JPH075850B2 - Colorants and their use - Google Patents

Description

TECHNICAL FIELD The present invention relates to a colorant useful for electrophotographic liquid developers, printing inks, heat-sensitive transfer inks, paints and the like, and use thereof for electrophotographic liquid developers.

Prior art Electrophotographic liquid developers, printing inks, paints, and other vehicles that float colorants or toners are required to have good dispersion stability in terms of particle aggregation and sedimentation prevention.
In addition, when it is used as a copy, a printed matter, or a coated material, it is required that the coloring degree or the image density is high and the image is clear. On the other hand, waxes such as whale wax, carnauba wax, petroleum wax, and polyolefin wax such as low molecular weight polyethylene are made into fine particles in order to improve dispersion stability and coloring degree or image density. It is known to be added and dispersed. For example, a general liquid developer for electrophotography contains a pigment such as carbon black and a thermoplastic resin such as styrene resin and acrylic resin as main components, on which the polarity control of lecithin, metal soap, linseed oil, higher fatty acid, etc. The toner added with the agent is dispersed in a carrier liquid having a high insulating property and a low dielectric constant such as petroleum-based aliphatic hydrocarbons, but this type of liquid developer is inferior in dispersion stability and image density. Therefore, it has been proposed to add waxes. However, simply adding waxes lowers the image sharpness in the transfer and fixing steps to form a copied image, and especially when copying fine characters, the image is crushed and sometimes the image density is lowered. It was hot.

OBJECT The first object of the present invention is to provide a colorant having good dispersion stability, high coloring degree or image density, and capable of forming a clear copy, print or coating.

A second object of the present invention is to provide a liquid developer for electrophotography, which has good dispersion stability and does not cause deterioration of image sharpness and image density during the transfer and fixing steps.

The colorant of the present invention is obtained by coating the surfaces of pigment particles with a polyolefin-maleic anhydride copolymer, and the liquid developer of the present invention has a colorant in a carrier liquid having high insulation and a low dielectric constant. A liquid developer for electrophotography in which a toner containing a resin as a main component is dispersed, wherein the colorant contains a pigment coated with a polyolefin-maleic anhydride copolymer.

To make a colorant comprising the copolymer resin-coated pigment of the present invention, a method of dipping the resin solution in the pigment particles, spraying, coating with a method such as kneading, and then drying may be used, as is usually done. In the present invention, in order to coat the resin more densely, a water-containing paste of pigment particles (also referred to as a wet cake) is kneaded with a resin or a resin solution to replace the water surrounding the surface of the pigment particles with the resin or the resin solution, and then water. And / or it is preferable to disperse the pigment in the state of primary particles by utilizing a so-called flushing method in which the solvent is removed by a method such as decompression and drying. It has been found that the polyolefin-maleic anhydride copolymer used as the coating resin here is extremely effective in improving the dispersibility and coloring power of the pigment. The improvement in dispersibility is due to the affinity of the maleic anhydride component in the copolymer for the pigment, and the improvement in coloring power is due to the reaction between the maleic anhydride component and the basic group in the pigment. It is believed to be due to the tinting strength of the reactive pigment polymer formed.

Such a polyolefin-maleic anhydride copolymer can be obtained by a usual method for producing a graft copolymer, and can be easily obtained as a commercial product. For example, commercially available polyethylene-maleic anhydride copolymers include DIACALNER 30,30L, PAR30, PAN30 and the like.

An example of producing a polyolefin-maleic anhydride copolymer is shown below.

Production Example 1 Polyethylene wax (Sanwax 131 manufactured by Sanyo Kasei Co., Ltd.
P) 12Kg was charged into the reaction kettle, and after blowing N ₂ gas, 160 ℃
While heating and stirring, 1 Kg of maleic anhydride and 60 g of benzoyl peroxide were added, and the mixture was reacted at the temperature for 4 hours to prepare a polyethylene-maleic anhydride copolymer.

Production Example 2 Polyethylene wax (Polyethylene PED manufactured by Hoechst)
-521) Charge 10 kg into the reaction kettle, blow N ₂ gas, and
Heat to 65 ° C. and stir, 1.5 kg maleic anhydride and di-t
-Butyl peroxide (30 g) was added, and the mixture was reacted at the above temperature for 4 hours to prepare a polyethylene-maleic anhydride copolymer.

Production Example 3 10 kg of polyethylene wax (polyethylene AC-540 manufactured by Allied Chemical Co., Ltd.) was charged into a reaction kettle, and 1 kg of maleic anhydride and 40 g of di-t-butyl peroxide were added while heating and stirring at 190 ° C. The reaction was carried out at the temperature for 6 hours to prepare a polyethylene-maleic anhydride copolymer.

Production Example 4 Polypropylene wax (Mitsubishi Kasei dialen 30)
Charge 8 kg into the reaction kettle, heat to 150 ° C, and stir
Add 0.5 kg maleic anhydride, then add 1 benzoyl peroxide.
10 g was added 3 times in 0 minutes and the mixture was further reacted at the above temperature for 4 hours to prepare a polypropylene-maleic anhydride copolymer.

Production Example 5 Viscose manufactured by Sanyo Kasei Co., Ltd. as polypropylene wax
A polypropylene-maleic anhydride copolymer was produced in the same manner as in Production Example 4 except that 330P was used.

Production Example 6 As a polypropylene wax, Mitsubishi Kasei's dialen
Polypropylene was produced in the same manner as in Production Example 4 except that 20 was used.
A maleic anhydride copolymer was prepared.

The polyolefin-maleic anhydride copolymer obtained as described above may be used alone, but in the present invention, in order to further improve the dispersion stability of the colorant and the coloring power (however, black type), the resin Humic acid as a dispersant in the coating process of
It is preferable to add humic acids such as humic acid salts or humic acid derivatives (for example, nitrohumic acid). The appropriate amount of use is 10% by weight or less based on the pigment. In addition, since the humic acids are well adsorbed on the pigment particles due to the polyfunctional group, the colorant can be finely pulverized to the order of primary particles, and the electric charge and hence the electrostatic repulsion force are generated. It is considered that the improvement of the coloring power is due to the fact that the humic acids are similar to the structure of carbon black and are black.

Similarly, waxes such as those conventionally used in polyolefin-maleic anhydride copolymers can be used in combination to change the softening temperature of the colorant and improve its thermal properties. Examples of commercial products of such waxes include the following.

As the pigment which is the other component of the colorant, carbon black (commercially available, Degussa's Prinetex G, V, special black 15,4,4B; Mitsubishi Carbon's Mitsubishi # 44, # 30,
MA-11, MA-100; Rabot 30,40,1035 manufactured by KYABOT CORPORATION,
Conductor Tex SC, Mogul L, Elf Tex 8, Legal 400 etc. ), Phthalocyanine blue, phthalocyanine green, sky blue, rhodamine lake,
Malachite Green Lake, Methyl Violet Lake, Pekotsk Blue Lake, Naphthol Green B, Naphthol Green Y, Naphthol Yellow S, Resorfarst Yellow 2G, Permanent Red 4R, Brilliant Farst Scarlett, Hansa Yellow, Resolled Red, Benzine Yellow ， Rakelet C, Rakelet D, Brilliant Carmine 6B, Permanent Red F5R,
Pigment Scarlet 3B, Alkali Blue, Oil Blue, Oil Biolet, Methyl Orange, Fair Stred, Methyl Biolet, and the like. When carbon black is used as a pigment to obtain a black image, an organic pigment is usually used together for the complementary color of black.

The amount of the coating resin used for the colorant is appropriately about 40 to 90 parts by weight with respect to 1 part by weight of the pigment.

Next, in order to prepare the liquid developer of the present invention using the colorant obtained as described above, this colorant is a thermoplastic resin, and if necessary, a pigment of the same color system as the colorant, a complementary color pigment and / Or waxes may be kneaded with a small amount of carrier liquid to give a concentrated toner, which may be diluted and dispersed with an appropriate amount of carrier liquid. Here, the amount of the thermoplastic resin used is appropriately about 30 to 200 parts by weight per 1 part by weight of the colorant.

Examples of the thermoplastic resin include various acrylic or styrene resins. Specifically, acrylic acid, methacrylic acid or their esters [for example, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate,
Lauryl (meth) acrylate, butyl (meth) acrylate, ethyl (meth) acrylate, methyl (meth)
Acrylate, dimethylaminoethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, glycidyl (meth) acrylate, styrene or a derivative thereof (for example, vinyltoluene, chlorostyrene, aminostyrene, dimethylaminostyrene, nitrostyrene, vinylbenzoic acid). Etc.), vinylpyridine, vinylpyrrolidone, or other polymers or copolymers are used.

As the carrier liquid, a solvent having a high insulating property and a low dielectric constant, for example, a petroleum aliphatic hydrocarbon such as cyclohexane, n-hexane, n-heptane, n-nonane, n-octane, isooctane, isododecane, ligroin and a mixture thereof is used. (The commercially available product is Isopar E manufactured by ETSO Standard Oil Co.,
G, H, L, K and Ciel Sole 71 manufactured by Ciel Oil Co., Ltd., Solvetso 15
There is 0 etc. ) Is mentioned.

The present invention will be described below with reference to examples. Example 1
10 to 10 are examples of colorants, and Examples 11 to 18 are examples of liquid developers.

Example 1 Water 500 g Purintex G 30 g Alkaline blue 20 g Humic acid 10 g A mixture consisting of 10 g was thoroughly stirred and kneaded in a flasher,
600 g of the copolymer of Production Example 1 was added and further kneaded. Then, the mixture was heated under reduced pressure to remove water, and the obtained lump was crushed with a stone mill to prepare a colorant powder having a particle size of 0.05 to 0.1 µ.

Examples 2 to 10 Colorant powders were prepared in the same manner as in Example 1 except that the types and amounts of pigments, humic acids and copolymers were changed as shown in Table 1.

Example 11 Colorant of Example 1 40 g Raven 1035 12 g Methylene blue 2 g 2-Ethylhexyl methacrylate (2-EHMA) -Lauryl methacrylate (LMA) -Methacrylic acid (MAA) -Methyl methacrylate (MMA) (weight ratio 30/20/10 / 40) Copolymer 35g Kneading a composition consisting of 90g of Isopar H for 70 hours in a ball mill, then adding 360g of Isopar H and kneading for 1 hour to obtain a concentrated toner, and 140g of the toner is dispersed in Isopar H1 to obtain a liquid. I made a developer.

Examples 12 to 18 Liquid developers were prepared in the same manner as in Example 11 except that the compositions shown in Table 2 were used.

Next, in order to examine the dispersion stability of the eight liquid developers prepared as described above, each developer was allowed to stand at room temperature for 3 months, but neither toner aggregation nor sedimentation occurred. Also, each developer was set in a commercially available transfer type wet electrophotographic copying machine, and copying was performed using a paper having a smoothness of 10 seconds and a paper having a smoothness of 150 seconds, respectively, and the results shown in Table 3 were obtained. was gotten. The average particle diameter of the toner is also added to the table.

The ratio of the thickness of the portion corresponding to the original image line of the copy image formed on the paper for 10 seconds, and if this value is 1.10 or less, it can be said that there is substantially no transfer crushing.

Effect As described above, the colorant of the present invention is composed of a pigment coated with a polyolefin or maleic anhydride copolymer having high affinity and reactivity with the pigment as described above, and therefore, when it is particularly used in an electrophotographic liquid developer. Has the advantages of improved toner dispersion stability and coloring power, no toner aggregation or sedimentation even during long-term storage, high-density image formation, and no image crushing during transfer and fixing processes. ing.

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Claims (2)

[Claims] 1. A colorant comprising a pigment particle surface coated with a polyolefin-maleic anhydride copolymer. 2. A liquid developer for electrophotography comprising a toner having a colorant and a resin as a main component dispersed in a carrier liquid having a high insulating property and a low dielectric constant, wherein the colorant is a polyolefin-maleic anhydride copolymer. A liquid developer for electrophotography, comprising a pigment coated with a polymer.