JP6224392B2 - Brightness improvement agent for glossy colored paints - Google Patents

Description

  The present invention relates to a sharpness improving agent that improves the vividness of a finished coating film by adding it to a coating composition in which a pigment is dispersed.

In many paints and inks, a solid pigment is stably dispersed in a medium using a so-called pigment dispersant such as a surfactant or a polymer compound having a polar group. However, when an actually applied coating film is dried, a black paint or a dark-colored coating film may cause a so-called white blur, which looks whitish due to light adjustment. This phenomenon is particularly observed in water-based paints using water-based emulsion type resins.
As a method for improving this phenomenon, a method of dispersing carbon black in a black paint has been proposed. Patent Documents 2 to 6 propose a method for improving the dispersibility of carbon black in a paint resin by using an aqueous dispersion together with a dispersant. Patent Documents 7 to 13 propose a method for improving the jet blackness by improving the dispersibility of the carbon black itself by improving the carbon black production method. Further, in Patent Documents 14 to 22, the dispersion of carbon black is stabilized by polymerizing a vinyl polymer from the surface of the carbon black, and as a result, jet blackness is improved. On the other hand, in Patent Documents 23 to 28, for paints that require a higher appearance such as automobile paints, in addition to improving the dispersion of carbon black and organic pigments, the addition of colloidal particles or the improvement of the coating system can further increase jet blackness. High definition is achieved.

JP 2006-512988 A JP-A-11-189735 JP 11-189736 A JP 2000-212468 JP 2000-248194 A JP 2000-248197 A JP 2000-313820 A JP 2001-240767 A JP 2001-240766 A JP 2001-240768 A JP 2002-12792 A JP 2004-168898 A JP-A-2005-120223 JP 2000-63698 A JP 2006-285632 A JP-A-5-247151 JP-A-5-247152 JP-A-5-247152 JP-A-5-295052 JP-A-6-263830 JP-A-6-166706 JP 2000-154327 A JP2005-232249 JP 2006-299239 A JP 2002-275425 A JP-A-9-125007 JP2009-50807 JP2011-1536

Ohno, Mizuta, Sakurai: Proceedings of the 17th Microsphere Discussion Meeting, 99 (2012) K. Ohno, T .; Morinaga, K .; Koh, Y .; Tsujii, T .; Fukuda, Synthesis of Monodisperse Silica Particles Coated with Well-Defined, High-Density Polymer Breathed By Surface Trans-Initiated Atomized

However, even if the dispersibility of carbon black or organic pigment is improved, there is no effect of improving the so-called white blur, which is a phenomenon in which the coating film looks whitish due to irregular reflection of light derived from the coating resin. In other words, emulsion paints that are commonly used in water-based paints form a uniform film by coalescing emulsion particles in the drying process, but some of the particles are microphase-separated and light is diffusely reflected at the interface. It is said that white blur will occur. Also, oil-based paints, such as two-component urethane paints, have a microphase due to the fact that when the main resin and the resin used as the curing agent are mixed, the two resins are not completely compatible and have a sea-island structure. White blur due to irregular reflection of light from the separation interface may occur due to the paint environment. With paints consisting of multiple layers such as automobile paints, it is possible to improve the sharpness by improving the coating method, but with paints such as architectural paints that are painted with brushes or rollers. Difficult to improve. In Patent Document 22, white blurring is improved by using a dispersion composition of carbon black or an organic pigment in which colloidal particles having a particle diameter of 5 to 100 nm are adsorbed on the pigment surface. However, with general-purpose paints, it is difficult to use special pigments and painting methods in terms of cost.
Accordingly, the object of the present invention is to improve the white blur phenomenon caused by diffused reflection of light, which has not been achieved simply by improving the dispersibility of conventional carbon black and organic pigments in paint resins. The object is to provide a so-called sharpness improving agent that improves the sharpness.

  As a result of various studies, the present inventors have reached the present invention. According to Non-Patent Document 1, by adding a small amount of fine particles obtained by synthesizing a graft polymer from the surface of carbon black, high contrast of the color of the silica fine particle thin film having a structural color was achieved by absorbing scattered light by carbon black. It is described. Furthermore, according to Patent Document 1, a method of synthesizing a polymer having a uniform length by using a living radical polymerization method on the surface of silica fine particles has been achieved. That is, it can be easily estimated that the effect of uniformly dispersing fine particles using the steric repulsion effect of the polymer is higher than those in Patent Documents 14 to 21. By applying the living radical polymerization method from the fine particle surface of Patent Document 1 and synthesizing a polymer having a uniform chain length on the carbon black surface, the scattered light absorption effect according to the invention of Non-Patent Document 2 can be achieved. The effect of preventing irregular reflection of light can also be achieved by adding an additive obtained by synthesizing a polymer having a uniform chain length on the surface of carbon black to a general paint using the above phenomenon. As a result, it was found that an additive that synthesizes a polymer with a uniform chain length on the surface of carbon black exerts an effect of improving white blur regardless of the type of pigment used.

  The sharpness-improving agent of the present invention can be added to a colored paint in which a color pigment is dispersed to add a small amount of white blurring due to irregular reflection of light, which is observed in a dried coating film after coating, particularly a dark-colored paint. Effective in improving.

Shows a phenomenon in which aggregation occurs over time even when carbon black alone is dispersed by ultrasonic waves. Is a polymer graft chain synthesized on the surface of carbon black in FIG. 1 by a living radical polymerization method. Aggregation does not occur even when the solution is diluted with time. Is obtained by dispersing the carbon black of FIG. 1 using a commercially available pigment dispersant. General pigment dispersants aggregate carbon black gently, but have the effect of making it difficult to form larger aggregates due to the electrostatic repulsion effect of the pigment dispersant adsorbed on the carbon black surface. However, when the solution is extremely dilute, the effect is reduced, and carbon black is agglomerated.

  In the present specification, the “carbon black fine particles” are not particularly limited by the carbon black production method as long as they are carbon black particles having a primary particle diameter of 5 nm to 60 nm.

  In the present specification, the “composite fine particles” mean modified carbon black fine particles formed by bonding a polymer graft chain to the surface of the carbon black fine particles. In the present specification, “carbon black fine particles” are defined above. Is used in distinction.

  In the present specification, the “bond” means a bond formed by a general chemical reaction, and specifically includes a covalent bond and an ionic bond.

  In this specification, “living radical polymerization” means that the polymerization activity is maintained at the end of the produced polymer even after the completion of the polymerization reaction, as in a polymerization reaction with no or negligible chain transfer reaction and termination reaction. , Meaning that the polymerization reaction can be started again by adding a monomer. Living radical polymerization is characterized by the ability to synthesize polymers having an arbitrary average molecular weight by adjusting the concentration ratio of monomer and polymerization initiator, and the molecular weight distribution of the resulting polymer is extremely narrow. It can be applied to polymers. In this specification, living radical polymerization is abbreviated as “LRP”. Examples of the radically polymerizable monomer constituting the graft chain include ethyl allylate, methyl methacrylate, styrene, vinyl acetate, acrylonitrile and the like.

  In the present specification, “living radical polymerization conditions” is appropriately selected by those skilled in the art in order to ensure that the living radical polymerization based on the polymerization initiating group formed on the surface of the carbon black fine particles proceeds reliably and satisfactorily. It means adopting polymerization conditions.

  In the present specification, the “polymerization initiating group” means a group bonded to the surface of the carbon black fine particles by a monomer compound containing a group that plays a role in initiating a polymerization reaction, and the monomer compound has such a role. There is no particular limitation as long as it includes a group that fulfills the function.

(Description of Preferred Embodiment)
Hereinafter, preferred embodiments of the present invention will be described. The embodiments provided below are provided for a better understanding of the present invention, and it is understood that the scope of the present invention should not be limited to the following description. Therefore, it is obvious that those skilled in the art can make appropriate modifications within the scope of the present invention with reference to the description in the present specification.

  In one aspect, the present invention provides composite fine particles in which polymer graft chains are bonded to the surface of carbon black fine particles. By grafting the polymer graft chain onto the surface of the carbon black fine particles, a repulsive force against compression is obtained between the composite fine particles in the whole system in a good solvent, and the composite fine particles are uniformly dispersed in the paint system and diffusely reflected. It can absorb scattered light and interfere with it. In order for such composite fine particles to exert an influence on visible light, it is important that the length of the graft polymer on the surface of the carbon black fine particles can be uniformly dispersed without aggregation of the composite fine particles of each other, In general, the length of the graft polymer on the surface of the fine particles needs to be about several hundred nm. Although depending on the type of monomer, if the size of one molecule is about 0.1 nm, a molecular weight of several thousand or more is required to exert a sufficient steric repulsive force on the carbon black fine particles. Furthermore, the carbon black itself is not spherical but has a distorted shape, and the graft polymer density from the surface of the carbon black is not very high, so the graft polymer is not completely linear. More preferably, it is desirable to have a molecular weight of about several tens of thousands. The polymer graft chain is obtained by living radical polymerization of a monomer based on a polymerization initiating group on the surface of the carbon black fine particles. Examples of the monomer include acrylic acid derivatives, methacrylic acid derivatives, styrene derivatives, vinyl acetate, acrylonitrile, and combinations thereof, but are not limited thereto and are appropriately selected within the scope recognized by those skilled in the art. That is, a monomer capable of uniformly dispersing the polymer with respect to the paint to be added is selected. At this time, the monomer composition of the polymer is desirably a composition that can be uniformly dispersed in the coating resin to be added. Examples of the monomer selection criteria at this time include giving an appropriate solubility parameter (SP value) and surface tension value in accordance with the coating resin. In general, in order to uniformly disperse in a resin for paint, a monomer composition having an SP value of 8 to 11 as a graft polymer on the surface of the composite fine particles and a surface tension value of 31 mN / m (millinewton / meter) or more is used. preferable. When the SP value is out of this range, the compatibility with the resin is remarkably deteriorated and the possibility of separation is increased. Moreover, when the surface tension value of the graft polymer is less than 31 mN / m, surface activity occurs in the graft polymer, and the possibility of separation / aggregation due to orientation on the surface of the coating film increases.

  In order to uniformly act on the irregular reflection of visible light, the molecular weight distribution of the polymer graft chain is preferably 1 to 1.5, more preferably a value close to 1. However, if the molecular weight of the polymer graft chain is sufficiently large, the steric repulsion can be easily exerted, so that the effect can be exhibited even if the molecular weight distribution is increased. However, an extremely high molecular weight is not preferable because the compatibility with the coating resin deteriorates and is separated. Although it depends on the composition of the coating system and graft polymer to be added generally, the number average molecular weight is preferably 3000 to 100,000.

  The particle size of the carbon black fine particles is preferably as small as possible so as not to affect the color developability of the color pigment. In order to perform graft polymerization from the surface, carbon black fine particles having a particle size of 5 nm to 60 nm are preferable, and fine particles having a particle size of 10 nm to 30 m are more preferable. If the particle size is less than 5 nm, the grafting density is lowered when graft polymerization is performed from the surface of the fine particles, and as a result, carbon black is aggregated, and irregular reflection of visible light cannot be prevented. When the particle diameter exceeds 60 nm, the effect of interference of the obtained graft polymer fine particles on light is weak, which is not preferable.

  Since the carbon black fine particles used in the present invention may be those having a hydroxyl group on the surface, general commercially available products can be used as long as they are used as color pigments such as channel black and furnace black.

In another aspect, composite fine particles of the present invention in which polymer graft chains are bonded to the surface of carbon black fine particles are produced through the following steps:
a) a step of bonding a polymerization initiating group to the surface of the carbon black fine particles;
b) A step of contacting carbon black fine particles having a polymerization initiating group bonded to the surface and a monomer under living radical polymerization conditions to obtain composite fine particles in which polymer graft chains are bonded to the surface of the fine particles at a high density.

In a preferred embodiment, in order to form a polymerization initiating group for living radical polymerization on the surface of the carbon black fine particles in the step a), the following formula:
The procedure of bonding the polymerization initiating group-containing compound represented by the formula (1) to the surface of the carbon black fine particles is taken.

In the formula, R ₁ and R ₂ are preferably C1 or C2 alkyl. X ₁ and X ₂ are halogen atoms, and Br is particularly preferable. As used herein, “alkyl” refers to a monovalent group formed by loss of one hydrogen atom from an aliphatic hydrocarbon (alkane) such as methane, ethane, or propane, and is generally represented by C _n H _{2n + 1.} Where n is a positive integer. Representative examples of the polymerization initiator group-containing compound include (2-bromoisobutyryl bromide).

  By bringing the carbon black fine particles having a polymerization initiating group formed on the surface and the above-mentioned monomers into contact with each other under living radical polymerization conditions, the polymer graft chain has a high density and carbon. Composite fine particles bonded to the surface of the black fine particles can be obtained. Here, the kind of monomer brought into contact with the carbon black fine particles having a polymerization initiating group on the surface may be single or plural.

  A paint suitable for using the composite fine particles obtained in the present invention as a sharpness improving agent is a glossy paint. For example, when the additive of the present invention is added to high-gloss architectural paints, automotive color base paints, furniture paints, etc., the phenomenon of white blurring due to irregular reflection of light seen in the coating film after drying can be improved. it can. In particular, it is suitable for addition to dark paints in which white blur is conspicuous.

  The time when the sharpness improving agent according to the present invention is added to the paint is arbitrary, and can be added even during the process of kneading the pigment or after the paint is produced.

  The amount of the sharpness improving agent according to the present invention varies depending on the type of resin in the paint and the composition of the pigment, but carbon black usually contained in the additive (converted to carbon black alone, not composite fine particles) 0.0001 to 0.1% by weight, preferably 0.001 to 0.01% by weight, based on the weight of the paint vehicle.

  If the added amount of carbon black is less than 0.0001% by weight, the effect of improving the sharpness cannot be sufficiently provided. Even if it is added in an amount of more than 0.1% by weight, the effect of improving the sharpness cannot be sufficiently imparted due to a phenomenon considered to be due to the aggregation of the sharpness improving agent.

Next, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.
In the following, “parts” and “%” represent “parts by weight” and “% by weight”, respectively.

Production Example 1: Preparation of carbon black fine particles (1) having a polymerization initiating group bonded to the surface Introduction groups were introduced into the surface of carbon black fine particles by the following procedure. 5 g of carbon black fine particles FW-200 (manufactured by Orion Engineered Carbons Co., Ltd .; average particle size 13 nm) are added to 95 g of N, N-dimethylformamide (hereinafter referred to as DMF), and 1 hour using an ultrasonic disperser. Dispersed. While stirring this carbon black dispersion with a magnetic stirrer, 3.2 mL of 2-bromoisobutyryl bromide (hereinafter referred to as BIBB) was added. The mixture was stirred at room temperature for 18 hours and then 100 mL of ethanol was added. The mixture was further stirred at room temperature for 1 hour, and then the carbon black fine particles were collected by a centrifugal separator, washed with ethanol and toluene, and then stored in a 5% solution in toluene (hereinafter referred to as a carbon black initiator solution).

Production Example 2: In a 1000 ml reaction vessel equipped with a living radical polymerization stirrer using a carbon black fine particle (1) having a polymerization initiation group bonded to the surface , a reflux condenser, a thermometer, and a nitrogen gas inlet, Toluene (300 g), carbon black initiator solution prepared in Production Example 1 (40 g), ethyl methacrylate (228 g), ethyl 2-bromoisobutyrate (EtBrIB; 1.56 g), tin 2-ethylhexanoate ( II) (0.25 g) and glucose (0.14 g) were added, and after sufficiently degassing with nitrogen gas, copper (II) bromide (23 mg) and tris (2-pyridyl) previously dissolved in 10 g of DMF Methyl) amine (26 mg) was added. Thereafter, polymerization was carried out at 85 ° C. for 12 hours. The monomer conversion was determined by gas chromatography using n-octane as an internal standard, and the molecular weight and molecular weight distribution of the free polymer produced from EtBrIB were determined by GPC. Furthermore, the surface tension value of the free polymer (hereinafter referred to as ST value) was determined using the maximum bubble pressure method, and the SP value was determined by substituting the determined surface tension value into the Hildebrand equation. The number average molecular weight of the free polymer in the carbon black fine particles (PEMA-CB) grafted with poly (ethyl methacrylate) obtained by the above polymerization is 14230 (Mw / Mn = 1.19) in terms of polystyrene, monomer conversion rate Of 97%, ST value 35.6 mN / m, SP value 9.8. The grafted carbon black fine particles (PEMA-CB), that is, the numerical value converted to carbon black alone in the composite fine particles is diluted with toluene so that the concentration becomes 0.02%, and this is added to the sharpness improving agent sample ( It was used for the following paint test as A-1).

Production Example 3: A 1000 ml reaction vessel equipped with a living radical polymerization stirrer using a carbon black fine particle (1) having a polymerization initiation group bonded to the surface , a reflux condenser, a thermometer, and a nitrogen gas inlet, Toluene (300 g), carbon black initiator solution prepared in Production Example 1 (
40 g), methyl methacrylate (100 g), styrene (104 g), ethyl 2-bromoisobutyrate (EtBrIB; 3.9 g), tin (II) 2-ethylhexanoate (0.25 g), and glucose (0. 14 g), and after sufficiently degassing with nitrogen gas, copper (II) bromide (23 mg) and tris (2-pyridylmethyl) amine (26 mg) previously dissolved in 10 g of DMF were added. Thereafter, polymerization was carried out at 85 ° C. for 12 hours. The number average molecular weight of the free polymer in the carbon black fine particles (PMMA / St-carbon black) grafted with the poly (methacrylic acid / styrene copolymer) obtained by the above polymerization is 4690 (Mw / Mn = 1) in terms of polystyrene. 26), the monomer conversion was 98%, the ST value was 41.4 mN / m, and the SP value was 10.5. The grafted carbon black fine particles (PMMA / St-CB), that is, diluted with toluene so that the numerical value converted into carbon black alone in the composite fine particles becomes a concentration of 0.02%, and this is a sample for improving visual clarity It was used in the following paint test as (A-2).

Production Example 4: In a 1000 ml reaction vessel equipped with a living radical polymerization stirrer using a carbon black fine particle (1) having a polymerization initiator group bonded to the surface , a reflux condenser, a thermometer, and a nitrogen gas inlet, Toluene (300 g), carbon black initiator solution prepared in Production Example 1 (40 g), 2-methoxyethyl methacrylate (200 g), ethyl 2-bromoisobutyrate (EtBrIB; 0.45 g), 2-ethylhexane Copper (II) bromide (23 mg) and tris (preliminarily dissolved in 10 g of DMF were added after tin (II) oxide (0.25 g) and glucose (0.14 g) were added and thoroughly degassed with nitrogen gas. 2-Pyridylmethyl) amine (26 mg) was added. Thereafter, polymerization was carried out at 85 ° C. for 12 hours. The number average molecular weight of the free polymer in the carbon black fine particles (PMEMA-carbon black) grafted with poly (2-methoxyethyl methacrylate) obtained by the polymerization is 75600 (Mw / Mn = 1.47) in terms of polystyrene. The monomer conversion was 97%, the ST value was 34.5 mN / m, and the SP value was 9.2. The grafted carbon black fine particles (PEMA-CB), that is, the numerical value converted into carbon black alone in the composite fine particles is diluted with toluene so that the concentration becomes 0.02%. -3) was used in the following paint test.

Production Example 5: In a 1000 ml reaction vessel equipped with a living radical polymerization stirrer using a carbon black fine particle (1) having a polymerization initiation group bonded to the surface , a reflux condenser, a thermometer, and a nitrogen gas inlet. Toluene (300 g), carbon black initiator solution prepared in Production Example 1 (40 g), 2-methoxyethyl acrylate (200 g), ethyl 2-bromoisobutyrate (EtBrIB; 1.5 g), 2-ethylhexane Copper (II) bromide (23 mg) and tris (preliminarily dissolved in 10 g of DMF were added after tin (II) oxide (0.25 g) and glucose (0.14 g) were added and thoroughly degassed with nitrogen gas. 2-Pyridylmethyl) amine (26 mg) was added. Thereafter, polymerization was carried out at 85 ° C. for 12 hours. The number average molecular weight of the free polymer in the carbon black fine particles (P2MTA-CB) grafted with poly (2-methoxyethyl acrylate) obtained by the polymerization is 12800 (Mw / Mn = 1.15) in terms of polystyrene. Monomer conversion was 98%, ST value 32.4 mN / m, and SP value 9.1. The grafted carbon black fine particles (P2MTA-CB), that is, the value converted into carbon black alone in the composite fine particles is diluted with toluene so that the concentration becomes 0.02%, and this is added to the sharpness improving agent sample (A -4) was used in the following paint test.

Production Example 6: In a 1000 ml reaction vessel equipped with a living radical polymerization stirrer using a carbon black fine particle (1) having a polymerization initiation group bonded to the surface , a reflux condenser, a thermometer, and a nitrogen gas inlet. Toluene (228 g), carbon black initiator solution prepared in Production Example 1 (
40 g), ethyl methacrylate (114 g), ethyl 2-bromoisobutyrate (EtBrIB; 1.95 g), tin (II) 2-ethylhexanoate (0.25 g), and glucose (0.14 g), After sufficiently degassing with nitrogen gas, copper (II) bromide (23 mg) and tris (2-pyridylmethyl) amine (26 mg) previously dissolved in 10 g of DMF were added. Thereafter, sampling was performed at the time of polymerization at 85 ° C. for 4 hours. The number average molecular weight of the free polymer in the carbon black fine particles (PEMA-carbon black) grafted with poly (ethyl methacrylate) at this time is 11200 (Mw / Mn = 1.30) in terms of polystyrene, and the monomer conversion rate is It was 84%. To this reaction solution, benzyl methacrylate (176 g) and toluene (200 g) were further added and reacted at 85 ° C. for 12 hours. The number average molecular weight of the free polymer in the carbon black fine particles (PEMA / Bz-CB) grafted with poly (ethyl methacrylate-benzyl methacrylate) obtained by the above polymerization is 29800 (Mw / Mn = 1. 34) The monomer conversion rate was 94%, the ST value was 36.9 mN / m, and the SP value was 9.5. Since the molecular weight increases linearly with a narrow molecular weight distribution, it is considered that the block polymer has been synthesized. This grafted carbon bra CB), that is, diluted with toluene so that the numerical value converted into carbon black alone in the composite fine particles becomes a concentration of 0.02%, and this is used as a sharpness improving agent sample (A-5) It used for the following paint test.

Production Example 7: Preparation of carbon black fine particles (2) having a polymerization initiating group bonded to the surface MA-600 (manufactured by Mitsubishi Chemical Corporation; average particle size 20 nm) was used as the carbon black fine particles in Production Example 1. Prepared a carbon black initiator solution in the same manner as in Production Example 1.

Production Example 8: In a 1000 ml reaction vessel equipped with a living radical polymerization stirrer using a carbon black fine particle (2) having a polymerization initiation group bonded to the surface , a reflux condenser, a thermometer, and a nitrogen gas inlet, Toluene (300 g), carbon black initiator solution prepared in Production Example 7 (40 g), butyl methacrylate (200 g), ethyl 2-bromoisobutyrate (EtBrIB; 1.37 g), tin 2-ethylhexanoate ( II) (0.25 g) and glucose (0.14 g) were added, and after sufficiently degassing with nitrogen gas, copper (II) bromide (23 mg) and tris (2-pyridyl) previously dissolved in 10 g of DMF Methyl) amine (26 mg) was added. Thereafter, polymerization was carried out at 85 ° C. for 12 hours. The monomer conversion was determined by gas chromatography, and the molecular weight and molecular weight distribution of the free polymer produced from EtBrIB were determined by GPC. The number average molecular weight of the free polymer in the carbon black fine particles (PBMA-CB) grafted with poly (butyl methacrylate) obtained by the above polymerization is 21100 (Mw / Mn = 1.28) in terms of polystyrene, monomer conversion rate Was 99%, ST value 31.2 mN / m, and SP value 8.8. The grafted carbon black fine particles (PBMA-CB), that is, the numerical value converted into carbon black alone in the composite fine particles is diluted with toluene so that the concentration becomes 0.02%, and this is added to the sharpness improving agent sample (A It was used for the following paint test as -6).

Production Example 9: In a 1000 ml reaction vessel equipped with a living radical polymerization stirrer using a carbon black fine particle (2) having a polymerization initiation group bonded to the surface , a reflux condenser, a thermometer, and a nitrogen gas inlet. Toluene (300 g), carbon black initiator solution (40 g) prepared in Production Example 7, ethyl acrylate (100 g), styrene (50 g), vinyl acetate (20 g), acrylonitrile (30 g), ethyl 2-bromoisobuty A rate (EtBrIB; 1.36 g), tin (II) 2-ethylhexanoate (0.25 g), and glucose (0.14 g) were added, thoroughly deaerated with nitrogen gas, and then dissolved in 10 g of DMF in advance. Copper (II) bromide (23 mg) and tris (2-pyridylmethyl) amine (26 mg) were added. Thereafter, polymerization was carried out at 85 ° C. for 12 hours. The number average molecular weight of the free polymer in the carbon black fine particles (PEA / St / VAc / AN-CB) grafted with poly (ethyl acrylate-styrene-vinyl acetate-acrylonitrile copolymer) obtained by the above polymerization is polystyrene. 28800 (Mw / Mn = 1.25) in terms of conversion, the monomer conversion was 96%, the ST value was 37.0 mN / m, and the SP value was 10.2. The grafted carbon black fine particles (PEA / St / VAc / AN-CB), that is, diluted with toluene so that the numerical value converted into carbon black alone in the composite fine particles becomes a concentration of 0.02%, and this is clearly displayed. It used for the following paint test as a property improvement agent sample (A-7).

Production Example 10: A 1000 ml reaction vessel equipped with a living radical polymerization stirrer using a carbon black fine particle (2) having a polymerization initiator group bonded to its surface , a reflux condenser, a thermometer, and a nitrogen gas inlet, Toluene (300 g), carbon black initiator solution prepared in Production Example 7 (40 g), butyl acrylate (64 g), styrene (52 g), 2-methoxyethyl acrylate (65 g), ethyl 2-bromoisobutyrate (EtBrIB; 1.95 g), tin (II) 2-ethylhexanoate (0.25 g), and glucose (0.14 g) were added, degassed sufficiently with nitrogen gas, and then dissolved in 10 g of DMF in advance. Copper (II) chloride (23 mg) and tris (2-pyridylmethyl) amine (26 mg) were added. Thereafter, polymerization was carried out at 85 ° C. for 12 hours. The monomer conversion was determined by gas chromatography, and the molecular weight and molecular weight distribution of the free polymer produced from EtBrIB were determined by GPC. The number average molecular weight of the free polymer in the carbon black fine particles (PBA-2MTA-St-CB) grafted with poly (butyl acrylate-acrylate 2-methoxyethyl-styrene) obtained by the above polymerization is 36200 in terms of polystyrene. (Mw / Mn = 1.25), monomer conversion was 98%, ST value was 34.6 mN / m, and SP value was 9.5. This grafted carbon black fine particle (PBA-2MTA-St-CB), that is, the value converted to carbon black alone in the composite fine particle is diluted with toluene so that the concentration becomes 0.02%, and this is improved in sharpness It was used for the following paint test as an agent sample (A-8).

Production Comparative Example 1
In a 1000 ml reaction vessel equipped with a stirrer, reflux condenser, thermometer, and nitrogen gas inlet, toluene (300 g), carbon black initiator solution prepared in Production Example 1 (40 g), ethyl methacrylate (200 g) ), Ethyl 2-bromoisobutyrate (EtBrIB; 9.75 g), tin (II) 2-ethylhexanoate (0.25 g), and glucose (0.14 g), and after sufficient deaeration with nitrogen gas Copper (II) bromide (23 mg) and tris (2-pyridylmethyl) amine (26 mg), previously dissolved in 10 g DMF, were added. Thereafter, polymerization was carried out at 85 ° C. for 12 hours. The monomer conversion was determined by gas chromatography, and the molecular weight and molecular weight distribution of the free polymer produced from EtBrIB were determined by GPC. Furthermore, the ST value of the free polymer was determined using the maximum bubble pressure method, and the SP value was determined by substituting the determined surface tension value into the Hildebrand equation. The number average molecular weight of the free polymer in the carbon black fine particles (PEMA-CB) grafted with poly (ethyl methacrylate) obtained by the above polymerization is 2240 (Mw / Mn = 1.28) in terms of polystyrene, monomer conversion rate Was 98%, ST value was 41.1 mN / m, and SP value was 10.5. The grafted carbon black fine particles (PEMA-CB), that is, the numerical value converted to carbon black alone in the composite fine particles is diluted with toluene so that the concentration becomes 0.02%, and this is added to the sharpness improving agent sample (B -1) was used in the following paint test. However, since PEMA-carbon black precipitated with time, this solution was redispersed before use.

Production Comparative Example 2
In a 1000 ml reaction vessel equipped with a stirrer, reflux condenser, thermometer, and nitrogen gas inlet, toluene (300 g), carbon black initiator solution prepared in Production Example 1 (40 g) and butyl acrylate (200 g) ), Ethyl 2-bromoisobutyrate (EtBrIB; 0.38 g), tin (II) 2-ethylhexanoate (0.25 g), and glucose (0.14 g), and after sufficient deaeration with nitrogen gas Copper (II) bromide (23 mg) and tris (2-pyridylmethyl) amine (26 mg), previously dissolved in 10 g DMF, were added. Thereafter, polymerization was carried out at 85 ° C. for 12 hours. The number average molecular weight of the free polymer in the carbon black fine particles (PBA-CB) grafted with poly (butyl acrylate) obtained by the above polymerization is 10200 in terms of polystyrene (Mw / Mn = 1.65), monomer conversion rate Was 96%, ST value 30.7 mN / m, and SP value 8.9. The grafted carbon black fine particles (PBA-CB), that is, the numerical value converted into carbon black alone in the composite fine particles is diluted with toluene so that the concentration becomes 0.02%, and this is added to the sharpness improving agent sample (B -2) was used in the following paint test.

Production Comparative Example 3: Introduction of polymerization initiating groups on the surface of carbon black fine particles (3)
A carbon black initiator solution was prepared in the same manner as in Production Example 1 except that # 5 (manufactured by Mitsubishi Chemical Corporation; average particle size: 76 nm) was used as the carbon black fine particles of Production Example 1.

Production Comparative Example 4
In a 1000 ml reaction vessel equipped with a stirrer, reflux condenser, thermometer, and nitrogen gas inlet, toluene (300 g), carbon black initiator solution prepared in Production Comparative Example 3 (40 g), and ethyl methacrylate (228 g) ), Ethyl 2-bromoisobutyrate (EtBrIB; 0.65 g), tin (II) 2-ethylhexanoate (0.25 g), and glucose (0.14 g), and after sufficient deaeration with nitrogen gas Copper (II) bromide (23 mg) and tris (2-pyridylmethyl) amine (26 mg), previously dissolved in 10 g DMF, were added. Thereafter, polymerization was carried out at 85 ° C. for 12 hours. The number average molecular weight of the free polymer in the carbon black fine particles (PEMA-CB) grafted with poly (ethyl methacrylate) obtained by the above polymerization is 31150 (Mw / Mn = 1.38) in terms of polystyrene, monomer conversion rate Of 97%, ST value 35.6 mN / m, and SP value 9.7. The grafted carbon black fine particles (PEMA-CB), that is, the numerical value converted to carbon black alone in the composite fine particles is diluted with toluene so that the concentration becomes 0.02%, and this is added to the sharpness improving agent sample (B -3) was used in the following paint test. However, since PEMA-carbon black precipitated with time, this solution was redispersed before use.

Production Comparative Example 5
Carbon black fine particles FW-200 (10 g), AQ-1703N (Aqueous pigment dispersant for carbon black: manufactured by Enomoto Kasei Co., Ltd. (15 g)) and 90 g of deionized water were charged into a mayonnaise bottle and mixed with a lab disper. A suitable amount of glass beads (particle size 0.5 mm) was added to the sample and dispersed for 8 hours using a paint shaker to prepare a dispersion liquid, which was converted to carbon black alone to a concentration of 0.05%. The sample was diluted with deionized water and used in the following paint test as a sharpness improver sample (B-4), but this solution was redispersed during use because carbon black settled over time. used.

Measurement of particle size of carbon black dispersion for paint test Particle size measurement of carbon black dispersion for coating test is performed using dynamic light scattering particle size / particle size distribution measuring device (Microtrack: Nikkiso Co., Ltd.) Measured. Since this apparatus is a particle diameter / particle degree distribution measuring apparatus for fine particles, particles of 7 μm or more cannot be measured (measured at the same position). (Figs. 1-3)

Paint test example 1 ( Test with water-based glossy paint)
The above-mentioned test sample was added to a commercially available water-based glossy paint (for super outdoor use: manufactured by Asahi Pen Co., Ltd.) to evaluate the sharpness.

(Addition of carbon black dispersion)
The water-based super outdoor paint (black, green, and red colors) is converted to carbon black alone in the carbon black dispersion for the paint quality improving agents shown in Tables 1 and 2 for the paint. And 0.1% by weight, 0.05% by weight, 0.01% by weight, 0.005% by weight, 0.002% by weight, and 0.0001% by weight, respectively. For 2 minutes at 2000 rpm. After being left for 1 day, a coating test was conducted. At this time, the sample (B-2) had a tendency to separate from the paint. Since sample (B-2) has poor compatibility with this paint, it is considered that the additive was ejected from the paint.

(Application of test paint)
As described above, the black, green, and red water-based paints to which the sharpness improving agent was added were applied to a glass plate with a 100 μm applicator. After drying at room temperature for 24 hours, the clarity of each coating film was visually evaluated. The degree to which the white blur of the evaluation coating film was improved was visually evaluated in five stages from “obviously improved” (5) to “no improvement effect” (1).

  As shown in Tables 3 to 5, the grafted carbon black fine particles of the present invention can greatly improve the sharpness (white blur) just by adding about 0.002% by weight to the whole paint. Is clear.

Paint test example 2 ( Test with oil-based automobile repair paint)
The above-mentioned test sample was added to a commercially available one-pack base coat paint (Protouch, Blue Medium Metallic (one-pack special modified polyester paint: manufactured by Rock Paint Co., Ltd.)) to evaluate the vividness.

(Addition of carbon black dispersion)
Carbon black dispersion carbon based on the paint quality improvers shown in Table 1 and Table 2 in the blue medium paint in which the colorant (deep blue) is mixed with the medium metallic paint in a ratio of 100: 30. The amount converted into black alone was added so that it would be 0.02% by weight, 0.002% by weight, and 0.0001% by weight with respect to the water-based paint, respectively, and dispersed with a lab disperser at 2000 rpm for 2 minutes. . After being left for 1 day, a coating test was conducted. However, since sample (B-4) was an aqueous solution, it was not applied to this test.

(Application of test paint)
The prepared metallic base paint is diluted with a special thinner so that the viscosity of the paint is 13 seconds in Ford Cup # 4, and then the air-spray is used so that the coating film after drying becomes 15 μm. The test piece (car shape: 200 × 100 × 40 (mm): manufactured by TP Giken) was painted with air spray. This coating film was dried at room temperature for 10 minutes, and then a two-component top clear (multi-top clear SH) paint was applied using an air spray so that the film thickness after drying was 30 μm. After leaving still at room temperature for 5 minutes, it dried in 60 degreeC oven for 60 minutes.

(Evaluation of coating film)
The visibility of each coating film was visually evaluated. Metallic paint is a mixture of fine aluminum particles called aluminum flakes mixed with transparent resin (clear), so the appearance changes depending on the angle due to the difference in the arrangement of the particles (flip-flop property) . Depending on the paint conditions, white paint will appear in dark paints when viewed from an oblique direction.
The degree of improvement in the white blurring of the evaluation coating film was visually confirmed as “clearly improved” (○), “
Evaluation was made in three stages: “With improvement effect” (Δ) and “No improvement effect” (×).

  From the results shown in Table 6, the grafted carbon black fine particles of the present invention can be applied to oil-based paints by adding only about 0.002% by weight. On the other hand, it can be seen that white blurring is improved.

Paint test example 3 (Test 2 with oil-based automotive repair paint)
The test sample was added to the two-pack type clear paint used in Paint Test Example 2 (multi-top clear SH: manufactured by Rock Paint Co., Ltd.) to evaluate the vividness.

(Addition of carbon black dispersion)
Numerical values obtained by converting the sharpness improving agents shown in Table 1 and Table 2 into the main component of a two-component clear paint (multi-top clear SH: acrylic resin paint) and converted into carbon black alone in a carbon black dispersion for the paint. The components were added at 0.02 wt%, 0.002 wt%, and 0.0001 wt% with respect to the paint, respectively, and dispersed with a lab disper at 2000 rpm for 2 minutes. After being left for 1 day, a coating test was conducted. However, since sample (B-4) was an aqueous solution, it was not applied to this test.

(Base paint application)
After diluting the blue medium paint in which the colorant (deep blue) is mixed with the medium metallic paint so that it becomes 100: 30, using a special thinner, the viscosity of the paint is 13 seconds in Ford Cup # 4. Using an air spray, an automobile type test piece (car shape: 200 × 100 × 40 (mm): manufactured by TP Giken) was applied by air spray so that the coating film after drying was 15 μm. This coating film is dried at room temperature for 10 minutes, mixed with a two-component topcoat clear to which a carbon black dispersion is added, and a curing agent is mixed in a ratio of main agent: curing agent = 3: 1. After moderate stirring, air spraying is performed. It was used so that the film thickness after drying would be 30 μm. After leaving still at room temperature for 5 minutes, it dried in 60 degreeC oven for 60 minutes.

(Evaluation of coating film)
The visibility of each coating film was visually evaluated. The purpose of this test is to observe whether or not the carbon black dispersion added to the clear layer can improve the hue change (white blur) derived from the interface between the clear layer and the base coat layer.
The degree of improvement in the white blurring of the evaluation coating film was visually confirmed as “clearly improved” (○), “
Evaluation was made in three stages: “With improvement effect” (Δ) and “No improvement effect” (×).

From the results shown in Table 7, it can be seen that even if the grafted carbon black fine particles of the present invention are added to the clear paint, the effect of improving the sharpness is recognized.
Further, the carbon black dispersion did not inhibit the clearness of the clear paint at the addition amount in this range.

Claims (5)

Carbon black having a number average molecular weight of 3000 to 100,000 and an ST value of 31 mN / m or more, a polymer black chain having an average particle diameter of 5 to 20 nm with a uniform chain length and density that affects interference due to light wavelength A sharpness-improving agent that comprises composite fine particles bonded to the surface of fine particles and is added to a coating composition to improve the vividness of the finished coating film. The polymer graft chains was a base point of polymerization initiation groups on the carbon black fine surface, you form acrylic acid derivatives, methacrylic acid derivatives, styrene derivatives, by living radical polymerization of vinyl acetate or acrylonitrile, according to claim 1 For producing a sharpness improving agent. The polymer graft chain is represented by the following formula:
(Wherein R ₁ and R ₂ represent an alkyl group having 1 or 2 carbon atoms, and X ₁ and X ₂ represent a halogen atom) and formed by bonding to the surface of the carbon black fine particles. and a base point of polymerization initiation groups, acrylic acid derivatives, formed methacrylic acid derivatives, styrene derivatives, by living radical polymerization of vinyl acetate or acrylonitrile, method for producing a sharpness improving agent according to claim 1. The following steps:
a) a step of bonding a polymerization initiating group to the surface of the carbon black fine particles; and b) a polymer graft chain by contacting the carbon black fine particles having a polymerization initiating group bonded to the surface with a monomer under living radical polymerization conditions. A method for producing composite fine particles in which a polymer graft chain is bonded to the surface of carbon black fine particles according to any one of claims 1 to 3, comprising a step of obtaining composite fine particles bonded to the surface of carbon black fine particles.   A coating composition in which a pigment is dispersed in the sharpness improving agent according to any one of claims 1 to 3, based on a solid content weight of carbon black, 0.0001 to 0.1% by weight. A method to improve the vividness of the finished coating film by adding.