Zinc oxide particle modified with phosphonocarboxylic acid and use of same

p0001The invention relates to nanoparticulate zinc oxide, which is coated with a phosphonocarboxylic acid, and the use of nanoparticulate zinc oxide.

p0002The importance of water-based binder systems as coating systems for industrial applications becomes increasingly larger. Reason for this is mainly legal obligations with regard to the environmental impact to be used coating and binder systems, such as the VOC directive. However, water-based systems often show any disadvantages versus the solvent-based systems, such as a low blocking resistance or long drying times, which greatly delay further processing or use of, for example, painted parts.

p0003Zinc oxide is already used for various purposes in water-based paints. Well known is its use as a white pigment. In wood coatings, ZnO is used, among other zinc salts as an additive to prevent the bleeding of tannins. It is also used in primers to metals as adhesion promoters. Zinc oxide particles are used having a diameter of more than 1 micron for these applications.

p0004Zinc oxide and other metal oxides are also used in paints to improve UV protection, solvent resistance and surface hardness. In<patcit id="pcit0001" dnum="WO2008049679A"><text>WO 2008/049679</text></patcit> is described on an organic solvent based, in order to achieve an improvement in the scratch resistance and the flexibility of the use of nanoparticles for coatings. <patcit id="pcit0002" dnum="US6342556B1"><text>US-B1-6342556</text></patcit> describes the use of ZnO particles having a diameter of 10 to 80 nm in water in combination with coatings for improved UV protection of wood.

p0005<patcit id="pcit0003" dnum="WO2005071002A"><text>WO 2005/071002</text></patcit> relates to the use of a dispersion containing ZnO having a BET surface of 10 to 200 m²/ G as a transparent UV protection in paints. In the ZnO particles described in this application is pyrogenically prepared particles which have dispersion in an average secondary particle size of less than 300 nm. Although these pyrogenic particles have a specific surface on the order of nanoparticulate zinc oxide, with them, however, can not establish a transparent layers. This in<patcit id="pcit0004" dnum="WO2005071002A"><text>WO 2005/071002</text></patcit> specified additive is therefore unsuitable for use in transparent lacquer systems.

p0006In <patcit id="pcit0005" dnum="WO2005071029A"><text>WO 2005/071029</text></patcit> Zinc oxide is used with a particle diameter less than 100 nm in order to improve the surface hardness and the scratch resistance of polyurethane (PUR) lacquers. <patcit id="pcit0006" dnum="WO2006023064A"><text>WO 2006/023064</text></patcit> relates to the use of ZnO dispersions in PUR binders for preparing scratch-resistant floor coatings. In<patcit id="pcit0007" dnum="WO2006023064A"><text>W02006 / 023064</text></patcit> the production of scratch-resistant wood protection coatings through the use of ZnO dispersions is described in acrylic binders.

p0007<patcit id="pcit0008" dnum="WO2006023064A"><text>WO 2006/023064</text></patcit> describes the use of 2 to 20% nanoscale zinc oxide in acrylate paints and coatings, for example to improve adhesion, Tanninbeständigkeit or corrosion resistance. Since the share of relatively expensive ZnO is more than 2%, the composition is economical for the area of ​​topcoats often difficult to enforce.<patcit id="pcit0009" dnum="WO2006023065A"><text>WO 2006/023065</text></patcit> relates to coating compositions, the microscale TiO₂contain pigments and nanoscale metal such as ZnO, wherein the nanoscale metal for a uniform spacing of TiO₂Pigments is to give the layer.

p0008<patcit id="pcit0010" dnum="WO2005119359A"><text>WO 2005/119359</text></patcit> and <patcit id="pcit0011" dnum="US20030180466A1"><text>US-A1-2003 / 0180466</text></patcit> describe film-forming compositions, the binder, nanoparticles, surfactant and a polymeric dispersant include, in order to improve the abrasion resistance of substrates coated therewith.

p0009<patcit id="pcit0012" dnum="WO2008064114A"><text>WO 2008/064114</text></patcit> relates to the use of ZnO-particles having a diameter of less than 1 micron in an acrylate hybrid lacquer to improve the solvent resistance, humidity resistance and UV resistance.

p0010In <patcit id="pcit0013" dnum="DE102007032189A1"><text>DE 102007032189 A1</text></patcit> A special, manufactured by sol-gel method in organic solvents described nanoscale ZnO which can be surface modified with Si-containing molecules. Thus obtained ZnO particle dispersions in organic solvents can be used as a catalyst to increase the rate of crosslinking, for example with 2-component PU paints. The disadvantage is in addition to the complicated production process, that the system can only be used for solvent-borne coatings and for 2K systems. The greatly shortened pot life is a further disadvantage, because the window of opportunity for further processing is significantly restricted.

p0011For the preparation of stable coating or binder dispersions containing ZnO, it is necessary that the ZnO particles having a charge of the same. Water-based binder systems, including coating compositions and latex dispersions, often consist of anionically stabilized particles. Many of these dispersions are adjusted to a pH of 7 to 9 The isoelectric point of ZnO is at a pH of about 9 to 9.5. Therefore, ZnO particles are with a pH of less than 9 remain positive and thus cationic. The adjustment of the pH of a ZnO dispersion above the isoelectric point, so as to obtain negatively charged particles, is not possible because of the amphoteric property of the zinc oxide since it is then dissolves.

p0012<patcit id="pcit0014" dnum="DE10163256A1"><text>DE 10163256 A1</text></patcit> discloses a zinc oxide which is surface modified with an oligo- or polyethylene glycol acid. The thus surface-modified zinc oxide can be dispersed in water. A disadvantage is the modification of the zinc oxide in a non-aqueous environment. To obtain an aqueous dispersion, the organic solvent must be removed and then the polyethylene glycol acid with an oligo-modified ZnO are redispersed in water first. The application of the dispersion is limited if the positive zeta potential.

p0013One possibility for the stabilization of ZnO is the shift of the isoelectric point towards lower pH-values. To this end, polyelectrolytes can be used. In<patcit id="pcit0015" dnum="WO9524359A"><text>WO 95/24359 A</text></patcit> the sodium salt of a polyacrylic acid is used as a grinding additive in the grinding of zinc oxide, for example. <nplcit id="ncit0001" npl-type="s"><text>E. Tang et. al., Appl. Surf. Sci., 252, 2006 5227-5232</text></nplcit> describe the use of a polymethacrylic acid having a molecular weight of less than 10,000 g / mol in water which is adjusted with NaOH to a pH of 5.0-5.5, for the stabilization of an aqueous zinc oxide dispersion. For the preparation of stable dispersions of nano-scale large amounts of polymethacrylic acid such as 10 to 50%, based on the nanoscale powder are required. In addition, there is a tendency for bridging at high solids contents.

p0014<patcit id="pcit0016" dnum="WO2007082155A"><text>WO 2007/082155</text></patcit> relates to the use of 2,3-dihydroxynaphthalene-6-sulfonic acid salts and Cathechin-3,5-disulfonates for the dispersion of zinc oxide in the presence of ethylene glycol, propylene glycol, glycerin or their monoethers. This also makes the isoelectric point is shifted to lower pH values. A disadvantage is that, strongly discolor the dispersions particularly under the influence of light or in the presence of transition metal ions, particularly iron ions, which greatly limits the application of the ZnO dispersion in paints.

p0015Another way to shift the isoelectric point to lower pH levels, is the envelope of the particles with a silica layer. SiO₂ has an isoelectric point of 2 and is negatively charged above this pH. <patcit id="pcit0017" dnum="DE10118309C2"><text>DE 10118309 C2</text></patcit> describes the preparation of an anionically stabilized aqueous dispersion of nanoparticulate zinc oxide and their use as vulcanization activator for the vulcanization of latex moldings. The negative charge is achieved on the particle by a coating with silicates. For this purpose, zinc oxide is dispersed at pH values ​​below the isoelectric point in water, and by adding alkali silicate solutions or water glass / base mixtures, so that ZnO is transhipped anionic. A disadvantage is the growth rate of silicates, which is to be controlled so that no larger agglomerates. By the alkali silicate introduced ions must then be removed from the dispersion to obtain a sufficient storage stability at economic levels.

p0016Phosphonates are used industrially in cooling water systems, desalination plants and in oil extraction, where they prevent the precipitation of salts. In the paper and textile industries, they are used as a stabilizer for peroxide bleaching, whereby metals are complexed, which otherwise inactivate the peroxide. 2-phosphono-1,2,4-butane tricarboxylic acid is used in the cooling and process water treatment as well as in the field of cleaning formulations as stone and corrosion inhibitor.

p0017<patcit id="pcit0018" dnum="EP0760387B1"><text>EP 0760387 B1</text></patcit> relates to an anticorrosive pigment of a Metallorganophosphonat. The pigments are prepared by reaction of organophosphonic acids or phosphonocarboxylic acids with appropriate polyvalent metal cations, such as oxides, hydroxides, carbonates, chlorides, nitrates or sulfates. When using oxides or hydroxides of a simple acid-base reaction takes place, whereby the oxides or hydroxides are converted into the corresponding phosphonate salts.

p0018There is therefore a need for additives for aqueous binder systems, such as coating systems that significantly reduces the drying time and the blocking resistance can be increased without deteriorating by the addition of large amounts of the overall profile of the binder system. In this case small amounts of less than 2 wt .-% already to achieve a significant effect, to not negatively affect the manufacturing costs and adversely affect the other properties of the binder system, in particular a varnish as little as possible.

p0019The object of the invention was to provide a material that the drying properties and the pore blocking water-based binder systems, especially coating systems improved.

p0020Surprisingly, it was found that in aqueous systems the binder by the use of ZnO nanoparticles, for example, raised as a powder or in form of a dispersion, the blocking resistance and the drying time is significantly reduced. The addition of the nanoscale ZnO particles to the aqueous binder system results in a surprisingly strong shortening of the drying time as well as a surprising improvement of the blocking resistance of the cured binder system, eg in a coated on a substrate and dried or cured coating as compared to coating materials which do not nanoscale ZnO particles.

p0021Although it is known that ZnO or Zn compounds catalyze the crosslinking of double bonds; However, it comes with the film formation process of aqueous dispersion paints or -bindemittelsystemen, especially at 1 K systems, not to a further cross-linking of, for example double bonds, but rather to a physical coalescence of the binder particles after removal of the liquid phase and, optionally, a temperature increase. Therefore, it was surprising that blocking resistance and drying time could be improved by the addition of nanoscale ZnO in the described systems.

p0022It has also been found that it is particularly advantageous if this nanoscale ZnO particles are used which are modified with a phosphonocarboxylic acid. The modified with phosphonocarboxylic nanoscale ZnO particles exhibit not only a greatly improved dispersibility in water, but also a very high compatibility with the dried paint films. This is demonstrated for example by increased transparency and haze of freedom of non-pigmented coating films that contain instead the conventional ZnO particles nanoscale ZnO particles modified with phosphonocarboxylic. Further advantages of the phosphonocarboxylic acid-modified nanoscale ZnO particles of the invention are the formation of a stable dispersion, and the possibility of ZnO dispersions to obtain smaller particles as compared to conventional ZnO dispersions.

p0023The present invention accordingly provides the use of nanoscale ZnO particles for improving the block resistance and / or for shortening the drying time of an aqueous binder system. The invention surface-modified nanoscale zinc oxide particles in which the zinc oxide particles with a phosphonocarboxylic acid, a salt of phosphonocarboxylic acid or a mixture thereof are surface-modified further relates. The invention is explained in detail below.

p0024The nanoscale ZnO particles are added as an additive to an aqueous binder system in order to shorten the drying time of the binder system and / or to increase the block resistance of the binder system. The drying time refers to the drying time of the aqueous binder system under given conditions, if correctly used, for example by applying an aqueous coating composition to a substrate and subsequent drying or curing. As known to those skilled is meant by the blocking resistance of the aqueous binder system, the following property of the dried or cured binder system. Under blocking the welding together of two coated articles under heat, pressure or humidity is to be understood. The blocking resistance is a measure of the blockage, which is evaluated on a scale of 0 to. 5 Here, the lower the value the lower the blockage. The Verblockungsprüfung carried out according to Directive 6 "blocking of paint systems on wood windows" (03/99) of the Institute for Window Technology eV, Rosenheim.

p0025The aqueous binder system to the nanoscale ZnO particles are added as an additive used according to the invention, it can be any conventional, known to those skilled aqueous binder system. Such water-based binder systems are commercially available. The binder system is water-based, ie a major proportion, eg at least 20 wt .-%, of the solvent used in the binder system is water. In the aqueous binder system may, as appropriate, organic solvent be contained, the binder system includes but usually less than 20 wt .-%, preferably less than 10 wt .-%, of organic solvents, based on the total weight of the binder system.

p0026The aqueous binder system comprises one or more organic or inorganic binder. This can be any customary for aqueous binder systems binder. Examples of suitable binders include polyester, polyester, polyester urethane acrylates, polyurethanes, here among others 1K systems and 2-component systems, pure acrylates, acrylate copolymers, in this case, among other acrylate-styrene copolymers, butyl acrylate-styrene copolymers, methyl methacrylate-butyl acrylate copolymers, acrylate -Vinylacetat copolymers, acrylate-polyurethane copolymers (hybrid polymers), acrylate-epoxy copolymers and aromatic epoxy acrylates, styrene-butadiene copolymers, polybutadienes, latex, epoxies, polyamides, polyimides, polyolefins, polychloroprene, phenolic resins, ethylene vinyl acetates, melamine-formaldehyde resins and silicones. As the aqueous binder system binder aqueous emulsions or dispersions of the aforementioned polymers or binders may be used.

p0027These known aqueous binder systems may preferably be used to form films or coating films, that is, the aqueous binder system is preferably a coating composition or a paint. Water-based paint systems are a particularly suitable application for the inventive use. These are suitable for the coating of optionally pre-coated substrates of all types, including paper, glass, metal, ceramics, wood, stone or plastic. The substrate may be in any form such as plate, sheet or as a surface of any desired article.

p0028Other possible applications of the binder systems are, for example as an adhesive or for sealing. A further application can find the aqueous binder systems as a traditional binder, for example in the textile industry, in the aqueous binder systems, inter alia in the production of so-called non-wovens, for example, nonwoven fabrics may be used. Here are, in simple terms, glued together textile fibers with a binder system to form a flat fabric. Aqueous binder systems are also used for non textile applications, such as fiber mats, such as rock wool, inter alia, for the isolation.

p0029The aqueous binder system may act as a water-based coating, an aqueous adhesive, an aqueous sealing compound or an aqueous binder therefore to produce an aqueous varnish is preferred. These binder systems may in addition to the binder and the solvent comprise further components which are commonly used in such aqueous binder systems, such as paints, adhesives, sealants or binders. The nanoscale ZnO particles can be added according to the use of the invention for coating, adhesive, sealant or to tie that already contain all the required components. The addition of the nanoscale ZnO particles and the respective optional additional components to the aqueous binder system, however, is arbitrary.

p0030The aqueous binder system may in addition to the binder and the solvent comprise further components which are commonly used in binder systems. Examples of such components that are suitable for aqueous binder systems, such as paints, adhesives, sealants or binders, in particular paints, are plasticizers, dyes, fillers, pigments and additives such as leveling agents, drying agents, antiskinning agents, curing accelerators, wetting agents and anti-settling agents. The aqueous coating may be transparent or colored, ie a varnish or a pigmented paint.

p0031The ZnO particles used are nanoscale. Nanoscale particles are customary in the art particle understood with an average particle diameter of less than 1 micron. The average particle diameter, also known as d₅₀designated value, here refers to the volume average particle diameter. The average particle diameter can be determined by a dynamic light scattering method, for example, with the measuring instrument Nanotrac Particle Size Analyzer from Microtrac Inc., USA. The average particle diameter or d₅₀Value results from the particle size distribution. The d₅₀Value is defined such that 50 volume percent of the particles have a diameter which is smaller than the D₅₀-Value. Correspondingly, 50 volume percent of the particles have a diameter which is larger than the d₅₀-Is worth. Analogously, the d₉₀Value or d₉₀Particle diameter is defined such that 90 volume percent of the particles have a diameter less than the d₉₀-Is worth.

p0032The average particle diameter or d₅₀Value of the nanoscale ZnO particles is below 1 micron and preferably no more than 500 nm, particularly preferably not more than 100 nm. The ZnO particles have nanoscale further preferably a d₉₀Particle diameter of not more than 500 nm, and particularly preferably not more than 200 nm.

p0033Nanoscale ZnO particles are known and are commercially available or can be prepared readily known to the skilled worker. The zinc oxide may, for example, by flame pyrolysis, are prepared via precipitation reactions or sol-gel reactions. The zinc oxide particles can be made of ZnO. However, the zinc oxide particles used herein include particles of zinc oxide containing a dopant in the crystal lattice, and doped zinc oxides, and particles having a core-shell structure, the surface or shell of zinc oxide, or particles of zinc oxide on the surface included. The ZnO particles may also be such as known in the art with suitable compounds, such as modifying agents, surfactants or stabilizers, surface-modified. Such surface-modified or stabilized nanoscale ZnO powder or nanoscale ZnO dispersions are conventional and commercially available.

p0034The nanoscale zinc oxide particles are added as an additive to the binder system to achieve the property improvements mentioned. The zinc oxide particles can be added as an additive in any form, for example as a powder or in the form of a dispersion of the ZnO particles in a liquid medium, for example water or an organic solvent such as an alcohol, or a mixture thereof, with an aqueous liquid medium is preferred. The preferred aqueous liquid medium may optionally also contain organic solvent, for example, less than 20 wt .-%, preferably less than 10 wt .-% and more preferably less than 5 wt .-%, based on the total weight of water and organic solvent in the aqueous dispersion. The addition of the nanoscale ZnO particles to the aqueous binder system can be done by simply pouring or pouring and mixing. Optionally, a dispersing process described below for better dispersion or homogenization are used.

p0035Provided that the ZnO particles are added in the form of a dispersion of the binder system, the amount of ZnO in the dispersion may vary within wide ranges. The content of ZnO nano-particles in the dispersion, preferably an aqueous dispersion, for example from 1 to 75 wt .-% can, preferably 5 to 70 wt .-% and in particular 15 to 65 wt .-%, based on the total weight of the aqueous dispersion.

p0036containing the ZnO particles or the ZnO particle dispersion to be added as an additive to the binder system, may also contain other, per se known adjuvants, to adjust other properties of the additive or of the binder system in a suitable manner as needed. Examples of such adjuvants are ethylene glycol and derivatives thereof, propylene glycol and derivatives thereof, glycerine and derivatives thereof, defoamers, leveling agents, thickeners, rheology additives, wetting agents, preservatives, and anticorrosion agents.

p0037To prepare the dispersion of the nanoscale ZnO particles in a liquid medium known dispersing or dispersing devices can be used, for example, rotor-stator systems, ultrasound or rolling mills. Such dispersion and suitable dispersing devices are for example in the<patcit id="pcit0019" dnum="WO2004069400A"><text>WO 2004/069400</text></patcit> (<patcit id="pcit0020" dnum="DE10304849A1"><text>DE 10304849 A1</text></patcit>), Which is incorporated by reference.

p0038The ZnO particles may, for example, with a dispersion in a liquid medium, preferably an aqueous medium are dispersed. Suitable dispersion devices such as mills, compounders, roll mills, nozzle jet dispersers, particularly homogenizers, turbomixer, mills with loose grinding media, especially stirred, Scherwalzenkneter, mortar mills, colloid mills and roll mills. Highly suitable mills, especially stirred, with very small grinding media, for example, grinding media with a diameter of not more than 2.5 mm, preferably not more than 1.5 mm and more preferably not more than 1.0 mm and not less than 0.005 mm, preferably not smaller than 0.02 mm, more preferably used is not less than 0.05 mm.

p0039By dispersing a grinding or crushing of the ZnO particles can be carried out so that the nanoscale ZnO particles of the desired size are only formed by the dispersing treatment. Therefore, used as starting materials ZnO particles can be greater than that obtained after the dispersion treatment.

p0040The proportion of nanoscale ZnO particles in the aqueous binder system may vary within wide ranges. The proportion of nanoscale ZnO particles in the aqueous binder system may for example in the range of 0.01 to 10 wt .-%, preferably 0.1 to 5 wt .-% and more preferably 0.1 to 2 wt .-%, based on the solids content of the aqueous binder system are.

p0041The addition of the nanoscale ZnO particles, preferably in the form of an aqueous dispersion, described above to the aqueous binder system performs as has been to increase the block resistance and to reduce the drying time of the binder system. Particularly good results were obtained when the zinc oxide particles particles were used which have been modified at the surface with phosphonocarboxylic acid. Surprisingly, it was observed when using modified with phosphonocarboxylic ZnO particles and a reduced turbidity, which is commonly observed in conventional ZnO particles. This is for example the case of transparent coatings and generally in all applications where the visual appearance is important, advantageous. In addition, more stable compared with conventional ZnO dispersions ZnO dispersions and, if necessary obtained with a smaller average particle diameter. The use of these modified phosphonocarboxylic ZnO particles is therefore preferred. Such modified with phosphonocarboxylic ZnO particles are not yet described in the prior art to date, and an aspect of the present invention. Therefore, they are explained in detail below.

p0042For the modified phosphonocarboxylic nanoscale ZnO particles all the information mentioned above apply equally, for example to the nanoscale ZnO particles, the nanoscale ZnO particles-containing dispersions, to their use and the aqueous binder systems, the proportion of nanoscale ZnO particles in the aqueous but binder system, etc. the ZnO-particles are further be modified or coated on the surface with phosphonocarboxylic acid, a salt of phosphonocarboxylic acid or a mixture thereof. The thus obtained modified ZnO particles are in this specification, sometimes simply referred to as modified with phosphonocarboxylic ZnO particles.

p0043Phosphonocarboxylic acids are known and are commercially available or can be prepared by known methods easily. All known phosphonocarboxylic acids or their salts are also suitable. The phosphonocarboxylic may include one or more phosphono (-PO (OH)₂), Wherein one or two phosphono groups are preferred. The phosphonocarboxylic acid may be one or more carboxyl groups (-COOH), wherein preferably at least 2 and particularly preferably 3 carboxyl groups are included. The phosphonocarboxylic acid may optionally contain additional functional groups, for example one or more hydroxy groups. It is preferable that the phosphonocarboxylic acid in an aliphatic carboxylic acid or an aliphatic hydroxycarboxylic acid, each of the at least one phosphono group and 1, 2, 3, 4 or more carboxyl groups, said carboxyl groups 2 and 3 in particular are preferred.

p0044Suitable examples of usable phosphonocarboxylic acids are Monophosphonocarbonsäuren of the general formula R¹R²C (PO₃H₂) (CO₂H) wherein R¹ and R² may be the same or different and are each selected from -H, -OH, -CH₃, -C₂H₅, -C₃H₇, -CH (CO₂H) -CH₂CO₂H and -CH₂- (CH₂)_nCO₂H wherein n is an integer from 0 to 18, and Diphosphonoalkancarbonsäuren of the general formula R³R⁴C (PO₃H₂)₂Wherein R³ and R⁴ may be the same or different and are each selected from -H, -OH, -CH₃, -C₂H₅, -C₃H₇, -CH (CO₂H) -CH₂CO₂H and -CH₂- (CH₂)_nCO₂H wherein n is an integer from 0 to 18, wherein at least one of the radicals R³ and R⁴ a group with at least one -CO₂H, and salts and Monophosphonocarbonsäuren Diphosphonoalkancarbonsäuren.

p0045Examples of specific suitable phosphonocarboxylic acids are phosphonoacetic acid, 2-carboxyethane, 2-hydroxy-2-phosphonoacetic acid, 2-phosphono-1,2,4-butanetricarboxylic acid (PBTC) and its salts. 2-phosphono-1,2,4-butanetricarboxylic acid and its salts are particularly preferred and are commercially available. For example, a 50% aqueous solution of 2-phosphono-1,2,4-butane tricarboxylic acid (Bayhibit^® AM) or the tetrasodium salt of 2-phosphono-1,2,4-butane tricarboxylic acid (Bayhibit^® sold S) from Lanxess AG.

p0046There may be a phosphonocarboxylic acid or a mixture of two or more phosphonocarboxylic acids are used for surface modification of the nanoscale ZnO particles. The phosphonocarboxylic acid or phosphonocarboxylic acids can also be used in form of their salts or preferably as a mixture of phosphonocarboxylic acid and a salt of phosphonocarboxylic acid.

p0047Since it is di- or polybasic acids at the phosphonocarboxylic acids, various salts are possible. It can for example be a salt in which all the acid groups are neutralized, or salt, in which only a part of the acid groups is neutralized. Preferably a mixture of phosphonocarboxylic acid and one or more salts is used by one or more conjugate bases of phosphonocarboxylic acid, wherein the ratio of phosphonocarboxylic acid and salt of phosphonocarboxylic acid is suitably such that 2% are neutralized to 75% of all the acid groups of the phosphonocarboxylic acid and in the form of conjugate base or as a salt, and corresponding to 98% to be 25% of all acid groups of the phosphonocarboxylic acid in the acid form.

p0048It may be a commercially available salt of a phosphonocarboxylic acid can be used. A salt may be formed from a phosphonocarboxylic by adding a suitable base also readily. In general, the neutralization is preferably carried out with the base thereof, in a solvent, for example in water, an organic solvent or a mixture thereof. Preferred is water or an aqueous liquid is used as solvent. The salt formed may be isolated, usually it is expedient to use the so-formed solution of the salt directly for the reaction with the nanoscale ZnO particles. It is also conceivable to mix the first nanoscale ZnO particles having the phosphonocarboxylic acid and then to add the base in a suitable amount.

p0049Suitable bases for preparing the salts are all standard, used in the art bases. It can be used, for example bases, include or form the bivalent or trivalent cations. Examples of such bases are CaO, Ca (OH)₂, Mg (OH)₂, Sr (OH)₂ and Ba (OH)₂, but bases are preferably used include the monovalent cations or form, said alkali metal and ammonium cations are especially preferred. Alkali metal cations are Li, Na, K, Rb and Cs cations. Suitable bases are, for example, NaOH, KOH, ammonia water, primary, secondary, tertiary amines, such as triethanolamine, and quaternary ammonium compounds such as tetramethylammonium hydroxide. Accordingly, the salts of phosphonocarboxylic acid may be salts with di- or trivalent cations, but they are preferably salts of phosphonocarboxylic acid with monovalent cations, more preferably alkali metal and ammonium salts, more preferably sodium, potassium or ammonium salts.

p0050As explained above, are preferably mixtures of phosphonocarboxylic acid and salts of phosphonocarboxylic acid used. To prepare phosphonocarboxylic and salt of phosphonocarboxylic acid can be mixed as starting materials in a suitable ratio. The mixture may also be obtained by adding an appropriate amount of base to a phosphonocarboxylic acid, so that the salt "in situ" is formed. One can also start from a salt of phosphonocarboxylic and form by adding an appropriate amount of acid, such as hydrochloric acid, sulfuric acid or acetic acid, the corresponding phosphonocarboxylic "in situ". The skilled worker may prepare such mixtures of phosphonocarboxylic and salts of phosphonocarboxylic the desired ratio readily.

p0051As already indicated 2-phosphono-1,2,4-butanetricarboxylic acid (PBTC), salts of the PBTC, and mixtures of PBTC and salts of PBTC particularly preferred for modification of the ZnO particles used. The salts of PBTC is preferably salts of monovalent cations, in particular alkali metal and ammonium salts, with Na, K and ammonium salts are particularly preferred.

p0052In the preferably used mixtures of PBTC and salts of PBTC with monovalent cations M⁺, Wherein M⁺ preferably alkali or ammonium, or the salts of PBTC is the molar ratio of M⁺PBTC for example in the range of 0.1: 1 to 4: 1, preferably in the range from 0.1: 1 to 3: 1 and most preferably from 0.1: 1 to 1.8: 1st Such mixtures can be obtained eg by reacting the corresponding bases with PBTC or by mixing and reacting with the PBCT Tetraalkali- or tetra ammonium salt of 2-phosphono-1,2,4-butane tricarboxylic acid.

p0053The exact mechanism of attachment of the phosphonocarboxylic acid or salts thereof, for the surface modification of ZnO particles with phosphonocarboxylic acid or salts thereof is not known in detail. Without wishing to be bound by theory, but believed that the phosphonocarboxylic or salt thereof on the phosphonate function, alone or together with a carboxylate function, a complex with surface groups on the ZnO particles forms. It could also be alternatively or additionally possible that zinc ions a complex with the phosphonocarboxylic or their salt forms, or vehicle is then coordinately bonded to the surface of the ZnO particles.

p0054The nanoscale ZnO particles which are modified on the surface with phosphonocarboxylic acid, a salt of phosphonocarboxylic acid or a mixture thereof, obtained by reaction of phosphonocarboxylic acid, a salt of phosphonocarboxylic acid or a mixture thereof with ZnO particles. The reaction can be carried out without a solvent, but is conveniently carried out in a solvent. As a solvent, the above-described liquid medium, preferably the aqueous liquid medium, may be used to prepare the dispersion of the ZnO particles, so reference is made to the local information. The order of mixing the components is arbitrary.

p0055The ratio of phosphonocarboxylic and Phosphonocarbonsäuresalz to ZnO particles can vary within wide ranges, but is as expediently in the range from 0.005 mmol to 10 mmol phosphonocarboxylic and Phosphonocarbonsäuresalz per g of zinc oxide, preferably in the range of 0.01 to 8 mmol phosphonocarboxylic and Phosphonocarbonsäuresalz per g zinc oxide, and more preferably from 0.05 to 1 mmol per g Phosphonocarbonsäuresalz phosphonocarboxylic acid and zinc oxide.

p0056In an expedient embodiment, for example, first phosphonocarboxylic a salt of a phosphonocarboxylic acid or a mixture of phosphonocarboxylic and salt of phosphonocarboxylic acid in the liquid medium presented as explained above, or formed. For this purpose, ZnO particles, either as a dispersion or, preferably, as a powder, was added. The mixture is then preferably subjected to a dispersing process.

p0057It can be used in the same way, the dispersion or dispersing the above-mentioned for the preparation of the dispersion of the nanoscale ZnO particles, so reference is made to the above details. The only difference is the additional use of Phosphonocarbonsäurekomponente. The modification of the ZnO particles by the phosphonocarboxylic acid, a salt of phosphonocarboxylic acid or a mixture thereof at the surface is generally carried out even at room temperature (20 ° C) and is supported by the dispersion treatment. The reaction can be carried out, if required, at higher temperatures.

p0058It is preferable for the dispersing of the ZnO particles in a liquid medium in the presence of the phosphonocarboxylic acid, a salt of phosphonocarboxylic acid or a mixture thereof in a mill, preferably an agitated ball mill, with very small grinding bodies, for example grinding media having a diameter of not more than 2.5 mm, more preferably not more than 1.5 mm and particularly preferably carry not more than 1.0 mm and not smaller than 0.005 mm, preferably not smaller than 0.02 mm, more preferably not less than 0.05 mm. In this way a very rapid dispersion and modification of the ZnO particles is simultaneously achieved and maintained an extremely stable dispersion.

p0059Since it can as explained above coming through the dispersion treatment also to a grinding or comminution of the ZnO particles, the ZnO-particles used as starting products can also have a larger average particle diameter than those obtained after the dispersion treatment with phosphonocarboxylic acid modified nanoscale ZnO particles. However, it is generally preferred to use nanoscale ZnO particles as starting materials.

p0060The dispersion obtained can be used as such. Surprisingly, this dispersion is largely clear, turbidity can not be found. By separation of the liquid medium by a conventional method such as centrifugation or evaporation, the phosphonocarboxylic acid with modified nanoscale ZnO particles can be obtained in powder form.

p0061As explained above, the phosphonocarboxylic acid with modified nanoscale ZnO particles can be used as a dispersion or as a powder, to increase the block resistance and / or for reducing the drying time of aqueous binder systems. You can also make the used for all applications for which it is known the use of nanoparticle zinc oxide. Thus, with phosphonocarboxylic acid modified nanoscale ZnO particles according to the invention, for example as a vulcanization activator for the vulcanization of latex moldings, as UV-protection, as a catalyst for the preparation of optical systems, for the production of electronic components or for changing optical or electronic properties use of substrates or bulk materials.

p0062The invention is illustrated hereinafter by examples, but are not to limit the scope of the present invention.

example 1

p0063397.49 g of 2-phosphono-1,2,4-butane tricarboxylic acid solution (Bayhibit AM, mass fraction 50%, Lanxess AG) were mixed with 29.55 g NaOH. There was obtained a solution having a pH value of 2.5. This was mixed with 2562.96 g H₂O and stirred. Subsequently, 2000 g ZnO (Zinc Oxide Microsun P99 / 30, Micronisers Pty Ltd) was added with stirring. The suspension was in an agitated ball mill (Drais PML-H / V) with zirconia milling media (YZT, Tosoh) having a diameter between 0.3-0.4 mm, milled in a continuous cycle 615 min. There was a zinc oxide dispersion obtained, which have an average particle diameter (d₅₀) Of 52 nm and a d₉₀Value (volume distribution) has in the particle size distribution of 93 nm. The dispersion was stable for several months.

example 2

p0064369.02 g of 2-phosphono-1,2,4-butane tricarboxylic acid solution (Bayhibit AM, mass fraction 50%, Lanxess AG) were mixed with 163.37 g of the tetrasodium salt of 2-phosphono-1,2,4-butane tricarboxylic acid ( Bayhibit S, Lanxess AG) are added. Thereafter, 4922 g of H₂O are then added and stirred until a solution was obtained. Subsequently, 5000 g ZnO (Zinc Oxide Microsun P99 / 30, Micronisers Pty Ltd) was added with stirring. The suspension was in an agitated ball mill (Drais PML-H / V) with zirconia milling media (YZT, Tosoh) having a diameter between 0.3-0.4 mm, milled in a continuous cycle 1035 min. There was a zinc oxide dispersion obtained, which have an average particle diameter (d₅₀) Of 47 nm and a d₉₀Value (volume distribution) has in the particle size distribution of 88 nm. The dispersion was stable for several months.

example 3

p0065125.05 g of 2-phosphono-1,2,4-butane tricarboxylic acid solution (Bayhibit AM, mass fraction 50%, Lanxess AG) were mixed with 12.65 g KOH. Thereafter, 1216 g of H₂O are then added and stirred until a solution was obtained. Subsequently, 1250 g ZnO (Zinc Oxide Microsun P99 / 30, Micronisers Pty Ltd) was added with stirring. The suspension was in an agitated ball mill (Drais PML-H / V) with zirconium oxide grinding balls (YZT, Tosoh) having a diameter between 0.3-0.4 mm, milled in a continuous cycle 250 min. There was a zinc oxide dispersion obtained, which have an average particle diameter (d₅₀) Of 56 nm and a d₉₀Value (volume distribution) has in the particle size distribution of 100 nm. The dispersion was stable for several months.

example 4

p0066246 g of 2-phosphono-1,2,4-butane tricarboxylic acid solution (Bayhibit AM, mass fraction 50%, Lanxess AG) were mixed with 18.11 g NaOH. There was obtained a solution having a pH value of 2.5. This was 2230 g H₂O and stirred. Subsequently, 2500 g ZnO (Zinc Oxide Microsun P99 / 30, Micronisers Pty Ltd) was added with stirring. The suspension was in an agitated ball mill (Drais PML-H / V) pre-ground with zirconia milling media (YZT, Tosoh) having a diameter between 0.3-0.4 mm, in a continuous cycle 600 min. The dispersion in a stirred ball mill (MicroMedia MMP1, Buhler AG) with zirconia milling media (YZT, Tosoh) having a diameter between 0.1-0.2 mm, in a continuous cycle 100 min ground was. There was a zinc oxide dispersion obtained, which have an average particle diameter (d₅₀) Of 46 nm and a d₉₀Value (volume distribution) has in the particle size distribution of 76 nm. After storage of the dispersion at 40 ° C for 9 months changed the (d₅₀) 48 nm and d₉₀ Value at 80 nm, which is within the measurement uncertainty. At 70 ° C, the particle size distribution changed within 3 months on a d₉₀Value at 107 nm.

example 5

p0067For Example 5 Mixtures of additives and a paint formulation (see Table 1.) Were prepared on an acrylate basis, so that in the dried layer total of 0.9 wt .-% ZnO additive were included (s. Table 2 and Table 3 ). The ZnO dispersion used was modified with phosphonocarboxylic ZnO dispersion according to Example 1 and had a solids content of 40%. The to be tested paints were the one with a wet film thickness of 400 microns on plastic films (Leneta® transparencies, load of 2.5 kg mass piece), the other in three layers with a consumption of approx 100 g / m² on wood specimens applied (three-layer panels made of spruce, with load 7 kg mass piece). The test was carried out after a drying time of 2 days. The Verblockungsprüfung of lacquers prepared was carried out in accordance with Directive 6 "blocking of paint systems on wood windows" (03/99) of the Institute for Window Technology eV, Rosenheim. For comparison, the same mixture but was tested without ZnO additive.<tables id="tabl0001" num="0001"><table frame="all"><title>Table 1: composition of the paint formulation 1 used without ZnO additive</title><tgroup cols="3"><colspec colnum="1" colname="col1" colwidth="46mm" /><colspec colnum="2" colname="col2" colwidth="43mm" /><colspec colnum="3" colname="col3" colwidth="36mm" /><thead><row><entry valign="top">adding step</entry><entry valign="top">ingredient</entry><entry valign="top">Weight [g]</entry></row></thead><tbody><row><entry>1.</entry><entry>Primal AC-337 ER</entry><entry align="right">195.00</entry></row><row><entry>. 2</entry><entry>Tego Foamex 825</entry><entry align="right">0.60</entry></row><row><entry>. 3</entry><entry>water</entry><entry align="right">30,00</entry></row><row><entry>. 4</entry><entry>Texanol</entry><entry align="right">6.90</entry></row><row><entry>. 5</entry><entry>Ammonia soln 25%</entry><entry align="right">0.78</entry></row><row><entry>. 6</entry><entry>water</entry><entry align="right">60,00</entry></row><row><entry>. 7</entry><entry>Acrysol RM-12W</entry><entry align="right">2.01</entry></row><row><entry>8th.</entry><entry>water</entry><entry align="right">0.30</entry></row></tbody></tgroup></table></tables><tables id="tabl0002" num="0002"><table frame="all"><title>Table 2: Results for the Verblockungstests on plastic film</title><tgroup cols="6"><colspec colnum="1" colname="col1" colwidth="10mm" /><colspec colnum="2" colname="col2" colwidth="22mm" /><colspec colnum="3" colname="col3" colwidth="15mm" /><colspec colnum="4" colname="col4" colwidth="41mm" /><colspec colnum="5" colname="col5" colwidth="38mm" /><colspec colnum="6" colname="col6" colwidth="41mm" /><thead><row><entry morerows="1" rowsep="1" valign="top">No.</entry><entry morerows="1" rowsep="1" valign="top">paint system</entry><entry morerows="1" rowsep="1" valign="top">additive</entry><entry morerows="1" rowsep="1" valign="top">Additive content (mass fraction in dry coat) /%</entry><entry namest="col5" nameend="col6" align="center" valign="top">Verblockungskennzahl</entry></row><row><entry colsep="0" valign="top">after moisture exposure</entry><entry colsep="0" valign="top">after exposure to heat</entry></row></thead><tbody><row><entry>1</entry><entry>1</entry><entry>ZnO</entry><entry>0.9</entry><entry align="center">1</entry><entry align="center">1-2</entry></row><row><entry>2</entry><entry>1</entry><entry>-</entry><entry>-</entry><entry align="center">2-3</entry><entry align="center">5</entry></row></tbody></tgroup></table></tables><tables id="tabl0003" num="0003"><table frame="all"><title>Table 3: Results for Verblockungstests on wood</title><tgroup cols="6"><colspec colnum="1" colname="col1" colwidth="10mm" /><colspec colnum="2" colname="col2" colwidth="22mm" /><colspec colnum="3" colname="col3" colwidth="15mm" /><colspec colnum="4" colname="col4" colwidth="39mm" /><colspec colnum="5" colname="col5" colwidth="39mm" /><colspec colnum="6" colname="col6" colwidth="42mm" /><thead><row><entry morerows="1" valign="top">No.</entry><entry morerows="1" valign="top">paint system</entry><entry morerows="1" valign="top">additive</entry><entry morerows="1" valign="top">Additive content (mass fraction in dry coat) /%</entry><entry namest="col5" nameend="col6" align="left" valign="top">Verblockungskennzahl</entry></row><row><entry valign="top">load by humidity</entry><entry valign="top">load by temperature</entry></row></thead><tbody><row><entry>3</entry><entry>1</entry><entry>ZnO</entry><entry align="center">0.9</entry><entry>2</entry><entry>2</entry></row><row><entry>4</entry><entry>1</entry><entry>-</entry><entry align="center">-</entry><entry>5</entry><entry>5</entry></row></tbody></tgroup></table></tables>

p0068The results in Table 2 and 3 show that the use of nanoscale ZnO particles in the examined varnish improves the blocking resistance. The indicator for blocking resistance on plastic film is improved after moisture exposure of 2-3 to 1 and the temperature load of 5 to 1-2. The results in Table 3 show that the code for blocking resistance after moisture exposure and after exposure to heat from 5 improved to 2 by the use of nano-ZnO particles.

example 6

p0069It (Table 4 s.) Mixtures of additives and a paint formulation based on acrylate prepared so that in the dried layer total of 0.9% ZnO additive were included (see. Table 4). The PBTC-ZnO dispersion prepared in Example 1 and had a solids content of 40% to. Further, commercially available nanoscale ZnO dispersions (Nanobyk^® 3840 Byk (ZnO-Byk) and Zano^® W-084 Umicore (Zano W-084)) used in the same concentration. As comparison, the same paint formulation was tested but without ZnO dispersion.

p0070The polymer dispersions with the additives added were homogenized and knife-coated onto glass plates with a wet film thickness of 100 microns was achieved. The wet films were dried at room temperature. The drying time to drying level 4 was determined to DIN 53150th The drying time up to the drying degree 4 (s. Table 4) is reduced through the use of ZnO of about 48 h to 20 h.<tables id="tabl0004" num="0004"><table frame="all"><title>Table 4: Results of the measurement of the drying time</title><tgroup cols="5"><colspec colnum="1" colname="col1" colwidth="10mm" /><colspec colnum="2" colname="col2" colwidth="22mm" /><colspec colnum="3" colname="col3" colwidth="22mm" /><colspec colnum="4" colname="col4" colwidth="55mm" /><colspec colnum="5" colname="col5" colwidth="58mm" /><thead><row><entry valign="top">No.</entry><entry valign="top">paint system</entry><entry valign="top">additive</entry><entry align="center" valign="top">Additive content (mass fraction in dry coat) /%</entry><entry align="center" valign="top">Drying time to drying level 4 / h</entry></row></thead><tbody><row><entry>5</entry><entry>1</entry><entry>ZnO PBTC</entry><entry align="center">0.9</entry><entry align="center">20 h</entry></row><row><entry>6</entry><entry>1</entry><entry>ZnO-Byk</entry><entry align="center">0.9</entry><entry align="center">20 h</entry></row><row><entry>7</entry><entry>1</entry><entry>Zano W-084</entry><entry align="center">0.9</entry><entry align="center">20 h</entry></row><row><entry>8th</entry><entry>1</entry><entry align="center">-</entry><entry align="center">-</entry><entry align="center">> 48 h</entry></row></tbody></tgroup></table></tables>

example 7

p0071222.47 g of 2-phosphono-1,2,4-butane tricarboxylic acid solution (Bayhibit AM, mass fraction 50%, Lanxess AG) were mixed with 22.03 g of the tetrasodium salt of 2-phosphono-1,2,4-butane tricarboxylic acid ( Bayhibit S, Lanxess AG), 34.10 g of triethanolamine and 2.50 g of sodium hydroxide. Thereafter, 3147.4 g H₂O are then added and stirred until a solution was obtained. Subsequently, 2571 g ZnO (30 Zano, Umicore) were added with stirring. The suspension was in an agitated ball mill (Drais PML-H / V) with zirconia milling media (YZT, Tosoh) having a diameter between 0.3-0.4 mm, pre-ground in a continuous cycle 280 min. The dispersion in a stirred ball mill (MicroMedia MMP1, Buhler AG) with zirconia milling media (YZT, Tosoh) having a diameter between 0.1-0.2 mm, milled in a continuous cycle 90 min. There was a zinc oxide dispersion obtained, which have an average particle diameter (d₅₀) Of 49 nm and a d₉₀Value (volume distribution) has in the particle size distribution of 89 nm.

example 8

p0072To 4300 g H₂O were added 625.34 g of 2-phosphono-1,2,4-butane tricarboxylic acid solution (Bayhibit AM, mass fraction 50%, Lanxess AG) and 46.41 g of sodium hydroxide. Then was stirred until a solution has formed so long. Then 5000 g ZnO (Activox R 50, Rockwood Pigments UK Durham) were added with stirring. The suspension was in an agitated ball mill (Drais PML-H / V) with zirconia milling media (YZT, Tosoh) having a diameter between 0.3-0.4 mm, pre-ground in a continuous cycle 47 min. The dispersion in a stirred ball mill (MicroMedia MMP1, Buhler AG) was milled with zirconia balls (YZT, Tosoh) having a diameter between 0.1-0.2 mm, in a continuous cycle 265 min. There was a zinc oxide dispersion obtained, which have an average particle diameter (d₅₀) Of 64 nm and a d₉₀Value (volume distribution) has in the particle size distribution of 98 nm.

example 9

p0073At 1300g H₂O were added 100,17g a 2-phosphono-1,2,4-butane tricarboxylic acid solution (Bayhibit AM, mass fraction 50%, Lanxess AG) and 67.71 g of a 25% tetramethylammonium. Subsequently, 1000 g ZnO (30 Zano, Umicore) were added with stirring. The suspension was in an agitated ball mill (Drais PML-H / V) with zirconia milling media (YZT, Tosoh) having a diameter between 0.3-0.4 mm, in a continuous cycle 360 ​​min ground. There was a zinc oxide dispersion obtained, which have an average particle diameter (d₅₀) Of 56 nm and a d₉₀Value (volume distribution) in the particle size distribution of 112 nm.

example 10

p0074To 1000 g of H₂O were added 36 g of phosphonoacetic acid (Sigma-Aldrich) and 8.08 g of sodium hydroxide. Subsequently, 1000 g ZnO (30 Zano, Umicore) were added with stirring. The suspension was in an agitated ball mill (Drais PML-H / V) with zirconia milling media (YZT, Tosoh) having a diameter between 0.3-0.4 mm, in a continuous cycle 160 min ground. There was a zinc oxide dispersion obtained, which have an average particle diameter (d₅₀) Of 70 nm and a d₉₀Value (volume distribution) in the particle size distribution of 166 nm.

example 11

p0075For measuring the UV / Vis transmission blends were prepared from an acrylate binder and ZnO different dispersions. For this purpose, the surface-modified ZnO dispersion of Example 2 and commercially available nanoscale ZnO dispersions (Nanobyk^® 3840 and Zano W-084) used. As a physically curing acrylate, a mixture of 200.3 g Revertex^® LS 1032-1 binder and 12.8 g Texanol used. The ZnO dispersions were mixed with the binder / Texanol mixture in the ratio shown in Table 5, applied with a doctor blade on glass plates and dried at room temperature. It layers were obtained having an average thickness of about 55 microns. The transmission was in the UV / Vis spectrometer (UV-2401 PC, Shimadzu) against a control sample which contained no zinc oxide, in the wavelength range of 350 - 800 nm measured.<tables id="tabl0005" num="0005"><table frame="all"><title>Table 5 Composition of the investigated layers.</title><tgroup cols="6"><colspec colnum="1" colname="col1" colwidth="27mm" /><colspec colnum="2" colname="col2" colwidth="28mm" /><colspec colnum="3" colname="col3" colwidth="28mm" /><colspec colnum="4" colname="col4" colwidth="29mm" /><colspec colnum="5" colname="col5" colwidth="28mm" /><colspec colnum="6" colname="col6" colwidth="28mm" /><thead><row><entry valign="top">ZnO</entry><entry valign="top">Volume acrylate (g)</entry><entry valign="top">Volume ZnO Dis dispersion (g)</entry><entry valign="top">Amount acrylate in dry film (%)</entry><entry valign="top">Volume ZnO in dry film em (%)</entry><entry valign="top">98% transmittance reached at (nm)</entry></row></thead><tbody><row><entry>according to Example 2</entry><entry>20.0</entry><entry>0.36</entry><entry>98.2</entry><entry>1.8</entry><entry align="center">589</entry></row><row><entry>Zano W-084</entry><entry>20.0</entry><entry>0.35</entry><entry>98.2</entry><entry>1.8</entry><entry align="center">619</entry></row><row><entry>Nanobyk 3840</entry><entry>20.0</entry><entry>0.43</entry><entry>98.2</entry><entry>1.8</entry><entry>less 98% in the area under investigation wavelengths</entry></row></tbody></tgroup></table></tables>

p0076Here, it was found that according to Example 2, a 98% transmission was obtained at a wavelength of 589 nm with the surface-modified ZnO invention. In comparison, it was found that the sample with Zano W-084 achieved a transmittance of 98% only at a wavelength of 619 nm. The comparative sample with Nanobyk 3840 showed no transmission of over 98% in the studied wavelength range.