JPH05339516A - Production of graft carbon and recording ink containing the same - Google Patents

Abstract

PURPOSE:To obtain an ink for ink-jet recording which has excellent storage stability and does not run on plain or reclaimed paper on the market to attain high print quality. CONSTITUTION:The title ink, which is an aqueous pigment dispersion for ink-jet recording, contains a surface-treated carbon black produced by treating a carbon black with ultraviolet or ozone at ordinary pressure and thermally grafting a vinyl monomer onto the resulting carbon black.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based pigment-dispersed recording ink, which is excellent in storage stability and has high printing quality without bleeding on plain paper or recycled paper which is generally commercially available. In particular, it relates to an inkjet recording ink.

[0002]

2. Description of the Related Art Conventionally, water-based pigment inks used for ink jet recording and the like are difficult to disperse in water because the pigments are essentially hydrophobic, so that the ink lacks storage stability. Therefore, as a means for solving the problem, there is a method in which the surface of carbon black is made hydrophilic by graft polymerization treatment to enhance the dispersibility.
9369.

Here, for graft polymerization, carbon black is stirred with a peroxide such as metal acrylate or ammonium acrylate to generate a graft reaction site, and then in the presence of a radical polymerization initiator and an amine radical polymerization accelerator. A method of polymerizing monomers is shown. An ink jet recording ink using this graft carbon black is obtained by diluting a polymerization reaction suspension containing the graft carbon black and adding a conventional ink jet additive such as a wetting agent.

However, in such a proposal, the ink contains impurities such as a peroxide ion, a radical polymerization initiator, an amine radical polymerization accelerator, and unreacted monomers and a by-product homopolymer. Therefore, when printing is performed on plain paper or recycled paper, there is a problem that high quality printing cannot be obtained because the ink spreads along the fibers of the paper to cause bleeding.

[0005]

SUMMARY OF THE INVENTION The present invention is intended to solve such problems, and provides an ink jet recording apparatus for recording characters / images with liquid ink.
It is an object of the present invention to provide an inkjet recording ink capable of obtaining high-quality recording that does not cause bleeding on plain paper or recycled paper that is generally commercially available and that has excellent storage stability.

[0006]

In the recording ink of the present invention, carbon black is subjected to (1) UV treatment or ozone treatment under normal pressure and (2) graft polymerization of a vinyl group-containing monomer by thermal polymerization. In the production method including the step, the surface-treated carbon black is dispersed in water or / and a water-soluble organic solvent.

According to the present invention, the surface of carbon black is coated with a resin that is at least partially soluble in water and a water-soluble organic solvent, so that the dispersibility in a dispersion medium is improved, and further, ink ejection is performed. When the ink jet recording ink droplets ejected from the nozzle adhere to the recording paper, the polymer chains that cover the surface of the particles are entangled and aggregated, and the particles are dispersed by being entangled with the cellulose fibers of the recording paper. It does not spread along the cellulose fiber with the medium. Further, the presence of impurities such as salts and radical polymerization agents in the ink induces printing bleeding, but in the present invention, graft polymerization can be carried out without containing these impurities, and unreacted monomers and homopolymers are removed. By doing so, bleeding of printing is further prevented.

As the carbon black in the present invention, carbon black produced by a commonly known method such as a contact method, a furnace method, a thermal method or the like can be used, and the surface thereof has a functional group such as a carboxyl group, a hydroxyl group or a carbonyl group. The group exists. By polymerizing these functional groups and the vinyl group-containing monomer used in the present invention, carbon black having excellent dispersibility in water or a water-soluble organic solvent can be obtained.

Specific examples of the monomer having a vinyl group used in the present invention include acrylamide, N, N-dimethylacrylamide, acrylic acid, acrylonitrile, methacrylic acid, methyl methacrylate, vinyl acetic acid (polyvinyl derived from vinyl acetic acid. Alcohol) etc. are mentioned, and acrylamide is the most preferable.

UV treatment or ozone treatment increases the activity of the surface of carbon black. Specifically, it is for producing a peroxide on the surface of carbon black, and for the monomer having a vinyl group to be directly graft-polymerized on the surface of carbon black. The processing time is 5 minutes to 2 hours. Longer processing time is not preferable because it decomposes the generated peroxide on the contrary.

Polymerization is carried out by blowing nitrogen and then applying heat to remove oxygen serving as a polymerization inhibitor. At this time, the bond of the hydroxyl group is broken from the peroxide on the surface of the carbon black, and the polymerization and grafting of the monomer occur simultaneously.

The reaction time is 30 minutes to 6 hours. Longer reaction times are harmless but uneconomical. The reaction temperature is 30 ° C to 80 ° C. After cooling, the homopolymer formed as a by-product can be removed by a conventional method such as freeze-drying or centrifugation. Further, since the unreacted monomer has a high solubility in water, it is washed with hot water.

In obtaining the treated carbon black in the present invention, the surface treatment of the carbon black is uniformly performed, and the carbon black and the monomer having a vinyl group are firmly bonded to each other, and the resulting treated carbon black is used as an aqueous ink jet. In order to improve the dispersibility in the recording ink, the ratio of carbon black / monomer having a vinyl group is preferably 10/1 to 10/100 by weight.

The surface-treated carbon black thus obtained is easily dispersed in water or a water-soluble organic solvent.
Specific examples of the water-soluble organic solvent include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol # 200, # 30.
0, # 400 and other polyhydric alcohols, triethylene glycol monomethyl ether, methanol and other polyhydric alcohol alkyl ether derivatives, glyceryl monoacetate and other polyhydric alcohol ester derivatives, N-methyl-2-pyrrolidone, etc. And a lower alcohol having 1 to 6 carbon atoms such as ethanol, n-propanol, and iso-propanol.

The amount of the above water-soluble organic solvent used is 40% by weight or less, preferably 3 to 30% with respect to the total weight of the ink.
% By weight.

Since the surface-treated carbon black can be easily dispersed in water and a water-soluble organic solvent, it does not require a high shearing force in a dispersing machine such as a ball mill, a sand mill or a roll mill, and an ultrasonic homogenizer such as an ultrasonic homogenizer. A sonic disperser can be used for sufficient dispersion.

The amount of the surface-treated carbon black used in the ink should be taken into consideration in consideration of the degree of polymerization by the surface treatment, but in consideration of the color density of the ink and the prevention of clogging of the ink ejection nozzle, it is 0.5 to 0.5. Used in a proportion of 20% by weight. It is preferably 1 to 10% by weight.

In addition to the above, additives such as a viscosity adjusting agent, a surface tension adjusting agent and a pH adjusting agent for controlling the physical properties of the ink, an antifungal agent, an antiseptic agent, and a resin as a binder may be appropriately added. You can

[0019]

[Examples] The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1 Component Carbon black # 25 20 parts by weight (manufactured by Mitsubishi Kasei Co., Ltd.) Acrylamide 10 parts by weight Pure water 90 parts by weight Component Surface-treated carbon black 5 parts by weight Glycerin 2 parts by weight Ethanol 6 parts by weight Pure water 87 parts by weight of carbon black 3 under high pressure mercury lamp (400w)
UV treatment is carried out for 0 minutes, the treated components such as carbon black are mixed, and the mixture is stirred at 65 ° C. while blowing nitrogen gas into the solution and polymerized for 1 hour. The polymer was sufficiently removed with a centrifuge at 12,000 rpm for 1 hour to remove the homopolymer, washed with hot water for 3 hours while stirring, and then dried, and then the components were mixed and the particle size was adjusted with an ultrasonic homogenizer. Coarse particles and dust were removed with a 5 μm membrane filter to obtain an inkjet recording ink.

Example 2 Component Carbon black MA-7 10 parts by weight (manufactured by Mitsubishi Kasei Co., Ltd.) Acrylic acid 90 parts by weight Pure water 210 parts by weight Component surface-treated carbon black 3 parts by weight Glycerin 10 parts by weight 1-Propanol 4 Part by weight Pure water 83 parts by weight Carbon black 2 under high pressure mercury lamp (400w)
UV treatment is carried out for 0 minutes, the treated components such as carbon black are mixed, and the mixture is stirred at 60 ° C. while blowing nitrogen gas into the solution and polymerized for 2 hours. The polymer was thoroughly removed with a centrifuge at 12,000 rpm for 90 minutes to remove the homopolymer, washed with hot water for 3 hours with stirring, and then dried, and then the components were mixed and the particle size was adjusted with an ultrasonic homogenizer. Coarse particles and dust were removed with a 5 μm membrane filter to obtain an inkjet recording ink.

Example 3 Component carbon black MA-600 10 parts by weight (manufactured by Mitsubishi Kasei Co., Ltd.) N, N-dimethylacrylamide 50 parts by weight Pure water 200 parts by weight Component surface-treated carbon black 3 parts by weight Ethylene glycol 4 parts by weight Part Ethanol 5 parts by weight Pure water 88 parts by weight Carbon black is subjected to ozone treatment with an ozone generator having a voltage of 50 V, a frequency of 60 Hz and an oxygen flow rate of 50 ml / min, and the components such as the treated carbon black are mixed and nitrogen gas is dissolved. While blowing in, the mixture is stirred at 50 ° C. and polymerized for 3 hours. Centrifuge the polymer to 1000
The homopolymer was sufficiently removed at 0 rpm × 90 minutes, washed with hot water for 3 hours while stirring, and then dried, then the components were mixed, and the particle size was adjusted with an ultrasonic homogenizer to 5 μm.
Coarse particles and dust were removed with a membrane filter of No. 1 to obtain an ink for inkjet recording.

Comparative Example 1 Grafted carbon black (# 25) 5 parts by weight Acrylamide 1 part by weight Glycerin 2 parts by weight Ethanol 6 parts by weight Pure water 86 parts by weight Comparative Example 2 Carbon black MA-7 3 parts by weight Direct Yellow 86 (dispersant) ) 0.5 parts by weight Glycerin 10 parts by weight 1-propanol 4 parts by weight Pure water 82.5 parts by weight Comparative Examples 1 and 2 adjust the particle size with an ultrasonic homogenizer,
Coarse particles and dust were removed with a 5 μm membrane filter to obtain an inkjet recording ink.

The graft carbon black of Comparative Example 1 was grafted in the same manner as in Example 1.

Comparative Example 3 Component Carbon black MA-7 50 parts by weight Pure water 300 parts by weight Ethanol 30 parts by weight Ammonium persulfate 5 parts by weight N-Tetraethyl-ethylenediamine 0.2 parts by weight Component acrylic acid 50.2 parts by weight Ammonium persulfate 1 Parts by weight Component polymerization reaction suspension 100 parts by weight Glycerin 20 parts by weight Pure water 200 parts by weight Component carbon black, pure water and ethanol are mixed and stirred. Then ammonium persulfate and N-tetraethyl-ethylenediamine are added and the mixture is stirred at 90 ° C. for 18 hours. Then the ingredients are added and the mixture is heated at 95 ° C for 2
Stir and reflux for 4 hours. After cooling, the polymerization reaction suspension was diluted with the ratio of the components, the particle size was adjusted with an ultrasonic homogenizer, and coarse particles and dust were removed with a 5 μm membrane filter to obtain an inkjet recording ink.

Using the ink thus obtained, a test was conducted by the evaluation method shown below.

Print quality (bleeding) HG-5130 (manufactured by Seiko Epson) is used to print on Xerox P (Fuji Xerox trademark), which is a typical general-purpose plain paper, and Xerox R (Fuji Xerox trademark), which is a typical recycled paper. , Bleeding is evaluated according to the following criteria.

Clear printing without bleeding ○ Whisker-like bleeding occurs △ Blurring so that the contours of the characters are not clear × Storage stability 50 cc of ink is collected in a Labran screw tube bottle (manufactured by Inei Seieido Co., Ltd.) After standing at 70 ° C. and −20 ° C. for 100 hours, the presence or absence of sedimentation of carbon black was examined.

No sedimentation ○ Sedimentation × The above results are shown in Table 1.

[0030]

[Table 1]

As is apparent from Table 1, an ink prepared by diluting a polymerization reaction suspension containing carbon black obtained by graft-polymerizing a monomer having a vinyl group by forming an active site with a peroxide as in Comparative Example 3. However, although the storage stability was good, the printing was bleeding and high printing quality could not be obtained. However, as shown in the examples, the pigment ink in which the active sites are formed by UV treatment or ozone treatment under normal pressure and the monomer having a vinyl group is graft-polymerized to carbon black by thermal polymerization has good printing quality and is stable in storage. It was an ink with excellent properties.

[0032]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, an ink jet recording ink in which a pigment surface-treated by graft polymerization of a monomer having a vinyl group on a carbon black surface is dispersed is excellent in storage stability, and further, It is possible to obtain an inkjet recording ink that does not cause bleeding on plain paper and recycled paper that are generally commercially available and that can obtain high printing quality.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI technical display location // C08F 2/44 MCQ 7442-4J (72) Inventor Taku Aoyama 3-3 Yamato, Suwa City, Nagano Prefecture No. 5 within Seiko Epson Corporation

Claims (2)

[Claims] 1. A graft carbon comprising the steps of: (1) subjecting carbon black to UV treatment or ozone treatment under normal pressure; and (2) graft polymerizing a monomer having a vinyl group by thermal polymerization. Production method. 2. A recording ink comprising the carbon black surface-treated by the above manufacturing method dispersed in water or / and a water-soluble organic solvent.