Method for preparing foam particles with a pigmented surface coating

Abstract

The present invention relates to a method for preparation of coated foam particles comprising mixing the foam particles with an aqueous polyurethane dispersion (component A) and an aqueous pigment paste (component B), wherein the aqueous polyurethane dispersion comprises a polyurethane with a K-value in the range from 40 to 100 determined according to DIN EN ISO 1628-1 2021 and, wherein the aqueous pigment paste (component B) comprises at least one pigment (a-1) and at least one anionic binder (a-2) and / or at least one nonionic binder (a-3). The invention is further directed to a molded part comprising the foam particles with the pigmented surface coating, a method to prepare the particle foam molded part and the use of the particle foam molded part in shoe soles, part of shoe soles, shoe intermediate soles shoe insoles, damping elements, cushioning elements, protective devices, underlays, grips, flooring, mattresses, sporting goods, bicycle saddles, tires and in automotive interiors and exteriors.

Description

Method for preparing foam particles with a pigmented surface coatingDescriptionBackground of the inventionThe present invention relates to a method for preparation of coated foam particles comprising mixing the foam particles with an aqueous polyurethane dispersion (component A) and an aqueous pigment paste (component B). The invention is further directed to a molded part comprising the foam particles with the pigmented surface coating, a method to prepare the particle foam molded part and the use of the particle foam molded part in shoe soles, part of shoe soles, shoe intermediate soles shoe insoles, damping elements, cushioning elements, protective devices, underlays, grips, flooring, mattresses, sporting goods, bicycle saddles, tires and in automotive interiors and exteriors.Particle foams have been known for a long time and are usually processed into molded parts, whereby the foam particles are fused, glued or loosely embedded in a binder system (typically isocyanate containing binders), depending on their chemical nature. While thermoplastic foam particles can be fused, the processing of cross-linked foam particles usually requires irreversible bonding. In case of thermoplastic materials for fusing, the foam particles must be softened on the surface in a controlled manner to prevent the foam structure from collapsing. Especially in the case of polymers with a high softening temperature, the welding of the foam particles can no longer be carried out with conventional heating presses, because the high temperatures on the molding tools, combined with the poor thermal conductivity of polymeric foam particles, lead to a foam-structure damaging temperature gradient during the molding process. For this reason, the energy-intensive steam-chest molding process has become established for such polymeric foam particles.Since superheated steam fusion has very high energy requirements, in recent years, there has been increasing search for alternatives. One alternative possibility to fuse the foam particles is to supply the required energy through an electromagnetic field. Using electromagnetic radiation or an electromagnetic field to provide the energy required for the molding process is described in general in EP3698949 A1 and WO2017 / 125410 A1 for different foam particles. Especially in WO2017 / 125410 A1 it is shown that a foam molding with homogeneously fused foam particles can be achieved by using an electromagnetic field to apply the energy.Fusing foam particles through an electromagnetic field requires a certain excitability of the particle foams regarding electromagnetic radiation which results from their specific dielectric properties. A low material specific excitability regarding electromagnetic radiation will lead to high cycle times and, therefore, result in inefficient molding processes. This issue is addressed by US2018 / 0051171 A1 which relates to foam beads based on thermoplastic elastomers having a coating comprising electrically conductive substances, to processes for producing same by coating the foam beads with an emulsion of a conductive substance in a plasticizer, and to processes for producing bead foams by joining the foam beads together thermally via high-frequency electromagnetic radiation. However,another task is to control the molding process in such a way that, on the one hand, the surfaces of the foam particles weld together sufficiently but at the same time the foam structure of the particles does not collapse leading for example to an unfavorable density increase.A further approach is the coating of foam particles with a water-based binder which can be reactivated by suitable solvents or heat as described in WO / 2022 / 223438. This process has the advantage that the coating with the binder can result in a commercial product, so that an end user can simply use a solvent, e.g. , water, or heat to prepare the shaped body. However, in order to enable the end user to make efficient use of already coated particles, the coated particles should be flowable, shelf-stable and non-sticky.The European patent application with application number EP22202204.8 relates to storage stable coated particles and shaped bodies comprising said coated particles as well as a process for the preparation for the preparation of storage-stable coated particles of a moldable thermoplastic particle foam comprising the steps of a1) bringing the particles into contact with an aqueous polyurethane dispersion, the polyurethane having a K-value according to DIN EN ISO 1628-1 2021 in the range from higher than 50 to lower than 100.Additionally, for many applications, it is desirable to use colored or pigmented foam particles to obtain colored molded parts. The prior art discloses, for example, the bonding or foaming of particle foams by means of colored polyurethane binders or polyurethane system foams (WO 2008 / 087078 A1). However, particles coated with crosslinked binders can no longer be subjected to thermoplastic fusion.The prior art also discloses the production of foamed particles from bulk-colored TPU or the incorporation of dyebatches during the foam-extrusion process. However, the colour-intensity and homogeneity of the resulting foam particles is strongly dependent on the local foam density. WO 2015 / 165724 A1 describes the coating of the final molded part produced from thermoplastic polyurethane foam particles.To save this additional post-molding step, it is advantageous to provide the end-user with ready-dyed, storage stable and moldable foam particles. The generation of dyed foam particles is for example described in US10189192 B2 or in WO201981644 A1. US10189192 describes the dying of pellets with a nonionic or anionic dye (1) before foaming, during foaming by (2) infusing the particles with a supercritical fluid in which the dyes are dissolved or dispersed optionally together with a polar liquid or (3) by immersion the pellets in a heated fluid, which serves for expansion, where the heated fluid contains the dye or (4) after foaming. WO201981644 describes a process for producing colored foamed elastomer particles, wherein the foamed particles are contacted with a mixture comprising a dye and a carrier fluid to obtain colored foamed particles. Therein the carrier fluid has a polarity suitable for sorption of the carrier fluid into the elastomer. However, coloring via a sorption process can affect the mechanics of the foam particles, if, for example, the dye-solution used acts as a plasticizer. In addition, coloring via dye-solutions does not enable molding processes that are independent of particle chemistry.It was therefore an object of the present invention to remedy the disadvantages mentioned and to provide a method for the preparation of storage stable, moldable foam particles with a homogeneous pigmented surface coating, that are suitable for further processing via steamless molding into lightweight components with good mechanical properties. Furthermore, it was an object of the present invention to provide a method for preparing pigment-coated foam particles, which can be applied independent from the chemical nature of the foam particles and allows for a further processing of the coated foam particles via steamless thermo-pressing into molded parts.The problem is solved by a method for preparation of coated foam particles comprising mixing the foam particles with an aqueous polyurethane dispersion (component A) and an aqueous pigment paste (component B), wherein the aqueous polyurethane dispersion comprises a polyurethane with a K-value in the range from 40 to 100 determined according to DIN EN ISO 1628-1 2021 and, the aqueous pigment paste (component B) comprises at least one pigment (a-1) and at least one anionic binder (a-2) and / or at least one nonionic binder (a-3).Detailed description of the inventionWith regards to the invention, the following can be stated specifically:According to the present invention, the object is solved by a method for preparation of coated foam particles comprising mixing the foam particles with an aqueous polyurethane dispersion (component A) and an aqueous pigment paste (component B), wherein the aqueous polyurethane dispersion comprises a polyurethane with a K- value in the range from 40 to 100 determined according to DIN EN ISO 1628-1 2021 and, wherein the aqueous pigment paste (component B) comprises at least one pigment (a-1) and at least one anionic binder (a-2) and / or at least one nonionic binder (a-3).Surprisingly, it was found that the method according to the invention leads to storage stable, moldable foam particles with a homogeneous pigmented surface coating. The aqueous polyurethane dispersion and the aqueous pigment paste are compatible, resulting in a shelf-stable mixture. In addition, the advantageous flow properties of the mixture make it easy to apply it to the particles and, thus, achieve a homogeneous coating layer with a uniform color effect.Surprisingly the pigmented coating is tack-free at room temperature. However, when the coated foam particles are heated under compression, such as in a hot-press process, the coating melts or softens and allows bridging of foam particles upon cooling.Moreover, the foam particles with pigmented surface coating show surprisingly an improved flow behavior, which is a very important factor when foam particles are stored for a long time, e.g. in octabins, as a clogging of the foamparticles during storage causes unpleasant problems at the customer site, additional to very interesting antistatic properties.The pigmented surface coating of the foam particles allows for a further processing into low-density molded parts via thermo-pressing and, thus, without the need of high energy consuming steam. Since the required processing temperatures for the molding process are determined by the thermal properties of the coating, the molding temperature can be lowered for many foam particles, such as thermoplastic polyurethane foam particles. This makes it possible to produce molded parts out of the foam particles more gently and preserving the foam structure. The inventive pigmented coating on the surface of foam particles has in addition the advantage that foam particles of different size and chemistry (e.g., styrene polymer foam particles, polyurethane foam particles, polyamide foam particles, thermoplastic elastomer foam particles, polyolefine foam particles) can be bond together as the adhesive capability comes from the coating and not from the softening or melting of the wall of the foam particles. This has the advantage that also foam particles with a high melting or softening point can be worked at a moderate temperature into a 3D molded part without the use of steam.Moreover, in contrast to steam-based processes the molded parts are not wet after demolding and, therefore timeconsuming annealing to remove the moisture is eliminated.Foam particlesFoam particles or also foam beads or foam granules in the sense of the present invention refers to a foam in the form of a lot of loose particles of the same chemical nature, the average length of the particles preferably being in the range of 1 to 20 mm. In the case of non-spherical, e.g., oval particles average length means the longest dimension by length, (determined by 3D evaluation of the granules, for example by means of dynamic image analysis with an optical measuring device named "PartAn 3D”, Microtrac).The single foam granules according to the present invention preferably have an average mass in the range of 0,1 to 50 mg, preferable in the range between 0,5 and 45 mg. The average mass means in this context the arithmetic mean based on a sample size of 10 different particles wherein each particle is weighted three times.The foam particles according to the invention usually have a bulk density of 20 g / l to 350 g / l, preferably 30 g / l to 250 g / l, more preferably 40 g / l to 200 g / l. The bulk density is measured analogously to DIN ISO 60:1999, wherein the determination of the above values in contrast to the standard, a vessel with 10 1 volume is used instead of a vessel with 0,1 1 volume, since especially for the foam particles with low density and large mass a measurement with only 0,1 I volume is too inaccurate.In a preferred embodiment of the method the foam particles are selected from the group consisting of styrene polymer foam particles, polyurethane foam particles, polyamide foam particles, thermoplastic elastomer foam particles, polyolefine foam particles and mixtures thereof.In a preferred embodiment of the method the foam particles are thermoplastic polyurethane foam particles. Thermoplastic polyurethane foam particles according to the present invention are expanded foam particles and belong to the group of particle foams, which are also referred to as foamed pellets (or bead foams, particle foam, expanded thermoplastic elastomer particles or expanded thermoplastic polyurethane beads). Particle foams and moldings (also referred to as molded article) made therefrom, based on thermoplastic polyurethanes or other thermoplastic elastomers, are known (for example WO 94 / 20568A1, WO 2007 / 082838 A1, WO2017 / 030835 A1, WO 2013 / 153190 A1, WO 2010 / 010010 A1, WO 2019 / 202095, WO 2018 / 087362) and can be used in many ways.It is also possible in accordance with the invention to use mixtures of different foam particles. In a preferred embodiment the foam particles comprise at least two foam particles based on different polymers or different particle size.Two or more foam particles in the sense of the present invention refers to a mixture of different lots of loose foam particles, wherein the lots differ in their chemical nature.In principle, all types of foam particles can be mixed regardless of their thermal properties such as melting point or glass transition.It is for example possible that the foam particles comprise at least two thermoplastic foam particles selected from the group consisting of styrene polymer foam particles, polyamide foam particles, thermoplastic elastomer foam particles, polyolefin foam particles and mixtures thereof.Aqueous polyurethane dispersion (component A)The aqueous polyurethane dispersion as component A comprises a polyurethane with a K-value in the range from 40 to 100 determined according to DIN EN ISO 1628-1 2021.The K-value is a relative viscosity number, which is determined in analogy to DIN EN ISO 1628-1 2021 at 25°C. It comprises the flow rate of a 1 weight-% strength solution of the polyurethane in DMF, relative to the flow rate of pure DMF, and characterizes the average molecular weight of the polyurethane.Preferably, the aqueous polyurethane dispersion (component A) used in the method of the present invention has a solid content of at least 40 wt.-% based on the total weight of the dispersion, more preferably in the range of from 45 wt.-% to 60 wt.-% based on the total weight of the dispersion.Preferably, the polyurethane of the aqueous polyurethane (component A) has a viscosity of less than 300 mPas at 23 °C, preferably less than 200 mPas at 23 °C, measured according to DIN EN ISO 3219-2:2021 at 23°C and a shear rate of 250 s1.In a preferred embodiment of the method the polyurethane dispersion (component A) has a glass transition temperature Tgmeasured according to DIN EN ISO 11357-2 2018 from -10°C to -80°C and a melting temperature Tmof in the range from 30°C to 100°C measured according to DIN EN ISO 11357-3 (2018) by heating with 20 K / min after cooling to -80°C.Preferably, the polyurethane dispersion according to the present invention has a glass transition temperature Tgof below 0 °C, more preferably from -10 °C to -80 °C, even more preferably, from -20 °C to -75°C, even more preferably from -30 °C to -70 °C, even more preferably from -40 °C to -65 °C, even more preferably, from -45 °C to - 60 °C.The glass transition temperature can be determined by differential scanning calorimetry according to DIN EN ISO 11357-2 (2014), as so-called midpoint temperature. The glass transition temperature of the polymer in the polymer dispersion is the glass transition temperature obtained when evaluating the second heating curve (heating rate 20°C / min).In a preferred embodiment of the present invention, the aqueous polyurethane dispersion has at least a first glass transition temperature Tgiand a second glass transition temperature Tg2, wherein Tgiis below 0°C and Tg2 is higher than 25 °C. More preferably, Tg2 is higher than 40 °C, even more preferably higher than 50 °C, even more preferably higher than 60 °C. Typically, the polyurethane of the aqueous polyurethane dispersion has a Tgifrom -10 °C to -60 °C and a Tg2 from 60 °C to 90 °C. Preferably, the polyurethane has exactly two Tg.Preferably, the aqueous polyurethane dispersion (component A) has a melting temperature Tmof in the range from 30 °C to 100 °C, preferably from 40 °C to 80 °C.Melting-points and enthalpy ef fusion are determined according to DIN EN ISO 11357-3 (2018) (melting point = peak temperature) by heating with 20 K / min after cooling to -80°C; while enthalpy of fusion of the second run (Delta H2) is calculated from the area of second melting only.Tgand Tmof the aqueous polyurethane dispersion means according to the present invention that the aqueous polyurethane dispersion is dried and Tgand Tmvalues are determined from the resulting film.In general, the aqueous polyurethane dispersion used in the process of the present invention can be prepared by methods known in the art. Exemplary methods are described in WO 2021 / 249749 A1Accordingly, an aqueous polyurethane dispersion comprises at least one polyurethane as polymeric binder dispersed in water, and optionally additives. Preferred additives are selected from the group consisting of ionic surfactants, nonionic surfactants, rheology modifiers (including thickeners), anti-blocking additives, other aqueous dispersions, crosslinkers, plasticizers, stabilizers against hydrolytic degradation, biocides, fillers and antifoam agents. The polymeric binder preferably takes the form of dispersion in water or else in a mixture made of predominantly water and of water-soluble organic solvents with boiling points, which are preferably below 150°C (1 bar). Particular preference is given to water as sole solvent.The polyurethane dispersion used in the method of the invention comprises at least one polyurethane. Suitable polyurethanes are obtainable in principle through reaction of at least one polyisocyanate with at least one compound, which has at least two groups reactive toward isocyanate groups. Polyurethanes also encompass what are called polyurethane-polyureas, which as well as polyurethane groups also have urea groups as well.The polyurethane dispersion (component A) according to the present invention preferably comprises at least one polyurethane which comprises in copolymerized form at least one polyisocyanate and at least one polyol. The polyurethane dispersion preferably comprise at least one polyurethane which comprises in copolymerized form at least one polyisocyanate and a diol component, of which a) 10 -100 mol%, based on the total amount of the diols, have a molecular weight of 500 to 5000 g / mol and b) 0 - 90 mol%, based on the total amount of the diols, have a molecular weight of 60 to less than 500 g / mol. Polymeric polyols are preferred. Suitable polymeric polyols are preferably selected from polyester diols, polyether diols, and mixtures thereof. The polymeric polyol preferably has a number-average molecular weight in the range from about 500 to 5000 g / mol.The polyurethane is preferably synthesized to an extent of at least 40% by weight, more preferably at least 60% by weight, and very preferably at least 80% by weight, based on the total weight of the monomers used in preparing the polyurethane, of at least one diisocyanate and at least one polyether diol and / or polyester diol. Suitable further synthesis components to 100% by weight are, for example, polyisocyanates having at least three NCO groups, and compounds that are different from the polymeric polyols and have at least two groups reactive toward isocyanate groups. These include, for example, non-polymeric diols; diamines; polymers different from polymeric polyols and having at least two active hydrogen atoms per molecule; compounds which have two active hydrogen atoms and at least one ionogenic or ionic group per molecule; and mixtures thereof.The polyurethane of the aqueous polyurethane dispersion may have crystallinity.Preferred polyurethanes with crystallinity are synthesized from:(i) at least one monomeric diisocyanate,(ii) at least one diol comprising a diol having a number-average molecular weight in the range from 500 to 5000 g / mol,(iii) at least one monomer, different from the monomers (i) and (ii), having at least one isocyanate group or at least one group reactive toward isocyanate groups, and additionally carrying at least one hydrophilic group or potentially hydrophilic group,(iv) optionally at least one further compound, different from the monomers (i) to (iii), having at least two reactive groups selected from alcoholic hydroxyl groups, primary or secondary amino groups or isocyanate groups, and(v) optionally at least one monofunctional compound, different from the monomers (i) to (iv), having a reactive group which is an alcoholic hydroxyl group, a primary or secondary amino group or an isocyanate group.Preferably, the polyurethane dispersion is an anionic polyurethane dispersion made with low amount of aromatic diisocyanates or no aromatic diisocyanates, e.g. less than 60 mol%, based on the sum of all organic diisocyanates a). The anionic groups of the anionic polyurethane are preferably selected from carboxylate groups and sulfonate groups. The same applies to the polyurethane comprised in the at least partly coated particle and shaped body according to the present invention.Suitable monomeric diisocyanates (i) and diols (ii) are described in the EP patent application EP22202204.8.In order to make the polyurethanes dispersible in water they comprise as synthesis components monomers (iii), which carry at least one isocyanate group or at least one group reactive toward isocyanate groups and, furthermore, at least one hydrophilic group or a group which can be converted into a hydrophilic group. In the text below, the term "hydrophilic groups or potentially hydrophilic groups” is abbreviated to "(potentially) hydrophilic groups”. The (potentially) hydrophilic groups react with isocyanates at a substantially slower rate than do the functional groups of the monomers used to synthesize the polymer main chain. The fraction of the components having (potentially) hydrophilic groups among the total quantity of components (i) to (v) is generally such that the molar amount of the (potentially) hydrophilic groups, based on the amount by weight of all monomers (i) to (v), is from 30 to 1000, preferably 50 to 500, and more preferably 80 to 300 mmol / kg. The (potentially) hydrophilic groups can be nonionic or, preferably, (potentially) ionic hydrophilic groups.Particular suitable nonionic hydrophilic groups and ionic hydrophilic groups are described in the EP patent application EP22202204.8.The monomers (iv), which are different from the monomers (i) to (iii) and which may also be constituents of the polyurethane, may serve for crosslinking or chain extension. They may comprise nonphenolic alcohols with a functionality of more than 2, amines having 2 or more primary and / or secondary amino groups, and compounds which as well as one or more alcoholic hydroxyl groups carry one or more primary and / or secondary amino groups. Alcohols having a functionality of more than 2, which may be used in order to set a certain degree of branching or crosslinking, include for example trimethylolpropane, glycerol, or sugars. Other suitable compounds (d) are alpha, omega-diaminopolyethers, which are preparable by aminating polyalkylene oxides with ammonia. Compounds(d) are, for example, also isocyanates, which as well as free isocyanate groups carry further, masked isocyanate groups, e.g., uretdione groups or carbodiimide groups.Monomers (v), which are used optionally, are monoisocyanates, monoalcohols, and mono primary and -secondary amines. Their fraction is generally not more than 10 mol%, based on the total molar amount of the monomers. These monofunctional compounds customarily carry further functional groups such as olefinic groups or carbonyl groups and serve to introduce into the polyurethane functional groups, which facilitate the dispersing and / or the crosslinking or further polymer-analogous reaction of the polyurethane. Monomers suitable for this purpose include those such as isopropenyl-a,a' -dimethylbenzyl isocyanate (TMI) and esters of acrylic or methacrylic acid such as hydroxyethyl acrylate or hydroxyethyl methacrylate.The polyurethane of the aqueous polyurethane dispersion having at least a first glass transition temperature Tgiand a second glass transition temperature Tg2 can be prepared from(i) at least one organic diisocyanate, selected from diisocyanates of the formula X(NCO)2, where X is a noncyclic aliphatic hydrocarbon radical having 4 to 15 carbon atoms, a cycloaliphatic hydrocarbon radical having 6 to 15 carbon atoms, an aromatic hydrocarbon radical having 6 to 15 carbon atoms, or an araliphatic hydrocarbon radical having 7 to 15 carbon atoms, wherein the amount of aromatic diisocyanates is less than 60 mol-%, based on the sum of all organic diisocyanates a);(ii) at least one dihydroxy compound having a molecular weight of 500 g / mol to 5000 g / mol and selected from the group consisting of polyesterdiols, polyetherols and polytetrahydrofuran;(iii) at least one dihydroxy compound selected from the group consisting of branched or unbranched acyclic diols having 2 to 8 C atoms, and cyclic diols having 3 to 8 C atoms, the at least dihydroxy compound having preferably a molecular weight from 62 g / mol to 200 g / mol.(iv) at least one compound having at least one group reactive toward isocyanate groups, and additionally carrying at least one ionic group or one group which can be converted into an ionic group, wherein the compounds c) preferably contain a group selected from carboxylate groups and sulfonate groups,(v) optionally further compounds different from a) to c).Preferred polyurethanes are synthesized from:(i) at least one monomeric diisocyanate, the at least diols (ii) and (iii), (iv) at least one monomer, different from the monomers (i) to (iii), having at least one isocyanate group or at least one group reactive toward isocyanate groups, and additionally carrying at least one hydrophilic group or potentially hydrophilic group, (v) optionally at least one further compound, different from the monomers (i) to (iv), having at least two reactive groups selected from alcoholic hydroxyl groups, primary or secondary amino groups or isocyanate groups, and (vi) optionally at least one monofunctional compound, different from the monomers (i) to (v), having a reactive group which is an alcoholic hydroxyl group, a primary or secondary amino group or an isocyanate group.Preferably, the polyurethane dispersion is an anionic polyurethane dispersion made with low amount of aromatic diisocyanates or no aromatic diisocyanates, e.g. less than 60 mol%, based on the sum of all organic diisocyanates (i). The anionic groups of the anionic polyurethane are preferably selected from carboxylate groups and sulfonate groups. The same applies to the polyurethane comprised in the at least partly coated particle and shaped body according to the present invention.Particular mention may be made as monomers (i) of diisocyanates X(NCO)2, where X is a noncyclic aliphatic hydrocarbon radical having 4 to 15 carbon atoms, a cycloaliphatic or aromatic hydrocarbon radical having 6 to 15 carbon atoms, or an araliphatic hydrocarbon radical having 7 to 15 carbon atoms. Examples of such diisocyanates include tetramethylene diisocyanate, hexamethylene diisocyanate (HD I), dodecamethylene diisocyanate, 1 ,4-diiso- cyanatocyclohexane, 1-isocyanato-3,5,5-trimethyl-3-isocyanatomethyl-cyclohexane (IPDI), 2,2- bis(4- isocyanatocyclohexyl)-propane, trimethylhexane diisocyanate, 1,4-diisocyanatobenzene, 2,4-diisocyanatotoluene, 2,6-diisocyanatotoluene (TDI), 4,4'-diisocyanato-diphenylmethane, 2,4'-diisocyanatodiphenylmethane, p-xylylene diisocyanate, tetramethylxylylene diisocyanate (TMXDI), the isomers of bis(4-isocyanatocyclohexyl)methane (HMDI) such as the trans / trans, the cis / cis, and the cis / trans isomers, and mixtures of these compounds. Diisocyanates of this kind are available commercially. With particular preference the diisocyanate is selected from the group consisting of hexamethylene diisocyanate, 1-isocyanato-3,5,5-trimethyl-3-isocyanato- methylcyclohexane, 2,6- diisocyanatotoluene, and tetramethylxylylene diisocyanate, or a mixture thereof. Particularly important mixtures of these isocyanates are the mixtures of the respective structural isomers of diisocyanatotoluene and diisocyanatodiphenylmethane; the mixture of 80 mol% 2,4-diisocyanatotoluene and 20 mol% 2,6-diisocyanatotoluene is particularly suitable. Also of particular advantage are the mixtures of aromatic isocyanates such as 2,4- diisocyanatotoluene and / or 2,6-diisocyanatotoluene with aliphatic or cycloaliphatic isocyanates such as hexamethylene diisocyanate or IPDI, in which case the preferred molar mixing ratio of the aliphatic to the aromatic isocyanates is 1 :9 to 9:1, more particularly 4:1 to 1 :4. It is also preferred that only aliphatic isocyanates are used.The diols (ii) may be polyester polyols, which are known, for example, from Ullmanns Enzyklopadie der technischen Chemie, 4th edition, volume 19, pp. 62 to 65. It is preferred to use polyester polyols which are obtained by reacting dihydric alcohols with dibasic carboxylic acids. Instead of the free polycarboxylic acids it is also possible to use the corresponding polycarboxylic anhydrides or corresponding polycarboxylic esters of lower alcohols or mixtures thereof to prepare the polyester polyols. The polycarboxylic acids can be aliphatic, cyclo aliphatic, araliphatic, aromatic or heterocyclic and can optionally be substituted, by halogen atoms for example, and / or unsaturated. Examples thereof include the following: suberic acid, azelaic acid, phthalic acid, isophthalic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrachlorophthalic anhydride, endomethylene tetrahydrophthalic anhydride, glutaric anhydride, maleic acid, maleic anhydride, fumaric acid, and dimeric fatty acids. Preferred dicarboxylic acids are those of the general formula HOOC-(CH2)y-COOH, where y is a number from 1 to 20, preferably an even number from 2 to 20, examples being succinic acid, adipic acid, sebacic acid, and dodecane dicarboxylic acid. Examples of suitable dihydric alcohols include ethylene glycol, propane-1,2- diol, propane-1, 3-diol, butane-1, 3-diol, butene-1, 4-diol, butyne- 1 ,4-diol, pentane-1, 5-diol, neopentyl glycol, bis(hydroxymethyl) cyclohexanes such as 1,4-bis(hydroxymethyl)cyclohexane, 2-methylpropane-1, 3-diol, methylpentanediols, and also diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, and dibutylene glycol and polybutylene glycols. To obtain crystallinity preferred alcohols are those of the general formula HO-(CH2)X- OH, where x is a number from 1 to 20, preferably an even number from 2 to 20. Examples of such alcohols are ethylene glycol, butane-1, 4-diol, hexane-1, 6-diol, octane-1, 8-diol, and dodecane-1 , 12-diol.The diols (II) may also be polytetrahydrofuran. Suitable polytetrahydrofurans can be prepared by cationic polymerization of tetrahydrofuran in the presence of acidic catalysts, such as sulfuric acid or fluorosulfuric acid, for example. Preparation processes of this kind are known to the skilled person.The diols (II) may also be polyether diols. Polyether diols are obtainable in particular by polymerizing ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, styrene oxide or epichlorohydrin with itself, in the presence of BF3 for example, or by subjecting these compounds, optionally in a mixture or in succession, to addition reaction with starter components containing reactive hydrogen atoms, such as alcohols or amines, examples being water, ethylene glycol, propane-1, 2-diol, propane-1, 3-diol, 2,2-bis(4-hydroxyphenyl)propane, and aniline. Particular preference is given to polyether diols with a molecular weight of 500 to 5000, and in particular 600 to 4500.In a preferred embodiment of the method the polyurethane dispersion (component A) has at least a first glass transition temperature and a second glass transition measured according to DIN EN ISO 11357-2 2018, wherein Tgiis below 0°C and Tg2 is higher than 25°C.Aqueous pigment Paste (Component B)The aqueous pigment paste (component B) comprises at least one pigment (a-1) and at least one anionic binder (a- 2) and / or at least one nonionic binder (a-3).A pigment paste may refer to a preparation of pigment(s) in a carrier material (e.g. media) in which the pigment(s) are present in a higher concentration than is required for the subsequent application, e.g. than for coloring the foam particles. The carrier material may include solutions or dispersions of binder(s) in organic solvents and / or water, to which wetting agents and sometimes other additives may be added. The carrier material may correspond to application medium or may be compatible with it. "Aqueous pigment paste” refers to a pigment paste which is not based exclusively on organic solvents. Indeed, a pigment paste of this kind based on organic solvents contains exclusively organic solvents and no water for dissolving and / or dispersing the components, or is a paste prepared not explicitly with addition of water; instead, water enters the paste only in the form of an impurity, atmospheric moisture, and / or as a solvent for any specific additives used. Such a paste - in contrast to an aqueous pigment paste - would be referred to as solvent-based or as "based on organic solvents”. "Aqueous” in the context of the present invention is preferably to be understood to mean that the pigment paste in question has a water fraction of at least 20 wt%, preferably at least 25 wt%, very preferably at least 30 wt%, based in each case on the total amount of the solventspresent (i ,e. , water and organic solvents). Preferably in turn, the water fraction is 60 to 100 wt%, more particularly 70 to 98 wt%, very preferably 75 to 95 wt%, based in each case on the total amount of the solvents present.In relation to the term "binder”, refer to Rbmpp-Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, pages 73 and 74, “Bindemittel” and to DIN EN 971-1 : 1996-09. Binders are organic, predominantly polymeric compounds that are responsible for film formation in coating materials and printing inks. They represent the non-volatile part of the coating material without pigments and fillers. Binders are present in liquid coatings in solution or dispersion, they ensure the anchoring of pigments and fillers in the film and the adhesion of the film to the substrate.An anionic binder (also referred to as anionically stabilized binder) is understood here to mean a binder containing multiple negative charges that are stabilized by cations. Anionic binders include binders comprising certain ionizable groups which can be converted by neutralizing agents in anionic groups (also denoted as potentially anionic groups). Examples of such groups which can be converted into anionic groups by neutralizing agents include, for example, carboxylic, sulfonic and / or phosphonic acid groups, especially carboxylic acid groups. A neutralization agent is understood here to mean a base, preferably an organic base.A nonionic binder (also referred to as nonionically stabilized) binder is understand here to mean binder with monomer units having anchor groups for interaction and stable dispersion of color pigments (a-1), and also monomer units having hydrophilic sections for stabilization of the nonionic binder in aqueous solution. Nonionic binders may not contain anionic or cationic groups or groups that may be converted into anionic or cationic groups. Examples of nonionic groups include poly(oxyalkylene) groups, more particularly poly(oxyethylene) and / or poly(oxypropylene) groups.Such anionic groups and nonionic groups allow to improve the dispersibility of the respective binders in an aqueous medium and hence allows to use such aqueous dispersions including anionic and / or nonionic binder(s) as carrier medium to prepare aqueous pigment pastes.In a preferred embodiment of the method the component B of the composition (Z) has a VOC value of less than or equal to 250 g / L. The VOC value in this context is defined as follows: VOC (g / L) = (total weight of volatile constituents (g) - total weight of water (g)) I (volume of coating material (L) - volume of water (L)). Volatile constituents for the present purposes are compounds which at processing temperature, especially at 20°C, have a vapor pressure of more than 10 pascals (cf. BlmSchV 31 also corresponding VOC Directives and VOC Regulations of the EU). Furthermore, volatile constituents are organic compounds which have a starting boiling point of less than or equal to 250°C under a standard pressure of 101 .3 kPa (cf. Directive 2004 / 42 / EC of the European Parliament and of the Council). Use of aqueous pigment pastes having such low VOC values avoids generation of VOC during production of the colored component, hence resulting in a more sustainable production of colored components form the coated foam particles produced by the inventive method.To achieve this VOC content, the aqueous pigment paste ought to include as little organic solvents as possible. In one particularly preferred embodiment of the first subject of the invention, therefore, the at least one pigment paste comprises organic solvent in a total amount of 0 to 10 wt%, preferably of 0 to 9.5 wt%, more particularly of 0 to 9 wt%, based in each case on the total weight of the aqueous pigment paste. The term "organic solvent” refers to volatile compounds which at 20°C have a vapor pressure of more than 10 pascals and / or which possess an initial boiling point of less than or equal to 250°C at a standard pressure of 101.3 kPa.Pigment (a-1):The pigment may be a color pigment and / or an effect pigment. Preferably, the pigment paste A may include either color pigments or effect pigments. Hence, a color paste including color pigment(s) may be free, e.g. may include 0 % by weight based on the total weight of the pigment paste, of effect pigment(s). Likewise, a color paste including effect pigment(s) may be free, e.g. may include 0 % by weight based on the total weight of the pigment paste, of color pigment(s). A corresponding definition of pigments and further specifications thereof is regulated in DIN 55943 (date: October 2001). Effect pigments are those pigments which produce a decorative effect in coating finishes and may additionally, but not exclusively, produce a coloring effect. The effect pigments are notable in particular for a plateletlike construction. Such effect pigments are known to those skilled in the art and are described, for example, in Rbmpp-Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, pages 176 and 451.The color pigment is preferably selected from the group of inorganic and / or organic color pigments and / or fillers.Particularly preferred organic color pigments are selected from the group of (I) monoazo pigments, such as C.l. Pigment Brown 25, C.l. Pigment Orange 5, 36 and 67, C.l. Pigment Orange 5, 36 and 67, C.l. Pigment Red 3, 48:2, 48:3, 48:4, 52:2, 63, 112 and 170, and C. I. Pigment Yellow 3, 74, 151 and 183; (II) disazo pigments, such as C.l. Pigment Red 144, 166, 214 and 242, C.l. Pigment Red 144, 166, 214 and 242 and C.l. Pigment Yellow 83; (ill) anthraquinone pigments, such as C.l. Pigment Yellow 147 and 177 and C. I. Pigment Violet 31; (iv) benzimidazole pigments, such as C.l. Pigment Orange 64; (v) quinacridone pigments, such as C.l. Pigment Orange 48 and 49, C.l. Pigment Red 122, 202 and 206, and C.l. Pigment Violet 19; (vi) quinophthalone pigments, such as C.l. Pigment Yellow 138; (vii) diketopyrrolopyrrole pigments, such as C.l. Pigment Orange 71 and 73 and C.l. Pigment Red, 254, 255, 264 and 270; (viii) dioxazine pigments, such as C.l. Pigment Violet 23 and 37; (lx) indanthrone pigments, such as C.l. Pigment Blue 60; (x) isoindoline pigments, such as C.l. Pigment Yellow 139 and 185; (xi) isoindolinone pigments, such as C.l. Pigment Orange 61 and C.l. Pigment Yellow 109 and 110; (xii) metal complex pigments, such as C.l. Pigment Yellow 153; (xiii) perinone pigments, such as C.l. Pigment Orange 43; (xiv) perylene pigments, such as C.l. Pigment Black 32, C. I. Pigment Red 149, 178 and 179 and C.l. Pigment Violet 29; (xv) phthalocyanine pigments, such as C.l. Pigment Violet 29, C.l. Pigment Blue 15, 15:1, 15:2, 15:3, 15:4, 15:6 and 16 and C. I. Pigment Green 7 and 36; (xvi) aniline black, such as C.l. Pigment Black 1; (xvii) azomethine pigments; and (xviii) mixtures thereof.Particularly preferred inorganic color pigments are selected from the group of (I) white pigments, such as titanium dioxide (C. I. Pigment White 6), zinc white, dye zinc oxide, zinc sulfide, lithopone; (ii) black pigments, such as iron oxide black (C.l. Pigment Black 11), iron-manganese black, spinel black (C.l. Pigment Black 27), carbon black (C.l. Pigment Black 7); (iii) colored pigments, such as ultramarine green, ultramarine blue, manganese blue, ultramarine violet, manganese violet, iron oxide red (C.l. Pigment Red 101), molybdate red (C.l. Pigment Red 104), ultramarine red, iron oxide brown, mixed brown, spinel and corundum phases (C.l. Pigment Brown 24, 29 and 31), iron oxide yellow (C.l. Pigment Yellow 42), bismuth vanadate (C.l. Pigment Yellow 184); and (iv) mixtures thereof.Examples of inorganic pigments commonly used as fillers include transparent silica, quartz flour, aluminum oxide, aluminum hydroxide, natural mica, natural and precipitated chalk and barium sulfate.The aqueous pigment paste A may contain the at least one color pigment (a-1) in a total amount of from 0.08 to 50% by weight, preferably from 2.5 to 47% by weight, based on the total weight of the aqueous pigment paste A.The aqueous pigment paste A may comprise the at least one effect pigment (a-1) in a total amount of 5 to 35 wt%, preferably of 6 to 30 wt%, based on the total weight of the aqueous pigment paste A.Binders:The aqueous pigment paste preferably comprises the at least one anionic binder (a-2) and / or the at least one nonionic binder (a-3), more particularly a mixture of the anionic binder (a-2) described below and the nonionic binder (a-3) described below, in a total amount of 5 to 35 wt%, preferably of 10 to 30 wt%, more particularly of 11 to 25 wt%, based in each case on the total weight of the aqueous pigment paste. If there is more than one anionic binder (a-2) and / or one nonionic binder (a-3) present, then these total amounts are based on the sum of the amount of all the anionic and nonionic binders used. The total amounts recited above permit a stable dispersion of the effect pigment (a-1) and any further color pigments and / or fillers, thus giving the aqueous pigment paste high stability on storage.The term anionic binder is also referred to as anionically stabilized binder. The term nonionic binder is also referred to as nonionically stabilized binder.In a preferred embodiment of the method the anionic binder (a-2) of component B is an anionic polyurethane polymer in dispersion in water, wherein the anionic polyurethane polymer has an acid number of 20 to 40 mg KOH / g, based on the solids content, wherein the dispersion has a pH of 7.0 to 8.0, and, wherein the dispersion comprises a polyol, more particularly a polypropylene glycol, having a number average molar mass of 500 to 1500 Da.The anionic polyurethane polymers are obtainable by the reaction of a prepolymer containing isocyanate groups with compounds that are reactive toward isocyanate groups, as described for example in the laid-open specification DE 199 21 457 A1 . This reaction of the components takes place in accordance with the well-known methods of organicchemistry (cf., e.g., Kunststoff-Handbuch, Volume 7: Polyurethane, edited by Dr. Y. Oertel, Carl Hanser Verlag, Munich, Vienna 1983).The generation of anionic polyurethane polymer suitable for preparing the aqueous pigment paste (component B) according to the invention is described in US 2022 / 0259446 A1 (paragraphs

[0056] -

[0072] ).In the context of the present invention, the anionic polyurethane polymer is obtainable with particular preference by reaction of a NCO prepolymer with a modifier in the form of a polyol, especially trimethylolpropane, the NCO prepolymer being obtainable by reaction of(I) 55 to 70 wt%, based on the total weight of the compounds (I) to (iv), of at least one polyester polyol having an OH number of 40 to 100 mg KOH / g, based on the solids content, and a number-average molecular weight Mnof 1000 to 3000 Da, with the polyester polyol preferably containing no olefinic double bonds,(II) 3 to 7 wt%, based on the total weight of the compounds (I) to (iv), of at least one alkanoic acid having 3 to 8 carbon atoms and also two hydroxyl groups on the alpha carbon atom, especially dimethylolpropionic acid,(ill) 0.5 to 3 wt%, based on the total weight of the compounds (I) to (iv), of at least one polyol of the formula (1) where Ri = R2 = methyl, and(iv) 25 to 30 wt%, based on the total weight of the compounds (I) to (iv), of at least one diisocyanate of the formula (2) where X = dicyclohexylmethyl radical and R3 = R4 = hydrogen.The equivalents ratio of the prepolymer to the modifier is preferably between 2.0 : 1 .0 and 1 .0: 2.0, especially between 1.1 : 1 and 1 : 1.1.It is an advantage in accordance with the invention if the anionic polyurethane polymer has a number-average molecular weight Mnof 750 to 2 000 000, preferably 750 to 1 000 000, more preferably 750 to 500 000, and more particularly 950 to 15 000 daltons, an acid number of 5 to 150, preferably 10 to 100, more preferably 15 to 80, and more particularly 20 to 35 mg KOH / g, and an OH number of 1 to 150, preferably 2 to 100, more preferably 5 to 70, and especially 10 to 25 mg KOH / g.The anionic polyurethane polymer is neutralized with a base, preferably with an organic base, more particularly with N,N‘-dimethylethanolamine, the base being added in an amount such that a degree of neutralization of 50% to 100%, preferably of 60% to 80%, is achieved. As a result of the addition of the base, the dispersion has a pH of 7.0 to 8.0.To facilitate the dispersing of the partially neutralized anionic polyurethane polymer in water, an alkylene glycol is added, preferably propylene glycol, having a number average molar mass Mnof 800 to 1500 Da.The anionic binder (a-2), especially the above-described anionic polyurethane polymer, is present in the aqueous pigment paste (component B) preferably in certain total amounts. The aqueous pigment paste (component B)preferably comprises the at least one anionic binder (a-2), preferably the above-described anionic polyurethane polymer, in a total amount of 5 to 30 wt%, preferably of 10 to 25 wt%, more particularly of 11 to 20 wt%, based in each case on the total weight of the aqueous pigment paste (component B). Where different anionic binders (a-2) are used, the sum of all anionic binders (a-2) corresponds to the total amounts indicated above. With preference in accordance with the invention, the aqueous pigment paste (component B) comprises only a single anionic binder (a-2), and therefore no mixture of different anionic binders is used. The use of the anionic binder (a-2), especially of the aqueous, anionic polyurethane polymer dispersion, as the sole anionic binder, in aqueous pigment paste (component B) leads to outstanding stabilization of the effect pigments and hence to a high storage stability of the pigment pastes.Instead of the anionic binder (a-2), the aqueous pigment paste A may also comprise at least one nonionic binder (a-3). In one preferred embodiment, the aqueous pigment paste A comprises a mixture of an anionic binder (a-2), especially of the above-described anionic polyurethane polymer, and a nonionic binder (a-3).Particularly preferred nonionic binders (a-3) are selected from nonionically stabilized acrylate copolymers in dispersion in water, with the acrylate copolymers comprising monomer units having anchor groups for interaction and stable dispersion of effect pigments (a-1), and also monomer units having hydrophilic sections for stabilization of the nonionically stabilized acrylate copolymer in aqueous solution.In a preferred embodiment of the method the nonionic binder (a-3) of component B is a nonionically stabilized acrylate copolymer in dispersion in water, the nonionically stabilized acrylate copolymer being obtainable by reaction of:(b1) at least one anchor group monomer unit having at least one ionizable functional group with active hydrogen, or a combination thereof, wherein- the ionizable functionality is other than a carboxylic acid group in which the carbonyl carbon is separated from the closest ethy lenically unsaturated carbon by at least four atoms,- the anchor group monomer units contain no polyoxyalkylene groups, and- one of the anchor group monomer units is copolymerized 1-(2-methacryloyloxyethyl)-2- imidazolidinone;(b2) 5 % to 45 % by weight, based on the total weight of the monomers, of at least one monomer unit comprising a polyoxyalkylene group, a gamma-hydroxycarbamate group, a beta-hydroxycarbamate group, and a combination thereof; and(b3) 1% to 50% by weight, based on the total weight of the monomers, of at least one aromatic unit.Suitable monomers for the anchor group monomer unit (b1) are described in US 2022 / 0259446 A1 (paragraph

[0092] ). Suitable examples of monomer units (b2) are described in US 2022 / 0259446 A1 (paragraph

[0093] ) and preferred aromatic monomer units (b3) can be found in US 2022 / 0259446 A1 (paragraph

[0094] ). Besides the aboverecited monomers (b1) to (b3) further ethylenically unsaturated nonionic monomers such as described for example in US 2022 / 0259446 (paragraph

[0095] ) may be used for preparing the acrylate copolymer.The nonionically stabilized acrylate copolymer may be prepared by known methods, such as bulk or solution polymerization. The polymerization may be carried out as a volatile radical polymerization. The free radicals are provided typically by a redox initiator or an organic peroxo or azo compound. Suitable initiators are selected from the group of ammonium peroxydisulfate, potassium peroxydisulfate, sodium metabisulfite, hydrogen peroxide, tert-butyl hydroperoxide, dilauryl peroxide, tert-butyl peroxybenzoate, tert-butyl per-2-ethylhexanoate, di-tert-butyl peroxide, 2,2‘-azobis(isobutyronitrile), 2,2‘-azobis(isovaleronitrile), and also redox initiators such as ammonium peroxydisulfate and sodium metabisulfite with iron(ll) ammonium sulfate. Moreover, the polymerization may be carried out as an anionic, cationic, and controlled radical polymerization.The nonionically stabilized acrylate copolymer preferably has a weight-average molecular weight Mwof 8000 to 70 000 Da, the molecular weight Mwbeing determined by gel permeation chromatography using polymethyl methacrylate as a standard. The glass transition temperature Tgof the nonionically stabilized acrylate copolymer is preferably from -30 to 180°C, more particularly from 0 to 120°C and may be determined using differential scanning calorimetry (DSC).In a preferred embodiment of the method, component B has a weight ratio of the total amount of nonionic binder (a- 3) to the total amount of anionic binder (a-2) of 0.1 to 3, more particularly of 0.25 to 1 .5, based in each case on the solid content of the binders.In a preferred embodiment of the method component B comprises organic solvent in a total amount of 0% to 10 % by weight, preferably of 0 % to 9.8 % by weight based in each case on the total weight of the aqueous pigment paste.Component B may further comprise other customary additives, such as crosslinking agents, coatings additives, thickeners, and radiation-curable constituents. Suitable further constituents are listed for example in DE 199 21 457 A1.The aqueous pigment paste is generally prepared by initially introducing the anionic binder (a-2) and mixing it with water, additives, pigment, or a paste of the effect-imparting and optionally color-imparting pigment (a-1) in solvent. Then the nonionic binder (a-3) is added, and mixing is repeated. In the case of plated-shaped effect pigments, care should be taken not to damage them during mixing.Mixing composition ZThe components of composition Z according to the invention can be added separately during the coating process or being premixed. In a preferred embodiment component A, component B and component C are premixed before being applied to the foam particles. The obtained composition Z is storage stable.Suitable mixing methods for preparing composition Z are known to the person skilled in the art.In a preferred embodiment the method is characterized in that the composition Z contains:(A) from 50 to 98% by weight of the aqueous polyurethane dispersion as component A,(B) from 2 to 50% by weight of the aqueous pigment paste as component B and(C) from 0 to 10% by weight of additives as component C, wherein the entirety of components A, B and C provides 100% by weight.In an embodiment the anionic binder (a-2) of component B and the aqueous polyurethane dispersion as component A comprise the same polyurethane. In an embodiment component A and the binder a-2 of component B are the same aqueous polyurethane dispersion and more preferable the polyurethane of the aqueous polyurethane dispersion is thermoplastic. Thermoplastic means that the polyurethane becomes soft and moldable when heated and does not crosslink under the exposure of heat.Coating ProcessA pigmented surface coating in the sense of the present invention refers to a coating with a polymeric composition, also referred to as coating material, which is bound to the particle surface as patches, or a continuous shell-like layer, wherein the surface of the foam particles may be completely or partially covered with the coating material.In a preferred embodiment the pigmented surface coating forms a continuous shell-like layer on the foam particles.In a preferred embodiment the pigmented surface coating is in the solid state at ambient conditions.In a preferred embodiment the pigmented surface coating is thermoplastic. Thermoplastic coating in the sense of the present invention means that the at room temperature solid coating becomes soft and moldable when heated. Unlike a reactive coating which crosslinks under the exposure of heat, the thermoplastic coating can be softened, molded and reshaped multiple times without significant chemical changes.In general, common methods for coating, like spray coating, e.g., as described in EP0009727A1 can be used. In a preferred embodiment, the foam particles are spray coated keeping them in motion via blowing them with e.g., air or mixtures of different gases.In a preferred embodiment the coating of the foam particles is achieved by bringing the foam particles into contact with the coating material in form of an aqueous dispersion. To obtain a sufficient surface coating, preferably, the foam particles are kept in motion while applying the aqueous dispersion by devices known to the person skilled in the art, such as for example kitchen mixer, cement mixer, conveyor belt, vibrating channel, or spray coating drum.In a preferred embodiment the method is comprising the steps of(a1) bringing foam particles into contact with a composition (Z) prepared from at least an aqueous polyurethane dispersion as component A and an aqueous pigment paste as component B, (a2) drying the coated particles, wherein component B comprises at least one pigment (a-1) and at least one anionic binder (a-2) and / or at least one nonionic binder (a-3).The first step can be carried out by methods known to the person skilled in the art, such as mixing the foam particles with the polymeric solution by drum mixers or rotor-stator mixers. For the drying step in principle, all suitable methods are possible, like convective drying, contact drying, infrared drying and, also microwave technology.In a preferred embodiment of the method in step (a1) the bringing into contact is realized by mixing or spraying.The step 82) refers to the drying the coated particles. In principle, all suitable methods are possible, like convective drying, contact drying, infrared drying and also microwave technology.In the case of contact drying, the temperature difference between the product and the wall in should be limited to 1 - 100 K, in the case of convective drying the gas composition can be N2 or air. The gas quantity is preferably 1-1000 liters / min per 1 kg product and the product temperature in the mixer should be between 1°C and 100°C, preferably 10°C to 60°C.Preferably, during step 32) the at least partly coated particles are kept moving. This can prevent agglomeration of the particles. Preferably, during step 32) the at least partly coated particles are kept moving until the particles are tacky- free, preferably until a residual water content of 3 % or lower based on the total weight of the at least partly coated particle.Preferably, after step ai) and before step 82) the particles are separated from each other. This can be achieved, e.g. by using a vibrating belt or the like. In addition, this option prevents agglomeration of the particles.In a preferred embodiment of the method the coated foam particles are coated in an amount from 0.5% to 40% by weight based on the total weight of foam particle and coating, preferably from 5 wt.-% to 25 wt.-% based on the total weight of particle and coating. Preferably, the at least partly coated particles are coated in an amount of at least 90 %, preferably at least 95 %, more preferably at least 99 %, more preferably fully coated based on the total surface of the particle.A further aspect of the invention relates to a coated foam particle, wherein the coating is a dried composition (Z) comprising an aqueous polyurethane dispersion as component A and an aqueous pigment paste as component B and, wherein component B comprises at least one pigment (a-1) and at least one anionic binder (a-2) and / or at least one nonionic binder (a-3).A further aspect of the invention relates to a process for the preparation of a particle foam molded part comprising the steps of(d) coating of foam particles by mixing the foam particles with an aqueous polyurethane dispersion as component A and an aqueous pigment paste as component B,(c2) filling the coated foam particles in a mold,(c3) fusing the coated foam particles into a particle foam molded part by supplying energy.In a preferred embodiment of the process for the preparation of a particle foam molded part the fusing in step (c3) is carried out by steamless thermo-pressing.In a preferred embodiment the thermo-pressing is carried out at a temperature of from 80°C to 140°C.A further aspect of the invention relates to the use of the particle foam molded part according to the invention in shoe soles, part of shoe soles, shoe intermediate soles shoe insoles, damping elements, cushioning elements, protective devices, underlays, grips, flooring, mattresses, sporting goods, bicycle saddles, tires and in automotive interiors and exteriors.In a preferred embodiment of the method component B comprises organic solvent in a total amount of 0% to 10 % by weight, preferably of 0 % to 9.8 % by weight based in each case on the total weight of the aqueous pigment paste PP.A further aspect of the invention relates to a coated foam particle, wherein the coating is a dried composition (Z) comprising an aqueous polyurethane dispersion as component A and an aqueous pigment paste as component B and, wherein component B comprises at least one pigment (a-1) and at least one anionic binder (a-2) and / or at least one nonionic binder (a-3), and, wherein the aqueous polyurethane dispersion comprises a polyurethane with a K- value in the range from 40 to 100 determined according to DIN EN ISO 1628-1 2021.A further aspect of the invention relates to a particle foam molded part comprising coated foam particles according to the invention.ExamplesThe inventive and comparative examples below serve to illustrate the invention but should not be interpreted as imposing any restriction.Unless indicated otherwise, the amounts in parts are parts by weight, and the amounts in percent are percentages by weight, in each case.The Viscosity is measured according to DIN EN ISO 3219-2:2021 at 23°C and a shear rate of 250 s1.The dispersions are dried in a mold at 40°C for 3 days and then at 23°C for 7 days. Thermal properties are measured by differential scanning calorimetry.Glass-transition temperature (as the midpoint temperature of the second heating curve at a heating rate of 20 K / min), melting-points and enthalpy ef fusion are determined according to DIN ISO 11357 (2018) (melting point = peak temperature) by heating with 20 K / min after cooling to -80°C, while enthalpy ef fusion of the second run (Delta H2) is calculated from the area of second melting only; a) from a film at its untreated state (drying see above) Tm1, Delta H1 b) after heating the polyurethane films to 130 °C, cooling with 20 K / min to -80°C; reheating with 20k / min-> Tm2 delta H2The K-value was determined according to DIN EN ISO 1628-1 :2021Preparation of aqueous polyurethane dispersions (component A) for coatingDispersion 11039 g of a polyesterdiol from Adipic acid and Isophthalic acid (molar ratio of 1 :1) and 1,6 g Hexanediol (molecular weight 2000 g / mol; (monomer b1 )), 104,6 g of Dimethylolpropionic acid (DMPA, (monomer c)), 186.8 g Butanediol- 1,4 (monomer b2) were reacted with 900 g isophorone diisocyanate (IPDI (monomer a)) in 530 g dry acetone in a pressurized reactor; starting at 50°C, increasing the temperature in 30 min to 90°C, then as 90°C is reached keeping the temperature constant for 8 h at 2.9 bar. After that, the obtained mixture was diluted with 1852 g acetone, cooled to 40°C and expanded to atmospheric pressure. The NCO-value was determined to 1.2%. Then 10.2 g of Isophoronediamine (monomer d) were added in a shot, followed by adding 81 g Diethylethanolamine (neutralization agent) within a period of 5 min. After 5 min stirring, the dispersion step was continued by adding 3567 g deionized water within a period of 37 min at 30°C, followed by an addition of 19.8 Diethylenetriamine (monomer d) stirred in 340 g deionized water within a period of 30 min. After that, the acetone was removed by vacuum distillation with the help of 0.23 g of defoamer (FoamStar PB 2724, BASF), resulting in Dispersion 1 with a solids content of 37.4%.The properties of the obtained dispersion 1 are shown in Table 1a.Table 1aDispersion 2676 g of a polyesterdiol with a molecular weight of 2493 g / mol (based on adipic acid and 1 ,4-butanediol, (monomer b1)) were reacted with 0.11 g titaniumtetrabutylate, 40 g isophorone diisocyanate (IPDI, (monomer a)), 0.77 g NCO- terminated polycarbodiimid (Elastostab H02, BASF, (monomer d)) at 60°C in 153 g dry acetone for 60 min. Then, 37.8 g 1,6-hexane diisocyanate (HDI, monomer a)) was added and the temperature raised to 74°C. The reaction was continued until the NCO-value has fallen below 1 .25%. The mixture was diluted with 539 g acetone and cooled to 35- 40°C. Then 22.4 g of aminoethyl aminoethansulfonate sodium salt (50% aqueous solution, (monomer c)) diluted with 22 g demineralized water was added within a period of 3 min, followed by adding 4.6 g isophorone diamine, (monomer d) diluted in 23 g demineralized water within a period of 3 min. Before dispergation, 38.7 g of a 20% aqueous solution of alky! polyethylene glycol ether made from a linear, saturated C16C18 fatty alcohol with 18 moles of ethylene oxide, 20% active (e.g., Lutensol AT18 from BASF) was added. In the next step, the dispergation of the produced compound with 463 g demineralized water was carried out by using an anchor stirrer over a period of 15 min. Immediately after the water feed, additionally 4 g of N-(2- aminoethyl)-ethanolamine (monomer d)) solved in 30 g water was added during the dispergation. During dispergation an additional amount of 200 g demineralized water was added.After the dispergation step, the acetone was removed by vacuum distillation with the help of two drops of defoamer (FoamStar PB 2724, BASF) and the solids content of the obtained semicrystalline dispersion adjusted to 50% by addition of controlled amount of water. The properties of the obtained dispersion are shown in Table 1b.Table 1bComparative Dispersion D3: (K value lower than 40)537g of a polyesterdiol made of adipic acid, ethyleneglycol and diethyleneglycol (OH-number = 37,6 mg KOH / g), 6 g dimethylolpropionic acid (DMPA) are reacted at 94°C in 36 g water-free acetone with 31,5 g hexamethylene diisocyanate until the NCO-Value of <0,1% is reached. The mixture is then diluted with 398 g of acetone and cooled to 55°C.The mixture is neutralized with 17,1 g of a 10 % strength of aqueous sodium hydroxide solution and the mixture is dispersed using 846 g of deionized water. The acetone is removed by vacuum distillation which leads to a solids content of 44%. The properties of the obtained dispersion are shown in Table 2. As can be seen there is no melting point detected and only one glass transition appears.Table 2Foam particlesExperiments were carried out with thermoplastic polyurethane foam particles (E-TPU) made according to WO2013 / 153190 A1. The formulation of the thermoplastic polyurethanes (TPU) used as precursor material for the foam particles as well as the composition of the foam particles and their bulk density and particle weight are shown in Table 3, wherein Polytetrahydrofuran is abbreviated to PTHF and Diphenylmethylenediisocyanate is abbreviated to MDI, and Mn denotes the number average molecular weight.Table 3Preparation of aqueous pigment pastes The aqueous pigment pastes used for the inventive examples were prepared according to US20220259446 A1 .1 . Preparation of anionic binder (a-2)1.1 Preparation of the polyester resin PE155 wt % of a commercial dimer fatty acid (iodine number of 10 mg h / g, monomer content of max. 0.1%, trimer content of not more than 2%, acid number of 195 to 200 mg KOH / g, saponification number of 197 to 202 mg KOH / g), 30 wt % of 1 ,6-hexanediol and 15 wt % ofisophthalic acid are condensed with addition of cyclohexane as azeotrope former to an acid number (determined relative to nonvolatile fraction) of 3 to 4 mg KOH / g. Any cyclohexane present is removed under reduced pressure and the polyester is diluted with methyl ethyl ketone to a solids content of 73%. The resulting polyester resin PE1 has an OH number (solids) of 71 to 75 mg KOH / g and a calculated molecular weight of 1400 D.1 .2 Preparation of the anionic binder (a-2)Under nitrogen as inert gas atmosphere, 4.36 parts of dimethylolpropionic acid, 23.5 parts of dicyclohexylmethane 4, 4'-diisocy anate, 0.9 part of neopentyl glycol and 48.75 parts of the polyester PE1 are combined. Following addition of methyl ethyl ketone, the mixture is reacted with stirring (at a solids content of 67±1 % by weight) at 80-82° C. The reaction is monitored by determination of the isocyanate content of the solution. When a constant value is reached for the isocyanate content, of 1.0% to 1.2% (based on solution), trimethylolpropane (TMP) is added for chain extension, in an NCO: TMP ratio of 1 : 1.1 , the prepolymer is reacted to give an OH-functional polyurethane polymer having an arithmetic OH number of 17 mg KOH / g (based on resin solids). The polymer is then neutralized to an extent of 70% with N, N '-d I methy leth anol am I ne, and dispersed by addition of water and of a polypropylene glycol having a number average molar mass of 900 D. The methyl ethyl ketone is then removed by distillation The anionic polyurethane polymer dispersion thus obtained has a solids content of 29%-31 % and a pH of 7.7 and contains 20% of polypropylene glycol, based on the polyurethane polymer content.2. Preparation of nonionic binder (a-3)A stirred tank equipped with two separate feed lines, anchor stirrer and thermometer is charged with a mixture of butyl glycol and water (1 : 1). The stirred tank is subsequently subjected to nitrogen with an absolute pressure of 2.5 bar. With continuing stirring, a mixture of 3.7 parts of butyl glycol and 6.4 parts of tert-butyl peroxy-2-ethylhexanoate is metered in via a feed line over 4 hours and 45 minutes. Via the second feed, a mixture of 26 parts of methacrylic ester of methoxypolyethylene glycol having a number average molar mass of 2000 D in the form of a 50% strength aqueous solution (e.g., BisomerS20W® from GEO Speciality Chemicals), 8.55 parts of styrene, 4.7 parts of n-butyl acrylate, 8.34 parts of N-(2-methacryloyloxyethyl)ethyleneurea in the form of 50% strength aqueous solution, 3.36 parts of methyl methacrylate, 0.84 part of N,N'-dimethylaminopropylmethacrylamide, 6.5 parts of hydroxyethyl methacrylate and 18.5 parts of butyl glycol is metered over 4 hours and 30 minutes, with the second feed starting 15 minutes after the beginning of the first feed. After a postpolymerization phase of 60 minutes, butyl glycol is used to set a water: Butyl glycol ratio=45:55 at a solids content of 45%±1 %. The acid number of the resin is 4.0 to 6.0 mg KOH / g, based on the solids content.3. Preparation of component B3.1 Preparation of Pigment Paste RedThe preparation of Pigment Paste Red was conducted according to Example 2.4 of US20220259446 A1 (passage

[0381] ).Added with stirring to a mixture of 21 parts of D2, 17.6 parts of water and 1 .25 parts of 1-propoxy-2-propanol are 15 parts of a red pigment (Pigment Red 177). The mixture is subsequently admixed with three parts of water, 0.2 part of a 10% strength N,N'-dimethylethanolamine solution, 0.25 part of a commercial dispersing additive (Disperbyk 180) and 31 .7 parts of D1 . The mixture is dispersed on a bead mill, then made up with 4.5 parts of water and 5.5 parts of D1, and finally filtered. The Pigment Paste Red has a VOC of 221 g / L.3.2 Preparation of Pigment Paste WhiteThe preparation of Pigment Paste Black was conducted according to Example 2.7 of US20220259446 A1 (passage

[0387] ).Added with intensive stirring to a mixture of 10.55 parts of D2, 20 parts of D1, 4 parts of butyl glycol, 0.9 part of wetting agent (BYK 199), 0.45 part of a silane-modified silica (Aerosil R805), 1.2 parts of a 10% strength N,N'- dimethylethanolamine solution and 9.4 parts of water are 48.5 parts of titanium dioxide of the rutile type. This mixture is treated on a dissolver at high stirring speed and dispersed on a bead mill. This dispersion is subsequently made up with an additional 5 parts of DI. The Pigment Paste White has a VOC of 231 g / L.3.3 Preparation of Pigment Paste BlackThe preparation of Pigment Paste Black was conducted according to Example 2.2 of US20220259446 A1 (passage

[0377] ).Incorporated by stirring with strong shearing into a mixture of 14.8 parts of D2, 53.6 parts of D1 and 13.5 parts of water are 1 part of solvent-free wetting agent (BYK 345), 2.4 parts of butyl glycol, 1 .5 parts of a 10% strength N,N'- dimethylethanolamine solution, 0.5 part of a commercial surface-active additive (BYK 199), 1.5 parts of talc and 4.4 parts of carbon black (Color Black FW171). The mixture is dispersed on a bead mill, made up with a further 1.5 parts of water, 5 parts of D1 and 0.3 part of commercial PU thickener (Acrysol RM8), and then filtered. The resulting Pigment Paste Black has a VOC value of 186 g / L.Preparation of coated foam particles with pigmented surface coatingExamples 1 to 3 and Comparative Example 7To produce foam particles with a pigmented surface coating, the aqueous polyurethane dispersion (component A) was first mixed with the pigmented paste (component B). The resulting dispersion mixture (composition Z) was then fed in a dispersion mixer (Vollrath dissolver) together with a defined amount of foam particles and mixed for 60 s at room temperature. Afterwards, the wetted foam particles were spread on Teflon foils and dried there at room temperature for about 10 minutes, keeping attention to isolate them from each other. Afterwards, the coated foam particles were collected. An overview of the used raw materials and the compositions is given in Table 4. In case of the inventive examples 1 to 3 the obtained coated foam particles are non-sticky, homogeneously colored, storage stable and can be collected without agglomeration.In case of comparative Example 7, the obtained coating is a very sticky film. Therefore, the obtained coated foam particles tend to agglomerate and, thus, are neither storable nor free-flowable.Comparative Examples 4-5Micronized ash was mixed with aqueous polyurethane dispersion (see Table 4). The mixture was let on the shell and within 5 minutes sedimentation was observed. Thus, in contrast to examples 1 to 3 the mixture of micronized ash and aqueous polyurethane dispersion is not storage stable. In order to allow for a homogeneous coating, the micronized ash had to be mixed simultaneously with the polyurethane dispersion and the foam particles by means of a dissolver (Vollrath) for 60s at room temperature. Later the beads were let drying at RT on a Teflon foil, keeping attention to isolate them from each other. After a time of around 10 minutes the beads were collected. The coated beads are non-sticky, storage stable and can be collected without agglomeration.Comparative Example 6A roller bottle is initially charged in each case with 60 g of dye (Neozapon Black X55), after the addition of 200 g of glycerol triacetate (triacetin). Once the bottles had been sealed tight, they were agitated on a roller belt at room temperature overnight. The 30% solutions or dispersions of the colorants obtained were then diluted with further triacetin according to the desired color intensity.12 kg of the E-TPU 1 were weighed into a 200 L lidded drum. After the color solution had been added, the lidded drum was firmly closed and secured in a drum-hoop mixer. After agitation for 8 hours, the drum was removed from the mixer and opened. The colored particles were removed from the vessel; the colors had penetrated the foam particles.Table 4In table 4, the mass fraction of the dried coating layer is calculated from the mass fraction of the amount of the aqueous dispersions (sum of component A, B and C) applied to the foam particles and the solid content therein, e.g., 5 g aqueous dispersion were mixed with 95 g of foam particles means a weight fraction of 5% dispersions, with asolid content of 50% (calculated from the single solid contents according to the proportions of components A, B and C) results in 2.5 % mass fraction of the dried coating layer.Preparation of particle foam molded partsThe prepared foam particles as listed in Table 4 were placed in a preheated mold of dimension ((16.3x9.6x3.3) cm3(length, width, depth), which was previously sprayed with a silicone-based release agent (Indrosil 2000). The filled mold was covered with a mold lid (also sprayed with Indrosil 2000), which allows a compression / compaction of 50%. The foam particles were compression molded at a mold temperature of 140°C for 10 min, followed by a cooling time of 5 min before demolding.In contrast to steam chest molding, the obtained particle foam molded parts do not need to be stored or annealed, e.g., for drying purposes. Instead, the molded parts can be processed directly.The obtained plates were analyzed regarding tensile strength and elongation measured according to ASTM D 5035:2011, where instead of fabric strips (150 x 25.4 x 1.6) mm3 e-TPU strips were used. Furthermore, the rebound was measured according to DIN 53512:2000-4 and the density of the obtained 3 D parts measured according to DIN EN ISO 845:2009-10. An overview for the different examples and comparative examples is given in Table 5. Additionally, the color appearance of the molded part was rated, wherein 3 means excellent and homogeneous color appearance and 1 means poor and inhomogeneous coloration.Table 5The experiments show that the inventive coated foam particles incorporation are storage stable and can be processed via thermo-pressing into molded parts with good mechanical properties, low density and excellent color appearance. In contrast, if the coloration is conducted via sorption process, the molding via thermos-pressing leads to insufficient molded parts and, therefore the use of steam-chest molding is required.

Claims

Claims1 . A method for preparation of coated foam particles comprising mixing the foam particles with at least one aqueous polyurethane dispersion (component A) and at least one aqueous pigment paste (component B), wherein the at least one aqueous polyurethane dispersion comprises a polyurethane with a K-value in the range from 40 to 100 determined according to DIN EN ISO 1628-1 2021 and, wherein the aqueous pigment paste (component B) comprises at least one pigment (a-1) and at least one anionic binder (a-2) and / or at least one nonionic binder (a-3).

2. The method according to claim 1 comprising the steps of(a1) bringing foam particles into contact with a composition (Z) prepared from the at least one aqueous polyurethane dispersion (component A) and the at least one aqueous pigment paste (component B),(a2) drying the coated particles.

3. The method according to claim 1 or 2, wherein the at least one aqueous pigment paste (component B) has a VOC value of less than or equal to 250 g / L.

4. The method according to any of claims 1 to 3, wherein the foam particles are selected from the group consisting of styrene polymer foam particles, polyurethane foam particles, polyamide foam particles, thermoplastic elastomer foam particles, polyolefine foam particles and mixtures thereof.

5. The method according to any of claims 1 to 4, wherein the foam particles are thermoplastic polyurethane foam particles.

6. The method according to any of claims 1 to 5, wherein the polyurethane dispersion (component A) has a glass transition temperature Tgmeasured according to DIN EN ISO 11357-2 2018 from -10°C to -80°C and a melting temperature Tmof in the range from 30°C to 100°C determined according to DIN EN ISO 11357-3 (2018) by heating with 20 K / min after cooling to -80°C.

7. The method according to any of claims 1 to 6, wherein the polyurethane dispersion (component A) has at least a first glass transition temperature and a second glass transition measured according to DIN EN ISO 11357-2 2018, wherein Tgiis below 0°C and Tg2 is higher than 25°C.

8. The method according to any of claims 1 to 7, wherein the anionic binder (a-2) of component B is an anionic polyurethane polymer in dispersion in water, wherein the anionic polyurethane polymer has an acid number of 20 to 40 mg KOH / g, based on the solids content, wherein the dispersion has a pH of 7.0 to 8.0, and, wherein the dispersion comprises a polyol, more particularly a polypropylene glycol, having a number average molar mass of 500 to 1500 Da.

9. The method according to any of claims 1 to 8, wherein the nonionic binder (a-3) of component B is a nonionically stabilized acrylate copolymer in dispersion in water, the nonionically stabilized acrylate copolymer being obtainable by reaction of:(b1) at least one anchor group monomer unit having at least one ionizable functional group with active hydrogen, or a combination thereof, wherein the ionizable functionality is other than a carboxylic acid group in which the carbonyl carbon is separated from the closest ethy lenical ly unsaturated carbon by at least four atoms, the anchor group monomer units contain no polyoxyalkylene groups, and one of the anchor group monomer units is copolymerized 1-(2-methacryloyloxyethyl)-2- imidazolidinone;(b2) 5 % to 45 % by weight, based on the total weight of the monomers, of at least one monomer unit comprising a polyoxyalkylene group, a gamma-hydroxycarbamate group, a beta-hydroxycarbamate group, and a combination thereof; and(b3) 1% to 50% by weight, based on the total weight of the monomers, of at least one aromatic unit.

10. The method according to any of claims 1 to 9, wherein component B has a weight ratio of the total amount of nonionic binder (a-3) to the total amount of anionic binder (a-2) of 0.1 to 3, more particularly of 0.25 to 1.5, based in each case on the solid content of the binders.11 . The method according to any of claims 1 to 10, wherein component B comprises organic solvent in a total amount of 0% to 10 % by weight, preferably of 0 % to 9.8 % by weight based in each case on the total weight of the aqueous pigment paste PP.

12. The method according to any of claims 1 to 11, characterized in that the composition Z contains:(A) from 50 to 98% by weight of the aqueous polyurethane dispersion,(B) from 2 to 50% by weight of the aqueous pigment paste and(C) from 0 to 10% by weight of additives, wherein the entirety of components A, B and C provides 100% by weight.

13. The method according to any of claims 2 to 12, wherein in step (a1) the bringing into contact is realized by mixing or spraying.

14. The method according to any of claims 1 to 13, wherein the coated foam particles are coated in an amount from 0.5% to 40% by weight based on the total weight of foam particle and coating.

15. A process for the preparation of a particle foam molded part comprising the steps of(d) coating of foam particles according to method of any of claims 1 to 14,(c2) filling the coated foam particles in a mold,(c3) fusing the coated foam particles into a particle foam molded part by supplying energy.

16. The process of claim 15, wherein the fusing in step (c3) is carried out by steamless thermo-pressing.

17. The process of claim 16, wherein the thermo-pressing is carried out at a temperature of from 80°C to 140°C.

18. A coated foam particle, wherein the coating is a dried composition (Z) comprising an aqueous polyurethane dispersion as component A and an aqueous pigment paste as component B and, wherein component B comprises at least one pigment (a-1) and at least one anionic binder (a-2) and / or at least one nonionic binder (a-3), and, wherein the aqueous polyurethane dispersion comprises a polyurethane with a K-value in the range from 40 to 100 determined according to DIN EN ISO 1628-1 2021.

19. A particle foam molded part comprising coated foam particles according to claim 18.

20. Use of the particle foam molded part according to claim 19 in shoe soles, part of shoe soles, shoe intermediate soles shoe insoles, damping elements, cushioning elements, protective devices, underlays, grips, flooring, mattresses, sporting goods, bicycle saddles, tires and in automotive interiors and exteriors

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