Matting agent for UV varnishes

Abstract

The invention relates to matted UV varnishes comprising silicon dioxide, the surface thereof having been modified by means of treatment with a multiple bond organopolysiloxane so as to be particularly well-suited for use as a matting material for UV varnishes, and to a method for producing same.

Claims

1. A UV coating material, comprising: a surface-modified silicon dioxide particle, wherein at least a part of the silicon dioxide particle is coated with an organopolysiloxane which is a polyoxyalkylene-modified siloxane derivative of the formula (I) ##STR00007## wherein R.sup.1 and/or R.sup.7=R.sup.2 or [R.sup.4].sub.w[R.sup.5].sub.x[R.sup.6].sub.yR.sup.8, R.sup.2=R.sup.3 or R.sup.3 stands for identical or different alkyl radicals or alkylene radicals having 1 to 24 carbon atoms or optionally substituted phenyl radicals having up to 24 carbon atoms, R.sup.4=a divalent radical of the formula O, NH, NR.sup.2, S or a radical of the formula (OSi(CH.sub.3).sub.2).sub.u, where u=1 to 200, R.sup.5=identical or different alkyl radicals or alkylene radicals having 1 to 24 carbon atoms, or C.sub.nH.sub.2n-fR.sup.2.sub.fR.sup.4C.sub.mH.sub.2m-gR.sup.2.sub.g, where f=0 to 12, g=0 to 12, n=1 to 18, m=1 to 18, R.sup.6=O(C.sub.2H.sub.4-aR.sup.2.sub.aO).sub.b(C.sub.cH.sub.2cO).sub.d, where a=0 to 3, b=0 to 100, c=2 to 12, d=0 to 100, the sum (b+d)=1 to 200, and the sequence of the individual polyoxyalkylene segments (C.sub.2H.sub.4-aR.sup.2.sub.aO).sub.b and (C.sub.cH.sub.2cO).sub.d is arbitrary, or R.sup.6=O.sub.eC.sub.hH.sub.2hC.sub.iH.sub.2i-jR.sup.9.sub.j, where e=0, h=0 to 24, i=0 to 24, j=1 to 3, and R.sup.9 in each case is a divalent radical of the formula O, a hydroxyl group, a radical of the formula C.sub.h1H.sub.2h or a radical of the formula C.sub.kH.sub.2k-l(OH).sub.l, where k=0 to 24 and l=1 to 3, R.sup.8=a hydrogen radical or a monovalent organic radical, if y is 1, it being necessary for there to be at least one hydrogen radical per molecule, or is an OH group or a monovalent organic radical, with y=0, there being at least one OH group per molecule, v=0 to 200, w=1, x=1, y=0 or 1, z=1 to 200, and the sum (w+x+y)=2 or 3.

2. The UV coating material of claim 1, wherein the silicon dioxide particle is a precipitated silica, a fumed silica, a semigel, or a silica gel.

3. The UV coating material of claim 1, wherein the surface-modified silicon dioxide particle has a d.sub.50 of from 1 to 50 m, a DBP of from 100 to 600 g/100 g, a C content of from 1% to 20% by weight, or a combination thereof.

4. The UV coating material of claim 1, wherein the UV coating material has a refractive index of n.sub.D20=1.4000 to 1.5000, the UV coating material comprises 5% by weight of the surface-modified silicon dioxide particle, and a transmittance of the UV coating material is at least 20% improved over an otherwise identical coating material comprising 5% by weight of a reference silicon dioxide treated with a polyethylene wax and not with the surface-modified silicon dioxide particle.

5. The UV coating material of claim 1, wherein the organopolysiloxane has a polyether excess of from 5% to 50% by weight.

6. The UV coating material of claim 1, wherein the UV coating material is a clear coating material or a pigmented coating material.

7. The UV coating material of claim 1, further comprising: a binder based on a reactive monomer, based on a reactive oligomer, or based on both.

8. The UV coating material of claim 1, comprising: from 3% to 30% by weight of the organopolysiloxane-modified silicon dioxide particle; of at least one component selected from the group consisting of a photoinitiator, a flow control agent, an antioxidant, a pigment, a microcrystalline wax, an organic solvent, and water; or of both the organopolysiloxane-modified silicon dioxide particle and the at least one component.

9. A process for preparing the UV coating material of claim 1, the process comprising: contacting a dried silicon dioxide, a suspension of silicon dioxide, or a filter cake with at least one organopolysiloxane comprising a multiple bond.

10. The process of claim 9, comprising: reacting an alkali metal silicate solution with an acidifier, further adding an acidifier to set a pH of from 7 to 2, to obtain a silicon dioxide suspension, isolating precipitated solid from the silicon dioxide suspension by filtration, and drying the solid by slow drying or rapid drying to obtain a dried silicon dioxide, such that the dried silicon dioxide has a residual moisture content of less than 10%, treating the dried silicon dioxide with an organopolysiloxane comprising a multiple bond, or a combination thereof.

11. The process of claim 9, wherein a content of the organopolysiloxane is from 0.5% to 30% by weight, and -the organopolysiloxane comprises a carbon-carbon double bond, a carbon-carbon triple bond, or both.

12. The process of claim 10, further comprising: resuspending the precipitated solid isolated by filtration with water, sulphuric acid, or a mixture of water and sulphuric acid, then adding to the suspension a surface-modifying organopolysiloxane comprising a carbon-carbon double bond, a carbon-carbon triple bond, or both, and drying the resulting suspension.

13. The process of claim 10, further comprising: admixing and intimately mixing the dried silicon dioxide with a surface-modifying organopolysiloxane comprising a carbon-carbon double bond, a carbon-carbon triple bond, or both.

14. The process of claim 13, further comprising: further mixing the dried silicon dioxide and the organopolysiloxane for 0-2 h, heat treating the dried silicon dioxide and the organopolysiloxane at from 20 to 150 C., or both.

15. The process of claim 9, further comprising: grinding surface-modified silicon dioxide, separating off dried silicon dioxide particles having a diameter of more than 50 m, or both.

16. The process of claim 9, further comprising: simultaneously grinding and surface-modifying, in a milling apparatus, a silicon dioxide, a semigel, or a silica gel.

17. The process of claim 16, wherein the milling apparatus employs a milling gas with a pressure of 4 bar (abs), a temperature of less than or equal to 180 C., or both.

Description

Inventive Example 1

(1) In an AFG 200 Aeroplex opposed-jet fluid-bed mill from Hosokawa Alpine AG, the precipitated silica ACEMATT HK400 from Evonik Degussa GmbH was ground at a grinding-air entry temperature of 76 C. (internal grinding chamber temperature 60 C.) and a pressure of 0.4 bar (abs), and coated with the silicone polyether acrylate Tego Rad 2300 from Evonik Goldschmidt GmbH. The coating agent is introduced into the mill via a two-fluid nozzle which is located in the same plane as the grinding nozzles (3 grinding nozzles at a spacing of 120, and between two of these grinding nozzles the two-fluid nozzle, at a spacing of 60). The amount of silicone polyether acrylate is calculated so as to give a carbon content, based on the total weight of the end product, of 3.2% by weight. The product has a d.sub.50 value of 4.7 m.

Comparative Example 1

(2) Corresponding to Example 1 of DE 102004029069, i.e. a matting agent silica coated with a polyorganosiloxane without multiple bond.

Comparative Example 2

(3) This is the commercially available product Gasil UV 70 C from PQ Corporation, a matting agent developed and sold especially for UV coating materials.

Example 2

(4) A UV coating material matted with the matting agents identified above was prepared as follows:

(5) Formula

(6) TABLE-US-00005 Item Raw material Purity Manufacturer Amount 1 Laromer LR 8889 as-supplied form BASF 77.70 2 HDDA as-supplied form BASF 19.40 3 Irgacure 184 as-supplied form Ciba 2.50 4 Irgacure 819 as-supplied form Ciba 0.40 Total 100.00

(7) The individual raw materials are gradually weighed out in the above sequence, and homogenized using a laboratory dissolver. Homogenisation must take place in each case after items 3 and 4. After item 4, the base clear coat is stirred until all of the solid components have fully dissolved.

(8) Preparation of the Matted Clear Coating Material:

(9) Prior to use, the glossy base coating material is homogenized with a paddle stirrer at 2000 rpm. In 100 parts by weight of this base coating material, the matting agents under investigation are tested against the corresponding standard specimens a) with the same initial mass (in order to illustrate differences in the reflectometer values of the applied matting coating material), b) with different initial masses (in order to obtain the same reflectometer value at 15 m dry film thickness), and c) with different initial masses (in order to determine the achievable reflectometer values for a given viscosity).

(10) Following careful incorporation using a spatula, the matting agent is dispersed with a paddle stirrer at 2000 rpm for 10 minutes in a 350 ml PE beaker.

(11) Processing and Testing of the Matt Coating Material Produced:

(12) After the matting agents have been dispersed, application takes place with wire-wound applicators in sizes of 20 m, 40 m, 60 m and 80 m to BYK test cards 2854. Determination should always be carried out in duplicate. Following application, the coating films are cured in a UV unit from IST Metz GmbH. It must be ensured that the Hg lamp is selected with an output of 100%, and the belt speed is 2 m/min. The reflectometer value and the density can be determined immediately, while the viscosity of the liquid coating material is not determined until the next day, using the Rheolab QC.

(13) The results of the investigations are given in Tables 3 and 4 below:

(14) TABLE-US-00006 TABLE 3 Test of the gloss properties of the UV coating materials Application by wire-wound applicator to Byk test cards 2854 20 m 40 m 60 m 80 m UV drying 1 2 m/min, Reflectometer Reflectometer Reflectometer Reflectometer Hg lamp 200 W/cm value value value value Dispersing: 10 min paddle stirrer, 45 mm, 2000 rpm 85 85 85 85 PE beaker 350 ml 60 85 60 60 85 60 60 85 60 60 85 60 Inventive Example 1 13.0 g 13.4 67.3 53.9 10.4 60.2 49.8 9.4 57.6 48.2 9.1 57.7 48.6 Comparative Example 1 15.0 g 15.5 70.8 55.3 12.3 65.1 52.8 10.0 60.7 50.7 8.9 57.4 48.5 Comparative Example 2 13.0 g 18.6 67.2 48.6 17.3 66.4 49.1 14.9 63.4 48.5 12.7 59.4 46.7 Density/Transparency Inventive Example 1 1.62 Comparative Example 2 1.57 Comparative Example 1 1.58

(15) As is evident from Table 3, the product according to the invention shows significantly better matting properties, especially at thin film thicknesses. Moreover, it shows a greater transparency when used at the same initial mass as the comparative examples.

(16) TABLE-US-00007 TABLE 4 Test of the rheological properties of the UV coating materials Conc. MM g/ D = Rheolab QC 100 g coating D = 1 D = 10 D = 25 D = 100 D = 250 1000 Inventive Example 1 13.0 g 1420 419 328 277 260 245 Comparative Example 1 15.0 g 1820 805 701 613 570 483 Comparative Example 2 13.0 g 8260 1040 541 280 218 180

(17) From Table 4 it is clear that the product according to the invention exhibits significant advantages in rheology and has a much lower structural viscosity. This is a major advantage in the context of the processing of such coating materials in industrial processing operations.