WO2000001780A2

WO2000001780A2 - Waterborne epoxy resin coating compositions

Info

Publication number: WO2000001780A2
Application number: PCT/EP1999/004346
Authority: WO
Inventors: Bastiaan Anton Van De Werff
Original assignee: Shell Internationale Research Maatschappij BV
Current assignee: Shell Internationale Research Maatschappij BV
Priority date: 1998-07-03
Filing date: 1999-06-23
Publication date: 2000-01-13
Anticipated expiration: 2001-01-03
Also published as: AU4615399A; WO2000001780A3

Abstract

Waterborne primer coating composition comprising at least: (a) an aqueous epoxy resin dispersion, comprising at least one two-functional or polyfunctional epoxy resin, (b) an aqueous dispersion and/or a solution of an epoxy resin hardener, (c) aqueous bitumen dispersion, and optionally (d) fillers, pigments, additives, wherein component (b) is preferably a polyfunctional amine, which can be applied for curing at ambient temperature; and cured waterborne primer coating films on a shaped metal surface derived from said compositions.

Description

WATERBORNE EPOXY RESIN COATING COMPOSITIONS

The present invention relates to waterbome epoxy resin coating compositions and in particular to waterbome epoxy resin primer compositions, to be applied on metal surfaces and in particular steel surfaces. More in particular the invention relates to waterbome epoxy resin primer compositions to be applied on metal surfaces, such as steel pipes, which are subsequently overcoated with a bitumen composition.

Such compositions were known from Newsletter, April 1998, Nr. 3 from PH0NIX, disclosing a 2 component system of emulsions of epoxy resms and of a polyfunctional epoxy curing agent (PH0NIX is a trademark) .

However, a clear disadvantage of said applied primer compositions was the inferior intercoat adhesion between the primer layer and a subsequent bitumen layer, which could not meet the modern requirements of pipeline protection, and an object of the present invention was therefore, to improve said intercoat adhesion. More in particular an ob ect of the present invention was to improve the intercoat adhesion between the primer coating layer and modified bitumen topcoat compositions, comprising bitumen and minor amounts of elastomers and preferably block copolymers of alkadiene such as butadiene or isoprene and monovmylarenes such as styrene .

As a result of extensive research and experimentation said improved primer coating composition aimed as has surprisingly been found. Accordingly, the invention relates to waterbome primer coating composition comprising

(a) at least one aqueous epoxy resin dispersion, comprising at least one, two-functional or polyfunctional epoxy resin,

(b) at least one aqueous dispersion and/or a solution of an epoxy resin hardener,

(c) at least one aqueous bitumen dispersion, and optionally (d) fillers, pigments, additives.

As component (a) preferably dispersions of epoxy resins are used, wherein the epoxy resins have an epoxy equivalent weignt of at least 50C and lr particular from 500 to 2000 and more preferably from 1400 to 2000. Suitable epoxy resins include reaction products of epichlorohydrm with bisphenol A or bisphenol F containing at least two oxirane rings; epoxidized novolac resins formed by a reaction of epichlorohydrm with the reaction product of phenol or alkylphenol (the alkyl having 1-10 C-atoms) and formaldehyde; reaction products of epichlorohydrm and an aliphatic polyol, such as glycerol .

Examples of more preferred epoxy resins to be dispersed are those of the EPON 1007 or EPIKOTE 1007 and EPON 1001 or EPIKOTE 1001 resin types (EPON and EPIKOTE are trademarks) . Examples of particularly preferred dispersions to be applied are the commercially available epoxy resin dispersions EPI-REZ 3520 Y-55, EPI-REZ 5522 WY-55 and EPI-REZ 3510 W-60 (EPI-REZ is a trademark) .

As component (b) in principle any compound which can efficiently cure the included epoxy resin components, can be applied, such as functional amine compounds, functional phenolic resins, functional anhydrides or carboxylic acids, comprising at least one functional group but preferably more functional groups. Preferably the polyfunctional amme compounds, which enable curing at ambient temperatures, are included in the present primer coating compositions.

Any non-polymeric polyfunctional amme having at least 2 primary or secondary ammo groups can be employed as the amme-functional curing agent m the present invention. Such amines include aliphatic and cycloaliphatic amines each having 2 to 10 primary or secondary ammo groups and 2 to 100 carbon atoms. Preferred non-polymeric polyfunctional amines include 2 to 4 primary ammo groups and 2 to 20 carbon atoms.

Suitable polyfunctional amines include, but are not limited to, hexamethylene diamine; 2-methyl pentamethyl- ene diamme; 1,3-dιammo propane; 1,3-dιammo pentane; dodecane diamme; 1,2-dιamιno cyclohexane; 1,4-dιammo cyclohexane; para-phenylene diamme; 3-methyl piperidme; piperazine; N-amino ethylpiperazme; isophorone diamme; bis-hexamethylene triamme; diethylene triamme; ethylene diamme; diethylamme triamme; triethylene tetramme; tris (2-ammoethyl ) amme; ethylene oxide-amme; poly- oxyalkylene amines having from 2 to 6 oxyalkylene units and preferably from 2 to 4 oxypropylene units, such as, JEFFAMINE D, ED and T (JEFFAMINE is a trademark) series polyoxypropylene amme; amme-functional acrylic resins, disclosed in e.g. US Patent No. 4,120,839; tπmethyl hexamethylene diamme; and tetraethylene pentamme. Mixtures of these amme-functional curing agents and adducts of these amines and an epoxy group containing compound, and polyamide amines derived from aliphatic polyamme and a dimer of an unsaturated aliphatic fatty acid, can also be used. The most preferred epoxy curing agent is an epoxy amme adduct such as EPICURE 8290 Y-60, which is obtainable by the reaction between an epoxy phenolic novolac and triethylene tetramine (TETA) and further reaction of the resulting amme adduct with a mono- di-, tπ-glycidylether modifier and preferably monoglycidyl ether e.g. a cresyl glycidyl ether

(HELOXY 62 modifier) (HELOXY and EPICURE are trademarks) .^"

In combination with the above-mentioned hardeners, curing accelerators can be used. Such accelerators include: quaternary ammonium salts such as tetraethyl- ammonium chloride, tetraethylammonium bromide, cetyltri- methylammonium chloride, etc.; tertiary amines such as benzyldimethylamme, tπethylamme, 2,4,6-(tns- dimethylammoethyl ) -phenol, etc.; amme hardening catalysts such as 2-methyl-4-methylιmιdazole, 2-phenylιmιdazole, l-benzyl-2-methylιmιdazole, 2-ethyl-4-methyllmidazoleazme, lmidazoleazmes containing 11 carbon atoms (not including hexamethylene tetramine) ; lithium salts such as lithium cnloπde, lithium bromide, lithium iodide, etc., and the like. These accelerators are usually used m an amount of 0-10% by weight of the epoxy resm used and preferably of 0 to 3%.

The fillers and/or pigments applied as component (d) , can be selected from a great variety of commercially available compounds, which can provide m principle colour and barrier properties. More specifically the fillers and/or pigments can be selected from titanium dioxide, barytes, talk, calcytes, clay, kaolin, carbon black and the like, or mixtures thereof. Anti-corrosion pigments can also be included alone or in addition to other pigments and/or fillers. As examples of such anti-corrosion pigments can be mentioned, however without any limitation, zinc dust, zinc oxide, talc, silica dust, copper dust (especially suitable for anti- fouling pamts in marine environments, such as ship hulls and bottoms and offshore equipment), zinc phosphates, modified zinc phosphates, such as hydrates (e.g. HEUCOPHOS ZMP, ZPA, SAPP (HEUCOPHOS is a trademark) , and calcium exchange pigments e.g. SHIELDEX pigments (SHIELDEX is a trademark) .

Zinc phosphates or modified zinc phosphates or calcium exchange pigments are preferred. The amount of pigments and fillers is in the range of from 0 to 45 vol%, relative to the total solids m the final composition .

Additives, wetting and dispersing additives which can stabilize tne pigments in the continuous aqueous phase, and defoammg agents, can optionally be incorporated into the present compositions, e.g. BYK 190, 154, 33. The total amount of additives normally is m the range of from 0 to 10 wt% relative to the total weight of solids of component (d) .

The bitumen dispersion can be obtained by dispersion of bitumen in the presence of a surfactant, being non- lonic, anionic or cationic, and preferably non-ionic, an amount of from 0.5 to 6% by weight, relative to the solid bitumen weight.

The bitumen materials used m this invention include: lake asphalt such as Trinidad Epure, gilsonite, pyrobitumen, etc.; natural bitumen such as rock bitumen; cutback bitumen therefrom; petroleum bitumen and petroleum pitch such as straight asphalt and blown bitumen produced in the process of refining petroleum; cutback asphalt therefrom; mixed bitumen such as pitch bitumen, astar, etc.; flux oil, cycle oil from catalytic decomposition of heavy crude oil, cycle oil from catalytic decomposition of light crude oil, etc. The lubricating oil materials used in this invention include lube cut and petroleum process oil obtained by extraction, refining and hydrogenation, etc., of the lube cut or other distillation fractions of petroleum as well as any mixture of the above. Especially preferred are bitumens, having a PEN grade from 20 to 300 dmm at 25 °C. PEN grade definitions and test methods are known from e.g. Shell Bitumen Industrial Handbook, 1995, London, p. 63, 64 and 100-104.

The penetration grade (PEN) is a measurement wherein a needle of specified dimensions is allowed to penetrate into a sample of bitumen, under a known load (100 g) at a fixed temperature (25 °C) for a known time period (5 seconds). The distance over which a needle penetrates, is measured in decimillimetres (dmm) and is termed the penetration.

Said bitumen can if desired be modified with thermoplastic elastomers, such as butadiene-styrene block copolymers or isoprene-styrene block copolymers and preferably hydrogenated block copolymers of butadiene- styrene or isoprene-styrene (e.g. KRATON D or KRATON G block copolymers (KRATON is a trademark) ) , optionally mixed with polyolefms, an amount of from 0 to 15 wt% calculated on solid bitumen and preferably from 0 to 5% by weight. The bitumen component is incorporated into the primer - composition of the present invention, in amounts ranging from 0.5 to 50% by weight and preferably from 5 to 30% by weight, relative to the weight of the polymeric solids of the coating composition (i.e. weight of epoxy resm and curing agent) .

It will be appreciated that aqueous primer coating compositions as specified hereinbefore, and comprising m addition to water minor amounts of co-solvents, will also be covered by the present invention. Suitable co-solvents can be selected from poly (alkylene) glycol ethers (e.g. ethylene glycol propylether or ethylene glycol monobutyl ether) , or alkanols or ketones having 1-4 carbon atoms and can be used in amounts of from 0 to 25% by weight, relative to the weight of water, and preferably from 0 to 10% by weight.

Flash rust inhibitors, such as tertiary amines, nitrite salts and the like, can also be included as an optional additional additive in the primer coating compositions of the present invention, in an amount of from 0 to 3% by weight, relative to the total weight of solids of the coating composition (i.e. the weight of all polymeric materials, pigments, fillers) .

The components (a) and (b) of the coating composition of the present invention, have to be stored separately until the user is ready for the actual coating processing. It will be appreciated that one of these components (a) or (b) can be included in an intermediate precomposition with other ingredients (c) and (d) . The number equivalent amount of component (a) is stoichiometrically selected based on the number equivalent amount of component (b) present in the complete coating composition. The stoichiometric ratio of the epoxy resin component to the functional curing agent varies in the range of from 0.8 to 2 and preferably from 1 to 1.5. Most preferably the stoichiometric ratio is from 1.1 to 1.3.

Preferably, the cross-linking component is emulsified in water or in water and a suitable co-solvent, such as poly (alkylene) glycol ethers, (e.g. ethylene glycol propyl ether or ethylene glycol monobutyl ether) , or alkanols or ketones having 1-4 carbon atoms. The epoxy resin component in an emulsified form, containing liquid epoxy resin or epoxy resin solution, is preferred. It was surprisingly found that the complete coating compositions, as specified hereinbefore, when applied as primer on metal and preferably steel surfaces, provided a significantly increased intercoat adhesion when covered with a topcoat layer of bitumen or modified bitumen enamel, e.g. BITUSEAL (BITUSEAL is a trademark for a coating of bitumen, modified with styrene-butadiene block copolymer in an amount of about 9 wt% relative to the weight of the total composition) . Pull off testing has been shown an increase in intercoat adhesion of 30 to 50% of the present primer compositions, depending on the modification type and intensity.

The coating composition is applied in general in layers of a thickness in the range from 10 to 200 microns dry film thickness, while the steel surface to be treated has a temperature in the range of from 5 to 90 °C and preferably from 5 to 45 °C.

After curing, normally within a period of from 5 to 60 minutes and preferably from 20 to 45 minutes, the primer layer is overcoated with straight bitumen or modified bitumen at a temperature between 160 to 220 °C, using conventional equipment.

The coating systems are used as external coatings for in particular pipelines to protect against corrosion which if desired can be overcoated with concrete to provide negative buoyancy.

It is true, that from US patent No. 4,360,608 is known a polymer system comprising an epoxy resin, bitumen and co-solubilizer (surfactant) and an epoxy resin hardener, wherein the co-solubilizer is needed to enable the achievement of a homogeneous mixture of epoxy and bitumen without demixing. Although said polymer systems were indicated to be used as in principle as paints for anti-corrosion properties, no reference to any dispersion in water as continuous phase, of the epoxy resin and the hardener and the bitumen was made to reach the improved adhesion . It will be appreciated that another aspect of the present invention is formed by dried and cured primer coating films on shaped metal surfaces (e.g. a coated steel pipe), and by said coating films, combined with a separate adhering second coating layer, i.e. the complete systems of successive coating layers.

The invention is further illustrated by the following examples, however, without restricting its scope to these embodiments . EXAMPLE 1 14 Grams of EPI-REZ 5522-WY-55 was mixed with

1.75 grams of EPI-CURE 8290-Y-60 together with 1.25 grams of water and with 3.94 grams of bitumen emulsion (non- ionically stabilized solids content of 67 %wt) , having a PEN grade of 100 at 25 °C, and in which the water content was increased to 1.84 grams.

After stirring the coating mixture was applied to cold rolled steel panels (degreased with acetone) . The mixture was allowed to cure at 40 °C in an air circulated oven. After 1 hour curing time, the panel was removed from the oven and directly overcoated with BITUSEAL of

190 °C and allowed to cool down. An aluminium strip with a thickness of 0.5 mm was put on top of the BITUSEAL layer. After 1 week storage at 23 °C and 50% relative humidity the panel with the coating system was cut into strips of 3.5 cm. The intercoat adhesion between the epoxy/bitumen coating and BITUSEAL layer was determined by recording the required force for 90 ° pull-off.

Sample width was 2.5 cm. The intercoat adhesion showed to be 140 N. Comparative Example

14 Grams of EPI-REZ 5522-WY-55 was mixed with 1.75 grams of EPI-CURE 8290-Y-60 together with 1.25 grams of water. After stirring the coating mixture was applied to cold rolled steel panels (degreased with Acetone) . The mixture was allowed to cure at 40 °C in an air circulated oven. After 1 hour curing time, the panel was removed from the oven and directly overcoated with BITUSEAL of 190 °C and allowed to cool down. An aluminium strip with a thickness of 0.5 mm was put on top of the BITUSEAL layer. After 1 week storage at 23 °C and 50% relative humidity the panel with the coating system was cut into strips of 3.5 cm. Tne intercoat adhesion between the epoxy and BITUSEAL layer was determined by recording the required force for 90 ° pull-ofF.

Sample width was 2.5 cm. The intercoat adhesion showed to be 100 N. EXAMPLE 2

14 grams of EPI-REZ 5522-WY-55 was mixed with 1.75 grams of EPI-CURE 8290-Y-60 together with 1.25 grams of water and 3.77 grams of bitumen emulsion (non-ionically stabilized solids content of 70.5 wt%) having a PEN grade of 200 at 25 °C, and in which the water content was increased to 1.84 grams. After stirring the coating mixture was applied to cold rolled steel panels (degreased with acetone) . The mixture was allowed to cure at 40 °C in air circulated oven. After 1 hour curing time, the panel was removed from the oven and directly overcoated with BITUSEAL of 190 °C and allowed to cool down. After 1 week storage at 23 °C and 50% relative humidity the intercoat adhesion between the BITUSEAL and the primer was measured. Results were similar as in Example 1. EXAMPLE 3

Instead of 200 PEN grade bitumen emulsion, as used in Example 2 a bitumen emulsion (lonically stabilized having a PEN grade of 50 at 25 °C) was added in the same weight ratios compared to Example 2. The observed intercoat adhesion was similar as in Example 1 and 2.

In additional experiments the EPI-REZ 5522 WY-55 was replaced by EPI-REZ 3520 WY-55 and EPI-CURE 8290-Y-60 was replaced by EPI-CURE 8540, while similar properties were reached.

Claims

A I M S

1. Waterbo e primer coating composition comprising (a) at least one aqueous epoxy resm dispersion, comprising at least one two-functional or polyfunctional epoxy resm, (b) at least one aqueous dispersion and/or a solution of an epoxy resm hardener,

(c) at least one aqueous bitumen dispersion, and optionally

(d) fillers, pigments, additives.

2. Waterbo e primer coating composition according to claim 1, characterized m that the epoxy resm has an epoxy equivalent weight of from 1400 to 2000.

3. Waterbome primer coating composition according to claims 1 and 2, characterized m that as epoxy hardener a polyfunctional am e, which can be applied at ambient temperature, is used.

4. Waterbo e primer coating composition according to claims 1 to 3, characterized n that an epoxy amme adduct has been included wnicn is obtainable by the reaction between an epoxy phenolic novolac and triethylene tetramime (TETA) and further reaction of the resulting amme adduct with a mono-, di- or tri- glycidylether modifier and preferably a monoglycidyl- ether .

5. Waterbo e primer coating composition according to claims 1-4, characterized in that it comprises as anti- corrosion pigment zmc phosphate, modified zmc phosphate or calcium exchange pigments.

6. Waterbo e primer coating composition according to claims 1-5, characterized m that the stoichiometric ratio between the epoxy resin and the functional curing agent is in the range of from 1.1 to 1.3.

7. Cured waterbo e primer coating films on a shaped metal surface derived from the compositions according to claims 1-6.

8. Cured waterbo e primer coating films according to claim 7, combined with an adhered second bituminous coating layer.