JPH0473442B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is applicable to dry development methods for developing electrostatic images in electrophotography, electrostatic recording, electrostatic printing, etc., namely, cascade method, bristle brush method, magnetic brush method, impression method, powder method, etc. This invention relates to a method for producing a resin for toner that has little irritating odor when melted and has excellent electrical properties as a binder for toner used in the cloud method and the like. [Prior Art] In the dry development method, an electrostatic image formed on a photoconductive photoreceptor or an electrostatic recording medium is developed with toner and then fixed. Fixing is done by directly fusing the toner image obtained by development onto a photoconductive photoreceptor or electrostatic recording medium, or by transferring the toner image onto paper or film and then fusing it onto a transfer sheet. It is done by letting Fusing of the toner image is accomplished by contact with solvent vapor, pressure, and heat;
The heating method includes a non-contact heating method using an electric oven and a pressure heating method using a heating roller. Toners used in the dry development method include one-component toners and two-component toners. Two-component toner is produced by first melting and kneading the resin, colorant, charge control agent, and other necessary additives and thoroughly dispersing them.
It is then coarsely pulverized, finely pulverized, and classified into a predetermined particle size range for production. A one-component toner is produced in the same manner as in the two-component toner by adding magnetic iron powder in addition to each component of the two-component toner. Since the resin is the main component in the toner formulation, it controls most of the performance required of the toner. For this reason, resins for toners are required to have good colorant dispersibility in the melt-kneading process and good pulverization properties in the pulverization process in toner production, and also have good fixing properties, offset properties, Various performances are required, including good blocking properties and electrical properties. Epoxy resins, polyester resins, polystyrene resins, methacrylic resins, and the like are known as resins used in toner production. However, as resins that meet the ever-increasing demands for lower temperature and faster fixing processes, currently homopolymer or copolymer resins of monomers having polymerizable vinyl groups (hereinafter referred to as monomers), especially Copolymer resins of styrene or its derivatives are mainly used. Solution polymerization, emulsion polymerization, bulk polymerization, and suspension polymerization can all be used to homopolymerize or copolymerize monomers, but toner resins with the various properties described above can be used. Suspension polymerization is the most suitable method for manufacturing at low cost. Toner resin produced by the conventional suspension polymerization method is produced by adding a monomer with a polymerization initiator dissolved in water containing a suspension dispersion stabilizer, heating it while stirring to complete polymerization, and then washing, dehydrating, Manufactured dry. Azo compounds and peroxides are generally used as polymerization initiators in this case, but relatively large amounts of polymerization initiators are often used in the production of toner resins, especially when styrene is used as a monomer. When a large amount of a polymer or a derivative thereof is contained, the polymerization rate is low, so it is inevitable to use a large amount of a polymerization initiator to complete the polymerization. If a large amount of an azo compound is used as a polymerization initiator, some or all of the suspended particles become floating polymers due to the nitrogen gas generated during decomposition, making it impossible to produce a resin in good yield. Peroxides are often used as preferred polymerization initiators without such problems. [Problems to be Solved by the Invention] Conventional toners manufactured by suspension polymerization of monomers alone or mixtures, particularly monomers containing a large amount of styrene or its derivatives, using peroxides. When resin becomes molten during the melting and kneading process during toner manufacturing and the fixing process when toner is used, it emits an irritating odor, making it unfavorable for the working environment and causing discomfort. In addition, the electrical properties are highly dependent on humidity, making it difficult to obtain a good toner, and an improvement has been desired. [Means for Solving the Problems, Their Actions, and Effects of the Invention] The present inventors investigated the cause of the irritating odor during melting and the deterioration of the electrical properties of toner, and found that the resin used was dissolved in a solvent. or swell,
After repeated purification by reprecipitation with a poor solvent, the irritating odor disappeared and the electrical properties of the toner were also significantly improved, indicating that impurities contained in the resin were the cause. Since unreacted monomer generally remains in the resin obtained by mixing monomers, we thought that this monomer might be the cause.
Attempts were made to reduce the remaining monomer by increasing drying and degassing with a vented extruder, but these problems could not be resolved. Therefore, the present inventors investigated an industrial method to reduce the impurities that generate a pungent odor when melted, and found that toner resin was produced by suspension polymerizing monomers using peroxide as a polymerization initiator. In the manufacturing method, after the polymerization is substantially completed, an alkali metal hydroxide is added and heat treatment is performed at a temperature higher than the glass transition temperature (hereinafter referred to as Tg) of the resulting resin within a range that does not cause hydrolysis of the resin. It was discovered that the irritating odor at the time of melting and the electrical properties of the toner could be significantly improved by doing so, and the present invention was completed.
From this, it is considered that these causes are caused by acidic impurities brought in from the raw materials or generated during polymerization, especially acidic impurities generated by decomposition of the polymerization initiator. The present invention involves carrying out suspension polymerization of a monomer having a polymerizable vinyl group using a peroxide as a polymerization initiator.
In a method for producing a toner resin with a Tg of 50 to 100°C, after the polymerization is substantially completed, an alkali metal hydroxide is added to the polymerization system, and the resin is hydrated at a temperature higher than the Tg of the resulting resin. A method for producing a resin for toner is characterized in that it includes a step of heat treatment in a range that does not cause decomposition. Suspension polymerization in the present invention is carried out by a known method until the polymerization is substantially completed. First, water, a suspension dispersion stabilizer, and a dispersion aid if necessary are added to a reactor equipped with a thermometer in an amount of 1 to 10 times, preferably 2 to 4 times, the amount of water, a suspension dispersion stabilizer, and a dispersion aid if necessary, and then stirred at room temperature or Adding the monomers, polymerization initiator and, if necessary, chain transfer agent while heating, and heating to a predetermined polymerization temperature until the polymerization is substantially complete, i.e., the degree of polymerization is at least 95%. Continue heating until. The monomers used in the present invention are applicable to all those conventionally used in toner resins.
Specific examples thereof include styrene, α-methylstyrene, p-methyl group, m-methyl group, p-methyl group, p-ethyl group, 2,4-dimethyl group, p-butyl group, p- Styrene derivatives having hexyl group, p-octyl group, p-nonyl group, p-decyl group, p-methoxy group, p-phenyl group, etc., general formula: CH ₂ =CR-COOR' (however,
R represents hydrogen or a methyl group),
R' is a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s
-butyl group, t-butyl group, n-pentyl group, n
-hexyl group, n-octyl group, 2-ethylhexyl group, n-nonyl group, isononyl group, decyl group, dodecyl group, tridecyl group, stearyl group,
Acrylic or methacrylic esters such as docosyl, cyclohexyl, benzyl, phenyl, methoxyethyl, ethoxyethyl, butoxyethyl, phenoxyethyl, vinyl esters such as vinyl acetate and vinyl propionate , acrylonitrile, methacrylonitrile, and other acrylic acid or methacrylic acid derivatives. The monomer in the present invention is the monomer of the resin obtained.
They are used alone or as a mixed system with a Tg of 50 to 100°C, preferably 55 to 80°C. This is because if the Tg of the obtained resin is less than 50°C, a toner with good blocking properties cannot be obtained, and if it is 100°C or more, a toner with good fixing properties cannot be obtained. In the present invention, the monomers include styrene, derivatives thereof,
It is particularly effective when producing resins containing acrylic esters and methacrylic esters as main constituents. In general, Tg differs slightly depending on the measurement method and measurement conditions, but Tg in the present invention is determined by measuring the chart baseline and Tg at a heating rate of 10°C/min using a differential scanning calorimeter (hereinafter referred to as DSC). Defined as the intersection of endothermic curves. In the present invention, when a monomer having at least two polymerizable vinyl groups (hereinafter referred to as a crosslinkable monomer) is used as a part of the monomers having a polymerizable vinyl group, it is possible to fix the toner using a heating roller. It is possible to significantly improve the offset property of 2
Specific examples of crosslinkable monomers having 2 polymerizable vinyl groups include aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, and derivatives thereof, ethylene glycol, 1,3-butanediol, 1,4-butane Examples include diacrylates or dimethacrylates of dihydric alcohols such as diol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and polyethylene glycol. Specific examples of the crosslinkable monomer having three or more polymerizable vinyl groups include triacrylate or trimethacrylate of polyhydric alcohols such as glycerin and trimethylolpropane. The crosslinking monomer is 0.05 to 10 of the monomer.
% by weight, preferably 0.1 to 5% by weight. If the crosslinking monomer content is less than 0.05% by weight, the offset properties of the resulting toner in heated roller fixing systems cannot be sufficiently enhanced, and if it is more than 10% by weight, the resulting resin may become difficult or impossible to melt and knead. The resulting toner has poor fixing properties. In addition to suspension polymerization of monomers, the present invention can also be applied to the case of polymerizing a mixture of a monomer and a resin that has been partially polymerized in advance, or a monomer in which a previously polymerized resin has been dissolved. be done. At this time, by making the molecular weights of the coexisting resin and the resin produced by post-polymerization different and widening the molecular weight distribution, it is possible to improve the offset property of the toner in the heated roller fixing system. As the polymerization initiator in the present invention, a known peroxide having radical polymerization activity is used. Specific examples include di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, acetyl peroxide, isobutyl peroxide, octanonyl peroxide, decanonyl peroxide, lauroyl peroxide,
3,5,5-trimethylhexanoyl peroxide, benzoyl peroxide, m-toluoyl peroxide, t-butyl peroxyacetate,
t-Butyl peroxyisobutyrate, t-butyl peroxide pivalate, t-butyl peroxy neodecanoate, cumyl peroxy neodecanoate, t-butyl peroxy 2-ethylhexanoate, t-butyl Peroxy 3,5,5-
Trimethylhexanoate, t-butylperoxylaurate, t-butylperoxybenzoate, t-butylperoxyisopropyl carbonate, etc. can be mentioned, but among them, they have a long-lasting polymerization activity for monomers and a relatively short time. octanonyl peroxide, from the point of completing the polymerization with
Particularly effective in the present invention are decanonyl peroxide, lauroyl peroxide, benzoyl peroxide, m-toluoyl peroxide, and the like. These polymerization initiators are used in an amount necessary to complete polymerization in a relatively short period of time, but generally 0.1 to 10 parts by weight per 100 parts by weight of monomers.
Preferably 0.5 to 5 parts by weight are used. The present invention is applied when a peroxide is used as at least a part of the polymerization initiator, and an azo compound such as azobisisobutylnitrile or 2,2'-azobis-(2,4-dimethylvaleronitrile) is used as a part of the polymerization initiator. This also includes cases where they are used together. Chain transfer agents used as necessary in the present invention include known ones, such as n-octyl mercaptan, n-dodecyl mercaptan, t-
Examples include dodecyl mercaptan and 2-ethylhexyl thioglycolate. If these chain transfer agents remain in the resin, they will cause a bad odor when melted, so if they are used, they should be kept to a minimum. Known suspension and dispersion stabilizers can be used in the present invention. Specific examples include polyvinyl alcohol, partially saponified polyvinyl alcohol, sodium or potassium salts of homopolymers or copolymers of acrylic acid or methacrylic acid, water-soluble resins such as carboxymethyl cellulose, gelatin, and starch, barium sulfate, Examples include poorly 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 polymerization and alkali treatment without coagulating the resulting resin particles, but generally 0.01 to 5 parts by weight per 100 parts by weight of water.
Parts by weight are used, preferably 0.05 to 2 parts by weight. Dispersion aids that may be 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 monomer to be polymerized and the type and amount of the polymerization initiator, but generally the temperature is 5 to 130°C, preferably 70 to 100°C, and the time is 1. Approximately 10 to 10 hours is appropriate. The most important thing in the present invention is that after the polymerization is substantially completed, an alkali metal hydroxide is added to the polymerization system, and alkali treatment is performed at a temperature higher than the Tg of the resulting resin within a range that does not hydrolyze the resin. By doing so, the purpose is to remove acidic impurities that give off an irritating odor when melted and have an adverse effect on the electrical properties of the toner. In a suspension that has completed polymerization, acidic impurities are distributed between the resin particle phase and the aqueous phase at a certain ratio (partition coefficient), but generally most of the acidic impurities are distributed to the particle phase and are transferred from within the particles to the aqueous phase. Due to the slow diffusion rate, it is impossible to remove by washing with water alone. In order to remove acidic impurities within the particles, it is important to increase the partitioning into the aqueous phase and the speed to partition equilibrium. According to the method of the present invention, by adding alkali after polymerization, acidic impurities turn into water-soluble salts and have significantly increased solubility in the aqueous phase, and by alkali treatment at a temperature higher than the Tg of the resulting resin, acidic impurities The diffusion rate from inside the particles to the aqueous phase is significantly increased, making it possible to remove it with a short alkali treatment. This effect is equally remarkable even when the acidic impurity is water-insoluble or poorly soluble. The alkali treatment is carried out after the polymerization is substantially completed, that is, when the polymerization rate reaches at least 95%. If the time is earlier than this, a large amount of monomer will remain in the resin, which is not preferable. In alkaline treatment, care must be taken to avoid hydrolysis of the resin. There is no problem when the monomer is a resin consisting only of styrene or its derivatives, but when using the above-mentioned acrylic acid alkyl esters, methacrylic acid alkyl esters, vinyl esters, etc., the amount of alkali added in the alkali treatment is too large. If the treatment time is too long, there is a risk of hydrolysis. If hydrolyzed, the electrical properties of the toner and offset properties in heated roller fixing systems will deteriorate, so it is important to perform alkali treatment within a range that does not cause hydrolysis.
From this point of view, alkali treatment at a temperature higher than the Tg of the resin is a necessary condition, which makes it possible to efficiently remove acidic impurities in a short time. In addition, it is preferable that styrene or its derivatives account for at least 50% by weight of the monomer used to produce the resin by polymerization, not only from the viewpoint of general performance as a toner, but also from the viewpoint of hydration with alkali. Since decomposability is reduced, acidic impurities can be removed more fully. All alkalis can be used for alkaline treatment to remove acidic impurities. However, those that have a bad odor are problematic to handle, and those that easily dissolve into particles or create acidic impurities and insoluble salts may make it difficult to remove alkalis or salts, which may affect the electrical properties of the toner. Therefore, alkali metal hydroxides are used in the alkali treatment of the present invention, and specific examples thereof include:
Examples include hydroxides of alkali metals such as lithium, sodium, potassium, and rubidium, but sodium hydroxide and potassium hydroxide are the most preferred because they are inexpensive. The alkali metal hydroxide is used in the minimum amount necessary to remove acidic impurities, generally 0.01 to 1 part by weight, preferably 0.01 to 1 part by weight per 100 parts by weight of water.
0.05 to 0.5 parts by weight are used. If it is less than 0.01 part by weight, acidic impurities cannot be removed sufficiently, and if it is more than 1 part by weight, it is excessive for removing acidic impurities, and a large amount of neutralizing agent is required for wastewater treatment, causing high costs. This is because it will cause it to decompose. After the alkali treatment, sufficient water washing and dehydration are performed to remove the alkali, and finally drying is performed, using known methods. Centrifugal dehydrators, super decanters, etc. are used for washing and dehydration, and box dryers, vacuum dryers, etc. are used for drying. An acid treatment can also be performed to completely remove alkali during water washing. [Examples] Next, the present invention will be illustrated by Examples, but the embodiments of the present invention are not limited thereto. In addition, the number of parts in the examples is expressed by weight unless otherwise specified. Comparative Example 1 In a pressurizable reactor equipped with a stirrer, condenser, and thermometer, 300 parts of water and partially saponified polyvinyl alcohol (Gohsenol GH- manufactured by Nippon Gosei Chemical Industry Co., Ltd.) were added.
20) Add 0.5 parts of styrene and 75.7 parts of n-butyl acrylate while stirring at a rotation speed of 350 rpm.
A solution of 3 parts of benzoyl peroxide dissolved in 1 part, 6 parts of n-butyl methacrylate, and 0.3 parts of divinylbenzene was added, heated to a temperature of 85 DEG C., and maintained for 6 hours to complete polymerization. The product was cooled, thoroughly washed with water, dehydrated using a centrifugal dehydrator, and then dried at 50°C for 24 hours using a hot air circulation dryer to obtain 98.5 parts of fine granular resin <R-1>. Resin <R-1> is
Tg measured by DSC is 64℃, acid value is 1.8mgKOH/
g, the total amount of residual monomers was 680 ppm. Then,
45 parts of resin <R-1>, 3.5 parts of carbon black (#30 made by Mitsubishi Chemical Industries, Ltd.), and 1.5 parts of nigrosine were placed in a V-type blender, premixed for about 1 hour, and then mixed at 180°C using a tabletop kneader for 30 minutes. Kneaded in minutes. The kneaded material was cooled, pre-pulverized, then pulverized with a jet mill and classified to prepare a toner having an average particle size of 15 μm. A developer was prepared by mixing 3 parts of the obtained toner with 97 parts of a magnetic iron powder carrier that passes through a 200-mesh sieve but not a 300-mesh sieve. Image formation was carried out using a plain paper copying machine having a fixing roller, the other of which was lined with silicone resin, at a fixing roller temperature of 190° C. in an atmosphere of 60% relative humidity. As a result, the fixing properties of the toner were good, and the obtained images were free from fogging and density unevenness, and the image density was high and clear. Furthermore, when images were repeatedly formed using this developer, there was almost no toner contamination on the carrier, and no toner filming on the fixing roller or offset to the image was observed. Further, the toner remained in good condition without blocking even after being left in an atmosphere at 55° C. for one week. However, although this resin and toner have almost no odor at room temperature, they emit a strong irritating odor from the kneader for melt-kneading and from the fusing roller when image formation is repeated, and in an atmosphere with relative humidity of 85%, the odor is strong. When formed, the image density was significantly reduced and the toner was insufficient. These results are shown in Table-1. Example 1 Comparative Example 1 except that after suspension polymerization was completed under the same conditions as Comparative Example 1, 0.5 part of sodium hydroxide was added to the reaction system at a temperature of 85°C while stirring, and alkali treatment was performed for 30 minutes. Similarly, fine particulate resin <R
-2> was obtained. Resin <R-2> has a Tg of 64℃,
Acid value is 0.6mgKOH/g, total residual monomer
It was 660ppm. A toner was prepared in the same manner as in Comparative Example 1, and an image was formed. The results are shown in Table 1, and the general performance of the toner was as good as in Comparative Example 1. However, when the melt-kneading kneader and image formation were repeated, there was almost no irritating odor from the fixing roller, and when the image was formed in an atmosphere with a humidity of 85%, there was little decrease in image density, thus eliminating the drawbacks of Comparative Example 1. It was significantly improved by alkali treatment. The acid value of resin <R-2> is that of Comparative Example 1.
It is thought that the alkali treatment removed acidic impurities, resulting in the above improvement.

【table】

[Table] Example 2 Resin <R-3> was prepared in the same manner as in Example 1 except that the alkali treatment temperature was 20, 40, 60, 70, and 100°C.
<R-7> was obtained. The alkali treatment at temperatures above 100°C was carried out under pressure to prevent foaming due to boiling (the same applies below). Table 2 shows the characteristic values of the resin and the performance of the toner obtained in the same manner as Comparative Example 1. Table-2
According to Table 1, the image density of the toner at high humidity and the irritating odor during melting and fixing were significantly improved when the alkali treatment temperature was set at or above the Tg of the resin. Furthermore, as shown in Tables 1 and 2, the amount of residual monomer hardly changes depending on the presence or absence of alkali treatment.
It can be seen that these improvements are independent of the amount of residual monomer.

[Table] Example 3 Resin<R-8
> to <R-12> were obtained. Table 3 shows the characteristic values of the resin and the performance of the toner obtained in the same manner as Comparative Example 1.
Shown below. From the results in Table 3 and Table 1, the image density of the toner at high humidity and the irritating odor during melting and fixing are both improved by alkali treatment, but if the alkali treatment time is too long, the resin will hydrolyze. In this case, it is preferable to carry out alkali treatment for up to 120 minutes, since this results in a decrease in offset properties.

[Table] Example 4 In alkaline treatment, sodium hydroxide 0.2,
Resin<R-13
> to <R-17> were obtained. Table 4 shows the characteristic values of the resin and the performance of the toner obtained in the same manner as Comparative Example 1.
Shown below. From the results in Table 4, Table 1, and Table 3, the image density of toner at high humidity and the irritating odor during melting and fixing are all improved by alkali treatment, but the addition of sodium hydroxide during alkali treatment If the amount is too large, the resin will be hydrolyzed and the offset properties will deteriorate, so in this case, an alkali treatment of 2 parts or less is preferred.

[Table] Example 5 Resins <R-18> to <R-29> were obtained in the same manner as in Comparative Example 1 and Example 1 except as specified in Table-5. Table 5 shows the characteristic values of the resin and the performance of the toner obtained in the same manner as Comparative Example 1. Table-5 and Table-1
The results show that the image density of the toner at high humidity and the irritating odor during melting and fixing are both improved by alkali treatment, but the Tg of the resulting resin is 50°C.
If it is below, the resulting toner will have poor blocking properties.

【table】

[Table] Example 6 Resins <R-30> to <R-37> were obtained in the same manner as in Example 1 except as specified in Table-6. In addition, resins <R-38> to <R-45 that omit alkali treatment corresponding to resins <R-30> to <R-37>
> obtained. Table 6 shows these resin characteristic values and the performance of the toner obtained in the same manner as Comparative Example 1. From the results of Table-6 and Table-1, resin <R-37> and <R-
With the exception of 45>, the alkali-treated samples had better image density at high humidity and irritating odor during melting and fixing compared to the corresponding samples. Also, as the amount of crosslinking monomer increases, the offset property becomes better, but resins containing 10% or more of crosslinking monomer <R-38
> and <R-45> were unsuitable because the resins could not be melted and kneaded and toners could not be obtained.

[Table] Related.
Example 7 Resins <R-46> to <R-53> were obtained in the same manner as in Comparative Example 1 and Example 1 except as specified in Table-7. Table 7 shows the characteristic values of the resin and the performance of the toner obtained in the same manner as Comparative Example 1. The results in Table 7 show that the image density of the toner at high humidity and the irritating odor at the time of melting and fixing are both improved by alkali treatment, but when the styrene content is less than 50%, the general performance of the toner, especially the Image density and offset properties when wet are reduced.

【table】

[Table] Blocking property: All ◎

Claims (1)

[Claims] 1. A method for producing a toner resin having a glass transition temperature of 50 to 100°C by suspension polymerizing a monomer having a polymerizable vinyl group using a peroxide as a polymerization initiator, After the polymerization is substantially completed, it is characterized by including the step of adding an alkali metal hydroxide to the polymerization system and heat-treating the resin at a temperature higher than the glass transition temperature of the resulting resin within a range that does not hydrolyze the resin. A method for producing resin for toner. 2 0.05 to 0.05 of a monomer having a polymerizable vinyl group
2. The method for producing a toner resin according to claim 1, wherein 10% by weight is a monomer having at least two polymerizable vinyl groups. 3 At least a monomer having a polymerizable vinyl group
3. The method for producing a toner resin according to claim 1 or 2, wherein 50% by weight is styrene or a derivative thereof.