JPH01105959A - White toner - Google Patents

Abstract

PURPOSE:To prevent the scattering of a toner and to improve the electrostatic chargeability and weather resistance by treating titanium oxide with aliphat. carboxylic acid at a specified temp. or above. CONSTITUTION:A white toner is composed of titanium oxide as a white pigment and a binding resin. The titanium oxide has been treated with aliphat. carboxylic acid having >=40 deg.C m.p. By the treatment, the hydrophobic property of the titanium oxide is improved, the compatibility with the binding resin is increased and the dispersibility in the toner is improved, so the scattering of the toner is prevented and the toner has satisfactory weather resistance.

Description

[Detailed description of the invention] Industrial applications The present invention relates to toner used in electrophotographic reproduction.

The color of a copy image of conventional electrophotography is generally black, but recently it is also possible to obtain copy images of various colors (color images).

Among color images, white images are formed from white toner on colored paper such as black, and have a different visual beauty from black images. White toner is a white pigment represented by titanium oxide,
Consists of binder resin and other additives.

However, such white toner poses problems such as toner scattering, fogging, and a decrease in toner chargeability.

Toner scattering, fogging, etc. are related to the charging characteristics of the toner, and a decrease in toner charging characteristics is related to the weather resistance of the toner, but in general, both of the above defects are caused by inorganic titanium oxide and organic materials. This is thought to be due to poor compatibility with the binder resin.

Problems to be Solved by the Invention It is an object of the present invention to solve the above-mentioned problems of white toner, and to provide a white toner that does not cause toner scattering and has excellent charging properties and weather resistance.

Means for Solving the Problems The present invention provides a white toner for developing electrostatic images containing at least a thermoplastic resin and titanium oxide, in which the titanium oxide is treated with an aliphatic carboxylic acid having a melting point of 40° C. or higher. The present invention relates to a white toner characterized by:

The white toner of the present invention comprises at least a titanium oxide white pigment and a binder resin, and the titanium oxide is treated with an aliphatic carboxylic acid having a melting point of 40°C or higher (this treatment is hereinafter referred to as "
aliphatic carboxylic acid treatment). When titanium oxide is treated with aliphatic carboxylic acid, its hydrophobicity is improved and its compatibility with the binder resin is increased. As a result, the dispersibility of titanium oxide in toner is improved, toner scattering does not occur, and weather resistance is improved. Excellent toner can be obtained.

The organic acid that can be used in the present invention may be any aliphatic carboxylic acid with a melting point of 40°C or higher, such as saturated fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, and behenic acid. Group carboxylic acids can be used, with stearic acid and palmitic acid being particularly preferred. Aliphatic carboxylic acids having a melting point lower than 40° C. are undesirable because they have poor toner storage stability due to their melting properties and also cause filming during exposure.

As a method for treating titanium oxide with aliphatic carboxylic acid, titanium oxide is dispersed in a solution in which the above-mentioned aliphatic carboxylic acid is dissolved, and after stirring and mixing at a constant temperature for a certain period of time, titanium oxide is separated and removed by means such as filtration. This can be done by drying (solution immersion method). Another method is to spray a solution of an aliphatic carboxylic acid onto titanium oxide and dry it (spray drying method).

First, the solution immersion method will be described below.

The solvent used for the aliphatic carboxylic acid treatment is not particularly limited as long as it is inert to the aliphatic carboxylic acid and can be easily removed by drying, such as chloroform, ethyl alcohol, ether, and benzene.

The amount of organic solvent to be used varies depending on the aliphatic carboxylic acid used, but is generally 10 to 5,000 times the weight of titanium oxide, preferably 15 to 1,000 times, more preferably 2 times by weight.
0 to 500ff1m times.

If the amount is less than 10 times by weight, the titanium oxides will coagulate with each other, and the dispersibility of the titanium oxides in the binder resin, which will be described later, will worsen, and the problem of toner scattering will not be solved. When the amount is more than 5,000 times by weight, the effect of aliphatic carboxylic acid treatment is weakened, and the effect of the present invention is lost.

The mixing ratio of aliphatic carboxylic acid and titanium oxide in the aliphatic carboxylic acid treatment varies depending on the aliphatic carboxylic acid used, but generally the amount of aliphatic carboxylic acid added to titanium oxide is 0.01 to 30% by weight, preferably 0.01% by weight. 05-2
0% by weight, more preferably 0.1 to 10% by weight.

If the amount added is less than 0.01% by weight, the effect of the coupling treatment according to the present invention cannot be obtained, and if the amount added is more than 30% by weight, the titanium oxides will coagulate with each other, which will instead cause the binding described below. The dispersibility of titanium oxide in the resin deteriorates, and problems such as toner scattering are not solved.

Although it varies depending on the organic solvent and aliphatic carboxylic acid used,
The aliphatic carboxylic acid treatment temperature is 10 to 80°C, preferably 10 to 70°C, more preferably 20 to 60°C. If the temperature is higher than 80°C, the organic solvent will evaporate, making it impossible to carry out aliphatic carboxylic acid treatment.

Further, if the temperature is lower than 10°C, the aliphatic carboxylic acid treatment cannot be carried out sufficiently.

The aliphatic carboxylic acid treatment time (stirring and mixing time) is 0.
．． 01 to 12 hours, preferably 0.1 to 10 hours, more preferably 0.5 to 5 hours. If the time is shorter than 0.001 hours, the aliphatic carboxylic acid treatment cannot be carried out sufficiently.

Moreover, if the time is longer than 12 hours, the organic solvent will evaporate, making it impossible to carry out the aliphatic carbon treatment.

In the spray drying method, the same type of solution used in the molten Ti or dipping method can be used, but a solution with a concentration about half lower than that used in the solution dipping method within the above usage amount range of aliphatic carboxylic acid. Approximately the same conditions as in the solution immersion method can be applied, except that .

The titanium oxide may be produced by any method such as a sulfuric acid method, a chlorine method, or a gas phase method, and any crystal form of anatase type, rutile type, or pulcite type can be used. The content of the aliphatic carboxylic acid-treated titanium oxide white pigment is as follows:
15 to 60 parts by weight, preferably 15 to 00 parts by weight
~50 parts by weight, more preferably 20 to 40 parts by weight. If it is less than 15 parts by weight, a white image with sufficient density cannot be obtained, and if it is more than 60 parts by weight, the binding and dispersibility between the pigment and the binder resin will deteriorate, resulting in problems such as toner scattering, fogging, and fixing properties. Adversely affect.

The binder resin is preferably a thermoplastic resin, and such resins include polystyrene, poly-p-chlorostyrene,
Monopolymers of styrene and its substituted products such as polyvinyltoluene, styrene-p-chlorostyrene copolymers, styrene-propylene copolymers, styrene-vinyltoluene copolymers, styrene-hinylnaphthalene copolymers, styrene- Methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-(methacrylic acid) Ethyl copolymer, styrene-butyl methacrylate copolymer, styrene-d-chloromethyl methacrylate copolymer, styrene or its substituted monomer, or acrylic acid, methacrylic acid and its ester monomer and conventional Known amino groups, glycidoquine groups, mercapto groups, ureido groups, quaternary ammonium groups,
Copolymers with vinyl monomers containing nitrogen-containing heterocycles (including quaternized products), styrene-acrylonitrile copolymers, styrene-vinyl methyl ether copolymers, styrene-vinylethyl ether copolymers, Styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer, etc. Styrenic copolymer, polymethyl methacrylate, polybutadiene methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyamide, polyacrylic acid resin, rosin, modified rosin , terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, etc. can be used alone or in combination.

The white toner of the present invention may further contain other additives such as charge control agents, waxes, and the like.

As the charge control agent, either a positive charge control agent or a negative charge control agent can be used.

Among charge control agents, typical ones that impart positive chargeability to toner include amino compounds, quaternary ammonium compounds, alkylamides, phosphorus and tungsten compounds, etc. Typical examples of these compounds include naphthenic acid metal salts, fatty acid metal salts, salicylic acid, reaction products of its derivatives and metal salts, reaction products of its derivatives and metal salts, electron-accepting compounds, etc. can be mentioned. This charge control agent is usually
It is mixed and dispersed in a proportion of 1 to 20 parts by weight based on 100 parts by weight of the thermoplastic resin. They can be used alone or in combination of two or more.

As waxes, waxes made of low-molecular m-olefin polymers can be used.

The low molecular weight olefin polymer is an olefin polymer containing only olefin as a monomer component or an olefin copolymer containing a monomer other than olefin as a monomer component, and has a low molecular weight.

Examples of low molecular weight olefin polymers include low molecular weight homopolymers, copolymers or modified products thereof, such as low molecular weight homopolymers and copolymers of formula 0 (wherein R is a hydrogen atom or an alkyl group having 4 or less carbon atoms). molecular weight polyethylene, polypropylene, α or β polybutylene, ethylene-propylene copolymer,
In addition to polyethylene wax, oxidized polyethylene and chlorinated products, ethylene or propylene is the main ingredient,
Modified with one or more other ethylenically unsaturated monomers such as vinyl acetate, maleic anhydride, acrylic acid or its esters, methacrylic acid or its esters, acrylamide, methacrylamide, acrylonitrile, methacrylatrile, etc. Random copolymers, block copolymers, or graft copolymers with low molecular weights are used.

Other examples include naturally occurring waxes such as vegetable waxes, animal waxes, solid fats, and mineral waxes, as well as waxes such as higher fatty acids or their derivatives, candelilla wax, carnauba wax, rice wax, Vegetable waxes such as tree wax, palm wax, auriculie wax, sugarcane wax, esparto wax, and park wax; animal waxes such as beeswax, lanolin, and squeeze wax; mineral waxes such as montan wax, oshikerite, and ceresin; and paraffin. Petroleum waxes such as wax, microcrystalline wax and petrolactam, synthetic hydrocarbons such as Fischer-Tropsch wax (Sasol wax), Monk wax derivatives,
Modified waxes such as paraffin wax derivatives and microcrystalline wax derivatives, hydrogenated waxes such as hydrogenated castor oil and hydrogenated castor oil derivatives, their amides, esters, derivatives such as metal soaps, higher (03 to Ctt) saturated fatty acid amides, unsaturated fatty acids Amides and hydroxy fatty acid amides, N-methylol fatty acid amides, N, N'
- Amide waxes such as methylene fatty acid amide, N,N'-ethylene fatty acid amide, dialkyl ketones of higher fatty acids, waxy fatty acid amines, imides, glycerides (
fats and oils such as acylglycerin), -hydric alcohol fatty acid esters, glycerin fatty acid esters, glycol fatty acid esters, sorbitan fatty acid esters, polyoxyethylene fatty acid esters, ethylenes such as phthalate esters, calcium stearate, aluminum stearate, magnesium stearate, Alkali metal salts, alkaline earth metal salts, zinc salts, aluminum salts and other metal salts of higher fatty acids such as calcium palmitate; Hydrazides of higher fatty acids such as palmitic acid hydrazide and stearic acid hydrazide; p-hydroxyanilide of myrisdylenic acid; p-Hydroquinoanilide of higher fatty acids such as p-hydroxyanilide of stearic acid: β-diethylaminoethyl ester hydrochloride of lauric acid, β- of stearic acid
β-diethylaminoethyl ester hydrochloride of higher fatty acids, such as diethylaminoethyl ester hydrochloride, higher fatty acid amide-formaldehyde condensate, such as nistearic acid amide-formaldehyde condensate, palmitic acid amide-formaldehyde condensate, petroleum residues such as Niasfald, Gilt'nite, etc. Rubbers such as rubber, nitrile rubber, and chlorinated rubber, synthetic hydrocarbons such as Fischer Trobunyu wax and derivatives, halogenated hydrocarbons such as chlorinated paraffin and chlorinated propylene, hardening of hardened castor oil, hardened tallow oil, etc. Oils and the like can be mentioned, and these can be used alone or in combination or mixture with the above-mentioned low molecular weight olefin polymer.

The white toner of the present invention is produced by thoroughly mixing the composition of the various components mentioned above, then kneading the mixture until it becomes sufficiently uniform, cooling it, and pulverizing it with a pulverizer such as a jet pulverizer. Coarse powder and fine powder are removed by classification to obtain a white toner having a particle size of 5 to 25 μm and an average particle size of 13 to 14 μm.

The toner of the present invention may further contain a fluidizing agent (external addition). Glidants include silica, aluminum oxide,
There are titanium oxide, warp/aluminum oxide mixtures, silica/titanium oxide mixtures, etc.

The white toner of the present invention can be mixed with a suitable carrier to form a two-component developer, for example. As the carrier, when implementing the cascade development method, resin-coated glass beads, steel balls, etc. are used, and when implementing the magnetic brush development method, ferrite, fine iron powder, or a so-called binder type microcarrier is used. On the other hand, it is also possible to use the valve magnetic toner as the l component by charging it with a developing sleeve or the like.

The present invention will be explained below with reference to Examples.

Aliphatic carboxylic acid treatment example 1 3 g of stearic acid (manufactured by Kanto Kagaku Co., Ltd.; reagent grade 1) was mixed in 20 OiQ of hot ethyl alcohol, and stirred for about 10 minutes with a TK homogenizer (manufactured by Tokushu Ki Kogyo Co., Ltd.) to uniformly disperse it. let

100 g of titanium dioxide KR310 (manufactured by Titan Kogyo Co., Ltd.) is added to the obtained dispersion solution, and the mixture is slowly stirred for about 15 minutes. Thereafter, it was filtered with a vacuum filter, dried with hot air at 50°C for 3 hours, vacuum dried at 50°C for 5 hours, and then dispersed with a TK homogenizer at 200 rpm for 5 minutes to obtain titanium oxide 1 according to the present invention.

Aliphatic carboxylic acid treatment example 2 Stearic acid 209 (manufactured by Kanto Kagaku Co., Ltd.; reagent grade 1) is mixed with 250 Mg of hot ethyl alcohol, and stirred for about 10 minutes using a TK homogenizer to uniformly disperse the mixture.

The obtained dispersion solution was directly sprayed onto 100 g of titanium dioxide KR310 (manufactured by Titanium Kogyo Co., Ltd.), then dried with hot air at 50°C for 3 hours, further vacuum-dried at 50°C for 5 hours, and then sprayed with a homogenizer at 2000 rpm for 3 hours. After dispersing for a minute, titanium oxide 2 according to the present invention was obtained.

Aliphatic carboxylic acid treatment example 3 In place of using 3 g of stearic acid (manufactured by Kanto Kagaku Co., Ltd.) in aliphatic carboxylic acid treatment example I, stearic acid (
Titanium oxide 3 was obtained in the same manner as aliphatic carboxylic acid treatment I, except that the amount was 0.05 g (manufactured by Kanto Kagaku Co., Ltd.).

Aliphatic carboxylic acid treatment example 4 In place of using 3 g of stearic acid (manufactured by Kanto Kagaku Co., Ltd.) in aliphatic carboxylic acid treatment example 1, stearic acid (
Titanium oxide 4 was obtained in the same manner as in aliphatic carboxylic acid treatment 1, except that the amount was 30 g (manufactured by Kanto Kagaku Co., Ltd.).

Example 1 Titanium oxide 1 40 parts by weight (60:
40. The raw materials having Tg = 56°C and amine value = 174) were thoroughly mixed in a Henschel mixer, kneaded in a twin-screw extruder, and then cooled. The kneaded material was coarsely pulverized, then pulverized with a jet pulverizer, and subjected to air classification to obtain particles having a particle size of 5 to 25 μm (average particle size I: 3.3 μm).

Thereafter, 0.2 of Aerosil R972 (hydrophobic silica; manufactured by Nippon Aerosil Co., Ltd.) was mixed in to form a toner l.

Example 2 Bisphenol A type polyester resin (softening point -120
2℃, Tg・64℃), 100 parts by weight, titanium oxide 2
The same procedure as in Example 1 was carried out except that 30 parts by weight of was used.
Toner 2 (average particle size: 13.4 μm) was obtained.

Example 3 The same procedure as Example 1 was carried out except that 40 parts by weight of titanium oxide 3 was used instead of 40 parts by weight of titanium oxide 1 in Example I, and toner 3 (average particle size 13.6 μm
) was obtained.

Example 4 The same procedure as Example 1 was carried out except that 40 parts by weight of titanium oxide 4 was used instead of using 40 parts by weight of titanium oxide 1 in Example 1, and toner 4 (average particle size 13.5 μm
) was obtained.

Comparative Example 1 In place of using 40 parts by weight of titanium oxide 1 in Example 1, titanium oxide KR-310 (manufactured by Titanium Kogyo Co., Ltd.) was used.
The same procedure as in Example 1 was carried out except that 50 parts by weight of was used.
Toner 5 (average particle size: 13.9 μm) was obtained.

Preparation of carrier (A) Styrene-acrylic copolymer resin (Bryolide AC
L, made by Gutdeyer Co., Ltd.) 100 parts by weight, magnetic powder (Mapico Black 500; made by Methane Kogyo Co., Ltd.) 200 parts by weight, carbon black (MA#8: made by Mitsubishi Chemical Industries, Ltd.) 4 heavy machinery parts, silica (#200; Japan) (manufactured by Aerosil) were mixed in a ball mill and kneaded with three rolls. The kneaded material is pulverized using a pin mill and classified using a wind classifier.

A carrier (A) with an average particle diameter of 40 μm and a volume specific resistance of Ω·cm was obtained.

Preparation of carrier (B) Polyester resin (softening point 123°C; glass transition point 6
5°C) 100 heavy bases, inorganic magnetic powder (manufactured by Toda Kogyo Co., Ltd.)
EPT-1000) 500 parts by weight, carbon black (
2 parts by weight of MA#8 (manufactured by Mitsubishi Chemical Industries, Ltd.) were thoroughly mixed and pulverized using a Henschel mixer, and then the cylinder part 16
The mixture was melted and kneaded using an extrusion kneader set at 0° C. and 150° C. at the cylinder head. After cooling, the kneaded material was finely pulverized using a jet mill, and then classified using a classifier to obtain a magnetic carrier (B) having an average particle size of 55 μm.

The powder electrical resistivity of the obtained carrier was 7.08xlQ+
It was 3Ω・CJI. The applied magnetic field of this carrier is 100
At the source of 00e, the magnetic flux density Bm is 1082G1, the amount of magnetization σ is 45, 6 emu/gs, and the residual magnetization Ha is 217°6
It was G.

Carrier (C) In addition to the carriers (A) and (B) above, a ferrite-based coated carrier (C)...average particle size 62μ, electrical resistance 5
×10 Ω・C shoulder (100 V/c was used.

The white toner obtained in Toner Evaluation Examples 1 to 4 and Comparative Example 1 and carriers (A), (B), and (C) were mixed at a toner mixing ratio of 10.
A developer was prepared in wt%, and the amount of toner charge was measured. The above results are summarized in Table 1.

Further, a copy image was formed on a transfer paper using EP450Z or EP550Z (manufactured by Minolta Camera Co., Ltd.) using the carrier (B) developer.

Furthermore, 10,000 sheets were continuously copied and changes in toner charge m and background fog were observed. In addition, in the initial stage, the prepared developer was placed under high temperature and high humidity (35°C, 85%) for 2 hours.
The sample was left standing for a day, and the change in the amount of charge was then measured.

The above results are summarized in Table 2.

The background fog in Table 2 was evaluated and ranked as follows.

Background fog The background fog due to toner scattering was visually observed as ○ if it was good, △ if it was somewhat good, and × if it was bad.

Effects of the Invention The white toner prepared from titanium oxide treated with aliphatic carboxylic acid according to the present invention has excellent weather resistance and does not cause toner scattering, fogging, etc.

Patent applicant: Minolta Camera Co., Ltd.

Claims (1)

[Claims] 1. A white toner for developing electrostatic images containing at least a thermoplastic resin and titanium oxide, characterized in that the titanium oxide is treated with an organic acid having a melting point of 40° C. or higher.