PARTICLE-CONTAINING COMPOSITION FOR THE PRODUCTION OF LOW-WEAR ANTI-ADHESIVE COATINGS

Description

[0001] The present invention relates to a composition for producing particle-containing coatings, the use of such compositions for coating surfaces and a product coated with the composition for a printing machine.

[0002] In the various machines used in the graphic arts industry for prepress, print production, and postpress, substrates such as paper, cardboard, or film are conveyed and processed. Substrates can be conveyed in printing presses using rotating cylinders, which have substrate-contacting surfaces for this purpose, either in the form of coated cylinders or in the form of replaceable cylinder jackets. These substrate-contacting surfaces generally have two desirable properties: first, anti-adhesive properties—i.e., ink-, varnish-, and dirt-repellent properties. Second, these surfaces should be as wear-resistant as possible, so that replacement is rarely necessary.The known surface coatings for substrate-contacting surfaces are generally not smooth, but exhibit a certain degree of roughness. This is intended, among other things, to reduce the contact area for the substrate and to better utilize the aforementioned surface properties of anti-adhesiveness and wear resistance.

[0003] The state of the art describes, in principle, various methods for producing anti-adhesive and wear-resistant surfaces for printing press cylinders. In addition to electroplating, embossing, laser coating, thermal spraying, and combinations thereof, sol-gel processes can also be used.

[0004] Compositions for producing anti-adhesive and abrasion-resistant coatings for printing press cylinders based on sol-gel technology using silicon oxide sols and with the addition of hard solid particles are described in principle in the prior art.

[0005] DE 10 2012 004 278 A1 describes abrasion-resistant and anti-adhesive surface coatings for printing press cylinders based on sol-gel processes.

[0006] DE 10 2011 010 718 A1 describes compositions for producing abrasion-resistant and anti-adhesive coatings for printing press cylinders using sol-gel technology, wherein the coated surfaces comprise hard microparticles.

[0007] Document US9321078 discloses a sol-gel matrix and particles with a size of 1 to 5 micrometers and agglomerates with a size of 10 to 50 micrometers.

[0008] There is still a need for compositions comprising hard solid particles with which surface coatings on printing press cylinders or surface coatings on cylinder covers for printing press cylinders can be produced, which, in addition to their anti-adhesive properties, have lower abrasion and thus higher wear resistance.

[0009] It is therefore an object of the present invention to provide compositions with which particularly wear-resistant substrate-contacting surfaces comprising hard solid particles with, at the same time, practical anti-adhesive properties can be produced.

[0010] Surprisingly, it has now been discovered that coatings produced from mixtures of silicon oxide sols comprising hard solid particles with particle sizes of between 1 and 2 µm on the one hand and less than 1 µm on the other hand are anti-adhesive and particularly abrasion-resistant when the two different sized solid particle types are used in approximately the same mixing ratio. Such particle-containing coatings exhibit particularly suitable roughness parameters for practical use, in particular optimal Rp and Rk values.

[0011] The compositions according to the invention can be used to produce particle-containing coatings that contact the printing substrate and, due to their anti-adhesive and particularly low-wear properties, withstand a particularly high number of printing runs without wearing off. Coatings on printing press cylinders and coated cylinder covers for printing press cylinders can be produced comparatively easily and cost-effectively using these compositions. Complex and expensive electroplating processes, embossing and laser processes, and thermal spraying processes are not required.

[0012] Accordingly, a first aspect of the present invention relates to a composition for producing particle-containing coatings, comprising the following components A) and B): A) at least one sol-gel precursor compound and B) solid particles P1) which have a Sauter diameter d 32 in the range from 1.0 µm to 2.0 µm, measured by dynamic light scattering, and solid particles P2) which have a Sauter diameter d 32 of less than 1.0 µm, measured by dynamic light scattering, wherein the ratio of the solid particles P1) to the solid particles P2) is in the range from 1.5 : 1 to 1 : 1.5.

[0013] In a preferred embodiment, the solid particles P1) have a Sauter diameter d 32 in the range from 1.0 µm to 2.0 µm, measured by dynamic light scattering, and the solid particles P2) have a Sauter diameter d 32 of less than 0.5 µm, measured by dynamic light scattering. In a particularly preferred embodiment, the solid particles P1) have a Sauter diameter d 32 in the range from 1.1 µm to 1.8 µm, measured by dynamic light scattering, preferably in the range from 1.2 µm to 1.6 µm, measured by dynamic light scattering, and the solid particles P2) have a Sauter diameter d 32 of less than 0.5 µm, measured by dynamic light scattering.

[0014] In a further preferred embodiment, the solid particles P1) have a Sauter diameter d 32 in the range from 1.0 µm to 2.0 µm, measured by means of dynamic light scattering, and the solid particles P2) have a Sauter diameter d 32 in the range from 0.01 µm to 0.5 µm, measured by means of dynamic light scattering, preferably in the range from 0.05 µm to 0.5 µm, measured by means of dynamic light scattering. In a particularly preferred embodiment, the solid particles P1) have a Sauter diameter d 32 in the range from 1.1 µm to 1.8 µm, measured by means of dynamic light scattering, preferably in the range from 1.2 µm to 1.6 µm, measured by means of dynamic light scattering, and the solid particles P2) have a Sauter diameter d 32 in the range from 0.01 µm to 0.5 µm, measured by means of dynamic light scattering, preferably in the range from 0.05 µm to 0.5 µm, measured by means of dynamic light scattering.

[0015] The Sauter diameter d 32 is known in principle to those skilled in the art. This describes the calculated diameter of fictitious spheres, which is obtained by mathematically transforming the total volume of the collective of the individual solid particles P1) or P2) into spheres of equal size, which in total have the same volume and the same surface area as the collective of the individual solid particles P1) or P2). The Sauter diameter d 32 is determined according to DIN ISO 13320 using dynamic light scattering.

[0016] The solid particles P1) and P2) each preferably have an aspect ratio of less than 5:1, particularly preferably less than 3:1, and most preferably less than 2:1. In a preferred embodiment, the solid particles P1) and P2) each have an approximately spherical structure.

[0017] According to the invention, in component B), the ratio of solid particles P1) to solid particles P2) is in the range from 1.5:1 to 1:1.5, preferably in the range from 1.3:1 to 1:1.3, and particularly preferably in the range from 1.1:1 to 1:1.1. The ratio here is understood to mean the numerical ratio. In other words, component B) particularly preferably contains approximately the same number of solid particles P1) and solid particles P2) and, at most, a slight numerical excess of one of the two solid particles P1) or P2).

[0018] The composition according to the invention for producing particle-containing coatings comprises the solid particles P1) preferably in an amount in the range from 1 to 40% by weight, particularly preferably in the range from 2 to 30% by weight and very particularly preferably in the range from 5 to 20% by weight, based on the total composition, and the solid particles P2) preferably in an amount in the range from 0.5 to 35% by weight, particularly preferably in the range from 1 to 25% by weight and very particularly preferably in the range from 2 to 20% by weight, based on the total composition.

[0019] In a preferred embodiment, the amount of component B), i.e. the amount of solid particles P1) plus the amount of solid particles P2), is in the range from 2 to 50 wt.%, preferably in the range from 3 to 40 wt.% and particularly preferably in the range from 5 to 30 wt.%, based on the total composition.

[0020] The solid particles P1) and P2) used in the compositions according to the invention are hard solid particles. In a preferred embodiment, the solid particles P1) and the solid particles P2) each have a Mohs hardness of 7 or more.

[0021] The solid particles P1) can all consist of the same material or be a mixture of different materials. Furthermore, the solid particles P2) can all consist of the same material or be a mixture of different materials. In a preferred embodiment, the solid particles P1) all consist of the same material. In a further preferred embodiment, the solid particles P2) all consist of the same material. In a particularly preferred embodiment, both the solid particles P1) and the solid particles P2) all consist of the same material.

[0022] In a preferred embodiment, the solid particles P1) and the solid particles P2) are each independently selected from quartz particles, corundum particles, silicon carbide particles, diamond particles, and mixtures thereof. In a particularly preferred embodiment, the solid particles P1) and the solid particles P2) are each selected from silicon carbide particles.

[0023] The compositions according to the invention comprise, as component A), at least one sol-gel precursor compound. Precursor compounds for sol-gel processes are known in principle to those skilled in the art. These are starting compounds for the sol-gel process. These are compounds that generally crosslink by hydrolysis and / or condensation and form gels. Dry surface coatings can then be produced from the resulting gels by further processing steps described in principle in the prior art.

[0024] Accordingly, in a preferred embodiment of the invention, component A) is hydrolyzable and / or condensable.

[0025] In a further preferred embodiment, component A) comprises at least one of the elements B, Si, Al, Zr and Ti, preferably at least one of the elements Si and Ti. In a particularly preferred embodiment, component A) comprises the element Si.

[0026] In a further preferred embodiment, component A) comprises at least one alkoxide, preferably an alkoxide having 1 to 20 C atoms, particularly preferably having 1 to 10 C atoms, preferably ethanolate, propoxide or butoxide.

[0027] In a preferred embodiment, component A) comprises at least one compound selected from organic silicon compounds. In a particularly preferred embodiment, component A) comprises at least one organic silicon compound that is hydrolyzable and / or condensable.

[0028] In a further preferred embodiment, component A) comprises at least one silicon oxide sol. Silicon oxide sols are known in principle to those skilled in the art. These are silicon-based sols that are used industrially, for example, in sol-gel processes for producing solid surface coatings from colloidal dispersions. Silicon oxide sols are described, for example, in DE 100 04 132 A1, DE 199 52 323 A1 and the references cited therein. Such silicon oxide sols are commercially available, for example, from FEW Chemicals GmbH, Bitterfeld-Wolfen, Germany.

[0029] In a further preferred embodiment, component A) comprises at least one compound selected from compounds of the formula (I) R 1< a Si(R 2< ) 4-a (I) wherein a represents 1, 2 or 3, R 1< independently of one another represents a saturated or unsaturated hydrocarbon radical having 1 to 20 C atoms, which may have one or more double bonds and / or triple bonds and which may be substituted or unsubstituted, R 2< independently of one another represents H, halogen or OR 4<, where R 4< represents a saturated or unsaturated hydrocarbon radical having 1 to 20 C atoms, which may have one or more double bonds and / or triple bonds and which may be substituted or unsubstituted and their hydrolysis products and condensation products.

[0030] In a particularly preferred embodiment, component A) comprises at least one compound selected from compounds of the above-mentioned formula (I), wherein R 1< independently of one another represents C 1 -C 20 alkyl, C 2 -C 20 alkenyl, C 2 -C 20 alkynyl, C 6 -C 14 aryl, C 7 -C 20 arylalkyl, C 7 -C 20 alkylaryl, C 8 -C 20 arylalkenyl, C 8 -C 20 alkenylaryl, C 8 -C 20 arylalkynyl or C 8 -C 20 alkynylaryl, where the radicals R 1< may carry one or more substituents selected from halogens and optionally substituted amino groups, aldehyde groups, keto groups, C 1 -C 20 alkylcarbonyl groups, carboxy groups, mercapto groups, cyano groups, hydroxy groups, C 1 -C 20 alkoxy groups, C 1 -C 20 -alkoxycarbonyl groups, sulfonic acid groups, phosphoric acid groups, acryloxy groups, methacryloxy groups, epoxy groups and vinyl groups, R 2< independently of one another represents H, halogen, C 1 -C 20 -alkoxy, C 6 -C 14 -aryloxy or C 1 -C 20 -alkoxy-C 1 -C 20 -alkoxy and their hydrolysis products and condensation products.

[0031] In a particularly preferred embodiment, component A) comprises at least one compound selected from compounds of the above-mentioned formula (I), wherein R 1< is independently selected from 3-aminopropyl, 3-glycidoxypropyl, 3-methacryloxypropyl, N-(2-aminoethyl)-3-aminopropyl, 3-mercaptopropyl, 3-isocyanatopropyl and 3-(C 1 -C 20 alkyl)-carbamatopropyl.

[0032] In a further particularly preferred embodiment, component A) comprises at least one compound which is selected from compounds of the above-mentioned formula (I), in which R 2< is independently selected from chlorine, C 1 -C 10 alkoxy, C 1 -C 10 alkoxy-C 1 -C 10 alkoxy and C 6 -C 10 aryloxy.

[0033] In a preferred embodiment, the composition according to the invention comprises component A) in an amount in the range from 10 to 99 mol%, preferably in the range from 20 to 90 mol%, based on the total composition.

[0034] In a further preferred embodiment, the composition according to the invention comprises component A) in an amount in the range from 10 to 99% by weight, preferably in the range from 20 to 80% by weight, based on the total composition.

[0035] In a further preferred embodiment, the composition according to the invention comprises a further component which is selected from component C) C) at least one compound of the formula (II) M(OR 3< ) n (II) wherein n stands for 2, 3 or 4, M stands for B, Al, Si, Ti or Zr, R 3< independently of one another stands for C 1 -C 20 alkyl, C 6 -C 14 aryl, C 1 -C 20 acyl or C 1 -C 20 alkoxy-C 1 -C 20 alkyl and their hydrolysis products and condensation products.

[0036] In a particularly preferred embodiment, the at least one compound of formula (II) is selected from tetra-C 1 -C 20 -alkoxysilanes. In a very particularly preferred embodiment, the at least one compound of formula (II) is selected from tetraethoxysilane, tetramethoxysilane, and tetra-i-propylsilane, specifically tetraethoxysilane.

[0037] In a preferred embodiment, the composition according to the invention comprises component C) in an amount in the range from 0.1 to 90 mol%, preferably in the range from 1 to 80 mol%, based on the total composition.

[0038] In a further preferred embodiment, the composition according to the invention comprises component C) in an amount in the range from 1 to 90% by weight, preferably in the range from 10 to 70% by weight, based on the total composition.

[0039] In a further preferred embodiment, the composition according to the invention comprises a further component which is selected from component D) D) at least one fluorine-containing organic compound which is selected from fluorine-containing polyethers and organic silicon compounds having at least one fluorine-containing side chain and their hydrolysis products and condensation products.

[0040] In a particularly preferred embodiment, component D) comprises at least one organic silicon compound having at least one fluorine-containing side chain and at least one hydrolyzable silyl radical attached via a hydrocarbon chain. In a further particularly preferred embodiment, component D) comprises fluorine-containing polyethers comprising structural units selected from tetrafluoroethylene oxide units and hexafluoropropylene oxide units. In a very particularly preferred embodiment, component D) comprises fluorine-containing polyethers comprising structural units selected from tetrafluoroethylene oxide units and hexafluoropropylene oxide units, and at least one hydrolyzable silyl radical attached via a hydrocarbon chain.

[0041] In a preferred embodiment, the composition according to the invention comprises component D) in an amount in the range from 0.05 to 20 mol%, preferably in an amount in the range from 1 to 10 mol%, based on the total composition.

[0042] In a further preferred embodiment, the composition according to the invention comprises component D) in an amount in the range from 0.1 to 60% by weight, preferably in the range from 5 to 50% by weight, based on the total composition.

[0043] The compositions according to the invention can be prepared, for example, by providing a first composition which comprises a component A) and solid particles P1), and providing a second composition which comprises a component A) and solid particles P2), and mixing the first composition and the second composition with one another, for example by stirring.

[0044] The present invention further provides the use of a composition according to the invention for coating metal surfaces, ceramic surfaces, plastic surfaces, glass surfaces, stone surfaces, wood surfaces, and combinations thereof. The coating can be applied by methods described in principle in the prior art for sol-gel coatings, for example by spraying, dipping, pouring, and the like.

[0045] The present invention further provides a coated product for a printing press, which at least temporarily contacts a printing substrate with a contact surface during a printing process, wherein the contact surface has been coated at least in partial areas with a composition according to the invention. In a preferred embodiment, the coated product for a printing press according to the invention is a replaceable cylinder assembly for a sheet-transporting cylinder of a rotary printing press or a sheet-transporting cylinder of a rotary printing press.

[0046] The production of a coated product according to the invention, namely a replaceable cylinder elevator, can be carried out, for example, by the following procedure: A smooth base plate made of stainless steel, plastic, brass, or aluminum with a thickness of less than 0.5 µm is provided, which is roughened by grinding with a hand-held grinder in order to achieve better adhesion of the overlying layers by increasing the surface volume. Alternatively, mechanical grinding processes, etching processes, and / or laser processes can also be used. Subsequently, to improve the adhesion of the overlying layer, an adhesion promoter layer, which can also be referred to as a primer, is applied, for example by spraying. A composition according to the invention comprising a silicon oxide sol and silicon carbide particles as P1) and P2) is then applied, for example by spraying.The same numerical quantity of silicon carbide particles P1) and silicon carbide particles P2) is used, i.e. in a ratio of 1:1. The sprayed coating is then thermally dried in the temperature range from 160 to 180 °C. One or more layers of silicon oxide sol, preferably two layers of silicon oxide sol, to which no solid particles have been added, are then applied, for example by spraying. These top layers lead to even greater wear resistance of the cylinder packing. Alternatively or in addition to the silicon oxide sol top layer, one or more layers of silicone can also be applied. The applied top layers are also thermally dried in the temperature range from 160 to 180 °C. The result is a cylinder packing for a rotary printing press that only needs to be replaced due to mechanical wear after well over a million printing cycles.

[0047] Alternatively, a cylinder for a rotary printing press can be directly roughened, provided with an adhesion promoter, coated with the composition of the invention, and provided with one or more cover layers using processes similar to those already mentioned for cylinder coating. The result is a printing press cylinder for transporting printed sheets that only wears out after well over a million printing operations and must be replaced from the printing press. Figure 1 shows a photograph of a cylinder packing produced according to the process described above. A silicon oxide sol was used that contained only solid particles P1), namely silicon carbide particles with a Sauter diameter d 32 in the range of 1.0 µm to 2.0 µm. The surface structure was not well suited for practical use in the printing press. Figure 2shows a photograph of a cylinder packing produced according to the process described above. A silicon oxide sol was used that contained only solid particles P2), namely silicon carbide particles with a Sauter diameter d 32 of less than 1.0 µm. The surface structure was not well suited for practical use in the printing press. Figure 3 shows a photograph of a cylinder packing produced according to the process described above. A silicon oxide sol with silicon carbide particles was used, namely a 2:1 mixture of solid particles P2) to solid particles P1). The surface structure was not well suited for practical use in the printing press. Figure 4 shows a photograph of the Figure 3The cylinder packing shown here was additionally coated with a sol-gel protective layer without the addition of solid particles. The surface structure was not well suited for practical use in the printing press. Figure 5 shows a photograph of a cylinder packing according to the invention, produced according to the process described above. A silicon oxide sol with silicon carbide particles was used, namely a 1:1 mixture of solid particles P2) to solid particles P1), which was additionally coated with two sol-gel protective layers without the addition of solid particles. The surface structure was very well suited for practical use in the printing press.

Claims

1. A composition for producing particle-containing coatings comprising the following components: A) at least one sol-gel precursor compound and B) solid particles P1), which exhibit a Sauter diameter d32 in the range of 1.0 µm to 2.0 µm, measured by dynamic light scattering, and solid particles P2), which exhibit a Sauter diameter d32 of less than 1.0 µm, measured in accordance with DIN ISO 13320 by means of dynamic light scattering, wherein the quantitative ratio of the solid particles P1) to the solid particles P2) is in the range of 1.5 : 1 to 1 : 1.5.

2. The composition according to claim 1, wherein component A) is hydrolyzable and / or condensable.

3. The composition according to any one of the preceding claims, wherein said component A) comprises at least one of the elements B, Si, Al, Zr and Ti.

4. The composition according to any one of the preceding claims, wherein said component A) comprises at least one alkoxide.

5. The composition according to any one of the preceding claims, wherein said component A) comprises at least one silicon compound.

6. The composition according to any one of the preceding claims, wherein said component A) comprises at least one silica sol.

7. The composition according to any one of the preceding claims, wherein said component A) comprises at least one compound selected from organic silicon compounds of formula (I)         R1aSi(R2)4-a     (I) wherein a stands for 1, 2 or 3, R1 independently of one another represents a saturated or unsaturated hydrocarbon radical having 1 to 20 carbon atoms, which may contain one or more double bonds and / or triple bonds, and which may be substituted or unsubstituted, R2 independently of one another represents H, halogen or OR4, wherein R4 represents a saturated or unsaturated hydrocarbon radical having 1 to 20 carbon atoms, which may contain one or more double bonds and / or triple bonds, and which may be substituted or unsubstituted and their hydrolysis products and condensation products.

8. The composition according to claim 7, wherein said component A) comprises at least one compound selected from compounds of formula (I) according to claim 7, wherein R1 independently of one another represents C1-C20-alkyl, C2-C20-alkenyl, C2-C20 alkynyl, C6-C14 aryl, C7-C20 arylalkyl, C7-C20 alkylaryl, C8-C20 arylalkenyl, C8-C20 alkenylaryl, C8-C20 arylalkynyl or C8-C20 alkynylaryl, wherein the radicals R1 may carry one or more substituents which are selected from halogens and optionally substituted amino groups, aldehyde groups, keto groups, C1-C20 alkylcarbonyl groups, carboxy groups, mercapto groups, cyano groups, hydroxy groups, C1-C20 alkoxygroups, C1-C20 alkoxycarbonyl groups, sulfonic acid groups, phosphoric acid groups, acryloxy groups, methacryloyloxy groups, epoxy groups and vinyl groups, R2 independently represents H, halogen, C1-C20 alkoxy, C6-C14 aryloxy or C1-C20 alkoxy-C1-C20 alkoxy and their hydrolysis products and condensation products.

9. The composition according to any one of the preceding claims, wherein the amount of said component A) is in the range from 20 to 80% by weight, based on the total composition.

10. The composition according to any one of the preceding claims, wherein said solid particles P1) and said solid particles P2) each have a Mohs hardness of 7 or more.

11. The composition according to claim 10, wherein said solid particles P1) and said solid particles P2) are each independently selected from quartz particles, corundum particles, silicon carbide particles, diamond particles and mixtures thereof, in particular from silicon carbide particles.

12. The composition according to any one of the preceding claims, wherein the amount of component B) is in the range of 5 to 30% by weight, based on the total composition.

13. Use of a composition according to any one of the claims 1 to 12 for coating metal surfaces, ceramic surfaces, plastic surfaces, glass surfaces, stone surfaces, wood surfaces and combinations thereof.

14. Coated product for a printing machine, which during a printing process at least temporarily contacts a printing substrate with a contact surface, wherein the contact surface has been coated at least in partial areas with a composition according to one of claims 1 to 12.

15. A coated product for a printing press in accordance with claim 14, wherein the product is an exchangeable cylinder jacket for a sheet-transporting cylinder of a rotary printing press or a sheet-transporting cylinder for a rotary printing press.