JPS5911900B2 - Manufacturing method of dry developer for electrophotography - Google Patents

Description

[Detailed description of the invention] The present invention always provides clear images even during long-term use.

The present invention relates to a method for producing an electrophotographic dry developer that maintains uniform copy image quality. BACKGROUND ART In recent years, among various copying methods, an electrophotographic method called plain paper copying is rapidly becoming popular because it has excellent image clarity and permanent retention, and is easy to use.

The typical developing method for Plain Paper Copy 5- is a dry development method, in which a developer made of triboelectrically charged colored resin powder is electrostatically transferred to paper, and then heated and fixed to form an image. get. Conventionally, dry-type developers are made by combining solid polymers such as polystyrene, methacrylate copolymer resins, epoxy resins, or polyester resins with colorants and charge control agents such as carbon black.
It is produced by kneading a solid polymer in a heated molten state using a heatable kneading machine such as a mixer, heated roll, or extruder, followed by cooling and finely pulverizing. However, in such conventional methods, it is actually difficult to sufficiently cross-disperse colorants such as carbon black into solid polymers, and therefore long kneading times are required. As a result of insufficient dispersion, the image feels sticky (a state in which the developer is thickly fixed to the image) and the clarity is reduced.

In order to improve the texture of the image, it is necessary to increase the amount of developer transferred, but in this case, even non-developed areas are contaminated with developer, resulting in so-called fog! 5 Elephants often occur. On the other hand, attempts have been made to adjust triboelectric charging properties and anti-offset properties by using a combination of multi-component resins, but with the above manufacturing method, it is difficult to completely uniformly disperse the multiple resin components and charging agents. Therefore, the components of the 10 powder particles of the developer are not necessarily the same, and the charging characteristics will differ when this developer is recycled over a long period of time. Charged powder and negatively charged powder will coexist, making it impossible to obtain a copied image of constant quality. 35 The present invention aims to provide a method for producing a dry developer in which the defects of the electrophotographic dry developer produced by the conventional method described above are eliminated, and in particular aims to achieve the following technical problems. shall be.

(1) A coloring agent such as carbon black is uniformly and finely dispersed in the developer, and by using a small amount of the developing agent, a clear copy image with a fleshy feel can be obtained.

(2) The colorant (including the charge control agent) is uniformly dispersed in the developer, and even when multiple resins are used, the charging characteristics of each powder particle are uniform, making it possible to use them repeatedly over a long period of time. Also, a uniform copy image can always be obtained.

(3) The manufacturing method does not require a heating, melting, and kneading process, and energy consumption for developer manufacturing can be reduced.

The configuration of the present invention will be described in detail below. As a result of intensive studies to solve the above-mentioned technical problems, the present inventors have found that the inner side of the polymer matrix is 1 to 501.
! The present invention was achieved by discovering that the above-mentioned object can be achieved by pouring the polymer into a mold and controlling the polymerization temperature distribution.

That is, the present invention comprises a polymer^, a pinyl monomer B) which is in a quantitative ratio of 95 to 60 parts by weight based on 5 to 40 parts by weight of the polymer (4) and is capable of dissolving solids, and a colored After kneading and dispersing the needle 0 and the polymerization initiator ◎, the mold can be released and the inner distance is 1 to 50]111! Pour into the formwork which is 4
This is a method for producing a powdery electrophotographic dry developer, which is characterized in that the vinyl monomer contained therein is polymerized by heating to 0 to 150[deg.] C., followed by cooling, demolding, and pulverization.

The polymer carrier used in the present invention is a natural or synthetic polymer, such as polystyrene, styrene copolymer resin, methacrylic acid ester copolymer resin, epoxy resin, polyester resin, polyvinyl butyral resin, polyvinyl acetal resin, novolac resin, etc. Various polymers are used, such as resins, ketone resins, petroleum resins, and rosins. The above polymer is required to be soluble in at least one vinyl monomer. Further, although it is generally solid at room temperature, it is desirable to have a softening point in the temperature range of 40 to 130° C., since this will improve the storage stability and heat fixability of the final developer. Among the above-mentioned polymers (4), styrene copolymer resins and methacrylic acid ester copolymer resins in particular have a wide range of applications because they can be copolymerized with a very wide variety of pinyl monomers. It is also preferable from the point of view of solubility in the body.

In addition to styrene and methacrylic esters, aromatic vinyl monomers such as vinyltoluene and Nitrile group-containing vinyl monomers such as acrylic acid esters, acrylonitrile, and methacrylonitrile; Mono- or diesters of unsaturated carboxylic acids and unsaturated dibasic acids; Vinyl alcohol esters; vinyl chloride, vinylidene chloride, Halogen-containing monomers such as vinyl fluoride and vinylidene fluoride; amide group-containing monomers such as acrylamide, methacrylamide, methylolacrylamide, t-butylacrylamide, dimethylacrylamide, diacetone acrylamide, and vinylpyrrolidone are used. In addition, the above-mentioned polyester resin is a condensation resin of polybasic acid and polyhydric alcohol,
Particularly preferred are those having a softening point of 60 to 120°C. The most common epoxy resins mentioned above are those made from bisphenol A and epichlorohydrin, but other types include bisphenol F type epoxy resin, which is a polymer of novolak and epichlorohydrin, and bisphenol A and aromatic epoxy resins. Ether made by reacting epichlorohydrin with group dibasic acid.
Ester copolymerization type epoxy resins may also be used, and it is also possible to use epoxy resin derivatives obtained by adding amino acids, phenols, or carboxylic acids to epoxy resins. In addition, the above-mentioned novolak resin is a condensation resin of phenol and formaldehyde, ketone resin is a condensation resin of ketones such as acetone and formaldehyde, and petroleum resin is a polymer of C5 to C, naphthene fractions. Rosin is a natural resin with an abietic acid structure, and any of these can be used alone or in combination of two or more in the present invention. Next, as a vinyl monomer (B) that can dissolve the polymer, for example, styrene, vinyl toluene,
Aromatic vinyl monomers such as α-methylstyrene; methyl acrylate, methyl methacrylate, ethyl acrylate,
Ethyl methacrylate, isopropyl acrylate, isopropyl methacrylate, n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, lauryl acrylate, Lauryl methacrylate, stearyl acrylate, stearyl methacrylate, oleyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, glycidyl acrylate, glycidyl methacrylate, methacrylate Acid β-
Methylglycidyl, cyclohexyl acrylate, cyclohexyl methacrylate, furfuryl methacrylate, tetrahydrofurfuryl methacrylate, benzyl acrylate, benzyl methacrylate, methoxyethyl methacrylate, isopropoxyethyl methacrylate, butoxyethyl methacrylate, dimethylaminoethyl acrylate , acrylic acid or methacrylic acid esters such as dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate; nitrile group-containing vinyl monomers such as acrylonitrile and methacrylonitrile; vinyl alcohol monomers such as vinyl acetate and vinyl propionate. Unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic anhydride, fumaric acid, cinnamic acid; monomethyl maleate, dimethyl maleate, monobutyl maleate, dibutyl maleate ester , fumaric acid dimethyl ester, fumaric acid monobutyl ester, fumaric acid dibutyl ester, fumaric acid monooctyl ester, fumaric acid dioctyl ester, itaconic acid monomethyl ester, itaconic acid dibutyl ester, itaconic acid dioctyl ester, etc. Examples include mono- or dialkyl esters; amide group-containing monomers such as vinylpyrrolidone and dimethylacrylamide; halogen-containing vinyl monomers such as vinyl chloride, vinylidene chloride, vinyl fluoride, and vinylidene fluoride.

One or two of these suitable for polymer (A)
Selected polymer A can be pre-dissolved with (B) to prepare a syrup-like liquid or can be used together with other (C) a)). The selection of the monomer (8) is such that the monomer alone or a mixture of monomers always dissolves the polymer (4), and when two or more types of monomers are used, it is preferable to select the monomer (8). ) Selection is based on the criteria that they copolymerize with each other, and that the polymer obtained by polymerization within the casting form is solid at room temperature, and that its softening point is preferably in the temperature range of 50 to 150°C. be done.

The ratio of polymer (4) and monomer (8) in which it is dissolved is 9 parts by weight of monomer (B) to 5 to 40 parts by weight of polymer (4).
The proportion is 5 to 60 parts by weight, preferably 90 to 70 parts by weight of monomer to 10 to 30 parts by weight of polymer. If the amount of the polymer is less than 5 parts by weight or more than 40 parts by weight, problems such as non-uniform dispersion of the colorant, sedimentation of the colorant, and difficulty in pouring into the mold will occur in either case. . In the present invention, (A) to D may be mixed simultaneously and kneaded and dispersed, but it is particularly preferable to prepare a syrup-like liquid by dissolving the polymer (4) in the monomer (8) in advance. preferable.

Such a preparation method includes a method of dissolving the solid polymer (self) described above in monomer B), and when the polymer (4) is a vinyl polymer, the raw material monomer is preliminarily dissolved. There are a method of using a bulk polymerized polymer solution (a mixture of a polymer and its monomer), and a method of adding another kind of monomer (provided) to the above-mentioned preliminarily polymerized polymer solution. The syrup obtained in this way was heated at 20°C for 1 hour to ensure uniform dispersion of the colorant and to facilitate pouring into the mold.
Preferably, it has a viscosity of 0.00 to 2000 centipoise. The most typical colorant K) used in the present invention is carbon black.

In addition, one or more of known pigments or dyes such as iron oxide, manganese blue, cadmium yellow cadmium red, benzidine yellow, phthalocyanine blue, phthalocyanine green, quinacridone, and titanium oxide may be used. The usage ratio of colorant 0 is
It is usually used at a concentration of 2 to 25 parts by weight per 100 parts by weight of the above syrupy liquid, and is used not only for monochrome photography but also for coloring.
The developer of the present invention can also be used for color photography by selecting the following. Furthermore, for the purpose of adjusting the polarity and charge amount of the developer, dyes such as azo dyes, triphenylmethane dyes, azine dyes, quinone imine dyes, and anthraquinone dyes, and fatty acid salts of these dyes are added. Dye derivatives, or known charge control agents such as fatty acid salts, quaternary ammonium salts of aliphatic sulfonic acids, and chlorinated paraffins are usually used in combination with colorants such as carbon black. In addition, for example, silicone, wax,
Mold release aids such as fatty acids, fatty acid metal salts, fatty acid amides, and low polymerization degree polyolefins, colorant dispersion promoting aids, and smoothing aids that aid the heat fixability of developers, plasticizers, and other aids are also available. It can be used in addition with coloring agents. In the case where the colored pigment is preliminarily dispersed in the syrupy liquid, a method generally used for dispersing pigments in liquid paints and the like may be used.

Next, examples of the polymerization initiator ◎ used in the present invention include diacyl peroxides such as benzoyl peroxide and lauroyl peroxide; t-butylperoxyoctoate, t-
Butyl peroxybenzoate, 2,5-dimethyl-2
・Peroxy esters such as 5-di(benzoylperoxy)hexane; t-butyl hydroperoxide,
Hydroperoxides such as cumene hydroperoxide and diisopropylbenzene hydroperoxide; dialkyl peroxides such as dicumyl peroxide and di-t-butyl peroxide; methyl ethyl ketone peroxide, cyclohexane peroxide, di-t-butyl peroxide Ketone peroxides such as -3,3,5-trimethylcyclohexane; various peroxides such as diisopropyl peroxydicarbonate, peroxycarbonate such as t-butylperoxyisopropyl carbonate, and azobisisobutyronitrile , azobisvaleronitrile, azobispropionitrile, azobiscyanovaleric acid,
Azonitriles such as azobiscyclohexanecarbonitrile are used.

The amount of the polymerization initiator (self) used is usually in the range of 0.1 to 5.0 parts by weight per 100 parts by weight of the syrupy liquid containing colored O. When the weight average molecular weight is 20,000 or more, it is generally used in an amount of 2.0 to 5.0 parts by weight, and when it is less than 20,000, it is generally used in an amount of 0.1 to 3.0 parts by weight.

In this way, it is preferable to adjust the weight average molecular weight of all resin components finally obtained after polymerization to a range of 20,000 to 10,000. In addition, the polymerization initiator 9 contains a molecular weight regulator such as mercaptans, iron, cobalt, zinc, lead,
It is also possible to use a polymerization initiation accelerator such as a metal ion such as molybdenum, manganese, rubidium, or copper, or a metal ion organic acid salt, or a tertiary amine. Next, the kneading and dispersion referred to in the present invention means mixing (4) to D,
The colorant C) is dispersed by kneading until the maximum particle size of the colorant becomes about 1 μm or less.

For this kneading, ordinary kneading machines such as ball mills, sand mills, pebble mills, roll mills, etc. can be used. According to these kneaders, it is possible to easily achieve the dispersion state of the colorant having a maximum particle size of 1 μm or less, which is the goal of the present invention. There is no particular restriction on the order of mixing (A) to (B), but as mentioned above, colorant 0 is kneaded and dispersed in a syrupy liquid consisting of (5) and (B) in advance, and then polymerization is started. Particularly preferred is a method in which Agent 9 is added and mixed. Next, the liquid obtained by kneading and dispersing (8 to ◎) in this manner is applied to glass, stainless steel, aluminum, chrome-plated iron plate, high-density polyethylene, polypropylene, polyvinyl fluoride, polypylidene fluoride, polytetra Inject into molds made of fluoroethylene, polyester, etc.

The formwork can have a structure commonly used in casting polymerization, but in order to easily release the polymerized material after polymerizing the syrupy liquid, it is possible to use a formwork around the periphery of the two panels or sheets. Insert the gasket and make sure that the inner gap is 1
It is preferable to form a shape in which they are glued together so that the thickness is ~50+. A syrupy liquid is injected between the slits, and the upper part is sealed with a gasket. The larger the gap inside the formwork,
Although productivity is improved, if this exceeds the above-mentioned upper limit of 50 ml, the temperature distribution of the injected material will fluctuate greatly due to the heat of polymerization, making it difficult to control the degree of polymerization of the resulting resin.
On the other hand, in order to facilitate the removal of the formwork, it is also possible to apply a mold release agent to the base material of the formwork, or to use a film of polyolefin, polyfluorocarbon, polyester, polyamide, etc. on the inner surface of the formwork. It is. The formwork filled with syrup is heated by placing it in hot water or in a heating oven.

The heating temperature is appropriately selected depending on the type of polymerization initiator used, but is generally in the range of 40 to 150°C. The temperature is usually maintained within the range of 40 to 95°C. The heating time at this temperature is usually 1 to 8 hours, during which time more than 90% of the vinyl monomer is polymerized. In order to reduce the residual monomer, preferably the mold is transferred to a heating furnace maintained at 100 to 150 ° C. and heating is continued for an additional 1 to 5 hours,
The amount of vinyl monomer remaining after completing the polymerization is 1.0%.
Do the following. If the heating temperature mentioned above is less than 40°C, it will take a long time to polymerize the vinyl monomer, and
If the temperature exceeds ℃, a pressure-resistant container is required, so it cannot be used. Next, the mold is cooled and then removed to obtain a colored resin plate.

After this plate-like resin is pulverized using a pulverizer, coarse particles are removed using a blue or air classifier to obtain a powdered dry developer for electrostatic copying according to the present invention. The degree of pulverization is preferably such that the powder particle size of this developer is 50μ or less,
In particular, it is preferably in the range of 5 to 40μ. According to the present invention, it is possible to obtain a dry developer which has a significantly clearer image quality than conventional dry developers for electrophotography and retains clear images even after repeated use over a long period of time.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Polystyrene polymer 350 with a weight average molecular weight of 11000
7 was dissolved in 650t of styrene, and carbon black 10
After adding 0t and Nigrosine (quinone imine dye) 207 as a charge control agent, kneading and dispersing in a ball mill for 8 hours, and confirming that the carbon black particles were dispersed to 1μ or less, 10t of benzoyl peroxide was added. Dissolved.

A formwork made by gluing two tempered glass plates (200 x 300 x 5 mm) with a 10 mm thick gasket in between,
The above dispersion was injected, immersed in 80°C hot water for 4 hours, then transferred to 95°C hot water and heated for 4 hours, then cooled and the mold was removed to obtain a colored polymer sheet. Ta.

After coarsely pulverizing this sheet-like polymer, it was finely pulverized using a dinit pulverizer, and particles of 50 μm or more were classified and removed to obtain a powdery electrophotographic dry developer.

The obtained developer was evaluated using an electrophotographic copying machine (3600R, manufactured by Fuji Xerox Co., Ltd.) using a steel carrier, and as a result, a clear copy image with a solid feel and no fog was obtained. Furthermore, even after using the photoreceptor 2000 times, no deterioration in sharpness was observed, and this developer
t and iron oxide carrier - 100 t were sealed in a cylindrical container with an internal volume of 11 and allowed to cool for 48 hours. The aged developer was removed from the surface of the carrier by air blowing and evaluated in the same manner as above. A clear image was obtained. Example 2 Styrene 50% by weight, methyl methacrylate 30% by weight,
2007 copolymer (weight average molecular weight 45,000) consisting of 20% by weight of 2-ethylhexyl acrylate, 200 t of vinyl toluene, 300 ft of methyl methacrylate, 150 t of isobutyl methacrylate, 20 t of hydroxypropyl methacrylate, 30 t of monobutyl fumarate.
was dissolved in the monomer mixture.

Add Carpon Black 1007 and Nigrosine 20t to this, knead and disperse in a sand mill for 4 hours, and after confirming that the carbon black particles have been dispersed to 1μ or less, benzoyl peroxide 407 is dissolved and carried out. It was poured into a tempered glass mold similar to Example 1. This mold was immersed in warm water at 80° C. for 3 hours, then heated at 120° C. for 2 hours, and then cooled, demolded, crushed, and classified in the same manner as in Example 1 to obtain an electrophotographic developer. The obtained developer was evaluated in the same manner as in Example 1.
A clear image similar to that was obtained.

Example 3 Methyl methacrylate 50% by weight, acrylonitrile 20%
Copolymer (weight average molecular weight 60,000) 1507 consisting of n-butyl methacrylate 30% by weight and cyclopentadiene petroleum resin 507, methyl methacrylate 500y1 acrylonitrile 100tbutyl acrylate 1807, dimethylaminoethyl acrylate 20y
was dissolved in the monomer mixture.

To this, 100t of carbon black and 20y of nigrosine were added and kneaded and dispersed in a sand mill for 3 hours. After confirming that the carbon black particles were dispersed to a size of 1μ or less, azobisisobutyronitrile 30' and t-butyl Dissolve peroxybenzoate 5f and spread it on two polished stainless steel plates (200x3.00x1mu) with a thickness of 6.
1! It was injected into a mold that was glued together with a gasket of 1. This formwork is soaked in 70℃ hot water for 4f! After being immersed for 8 hours and further heated in a hot air dryer at 110° C. for 3 hours, the mixture was cooled, demolded, crushed, and classified in the same manner as in Example 1 to obtain an electrophotographic developer. The obtained developer was evaluated in the same manner as in Example 1, and a clear image similar to that in Example 1 was obtained.

Example 4 Terephthalic acid, isophthalic acid, ethylene glycol, 1
・200r of polyester resin (weight average molecular weight 8000) consisting of 6 hexanediol and 50r of polyvinyl butyral resin were dissolved in a monomer mixture of 200t of styrene, 200r of methyl methacrylate, 100r of acrylonitrile, 100r of vinylpyrrolidone, 100f of dimethylacrylamide, 50r of butoxyethyl methacrylate. .

Add to this 100t of carbon black and 20t of nigrosine.
After adding t and kneading and dispersing in a ball mill for 6 hours and confirming that the carbon black particles were dispersed to a size of 1μ or less, benzoyl peroxide 20r and di-t-butylveroxine 3,3,5-trimethylcyclohexanone were added. 10r
was dissolved and poured into the same mold as in Example 3. This formwork was immersed in hot water at 85°C for 3 hours, then heated in a hot air dryer at 100°C for 3 hours, and then cooled, demolded, crushed, and classified in the same manner as in Example 1, and developed for electrophotography. obtained the drug. The obtained developer was evaluated in the same manner as in Example 1, and clear images similar to those in Example 1 were obtained.

Example 5 Epoxy resin (trade name: Epicoat 1004, manufactured by Shell Chemical Co., Ltd.) 200f, which is a condensation product of pisphenol A and epichlorohydrin, and novolac resin (average degree of polymerization 6.5)
) 150t to 200 styrene? , methyl methacrylate 2
00f, dissolved in a monomer mixture consisting of 50t of hydroxyethyl methacrylate.

This includes Carbon Black 1005r and Nigrosine 2.
After confirming that the carbon black particles were dispersed until the carbon black particles were 1μ or less, 100y of glycidyl methacrylate and 100y of styrene were added.
The solution was diluted by adding 100ml of diisopropyl peroxycarbonate, 10r1 of diisopropyl peroxycarbonate, 5t of benzoyl peroxide and 5V of cumene hydroperoxide, and poured into the same mold as in Example 1. This mold was immersed in hot water at 60°C for 2 hours, then in hot water at 80°C for 2 hours, then heated in a hot air dryer at 130°C for 2 hours, and then cooled, demolded, crushed, and classified in the same manner as in Example 1. An electrophotographic developer was obtained. The obtained developer was evaluated in the same manner as in Example 1, and a clear image similar to that in Example 1 was obtained.

Example 6 Novolac type epoxy resin (product name: “DEN439
(manufactured by Tau Chemical Co., Ltd.), 100 f of an epoxy resin derivative with 1/2 of the total epoxy groups added with dimethylamine, 50 tons of rosin, and 50 f of vinyl chloride vinyl acetate copolymer, 400 tons of methyl methacrylate, 200 tons of styrene.
It was dissolved in a monomer mixture of ethyl acrylate 150r and acrylic acid 50f7.

Add to this carbon black 100r and nigrosine 20
After adding r and kneading and dispersing in a sand mill for 3 hours and confirming that the carbon black particles were dispersed to a size of 1μ or less, azobiscyanovaleric acid 10V and dit
-Butyl peroxide 3y was dissolved and poured into the same mold as in Example 1. This formwork was immersed in hot water at 70°C for 5 hours, then heated in a hot air dryer at 140°C for 2 hours, and then cooled, demolded, crushed, and classified in the same manner as in Example 1, and developed for electrophotography. obtained the drug. The obtained developer was evaluated in the same manner as in Example 1, and a clear image similar to that in Example 1 was obtained.

Comparative Example 1 100f of carbon black and 201 nigrosine were added to 1000t of the polystyrene polymer with a weight average molecular weight of 11000 used in Example 1, and the mixture was mixed in a Banbury mixer.
After kneading and dispersing in a molten state while heating to 25° C., the mixture was cooled, crushed, and classified in the same manner as in Example 1 to obtain an electrophotographic developer for comparative testing.

The obtained developer was evaluated in the same manner as in Example 1, but the obtained image was unclear due to significant capri in the non-image area, and when the photoreceptor was used repeatedly, Significant contamination occurred and only poor images were obtained.

Comparative Example 2 350 t of the polystyrene polymer having a weight average molecular weight of 11,000 used in Example 1 was dissolved in 650 y of styrene, and 10 t of benzoyl peroxide was further dissolved and poured into the same mold as in Example 1.

This mold was immersed in hot water at 80° C. for 4 hours and then in hot water at 95° C. for 4 hours, then cooled, demolded, and coarsely ground. Carbon Black 100y and Nigrosine 207 were added to this, and as in Comparative Example 1, they were kneaded and dispersed while heating to 140°C in a Banbury mixer, and then pulverized and classified. obtained the drug. The obtained developer was evaluated in the same manner as in Example 1, and although the obtained image had slight fog in the non-image area, it had a poor texture and poor clarity. As the photoreceptor was repeatedly used, fogging in non-image areas became more severe and the image quality deteriorated.

Furthermore, in the evaluation of copies after aging obtained by cooling with a carrier according to the method of Example 1, fogging was severe and clear images could not be obtained. Comparative Example 3 The syrupy liquid used in Example 1, that is, 1,750 tons of polystyrene polymer having a weight average molecular weight of 11,000, was dissolved in 3,250 tons of styrene, and 500 y of Power Bomb Black and 1 liter of nigrosine (quinone imine dye) as a charge control agent were dissolved.
00f was added and kneaded and dispersed in a ball mill for 8 hours.
After confirming that the carbon black particles were dispersed to a size of 1μ or less, 50t of benzoyl peroxide was dissolved in two tempered glass plates (200W! l x 300m).
The mixture was poured into a mold made of 60 mm thick gaskets sandwiched together (m x 50 mm) and immersed in warm water at 80°C.

After about 40 minutes, a syrup-like liquid in a gas-liquid mixture state began to flow out to the hot water side from between the gaskets, and after an hour, almost all of it had flowed out, and a colored polymer sheet was not obtained. Ta. Because this was carried out by static polymerization, the heat of polymerization could not be removed, and the temperature of the polymerization solution rose above the boiling point of the monomer, causing the internal pressure of the mold to rise, resulting in areas with weak pressure resistance,
In other words, it is thought that it began to erupt from between the gaskets.

Claims (1)

[Claims] 1. A vinyl monomer (B) that is in a quantitative proportion of 95 to 60 parts by weight based on 5 to 40 parts by weight of the polymer (A) and that can dissolve (A), and a coloring. After kneading and dispersing the agent (C) and the polymerization initiator (D), they are poured into a mold that is releasable and has an inner interval of 1 to 50 mm.
A method for producing a powdered dry developer for electrophotography, which comprises heating to 150° C. to polymerize the vinyl monomer contained therein, followed by cooling, demolding, and pulverization.