WO1997044399A1

WO1997044399A1 - Radiation curable binder composition

Info

Publication number: WO1997044399A1
Application number: PCT/NL1997/000275
Authority: WO
Inventors: Johan Franz Gradus Antonius Jansen; Dirk Armand Wim Stanssens
Original assignee: Dsm N.V.
Priority date: 1996-05-17
Filing date: 1997-05-16
Publication date: 1997-11-27
Also published as: AU2914097A

Abstract

The invention relates to a radiation curable binder composition comprising: a) a compound having an ethylenic unsaturation attached to an electron withdrawing group and b) a compound comprising at least one allyl group. The composition also comprises a compound having an ethylenic unsaturation attached to an electron donating group such as, for example, a vinylether, vinylester, vinylimide, vinylamide, vinylsilane or vinylsulfide group. Compound a) is, for example, an unsaturated compound comprising at least one maleate, fumarate, itaconate, citraconate or mesaconate group.

Description

RADIATION CURABLE BINDER COMPOSITION

The invention relates to a radiation curable binder composition comprising a) a compound having an ethylenic unsaturation attached to an electron withdrawing group and b) a compound comprising at least one allyl group. Such a composition is described in Powder

Paint Colour Journal (June 1995, at pages 35-36) by Sόrensen. It is a disadvantage of these systems that they cure relatively slowly by influence of ultraviolet light. It is an object of the present invention to provide a radiation curable binder composition comprising a) and b) that cures fastly. The system also has not to result in environmental and health problems. The invention is characterized in that the composition also comprises a compound c) having an ethylenic unsaturation attached to an electron donating group.

The replacement of a part of the compound having allyl double bounds by compound c) results in a system having a fast cure and having no toxic problems. Furthermore the obtained coating composition has the desired characteristics such as, for example, hardness, chemical resistance, scratch resistance and flexibility. Generally, the radiation curable binder composition further comprises a photoinitiator.

According to a preferred embodiment of the invention component c) is a vinylether, vinylester, vinylimide, vinylamide, vinylsilane, vinylsulfide or a styrene substituted with an electron donating group.

Most preferably component c) is a vinylether, vinylester or vinylamide group. Preferably, this unsaturated compound comprising at least one vinyl group is a vinylether group comprising polymer, oligomer or monomer in which the polymer, oligomer or monomer has 1-10 vinylether groups. According to a further preferred embodiment of the invention the vinylether group comprising compound has at least two functional groups.

The molecular weight (Mn) of the vinylether compound is in general higher than 90, preferably higher than 100. In general, the molecular weight is lower than 5000, preferably lower than 3000.

Examples of suitable vinylether groups comprising compounds are described in EP-A-462204 and EP-A-462183 which disclosures are herewith incorporated by reference. Suitable examples of mono- and divinylether compounds include butylvinylether , cyclohexyldimethanoldivinylether, butyldivinylether , triethyleneglycoldivinylether and hydroxybutyl- vinylether.

Very suitable oligomers and polymers are polyurethanes having a polyester, polyether or polycarbonate backbone and vinylether end groups, made by reaction of a hydroxyalkylvinylether, a polyisocyanate and a hydroxyfunctional oligomer. This oligomer being a polyester, polyether or polycarbonate may have a molecular weight between 200 and 2000. Other suitable oligomers are based on addition products of hydroxyalkylvinylethers and iso- cyanates. Examples of suitable isocyanates include isophorone diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, methylene bis- cyclohexylisocyanate and their derivatives.

Preferably, compound a) is an unsaturated compound comprising at least one maleate, fumarate, itaconate, citraconate or mesaconate group and mixtures thereof. Also amine derivates, for example, maleimides, fumaramides, amide esters and amide acids can be applied. The unsaturated compound a) and the unsaturated compound c) can also be combined in one molecule. For instance, a vinylether end-capped polyurethane having an hydroxyfunctional unsaturated polyester as a backbone, can be used. Further, dual functional monomers as described in EP-A-462204 are suitable as well.

According to a preferred embodiment of the invention the unsaturation equivalent weight (WPU) ratio b):c) is between 9:1 and 1:9. More preferably, this ratio is between 8:2 and 1:9.

According to another preferred embodiment of the invention the unsaturation equivalent weight (WPU) ratio a):(b)+c)) is between 1,2:1 and 1:1,2. More preferably, this ratio is virtually 1:1.

Preferably the unsaturated compound comprising at least one maleate, fumarate, itaconate, citraconate or mesaconate group is an unsaturated polyester, an oligomer or a monomer. Preferably, the unsaturated compound a) comprises at least one maleate or fumarate group.

As an unsaturated polyester, generally known unsaturated polyesters with a molecular weight (M_n) between 800 and 5000 can be used. These polyesters generally are based on one or more diacids and one or more diols, the diacids are at least in part ethylenically unsaturated diacids. As component a) also oligomers having a M_n in the range of, for example, 400-800 can be applied. Suitable diacids include, for example, maleic acid (anhydride), fumaric acid, itaconic acid (anhydride), citraconic acid (anhydride) mesaconic acid, phthalic acid (anhydride) adipic acid, terephthalic acid, isophthalic acid, malonic acid, succinic acid, glutaric acid, sebacic acid, and 1,4- cyclohexane dicarboxylic acid.

Suitable diols include, for example, ethyleneglycol, butanediol, neopentylglycol, hexanediol, 1,4-cyclohexane diol, 1,4- cyclohexanedimethanol, propyleneglycol, diethylene glycol, alkoxylated bisphenol-A, and alkoxylated hydrogenated bisphenol-A.

The diacids and diols may be combined with mono-, tri- or tetra-functional alcohols or acids. Suitable compounds are for example ethanol, butanol, 2- ethylhexanol, saturated and unsaturated fatty acids, trimellitic acid, trimethylolpropane, glycerol, pentaerythritol and the like.

The amount of unsaturation of the unsaturated compound generally is given as the molecular weight per double bond, and is generally between 150-2000. Preferably, the molecular weight per double bond is 180-1500.

Apart from, or in combination with unsaturated polyesters, this unsaturated compound may also be an oligomer or a monomer. It is possible to use a maleate or fumarate end-capped oligomer with one or more unsaturated groups. Also, monomeric species such as, for example, dioctylmaleate can be applied. Further suitable maleate or fumarate functional compounds are described in EP-A-462204 and EP-A-462183, which disclosures are herewith incorporated by reference.

Thus, this type of unsaturated compound in general will have a molecular weight (Mn) higher than 140, preferably higher than 200, and will have a molecular weight lower than 5000, preferably lower than 3000. The number of unsaturations per molecule generally will be -on average- between 1 and 10. Preferably, the number of unsaturations per molecule is between 1-5.

In one preferred embodiment of the invention, an oligomer is used with a molecular weight between 200-1500, which comprises 2-4 unsaturated groups per molecule.

In a further preferred embodiment of the invention, a monomer or oligomer is used with 1-3 unsaturations per molecule, to adjust the viscosity of the coating compostion.

Preferably, the compound having at least one allyl group has 1-12 allyl groups. More preferably, this compound has two or more allyl groups.

Preferably, the compound has allylether groups and further ether, ester or urethane groups.

Preferably, the compound having allyl groups has a molecular weight higher than 100, more preferably higher than 300. Preferably, the compound has a molecular weight lower than 3000, preferably lower than 1200.

According to a preferred embodiment of the invention the oligomer is an allyl ether-ester, more preferably being the ester of trimethylolpropane diallyl ether or pentaerythritol triallyl ether and a polycarboxylic acid (anhydride).

Suitable polycarboxylic acids and polycarboxylic acid anhydrides include for example, trimellitic acid (anhydride), isophthalic acid, adipic acid, phthalic acid (anhydride), cyclohexanedi- carboxylic acid, tetrahydrophthalic acid (anhydride) and hexahydrophthalic acid (anhydride). Preferably, trimellitic acid (anhydride), isophthalic acid, adipic acid and/or 1,4-cyclohexanedicarboxylic acid is used as the polycarboxylic acid (anhydride).

The allyl ether groups containing ester can be prepared by carrying out a condensation reaction between a polycarboxylic acid (anhydride) and an allyl ether alcohol at temperatures between, for example, 150°C and 200°C, over, for example, between 3 and 6 hours. The molar ratio of allyl ether alcohol:polycarboxylic acid (anhydride) is preferably between about 1:1 and 4:1.

The oligomers can be either liquid or solid compounds. It is also possible to use as the compound b) an allylester, for example, a diallylphtalate.

It is also possible to use as the allylcompound allylamines and their derivatives like the Michael addition reaction product, for example, of (di)allylamine and an unsaturated polyester, the amides of (di)allylamines and carboxylic acids or their derivatives, or the addition product of (di)allylamine and an isocyanate derivative. The preparation of the oligomers containing allyl groups and urethane groups may be carried out by adding the compounds containing allyl groups to compounds containing isocyanate groups at temperatures between 70°C and 120°C. A suitable solvent for this reaction is, for example, toluene. The solvent is removed after the reaction.

Suitable oligomers containing allyl groups and urethane groups may be based on compounds containing allyl groups such as, for example, allyl alcohol, trimethylolpropane diallyl ether, allyl glycidyl ethers and pentaerythritol triallyl ether. Suitable isocyanates include for example isophorone diisocyanate, toluene diisocyanate, hexamethylene diisocyanate and methylene bis- cyclohexylisocyanate and their derivatives (for instance Tolonate HDT™ of Rhone Poulenc).

According to a further preferred embodiment of the invention compound b) is trisallylcyanurate or trisallylisocyanurate. The coating composition comprising the radiation curable binder composition may further comprise suitable pigments, stabilisers and other additives.

The coating composition may comprise a solvent but preferably the composition is a solvent free composition.

The coating can be applied as a water based coating, as a solvent based coating, as a high solids coating and as a 100% solids coating. According to a preferred embodiment of the invention the coating is applied as a powder coating. The compositions are subjected to irradiation, preferably electron beam (EB) or ultraviolet light (UV) to cause polymerization of the coating composition.

The most preferred irradiation source is ultraviolet light. Ultraviolet light is preferably high intensity light to provide a dosage of at least about 0.2 joules per square centimeter of surface area of the composition being polymerized to achieve reasonable curing rates. In the event that lower energy light is to be applied, it may then be desired to subject the compositions also to elevated temperatures in order to reduce the time for adequate polymerization to occur. In addition, the ultraviolet light employed typically has substantial magnitudes at wavelengths of at least about 310 nanometers. Suitable lamps employed to provide the desired high intensity and availability of wavelength and spectral distribution include that available from Fusion Systems, Corp. under the trade designation F-450 model with a D bulb. At typical band speeds of about 6 to about 30 meter per minute such gives a peak irradiance of about 1 to about 2.6 watt/cm² of the surface area of the composition.

A very suitable UV-lamp is the Excimer lamp (Rad Tech. Europe 95, Maastricht, September 25-27, 1995, Conference Proceedings, pages 48-52).

A coating compositions comprising the radiation curable binder composition according to the present invention can be applied on substrates such as, for example, plastic, paper, leather, glass, wood and metal.

The composition according to the present invention can be polymerised in the presence of a photoinitiator but can also be polymerised in the absence of a photoinitiator.

Suitable photoinitiators allow for initiation of the curing process with exposure to light having wavelengths between about 200 nm and about 600 nm. Suitable photoinitiators have ketone functionalities and can be aromatic such as, for example, benzophenone. Darocur 1173® (Ciba) is a suitable benzyl-ketal-based photoinitiator, which contains 2-hydroxy-2-methyl-l- phenylpropane-1-one as an active component. Irgacure 184® (Ciba) is an aryl ketone containing hydroxycyclohexyl phenyl ketone as active component, and is a suitable photoinitiator. Irgacure 369® (active component 2-benzyl-2-dimethylaminol-l-(4- morpholinophenyl)-butanone-l) is also suitable. Acyl phosphines, such as for example 2,4,6,-trimethylbenzoyl diphenyl phosphone oxide (Lucerine TPO®, BASF) can also be used, as can Quantacure CPTX® (Octel Chemicals), which contains l-chloro-4-propoxy thioxanthone as active component. Chemical derivatives of these photoinitiators are suitable, as are mixtures of these photoinitiators. A suitable combination of photoinitiators is Irgacure 1800™ (Ciba) consisting of 75% by weight Irgacure 184™ and 25% by weight (bis- (2,6-dimethoxy benzoyl)-2,4,4-trimethylpentyl fosfine oxide). Other suitable photoinitiators can be of the Norrish-II-type, for example, benzophenone amine and antra chinon amine.

The invention will be further elucidated by the following non-limiting examples.

Examples I-IX and Comparative Experiment A

A solution (see Table I) of 10 parts by weight of a solid unsaturated polyester (Uralac XP 3125, DSM Resins), triallylcyanurate (TAC), triethylene glycol divinylether (DVE) and 0,1 parts by weight of a photoinitiator (Irgacure 184™) was prepared at room temperature.

The amounts TAC and DVE in Table I are given in parts by weight. The mixture was dissolved in 10 parts by weight tetrahydrofuran.

The composition was applied on a substrate (150 μm on an alumina 0 panel) and the solvent was evaporated overnight.

The resulting powder coatings were cured under a mercury UV-lamp with a peak intensity of 0,3 Watt/cm² and a total dose of 2 J/cm² after 8 seconds irradiation. The cure was monitored by means of Kδnig pendulum hardness (according to DIN 53157; ISO 1522).

Table I

1) ratio unsaturation equivalent weight. 2) time necessary to obtain the maximum pendulus hardness. After irradiation (in all examples and the experiment) a coating was formed (the acetone resistance test resulted always in ADR > 100 which indicates full curing).

Example X

A mixture consisting of 4 parts by weight unsaturated polyester (Uralac ZW 3368 UV of DSM Resins), 0,48 parts by weight triethylene glycol divinylether (DVE), 0,94 parts by weight trisallylcyanurate (TAC) and 0,08 parts by weight photoinitiator (Darocure 1173™) was prepared at room temperature.

The coatings were obtained after curing as described in the foregoing examples.

The cure time was 8 sec and the acetone resistance test resulted in an ADR > 100.

Comparative Experiment B Example X was repeated with the exception that instead of the combination consisting of 0,48 parts by weight DVE and 0.94 parts by weight TAC 1,34 parts by weight TAC were used.

The cure time was 32 sec. and the acetone resistance test in an ADR > 100.

The examples and comparative experiments show clearly that the replacement of a part of the trisallylcyanurate by the vinylether results in a faster curing.

Example XI

Preparation of a powder coating

173.3 parts by weight unsaturated polyester

(Uralac XP3125), 17.0 parts by weight solid vinylether (Uralac ZW3307P), 9.3 parts by weight N,N- diallylmelamine, 2 parts by weight of Irgacure 184®

(Ciba) and 2 parts by weight of flow control agent (Resiflow PV™) were homogeneously blended in a Prism extruder at 70°C and 200 rpm. The WPU ratio allyl : vinyl was 1 : 1. After cooling, the paint was ground and screened, and the fraction having a particle size of less than 90 μm was then applied, with the aid of an electrostatic spray apparatus, to MDF panels in layers having a thickness of approximately 100 μm.

The powder coating obtained was heated at 80°C for 90 seconds with IR lamps whereupon the powder layer was liquified. After that, the panel, which was still warm, was cured by UV radiation (1 J/cm², measured with an IL 390 light bug).

The coating obtained had good flow properties (determined visually) and a good acetone resistance (no damage to the coating after 100 acetone double rubs).

Example XII

Preparation of a powder coating

176.5 parts by weight unsaturated polyester (Uralac XP3125), 17 parts by weight solid vinylether

(Uralac ZW3307P), 6.5 parts by weight N,N-diallylurea, 2 parts by weight of Irgacure 184® (Ciba) and 1.3 parts by weight or flow control agent (Resiflow PV™) were homogeneously blended in a Prism extruder at 70°C and 200 rpm. The WPU ratio allyl : vinyl was 1 : 1. After cooling, the paint was ground and screened, and the fraction having a particle size of less than 90 μm was then applied, with the aid of an electrostatic spray apparatus, to MDF panels in layers having a thickness of approximately 100 μm.

The powder coating obtained was heated to 80°C for 90 seconds with IR lamps whereupon the powder layer was liquified. After that, the panel, which was still warm, was cured by UV radiation (1 J/cm², measured with an IL 390 light bug).

The coating obtained had reasonable flow (determined visually) and a good acetone resistance (no damage to the coating after 100 acetone double rubs).

Example XIII

Preparation of a powder coating 175 parts by weight unsaturated polyester

(Uralac XP3125), 17 parts by weight solid vinylether (Uralac ZW3307P), 8 parts weight triallylcyanurate, 2 parts by weight of Irgacure 184® (Ciba) and 1.3 parts by weight or flow control agent (Resiflow PV™) were homogeneously blended in a Prism extruder at 70°C and 200 rpm. The WPU ratio allyl:vinyl was 1:1. After cooling, the paint was ground and screened, and the fraction having a particle size of less than 90 μm was then applied, with the aid of an electrostatic spray apparatus, to MDF panels in layers having a thickness of approximately 100 μm.

The powder coating obtained was heated for 90 seconds to 80°C with IR lamps whereupon the powder layer was liquified. After that, the panel, which was still warm, was cured by UV radiation (1 J/cm², measured with an IL 390 light bug).

The coating obtained had good flow properties (determined visually) and a reasonable acetone resistance (no damage to the coating after 100 acetone double rubs).

Claims

1. Radiation curable binder composition comprising a) a compound having an ethylenic unsaturation attached to an electron withdrawing group and b) a compound comprising at least one allyl group characterized in that, the composition comprises a compound c) having an ethylenic unsaturation attached to an electron donating group.

2. Composition according to Claim 1, characterized in that compound c) is a vinylether, vinylester, vinylimide, vinylamide, vinylsilane, vinylsulfide or a styrene substituted with an electron donating group.

3. Composition according to Claim 2, characterized in that compound c) is a vinylether or a vinylester.

4. Composition according to Claim 3, characterized in that the vinylether has at least two functional groups.

5. Composition according to any one of Claims 1-4, characterized in that the unsaturation equivalent weight ratio b):c) is between 1:9 and 9:1.

6. Composition according to any one of Claims 1-5, characterized in that the unsaturation equivalent weight ratio a):(b)+c)) is between 1,2:1 and 1:1.2.

7. Composition according to any one of Claims 1-6, characterized in that compound a) is an unsaturated compound comprising at least one maleate, fumarate, itaconate, citraconate, mesaconate group or amine derivatives thereof.

8. Composition according to Claim 7, characterized in that compound a) is an unsaturated polyester, an oligomer or a monomer.

9. Composition according to any one of Claims 1-8, characterized in that compound b) is trisallylisocyanurate or triallylcyanurate.

10. Composition according to any one of Claims 1-9, characterized in that the composition comprises a photoinitiator.

11. Coating composition comprising a radiation curable binder composition according to any one of Claims 1-10.

12. Powder coating composition comprising a radiation curable binder composition according to any one of Claims 1-10.