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
  • C08G59/14—Polycondensates modified by chemical after-treatment
  • C08G59/1433—Polycondensates modified by chemical after-treatment with organic low-molecular-weight compounds
  • C08G59/1438—Polycondensates modified by chemical after-treatment with organic low-molecular-weight compounds containing oxygen
  • C08G59/145—Compounds containing one epoxy group
• • 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
  • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
  • C09D5/44—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes for electrophoretic applications
  • C09D5/4419—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes for electrophoretic applications with polymers obtained otherwise than by polymerisation reactions only involving carbon-to-carbon unsaturated bonds
  • C09D5/443—Polyepoxides
  • C09D5/4434—Polyepoxides characterised by the nature of the epoxy binder
  • C09D5/4442—Binder characterised by functional groups
  • C09D5/4446—Aliphatic groups, e.g. ester

Definitions

• the invention is concerned with novel resinous binders containing tertiary amino groups which are useful for coating articles by means of cathodic electrodeposition.
• the present invention is also concerned with the preparation of such binders as well as coating compositions containing them.
• Resinous binders of this type wherein C I is derived from a diamine or a primary monoamine, are known from GB - A - 1 461 823.
• a disadvantage of such binders is that they produce rough, incoherent coatings having poor corrosion resistance on bare steel substrates i.e. steel which has not been phosphated. It has also been proposed to incorporate residues of unsaturated fatty acids into such resinous binders e.g. see GB-A- 1 307 585. Although such binders form smoother coatings on bare steel substrates they still have a poor corrosion resistance.
• binders contain at least one group derived from a glycidyl ester of a C 6 to C 20 carboxylic acid then the coatings prepared therefrom are smooth and glossy and have good corrosion resistance even when deposited upon bare steel substrates.
• the present invention is concerned with a resinous binder of formula:- wherein
• the group R 1 may be directly attached to at least one of the groups A, B, or C, or indirectly through an intermediate group which is preferably the residue of a di- or tricarboxylic acid; m is preferably an integer of from 1 to 3, n is preferably an integer of from 1 to 4, and R 2 is preferably a secondary or tertiary C 8 to C 10 alkyl group.
• One suitable method (method I) of preparing resinous binders of formula III comprises reacting a resinous binder of formula I with
• the resinous binders of formula I are prepared by reacting a diglycidyl ether of formula:- wherein
• resinous binders wherein m is 0, are obtained by reacting about 2 epoxy equivalents of the diglycidyl ether with about 2 moles of the secondary monoamine; resinous binders, wherein m is 1, are obtained by reacting about 4 epoxy equivalents of the diglycidyl ether with about 2 moles of the secondary monoamine and about 1 mole of the compound having at least two sites capable of reacting with glycidyl ether groups; resinous binders, wherein m is 2, are obtained by reacting about 6 epoxy equivalents of the diglycidyl ether with about 2 moles of the secondary monoamine and about 2 moles of the compound having at least two sites capable of reacting with glycidyl ether groups; and resinous binders, wherein m is 3, are obtained by reacting about 8 epoxy equivalents of the diglycidyl ether with about 2 moles of the secondary monoamine and about 3
• the diglycidyl ethers of formula VII are well known compounds and are available commercially usually as mixtures of compounds having on average more than one glycidyl group per molecule.
• Theoretically diglycidyl ethers of dihydric phenols have two epoxy groups per molecule but some of the terminal glycidyl groups may be hydrated during the preparation to groups.
• diglycidyl ether to be used is indicated by its number of epoxy equivalents.
• Preferred diglycidyl ethers are those wherein R is a group of formula:- wherein
• Suitable secondary monoamines are heterocyclic amines, e.g. piperidine and morpholine; dialkylamines, such as di(C, to C B )alkylamines e.g. dimethylamine, diethylamine, dipropylamines, dibutylamines, dipentylamines and methylethylamine; dialkanolamines, such as di(C I to C 6 )alkanolamines e.g. diethanolamine and dipropanolamines such as diisopropanolamine, and N-alkylalkanolamines such as N-(C 1 to C 6 )alkyl(C 1 to C 6 )alkanolamines e.g.
• dialkylamines such as di(C, to C B )alkylamines e.g. dimethylamine, diethylamine, dipropylamines, dibutylamines, dipentylamines and methyleth
• the secondary monoamines may be further substituted e.g. by alkoxy or carboxyl groups. It can be seen from formula I that such resinous binders have at least two secondary hydroxyl groups which are capable of reacting in method I (A) or (B).
• the secondary monoamine an alkanolamine since the resulting resinous binders have additional hydroxyl groups which may also react in method I (A) or (B); consequently it is possible to react more of the components in (A) or (B) and to produce a resinous binder of formula III which in addition to having R I groups also has several unreacted hydroxyl groups which is considered to be advantageous insofar as such binders are to be used in cathodic electrodeposition processes.
• the most preferred secondary monoamines are diethanolamine and di-iso-propanolamine.
• Suitable compounds having at least two sites capable of reacting with glycidyl ether groups, and which therefore form the linking groups C I or C are polyols, adducts of polyols and polycarboxylic acid anhydrides, and polycarboxylic acids. Preferred are amines having as reactive sites one or more primary or at least 2 secondary amine groups.
• polyols are alkylene glycols and polyoxyalkylene glycols e.g. hexylene glycol, polyoxyethylene glycol and polyoxypropylene glycol; polyhydric phenols e.g. diphenylolmethane and diphenylolpropane.
• polycarboxylic acids and anhydrides examples include maleic, succinic, dodecenylsuccinic, glutaric, adipic, phthalic, tetrahydrophthalic, hexahydrophthalic, endomethylene tetrahydrophthalic, methyl endomethylene tetrahydrophthalic acid and trimellitic acid and their anhydrides.
• Examples of amines having one or more primary amine or at least 2 secondary amine groups per moleculare are: C 2 to C lo alkylene primary diamines, such as ethylene diamine, hexylene diamine (1,6-diaminohexane); poly(C 2 to C 10 )alkylene polyamines, such as diethylene triamine, triethylentetramine, piperazine, N-(2-aminoethyl)piperazine; polyether primary diamines such as 4,9-dioxa-1,12-dodecane diamine; primary mono(C 1 to C B )alkyl and (C, to C 6 )alkanol amines such as methylamine, butylamine, monoethanolamine, mono-isopropanolamine, from which the alkanolamines are preferred.
• C 2 to C lo alkylene primary diamines such as ethylene diamine, hexylene diamine (1,6-diaminohexan
• amines may further contain tertiary amine groups; examples are 1-(N,N-dimethylamino-3-aminopropane, 1-(N,N-diethyl)amino-4-aminobutane, and 1-N,N-bis (3-aminopropyl)methylamine.
• Primary monoamines may be further substituted by alkoxy, carboxy or sulphonyl groups; examples are 3-ethoxy propylamine, glycine, alanine, p-amino benzoic acid, sulphanilic acid, and sulphanilamide. Presence of a built-in acidic group may improve the cure with cross-linking resins.
• a built-in sulphonic acid group is preferably deactivated at room temperature by reacting the resinous binder with an excess of glycidyl ester; at stoving temperature the sulphonic acid group is set free and can exert its cure-improving properties.
• the preparation of the resinous binders of formula I may be carried out at elevated temperatures e.g. at a temperature in the range of from 50 to 150°C and in the presence of non-reactive solvents such as glycol ethers and ketones.
• Glycol ethers are usually non-reactive below 100°C.
• mixtures of diglycidyl ethers of formula VII, mixtures of secondary monoamines and/or mixtures of compounds having at least two reactive sites capable of reacting with glycidyl groups may be used.
• a preferred component (c) is a mixture of
• the resinous binders of formula I may then be etherified with a glycidyl ester of formula VI (method I(A)).
• Preferred esters are glycidyl esters of saturated aliphatic monocarboxylic acids in which the carboxyl group is attached to an alpha-branched carbon atom, i.e. a tertiary or quaternary carbon atom, and which carboxylic acids have preferably 9 to 11 carbon atoms per molecule.
• the amount of glycidyl ester used may vary considerably and will depend on the number of reactive sites available in the resinous binder of formula I.
• the reaction may be carried out at a temperature of from 50 to 150°C and in the presence of non-reactive solvents such as glycol ethers and ketones.
• Catalysts may be used e.g. quaternary ammonium salts or hydroxides, phosphonium salts, tertiary amines or phosphines or salts thereof, alkalimetalhydroxides, lithium halides and stannous salts of monocarboxylic acids.
• the resinous binders of formula I may be reacted with a cyclic carboxylic acid anhydride and a glycidyl ester of formula VI (method I(B)).
• Preferred glycidyl esters are those described above.
• Preferred cyclic carboxylic acid anhydrides which may also contain a carboxylic acid group, are the anhydrides of aliphatic cyclic dicarboxylic acids such as maleic, succinic, dodecenylsuccinic, glutaric and adipic acids, and carbocyclic anhydrides such as the anhydrides of aromatic or alicyclic dicarboxylic acids e.g.
• anhydride containing a further carboxylic acid group examples are trimellitic anhydride and adducts of maleic anhydride and ethylenically unsaturated fatty acids.
• the amount of anhydride used may vary considerably and depends on the number of reactive sites of the resinous binder 2 of formula I but is suitably from 0.5 to 4.5 moles per mole of resinous binder of formula I.
• the amount of the anhydride and glycidyl ester may vary considerably but is preferably such that the resinous binder of formula III is substantially free of carboxylic acid groups.
• the reaction is suitably carried out at a temperature of from 50 to 150°C and may be carried out in the presence of non-reactive solvents such as glycol ethers and ketones.
• Another suitable method (method II) of preparing resinous binders of formula III comprises reacting a diglycidyl ether of formula VII with a secondary monoamine and, optionally, a compound having at least two sites capable of reacting with glycidyl ether groups, wherein at least one of the reactants is substituted by at least one R, group as defined above and wherein the amounts of the reactants are such that the number of epoxy equivalents of the diglycidyl ether is substantially equal to the number of reactive sites of the other reactants.
• Method II is-particularly suitable for preparing resinous binders of formula III wherein m is 1 to 6 by reacting
• resinous binders of formula III wherein m is 1, are obtained by reacting about 4 epoxy equivalents of the diglycidyl ether with about 2 moles of the secondary monoamine and about 1 mole of the reaction product of (c) and (d) and so on. Suitable diglycidyl ethers, secondary monoamines and glycidyl esters are described above.
• Suitable compounds of type (c) are polyamines containing at least two primary amino groups, such as C 2 to C lo alkylene primary diamines, poly(C 2 to C l0 )alkylene polyamines and polyether primary diamines of the type discussed above with hexamethylene diamine being preferred, and compounds containing a cyclic carboxylic anhydride group and a carboxylic acid group of the type discussed above with trimellitic anhydride or trimellitic anhydride/polyoxyalkylene glycol adducts being preferred.
• Suitable adducts may be prepared by reacting a polyoxyalkylene glycol with about 200 mole % of trimellitic anhydride.
• compound (c) is a polyamine
• preferred reaction products are obtained by reacting about 1 mole of an alkylene primary diamine with about 2 epoxy equivalents of the glycidyl ester of formula VI.
• compound (c) is the above trimellitic anhydride/polyoxyalkylene glycol adduct
• preferred reaction products are obtained by reacting the adduct with about 2 epoxy equivalents of the glycidyl ester of formula VI.
• the above method may be carried out in several stages e.g. the diglycidyl ether of formula VII may be pre-reacted with the secondary monoamine. All of the above reactions may be carried out at elevated temperature, e.g. at a temperature of from 50 to 150°C, and in the presence of non-reactive solvents such as glycol ethers and ketones.
• reaction products of (c) and (d) wherein (c) has at least three sites capable of reacting with glycidyl groups and the reaction product has two sites capable of reacting with glycidyl ether groups; an example is the reaction product of 1 mole of 1,6-diaminohexane and two moles of (d).
• reaction products of this type may have more than two, for example 3 or 4, sites reactive with glycidyl ether groups, as exemplified by the reaction products of 1 mole of diethylene triamine or triethylene tetramine with 2 moles of (d); such products have 3 and 4 reactive sites, respectively, and will form with adducts of (a) and (b) resinous binders which are "star-shaped", that is to'say that the groups C in the formula III contains one or more side chains -B-A.
• the resinous binders of formula III may contain from 1 to 6 perferably 2 to 4 groups, derived from the glycidyl ester of formula VI. Usually the weight of such groups varies from about 10 to 50% weight of the resinous binder. Moreover, preferred resinous binders of formula III have a hydroxyl content of from 200 to 600 meq/100 g, more preferably from 200 to 400 meq/100 g, for improved corrosion resistance on bare steel. In addition, preferred resinous binders have preferred calculated average molecular weights of from 2000 to 5000.
• the resinous binders of formula III are particularly suitable as components of aqueous coating compositions for use in cathodic electrodeposition processes. Accordingly the invention is also concerned with thermosetting coating compositions, such as water-dilutable binder concentrates and aqueous coating compositions comprising a resinous binder of formula III, which may have been prepared as hereinbefore described, wherein at least about 20% of the amino groups are neutralised by an acid.
• Suitable aqueous coating compositions comprise about 2 to 20%w of the resinous binder of formula III.
• the acid which has the effect of making the resinous binder water-soluble as well as making it susceptible to cathodic electrodeposition may be inorganic e.g. hydrochloric, sulphuric acid, or organic e.g. formic, acetic, maleic, citric or lactic acid, with lactic acid being preferred. Usually from 20 to 100% of the amino groups are neutralized by the acid.
• the binder concentrate and the aqueous coating composition contains preferably a cross-linking agent such as melamine/formaldehyde; benzoguanamine/formaldehyde; urea/formaldehyde and phenol/formaldehyde resins, with alkoxylated melamine e.g. hexamethoxymethylmelamine resins being preferred.
• Suitable amounts of cross-linking agents are from 1 to 50%w, preferably from 5 to 25%w, based on the weight of the resinous binder of formula III.
• the aqueous compositions may also contain other components such as solvents e.g. glycol ethers, pigments, fillers, dispersing agents and stabilizers.
• the aqueous coating compositions are preferably prepared by dissolving the resinous binder in a solvent such as a glycol ether, adding the cross-linking agent and acid followed by the addition of water, preferably demineralized water.
• a solvent such as a glycol ether
• Values for pH are usually of from 3.0 to 6.0 but may be above 6.0.
• the compositions are particularly suitable for coating bare steel substrates they may also be used for coating phosphatized steel substrates.
• the diglycidyl ethers (named Polyethers) used therein were commercial polyglycidyl ethers of 2,2- bis(4-hydroxyphenyl)propane (also known as Bisphenol A) having the following properties:
• the glycidyl ester C10E was a commercial glycidyl ester of saturated aliphatic monocarboxylic acids in which the carboxyl group is attached to a tertiary or quaternary carbon atom, and which carboxylic acids have on average 10 carbon atoms per molecule; the epoxy molar mass was 250.
• Polyether E (1786 g; 2.0 epoxy equivalents) was melted and reacted with diethanolamine (210 g; 2.0 mole) at 135°C for 5 hours.
• the resulting resinous binder had a nitrogen content of 1.00 meq/g, a residual epoxy content of below 0.02 meq/g and a calculated aliphatic hydroxy content of about 600 meq/100 g.
• a resinous binder (200 g, 0.1 mole) prepared according to Example 1 was melted and mixed with succinic anhydride (20 g, 0.2 mole) for 5 minutes at 145°C.
• Glycidyl ester C10E 60 g; 0.24 epoxy equivalents was added and the reaction continued for 1 hour at 135°C.
• the resulting resinous binder had a nitrogen content of 0.71 meq/g, an acid content of 0.04 meq/g and a calculated aliphatic hydroxy content of about 430 meq/100 g.
• About 21.4%w of the resinous binder was derived from the glycidyl ester.
• a resinous binder (200 g; 0.1 mole) prepared according to Example 1 was melted and reacted with glycidyl ester C10E (74.4 g; 0.3 epoxy equivalents) in the presence of benzyldimethylamine (0.27 g), as etherification catalyst, for 6 hours at 140°C.
• the resulting resinous binder had a nitrogen content of 0.73 meq/g; a residual epoxy equivalent of 0.03 meq/g and a calculated aliphatic hydroxy content of about 440 meq/100 g.
• About 27.1%w of the resinous binder was derived from the glycidyl ester.
• the resulting resinous binder had a nitrogen content of 1.35 meq/g, a residual epoxy content of 0 and a calculated aliphatic hydroxy content of about 670 meq/100 g.
• a resinous binder (233 g; 0.3 mole) prepared according to Example 4 was melted and a blend of trimellitic anhydride (19.2 g; 0.1 mole), glycidyl ester C10E (62.5 g; 0.25 epoxy equivalents) and dry acetone (40 g) added gradually (over 0.5 hour) thereto whilst maintaining the temperature at 130°C and distilling off the acetone. After addition, the reaction was continued for 2 hours at 135°C.
• the resulting resinous binder had a nitrogen content of 0.98 meq/g, an acid content of 0.02 meq/g, an epoxy content of 0.08 meq/g and a calculated aliphatic hydroxy content of about 500 meq/100 g.
• About 20.5%w of the resinous binder was derived from the glycidyl ester.
• Example 6 was repeated with the difference that in step (b) the solution obtained in step (a) was added to a solution obtained as follows.
• the resulting solution of resinous binder had a nitrogen content of 1.05 meq/g solution and a calculated solids content of 73.5%w.
• Glycidyl ester C10E 250 g; 1.0 epoxy equivalents was added gradually (over 0.5 hour) to a solution of ethylene diamine (30 g; 0.5 mole) in ethylene glycol monobutyl ether (50 g). The temperature was not allowed to exceed 80°C. The resulting clear solution had an epoxy value of 0.
• a solution of sulphanilic acid (17.3 g, 0.1 mole) and diethanolamine (42.0 g. 0.4 mole) in water (30 g) was then added followed by a solution of Polyether A (304 g; 1.6 epoxy equivalents) in ethylene glycol monobutyl ether (170 g). The mixture was then stirred at 80°C for 1 hour and at 110°C for 2 hours.
• the resulting clear solution had a nitrogen content of 1.81 meq/g solution, an epoxy content of 0, a residual acid content of 0.10 meq/g solution and a solids content of 72.0%w.
• About 38.8%w of the resinous binder was derived from the glycidyl ester.
• a resinous binder (200 g; 0.1 mole) prepared according to Example 1 was reacted with linseed oil fatty acid (54.6 g, 0.2 mole) in the presence of toluene (25 g) and stannous octoate (0.8 g) at 220°C for 1 hour whilst removing the water of esterification (335 g) and toluene (20 g) azeotropically.
• the resulting resinous binder had a nitrogen content of 0.76 meq/g and a residual acid value of 0.02 meq/g.
• Coating compositions were prepared from the resinous binders, or solutions thereof, obtained in Examples 1 to 10.
• the general procedure was to dissolve the resinous binder, if necessary, in a solvent (ethylene glycol monobutyl ether was used except in Examples 14, 15 and 18 where a mixture of this ether (16.7 g) and isophorone (8.3 g) was used) followed by the addition of a cross-linking agent "Cymel” 301 (hexamethoxymethyl melamine) and lactic acid. Demineralized water was then added slowly.
• the compositions had a 10%w solids content.
• the amounts of the components are given in Table 1.
• the coating compositions prepared according to Examples 11 to 20 were cathodically electrodeposited onto solvent degreased steel panels at a temperature of 25 ⁇ 1°C and voltages of from 50 to 200 volts (direct current). The coatings were cured at 180°C for 30 minutes. The panels were examined visually and the thickness of the coatings determined. The coated panels obtained from compositions of the present invention were then subjected to a salt spray corrosion resistance test (ASTM B 117-64; 10 days). The appearances of the coated panels prepared from the comparative compositions, except Example 30, were such that it was not considered worthwhile to carry out this salt spray test. The results are given in Table II.
• Binder with sulphanilamide and trimellitic anhydride Binder with sulphanilamide and trimellitic anhydride.
• Trimellitic anhydride (19.2 g; 0.1 mole) and glycidyl ester C10E (50 g; 0.2 mole) were added and the mixture was kept at 115°C for 2t hours.
• the cured films (25 micrometer) were smooth and glossy; the impact resistance (Erichsen reverse) was >90 kgcm ( > 9 Nm), the methylethyl ketone resistance 50 double rubs, and the salt spray resistance 5-10 mm from scratch.
• a pigmented binder A pigmented binder.
• the (epoxy + N) content is then below 1.35 meq/g solids, the acid content is 0.04 meq/g solids, and the solids content is 72.7%w.
• the product is an adduct having on average 4 NH functions per molecule.
• Binder with sulphanilamide, cure with phenolic resin

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• 1978
  • 1978-06-01 DE DE7878200031T patent/DE2861731D1/de not_active Expired
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