GB1562759A

GB1562759A - Protective coating of surfaces

Info

Publication number: GB1562759A
Application number: GB31132/77A
Authority: GB
Original assignee: REEF TECHNICAL DEV Ltd
Current assignee: REEF TECHNICAL DEV Ltd
Priority date: 1976-07-27
Filing date: 1977-07-25
Publication date: 1980-03-19
Also published as: ZA764496B

Description

(54) PROTECTIVE COATING OF SURFACES (71) We, REEF TECHNICAL DE- VELOPMENTS (PROPRIETARY) LIMI TED, a company registered according to the laws of the Republic of South Africa, of 5 Seller Road, Boksburg East, Transvaal, Republic of South Africa, 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 relates to coating compositions, in particular to primer, rust preventive, and/or cleaning or testing compositions which leave a coating on a substrate cleaned or tested.

It is often necessary to protect a substrate pending the application of a coating of paint.

For example, a metal such as a steel substrate must be protected against rusting. Various rustproofing compositions are known, and could be used, but the majority have the failing that they do not provide acceptable surfaces for subsequent painting, and have to be removed before the substrate can be painted.

Further, it is often necessary to clean articles to remove oils, dirt and grease, and yet to have a surface which is ready for painting with out further treatment.

Pressure testing of metal equipment is often conducted by immersion in a suitable fluid, which is preferably rust preventive, and it is advantageous if the fluid used is such that the article after testing can merely be allowed to dry before painting.

According to the present invention there is provided a coating composition comprising an aqueous solution or dispersion having a basic pH value of a basic salt of phosphoric acid monoesterified with a group of the formula R(CH2O-)-n wherein R is C6-C12 alkyl, cycloalkyl, or substituted or unsubstituted aromatic, and n is 2-20, the base being selected from ammonia, and C16 primary, secondary, and tertiary amines and alkanolamines.

The pH value of the composition may suitably be in the range 8 to 9.5, and the concentration of the salt in the solution or dispersion in the range 0.2 to 20 per cent by weight.

The concentration of salt in the composition employed will however depend to a large extent on the thickness of the coating desired, and the mode of application.

For example, in the case of application by dipping the concentration will normally be in the range 0.2 to 5 per cent by weight, whereas concentrations up to 20 per cent by weight may be used for application by spraying or roller coating.

If desired the compositions may conveniently be supplied in the form of a concentrate (say 20 per cent by weight) for subsequent dilution.

The basic salts upon which the coating compositions of the invention are based are water-soluble or water-dispersible, and also at least partially soluble in conventional organicsolvents used in paint such as alcohols, ketones, and hydrocarbons, for example methylethylketone.

The specific base, and group of formula R(CH20-)-n which are present in the salt are not critical, provided the above conditions are met. Generally however, the solubility in organic solvents will be better where n is in the range 2 to 5.

In one particular embodiment, the phosphoric acid monoester may be an ethoxylated aliphatic monoester of phosphoric acid of the type sold by G.A.F. of West Germany under the trade name ' LM 400".

In another, it may be an ethoxylated aromatic monoester of phosphoric acid of the type sold by G.A.F. of West Germany under the trade name "RE 610 ".

In the first case the base may be triethanolamine, in the latter, morpholine.

The invention also provides a method for treating a substrate comprising applying to the substrate a coating composition as set out above, and allowing the composition to dry on the substrate.

It further provides a method for painting a substrate with an organic-solvent based paint, comprising applying to the substrate a coating composition as set out above, allowing the composition to dry on the substrate, and applying the paint to the coated substrate.

The invention further extends to substrates coated or painted by either of the above methods.

Further according to the invention there is provided an article coated with a first coating of a coating composition of the invention as set out above, and, superimposed on this first coating, a second coating of an organicsolvent based paint.

The coating compositions of the invention have important industrial advantages. In addition to being suitable for rust preventive and/ or cleaning applications, they dry on a substrate to form a surface which is completely acceptable to normal paints based on organic solvents. Accordingly, the compositions of the invention make ideal primers. Articles to which they have been applied for rust prevention need no cleaning or special treatment before they can be painted. And articles cleaned or pressure tested using compositions of the invention can merely be allowed to dry before painting.

Coatings of organic-solvent based paints applied to substrates treated with compositions of the invention show excellent adherence.

This may possibly be explained as follows.

If paints are applied to conventional watersoluble protective coatings, moisture pentrating through the paint layer tends to dissolve the protective layer and cause blistering and peeling. Such coatings are of course not intended as primers for subsequent paint application, and should be removed prior to painting, but economics and time often dictate otherwise. In the case of the compositions of the invention however, the basic salts are at least partially soluble in organic solvents, and are presumably incorporated to some extent by freshly applied organic-solvent based paints.

Thus an essentially homogeneous layer is formed which bonds directly onto the surface. Whether or not this is a correct explanation, the fact remains that the paint coatings are firmly adherent.

The following examples illustrate some specific examples of coating compositions of the invention.

Example 1.

A rust preventive composition based on the ethoxylated aliphatic monoester of phosphoric acid sold under the trade name "LM 400 by G.A.F. of West Germany, was neutralised to a pH of 9.0 by the addition of triethanolamine. Dispersions varying in concentration from 0.3-2 percent by weight were prepared in water and applied to steel panels. In each case they dried to form coatings which inhibited corrosion and resisted humidity for up to 100 hours.

Conventional MEK (methylethylketone) based drum paint was then applied to the coated panels. It was found that not only did the coatings prove wholly acceptable to the paint but that in fact the adherence of the paint was significantly improved with respect to that exhibited by a coating of a similar paint applied to a bare steel surface. This characteristic was more evident with thicker primer coatings.

When the paint coatings were dry, the panels were immersed in water at 40 C for 24 hours, then removed and subjected to cross-hatch tests. No loss of adhesion of the paint coating was observed.

For comparison purposes a similar test was conducted with a panel which before painting had been coated with a conventional waterbased protective coating. Blistering of the paint coating was observed.

Example 2.

A composition comprising the ethoxylated aromatic monoester of phosphoric acid sold by G.A.F. of West Germany under the trade name "RE 610"+, neutralised with morpholine to a pH of 8--9.5 was prepared.

Similar dispersions were prepared, and tests conducted, to those described in Example 1, once again with excellent results.

These compositions also showed excellent properties for cleaning articles of oil and grease, and for use in pressure testing. (For high pressure cleaning or testing, or when the water used is hard, minor amounts of conventional non-ionic wetting agents, coupling agents, and water softeners may be added to prevent foaming and hard-water cloudiness.) Steel articles cleaned and tested, and allowed to dry, did not rust, and readily accepted paint with good adhesion.

For cleaning purposes dispersions of concentration 0.2 to 2 per cent by weight were employed; for pressure testing 0.1 to 1 per cent by weight * The manufacturer's specifications of the products LM 400 and RE 610 are as follows:

LM 400 RE 61D Acid Number 5164 62-72 Specific gravity (Ib/gal) 1 8.8 9.2 Solubility in:: mineral oil soluble dispersible kerosene ., insoluble vegetable oil xylene ., soluble perchloroethylene ., " ethanol water dispersible WHAT WE CLAIM IS: 1.A coating composition comprising an aqueous solution or dispersion having a basic pH value of a basic salt of phosphoric acid monoesterified with a group of the formula R(CHPO-)-, wherein R is C6-C12 alkyl, cycloalkyl, or substituted or unsubstituted aromatic, and n is 2-20, the base being selected from ammonia, and C1-C6 primary, secondary and tertiary amines and alkanolamines.

2. A coating composition of claim 1 wherein n is 2-5.

3. A coating composition of claim 1 or 2 wherein the phosphoric acid monoester is an ethesylated aliphatic monoester of phosphoric add.

4. A coating composition of claim 1 or 2 wherein the phosphoric acid monoester is an ethoxylated aromatic monoester of phos phoric acid.

5. A coating composition of claim 3 wherein the base is triethanolamine.

6. A coating composition of claim 4 wherein the base is morpholine.

7. A coating composition of any of claims 1 to 6 wherein the pH is in the range 8 to 9.5.

8. A coating composition of any of claims 1 to 7 wherein the concentration of the salt in the aqueous solution or dispersion is in the range 0.2 to 20 per cent by weight 9. A coating composition of any of claims 1 to 8 in the form of a concentrate.

10. A method for treating a substrate com prising applying to the substrate a coating composition of any of claims 1 to 8 and allowing the composition to dry on the substrate.

11. A methodX~pai ting a substrate with an organic-solvent based paint comprising applying to the substrate a coating composition of any of claims 1 to 8, allowing the composition to dry on the substrate, and applying the paint to the coated substrate.

12. An article coated with a first coating of a coating composition of any of claims 1 to 8 and superimposed on this first coating, a second coating of an organic-solvent based paint.

13. A coating composition of claim 1 substantially as herein described.

14. A coating composition substantially as described in Example 1 or Example 2.

15. A concentrate of claim 9 substantially as herein described.

16. A method for treating a substrate according to daim 10 substantially as herein described.

17. A method for treating a substrate substantially as described in Example 1 or 2.

18. A method for painting a substrate with an organic-solvent based paint according to claim 11 substantially as herein described.

19. A method for painting a substrate with an organic-solvent based paint substantially as described in Example 1 or 2.

20. An article of claim 12 substantially as herein described.

21. A substrate that has been treated by a method of any of claims 10, 16 and 17.

22. A substrate that has been painted with an organic-solvent based paint by a method of any of claims 11, 18 and 19.

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

Claims

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

LM 400 RE 61D Acid Number 5164 62-72 Specific gravity (Ib/gal) 1 8.8 9.2 Solubility in: mineral oil soluble dispersible kerosene ., insoluble vegetable oil xylene ., soluble perchloroethylene ., " ethanol water dispersible WHAT WE CLAIM IS: 1.A coating composition comprising an aqueous solution or dispersion having a basic pH value of a basic salt of phosphoric acid monoesterified with a group of the formula R(CHPO-)-, wherein R is C6-C12 alkyl, cycloalkyl, or substituted or unsubstituted aromatic, and n is 2-20, the base being selected from ammonia, and C1-C6 primary, secondary and tertiary amines and alkanolamines.
2. A coating composition of claim 1 wherein n is 2-5.
3. A coating composition of claim 1 or 2 wherein the phosphoric acid monoester is an ethesylated aliphatic monoester of phosphoric add.
4. A coating composition of claim 1 or 2 wherein the phosphoric acid monoester is an ethoxylated aromatic monoester of phos phoric acid.
5. A coating composition of claim 3 wherein the base is triethanolamine.
6. A coating composition of claim 4 wherein the base is morpholine.
7. A coating composition of any of claims 1 to 6 wherein the pH is in the range 8 to

9.5.
8. A coating composition of any of claims 1 to 7 wherein the concentration of the salt in the aqueous solution or dispersion is in the range 0.2 to 20 per cent by weight
9. A coating composition of any of claims 1 to 8 in the form of a concentrate.
10. A method for treating a substrate com prising applying to the substrate a coating composition of any of claims 1 to 8 and allowing the composition to dry on the substrate.
11. A methodX~pai ting a substrate with an organic-solvent based paint comprising applying to the substrate a coating composition of any of claims 1 to 8, allowing the composition to dry on the substrate, and applying the paint to the coated substrate.
12. An article coated with a first coating of a coating composition of any of claims 1 to 8 and superimposed on this first coating, a second coating of an organic-solvent based paint.
13. A coating composition of claim 1 substantially as herein described.
14. A coating composition substantially as described in Example 1 or Example 2.
15. A concentrate of claim 9 substantially as herein described.
16. A method for treating a substrate according to daim 10 substantially as herein described.
17. A method for treating a substrate substantially as described in Example 1 or 2.
18. A method for painting a substrate with an organic-solvent based paint according to claim 11 substantially as herein described.
19. A method for painting a substrate with an organic-solvent based paint substantially as described in Example 1 or 2.
20. An article of claim 12 substantially as herein described.
21. A substrate that has been treated by a method of any of claims 10, 16 and 17.
22. A substrate that has been painted with an organic-solvent based paint by a method of any of claims 11, 18 and 19.