JP2004004999A - Binder resin and electrophotographic developing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a binder resin giving an odorless toner excellent in blocking resistance and resistance to a vinyl chloride plasticizer and to provide an electrophotographic developing method. <P>SOLUTION: The binder resin contained in a toner comprises styrene and/or its derivative and a (meth)acrylic ester as principal components, the glass transition temperature of the binder resin is 50-100°C and the amount of residual monomers in the binder resin is ≤200 ppm, but the binder resin is not a resin which is a polymer obtained by polymerization in the presence of ≥10 wt.% plasticizer based on the total weight of monomers and the plasticizer. Electrophotographic development is carried out using a toner comprising the binder resin and a colorant. <P>COPYRIGHT: (C)2004,JPO

Description

(4) The present invention relates to a binder resin and an electrophotographic developing method.

Conventionally, many inventions have been made on resins for dry toners, and various physical properties of toners have been improved.
However, conventionally used toner resins or toners contain a large amount of residual monomers, which cause odor during toner production, particularly during melt-kneading, which makes the working environment worse, or causes odor during copying, resulting in discomfort. It has a problem of giving, and there is a strong demand for its improvement.

In such a situation, in order to solve this problem, the polymerization temperature is maintained at or higher than the polymerization temperature for a long time after the completion of the polymerization, or a solid resin obtained by dehydration and drying after the completion of the polymerization is obtained by using an extruder or the like. A method of removing residual monomers in a molten state and the like are disclosed. However, these methods have complicated processes, increase the cost, and have a problem of quality deterioration due to melting and kneading, etc., and it is expected that a toner resin or toner which is simple in a short time and has very little residual monomer will appear. Have been.

The present inventors have conducted intensive studies to achieve the above object, but surprisingly, by reducing the residual monomer in the toner resin to a specific concentration or less, the odor of the toner resin and the toner is reduced. Is significantly improved, and at the same time, the blocking resistance and the PVC plasticizer resistance of the toner are also improved. In addition, by adopting a specific processing step in the resin production method, the residual monomer in the resin can be shortened in a short time. Has been found to be able to be removed, and the present invention has been achieved.

The gist of the present invention is a binder resin contained in a toner, wherein the binder resin contains styrene and / or a derivative thereof and a (meth) acrylic acid ester as a main component. A binder resin having a glass transition point of 50 to 100 ° C. and a residual monomer amount of 200 ppm or less (provided that the binder resin is 10% by weight based on the total weight of the monomer and the plasticizer). Excluding a resin which is a polymer obtained by polymerizing in the presence of at least plasticizer by weight.

First, the binder resin of the present invention will be described. As the binder resin of the present invention, a generally known radical polymer which can be produced by suspension polymerization can be used. Specific examples of the monomers used to obtain these resins include styrene, α-methylstyrene, p-methyl group, m-methyl group, p-methyl group, p-ethyl group, Styrene derivatives having 4-dimethyl group, p-butyl group, p-hexyl group, p-octyl group, p-nonyl group, p-decyl group, p-methoxy group, p-phenyl group, etc., general formula: CH ₂ = CR-COOR '(where R represents hydrogen or a methyl group), wherein R' is a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, t-butyl group, n-bentyl group, n-hexyl group, n-octyl group, 2-ethylhexyl group, n-nonyl group, isononyl group, decyl group, dodecyl group, tridecyl group, stearyl group, docosyl group, Vinyl esters such as acrylates or methacrylates such as clohexyl, benzyl, phenyl, methoxyethyl, ethoxyethyl, butoxyethyl, phenoxyethyl, vinyl acetate, vinyl propionate, and acrylonitrile And monomers such as acrylic acid or methacrylic acid derivatives such as methacrylonitrile, and the like, and may be used alone or as a mixture depending on the purpose.

For example, typical examples include styrene and / or a derivative thereof, and a monomer mixture containing an alkyl (meth) acrylate as a main component.
Further, the glass transition point (Tg) of the obtained binder resin is preferably from 50 to 100 ° C, particularly preferably from 55 to 80 ° C, from the viewpoint of blocking resistance and fixability.
In general, Tg slightly varies depending on the measurement method and measurement conditions. However, the Tg in the present invention is measured by a differential scanning calorimeter (hereinafter, referred to as DSC) at a heating rate of 10 ° C./min. Defined as the intersection of the endothermic curves.

In the present invention, the amount of the residual monomer in the binder resin needs to be 200 ppm or less. If the amount of the residual monomer exceeds 200 ppm, the blocking resistance and the PVC plasticizer resistance decrease, and the problem of odor remains unpreferably. This residual monomer amount is preferably in the range of 110 ppm or less, and more preferably in the range of 90 ppm or less.
As a specific method for reducing the amount of residual monomers in the binder resin to 200 ppm or less, a monomer mixture constituting the binder resin is synthesized by a polymerization method such as suspension polymerization, and then the Tg of the resin from which the dispersion is obtained is obtained. While heating to the above temperature, 5 to 50% by weight of water based on the amount of water in the dispersion is distilled off as steam. Further, if a larger amount of air or nitrogen is blown in or the dispersion is heated to near the boiling point, the object can be achieved in a shorter time.

In the present invention, the heating temperature for distilling water as water vapor needs to be equal to or higher than the Tg of the resin to be obtained. If the temperature is lower than Tg, the residual monomer in the resin is trapped in the resin, and the amount of the residual monomer is reduced. Is less than 200 ppm.
In the above method, the amount of water to be distilled off must be at least 5% by weight based on the amount of water in the resin dispersion after suspension polymerization, and if it is lower than this, the residual monomer in the resin is reduced to 200 ppm or less. Difficult to do. On the other hand, if the content exceeds 60% by weight, the effect of reducing the residual monomer is small, and problems such as secondary aggregation of the resin and an increase in the amount of cullet tend to occur, which is not preferable.

懸 濁 The suspension polymerization in the present invention is carried out by a known method until the polymerization is substantially completed. First, a reactor equipped with a thermometer is charged with 1 to 10 times, preferably 2 to 4 times, of water, a suspension / dispersion stabilizer and, if necessary, a dispersing aid with respect to a monomer, followed by stirring. While heating, a monomer, a polymerization initiator and, if necessary, a chain transfer agent are added and the mixture is heated to a predetermined polymerization temperature, and the polymerization is substantially completed, that is, until the conversion is at least 95%. Keep warm.

重合 As the polymerization initiator in the present invention, a known initiator having radical polymerization activity is used. Specific examples thereof include di-t-butyl peroxide, t-butyl cumyl peroxide, digyl peroxide, acetyl peroxide, isobutyryl peroxide, octonyl peroxide, decanonyl peroxide, lauroyl peroxide, 3 , 5,5-trimethylhexanoyl peroxide, benzoyl peroxide, m-toluoyl peroxide, t-butylperoxyacetate, t-butylperoxyisobutyrate, t-butylperoxypiparate, t-butylperoxide Oxyneodecanoate, cumylperoxyneodecanoate, t-butylperoxy 2-ethylhexanoate, t-butylperoxy 3,5,5-trimethylhexanoate, t-butylperoxylaurate, t-butyl peroxybenzoate, t Butyl peroxyisopropyl carbonate may be mentioned, among which octonyl peroxide, decanonyl peroxide, lauroyl peroxide, and benzoyl are preferable in view of the persistence of the polymerization activity for the monomer and the completion of the polymerization in a relatively short time. Peroxides such as peroxide and m-toluoyl peroxide are particularly effective in the present invention. In addition, azo compounds such as azobisisobutyronitrile and 2,2'-azobis- (2,4-dimethylvaleronitrile) can also be used. These polymerization initiators are used in an amount necessary to complete the polymerization in a relatively short time, but generally 0.1 to 10 parts by weight, preferably 0.5 to 10 parts by weight, per 100 parts by weight of the monomer. To 5 parts by weight are used. The present invention is applied to the case where a peroxide is used as at least a part of the polymerization initiator, and partially includes an azo compound such as azobisisobutylnitrile and 2,2'azobis- (2,4-dimethylvaleronitrile). The case where they are used in combination is also included.

連鎖 As the chain transfer agent used as required in the present invention, known ones, for example, n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, 2-ethylhexyl thioglycolate and the like can be mentioned. When these chain transfer agents remain in the resin, they cause odor at the time of melting. Therefore, when used, they should be minimized.

公 知 Known suspension and dispersion stabilizers are used in the present invention. Specific examples thereof include polyvinyl alcohol, partially saponified polyvinyl alcohol, sodium or potassium salts of a homopolymer or copolymer of acrylic acid or methacrylic acid, carboxymethylcellulose, gelatin, water-soluble resins such as starch, barium sulfate, Examples thereof include hardly water-soluble or insoluble inorganic powders such as calcium sulfate, barium carbonate, calcium carbonate, magnesium carbonate, and calcium phosphate. These suspension dispersion stabilizers are used in an amount necessary to complete the operation without coagulation during polymerization and treatment with an alkali and a solvent (hereinafter referred to as alkali-solvent treatment), and Generally, it is used in an amount of 0.01 to 5 parts by weight, preferably 0.05 to 2 parts by weight, based on 100 parts by weight of water. Further, examples of the dispersing aid used if necessary in the present invention include electrolytes such as sodium chloride, potassium chloride, sodium sulfate, and potassium sulfate.

The conditions for suspension polymerization in the present invention vary depending on the type of the monomer to be polymerized and the type and amount of the polymerization initiator, but generally the temperature is 50 to 130 ° C, preferably 70 to 100 ° C, and the time is 1 to 10 ° C. Time is appropriate.
In the present invention, the toner contains at least a coloring agent such as the binder resin and carbon black as described above, and the residual monomer amount of the toner is reduced with decreasing the residual monomer amount of the binder resin used. It is reduced.

The composition ratio of each component in the toner is not particularly limited, and may be approximately the same as that of a commonly used toner. For example, the binder resin and the colorant can be used in a weight ratio of about 60 to 98: 2 to 40.
Further, for example, the toner is kneaded at a temperature of about 150 ° C. using a kneader such as a twin-screw extruder, and then finely pulverized and classified using a jet mill or the like. Is performed to form a toner. The obtained toner particles preferably have an average particle size of about 5 to 15 μm. Note that, in addition to the binder resin and the colorant, additives such as a charge control agent, an anti-offset agent, and magnetic powder may be used in the toner.

Next, an example is shown and the present invention is explained. In the examples, parts are parts by weight unless otherwise specified.
[Examples 1 to 3, Comparative Example 1]
79.7 parts of styrene, 20 parts of n-butyl acrylate, 0.3 parts of divinylbenzene are added to a mixture of 300 parts of water and 0.2 parts of partially saponified polyvinyl alcohol (Gohsenol GH-20 manufactured by Nippon Chemical Industry Co., Ltd.). Then, 3 parts of benzoyl peroxide was added, and the temperature was raised to 85 ° C., and then suspension polymerization was performed for 2 hours to complete the polymerization. Thereafter, the temperature was raised to 103 ° C., and as shown in Table 1, water was distilled off at 5%, 20%, 40%, and 50% with respect to the amount of water in the system, respectively. The residual monomers in the obtained resin were measured by gas chromatography to be 200 ppm, 110 ppm, 90 ppm and 80 ppm, respectively. In the case where 60% of water was distilled off, secondary agglomeration was severe on the way, and the process was stopped because no resin powder for toner was obtained.

5 parts of carbon black (# 30 manufactured by Mitsubishi Kasei Kogyo Co., Ltd.) and 25 parts of a charge control agent (Bontron S-31 manufactured by Orient Chemical Co., Ltd.) were added to 92.5 parts of each of the obtained resins in a biaxial manner. The mixture was kneaded with an extruder at 150 ° C. for about 5 minutes, cooled and then finely pulverized with a jet mill to collect 5 to 15 μm particles to produce a toner.
The Tg of each of the produced toners was measured, and the blocking resistance, PVC plasticizer resistance, and odor were evaluated. Table 1 shows the obtained results.
[Comparative Examples 2 to 4]
After completion of the suspension polymerization in the same manner as in Examples 1 to 3, the resin was immediately taken out, the resin was heated to 92 ° C. after polymerization and held for 2 hours, and the resin was taken out. , Dried at 50 ° C. for 20 hours, and subjected to residual monomer treatment at 150 ° C. for 5 minutes through an extruder, and evaluated in the same manner as in Examples 1 to 3. Table 1 shows the obtained results.

As described in detail above, according to the present invention, by using a binder resin having a small amount of residual monomer in a toner, it has no odor and exhibits excellent effects in blocking resistance and PVC plasticizer resistance. It is.

Claims (5)

A binder resin contained in a toner, wherein the binder resin contains styrene and / or a derivative thereof and a (meth) acrylate ester as a main component, and the glass transition point of the binder resin is 50 to 50. A binder resin having a temperature of 100 ° C. and a residual monomer content of 200 ppm or less. However, a resin that is a polymer obtained by polymerizing the binder resin in the presence of 10% by weight or more of the plasticizer based on the total weight of the monomer and the plasticizer is excluded. 2. The binder resin according to claim 1, wherein the amount of the residual monomer is 110 ppm or less. 2. The binder resin according to claim 1, wherein the amount of the residual monomer is 90 ppm or less. バ イ ン ダ ー The binder resin according to any one of claims 1 to 3, wherein the glass transition point is 50 to 80 ° C. (5) A developing method, wherein electrophotography is performed using the toner containing the binder resin and the colorant according to any one of (1) to (4).