EP1776412A1

EP1776412A1 - Hardening accelerator

Info

Publication number: EP1776412A1
Application number: EP05775134A
Authority: EP
Inventors: Adalbert Huber; Marc Entenmann; Alfred Hennemann; Matthias Koch
Original assignee: Merck Patent GmbH
Current assignee: Merck Patent GmbH
Priority date: 2004-08-12
Filing date: 2005-08-08
Publication date: 2007-04-25
Also published as: US9114983B2; US20090288581A1; TW200621865A; WO2006018169A1; DE102004039358A1

Abstract

The invention relates to nanoparticulate hardening accelerators, preparations produced therefrom, especially master batches containing nanoparticles, and the use thereof in polymer matrices, particularly all types of lacquers and printing inks which have to meet very strict requirements regarding the neutrality or transparency of the colors.

Description

hardening accelerator

The present invention relates to nanoparticulate curing accelerators, preparations prepared therefrom, in particular masterbatches containing nanoparticles and their use in polymer matrices, in particular paints and printing inks of all kinds, which place the highest demands on color neutrality or transparency.

Nanopartite doped compounds, in particular doping of tin oxides with antimony and / or indium play a role in many applications in which the outstanding physical properties such as electrical conductivity, thermal conductivity, absorption of long-wave and very short-wave radiation must be combined with transparency and color neutrality in the visual Light range at low application concentration.

Crucial to the extent to which these properties, however, come into effect in the respective matrix, is the actual separation of the particles as nanoparticles in the active matrix. This singulation is essentially dependent on the design of the surface of the nanoparticles, since these decide on the interaction, the wetting, the flocculation stability and thus the effectiveness in the application matrix. This surface must be produced during the production of the nanoparticles and thus depends on the manufacturing process. In the case of nanoparticles, consequently, the material structure, the doping, the

Incorporation of impurities essentially a question of the manufacturing process.

In the most common methods for producing doped tin oxide nanoparticles, the nanoparticle is produced either by solvolysis or by electrochemical means. The surface of the particles is modified in situ, stabilizing the particle and adapting it to the application matrix. However, it is disadvantageous that in these processes it can not be ruled out entirely that some of these inclusions of surface modifying agents can be incorporated into the nanoparticles themselves, or to incompatibility with the matrix, comes. This often reduces the applicability of the doped, in particular tin oxide-based, nanoparticles thus produced. Furthermore, these methods are often difficult to ascertain and are not economical for the quantities needed in the paint area.

The object of the present invention is to provide nanoparticulate semiconductor materials which do not have the abovementioned disadvantages.

Surprisingly, it has now been found that the surface of nanoparticulate semiconductor materials can be favorably influenced if coarser-particle precursors serve as the basis for the preparation of nanoparticles. The advantages are, in particular, the achievable high purity of the surface, especially if the stabilization of the nanoparticles does not take place as usual with dispersing additives, but rather electrostatically in aqueous media via the setting of a zeta potential which is sufficient in terms of magnitude. Preferably, the zeta potential is> 30 mV, in particular> 60 mV.

The present invention thus nanoparticulate semiconductor materials prepared by coarse-particle precursors, in the particle size range of 0.1 to 50 microns, in the aqueous medium at a pH of 6-11, ground.

The nanoparticles produced in this way are characterized by their high purity, their absence of foreign substances and their high absorption in the IR range.

The invention furthermore relates to the use of the nanoparticulate semiconductor materials according to the invention for the IR curing of polymer matrices, in particular in the field of lacquers and printing inks, and to the use of the nanoparticulate semiconductor materials in polymer masterbatches and polymer preparations.

Suitable precursors having particle sizes of from 0.1 to 50 μm, preferably from 0.5 to 20 μm and in particular from 1 to 10 μm, are used of mechanical energy in aqueous media, preferably water or water-miscible organic solvents, such as methanol, ethanol, diols, triols, at a pH of 6-11, crushed. Semiconductor materials produced in this way are characterized by being very stable and having a very pure surface and composition. Nanoparticles prepared in this way can be dried after the milling or they are added in solution to the aqueous application systems. It is also possible to add additives, in particular thickeners, wetting agents, dispersing aids and other additives, during or after the grinding process in order to increase the compatibility with different matrices. The additives may be polymeric, oligomeric and monomeric additives. These preparations consisting of nanoparticles, additives and optionally water or water / solvent mixture can thus be both solid and liquid preparations.

The present invention also relates to preparations containing nanoparticles, additives and optionally water or a water / solvent mixture. These preparations can be used for example in matrix polymers, such as. As polymer masterbatches and find in polymer preparations application.

When incorporating the nanoparticles into nonaqueous systems, the nanoparticles are previously stripped of the aqueous medium, e.g. by drying or slow evaporation using strong mechanical shear. Subsequently, the dry or dried nanoparticles are introduced into a matrix polymer melt using high shear energies. Additives of excipients which facilitate the homogeneous incorporation of the nanoparticles into the polymer melt, e.g. amphiphilic nonionic copolymers, e.g. Polyether-based polymer systems often facilitate the transfer of the nanoparticles into the corresponding melt of the matrix polymer.

Often, the electrostatically stabilized, aqueous dispersion can be added directly into the polymer melt using an extruder by the action of high shear forces. If necessary, you can - A -

Additives are added. In this way, it is possible to produce masterbatches or polymer preparations which contain the nanoparticles according to the invention in concentrations of up to 30%, preferably 1-30%, in particular 5-10%. These can then be used in powder clearcoat systems, the effective concentration being about 0.3-0.8% of nanoparticles based on solid polymer. The clearcoat systems produced in this way exhibit significantly increased heating rates on IR irradiation.

Suitable light and transparent semiconductor materials as IR curing accelerators are, in particular, indium (III) oxide, tin, tin (IV) oxide, zinc oxide, antimony and mixtures thereof. Very particular preference is given to tin oxide.

Particularly preferred IR curing accelerators are tin (IV) oxide,

Antimony (III) oxide, indium tin oxide (ITO) or antimony (III) oxide and mixtures thereof. In particular, doped tin oxides additionally show a strong absorption in the UV range, which is very advantageous in clearcoat systems, since typical UV protective pigments, such as, for example, TiO ₂ pigments, are absent in high concentrations. An additional UV protection is therefore desirable, especially in clearcoat systems.

The nanoparticulate semiconductor materials according to the invention generally have a primary particle average particle sizes (d ₅ o) of 10 to 80 nm, preferably from 20 to 50 nm, especially 20 to 30 microns.

In the homogeneously constructed semiconductors, the semiconductor material is preferably constructed microcrystalline.

Particularly preferred curing accelerators are transparent or light-colored semiconductor materials with a powder resistance of <20 Ω • m, preferably of <5 Ω • m.

A particularly preferred curing accelerator is an antimony (III) oxide-doped tin (IV) oxide. Further preferred are additions of indium oxides as dopants. In addition to antimony (III), preferably antimony (III) oxide, halides, preferably chlorides and fluorides, are furthermore suitable as dopant, in particular for tin oxides.

The doping is dependent on the semiconductor material used and is generally 0.5 to 30% by weight, preferably 2 to 25% by weight, in particular 5 to 16% by weight, based on the semiconductor material.

Tin oxides are preferably doped with 0.5 to 30% by weight, in particular 1 to 12% by weight and very particularly preferably 5 to 10% by weight. The dopants used are preferably antimony or antimony compounds.

Furthermore, it is also possible to use mixtures of nanoparticulate semiconductor materials as curing accelerators, in particular of polymer matrices such as lacquers and printing inks, wherein the mixing ratio has no limits.

Preferred mixtures are indium-tin oxides with doped tin (IV) oxides and indium-tin oxide with doped zinc oxides. And nanoparticles of the present invention with platelet-curing accelerators, such as Minatec.RTM ^® 30 or Minatec.RTM ^® 31, products can continue in a particular embodiment, Merck KGaA, are mixed Fa.. The latter preferably have particle sizes of 5-100 μm. This mixture of nanoparticles / platelets preferably contains 2-98% by weight, in particular 50-98% by weight and very particularly preferably 80-98% by weight of the nanoparticulate semiconductor materials according to the invention. Such mixtures of platelet-shaped curing accelerators, which ensure an excellent surface coverage which is as transparent as possible, preferably in the visible light range, with nanoparticles according to the invention, which additionally have good thermal conductivity and which ensure strong IR absorption and heat conduction within the matrix volume, are advantageous for all Polymer matrices known to the person skilled in the art. Mixtures of two, three or more nanoparticulate semiconductor materials can also be added to the application systems. The total concentration depends on the application system. For example, in the paint system or in the printing ink, the total concentration of semiconductor material mixture should not exceed 10

% By weight based on the application system.

The curing accelerator (s) are preferably added to the paint system or the printing ink in amounts of from 0.01 to 10.0% by weight, in particular from 0.01 to 8.0% by weight, particularly preferably in amounts of 0.05 - 5.0 wt.%, Based on the paint or the ink added.

The nanoparticulate semiconductor materials according to the invention are prepared by milling a suitable precursor having particle sizes of particle size range from 0.1 to 50 .mu.m, preferably from 0.5 to 10 .mu.m, in particular from 1 to 10 .mu.m, in water or in an aqueous solvent mixture. Suitable precursors are in particular doped or undoped, light and transparent Halbleiter¬ materials, in particular indium oxide, tin, tin oxide, antimony and mixtures thereof. Very particular preference is given to tin oxide, in particular antimony-doped tin oxide. Suitable precursors are commercially available, for. B. from the company. Merck KGaA under the brand Minatec ^® 230th

Preferably, the milling of the precursor takes place in water. However, it is also possible to use mixtures of water and organic solvents which are readily soluble in water. Suitable organic solvents are in particular alcohols, e.g. Ethanol, propanol, butanol, cyclohexanol, glycols, e.g. Ethylene or propylene glycols.

Suitable mills are ball mills, bead mills, and more

Expert known and suitable grinding units, which allow an intense dissipation of the heat generated as well as a high degree of filling Mahlkörpem and further a strong input of mechanical energy. During grinding, the pH is adjusted to 6-11, preferably pH 8-11. The pH depends on the precursor used and can easily be determined by the person skilled in the art. The grinding process lasts 2 to 48 hours, preferably 10 to 24 hours, depending on the precursor used.

Subsequently, a drying process can take place. The nanoparticles are necessary unless removed by centrifugation, and then out at temperatures from 40 to 130 ⁰ C, particularly 50-80 ⁰ C, preferably by applying vacuum dried.

The milling is preferably carried out at concentrations of the precursor material of 5 to 20%, particularly preferably at concentrations of Precursor¬ material of 10 to 20%, depending on the viscosity of the resulting nanoparticle dispersion. It should also be sought as high as possible filling level of hard finely divided grinding media.

Nanoparticulate doped tin oxides are preferably prepared by coarse-particle precursors in the particle size range from 0.1 to 50 .mu.m, in particular 1 to 10 .mu.m, at a pH of 9-11, an intensive

Grinding, preferably using zirconia grinding media or grinding media of comparable or higher hardness, are subjected.

The IR curing accelerator according to the invention, alone or in

Combination with platelet-shaped curing accelerators is stirred before application to an object, for example a lacquer or an ink. This is preferably done using a high speed stirrer or, in the case of hard dispersible, mechanically insensitive cure accelerators, by using a bead mill or shaker. Other dispersing units known to those skilled in the art are also possible. Finally, the paint or ink in the air is physically cured using IR irradiation, or chemically crosslinked. By curing accelerator, the curing time of the paint layer or the ink is very much shortened, or the use of IR drying in transparent paint systems, such as powder coatings, only economically feasible, as these themselves, as an organic compound hardly absorb in the near, high-energy infrared range. The more efficient effect can easily be determined by the significantly accelerated temperature development on IR irradiation of a transparent polymer layer which contains nanoparticles according to the invention in comparison to the corresponding sample without the particles according to the invention.

The nanoparticulate IR curing accelerators according to the invention are therefore suitable, in particular because of their transparency, for IR clearcoat materials of all kinds.

Furthermore, it has been found that the acceleration of the curing can also have a positive effect on overlying IR lacquer layers, depending on the pigmentation of these overlying lacquer layers and the heat influences.

The invention furthermore relates to polymer matrices, such as e.g. Printing inks, industrial coatings and automotive coatings, including clearcoats containing the nanoparticle IR curing accelerator according to the invention.

Suitable coating systems include, in particular, IR-curable coatings in the field of powder coatings, as well as solvent-based systems. Also suitable are film applications and plastic welding, as well as solvent-based or aqueous IR printing inks for all common types of printing, such as e.g. Gravure printing, flexo printing, letterpress printing, textile printing, offset printing, screen printing, security printing.

The following examples are intended to illustrate the invention without, however, limiting it. Examples

Example 1: Preparation of a nanoparticulate antimony-doped tin oxide

To prepare a antimony-doped tin oxide about 13 nanoparticulate compositions are in a stirred ball mill percent of approximately 1 - (. Minatec.RTM ^® 230 from Merck KGaA) 10 microns large precursor added zirconia grinding media having 0.35 mm diameter (filling degree φ = 0, 8) and ground at pH 11 for 24 hours. The d ₅₀ value of the particle size is about 50 nm.

Example 2: Preparation of transparent IR-absorbing polymer matrices

A hydroclearcoat is mixed with in each case 0.5% nanoparticulate zinc oxide, tin oxide and the antimony-doped tin oxide nanoparticles from Example 1 and applied at a constant layer thickness to a metal substrate. The development of the surface and substrate temperature is measured as a function of time when irradiated with an IR source.

From Table 1 it can be seen that for the clearcoat with the nanoparticles according to the invention the most strongly accelerated heat development (Tmax _> measured after 20 sec irradiation) is obtained. However, the Farb¬ differences (.DELTA.E) to the clearcoat system are very low compared to nano¬ teiligem tin oxide or zinc oxide. Since it nm in the inventive particles to nano-particle materials of d ₅ o = 50 acts with low absorption (Figure 1), they continue to show a high transparency. Table 1 :

Example 3 Production of a Powder Clearcoat Masterbatch

5% of the nanoparticulate antimony-doped zinc oxide (based on the solids) from Example 1 (Cytec, West Paterson, USA Fa.) 633 with Crylcoat ^® were added and pre-dried 2 h at 25 ⁰ C and 50 mbar. In the subsequent extrusion, the residual water is separated via the degassing. A transparent powder coating masterbatch is obtained which contains the nanoparticulate antimony-doped zinc oxide according to the invention in a finely dispersed state.

Example 4: Preparation and comparison of color-neutral, preferably transparent IR-absorbing powder coating systems

The heating behavior is tested on aluminum sheets after the electrostatic powder coating application. For this purpose, the surface temperature is measured during irradiation with an IR source. The following 3 samples are compared:

Powder coating sample 1: Preparation of an antimony-doped zinc oxide powder clearcoat containing nanoparticulate antimony-doped zinc oxide

4 m% masterbatch according to Example 3, 4.4 m% Primid XL 552 (EMS-PRIMID ₁ Doma / Ems, Switzerland) and 0.5 m% benzoin (Merck KGaA, Darmstadt, Germany) are used in 91, 1 m% Crylcoat ^® 633 (Fa. Cytec, West Paterson, USA) by coextrusion using a Busskneters (TCS 30) at 110 ⁰ C and 300 U / min incorporated. (Corresponds to a content of 0.2 m% nanoparticles according to the invention from Example 1 in the powder coating).

Powder coating sample 2: comparative sample pigmented with precursor Minatec ^® 230

0.2% m Minatec.RTM ^® 230 (Fa. Merck KGaA, Darmstadt, Germany), 4.4 m% Primid XL 552 (Fa. EMS-PRIMID, Doma / Ems, Switzerland) and 0.5% benzoin m (Fa. Merck KGaA, Darmstadt, Germany) in 94.9% m Crylcoat ^® 633 (Fa. Cytec, West Paterson, USA) analogously to powder coating sample 1 incorporated.

Powder coating sample 3: Comparative sample of unpigmented powder clearcoat

4,4 m% Primid XL 552 (Fa. EMS-PRIMID, Doma / Ems, Switzerland) and 0.5% benzoin m (Fa. Merck KGaA, Darmstadt, Germany) are dissolved in 95.1 m% Crylcoat ^® 633 (from Cytec, West Paterson, USA) were incorporated analogously to powder coating samples 1 and 2.

From Figure 2 it can be seen that the powder clearcoat, which contains the nanoparticle preparation according to the invention according to Example 3, achieves the fastest or largest heating. A significantly worse temperature development shows the precursor Minatec ^® 230 pigmented powder coating sample 2, which is visually not completely transparent. The unpigmented powder clearcoat has a very slow temperature development. Furthermore, it is found that only powder coating sample 1 achieves the necessary for complete crosslinking high temperatures by IR irradiation.

Claims

claims

1. Nanoparticulate semiconductor materials are prepared by milling semiconductor materials in an aqueous medium at a pH of 6-11 and a particle size of 0.1 to 50 microns.

2. nanoparticulate semiconductor materials according to claim 1, characterized in that they have as primary particles average particle sizes (d ₅ o) of 10 to 80 nm.

3. Nanoparticulate semiconductor materials according to claim 1 or 2, characterized in that they consist of indium (III) oxide, indium tin oxide (ITO), antimony (III) oxide, tin (IV) oxide, zinc oxide or mixtures thereof.

4. Nanoparticulate semiconductor materials according to one of claims 1 to 3, characterized in that they are doped with antimony (III) or halides.

5. Nanoparticulate semiconductor materials according to claim 4, characterized in that the semiconductor material is an antimony (III) oxide-doped tin (IV) oxide.

6. Nanoparticulate semiconductor materials according to claim 4 or 5, characterized in that the doping 0.5 to 30 wt.% Based on the semiconductor material.

7. Nanoparticulate semiconductor materials according to one of claims 1 to 6, characterized in that the semiconductor material is microcrystalline.

8. Use of nanoparticulate semiconductor materials according to one of claims 1 to 7 as IR curing accelerator in solid and liquid preparations, matrix polymers, polymer preparations, industrial coatings, automotive coatings, clearcoat systems, powder coatings, in

Plastics and films.

9. Use according to claim 8, characterized in that the application systems contain one or more nanoparticulate Halbleit¬ materials according to one of claims 1 to 7.

10. paints and printing inks, characterized in that they are 0.01 - 10

% By weight of nanoparticulate semiconductor materials according to one of Claims 1 to 7, based on the lacquer or the printing ink as IR curing accelerator.

11. Polymer masterbatches and polymer preparations, characterized in that they contain 1-30 wt.% Of nanoparticulate Halbleit¬ materials according to one of claims 1 to 7 based on the polymer masterbatch or the polymer preparation.

12. Solid and liquid preparations, characterized in that they contain one or more nanoparticulate semiconductor materials according to any one of claims 1 to 7, additives and optionally water or a water / solvent mixture.

13. Use of the preparations according to claim 12 in matrix polymers and polymer preparations.