Use of modified effect pigments in radiation-curable coating compositions

Abstract

The present invention relates to the use of a modified effect pigment in a radiation-curable coating composition, wherein the modified effect pigment is an effect pigment that is coated with at least one metal oxide layer to which at least one organic compound having one or more functional groups with a carbon-carbon multiple bond is bound. The invention is particularly suitable for metallic effect pigments, in particular aluminum pigments. A further part of the invention is the use of a modified effect pigment in a radiation-curable coating composition, wherein the modified effect pigment is an effect pigment to which at least one organic compound having one or more functional groups with a carbon-carbon multiple bond is bound. The radiation-curable, preferably UV-curable, coating compositions can in particular be lacquers, paints, printing inks, nail varnish or plastics.

Claims

1. A process for the production of a radiation-curing coating composition, comprising mixing a modified effect pigment the modified effect pigment with a coating composition comprised of prepolymer binders, monomers and curing of the coating composition upon exposure to UV light and/or electron beams, thereby forming the cured coating composition, wherein the modified effect pigment has no organic oligomers or polymers and is an effect pigment that is coated with at least one layer of a metal oxide and comprises silicon dioxide, aluminium oxide, titanium dioxide, iron oxide, tin oxide, zinc oxide or mixtures thereof, and at least one organic compound having one or more functional groups with a carbon-carbon multiple bond, wherein the organic compound is bound to the layer of a metal oxide.

2. The process according to claim 1, wherein the modified effect pigment is present as a dispersion.

3. The process according to claim 1, wherein the radiation-curable coating composition is a UV-curable coating composition.

4. The process according to claim 1, wherein the organic compound of the modified effect pigment in the cured coating is co-crosslinked with a binder of the coating.

5. The process according to claim 1, wherein the carbon-carbon multiple bond is CC.

6. The process according to claim 1, wherein the functional group is an acrylate group, a methacrylate group, a strained ring system or a vinyl group.

7. The process according to claim 1, wherein the at least one organic compound is a monomeric compound.

8. The process according to claim 1, wherein the at least one organic compound is an acrylic silane, a methacrylic silane, a maleic anhydride, a vinyl phosphonic acid or a vinyl phosphonate.

9. The process according to claim 1, wherein the at least one organic compound is bound covalently to the metal oxide layer on the effect pigment via a silane group, a phosphonate group, a titanate, a borate or one of the acid groups.

10. The process according to claim 1, wherein the organic compounds are bound to the effect pigment via a silane group, a phosphonate group, a titanate, a borate or one of the acid groups.

11. The process according to claim 1, wherein the effect pigment is a metallic effect pigment selected from the group consisting of aluminum, titanium, zirconium, copper, zinc, gold, silver, silicon, tin, steel, iron and alloys thereof or mixtures thereof, or the effect pigment is a pearlescent pigment, mica or mixtures thereof.

12. The process according to claim 1, wherein the radiation-curable coating composition is a solvent-based system, a solvent-free system, a UV/water hybrid system or an electron beam system.

13. The process according to claim 1, wherein the radiation-curable composition additionally comprises radically or cationically polymerizable monomers or binders and optionally photoinitiators.

14. The process according to claim 13, wherein the monomers are acrylate monomers, methacrylate monomers or vinyl monomers.

15. The process according to claim 1, wherein said coating composition is a lacquer, paint, printing ink, nail varnish, ink, surface coating or plastic.

16. The process according to claim 1 wherein the monomer is a reactive diluent.

17. The process according to claim 1 wherein the coating composition additionally comprises a volatile solvent and wherein the solvent is removed by physical drying prior to curing.

Description

EXAMPLES

Example 1

(1) 430 g of the aluminum pigment (Decomet) 1002 from Schlenk Metallic Pigments, 10% in isopropanol) was coated in the first step with 10% (based on the aluminum portion) SiO.sub.2. In the subsequent modification step, 150 g isopropanol was added and the mixture was heated to 40 C. accompanied by stirring. After this temperature was reached, 6 g of ammonia and 0.6 g of the methacrylate-functional silane Dow Corning Z 6030 from Dow Corning were added and the mixture was stirred for a further 2 h.

(2) Next, this pigment dispersion was adjusted to a solids content of 10%.

(3) 8 g of pigment dispersion were then mixed with 12 g of the UV printing ink Varnish UV VP/12213 from Schlenk (an acrylate-based UV printing ink) using a blade agitator at a rotational speed of 20 rpm until a homogeneous mixture was formed.

(4) Next, the printing ink that was obtained was applied onto a Chromolux 700 paper substrate by intaglio printing (using an Erichsen Gravure Proofer) at 150 lines/inch.

(5) Prior to UV curing, the prints were stored at 80 C. for 30 min so that the solvent portions could escape completely. The UV curing took place at a band speed of 10 m/min and an emitter lamp intensity of 184 W/cm.sup.2.

(6) The results of the printing ink according to the invention for hiding power, gloss and abrasion resistance are shown in Table 1.

Example 2

(7) Production and application as in Example 1, wherein 1.2 g of the silane Dow Corning Z 6030 were employed for modifying the effect pigment.

Example 3

(8) Production and application as in Example 1, wherein 2.4 g of the silane Dow Corning Z 6030 were employed for modifying the effect pigment.

Comparison Example A

(9) Instead of a pigment dispersion according to the invention with specially modified pigments, a dispersion with leafing pigment (Decomet UV 2798/10) was used. All the other data on the production of the printing ink and its application correspond to those of Examples 1 to 3.

Comparison Example B

(10) Instead of a pigment dispersion according to the invention with specially modified pigments, a dispersion with unmodified, uncoated pigment (Decomet 1002, 10% slurry in isopropanol) was used. All the other data on the production of the printing ink and its application correspond to those of Examples 1 to 3.

Comparison Example C

(11) Instead of a pigment dispersion according to the invention with specially modified pigments, a dispersion with unmodified pigment coated only with a silicon dioxide was used. This was produced in analogy to Ex. 1, but omitting the modification step with the methacrylic-functionalized silane. All the other data on the production of the printing ink and its application correspond to those of Examples 1 to 3.

(12) In the following Table 1, the results of the examples according to the invention and the comparison examples are listed.

(13) TABLE-US-00002 TABLE 1 Abrasion Abrasion test.sup.3 test.sup.4 Abrasion Printing Gloss Rubbing Printed test ink Hiding power.sup.1 points.sup.2 surface paper Sum Ex. 1 0.60 382 5 4.5 9.5 Ex. 2 0.63 384 5 4.5 9.5 Ex. 3 0.58 350 4 3.5 7.5 Comp. A 1.56 475 1.5 1 2.5 Comp. B 0.59 362 3 2 5 Comp. C 0.44 299 3.5 3 6.5 .sup.1Measurement of intaglio printing using a densitometer (Techkon RT120) after previous calibration of the substrate .sup.2Measurement of intaglio printing using a reflectometer (Byk micro-gloss instrument) at 60, measurement based on DIN 67530, adapted to higher values. Very good: values of 370 and more, good: values of more than 300 to less than 370, poor: values of less than 300 .sup.3,4Abrasion test based on ISO 105-A03 DIN EN 20105-A03:1994 Evaluation of colour fastness using the grey scale. The abrasion test is evaluated visually with reference to staining of the rubbing surface (3) and damage to the printed paper (4). Definitive evaluation of abrasion resistance is the sum (5) of the evaluations of abrasion: rubbing surface (3) and abrasion: printed paper (4). Score 5: very good, score 4: good, score 3: poor, score 2: very poor, score 1: extremely poor. The determination of abrasion resistance takes place after abrasion loading by a Prfbau instrument after conditioning the prints at ambient temperature for at least 24 h. Paper circles (standard white paper 80 g/m.sup.2) with a 4.5 cm diameter were punched out and moved over the intaglio printing with a rotary motion (4 revolutions per 60 double strokes) with a total load of approx. 613 g in the form of 120 double strokes.

(14) The results show that the use of the modified pigments according to the invention in UV printing inks is clearly superior in terms of abrasion resistance to the use of leafing pigments or pigments that are coated only with a silicon dioxide layer or uncoated. The hiding power and gloss of examples 1 to 3 correspond to the versions of comparable unmodified, uncoated pigments. Compared with unmodified silicon dioxide-coated pigments, the pigments according to the invention exhibit better hiding power, better gloss and better abrasion resistance.