Patent Application
20180163081
The invention relates generally to RMA crosslinkable compositions, in particular coating compositions, more in particular pigmented coating compositions (paints) with improved adhesion to substrates. The invention further relates to an adhesion promotor for improving adhesion on a substrate surface of an RMA crosslinkable composition, a method for applying a RMA crosslinked coating layer with improved adhesion and a kit of parts and premixes for use in said method.
RMA crosslinkable compositions are compositions comprising at least one crosslinkable component comprising reactive components A and B each comprising at least 2 reactive groups wherein the at least 2 reactive groups of component A are acidic protons (C—H) in activated methylene or methine groups (RMA donor group), and the at least 2 reactive groups of component B are activated unsaturated groups (C═C) (RMA acceptor group). These reactive groups react to achieve crosslinking by Real Michael Addition (RMA) reaction between said at least one crosslinkable components in the presence of a base catalyst (C).
Such RMA crosslinkable compositions are described in EP2556108. Herein a special catalyst C is described which is a substituted carbonate catalyst which decomposes in a coating layer to generate carbon dioxide which evaporates from the applied curing coating layer and a strong base which starts the RMA crosslinking reaction. The catalyst provides long pot-life and at the same time a high reactivity and fast cure when applied as a coating layer where CO2 can escape.
The problem underlying the invention is that the RMA crosslinkable compositions may show undesirably poor adhesion properties in particular to polar surfaces for example in direct to metal applications. To achieve adhesion the metal surface may have to be pretreated with a primer layer or with known metal pretreatments like silane treatment.
In the General Industrial, Marine, Protective, and ACE markets, topcoats are usually applied over an epoxy-amine primer. Adhesion studies of coatings based on RMA crosslinkable compositions were carried out over many different types of commercially available epoxy primers used in a wide field of end use applications including general industry, ACE and protective coatings. However, known epoxy primers do not always give good adhesion results for coatings based on RMA crosslinkable compositions.
Alkoxy-silanes are known adhesion promoters. However, the problem with these alkoxysilane adhesion promoters in RMA compositions is that they do not always give stable paint formulations in particular in pigmented coating compositions. Adhesion performance of alkoxysilanes incorporated in a pack containing the binder components may show poor shelf stability.
Therefore the desire remains to more adequately improve the adhesion of RMA crosslinkable compositions, in particular coating compositions, in particular in pigmented coating compositions comprising the crosslinkable composition as the binder system for the coating and there is a need for adhesion promotors for improving the adhesion of RMA crosslinkable compositions.
According to the invention this problem has been solved by a crosslinkable composition which crosslinkable by real Michael addition (RMA) reaction comprising
It was found that the stability problem with alkoxysilane adhesion promotors is present in particular when water or pigments or both are present. It is believed that the siloxy groups may react with water or the pigment surface, thus losing their substrate adhesion promoting abilities. Also, these alkoxysilanes are not stable in basic or acidic aqueous media. Therefore it appears that alkoxysilanes tend to lose adhesion performance over time.
The RMA crosslinkable composition as described is highly reactive and crosslinks within a short time. Therefore the RMA crosslinkable composition is described as it is delivered in the form of a kit of parts comprising two or more parts (preferably 2) comprising the components A, B, C, P and optional components D and T.
The RMA crosslinkable composition can be used for different applications including coatings, adhesives, inks, synthetic resin flooring or binder in structural composites, but preferably is a coating composition (i.e. a lacquer or paint) optionally comprising further usual coating additives as may required for the envisaged application.
The adhesion promotor P may comprise more than one alkoxysilane and more than one functional group X but good results are obtained with an functional alkoxysilane with the general formula (X(CH2)n)mSi(OR)4−m, where m is 1, 2 or 3; n is 1-20, R is methyl, ethyl, propyl, isopropyl, butyl or isobutyl and X is a functional group reactable with component A or component B or a precursor thereof, preferably a moisture deblockable precursor.
The pre-mix further may comprise a water scavenger, preferably chosen from the group of silanes, oxazolidines or molsieves to ensure that the water cannot inactive adhesion promotion performance.
In the adhesion promotion pre-mix the functional alkoxysilane adhesion promotor P is preferably admixed either with the catalyst C or with an organic solvent T or combinations thereof. The invention also relates to a water and pigment free adhesion promotion pre-mix comprising adhesion promotor P, optionally a water scavenger, substantially no components A and B, base catalyst C, organic solvent T, and optionally D, preferably only C, T and P. Preferably catalyst C herein is a carbondioxide blocked strong base catalyst preferably alkyl carbonate, preferably metho- or ethocarbonate or bicarbonate and T is an alcohol, preferably methanol or ethanol. It was found that this premix has a good shelf life (storage stability).
It was found that the adhesion promotor P is an effective adhesion promoter in RMA crosslinkable compositions even for direct to metal applications. The functional group X reactable with component A or component B is chemically bonded to the crosslinked network and the alkoxysilane group provides chemical bond with the substrate surface.
The crosslinkable composition preferably comprises a crosslinkable component with component A being predominantly a malonate or an acetoacetate and a crosslinkable component with component B being an acryloyl and therefore the preferred adhesion promotors have one or more functional groups X reactable with malonate or acetoacetate and/or with the acryloyl.
Suitable functional groups X reactable with component A or component B are primary or secondary amine, a thiol, isocyanate, epoxy, aldehyde or a RMA reactable component A′ or B′ which are same or different from the reactive components A and/or B in the RMA crosslinkable components.
Adhesion promotor wherein functional groups X is a component A′ or B′ can be produced by forming an adduct of an adhesion promotor having a moiety comprising one or more functional groups X being primary or secondary amine, thiol, isocyanate, aldehyde or epoxy, preferably primary or secondary amine, and reacting X with a component A′ or B′ so that A′ or B′ become the functional group X in the adhesion promotor P.
In this reaction product the A′ must have activated C—H to react with component B on the crosslinkable component and B′ must have activated C═C to react with component A on the crosslinkable component. So in case X reacts with C═C in component B′, said component B′ must be polyfunctional and the amount of X should be chosen to leave C═C functionality in the adhesion promotor. The same applies to the adduct formation of component A′.
This reaction is done outside the RMA coating composition and the obtained reaction product be added as a separate component as adhesion promotor to an RMA crosslinkable composition.
The one or more functional groups X can be a polyfunctional reactive component B′ reactive with a crosslinkable component with reactive component A and preferably are a reaction product of the functional alkoxysilane adhesion promotor, preferably the adhesion promotor is a reaction product of an amine functional alkoxysilane, with a reactive component B′ and, said reaction product comprising one or more reactive component B′ as functional groups X.
Alternatively the one or more functional groups X are a polyfunctional reactive component A′ reactive with a crosslinkable component with reactive component B, and preferably the adhesion promotor is a reaction product of the functional alkoxysilane adhesion promotor, preferably an amine functional alkoxysilane, with a reactive component A′ and, said reaction product comprising one or more reactive component A′ as functional groups X.
The invention also relates to an adhesion promotor for improving adhesion of an RMA crosslinkable composition as described above said adhesion promotor being a functional alkoxysilane as described above wherein X is a reactive component B′ reactable with component A or a component A′ reactable with component B wherein reactable component A′ or B′ are same or different from the reactive components A and/or B of the RMA crosslinkable components.
The adhesion promotor preferably is a reaction product of the functional alkoxysilane wherein functional group X is an amine and an acetoacetate functional reactive component A′, said reaction product comprising component A′ as functional groups X bonded over an enamine bond to the functional alkoxysilane preferably being a reaction product of the functional alkoxysilane wherein functional group X is an amine and a polyfunctional acetoacetate, in particular the enamine reaction product of trifunctional acetoacetate compound with aminomethylpyridine
Alternatively the adhesion promotor is a reaction product of the functional alkoxysilane wherein functional group X is an amine and a polyfunctional reactive component B′, in particular a tri- or tetraacrylate, said reaction product comprising component B′ as functional groups X bonded by Michael addition to the functional alkoxysilane.
Alternatively the adhesion promotor has moisture deblockable precursors of X which when exposed to water, present in the RMA composition or on the substrate surface, convert to X. Prefered are moisture deblockable primary or secondary amine, preferably a ketimine, aldimine or oxazolidine.
Good results were obtained with aminopropyl triethoxysilane aminopropyl trim ethoxysilane and N(beta-am inoethyl) gamma-aminopropyltrimethoxy-silane as described in the examples.
The adhesion promotion pre-mix can be the functional alkoxysilane adhesion promotor P admixed either with the catalyst C or with an organic solvent T or combinations thereof. Alternatively, the adhesion promotion pre-mix may comprise a reaction product of the functional alkoxysilane adhesion promotor P and the crosslinkable component comprising reactive component B.
The invention also relates to a method for applying a RMA crosslinked coating with improved adhesion on a substrate surface comprising
In the RMA crosslinkable composition according to the invention, the weight amount of adhesion promotor P, in case of an adduct of an adhesion promotor P with said reactive components A′ or B′ not including the weight of reactive components A′ or B′, is between 0.1 and 10 wt % relative to the total weight of the crosslinkable components, preferably 0.2-5, more preferably 0.5-4 and most preferably 1-2 wt %.
Preferably in the crosslinkable composition the molar ratio of C═C to C═C reactive groups, including C—H in reactive component A, functional groups X in adhesion promotor P and groups X—H in D is between 0.3 and 3, preferably 0.5-2 and even more preferably 0.75-1.5.
In a particular embodiment of the method of the invention the application method is spraying and adhesion promotor P is dissolved in an organic solvent added to dilute the RMA composition to spraying viscosity. A mixture of at least one part comprising catalyst C and at least one other parts comprising pigments or water or both is diluted to a spraying viscosity with an organic solvent just before spraying and the alkoxysilane adhesion promotor is dissolved in said organic solvent.
The method is particularly useful for improving adhesion direct to metal, wherein the metal surface may be chemically treated and modified but not coated with a primer layer comprising a polymer binder.
In another aspect the invention relates to a method for applying a RMA crosslinked coating with improved adhesion on a substrate surface comprising the steps of
It has been found that improved adhesion can also be obtained on an epoxy primer layer.
Reference is made to EP2556108 and EP2764035 for detailed description of all components in the RMA crosslinkable composition A, B C or D, their preparation, the amounts used in the RMA crosslinkable composition as well as for measurement methods and definitions and the description thereof is hereby incorporated by reference and applicable unless described otherwise herein. Most important features are described below in summary.
It is preferred that reactive component A is malonate or acetoacetate, preferably dominantly malonate, and reactive component B is acryloyl. It is preferred that the one or more reactive components A in the crosslinkable component predominantly comprise one type of reactive components, predominantly meaning preferably more than 50, 75, 90 and most preferably 100% of the C—H reactive groups in crosslinkable component A are from one type of reactive component A, preferably from malonate or acetoacetate and most preferably consisting predominantly of malonate and acetoacetate or acetylacetone as the remainder component A. The most preferred component B is an acryloyl.
The reactive components A and B are preferably build into a polymer chain or pending or terminal pending on a polymer chain. Preferably, the one or more crosslinkable components are one or more polymers chosen from the group of polyesters, alkyds, polyurethanes, polyacrylates, epoxy resins, polyamides and polyvinyl resins which contain components A or B in the main chain, pendant, terminal or combinations thereof.
The one or more RMA crosslinkable components can be monomeric but preferably at least one crosslinkable component is a polymeric component with a weight average molecular weight Mw of at least 250 gr/mol, preferably a polymer having Mw between 250, 300 and 5000, more preferably between 400 and 4000 or 500 and 3000 gr/mol (as determined by GPC).
The relative amounts of the crosslinkable components in the RMA crosslinkable composition are chosen such that the molar ratio of activated unsaturated reactive group C═C in reactive component B to the activated acidic reactive groups C—H in reactive component A is between 0.5 and 2 and preferably between 0.75-1.5 or 0.8-1.2.
In case components D or Por both are present that comprise reactive groups X—H and can react with B, the molar ratio of activated unsaturated reactive group C═C in reactive component B to the total number of reactive groups C—H in reactive component A and reactive groups X—H in component D and P is between 0.3 and 3, preferably 0.5-2 and even more preferably 0.75-1.5 or 0.8-1.2.
The total amount of monofunctional material is preferably low, otherwise it will negatively affect coating properties. Preferably the total amount monofunctional reactive solvent is less than 10, preferably less than 5, 3 or even 2 wt %.
The RMA crosslinkable composition preferably further comprises a reactivity moderator D comprising an X—H group that is also a Michael addition donor reactable with component B under the action of catalyst C, wherein X is C, N, P, O or S or an alcohol with 2 to 12 carbon atoms or both for improving open time and hence working time of application of the floor coating composition on a floor.
The X—H group in component D, preferably an N—H group containing component, has a pKa (defined in aqueous environment) of at least one unit, preferably two units, less than that of the C—H groups in predominant component A, preferably the pKa of the X—H group in component D is lower than 13, preferable lower than 12, more preferably lower than 11, most preferably lower than 10; it is preferably higher than 7, more preferably 8, more preferably higher than 8.5.
The component D preferably comprises a molecule containing the N—H as part of a group —(C═O)—NH—(C═O)—, or of a group —NH—(O═S═O)— or a heterocycle in which the nitrogen of the N—H group is contained in a heterocyclic ring preferably chosen from the group of a substituted or unsubstituted succinimide, glutarimide, hydantoin, triazole, pyrazole, immidazole or uracil, preferably chosen from the group of succinimides, benzotriazoles and triazoles.
The component D is present in an amount between 0.1 and 10 wt %, preferably 0.2 and 7 wt %, 0.2 and 5 wt %, 0.2 and 3 wt %, more preferably 0.5 and 2 wt % relative to the total amount of the crosslinkable components A or B and component D. The component D is present in such amount that the amount of X—H groups in component D is no more than 30 mole %, preferably no more than 20, more preferably no more than 10, most preferably no more than 5 mole % relative to C—H donor groups from component A present in the crosslinkable polymer.
The catalyst C can be a carbon dioxide blocked strong base catalyst, preferably a quaternary alkyl ammonium bi- or alkylcarbonate (as described in EP2556108). As this catalyst generates CO2 it is preferred for use in coating layers with a thickness up to 500, 400, 300, 200 or 150 micrometer.
A homogeneous base catalyst C, which is more suitable for thicker coating layers, are described in EP0326723 which is a catalyst consisting of the combination of a tertiary amine and an epoxide.
A preferred homogeneous catalyst C is a salt of a basic anion X— from an acidic X—H group containing compound wherein X is N, P, O, S or C, and wherein anion X— is a Michael Addition donor reactable with component B and anion X— is characterized by a pKa(C) of the corresponding acid X—H of more than two units lower than the pKa(A) of the majority component A and being lower than 10.5. Details of this catalyst are described in PCT/EP2014/056953, which is hereby incorporated by reference.
Other catalysts C that are especially useful in applications in which there is no large surface available for allowing CO2 to evaporate such as in the case of thick films applications, have been described in WO2014166880A1.
In view of the fact that the RMA crosslinking reaction is base catalyzed, acidic components should not be used in the composition such that the acid base reaction between catalyst C and A and optionally D is not interfered. Preferably the composition is free of acidic components.
The RMA composition may comprise one or more organic solvents T required for dissolving certain components or for adjusting the RMA composition to an appropriate handling viscosity (eg for spraying application). Organic solvents for use in RMA crosslinkable compositions are common coating solvents that do not contain acid impurities like alkylacetate (preferably butyl or hexyl acetate), alcohol (preferably C2-C6 alcohol), N alkylpyrrolidine, glycolether, Di-propylene Glycol Methyl Ether, Dipropylene Glycol Methyl Ether, Propylene Glycol Methyl Ether Acetate, ketones etc.
The amount of volatile solvent can be between 0 and 60, 50 or 40 wt % but in view of QESH preferably the composition has a low volatile organic compounds (VOC) content and therefore the amount of volatile organic solvent is preferably less than 30, 25, 20, 15, 10, 5 and most preferably less than 2 or even 1 wt % relative to the total of the crosslinkable components A and B.
In particular where a low viscosity and a low VOC is required it is preferred that the RMA crosslinkable composition comprises one or more reactive solvents which react with crosslinkable components A or B. The one or more reactive solvents are preferably selected from the group of monomeric or dimeric components A, monomeric or dimeric components B, compounds A′ having only 1 reactive acidic protons (C—H) in activated methylene or methine groups, compounds B′ having only 1 reactive unsaturated groups (C═C), most preferably acetoacetate, malonate. The total amount of volatile organic solvent plus reactive solvents is between 0 and 30 wt % and the volatile organic solvent is less than 5 wt % relative to the total weight of the RMA composition.
Alkoxysilane adhesion promoters suitable for use in the invention are preferably defined as compounds with the formula (X(CH2)n)mSi(OR)4−m, where m is 1, 2 or 3; n is 1-20, R is methyl, ethyl, propyl, isopropyl, butyl, isobutyl and X is any functionality which can react with RMA crosslinkable components, preferably comprising a malonate or acetoacetate and/or acryloyl moiety, preferably a primary amine, secondary amine, isocyanate, epoxy, thiol or activated C═C unsaturated groups. Using these functional alkoxysilanes adhesion promoters, the siloxane groups can form chemical bonds with reactive groups on the surface of the substrate, such as OH-functionalities and the remaining functional group on these adhesion promoters is then able to react with the crosslinked network formed by the RMA crosslinkable composition.
It was further surprisingly found that alkoxysilane adhesion promoters can be used in alcoholic basic RMA crosslinking catalysts, or in thinner components (with or without water scavenger) to yield stable formulations that improve the adhesion of paints on substrates.
The following is a description of certain embodiments of the invention, given by way of example only.
Abbreviations of adhesion promoters used in the examples are given in Table 1:
The results of adhesion stated in the following examples are based on the cross cut adhesion test following the ISO/DIN 2409, ASTM D3359 protocol. The ranking is briefly summarized as follows:
To test the adhesion of given examples and comparative examples films were applied on two types of metal substrates Gardobond 26S 6800 OC and Gardobond C. Gardobond© is a trade name of the German producer “Chemetall”. Other example relate to adhesion on aluminium (Q-panel Al-46).
General Procedure for Mixing Formulations with All Other Adhesion Promoters
The malonate polyester, DiTMPTA and n-propanol were transferred to a flask and mixed. After obtaining a homogeneous mixture the stated amount of adhesion promoter was added. The solutions were then stirred overnight. Prior to use all mentioned formulations were activated by adding the stated amount of initiator which is a tetrabutylam monium hydroxide TBAH solution reactively blocked with diethylcarbonate, with a base concentration of 0.928 meq/g solution (see procedure for preparation of initiator solutions). The initiator is also referred to herein as catalyst CAT4.
This resin is prepared as follows: into a reactor provided with a distilling column filed with Raschig rings were brought 382 g of neopentyl glycol, 262.8 g of hexahydrophthalic anhydride and 0.2 g of butyl stannoic acid. The mixture was polymerised at 240° C. under nitrogen to an acid value of 0.2 mg KOH/g. The mixture was cooled down to 130° C. and 355 g of diethylmalonate was added. The reaction mixture was heated to 170° C. and ethanol was removed under reduced pressure. Part the resin was modified by addition of succinimide as reactivity moderator; when the viscosity at 100° C. reached 0.5 Pa.s the material was cooled down to 140° and 11.2 grams of solid succinimide were added (MPE1S). This mixture was stirred until all succinimide was dissolved. Both resins were diluted with butyl acetate to 85% solids, to yield a material with OH value 16 mg KOH/g, GPC Mn 1750, and a malonate equivalent weight of 350 (active C—H EQW 175)
We use different layers of tape to create different spacers for the doctor's blade. This results in a variety of cured film thickness, in the examples beneath a range of 50 to 80 microns. Curing is done at 22° C. and a relatively humidity of 45-65%. The adhesion is tested after 24 hours under these conditions.
Series 1: Examples and Comparative Samples with Amino Alkoxy Silanes
All formulations of next table were prepared by mixing the malonate polyester with DiTMPTA and n-propanol. The comparative samples are then ready to activate and cure.
In example 9 the additional component aminopropyl triethoxy silane was, prior to activation with the blocked TBAH, added to the clear coat composition. In example 10 vinyltrimethoxysilane was added to the clear coat and stirred for one night, to allow water scavenging. Then aminopropyltriethoxysilane was added and the varnish was activated and cured.
In both examples 9 and 10 only a part of the stock solution was used and the actual amount of initiator was related to the amount of the smaller sample and the total amount initiator needed to complete the lacquer.
The malonate polyester MPE1, DiTMPTA and n-propanol were transferred to a flask and mixed. The vinyl trimethoxysilane is then added and the sample is stirred overnight. Then aminopropyltriethoxysilane was added, and stirred well. In comparative examples the step with vinyl trim ethoxy silane was omitted.
Of the freshly prepared solutions, a part was isolated, activated and applied on a substrate. The remaining part of the stock solution was sealed and placed in an oven at 60° C. Every week the samples were opened, exposed to air and sealed again. At the given time interval again a part of the stock solution was isolated, activated and applied onto a metal substrate.
The amount initiator is the amount needed for the total formulation. Since from the stock solution smaller samples were taken, the actual amount initiator was relatively to total amount clear coat and the stated total amount imitator.
Thinners were prepared by mixing solvent and aminosilane as described in Table 6 below. Aging experiments were done by keeping the solution at a specified temperature and for a specified time to establish the stability of the solution and its effect on the coating properties.
Paints were prepared by mixing the components as described in Table 7 below.
Paint A is based MPE1 and MPE1S. The succinimide containing resin was mixed with same resin not containing the succinimide and 1,2,4 triazole as adhesion promotor.
Paint B was prepared from a malonate functional alkyd MA9. MA9 is a malonated alkyd using coconut oil as the oil component, an oil length of 30%, an OH value of 108 mg KOH/g, a GPC Mn of 1800 and an Mw of 4350. The malonate equivalent weight of this material is 360 (active C—H equivalent weight 180). This resin was mixed with trimethylol (TMP) reacted with acetoacetate as reactivity moderator and a small amount of Silmer silicone reactive prepolymer.
Paint C was prepared as in Paint A except that Paint C comprises an aminosilane adhesion promotor.
Paint D was prepared from a Malonate functional polyester as described above further comprising malonated TMP but no adhesion improver which was tested on a primer of a ketimine modified epoxy primer paint.
Catalyst compositions were prepared by mixing components specified in Table 8. Catalyst 1 and 4 did not comprise an adhesion improver. Catalyst 2 and 3 did comprise an adhesion improver.
Thinner 1 was aged for 1 month at 40° C. 33.25 grams of Catalyst 1 and 70 grams of aged Thinner 1 were subsequently added to 936 grams of Paint A. This mixture was sprayed on a Gardobond 26S/60/OC panel (a Zinc phosphated steel substrate) with a dry layer thickness of 120 μm. After 1 day at room temperature and 1 hour at 60° C., adhesion was determined to be very good. The adhesion was tested using the cross-cut adhesion test as described in ASTM D3359.
The same composition as in Example 12 was sprayed on an electroplated zinc steel panel with a dry layer thickness of 65 μm. After 1 day at room temperature, adhesion was determined to be very good.
Example 13 was repeated except that aged Thinner 2 was used (1 month at 40° C.). Adhesion was determined to be very good.
Catalyst 2 was aged for 77 days at 25° C. 0.86 grams of aged Catalyst 2 was added to 18 grams of Paint B. This mixture was sprayed onto two Bonderite 1000 treated steel panels with a dry layer thickness of 60 μm; one of the panels was baked for 30 minutes at 66° C. and the other was allowed to dry at room temperature. After 1 day at room temperature, adhesion on both panels was determined to be very good, 100% adhesion.
An epoxy amine ecoat from PPG as described below in Example 17 with an excess of epoxy groups (and therefore assumed to have no free reactive amine groups) was applied on a metal panel and subsequently baked for 30 min at 180° C. The composition of Example 12 was sprayed onto said baked primer with a dry layer thickness of 60 μm. After 1 day at room temperature, adhesion was determined to be very good.
An epoxy paint, Aquapon 97-137 was activated with hardener 97-1200 at the volume ratio suggested by the producer (PPG). Then Setalux 10-1440, which is a ketimine functional resin, was added at a level of 5% by volume to the epoxy paint and thoroughly mixed and then applied onto a metal panel and dried for 24 hours. 18 grams of Paint D (having no adhesion improver) was mixed with 0.53 grams of Catalyst 1 and then sprayed onto the day-old primed panels, flashed for 10 minutes at room temperature and then baked for 15 minutes at 66° C. After cooling, adhesion was tested using the cross-cut adhesion test as described in ASTM D3359 and found to be very good.
An epoxy paint, Aquapon 97-137 was activated with hardener 97-1200 at the volume ratio suggested by the producer (PPG). Then a ketimine prepared from reacting 1 mole of diethylenetriamine with 2 moles of methyl isobutyl ketone, was added at a level of 5% by volume to the epoxy paint and thoroughly mixed and then applied onto a metal panel and dried for 24 hours. 18 grams of Paint D was mixed with 0.53 grams of Catalyst 1 and then sprayed onto the day-old primed panels, flashed for 10 minutes at room temperature and then baked for 15 minutes at 66° C. After cooling, adhesion was tested using the cross-cut adhesion test as described in ASTM D3359 and found to be very good.
Paint C was aged for 1 month at 40° C. 33.25 grams of Catalyst 1 and 55 grams of Thinner 3 were subsequently added to 951 grams of aged Paint C. This mixture was sprayed on an electroplated zinc steel panel with a dry layer thickness of 65 μm. After 1 day at room temperature, adhesion was determined to be very bad. The comparative example shows that the adhesion promotor should preferably not be included in the composition that also comprises the pigments.
Catalyst 3 was aged for 1 month, after which lumps and crystals of solid material were observed. The comparative example shows that the adhesion promotor should preferably not be included in an aqueous catalyst composition, whereas it is no problem to include it in the non-aqueous catalyst composition.
33.25 grams of Catalyst 1, 55 grams of Thinner 3 and 936 grams of Paint A were mixed. This mixture was sprayed on an electroplated zinc steel panel with a dry layer thickness of 65 μm. After 1 day at room temperature, adhesion was determined to be very bad. The comparative example shows that the aminosilane adhesion promotor should be included in the composition to get good results.
An epoxy amine ecoat (available from PPG) with an excess of epoxy groups was applied on a metal panel and subsequently baked for 30 min at 180° C. 33.25 grams of Catalyst 1 and 55 grams Thinner 3 were subsequently added to 936 grams of Paint A. This mixture was sprayed onto said baked primer with a dry layer thickness of 60 μm. After 1 day at room temperature, adhesion was determined to be very bad. The comparative example shows that the aminosilane adhesion promotor should be included in the composition to get good results even in combination with this primer.
18 grams of Paint B was mixed with 0.68 grams of Catalyst 4a and then sprayed onto two Bonderite 1000 treated steel panels with a dry layer thickness of 60 μm; one of the panels was baked for 30 minutes at 66° C. and the other was allowed to dry at room temperature. After 1 day at room temperature, adhesion on both panels was determined to be very bad, 100% adhesion failure.
An epoxy paint, Aquapon 97-137 was activated with hardener 97-1200 at the volume ratio suggested by the producer (PPG). The primer was then applied onto a metal panel and dried for 24 hours. 18 grams of Paint D was mixed with 0.53 grams of Catalyst 1 and then sprayed onto the day-old primed panels, flashed for 10 minutes at room temperature and then baked for 15 minutes at 66° C. After cooling, adhesion was tested using the cross-cut adhesion test as described in ASTM D3359 and found to be very bad. It shows that a paint without adhesion improver on this standard epoxy primer does not show sufficient adhesion, whereas modifying the epoxy primer or adding of an adhesion promotor according to the invention does result in good adhesion.
A solution of tetrabutylammonium hydroxide in methanol is subjected to a solvent switch, by concentrating in a rotating film evaporator at 35° C. under reduced pressure, after adding ethanol. Fresh ethanol is added at various moments while removing methanol. The distillation is finished at a residual methanol content of 4.5 wt % as confirmed by GC analysis. Next, the solution is neutralized by bubbling gaseous CO2 through the liquid via a glass inlet tube at room temperature. The reaction was judged to be finished when a water diluted sample indicates a pH of <8.5; final base content is 1.6 eq/kg solution as determined by potentiometric titration with 0.1 M HCl. This CAT-E was used to prepare the following solutions containing aminosilanes (ex Aldrich):
Both fresh catalyst solutions were added to a standard clear coat composition, sprayed, cured (20 hours ambient); the cured films were tested on adhesion.
Both solutions CP1 and CP2 were aged in a closed bottle at 40° C. The aged solution were added to similar clear coat formulations, cured 1 day at RT, and tested on adhesion.
It can be seen that the adhesion performance is stable and remains good upon storage of the aminosilanes in these catalyst formulations, this in contrast to storage in a pack containing reactive components A and B.
Added to a 100 ml round-bottomed flask were 4.5 g of aminopropyl-trimethoxysilane, 7 g of ethylacetate and 19.3 g of TMP triacetoacetate, along with a magnetic stirrer. The flask was then placed in a water bath to help keep the reaction at ambient conditions. The contents were left stirring for 6 hours before adding 3 g of activated 4 A molecular sieves to absorb the water produced as part of the equilibrium reaction. The flask was left overnight and the contents were filtered, and solvent removed in vacuo.
The enamine adduct prepared (TAS1, 10 g) was formulated with 74 g of MPE1, 30.5 g of DTMPTA, 7 g of butylacetate, 10 g of n-propanol and 5.6 g of CAT4, and subsequently applied to a Gardobond 26S 68000C substrate. Adhesion was tested after 1 day of ambient cure and found to be good (score 0). A similar formulation without TAS1 gave poor adhesion (score 5).
Thus, the invention has been described by reference to certain embodiments discussed above. It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those of skill in the art.
Further modifications in addition to those described above may be made to the structures and techniques described herein without departing from the spirit and scope of the invention. Accordingly, although specific embodiments have been described, these are examples only and are not limiting upon the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 15169717.4 | May 2015 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2016/058525 | 4/18/2016 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62148966 | Apr 2015 | US |
