GB1604070A

GB1604070A - Binders

Info

Publication number: GB1604070A
Application number: GB26039/78A
Authority: GB
Original assignee: Vianova Resins AG
Current assignee: Allnex Austria GmbH
Priority date: 1977-09-23
Filing date: 1978-05-31
Publication date: 1981-12-02
Also published as: BR7805272A; SU818491A3; IT7828013A0; FR2404058A2; AT353911B; CA1113630A; ATA681677A; JPS5447733A; SE7808186L; IT1159116B; DE2831382A1; ZA783924B; ES472330A2

Description

(54) IMPROVEMENTS IN OR RELATING TO BINDERS (71) We,VIANOVA KUNSTHARZ AKTIENGESELLSCHAFT, an Austrian Body Corporate of Altmannsdorferstrasse 104, A-1120 Vienna, Austria, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in any by the following statement: This invention relates to improvements in or relating to binders. In particular, the invention relates to binders which are water dilutable which may be used in the formulation of surface coating compositions which deposit at the cathode when subjected to a process of electrodeposition.

Our copending patent application No. 6701/78 (Specification No. 1602132) discloses cathodically depositable water dilutable coating compositions based on coating systems containing basic groups, optionally containing pigments, dye-stuffs, extenders, solvents, paint additives and additional crosslinkers, and which are characterised in that the basic binder system contains a portion of acid groups in addition to the basic groups, the ratio between the two types of group being such that the ratio of the amine number to the acid number of the binder is from 97: 3 to 65 : 35 (measured as mg KOH/g). The acid and basic groups are either attached to the same macromolecule or to separate macromolecules.

The advantages connected with the presence of acid groups in basic coating compositions are related to the better crosslinking properties of the cured film, and to reduced curing temperatures compared to basic binders without acid groups.

We have now found that the properties of the coating compositions of our aboveidentified patent application No. 6701/78 (Serial No. 1602132) may be improved further if at least one of the components of the basic binder system is modified by a partially blocked polyisocyanate.

Thus, according to one aspect the present invention provides a binder for use in the production of cathodically depositable water dilutable coating compositions which comprises a macromolecular component containing basic nitrogen groups and acidic groups or, in physical admixture or chemically combined, a macromolecular component containing basic nitrogen groups and a macromolecular component containing acidic groups, such that the ratio of the amine number to the acid number of the binder is from 97 : 3 to 65 : 35, the reactive group of at least one of the said components present in the binder being modified by reaction with a compound of the formula OCN - R t NH - CO - R ], I (wherein R is an aliphatic hydrocarbon radical or an aromatic or cycloaliphatic nucleus, optionally substituted with alkyl groups; R' is a radical obtained by the loss of a reactive hydrogen atom from a saturated or unsaturated alcohol, a phenol optionally substituted by one or more alkyl radicals, a cyclic lactam, an aldoxime or ketoxime, an acetoacetic acid ester and/or a hydroxamic acid ester; and n is 1, 2 or 3).

From another aspect the present invention provides cathodically depositable water dilutable coating compositions comprising a binder according to the invention.

If desired the compositions according to the present invention may additionally contain one or more pigments, dyes, extenders, solvents, additional crosslinking agents and/or conventional coating additives.

The coating compositions according to the invention have improved properties compared to the products of patent application No. 6701/78 (Serial No. 1602132) in that they show better depositability so that the deposition of the coatings is enhanced on areas remote or shielded from the anode. Furthermore, the sensitivity of the coatings to residual aqueous coating composition, rinse water, or impurities of the deposited dry film is considerably reduced, which in turn leads to improved cured coatings.

A particular advantage of the present compositions over those of patent application No.

6701/78 (Serial No. 1602132) is the enhancement of corrosion resistance of the coatings of the present invention.

Various methods for the synthesis using a variety of raw materials, of basic nitrogen group containing binders have been described. Our patent application No. 6701/78 (Serial No. 1602132) gives, by way of example, a survey of the various methods leading to suitable products. Coating compositions particularly suitable for the modification according to the present invention are those consisting of several components, at least one of which, and preferably all of which, carry basic groups. In addition, at least one of the components carries the corresponding quantity of acidic groups.

The basic groups of the macromolecules may be introduced by condensation of dicarboxylic acid anhydrides with primary/tertiary diamines, with the correspondmg formation of water. Preferred starting materials are the succinic anhydride derivatives mentioned in patent application No. 6701/78 (Serial No. 1602132) or Diels-Alder adducts formed by addition of a, B-unsaturated dicarboxylic acid anhydrides to compounds containing isolated or conjugated double bonds.

Examples of such adducts are those of maleic anhydride to unsaturated oils, fatty acids and rosin acids, to diene polymers and unsaturated hydrocarbon resins. Furthermore, copolymers incorporating anhydrides, such as styrene-maleic anhydride copolymers, may be used in the compositions of the invention. Oligomeric liquid polymers of dienes are particularly referred for adduct formation, especially of 1,3-butadiene. The quantity of added dicarboxylic anhydride generally lies between 10 and 25% by weight.

The adduct anhydrides are partially reacted with primary/tertiary diamines, thereby forming water, and thus introducing basic tertiary nitrogen atoms besides amide and imide groups. The quantity of diamine compound is preferably chosen such that for 1 mole of anhydride group 0.3 - 0.8 moles of diamine are used. Thereby, a residual quantity of carboxy groups is provided, which subsequently is set free from the latent form of the residual anhydride groups by reaction with water or monohydric alcohols.

Examples of diamines which may be used are dimethylaminoethylamine, diethylami noethylamine, dimethylaminopropylamine, diethylaminopropylamine and homologues thereof. The diamine is conveniently added at a temperature of from 50"C to 1800C. The reaction is completed at a temperature of from 160 to 220"C, the formation of the preferably desired acid imide group being detected by the quantity of the water formed or by nucleus magnetic resonance spectroscopy. At lower reaction temperatures the formation of an acid amide group only may be detected by n.m.r. measurements.

Further components of this particularly preferred embodiment are the reaction products of epoxy group containing compounds particularly of polyglycidyl ethers of polyhydric phenols, such as bisphenol A, or of novolak resins with secondary amines. Convenient epoxy compounds are also polymers carrying epoxy groups, based on dienes or acrylic copolymers. For reaction therewith secondary aliphatic or cycloliphatic amines may be used, such as a derivative of diethylene triamine in which both primary amino functions are masked by ketoimine formation with at least 2 moles of a ketone.

The reaction of the secondary amine or alkanolamine to the epoxy resin is conveniently carried out at a temperature of from 30 to 1500C and is generally an exothermic reaction.

When the preferred epoxy resin melts at higher temperatures it is advantageous to coemploy solvents inert to epoxy groups, secondary amines and hydroxy groups. Such solvents are for example ketones, such as methylethylketone and methylisobutylketone; esters, such as ethylacetate, butyl acetate and ethylene glycol monoethyl ether acetate; and ethers, such as tetrahydrofuran and ethyleneglycoldiethylether.

The quantity of secondary amine or alkanolamine is preferably chosen such that the final component has an amine number of between 35 and 120 mg KOII/g. In general this value is obtained, even if not all epoxy groups are consumed in the reaction with the amine compound. In the latter case it is of advantage to esterify the remaining hydroxy groups with saturated or unsaturated carboxylic acids.

The modification of at least one of the components constituting the coating composition of the invention is carried out by reaction with a compound of the general formula OCN - R RjNH -CO - R' Sn (I) (wherein R,R' and n are as hereinbefore defined).

These compounds are partially blocked polyisocyanates, and may be obtained by reaction of polyisocyanates, preferably polyisocyanates carrying isocyanate groups with different reactivity. 2,4-Toluene diisocyanate is preferably used, one of the isocyanate groups thereof being blocked with one or more monohydric alcohols, phenols, oximes, cyclic lactams or acetoacetic acid esters. The blocking agents may also carry polymerisable double bonds, for example they may be monohydroxyacrylates. The partially blocked polyisocyanates preferably contain an average of one free isocyanate group.

The reaction of the partially blocked polyisocyanate with one of the components of the coating composition is conveniently carried out at a temperature of from 60 to 1600C, optionally in the presence of a solvent inert to isocyanates, and is carried on until the free isocyanate groups are substantially all consumed. The highest applicable reaction temperature is governed by the nature of the blocking agent. The progress of the reaction is reflected by a decreasing isocyanate content, and optionally also a decreasing acid value, the acid value becoming constant in the range of from 5 to 46 mg KOH/g at the end of the reaction. The amine number of the reaction product is generally from 25 to 70 mg KOH/g.

For easier handling, the components, subsequent to the reaction with the partially blocked polyisocyanate, may be diluted with solvents. Suitable solvents are for example lower alkyl glycol ethers, such as ethyleneglycolmonoethylether, ethyleneglycol monoisopropylether, ethyleneglycol monobutylether. Other solvents which may be used are for example alcohols such as ethanol, propanol, isopropanol and butanol. If desired the products may be neutralised with acids and/or diluted with water. Suitable acids are mainly monobasic lower organic acids such as formic acid, acetic acid and lactic acid.

We have found it to be advantageous with regard to the corrosion resistance towards salt solutions of the coatings, to enhance the hardening tendency of the coating compositions by the introduction of an additional crosslinking component. Examples of such crosslinking agents are phenol-formaldehyde condensation products of the resol type. Particularly preferred is the use of a phenol-formaldehyde condensation product, the phenolic hydroxy groups of which are etherified with allyl alcohol. The amount of crosslinking agent may range between 3 and 20% by weight of total binder composition. Since the crosslinkers are in most cases not directly water soluble, they may be co-reacted with at last one of the binder components by careful condensation. The temperatures required in general for this purpose are from 60 to 1200C, and the reaction time from 1 to 6 hours.

Other crosslinking agents which may be used are completely blocked polyisocyanate compounds. In constitution they may be equivalent to the above described partially blocked polyisocyanate compounds, with the exception that they do not carry free isocyanate groups.

These crosslinking components and the other optional resin components forming the total composition, may be present either in physical admixture or as a reaction product resulting from careful condensation. In the latter case, care should be taken to ensure that the molecular size increase does not surpass the limit for satisfactory dilutability with water.

As indicated above, the binders according to the invention may be processed together with pigments, extenders, anticorrosion pigments and optionally paint additives or crosslinking catalysts to give the coating compositions.

Examples of such pigments are titanium dioxide, carbon black, iron oxides and phthalocyanines; and examples of anticorrosion pigments are lead silicate, lead oxide, lead chromate, lead silico-chromate and strontium chromate. Extenders which may be used include aluminium silicate, talc, barium sulfate and highly dispersed diatomaceous earth.

The basic nitrogen atoms of the binders of the invention may be neutralised partially or totally with organic and/or inorganic acids, the degree of neutralisation depending on the particular binder system. In general, enough acid is added to give a coating composition which in its form of application at a pH-value of from 4 to 9, preferably 5 to 7, is water dilutable or dispersable. The concentration of the binder in water generally lies in the range of 3 to 30% by weight, preferably 5 to 15% by weight.

For deposition, an aqueous solution of the coating composition containing the binder of the invention is contacted with an electrically conductive anode and an electrically conductive cathode, the surface of the cathode being coated with the coating composition.

A variety of electrically conductive substrates may be coated, in particular, metallic substrates like steel, aluminium, copper etc., but also metallized plastics or other materials covered with a conductive coat.

After deposition, the coating is optionally rinsed with water and cured at elevated temperature. For such curing, temperatures of from 130 to 220"C, preferably 150 to 1900C may be used. Curing time is generally from 5 to 30 minutes, preferably 10 to 25 minutes.

The following Examples illustrate the invention, without limiting its scope: Partial Component A 1: 400 g of linseed oil, 0.1 g of N,N'-diphenyl-p-phenylene diamine and 100 g of maleic anhydride are heated to 200 C, while stirring and in the presence of an inert gas; the temperature is maintained for about 3 hours. After cooling to 1500C, 0.2 g of 2,6-di-tertiary-butyl-4-methyl-phenol and 65 g of N,N'-diethylaminopropylamine are added slowly, while refluxing. The batch is reheated to 200"C, and about 8 g of water is formed. At 1200C, the batch is diluted with 62 g of ethyleneglycol monoethylether acetate. At 90"C, while refluxing, 15 g of methanol are slowly added. The acid value of the resin solids is about 47 mg KOH/g. The reaction mass is further diluted with 318 g of ethyleneglycol monoethyl ether acetate and 0.74 ml of stannous dibutyldilaurate are added.

At 60"C 195 g of the urethane compound described below are added and the blend is heated to 140"C. The acid value of the resin solids drops to about 20 mg KOH/g within 2 hours. At the end of the reaction, the resin solution is cooled. The Gardner viscosity of a solution of 6 g of reaction mass and 4 g of ethyleneglycol monoethylether acetate is K. The amine value of the resin solids is 45 mg KOH/g (DIN 53 176), the acid value 19.4 mg KOH/g, and the solids content of the resin solution is 60%. The urethane compound used above was prepared from 174 g of toluene diisocyanate (isomer blend of 80% of 2,4-diisocyanate and 20% of 2,6-diisocyanate), 60 g of isopropanol and 156 g of ethyleneglycolmonoethylether acetate by reaction at 600C until an NCO-value of 18 is obtained.

Determination of the NCO-value: About 2 g of the sample are exactly weighed into a dry Erlenmeyer flask and dissolved in toluol with gentle heating. Exactly 10 ml of reaction solution (prepared by dissolution of 0.5 moles of diisobutylamine in 940 ml of toluol) is added with a pipette. After 3 minutes of reaction time at room temperature a few drops of bromophenol blue indicator (methanol solution) are added and the sample is titrated with 0.5 N alcoholic HCI until the colour turns yellow. A blank test is made the same way.

B = consumption 0.5 N HCl for blank test V = consumption 0.5 N HCI of sample A = theoretical consumption of 0.5 N HCI for neutralisation of the basicity of the resin E = weigh-out in g B-V+A NCO - value: E Partial Component A 2: 500 g of a liquid polybutadiene the viscosity of which is about 900 mPas at 45"C, and more than 90% of the double bonds of which are in the 1,2-vinyl configuration, are heated together with 0.1 g of N,N'-diphenyl-p-phenylene diamine and 100 g of maleic anhydride to 200"C while stirring and in the presence of an inert gas, and are held at this temperature for about 4 hours. At 1500C while refluxing, 68 g of N,N'-dimethylaminopropylamine and 0.25 g of 2,6-di-tertiary butyl-4-methylphenol are slowly added. The batch is reheated to 200"C and the water formed is removed with the aid of azeotropic distillation with toluol for a period of about 1 hour, after which time water formation is essentially finished. At 1300C, the batch is diluted with 166 g ethylene glycol monoethylether acetate and, at 90"C, while refluxing, 10 g methanol are added.

The batch is diluted with ethylglycol acetate to a solids content of 66% and, at 1200C, while refluxing, 0.7 g of stannous dibutyl dilaurate and 253 g of the urethane compound described below are added. The acid value of the resin solids falls from the initial value of about 20 mg KOII/g to 10 - 16 mg KOH/g within a period of 2 hours at 1200C. The reaction product is cooled and diluted to 60% with ethylene glycol monoethylether. The amine value of the resin solids is about 50 mg KOH/g.

The urethane compound used in this reaction was prepared from 174 g of toluene diisocyanate (isomer blend), 0.3 g of stannous dibutyldilaurate, 203 g of water-free ethylglycol acetate and 130 g of ethyl acetoacetate by reaction at 1200C until an NCO-value of 16 was reached.

Partial Component A 3: 380 g of a liquid polybutadiene with an average molecular weight of 1500, a viscosity of 7 poise at 25"C and a structure with about 20% of 1,2-vinyl configuration, 40% 1,4-trans- and 40% 1,4-cis-configuration, are heated to 2000C together with 0.1 g of N,N'-diphenyl-pphenylene diamine and 100 g of maleic anhydride, while stirring and under an inert gas atmosphere. After 3 to 4 hours no free maleic anhydride can be traced. At 1500C, 0.19 g of 2,6-ditertiary butyl-4-methylphenol and 78 of N,N'-diethylaminopropylamine are added.

The batch is heated to 200 C and water elimination is aided by azeotropic distillation with toluene. When water formation is complete the entraining agent is distilled off under vacuum. At 120 C, the batch is diluted with 140 g of ethylglycolacetate and, for the alcoholysis of the remaining anhydride, 30 g of n-butanol are added. The acid value of the non-volatile substance of the resin is about 40 mg KOH/g.

At 100"C, 110 g of the urethane compound described below are slowly added, 0.65 g of stannous dibutyldilaurate are also added and the batch is heated to 1200C. The acid value falls to 18 - 20 mg KOH/g. The amine value of the resin solids is 53 mg KOH/g (DIN 53 176). The solids content of the resin solution is adjusted to 55% with ethyleneglycol monoethyl ether.

The urethane compound used in the above reaction was prepared from 174 g of toluene diisocyanate (isomer blend), 113 g of e-caprolactam and 191 g of ethylene-glycol monoethyl ether acetate by reaction at 60"C, until an NCO-value of 15 was obtained. The content of urethane compound is about 60%.

Partial Component A 4: Half of the linseed oil of Partial Component A 1 is replaced by the same quantity of a liquid poly-1,3-pentadiene with a molecular weight of about 1000 and a viscosity of 300 Poise/300C. The component is prepared the same way as Partial Component A 1.

Partial Component A 5: 400 g of a liquid polybutadiene with a viscosity of 800mPas at 200C, an iodine number of 450 g/100 g, with 70% of 1,4-cis and 28% of 1,4-trans configuration, is heated to 200"C together with 0.1 g of N,N'-diphenyl-p-phenylene diamine and 100 g of maleic anhydride, while stirring and under an inert gas atmosphere. The batch is held at this temperature for about 3 hours. After cooling to 1500C, while refluxing, 0.2 g of 2,6-ditertiary butyl-4methylphenol and 26 g of N,N'-diethylaminopropylamine are slowly added. The batch is reheated to 2000C, about 3 g of water being formed, which is eliminated.

At 1200C, the batch is diluted with 134 g of ethyleneglycol monoethyletheracetate. At 90"C, while refluxing 14 g of distilled water are slowly added. The acid value of the resin solids is about 145 - 155 mg KOH/g. The reaction mass is further diluted with 224 g of ethyleneglycol monoethylether acetate; 0.7 ml of stannous dibutyldilaurate are added.

At 1200C, 253 g of the urethane compound described below are slowly added and the batch is heated to 140"C. The acid value of the resin falls within 2 hours to about 90 mg KOH/g. At the end of the reaction, the resin solution is cooled. The viscosity of a solution of 6 g reaction mass and 4 g of ethylene glycol monoethylether acetate is M-N Gardner. The amine value of the resin solids is 16 mg KOH/g (DIN 53176), the solids content of the resin solution is 60%.

The urethane compound used for the reaction was prepared from 174 g of toluene diisocyanate (isomer blend of 80%of 2,4 diisocyanate and 20% of 2,6-diisocyanate), 130 g of 2-ethylhexanol and 203 g of ethyleneglycol monoethylether acetate through reaction at 60"C until an NCO-value of 14 is obtained.

Partial Component A 6: 400 g of a polybutadiene oil with a molecular weight of 1400 and a structure of about 75% 1,4-cis and about 25% of 1,4-trans configuration are reacted with 100 g maleic anhydride and 4 g of a copper naphthenate solution with a metal content of 9% at 200"C, until the content of free maleic anhydride has fallen below 1%. The viscosity of a solution of 72 g of adduct and 48 g of ethyleneglycol-monoethylether acetate is about 80 seconds (DIN 53 211), and the acid value 200 mg KOH/g. The temperature is then reduced to 1200C and the batch is diluted with 50 g of diacetone alcohol. At 100"C, the adduct is semi-esterified with methanol. When the acid value has reached a constant level, the solids content is adjusted to 70% with about 170 g of isopropylalcohol. The acid value of the resin solids is about 90 mg KOH/g.

Partial Component A 7: 500 g of linseed oil are reacted with 100 g maleic anhydride in the resence of 5 g of a copper naphthenate solution - containing 9% copper metal - at 2000C for about 5 hours, until no free maleic anhydride can be traced. The viscosity of a solution of 80 g of the adduct and 40 g of ethylene glycol monoethylether acetate is about 50 seconds (DIN 53211).

At 90"C, 20 g of water are slowly added and then 2 g of triethylamine. The reaction mass is held for 3 hours at between 90 to 100"C and then slowly diluted with isopropanol to a solids content of 80%. The acid value of the binder solids is 145 - 160 mg KOH/g.

Partial Component B 1: 950 g of a commercially available bisphenolglycidyl ether with an epoxy equivalent weight of 950 - 1000 are heated with 192 g of ethyleneglycol monoethylether acetate to 100"C, while stirring and held, until a homogeneous solution has formed. Then, 98 g tall oil fatty acids and 1 g of triethylamine are added and the batch is heated to 1300C, until the acid value is below 1 mg KOH/g. At 100"C 44 g of diethylamine are slowly added while refluxing. The batch is reheated to 1300C and stirred for another hour at this temperature.

The viscosity of a solution of 55 g of reaction mass and 45 g of ethylglycol is N, Gardner.

The batch is diluted with 45 g of ethyleneglycol monoethylether. At 80"C 186 g of a bisphenolresol, 65%, is added which is prepared by alkaline condensation of 1 mole bisphenol and 4 moles of formaldehyde. After 5 hours of reaction time at 80"C, the batch is diluted with ethyleneglycol monoethylether to a total solids content of 70%. The amine value of the non-volatile portion is 28 mg KOH/g, the viscosity of a solution of 10 parts by weight of reaction product and 5 parts by weight of ethyleneglycol monoethylether is K, Gardner.

Partial Component B 2: 475 g of an available bisphenol glycidylether with an epoxy equivalent weight of 450 - 500 are dissolved homogeneously in 96 g of ethylene glycol monoethyl ether acetate at 100"C, while stirring. Then 22 g of acrylic acid, 0.022 g of hydroquinone and 1 g of triethylamine are added and reacted at 1300C, until an acid value of 1 mg KOH/g is reached. At 100"C 52 g of diethanolamine are added and the batch is held at 1300C for 1 hour.The batch is diluted with ethylene glycol monoethyl ether acetate to a solids content of 78% and is reacted at 80"C for 5 hours with 61 g of an available methylolphenolallyl ether (viscosity 30 Poise at 25"C). The batch is futher diluted to 60% solids with ethylene glycol monoethyl ether acetate and at 60"C 217 g of the urethane compound described below are added, together with 0.74 g of stannous dibutyldilaurate. The reaction is carried out at 800C until an NCO-value of zero is attained.

The reaction product has a solids content of 60%, the amine value is 38 mg KOH/g (DIN 53 176) for the non-volatile portion.

The urethane compound used in this reaction was prepared from 174 g of toluene diisocyanate (isomer blend) and 87 g methylethylketoxime and 174 g of ethylene glycol monoethyl ether acetate, the oxime being added at 30"C and the reaction being finalized at 60"C, until an NCO-value of 17 is attained.

Partial Component B 3: 103 g of diethylenetriamine and 220 g of methylisobutylketone are heated to boiling temperature in a reaction flask equipped with reflux condenser and a water separator, until about 36 ml of water have separated. After distillation of the surplus ketone, about 270 g of the diketimine of diethylenetriamine are obtained.

In another reaction vessel equipped with stirrer and thermometer, 475 g of an available bisphenolglycidyl ether with an epoxy equivalent weight of 450 - 500 are dissolved homogeneously at 100"C in 126 g of ethylene glycol monoethyl ether acetate. Then 140 g of dehydrated castor oil fatty acid and 1 g triethylamine are added and reacted at 1200C, until the acid value has fallen below 1 mg KOH/g. At 90"C, 123 g of the above ketimine are added and the batch is heated to 1300C. A sample of the reaction mass, with a little ethylene glycol monobutyl ether and acetic acid, is clearly soluble in water. The viscosity of a solution of 4 g of reaction mass and 6 g ethylene glycol monoethyl ether is L, Gardner.

The batch is cooled to 90"C and 32 g water and 100 g of ethylene glycol monoethyl ether are added. A resin solution with 70% solids content is obtained. The amine value of the non-volatile portion is about 80 mg KOH/g.

Partial Component B 4: 500 g of linseed oil are reacted with 100 g maleic anhydride at 200 C in the presence of 5 g of a copper naphthenate solution with 9% Cu, until the content of free maleic anhydride has fallen below 1%. The viscosity of a solution of XO g of adduct and 4í) g Or ethylene glycol monoethyl ether acetate is about 50 seconds (DIN 53211), the acid vilie 17() mg K()l l/g.

At 150 C. 130 g of diethylaminopropylamine are added over one hour and the batch is held at 180 C. until the total quantity of amine has reacted. After cooling lo 120 C, the solids content is adjusted to 80% with 175 g of ethylene glycol monoethyl cllicr. (Amine number 80 mg KOH/g).

Examples 1 - 7: The partial components are blended as listed in Table 1. The quantities refer to resin solids.

TABLE 1 Partial Components ratio amine value acid value Example 1 50 A 1 50 B 1 79 21 Example 2 60 A 2 40 B 3 89 11 Example 3 40 A 3 60 B 2 85 15 Example 4 30 A 4 70 B 3 92 8 Example 5 20 A 5 80 B 4 79 21 Comparison Example 6 20 A 6 80 B 4 78 22 Example 7 10 A 7 90 B 2 70 30 Example 8: At reflux temperature, 238 g of dimethylaminomethylmethacrylate, 24 g of acrylic acid, 410 g of 2-ethylhexylacrylate, 340 g of styrene are copolymerised in 1000 g of ethylene glycol monoethyl ether acetate in the presence of 20 g of dodecylmercaptan and 20 g of azodiisobutyronitrile, until the solids content has reached 48.4%.

The amine value of the copolymer, on resin solids, is about 84 mg KOH/g, the acid value about 18 mg KOH/g. At 80 C, 124 g of the urethane compound described below are added and the temperature of 80 C held, until the NCO-value reaches zero and the resin solution has become water dilutable upon neutralisation with acids. The solids content of the resin solution is 51%, the amine value of the resin solids is about 75 mg KOII/g, the acid value about 8 mg KOH/g (base - acid ratio 90 10 mg KOH/g).

The urethane compound used in this reaction was prepared from 222 g isophorone diisocyanate and 13U g 8-hydroxy-ethylmethacrylate, in the presence of 1.3 g of hydroquinone, by reaction at 80 C, until the NCO-value was 12.

Evaluation of the Binders: Each 100 g of the listed binders, resin solids, were mixed with the required quantity of acid and, while stirring, made up to 1000 g with deionized water. From the 10% solutions, steel panels wired as cathodes were coated electrophoretically. The deposition time was 60 seconds in all cases. The coated substrates were rinsed with deionized water and cured at elevated temperature. The average film thickness of the cured films was, from 13 to 17 llm.

Table 2 gives the compiled results.

TABLE 2 Neutralisation Deposition Evaluation 1) 2) 3) 4) 5) Resistance 8) Quantity Type pH Volt Cure Hardness Inden- Throwing min/ C tation Power 6) 7) (cm) 1 3.4 M 6.3 270 30/200 200 8.5 800 500 18.8 2 1.2 A 6.5 300 20/180 180 8.0 600 450 19.2 3 3.0 E 6.0 270 20/160 150 8.2 1000 500 17.3 4 2.9 A 5.8 230 20/170 170 6.5 500 450 16.2 5 6.8 M 5.5 260 30/190 180 7.3 800 500 16.0 6* 6.8 E 6.0 230 20/180 175 7.9 480 360 13.0 7 3.8 E 5.6 260 30/190 190 7.4 700 420 17.1 8 6.8 M 5.6 280 30/180 175 7.7 800 400 15.5 * Comparison example Key to Table 2 1) Quantity of acid in g for 100 g resin solids 2) E: acetic acid 80%, aqueous) M: lactic acid 80%, aqueous) A: formic acid (80%, aqueous) 3) measured on a 10% aqueous solution 4) König pendulum hardness, DIN 53 157 (seconds) 5) Erichsen indentation DIN 53 156 (mm) 6) hours of water soak at 400C until blistering and corrosion become visible 7) ASTM-B-117-64 salt spray: 2mm of corrosion at the cross incision after the recorded hours. For this test degreased non-pretreated steel panels were coated with a pigmented paint containing 100 parts by weight of resin solids, 20 parts by weight of aluminium silicate pigment and 2 parts by weight of carbon black.

8) Determination of Throwing Power: A plastic cylinder of 400 mm height and 60 mm diameter is filled with 1 litre of paint. In a distance of about 1 mm from the bottom of the cylinder a steel disc is mounted as anode, having a diameter of 53 mm. The cathode is a square hollow bar with the dimensions: 300 mm length and 10 mm of clear width, having fixed inside in diagonal position a steel strip of 300 x 14 x 3 mm. The cathode is immersed into the paint to a length of 270 mm. Paint temperature is 25"C. During deposition, the temperature should not rise by more than 1 or 2"C. Deposition is carried with constant voltage for 3 minutes. The deposition voltage is chosen such that substantially no over-deposition is effected at the outside of the cathode square.After deposition the steel strip is removed from the cathode and rinsed with tap water. The film is cured in an air circulation oven for 30 minutes at 1800C. The visible length of deposition on the strip is recorded as the "throwing power".

WHAT WE CLAIM IS: 1. A binder for use in the production of cathodically depositable water dilutable coating compositions which comprises a macromolecular component containing basic nitrogen groups and acidic groups, or, in physical admixture or chemically combined, a macromolecular component containing basic nitrogen groups and a macromolecular component containing acidic groups, such that the ratio of the amine number to the acid number of the binder is from 97 : 3 to 65 : 35, the reactive group of at last one of the said components present in the binder being modified by reaction with a compound of formula OCN - R t NH -CO - R' ] n (I) (wherein R is an aliphatic hydrocarbon radical or an aromatic or cycloaliphatic nucleus optionally substituted by alkyl groups;R' is a radical obtained by the loss of a reactive hydrogen atom from a saturated or unsaturated alcohol, a phenol optionally substituted by one or more alkyl groups, a cyclic lactam, an aldoxime or ketoxime, an acetoacetic acid ester and/or a hydroxamic acid ester; and n is an integer of from 1 to 3).

2. A binder as claimed in claim 1 wherein the basic groups are formed by condensation of a dicarboxylic acid anhydride with primary/tertiary diamines.

3. A binder as claimed in claim 2 wherein the dicarboxylic acid anhydride comprises a succinic anhydride derivative or a Diels-Alder adduct formed by addition of an a,ss-unsaturated dicarboxylic acid anhydride to a compound containing isolated or conjugated double bonds.

4. A binder as claimed in either of claims 2 and 3 wherein the primary/tertiary diamine comprises dimethylaminoethylamine, diethylaminoethylamine, dimethylaminopropylamine, diethylaminopropylamine or homologues thereof.

5. A binder as claimed in any of the preceding claims additionally containing a reaction product of an epoxy group containing compound with a secondary amine or alkanolamine.

6. A binder as claimed in claim 5 wherein the epoxy group containing compound comprises a polyglycidyl ether of a polyhydric phenol, a novolak resin or an epoxy group containing diene or acrylic copolymer.

7. A binder as claimed in any of the preceding claims wherein the compound of formula I as defined in claim 1 comprises 2,4-toluene diisocyanate, one of the isocyanate groups of which has been blocked with one or more monohydric alcohols, phenols, oximes, cyclic lactams or acetoacetic acid esters.

8. A binder as claimed in any of the preceding claims wherein the basic nitrogen atoms thereof are at least partially neutralised with an organic and/or inorganic acid.

9. A binder as claimed in claim 1 substantially as herein described.

10. A binder as claimed in claim 1 substantially as herein described with reference to

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

Key to Table 2 1) Quantity of acid in g for 100 g resin solids 2) E: acetic acid 80%, aqueous) M: lactic acid 80%, aqueous) A: formic acid (80%, aqueous) 3) measured on a 10% aqueous solution 4) König pendulum hardness, DIN 53 157 (seconds) 5) Erichsen indentation DIN 53 156 (mm) 6) hours of water soak at 400C until blistering and corrosion become visible 7) ASTM-B-117-64 salt spray: 2mm of corrosion at the cross incision after the recorded hours. For this test degreased non-pretreated steel panels were coated with a pigmented paint containing 100 parts by weight of resin solids, 20 parts by weight of aluminium silicate pigment and 2 parts by weight of carbon black.

8) Determination of Throwing Power: A plastic cylinder of 400 mm height and 60 mm diameter is filled with 1 litre of paint. In a distance of about 1 mm from the bottom of the cylinder a steel disc is mounted as anode, having a diameter of 53 mm. The cathode is a square hollow bar with the dimensions: 300 mm length and 10 mm of clear width, having fixed inside in diagonal position a steel strip of 300 x 14 x 3 mm. The cathode is immersed into the paint to a length of 270 mm. Paint temperature is 25"C. During deposition, the temperature should not rise by more than 1 or 2"C. Deposition is carried with constant voltage for 3 minutes. The deposition voltage is chosen such that substantially no over-deposition is effected at the outside of the cathode square.After deposition the steel strip is removed from the cathode and rinsed with tap water. The film is cured in an air circulation oven for 30 minutes at 1800C. The visible length of deposition on the strip is recorded as the "throwing power".

WHAT WE CLAIM IS: 1. A binder for use in the production of cathodically depositable water dilutable coating compositions which comprises a macromolecular component containing basic nitrogen groups and acidic groups, or, in physical admixture or chemically combined, a macromolecular component containing basic nitrogen groups and a macromolecular component containing acidic groups, such that the ratio of the amine number to the acid number of the binder is from 97 : 3 to 65 : 35, the reactive group of at last one of the said components present in the binder being modified by reaction with a compound of formula OCN - R t NH -CO - R' ] n (I) (wherein R is an aliphatic hydrocarbon radical or an aromatic or cycloaliphatic nucleus optionally substituted by alkyl groups;R' is a radical obtained by the loss of a reactive hydrogen atom from a saturated or unsaturated alcohol, a phenol optionally substituted by one or more alkyl groups, a cyclic lactam, an aldoxime or ketoxime, an acetoacetic acid ester and/or a hydroxamic acid ester; and n is an integer of from 1 to 3).
2. A binder as claimed in claim 1 wherein the basic groups are formed by condensation of a dicarboxylic acid anhydride with primary/tertiary diamines.
3. A binder as claimed in claim 2 wherein the dicarboxylic acid anhydride comprises a succinic anhydride derivative or a Diels-Alder adduct formed by addition of an a,ss-unsaturated dicarboxylic acid anhydride to a compound containing isolated or conjugated double bonds.
4. A binder as claimed in either of claims 2 and 3 wherein the primary/tertiary diamine comprises dimethylaminoethylamine, diethylaminoethylamine, dimethylaminopropylamine, diethylaminopropylamine or homologues thereof.
5. A binder as claimed in any of the preceding claims additionally containing a reaction product of an epoxy group containing compound with a secondary amine or alkanolamine.
6. A binder as claimed in claim 5 wherein the epoxy group containing compound comprises a polyglycidyl ether of a polyhydric phenol, a novolak resin or an epoxy group containing diene or acrylic copolymer.
7. A binder as claimed in any of the preceding claims wherein the compound of formula I as defined in claim 1 comprises 2,4-toluene diisocyanate, one of the isocyanate groups of which has been blocked with one or more monohydric alcohols, phenols, oximes, cyclic lactams or acetoacetic acid esters.
8. A binder as claimed in any of the preceding claims wherein the basic nitrogen atoms thereof are at least partially neutralised with an organic and/or inorganic acid.
9. A binder as claimed in claim 1 substantially as herein described.
10. A binder as claimed in claim 1 substantially as herein described with reference to

Examples 1 to 5, 7 and 8.
11. A cathodically depositable water dilutable coating composition comprising at least one binder as claimed in any of the preceding claims.
12. A composition as claimed in claim 11 additionally containing one or more pigments, dyes, extenders, solvents, additional crosslinking agents and/or conventional coating additives.
13. A composition as claimed in claim 11 substantially as herein described.
14. A composition as claimed in claim 11 substantially as herein described with reference to any of Examples 1 to 5, 7 and 8.
15. A method of coating an electrically conductive substrate which comprises contacting said substrate with an aqueous solution of a composition as claimed in any of claims 11 to 14, and passing an electric current through said solution in a manner such that said substrate forms a cathode.
16. A method as claimed in claim 15 substantially as herein described.
17. A method as claimed in claim 15 substantially as herein described with reference to any of Examples 1 to 5, 7 and 8.
18. A substrate coated with a coating composition as claimed in any of claims 11 to 14.