GB1576159A - Cathodically depositable thermosetting resin binders - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO CATHODICALLY DEPOSITABLE THERMOSETTING RESIN 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 and by the following statement: This invention is concerned with improvements in or relating to thermosetting resins. In particular the invention is concerned with the preparation of resins for use in a process of electrodeposition which deposit at the cathode.

In preparing such resins it is necessary to introduce into or form resins possessing basic functional groups which may be neutralised at least partially with inorganic or organic acids.

The introduction of basic functional groups such as, for example, a basic nitrogen atom may be effected by reaction of an epoxy group with a secondary amine as described in German Offenlegungschrift 2603666 or by copolymerisation of an a,ss-unsaturated monomer carrying a basic nitrogen function, with other a,p-unsaturated monomers as described in German Auslegeschrift 2237114. However, both these methods involve the use of reaction components which are not readily available and which moreover are very expensive. Nevertheless cathodically depositable electrodeposition paints possess a number of attractive advantages an important one of which is the avoidance of dissolution of the metallic substrate during deposition.

We have now been able to prepare, with advantage, binders which deposit at the cathode by reacting certain types of hydroxy group containing substances. In particular we have used resinous precondensates and polymers which include a chain of covalently linked carbon atoms thereby rendering the polymer substantially non-saponifiable.

According to the invention there is provided a process for the production of a binder which is water-dilutable upon partial or total neutralisation with an acid which comprises reacting, until an NCO-value of zero or practically zero is obtained, (A) a hydroxyl group containing substance with a hydroxyl number of at least 40 mg KOH/g which is either (i) a polycondensate with an average maximum molecular weight of 5000 or (ii) a diene polymer with an average maximum molecular weight of 4000, and (B) a compound having an average of from 0.8 to 1.5 free isocyanate groups per molecule and at least one basic nitrogen atom bonded to an aliphatic carbon atom.

The cross-linking properties of binders prepared in accordance with the invention may be enhanced by core action of components (A) and (B) with a compound having an average of from 0.8 to 1.5 free isocyanate groups per molecule and from 1 to 3 olefinically unsaturated bonds.

Suitable hydroxy group containing polycondensates may be readily prepared from commercially available raw materials. These are for example hydroxy-rich polyesters obtained by esterification of diols or polyols with monocarboxylic, dicarboxylic or polycarboxylic acids or, where appropriate, their anhydrides. Such polyesters will be resin-like condensates with an average maximum molecular weight of 5000 carrying sufficient free hydroxy groups to give a hydroxy number of at least 40 mg KOH/g and at least 2 ester linkages besides other additional modifications.

Suitable diols or polyols include ethylene glycol, propylene glycol, butane diol, neopentyl glycol, hexane diol, diols derived from 4,4'-dihydroxydiphenyl- 2,2-propane, such as 1,1'isopropylidene-bis -(p-phenylene-oxy)-di- p-ethanol or the corresponding -di-propanol-2-, glycerol, trimethylol propane, trimethylol ethane, pentraerythritol, castor oil and tris hydroxyethylisocyanurate. Other suitable polyols include resin-like polyols such as copolymers of styrene with allyl alcohol, carrying in the molecule an average of 5 hydroxy groups or compounds with latent hydroxy groups such as glycidyl esters or glycidyl ethers.

Suitable polycarboxylic acids and anhydrides include malonic acid, succinic acid, adipic acid, sebacic acid, maleic acid, maleic anhydride, fumaric acid, o-phthalic acid, phthalic anhydride, as well as the isomeric or substituted phthalic acids, trimellitic anhydride, triscarboxyethylisocyanurate and dimerised isolene fatty acids, i.e. dimers of fatty acids containing isolated double bonds. The latter substances being preferably used to increase the molecular weight of the polyester.

Suitable monocarboxylic acids include capronic acid, nonanoic acid, decane acid, sorbic acid, benzoic acid, p-butyl benzoic acid, as well as the unsaturated and saturated fatty acids of the vegetable and animal oils or fats.

Resin-like hydroxy group containing polycondensates may also be modified polyesters which, in addition to requiring two ester linkages also contain urethane groups in the molecule constitution. Additionally the polycondensate may have been copolymerised with an a,p-ethylenically unsaturated compound such as a vinyl compound or a vinylidene compound for example an alkyl acrylate, a hydroxy alkyl acrylate, acrylamide, acrylonitrile, the copolymerisation may be carried out in the usual manner in the presence of solvents and initiators forming radicals. In particular, copolymerisation may be used to modify hydroxy group containing resin-like polycondensates containing unsaturated fatty acids. By the term hydroxy groups containing resin-like polycondensates we mean such modified substances as may be obtained by condensation at elevated temperature of heat-reactive phenolic resins with unsaturated fatty acid esters.

Other suitable polyesters are obtained by condensation of substances carrying, preferably, aliphatic chain end carboxy groups and amino alcohols such as trishydroxymethyl amine to yield substances with oxazoline rings and containing free hydroxy groups.

Unsaturated polymers of dienes with free hydroxy groups suitable for use in the process according to the invention include copolymers of alkane dienes or cycloalkanedienes with hydroxy group containing monovinyl compounds and optionally subordinate quantities of other monovinyl compounds. Suitable diene compounds include 1,3-butadiene, 1,3pentadiene, cyclopentadiene and isoprene. Suitable hydroxy group containing monovinyl compounds are allyl alcohol or hydroxy alkyl esters or hydroxyalkylene oxide esters of acrylic or methacrylic acid.

Hydroxyl groups which are generally at the chain end may also be introduced to diene polymers by the reaction of so called "living polymers" with alkylene oxides, preferably ethylene oxide.

A group of diene polymers with latent hydroxy groups are epoxidation products of diene polymers. The products may be prepared by treatment of liquid diene polymers with per-formic acid or per-acetic acid.

An oxirane group is considered to be a latent hydroxy group because a hydroxy group is set free upon reaction with compounds carrying an active hydrogen atom. This reaction can be carried out at temperatures of up to 150C either with monocarboxylic acids or saturated or unsaturated fatty acids such as benzoic acid, p-t.butylbenzoic acid and sorbic acid and may optionally be accelerated by alkaline catalysts.

Another possibility of setting free hydroxy groups from partially epoxidised diene polymers being of advantage for the products produced according to the invention is to react an epoxy group with secondary alkylamines or secondary alkanol amines, such as diethylamine, diethanolamine and diisopropylamine. The introduction of the nitrogen atom into the polymer chain increases the basic character of the macromolecule in the desired way.

The secondary hydroxy group formed on opening the oxirane ring reacts with the isocyanate containing components in the process according to the invention.

The hydroxy group containing substances described above are reacted in the process according ot the invention with a compound possessing at least one basic nitrogen atom and having an average of from 0.8 to 1.5 isocyanate groups per molecule. Preferably the compound contains an average of about one isocyanate group per molecule.

Such compounds may be prepared in a separate step by reacting diisocyanates or polyisocyanates with less than a stoichiometric quantity of an amine of the general formula

wherein R is a hydroxyalkyl radical and R1 and R2 which may be the same or different are alky 1 or cycloalkyl groups. Dialkylalkanol amines are preferred such as dimethyl ethanolamine, diethylethanolamine or higher homologues and isomers.

Suitable di- or polyisocyanates are aromatic isocyanates such as 2,4- or 2,6-tolylene diisocyanate or mixtures thereof, 4,4'-diphenyl- methanediisocyanate or cycloaliphatic isocyanates such as isophorone diisocyanate, cyclohexane-1,4- diisocyanate, as well as aliphatic isocyanates, such as trimethylhexamethylene -1,6-diisocyanate and trishexamethylene- triisocyanate.

The reaction between the amine and the di- or polyisocyanate may be carried out at from 0 to 800C, preferably at from 20 to 50"C. The weight ratios of the reaction partners are so chosen that the compound formed has from 0.8 to 1.5, preferably one free isocyanate group.

This product is referred to below as "basic isocyanate intermediate".

As mentioned above the thermal cross-linking reaction of the cathodically deposited film may be enhanced by the use of compounds having from 0.8 to 1.5 free isocyanate groups in the molecule and from 1 to 3 olefinically unsaturated double bonds. These compounds are prepared in a separate reaction step from the aforementioned di or polyisocyanates and reaction partners which carry at least one isocyanate reactive hydrogen atom and from 1 to 3 olefinic double bonds. Suitable such unsaturated compounds include hydroxyalkyl esters of acrylic or methacrylic acid, triethyleneglycol monoacrylate or monomethacrylate, trimethylolpropanediacrylate or dimethacrylate, allyl alcohol, tripropyleneglycol monoabietate, oleyl alcohol or linoleyl alcohol.

The reaction between the diisocyanate or polyisocyanate and the isocyanate reactive olefinically unsaturated compound may be carried out in isocyanate inert solvents at temperatures of from 10 to 100 C, preferably from 50 to 80"C, if desired in the presence of catalysts, for example organic stannous compounds. The weight ratios of the reaction partners are chosen such that the formed compound carries from 0.8 to 1.5, preferably one free isocyanate group in the molecule. The compound is referred to below as "olefinically unsaturated isocyanate intermediate".

The process of the present invention may be effected by dissolving the hydroxy-group containing substance in an isocyanate-inert solvent and effecting the reaction at from 10 to 100"C, preferably from 50 to 80"C, with the chosen quantity of basic isocyanate intermediate. The reaction may be effected with the conjoint use of an olefinically unsaturated isocyanate intermediate and optionally in the presence of catalysts, for example organic stannous compounds, until an NCO-value of 0 or practically 0 is obtained.

The quantity of basic isocyanate intermediate is desirably chosen such that the basicity of the binder upon partial or total neutralisation with an acid is such to give sufficient water dilutability at a pH-value of from 4 to 9, preferably 6 to 8. The reaction between the hydroxy group containing substance, the basic isocyanate intermediate and the olefinically unsaturated intermediate may be effected in random sequence, separately or jointly.

In order to reduce the stoving temperatures or in order to obtain a particular corrosion protection it is optionally of advantage to coemploy additional known crosslinkers, such as melamine-, urea-, benzoguanamine-, acetoguanamine,- phenol-formaldehyde condensates.

Such resins are prepared according to known methods by alkaline condensation of formaldehyde or of formaldehyde-splitting substances with urea, melamine, benzoguanamine, acetoguanamine, phenol, cresol, p-t-butylphenol or Bisphenol A. The methylol compounds may be optionally etherified with alcohols. A preferred product in this group is a reaction product of phenol with formaldehyde carrying allyl ether groups in addition. If the crosslinkers are non-water-soluble, it is advantageous to combine them by careful condensation with the binder of the invention at temperatures of from 50 to 1200C. The reaction is carried to excellent dilutability with water of the reaction mass upon neutralisation with low molecular weight organic acids.

The basic nitrogen atoms of the coating compositions of the invention are partially or totally netutralised with organic and/or inorganic acids. The degree of neutralisation in the individual case depends upon the properties of the binder used. In general that much acid is added to allow dispersion or dilution with water at a pH-value of the coating of from 4 to 9, preferably of from 6 to 8.

The concentration in water of the binder depends upon the parameters of electrodeposition and may be from 3 to 30%, preferably from 5 to 15% by weight. The applied coating composition may contain various additives such as pigments, extenders and surface active agents.

Upon electrodeposition the binder of the invention as a vehicle of the aqueous coating composition is wired to a conductive anode and cathode, the surface of the cathode being coated with the coating composition. The conductive substrates to be coated may be of a variety of materials, preferably metals such as steel, aluminium or copper, although other metalised materials or materials rendered conductive through a conductive coating may also be used.

After deposition, the coating may be cured at a stoving schedule of from 130 to 2000C, preferably 150 to 1800C for about 5 to 30 minutes, preferably 10 to 25 minutes.

The following examples illustrate the invention withuout limiting the scope of it: Preparation of the intermediates; (A) Hydroxy groups containing polycondensates having an average maximum molecular weight of 5000 in accordance with component A(i) of the invention Intermediate (A 1) 79g of isononanoic acid, 89g of tall oil fatty acids, 102g of pentaerythritol, 45g of trimethylolpropane and 120g of isophthalic acid are charged to a three-neck flask equipped with a Dean and Stark receiver, reflux condensor and inert gas charge and are heated to 230"C with stirring. As soon as the acid value has fallen to below 12 mg KOH/g, azeotropic solvent cook with xylene is started. When the acid value has fallen to below 3 mg KOH/g and the quantity of reaction water has attained 42g, the solvent is vacuum-stripped at falling temperature. The finished Intermediate A 1 has a solids content of at least 99%, an intrinsic viscosity of 6 ml/g (measured in dimethylformamide at 20"C) and a hydroxyl number of 250 mg KOH/ g.

Intermediate (A 2) In the apparatus described above 300 g of tung oil are heated to 1000C. At this temperature a blend of 0.5g of potassium hydroxide in 0.5g of monoethylene glycol is added. The temperature is raised to 1600C and 48g of pentaerythritol and 48g of trimethylolpropane are added. The temperature is now raised to 2200C and held, until solublility in ethanol remains constant. The temperature is reduced to 800C and 113g of a heat-reactive phenolic resin (prepared in alkaline solution from p-t-butylphenol and formaldehyde) are added slowly.

The reaction is finished, if the viscosity of a solution of 72g of Intermediate A 2 and 48g of ethylene glycol monoethyletheracetate has attained a value of about 100 s (DIN 53 211). The hydroxyl number of the phenolmodified polyester is 280 mg KOH/g.

Intermediate (A 3) 220g of a copolymer of styrene and allylalcohol with a hydroxyl number of 250 mg KOH/g are heated to 220"C together with 140g of tall oil fatty acid. As soon as the acid value has fallen below 12 mg KOH/g, the reaction water is eliminated by azeotropic distillation with xylene and, when the acid value reaches 3 mg KOH/g, the xylene is vacuum-stripped with falling temperature. The solids content of Intermediate A 3 is a minimum of 99%, the hydroxyl number is 80 mg KOH/g.

Intermediate (A 4) 300 g of dehydrated castor oil and 60g of linseed oil are heated to 1500C while stirring.

With vigorous stirring, at this temperature, a blend of 80g vinyltoluene and 0.8g of di-t-butyl peroxide is continuously added. Within one hour the temperature is raised to 200"C and held, until 90% of monomer has reacted. At falling temperature, the excess vinyltoluene is vacuum-stripped and the temperature is reduced to 1800C. 1 17g of trimethylolpropane, 1g of calcium naphthenate, (4%) and solution of 0.5g of potassium hydroxide in 0.5g of monoethylene glycol and are now added. After this addition the temperature is raised to 240"C and the reaction is ended, if the solubility in n-butanol remains constant. The vinylated polyester has a hydroxyl number of 245 mg KOH/g.

Intermediate (A 5).

In a round flask equpped with stirrer, thermometer, reflux condensor and Dean and Stark receiver 485g of dimethylterephthalate and 555g of neopentylglycol are charged and slowly heated to 1700C - 200"C while stirring. At this temperature the reaction is carried on until the theoretical quantity of methanol has distilled. 645g of adipic acid are then added and, using xylene as entraining agent, the reaction is carried on at 170 to 2000C until an acid value of 131 mg KOH/g is obtained. Then, at 150 to 1600C, 415g of trishydroxymethyl aminomethane are added the temperature is raised to 170 to 1900C and held, until an acid value of below 1 mg KOH/g is attained. The reaction product is diluted at 1200C with ethyleneglycolmonoethyletheracetate to a solids content of 75% and has a hydroxyl number of 224 mg KOH/g.

(AA) Hydroxyl groups containing diene polymers having an average molecular weight of 4000, in accordance with component A(ii) ofthe invention.

Intermediate (AA 1) Commercially available liquid polybutadiene with a hydroxyl number of 67 mg KOH/g, a molecular weight of about 1400 and a microstructure of about 90%1,2-vinyl- and about 10% of 1,4-trans configuration.

(Polybutadiene G 1000 of Nippon Soda Co. Ltd.) Intermediate (AA 2) A commercially available liquid polybutadiene with a hydroxyl number of 47 mg KOH/g, a molecular weight of about 2800 and a microstructure of about 20% 1,2-vinyl-, about 60% of 1,4-trans and about 20%1 ,4-cis-configuration.

(Polybutadiene R 45 HT of Arco Chemical Comp.) Intermediate (AA 3) In a three-neck flask equipped with stirrer, inert gas duct and reflux condensor, 1 000g of an epoxidised polybutadiene (1) are heated to 1000C and mixed with 885g of p-t-butylbenzoic acid and 2g of triethylamine. The temperature is raised to 180"C and the reaction is carried to an acid value of below 3 mg KOH/g. The hydroxyl number of the end product is about 200 mg KOH/g.

(1) The epoxidised polybutadiene has a molecular weight of about 1500, an epoxy equivalent of about 160, and a microstructure of 75% of 1,4-cis and 25% of 1,4-trans configuration.

Intermediate (AA 4) 1 000g of the epoxidised polybutadiene used for intermediate (AA 3) are heated to 1 800C over a period of 3 hours together with 525g of diethanolamine, under reflux and inert gas protection. After another three hours at this temperature, 95% of the amine used have reacted. A product with a hydroxyl number of about 600 mg KOH/g results.

(B) Basic isocyanate intermediates Intermediate Bl) 174g of tolylene diisocyanate (a blend of 80%of 2,4- and 20%of 2,6-isomers) are charged to a three-neck flask equipped with reflux condensor and inert gas duct, and, with absolute protection from moisture and effective cooling 89g of dimethylethanolamine (60% in ethyleneglycolmonoethylether acetate) are continuously added. The reaction temperature must not surpass 25"C. The reaction is finished, if the theoretical isocyanate value of 16% is obtained or underpassed.

Intermediate (B 2) 174g of tolylene diisocyanate (a blend of 80% of 2,4-and 20% of 2,6- isomers) are mixed with 1 94g of ethylene glycolmonoethylether acetate in a three-neck flask equipped with reflux condensor and inert gas duct. Access of moisture is absolutely prevented. With intense cooling, 11 7g of diethylethanolamine are added continuously over a period of 1 hour at a temperature of below 25"C. The isocyanate value of the final product is 14.4%.

(C) Olefinically unsaturated isocyanate intermediates Intermediate (C I) 168g of hexamethylene diisocyanate are mixed with 200g of ethyleneglycolmonoethylether acetate in a three-neck flask equipped with reflux condensor and inert gas duct and total prevention of moisture acess and are heated to 600C. At this temperature a blend of 130g of hydroxyethylmethacrylate, stabilised with 0.1g of hydroquinone, are added dropwise. After about 2 hours the reaction is finished, if the isocyanate value has attained 14.1% or slightly less.

Intermediate (C 2) In a three-neck flask equipped with reflux condensor and inert gas duct, with no possible access of moisture, 222g of isophorone diisocyanate are blended with 325g of ethylene glycol monoethylether acetate and heated to 40"C. 265g of linoleyl alcohol are added continuously and, after the end of the addition, the temperature is raised to 900C and held, until the isocyanate value has attained 8.6%.

Examples 1-11 In a reaction vessel equipped with stirrer, addition funnel, thermometer and reflux condensor, the hydroxy-rich polycondensate (Intermediate A) or diene polymer (Intermediate AA), optionally in the presence of siocyanate inert solvents such as ethylene glycol monoethylether acetate, is blended with the basic isocyanate intermediate (Intermediate B) while preventing access of moisture, and is reacted completely at 40 to 1000C. Subsequently, the reaction product is, if desired mixed with an a,P-olefinically unsaturated isocyanate intermediate (Intermediate C) and reacted, also at from 40 to 100"C, until an NCO-value of 0 or practically 0 is obtained.

The reaction of Intermediate A or AA with Intermediate B and Intermediate C may also be effected in one reaction step at from 40 to 100"C, with little affect on the results obtained.

It is also possible, to blend the described reaction products with crosslinkers, such as urea resins, melamine resins or phenol-formaldehyde resins. It is of advantage to carefully react with the cross-linker until substantial water solubility is attained.

The quantities of Intermediates used and the reaction conditions employed are set out in Table 1.

Table I

Intermediates (g) +) Crosslinkers (g) +) Reaction Conditions h/ C 1 1000 A 3 440 B 1 - - - - 1/40 2 1000 A 2 440 B 1 203 C2 342 BP - - 2/50++) 3 1000 A 1 485 B 2 - - - - 4/40 4 1000 A 1 440 B 1 203 C2 - - 357 PA 3/60+++) 5 1000 A 4 485 B 2 125 C1 - 342 ML - 3/80++) 6 1000 A 5 395 B 1 455 C1 - - - 2/70+++) 7 1000 A 5 395 B 1 317 C 1 - - - 2/70+++) 8 1000 AA1 485 B 2 - - - - 1/55 9 1000 AA2 352 B 1 - - - - 1/40 10 1887 AA3 485 B 2 249 C1 580 BP 0 1/80++) 11 1525 AA4 220 B 1 253 C2 - - 452 PA 3/60+++) All quantities refer to resin solids ++) Reactions with Intermediates B and C performed sequentially.

+++) Simultaneous reaction with Intermediates B and C Key to abbreviations in Table 1: BP: Bisphenol A-formaldehyde resin ML: Melamine-formaldehyde resin PA : Phenol-formaldehyde resin with allyl ether groups ("Methylon" 75108 of General Electric -the word "Methylon" is a registered Trade Mark).

Evaluation of the binders 100g resin solids samples of each of the binders were mixed with the corresponding quantity of acid and made up to 1000g with deionised water while stirring. The 10%solutions were deposited with direct current on steel panels as cathode. Deposition time in all cases was 60 seconds. The coated substrates were rinsed with deionised water and cured at elevated temperature. Average film thickness of the cured films was from 13 to 17 ill. Table 2 gives a summary of the results obtained on assessment of the products.

TABLE 2

Neutralisation Deposition Evaluation Quantity1) type 2) p Volt cure hardness 4) inden5) resismin/ C tation tance6) 7) 1 3.5 E 5.8 150 20/190 160 7.9 320/240 2 3.8 M 6.2 180 30/180 165 7.1 360/120 3 4.0 M 6.0 200 25/180 170 8.0 360/240 4 3.8 E 6.0 250 25/180 185 8.5 480/360 5 3.6 E 5.9 230 30/170 175 7.9 360/240 6 4.0 E 6.1 180 30/180 170 8.4 400/240 7 3.9 M 6.0 190 30/180 180 8.8 400/200 8 3.8 E 6.0 190 20/190 165 7.8 320/120 9 3.5 M 5.8 180 30/180 155 7.2 320/240 10 4.0 M 6.2 240 30/170 185 8.1 320/360 11 3.8 E 6.0 220 25/180 170 8.3 480/360 l) quantity of acid in g added to 100g of resin solids 2) E: acetic acid, M: lactic acid 3) measured on a 10% aqueous solution 4) Knig pendulum hardness DIN 53 157 (sec) 5) Erichsen identation DIN 53 156 (mm) 6) hours of water soak at 40"C until corrosion or blistering become visible 7) salt spray ASTM-B 117-64: 2mm of corrosion at the cross incision after the stated hours For this test degreased non-pretreated steel panels were coated with a pigmented paint consisting of 100 parts by weight of resin solids, 20 parts by weight of aluminium silicate pigment and 2 parts by weight of carbon black.

Claims (31)

WHAT WE CLAIM IS:

1. A process for the production of a binder which is water-dilutable upon partial or total neutralisation with an acid which comprises reacting, until an NCO-value of zero or practically zero is obtained, (A) a hydroxyl group containing substance with a hydroxyl number of at least 40 mg KOH/g which is either (i) a polycondensate with an average maximum molecular weight of 5000 or (ii) a diene polymer with an average maximum molecular weight of 4000, and (B) a compound having an average of from 0.8 to 1.5 free isocyanate groups per molecule and at least one basic nitrogen atom bonded to an aliphatic carbon atom.

2. A process as claimed in claim 1 wherein compound (B) has an average of 1 free isocyanate group per molecule.

3. A process as claimed in claim 1 or claim 2 effected at a temperature of from 10 to 100"C.

4. A process as claimed in claim 3 effected at from 50 to 80"C.

5. A process as claimed in any of the preceding claims which includes reaction with.a compound (C) having an average of from 0.8 to 1.5 free isocyanate groups per molecule and from 1 to 3 olefinic double bonds per molecule.

6. A process as claimed in claim 5 wherein compound (C) has an average of 1 free isocyanate group per molecule.

7. A process as claimed in any of the preceding claims effected in the presence of an isocyanate inert solvent.

8. A process as claimed in any of claims 5 to 7 wherein reaction of substance (A) with compounds (B) and (C) is carried out sequentially in random sequence or simultaneously.

9. A process as claimed in any of the preceding claims effected in the presence of a catalyst.

10. A process as claimed in claim 9 wherein the catalyst is an organic stannous compound.

11. A process as claimed in any of the preceding claims wherein substance A(i) is a polyester with at least 2 ester linkages in the molecule.

12. A process as claimed in claim 11 wherein substance A(i) contains urethane linkages.

13. A process as claimed in any of the preceding claims wherein substance A(i) is an oil or fatty acid modified polyester resin.

14. A process as claimed in any of claims 11-13 wherein substance A(i) is modified by copolymerisation with vinyl and/or vinylidene compounds.

15. A process as claimed in any of claims 11, 12, and 14 wherein the polyester includes oxazoline ring structures.

16. A process as claimed in any of claims 1-10 wherein substance A(ii) is a copolymer of a diene with a hydroxy group containing monovinyl compound.

17. A process as claimed in any of claims 1-10 or 16 wherein substance A(ii) is a diene polymer with chain end hydroxy groups.

18. A process as claimed in any of claims 1-10, 16 or 17 wherein substance A (ii) is a reaction product of an epoxidised diene polymer with a compound carrying an active hydrogen atom.

19. A process as claimed in any of the preceding claims wherein compound (B) is a reaction product of a di- or polyisocyanate with a less than stoichiometric quantity of an amine of the general formula

wherein R is a hydroxyalkyl group and R1 and R2 which may be the same or different are alkyl or cycloalkyl groups.

20. A process as claimed in any of claims 5-19 wherein compound (C) is a reaction product of a di- or polyisocyanate with a compound carrying at least one isocyanate reactive hydrogen atom and from 1 to 3 olefinic double bonds.

21. A process as claimed in any of the preceding claims wherein an additional crosslinker is blended or reacted with the reaction product.

22. A process as claimed in claim 21 wherein the additional crosslinker is a urea-, melamine- or phenol-form aldehyde condensate.

23. A process as claimed in claim 22 wherein the additional crosslinker is a phenol-form aldehyde condensate carrying allyl-ether groups.

24. A process as claimed in any of claims 21-23 wherein reaction with the additional crosslinker is carried out at from 50 to 1200C.

25. A process as claimed in claim 1 substantially as described herein.

26. A process as claimed in claim 1 substantially as described herein with reference to the Examples.

27. A binder whenever prepared by a process as claimed in any of the preceding claims.

28. A process for manufacturing a cathodically depositable surface coating composition which comprises at least partially neutralising with an acid a binder as claimed in claim 27.

29. A process as claimed in claim 28 substantially as described herein.

30. A process as claimed in claim 28 substantially as described herein with reference to the Examples.

31. A cathodically depositable surface coating composition whenever prepared by a process as claimed in any of claims 28-30.