METHOD OF PREPARING A COMPOSITION CONTAINING A DISPERSED PIGMENT

Abstract: A composition containing dispersed pigment comprises, as a dispersing agent, a reaction product of at least one of the polyamines having two or more primary amino groups and/or secondary amino groups and at least one of the polyisocyanates having two or more isocyanate groups.

Description: FIELD OF THE INVENTION This invention concerns a method for preparing a composition containing a pigment which is dispersed in a reaction product of polyamines and polyisocyanates, which composition possesses excellent dispersion stability in respect of the pigment, low thixotropy and excellent flow characteristics. DESCRIPTION OF THE PRIOR ART In conventionally prepared compositions containing pigments, resins and solvents, if the dispersibility of the pigment in the resin is poor, the composition containing the dispersed pigment exhibits remarkable thixotropy due to the flocculation of the pigment. Further, since paint films formed by applying such a composition containing flocculated pigments cause various problems, such as degradation in the gloss, decrease in the distinctness of image, reduction in the color strength, flooding, etc., satisfactory results cannot be obtained with such compositions containing a dispersed pigment. In order to overcome the foregoing problems, various inventions have been proposed as described below. (1) The method of incorporating certain pigment derivatives into a pigment as disclosed in Japanese Patent Laid-open No. 18736/1976 cannot be applied generally, since for various pigments such pigment derivatives are colored by those structures. (2) More has also been disclosed, for example, in Japanese Patent Laid-Open No. 160396/1975, in British Patent Specifications Nos. 1 393 401 and 1 393 402 and in DE-OS 20 41 033 a technique of utilizing, as a dispersing agent, compounds obtained by reacting three groups of compounds, that is, organic compounds having at least two isocyanate groups, i.e., polyisocyanates (group A), organic compounds having at least two functional groups reactive with the isocyanate groups, for example, amino groups or hydroxyl groups (group B) and polymers (group C) having one functional group reactive with the isocyanate groups. These dispersing agents have, however, certain disadvantages as described below. The design concept for the dispersing agent of this type is to prepare a block structure comprising chains that can be solvated with solvents and polar anchor group portions adsorptive to the pigment as stated by A. Topham in "Progress in Organic Coatings", Vol. 5 (1977), pp 237 to 243. When employing this technique, it is necessary to prepare a composition containing a dispersed pigment, additionally the dispersing agents as described above, and a solvent. In the case of preparing paints by using the composition, it is generally further necessary to add various types of resins as the film forming vehicles. In this case the type and amount of the vehicle resins to be added as the film forming ingredients are restricted in view of their compatibility with the polymer constituting the dispersing agent. Accordingly, it has been difficult to use such dispersing agents for general purpose applications. Particularly, they have an insufficient dispersing effect for pigments with poor dispersibility, for example, quinacridone pigments. Furthermore, problems may occur as regards the durability or other areas of film performance of the paint films containing a large amount of dispersing agent used for dispersing pigments as described in the prior art and literature. The production steps required to put to practice this prior art technique are rather complicated, since the dispersing agent must be prepared separately and also the polymers of the group C necessary for synthesizing the dispersing agent must be prepared in a separate step. In example 1 of the aforementioned DE-OS 20 41 033 there is described the synthesis of a polyurea compound by reacting tolylene diisocyanate with a commercially available mixture of unsaturated amines, primarily consisting of oleylamine. This reaction product is used in example 15 to prepare a pigment dispersion. The pigment component is used in the form of a water-containing filter cake (37 parts H₂O + 16 parts dry pigment) and the water is separated from the pigment by mixing the cake with toluene in which the reaction product of example 1 had been dissolved. The pigment containing toluene phase is then heated in order to separate the solvent by evaporation. The pigment is then re-dispersed in toluene and this suspension is mixed with a white paint. When using compositions comprising dispersed pigments and the conventional dispersing agents as described above together with vehicle resins for the preparation of paints, there is always the risk that they produce undesirable effects on the paints and the condition of the paint films,due to the restriction caused from the composition of the dispersing agents, such as poor compatibility between the dispersing agents and the vehicle resins, due to restrictions as regards the types of solvents to be used or due to reduction in the water resistance of the paint films. SUMMARY OF THE INVENTION It is the object of this invention to provide a method of preparing a composition containing dispersed pigment that is excellent in dispersion stability of the pigments, can be applied to a wide range of pigments, is easily to be performed and does not restrict the solvents that may be used. The term "dispersion stability" used herein means that a pigment can be finely dispersed and that the dispersed pigment is present in a stable state with no flocculation. The method according to the invention is based on the concept that dispersing agents must be prepared in situ from polyamines and polyisocyanates in the presence of a vehicle resin. The invention therefore concerns a method of preparing a composition containing a dispersed pigment, wherein at least one polyamine havint two or more of primary amino groups and/or secondary amino groups, at least one polyisocyanate having two or more of isocyanate groups, a vehicle resin and an organic solvent are blended and the polyamines and polyisocyanates are reacted in situ, and thereafter, the pigments are blended and dispersed. According to another embodiment, this invention concerns a method of preparing a composition containing a dispersed pigment, wherein a pigment, a vehicle resin and an organic solvent are mixed and dispersed, and, thereafter, at least one polyamine having two or more of primary amino groups and/or secondary amino groups, at least one polyisocyanate having two or more of isocyanate groups are blended and the polyamines and polyisocyanates are reacted in situ. According to a third embodiment , this invention concerns a method of preparing a composition containing a dispersed pigment, wherein at least one polyamine having two or more of primary amino groups and/or secondary amino groups, at least one polyisocyanate having two or more of isocyanate groups are added to and dispersed in the pigment, the vehicle resin and the organic solvent while mixing and dispersing them, and the polyamines and polyisocyanates are reacted in situ. DETAILED DESCRIPTION OF THE INVENTION (Pigments) In this invention, various types of inorganic pigments or organic pigments that are usually employed in the paint or printing ink industry can be used. The inorganic pigments can include, for example, zinc white, titanium dioxide, antimony white, iron oxide red, iron oxide yellow, transparent iron oxide, red lead, cadmium yellow, zinc sulfide, lithopone, barium sulfate, lead sulfate, barium carbonate, white lead, alumina white and carbon black. The organic pigments can include, for example, various pigments such as azo series, polycondensation azo series, metal complex azo series, benzimidazolone series, phthalocyanine blue series, phthalocyanine green series, thioindigo series, anthraquinone series, flavanthrone series, indanthrene series, anthrapyrimidine series, pyranthrone series, isoindolinone series, perylene series, perinone series and quinacridone. This invention is most beneficial when using carbon black and organic pigments which have been considered as difficult to disperse. (Resins) As the vehicle resins usable in this invention, those vehicle resins usually employed in the preparation of paints and printing inks can advantageously be used and include, for example, alkyd resins, polyester resins, acrylic resins, vinyl resins such as polyvinyl chloride, polyvinyl acetate, chlorinated polyolefins and polyamide resins. (Polyamines) The polyamines having two or more primary and/or secondary amino groups, usable in this invention can include various kinds of polyamines, for example, ethylenediamine, 1,3-propylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, bisaminopropylpiperazine, bisaminopyridine, xylylenediamine, metaphenylenediamine, 4,4'-diaminodiphenylmethane and polyethyleneimine. Among them, those polyamines having three or more of primary and/or secondary amino groups or those polyamines having two or more primary and/or secondary amino groups and one or more tertiary amino groups are used preferably. Preferred polyamines include, for example, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine prepared through cationic polymerization of ethyleneimine, that is, commercially available polyethyleneimine represented by the structure as shown in the following formula (A), bisaminopropyl piperazine and bisaminopyridine : (Polyisocyanates) The polyisocyanates usable in this invention can include, for example, diisocyanate compounds such as tolylene diisocyanate (TDI), 4,4-diphenyl methane diisocyanate (MDI), xylylene diisocyanate (XDI), hexamethylene diisocyanate, hydrogenated MDI, hydrogenated TDI, hydrogenated XDI and isophorone diisocyanate. More preferably, the use of higher polyfunctional polyisocyanate compounds is advantageous. Such compounds can include, for example, those compounds prepared by reacting polyols with diisocyanates such as represented by formulas (1) - (4), those compounds prepared through biuret reaction from diisocyanates, for example, represented by formula (5), those compounds prepared through the ring formation of diisocyanates such as compounds represented by the formulas (6) - (8) and those compounds represented by the formulas (9) and (10). where n represents an integer from 1 to 4. Commercially available products containing the above-mentioned compounds as the main ingredient are exemplified as described below. Coronate HL (trade name of products available from Nippon Polyurethane Industries Co., Ltd.) containing the compound of formula (1) as the main ingredient. Sumidur L (trade name of products available from Sumitomo Bayer Urethane Co., Ltd.) containing the compound of formula (2) as the main ingredient. Takenate D 110N (trade name of products available from Takeda Chemical Industries Co., Ltd.) containing the compound of formula (3) as the main ingredient. Takenate D-120N (trade name of products available from Takeda Chemical Industries Co., Ltd.) containing the compound of formula (4) as the main ingredient. Takenate D-165N, Takenate D-165N-90CX (trade name of products available from Takeda Chemical Industries Co., Ltd.), Sumidur N (trade name of products available from Sumitomo Bayer Urethane Co., Ltd.) containing the compound of formula (5) as the main ingredient. Coronate EH (trade name of products available from Nippon Polyurethane Industries Co., Ltd.) containing the compound of formula (6) as the main ingredient. Desmodule IL (trade name of products available from Bayer AG) containing the compound of formula (7) as the main ingredient. Desmodule HL (trade name of products available from Bayer AG) containing the compound of formula (8) as the main ingredient. Desmodule R (trade name of products available from Bayer AG) containing the compound of the formula (9) as the main ingredient. Millionate MR (trade name of products available from Nippon Polyurethane Industries Co., Ltd.) containing the compound of the formula (10) as the main ingredient. Each of the commercial products is not a pure chemical but a mixture of a compound of the structure shown by each of the formulas as the main ingredient and a compound of a structure similar to that of the main ingredient, and the respective products have an average number of functional groups (number of isocyanate groups per average molecular weight) of from 2.5 to 6. (Organic Solvents) The solvents usable in this invention are those ordinarily employed in the paint and printing ink industries, and can include, for example, hydrocarbon series solvents such as toluene, xylene, Solvesso 100 and Solvesso 150 (trade name of products available from Esso Standard Co. Ltd.), ester series solvents such as ethyl acetate and butyl acetate, ketone series solvents such as methyl ethyl ketone and methyl isobutyl ketone and ether series solvents such as ethylene glycol monoethyl ether and ethylene glycol mono-normal butyl ether. These solvents may be used alone or as a mixture of two or more different solvents. (Mixing Ratio of Polyamines and Polyisocyanates) The polyamines and polyisocyanates are preferably used in such a blending ratio that primary and/or secondary amino groups are present at least in an amount stoichiometrically equivalent to the isocyanate groups, and it is generally preferred to use the amino groups in excess of the stoichiometrically equivalent amount to the isocyanate groups. In this embodiment is is generally advantageous to use and blend polyamines containing three or more primary and/or secondary amino groups in such an amount that at least two of the amino groups can react with the isocyanate groups. In the case of using polyamines containing primary and/or secondary amino groups and tertiary amino groups, it is generally advantageous to blend polyisocyanates such that the isocyanate groups are present in an amount stoichiometrically equal to or less than equivalent to the primary and/or secondary amino groups. More preferably, a polyamine containing four or more primary and/or secondary amino groups and a polyisocyanate having an average number of functional groups (that is, the number of isocyanate groups/average molecular weight) of 2.5 to 6 are used and blended such that at least three amino groups of the polyamine are reacted with the isocyanate groups. Also in these cases, preferably the polyamines are blended in such an amount as containing amino groups in total (primary amino groups, secondary amino groups and tertiary amino groups) of from 1.05 to 5 times of the stoichiometrically equivalent amount relative to the isocyanate groups contained in the polyisocyanates. (Mixing Ratio of Pigments and Other Ingredients) The mixing ratio between the total amount of the polyamines and the polyisocyanates and the pigments, based on 100 % by weight of the total amount of the polyamines, the polyisocyanates and the pigments, has to be such that from 99.9 to 70 % by weight of the pigments are mixed with from 0.1 to 30 % by weight of the total amount of the polyamines and the polyisocyanates. A more preferred mixing ratio is from 99 to 80 parts by weight of the pigments based on from 1 to 20 parts by weight of the total amount of the polyamines and the polyisocyanates. If the amount of the polyamines and the polyisocyanates used is less than 0.1 % by weight, no sufficient effect of this invention can be attained. While on the other hand, if it exceeds 30 % by weight, the viscosity of the composition containing the dispersed pigment is significantly and undesirably increased. (Mixing Ratio of Resins and Pigments) The mixing ratio between the vehicle resins and the pigments in the composition containing the dispersed pigment and prepared according to this invention usually ranges from 98 to 10 parts by weight of the pigments based on from 2 to 90 parts by weight of the solid component in the vehicle resins. A more preferred blending ratio ranges from 97 to 30 parts by weight of the pigments based on from 3 to 70 parts by weight of the solid component in the vehicle resins. (In-Situ Reaction of Polyamines and Polyisocyanates) Vehicle resins generally employed in the paint or printing ink industries have hydroxyl groups or carboxyl groups as the functional groups, which are in most cases reactive with isocyanate groups. Surprisingly, however, if the in-situ reaction is carried out between the amines and the isocyanates in the presence of the vehicle resins, substantial reactions occur only between the amines and the isocyanates. This can be confirmed by determining the amount of unreacted amino groups after the reaction between the amines and the isocyanate by potentiometric titration as shown in Examples 2 and 3. That is, the amount of the unreacted amino groups is substantially equal to the difference between the amount of the amino groups and that of the isocyanate groups used for the reaction. Although the amines and the isocyanates generally undergo a rapid chemical reaction at a room temperature, the temperature may be increased or organotin compounds or the like may be used as a catalyst in a case where it is required to complete the chemical reaction more quickly. Dispersing compounds prepared by mixing and reacting the amines and the isocyanates in the absence of pigments and vehicles are generally difficult to be dissolved in the solvents usually employed in the paint and printing ink industries. For instance, if polyamines and polyisocyanates are reacted in the absence of vehicle resins in a solvent such as toluene, precipitation occurs. If, however, the polyamines and the polyisocyanates are reacted according to the present invention in solutions containing vehicle resins and, optionally, organic solvents, the materials resulting from the in-situ reaction are dissolved or finely dispersed in the solution of the resins. Particularly, in a case where the polyamines and the polyisocyanates are reacted at such a blending ratio that the amino groups are in excess of the stoichiometrically equivalent amount to the isocyanate groups contained in the polyisocyanate and the vehicle resins are having polar functional groups such as carboxyl groups, organic solvents optionally being present, the reaction products are especially well dissolved, which is excellent for dispersing the pigments. It has been found that when the pigments are dispersed in a mixture comprising the in-situ reaction products of the polyamines and polyisocyanates, the vehicle resins and, optionally, organic solvents as described above, the reaction products can provide a very beneficial effect of stabilizing the dispersed pigments. (Preparation of Composition containing Dispersed Pigment) A particularly preferred method for preparing a composition containing dispersed pigment comprises adding polyamines and polyisocyanates to a mixture of pigments, solution of vehicle resins and an optional organic solvent while the said mixture being dispersed. Another preferred embodiment comprises adding polyamines and polyisocyanates to a mixture of vehicle resins and an optional organic solvent, then adding pigments to the said mixture, and after that, dispersing the pigments. As the dispersing equipment for pigments in this case, those usually employed in the paint or printing industries, for example, a sand grinding mill, ball mill, roll mill, attritor and dissolver, can be used as required. (Advantage of the Invention) In accordance with this invention, a composition containing dispersed pigment which is excellent as regards dispersion stability and has good flowing characteristics can be obtained in an extremely simple process. This invention, when practiced, can provide various industrial advantages such as simplification of the production steps which have hitherto brought about problems in the prior art, as well as improvement in the dispersibility and the stability of the pigment dispersions, elimination of the restriction on resins used together caused by the compatibility and the like. Furthermore, since blending ratios of the dispersing agent usable in the present invention are in the range of from 0.1 to 30 % by weight based on the total amount of the pigments and dispersing agent, while about 4.8 to 50 % by weight of dispersing agent based on the total amount of the pigments and dispersing agent have been required in the prior art, the amount of vehicle resins used and the range for selecting them can be greatly extended. Accordingly, the durability and other performance characteristics of the paint films when using the compositions prepared according to this invention do not substantially suffer from undesired effects caused by the composition containing dispersed pigment. Paint, printing ink, and the like prepared by using the compositions containing the dispersed pigment made according to this invention can provide paint films which are excellent in gloss, distinctness of image, color strength, flooding and the like. Furthermore, the dispersing agent prepared by an in-situ reaction according to this invention can easily be synthesized in the presence of a wide variety of vehicle resins which are suitable for use in a paint or the like, whereby the drawbacks involved in the conventional dispersing agents can be eliminated. Embodiment of the Invention The following examples of this invention and Comparative Examples shown below are given solely for the easy understanding of this invention, which are thus in no way restrictive. In the following Examples and Comparative Examples, "part" means parts by weight and "%" means % by weight unless otherwise specified. Example 1 a) 50 parts of a short oil alkyd resin modified with coconut oil (acid value 8, a hydroxy value 80, 60 % solid content), 30 parts of methyl isobutyl ketone and 20 parts of Cinquasia red Y (trade name of products of quinacridone series organic pigment, manufactured by E.I. du Pont de Nemours & Company) were subjected to a dispersing treatment by a sand grind mill for 10 min and, thereafter, 0.28 parts of ethylene diamine were added to the thus formed mixture. Further, while continuing the dispersing treatment, 1.22 parts of 4,4'-methylene bis[cyclohexylisocyanate] (hydrogenated MDI) were added to the mixture formed by the mixing treatment as described above, and the dispersing treatment was continued for further 20 minutes. A composition containing the dispersed pigment (1) was thus prepared. b) For comparison, the same 50 parts of the coconut oil modified alkyd resin, 30 parts of the methyl isobutyl ketone and 20 parts of the Cinquasia red Y were subjected to the dispersing treatment in a sand grind mill for 30 minutes to prepare a composition containing the dispersed pigment (2). The viscosity of the composition containing dispersed pigment (1) and that of the composition containing dispersed pigment (2) were measured by a Model E viscometer (manufactured by Tokyo Keiki Co., Ltd.). The results are shown in Table 1. It is apparent from the results of the above-described experiment that the composition containing dispersed pigment (1) prepared by the method according to this invention has excellent flow characteristics with lower thixotropy. Example 2 a) 0.63 parts of tetraethylenepentamine were added to a mixture of 50 parts of the coconut oil modified alkyd resin as used in Example 1 and 30 parts of Solvesso 100 (trade name of products (hydrocarbon solvents) available from Esso Standard Co., Ltd.) and 0.87 parts Of 4,4'-methylene bis[cyclohexylisocyanate] (hydrogenated MDI) were added to the thus obtained mixture being stirred with a dissolver. When measuring the amount of amino groups contained in the thus obtained resin solution in acetic acid by way of potentiometric titration using perchloric acid as a titration reagent, 0.123 mmol of perchloric acid was required for neutralizing 1 g of the resin solution. The amount is equal to the difference between the amount of the amino groups in the tetraethylene-pentamine and the amount of the isocyanate groups added. Since it was confirmed by way of the potentiometric titration that the alkyd resin and Solvesso 100 had no amino groups, it was ensured that the isocyanate groups added had reacted partially with the amino groups of tetraethylenepentamine. 20 parts of the same pigments as in Example 1 were added to 81.5 parts of the resin solution as described above and the thus obtained mixture was subjected to dispersing by a sand grinding mill for 30 minutes to thereby obtain a composition containing the dispersed pigment (3). b) Further, a composition containing dispersed pigment (4) was obtained with the same procedures as above, except for using 0.4 parts of tetraethylenepentamine and 1.1 parts of 4,4'-methylene bis[cyclohexylisocyanate] (hydrogenated MDI). c) Further, a composition containing dispersed pigment (5) was obtained in the same procedures while replacing tetraethylenepentamine with 0.28 parts of ethylene diamine and using 1.22 parts of 4,4'-methylene bis[cyclohexylisocyanate] (hydrogenated MDI). d) For comparison 20 parts of the same pigment as described above were added to 50 parts of the alkyd resin and 30 parts of the Solvesso 100 also as described above and the thus obtained mixture was subjected to the dispersing treatment in a sand grind mill for 30 minutes to obtain a composition containing dispersed pigment (6). The viscosity for each of the compositions containing dispersed pigment was measured by a Model E viscometer manufactured by Tokyo Keiki Co., Ltd. The results are shown in Table 2. The compositions containing dispersed pigment (3) and (4) exhibited excellent flow characteristics with lower thixotropy. e) 50 parts of the same coconut oil modified alkyd resins as described above and 30 parts of Uvan 128, (trade name of melamine formaldehyde resin varnish manufactured by Mitsui Toatsu Chemical Co., Ltd.) are used to thereby prepare a baking type alkyd melamine resin paint. Each of the paints as described above was diluted with a thinner to a viscosity suitable for spraying and then spray coated on a tin plate. The thus coated tin plate was kept in the air at 140°C for 30 minutes and, thereafter, 20° gloss and 60° gloss for the paint film were measured. Further, after applying each of the diluted paints on the tin plate by way of flow coating (which means such a coating process of putting approx. 5 ccm of paint on a tin plate sized 50 mm x 150 mm, coating the tin plate by disposing the plate vertically thereby causing the paint to flow downwardly and then keeping as it is for 10 minutes), the coated tin plate was kept in air at 140°C for 30 minutes and the paint film was baked. The 20° gloss of the paint film thus obtained was measured. The results are as shown in Table 3. It is apparent from Table 3 that the compositions containing dispersed pigment (3) and (4) are excellent, with the composition containing dispersed pigment (4) being particularly excellent. Tetraethylenepentamine and polyisocyanate compounds were blended in such amounts that two out of the five amino groups of tetraethylenepentamine were reacted with the isocyanate groups in the composition containing dispersed pigment (3). Tetraethylenepentamine and polyisocyanate compounds were blended in such amounts that four amino groups of the tetraethylenepentamine were reacted with the isocyanate groups in the composition containing dispersed pigment (4). In this way, by reacting more amino groups comprised by the polyamine used, the effect of this invention can further be improved. In the composition containing the dispersed pigment (5), ethylenediamine was used and it was blended with the polyisocyanate compound in such amounts that all of the amino groups were reacted with the isocyanate groups. Although the composition containing dispersed pigment (5) was superior as compared with the composition containing dispersed pigment (6) used for comparison, it was inferior to the compositions containing dispersed pigment (3) and (4). These experiments demonstrated the fact that the use of amino groups in a stoichiometrical excess with respect to the isocyanate groups is preferred so that the in-situ reaction product of the polyamine and the polyisocyanate still contains amino groups. Example 3 a) 0.32 parts of tetraethylenepentamine were added to a mixture of 50 parts of the coconut oil modified alkyd resin as used in Example 1 and 30 parts of Solvesso 100 (trade name of products manufactured by Esso Standard Co., Ltd.). 1.18 parts of a trimer of hexamethylene-1,6-diisocyanate having a biuret structure, that is, Takenate D-165N-90CX (trade name of products available from Takeda Chemical Industries Co., Ltd.) (amine equivalent 200) was added to the thus obtained mixture under stirring by a dissolver. The mixture was stirred by the dissolver for further 30 minutes, produced a resin solution (A). The amount of the amino groups contained in one g of the thus obtained resin solution (A) was measured by the method as described in Example 2. It was equivalent to 0.03 mmol of perchloric acid, which was equal to the difference between the amount of the amino groups and that of the isocyanate groups added. b) 20 parts of the same pigment as in Example 1 were added to 81.5 parts of the resin solution (A) and the thus obtained mixture was subjected to a dispersing treatment by a sand grind mill for 30 minutes to form a composition containing dispersed pigment (7). The viscosity was measured by a Model E viscometer manufactured by Tokyo Keiki Co., Ltd. The composition containing dispersed pigment (7) had a viscosity lower than that for each of the compositions containing the dispersed pigment in Example 2 (see Table 2) as shown in Table 4 and exhibited excellent flow characteristics with lower thixotropy. c) To 100 parts of the composition containing dispersed pigment (7) as described above, were added the same 50 parts of the coconut oil modified alkyd resin and 30 parts of the melamine formaldehyde resin varnish as in Example 2 to prepare a baking type melamine alkyd resin paint. The paint was diluted with a thinner to a viscosity suitable for spraying and spray coated onto a tin plate. The thus obtained tin plate was kept in air at 140°C for 30 minutes, which baked the paint film. 20° gloss and 60° gloss of the thus obtained paint film, as well as the 20° gloss of the paint film obtained by the flow coating were measured. The results are shown in Table 5. The composition containing dispersed pigment (7) exhibited superior results to the composition containing dispersed pigment (4) in Example 2 by using a polyfunctional polyisocyanate having more than 2 isocyanate groups. Example 4 a) 0.63 parts of tetraethylenepentamine were combined with 30 parts of methyl isobutyl ketone and the thus obtained mixture was stirred in a dissolver. 0.87 parts of 4,4'-methylene bis[cyclohexylisocyanate] (hydrogenated MDI) were added to the above-mentioned mixture under stirring. A rapid exothermic reaction occurred to form white precipitates. To the thus obtained mixture of reaction product and methyl ethyl ketone, were added the same 50 parts of the coconut oil - modified alkyd resin and 20 parts of pigments as used in Example 1 and 120 parts of glass beads of 1.5 mm⊘. The thus obtained mixture was subjected to a dispersing treatment in a paint shaker for 2 hours to form a composition containing dispersed pigment (8). b) The same 50 parts of the coconut oil - modified alkyd resin and 0.63 parts of tetraethylenepentamine as described above were added to 30 parts of methyl isobutyl ketone, and 0.87 parts of 4,4'-methylene bis[cyclohexylisocyanate] (hydrogenated MDI) were added to the thus formed mixture under stirring by a dissolver, followed by continued stirring for further 30 minutes. To the thus obtained resin solution were added 20 parts of the same pigment as in Example 1 and 120 parts of glass beads of 1.5 mm⊘ and the obtained mixture was shaken in a paint shaker for 2 hours to prepare a composition containing dispersed pigment (9). c) To each 100 parts of the composition containing dispersed pigment (2) in Example 1 and compositions containing dispersed pigments (8) and (9) in this example, were added the same 50 parts of the coconut oil modified alkyd resin and 30 parts of melamine resin varnish as in Example 2, to prepare baking type melamine alkyd resin paints, respectively. The paints were diluted with a thinner to a viscosity suitable for spraying. Each of the thus obtained diluted paints was flow-coated on a tin plate (after putting about 5 ccm of paint to the upper part of a tin plate sized 50 mm x 150 mm, the paint was caused to flow downwardly by disposing the tin plate vertically to coat the tin plate and then kept as it was for 10 minutes). The thus coated tin plate was kept in air at 140°C for 30 minutes and the paint film was baked. The 20° gloss of the thus obtained paint film is shown in the following Table 6. As is apparent from Table 6, the composition containing dispersed pigment (9) had a most excellent performance, whereas the composition containing dispersed pigment (8), the preparation of which did not include an in-situ-reaction in the presence of a vehicle resin is inferior in gloss. Example 5 a) To each 81.5 parts of the resin solution (A) in Example 3, was added each 20 parts of Novoperm orange HL-70 (trade name of azo series pigment products, manufactured by Hoechst A.G.), Hostaperm yellow H-3G (trade name of azo series organic pigment of products manufactured by Hoechst A.G.) and Paliogen red L-3910HD (trade name of perylene series organic pigment of products, manufactured by BASF AG), respectively. The thus obtained mixtures were subjected to the dispersing treatment in a ball mill for 24 hours to prepare compositions containing dispersed pigment (10), (12) and (14), respectively. b) For the comparison, 20 parts of each of the pigments as described above were added to 50 parts of the coconut oil modified alkyd resin and 30 parts of Solvesso 100 (trade name of products manufactured by Esso Standard Co., Ltd.). The thus obtained mixtures were subjected to the dispersing procedures in a ball mill for 24 hours to form compositions containing dispersed pigment (11), (13) and (15). The viscosity for each of the compositions containing dispersed pigment is shown in the following Table 7. c) Further, 50 parts of coconut oil modified alkyd resin and 30 parts of melamine formaldehyde resin varnish were added to the respective compositions containing dispersed pigment as in Example 2, to prepare melamine alkyd resin paints. The thus prepared melamine alkyd resin paints were spray coated on tin plates and the thus coated tin plates were kept in air at 140°C for 30 minutes to effect paint films baking. The 20° gloss and the 60° gloss of the paint film thus obtained were measured. The results are also shown in the following Table 7. From the experiment as described above, it was found that the composition containing the dispersed pigment according to this invention had excellent performance compared with conventional dispersing methods of the pigments. Example 6 0.56 parts of diethylenetriamine were added to a mixture of 45 parts of the same alkyd resin as in Example 1 and 45 parts of xylene and the thus obtained mixture was stirred by a dissolver. 3.65 parts of an adduct of 3 mol of hexamethylene diisocyanate and 1 mol of trimethylol propane, that is, Coronate HL (trade name of products containing 25 % ethyl acetate and 12.5 % NCO, manufactured by Nippon Polyurethane Industries Co., Ltd.) were added to the above-mentioned mixture under stirring by a dissolver, to obtain a resin solution. Then, 10 parts of carbon black MA-100 (trade name of products available from Mitsubishi Chemical Industries Ltd.) were added to the resin solution and the thus obtained mixture was subjected to a dispersing treatment in a sand grind mill for 30 minutes. In this manner, a composition containing dispersed pigment (16) was obtained. For the comparison, a composition containing dispersed pigment (17) was prepared in the same procedures as described above without adding polyamine and polyisocyanate. The viscosity for each of the compositions was measured by a rotary Model E viscometer (manufactured by Tokyo Keiki Co., Ltd.). The results are shown in the following Table 8. Example 7 a) 50 parts of Acrydic A-405 (trade name of acrylic resin varnish products, available from Dainippon Ink & Chemicals, Inc.), 50 parts of xylene, 20 parts of Hostaperm yellow H-3G (trade name of products available from Hoechst AG) were subjected to dispersing treatment in a grind mill for five minutes. 0.32 parts of tetraethylenepentamine were added to the thus obtained mixture and 1.72 parts of Sumidur (trade name of products containing 16.5 % NCO, 12.5 % of methyl glycol acetate and 12.5 % of xylene, manufactured by Sumitomo Bayer Urethane Co. Ltd.) were added to the thus obtained mixture under the dispersing treatment and further subjected to a dispersing treatment for 25 minutes to obtain a dispersed paste (18). b) For the comparison, a composition containing dispersed pigment (19) was prepared without adding amine and isocyanate. 90 parts of Acrydic A-105 and 60 parts of Super Beckamine J-820 (trade name of products of melamine resin varnish, manufactured by Dainippon Ink & Chemical Industries Co., Ltd.) were added to the compositions containing dispersed pigments respectively, to prepare baking type melamine acrylic resin paints. Each of the paints was coated on a glass plate by using a 1.524 mm (6 mil) applicator and baked at 150°C for 30 minutes. The 20° gloss and the 60° gloss for the obtained paint film were measured. The results are shown in Table 9. Table 9 shows that the composition containing dispersed pigment (18) according to this invention is superior to the Comparative Example, that is, the composition containing dispersed pigment (19). Example 8 a) 25 parts of toluene and a further 20 parts of Transparent oxide red 30-1005 (trade name of products for transparent iron oxide pigment, manufactured by The Hilton-Davis Chemical Co.) were added to 60 parts of Acrydic A-405 (trade name of products manufactured by Dainippon Ink & Chemicals Industries Co., Ltd.), and the thus obtained mixture was subjected to a dispersing treatment by a sand grind mill for five minutes. 0.29 parts of tetraethylenepentamine were added to the thus obtained mixture and, while continuing the dispersing treatment to the mixture, 1.21 parts of Coronate EH (trade name of products containing 21.3 % NCO manufactured by Nippon Polyurethane Industries Co., Ltd.) were added and subjected to dispersing treatment for 25 minutes. In this way, a composition containing dispersed pigment (20) was obtained. For the comparison, a composition containing dispersed pigment (21) was prepared by the same dispersing treatment by a sand grind mill without adding amine and isocyanate. b) The viscosity for each of the compositions containing dispersed pigment was measured by a rotary Model E viscometer (manufactured by Tokyo Keiki Co., Ltd.), and 80 parts of Acrydic A-405 (trade name of products manufactured by Dainippon Ink & Chemical Industries Co., Ltd.) and 60 parts of Super Beckamine J-820 (trade name of products manufactured by Dainippon Ink & Chemical Industries Co., Ltd.) were added respectively to both of the compositions containing the dispersed pigment, to prepare baking type melamine acrylic resin paints. Each of the thus obtained paints was coated on a glass plate using a 1.524 mm (6 mil) applicator and baked at 150°C for 30 minutes. The 20° gloss and the 60° gloss for the paint film thus obtained were measured. The results are shown in Table 10. Table 10 shows that the composition containing dispersed pigment (20) according to this invention is superior to the Comparative Example, that is, the composition containing dispersed pigment (21). Comparative Example 1 The composition containing dispersed pigment prepared according to this invention, the composition containing dispersed pigment prepared by using the dispersing agent described in the example of Japanese Patent Laid-Open No. 160396/1975 and a composition containing dispersed pigment prepared by using a dispersing agent described as Agent 1 in the British Patent Specification No. 1393401 were compared with each other. Each of the dispersing agents is referred to hereinafter with the numbers as described below. To 20 parts of Cinquasia red Y (trade name of products available from E. I. du Pont de Nemours & Co.) were added 10 parts of each of the dispersing agents as the solid content and then Solvesso 100 (trade name of products available from Esso Standard Co., Ltd.), so as to make up the entire amount to 60 parts. The thus obtained mixture was subjected to dispersing treatment by a sand grind mill for 30 minutes and, thereafter, 40 parts of the coconut oil modified alkyd resin as described in Example 1 was added and subjected to a dispersing treatment for 10 minutes to obtain compositions containing dispersed pigment (22), (23) and (24) in order of the number of dispersing agent. To each 100 parts of the compositions containing dispersed pigment (3) and (4) in Example 2 and compositions containing dispersed pigment (22), (23) and (24) as described above, were added the same 50 parts of the coconut oil modified alkyd resin and 30 parts of the melamine resin varnish as in Example 2, to prepare baking type alkyd melamine resin paints. Each of the paints was diluted with a thinner to a viscosity suitable for spraying, coated onto a tin plate by way of flow coating and spray-coated and baked at 140°C for 30 minutes. Then, the 20° gloss on the thus obtained paint film was measured. The results are shown in Table 11. Table 11 shows that the dispersion composition according to this invention, that is, the compositions containing dispersed pigments (3) and (4) are more excellent in gloss behaviour.

Claims: A method of preparing a composition containig a dispersed pigment, wherein at least one polyamine having two or more of primary amino groups and / or secondary amino groups, at least one polyisocyanates having two or more of isocyanate groups, a vehicle resin and an organic solvent are blended and the polyamines and polyisocyanates are reacted in situ, and thereafter, the pigments are blended and dispersed. A method of preparing a composition containing a dispersed pigment, wherein a pigment, a vehicle resin and an organic solvent are mixed and dispersed and, thereafter, at least one polyamine having two or more of primary amino groups and or secondary amino groups, at least one polyisocyanates having two or more of isocyanate groups are blended and the polyamines and polyisocyanates are reacted in situ. A method of preparing a composition containing a dispersed pigment, wherein at least one polyamine having two or more of primary amino groups and / or secondary amino groups, at least one polyisocyanates having two or more of isocyanate groups are added to and dispersed in the pigment, a vehicle resin and the organic solvent while mixing and dispersing them, and the polyamines and polyisocyanates are reacted in situ. A method of preparing a composition containing a dispersed pigment as defined in claim 1 to 3, wherein the amino groups thereof are in excess of the stoichiometrically equivalent amount to the isocyanate groups contained in the polyisocyanate. A method of preparing a composition containing a dispersed pigment as defined in claim 1 to 4, wherein the average number of functional groups of the polyisocyanates is from 2.5 to 6. A method of preparing a composition containing a dispersed pigment as defined in claims 1 to 4, wherein the polyamines are blended in such an amount as containing amino groups from 1.05 to 5 times of the stoichiometrically equivalent amount relative to the isocyanate groups contained in the polyisocyanates and the polyamines and polyisocyanates are reacted in situ. A method of preparing a composition containing a dispersed pigment as defined in any one of claims 1 to 4, wherein the polyamines are selected from the group consisting of ethylene diamine, 1,3-propylenediamine, hexamethylenediamine, diethylenetriamine, triethylene tetramine, tetraethylene pentamine, pentaethylene hexamine, bisaminopropyl piperazine, bisaminopyridine, xylylenediamine, metaphenylenediamine, 4,4'-diaminodiphenyl methane and polyethyleneimine.

Inventors: GOUJI, HARUNORI, KATAOKA, HIROYOSHI, KATO, HISAO
Applicants: NIPPON PAINT CO., LTD.
Application year: 1985
Main classification: C09D17
IPC codes: C08G18, C09D11, C09C3, C09D7, D06P1, C09D201, C09B67, C09D17, B01F17, C09D175, B01J13