Method for continuous production of aqueous polyurethane-polyurea dispersions and aqueous polyurethane-polyurea dispersions

Abstract

The present invention relates to an aqueous polyurethane-polyurea dispersion and to a process for the continuous production of such an aqueous polyurethane-polyurea dispersion, comprising the use of a high shear dispersion device comprising specific rotor / stator units.

Description

[0001] The present invention relates to aqueous polyurea-polyurethane dispersions and also to a method for the continuous production of aqueous polyurethane-polyurea dispersions. These dispersions have excellent applicability in coating compositions, particularly aqueous pigmented coating compositions, and offer improved yellowing behavior. Furthermore, these dispersions can be produced with very low levels of organic solvents, without requiring a distillative removal step. Furthermore, the polymer particles contained in the dispersions have a very low particle size, resulting in excellent storage stability. Background Art

[0002] Aqueous dispersions of polyurethane and polyurethane-polyurea polymers are well known in the art. They have a wide range of applications in various industrial sectors, such as the coatings industry. In particular, these polymers are used as binder resins in coating materials and have a decisive influence on the properties and quality level of these materials.

[0003] The prior art describes multifunctional polyurethane and polyurethane-polyurea polymers and their use in, for example, automotive basecoat materials. To be suitable for such applications and sectors, dispersed polymer particles must have optimal and stable dispersion characteristics and a low particle size.

[0004] For example, WO 2014 / 007915 A1 discloses a method for producing a multi-coat automotive topcoat using an aqueous basecoat material comprising an aqueous dispersion of a polyurethane-polyurea resin produced via batch production. The use of the basecoat material has a positive influence on the optical properties, in particular minimizing gel spots.

[0005] WO 2016 / 091539 A1 describes high-quality aqueous polyurethane-polyurea dispersions containing microgel particles and their production via a batch process. These dispersions are used as binder resins in automotive basecoat compositions and contribute to improved properties such as stability against pinholes and cracking. During the production of these dispersions, relatively large amounts of organic solvents are required, which ultimately need to be distilled off to obtain aqueous dispersions with a low content of such organic solvents. Although WO 2016 / 091539 A1 generally discloses alkali metal hydroxides as neutralizing agents in an exhaustive list, only amine-based organic bases are of interest and practical use. The neutralizing agent is always added in the organic-based phase, i.e., before, during, or directly after the production of the corresponding polyurethane prepolymer. The basecoat compositions produced are characterized by their improved yellowing behavior (i.e., coatings including coatings based on aqueous basecoat compositions, such as multi-coat paint systems, tend to gradually yellow, ultimately leading to a reduction in optical quality).

[0006] In addition to the batch production of the corresponding polymers and dispersions, continuous production is also a focus of attention for polymer manufacturers. Obviously, this continuous production shows inherent advantages compared to batch production procedures, especially in the context of industrial-scale production.

[0007] For example, DE 10 2004 017 436 A1 discloses a complex process for the continuous production of aqueous polyurethane dispersions by mixing polyurethane prepolymers with water in a mixing nozzle to produce an aqueous preemulsion and homogenizing the preemulsion thus produced in a multi-step homogenizing nozzle.

[0008] EP 2157111 B1 discloses a method for producing waterborne polyurethaneurea resins by mixing a polyurethane prepolymer solution with a small amount of an organic solvent (ketone) and water. The prepolymer is prepared using a polyhydroxycarboxylic acid neutralized with an amine, meaning that the prepolymer is neutralized before mixing with water. This feature enables the prepolymer dispersion process to be carried out with very small amounts of organic solvent, meaning that the resulting dispersion also contains low levels of such solvent, eliminating the need for distillation. Although the document generally describes the dispersion process as being able to be carried out both batchwise and continuously via a rotor / stator unit, the working examples are exclusively batch processes.

[0009] The advantages of continuous production of aqueous resin dispersions, especially on an industrial scale, are self-evident. However, a major challenge associated with continuous dispersion processes must be recognized: the significant difference in viscosity between the aqueous phase (essentially water) on the one hand and the polyurethane prepolymer solution (the organic-based phase) on the other. Even when fed separately (i.e., in separate streams) to the dispersion unit, the significantly higher viscosity of the organic phase remains a problem. While various measures are known to reduce the viscosity of the organic phase, these are associated with certain disadvantages. For example, increasing the temperature of the polymer involves high energy consumption and, even more importantly, can lead to side reactions of isocyanate groups (the latter being particularly pronounced when commonly used neutralizing agents (tertiary amines) are already present at this stage). Increasing the amount of organic solvent in the organic phase obviously results in a similarly higher amount of organic solvent in the resulting aqueous dispersion (and ultimately requires distillation if a dispersion with a low organic volatile content is desired).

[0010] Purpose and technical solutions

[0011] In light of the foregoing, it is clear that there is a need for aqueous polyurea-polyurethane dispersions exhibiting improved yellowing behavior, as well as aqueous basecoat compositions containing such dispersions. Furthermore, it would be desirable to provide a method for the continuous production of such aqueous polyurethane-polyurea dispersions, which ensures optimal and stable dispersion characteristics by simultaneously enabling the production of dispersions with very low organic solvent contents. More specifically, these dispersions should be producible with such low organic solvent contents, even if the final, corresponding distillation step of the organic solvent is omitted.

[0012] It was found that the above objects are achieved by novel aqueous polyurethane-polyurea dispersions and a process for the continuous production of aqueous polyurethane-polyurea dispersions.

[0013] More specifically, the novel aqueous polyurethane-polyurea dispersion comprises polyurethane-polyurea particles having a volume-based average diameter of 50 to 500 nm, wherein the dispersion is further characterized by 0.125 to 0.625 meq / g (based on solids content) of MEQ base, whereby the production of the dispersion involves a neutralization step with at least one alkali metal hydroxide as a neutralizing agent.

[0014] Also discovered is a novel process for the continuous production of an aqueous polyurethane-polyurea dispersion comprising polyurethane-polyurea particles having a volume-based average diameter of 50 to 500 nm, wherein the dispersion is further characterized by 0.125 to 0.625 meq / g (based on solids content) of MEQ base, comprising the steps of:

[0015] (1) providing an organic-based phase (I) comprising

[0016] (a) at least one acid-functional polyurethane prepolymer containing isocyanate groups, and

[0017] (b) 0 to 20% by weight, based on the total weight of the organic-based phase (I), of at least one organic solvent,

[0018] (2) Providing aqueous phase (II)

[0019] (3) continuously feeding both the organic-based phase (I) and the aqueous phase (II) into a high shear dispersing device comprising a rotor / stator unit,

[0020] (3.1) wherein the organic-based phase (I) and the aqueous phase (II) are brought into contact within the rotor / stator unit rather than before reaching the rotor / stator unit, and

[0021] (3.2) wherein the organic phase (I) is fed into the rotor / stator unit in the form of multiple sub-feed streams via multiple inlets,

[0022] (4) continuously dispersing the organic-based phase (I) and the aqueous phase (II) in the rotor-stator unit, thereby producing an aqueous polyurethane-based dispersion,

[0023] (5) continuously discharging the aqueous polyurethane-based dispersion from the high shear dispersing device, thereby generating a volume flow of the dispersion, and

[0024] (6) feeding at least one chain extender into the aqueous polyurethane-based dispersion, thereby producing the aqueous polyurethane-polyurea dispersion,

[0025] The neutralization step wherein at least one alkali metal hydroxide is used as a neutralizing agent is carried out during the dispersion process according to steps (3) and (4) above. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A stator (10) is shown having three stator tooth groups (11) with teeth (12). The first tooth group (11) with the smallest diameter consists of a total of 24 teeth, which are spaced, for example, 2.0 mm apart from one another. The second tooth group (11) consists of 34 teeth (1.2 mm apart), while the group (11) with the largest diameter consists of 160 teeth (0.3 mm apart). A first inlet (13) and a second inlet (14) are also shown, which are arranged in a circular manner and have a uniform distance from one another. The figure shows one half of the stator in detail (i.e. with individual teeth (12) and also with the individual second inlet (14)), while the second half is a schematic diagram (the tooth groups are circular and the individual second inlet is not shown).

[0027] Figure 2 A rotor (20) is shown having four rotor tooth groups (21) with teeth (22). The first tooth group (21) with the smallest diameter consists of a total of 12 teeth, which are spaced, for example, 3.0 mm apart from one another. The second tooth group (20) consists of 28 teeth (1.6 mm apart), while the third group (20) consists of 70 teeth (0.6 mm apart). The fourth tooth group (20) with the largest diameter consists of 160 teeth (0.3 mm apart). Again, half of the diagram is a detailed view, while the other half has a schematic character.

[0028] Figure 3 Shown as Figure 1 and 2The superimposed rotor / stator unit thus specifically designates a first inlet (13), two second inlets (14), three stator tooth sets (11) and four rotor tooth sets (21). Furthermore, the stator tooth sets and the three rotor tooth sets are designated according to their position relative to the second inlet set. Thus, the rotor tooth set of which the second inlet is radially positioned on the outside is referred to as rotor tooth set (21a), while the corresponding stator tooth set is referred to as stator tooth set (11a). Furthermore, the rotor tooth set of which the second inlet is radially positioned on the inside is referred to as rotor tooth set (21b), while the corresponding stator tooth set is referred to as stator tooth set (11b). DETAILED DESCRIPTION

[0029] First, a novel approach is described.

[0030] In the first step (1) of the process according to the invention, an organic-based phase (I) is provided.

[0031] The organic-based phase (I) comprises at least one acid-functional polyurethane prepolymer (a) containing isocyanate groups.

[0032] Polyurethane polymers containing isocyanate groups and being acid-functional are generally known. For the purposes of this invention, the corresponding component (a) is referred to as a prepolymer for easier understanding. This component is actually a polymer (or oligomer) that can be called a precursor, as it serves as a starting component for preparing another component, specifically a polyurethane-polyurea polymer in an aqueous dispersion.

[0033] To prepare polyurethane prepolymers containing isocyanate groups and anionic groups and / or groups that can be converted into anionic groups, aliphatic, cycloaliphatic, aliphatic-cycloaliphatic, aromatic, aliphatic-aromatic and / or aliphatic-aromatic polyisocyanates known to the skilled worker can be used. Diisocyanates are preferably used. By way of example, the following diisocyanates may be mentioned: 1,3- or 1,4-phenylene diisocyanate, 2,4- or 2,6-tolylene diisocyanate, 4,4′- or 2,4′-diphenylmethane diisocyanate, 1,4- or 1,5-naphthylene diisocyanate, diisocyanatodiphenyl ether, trimethylene diisocyanate, tetramethylene diisocyanate, ethylethylene diisocyanate, 2,3-dimethylethylene diisocyanate, 1-methyltrimethylene diisocyanate, pentamethylene diisocyanate, 1,3-cyclopentylene diisocyanate, hexamethylene diisocyanate, cyclohexylene diisocyanate, 1,2-cyclohexylene diisocyanate, octamethylene diisocyanate, trimethylhexane diisocyanate, tetramethylhexane diisocyanate, decamethylene diisocyanate esters, dodecamethylene diisocyanate, tetradecamethylene diisocyanate, isophorone diisocyanate (IPDI), 2-isocyanatopropylcyclohexyl isocyanate, dicyclohexylmethane 2,4'-diisocyanate, dicyclohexylmethane 4,4'-diisocyanate, 1,4- or 1,3-bis(isocyanatomethyl)cyclohexane, 1,4- or 1,3- or 1,2-diisocyanatocyclohexane, 2,4- or 2,6-diisocyanato-1-methylcyclohexane, 1-isocyanatomethyl-5-isocyanato-1,3,3-trimethylcyclohexane, 2,3-bis(8-isocyanatooctyl)-4-octyl-5-hexylcyclohexene, tetramethylxylene diisocyanate (TMXDI) such as m-tetramethylxylene diisocyanate, or mixtures of these polyisocyanates. Of course, different dimers and trimers of the diisocyanates described, such as uretdiones and isocyanurates, can also be used. Polyisocyanates with higher isocyanate functionality can also be used. Examples are tris(4-isocyanatophenyl)methane, 1,3,4-triisocyanatobenzene, 2,4,6-triisocyanatotoluene, 1,3,5-tris(6-isocyanatohexylbiuret), and bis(2,5-diisocyanato-4-methylphenyl)methane. The functionality can optionally be reduced by reaction with monohydric alcohols and / or secondary amines. However, preference is given to using diisocyanates, more particularly aliphatic diisocyanates, such as hexamethylene diisocyanate, isophorone diisocyanate (IPDI), dicyclohexylmethane 4,4'-diisocyanate, 2,4- or 2,6-diisocyanato-1-methylcyclohexane, and m-tetramethylene xylene diisocyanate (m-TMXDI). When an isocyanate group is attached to an aliphatic group; in other words, when there is no aromatic carbon in the alpha position to the isocyanate group, the isocyanate is said to be aliphatic.

[0034] The prepolymer (a) is prepared by reacting the polyisocyanate with a polyol, more particularly a diol, generally to form a urethane.

[0035] Examples of polyols are the generally known polyester, polycarbonate, polyether, polydienes, polyolefins, poly(meth)acrylate and / or polysiloxane polyols, more particularly diols. Mixtures of polyols are likewise possible.

[0036] The preferred embodiment of suitable polyol is saturated or ethylenically unsaturated polyester polyol and / or polyether polyol.The polyol used is more particularly polyester polyol, especially those with a number average molecular weight of 400 to 5000 g / mol (about the measuring method, see the example section). Such polyester polyol, preferably polyester diol can be prepared in a known manner by esterification of the corresponding polycarboxylic acid, preferably dicarboxylic acid, and / or their anhydride and the corresponding polyol, preferably diol. Of course, alternatively, in addition, even proportionally, monocarboxylic acid and / or monohydric alcohol can be used for preparation. Polyester diol is preferably saturated, more particularly saturated and straight-chain.

[0037] Examples of suitable aromatic polycarboxylic acids for the preparation of such polyester polyols, preferably polyester diols, are phthalic acid, isophthalic acid, and terephthalic acid, of which isophthalic acid is advantageous and therefore preferably used. Examples of suitable aliphatic polycarboxylic acids are oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedicarboxylic acid, and dodecanedicarboxylic acid or in addition hexahydrophthalic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 4-methylhexahydrophthalic acid, tricyclodecanedicarboxylic acid, and tetrahydrophthalic acid. As dicarboxylic acids, dimer fatty acids or dimer fatty acids can also be used, as known, which are mixtures prepared by dimerizing unsaturated fatty acids and are available, for example, under the trade name Radiacid (from Oleon) or Pripol (from Croda). In this context, the use of such dimer fatty acids for the preparation of polyester diols is preferred. Polyols preferably used to prepare prepolymer (a) are therefore polyester diols prepared using dimer fatty acids. Particularly preferred are polyester diols in which at least 50 wt. %, preferably 55 to 75 wt. %, of the dicarboxylic acids used in their preparation are dimer fatty acids.

[0038] Examples of corresponding polyols for preparing polyester polyols, preferably polyester diols, are ethylene glycol, 1,2- or 1,3-propylene glycol, 1,2-, 1,3- or 1,4-butanediol, 1,2-, 1,3-, 1,4- or 1,5-pentanediol, 2,2-dimethyl-1,3-propylene glycol (neopentyl glycol), 2-methyl-2,4-pentanediol, 1,2-, 1,3-, 1,4-, 1,5- or 1,6-hexanediol, trimethylpentanediol, 1,2-, 1,3- or 1,4-cyclohexanediol, 1,2- 1,2-, 1,3- or 1,4-cyclohexanedimethanol, α-, ω-difunctional alcohols or α-, β-dihydroxyalkanes having eight to twenty-five carbon atoms, in particular 1,2-octanediol, 1,8-octanediol, 1,2-decanediol, 1,10-decanediol, 1,2-dodecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,2-octadecanediol, 1,18-octadecanediol, 1,2-heneicosanediol, 1,21-heneicosanediol and 1,25-pentacosanediol. Examples of corresponding polyols for preparing polyester polyols, preferably polyester diols, are polyols based on hydrogenation products of polycarboxylic acid methyl esters of dimerized and trimerized fatty acids, for example, dimer fatty C36 diol after hydrogenation of methyl esters of saturated dimerized C36 fatty acids (Pripol ® 2033; from Croda Corporation). Further examples of corresponding polyols for preparing polyester polyols, preferably polyester diols, are ethers or cyclic ether alcohols, such as diethylene glycol, triethylene glycol, tetraethylene glycol, 2,5-bis(hydroxymethyl)furan, 2,5-bis(hydroxymethyl)tetrahydrofuran, and cyclic ether alcohols based on carbohydrates, such as isosorbide, isomannide and isoidide, and ester alcohols, such as 3-hydroxy-2,2-dimethylpropyl-3-hydroxy-2,2-dimethylpropionate (neopentyl glycol mono(hydroxypivalate)).

[0039] Polyhydroxy-polyesters derived from polyhydroxyalkyl acids, such as poly-2-hydroxyacetic acid (polyglycolic acid) or polyhydroxypropionic acid, another name for which is poly(lactic acid) (polylactide), as well as polyhydroxyalkyl acids with a higher number of carbon atoms, can also be used. The direct method is based on the direct polycondensation of hydroxycarboxylic acids as α-, β-, γ-, or ω-hydroxy acids. Due to the presence of hydroxyl and carbonyl groups, examples of corresponding hydroxycarboxylic acids are 2-hydroxyacetic acid (glycolic acid), 2-hydroxypropionic acid, 3-hydroxypropionic acid (lactic acid), 3-hydroxy-2-methylpropionic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid, 5-hydroxyvaleric acid, up to 12-hydroxydodecanoic acid (sabinic acid) or 13-hydroxytridecanoic acid. Polyester diols based on polyhydroxyalkyl acids can also be formed, and preferably are formed, by ring-opening polymerization of cyclic oligomers, preferably dimers, of the corresponding hydroxycarboxylic acids, such as dilactide from the corresponding lactic acid to form the best-known biodegradable polymer, poly(lactic acid).

[0040] The term polyester diol is also understood to mean polylactone diols, which are obtained by reacting a lactone with a polyol as initiator, the polyol having active hydrogen groups; examples are ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, or 1,6-hexanediol, and are produced by ring-opening polymerization. Lactones that can be used to synthesize polyester polyols are butyrolactone, valerolactone, methylvalerolactone, caprolactone, methylcaprolactone, and 2-oxoctanone (heptanolactone). Preferred lactone polyols are referred to as polycaprolactone polyols.

[0041] Further examples of suitable polyols are polycarbonate polyols, more particularly polycarbonate diols. These polycarbonate polyols can be prepared by reacting polyols such as 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 2-methylpentane-1,3-diol, neopentyl glycol, 1,6-hexanediol, 2,2,4-trimethylpentane-1,3-diol, 2-butyl-3-ethylpropane-1,3-diol, trimethylolpropane or pentaerythritol, 1,4-bishydroxymethylcyclohexane, 2,2-bis(4-hydroxycyclohexyl)propane, diethylene glycol, triethylene glycol or tetraethylene glycol with dicarbonates such as dimethyl carbonate, diethyl carbonate or diphenyl carbonate, or phosgene.

[0042] Other oligomeric or polymeric hydroxy-functional compounds are polydienes or polyolefins having at least two preferably terminal hydroxyl groups per molecule. Particularly preferred are dihydroxy compounds based on polybutadiene, polyisoprene or polyolefins such as polyethylene (hydrogenated polybutadiene) and block copolymers of polybutadiene, polyisoprene or polyolefins with polystyrene.

[0043] Examples of polyether polyols include polyols of polyoxyethylene, polyoxypropylene, and polyoxybutylene, mixed and block copolymers thereof, either in block form or randomly distributed along the polymer chain, and polyoxytetramethylene (polytetrahydrofuran, e.g., PolyTHF 2000 from BASF SE) containing terminal OH groups, also referred to as diols. Diols are also preferred.

[0044] These polyols are conventional materials and are commercially available.

[0045] Suitable polyols are further exemplified by α,ω-dihydroxypoly(meth)acrylates (e.g. TEGO ® Diol MD 1000) and α,ω-polydialkylsiloxane diols, like polydimethylsiloxane diol.

[0046] The aforementioned polyols and / or diols can of course also be used directly for the preparation of the prepolymer (a), in other words reacted directly with the polyisocyanate.

[0047] Further possible substances for preparing the prepolymer (a) are polyamines, such as diamines and / or amino alcohols. Examples of diamines include hydrazine, alkyldiamines or cycloalkyldiamines, such as propylenediamine and 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, and examples of amino alcohols include ethanolamine or diethanolamine.

[0048] Prepolymer (a) is acid-functional (i.e., contains groups that can be converted into anionic groups using known neutralizing agents). As known to those skilled in the art, these groups are, for example, carboxylic acid, sulfonic acid, and / or phosphonic acid groups, with carboxylic acid groups being particularly preferred. The introduction of such groups is known to increase dispersibility in water. Depending on the conditions selected, the groups may be present proportionally or almost entirely in one form (e.g., carboxylic acid) or the other (carboxylate). A specific influencing factor is the use of a neutralizing agent, which will be described in more detail later. If prepolymer (a) is mixed with such a neutralizing agent, a certain amount of the acid groups is converted into corresponding base groups, whereby this amount corresponds to the amount of neutralizing agent. For example, if the polymer has a specific amount of carboxylic acid groups, some or all of these may be converted into carboxylate groups (the corresponding base) using such a neutralizing agent. The amount of carboxylic acid groups can be described by the acid number (determined as described in the Examples) or the MEQ acid (which is the molar amount of acid groups [mmol] per mass of polymer [g]). The amount of (corresponding) basic groups (e.g., carboxylate groups) can be described as MEQ base (i.e., molar amount of basic groups [mmol] / mass of polymer [g]). It can be determined experimentally via titration (DIN EN ISO 15880, see also examples) or calculated from the acid number of the unneutralized polymer and the amount of neutralizing agent used for neutralization.

[0049] The general principles and conditions for neutralization of acid groups and their conversion into corresponding basic groups have been described above by way of example in the context of prepolymer (a). However, preferably, prepolymer (a) itself is not neutralized in the context of the present invention. Rather, in the context of the process of the present invention, it is important to carry out the neutralization step later in the process, i.e., during the dispersion process described below (i.e., during the stage in which the prepolymer is dispersed with the aqueous phase, meaning that this is the stage at which the prepolymer conversion begins and ultimately produces the polyurethane-based dispersion). Ultimately, however, the corresponding acid groups of the prepolymer are also part of the polymeric species contained in the polyurethane-based dispersion or the ultimately produced polyurethane-polyurea dispersion. Therefore, it is clear that the neutralization principle is universally applicable.

[0050] To introduce the acid groups, during the preparation of the prepolymer (a), a starting compound containing, in addition to the groups (preferably hydroxyl groups) used for the reaction in the preparation of the urethane bond, further groups (e.g., carboxylic acid groups) can be used. In this way, the groups in question are introduced into the prepolymer.

[0051] Suitable compounds for introducing the preferred carboxylic acid groups are polyether polyols and / or polyester polyols, provided they contain carboxyl groups. However, the compounds preferably used are low-molecular-weight compounds having at least one carboxylic acid group and at least one functional group reactive toward isocyanate groups (preferably a hydroxyl group). In the context of the present invention, the term "low-molecular-weight compound" is understood to mean compounds that can be assigned a discrete molecular weight, such as preferably monomeric compounds, as opposed to higher-molecular-weight compounds (especially polymers). Therefore, low-molecular-weight compounds are not specifically polymers, as the latter are always mixtures of molecules and must be described using an average molecular weight. Preferably, the term "low-molecular-weight compound" is understood to mean a corresponding compound having a molecular weight of less than 300 g / mol. The preferred range is 100 to 200 g / mol.

[0052] Preferred compounds in this context are, for example, monocarboxylic acids containing two hydroxyl groups, such as, for example, dihydroxypropionic acid, dihydroxysuccinic acid, and dihydroxybenzoic acid. Very specific compounds are α,α-dimethylolalkanoic acids, such as 2,2-dimethylolacetic acid, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid and 2,2-dimethylolpentanoic acid, especially 2,2-dimethylolpropionic acid.

[0053] Therefore, the prepolymers (a) used in the process are preferably carboxyl-functional. They preferably have an acid number of 10 to 35 mg KOH / g, more particularly 15 to 23 mg KOH / g (based on the solids content). As already mentioned above, the prepolymers (a) used in the process are preferably not neutralized, which means that the MEQ base of the prepolymer (a) is 0 mmol / g or at least substantially 0 mmol / g.

[0054] As mentioned above, the prepolymer (a) is preferably formed from difunctional compounds like in particular diisocyanates and diols. It is therefore obvious that the prepolymer preferably has a linear character.

[0055] As outlined above, prepolymer (a) contains isocyanate groups. The polyurethane prepolymer preferably has an isocyanate equivalent weight of less than 3000 g / mol. More preferably, the isocyanate equivalent weight is less than 2500 g / mol. The preferred range is 500 to 3000 g / mol, even more preferably 1000 to 2500 g / mol (determined via the NCO content (solids content) of the prepolymer).

[0056] It is preferred that the prepolymer (a) has a number average molecular weight of at most 6000 g / mol, for example in the range of 1000 to 6000 g / mol, more preferably 2000 to 5000 g / mol. The relatively low molecular weight also results in a lower viscosity of the prepolymer, which means that a viscosity more compatible with the aqueous phase (II) described below is achieved and thus enhanced dispersibility is achieved.

[0057] Prepolymer (a) can be prepared by known and established methods in bulk or in solution, particularly preferably by reacting the starting compounds in an organic solvent (such as, preferably, methyl ethyl ketone) at a temperature of, for example, 60°C to 120°C, optionally using a catalyst typically used in polyurethane production. Such catalysts are known to those skilled in the art; an example is dibutyltin laurate. The procedure here is, of course, to select the ratio of the starting components so that the product (in other words, prepolymer (a)) contains isocyanate groups. It is also obvious that the solvents should be selected in such a way that they do not undergo any undesirable reactions with the functional groups of the starting compounds; in other words, they should be inert toward these groups, meaning that they do not hinder their reaction. The preparation is preferably carried out in an organic solvent (b), as described below. Furthermore, the fraction of organic solvent used to prepare prepolymer (a), based on the synthesis mixture (i.e., the mixture containing the starting compounds and the organic solvent), preferably does not exceed the fraction of organic solvent (b) in the organic-based phase, as defined below.

[0058] The organic-based phase (I) may also contain at least one organic solvent (b). Obviously, this organic solvent may be one or more of the organic solvents used during the preparation of the prepolymer (a).

[0059] As the organic solvent (b), those known to those skilled in the art can be used, and no particular limitation is imposed. For example, as the solvent (b), ketone, ether, ester, pyrrolidone, amide, morpholine, lactone, acetate or sulfoxide can be used. Specific examples of solvent (b) are methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, diethyl ether, dibutyl ether, dipropylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol acetate, toluene, methyl acetate, ethyl acetate, butyl acetate, propylene carbonate, cyclohexanone, acetone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, tetrahydrofuran, dioxane, N-formylmorpholine, dimethylformamide, or dimethyl sulfoxide, 3-methoxy-N,N-dimethylpropionamide, 3-butoxy-N,N-dimethylpropionamide, N-formylmorpholine, γ-butyrolactone, bis(2-(2-butoxyethoxy)ethoxy)methane.

[0060] The fraction of the at least one organic solvent (b) does not exceed 20% by weight (20 wt.%), based on the total weight of the organic-based phase (I). Consequently, the organic-based phase (I) can even be completely free of such organic solvents (which means that in this case, the organic-based phase can consist of the prepolymer (a)). However, in order to achieve a suitably low viscosity, the fraction of the at least one organic solvent (b) is preferably not less than 5% by weight. Preferably, the fraction is from 5% to 20% by weight, more preferably from 10% to 15% by weight, in each case based on the total weight of the organic-based phase. This relatively low fraction of organic solvent, together with the further features and technical characteristics of the process according to the invention as described below, ensures that the resulting aqueous polyurethane-polyurea dispersion can be prepared with a very low content of organic solvents, without requiring a corresponding distillation process of such solvents.

[0061] The solids content of the organic-based phase (I) is preferably at least 80% by weight, more preferably at least 85% by weight, but preferably less than 90% by weight. A preferred range is from 80% to 95% by weight, such as, for example, 85% to 90% by weight.

[0062] In the second step (2) of the process according to the invention, an aqueous phase (II) is provided. It is obvious that the second step can be carried out before or after the first step (1) or in parallel therewith.

[0063] The aqueous phase (II) obviously comprises water. Of course, in addition to water, the aqueous phase can also include typical auxiliary agents in proportion, such as typical emulsifiers and protective colloids. The compilation of suitable emulsifiers and protective colloids can be found in, for example, HoubenWeyl, Methoden der organischen Chemie [Organic Chemistry Methods], Volume XIV / 1 Makromolekulare Stoffe [Macromolecular Compounds], Georg Thieme Verlag [Georg Thieme Publishing House], Stuttgart 1961, page 411 and thereafter. In addition, the aqueous phase can include an alkali metal hydroxide as a neutralizing agent, which means that it helps or fully encompasses the necessary step of neutralization during the dispersion procedure. However, water certainly constitutes the major part of the aqueous phase (II), as, for example, at least 90% by weight or even at least 95% by weight.

[0064] In step (3) of the process of the present invention, the organic-based phase (I) and the aqueous-based phase (II) are continuously fed into a high-shear dispersion device comprising a rotor / stator unit. It is important that the two phases come into contact within the rotor / stator unit and therefore not before reaching the rotor / stator unit. As a standard, the high-shear dispersion device comprises one rotor / stator unit. In the unlikely event that more than one such unit is present in the device, the rotor / stator unit is of course the first unit into which both the organic-based phase (I) and the aqueous-based phase (II) are fed.

[0065] High shear dispersing devices comprising rotor / stator units and their use for continuous dispersing processes are well known in the art. For example, EP 1 489 130 B1 or US 8,669,401 B2 describe details of such units in the context of continuous production of polyurethane emulsions or wax dispersions.

[0066] Such rotor / stator units thus comprise a rotor subunit and a stator subunit. Both the rotor and stator subunits include at least one tooth set, whereby the teeth of each set are circumferentially arranged on a circle having a certain circumference and diameter. The at least one rotor set and the at least one stator set are aligned with each other so that the corresponding teeth of the rotor and stator (each describing a circle) are oriented concentrically with each other. In the case of more than one tooth set on the rotor and / or stator (which is preferred in the context of the present invention), the tooth sets of the rotor and stator are arranged alternately. In known rotor / stator units, the liquid component to be dispersed is introduced centrally into the device, and the corresponding rotation of the rotor exposes the liquid to centrifugal forces, ultimately propelling the medium outward. The rotor's motion also causes the rotor teeth to rotate relative to the stationary teeth of the stator, thereby exposing the liquid to shear as it flows outward through the unit's corresponding dynamically changing cavities / cavity dimensions. More specifically, the dynamic change in the cavities / cavity dimensions is due to the aforementioned rotation of the rotor teeth relative to the stationary stator teeth. Obviously, a variety of parameters and adjustments are possible, such as, for example, the number and size of teeth, the diameter of the tooth set (i.e., the circle on which the teeth are positioned), the width / distance of the gaps between tooth sets, and / or the distance between the rotor and stator tooth sets (i.e., the concentric distance between the teeth of a rotor tooth set and the teeth of an adjacent stator tooth set), or the number of rotor and stator tooth sets. These parameters are generally adjustable based on individual requirements and the general knowledge of those skilled in the art. Generally speaking, as the diameter of the tooth set increases, the number of teeth generally increases, while the size of the teeth and the width of the gaps decrease (which means that there is an increased number of broken walls and, therefore, shear stress (at a given rotor speed)).

[0067] Preferably, the rotor / stator unit comprises at least two tooth groups (21) of the rotor and at least two tooth groups (11) of the stator. Even more preferably, at least three tooth groups (21) of the rotor and at least three tooth groups (11) of the stator. Even more preferably, four tooth groups (21) of the rotor and three tooth groups (11) of the stator are included. As described above, the tooth groups (21) of the rotor and the tooth groups (11) of the stator are of course arranged alternately. Therefore, in the above case comprising four tooth groups (21) of the rotor and three tooth groups (11) of the stator, the first tooth group (21) of the rotor has the smallest overall diameter (and is therefore located most centrally) and the fourth tooth group (21) has the largest overall diameter (and is therefore located most externally).

[0068] (3.1) As mentioned above, the two phases, the organic-based phase (I) and the aqueous phase (II), come into contact within the rotor / stator unit and therefore not before reaching the rotor / stator unit. Therefore, it is obvious that the first requirement is that the two phases are supplied separately as two separate feed streams via two separate inlets to the high shear dispersing device and thus to the rotor / stator unit.

[0069] (3.2) Furthermore, it is crucial that the organic phase (I) is fed into the rotor / stator unit in the form of a plurality of sub-feed streams via a plurality of inlets. Thus, the organic phase (I), for example initially provided as one (main) feed stream, is divided into a plurality of sub-feed streams before reaching the rotor / stator unit and is thus supplied to the unit as such a plurality of sub-feed streams.

[0070] It has emerged that the above characteristics (3.1) and (3.2) are crucial for achieving the objective of the present application, namely to provide an aqueous polyurethane-polyurea dispersion that ensures optimal and stable dispersion characteristics of the dispersion by simultaneously enabling the production of the dispersion with very low contents of organic solvents. More specifically, the two separate feed streams (3.1) ensure continuous, constant, and controllable feeding of the two phases into the unit (as opposed to a single feed stream comprising both phases, since in this case the difference in viscosity of the two phases would prevent such continuous, constant, and controllable feeding), while the feeding of the organic phase in the form of multiple sub-feed streams (3.2) contributes to improving the dispersion efficiency.

[0071] Preferably, in a first aspect, the above principle involves a first inlet into the rotor / stator unit being centrally located within the unit, i.e., within the circle described by the smallest and therefore innermost tooth set (either the rotor or stator). This inlet is, of course, part of the stator. Therefore, this first aspect is equivalent to the inlet of a standard rotor / stator unit. This first inlet is provided for the feed streams of the aqueous phase (II) and the aqueous phase (II), respectively.

[0072] As described above, the novel process involves feeding the organic phase (I) via multiple inlets. To distinguish them from the primary inlet for the organic phase (I), these inlets may also be referred to as secondary inlets. These multiple inlets (i.e., multiple secondary inlets or secondary inlet groups) are provided for the organic phase (I) and multiple sub-feed streams of the organic phase (I), respectively. These inlets are, of course, part of the stator. The secondary inlet groups are created by dividing a single main inlet line into the rotor / stator unit. In other words, a single main feed line is divided into a corresponding number of supply inlets.

[0073] The number of second inlets constituting the second inlet group is preferably at least 5, more preferably at least 10 or even at least 20. Of course, the exact number of second inlets depends on other factors, such as the overall size of the corresponding rotor / stator unit or the size (i.e., inner diameter) of the inlets. The inner diameter of the second inlets can also vary and be selected according to individual requirements. For example, the appropriate size of the second inlet may be influenced by the viscosity of the organic phase (I) or its mass flow rate. Exemplary size ranges (which do not imply any limitation, but are merely preferred) may be 1.5 to 10 mm, such as, for example, 1.8 to 7.5 mm or 1.8 to 5 mm (inner diameter).

[0074] A decisive advantage of this arrangement is that the organic phase (I) is already exposed to a certain level of shear before even reaching the rotor / stator unit (due to the geometry of the multiple inlets, i.e. a relatively high number of wall surfaces and therefore significant turbulence). Furthermore, this means that the organic phase (I) is initially evenly distributed when it reaches the rotor / stator unit, not being fed via a single main feed stream but being divided into multiple sub-feed streams.

[0075] The second inlet group can be arranged in various types and arrangements. The second inlet, as part of the stator, can be located, for example, between the central first inlet and the stator's first set of teeth (i.e., the stator's set of teeth with the smallest diameter). Furthermore, the second inlet can be located between two sets of stator teeth. Obviously, a first portion of the second inlet can also be located between the central first inlet and the stator's first set of teeth, while a second portion is located between the two sets of stator teeth (or the second portion can even be divided into inlet groups located between different pairs of stator tooth groups). Preferably, at least a portion of the second inlet, and more preferably, the entire second inlet, is located between two sets of stator teeth.

[0076] Preferably, the second inlet openings, which are part of the stator, are circumferentially positioned on a circle having a certain circumference and diameter. The second inlets are preferably evenly distributed on the circle, i.e., positioned at a uniform distance from one another on such a circle. It follows from the above that it is preferred that this circle have a circumference and therefore a diameter that lies between the circumference and therefore a diameter of a first set of teeth of the stator and the circumference and therefore a diameter of a second set of teeth of the stator, meaning that the second inlet openings are positioned between the two sets of teeth of the stator.

[0077] Preferably, the second inlet set is a set of inlets (ie holes) positioned circumferentially on a circle having a circumference and diameter greater than the circumference and diameter of the at least one set of stator teeth and the at least one set of rotor teeth.

[0078] Preferably, a portion of the second inlets (preferably all of the second inlets) are positioned radially outside of at least one rotor tooth set and at least one stator tooth set, such as, for example, radially outside of two rotor tooth sets and one stator tooth set (located between the two rotor tooth sets). For greater clarity, the rotor tooth set of which the second inlets are radially outside may be referred to as rotor tooth set (21a), and the corresponding stator tooth set may be referred to as stator tooth set (11a).

[0079] Thus, in preferred embodiments, the second inlets are located at positions where the fluid entering the cell via the first inlet (ie the aqueous phase (II)) passes through in a form that has been exposed to shear through the cell.

[0080] Since the rotor and stator tooth sets in the rotor / stator arrangement are positioned concentrically to one another and, in the case of more than one rotor and / or stator tooth set, the rotor and stator tooth sets are arranged alternately, the second inlet set being part of the stator is preferably located on a circle which also at least substantially describes the circle of the rotor tooth sets (cf. Figure 3 ). Therefore, the second inlet set (which is the holes in the stator) is directly or approximately (i.e. slightly staggered) below the teeth of the corresponding rotor tooth set. The corresponding space defined by these conditions is the area where the first fluid entering the unit via the first inlet comes into contact with the second fluid entering the unit via the second inlet set.

[0081] Obviously, the organic phase (I) entering the unit via the second inlet set needs to be effectively dispersed with the aqueous phase (II) and, therefore, needs to be effectively exposed to shear in order to achieve appropriate dispersibility characteristics. Therefore, preferably, the rotor / stator unit includes at least one combination of a rotor tooth set and a stator tooth set radially outward from the location of the second inlet. Thus, where the second inlet set is arranged as a circle, the circumference and diameter of this circle are smaller than the circumference and diameter of the at least one stator tooth set and the at least one rotor tooth set.

[0082] Therefore, preferably, a portion of the second inlets (preferably all of the second inlets) are located radially inside at least one rotor tooth set and at least one stator tooth set, such as, for example, radially inside two rotor tooth sets and two stator tooth sets (alternatingly arranged). For greater clarity, the rotor tooth set in which the second inlets are located radially inside may be referred to as rotor tooth set (21b), and the corresponding stator tooth set may be referred to as stator tooth set (11b).

[0083] As is known to those skilled in the art, the viscosity of the organic phase, which contains a polyurethane prepolymer and a relatively low solvent content, is significantly higher than that of the aqueous phase. Surprisingly, the above arrangement overcomes these obstacles, i.e., ensures an efficient dispersion process despite the respective deviations in the viscosities of the phases to be mixed.

[0084] As mentioned above, the organic phase can be heated before being introduced into the high shear dispersing device and thus into the rotor / stator unit. Obviously, this is beneficial for reducing the viscosity. Preferably, the temperature of the organic phase (I) when introduced into the rotor / stator unit and when contacting with the aqueous phase (II) is at least 50°C, more preferably at least 65°C or even at least 75°C. The preferred range is 50°C to 160°C, more preferably 65°C to 140°C or even 75°C to 120°C.

[0085] When introduced into the rotor / stator unit, the organic phase preferably has a viscosity of less than 35 Pas, preferably 15 to 30 Pas (measured via a rotational viscometer at a shear rate of 10 / s). This viscosity can be achieved when the organic phase is heated to the temperatures described above.

[0086] Preferably, the temperature of the aqueous phase (II) when introduced into the rotor / stator unit and when contacting with the organic phase (I) is below 25° C., more preferably below 15° C. or even below 10° C. A preferred range is from 1° C. to 15° C., more preferably from 2° C. to 10° C. As is generally known, at such temperatures, the viscosity of water and therefore of the aqueous phase (II) will be significantly lower than the viscosity of the above-mentioned organic phase (I) (e.g., below 10 mPas at a shear rate of 1000 / s).

[0087] It is clear that the preferred low temperature of the aqueous phase serves to compensate for the preferred higher temperature of the organic phase, which means that after the phases are brought into contact and the continuous dispersion step (4) of the process according to the invention is started, the aqueous polyurethane-based dispersion formed can have a moderate temperature. In order to enhance this cooling effect, the rotor / stator unit or parts thereof can also be cooled by external measures. In principle, the same applies to the fluid conduit system connected to the outlet of the rotor / stator unit. Of course, the temperature also depends on the weight ratio of the two different phases and therefore the mass flow rate during the production of the aqueous polyurethane-based dispersion, but is preferably between 30°C and 80°C or even 40°C and 70°C when leaving the rotor / stator unit. One reason for this is that, unlike the prepolymer and the organic-based phase (I), the aqueous dispersion formed generally has a higher viscosity at higher temperatures, which means that too high a temperature can lead to improper flow.

[0088] The ratio of the mass flow of the organic phase (I) to the mass flow of the aqueous phase (II) upon entering the rotor / stator unit can be selected according to individual requirements, such as, for example, the desired solids content of the resulting dispersion. The ratio (I): (II) can be, for example, 1:4 to 1.5:1.

[0089] As already mentioned above, it is important that the production of aqueous polyurethane-polyurea dispersions involves a neutralization step with at least one alkali metal hydroxide as a neutralizing agent during the dispersion process according to steps (3) and (4) above. The term "dispersion procedure" refers to the actual dispersion step of steps (3) and (4) of the method according to the invention, i.e., the step of contacting the two phases within the rotor / stator unit and then dispersing them. During this process, it is clear that the acid groups initially present in the prepolymer are at least partially neutralized, i.e., converted into the corresponding base. Although, in principle, neutralization can take place not only during the dispersion process, but also before or after this dispersion process, it is preferred that this neutralization not take place before the dispersion step, for example, during or directly after the formation of the prepolymer. This results in the significant advantage that potential side reactions between the isocyanate groups and the neutralizing agent are avoided or at least reduced. The latter is particularly important when the organic-based phase is heated before the dispersion process in order to reduce its viscosity. Details are mentioned below.

[0090] As already mentioned above, neutralization during the dispersion process is preferably achieved by adding alkali metal hydroxide as neutralizing agent to the aqueous phase (II).

[0091] In the case of an additional neutralization step after the dispersion process, this can be carried out, for example, by simply adding the neutralizing agent (for example in the form of an aqueous solution) to the final storage container for the aqueous polyurethane-polyurea dispersion to be produced or in the form of a continuous feed, for example via a T-connection in a pipe system.

[0092] Preferably, in the process according to the invention, nitrogen-containing organic bases, such as amines, such as ammonia, trimethylamine, triethylamine, tributylamine, dimethylaniline, triphenylamine, dimethylethanolamine, methyldiethanolamine, or triethanolamine, and also mixtures thereof, are not used as neutralizing agents. Even more preferably, in the process according to the invention, only alkali metal hydroxides are used as neutralizing agents.

[0093] Once the aqueous polyurea-polyurethane dispersion is finally produced, it is characterized by an MEQ base of 0.125 to 0.625 mmol / g (based on solids). Therefore, in the case of a relatively high acid number of the prepolymer (a) used and thus the aqueous polyurea-polyurethane dispersion finally produced, a high degree of neutralization will lead to a relatively high MEQ base. In the case of a relatively low acid number of the prepolymer (a) used and thus the aqueous polyurea-polyurethane dispersion finally produced, a low degree of neutralization will lead to a relatively low MEQ base. A preferred range of MEQ base is 0.15 to 0.5 mmol / g or even 0.20 to 0.40 mmol / g.

[0094] In a preferred embodiment, the degree of neutralization of the aqueous polyurethane-polyurea dispersion finally produced is greater than 65%, such as, for example, greater than 66% or even greater than 70%. In short, the degree of neutralization of the aqueous polyurethane-polyurea dispersion finally obtained is preferably greater than 70% to 95%.

[0095] It is preferred to carry out a two-step neutralization process, namely a first neutralization step during the dispersion step as defined above and a second neutralization step after the dispersion step, preferably in the form of an alkali metal hydroxide added as the neutralizing agent to the final collection vessel. It follows that the first neutralization step is therefore preferably carried out at a temperature of the mixture to be neutralized of 30°C to 80°C or 40°C to 70°C. The second neutralization step is preferably carried out at a temperature of the mixture to be neutralized of less than 35°C, such as, for example, 10°C to 30°C (i.e., room temperature). The degree of neutralization achieved in the first step is therefore preferably between 50% and 70%, while the degree of neutralization achieved in the second step is greater than 70% to 95% (as the sum of the first and second steps) (the degree of neutralization is in each case calculated as the molar ratio of the potentially anionic groups present in the prepolymer to the amount of neutralizing groups in the neutralizing agent used (see the Examples section for further details), always taking into account the respective mass flows of the respective phases in the continuous process).

[0096] While neutralization may be relevant to stabilizing the aqueous polyurethane-polyurea dispersion, the addition of the neutralizing agent at different temperatures and / or conditions / reaction progression during the process of the present invention may have an impact on the viscosity and particle size of the final aqueous polyurethane-polyurea dispersion. In view of these effects, the above preferred embodiments contemplate optimizing the resulting aqueous polyurethane-polyurea dispersion.

[0097] During the continuous dispersion step (4), an aqueous dispersion containing the polyurethane-based substance is formed. Obviously, during this process and thereafter, a certain amount of the isocyanate groups of the prepolymer will react with water to form primary amino groups. These amino groups formed will then react with the remaining isocyanate groups of the prepolymer. These reactions will inevitably occur at the moment when the two phases (I) and (II) are brought into contact with each other, i.e., within the rotor / stator unit, and also during and after the continuous discharge of the aqueous polyurethane-based dispersion from the high-shear dispersing device in step (5) of the process according to the present invention.

[0098] Furthermore, in step (6) of the process of the present invention, at least one chain extender is continuously fed into the aqueous polyurethane-based dispersion discharged from the rotor / stator unit, thereby producing an aqueous polyurethane-polyurea dispersion. The chain extender thus reacts with the polyurethane-based substances in the polyurethane-based dispersion, more particularly with the isocyanate groups of these polyurethane-based substances. Therefore, it is obvious that care must be taken to ensure that a certain amount of isocyanate groups remains to react with the chain extender. As is known to those skilled in the art, the reaction of isocyanates with water (generating amino groups, which in turn consume further isocyanates) does not occur on an extremely fast reaction scale, which means that the addition and (fairly fast) reaction with the chain extender is possible. That is, the above-mentioned reactions and conversions proceed in parallel with one another. Ultimately, as a result of these intermolecular and intramolecular reactions or crosslinking, a dispersion comprising polyurethane-polyurea particles is formed.

[0099] As described above, in step (6), at least one chain extender is fed into the aqueous polyurethane-based dispersion discharged from the rotor / stator unit, which means that a chain extension reaction with isocyanate is carried out.

[0100] As chain extenders, those agents established and known to the person skilled in the art may be used. Thus, the chain extenders have an NH functionality, for example in the form of a primary or secondary amino group or a hydrazine moiety.

[0101] Exemplary chain extenders are thus aliphatic, aromatic or araliphatic (mixed aliphatic-aromatic) polyamines like diamines or triamines and also hydrazines or hydrazides.

[0102] Explicit examples are ethylenediamine (EDA), diethylenetriamine (DETA), 3-(2-aminoethylamino)propylamine (N3-amine), dipropylenetriamine (DPTA), triethylenetetramine (TETA), N,N'-bis-(3-aminopropyl)ethylenediamine (N4-amine), meta-xylylenediamine (MXDA), N-(2-aminoethyl)ethanolamine (AEEA), N-(2-aminoethyl)propanolamine (AEPA), 2-methylpentanediamine, etc., and mixtures thereof. Also suitable for practice in the present invention are 1,2-propylene diamine, 1,3-propylene diamine, 1,3-butylene diamine, 1,4-butylene diamine, 2,2-dimethylpropane-1,3-diamine, 1,6-hexamethylene diamine, octamethylene diamine, dimer fatty acid (C36) diamine, 1,2-cyclohexane diamine, 1,4-cyclohexane diamine, 2-methylcyclohexane-1,3-diamine, 4-methylcyclohexane-1,3-diamine, 3-(cyclohexylamino)propylamine, 4,4'-dicyclohexylmethanediamine, 2,4'-dicyclohexylmethanediamine, 3,3'-dimethyl-4,4'-dicyclohexylmethanediamine, 3,3'-dimethyl-2,4'-dicyclohexylmethanediamine, isophoronediamine, piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, 2-imidazolidinonediamine, 1,2-phenylenediamine, 1,4-phenylenediamine, 4,4'-diaminodiphenylmethane, 2,4'-diaminodiphenylmethane, 2 ,6-diamino-4-phenyltriazine, 2,4-diamino-6-phenyl-1,3,5-triazine, 3,3-dichlorobenzidine, 4,4'-methylene-bis-(2-chloroaniline), 3,3-dichloro-4,4-diaminodiphenylmethane, 4,7,10-trioxatridecan-1,13-diamine, 4,9-dioxadodecane-1,12-diamine, N-[3-(isodecyloxy)propyl]propane-1,3-diamine, sulfonated primary amines and and / or secondary amines such as N-(2-aminoethyl)-2-aminoethanesulfonic acid and its alkali metal salts, 2,4-diaminobenzenesulfonic acid and / or 4,4'-diaminodiphenyl sulfone, hydrazine, monomethylhydrazine (MMH), dihydrazides of dicarboxylic acids such as adipic acid dihydrazide (ADH), carbodihydrazide (CDH), sebacic acid dihydrazide (SDH), valine dihydrazide (VDH), isophthalic acid dihydrazide (IDH), eicosanedioic acid dihydrazide (LDH) and mixtures thereof.

[0103] Preferred chain extenders are polyamines having at least three amino groups, such as, for example, at least two primary amino groups and at least one secondary amino group. Even more preferably, there are exactly three amino groups, more particularly two primary amino groups and one secondary amino group. A preferred polyamine is diethylenetriamine.

[0104] The chain extender is preferably fed as an aqueous composition into the aqueous polyurethane-based dispersion discharged from the high-shear dispersing device and the rotor / stator unit, respectively. For example, the aqueous composition can be a solution or dispersion of the chain extender in water, having a chain extender concentration of between 5% and 20% by weight, based on the composition. Preferably, the aqueous composition is fed in a continuous manner. Obviously, the actual desired concentration of the chain extender can depend on various factors, such as the mass flow rate of the aqueous polyurethane-based dispersion discharged from the high-shear dispersing device, the concentration of the polyurethane-based material in the dispersion, the isocyanate content of the polyurethane-based material, or the mass flow rate of the composition containing the chain extender. In short, these parameters are adjustable according to individual requirements. The continuous feeding of the chain extender can be carried out via a T-joint in the piping system. To ensure proper mixing, a mixing device, such as a static mixer, can be placed in the system after the point where the chain extender is fed.

[0105] Preferably, the molar ratio of isocyanate groups of the polyurethane-based dispersion (calculated as the isocyanate groups contained in the prepolymer of the organic phase (I)) to the sum of the primary and secondary amino groups of the chain extender (calculated from the concentration of the corresponding agents in the aqueous composition) is greater than 0.8:1, for example from 0.8:1 to 3:1 or from 0.9:1 to 2:1.

[0106] Therefore, in a preferred embodiment, the continuous mass flow of the polyurethane-based dispersion and the continuous mass flow of the composition comprising the chain extender discharged from the high-shear dispersing device are adjusted in such a way that the molar ratio of the isocyanate groups of the polyurethane-based dispersion (calculated as the isocyanate groups contained in the prepolymer of the organic phase (I)) to the sum of the primary and secondary amino groups of the chain extender (calculated from the concentration of the corresponding agents in the aqueous composition) is greater than 0.8:1, for example from 0.8:1 to 3:1 or from 0.9:1 to 2:1.

[0107] Adding the chain extender only after the dispersion has left the high shear dispersing device has the advantage that effective crosslinking initiated by the chain extender does not take place within the device and thus possible clogging and blocking processes of the complex cavity system of the device are avoided.

[0108] On the other hand, as mentioned above, it is necessary to consider that the isocyanate reacts with water to produce amino groups and subsequently consumes additional isocyanate. Those skilled in the art can select and adjust appropriate conditions to ensure that the chain extender is added at a time point that still ensures an effective reaction between the isocyanate and the chain extender.

[0109] In a preferred embodiment, the duration between the point in time at which the dispersion exits the high-shear dispersing device and the point in time at which the chain extender is fed / added (hereinafter referred to as the "residence time") does not exceed 30 seconds. Preferably, the residence time does not exceed 20 seconds, or even 10 seconds or 5 seconds. The residence time (which is a statistically average figure) can be calculated by taking into account the mass flow rate of the aqueous polyurethane-based dispersion continuously discharged from the rotor / stator unit (and thus the high-shear dispersing device) and the volume of the polyurethane-based dispersion that must be conveyed through the corresponding piping system before the chain extender is fed / added (the volume calculated, for example, based on the inner diameter of the piping system and the distance between the point in time at which the aqueous polyurethane-based dispersion exits the high-shear dispersing device and the point in time at which the chain extender is added). More specifically, this calculation can be performed based on the following parameters: the mass flow rate, the inner diameter of the piping system, the length of the relevant piping system (from the high-shear dispersing device outlet to the point in time at which the chain extender is added), and the density of the aqueous dispersion exiting the high-shear dispersing device (for the calculation, the density at a temperature of 60°C is taken).

[0110] From the above it follows that the residence time is therefore the average time that part of the aqueous dispersion and therefore the polyurethane material is in contact with water but not with the chain extender.

[0111] Step (6) of the method according to the invention, i.e., feeding the chain extender and thereby initiating the reaction of the specific amino groups of the chain extender with the isocyanate, ultimately results in the production of an aqueous polyurethane-polyurea dispersion. The dispersion can, for example, be collected in a storage container. Of course, the dispersion can also be directly transported via a pipe system to further processes and corresponding equipment, such as processes and equipment for producing coating materials.

[0112] The resulting aqueous polyurethane-polyurea dispersion is characterized in that the polyurethane-polyurea particles present in the dispersion have an average particle size (volume-based average diameter) of 50 nm to 500 nm, more preferably 50 to 300 nm, and most preferably 50 to 250 nm (measured via photon correlation spectroscopy as described in the Examples section).

[0113] Another aspect of the present invention is an aqueous polyurethane-polyurea dispersion comprising polyurethane-polyurea particles having a volume-based average diameter of 50 to 500 nm. The dispersion is further characterized by an MEQ base of 0.125 to 0.625 mmol / g (based on solids content). Furthermore, it is important that the production of the dispersion involves a neutralization step using at least one alkali metal hydroxide as a neutralizing agent.

[0114] The aqueous polyurethane-polyurea dispersion preferably has a gel fraction of at least 60%, more preferably at least 70%, and particularly preferably at least 80%. Thus, the gel fraction can be up to 100% or approximately 100%, such as, for example, 99% or 98%. In this case, the entire or nearly the entire polyurethane-polyurea polymer is present in the form of crosslinked particles.

[0115] Therefore, the dispersion is preferably a microgel dispersion, i.e., a polymer dispersion in which, on the one hand, the polymer is present in the form of relatively small particles or microparticles, and, on the other hand, the polymer particles are at least partially intramolecularly crosslinked. As is known, such microgel dispersions offer significant advantages with regard to various properties of coating materials, such as, for example, automotive coating compositions, such as pigmented automotive coating compositions. These properties include, for example, excellent optical and mechanical properties of cured coatings produced from such coating materials, on the one hand, and high solids content and good storage stability of aqueous coating materials, in particular pigmented coating materials such as basecoat materials, on the other hand.

[0116] The fraction of polyurethane-polyurea polymer in the aqueous dispersion is preferably 25 to 55 wt. %, preferably 30 to 50 wt. %, more preferably 35 to 45 wt. %, in each case based on the total amount of the aqueous dispersion. It is therefore obvious that the solids content of the aqueous dispersion is preferably 25 to 55 wt. %, preferably 30 to 50 wt. %, more preferably 35 to 45 wt. %. The fraction of water in the dispersion is preferably 40 to 70 wt. %, preferably 45 to 65 wt. %, more preferably 50 to 60 wt. %, in each case based on the total amount of the dispersion.

[0117] The aqueous dispersion preferably consists to an extent of at least 90 wt.-% of the polyurethane-polyurea polymer and water (calculated as the sum of the fraction of water and the solids content in the dispersion (in wt.-%)).

[0118] In some embodiments, the organic solvent content of the aqueous dispersion is very low and preferably lower than 10 wt %. Specifically, and as also noted above, this very low content of organic solvent can be achieved without requiring any final distillation process for removing this type of organic solvent. Therefore, the method of the present invention preferably does not include such a distillation step (although this situation is not excluded, of course). In addition, when carrying out such a distillation step, it is obvious that only a small fraction of the organic solvent needs to be removed during this step. Therefore, when carrying out the distillation step, the energy consumption and / or time consuming of this step are relatively low compared to those known in the prior art.

[0119] In a preferred embodiment, the process of the invention therefore does not comprise a distillation step, or the process of the invention comprises a distillation step in which the organic solvent is distilled to a fraction of not more than 5 wt.-% of the aqueous dispersion before distillation, whereby the process still produces an aqueous polyurethane-polyurea dispersion having an organic solvent content of less than 10 wt.-%.

[0120] The following examples illustrate the present invention.

[0121] Examples

[0122] 1. Solid content

[0123] Unless otherwise stated, the solids content (hereinafter also referred to as solids fraction) is determined in accordance with DIN EN ISO 3251 at 130°C, 60 min, initial mass 1.0 g. If an official standard is cited in the context of the present invention, this naturally means the edition of the standard in force on the date of submission, or, if no edition was in force on that date, the last in force.

[0124] 2. Isocyanate content

[0125] The isocyanate content, also referred to below as the NCO content, is determined by adding an excess of a 2% strength N,N-dibutylamine solution in xylene to a homogeneous solution of the sample in acetone / N-ethylpyrrolidone (1:1 vol%) and performing potentiometric back titration of the excess amine with 0.1 N hydrochloric acid in accordance with DIN EN ISO 3251, DIN EN ISO 11909, and DIN EN ISO 14896. The NCO content of the polymer (based on solids) can be calculated in turn from the fraction of polymer in solution (solids content).

[0126] 3. Hydroxyl value

[0127] The hydroxyl number was determined according to R.-P. Krüger, R. Gnauck and R. Algeier, Plaste und Kautschuk, 20, 274 (1982) by complete hydrolysis of the excess acetic anhydride remaining after acetylation with acetic anhydride in a tetrahydrofuran (THF) / dimethylformamide (DMF) solution in the presence of 4-dimethylaminopyridine as a catalyst at room temperature and potentiometric back titration with alcoholic potassium hydroxide against acetic acid. In all cases, an acetylation time of 60 minutes was sufficient to ensure complete conversion.

[0128] 4. Acid value

[0129] The acid number is determined in accordance with DIN EN ISO 2114 using ethanolic potassium hydroxide in a homogeneous solution of tetrahydrofuran (THF) / water (9 parts by volume THF and 1 part by volume distilled water). Based on the determined acid number, the MEQ acid (in meq / g solids content) can be calculated as "MEQ acid = acid number / 56.105."

[0130] 5. MEQ base

[0131] The MEQ base (in meq / g solids content) is determined in accordance with DIN EN ISO 15880 in a homogeneous solution of tetrahydrofuran (THF) / water (9 parts by volume of THF and 1 part by volume of distilled water) by neutralization with hydrochloric acid.

[0132] 6. Neutralization

[0133] The degree of neutralization of a component is calculated from the amount of carboxylic acid groups present in the component (determined via the acid number) and the amount of neutralizing groups (i.e. base) of the neutralizing agent used. The degree of neutralization can also be calculated as

[0134] "Neutralization degree = (MEQ alkali / MEQ acid) * 100%".

[0135] 7.Solvent content

[0136] The amount of organic solvent in the mixture (if not determined / determinable by weighting during the production of such mixture) was determined by gas chromatography (Agilent 7890A, 50 μm silica capillary column with polyethylene glycol phase or 50 μm silica capillary column with polydimethylsiloxane phase, helium carrier gas, 250°C split injector, 40°C-220°C oven temperature, flame ionization detector, 275°C detector temperature, n-propyl glycol as internal standard).

[0137] 8. Number average molecular weight

[0138] Unless otherwise stated, the number-average molar mass (M n ) was used to determine the experimental calibration constant of the instrument used by means of a vapor pressure osmometer (VPO) 10.00 (from Knauer) in toluene using a concentration series at 50° C. with benzophenone as calibration substance, according to the method of E. Schröder, G. Müller, KF Arndt, “Leitfaden der Polymercharakterisierung” [Principles of Polymer Characterization], Akademie-Verlag [Academy of Sciences Publishing House], Berlin, pp. 47-54, 1982.

[0139] 9. Granularity

[0140] Depending on the (expected) size, the particle size is determined by laser diffraction or photon correlation spectroscopy (PCS). The defining parameter for describing the particle size according to the present invention is the volume-based mean diameter (also referred to as "D[4.3] / De Broucker mean" in the context of laser diffraction). For the sake of completeness, additional parameters are also determined (see below).

[0141] Therefore, for all samples with a volume-based mean diameter of at least 600 nm measured by laser diffraction, this method was used to describe / define the particle size. For all samples with a volume-based mean diameter below 600 nm measured by laser diffraction, a further measurement of the volume-based mean diameter was performed via PCS, which means that this method was used to describe / define the particle size. The reason is that PCS is known to give reliable measurement results in the lower particle size range, while laser diffraction is considered to be optimal for the correspondingly higher particle size range.

[0142] 9.1 Laser Diffraction

[0143] The values ​​describing the particle size are determined by laser diffraction using a Mastersizer 2000 particle size measuring instrument (from Malvern Instruments) according to ISO 13220. The instrument operates with a red light source (maximum 4 mW He-Ne, 633 nm) and a blue light source (maximum 0.3 mW LED, 470 nm). In order to set a concentration range suitable for the measurement, the sample is diluted with particle-free deionized water (refractive index: 1.33) as a dispersion medium, and depending on each sample, the light shading is set between 3% and 15%, and the measurement is performed in a "Hydro 2000G" dispersion unit (from Malvern Instruments). In each case, six measurements are performed at stirring speeds of 2000 1 / min and 3000 1 / min, and the measurement is repeated on a second freshly prepared sample. The particle size measuring instrument is validated using particle size standards in the range of 0.2 to 190 μm. The calculation of the parameters describing the particle size was performed by the MIE approximation using Malvern Instruments software (version 5.60) (see below).

[0144] Determine the following values:

[0145] (D[2,3]) Arithmetic mean of the surface averages of the individual preparations (Sauter diameter)

[0146] (D[4.3]) Arithmetic mean of the volume averages of the individual preparations (De Broucker mean, volume-based mean diameter)

[0147] d(0.1) 10% of the total volume of particles has a diameter smaller than this value

[0148] d(0.5) 50% of the total volume of particles has a diameter smaller than this value

[0149] d(0.9) 90% of the total volume of particles has a diameter smaller than this value

[0150] 9.2.PCS

[0151] Specifically used for the measurement is a Malvern Nano S90 (from Malvern Instruments) at 25°C ± 1°C. The instrument is equipped with a 4 mW He-Ne laser at 633 nm. The sample (i.e., aqueous dispersion) is diluted with particle-free deionized water as the dispersion medium and then measured in a 1 ml polystyrene cell with a suitable scattering intensity. With the help of Zetasizer analysis software version 6.32 (from Malvern Instruments), a digital correlator is used for evaluation. The measurement is carried out five times and repeated on a second freshly prepared sample. The standard deviation of the 5 determinations is ≤ 4%. The maximum deviation of the mean diameter based on volume for the five individual measurements is ± 15%. The reported particle size is the arithmetic mean of the mean diameter based on volume measured for the individual preparations. Verification is performed using polystyrene standards with a certified particle size between 50 and 3000 nm.

[0152] 10. Gel Fraction

[0153] In the context of the present invention, the gel fraction of polyurethane-polyurea particles (microgel particles) present in an aqueous dispersion is determined gravimetrically. Here, the polymer present is first isolated from a sample of the aqueous dispersion (initial mass 1.0 g) by freeze drying. After determining the curing temperature—the temperature below which the sample's electrical resistance shows no further change when the temperature is further reduced—the completely frozen sample undergoes its main drying, typically within a drying vacuum pressure range of between 5 mbar and 0.05 mbar, at a drying temperature 10°C below the curing temperature. Rapid freeze drying of the polymer is achieved by gradually increasing the temperature of the heated surface beneath the polymer to 25°C. After a typical drying time of 12 hours, the amount of isolated polymer (solid fraction, determined by freeze drying) is constant and does not change even with prolonged freeze drying. Subsequently, drying is performed at a surface temperature below the polymer of 30°C, with the ambient pressure reduced to a maximum value (typically between 0.05 and 0.03 mbar) to achieve optimal drying of the polymer.

[0154] The isolated polymer was then sintered in a forced air oven at 130° C. for one minute and thereafter extracted in excess tetrahydrofuran at 25° C. for 24 hours (ratio of tetrahydrofuran to solid fraction = 300:1). The insoluble fraction (gel fraction) of the isolated polymer was then separated on a suitable glass frit, dried in a forced air oven at 50° C. for 4 hours, and then reweighed.

[0155] Furthermore, it was determined that the gel fraction of the microgel particles was independent of the sintering time at a sintering temperature of 130°C and sintering times between one and twenty minutes. Therefore, it can be ruled out that crosslinking reactions after the separation of the polymer solids further increase the gel fraction.

[0156] The gel fraction determined in this way according to the invention is also referred to as gel fraction (freeze drying).

[0157] In parallel, the gel fraction, also referred to below as gel fraction (130°C), was determined gravimetrically by isolating a polymer sample from an aqueous dispersion (initial mass 1.0 g) at 130°C for 60 minutes (solids content). The mass of the polymer was determined, after which the polymer was extracted in excess tetrahydrofuran at 25°C for 24 hours, similar to the procedure described above, after which the insoluble portion (gel fraction) was separated, dried, and reweighed.

[0158] Example P1 Preparation of polyurethane prepolymer (a) and organic phase (I)

[0159] In a reaction vessel equipped with a stirrer, an internal thermometer, a reflux condenser and electric heating, 6110.6 parts by weight of linear polyester polyol and 289.9 parts by weight of dimethylol propionic acid (from GEO Specialty Chemicals) were dissolved in 650.0 parts by weight of methyl isobutyl ketone (from BASF AG) and 650.0 parts by weight of dipropylene glycol dimethyl ether (Proglyme ® , from BASF AG). Linear polyester diols are pre-dimerized with dimeric fatty acids (Radiacid ®0971 (from Olian), isophthalic acid (from BP Chemicals), and hexane-1,6-diol (from BASF AG) (starting materials: weight ratio of dimer fatty acid to isophthalic acid to hexane-1,6-diol = 54.32:16.08:29.60), and having a hydroxyl number of 75 mg KOH / g, based on the solids content, a water content according to Karl-Fischer of 0.02 wt.-%, an acid number of 3.5 mg KOH / g, based on the solids content, a calculated number-average molar mass of 1418 g / mol, and a number-average molar mass of 1390 g / mol, as determined by vapor pressure osmometry. To the resulting solution, 2269.9 parts by weight of dicyclohexylmethane 4,4′-diisocyanate (Desmodur®) with an isocyanate content of 32.0 wt.-% were added continuously at 30° C. ® W, from Bayer MaterialScience), and 10.4 parts by weight of dibutyltin dilaurate (from Merck). The mixture was then heated to 80°C with stirring. Stirring was continued at this temperature until the isocyanate content of the solution remained constant at 2.00% by weight.

[0160] Once it was determined that the isocyanate level was constant, the polyurethane prepolymer and the corresponding organic phase (I) were kept at 82°C under nitrogen and processed further over a period of 12 hours. During this time, the isocyanate level and viscosity remained constant.

[0161] The characteristics of the prepolymer / organic phase (I) are as follows:

[0162] Solid content (130°C, 60 min, 1 g): 87.1 wt.-%

[0163] NCO content (reactor) 2.00 wt.-%

[0164] Dipropylene glycol dimethyl ether content (GC): 6.5 wt.-%

[0165] Methyl isobutyl ketone content (GC): 6.4 wt.-%

[0166] Viscosity (80°C, rotational viscometer, shear rate = 10 / s): 17.6 Pa . s

[0167] Acid value (solids basis) 17.1 mg KOH / g

[0168] Number average molecular weight (VPO) 3500 g / mol

[0169] Example D1 Preparation of aqueous polyurethane-polyurea dispersion

[0170] The organic phase (I) P1 was loaded into a feed tank at 82°C under a nitrogen overpressure of 5.5 bar and then continuously fed into a high-shear dispersion device comprising a rotor / stator unit via a gear pump at a mass flow rate of 7.671 kg / hour through a stainless steel pipeline. The transfer line was insulated and heated to 82°C. In a second feed tank, an aqueous phase (II) consisting of a 0.639 wt.% sodium hydroxide (Merck) solution in deionized water was provided at 5°C and continuously fed into the high-shear dispersion device comprising a rotor / stator unit through a separate pipeline using an eccentric screw pump at a mass flow rate of 8.284 kg / hour. Both doses were stopped after 23 minutes and 28 seconds. At this point, 3000.0 g of the organic phase (I) and 3239.9 g of the aqueous phase (II) were supplied. During the entire process, the mass flow rates of the two phases as described above ensured a neutralization degree of 65% (first neutralization step).

[0171] The two flows are supplied in parallel (ie simultaneously) and then combined within the rotor / stator unit rather than before reaching the rotor / stator unit. More precisely, mainly as Figure 1 As shown, the two flows and therefore the phases are combined in the stator subunit. Thus, the aqueous phase (II) is supplied via a centrally positioned first inlet (13) and the organic phase (I) is fed in the form of a plurality of sub-feed streams via a plurality of second inlets (14). The high shear dispersing device is based on a Cavitron CD 1010 rotor / stator distributor from Hagen & Funke. In the setup of this example, the cylindrical stator subunit with a central inlet (13) further has 24 bores (i.e. a plurality of inlets (14)) with an inner diameter of 2 mm, which are arranged in the form of a circle and have a uniform distance from each other. The stator subunit is equipped with three stator tooth sets (11) (inner diameter: I - 35.2 mm, II - 52.5 mm, III - 63.5 mm) with a different number of teeth (12) (I - 24, II - 34, III - 160), whereby the bores are positioned as shown. Figure 1 Between the two stator tooth groups shown (i.e. between the group with the smallest diameter and the group with the medium diameter). The cylindrical rotor subunit is equipped with four rotor tooth groups (21) with different numbers of teeth (22) (I - 12, II - 28, III - 70, IV - 160). The rotor tooth groups are positioned alternately with the stator tooth groups, generally as Figure 3 shown, and can rotate at a maximum speed of 12,000 rpm.

[0172] The highly viscous organic-based phase (I) and the low-viscosity aqueous phase are dispersed intensively under high shear by passing through an inlet and then through the grooves between the teeth of the partially rotating tooth sets of the stator and rotor. The resulting dispersion is discharged from an outlet located outside the outermost rotor tooth set. To reduce the temperature of the discharged dispersion, the rotor / stator unit is fully jacketed and internally cooled, resulting in a temperature of approximately 55°C.

[0173] Chain extension was accomplished via a T-junction injector. The aqueous dispersion exiting the high-shear dispersing device was continuously passed through a corresponding piping system connected to one arm of the T-junction, while the chain extender was continuously fed via the second arm of the T-junction. More specifically, the chain extender was continuously fed as an aqueous solution (8.0 wt.-% diethylenetriamine in deionized water) using a double-piston pump at a mass flow rate of 0.971 kg / hour (again for a duration of 23 minutes 28 seconds, meaning a total supply of 379.7 g of aqueous amine solution). Downstream of the T-junction, a static mixer was used to effectively mix the polyurethane dispersion with the chain-extending amine. During the entire process, the mass flows of the aqueous dispersion exiting the high-shear dispersing device and the diethylenetriamine solution ensured a molar ratio of 1.62:1 between the isocyanate groups of the polyurethane-based dispersion (calculated as those contained in the prepolymer of the organic phase (I)) and the sum of the primary and secondary amino groups of the chain extender (calculated based on the corresponding diethylenetriamine concentration in the aqueous solution). The duration (residence time) between the point in time when the aqueous dispersion leaves the high shear dispersing device and the point in time when the chain extender is fed / added is calculated to be 6.7 s.

[0174] In the following, the different relevant parameters of the above-described process are summarized again. In addition, the characteristics of the produced aqueous polyurethane-polyurea dispersion D1 are listed.

[0175] Mass flow rate of organic phase (I) 7.671 kg / h

[0176] The mass flow rate of the aqueous phase (II) is 8.284 kg / h

[0177] The mass flow rate of the chain extender aqueous solution is 0.971 kg / hour

[0178] Mass flow rate of polyurethane-polyurea dispersion (total) 16.926 kg / hour

[0179] The inner diameter of the outlet pipe from the high shear dispersing unit to the injection point of the chain extender (T-joint) is 12 mm.

[0180] The distance from the high shear dispersing device to the chain extender addition point (T-joint) is 27.4 cm

[0181] Density of the aqueous dispersion discharged from the high shear dispersing device (60°C) 1.024 g / cm 3

[0182] Dwell time 6.7 s

[0183] Rotor speed 12000 rpm

[0184] The temperature of the organic phase (I) at the inlet of the high shear dispersing device was 82°C.

[0185] The temperature of the aqueous dispersion discharged from the high shear dispersing device when it reaches the T-junction is 54°C

[0186] Solid content (130°C, 60 min, 1 g): 40.2 wt.-%

[0187] Dipropylene glycol dimethyl ether (GC): 3.0 wt.-%

[0188] Methyl isobutyl ketone-Gehalt (GC): 2.9 wt.-%

[0189] Viscosity (23°C, original, rotational viscometer, shear rate = 1000 / s): 16 mPa . s

[0190] Acid value 17.6 mg KOH / g

[0191] Solid content

[0192] MEQ base 0.257 mmol / g

[0193] Solid content

[0194] Neutralization degree 82%

[0195] pH (23°C) 7.7

[0196] Particle size parameters (photon correlation spectroscopy):

[0197] Volume average particle size (i.e., volume-based average diameter) 181 nm

[0198] z-average particle size 177 nm

[0199] Gel fraction (130°C) 98.8 wt.-%

[0200] Gel fraction (freeze-dried) 98.5 wt.-%

[0201] The produced aqueous polyurethane-polyurea dispersion D1 has excellent storage stability. This dispersion is very suitable for use, for example, in basecoat compositions, such as automotive basecoat compositions. Therefore, this dispersion can be readily used to provide basecoat compositions and also multi-coat paint systems comprising basecoat films produced using such basecoat compositions. Specifically, this dispersion leads to significantly improved yellowing behavior (i.e., coatings, such as multi-coat paint systems, comprising coatings based on aqueous basecoat compositions containing this dispersion exhibit a very low tendency towards continuous yellowing, ultimately leading to an improved level of optical quality).

[0202] Example D2 Preparation of Waterborne Polyurethane-Polyurea Dispersion

[0203] As in Example D1, the preparation of aqueous polyurethane-polyurea dispersion D2 again involved the same overall general procedure as Example D1 with regard to the nature of the high shear dispersing apparatus. The deviations specifically consisted in the choice of neutralizing agent.

[0204] More specifically, the organic phase (I) P1 was loaded into a feed tank at 82°C under a nitrogen overpressure of 5.5 bar and then continuously fed to a high-shear dispersion device including a rotor / stator unit via a gear pump through a stainless steel pipeline at a mass flow rate of 7.004 kg / hour. The transfer line was insulated and heated to 82°C. In a second feed tank, an aqueous phase (II) consisting of a 0.383 wt.% lithium hydroxide (from Merck) solution in deionized water was provided at 5°C and continuously fed to the high-shear dispersion device including a rotor / stator unit through a separate pipeline using an eccentric screw pump at a mass flow rate of 7.554 kg / hour. Both doses were stopped after 25 minutes and 42 seconds. At this point, 3000.0 g of organic phase (I) and 3235.9 g of aqueous phase (II) were supplied. During the entire process, the mass flow rates of the two phases as described above ensured a neutralization degree of 65% (first neutralization step).

[0205] The two streams were supplied, combined and dispersed as described in Example D1. In order to reduce the temperature of the exiting dispersion, the rotor / stator unit was again fully jacketed and internally cooled.

[0206] Chain extension was also accomplished via a T-junction syringe. The aqueous dispersion discharged from the high-shear dispersing device was continuously fed through a corresponding piping system connected to one arm of the T-junction, while the chain extender was continuously fed via the second arm of the T-junction. More specifically, the chain extender was continuously fed as an aqueous solution (8.0 wt.-% diethylenetriamine in deionized water) using a double-piston pump at a mass flow rate of 0.887 kg / hour (for a duration of 25 minutes and 42 seconds, meaning a total supply of 379.7 g of aqueous amine solution). Downstream of the T-junction, a static mixer was again used to effectively mix the polyurethane dispersion with the chain-extending amine. The molar ratio of the isocyanate groups of the polyurethane-based dispersion (calculated as the isocyanate groups contained in the prepolymer of the organic phase (I)) to the sum of the primary and secondary amino groups of the chain extender (calculated based on the corresponding diethylenetriamine concentration in the aqueous solution) was again maintained at 1.62:1. The duration (residence time) between the point in time when the aqueous dispersion leaves the high shear dispersing device and the point in time when the chain extender is fed / added is calculated to be 7.4 s.

[0207] The continuously produced aqueous polyurethane-polyurea dispersion was collected in a collection vessel and cooled to 23° C. 32.4 g of a 10 wt.% lithium hydroxide solution in deionized water were added with stirring to give a degree of neutralization of 82% (second neutralization step). A white, stable, solids-rich, low-viscosity dispersion containing crosslinked particles was obtained that showed no sedimentation over a 12-month period.

[0208] In the following, the different relevant parameters of the above-described process are summarized again. In addition, the characteristics of the produced aqueous polyurethane-polyurea dispersion D2 are listed.

[0209] Mass flow rate of organic phase (I) 7.004 kg / h

[0210] The mass flow rate of the aqueous phase (II) is 7.554 kg / h

[0211] The mass flow rate of the chain extender aqueous solution is 0.887 kg / hour

[0212] Mass flow rate of polyurethane-polyurea dispersion (total) 15.445 kg / hour

[0213] The inner diameter of the outlet pipe from the high shear dispersing unit to the injection point of the chain extender (T-joint) is 12 mm.

[0214] The distance from the high shear dispersing device to the chain extender addition point (T-joint) is 27.4 cm

[0215] Density of the aqueous dispersion discharged from the high shear dispersing device (60°C) 1.024 g / cm3

[0216] Dwell time 7.4 s

[0217] Rotor speed 12000 rpm

[0218] The temperature of the organic phase (I) at the inlet of the high shear dispersing device was 82°C.

[0219] The temperature of the aqueous dispersion discharged from the high shear dispersing device when it reaches the T-junction is 55°C

[0220] Solid content (130°C, 60 min, 1 g): 40.0 wt.-%

[0221] Dipropylene glycol dimethyl ether (GC): 2.9 wt.-%

[0222] Methyl isobutyl ketone-Gehalt (GC): 2.9 wt.-%

[0223] Viscosity (23°C, original, rotational viscometer, shear rate = 1000 / s): 21 mPa . s

[0224] Acid value 18.5 mg KOH / g

[0225] Solid content

[0226] MEQ base 0.264 mmol / g

[0227] Solid content

[0228] Neutralization degree 80%

[0229] pH (23°C) 7.6

[0230] Particle size parameters (photon correlation spectroscopy):

[0231] Volume average particle size (i.e., volume-based average diameter) 174 nm

[0232] z-average particle size 178 nm

[0233] Gel fraction (130°C) 96.9 wt.-%

[0234] Gel fraction (freeze-dried) 96.0 wt.-%

[0235] The produced aqueous polyurethane-polyurea dispersion D2 has excellent storage stability. This dispersion is very suitable for use, for example, in basecoat compositions, such as automotive basecoat compositions. Therefore, this dispersion can be easily used to provide basecoat compositions and also multi-coat paint systems comprising basecoat films produced using such basecoat compositions. Specifically, this dispersion leads to significantly improved yellowing behavior (i.e., coatings, such as multi-coat paint systems, comprising coatings based on aqueous basecoat compositions containing this dispersion exhibit a very low tendency towards continuous yellowing, ultimately leading to an improved level of optical quality).

[0236] Example V1 Preparation of aqueous polyurethane-polyurea dispersion

[0237] As in Example D1, the preparation of aqueous polyurethane-polyurea dispersion V1 again involved the same general procedure as Example D1 with regard to the characteristics of the high shear dispersing apparatus (drilling, etc.). The deviations specifically consisted in the choice of neutralizing agent.

[0238] The organic phase (I), P1, was loaded into a feed tank at 82°C under a nitrogen overpressure of 5.0 bar and then continuously fed via a gear pump through stainless steel piping to a high-shear dispersing device comprising a rotor / stator unit at a mass flow rate of 7,600 kg / hour. The transfer line was insulated and heated to 82°C. In a second feed tank, an aqueous phase (II), consisting of a 2.056 wt.% solution of triethylamine (TEA) (from BASF SE) in deionized water, was provided at 5°C and continuously fed via a separate pipe to the high-shear dispersing device comprising a rotor / stator unit using an eccentric screw pump at a mass flow rate of 8.341 kg / hour. Both doses were stopped after 23 minutes and 41 seconds. At this point, 3000.0 g of the organic phase (I) and 3292.2 g of the aqueous phase (II) had been supplied. The mass flows of the two phases, as described above, ensured a neutralization degree of 84% throughout the entire process.

[0239] The two streams were supplied, combined and dispersed as described in Example D1. In order to reduce the temperature of the exiting dispersion, the rotor / stator unit was again fully jacketed and internally cooled.

[0240] Chain extension was again accomplished via a T-junction syringe. The aqueous dispersion exiting the high-shear dispersing device was continuously passed through a corresponding piping system connected to one arm of the T-junction, while the chain extender was continuously fed via the second arm of the T-junction. More specifically, the chain extender was continuously fed as an aqueous solution (8.0 wt.-% diethylenetriamine in deionized water) using a double-piston pump at a mass flow rate of 0.962 kg / hour (again for a duration of 23 minutes 41 seconds, meaning a total supply of 379.7 g of aqueous amine solution). Downstream of the T-junction, a static mixer was used to effectively mix the polyurethane dispersion with the chain-extending amine. During the entire process, the mass flows of the aqueous dispersion exiting the high-shear dispersing device and the diethylenetriamine solution ensured a molar ratio of 1.62:1 between the isocyanate groups of the polyurethane-based dispersion (calculated as the isocyanate groups contained in the prepolymer of the organic phase (I)) and the sum of the primary and secondary amino groups of the chain extender (calculated based on the corresponding diethylenetriamine concentration in the aqueous solution). The duration (residence time) between the point in time when the aqueous dispersion leaves the high shear dispersing device and the point in time when the chain extender is fed / added is calculated to be 6.8 s.

[0241] In the following, the different relevant parameters of the above methods are summarized again:

[0242] Mass flow rate of organic phase (I) 7.600 kg / h

[0243] The mass flow rate of the aqueous phase (II) is 8.341 kg / h

[0244] The mass flow rate of the chain extender aqueous solution is 0.962 kg / hour

[0245] Mass flow rate of polyurethane-polyurea dispersion (total) 16.903 kg / hour

[0246] The inner diameter of the outlet pipe from the high shear dispersing unit to the injection point of the chain extender (T-joint) is 12 mm.

[0247] The distance from the high shear dispersing device to the chain extender addition point (T-joint) is 27.4 cm

[0248] Density of the aqueous dispersion discharged from the high shear dispersing device (60°C) 1.024 g / cm 3

[0249] Dwell time 6.8 s

[0250] Rotor speed 12000 rpm

[0251] The temperature of the organic phase (I) at the inlet of the high shear dispersing device was 82°C.

[0252] The temperature of the aqueous dispersion discharged from the high shear dispersing device when it reaches the T-junction is 50°C

[0253] The continuously produced aqueous polyurethane-polyurea dispersion was collected in a collection vessel and cooled to 23° C. A white, stable, solids-rich, low-viscosity dispersion containing crosslinked particles was obtained and showed no sedimentation over a period of 6 months.

[0254] The characteristics of the produced aqueous polyurethane-polyurea dispersion V1 are as follows:

[0255] Solid content (130°C, 60 min, 1 g): 40.1 wt.-%

[0256] Dipropylene glycol dimethyl ether (GC): 3.0 wt.-%

[0257] Methyl isobutyl ketone-Gehalt (GC): 2.9 wt.-%

[0258] Viscosity (23°C, original, rotational viscometer, shear rate = 1000 / s): 39 mPa . s

[0259] Acid value 17.1 mg KOH / g

[0260] Solid content

[0261] MEQ base 0.256 mmol / g

[0262] Solid content

[0263] Neutralization degree 84%

[0264] pH (23°C) 7.6

[0265] Particle size parameters (laser diffraction):

[0266] d (0,1)0.5 µm

[0267] D[3,2]0.7 µm

[0268] d (0,5)0.8 µm

[0269] D[4,3] (i.e., volume-based average diameter) 1.1 µm

[0270] d (0,9)1.5 µm

[0271] Gel fraction (130°C) 88.9 wt.-%

[0272] Gel fraction (freeze-dried) 87.3 wt.-%

[0273] Example V2 Preparation of aqueous polyurethane-polyurea dispersion

[0274] As in Example D1, the preparation of aqueous polyurethane-polyurea dispersion V2 again involved the same general procedure as Example D1 with regard to the characteristics of the high shear dispersing apparatus (drilling, etc.). The deviations specifically consisted in the choice of neutralizing agent.

[0275] More specifically, the organic phase (I) P1 was loaded into a feed tank at 82°C under a nitrogen overpressure of 5.0 bar and then continuously fed via a gear pump at a mass flow rate of 7.171 kg / hour through a stainless steel pipe into a high shear dispersing device comprising a rotor / stator unit. The transfer pipe was insulated and heated to 82°C.

[0276] In a second feed tank, an aqueous phase (II) consisting of a 2.197 wt.% solution of triethylenediamine TEDA (1,4-diazabicyclo[2.2.2]octane, from BASF SE) in deionized water was supplied at 5°C and continuously fed via a separate line into the high-shear dispersing device comprising a rotor / stator unit using an eccentric screw pump at a mass flow rate of 8,166 kg / hour. Both dosing steps were stopped after 25 minutes and 6 seconds. At this point, 3000.0 g of the organic phase (I) and 3416.3 g of the aqueous phase (II) were supplied. The mass flow rates of the two phases ensured a neutralization degree of 84% throughout the entire process.

[0277] The two streams were supplied, combined and dispersed as described in Example D1. In order to reduce the temperature of the exiting dispersion, the rotor / stator unit was again fully jacketed and internally cooled.

[0278] Chain extension was similarly accomplished, again via a T-junction syringe. The aqueous dispersion exiting the high-shear dispersing device was continuously passed through a corresponding piping system connected to one arm of the T-junction, while the chain extender was continuously fed via the second arm of the T-junction. More specifically, the chain extender was continuously fed as an aqueous solution (8.0 wt.-% diethylenetriamine in deionized water) using a double-piston pump at a mass flow rate of 0.908 kg / hour (again for a duration of 25 minutes and 6 seconds, meaning a total of 379.7 g of aqueous amine solution was supplied). Downstream of the T-junction, a static mixer was used to effectively mix the polyurethane dispersion with the chain-extending amine. During the entire process, the mass flows of the aqueous dispersion and the diethylenetriamine solution exiting the high-shear dispersing device ensured a molar ratio of isocyanate groups of the polyurethane-based dispersion (calculated as the isocyanate groups contained in the prepolymer of the organic phase (I)) to the sum of the primary and secondary amino groups of the chain extender (calculated from the corresponding diethylenetriamine concentration in the aqueous solution) of 1.62:1. The duration (residence time) between the time the aqueous dispersion exited the high-shear dispersing device and the time the chain extender was fed / added was calculated to be 7.0 s.

[0279] In the following, the different relevant parameters of the above methods are summarized again:

[0280] Mass flow rate of organic phase (I) 7.171 kg / h

[0281] The mass flow rate of the aqueous phase (II) is 8.166 kg / h

[0282] The mass flow rate of the chain extender aqueous solution is 0.908 kg / hour

[0283] Mass flow rate of polyurethane-polyurea dispersion (total) 16.245 kg / hour

[0284] The inner diameter of the outlet pipe from the high shear dispersing unit to the injection point of the chain extender (T-joint) is 12 mm.

[0285] The distance from the high shear dispersing device to the chain extender addition point (T-joint) is 27.4 cm

[0286] Density of the aqueous dispersion discharged from the high shear dispersing device (60°C) 1.024 g / cm 3

[0287] Dwell time 7.0 s

[0288] Rotor speed 12000 rpm

[0289] The temperature of the organic phase (I) at the inlet of the high shear dispersing device was 82°C.

[0290] The temperature of the aqueous dispersion discharged from the high shear dispersing device when it reaches the T-junction is 52°C

[0291] The continuously produced aqueous polyurethane-polyurea dispersion was collected in a collection vessel and cooled to 23° C. A white, stable, solids-rich, low-viscosity dispersion containing crosslinked particles was obtained and showed no sedimentation over a period of 6 months.

[0292] The characteristics of the produced aqueous polyurethane-polyurea dispersion V2 are as follows:

[0293] Solid content (130°C, 60 min, 1 g): 39.8 wt.-%

[0294] Dipropylene glycol dimethyl ether (GC): 2.9 wt.-%

[0295] Methyl isobutyl ketone-Gehalt (GC): 2.9 wt.-%

[0296] Viscosity (23°C, original, rotational viscometer, shear rate = 1000 / s): 14 mPa . s

[0297] Acid value 17.5 mg KOH / g

[0298] Solid content

[0299] MEQ base 0.259 mmol / g

[0300] Solid content

[0301] Neutralization degree 83%

[0302] pH (23°C) 7.4

[0303] Particle size parameters (photon correlation spectroscopy):

[0304] Volume average particle size (i.e., volume-based average diameter) 540 nm

[0305] z-average particle size 666 nm

[0306] Gel fraction (130°C) 90.3 wt.-%

[0307] Gel fraction (freeze-dried) 87.7 wt.-%

[0308] The dispersion prepared above was used to prepare base yellowing test compositions BYTC. These comprised the dispersion and thus the polyurethane-polyurea polymer, water and low amounts of Na-Li-Mg-silicate clay and polypropylene glycol.

[0309] First, a wet film of BYTC was applied to a glass plate or a white-primer-coated aluminum plate using a 150- or 250-micron doctor blade. The wet film was dried at 60°C for 10 minutes and baked at 160°C for 60 minutes (overbake test at 160°C). These unpigmented films were transparent and contained only the polymer from the dispersion, along with low levels of clay and polypropylene glycol.

[0310] The yellowness index (YI) of the baked film (one layer) on a glass plate was measured using a spectrophotometer in transmission mode. In the case of a white primer-coated Al plate, the b* value of the baked BYTC (two layers) was measured using a spectrophotometer in reflection mode and compared to a reference (V1) neutralized with triethylamine. Negative Δb* values ​​indicate a more bluish color, while positive values ​​represent a more yellowish color relative to the reference and indicate yellowing.

[0311] Table 1 summarizes the respective results and data.

[0312] Table 1

[0313]

[0314] 1 Contains 3.0 wt.-% Laponite in deionized water ® RD (from Byk) and 3.0 wt.-% polypropylene glycol 900 (from Pluriol ® P 900 C).

[0315] 2 Dry at 60°C for 10 min and bake at 160°C for 60 min.

[0316] 3 The yellowness index (YI) is calculated from spectrophotometric data and describes the change in color of the test sample from transparent or white to yellow. Baked paint systems were measured on glass plates using an Agilent UV-VIS spectrophotometer (Cary 5000). The tristimulus values ​​X, Y, and Z were determined in the spectral range from 700 to 400 nm. To avoid radiation losses due to dispersion at the detector, an integrating sphere (Ulbricht globe) (Labshere 110 nm from Varian) was used. The yellowness index (YI) was calculated according to ASTM E313-15 using the following equation:

[0317] YI = 100 * (C x X - C z Z) / Y

[0318] In the formula, Cx and Cz are coefficients for a viewing angle of 10° using the lighting technology CIE illuminant C and CIE illuminant D65. CIE illuminant C and D65 represent average daylight with a color temperature of approximately 6500K.

[0319] 4 CIE illuminant C represents average daylight with a color temperature of 6774K.

[0320] 5 CIE illuminant D65 represents average daylight with a color temperature of 6504K.

[0321] 6 On Al panels, a white, waterborne BASF primer FU200201 (Frozen white) was baked at a panel temperature of 160° C. for 20 min, and then a second layer based on the binder yellowing test composition BYTC with polymers from dispersions D1, D2, V1 and V2 was applied.

[0322] 7 Color data for a two-layer white primer surfacer (BASF Primer Frozen White FU200201) with a second layer based on the yellowing test composition BYTC was measured using a Byk Mac I spectrophotometer (from Byk Gardner GmbH). Illumination was D65 (observer angle 10°), A (observer angle 10°), and TL84 (observer angle 10°). Using this instrument, L*, a*, and b* values ​​were measured for the two films. Values ​​on the b* axis of the CIELAB color space, extending from blue to yellow, were recorded to characterize yellowing. Negative Δb* values ​​indicate a more bluish color, while positive values ​​represent a more yellowish color. A system with triethylamine-neutralized polyureaurethane dispersion V1 was used as a hue reference.

[0323] 8 CIE illuminant A represents a conventional incandescent lamp with a color temperature of 2856K.

[0324] 9 CIE illuminant TL84 represents European and Japanese commercial light sources (supermarket lights) with a color temperature of 4100K.

[0325] Compared to the amine-neutralized dispersions, the inventive dispersions D1 and D2 exhibit a significantly reduced yellowness index YI. In the case of amine neutralization, triethylenediamine exhibits slightly reduced yellowing compared to triethylamine.

Claims

1. An aqueous polyurethane-polyurea dispersion comprising polyurethane-polyurea particles having a volume-based average diameter of 50 to 500 nm, wherein the dispersion is further characterized by 0.125 to 0.625 meq / g (based on solids content) of MEQ base, whereby the production of the dispersion involves a neutralization step with at least one alkali metal hydroxide as a neutralizing agent.

2. The aqueous polyurethane-polyurea dispersion according to claim 1, wherein The MEQ base is 0.15 to 0.50 meq / g (based on solids content).

3. The aqueous polyurethane-polyurea dispersion according to claim 1 or 2, wherein The degree of neutralization of the aqueous polyurethane-polyurea dispersion is greater than 65%.

4. The aqueous polyurethane-polyurea dispersion according to any one of claims 1 to 3, wherein The dispersion consists to an extent of at least 90% by weight of polyurethane-polyurea polymer and water (calculated as the sum of the fraction of water and the solids content in the dispersion (in wt.-%)).

5. A process for the continuous production of an aqueous polyurethane-polyurea dispersion comprising polyurethane-polyurea particles having a volume-based average diameter of 50 to 500 nm, wherein the dispersion is further characterized in that the MEQ base is 0.125 to 0.625 meq / g (based on solids content), the process comprising the steps of: (1) providing an organic-based phase (I) comprising (a) at least one acid-functional polyurethane prepolymer containing isocyanate groups, and (b) 0 to 20% by weight, based on the total weight of the organic-based phase (I), of at least one organic solvent, (2) Providing aqueous phase (II) (3) continuously feeding both the organic-based phase (I) and the aqueous phase (II) into a high shear dispersing device comprising a rotor / stator unit, (3.1) wherein the organic-based phase (I) and the aqueous phase (II) are brought into contact within the rotor / stator unit rather than before reaching the rotor / stator unit, and (3.2) wherein the organic phase (I) is fed into the rotor / stator unit in the form of multiple sub-feed streams via multiple inlets, (4) continuously dispersing the organic-based phase (I) and the aqueous phase (II) in the rotor-stator unit, thereby producing an aqueous polyurethane-based dispersion, (5) continuously discharging the aqueous polyurethane-based dispersion from the high shear dispersing device, thereby generating a volume flow of the dispersion, and (6) feeding at least one chain extender into the aqueous polyurethane-based dispersion, thereby producing the aqueous polyurethane-polyurea dispersion, The neutralization step in which at least one alkali metal hydroxide is used as a neutralizing agent is carried out during the dispersion process according to steps (3) and (4) above.

6. The method according to claim 5, wherein: Two neutralization steps are carried out with at least one alkali metal hydroxide as neutralizing agent, wherein the first neutralization step is carried out during the dispersion process according to steps (3) and (4) and the second neutralization step is carried out after the dispersion process according to steps (3) and (4), wherein the degree of neutralization achieved during the first step is 50% to 70% and the degree of neutralization achieved in the second step is greater than 70% to 95% (as the sum of the first and second neutralizations).

7. The method according to claim 6, wherein: The first neutralization step is carried out at a temperature of 40 to 70°C and the second neutralization step is carried out at a temperature of 10 to 30°C.

8. The method according to any one of claims 5 to 7 or the dispersion according to any one of claims 1 to 4, wherein The chain extender is chosen from aliphatic, aromatic or araliphatic (mixed aliphatic-aromatic) polyamines comprising at least two primary and / or secondary amino groups, preferably triamines having a total of three amino groups chosen from primary and secondary amino groups.

9. The method according to any one of claims 5 to 8, wherein The duration between the point in time when the dispersion leaves the high shear dispersing device and the point in time when the chain extender is fed does not exceed 30 seconds.

10. The method according to any one of claims 5 to 9 or the dispersion according to any one of claims 1 to 4, wherein The polyurethane-polyurea particles in the produced aqueous polyurethane-polyurea dispersion are characterized by a gel fraction of at least 70%. 11 . A waterborne basecoat composition comprising a pigment and the waterborne polyurethane-polyurea dispersion according to claim 1 and / or the waterborne polyurethane-polyurea dispersion prepared according to claim 5 .

12. The waterborne basecoat composition of claim 11 further comprising a melamine resin and also at least one hydroxy-functional polymer that is different from the polymer present in the aqueous dispersion.

13. A method for producing a multi-coat paint system, wherein: (1) applying the water-based basecoat composition to a substrate, (2) forming a polymer film from the coating material applied in stage (1), (3) applying a clearcoat material to the resulting basecoat film, and then (4) curing the base paint film and the clear paint film together, The water-based basecoat material used in stage (1) is the basecoat composition according to claim 11 or 12.

14. A multi-coat paint system produced by the method according to claim 13.

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