JPH08114945A - Production of resin for toner - Google Patents

Abstract

PURPOSE: To diminish materials which adversely affect a toner and to improve properties of the toner such as the emission of a foul order by successively carrying out hot water washing and acid washing after polymn. is practically finished. CONSTITUTION: After polymn. is practically finished, a hot water washing process is carried out without passing through acid washing and before acid washing. The hot water washing process is preferably repeated. A decantation method, a dehydration filtration method or a distilling-off method may be adopted as a concrete hot water washing method but at least one of the repeated hot water washing processes is carried out by the distilling-off method. After the hot water washing processes, an acid washing process is carried out. In this acid washing process, an acid is added to a resin slurry prepd. by a resin producing method and a dispersant for suspension polymn. such as inorg. powder is removed. After the acid washing process, the objective product is obtd. through washing, dehydrating and drying processes. A polymerizable monomer for the resin is, e.g. a vinyl monomer.

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 a resin for a toner used in a dry electrophotographic system, and more specifically, a resin for a toner which has little odor during copying or printing and is excellent in environmental friendliness. Is provided.

[0002]

2. Description of the Related Art In the dry electrophotographic method, an electrostatic latent electric image is generally formed on a photoreceptor containing a photoconductive substance by various means, and then the latent image is preliminarily formed in a carrier or a developing tank. This is a method of developing with a toner charged by contact with a wall or the like, transferring the toner image to paper or the like if necessary, and then fixing with heat, pressure or solvent vapor.

Toners for dry electrophotography are prepared by kneading various additives such as a binder resin, a colorant and a charge control agent, pulverizing them, and adjusting them to a predetermined particle size distribution. A styrene resin, a polyester resin, an epoxy resin, or the like is used as the binder resin for the toner, but the styrene resin is preferably used because of its cost and ease of production.

Solution polymerization, emulsion polymerization, suspension polymerization and the like are known for the production of the binder resin for toner, but the suspension polymerization is most suitable as the production method at low cost. The method for producing a resin by the suspension polymerization method is to add a polymerizable vinyl monomer, a polymerization initiator and the like to water containing a suspension polymerization dispersant and raise the temperature with stirring to carry out polymerization at a constant temperature, followed by washing after completion of the polymerization, It is dehydrated and dried before being commercialized.

However, in particular, the resin thus obtained contains a substance typified by a residual monomer, which exerts an unfavorable influence on the toner performance. It is known that these substances cause an odor at the time of copying, and also have an adverse effect on offset resistance, storability, fluidity, triboelectric chargeability and the like of the toner. Various attempts have been made to reduce harmful substances, for example, JP-A-64-70.
Japanese Patent No. 765 discloses a binder resin having a residual monomer content of 200 ppm or less.
No. 101746 discloses that the content of aldehydes is 0.
A binder resin for toner having a content of 01% by weight or less and a method for producing the same have been proposed. However, the levels are insufficient as compared with the levels currently required by the market, and further reduction of harmful substances is demanded.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing a binder resin for a toner, which reduces substances that adversely affect the toner and is excellent in odor and other properties. Among them, with respect to the odor, with the rapid spread of copiers, printers, fax machines, etc., the problem has been highlighted at the time of copying at the office or at home, especially when it is continuously performed, and reduction thereof is desired.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted diligent studies in order to reduce adverse substances represented by residual monomers. The inventors have found that the adverse effect substances in the resin can be reduced more than before by washing by the method, and the present invention has been completed. That is, the gist of the present invention is a method for producing a resin for a toner by polymerizing a polymerizable monomer, wherein after the polymerization is substantially completed, washing with hot water and then acid washing are performed. It exists in the manufacturing method of resin for use. The binder resin produced in the present invention is suitably used for a one-component developer, a two-component developer used together with a carrier, and any dry electrophotographic developer.

The applicant of the present invention has proposed reduction of impurities in the binder resin by post-polymerization acid washing and hot water washing in Japanese Patent Application No. 6-125098 and Japanese Patent Application No. 6-125099. These are excellent methods, but if acid washing is performed prior to hot water washing, the temperature at which stable treatment can be stably performed with hot water washing is limited to some extent, and the higher the temperature, the higher the temperature of the can wall,
There is a tendency to scale the stirring blades. Therefore, 65-85 degreeC is a preferable temperature range in these methods.

On the other hand, it can be expected that the higher the temperature of hot water washing, the greater the effect of removing impurities. Therefore, as a result of a technical study that enables hot water treatment at a high temperature without causing scaling, hot polymerization can be performed without acid cleaning after the polymerization is substantially completed. Arrived

That is, by carrying out hot water washing after the polymerization is substantially completed, it is possible to carry out hot water washing at high temperature without impairing the stability of the system and effectively reduce impurities in the resin. I found a thing. According to the present invention, the residual monomer is 5
A level of 0 ppm or less, which cannot be achieved by the prior art, can be achieved, and a high quality binder resin for toner can be produced. When suspension polymerization is used for the polymerization, hot water washing is performed by removing a part or most of water from the resin slurry, which is a reaction product after the completion of the polymerization reaction, and then adding water or hot water again if necessary. It is carried out by raising the temperature, keeping the temperature high, and stirring as necessary. Water is removed by a decantation method in which the resin slurry is allowed to stand, the resin is allowed to settle, and the supernatant is discarded by a pump, a dehydration filtration method using a centrifugal dehydrator, a distillation method, or the like. In the decantation method or the distillation method, water or hot water is added, and in the dehydration filtration method, the dehydrated cake is returned to the reaction can (or washing can) again, water or hot water is added, and the next hot water washing as a resin slurry is performed. Should be done. The hot water washing can be carried out at a temperature above the boiling point under pressure, but it is usually carried out at or near the boiling point. Of course, treatment at a lower temperature is also possible, but lower temperatures tend to require a longer time to obtain the same effect of removing impurities, and the removal effect remarkably lowers below the glass transition temperature of the resin.

The washing time with hot water varies depending on the washing method. For example, in the decantation method, about 1 to 4 hours are preferable, and if it is shorter than 1 hour, the effect of removing decomposition products is small, and conversely, it is longer than 4 hours. However, the amount of impurities removed is not significantly increased and is inefficient. Further, in the distillation method, the temperature is determined by the temperature of the resin slurry, the amount of water to be distilled off, etc., and cannot be generally stated. In any of these methods, stirring during hot water washing is preferable because the efficiency of removing impurities is improved.

The amount of water with respect to the resin is not particularly limited as long as it does not cause any inconvenience in normal slurry processing. The larger the number of hot water washes, the greater the effect of removing impurities. Usually, the residual monomer amount of 50 ppm can be achieved in 2 to 4 times. Hereinafter, an example of the present invention will be described. The method for producing the toner resin of the present invention will be described by taking as an example the case of producing by suspension polymerization using a polymerization initiator and a suspension polymerization dispersant.
The step of polymerizing the monomer in the present invention is carried out by a known method as follows, for example.

The polymerization vessel is charged with monomers and preferably 1 to 4 times the amount of water, more preferably 1.5 to 3 times the amount of water. When the amount of water is less than that of the monomer, it is difficult to control the temperature during the polymerization. Examples of the polymerizable monomer used in the present invention include vinyl-based monomers, and all known vinyl-based monomers can be used. Specific examples thereof include styrene, o-methylstyrene, and m.
-Styrenes such as methylstyrene, p-methylstyrene, ethylstyrene, propylstyrene, phenylstyrene, methoxystyrene, α-methylstyrene, α-ethylstyrene, methyl (meth) acrylate, ethyl (meth) acrylate, ( (Meth) propyl acrylate, (meth)
(Meth) acrylic esters such as phenyl acrylate,
Examples thereof include vinyl esters such as vinyl acetate and vinyl propionate, and (meth) acrylic acids such as (meth) acrylonitrile. The vinyl resin may be a homopolymer or a copolymer.

Known suspension polymerization dispersants are used. Specific examples thereof include polyvinyl alcohol, partially saponified polyvinyl alcohol, sodium salts or potassium salts of homopolymers or copolymers of acrylic acid or methacrylic acid, carboxymethyl cellulose, gelatin, water-soluble resins such as starch, barium sulfate. ,
Examples thereof include sparingly water-soluble or insoluble inorganic powders such as calcium sulfate, barium carbonate, calcium carbonate, magnesium carbonate, and calcium phosphate. Among them, inorganic powders that can be easily removed by acid washing or the like are more preferable.
These suspension polymerization dispersants are used in an amount necessary to complete the operation of the resin particles produced without solidifying in the polymerization and boiling point driving steps, but generally 10% of water is used.
It is preferably 0.5 parts by weight to 5 parts by weight, more preferably 1 part by weight to 3 parts by weight, relative to 0 parts by weight.

The amount of the suspension polymerization dispersant affects the particle size distribution of the resin produced, and the larger the amount, the finer the particle size. As the polymerization initiator, known peroxide-based polymerization initiators can be used. Specific examples thereof include octanonyl peroxide, decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, and m-toluoyl peroxide. The addition amount is preferably 5 to 15 parts by weight with respect to the monomer.

When the raw materials have been charged, the temperature is raised with stirring, and the polymerization is preferably carried out at 80 ° C. to 110 ° C., more preferably 90 ° C. to 100 ° C. The polymerization time is preferably 3 hours to 15 hours, more preferably 5 hours to 10 hours. If the polymerization time is short, the resin product yield and removal of residual monomers will be poor, and if the polymerization time is long, the resin production efficiency will be poor and the decomposition products of the peroxide polymerization initiator used as a polymerization initiator will increase. The problem occurs.

The most important aspect of the present invention is to carry out a hot water washing step after the polymerization is substantially completed without performing acid washing and prior to the acid washing, and preferably the hot water washing step is carried out. To repeat. As described above, the decantation method, the dehydration filtration method, the distillation method and the like are specific examples of the hot water washing method, but it is desirable to perform at least one hot water washing by the distillation method. In the distillation method, after removing a part or most of the water from the resin slurry, water or hot water is added again to heat the polymerization vessel and boil for several hours to distill the water content. When hot water washing is repeated, the steps of adding water or hot water, heating the polymerization vessel, and distilling off water are repeated. The heating time of the polymerizer is determined by the amount of water distilled off, but is usually 3 to 8 hours. The amount of water added is preferably 1 to 5 times, more preferably 2 to 4 times, the amount of the monomer.

By repeating this method a plurality of times, the residual monomer can be adjusted to a preferable concentration, for example, 50 ppm or less. When the hot water washing process is completed, the acid washing process is performed. The acid cleaning step of the present invention is to add an acid to a resin slurry obtained by a known resin production method to remove a suspension polymerization dispersant such as an inorganic powder. Examples of the acid used include strong acids such as hydrochloric acid, sulfuric acid, nitric acid, hydrobromic acid, chromic acid, iodic acid, zinc acid, zinc acid, and citric acid, acetic acid,
Examples thereof include weak acids such as boric acid, carbonic acid, hydrofluoric acid, phosphoric acid and nitrous acid.

Among them, nitric acid is preferable in terms of handling. Further, it is preferable to stir during the acid washing, because the stirring effect improves the removal effect. Further, when the pH after addition of the acid is 3 or less, the effect of removing the inorganic powder is improved, which is preferable. Acid cleaning time is 10
Minutes to 3 hours are preferable, and if shorter than 10 minutes, the effect of removing inorganic powder is small, and if longer than 3 hours, production efficiency deteriorates.

When the acid cleaning is completed, the product is manufactured through washing, dehydration and drying steps, which is a known method.
Usually, when a binder resin for a toner is produced by suspension polymerization, a monomer type and a monomer amount ratio suitable for achieving various properties required for a toner are selected, and a preferable molecular weight and other properties are realized. It is carried out under suitable polymerization conditions. The production method of the present invention can be carried out without being limited by the polymerization conditions.

[0021]

EXAMPLES The present invention will be described in detail below with reference to examples. Example 1

[0022]

[Table 1] Water 200 parts by weight Styrene monomer 80 parts by weight Butyl acrylate ester 20 parts by weight Suspension dispersion stabilizer (calcium phosphate) 2.5 parts by weight Polymerization initiator (benzoyl peroxide) 8 parts by weight Reaction temperature: 94 ° C Reaction Hours: 10 hours

The suspension polymerization reaction was completed under the above conditions.
After completion of the polymerization reaction, most of the water was removed by the decantation method, and then the hot water washing step by the distillation method was repeated twice. The first time, 400 parts of water was added, the internal temperature of the polymerization vessel was heated and boiled, and about 400 parts of water was distilled off over 5 hours. Thereafter, 400 parts of water was further added and the mixture was boiled to remove about 400 parts of water over 5 hours. Then, according to a usual method, acid washing with nitric acid, dehydration and drying were carried out to obtain a binder resin. The results are shown in Table 1. The amount of residual monomer in the resin was measured by gas chromatography.

Comparative Example 1 Table 1 shows the results obtained in the same manner as in Example 1 except that the hot water washing step was not performed. The amount of residual monomer is styrene (S
t) 5000 ppm, butyl acrylate (BAE) 9
It was very high at 300 ppm.

[0025]

[Table 2]

Comparative Example 2 After washing with hot water after the polymerization reaction and washing with acid using nitric acid, it was tried to heat the polymerization vessel and boil it to distill off water. Scaling seemed to occur on the blades, so I canceled it on the way. Example 2

[0027]

[Table 3] Water 300 parts by weight Styrene monomer 80 parts by weight Butyl acrylate ester 20 parts by weight Suspension dispersion stabilizer (calcium phosphate) 6 parts by weight Polymerization initiator (benzoyl peroxide) 8 parts by weight Reaction temperature: 94 ° C Reaction time: 8 hours

The suspension polymerization reaction was completed under the above conditions.
After the completion of the polymerization reaction, most of the water was removed by the decantation method, and the hot water washing step by the distillation method was repeated 3 times. The first time, add 300 parts of water, heat and boil,
About 300 parts of water was distilled off over 3 hours. Then, the same operation was repeated twice. Then, according to a usual method, acid washing with nitric acid, dehydration and drying were carried out to obtain a binder resin. Table 2 shows the results.

Comparative Example 3 Table 2 shows the results obtained in the same manner as in Example 2 except that the hot water washing step was not performed. Residual monomer amount is St4600
ppm and BAE8900ppm were very large.

[0030]

[Table 4]

Example 3 A black toner having an average particle size of 10 μm was prepared using the resin obtained in Example 1, and running evaluation was carried out using a copying machine of 40 sheets for 1 minute. Good results have been obtained. The image density is Macbeth reflection densitometer RD-9.
14 type, fog was measured with a Nippon Denshoku company whiteness meter Σ-80 type.

[0032]

[Table 5]

Comparative Example 4 As a result of the same test as in Example 3 except that the resin obtained in Comparative Example 1 was used, the fog was high and the toner consumption was high.
A large amount of toner was also scattered. Further, during running evaluation, there was an unpleasant odor originating from the residual monomer around the fixing device of the copying machine.

[0034]

EFFECTS OF THE INVENTION By adopting the method for producing a toner resin of the present invention, it is possible to provide a binder resin for a toner that reduces substances that adversely affect the toner and is excellent in odor and other properties. Become.

Claims (6)

[Claims] 1. A method for producing a resin for a toner by polymerizing a polymerizable monomer, wherein after the polymerization is substantially completed,
A method for producing a resin for toner, comprising performing hot water washing and then acid washing. 2. The method for producing a resin for toner according to claim 1, wherein the polymerizable monomer is a vinyl-based monomer. 3. The method for producing a toner resin according to claim 1, wherein hot water washing is repeated. 4. The method for producing a toner resin according to claim 1, wherein at least one washing with hot water is performed by a distillation method. 5. The method for producing a toner resin according to claim 1, wherein the polymerization of the polymerizable monomer is suspension polymerization. 6. The method for producing a toner resin according to claim 5, wherein an inorganic powder is used as the suspension polymerization dispersant.