JPH0546393B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a pigment dispersion method used in the production of paints, inks, etc., and a pigment dispersion device used to carry out this method. [Background Art] Coating compositions containing pigments, such as paints and inks, are generally prepared by processing a formulation containing the pigment, resin varnish, solvent, and optionally added additives in a sand grinder mill, attritor, ball mill, etc. It is made by dispersing it using a pigment dispersion device. However, in order to satisfy the various properties required for paints, inks, etc., it is necessary to select pigments, resins, and solvents from a very wide range. When resins or pigments with poor properties are used, performance such as image clarity and color separation during toning may deteriorate. Therefore, attempts have been made to solve this problem by varying the proportions of pigment, resin, and solvent used, and other manufacturing conditions when dispersing pigments using the dispersion equipment mentioned above, but so far no results have been fully satisfactory. No results have been obtained. [Purpose of the Invention] This invention was made in view of the above circumstances, and an object thereof is to provide a pigment dispersion method that can obtain a coating composition with excellent performance such as image clarity and color separation. It is said that [Disclosure of the Invention] In order to achieve the above-mentioned objects, the present invention processes a composition containing a pigment, a resin, and a solvent with a dispersion machine to make the pigment fine and uniformly disperse it in the composition. A dispersion step in which all or part of the solvent in the mixture obtained in this dispersion step is distilled off under reduced pressure conditions, and a mixture with a reduced solvent concentration is treated with a stirrer. The gist of the invention is a pigment dispersion method comprising an aging step of adsorbing a resin onto the pigment. This invention will be explained in detail below. In this invention, first, a mixture containing a pigment, a resin, and a solvent is treated with a pigment dispersion machine so that the pigment is finely divided and uniformly dispersed in the formulation. As the dispersing machine used in this dispersion step, for example, a batch type rotary media dispersing machine, a sand grinder, a ball mill, an attritor, etc. are used. After dispersion using these devices is complete, add resin varnish as necessary.
Stir and mix this evenly. In this case, although it varies depending on the type of pigment and the proportion of non-volatile content in the resin varnish, approximately 50 to
It is better to try to add resin varnish at a rate of 150% by weight. Next, this mixture is subjected to a solvent distillation step in which part or all of the solvent therein is distilled off under reduced pressure. Specifically, it is preferable that the nonvolatile content of the vehicle in the mixture is 60% or more. At this time, if the viscosity of the mixture becomes high and fluidity deteriorates, it is advisable to heat the mixture to about 60 to 130°C and keep it warm within this temperature range. Preferably, the mixture is kept stirring during the distillation. After the distillation is completed, the mixture with reduced solvent concentration is stirred for about 20 minutes or more, preferably 30 to 120 minutes, to carry out an aging step in which the resin is adsorbed onto the pigment in the mixture. For example, a butterfly mixer, a kneader, a planetary mixer (vertical kneader), a twin-screw dissolver, a batch-type rotary media disperser, etc. are used as the agitator used in this ripening process, but the pigment dispersion device described later When used, it is advantageous that the dispersion step, solvent distillation step, and aging step can be performed continuously without transferring the mixture. Ripening is preferably carried out at a temperature of 60-130°C. If the temperature is less than 60℃, the viscosity of the mixture will increase and the fluidity will deteriorate, so it will be difficult to obtain a sufficient aging effect, and if it exceeds 130℃,
This is because there is a tendency for the resin or pigment in the mixture to change in quality, which may impair product quality. Aged, the viscosity of the mixture is 100,000 cP
It is best to do so under the following conditions. This is because if it exceeds this range, the fluidity of the mixture deteriorates, and it tends to be difficult to achieve sufficient ripening effects. Thereafter, if necessary, the recovered solvent and other necessary raw materials are added to the mixture and mixed uniformly to obtain a coating composition. After dispersing the formulation, this coating composition is produced by distilling off all or part of the solvent in the resulting mixture to lower the solvent amount ratio and increase the resin amount ratio. The adsorption of the resin to the pigment is improved by removing the solvent that had adhered to the surface of the pigment, and then the resin is aged by stirring, etc., so it is thought that the resin is sufficiently adsorbed to the pigment. It will be done. Therefore, various performances such as gloss, sharpness, and color separation during color mixing are extremely excellent. FIG. 1 shows a pigment dispersion apparatus eminently suitable for use in carrying out the method of the invention. As shown in the figure, this pigment dispersion device has a vertically long container 1 whose bottom is narrower than the top, and its lid 2, and the upward opening of the container 1 is sealed with the lid 2. There is. The container 1 is for containing the mixed raw materials 3, and the raw materials 3 are contained inside the container 1.
A dispersion ball 4 is inserted to apply an impact force, a grinding force, etc. to the material, and a jacket 5 is provided on the lower outer periphery as a temperature control means for heating and cooling the blended raw materials 3 to adjust the temperature. It is being The dispersion sphere 4 is made of glass, steel, ceramic, zirconia, or the like. At the bottom of the container 1, there is provided an outlet 6 equipped with a valve 6b and filtration means such as a net 6a that does not allow the dispersion sphere 4 to pass through, but allows the processed material of the blended raw materials 3 to pass through. The lid 2 has an input port 2a for inputting the raw material 3 into the container 1, and a container 1.
A stirrer 7 is provided as a stirring means for stirring and dispersing the raw material 3 inside. Inlet port 2
a can be opened and closed with an input port cover 2b. The liquid raw material may not be introduced through the input port 2a, but may be introduced through a pipe connected to the lid 2. The stirrer 7 has its driving means 7a placed on the lid 2, and the stirring shaft 7b extends from the driving means 7a toward the bottom of the container 1. A disc-shaped stirring blade 7c is provided at the tip of the stirring shaft 7b.
is installed. It is preferable that the drive means 7a is equipped with a transmission so that the rotation speed can be changed. A capacitor 8 is arranged above the lid 2. This condenser 8 has an inlet 8a through which steam enters and an outlet 8b through which the recovered solvent exits, and these inlets and outlets are connected to the lid 2 by pipes 9 and 10, respectively. A vacuum pump suction port 8c provided above the condenser 8 is connected to a vacuum pump through piping, which is not shown in the figure. This vacuum pump is used as a vacuum generating means for reducing the pressure inside the container 1.
Cooling water enters the condenser 8 through a cooling water inlet 8d provided below, and cooling water exits from a cooling water outlet 8e provided above. A receiving tank (receiver) 11 for solvent recovery is provided below the condenser 8 and in the middle of the pipe 10, and valves are installed between the condenser 8 and the receiving tank 11 and between the receiving tank 11 and the lid 2. 12,1
3 are provided respectively. An example of producing a coating composition (pigment-containing resin composition) by implementing the pigment dispersion method according to the present invention using this pigment dispersion apparatus will be shown below. First, a pigment, a solvent, a resin varnish, and additives used as necessary are charged into the container 1 through the input port 2a, either sequentially or in a mixed state. Here, it is preferable that the input amount of the raw material is such that the volume ratio of the dispersion spheres 4 in the dispersion container 1 to the whole raw material is 1/2 to 2/1. Next, the inlet 2a is closed and the stirring blade 7c is rotated at high speed by the driving means 7a, thereby making the pigment fine and uniformly dispersing the pigment in the mixture, thereby dispersing the mixture. Dispersion time is usually 40 to 120 minutes, but varies depending on the type of pigment. After the dispersion is completed, a resin varnish is added as required, and the mixture obtained as described above or this mixture and the resin varnish are uniformly stirred and mixed using a stirrer 7. Next, the stirrer 7 is rotated at low speed, and the valve 12 is rotated at a low speed.
and close valve 13. The vacuum pump is operated to reduce the pressure inside the container 1 to about 30 to 100 mHg, and cooling water is allowed to flow into the condenser 8. and,
If necessary, steam or the like is passed through the jacket 5 to heat the mixture, and part or all of the solvent in the mixture is distilled off. At this time, if the fluidity becomes poor, pass steam etc. through the jacket 5 to cool the mixture.
It is best to heat it to around 130℃ and keep it warm within this temperature range. The solvent distilled off under reduced pressure is condensed in a condenser 8 and collected in a receiving tank 11. When the distillation is completed, the vacuum pump is stopped and the pressure inside the container 1 is returned to normal pressure. Next, depending on the properties of the pigment, resin, etc., the stirrer 7 is rotated at high speed or low speed to stir the mixture in the container 1, and the mixture is aged and the resin is sufficiently adsorbed to the pigment. prevent it from agglomerating. Thereafter, if necessary, the recovered solvent is returned to the container 1 by opening the valve 13 and mixed uniformly with the mixture remaining in the container 1 to obtain a coating composition. Then, this paint composition is taken out from the discharge port 6. In this way, when the dispersion method according to the present invention is carried out using one device, there is no need to transfer the mixture and the yield is improved, so the productivity of the coating composition is dramatically improved. Additionally, compared to the case where several devices are used, the installation space is smaller and cleaning is easier. The pigment dispersion method according to the present invention is not necessarily carried out using one apparatus as described above. The step of primarily dispersing the blend, the step of distilling off the solvent in the mixture, and the step of dispersing the mixture while aging may be performed using separate apparatuses. Next, examples and comparative examples of the pigment dispersion method according to the present invention will be explained. Example 1 First, a formulation having the composition shown in Table 1 was
The pigment was placed in a pigment dispersion apparatus shown in FIG. 1, and a dispersion process was performed for 60 minutes using steel beads as dispersion balls and rotating a stirring blade at a circumferential rotational speed of 10 m/s.

[Table] Next, 88 parts by weight of alkyd resin varnish (non-volatile content: 60%) was added to the mixture in the dispersion container, and then the temperature of the mixture was kept at 80 to 85°C. Then, seal the container with a lid and use a vacuum pump to pump the inside of the container for 40 minutes.
The pressure was reduced to mmHg. Rotating stirring blade at circumferential speed of 4 m/
83.5 parts by weight of the solvent in the mixture was distilled off while rotating at a speed of 100 s, so that the nonvolatile content of the vehicle component in the mixture was about 80%. And then increase the temperature of the mixture to 80~
The mixture was maintained at 85° C. to have a viscosity of 50,000 cP, and the mixture was stirred for 30 minutes by rotating a stirring blade at a circumferential speed of 4 m/s to carry out ripening. Thereafter, the mixture was adjusted to the final paint formulation to obtain the paint. Example 2 A paint was prepared in the same manner as in Example 1, except that after the nonvolatile content of the vehicle component in the mixture was adjusted to 93%, the viscosity of the mixture was adjusted to 120,000 cP and aged. Comparative Example 1 For comparison, a paint was manufactured using a conventional method. First, a mixture having the composition shown in Table 1 was dispersed using a rotary medium disperser, and after the dispersion was completed, the mixture was adjusted to the final coating composition to obtain a coating material. The paints obtained in Examples 1 and 2 and the paint obtained in Comparative Example 1 were evaluated for gloss and color separation during color mixing (rubbing color difference). The results are shown in Table 2. However, the evaluation of color separation was performed as follows. First, the black paint produced in Examples and Comparative Examples was mixed with standard white paint at a ratio of 1:9, stirred to be uniform, and then diluted to 15″/20°C with a #4 food cup using diluting thinner. did.
Next, the obtained adjusted paint was flow-coated onto a tin plate, and just before it was dry to the touch, a part of the coated surface was strongly rubbed, and then baked and dried to create a coated plate. The rubbing color difference is the difference in colorimetric values between the unrubbed area and the rubbed surface of the painted plate, expressed as ΔE.

Table 2 shows that the paints obtained in Example 1 and Example 2 are superior to the paint obtained in Comparative Example 1 in terms of gloss and color separation. Example 3 First, a formulation with the composition shown in Table 3 was
Dispersion treatment was carried out under the same conditions as in Example 1.

[Table] Next, 100 parts by weight of acrylic resin varnish (50% non-volatile content) was added to the mixture in the dispersion container, and then 90 parts by weight of the solvent in the mixture was distilled off in the same manner as in Example 1. The non-volatile content of the vehicle components in the mixture was approximately 80%. Then, maintain the temperature of the mixture at 80-85℃ and make the viscosity of the mixture 50,000 cP.
Aging was carried out by stirring for 30 minutes by rotating a stirring blade at a circumferential rotational speed of 4 m/s. Thereafter, the mixture was adjusted to the final paint formulation to obtain the paint. Example 4 A paint was prepared in the same manner as in Example 3, except that the nonvolatile content of the vehicle component in the mixture was adjusted to 70% and the temperature of the mixture was maintained at 50° C. for aging. Example 5 A paint was prepared in the same manner as in Example 3, except that after the nonvolatile content of the vehicle component in the mixture was adjusted to 93%, the temperature of the mixture was maintained at 125° C. for aging. Comparative Example 2 For comparison, a paint was manufactured using a conventional method. First, a mixture having the composition shown in Table 3 was dispersed using a rotary medium disperser, and after the dispersion was completed, the mixture was adjusted to the final coating composition to obtain a coating material. Comparative Example 3 For comparison, a paint was produced as follows. First, a formulation having the composition shown in Table 3 was subjected to a dispersion treatment under the same conditions as in Example 1. Next, the solvent in the mixture was distilled off to concentrate the mixture, so that the viscosity of the mixture was about 200,000 cP at room temperature. Then, the mixture was kneaded (kneaded) at room temperature using a roll mill. Thereafter, the mixture was pelletized, and the pellets were dissolved in a solvent to adjust the final paint formulation to obtain a paint. The gloss and color separation during color mixing (rubbing color difference) of the paints obtained in Examples 3 to 5 and Comparative Examples 2 and 3 were evaluated. The results are shown in Table 4.

[Table] From Table 4, the paints obtained in Examples 3 to 5 are:
Compared to those obtained in Comparative Example 2 and Comparative Example 3,
It can be seen that the gloss and color separation properties are excellent. Examples 3 to 5 were obtained in Comparative Example 3.
The reason why the performance is inferior to that obtained in the above is thought to be that the mixture is insufficiently matured by kneading with a roll mill. In order to investigate the effect of ripening by stirring, Example 3
The pigment particle diameters (in μ) of the mixture obtained by dispersion and the mixture obtained by stirring and aging were measured by a light transmission centrifugal sedimentation method. The measurement results are shown in Table 5.

[Table] Generally, it is considered that the smaller the average particle diameter of the pigment, the better the performance of the paint. However, as shown in Table 5, the paint of Example 3 had
Although the average particle size after stirring and aging is almost the same as after dispersion, the performance is excellent as seen above. This is thought to be because the performance of the paint, such as color separation, is more influenced by resin adsorption onto the pigment surface than by the particle size. Example 6 Here, a metal complex azo pigment (CI
No.PIG.YELLOW-129) was used. This pigment has a very fine primary particle size and has poor affinity with resins, so conventional methods have been used to create paints that provide satisfactory performance such as transparency and gloss (especially 20° gloss). It was difficult to make. First, a formulation with the composition shown in Table 6 was prepared.
Dispersion treatment was carried out under the same conditions as in Example 1.

[Table] Next, 108 parts by weight of acrylic resin varnish (nonvolatile content 50%) was added to the mixture in the container, and the temperature of the mixture was kept at 80 to 85°C. Then, the container was sealed with a lid, and the pressure inside the container was reduced to approximately 40 mmHg using a vacuum pump. While rotating the stirring blade at a circumferential speed of 4 m/s, the solvent in the mixture was distilled off, so that the nonvolatile content of the vehicle component in the mixture was about 80%.
Then, ripening was carried out by rotating the stirring blade at a circumferential rotational speed of 4 m/s and stirring for about 40 minutes. The mixture was kept at 80-85°C until the end of ripening. After this, the mixture was adjusted to the final paint formulation to obtain the paint. Comparative Example 4 For comparison, a paint was manufactured using a conventional method. First, the formulations having the compositions shown in Table 6 were dispersed using a rotary media disperser, and after the dispersion was completed, the mixture was adjusted to the final coating formulation to obtain a coating material. The gloss and transparency (visual judgment) of the paint obtained in Example 6 and the paint obtained in Comparative Example 4 were evaluated. The results are shown in Table 7. However, regarding the transparency in the table, ◎ indicates good and △ indicates slightly poor.

Table 7 shows that the paint obtained in Example 6 is superior to that obtained in Comparative Example 4 in terms of gloss and transparency. Example 7 A paint was prepared in the same manner as in Example 1, except that a ball mill was used as the dispersion device and a butterfly mixer was used as the distillation and aging device. The gloss and color separation properties of the paint obtained in Example 7 were evaluated. The results are shown in Table 8.

〔Effect of the invention〕

Since the pigment dispersion method according to the present invention includes the aging step as described above, it is possible to obtain a coating composition with excellent performance such as image clarity and color separation properties.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of one embodiment of a pigment dispersion apparatus used for carrying out the present invention. 1... Container, 4... Dispersion sphere, 5... Jacket, 7... Stirrer, 8... Condenser, 11...
receiving tank.

Claims (1)

[Claims] 1. A dispersion step in which a blend containing a pigment, a resin, and a solvent is treated with a dispersion machine to make the pigment fine and uniformly dispersed in the blend; a solvent distillation step in which all or part of the solvent in the resulting mixture is distilled off under reduced pressure conditions, and an aging step in which the resin is adsorbed onto the pigment by treating the mixture with a reduced solvent concentration with a stirrer. Pigment dispersion method. 2. The pigment dispersion method according to claim 1, wherein the aging step is performed at a temperature of 60 to 120°C. 3. The pigment dispersion method according to claim 1 or 2, wherein the aging step is performed in a state where the viscosity of the mixture is 100,000 cp or less. 4. The pigment dispersion method according to any one of claims 1 to 3, wherein the steps from the dispersion step to the ripening step are performed continuously in the same container.