JPH0786180B2 - Method for producing colorant for plastics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing a coloring agent for plastics, and more specifically, an object thereof is to provide a coloring agent for high-concentration plastics having excellent dispersibility of a pigment.

(Prior art and its problems) Conventionally, as a colorant for plastics, a dry color in which a pigment is mixed with a dispersant, a masterbatch in which a pigment is kneaded with a carrier resin in a high concentration, and the like are widely used.

These plastic colorants are prepared by dispersing the pigment powder by melting and kneading the pigment powder and a dispersant or a supporting resin with a high shearing machine such as a roll, a kneader or an extruder, but the pigment powder once dried is coarse. Since a large number of such secondary agglomerated particles are present, it is very difficult to redisperse all of these coarse particles to a size of several μm or less. Particularly in the case of organic pigments, it is difficult to perform high-concentration fine dispersion because the oil absorption of the pigment is large.
In the conventional coloring of plastics, it is preferable that no coarse particles are present, but fine dispersion is not required so strictly.

On the other hand, in recent years, there has been a strong demand for high concentration and high dispersibility of pigments even in coloring plastics, and it is becoming difficult for conventional methods using powder pigments to cope with this.

Therefore, an object of the present invention is to provide a colorant for plastics in which a pigment is dispersed in a high concentration.

(Means for Solving Problems) The above object is achieved by the present invention described below.

That is, the present invention is a method for producing a colorant for plastics, which comprises kneading an aqueous pigment paste and a resin solution to transfer an aqueous phase pigment to a resin solution phase, and then removing water and an organic solvent. Is the way.

(Function) A pigment coloring agent for plastics containing no coarse particles is provided by transferring the pigment from the aqueous phase to the resin phase from the aqueous paste of the pigment which is not secondarily aggregated, without going through the powdering step of the pigment. It

(Preferred Embodiment) Next, the present invention will be described more specifically with reference to preferred embodiments.

The aqueous paste of the pigment used in the present invention is an aqueous paste obtained by producing the pigment in an aqueous phase and then filtering it without drying. Since such a pasty pigment does not undergo a drying step, the pigment particles do not secondary aggregate and remain as primary particles in most cases, and do not contain particles having a size of more than 10 μm.

As the pigment used in the present invention, any conventionally known pigment such as an azo pigment, a phthalocyanine pigment, a quinacridone pigment and a carbon black pigment can be used, and an organic pigment having high lipophilicity is particularly preferable. The solid content in the aqueous paste of the pigment is not particularly limited, but if the solid content is too low, it is uneconomical in the process, and if the solid content is too high, drying may occur on the surface to cause secondary agglomerated particles. Thus, the preferred solids range is a concentration of 25 to 80% by weight.

As the resin used in the present invention, any of the resin dispersants conventionally used as a dispersant for pigments and the resins used as a carrier resin for a masterbatch can be used. For example, as the dispersant, low molecular weight polyethylene, low molecular weight polypropylene, various waxes, etc. can be used, and as the resin, acrylic resin, styrene resin,
Examples thereof include acrylic-styrene resin, polyester resin, phenol resin, rosin-modified maleic acid resin, petroleum resin, epoxy resin, ABS resin, polycarbonate resin, polyvinyl chloride resin, polyvinyl acetate resin, and alkyd resin.

The method of the present invention is a method in which an aqueous paste of a pigment as described above and a solution of a resin as described above are kneaded in a kneader such as a flasher to transfer the pigment in the aqueous phase into the resin solution, which is used. As the organic solvent, an organic solvent immiscible with water such as toluene or xylene is used. The amount of the organic solvent used is the amount necessary for the resin to liquefy, and is generally used in such a ratio that the resin concentration becomes about 10 to 90%. The kneading in the flasher may be performed at room temperature, but usually 50 to 80 due to the frictional force in the flasher without heating.
It rises to about ℃. The temperature at the time of kneading is from room temperature to about 130 ° C., and when the temperature is higher than the boiling point of water, it is preferable to use a closed pressure flasher.

The mixing ratio of the pigment aqueous paste and the resin solution added to the flasher varies depending on the solid content of the pigment aqueous paste, the concentration of the resin solution, etc., but the pigment concentration of the obtained plastic colorant is 20 to 80% by weight. Ratios are preferred.

At the time of flushing, the pigment aqueous paste and the resin solution may be charged to the full capacity of the flasher,
A preferred method is a method in which the charge is divided into several times. That is, in the first charge, both were charged to a volume of about 1/5 to 1/2 of the capacity of the flasher to perform flushing, the separated water was discharged, and then the same amount of charge was performed to perform flushing. Drain the after water. The flushing efficiency can be remarkably improved by discharging the separated water as described above.

After the final flushing is complete, the residual water is removed, preferably under reduced pressure, to remove the residual water and organic solvent to give the desired plastic colorant.

(Effect) According to the present invention as described above, an aqueous paste of a pigment that has not been secondarily aggregated can be used without a powdering step of the pigment.
Transferring the pigment from the aqueous phase to the resin phase provides a plastic colorant that does not contain coarse particles.

(Example) Next, an Example is given and this invention is demonstrated still more concretely.
In the text, parts and% are based on weight unless otherwise specified.

Example 1 Aqueous paste of dimethylquinacridone pigment (solid content 30
%) 180 parts and 6 of acrylic styrene resin (manufactured by Sanyo Chemical Co., Ltd.)
Add 75 parts of 0% xylene solution to the flasher and keep at room temperature for 35
The separated water was discharged after kneading for a minute. Next, add 120 parts of the above-mentioned pigment aqueous paste and 50 parts of the same resin solution, and
The mixture was kneaded for 5 minutes, and the separated water was discharged. Furthermore, the same resin solution 3
After adding 75 parts, the mixture was kneaded at room temperature for 30 minutes, and the separated water was discharged. Finally, depressurize the flasher to 70 cmHg at 125 ° C.
After kneading for 2.5 hours, the mixture was cooled to obtain a powdery colorant for plastics of the present invention.

Optical microscope (400x) by dissolving the above colorants in toluene
When the dispersibility of the pigment was examined with, no coarse particles of 8 μm or more were observed.

Example 2 Polystyrene resin (Picolastic D-12 manufactured by Esso Co., Ltd.
Put 4200 parts of 50% toluene solution of 5) into the flasher,
Next, cyanine green aqueous press cake (solid content 42
%) 1,550 parts were added and well stirred for 60 minutes. After removing the separated water by decantation, kneading was further performed for 30 minutes. After that, water and solvent were removed while kneading under heating and reduced pressure (130 ° C., 70 cmHg) for 2 hours. Then, the mixture was cooled and pulverized to obtain a green colorant for plastic pellets of the present invention.

Optical microscope (400x) by dissolving the above colorants in toluene
When the dispersibility of the pigment was examined by means of the above, no coarse particles of 10 μm or more were observed.

Example 3 60 of polyacrylic resin (manufactured by Asahi Kasei, Styron 666)
% 1,500 parts toluene solution into a flasher, followed by disazo yellow aqueous presscake (35% solids) 2,
000 parts was added and well stirred for 45 minutes. After removing the separated water by decantation, 1,500 parts of the same resin solution was further added, and 1,400 parts of the same press cake was further added. Subsequently, the mixture was thoroughly kneaded for 45 minutes, the separated water was removed, and the mixture was further kneaded for 30 minutes. After that, under heating and reduced pressure (18
Water and solvent were removed while kneading at 0 ° C. and 70 cmHg) for 2.5 hours. Immediately thereafter, a yellow coloring agent for plastics of the present invention was obtained through an extruder.

Optical microscope (400x) by dissolving the above colorants in toluene
When the dispersibility of the pigment was examined with, no coarse particles of 5 μm or more were observed.

Claims (2)

[Claims] 1. A method for producing a colorant for plastics, which comprises kneading an aqueous paste of a pigment and a resin solution to transfer an aqueous phase pigment to a resin solution phase, and then removing water and an organic solvent. . 2. The method according to claim 1, wherein the aqueous pigment paste and the resin solution are sequentially added.