coating often pores, i.e. micro-cavities that extend to the metallic substrate expand. With the diisocyanate blocked with cyclic amidines according to the invention / Epoxy mixtures can provide pipes and containers with a permanent coating which does not have the disadvantages mentioned.

The for the preparation of the thermosetting mixtures according to the invention in The hardeners in question are diisocyanates blocked with cyclic amidines. the composition the diisocyanates on which these hardeners are based is not critical. Starting compounds suitable for capping with cyclic Amidines suitable for the production of the hardeners according to the invention are, for example, in Houben-Weyl, Methods of Organic Chemistry Vol. 14/2 pp. 61 - 70, or Annalen der Chemie 562, Pp. 75 - 136 (W. Siefken) listed. 1, 4-tetramethylene diisocyanate are mentioned, Bexamethylene diisocyanate-1,6, 1-isocyanato-3,5,5-trimethyl-3-isocyanatomethylcyclohexane (IPDI), 2,2,4- (2,4,4) -trimethylhexamethylene diisocyanate-1,6, 2,6-hexahydrotolylene diisocyanate.

As a rule, those that are technically easily accessible are particularly preferred Diisocyanates, e.g., hexamethylene diisocyanate- (1,6), isophorone diisocyanate, 2,4- (2,6) -hexahydrotolylene diisocyanate and any mixtures of these isomers, 2,2,4- (2,4,4) -trimethylhexamethylene diisocyanate-1,6.

In a first embodiment for the production of the invention Polyisocyanates, spec. Diisocyanates, without further modification with cJslischen amidines described below reacted so that the NCO groups completely blocked. According to a second embodiment for production the hardener according to the invention, this reaction of the isocyanate with the blocking agent so combined with a chain extension that the polyisocyanates with a insufficient amount of a di- or trifunctional chain extender be modified, this modification before and / or during and / or after the blocking of the excess isocyanate groups with the blocking agents takes place. The di- or trifunctional chain extenders act they are connections the molecular weight range 60 - 250, which have 2-3 hydroxyl groups. Examples of such polyhydric alcohol are ethylene glycol, 1,4-butanediol, 1,6-hexanonol, diethylene glycol, trimethylolpropane etc..

If the reaction of the polyisocyanates with the chain extender is carried out, the reactants at temperatures of 20-150 C, preferably 80 - 120 ° C reacted with each other in such a way that at any point in time of the reaction the isocyanate groups are in excess over the hydroxyl groups.

To carry out the blocking reaction is generally the Submitted polyisocyanate and the acyclic amidine at temperatures of 20-150 C, preferably 80 - 120 OC, slowly added. The reaction can be in substance or can also be carried out in the presence of suitable solvents.

Suitable solvents are e.g. benzene, toluene, DMF, ketones such as Acetone, cyclohexanone, MIBK. The reaction mixture is as long as specified Temperatures are maintained until the NCO content of the reaction mixture is below 0.5% by weight NCO has decreased.

Cyclic amidines of the following formula are used as blocking agents in the process according to the invention: R1, R2 "identical or different, alkyl, aryl, aralkyl, cycloalkyl, heterooyclene, -N (R3) 2, nitro groups, keto groups, ester groups, carbonamide groups; R3 - alkyl, cycloalkyl, aryl, H Blocking agents to be used in the process according to the invention are particularly preferred Compounds of the formula: where: 1. R1 = H; R3 - phenyl radical 2. R1 = CH3; R3 = phenyl radical 3. R1 = R = CE3 4. R3 - H; R1 = CH3 The molding compositions according to the invention are prepared by mixing the above diisocyanates blocked with cyclic amidines with the 1,2-epoxy compounds which contain more than one epoxy group per molecule. The epoxides of polyunsaturated hydrocarbons (vinylcyclohexene, dicyclopentadiene, cyclohexadiene, cyclododecadiene, cyclododecatriene, isoprene, 1,5-hexadiene, butadiene, polybutadienes, divinylbenzenes and the like), epoxy ethers of polyhydric alcohols and propylene glycols (ethylene and propylene glycols) are suitable for this purpose. Polyglycols, thiodiglycols, glycerine, pentaerythritol, sorbitol, polyvinyl alcohol, polyallyl alcohol, etc.), epoxy ethers of polyhydric phenols (resorcinol, hydroquinone, bis (4-hydroxyphenyl) methane, bis (4-hydroxy-3-methylphenyl) methane, Bis (4-hydroxy-3,5-dichlorophenyl) methane, bis (4-hydroxy-3,5-dibromophenyl) methane, bis (4-hydroxy-3,5-difluorophenyl) methane, 1, 1-bis (4-hydroxyphenyl) ethers, 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxy-3-methyl-phenyl) -propane, 2,2-bis - (4-hydroxy-3-chlorophenyl) propane, 2,2-bis (4-hydroxy -3, 5-dichlorophenyl) propane, bis (4-hydroxyphenyl) phenyl methane, bis (4- hydroxyphenyl) diphenyl methane, bis (4-hydroxyphenyl) -4'-methylphenyl methane, 1,1-bis (4- hydroxyphenyl) -2,2,2-trichloroethane, bis- (4-hydroxyphenyl) -4-chlorophenyl) -methane, 1,1-bis- (4-hydroxyphenyl) -cyclohexane, bis- (4-hydroxyphenyl) -cyclohexylmethane 4 , 4'-dihydroxydiphenyl, 2,2'-dihydroxydiphenyl, 4,4'-dihydroxydiphenyl sulfone and their hydroxyethyl ethers and the like, S- and N-containing epoxides (N, N-diglycidylaniline, N, N'-dimethyldiglycidyl-4, 4'-diaminediphenylmethane (triglycidyl isocyanurate) and epoxides which have been produced by conventional processes from polyunsaturated carboxylic acids or monounsaturated carboxylic acid esters of unsaturated alcohols, glycidyl esters, polyglycidyl esters, which can be obtained by polymerization or copolymerization of glycidyl esters of unsaturated acids.

Mixtures of these can be used just as well as the pure epoxides above with monoepoxides, optionally in the presence of solvents or plasticizers, implemented according to the present procedure. For example, the following Monoepoxides are used in a mixture with the aforementioned epoxy compounds; epoxidized monounsaturated hydrocarbons (butylene, cyclohexene, Styrene oxide etc.), halogen-containing epoxides such as epichlorohydrin, epoxy ethers of monohydric alcohols (Methyl, ethyl, butyl, 2-ethylhexyl, dodecyl alcohol, etc.), monohydric epoxy ethers Phenols (phenol, cresol and other phenols substituted in the ortho or para position), Glycidyl esters of unsaturated carboxylic acids, epoxidized esters of unsaturated alcohols or unsaturated carboxylic acids and diQ acetals of glycidaldehyde.

To produce the compositions according to the invention, some of the According to the invention, diisocyanates blocked with cyclic amidines by others known "hardeners" such as polyamines, polyamides, aminoamides, polyaminoatides, and dicyandiamide be replaced.

The compositions according to the invention are produced by mixing the diisocyanates blocked with cyclic amidines with the 1,2-epoxy resins or 122-epoxy compounds and shaping according to known methods and is shown in the examples will be explained in more detail Both moldings and coatings and impregnations can be used manufacture with it.

The cyclic amidine blocked diisocyanates of the present invention Invention are definite hardeners, i.e. the actual hardening or crosslinking expediently takes place at temperatures above 140 ° C, preferably between 150-200 ° C.

The production of the moldings and coatings according to the invention can possibly by adding accelerating substances, e.g. from the Group of mono- or polyhydric phenols, especially the aminophenols, the one or polyhydric alcohols or by compounds such as mercapto compounds, Thioethers, dithioethers or compounds with nitrogen-carbon-sulfur groups be shortened.

Also suitable are salts of hydrofluoric acid, in particular in the form of complex compounds.

Such compounds are e.g .: NH4 SOHN, NaSCN, KSCN, Mg (SCN) 2, Ca (SCN) 2, Zn (SCN) 2, Mn (SCN) 2, pyridine .HSCN, quinoline o HSON, aniline. HSCN, o- and p-toludine. HSCN, guanidine. HSCN, Cd (SCN) 3. 4 NH3, Zn (SCN) 2. 2 N2H4, Mn (SCN) 2 . 2 N2H4, s KSCN: [(CH2) 6N4], Zn (SCN) 2. (Pyridine) 4, Mn (C5H5N) 2. (SCN) 2, as well as [(NH2) 3CS] 3. KSCN.

The amount of accelerator added can be varied within a wide range can be varied. Typically, amounts of accelerator will be in the range from 0.05 to 10% by weight, preferably 0.5 to 5% by weight, based on the epoxide, applied, however Smaller or larger additives can sometimes be particularly advantageous.

The curing accelerators can be either in the mixture or in the epoxy or added to the hardener in the form of solid substance, dispersion or also in solution will.

Of course, fillers, dyes, pigments, Flexibilizers, solvents and other additives are added. It is a particular advantage of the method according to the invention that for intensive mixing of the additives mentioned is sufficient due to the extended processing time Time is available.

The mixtures are prepared by known methods, e.g. by kneading on the friction roller, in kneaders and extruders. In some cases it is also useful to mix it in solution. The invention The substances used have great advantages in terms of processing and storage stability at elevated temperatures.

Example 1 1 a) For a mewing of 222 parts by weight. Isophorone diisooyanate (IPDIj and 300 parts by weight of anhydrous acetone slowly became 292 at room temperature Parts by weight 2-phenylimidazoline, which in 500 parts by weight. dissolved in anhydrous acetone, added dropwise. After completion of the 2-phenylimidazoline addition, one hour at 50 oO heated. The acetone was distilled off. The last remains of acetone were through Removal of drying of the reaction product at 60 oC in the vacuum drying cabinet. That IPDI blocked with 2-phenylimidazoline is a white powder with a melting point from 104 00.

1b) 8.5 parts by weight of the blocked diisocyanate thus prepared with 91.5 parts by weight of a glycyl ether based on bisphenol-A, the epoxy value of which is 0.102 was mixed intensively on a friction roller at 80 ° C (5 minutes).

The gelation time of this mixture was approx. 200 seconds at 220.degree. It did not change even after storage at 50 ° C. for 24 hours. The one from this with 2-phenylimidazoline blocked isophorone diisocyanate / epoxy mixture produced Moldings which were cured for 20 minutes at 180 ° C. were very hard and transparent and had a smooth surface. They turned out to be against organic solvents resistant.

Example 2 2 a) To a melt of 320 parts by weight. 2-phenyl-4-methylimidazoline were 222 parts by weight. 1PDI is added dropwise so that the temperature in the reaction flask is not rises above 120 ° C. For completion of the reaction the reaction mixture was kept at 120 ° C. for 3 h. These conditions were enough for one almost complete conversion (NCO content of the reaction product 0.4%).

The reaction product is a white crystalline powder with a Melting point of 90-106 0c.

2 b) 10 parts by weight of the hardener produced in Example 2 a) with 90 wt. of a glyeidyl ether based on bisphenol A, the epoxy value of which is 0.102 was intimately mixed with one another at 80 oC in a twin-screw extruder. Of the The kneading resistance of this mixture, measured in a Brabender plastograph, was 80 ° C 1.4 kpm. After 4 weeks of storage at 40 ° C., a value of 1.45 kpm was measured. The moldings produced from this material by injection molding were after a Hardening time of 5 minutes at 200 ° C, very impact-resistant and dimensionally stable.

Example 3 50 parts by weight of the epoxy resin / hardener produced in Example 1b Mixtures were in 50 parts by weight. Isophorone dissolved. The viscosity of this solution was at 25 ° C 980 mPa-s. The viscosity rose after a storage time of 3 months 1 120 mPa's. The solution was applied to steel panels; the one obtained after flashing off Layer was heated to 200 ° C for 5 minutes. The film had an excellent one Course, was hard and flexible and was resistant to acetone. With a layer thickness From 30 - 40 Yes the pendulum hardness according to König was 170 seconds; the Erichsen cupping 10.2 mm.

Example 4 4 a) To 550 parts by weight. of the adduct described in Example 5 a from 2 moles of IPDI and 1 mole of diethylene glycol were 196 parts by weight at 100 ° C. 2,4-dimethylimidazoline added dropwise so that the temperature did not rise above 110 ° C.

After 2,4-dimethylimidazoline had been added, the reaction mixture became heated at 110 ° C for a further 2 hours. In the reaction product so produced NCO could no longer be detected.

The reaction product is a colorless powder with a melting point from 97 - 101 C.

4 b) 8.5 parts by weight of the compound prepared in 4 a were 91.5 Parts by weight of a glycidyl ether based on bisphenol A, the epoxy value of which was 0.102, intimately mixed on a friction roller at 80 ° C. The kneading resistance of this mixture, measured in a Brabender plastograph, was 1.6 kpm at 70 ° C.

After 24 hours of storage at 50 ° C., a value of 1.7 kpm (b. 70 ° C.) measured.

The moldings produced from this material by injection molding were very impact-resistant and dimensionally stable after a curing time of 5 minutes at 180 ° C.

Example 5 5 a) To 444 parts by weight. IPDI were at 80 ° C with good stirring 106 parts by weight Diethylene glycol added slowly.

After the addition of diethylene glycol, the mixture was heated at 80 ° C. for a further 2 hours. The NCO content of the IPDI / diethylene glycol mixture was then 15.1%.

5 b) At 550 wt. » of the adduct prepared in 5 a from 2 moles of IPDI and 1 mol of diethylene glycol were 292 parts by weight at 1120 ° C. in portions.

2-Phenylimidazoline added so that the temperature does not exceed 125 OC increased. After the 2-phenylimidazoline addition was complete, the reaction mixture became heated at 120 O for another hour. The reaction product is a pale yellow powder with a melting point of 113 ° C. 5 c) 10 parts by weight. of the hardener produced in 5 b were with 90 parts by weight. of a glycidyl ether based on bisphenol A with an epoxy value of 0.102 mixed in a twin screw extruder at 80 ° C. The kneading resistance of this The mixture, measured in a Brabender plastograph, was 1.5 kpm at 80 ° C. After 24 After storage at 40 ° C., a value of 1.6 kpm was measured.

One with this epoxy resin / hardener powder by pressing for 5 minutes Plate produced at 200 0 was very hard, transparent and resistant to acetone as well Resistant to methanol.

Claims (4)

Claims 1. Moldings and coating compositions made from a) 1,2-epoxy compounds with more than one epoxy group in the molecule b> Liisocyanates of the general formula blocked with ycl1sohen amidines m I 0.1; n - 2 - 12; -CH2-CH2-O-CH2-CH2-O-CH2-CH2-R1, R2, R3 - identical or different, H, alkyl, aralkyl, cycloalkyl R '= aliphatic or cycloaliphatic hydrocarbon radical and c) there are curing catalysts where b ), based on the total mass, is present in amounts of 2-15% by weight, preferably 6-12% by weight, and c), based on a), in amounts of 0.05-10% by weight. 2. Process for the production of molded bodies and coating compositions according to claim 1, characterized in that a) 1,2-epoxy compounds with more than one epoxy group in the molecule b) with cyclic amidines diioscyanates of the general formula m - 0.1; nr = 2-12 R = (CH2) n; -CH2-CH2-O-CH2-CH2-O-CH2-CH2-R1, R2, R3 = identical or different, H, alkyl, aralkyl, cycloalkyl R '= aliphatic or cycloaliphatic hydrocarbon radical and c) curing catalysts are used, where b), based on the total mass, is present in amounts of 2-15% by weight, preferably 6-12% by weight, and o), based on a), in amounts of 0.05-10% by weight. 3. molding and coating compositions according to claim 1, characterized in that that part of the diisocyanate blocked with the cyclic amidines by others known epoxy hardeners from the group of polyamines, polyamides, aminoamides, polyaminoamides or dicyandiamide is replaced. 4. Process for the production of moldings and coating compositions, according to claim 2, characterized in that part of the cyclic Amidines blocked Din so cyanats by other known epoxy hardeners from the group which replaces polyamines, polyamides, aminoamides, polyaminoamides or dicyandiamide.