Process for the manufacture of a crosslinkable composition

Abstract

The invention relates to a process for the preparation of a RMA crosslinkable composition 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 and the at least 2 reactive groups of component B are activated unsaturated groups C═C and base catalyst C and one or more N—H group containing reactivity moderating component D that are also a Michael addition donor reactable with component B under the action of catalyst C, characterized in that the one or more reactivity moderating components D have a melting temperature above 60° C. and is first dissolved in one or more crosslinkable components comprising reactive components A or B and the obtained pre-dissolved product is later mixed with other components of the RMA crosslinkable composition.

Claims

1. A moderator composition comprising: one or more RMA crosslinkable polymer components comprising one or more reactive components A comprising at least 2 acidic protons C—H in activated methylene or methine groups, and dissolved therein one or more N—H groups containing reactivity moderating components D that are a Michael addition donor reactable with a reactive component B comprising activated unsaturated groups C═C under the action of a base catalyst C, said reactivity moderating components D having a melting temperature above 60° C. and less than 300 gr/ltr of an organic solvent, said moderator composition being obtained by a process wherein the one or more RMA crosslinkable polymer components comprising the reactive component A are synthesized at a temperature above the melting temperature of the components D and the components D are added directly after the synthesis of said polymer and dissolved therein before cooling to a temperature below the melting temperature of the components D.

2. The moderator composition of claim 1, consisting essentially of the RMA crosslinkable polymer components comprising the reactive components A, wherein the reactive components A are malonate, comprising between 0.5 and 5 wt % of a dissolved succinimide or a triazole moderator D relative to the total amount of the RMA crosslinkable components comprising the reactive components A and the components D and comprising less than 300 gr/ltr of an organic solvent.

3. The moderator composition of claim 1, wherein the one or more RMA crosslinkable polymer components comprise a polymer chosen from the group of polyesters, polyurethanes, polyacrylates, epoxy resins, polyamides and polyvinyl resins, which contains the reactive components A in the main chain, pendant, terminal, or combinations thereof.

4. The moderator composition of claim 1, wherein the one or more RMA crosslinkable polymer components comprising the reactive components A have a weight average molecular weight Mw of at least 250 gr/mol.

5. The moderator composition of claim 1, wherein the one or more RMA crosslinkable polymer components comprising the reactive components A have a weight average molecular weight Mw between 300 and 5000 gr/mol.

6. The moderator composition of claim 1, wherein the one or more RMA crosslinkable polymer components comprise a polyester comprising the reactive components A which are synthesised by forming a polyester polymer using the reactive components A as monomer or by transesterification of polyester polymer with the reactive components A.

7. The moderator composition of claim 1, wherein the reactive components A are malonate or acetoacetate.

8. The moderator composition of claim 1, wherein the one or more RMA crosslinkable polymer components comprise both malonate and acetoacetate in the same molecule.

9. The moderator composition of claim 8, wherein more than 50% of the reactive components A are malonates.

10. The moderator composition of claim 1, wherein the N—H group in the components D has a pKa (defined in aqueous environment) of at least one unit less than that of the C—H groups in the reactive components A.

11. The moderator composition of claim 1, wherein the pKa of the N—H group in the components D is lower than 13.

12. The moderator composition of claim 1, wherein the components D comprise 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.

13. The moderator composition of claim 1, wherein the components D are selected from the group consisting of a substituted or unsubstituted succinimide, phthalimide, glutarimide, hydantoin, triazole, pyrazole, imidazole, uracil, and mixtures thereof.

14. The moderator composition of claim 1, wherein the components D are present in an amount between 0.1 and 10 wt %, relative to the total amount of the RMA crosslinkable polymer components comprising the reactive component A and the components D.

15. The moderator composition of claim 1, wherein the components D are present in such amount that the amount of N—H groups in the components D is no more than 30 mole %, relative to C—H donor groups from the reactive components A in the RMA crosslinkable polymer components.

16. The moderator composition of claim 1, comprising less than 200 gr/ltr of an organic solvent.

17. The moderator composition of claim 1, comprising less than 175 gr/ltr of an organic solvent.

18. A kit of parts comprising a first part comprising the moderator composition of claim 1 and a second part comprising a base catalyst C.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) Reference is made to EP2764035 for detailed description of all components A, B C or D, their preparation, the amounts used in the RMA crosslinkable composition as well as for measurement methods and definitions and is hereby incorporated by reference.

(2) Crosslinkable components can be monomers or polymers having 2 or more reactive groups for crosslinking. Polymers are considered to be compounds having at least 2 repeat units and typically have a weight average molecular weight (determined by GPC) of more than 250 gr/mol. The upper limit can be as high as 100000 or 200000 but for the application as coating resin the RMA crosslinkable compositions in view of viscosity are preferably between 250 (preferably 300, 400 or 500) and 5000 (preferably 4500 or 4000) gr/mol (GPC). The reactive components A and B can be pending, terminal or build into a polymer chain.

(3) Monomeric compounds can also be used as crosslinkable components A or B. For example diethylmalonate has 2 C—H groups that can react and hence can be used as crosslinkable component A. Trimethylolpropane triacrylate (TMPTA) has only one repeat unit but 3 reactive C═C groups for crosslinking. These monomer components A or B or mixtures thereof can react to form an RMA crosslinked network and can also be used as reactive diluents together with polymeric crosslinkable components comprising A, B or both to replace organic solvent and reduce VOC of the RMA crosslinkable composition. Optionally also monomer components A or B can be included in the RMA composition that have only 1 RMA reactive C—H or C═C group.

(4) Preferred crosslinkable components are A group containing polymers such as, for example, polyesters, polyurethanes, polyacrylates, epoxy resins, polyamides and polyvinyl resins containing groups A in the main chain, pendant or both. Component A preferably is malonate or acetoacetate. Components containing both malonate and acetoacetate groups in the same molecule are also suitable. Additionally, physical mixtures of malonate and acetoacetate group-containing components are suitable. The RMA reactive donor components A preferably predominantly originate are malonate groups, i.e. more than 50%, 75% or even 90% of reactive components A are malonate groups.

(5) Reactive component B generally can be ethylenically unsaturated components in which the carbon-carbon double bond is activated by an electron-withdrawing group, e.g. a carbonyl group in the alpha-position. Suitable components B are known in the art, for example acryloyl esters, acrylamides, alternatively polyesters based upon maleic, fumaric and/or itaconic acid (and maleic and itaconic anhydride and polyesters, polyurethanes, polyethers and/or alkyd resins containing pendant activated unsaturated groups. Acrylates, fumarates and maleates are preferred. Most preferably, the component B is an unsaturated acryloyl functional component. Further preferences regarding the crosslinkable component comprising reactive component B are described in EP2764035.

(6) Typically, the concentrations of the functional groups in components A and B, and their relative stoichiometry, are chosen such that good film properties following cure may be expected, with efficient use of these functional groups. Typically, stoichiometries C═C/C—H are chosen to be from 0.1 to 10, preferably 0.5 to 3, more preferably 0.7 to 3, most preferably 0.8/1.5. For this ratio, the N—H of component D is added to the C—H groups of component A.

(7) The base catalyst C can in principle be any known catalyst suitable for catalyzing RMA reactions. Preferably, in view of achieving good pot-life in combination with low temperature curing, the cross-linking composition comprises a catalyst system C comprising a strong based blocked by a volatile acid which is activated by evaporation of this acid. A suitable catalyst system C comprises a strong based blocked by a carbon dioxide, or the blocked catalytic species are of formula ROCO2-, R being an optionally substituted alkyl, preferably C1-C4 radical or hydrogen, preferably the catalyst comprises a blocked base anion and a quaternary ammonium or phosphonium cation. It is preferred that the crosslinking catalyst is utilized in an amount ranging between 0.001 and 0.3 meq/g solids, preferably between 0.01 and 0.2 meq/g solids, more preferably between 0.02 and 0.1 meq/g solids (meq/g solids defined as mmoles base relative to the total dry weight of the crosslinkable composition, not counting particulate fillers or pigments). Further preferences regarding the crosslinkable component comprising reactive component C are described in EP2764035

(8) The crosslinking composition can comprise a solvent, preferably an organic solvent. For CO2 deblocking catalyst systems, the inventors further found that advantages can be achieved in pot life if in the crosslinkable composition at least part of the solvent is a primary alcohol solvent. The solvent can be a mixture of a non-alcoholic solvent and an alcohol solvent.

(9) In summary the crosslinkable composition according to the invention comprises between 5 and 95 wt % of a crosslinkable component, preferably said polymeric component, comprising reactive component A with at least 2 acidic protons C—H in activated methylene or methine, and between 5 and 95 wt % of a crosslinkable component, preferably a low molecular weight component, comprising reactive component B with at least 2 activated unsaturated groups (wt % relative to the total weight of the crosslinkable composition) and a catalyst system C that contains, or is able to generate a basic catalyst capable of activating the RMA reaction between components A and B, at levels of 0.0001 and 0.5 meq/g solid components, wherein component D is present in quantities of at least 10, 20, 30, 40 or maybe even 50 mole % relative to base catalyst component C or base generated by catalyst component C, and preferably less than 30 mole % of C—H active groups from component A optionally a sag control agent (SCA), optionally between 0.1 and 80 wt % of solvent (preferably less than 45 wt %), preferably containing at least 1 wt % of a primary alcohol, optionally at least 0.2 wt % water.

(10) The crosslinkable composition typically and preferably is a 2K composition which is only formed shortly before the actual use, the invention also relates to a kit of parts for the manufacture of the composition according to the invention comprising a part 1 and part 2 wherein one part comprises the catalyst and the other does not comprise the catalyst C.

(11) The composition of the invention comprises component D as an additive for the improvement of the open time of the crosslinkable composition and for the improvement of the appearance and hardness of the resulting cured composition, in particular a coating.

(12) The N—H group in component D has a higher acidity than the C—H groups in component A, preferably being characterized in that component D has a pKa (defined in aqueous environment) of at least one unit, preferably two units, less than that of component A. Preferably the pKa of the N—H group in component D is lower than 13, preferable lower than 12, more preferably lower than 11 most preferably lower than 10. An excessive acidity may create problems with components in the catalyst system; therefore hence the pKa is preferably higher than 7, more preferably 8, more preferably higher than 8.5. The acidity difference assures that on application of the coating, component D is activated (deprotonated) preferentially over component A.

(13) In the cross-linking composition, the N—H groups in component D are present in an amount corresponding to at least 10, 20, 30 40, or even 50 mole %, preferable at least 100 mole %, most preferably at least 150 mole % relative to the amount of base to be generated by catalyst C. The appropriate amount is very much determined by the acid base characteristics of component D relative to component A, and the reactivity of the corresponding anions relative to B, so may vary for different systems. Typically the N—H groups in component D are present in an amount corresponding to 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. Preferably, the N—H functionality (number of groups per molecule) of component D is low, preferably less than 4, more preferably less than 2, most preferably it is 1.

(14) The invention also relates to crosslinkable composition obtainable according to the invention. This composition can be used to prepare a paint composition.

EXAMPLES

(15) The following is a description of certain embodiments of the invention, given by way of example only and with reference to the drawings.

Example 1

(16) The malonate functional resin PE is a polyester resin which has been trans-esterified with diethylmalonate. 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. When the viscosity at 100° C. reached 0.5 Pa.Math.s the material was cooled down to 140° and 11.2 grams of solid succinimide were added. This mixture was stirred until all succinimide was dissolved. The resin was further cooled and diluted with butyl acetate to 85% solids. After 6 month of storage at 4° C. no precipitate was formed.

(17) Examples of a paint formulation (i.e. a coating composition) are given below and are based on DTMPTA (di-trimethylolpropane tetra acrylate) as acryloyl acceptor (Miramer M410 mentioned in Table 1 is DTMPTA). The catalyst used is a mixture of tetra-butyl ammonium bicarbonate, diethylcarbonate and n-propanol with a concentration of 0.928 meq/g.

Example 2

(18) Formulation 1 was prepared as described in Table 1, using the succinimide containing resin as described in example 1. After pre-dissolving the 1,2,4-triazole in n-propanol, only liquid materials needed to be mixed. The resulting paint was applied on a metal panel with a dry film thickness of 60 μm, giving the results as described in Table 2, showing that this paint performed similarly compared to paints containing succinimide dissolved in n-propanol and butyl acetate as solvent.

Example 3

(19) Example 2 was repeated, but then after aging the succinimide modified resin for 6 months at room temperature. Similar results were obtained (Table 2).

Comparative Example 1

(20) Formulation 2 was prepared according to Table 1. Here, 2.3 grams of succinimide was dissolved along with 5.1 grams of 1,2,4-triazole in 65.6 grams of n-propanol and 43.7 grams of butyl acetate using an ultrasonic bath for 30 minutes. The resulting paint was applied on a metal panel, giving the results as described in Table 2.

Comparative Example 2

(21) Formulation 2 was prepared according to Table 1. Here, 2.3 grams of succinimide was dissolved along with 5.1 grams of 1,2,4-triazole in 65.6 grams of n-propanol and 43.7 grams of butyl acetate by magnetic stirring overnight. The resulting paint was applied on a metal panel, giving the results as described in Table 2.

(22) TABLE-US-00001 TABLE 1 Component Formulation 1 Formulation 2 Part 1 Malonate functional PE 139.4 328.9 Succinimide containing 192.2 0 malonate functional PE Pigment paste* 565.5 565.5 Pre-dissolve: Succinimide 0 2.3 1,2,4-triazole 4.8 4.8 Butyl acetate 0 40.0 n-propanol 27.0 65.9 Subsequently add Byk 310:315 1:4 2.8 2.8 Tinuvin 292 4.6 4.6 Part 2 catalyst 24.9 24.9 n-propanol 38.9 Dilute to spray viscosity Butyl acetate 55.3 15.7 *mix 32.0% of Miramer M410 with 65.1% of Kronos 2310 and 2.9% of disperbyk 163 and grind until the particle size is smaller than 10 μm

(23) TABLE-US-00002 TABLE 2 Ex. 2 Ex. 3 Comp. Ex. 1 Comp. Ex. 2 Drying time (min) 40 39 43 37 Persoz hardness (60 μm, 167 175 173 170 after 1 day) Gloss at 60° 90 90 90 90 Haze 9 10 11 9 VOC of Part 1 (g/L) 121 121 222 222

(24) The examples illustrate the advantages of the invention:

(25) 1) There is no need any more for time consuming and elaborate dissolving of component D in solvents. Instead, 2 liquid resins can simply and quickly be mixed.

(26) 2) Because the solid component D does not need to be dissolved any more, less solvent is needed in the A-component of the paint (Part 1 in Table 1). Instead, the ratio of part 1 and part 2 can be adapted more flexibly. This is relevant for application where the mixing ratio between part 1 and part 2 can be critical. Alternatively, the paint could be diluted to higher spray viscosities. In this way, the invention contributes to decreasing the VOC of the paint. The invention therefore also relates to crosslinkable composition obtainable according to the process of the invention, in particular to low VOC compositions.

(27) 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. For example, the succinimide may be any component D, in particular any N—H acidic component having a low solubility in organic solvents, in particular triazoles or imides. 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.