IE42967B1 - Improvements in or relating to plastisols - Google Patents

Abstract

Process for coating metal articles with PVC or vinyl chloride copolymers takes place by (1) using plastisols contng. finely divided PVC or vinyl chloride copolymers, standard plasticisers, fillers and additives and, as adhesive agents, (A) Schiff bases contng. 0.1-0.4 (0.1-1) azomethine gps./100 g. cpd. and/or (B) enamines contng. 0.1-1.4 (0.1-1) enamine gps./100 g. cpd., alone or in mixtures, in quantities of 0.1-4 (0.3-2) wt.% w.r.t. PVC compsn. and (2) stoving the coatings at 120-200 degrees C. Uses include coating automobile body sheet iron. The claimed plastisols can be stoved at relatively low temps., e.g. 120-160 degrees C., to give coatings which have good adhesive strength, without colour-changes, structural defects and blisters.

Description

This invention relates to plastisols based on vinyl chloride polymers.

Polyvinyl chloride and vinyl chloride co-polymers show good resistance to aggressive media,, and coatings of these materials are widely used for protection of surfaces, especially metallic surfaces, against corrosion.

Such coatings are applied primarily in the form of plasticisercontaining vinyl chloride polymers (plastisols) to the surface of the material to be protected by brushing, rolling or spraying. In a widely used fqrm, such coating compositions (plastisols) consist of a pastable polyvinyl chloride, which is distinguished, more especially, by a definite capacity for swelling in the plasticiser, and of a plasticiser or mixture of plasticisers, fillers, stabilisers and optionally colour pigments and substances that assist workability of polyvinyl chloride. i The formulation of plasticiser-containing polyvinyl coating compositions, their preparation and technical use, is extensively described in Krekeler Wick, Kunststoff-Handbuch (1963) Vol. II, Part 1, pages 396 et seq. According to this, the plastisols consist essentially of vinyl chloride homo-or co-polymers, plasticisers, small amounts of extenders, and, as additives, small amounts of stabilisers, pigments and fillers. 42387 It is known that an essentia! ‘Criterion for the quality of t protective coatings so applied is their adhesion to the coated material. This is especially important for coatings on metal objects. Loose adhesion of the protective coating increases the risk of the penetration of aggressive media, and it is possible, for example, for water to creep easily under the coating and corrode the metal. This is al! the more likely the weaker the acrtesior. of the protective film to the metal.

For modifying polyvinyl chloride plastisols it is known to use amines as additives, especially for improving adhesion. Aliphatic, cycloaliphatic and aromatic amines do indeed frequently exnibit an improvement in adhesion, but they may lead during baking to strong brown discolouration and blistering of the coating.

Accordingly, there exists a need for plastisols having an improved property picture, and for a method of working with these plastisols for producing coatings on metallic materials.

We have found that the adhesion of a plastisol composition may be improved by the use of (A) a Schiff's base compound containing o.l to 1.4 azomethine groups per TOO g of compound, or (8) an enamine compound containing 0.1 to 1.4 enamine groups per IOC g of compound.

The plastisol composition may comprise a vinyl chloride polymer component, a plasticiser component and a filler component, and suitably also contains an emulsifier and stabiliser component and optionally also a pigment component, and/or other additives conventionally used for plastisols. The adhesion promoter is advantageously present in an amount of at least 0.1%, and preferably no more than 4% by weight, calculated on the weight of all other ingredients in the composition.

Accordingly, the present invention provides a plastisol composition ’ I suitable for coating metals, which comprises I) a homo- or copolymer of vinyl chloride or a mixture of two or more such polymers, II) a plasticiser or mixture of two or more plasticisers, III) a filler or mixture of two or more fillers, and IV) an adhesion promoter comprising (A) a-Schiff's base compound having from 0.1 to 1.4 azomethine groups per 100 g of compound, or (B) an enamine compound having from 0.1 to 1.4 enamine groups per 100 g of compound, or a mixture of two or more such compounds, especially in an amount of from 0.1 to 4% by weight of all the other components.

The present invention also provides a process for the preparation of a coating on a metal surface, which comprises coating the surface with a stabilised plastisol composition of the present invention and baking the coating, preferably at a temperature in the range of from 120 to 200°C.

The polyvinyl chloride or vinyl chloride co-polymer should be finely divided and capable of swelling in the plasticiser.

A suitable plasticiser is, for example, phthalic acid di-2ethyl-hexyl ester. Two or more plasticisers may be present.

Suitable fillers are, for example, chalk and barium sulphate.

A mixture of two or more fillers may be present.

A suitable stabiliser is, for example, di-isobutyl-tin diisooctylthioglycollic acid ester.

Further details regarding the plastisol components are given in 10 Plastisols and Organosols (Deutsche Farben-Zeitschrift page 93 ff. 1965, and Polyvinylchloride (Kunststoff-Handbuch Vol. II pages 396-399).

Preferred Schiff's bases contain 0.1 to 1.0 azomethine groups per 100 g of compound and preferred enamines contain from 0.1 to 1.0 enamine groups per 100 g of compound.

A mixture of two or more such adhesion promoters may be present in the mixture. The total amount is preferably in the range of from 0.3 to 2% by weight. 967 A. special advantage of a plastisol of the present invention is that it can be baked even at relatively low temperatures, especially at a temperature in the range of from 120 to 160°C, more especially at 130 to 160°C, and produce coatings on metallic materials, for example, on sheet steel for bodies, which have a very good adhesion and are not subject to colour changes or to structural defects and blister formation.

The optimum quantities of adhesion promoter in the plastisol may be determined empirically or, if necessary, with regard to the content of azomethine groups or enamine groups.

The adhesion promoter for the present invention may contain, in addition to the groups typical of Schiff's bases or enamines, preferably also one or more of the following groupings (a) amine groups (b) urea groups and/or urethane groups (c) amide groups.

The preparation of the Schiff's bases and enamines from amines and ketones or aldehydes may be carried out by known methods such as have been described, for example, in Norton et al., Journal of Organic Chemistry, Vol. 19 II (1954) pages 1054-1065 and C. Mannich and H. Davidson, Ber. Dtsch. chem. Ges. 69 (1936) page 2106 et seq,, S.K, Halhotra in A.G. Cook Enamines pages 1-100 (56-65), and M. Dekker, New York, London 1969. 3 3 3 7 For example, the Schiff's bases or enamines containing amine groups may be prepared from polyamines and ketones or aldehydes; see, for example, adhesion promoters A, I and J.

TheSchiff's bases or enamines containing urea or urethane groups may be prepared respectively by reacting Schiff's bases or enamines containing amine or hydroxyl groups (prepared respectively from polyamines or hydroxyl group-containing amines) with monomeric isocyanates or pre-polymeric isocyanates. The use of pre-polymeric isocyanates prepared from polyols and polyisccyanates and containing urethane or biuret groups, with amine group-containing Schiff's bases or enamines gives products containing both urea and urethane groups. For examples of Schiff's bases and enamines containing urea and/or urethane groups; see, for example, adhesion promoters S, F,H and L.

Schiff's bases or enamines containing amide groups may be prepared by reaction of amide group-containing amines with ketones or aldehydes; see, for example, adhesion promoters C,D,E,G and K.

Amines suitable for the preparation of Schiffs' bases and enamines are, for example, aliphatic, cycloaliphatic, araliphatic and aromatic mono- and poly-amines, for example propylamine, isopropylamine, butylamine, cyclohexyl amine, hexamechylene diamine, 2,2,4(2, 4,4)-trimethyl-hexamethyIene diamine, 2,2- iimethyl-1,3-diamino-propane, 1,4-diamino-butane, nonamethylsne diamine, tris-(3-amino-propyl) amine, 3,3‘-dimethyl-4,4'-diamino-dicycioh -xylmethane, diaminocyclohexane, bis-(l ,4-aminomethyl)-cylohexane, 2-amino-methylcyclopentylamirie, 2,2rbis-(4-amino-cyclohexy1)-propane and 3-ami nomethyl3,5,5-trimethyl-cyclohexylamine; and also N-alkyl derivatives thereof wherein an alkyl group has from 1 to 4 carbon atoms, (such, for example, as N,N'-diisobuty1~2,2,4(4,4,2)-trimethyl-hexamethylene diamine and Ν,Ν'-diisobutyl-hexamethylene diamine); 4,4‘-di piperidylpropane, Ν-β-aminoethyl-piperazine, Ν-β -hydroxyethyl-piperazine, 4,4' dipiperazinyl-propane, tricyclodecane diamine, benzylamine,xylylene diamine, aniline, toluidine, phenylene diamine, toluylene diamine, 4,4'-diamino-diphenylmethane, 4,4‘-diaminodiphenyl-propane-2,2 and 3,3 dimethyl-4,4'-diamino-diphenyl-methane. Tris(3-aminopropyl)amine and dipiperidyl propane should especially be mentioned.

Condensation products of polycarboxylic acids with excess polyvalent amines may also be used for preparing the Schiff's base or enamine; these condensation products are referred to in the art as polyarainoamides and contain free amino groups. Preferred polyaminoamides are based on dimerised higher unsaturated fatty acids and polyalkylene-polyamines, for example diethylene triamine, triethylene tetramine or dipropylene triamine. The polyaminoamides based on dimerised fatty acids and polyamino-imidazolines, which are formed therefrom by splitting off a further mol of water, are known in the art as hardening agents for epoxy-resins (see, for example, German Patent Specification Nos. 972,757 and 1,420,472).

Ketones suitable for the preparation of Schiff's bases and enamines 2 β 6 7 are, for example, acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, cyclohexanone,cyclopentanone, diisobutyl ketone, 3,3,5-trimethyl-cyclohexanone and methyl phenyl ketone; and suitable aldehydes are, for example, acetaldehyde, butyraldehyde, isobutyraldehyde and benzaldehyde.

The Schiff's bases and enamines may be monomeric or prepolymeric compounds; for example, adducts of monomeric isocyanates or prepolymeric isocyanates with Schiff's bases or enamines that contain hydroxyl or amino groups, may be used. For example, an addition product of a diisocyanate and a Schiff's base may be used; the diisocyanate component may be, for example, isocyanatomeihyl-3,5,5- trimethyl-eyciohexyl isocyanate (isophoror.e di isocyanate) or an isocyanate-containing pre-adduct thereof; the Schiff's base or enamine component may be prepared from an amine such, for example, as diethylene triamine.

One or more Schiff's bases and/or one or more enamines may be added to the plastisol.

The following Examples illustrate the invention. Parts mentioned are parts by weight.

Examples A to L The preparation of adhesion promoters for the plastisols of the - 10 invention (for azomethine/enamine contents see Table I below) Example A A Schiff's base containing amine groups from tris-(3aminopropyl)-amine and methyl isobutyl ketone: 188 g of tris-(3-aminopropy1)-amine, amine number 1190, were heated at the boil with 600 g Of methyl isobutyl ketone with the use of a water separator to remove the water formed in the reaction. Refluxing was continued until water was no longer formed. Excess ketone was distilled off when the reaction terminated.

Example B A Schiff's base containing urethane and urea groups: A Schiff's base was prepared by the method described in Example A from diethylene triamine and methyl isobutyl ketone; 206 g of diethylene triamine were refluxed with 500 g (approximately 25% excess) using a water separator. After the calculated quantity of water had been distilled off, the excess ketone was removed under vacuum; the amine number of,the product was 585. 138.5 g of a 57.8% by weight solution in ethyl glycol acetate of an addition product of 3 mol of isophorone diisocyanate and 1 mol of trimethylolpropane having an NCO-content of 9.1% were added dropwise to 86.4 g of the Schiff's base at 30 to 35°C in the course of 5 hours.

Before working up, 60 parts of the above product are advantageously mixed with 40 parts of methyl isobutyl ketone.

Example C A Schiff's base containing amide groups: A polyamino-imidazoline (amine number 400, viscosity 5 poises at 75°C) was prepared from 1982 parts of dimerised tall oil fatty acid (12% of monomeric fatty acid, 71% of dimeric fatty acid, 17% of trimeric fatty acid) and 1018 parts of tri ethylene tetramine. 42S67 - 11 200 g of the polyafflino-iniidazoline were heated under reflux with 150 g of methyl isobutyl ketone (simultaneously acting as an entraining agent) with the use of a water separator. The water so formed was separated off.

When water no longer formed, the reaction was complete and the excess ketone was distilled off. The amir.e number of the reaction product was 323.

Example 0 A Schiff's base containing amide groups: A polyamino-amide, amide number 354 was prepared from difflerised tall oil fatty acid having a dimer content of 95½ and tris-(3-aminopropyl)amine in the molar ratio 1:2.

Linder the same reaction conditions as those used for adhesion promoter (C), a Schiff's base was prepared from 950 g of the polyamino-amide and 800 g of methyl-isobutyl ketone.

Example E A Schiff's base containing amide groups: 200 g of the polyamino-araide (containing imidazoline groups) used for adhesion promoter C having an amine number of 400 were heated under reflux with 71 g of trimethyl-cyclohexanone and 250 ml of toluene as entraining agent. The reaction water formed in this case was completely separated by means of a water separator. Then toluene and the excess . - .12 . -. ketone were distilled off. The amine number of the reaction product was 296.

Example F A Schiff's base containing urea groups: Diethylene triamine and methyl isobutyl ketone (in excess) were reacted according to a known method(see Example B) to produce the corresponding diketimine. After complete removal of the water and the excess ketone- finally' in vacuo, a product having an amine number of 615 was obtained (theoretical amine number 630). 110 g of the ketimine so prepared were heated to 120°C, and 44.4 g of isophorone diisocyanate were added dropwise at that temperature, while stirring vigorously. A viscous product was obtained having the following characteristic values: Residue-N=C=Q: about 1% Amine number: about 295.

For use in practice - as described in Example 7 it is recommended to dilute the reaction product with xylene to give a solution of 75% strength. It is also possible to use ethyl glycol acetate as solvent.

EXAMPLE G A Schiff's base containing amide groups: 2180 g of adipic acid and 43::0 g of triethylene tetramine (molar proportions 1:2) were reacte- in a stainless steel vessel of 15 1 capacity to form the corresponding amino-amide. After removing the residual water of condensation, the reaction product was cooled 2 3 υ 7 under a water jet vacuum to about 50°C, and 3760 g of methyl isobutyl ketone were added while stirring. 8y distilling off the water of condensation and removing the excess ethyl isobutyl ketone finally under a water jet vacuum - 7225 g of a viscous product having an amine number of about 495 were obtained.

Example H A Schiff's base containing biuret groups: A Schiff's base was prepared by the method described in Example B from diethylene triamine and methyl isobutyl ketone; the amine number of the product was 610. 217 g of a 75% solution in ethyl glycol acetate of a tri-isocyanate (NCO-content of the 75% strength solution = 14.8%) prepared from 9 g of water and 333 g of isophorone diisocyanate were added dropwise to 211 g of the Schiff's base, while cooling well (maximum temperature 35-40°C). The viscous solution obtained after the exothermic reaction subsided was diluted with further ethyl glycol acetate to give a solution of 80% strength. The amine number was 184 (for the solution of 80% strength).

Example I An enamine containing amine groups from di piperidyl-propane and 3,3,5-trimethyl-cyclohexanone: 300 ml of toluene and 2 al of formic acid were added to 315 g of dipiperidyl-groups and 570 g of 3,3,5(3,5,5)-trimethyl-cyclohexanone (isomeric mixture), and the whole was heated under nitrogen while 567 stirring under a water separator. When the calculated quantity of water had distilled off, the solvent and excess trimethylcyclohexanone were removed in vacuo. A viscous product having an amine number of 245 was obtained.

Example J An enamine container amine groups from di piperidyl-propane and isobutyraldehyde; In a manner ahalogous to that in Example (I), 200 g of dipiperidylpropane were reacted with 180 g of isobutyraldehyde under reflux in 200 ml of toluene containin'! about 1% of tonsil ACC-FF using a water separator. After the calculated quantity of water had been distilled off, toluene and excess isobutyraldehyde were drawn off under vacuum. A product having an amine number of 347 was obtained.

Example K A ketamine containing amide groups from an aminoamide and methyl isobutyl ketone: 200 g of a reaction product of tall oil fatty acid and triethylene tetramine having an amine' number of 376 were heated under reflux with 150 g of methyl isobu /1 ketone, which simultaneously acts as an entraining agent, with ie use of a water separator. The water formed was thus separated. After the reaction had terminated and the excess ketone had been 'iistilled off, a product of low viscosity having an amine number of ;::5 was obtained.

Example L - 15 -52S 6? A Schiff's base containing urea groups: reaction product of partially masked (caprolactam) isophorone diisocyanate and a Schiff's base from diethylene triamine and methyl isobutyl ketone: 1,556 g of isophorone diisocyanate were heated under nitrogen to 80-90°C. In the course of about two hours, 7S2 g of caprolactam were added in portions, and owing to the exothermic reaction, the heating was discontinued. The reaction product was further stirred at 80 to 90°C until the ii=C=0 content was 12,5%. Sy the addition of 414 g of ethyl glycol acetate, a solution of 85% strength was obtaineo. 2,500 g of the 35% solution of partially masked isophorone diisocyanate were added dropwise over 5 hours to 1,748 g of a Schiff's base prepared from diethylene triamine and methyl isobutyl ketone (which acts both as reactant and entraining agent) and having an amine number of 510, at room temperature while cooling. By the addition of a further 156 g of ethyl glycol acetate, a solution of 80% strength of the reaction product having the characteristic values: Residue (1=0=0: 0.4% amine number; 169 was obtained.

Examples 1 to 13 The testing of adhesion promoters A to L in plastisol compositions Plastisol composition Parts of a commercially available pastable polyvinyl chloride having a K-value of 70 containing an emulsifier - 16 55 parts of phthalic di-2-ethyl-hexyl ester 100 parts of a filler mixture consisting of 50% chalk and 50% of barium sulphate 1.5 parts of di-isobutyl-tin dnsooctyl-thioglycollic acid ester.

Method of preparation and testing The plastisol was prepared in a manner known per se by mixing intimately the polyvinyl chloride powder and plasticising agent with fillers and the stabiliser.

The adhesion promoter specified in the following Examples was then 10 added by stirring, and the finished plastisol was applied by means of a coating device to a metal sheet in a layer increasing in thickness from 0 to 3 mm and having a width of layer of 3 cm. The coating so produced was baked under conditions close to those used in practice for half an hour at the. specified temperature in a drying cabinet in which air circulated.

The metal sheet was removed from the cabinet and cooled to room temperature. A visual and manual assessment of the polyvinyl chloride coating was then carried out.

Criteria of the assessment: (a) Adhesiveness of the film to the metal: The plastisol film was cut with a knife in a crescent shape, and by separating it the filmmetal adhesion was determined qualitatively (b) Colour change: The coatings were assessed with regard to the degree of discoloration. 25 (c) Determination of the listering character of the coating: Visual assessment of the b isters to be seen on the cut surface. - 17 42387 Example 1 0.3 g of the adhesion promoter C were mixed with 100 g of the above-mentioned plastisol, the plastisol thus modified was applied in the manner described above to a lacquered metal sheet, and baking was carried out for 30 minutes at 160°C. The adhesion of the coating was very good and no colour changes occurred. for comparison, the known poiyamino-imidazoline (amine number 400, viscosity 5 poises at 75°C), prepared from 1982 parts of dimerised tall oil fatty acid (12% of monomeric fatty acid, 71% of dimeric fatty acid and 17% of trimeric fatty acid) and 1018 parts of triethylene tetramine was used in the above-mentioned quantity and under the conditions given above as adhesion promoter. A yellowbrown discoloration of the coating occurred.

Example 2 1.0 g of the adhesion promoter C was mixed with 100 g of the abovementioned plastisol, the plastisol so modified was applied in the manner described above to a lacquered metal sheet, and baked for 30 minutes at 130°C. The adhesion of the coating was very good, whereas in a comparative test using in the same way the known polyaminoimidazoline described in Example 1, the adhesion was only just sufficient.

Example 3 1.0 g of adhesion promoter A was mixed with 100 g of the above- 18 29S7 mentioned plastisol, the plastisol so modified was applied in the manner described above to a lacquered metal sheet and baked for 30 minutes at 160°C. The adhesion of the coating was very good. Mo structural damage was caused by the formation of blisters. In a comparative test using the known adhesion promoter described in Example 1? blisters were formed. * s Example 4 0.5 g of the adhesion promoter D was mixed with 100 g of the above-mentioned plastisol, the plastisol so modified was applied in the manner described above to a lacquered metal sheet, and baked for 30 minutes at 160°C. The adhesion of the coating was very good and no colour change occurred, whereas in a comparative test, a coating, prepared in the same way but with the known adhesion promoter described in Example!, exhibited a yellow-brown discoloration.

Example 5 1.0 g of the adhesion promoter E was mixed with 100 g of the abovementioned plastisol, the plastisol so modified was applied in the manner described above to a lacquered metal sheet, and baked for 30 minutes at 16O°C. The adhesion of the coating was very good with only trivial discoloration. However, in a comparative test with the known adhesion prcnoter described in Example 1, a brown coloration was found.

Example 6 1.0 g of the adhesion promoter B was mixed with 100 g of the abovementioned plastisol, the plastisol so modified was applied in the manner described above to a non-lacquered metal sheet, and baked 2 S G 7 - 13 for 30 minutes at I60°C. The adhesion of tne coating was very good. No colour change occurred. In a comparative test, a coating, prepared in the same way Out with the known adhesion promoter described in Example 1, exhibited an insufficient adhesion and a brown coloration.

Example 7 2.0 g of the adhesion promoter F were mixed with 100 g of the plastisol mentioned above, the plastisol so modified was applied in the manner described to a lacquered and to a non-lacquered metal sheet, and baked for 30 minutes at 130°C. No colour change occurred. The adhesion of the coating was very good in both cases, whereby advantages resulted as shown by comparison tests as described in Examples 1 to 6; the adhesion of this particular adhesion promoter to non-lacquered metal sheet is ah important advantage here.

Example 8. 2.0 g of the adhesion promoter G were mixed with 100 g of the above-mentioned plastisol, the plastisol so modified was applied in the manner described to a lacquered metal sheet, and baked for 30 minutes at 120°C. The adhesion of the coating was very good and only slight yellow discoloration occurred.

Example S 2.0 g of adhesion promoter H were mixed with 100 g of the above- 20 mentioned plastisol. The plastisol so modified was applied in the manner described to a lacquered and to a non-lacquered metal sheet, and baked for 30 minutes at 150°C. The adhesion of the coating, which had only a slight yellow discoloration, was very good in both cases.

Example 10 1.0 g of adhesion promoter I was mixed with 100 g of the abovementioned plastisol. The plastisol so modified was applied in the manner described to a lacquered metal sheet, and baked for 30 minutes at 160°C. The adhesion of the brownish coating was good, and the film showed no blisters.

Example 11 1.0 g of adhesion promoter J was mixed with 100 g of the abovementioned plastisol. The plastisol so modified was applied in the manner described to a lacquered metal sheet, and baked for 30 minutes at 160°C. The adhesion of the brownish coating was very good.

Example 12 0.3 g of adhesion promoter K was mixed with 100 g of the abovementioned plastisol. .The plastisol so modified was applied in the manner described to a lacquered metal sheet, and baked for 20 minutes at 160°C. The adhesion of the yellowish coating was very good.

Example 13 g of adhesion promoter L were mixed with 100 g of the above42S87 - 21 mentioned plastisol. The plastisol so modified was applied in the manner described to a lacquered and to a non-lacquered metal sheet, and baked for 30 minutes at 150°C. The adhesion of the slightly yellowish and blister-free coating was in both cases very good.

Table 1 Azomethine/enamine groups per 100 g of compound A B 0.69 0.75 D 0.32 D 0.1S G 0.38 H 0.42 J 0.65 K 0.20 10 C 0.21 F 0.53 I 0.45 L 0.33

Claims (25)

1. CLAIMS:1. A plastisol which comprises I) a homo- or co-polymer of vinyl chloride or a mixture of two or more such polymers, II) a plasticiser or a mixture of two or more plasticisers, III) a filler or a mixture of two or more fillers, and IV) an adhesion promoter component, which comprises » (A) a Schiff's base compound having from 0.1 to 1.4 azomethine groups per 100 g of compound, or (B) an enamine compound having from 0.1 to 1.4 enamine groups per 100 g of compound, or a mixture of two or more such adhesion promoters.

2. A plastisol composition as claimed in claim 1, wherein component IV is present in an amount of from 0.1 to 4% by weight, based on.the sum of all other components in the composition.

3. A plastisol composition as claimed in claim 2, wherein component IV is present in an amount of from 0.3 to 2« by weight, based on the sum of all other components in the composition.

4. A plastisol composition as claimed in any one of claims 1 to 3, wherein component IV comprises a Schiff's base having from 0.1 to 1 azomethine group per 100 -j of compound, 5. A plastisol composition as claimed in any one of claims 1 to 4, wherein component IV comprises an enamine having from 0.1 to 1 enamine group per 100 g of compound. / 5 Ο Ο s'* ί*··ί Α»ι iy β

5. A plastisol composition as claimed in any one of claims 1 to 5, wherein component IV comprises a Schiff's base or enamine containing one or more of the following groups (a) amine groups, (b) urea and/or urethane groups, (c) amide groups.

6. 7. A plastisol composition as claimed in claim 5, wherein component IV comprises an adduct of a monomeric isocyanate or a prepolyraeric isocyanate with a Schiff's base or enamine containing a hydroxyl or amino group.

7. 8. A plastisol composition as claimed in claim 7, wherein component IV comprises an adduct of isophorone diisocyanate and a Schiff's base or enamine prepared from diethylene triamine.

8. 9. A plastisol composition as claimed in claim 6, wherein component IV comprises a Schiff's base or enamine prepared from a polyaminoamide or polyaminoimidazoline.

9. 10. A plastisol composition as claimed in claim 9, wherein the polyaminoamide is prepared from a dimerised higher unsaturated fatty acid and diethylene triamine or triethylene tetramine.

10. 11. A plastisol composition as claimed in claim 6, wherein component IV comprises a Schiff's base or enamine prepared from tris(3-aminopropyl) amine or dipiperidyl propane. 507 - 24

11. 12. A plastisol composition as claimed in any one of claims 1 to 11, wherein the Schiff‘s base or enamine is prepared from methyl isobutyl ketone, 3,3,5-trimethylcyclohexanone or isobutyraldehyde.

12. 13. A plastisol composition as claimed in any one of claims 1 to 3, wherein component IV is as specified in any one of Examples A to L herein.

13. 14. A plastisol composition as claimed in any one of claims 1 to 13, which contains one or more stabilisers.

14. 15. A plastisol composition as claimed in claim 15, wherein the stabiliser is di isobutyl-tin diisoctyl-thioglycollic acid ester.

15. 16. A plastisol composition as claimed in any one of claims 1 to 15, which contains one or more emulsifiers.

16. 17. A plastisol composition as claimed in any one of claims 1 to 16, which contains a pigment.

17. 18. A plastisol composition as claimed in any one of claims 1 to 17, wherein the plasticiser is phthalic acid di-2-ethylhexyl ester.

18. 19. A plastisol composition as claimed in claim 1, substantially as described in any one of Examples 1 to 13 herein.

19. 20. A coating which has been prepared by applying a plastisol composition as claimed in any one of claims 1 to 19 to a surface and baking the surface.

20. 21. A process for preparing a coating on a metal surface, 5 which comprises coating the surface with a plastisol composition as claimed in claim 14 or claim 15, and baking the coating.

21. 22. A process as claimed in claim 21, wherein the coating is baked at a temperature in the range of from 120 to 200°C.

22. 23. A process as claimed in claim 22, wherein the temperature 10 is in the range of from 120 to 160°C.

23. 24. A process as claimed in claim 23, wherein the temperature is in the range of from 130 to 160°C.

24. 25. A process as claimed in any one of claims 21 to 24, wherein the metal surface is a sheet steel surface. 15 25. A process as claimed in claim 21, carried out substantially as described in any one of Examples 1 to 13 herein.

25. 27. A coating on a metal surface, whenever prepared by a process as claimed in any one Of claims 21 to 25.