JPS61176604A - Production of resin for toner - Google Patents

Abstract

PURPOSE:To produce a resin for toners having improved electrical properties with little irritant smell in melting, by suspension polymerizing a vinyl group- containing monomer, adding a specific organic solvent to the polymerization system, and heat-treating resultant resin. CONSTITUTION:A monomer having polymerizable vinyl group [preferably a monomer containing >=50wt% styrene (derivative), and 0.05-10wt% thereof having >=2 polymerizable vinyl groups] is suspension polymerized in the presence of usually a peroxide or azo compound, etc. as a polymerization initiator to give a resin for toners having 50-100 deg.C glass transition temperature. After substantial completion of the polymerization, an organic solvent having 11-15 solubility parameter, e.g. methyl alcohol or isopropyl alcohol, is added to the polymerization system, and the resultant resin is then heat-treated at a temperature of the glass transition temperature thereof or above.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a dry development method, that is, a cascade method, for developing electrostatic images in electrophotography, electrostatic recording, electrostatic printing, etc.
A method for producing a toner resin that produces less unpleasant odor when melted and has excellent electrical properties as a toner binder used in the bristle brush method, magnetic brush method, impression method, powder cloud method, etc.

[Conventional technology]

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 fusing it onto a transfer sheet after transferring the toner image onto paper or film. The toner images are fused by contact with solvent vapor, pressure and heating, and the heating methods include a non-contact heating method using an electric oven and a pressure heating method using a heated roller.

Toners used in the dry development method include one-component toners and two-component toners. Two-component toner consists of resin,
Colorants, charge control agents, and other necessary additives are thoroughly melted and kneaded (=dispersed), then coarsely crushed, finely crushed,
It is manufactured by classifying it into a predetermined particle size range. The one-component toner is produced in the same way as the two-component toner described above by adding magnetic iron powder.

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 during toner manufacturing. Various performances are required, such as good offset properties, 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 (hereinafter referred to as monomers) having polymerizable vinyl groups are currently being used. 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. Polymerization initiators conveniently used at this time: Azo compounds and peroxides are generally used in the second case, but in the production of toner resins (in the second case, relatively large amounts of polymerization initiators are often used, especially monomers). When a large amount of styrene or its derivatives is contained as a polymer, the polymerization rate is low, so it is necessary to use a large amount of polymerization initiator to complete the polymerization. Some or all of the suspended particles may become floating polymers due to nitrogen gas, making it impossible to produce resin in good yield.
On the other hand, peroxides are often used as preferred polymerization initiators without such problems.

[Problem that the invention seeks to solve]

Conventional toner resins manufactured by suspension polymerization of monomers alone or mixtures, particularly monomers containing a large amount of styrene or its derivatives, require a melt-kneading process during toner production and a process for toner use. This is a problem because it generates an unpleasant odor when it becomes molten during the fixing process, and it is also a problem that it is difficult to obtain a good toner because its electrical properties are highly dependent on humidity. It was wanted.

c. Means for Solving Problems, Their Actions, and Effects of the Invention] The present inventors investigated the causes of the unpleasant odor during melting and the deterioration of the electrical properties of toner, and found that the resin used was dissolved in a solvent or After repeated purification by swelling and reprecipitating with a poor solvent, the unpleasant odor disappeared and the electrical properties of the toner were significantly improved, indicating that impurities contained in the resin were the cause. This impurity includes
Possible causes include unreacted monomers that generally remain in the resin obtained by polymerizing monomers, impurities introduced from raw materials, and impurities generated by side reactions during polymerization. Therefore, attempts were made to reduce the remaining monomer by strengthening drying or degassing with a vented extruder, but the unpleasant odor could not be sufficiently improved.

Therefore, the present inventors investigated an industrial method for reducing impurities that generate unpleasant odors during melting, and found a method for producing toner resin by suspension polymerization of monomers (2). After the polymerization is substantially completed, an M solvent having a solubility parameter (hereinafter referred to as SP value) of 11 to 15 is added, and heat treatment is performed at a temperature equal to or higher than the glass transition temperature (hereinafter referred to as Tg) of the resulting resin. The present invention was completed by discovering that the unpleasant odor during melting and the electrical properties of the toner could be significantly improved by doing so.

The present invention relates to a method for manufacturing a toner resin having a Tg of 50 to 100° C. by suspension polymerizing a monomer having a polymerizable vinyl group. After the polymerization is substantially completed, the polymerization system:
The present invention provides a method for producing a resin for toner, which includes a step of adding an organic solvent having a SP value of 11 to 15 and heat-treating the obtained resin at a temperature higher than Tg.

The suspension polymerization in the present invention is carried out by a known method until the completion of the polymerization. First, the amount of monomer is 1 to 10 times, preferably 2 to 4 times, in a reactor equipped with a thermometer. Add twice as much water, a suspension dispersion stabilizer, and a dispersion aid if necessary, stir, and then add monomers, a polymerization initiator, and a chain transfer agent if necessary at room temperature or with heating to achieve the desired polymerization. Heating is continued until a substantial ζ duplex is completed, ie, the degree of polymerization is at least 95 degrees.

The monomers used in the present invention are applicable to all those conventionally used in toner resins. Specific examples include styrene, α-methylstyrene, and p as a substituent.
-Methyl group, m-methyl group, p-methyl group, p-ethyl group, 2゜4-dimethyl group, p-butyl group, p-hexyl group, p-octyl group, p-nonyl group, p-decyl group , p
-Styrene derivatives having a methoxy group, p-phenyl group, etc., general formula: CH2= CB-COOR (however,
R represents hydrogen or a methyl group), R/ is a methyl group, an ethyl group, an n-propyl group, an isopropyl group,
n-butyl group, iptyl 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 Acrylic fi, which is a tridecyl, stearyl, tocosyl, cyclohexyl, benzyl, phenyl, methoxyethyl, ethoxyethyl, butoxyethyl, guenoxyethyl group, etc.
Monomers such as l esters or methacrylic acid esters, vinyl esters such as vinyl acetate and vinyl propionate, and acrylic acid or methacrylic acid derivatives such as acryl, ronitrile, and methacrylaterile can be mentioned. The monomer in the present invention (= is the Tg of the resin obtained)
is 50 to 100°C, preferably 55 to 80°C (
: It is conveniently used as a single system or a mixed system.

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.

The present invention makes it possible to obtain resins that exhibit particularly good toner performance when at least 50% of the monomers are styrene or its derivatives.

Generally, 2 Tg is the measurement method and measurement conditions; although it is slightly different from 2, Tg in the present invention is the baseline of the chart measured with a differential scanning calorimeter (hereinafter referred to as DSC) at a heating rate of 10°C/min. It is defined as the intersection of the endothermic curves near Tg and Tg.

In the present invention (2), a monomer having at least two polymerizable vinyl groups in a part of the monomer having polymerizable vinyl groups (
When a crosslinkable monomer (hereinafter referred to as a crosslinking monomer) is used, the offset property of toner in a heating roller fixed fixing method can be significantly improved. Specific examples of crosslinkable monomers having two polymerizable vinyl groups include aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, and derivatives thereof, ethylene glycol, 1,3-butanediol, ], 4- Examples include diacrylates or dimethacrylates of dihydric alcohols such as butanediol, 1,5-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and polyethylene glycol. Specific examples of crosslinkable monomers having three or more polymerizable vinyl groups include glycerin,
Examples include triacrylates or trimethylates of polyhydric alcohols such as trimethylolpropane.

The crosslinkable monomer is 0.05 to 10% by weight of the monomer,
Preferably, a weight ratio of 0.1 to 5 is used.

If the crosslinking monomer content is less than 0.05 parts by weight, it will not be possible to sufficiently improve the offset properties of the resulting toner in the constant fixing method using heated rollers, and if it is more than 100 parts by weight, the resulting resin will have difficulty or become impossible to melt and cross-wire. or 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 varying the molecular weights of the coexisting resin and the resin produced by post-polymerization to widen the molecular weight distribution, it is possible to improve the offset property of the toner in the heating roller fixed fixing method.

The polymerization initiators used in the present invention include known ones, peroxides such as octanonyl peroxide, decanonyl peroxide, lauroyl peroxide, benzoyl peroxide, and rn-toluoyl peroxide, or azobisisobutylnitrile, 2 ,2'-azobis-(2,4
-Azo compounds such as dimethylvaleronitrile are commonly used. 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, preferably 0.5 parts by weight, per 100 parts by weight of monomers. 5 parts by weight are used.

Chain transfer agents that may be used according to the present invention include known ones, such as n-ogtylmercaptan, n-dodecylmercaptan, t-dodecylmercaptan, 2-ethylhexyl thioglycolate, etc. 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 the minimum necessary.

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 conveniently used in an amount necessary so that the resulting resin particles can stably complete the operation without coagulating during polymerization and heat treatment. Generally 0 per 100 parts by weight of water
．． 0.01 to 5 parts by weight, preferably 0.05 to 2 parts by weight. Further, as dispersion aids which may be conveniently used if necessary in the present invention, electrolytes such as sodium chloride, potassium chloride, sodium sulfate and potassium sulfate can be mentioned.

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 second temperature is 50 to 130°C, preferably 1. The appropriate temperature is 70 to 100°C and the time is about 1 to 10 hours.

The most important thing in the present invention is that after the polymerization is substantially completed, a +-m solvent with an SP value of ]1 to 15 is added to the polymerization system, and heat treatment is performed at a temperature higher than the Tg of the resulting resin. The objective is to remove impurities that cause unpleasant odors when melted and adversely affect the electrical properties of toner. In the suspension after polymerization, impurities are distributed between the resin particle phase and the aqueous phase at a certain ratio (partition coefficient). Impurities that are largely distributed in the aqueous phase can be removed by known methods, but impurities that are largely distributed in the particle phase generally cannot be removed by washing with water because the rate of diffusion from inside the particles to the aqueous phase is slow. be. Inconsequential within the particle. According to the method of the present invention, the solubility of impurities in the aqueous phase is increased by adding a single solvent having an SP value of 11 to 15 to the polymerization system after one polymerization, and the resulting resin is heat-treated at a temperature higher than the Tg. This significantly increases the rate of diffusion of impurities from inside the particles into the aqueous phase, making it possible to remove them in a short period of time. The heat treatment of the present invention is carried out after the polymerization is substantially completed, that is, when the polymerization rate reaches at least a factor of 95 or higher. If the time is earlier than this, a large amount of monomer will remain in the resin, which is not preferable.

For the purpose of removing impurities, the organic solvent used must be water-soluble and not cause particles to aggregate during heat treatment. Toner resin S generally obtained by polymerizing monomers
Since the P value is between 9 and 10, solvents with an SP value within or near this range may dissolve in the resin particles or cause the particles to swell, making it impossible to carry out treatment operations to remove impurities, or conversely, causing the particles to dissolve inside the particles. remains and causes odor. That SP
When I checked the value limit, it was 11. Also, the SP value is 1
Solvents with a molecular weight of 5 or more have little effect on increasing the solubility of impurities in the aqueous phase and do not meet the purpose of the present invention. Specific examples include methyl alcohol, ethyl alcohol, n-7′ lobil alcohol, inopropyl alcohol, n-7” methyl alcohol, s-7” methyl alcohol, t-butyl alcohol, isobutyl alcohol, cyclohexyl alcohol, and allyl alcohol. , ethylene glycol, propylene glycol, nitroethane, dimethylformamide, acetonitrile, and ethylene oxide. Methyl alcohol, ethyl alcohol, and isopropyl alcohol are particularly preferred.This organic solvent is added in an amount necessary for removing impurities, but in the present invention, it is added in an amount of 0.5 to 10 parts by weight per 100 parts by weight of water in the polymerization system. , preferably ] to 5 parts by weight.If it is less than 0.5 parts by weight, impurities cannot be removed sufficiently, and if it is more than 10 parts by weight, it is excessive for the purpose of removing impurities and increases the cost. This is not preferable because it causes agglomeration.

After heat treatment, the material is thoroughly washed with water, dehydrated, and finally dried using known methods.Centrifugal dehydrators, super decanters, etc. are used for washing and dehydration, and box-type decanters are used for drying. A dryer, a vacuum dryer, etc. are used.

〔Example〕

Next, the present invention will be illustrated by examples, but the embodiments of the present invention are not limited thereto. In addition,
Parts in the examples are expressed by weight unless otherwise specified.

Comparative Example 1 300 parts of water and 0.5 parts of partially saponified polyvinyl alcohol (Gohsenol GH-20 manufactured by Nippon Gosei Chemical Industry Co., Ltd.) were placed in a pressurizable reactor equipped with a stirrer, a condenser, and a thermometer, and the mixture was stirred at a rotation speed of 350 rpm. While doing so, styrene 7
A solution of 3 parts of benzoyl peroxide dissolved in 5.7 parts of 5.7 parts of n-butyl acrylate, 18 parts of n-butyl methacrylate, and 0.3 parts of divinylbenzene was heated to 85°C and held for 6 hours. The polymerization was completed.

The product was cooled, thoroughly washed with water (two times), 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 a fine granular resin <R-1>.Resin <R
, -1> has a Tg measured by DSC of 64°C and an acid value of 1.
8 to KOH/l, and the residual monomer amount was 680 ppm in total.

Next, 5 parts of resin <R-1>, 3.5 parts of carbon black (Mitsubishi Chemical Corporation +30), and 1.5 parts of nigrosine were added to V
The mixture was placed in a mold pretadder, premixed for about 1 hour, and then kneaded at 180° C. for 30 minutes using a tabletop Nigoo. The kneaded material was cooled, pre-pulverized, pulverized with a jet mill, and classified to prepare a toner having an average particle size of 5 μm. A developer was prepared by mixing 3 parts of the obtained toner with 97 parts of a carrier of magnetic iron powder that passes through a 200-mesh sieve but not through 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, in an atmosphere with a relative humidity of 60 psi and a fixing roller temperature of 190.degree.

As a result, the fixability of the toner was good, and the resulting image was free from capri 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 on 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 unpleasant odor from the kneader for melting and kneading and from the fusing roller when image formation is repeated, and in an atmosphere with a relative humidity of 85°C, the odor is strong and unpleasant. When formed, the image density was significantly reduced and the toner was insufficient. These results are shown in Table 1.

Example 1 After completing suspension polymerization under the same conditions as Comparative Example 1, methyl alcohol (
A fine granular resin <R-2> was obtained in the same manner as in Comparative Example except that 6 parts of SP value 14.5) were added and treated with a solvent for 30 minutes. Resin table~1 <Judgment (5-level display): (Good) Q>O>@>Δ> × (Poor) (Same below) <
R-2>Ha Tg is 64℃, e value 1.2qKOH/
f, the total amount of residual monomer was 350 ppm. Next, 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.

Furthermore, when the melt-kneading kneader and image formation were repeated, almost no unpleasant odor from the fixing roller was generated. Furthermore, the image density was considerably improved when an image was formed in an atmosphere with a humidity of 85III. Compared to the resin (R-1) of Comparative Example 1, the resin (R-2> had an acid value of about 273 and a residual monomer content of about ]/2, and therefore the above improvements were made. Conceivable.

Example 2 Resins <R-3> to R-7> were obtained in the same manner as in Example 1, except that the solvent treatment temperature was 20.40°C, 60.70°C and 100°C. The solvent treatment at 100° C. or higher was performed under pressure to prevent foaming due to boiling (the same applies hereinafter). Table 2 shows the characteristic values of the resin and the performance of the toner obtained in the same manner as Comparative Example 1. Tables 2 and 1 show that when the temperature of solvent treatment is set higher than the Tg of the resin, the unpleasant odor during toner melting and fixing is significantly improved, and the image density when toner is highly humid is also improved. Much improved.

Example 3 Instead of methyl alcohol in Example 1, ethyl alcohol (sp value 12.7, the same applies hereinafter), inpropyl alcohol (11,5), n-butyl alcohol (11,4)
, acetone (10,0), methyl ethyl ketone (9,6
), tetrahydrofuran (9,3), toluene (8,9
), vinegar #2 n-butyl (8,3), n-hexane (7,
3) was subjected to solvent treatment in the same manner as in Example 1.
The process from noethyl alcohol to n-butyl alcohol was the same as in Example 1 (= processing was possible without particular agglomeration, and resin <R-8> or R-10> was obtained. Table 3 (= shows. Also, the performance of the toner obtained in the same manner as Comparative Example 1 is exactly the same as that of the example, and the unpleasant odor at the time of melting and fixing was both improved by solvent treatment. The image density at high humidity was also considerably improved. However, when using the above-mentioned solvents from acetone to n-hexane, particles agglomerated during processing and it was not possible to remove impurities sufficiently. Therefore, as an additive solvent, one with an SP value of 11 to 15 is good;
The following are inappropriate.

Example 4 Solvent treatment was carried out in the same manner as in Example 1 except that the amount of methyl alcohol added was changed as shown in Table 4. The system in which the amount of methyl alcohol added is small is the resin (R-17
> or FL-19> was obtained. Resin <R-17>
Table 4 shows the characteristic values of Iku-18 and the performance of the toner obtained in the same manner as in Comparative Example 1. Tables 4 and 1 show that the unpleasant odor during toner melting and fixing was improved by the solvent treatment. However, in the system in which the amount of methyl alcohol added was 45 parts, agglomeration was severe during treatment, making operation impossible and no resin could be obtained. Table 5 shows the characteristic values of the resins obtained from the resins G-21 to 32 and the performance of the toner obtained in the same manner as in Comparative Example 1. From the results shown in Tables 5 and 1, the unpleasant odor at the time of melting and fixing was both improved by solvent treatment, and the image density of the toner at high humidity was also significantly improved. However, when the Tg of the resulting resin was 50° C. or less, the blocking properties of the resulting toner were poor.

Example 6 Resin<R
-30> or R-37> were obtained.

In addition, resins (R-41> or R-48) corresponding to resins (R, -33> or R-40> without solvent treatment)
> obtained. The performance of toner obtained using these resins in the same manner as in Comparative Example 1 was evaluated. Resin <R-40> and <R-
The samples treated with solvent except for 48> had less unpleasant odor during melting and fixing than the corresponding samples, and the image density at high humidity was considerably improved. Further (= as the amount of crosslinking monomer increases, the offset property becomes better, but resin <R-40> with the amount of crosslinking monomer of 10 or more) and (
R-48> was unsuitable because the resin could not be melted and kneaded and a toner could not be obtained.

Example 7 Resins <R-49> to R-56> 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. From the results in Tables 7 and 1, the unpleasant odors during toner melting and fixing were both improved by solvent treatment, and the image density at high humidity was also significantly improved.

When the styrene content is less than 50%, the general performance of the toner deteriorates.

Claims (3)

[Claims] (1) In a method for producing a toner resin having a glass transition temperature of 50 to 100°C by suspension polymerization of a monomer having a polymerizable vinyl group, after the polymerization is substantially completed, the monomer is soluble in the polymerization system. A method for producing a resin for toner, comprising the steps of adding an organic solvent having a parameter of 11 to 15 and heat-treating the obtained resin at a temperature equal to or higher than the glass transition temperature. (2) The toner resin according to claim (1), wherein 0.05 to 10% by weight of the monomer having a polymerizable vinyl group is a monomer having at least two polymerizable vinyl groups. Manufacturing method. (3) at least 50 monomers having polymerizable vinyl groups;
The method for producing a resin for toner according to claim (1) or (2), wherein the weight percent is styrene or a derivative thereof.