NL1012587C2 - Nanocomposite coating composition, contains layered inorganic filler which has been modified using a compound with at least two ionic groups - Google Patents

Abstract

A coating composition contains a layered inorganic filler which has been subjected to ion exchange using a modifier comprising at least two ionic groups which are separated from each other by at least 4 atoms. The modified filler is dispersed in a diluent with a polymer and optionally an initiator.

Description

Title: Color pigment

The invention relates to a method for preparing a color pigment. The invention further relates to the coloring pigment and its use for coloring substrates.

In the context of the invention, a color pigment is understood to mean a material which can impart a certain, desired color to a substrate of a different material. In addition to color, a color pigment provides coverage and improves the durability of the substrate by absorbing and / or reflecting part of the incident light. According to the invention, a color pigment is therefore distinguished from a colorant. Although a dye is capable of coloring a substrate, it does not have the other mentioned properties that a coloring pigment does.

Polymeric materials are usually colored with inorganic pigments. These provide good color stability against light, oxygen and heat. However, these pigments have limitations in terms of color and color intensity. In addition, inorganic pigments are less desirable for environmental reasons. For example, many inorganic pigments contain heavy metals.

Organic pigments not only offer a wider range of color options with higher intensities, but are also degraded faster and better in the environment, for example under the influence of oxygen. However, a major drawback of organic dyes is that they have relatively low temperature and UV stability. In addition, these materials tend to leach when substrates stained with them are used.

Attempts have been described in the literature to combine the advantages of the known inorganic and organic: I 2 3 b / 2 pigments. U.S. Pat. No. 3,950,180 discloses a composite material based on an organic basic dye and a mineral, a zeolite or montmorillonite. However, it has been found that the dye is not very homogeneously distributed over the mineral. Also, a substrate cannot be colored sufficiently homogeneously with such a composite material.

International patent application 92/00355 describes a color pigment based on a layered double hydroxide and a water-soluble anionic dye. According to a first possibility, this coloring pigment is prepared by calcining the layered double hydroxide, displacing carbonate ions between the clay plates, and then subjecting them to ion exchange with the dye. According to a second possibility, the layered double hydroxide is formed in situ in the presence of the dye. Nor is the dye homogeneously distributed over the clay (the layered double hydroxide) in the color pigment obtained according to either of the two possibilities. Even with this coloring pigment, a substrate cannot be colored homogeneously enough.

It is an object of the invention to provide a color pigment that combines the advantages of the known organic pigments with those of the known inorganic color pigments, and that polymer materials can be colored in an efficient, homogeneous manner. A class of color pigments with which a large number of different colors of high intensity can be given to a polymer substrate is envisaged, which color pigments are readily and rapidly degradable in the environment. Furthermore, the color pigment must be stable under the influence of light, oxygen and heat.

Surprisingly, it has now been found that the stated objectives can be achieved by preparing a coloring pigment from an organic dye and a clay. The 10 1 2 5 8? The invention therefore relates to a method for preparing a color pigment, in which an anionic or cationic clay, which clay contains substantially no agglomerates of clay plates, is subjected to an ion exchange with an organic dye.

It has been found that the present process results in a very high intensity color pigment. In other words, to obtain the same color intensity as with a prior art color pigment, a much smaller amount of color pigment will suffice. Furthermore, any color shade can be achieved which can also be created with known organic pigments. Another great advantage of the invention is that the color pigment can be absorbed very well in substrates. A very homogeneous color effect is obtained, in which substantially no individual color pigment particles are discernible. The leaching of the color pigment does not occur, or at least to a much lesser degree than with the known organic pigments. Furthermore, the present color pigment is very stable, compared to organic dyes, under the influence of light, oxygen and heat and presents little or no risk to the environment.

The clay used in the present method is an anionic or a cationic clay. In principle, any anionic or cationic clay obtained synthetically or from a natural source can be used. Suitable examples can be selected from the classes of smectites, hydrotalcites and layered double hydroxide. Particular preference is given to cationic clays, such as sodium or hydrogen montmorillonite, and hydrotalcites.

As indicated above, it is an important aspect of the invention that the clay contains substantially no clay plate agglomerates. All 35 clay types consist of a picture structure. Under normal circumstances these platelets form agglomerates, the clay platelets stacking on top of each other. According to the invention, these agglomerates must be substantially broken, so that the distance between the clay plates is at least 50 A, preferably at least 75 A, 5 and even more preferably at least 100 A. This distance can be suitably determined using X-ray diffraction techniques.

An example of a suitable way to break, ie deagglomerate, the agglomerates in the clay is a method in which the clay is dispersed in, preferably, water which is substantially free of ions. This water preferably has a temperature of 20-60 ° C. Preferably, the amount of clay is not more than 10% by weight, based on the dispersion, so that the viscosity remains low. This has a positive effect on the processability of the dispersion. The clay is then allowed to swell for a period of between half an hour and several hours. Other methods of breaking up the agglomerates in the clay are known to the person skilled in the art.

The clay thus obtained is ion-exchanged with an organic dye which provides the desired color. The organic dye is preferably an ionic dye, so that the ion exchange can be carried out in a simple manner. Examples of suitable dyes are listed in Ullmanns

Encyklopadie der Technische Chemie, Vol. 11, Verlag Chemie, Weinheim, 1976 under "Farbstoffen" and include acridine dyes, anthraquinone dyes, azine (incl. Oxazine and Thiazine) dyes, azo dyes, quinophthalone dyes, natural dyes, formazan dyes, indigo and indigo dyes, indicator dyes, cationic dyes, leucoku chicken dyes, methine (incl. Azomethine) dyes, microscopic dyes, 35 naphto and benzoquinone dyes, nitro and nitroso dyes, phthalocyanine dyes, reactant dyes, methane and diary. Suitable organic dyes are divided by color into the following groups (see Ullman Band 11): direct dyes, developing dyes, oxidation dyes, cationic (basic) dyes, tub dyes, leucoku chicken dyes, reactive dyes, and acid dyes.

Preference is given to cationic and anionic dyes and dyes which can be brought into cationic or anionic form by protonation or deprotonation. These are, for example, dyes with N +, P +, S + functionalities and / or derivatives thereof.

In addition, preference is given to dyes with anionic functionalities such as RC02 ', RP (0) 022 "and RS03", where R is defined as an alkyl, aryl or alkylaryl group. Also, dyes with a charge center of gravity are preferred.

The ion exchange can take place by adding a solution of the dye to a dispersion of the clay in warm water, preferably the dispersion described above. The dye is preferably dissolved in water at a concentration between 1% and 50%. The amount of dye used in the ion exchange is selected depending on the ion exchange capacity (CEC) of the clay and molar mass and number of reactive groups of the dye. The color shade of the color pigment to be prepared can be adjusted by means of the amount of dye. The pH of the dye solution is preferably between 2 and 10.30 depending on the selected clay and the dye, and can be adjusted with suitable buffers.

An advantage of the invention is that the loading of the clay with the dye can be very high. The amount of dye per amount of clay that can be achieved is significantly higher than that which can be achieved by the methods of preparing a clay based pigment and an organic dye of the prior art. The amount of clay relative to the amount of dye is preferably chosen so that the coloring pigment contains from 2 to 90% by weight, particularly preferably from 5 to 45% by weight, of pigment.

Under certain circumstances, however, it is desirable not to realize the maximum loading of the clay with dye. The remaining loading capacity can then be used to include additives in the color pigment at 10. Examples of preferred additives are surfactants. These can increase compatibility between the color pigment and a substrate to be colored with it. Examples of suitable surfactants in this connection are quaternary ammonium compounds, such as octadecylammonium bromide, (ar) alkyl sulfonic acids and sulfates, such as dodecyl sulfate, alkyl carboxylic acids and block copolymers built from hydrophilic and hydrophobic blocks. The nature of the desired surfactant 20 can be suitably tailored to the substrate one wishes to color. The amount of surfactant will depend on the type of pigment and the substrate to be colored. Typically this amount will be between 0 and 90, preferably between 0 and 30 mol%, based on the amount of pigment.

After the ion exchange, the color pigment is preferably washed several times with water and filtered. If desired, the material can be dried, for example in an oven or by spray or freeze drying, after which it can be ground into a powder to improve processability.

The invention also relates to the use of the coloring pigment obtainable in the above-described manner for coloring substrates. It has been found that the coloring pigment is particularly suitable for coloring substrates of polymeric material. It is possible to color bulk material as well as to color a coating or coating of a polymer material. Polymers that have been found to be particularly good at coloring are polyurethanes, poly (meth) acrylates, polyolefins, such as polyethylene or polypropylene, polyesters and polystyrene.

When the present color pigment is to be incorporated into a bulk material, it can be added to a melt of the material and / or homogeneously distributed in the bulk material by shearing forces, for example by extrusion. When the color pigment is to be incorporated into a coating or coating, it can be suitably added to the liquid material used to form the coating or coating. This liquid material can then, after stirring well, be applied in the usual manner to a substrate and cured into a coating layer. The substrate in this connection can be of any kind, such as polymeric material, ceramic, glass, metal, wood, textile (clothing) and the like.

A color pigment according to the invention can be distributed very homogeneously over a substrate, so that no color pigment particles are detectable whatsoever. The present coloring pigment therefore combines the properties of a pigment with those of a dye. The color pigment consists of particles smaller than the wavelength of the light. For that reason, the color pigment can also be referred to by the term 'nanopigment1.

The color that can be given to a substrate is extremely intense and essentially does not bleed or bleed. It has also been found that the color pigment has a firming effect on a substrate. The colored substrate is considerably more stable under the influence of light, heat or oxygen and has improved mechanical properties, such as greater tensile strength and impact resistance.

10 1 2 58 7 δ

The invention will now be further elucidated by means of the following examples.

Example 1 Ten grams of a montmorillonite clay EXM 757 with a cation exchange capacity of 95 meq./100 g was dispersed in 1 liter of deionized water at 50 ° C. The clay was allowed to swell over a 2 hour period until complete exfoliation had occurred. The distance between the clay plates was determined to be 12.1 Å by X-ray diffraction.

The clay thus obtained was subjected to an ion exchange with Methylene Blue (MB). 3.0 grams MB was used for a complete exchange. This gave a blue color pigment which was washed, filtered and freeze dried. The distance between the clay plates was determined to be 15.6 Å by X-ray diffraction.

A Thermal Gravimetric Analysis (TGA) was made from this color pigment using a device available for this purpose available from Perkin Elmer to compare the thermal stability of the color pigment with that of MB per se. The results are shown in Figure 1. In Figure 1, the line with the symbol — toont— shows the data obtained for pure methylene blue, the symbol —B— the corrected data obtained for methylene blue in clay, and –A— the factual data obtained for methylene blue in clay.

The actual data obtained was corrected for the amount of clay in the sample. Since the clay used contains about 24% MB, a calculation was made to an amount of pure MB. It can be seen that the thermal stability of the color pigment obtained according to this example is at least 100 K higher than that of pure MB. 35 10 1 2 5 8 7 9

Example 2

The color pigment obtained in example 1 was used in different coatings (paint): - a water-based polyether 5 polyurethane coating for concrete; - a water-based polycarbonate polyurethane coating for metal; - a water-based polyacrylate coating for metal; and 10 - an isopropanol-based hybrid silicate coating for steel scratch protection.

In each coating, the color pigment was included at three concentrations: 1, 2 and 5% by weight. This was done by dispersing the color pigment in the paint using ultrasonic activation. After several hours, a substrate was painted with the coatings and they were cured. The color intensity and homogeneity of the coatings was very high. With the aid of light microscopy, no inhomogeneities were observed in the coatings.

20

Example 3

Ten grams of a montmorillonite clay EXM 757 with a cation exchange capacity of 95 meq./100 g was dispersed in 1 liter of deionized water at 50 ° C. The clay was allowed to swell over a 2 hour period until complete exfoliation had occurred. The distance between the clay plates was determined to be 12.1 A by X-ray diffraction.

The clay thus obtained was subjected to an ion exchange with Methylene Red (MR). 2.6 grams of MR were used for a complete exchange. This gave a red color pigment which was washed, filtered and freeze dried. The distance between the clay plates was determined by X-ray diffraction to be 23.9 Å 35.

10 1 2 58 7 3 ..., 10.

Example 4

The color pigment obtained in example 1 was used in different coatings (paint): - a water-based aliphatic polyurethane coating for concrete; - a water-based polycarbonate polyurethane coating for metal; - a water-based polyacrylate coating for metal; and 10 - a water-based aromatic polyester coating.

In each coating, the color pigment was included at three concentrations: 1, 2 and 5% by weight. This was done by dispersing the color pigment in the paint using ultrasonic activation. After several hours, a substrate was painted with the coatings and they were cured. The color intensity and homogeneity of the coatings was very high. With the aid of light microscopy, no inhomogeneities were observed in the coatings.

X-ray diffraction spectra were included of the color pigment per se and of the aromatic polyester coating with 2% by weight of color pigment. The color pigment showed peaks at 3.69 °, 2Θ; 7.36 °, 2Θ. The coating spectrum showed no peaks at those places, indicating that the clay was nanoscopically dispersed.

Example 5

Ten grams of a montmorillonite clay EXM 757 with a cation exchange capacity of 95 meq./100 g was dispersed in 1 liter of deionized water at 50 ° C. The clay was allowed to swell over a 2 hour period until complete exfoliation had occurred. The distance between the clay plates was determined by X-ray diffraction to be 12.1 Å.

The clay thus obtained was ion-exchanged with Methylene Green (MG). 4.1 grams of MG were used for a 10 1 2 5 8 7 11 complete exchange. This gave a blue-green color pigment, which was washed, filtered and freeze-dried. The distance between the clay plates was determined by X-ray diffraction to be 15.5 A 5.

Example 6

Ten grams of a montmorillonite clay EXM 757 with a cation exchange capacity of 95 meq./100 g was dispersed in 1 liter of deionized water at 50 ° C. The clay was allowed to swell over a 2 hour period until complete exfoliation had occurred. The distance between the clay plates was determined to be 12.1 A by X-ray diffraction.

The clay thus obtained was ion-exchanged with Malachite Green (MaG). 3.3 grams of MaG was used for a complete exchange. This gave a blue-green color pigment, which was washed, filtered and freeze-dried. It was determined by X-ray diffraction that the distance between the clay plates was 22 Å.

Example 7

Ten grams of a montmorillonite clay EXM 757 with a cation exchange capacity of 95 meq./100 g was dispersed in 1 liter of deionized water at 50 ° C. The clay was allowed to swell over a 2 hour period until complete exfoliation had occurred. It was determined by X-ray diffraction that the distance between the 30 clay plates was 12.1 Å.

The clay thus obtained was ion-exchanged with Brilliant Green (BG). 4.6 BG was used for a complete exchange. This gave a green color pigment which was washed, filtered and freeze dried. The distance between the clay plates was determined by X-ray diffraction to be 22.7 Å.

12

Example 8

The preparations of the color pigments of Examples 1, 3 and 5-7 were repeated with another clay, namely a Bentonite with a cation exchange capacity of 85 meq./100 g. The use of this clay, which has larger clay platelets, yielded comparable results in terms of color intensity.

10 Example 9

Ten grams of a synthetic hydrotalcite (Mg3ZnAl2 (OH) 12CO3.4H20) was dispersed in 1 liter of deionized water at 40 ° C at a pH of 3. The pH was adjusted with a 5 M HCl solution and checked with 15 pH paper . The clay was allowed to swell over a 1 hour period until complete exfoliation had occurred.

The clay thus obtained was ion-exchanged with Methyl Red. This dye was used in a 2: 1 molar ratio to the hydrotalcite. This gave a yellow color pigment which was washed, filtered, lyophilized and ground.

Example 10

Ten grams of a synthetic hydrotalcite 25 (Mg3ZnAl2 (OH) 12CO3.4H20) was dispersed in 1 liter of deionized water at 40 ° C at a pH of 3. The pH was adjusted with a 5 M HCl solution and checked with pH paper . The clay was allowed to swell over a 1 hour period until complete exfoliation had occurred.

The clay thus obtained was ion-exchanged with Fluorescein. This dye was used in a 2: 1 molar ratio to the hydrotalcite. This gave a red color pigment, which was washed, filtered, freeze-dried and ground.

10 1 2 58 7

Claims (10)

1. A method of preparing a coloring pigment, wherein an anionic or cationic clay, which clay contains substantially no agglomerates of clay platelets, is subjected to an ion exchange with an organic dye. A method according to claim 1, wherein the clay has been pre-treated in which the clay plate agglomerates are substantially broken. 3. Method according to claim 2, wherein the treatment of the clay consists of dispersing and swelling the clay in water which is substantially free of ions at a temperature between 20 and 60 ° C. 4. A method according to any one of the preceding claims, wherein the clay comprises clay plates, wherein the mutual distance between the clay plates is at least 50 Å. The method according to any of the preceding claims, wherein the clay is selected from the group of teas, layered double hydroxides and hydrotalcites. 6. The method of any preceding claim, wherein the organic dye is selected from the group of acridine dyes, anthraquinone dyes, azine (incl. Oxazine and Thiazine) dyes, azo dyes, quinophthalone dyes, natural dyes, formazan dyes, indigo and Indigoide dyes, indicator dyes, cationic dyes, leucoku chicken dyes, methine (incl. Azomethine) dyes, microscope dyes, naphto and benzoquinone dyes, nitro and nitroso dyes, phthalocyanine dyes, reactive dyes, and tri and diarylmethane dyes. The method according to any of the preceding claims, wherein a surfactant is present during the ion exchange. 4 a $ 0 e Q 7? ij U J y I Color pigment available in a method according to any one of the preceding claims. Use of a coloring pigment according to claim 8 for coloring a polymeric material. Polymeric material colored with a color pigment according to claim 8. 10 1 2 5 8 7