JPH0341471A - Production of toner for developing electrostatic charge image - Google Patents

Abstract

PURPOSE:To compatibly obtain both of sufficient offsettability and fixability by subjecting a crosslinked resin to a required treatment to form a binder resin from which a gel component is removed, compounding this resin with a compounded material essentially consisting of a coloring material and subjecting the mixture to a required treatment. CONSTITUTION:The binder resin from which the gel component of the crosslinked structure is removes is formed when the crosslinked resin having the crosslinked structure in the molecule is previously subjected to a thermally melting and kneading treatment. This binder resin is mixed with the compounded material essencially consisting of the coloring material and the mixture is thermally melted, kneaded and group to form the toner. The toner for developing electrostatic images which has the sufficient offsettability, is enhanced is the fixability by the absence of the gel component, and has the electrostatic characteristics to provide no hindrance in practicable use in thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a toner for developing electrostatic images in electrophotography, electrostatic printing, or the like.

[Conventional technology]

In copiers and printers that use electrophotography, it is desired that toner for developing electrostatic images (hereinafter referred to as toner) exhibit good fixing properties in addition to obtaining clear images. This is an important element.

It has been well known to use a binder resin having a high molecular weight or having many branches in order to improve the offset resistance of toner. As a method for obtaining such a binder resin,
The molecular weight distribution of the binder resin can be divided into a high molecular weight part and a low molecular weight part by two-stage polymerization, the high molecular weight part and the low molecular weight part can be polymerized separately and then blended, or a part of the molecular structure of the binder resin can be divided into two parts. A method using a so-called crosslinked resin, which has been crosslinked to form a crosslinked structure, has been carried out.

However, methods using two-stage polymerization of binder resins and methods using blended resins tend to produce linear molecules;
Furthermore, it has been difficult to produce toners with sufficient offset resistance because it is difficult to efficiently generate toners with large molecular weights.

In addition, in the method using cross-linked resin, the state of molecular chain scission of the cross-linked structure and the dispersibility of the colorant and charge control agent are interrelated during melt-kneading, so it is possible to create a toner with stable characteristics while satisfying fixing properties. was difficult to obtain. Therefore, it is extremely difficult to stably control the dispersibility of colorants and charge control agents, which can provide optimal characteristics for toners, as the melt viscosity during kneading differs due to the difference in crosslinking strength between the lofts of the crosslinked resin. Met. Furthermore, if the crosslinking of the crosslinked resin itself is related to the optimal dispersibility of the colorant and charge control agent, and if the crosslinking remains and gel components are present in the toner after kneading, the fixing performance will deteriorate. was inviting.

[Problem to be solved by the invention]

The present invention provides a method for producing a toner for developing an electrostatic image, which has both sufficient anti-offset properties and fixing properties, and also has charging properties that do not cause any problems in practical use as a toner.

[Means to solve the problem]

In the present invention, a crosslinked resin having a crosslinked structure in its molecules is not subjected to heat melt kneading treatment in advance to remove the gel component of the crosslinked structure to create a binder resin, and then the binder resin is This is a method for producing a toner for developing an electrostatic image, which is characterized by mixing with a compounding material containing a colorant as a main component, hot-melting, kneading, and pulverizing the toner.

The present invention will be explained in detail below.

The crosslinked resin in the present invention can be used without any particular restriction as long as it is a crosslinked resin used for toner, but a crosslinked resin that is crosslinked (self-crosslinked) by heat during the kneading step is not preferred. Examples of crosslinked resins that do not self-crosslink include styrene-based and polyester-based crosslinked resins, and these crosslinked resins can be suitably used in the present invention.

Specifically, as a styrene-based crosslinked resin, a desired crosslinked resin can be obtained by adding a crosslinking agent to a polymerizable monomer and performing polymerization by suspension polymerization or solution polymerization. Examples of the above polymerizable monomer include styrene, O-methylstyrene, m
-Methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene,
3.4 dichlorostyrene, p-ethylstyrene, 2,4
Dimethylstyrene, p-n-butylstyrene, p-te
rt-butylstyrene, p-n-hexylstyrene, p
-n-octylstyrene, p-n-nonylstyrene, p
- Styrene and its derivatives such as n-decylstyrene;
Ethylenically unsaturated monoolefins such as ethylene, propylene, butylene, isopretin, etc.; Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride; Vinyl acetate, vinyl propionate, vinyl henzoate, etc. Organic acid vinyl esters; methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, methacrylic acid 2
- Methacrylic acid and its derivatives such as ethylhexyl, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate; acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate , propyl acrylate, n-octyl acrylate,
Dodecyl acrylate, 2-ethylhexyl acrylate,
stearyl acrylate, 2-chloroethyl acrylate,
Acrylic acid and its derivatives such as phenyl acrylate;
Vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone, etc.
Examples include N-vinyl compounds such as N-vinylcarbazole, N-vinylindole, and N-vinylpyrrolidone; vinylnaphthalenes; and polymerizable monomers such as acrylonitrile, methacrylnitrile, and acrylamide.

These polymerizable monomers may be used alone or in combination of two or more if necessary.

The crosslinking agent is mainly a compound having a polymerizable double bond in the structure, such as aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene and their derivatives, such as diethylene glycol methacrylate, diethylene glycol acrylate, triethylene Diethylene carboxylic acid esters such as glycol methacrylate, trimethylolpropane trimethacrylate and allyl methacrylate, divinylated metals such as divinyl ether, divinyl sulfide and divinyl sulfone, and compounds having three or more vinyl groups are used singly or as a mixture.

Examples of polyester crosslinked resins include ethylene glycol, diethylene glycol, triethylene glycol,
Trifunctional monomers are added to polyesters with unsaturated double bonds obtained by polycondensation of polyhydric alcohols such as propylene glycol and polybasic acids such as phthalic anhydride, maleic anhydride, fumaric acid, and adipic acid. A crosslinked resin can be obtained by adding a compound such as a trial alcohol such as glycerin, a tricarboxylic acid such as trimethic acid, etc.

In the present invention, the above-mentioned crosslinked resin is preliminarily mixed in a single-screw kneader, twin-screw kneader, pressure kneader, or Banbury mixer.
A binder resin for toner is prepared by subjecting the resin to hot melt kneading using a device such as an extruder to cut the crosslinked structure in the molecule and remove the gel component.

Thereafter, the binder resin, colorant, charge control agent, etc. are hot-melted and kneaded, pulverized, and classified to obtain the toner for developing an electrostatic image of the present invention.

The gel content of the crosslinked resin as used in the present invention is determined by the following measuring method.

That is, 1 g of crosslinked resin is mixed with 100 c of tetrahydrofuran.
The solution is filtered through a filter paper, the weight of the gel remaining on the filter paper is measured, and the weight is divided by 1 g of crosslinked resin to determine the percentage.

The method for producing a toner for developing electrostatic images of the present invention involves removing the gel content of the crosslinked resin in advance before kneading the binder resin, which uses a crosslinked resin as a starting material, with a colorant, a charge control agent, etc. The fixing properties of the toner are good.

Furthermore, the kneading conditions for pre-treatment of the crosslinked resin were adjusted as appropriate.
Since the molecular weight and molecular weight distribution of the crosslinked resin can be adjusted by the roll, the triboelectric charging characteristics of the toner can be arbitrarily controlled by adjusting the dispersibility of the colorant and charge control agent while giving the toner the desired fixing properties. I can do it.

〔Example〕

Next, the present invention will be explained with reference to examples. In addition, all parts are parts by weight, and the formulation is not shown here.

Example 1 Styrene-acrylic copolymer resin A (Mn=5000
, Mw = 110000, Mw/Mn = 22.
0, gel content - 35%) in a pressure kneader.
Styrene-acrylic copolymer resin B (Mn
= 6000, old = 185000, gel content - 0%) was obtained.

Using the styrene-acrylic copolymer resin B, the following formulation was used, and after kneading, pulverizing, and classifying, the average particle size was 12 μm.
A toner for developing an electrostatic image according to the present invention was prepared.

Example 2 Polyester resin C (Mn = 7000, Mw =
150000, Mw/Mn=21.4, gel content=42
%) was kneaded with a pressure kneader to obtain polyester resin D (Mn = 7500, Mw = 21
5000, gel content -0%) was obtained.

Using the polyester resin, a toner for developing an electrostatic image according to the present invention having an average particle diameter of 12 μm was prepared by kneading, pulverizing, and classifying the mixture as shown below.

Example 3 Styrene-acrylic copolymer resin E (Mn = 43
00, Mw-148000, lh/Mn = 34.
4. Gel content - 28%) was kneaded in a twin-screw kneader to form a styrene-acrylic copolymer resin F (Mn=
4800. A binder resin having Mw=0 167,000 and gel content=0% was obtained.

The styrene-acrylic copolymer resin F was kneaded, pulverized, and classified to have an average particle size of 12 μm using the following formulation.
A toner for developing an electrostatic image according to the present invention was prepared.

Comparative Example 1 In place of the styrene-acrylic copolymer resin B in Example 1, styrene-acrylic copolymer resin A which had not been pre-kneaded was blended into the toner, and the other conditions were the same as in Example 1. A toner was prepared. Here, the gel content of the toner was 20%.

1 Comparative Example 2 In Example 1, instead of the styrene-acrylic copolymer resin B, styrene-acrylic copolymer resin A, which had not been pre-kneaded, was blended into the toner, and the kneading conditions were changed so that the gel content was 0. % comparison toner was prepared.

Comparative Example 3 A comparative toner was prepared in the same manner as in Example 2 except that in place of the polyester resin in Example 2, polyester resin C which had not been pre-kneaded was blended into the toner. Here, the gel content of the toner was 23%.

Comparative Example 4 A comparative toner with a gel content of 0% was prepared by blending polyester resin C, which had not been pre-kneaded, into the toner instead of the polyester resin in Example 2, and changing the kneading conditions.

Comparative Example 5 A comparison was made in the same manner as in Example 3 except that in place of the styrene-acrylic copolymer resin F in Example 3, styrene 2 acrylic copolymer resin E without pre-kneading was blended into the toner. I made a toner for it. Here, the gel content of the toner was 15%.

5 parts of each of the electrostatic image developing toner produced by the manufacturing method of the present invention based on Examples 1 to 3 and the comparative toner based on Comparative Examples 1 to 5 were added to a silicone resin-coated ferrite carrier (manufactured by Nippon Tetsuko Co., Ltd.). l-95-100) 100
A developer was prepared.

Using these developers, offset resistance and fixing performance, that is, minimum fixing strength, were evaluated using an external fixing device that was a modified commercial copying machine. In addition, 50,000 sheets were continuously copied using a commercially available copying machine (ReoDry 7720 manufactured by Toshiba Corporation), and the image density and charge amount during continuous copying were evaluated.

As a result, the off-cent resistance of the electrostatic image developing toner produced by the production method of the present invention in Examples 1 to 3 was practically sufficient. Table 1 also shows the results of minimum fixing strength, image density, and charge amount. However, the minimum fixing strength was evaluated as follows.

3. That is, a fixing device consisting of a heat roller whose surface layer is made of Teflon and a pressure roller whose surface layer is made of silicone rubber is adjusted so that the roll pressure is 30 kg/cm and the roll speed is 170 mm/sec. The set temperature of the heat roller is set to 190° C., and the toner image is fixed by the sample toner transferred onto the transfer paper. At this time, a toner image on the transfer paper whose image density is changed in stages is used. Next, the formed fixed image is rubbed with a cotton pad (trade name: PPC pad, manufactured by Dainisoku Co., Ltd.). The image density of the rubbed fixed charge image was divided by the image density before rubbing, the value was expressed as a percentage, and the lowest value was taken as the minimum fixing strength.

4 15 As is clear from the results in Table 1, the toner for developing electrostatic images produced by the production method of the present invention had high offset resistance, minimum fixing strength, and stable image density during continuous copying.

On the other hand, in Comparative Examples 1 and 3.5, the minimum fixing strength was low, and in Comparative Example 2.4, there was a tendency for the image density to decrease during continuous copying.

〔Effect of the invention〕

The method for producing a toner for developing an electrostatic image according to the present invention can provide a toner for developing an electrostatic image that has sufficient fixability while maintaining stable image density.

Claims (1)

[Claims] A cross-linked resin having a cross-linked structure in its molecules is preheated and kneaded to remove the gel component of the cross-linked structure to create a binder resin, and then the binder resin is mixed with a colorant as the main component. 1. A method for producing a toner for developing an electrostatic image, which comprises mixing with a compounding material, hot-melting, kneading, and pulverizing the toner.