Silica containing dispersion comprising polyamine-grafted-polyacrylate copolymer

Abstract

In a first aspect, the invention is related to a silica containing dispersion comprising: (a) in the range of from 30 to 98 weight-% of a mixture comprising a resin and a compound having at least one (meth)acrylate group; (b) in the range of from 1 to 30 weight-% of silica; and (c) in the range of from 0.1 to 10 weight-% of a polyamine-grafted-polyacrylate copolymer; wherein the total weight of the silica dispersion are 100 weight-%. A second aspect of the invention is directed to the use of a silica containing dispersion according to the first aspect of the invention as coating agent. A third aspect of the invention relates to a method for coating of a surface. In a fourth aspect, the invention is directed to the use of a polyamine-grafted-polyacrylate copolymer according to (c) of the first aspect of the invention as dispersant for silica. A fifth aspect of the invention relates to a method for preparing a resin composition having silica dispersed therein. A sixth aspect is directed to a silica containing dispersion, obtained or obtainable by the method of the second aspect of the invention. A seventh aspect of the invention is related to a method for preparing a silica containing coating, and an eight aspect of the invention is directed to a coating, obtained or obtainable by the method of the seventh aspect of the invention.

Description

[0001] Silica containing dispersion comprising polyamine-grafted-polyacrylate copolymer

[0002] In a first aspect, the invention is related to a silica containing dispersion comprising: (a) in the range of from 30 to 98 weight-% of a mixture comprising a resin and a compound having at least one (meth)acrylate group; (b) in the range of from 1 to 30 weight-% of silica; and (c) in the range of from 0.1 to 10 weight-% of a polyamine-grafted-polyacrylate copolymer; wherein the total weight of the silica dispersion are 100 weight-%.

[0003] A second aspect of the invention is directed to the use of a silica containing dispersion according to the first aspect of the invention as coating agent. A third aspect of the invention relates to a method for coating of a surface. In a fourth aspect, the invention is directed to the use of a polyamine-grafted-polyacrylate copolymer according to (c) of the first aspect of the invention as dispersant for silica. A fifth aspect of the invention relates to a method for preparing a resin composition having silica dispersed therein. A sixth aspect is directed to a silica containing dispersion, obtained or obtainable by the method of the second aspect of the invention. A seventh aspect of the invention is related to a method for preparing a silica containing coating, and an eight aspect of the invention is directed to a coating, obtained or obtainable by the method of the seventh aspect of the invention.

[0004] State of the art

[0005] Coatings often require a certain degree of matting and thus any coating formulation has to ensure that its “matting power” is sufficiently high. Silica is widely used in the coatings industry as a cost-efficient filler, matting agent and for rheological control. Silica dispersions are used in a wide range of applications such as coating compositions and enhancing mechanical properties of a coating film. However, a stable embedding of silica into a coating formulation is often associated with problems regarding stability of the resulting dispersion due to sedimentation and agglomeration of silica particles. Dispersants are thus used to stabilize silica containing dispersions. For example, US 2021 / 198513 A1 discloses a dispersant selected from the group consisting of polyacrylic acid dispersants, polycarboxylic acid dispersants, phosphoric acid dispersants, and silicone dispersants; and WO 2023 / 073184 A1 describes a polyalkyleneamine polyester based dispersant.

[0006] WO 2008 / 107326 A1 discloses a liquid polyamine-g-polyacrylate grafted copolymer blend, a process for its preparation and the use thereof as dispersant, wherein a plurality of application fields, such as for coatings, inks, electronic materials are indicated. The component to be dispersed is only in the examples indicated as being a pigment for a paint formulation. However, it is still difficult to obtain a stable dispersion comprising silica, which also exhibits a suitable viscosity, especially if UV or radiation curable resins are also to be present within the dispersion. Thus, there is an ongoing demand for dispersants useful for silica containing dispersions, which on one hand have a sufficient viscosity and on the other hand give a convenient matting, expressed by example by a low Gloss 60°, once the related dispersion has been applied as a coating and cured by radiation and / or UV light.

[0007] Therefore, it was an object of the present invention to provide a silica containing dispersion with a suitable dispersant, which allows a suitable viscosity of the dispersion and furthermore provides a sufficient matting effect once applied as a coating.

[0008] Surprisingly, it was found that this object can be solved by a silica containing dispersion comprising a polyamine-grafted-polyacrylate copolymer. Said silica containing dispersion exhibits a viscosity (at 1 S'1) in the range of from 2000 to 12000 mPas, determined in analogy to DIN 53019-1 :2008-09 and a cured coating prepared therefrom has only a Gloss 60° value in the range of 1 to 30, determined according to DIN 67530 : 1982-01.

[0009] In a first aspect, the invention is thus directed to a silica containing dispersion comprising:

[0010] (a) in the range of from 30 to 98 weight-% of a mixture comprising a resin and a compound having at least one (meth)acrylate group;

[0011] (b) in the range of from 1 to 30 weight-% of silica;

[0012] (c) in the range of from 0.1 to 10 weight-% of a polyamine-grafted-polyacrylate copolymer; wherein the total weight of the silica dispersion are 100 weight-%.

[0013] The polyamine-grafted-polyacrylate copolymer of (c)

[0014] In some preferred embodiments of the silica containing dispersion, the polyamine-grafted-polyacrylate copolymer of (c) is obtained or obtainable from a grafting reaction of a polyamine and an alkyl acrylate monomer. The term "grafted" as used herein refers to a copolymer made by a so called "grafting reaction", wherein alkyl acrylate groups are attached as pendent groups along a polyamine backbone. Side chains are build up after being grafted to the polyamine backbone. Conditions and reactants (polyamine, alkyl acrylate monomer), solvents, as well as suitable free radical initiators of a grafting reaction are known to the skilled person. For a polyamine-grafted-polyacrylate copolymer as of (c), the grafting reaction is disclosed in detail, for example, in WO 2008 / 107326 A1 , see especially page 4, line 17 to page 15, line 21. In some preferred embodiments of the silica containing dispersion, the polyamine is selected from the group consisting of poly(C2 to Ce alkylene imine), polyvinylamine, polyallylamine and poly(amide-amine) dendrimer; wherein preferably, the polyamine comprises at least, more preferably is, a poly(C2 to Ce alkylene imine), more preferably polyethyleneimine and / or polypropyl- enimine, more preferably the polyamine comprises, more preferably is, polyethyleneimine.

[0015] In some preferred embodiments of the silica containing dispersion, the polyamine has a weight average molecular weight (Mw) in the range of from 200 to 20000 g / mol, more preferably in the range of from 500 to 15000 g / mol, more preferably in the range of from 800 to 10000 g / mol.

[0016] In some preferred embodiments of the silica containing dispersion, the alkyl acrylate monomer is a C1 to C26 alkyl acrylate, wherein the alkyl chain is branched or unbranched, preferably a C2 to C24 alkyl acrylate with a branched or unbranched alkyl chain, more preferably a C4 to C22 alkyl acrylate with a branched or unbranched alkyl chain, more preferably the acrylate is selected from the group consisting of n-butyl acrylate, 2-ethyl hexyl acrylate, heptadecyl acrylate, docosyl acrylate and mixture of two or more thereof.

[0017] In some preferred embodiments of the silica containing dispersion, the polyamine-grafted-poly- acrylate copolymer of (c) is obtained or obtainable from grafting a polyethyleneimine with n-butyl acrylate.

[0018] In some preferred embodiments of the silica containing dispersion, polyamine and alkyl acrylate monomer are reacted in a weight-based ratio polyamine to alkyl acrylate monomer in the range of from 1:20 to 1:1 , preferably in the range of from 1 :10 to 1 :1 , more preferably in the range of from 1:9 to 1 :4.

[0019] In some preferred embodiments of the silica containing dispersion, polyamine and alkyl acrylate monomer are reacted in an organic solvent, preferably in butyl acetate; and / or, preferably and, at a temperature in the range of from 10 °C to a temperature below the boiling point of the organic solvent.

[0020] In some preferred embodiments of the silica containing dispersion, polyamine and alkyl acrylate monomer are reacted in the presence of an initiator, preferably a free radical initiator, more preferably a free radical initiator selected from the group consisting of a 2,2’-azo-bis(isobu- tyronitrile, AIBN), potassium persulfate, 2,2’-azobis(2-amidinopropane), dihydrochloride, alkyl hydroperoxide, and mixtures of two or more thereof, wherein the alkyl hydroperoxide is preferably selected from the group consisting of benzoyl peroxide, di-tert-butyl peroxide, t-butylperoxy- 2-ethylhexanoate, t-butyl hydroperoxide, cumene hydroperoxide, p-isopropyl cumene hydroperoxide, p-menthane hydroperoxide, pinane hydroperoxide, and mixtures of two or more thereof, wherein the free radical initiator preferably comprises, more preferably is, t-butylperoxy-2- ethylhexanoate; and / or, preferably and, wherein the free radial initiator is used in a weight based ratio of free radical initiator to acrylate in the range of from 0.05:100 to 5:100.

[0021] In some preferred embodiments of the silica containing dispersion, the polyamine-grafted-poly- acrylate copolymer of (c) has an average molecular weight Mw in the range of from 2000 to 100000 g / mol, preferably in the range of from 4000 to 20000 g / mol, more preferably in the range of from 5000 to 17000 g / mol, determined according to DIN 55672-1.

[0022] In some preferred embodiments of the silica containing dispersion, the polyamine-grafted-poly- acrylate copolymer of (c) has a polydispersity index (PDI) in the range of from 1 to 4, preferably in the range of from 1.5 to 3.5, more preferably in the range of from 1 .8 to 3.2.

[0023] In some preferred embodiments of the silica containing dispersion, the polyamine-grafted-poly- acrylate copolymer of (c) has an amine number in the range of from 30 to 400 mgKOH / g, preferably in the range of from 100 to 300 mgKOH / g, determined according to DIN 53176:2002-11.

[0024] In some preferred embodiments of the silica containing dispersion, at least a part of the C1 to C26 alkyl groups of the alkyl acrylate in the polyamine-grafted-polyacrylate copolymer of (c) are replaced by another residue R, wherein the other residue R is preferably a C1-22 alkyl group, optionally substituted by an ether bridged irradiation reactive group, wherein the irradiation reactive group is preferably selected from, vinyl group, methoxy substituted or unsubstitited benzo- phenonyl group, and 2-hydroxy-2-methyl propiophenonyl group. Preferably, the replacement is done by transesterification with R-OH, wherein “R” represents the other residue R defined above, preferably in the presence of a transesterification catalyst, more preferably in the presence of titanium(IV) butoxide.

[0025] Silica of (b)

[0026] In some preferred embodiments of the silica containing dispersion, the silica of (b) is selected from the group consisting of amorphous silica and crystalline silica, wherein the silica is unmodified or modified with an organic compound, preferably with an organic wax. In some preferred embodiments, the particle size (d50) of the silica is in the range of 1 to 30 pm, more preferably in the range of from 2 to 20 pm, more preferably in the range of from 3 to 10 pm, more preferably in the range of from 7.6 to 9.2 pm, determined according to DIN 66133. Mixture of (a)

[0027] In some preferred embodiments of the silica containing dispersion, the resin in the mixture of (a) is selected from the group consisting of polyurethane resin, polyether resin, epoxy resin, polyester resin and mixtures of two or more of these resins, wherein the resin is saturated or at least partially unsaturated, wherein the resin preferably comprises at least one polyester resin, more preferably at least one unsaturated polyester resin. The resin is saturated or at least partially unsaturated, wherein an at least partial unsaturation is preferred for UV curable coating systems.

[0028] In some preferred embodiments of the silica containing dispersion, the compound having at least one (meth)acrylate group is selected from the group consisting of dipropylene glycol di(meth)acrylate, 1 ,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane ethoxy tri(meth)acrylate, 2-phenoxyethyl (meth)acrylate, glyceryl tetrapropylene tri(meth)acrylate and mixtures of two or more thereof, wherein preferably the compound having at least one (meth)acrylate group comprises at least dipropylene glycol diacrylate. The wording “(meth)arylate” represents acrylate as well as methacrylate. The co pound having at least one (meth)acrylate group functions as a UV curable or radiation curable reactive diluent. The mixture of (a) is generally a UV curable formulation, which contains at least a UV curable resin and one or more UV monomers.

[0029] In some preferred embodiments of the silica containing dispersion, resin and compound having at least one (meth)acrylate group are mixed in the mixture of (a) in a weight based ratio in the range of 1000:1 to 1 :2, preferably in the range of from 40:1 to 1 :2, more preferably in the range of from 6: 1 to 1 : 1.

[0030] In some preferred embodiments, the silica containing dispersion has a viscosity (at 1 S'1) in the range of from 2000 to 12000 mPas, preferably in the range of from 3000 to 11000 mPas, more preferably in the range of from 3500 to 10500 mPas, determined in analogy to DIN 53019- 1 :2008-09.

[0031] 2ndaspect - Use of silica containing dispersion

[0032] A second aspect of the invention is directed to the use of a silica containing dispersion according to the first aspect of the invention as coating agent. All details, embodiments and preferred embodiments described above for the first aspect of the invention apply also for the second aspect of the invention.

[0033] The silica containing dispersion can be used as a coating agent for any possible surface without limitation, for example, for 3C coatings for various electronic devices such as smartphones, tablets, and laptops, wherein the coating provides a protective layer on the device’s display, or for wood coating and the like.

[0034] 3rdaspect - method for coating of a surface

[0035] A third aspect of the invention is directed to a method for coating of a surface comprising:

[0036] (i) providing a silica containing dispersion according the first aspect of the invention;

[0037] (ii) applying the dispersion provided in (i) onto a surface, thereby obtaining a layer of the dispersion on the surface;

[0038] (iii) hardening the layer obtained in (ii) on the surface, preferably by UV radiation.

[0039] All details, embodiments and preferred embodiments described above for the first aspect of the invention or for the second aspect of the invention apply also for the third aspect of the invention.

[0040] 4thaspect - Use of polyamine-grafted-polyacrylate copolymer

[0041] A fourth aspect of the invention relates to the use of a polyamine-grafted-polyacrylate copolymer according to (c) of the first aspect of the invention as dispersant for silica, preferably as dispersant for dispersing silica in a resin based formulation.

[0042] All details, embodiments and preferred embodiments described above for the first aspect of the invention, especially for(c) of the first aspect of the invention, for the second aspect of the invention, or for the third aspect of the invention apply also for the fourth aspect of the invention.

[0043] In some preferred embodiments of the use of a polyamine-grafted-polyacrylate copolymer according to (c), the resin based formulation comprises a resin and a compound having at least one (meth)acrylate group, preferably a polyester resin and a dipropylene glycol diacrylate.

[0044] In some preferred embodiments of the use of a polyamine-grafted-polyacrylate copolymer according to (c), the resin based formulation is UV curable and / or curable by irradiation. 5thaspect - method for preparing a resin composition having silica dispersed therein

[0045] A fifth aspect of the invention is directed to a method for preparing a resin composition having silica dispersed therein, the method comprising:

[0046] (A) Providing a composition comprising a polyamine-grafted-polyacrylate copolymer according to (c) as defined in the first aspect of the invention as dispersant; silica, a resin and a compound comprising at least one (meth)acrylate group;

[0047] (B) Mixing dispersant, resin and a compound comprising at least one (meth)acrylate group, thereby obtaining a mixture thereof;

[0048] (C) Adding silica to the mixture obtained in (B), preferably under mixing, thereby obtaining a dispersion comprising silica, dispersant, resin and a compound comprising at least one (meth) acrylate group.

[0049] All details, embodiments and preferred embodiments described above for the first aspect of the invention, especially for(c) of the first aspect of the invention, for the second aspect of the invention, for the third aspect of the invention, or for the fourth aspect of the invention apply also for the fifth aspect of the invention.

[0050] 6thaspect - Silica containing dispersion

[0051] A sixth aspect of the invention relates to a silica containing dispersion, obtained or obtainable by the method of the fifth aspect.

[0052] All details, embodiments and preferred embodiments described above for the first aspect of the invention, especially for(c) of the first aspect of the invention, for the second aspect of the invention, for the third aspect of the invention, for the fourth aspect of the invention, or for the fifth aspect of the invention apply also for the sixth aspect of the invention.

[0053] In some preferred embodiments, the silica containing dispersion has a viscosity (at 1 S'1) in the range of from 2000 to 12000 mPas, preferably in the range of from 3000 to 11000 mPas, more preferably in the range of from 3500 to 10500 mPas, determined in analogy to DIN 53019- 1 :2008-09.

[0054] 7thaspect - method for preparing a silica containing coating

[0055] A seventh aspect of the invention relates to a method for preparing a silica containing coating, the method comprising (A) Providing a composition comprising a polyamine-grafted-polyacrylate copolymer according to (c) as defined in the first aspect of the invention as dispersant; silica, resin and a compound comprising at least one (meth)acrylate group;

[0056] (B) Mixing dispersant, resin and compound comprising at least one (meth)acrylate group, thereby obtaining a mixture thereof;

[0057] (C) Adding silica to the mixture obtained in (B), preferably under mixing, thereby obtaining a dispersion comprising silica, dispersant, resin and compound comprising at least one (meth) acrylate group;

[0058] (D) Curing the dispersion obtained in (C), preferably by UV application and / or irradiation.

[0059] All details, embodiments and preferred embodiments described above for the first aspect of the invention, especially for(c) of the first aspect of the invention, for the second aspect of the invention, for the third aspect of the invention, for the fourth aspect of the invention, for the fifth aspect of the invention, or the sixth aspect of the invention apply also for the seventh aspect of the invention.

[0060] 8thaspect - coating

[0061] An eight aspect of the invention relates to a coating, obtained or obtainable by the method of the seventh aspect.

[0062] All details, embodiments and preferred embodiments described above for the first aspect of the invention, especially for(c) of the first aspect of the invention, for the second aspect of the invention, for the third aspect of the invention, for the fourth aspect of the invention, for the fifth aspect of the invention, the sixth aspect of the invention, or the seventh aspect of the invention apply also for the eight aspect of the invention.

[0063] In some preferred embodiments, the coating has a Gloss 60° value in the range of 1 to 30, preferably in the range of 2 to 25, more preferably in the range of from 5 to 20, determined according to DIN 67530 : 1982-01.

[0064] The present invention is further illustrated by the following set of embodiments and combinations of embodiments resulting from the dependencies and back-references as indicated. In particular, it is noted that in each instance where a range of embodiments is mentioned, for example in the context of a term such as "the silica containing dispersion of any one of embodiments 1 to 4", every embodiment in this range is meant to be explicitly disclosed for the skilled person, i.e. the wording of this term is to be understood by the skilled person as being synonymous to "the silica containing dispersion of any one of embodiments 1 , 2, 3 and 4". Further, it is explicitly noted that the following set of embodiments represents a suitably structured part of the general description directed to preferred aspects of the present invention, and, thus, suitably supports, but does not represent the claims of the present invention.

[0065] Embodiment 1 : A silica containing dispersion comprising:

[0066] (a) in the range of from 30 to 98 weight-% of a mixture comprising a resin and a compound having at least one (meth)acrylate group;

[0067] (b) in the range of from 1 to 30 weight-% of silica;

[0068] (c) in the range of from 0.1 to 10 weight-% of a polyamine-grafted-polyacrylate copolymer; wherein the total weight of the silica dispersion are 100 weight-%.

[0069] Embodiment 2: The silica containing dispersion of embodiment 1 , wherein the polyamine- grafted-polyacrylate copolymer of (c) is obtained or obtainable from a grafting reaction of a polyamine and an alkyl acrylate monomer.

[0070] Embodiment 3: The silica containing dispersion of embodiment 2, wherein the polyamine is selected from the group consisting of poly(C2 to Ce alkylene imine), polyvinylamine, polyallylamine and poly(amide-amine) dendrimer; wherein preferably, the polyamine comprises at least, more preferably is, a poly(C2 to Ce alkylene imine), more preferably polyethyleneimine and / or polypro- pylenimine, more preferably the polyamine comprises, more preferably is, polyethyleneimine.

[0071] Embodiment 4: The silica containing dispersion of embodiment 3, wherein the polyamine has a weight average molecular weight (Mw) in the range of from 200 to 20000 g / mol, more preferably in the range of from 500 to 15000 g / mol, more preferably in the range of from 800 to 10000 g / mol.

[0072] Embodiment 5: The silica containing dispersion of any one of embodiments 2 to 4, wherein the alkyl acrylate monomer is a C1 to C26 alkyl acrylate, wherein the alkyl chain is branched or unbranched, preferably a C2 to C24 alkyl acrylate with a branched or unbranched alkyl chain, more preferably a C4 to C22 alkyl acrylate with a branched or unbranched alkyl chain, more preferably the acrylate is selected from the group consisting of n-butyl acrylate, 2-ethyl hexyl acrylate, heptadecyl acrylate, docosyl acrylate and mixture of two or more thereof.

[0073] Embodiment 6: The silica containing dispersion of any one of embodiments 2 to 5, wherein the polyamine-grafted-polyacrylate copolymer of (c) is obtained or obtainable from grafting a polyethyleneimine with n-butyl acrylate. Embodiment 7: The silica containing dispersion of any one of embodiments 2 to 6, wherein polyamine and alkyl acrylate monomer are reacted in a weight-based ratio polyamine to alkyl acrylate monomer in the range of from 1 :20 to 1:1 , preferably in the range of from 1:10 to 1 :1, more preferably in the range of from 1 :9 to 1 :4.

[0074] Embodiment 8: The silica containing dispersion of any one of embodiments 2 to 7, wherein polyamine and alkyl acrylate monomer are reacted in an organic solvent, preferably in butyl acetate; and / or, preferably and, at a temperature in the range of from 10°C to a temperature below the boiling point of the organic solvent.

[0075] Embodiment 9: The silica containing dispersion of any one of embodiments 2 to 8, wherein polyamine and alkyl acrylate monomer are reacted in the presence of an initiator, preferably a free radical initiator, more preferably a free radical initiator selected from the group consisting of a 2,2’-azo-bis(isobutyronitrile, AIBN), potassium persulfate, 2,2’-azobis(2-amidinopropane), dihydrochloride, alkyl hydroperoxide, and mixtures of two or more thereof, wherein the alkyl hydroperoxide is preferably selected from the group consisting of benzoyl peroxide, di-tert-butyl peroxide, t-butylperoxy-2-ethylhexanoate, t-butyl hydroperoxide, cumene hydroperoxide, p-isopropyl cumene hydroperoxide, p-menthane hydroperoxide, pinane hydroperoxide, and mixtures of two or more thereof, wherein the free radical initiator preferably comprises, more preferably is, t-bu- tylperoxy-2-ethylhexanoate; and / or, preferably and, wherein the free radial initiator is used in a weight based ratio of free radical initiator to acrylate in the range of from 0.05:100 to 5:100.

[0076] Embodiment 10: The silica containing dispersion of any one of embodiments 1 to 9, wherein the polyamine-grafted-polyacrylate copolymer of (c) has an average molecular weight Mw in the range of from 2000 to 100000 g / mol, preferably in the range of from 4000 to 20000 g / mol, more preferably in the range of from 5000 to 17000 g / mol, determined according to DIN 55672-1.

[0077] Embodiment 11: The silica containing dispersion of any one of embodiments 1 to 10, wherein the polyamine-grafted-polyacrylate copolymer of (c) has a polydispersity index (PDI) In the range of from 1 to 4, preferably in the range of from 1.5 to 3.5, more preferably in the range of from 1.8 to 3.2.

[0078] Embodiment 12: The silica containing dispersion of any one of embodiments 1 to 11 , wherein the polyamine-grafted-polyacrylate copolymer of (c) has an amine number in the range of from 30 to 400 mgKOH / g, preferably in the range of from 100 to 300 mgKOH / g, determined according to DIN 53176:2002-11. Embodiment 13: The silica containing dispersion of any one of embodiments 1 to 12, wherein in the polyamine-grafted-polyacrylate copolymer of (c) at least a part of the C1 to C26 alkyl groups of the alkyl acrylate are replaced by another residue R, wherein the other residue R is preferably a C1-22 alkyl group, optionally substituted by an ether bridged irradiation reactive group, wherein the irradiation reactive group is preferably selected from, vinyl group, methoxy substituted or unsubstitited benzophenonyl group, and 2-hydroxy-2-methyl propiophenonyl group.

[0079] Embodiment 14: The silica containing dispersion of embodiment 13, wherein the replacement was done by transesterification with R-OH, preferably in the presence of a transesterification catalyst, more preferably in the presence of titanium(IV) butoxide.

[0080] Embodiment 15: The silica containing dispersion of any one of embodiments 1 to 14, wherein the silica of (b) is selected from the group consisting of amorphous silica and crystalline silica, wherein the silica is unmodified or modified with an organic compound, preferably with an organic wax.

[0081] Embodiment 16: The silica containing dispersion of any one of embodiments 1 to 15, wherein the resin in the mixture of (a) is selected from the group consisting of polyurethane resin, polyether resin, epoxy resin, polyester resin and mixtures of two or more of these resins, wherein the resin is saturated or at least partially unsaturated, wherein the resin preferably comprises at least one polyester resin, more preferably at least one unsaturated polyester resin.

[0082] Embodiment 17: The silica containing dispersion of any one of embodiments 1 to 16, wherein the compound having at least one (meth)acrylate group is selected from the group consisting of dipropylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane ethoxy tri(meth)acrylate, 2-phenoxyethyl (meth)acrylate, glyceryl tetrapropylene tri(meth)acrylate and mixtures of two or more thereof, wherein preferably the compound having at least one (meth)acrylate group comprises at least dipropylene glycol diacrylate.

[0083] Embodiment 18: The silica containing dispersion of any one of embodiments 1 to 17, wherein resin and compound having at least one (meth)acrylate group are mixed in the mixture of (a) in a weight based ratio in the range of 1000:1 to 1 :2, preferably in the range of from 40:1 to 1:2, more preferably in the range of from 6:1 to 1:1. Embodiment 19: The silica containing dispersion of any one of embodiments 1 to 18, having a viscosity (at 1 S'1) in the range of from 2000 to 12000 mPas, preferably in the range of from 3000 to 11000 mPas, more preferably in the range of from 3500 to 10500 mPas, determined in analogy to DIN 53019-1 :2008-09.

[0084] Embodiment 20: Use of a silica containing dispersion according to any one of embodiments 1 to 19 as coating agent.

[0085] Embodiment 21: A method for coating of a surface comprising:

[0086] (i) providing a silica containing dispersion according to any one of embodiments 1 to 19;

[0087] (ii) applying the dispersion provided in (i) onto a surface, thereby obtaining a layer of the dispersion on the surface;

[0088] (iii) hardening the layer obtained in (ii) on the surface, preferably by UV radiation.

[0089] Embodiment 22: Use of a polyamine-grafted-polyacrylate copolymer according to (c) of any one of embodiments 1 to 14 as dispersant for silica, preferably as dispersant for dispersing silica in a resin based formulation.

[0090] Embodiment 23: The use according to embodiment 22, wherein the resin based formulation comprises a resin and a compound having at least one (meth)acrylate group, preferably a polyester resin and a dipropylene glycol diacrylate.

[0091] Embodiment 24: The use according to embodiment 22 or 23, wherein the resin based formulation is UV curable and / or curable by irradiation.

[0092] Embodiment 25: A method for preparing a resin composition having silica dispersed therein, the method comprising:

[0093] (A) Providing a composition comprising a polyamine-grafted-polyacrylate copolymer according to (c) as defined in any one of embodiments 1 to 14 as dispersant; silica, a resin and a compound comprising at least one (meth)acrylate group;

[0094] (B) Mixing dispersant, resin and a compound comprising at least one (meth)acrylate group, thereby obtaining a mixture thereof;

[0095] (C) Adding silica to the mixture obtained in (B), preferably under mixing, thereby obtaining a dispersion comprising silica, dispersant, resin and a compound comprising at least one (meth) acrylate group. Embodiment 26: A silica containing dispersion, obtained or obtainable by the method of embodiment 25.

[0096] Embodiment 27: The silica containing dispersion of embodiment 26, having a viscosity (at 1 S'1) in the range of from 2000 to 12000 mPas, preferably in the range of from 3000 to 11000 mPas, more preferably in the range of from 3500 to 10500 mPas, determined in analogy to DIN 53019- 1 :2008-09.

[0097] Embodiment 28: A method for preparing a silica containing coating, the method comprising

[0098] (A) Providing a composition comprising a polyamine-grafted-polyacrylate copolymer according to (c) as defined in any one of embodiments 1 to 14 as dispersant; silica, resin and a compound comprising at least one (meth)acrylate group;

[0099] (B) Mixing dispersant, resin and compound comprising at least one (meth)acrylate group, thereby obtaining a mixture thereof;

[0100] (C) Adding silica to the mixture obtained in (B), preferably under mixing, thereby obtaining a dispersion comprising silica, dispersant, resin and compound comprising at least one (meth) acrylate group;

[0101] (D) Curing the dispersion obtained in (C), preferably by UV application and / or irradiation.

[0102] Embodiment 29: A coating, obtained or obtainable by the method of embodiment 28.

[0103] Embodiment 30: The coating of embodiment 29, having a Gloss 60° value in the range of 1 to 30, preferably in the range of 2 to 25, more preferably in the range of from 5 to 20, determined according to DIN 67530:1982-01.

[0104] The present invention is further illustrated by the following reference examples, comparative examples, and examples.

[0105] Examples

[0106] Methods

[0107] Molecular weight: The Molecular weight (Mw) was determined according to DIN 55672-1.

[0108] Polydispersity: calculated as the ratio of weight average molecular weight divided by number average molecular weight (PDI).

[0109] Amine number: The amine number was determined according to DIN 53176:2002-11. Viscosity: Viscosity was determined by analogy to DIN 53019-1 :2008-09, using a Thermo-Haake RheoStress 600 equipment under the CR mode at 22°C and a shear rate of 1 sec1(Spindle CP50).

[0110] Gloss: Gloss 60° was determined according to DIN 67530:1982-01 using a commercial reflectometer (Micro-Tri-Gloss reflectometer from BYK Gard- ner).

[0111] Materials

[0112] Reference Examples: Preparation of Polyamine-g-polyacrylate dispersants

[0113] Dispersant D1 A mixture of 10 g BuOAc, 5 g PEI 10k, and 15 g nBA was stirred and slowly heat up to 90 °C. Then, 80 g nBA and 0.2 g tBPEH were dosed into the reactor over 2 hours. The mixture was kept under stirring at 90 °C until the acrylate was completely reacted (control via H-NMR, complete reaction was determined in that there was no peak at 5.8ppm, 6.1 ppm and 6.4ppm). The solvent BuOAc was removed under vacuum. A liquid yellowish dispersant was obtained with an amine number of 51 mgKOH / g (GPC: Mw of 16,000 g / mol, PDI of 3.0).

[0114] Dispersants D2-D10

[0115] Dispersants 2-10 were prepared as described above for Dispersant 1 with different amount and type of raw materials as listed in Table 1 :

[0116] Table 1

[0117] Compositions of Dispersants 2-10

[0118] Dispersant D11

[0119] A mixture of 75 g of Dispersant 3 and 25 g of the mixture of alcohols 125 was stirred at 140 °C in the presence of 0.5 g titanium(IV) butoxide, then vacuum was applied until no further n-buta- nol could be removed. The obtained dispersant D11 was a viscous yellowish liquid with an amine number of 161 mgKOH / g (GPC: Mw of 6500 g / mol, PDI of 2.7).

[0120] Dispersant D12

[0121] A mixture of 90 g of Dispersant 2 and 10 g 4-hydroxybutylvinylether was stirred at 140 °C in the presence of 0.5 g titanium(IV) butoxide, then vacuum was applied until no further n-butanol could be removed. The obtained dispersant D12 was a viscous yellowish liquid with an amine number of 109 mgKOH / g (GPC: Mw of 7500 g / mol, PDI of 2.3).

[0122] Dispersant D13

[0123] A mixture of 90 g of Dispersant 1 and 10 g 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophe- none was stirred at 140 °C in the presence of 0.5g titanium(IV) butoxide, then vacuum was applied until no further n-butanol could be removed. The obtained dispersant D13 was a viscous yellowish liquid with an amine number of 46 mgKOH / g (GPC: Mw of 15,200 g / mol, PDI of 2.9).

[0124] Dispersant D14

[0125] A mixture of 90 g of Dispersant 3 and 10 g 2-hydroxy-4-(2-hydroxyethoxy) benzophenone was stirred at 140 °C in the presence of 0.5 g titanium(IV) butoxide, then vacuum was applied until no further n-butanol could be removed. The obtained dispersant D14 was a viscous yellowish liquid with an amine number of 198 mgKOH / g (GPC: Mw of 6350 g / mol, PDI of 2.5). Examples 1 to 14: Preparation of Silica dispersion

[0126] The silica dispersions were prepared based on a composition as shown in Table 2, wherein the respective dispersant was used as indicated in Table 3. The unsaturated polyester and DPGDA were firstly added into the reactor. Defoamer, photoinitiator and Dispersant were added and stirred with a Dispermat until a homogeneous phase was obtained. Then, under stirring, solid silica was added slowly, followed by dispersion at high shear with the Dispermat at 3500 rpm for 10 min. The resulting dispersions had a performance as indicated in Table 3. The silica dispersion was applied on a black and white cardboard using a 12 pm wirebar. Then the applied coating was immediately cured with UV radiation and Gloss 60° was determined.

[0127] Table 2.

[0128] UV curable silica dispersion

[0129] Table 3. properties of the Silica dispersion

[0130] The cured films showed a satisfactory matting effect as indicated by Gloss 60° in Table 3, wherein a lower gloss meant better matting. Cited Literature

[0131] WO 2008 / 107326 A 1

[0132] US 2021 / 198513 A1

[0133] WO 2023 / 073184 A1

Claims

Claims1 . A silica containing dispersion comprising:(a) in the range of from 30 to 98 weight-% of a mixture comprising a resin and a compound having at least one (meth)acrylate group;(b) in the range of from 1 to 30 weight-% of silica;(c) in the range of from 0.1 to 10 weight-% of a polyamine-grafted-polyacrylate copolymer; wherein the total weight of the silica dispersion are 100 weight-%; wherein the resin of the mixture of (a) is selected from the group consisting of polyurethane resin, polyether resin, epoxy resin, polyester resin and mixtures of two or more of these resins; wherein the compound having at least one (meth)acrylate group of the mixture of (a) is selected from the group consisting of dipropylene glycol di(meth)acrylate, 1 ,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane ethoxy tri(meth)acrylate, 2-phenoxyethyl (meth)acrylate, glyceryl tetrapropylene tri(meth)acrylate and mixtures of two or more thereof; and wherein the polyamine-grafted-polyacrylate copolymer of (c) is obtained or obtainable from a grafting reaction of a polyamine and an alkyl acrylate monomer.

2. The silica containing dispersion of claim 1 , wherein the polyamine-grafted-polyacrylate copolymer of (c) is obtained or obtainable from a grafting reaction of a polyamine and an alkyl acrylate monomer; wherein the polyamine is selected from the group consisting of poly(C2 to Ce alkylene imine), polyvinylamine, polyallylamine and poly(amide-amine) dendrimer; wherein preferably, the polyamine comprises at least, more preferably is, a poly(C2 to Ce alkylene imine), more preferably polyethyleneimine and / or polypropylenimine, more preferably the polyamine comprises, more preferably is, polyethyleneimine; and / or wherein the alkyl acrylate monomer is a C1 to C26 alkyl acrylate, wherein the alkyl chain is branched or unbranched, preferably a C2 to C24 alkyl acrylate with a branched or unbranched alkyl chain, more preferably a C4 to C22 alkyl acrylate with a branched or unbranched alkyl chain, more preferably the acrylate is selected from the group consisting of n-butyl acrylate, 2-ethyl hexyl acrylate, heptadecyl acrylate, docosyl acrylate and mixture of two or more thereof.

3. The silica containing dispersion of claim 1or 2, wherein the polyamine-grafted-polyacrylate copolymer of (c) has an average molecular weight Mw in the range of from 2000 to 100000 g / mol, preferably in the range of from 4000 to 20000 g / mol, more preferably in the range of from 5000 to 17000 g / mol, determined according to DIN 55672-1 ; and / or wherein the polyamine-grafted-polyacrylate copolymer of (c) has a polydispersity index (PDI) In the range of from 1 to 4, preferably in the range of from 1.5 to 3.5, more preferably in the range of from 1 .8 to 3.2; and / or wherein the polyamine-grafted-polyacrylate copolymer of (c) has an amine number in the range of from 30 to 400 mgKOH / g, preferably in the range of from 100 to 300 mgKOH / g, determined according to DIN 53176:2002-11.

4. The silica containing dispersion of any one of claims 1 to 3, wherein in the polyamine- grafted-polyacrylate copolymer of (c) at least a part of the C1 to C26 alkyl groups of the alkyl acrylate are replaced by another residue R, wherein the other residue R is preferably a C1-22 alkyl group, optionally substituted by an ether bridged irradiation reactive group, wherein the irradiation reactive group is preferably selected from, vinyl group, methoxy substituted or unsubstitited benzophenonyl group, and 2-hydroxy-2-methyl propiophe- nonyl group, wherein the replacement was preferably done by transesterification with R- OH, preferably in the presence of a transesterification catalyst, more preferably in the presence of titanium(IV) butoxide.

5. The silica containing dispersion of any one of claims 1 to 4, wherein the silica of (b) is selected from the group consisting of amorphous silica and crystalline silica, wherein the silica is unmodified or modified with an organic compound, preferably with an organic wax.

6. The silica containing dispersion of any one of claims 1 to 5, wherein the resin in the mixture of (a) is selected from the group consisting of polyurethane resin, polyether resin, epoxy resin, polyester resin and mixtures of two or more of these resins, wherein the resin is saturated or at least partially unsaturated, wherein the resin preferably comprises at least one polyester resin, more preferably at least one unsaturated polyester resin.

7. The silica containing dispersion of any one of claims 1 to 6, wherein resin and compound having at least one (meth)acrylate group are mixed in the mixture of (a) in a weight based ratio in the range of 1000:1 to 1 :2, preferably in the range of from 40:1 to 1 :2, more preferably in the range of from 6: 1 to 1 : 1.

8. The silica containing dispersion of any one of claims 1 to 7, having a viscosity (at 1 S'1) in the range of from 2000 to 12000 mPas, preferably in the range of from 3000 to11000 mPas, more preferably in the range of from 3500 to 10500 mPas, determined in analogy to DIN 53019-1 :2008-09.

9. Use of a silica containing dispersion according to any one of claims 1 to 8 as coating agent.

10. A method for coating of a surface comprising:(i) providing a silica containing dispersion according to any one of claims 1 to 8;(ii) applying the dispersion provided in (i) onto a surface, thereby obtaining a layer of the dispersion on the surface;(iii) hardening the layer obtained in (ii) on the surface, preferably by UV radiation.

11. Use of a polyamine-grafted-polyacrylate copolymer according to (c) of any one of claims 1 to 4 as dispersant for silica, preferably as dispersant for dispersing silica in a resin based formulation.

12. A method for preparing a resin composition having silica dispersed therein, the method comprising:(A) Providing a composition comprising a polyamine-grafted-polyacrylate copolymer according to (c) as defined in any one of claims 1 to 4 as dispersant; silica, a resin and a compound comprising at least one (meth)acrylate group;(B) Mixing dispersant, resin and a compound comprising at least one (meth)acrylate group, thereby obtaining a mixture thereof;(C) Adding silica to the mixture obtained in (B), preferably under mixing, thereby obtaining a dispersion comprising silica, dispersant, resin and a compound comprising at least one (meth)acrylate group.

13. A silica containing dispersion, obtained or obtainable by the method of claim 12.

14. A method for preparing a silica containing coating, the method comprising(A) Providing a composition comprising a polyamine-grafted-polyacrylate copolymer according to (c) as defined in any one of claims 1 to 4 as dispersant; silica, resin and a compound comprising at least one (meth)acrylate group;(B) Mixing dispersant, resin and compound comprising at least one (meth)acrylate group, thereby obtaining a mixture thereof;(C) Adding silica to the mixture obtained in (B), preferably under mixing, thereby obtaining a dispersion comprising silica, dispersant, resin and compound comprising at least one (meth)acrylate group;(D) Curing the dispersion obtained in (C), preferably by UV application and / or irradiation.

15. A coating, obtained or obtainable by the method of claim 14.

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