JP3025748B2 - Manufacturing method of electrophotographic toner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an electrophotographic toner for a copying machine or a printer which employs heat roll fixing.

[0002]

2. Description of the Related Art In recent years, with the spread of copying machines and printers using an electrophotographic system including general households and the like, the use of low energy (mainly for the purpose of multifunctional copying machines and printers) has been promoted. Reduction of power consumption), speeding up for the purpose of spreading to the so-called gray area located at the border between the printing machine and copying machine, or lowering the roll pressure to simplify the fixing roll to reduce machine cost. Is desired. In addition, as copiers have become more sophisticated, since copiers equipped with a two-sided copy function and an automatic document feeder have become widespread, the fixing temperature of electrophotographic toner used in copiers and printers is low, and the There is a demand for a sheet having an excellent offset property and an excellent fixing strength to transfer paper in order to prevent stains during double-sided copying and the occurrence of stains in an automatic document feeder.

[0003] In response to the above requirements, attempts have been made to lower the fixing temperature by lowering the melting start temperature of the toner itself by including a crystalline substance such as natural wax in the electrophotographic toner. Conventionally, electrophotographic toners containing such a crystalline substance have been produced by hot-melt kneading, pulverization and classification. However, in such a manufacturing method in the prior art, the structure of the crystalline substance contained in the toner for electrophotography is changed by hot-melt kneading, and the melting point of the crystalline substance is changed before the hot-melt kneading. However, the melting point of the toner is lower than the melting point of the conductive material, which causes a problem that storage stability of the electrophotographic toner is deteriorated.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a production method capable of obtaining an electrophotographic toner which can be fixed at a low temperature without causing a storage problem.

[0005]

According to the present invention, a melting point of 50 ° C.
At least a binder resin and a colorant are added to a crystalline material having a temperature of 90 ° C. or less, and a hot melt-kneaded mixture is obtained to obtain a kneaded product. Then, the kneaded product is subjected to heat treatment, pulverized and classified. This is a method for producing a toner for electrophotography.

Hereinafter, the present invention will be described in detail. The present invention is characterized in that a heat treatment is performed on a kneaded product obtained by hot-melt kneading during the production of a toner. The reason why the kneaded material is subjected to heat treatment is that the crystallinity of the crystalline substance changes due to hot-melt kneading during the production of the toner, and the melting point is significantly lower than the melting point before kneading by 10 ° C. or more. The purpose is to solve. The heat treatment, which is a feature of the present invention,
The kneaded material after hot melt kneading for a predetermined time according to the heating temperature,
Processing by heat. In this case, the predetermined time is not particularly limited, but when the heat temperature is 35 ° C., 40 days a day.
C. is appropriate for 12 hours or 50.degree. C. for 1 hour, and the treatment may be performed until the crystal structure returns to the original state. Further, it is preferable that the treatment is performed until the melting point of the toner after classification, that is, the peak temperature of the heat of absorption of DSC becomes 60 ° C. or more. The temperature of the heat for processing the kneaded material is preferably higher than the glass transition point of the kneaded material and lower than the melting point of the kneaded material, because the melting point can be increased even if the heat treatment time is short, and the melting point can be easily returned to the melting point before kneading. However, the object of the present invention can be achieved by treating for a long time even at a temperature lower than the glass transition point of the kneaded material. Further, the temperature in the heat treatment may be a constant temperature treatment of the kneaded material, or may be changed by increasing or decreasing the temperature over time. The kneaded material immediately after the hot-melt kneading may be subjected to a heat treatment, or the heat-kneaded material may be subjected to a heat treatment after cooling for one day or more. The heat treatment is preferably performed by applying heat to the kneaded material using a thermostat capable of controlling the heat temperature, but the method is not limited as long as heat can be applied to the kneaded material, such as hot air treatment. . The hot melt kneading in the present invention may be performed using a single screw extruder or a twin screw extruder, etc., the pulverization may be performed using a hammer mill, a cutter mill, a jet mill, or the like. Good.

The crystalline substance used in the present invention is added to lower the melting start temperature of the toner and improve the low-temperature fixability. The lower the melting point of the crystalline substance, the better the low-temperature fixability. However, if the melting point is lower than 50 ° C., the storage stability is deteriorated.
If the melting point exceeds 90 ° C., the low-temperature fixability deteriorates. Therefore, the melting point range is from 50 ° C. to 90 ° C. Here, the melting point refers to the peak temperature of the amount of heat absorbed by DSC measurement. The method of measuring the peak temperature of the absorbed heat by DSC is performed as follows. For example, a differential scanning calorimeter SSC-5200 manufactured by Seiko Denshi Kogyo KK
As a measurement condition, about 10 mg of a crystalline substance was weighed and placed on a DSC, and 50 ml of N
₂ Inject gas. Then, the temperature is raised from 20 to 150 ° C. at a rate of 10 ° C. per minute, and the amount of heat absorbed at that time is measured. When a plurality of peaks are obtained, the peak temperature showing the maximum heat of absorption is defined as the melting point. The crystalline substance in the present invention refers to a substance that can clearly obtain a peak temperature in measurement of the calorific value of DSC,
Specific examples include hardened oils obtained by hydrogenating fats and oils mainly containing triglycerides of fatty acids and glycerin, natural waxes, ester waxes synthesized from fatty acids and alcohols, fatty acid amides, ketones, olefin waxes and the like. . Among these, hardened oils, natural waxes and ester waxes having particularly low melting points and excellent low-temperature fixability are preferably used in the present invention. The hydrogenated oil is obtained by adding about 0.2% of a reduced nickel catalyst to a triglyceryl ester of unsaturated fatty acid and glycerin, that is, a fat mainly containing glyceride, at a reaction temperature of 150 to 160 ° C. and a reaction pressure of 15 kg / cm ^3. And stirred for about 3 hours. Various hardened oils are obtained depending on the type of unsaturated fatty acid. Specific examples of the hardened oil include castor wax (castor hardened oil), rapeseed hardened oil, cottonseed hardened oil, olive hardened oil, and the like. Specific examples of the natural wax include rice wax, carnauba wax and the like. Specific examples of the ester wax include a monoester wax synthesized from a long-chain straight-chain saturated fatty acid and a long-chain straight-chain saturated alcohol, a diester wax synthesized from a polybasic acid and a long-chain straight-chain saturated alcohol, a triester wax, Oligoester waxes and the like. Also,
As the binder resin used in the present invention, a styrene resin,
Polyacrylic acid ester resin, styrene-methacrylic acid ester copolymer resin, polyvinyl chloride, polyvinyl acetate, polyvinylidene chloride, phenolic resin, epoxy resin, polyester resin and the like, especially for the purpose of improving the fixing performance The melting start temperature is preferably as low as possible. In addition, as a coloring agent, carbon black, nigrosine dye, aniline blue, calco oil blue,
Examples thereof include chrome yellow, ultramarine blue, Dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal, mixtures thereof, and others. It is necessary that these colorants are contained in a sufficient ratio to form a visible image having a sufficient image density, and usually a ratio of about 1 to 20 parts by weight based on 100 parts by weight of the binder resin. Is preferred. Further, a charge control agent, waxes such as polypropylene, and the like may be added to the electrophotographic toner of the present invention.

The melting start temperature of the electrophotographic toner obtained in the present invention is preferably 60 ° C. or more and less than 100 ° C. If the temperature is higher than 100 ° C., the fixing property is not sufficient, and if the temperature is lower than 60 ° C., the blocking property is deteriorated and a problem occurs in the storability. The melting start temperature means the temperature at which the plunger starts to fall. Measuring machine; Koka type flow tester CF-500 manufactured by Shimadzu Corporation Measurement conditions: Plunger: 1 cm ² Die diameter: 1 mm Die length: 1 mm Load: 20 kgF Preheating temperature: 50 to 80 ° C Preheating time: 300 sec Heating rate : 6 ° C / min

[0009] The electrophotographic toner obtained by the production method of the present invention is mixed with a carrier made of ferrite powder, iron powder or the like to form a two-component developer. When a magnetic material is contained, it may be used as it is as a one-component developer without mixing with a carrier for developing an electrostatic image, or may be mixed with a carrier and used as a two-component developer. Further, the present invention can be applied to a non-magnetic one-component developing method.

[0010]

The present invention will be described below with reference to examples. In the examples, parts are parts by weight. <Example 1> After mixing the above-mentioned raw materials with a super mixer and hot-melting and kneading to obtain a kneaded product, the kneaded product was left in a thermostat at 50 ° C. for 24 hours as a heat treatment, and cooled to room temperature (about 25 ° C.). Thereafter, through pulverization and classification, negatively chargeable toner base particles having an average particle diameter of 11 μm were obtained. Furthermore, 0.3 parts of hydrophobic silica (R-972 manufactured by Nippon Aerosil Co., Ltd.) was adhered to the surface of the toner base particles by a Henschel mixer to obtain an electrophotographic toner according to the present invention. The melting point of the kneaded product before the heat treatment was 52 ° C, but after the heat treatment, the melting point was 65 ° C. <Example 2> An electrophotographic toner according to the present invention was prepared in the same manner as in Example 1 using the above raw materials. In this example, the melting point of the kneaded product before the heat treatment was 53 ° C, but after the heat treatment the melting point was 67 ° C.

Example 3 1 mol of tetradecanoic acid, 2 mol of heptadecane 1ol and 0.5 mol of sulfuric acid were placed in a round-bottom flask equipped with a stirrer and a condenser, and heated at 130 ° C. for 4 hours.
Heated to reflux for hours. After removing the excess heptadecane 1ol, the residue was purified with methyl ether to obtain a monoester wax having a melting point of 65 ° C. used in the present invention. An electrophotographic toner according to the present invention was prepared in the same manner as in Example 1 using the above raw materials. In this example, the melting point of the kneaded material before the heat treatment was 58 ° C, but after the heat treatment, the melting point was 63 ° C. <Example 4> An electrophotographic toner according to the present invention was prepared in the same manner as in Example 1 using the above raw materials. In this example, the melting point of the kneaded product before the heat treatment was 56 ° C., but after the heat treatment, the melting point was 61 ° C.

<Embodiment 5> An electrophotographic toner according to the present invention was prepared in the same manner as in Example 1 using the above raw materials. In this example, the melting point of the kneaded material before the heat treatment was 59 ° C., but after the heat treatment, the melting point was 69 ° C. <Example 6> An electrophotographic toner according to the present invention was prepared in the same manner as in Example 1 using the above raw materials. In this example, the melting point of the kneaded product before the heat treatment was 79 ° C, but after the heat treatment the melting point was 83 ° C. Comparative Example 1 A comparative electrophotographic toner was obtained in the same manner as in Example 1 except that the toner was manufactured except for the heat treatment step. The melting point of the kneaded product after hot melt kneading was 52 ° C. <Comparative Example 2> A comparative electrophotographic toner was obtained in the same manner as in Example 2 except that the hardened rapeseed oil was omitted from the raw materials.

Next, the following tests were performed on the electrophotographic toners obtained from the above Examples and Comparative Examples. (1) Storage Property A 150 cc bottle was filled with 20 g of the toner, left in a constant temperature bath at 50 ° C. for 8 hours, and the caking state of the toner was visually checked to evaluate the storage property. The determination conditions are shown below. ：: No problem ×: The toner blocks and does not collapse even if shaken

(2) Non-offset temperature range 4 parts of each electrophotographic toner obtained in the above Examples and Comparative Examples, and 96 parts of a ferrite carrier without a resin coating (trade name: FL-1020, manufactured by Powder Tech Co.) Were mixed to prepare a two-component developer. Next, a commercially available copying machine (trade name: SF-980, manufactured by Sharp Corporation) is used by using the developer.
In 0), a plurality of belt-shaped unfixed images each having a length of 2 cm and a width of 5 cm were formed on A4 transfer paper. Next, a heat fixing roll having a surface layer formed of Teflon and a pressure fixing roll having a surface layer formed of silicone rubber rotate as a pair. A fixing device having a roll pressure of 1 kg / cm ² and a roll speed of 50 mm was used.
/ Sec, and the surface temperature of the heat-fixing roll was changed stepwise to fix the toner image on the transfer paper on which the unfixed image was formed at each surface temperature. At this time, observation was made as to whether or not the toner was contaminated in the blank portion, and a temperature region in which no contaminant was generated was defined as a non-offset temperature region. The difference between the maximum value and the minimum value in the non-offset temperature region was defined as the non-offset temperature width.

(3) Fixing Strength The surface temperature of the heat fixing roll of the fixing machine was set to 140 ° C., and the toner image on the transfer paper on which the unfixed image was formed was fixed. Then, the formed fixed image was rubbed with a cotton pad, and the fixing strength was calculated according to the following equation, which was used as an index of low energy fixing property. The image density was measured using a reflection densitometer RD-914 manufactured by Macbeth. Fixing strength (%) = Image density of fixed image after rubbing / Image density of fixed image before rubbing × 100 Table 1 shows the test results of the above items.

[0016]

[Table 1]

From the results shown in Table 1, the toner for electrophotography according to the production method of the present invention has practically no problem in storability and a non-offset temperature range of 60 to 70 ° C.
The fixing strength was 90% or more when the fixing temperature was 140 ° C., and good low-temperature fixing characteristics were exhibited. However, in Comparative Example 1, there was a problem in storage stability, and in Comparative Example 2, the fixing strength was 60%.
It was bad and had a practical problem.

[0018]

According to the production method of the present invention, it is possible to provide an electrophotographic toner which has good storage stability and can be fixed at a low temperature without practically causing problems such as occurrence of blocking.

Claims (6)

(57) [Claims] 1. A kneaded product obtained by adding at least a binder resin and a colorant to a crystalline substance having a melting point of 50 ° C. or more and 90 ° C. or less and hot-melting and kneading the resultant, and then subjecting the kneaded material to heat treatment, A method for producing a toner for electrophotography, comprising crushing and classifying. 2. The method for producing an electrophotographic toner according to claim 1, wherein the content of the crystalline substance is 3 to 30 parts by weight based on 100 parts by weight of the binder resin. 3. The method for producing an electrophotographic toner according to claim 1, wherein the crystalline substance is a hardened oil obtained by hydrogenating an oil or fat containing triglyceride as a main component. 4. The method for producing an electrophotographic toner according to claim 1, wherein the crystalline substance is a natural wax. 5. The method according to claim 1, wherein the crystalline substance is an ester wax synthesized from a fatty acid and an alcohol. 6. The method for producing an electrophotographic toner according to claim 1, wherein the temperature in the heat treatment is equal to or higher than the glass transition point of the kneaded material and equal to or lower than the melting point of the kneaded material.