WO1996001282A1

WO1996001282A1 - Water-based porphyrin coating system

Info

Publication number: WO1996001282A1
Application number: PCT/AU1995/000364
Authority: WO
Inventors: James Thomas Guthrie; Richard Alan Morris; Wei Dong He; Richard Mark Pashley; Barry Ninham; Timothy John Senden
Original assignee: Memtec Limited; The Australian National University
Priority date: 1994-07-01
Filing date: 1995-06-21
Publication date: 1996-01-18
Also published as: AUPM659494A0; AU2707795A

Abstract

A polymerisable porphyrin suitable for use in the formulation of water-based resins or coating compositions characterised in that it comprises the reaction product of: (a) one or more compounds selected from the group consisting of pyrrole and N-(lower)alkyl pyrroles, any of which may be optionally ring substituted with one or two non-deleterious substituents; (b) at least one α,β-unsaturated aldehyde; (c) at least one unsaturated and/or polymerisable organic acid. Water-based resins or coating compositions or systems, containing such polymerisable porphyrins.

Description

WATER-BASED PORPHYRIN COATING SYSTEM

This invention relates to coating compositions and in particular to water-based coating compositions involving resin systems based on polymerisable porphyrins.

In International Patent Application No. WO92/01007 (PCT/AU91/00298), we described how the condensation of a beta-unsaturated aldehyde, especially crotonaldehyde, and pyrrole can give rise to a monomeric product which contains porphyrin-bearing unsaturated substituents. This monomeric material, which we referred to as a "polymerisable porphyrin", then readily polymerises to produce polymeric product. Polymers made from the monomeric material, or copolymers formed from the polymerisable material and at least one other polymerisable monomer of a known type, can be used in the production of films, coatings and other structures. The closely related porphyrinogenic resins are the subject of International Patent Application No WO93/13150 (PCT/AU92/00682). Both of these publications are incorporated herein by reference.

Coating compositions based on polymerisable porphyrin or porphyrinogenic resin systems described in the aforementioned patent applications are generally formulated using non-aqueous organic solvents. Water-based coating formulations are desirable because it is generally easier to provide water-based coatings which are ecologically compatible and meet environmental protection requirements, than is the case with coatings based on non-aqueous solvents. Water-based coatings find use in various areas of application in building and engineering, e.g. for metal cladding; in the marine and automotive industries; in hostile environments such as metal containers, road marking or chemical process plants; and in the creation of non-slip surfaces.

We have now found that it is possible to produce polymerisable porphyrins which can be used in the formulation of water-based coating compositions. Such polymerisable porphyrins can be produced by a modification of the procedures described in WO92/01007. According to one aspect of the present invention there is provided a water-based resin or coating composition which comprises a polymerisable porphyrin.

According to a further aspect of the invention, a polymerisable porphyrin suitable for use in the formulation of water-based resins or coating compositions is produced by the reaction of:

(a) one or more compounds selected from the group consisting of pyrrole and N-(lower)alkyl pyrroles, any of which may be optionally ring substituted with one or two non-deleterious substituents; (b) at least one α,β-unsaturated aldehyde;

(c) at least one unsaturated and/or polymerisable organic acid.

The preferred pyrrole is N-methylpyrrole. Preferred aldehydes are those in which the aldehyde (CHO) group is attached to a carbon chain containing from 2 to 7 carbon atoms, more preferably from 3 to 6 carbon atoms. Specifically preferred aldehydes are crotonaldehyde or acrolein.

The reaction generally requires the presence of an acid catalyst, which is selected to suit the particular chosen reagents (a) and (b). The catalyst may be the organic acid (c) itself or it may be another acid, such as an inorganic acid, such as hydrochloric acid, an organic acid, such as acetic or propionic acid, or an acid anhydride, such as phthalic anhydride. Acids containing vinyl groups, such as acrylic acid, or triple bonds, such as acetylene dicarboxylic acid, are especially useful in providing the dual functionality of the polymerisable acid (c) and the catalyst.

Preparation of the polymerisable porphyrins of the invention involves relatively simple procedures. Generally the pyrrole, aldehyde and organic acid (and the additional acid catalyst, if required) are mixed together and allowed to react at room temperature. After a period of time, the "induction period", the mixture rapidly increases in viscosity as polymerisation proceeds.

Although the mechanism by which the polymerisation occurs and the chemical structure of the resulting product are not yet fully understood, it is believed that the reaction initially involves the reaction of the pyrrole and the aldehyde to form a porphyrin ring structure. Organic acid moieties from the acid (c) then become attached to free positions on the pyrrole rings by reaction between unsaturation in the acid and remaining double bonds of the pyrrole rings.

The extent of the reaction may be controlled by adding one or more suitable reagents which effectively terminate the polymerisation. For example, addition of a C_j- Cg aliphatic alcohol, such as butanol, results in "end-capping" of the carboxyl group of the organic acid. At the same time, me reaction product can be further modified by the addition of other reagents which have the effect of enhancing or modifying the hydrophilic character, and other properties of the final product. The addition of ammonia increases water solubility but generally this effect needs to be modified by the concomitant addition of an amine, preferably a hydroxyalkylamine, most preferably diethanolamine. The addition of butanol also aids overall water-solubility or water- dispersability of the product and glycol ethers or cyclic ethers, such as tetrahydrofuran, have a similar effect. Combinations of the above reagents are referred to herein collectively as "neutralising solutions".

The resin products of the invention can be used alone as coating compositions or as part of a coating system. Advantageously, they may be combined with other materials for this purpose, including known coating materials or compositions, or precursors of such materials.

Such coating systems include, for example, combinations of the porphyrinogenic resins with epoxy-, phenolic- or alkyd-based resins of known types.

Resin systems based on the polymerisable porphyrins of the invention can be formulated as additive components for known coating formulations, thereby to provide a water-based resin system capable of addition of existing coating formulations, eg. paints, varnishes and surface coating of all kinds, and to thus impart to such existing formulations the inherently useful properties of the porphyrinogenic resin system. Coatings or coating compositions in accordance with this invention find applications in a variety of fields, for example, they can be used in the paint industry generally and especially in anti-corrosion coatings for metals in the automotive, marine and general engineering industries. They can be utilised as decorative or protective coatings on various substrates, such as metals, paper and ceramics. They can be used as insulating coatings or as coatings for printing or masking substrates, e.g. in processes involving etching.

Other examples of such coating formulations include: antifouling coating compositions comprising a polymerisable porphyrin, water and a siloxane component; thermal insulation coating compositions comprising a polymerisable porphyrin, (foam) and water; flexible anticorrosion coating compositions comprising a polymerisable porphyrin, water and a synthetic rubber; and pigmented or coloured coating formulations comprising a polymerisable porphyrin; water and a pigment.

A typical water-based coating system, in accordance with this invention, consists of two major parts. The first part (Part A) is the water-based resin obtained as described above. The second part (Part B) is a pigmented resin mixture made from one or more selected commercial resins, and metal oxides. Mixing of the Part A resin, the Part B resin, together, optionally with additional commercial resins and additive coating modifiers, gives the total coating system.

The coatings can be applied to any appropriate substrate, for example, wood, raw or dressed timber, metals, ceramics, galvanised steel, aluminium, mild steel, stainless steel, other metal alloys and glass. The coatings can be applied by any suitable known method, for example, by dipping, brushing or, more effectively, by electrodeposition.

The resin products of the invention can be reacted with other unsaturated polymeric or polymerisable materials. Among the reagents which can be used for this purpose are polymerisable monomers, oligomers or other polymer precursors which possess appropriate reactive groups. Oligomer types which contain such groups include:

(i) melamine based oligomers

(ii) epoxy oligomers

(iii) polyurethane oligomers or

(iv) alkyd resin precursors.

Oligomers may be terminated ("end capped") or reactive.

Preferred oligomer types are the alkyd resin precursors, such as acrylic-melamine, melamine-alkyd or simple alkyd formations.

Examples include castor oil base alkyds, soya bean oil alkyds, rosin esters, -OH rich esters and COOH rich esters (rosin precursors), -OH deficient and -COOH deficient resins.

Such reactions may require the presence of a catalyst. Inorganic acids, such as HC1 or organic acids, especially acrylic acid, may be used as catalysts. Metal salts are also useful as catalysts, particularly salts of the Transition Metals (Groups 3 to 12 of the Periodic Table) and the heavier metals of Group 14. Apart from acting as catalysts, these metals can also form coordination complexes with porphyrinogenic moieties, giving rise to coloured products which are useful in coating formulations.

Conveniently, the metal halides may be used, examples of which are the chlorides of copper, iron(III), molybdenum, nickel, manganese, mercury and lead. The resin products of the invention have also been found to be capable of undergoing further reaction with metal surfaces and to thereby form strongly adherent coatings which are highly resistant to saline solutions and other corrosive materials.

The resin products of the invention (and their reaction products with other polymeric/polymerisable materials) are also capable of reaction with organic or inorganic pigments, transition metal oxides or transition metal complexes. The coloured coatings thus formed have excellent colour fastness and anticorrosive properties.

The invention is further described and illustrated by the following non-limiting examples. (All percentages are by weight).

Example 1. Preparation of Resin

(A) The formulation for a typical Part A resin is given in Table I. All parts and percentages are by weight

Table I Formulation for Part A resin

Materials Composition (%) Source

N-methylpyrrole 18.7 BASF

Crotonaldehyde 4.3 Aldrich

Acrylic acid 40.1 Aldrich

Neutralising 7.5 see Note solution

THF 2.6

butanol 10.7

Water 16.1

Note: The neutralising solution consists of 66.7% of 0.880 ammonia, 7.4% of diethanolamine, 11.1% of n-butanol and 14.8% THF.

The N-methylpyrrole, crotonaldehyde and acrylic acid were mixed and allowed to stand at room temperature for 3 hours. The neutralising solution was then added and mixed in. The mixture was heated at 60°-70°C for 1 hour after which the butanol, additional THF and water were added. Example 2. Preparation of Coating Composition

(i) The composition of the Part B resin is given in Table II.

Table II Composition of Part B resin

Materials Composition (%) Source

Resin BT336¹ 35 BIP Chemicals Ltd.

Water 15

ZnO 5 BDH Chemicals Ltd.

Aluminium silicate 15 Kalon

ZPZ² 5 Kalon

Fe₂O₃ 25 Kalon

(ii) The total coating formulation is given in Table III.

Table III Composition of total coating

Materials Composition (%) Source

Part A 45 See Example 1

Part B 35 see Table II

Resin BT309³ 17 BIP Chemicals Ltd.

Dow Corning 29⁴ 1 Dow Corning Ltd.

BYK032⁵ 2 BYK Chemicals Ltd. Example 3. Testing

The coating system whose composition is given in Table III was applied on to the surface of BHP zincalum panels. The general coating properties are given in Table IV.

Table IV General coating properties

Property Results

Surface cure @ 120°C⁶ 5 minutes

Thorough cure @ 120°C⁶ 60 minutes

7 Scratch resistance Good

T-bend⁸ 2T

Solvent resistance (Xylene)^y >50 DR

Gloss¹⁰ Good

Notes to the tables:

1 Resin BT336 is an amino-formaldehyde resin in an aqueous medium.

2 Heucophos ZPZ is a modified phosphate hydrate-based wetting agent manufactured by Heuback GmbH & Co., Germany.

Resin BT309 is an amino-formaldehyde, film-forming resin precursor in an aqueous medium.

Dow Corning Silicate Additive 29 contains the C-OH functional group. It is an additive designed to assist in levelling and flow-out. It also has anti-floating properties. 5 BYK Additive 032 is an emulsion of hydrophobic components and paraffin-based mineral oil, normally used as a paint additive.

6 Curing time

Curing of the coating can be classified into three stages. These are surface cure, through cure and full cure. In most coating application processes, it is desirable that the surface cure and the through cure should take short time while full cure takes relatively long time. This is because rapid surface cure and through cure ensure the existing of a rapid coating application process and the slower full cure gives a highly ordered crosslinking and complexing which consequently ensures the development of good coating properties.

Surface-cure Time

A dry cotton ball of about 5mm diameter is placed on the surface of the coating panel. The coating panel is placed about 10 - 15 cm from an air jet. Slight blowing is then applied on the cotton ball. Surface cure is considered to be achieved when the cotton ball can be blown off the coating surface and no cotton fibre sticks to the coating surface. The surface cure time is the time which elapses between the end of the coating application and the time when surface cure is confirmed.

Through Curing Time

A 20 x 20 mnr quantity filter paper is placed on the surface of coated panel. A 200g weight with circular bottom (1.13 cm in diameter) is then placed on top of the filter paper. After 30 seconds, the weight is removed and the coating panel turned upside down. Through cure is considered to have been realised if the filter paper falls of the coated surface and no fibre sticks to the coated surface. The time which elapses between the end of coating application and the time when through cure is achieved is the through cure time. Scratch Test: A coin is pulled across the coating surface. The coating has good scratch resistance when no coating is lifted.

8 T-Bend Test: The panel is bent over on itself (IT) and then again (2T) etc. The "T" value quoted is the highest one at which the film does not break up and cannot be easily removed by standard testing tapes.

9 Solvent Resistance: This is based on double rubs with tissue paper. A double rub is a to-and-fro rub. The double rub value quoted is when the colour of the coating appears on the tissue paper as a consequence of the coating dissolving in the solvent, i.e. xylene.

10 Gloss: The gloss of the coating is judged visually as good to bad with "good" meaning acceptable relative to the qualities required of a top coat.

The cured coated panels were subjected to saline immersion tests. The saline solution contained 5% of NaCl and had a pH of 7.0. The saline immersion tests were both conducted at ambient temperature and at 120°C. The observations are recorded as Table V.

Table V Results of saline immersion test

Period of test Observations

Ambient temperature

790 hours Coating remain unaffected

120°C

120 hours Coating lost gloss

264 hours Several pin-holes observed.

300 hours Rust in pin-holes observed.

360 hours Rust area observed. (1-1.2 mm diameter)

460 hours Rust area increased to 2.5-4 mm in diameter.

Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the invention includes all such variations and modifications which fall within its spirit and scope. The invention also includes all the steps, features, compositions and compounds referred to or indicated in this specification, individually or collectively, and any and all combinations of any two or more of said steps or features.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A polymerisable porphyrin suitable for use in the formulation of water-based resins or coating compositions characterised in that it comprises the reaction product of: (a) one or more compounds selected from the group consisting of pyrrole and

N-(lower)alkyl pyrroles, any of which may be optionally ring substituted with one or two non-deleterious substituents;

(b) at least one α,β-unsaturated aldehyde;

(c) at least one unsaturated and/or polymerisable organic acid.

2. A polymerisable porphyrin as claimed in Claim 1, characterised in that the pyrrole is N-methylpyrrole.

3. A polymerisable porphyrin as claimed in Claim 1 or Claim 2, characterised in that the aldehyde is one in which the aldehyde (CHO) group is attached to a carbon chain containing from 2 to 7 carbon atoms.

4. A polymerisable porphyrin as claimed in Claim 3, characterised in that the carbon chain of the aldehyde contains from 3 to 6 carbon atoms.

5. A polymerisable porphyrin as claimed in Claim 4, characterised in that the aldehyde is crotonaldehyde or acrolein.

6. A process for producing a polymerisable porphyrin suitable for use in formulation of water-based resins or coating compositions, characterised in that it comprises reacting together

(a) one or more compounds selected from the group consisting of pyrrole and N-(lower)alkyl pyrroles, any of which may be optionally ring substituted with one or two non-deleterious substituents; (b) at least one α,β-unsaturated aldehyde; and

(c) at least one unsaturated and/or polymerisable organic acid; in the presence of an acid catalyst.

7. A process as claimed in Claim 6, characterised in that the catalyst is the acid component (c).

8. A process as claimed in Claim 6, characterised in that the catalyst is an inorganic acid or an organic acid which is not the acid component (c).

9. A process as claimed in any one of Claims 6 to 8, characterised in that the extent of the reaction between the components (a), (b) and (c) is controlled by adding to the reaction mixture one or more reagents which effectively terminate the reaction.

10. A process as claimed in Claim 9, characterised in that the added reagent is a C Co aliphatic alcohol, ammonia, an amine or a mixture of any two or more of such reagents.

11. A process as claimed in Claim 10, characterised in that the added reagent includes a water-solubility-enhancing or water-dispersability-enhancing solvent.

12. A process as claimed in Claim 11, characterised in that the solvent is a glycol ether, or a cyclic ether.

13. A process as claimed in Claim 12, characterised in that the solvent is tetrahydrofuran.

14. A water-based resin or coating composition characterised in that it comprises a polymerisable porphyrin.

15. A water-based resin or coating composition characterised in that it comprises a polymerisable porphyrin as claimed in any one of Claims 1 to 5.

16. A resin coating system as claimed in Claim 14 or Claim 15, characterised in that it includes at least one other known coating material.

17. A resin coating system as claimed in Claim 16, characterised in that the polymerisable resin is reacted with at least one unsaturated polymeric or polymerisable material.

18. A resin coating system as claimed in Claim 17, characterised in that the polymerised or polymerisable material is one or more of the following: (i) a melamine based oligomer (ii) an epoxy oligomer (iii) a polyurethane oligomer or (iv) an alkyd resin precursor.

19. A resin coating system as claimed in Claim 17 or Claim 18, characterised in that the reaction is carried out in the presence of a catalyst selected from inorganic acids, organic acids and metal salts.

20. A resin coating system as claimed in Claim 19, wherein the catalyst is a salt of a metal selected from Groups 3 to 12 of the Periodic Table.

21. A resin coating system as claimed in Claim 20, characterised in that the metal salt is a chloride of copper, iron (III), molybdenum, nickel, manganese, mercury or lead.

22. A resin coating system as claimed in any one of Claims 17 to 21, characterised in that the crosslinked resin product is further reacted with an organic pigment, an inorganic pigment, a transition metal oxide or a transition metal complex.

23. A resin coating system as claimed in Claim 22, characterised in that the inorganic pigment is ferric oxide.