JPS5937008B2 - Manufacturing method of resin for electrophotographic toner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a resin suitable for an electrophotographic dry toner (colored resin powder) that can be easily heat-fixed and hardly causes an offset phenomenon.

In recent years, among the various copying methods, an electrophotographic method called plain paper copy (which has achieved remarkable growth due to its excellent image clarity, permanent retention, and ease of use.The representative method of plain paper copy) The most common development method is a dry development method, which uses a triboelectrically charged toner in the form of a fine powder as a developer.One of the problems with toners is that they cannot be easily heat-fixed in order to further improve copying speed. However, when improving heat fixing properties, toner tends to adhere to the fixing roll, resulting in the so-called offset phenomenon. At the same time, there is a strong desire to develop a toner resin that satisfies the above requirements.As a countermeasure to this problem, attempts have been made to reduce the temperature dependence of melt viscosity by using resins with a wide molecular weight distribution.

For example, there is a method in which high molecular weight resin and low molecular weight resin are mixed together with a colorant such as carbon black and kneaded in a molten state.In this method, only the low molecular weight resin is melted first, and during mixing As the shear force decreases, colorants such as carbon black will not be well dispersed, and high molecular weight resins will also become difficult to disperse uniformly, resulting in uneven triboelectric charging properties of the resulting toner particles and poor image quality. This may lead to a decrease in the level of Therefore, it is not possible to obtain a satisfactory toner resin by such a method, and it is necessary to establish an industrial method for producing a toner resin in which each particle of the toner powder uniformly contains a high molecular weight polymer and a low molecular weight polymer. This is the subject of the present invention. In addition, as a manufacturing method for resins with a wide molecular weight distribution, a method has been known in which a high molecular weight polymer is dissolved in a monomer and the polymerization is completed by suspension polymerization (with a number average molecular weight of 10,000
When producing the following polymers by suspension polymerization, it is generally difficult to maintain a stable suspension state, and often requires the use of a large amount of dispersant. The triboelectricity of the material decreases. Therefore, an object of the present invention is to provide a manufacturing method that does not cause such problems. The configuration will be described in detail below.

The vinyl polymer 1 of the present invention is a single or copolymer obtained by polymerizing one or more vinyl monomers, and can be used alone or as a mixture of two or more. can.

The vinyl copolymer of the present invention can be exemplified by the types of vinyl monomers that are its purchasing components, such as aromatic vinyl monomers such as styrene, vinyltoluene, α-methylstyrene, chlorostyrene; methyl acrylate, methyl methacrylate. , ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexynole acrylate, 2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate , stearyl methacrylate, hydroxyethyl acrylate Hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, glycidyl acrylate, glycidino methacrylate
, β-methylglycidyl acrylate, β-methacrylate
Methylglycidyl, cyclohexyl acrylate, methacrylate] Acrylic and methacrylic acid esters such as cyclohexyl lylate, benzyl acrylate, benzyl methacrylate, tetrahydrofurfurinole acrylate, tetrahydrofurfuryl methacrylate, and methoxyethyl methacrylate. Preferably, one or more of the following are pentapolymerized, and furthermore, for example, nitrile group-containing vinyl monomers such as acrylonitrile and methacrylonitrile; vinyl alcohol esters such as vinyl acetate and vinyl propionate; acrylic acid and methacrylic acid; , crotonic acid, itaconic acid, unsaturated carboxylic acids such as maleic anhydride, fumaric acid, cinnamic acid; monobutyl maleate, monoethyl fumarate, dibutyl fumarate, monomethyl itaconate, octyl itaconate, etc. Unsaturated: mono- or dialkyl esters of basic acids; halogen-containing monomers such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride; acrylamide, methacrylamide, methylol acrylamide, alkoxymethylol acrylamide, t- Copolymerization of amide group-containing vinyl monomers such as butylacrylamide, dimethylacrylamide, and diacetosoacrylamide; nitrogen-containing vinyl monomers such as dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, vinylpyrrolidone, and vinylpyridine. It is also possible to use them together as a comonomer.

The vinyl monomers used in the present invention may be used alone or as a mixture of two or more, but it is necessary that Polymer 1 can be dissolved uniformly, and from this point of view, the relationship between Polymer 1 and the monomers is Select the combination as appropriate.

Examples of vinyl monomers include those exemplified in the component 10) of the polymer. To prepare a syrupy liquid by dissolving Polymer 1 in a vinyl monomer, T-type vinyl monomers or a mixture of two or more types of vinyl monomers are usually dissolved by thermal polymerization or in the presence of a polymerization initiator. to adjust the polymerization rate to a range of 5 to 50% by weight, or
Alternatively, it is prepared by dissolving the polymer 1 previously produced by bulk polymerization, suspension polymerization, solution polymerization or emulsion polymerization in a vinyl monomer or a monomer mixture that is the same as or different from its constituent components; It is also possible to use two or more types of polymers 1 dissolved in vinyl monomers. It is essential that the copolymer 1 used in the present invention has a number average molecular weight of 10,000 or more, and if it is less than 10,000, the offset resistance will be poor.

The content of Polymer 1 in the syrupy liquid is related to the desired molecular weight distribution, and should be 5 to 50% by weight, particularly preferably 10 to 40% by weight. Polymer 1
If it is less than 5% by weight, the balance between heat fixability and offset resistance will be poor, while if it is more than 50% by weight, heat fixability and image clarity will deteriorate. In the method of the present invention, after adding a polymerization initiator to this syrupy liquid, for example, molds of metal plates such as glass plates, stainless steel plates, aluminum plates, chrome-plated plates, polyolefin sheets, polyfluorinated olefins, polyester or It is poured into a plastic form made of polyamide sheet or film, or a plastic laminate metal plate form, sealed to prevent the contents from leaking outside, and then placed in a hot water tank or drying oven to heat it. In this method, the polymerization of the monomers contained is completed, and a resin plate in which Polymer 1 is uniformly mixed is manufactured. Examples of the polymerization initiator used in this case include benzoyl peroxide, lauroyl peroxide,
Peroxides such as t-butyl perbenzoate, di-t-butyl peroxide, t-butyl peroctoate, t-butyl hydroperoxide, cumene hydroperoxide, or azobisisobutyronitrile, azobisvaleronitrile Azo-based polymerization initiators such as are commonly used. The polymer obtained by the above polymerization contains a polymer of vinyl monomer, Polymer 1, and optionally a polymer in which a vinyl monomer is graft-polymerized to Polymer 1, but the number average molecular weight of the polymer is It is an essential requirement of the present invention that the molecular weight is smaller than that of Coalescence 1 and that the ratio of the weight average molecular weight to the number average molecular weight of the polymer is 4 or more.

In order to satisfy this requirement, in the present invention, an appropriate polymerization initiator is selected, an appropriate amount thereof is used, and an appropriate polymerization temperature is adopted depending on each initiator. These numerical values vary depending on the combination of specific polymer 1 and vinyl monomer. In the present invention, in order to achieve this objective, one or more kinds of polymerization initiators are used, and the amount thereof is usually 1.8 to 8.0% by weight based on the monomer. On the other hand, the heating temperature of the formwork is appropriately selected depending on the type and amount of the polymerization initiator, but most commonly, it is 40 to 95℃ and 2 to 8℃.
After heating for a period of time, heating is preferably continued for 1 to 4 hours at 100 to 160° C. to reduce residual vinyl monomer as much as possible. The produced copolymer is released from the mold by a conventional method to obtain a toner resin. The ratio between the weight average molecular weight and the number average molecular weight defined in the present invention is a parameter indicating the spread of molecular weight distribution, and is measured by the GPC method.

Furthermore, in order to obtain the molecular weight and molecular weight distribution as described above, it is also possible to use molecular weight modifiers such as mercaptans, decomposition accelerators for polymerization initiators such as naphthenic acid metal salts, and amines. In order to promote mold release of the frame, known mold release additives may be added to the syrupy liquid.

In this way, a polymer is obtained. Vinyl polymer 1
Regarding the relationship between the molecular weight of a vinyl polymer and the molecular weight of a vinyl polymer, generally speaking, one with a lower molecular weight is dissolved in a vinyl monomer, and this is mixed with a higher molecular weight. There is a method in which the average molecular weight of the final product, the vinyl polymer, is made larger than the molecular weight of I by combining them to form a polymer or copolymer with a large molecular weight. By dissolving I in a vinyl monomer and polymerizing it to produce a polymer or copolymer with a small molecular weight, the average molecular weight of the final product vinyl polymer is made smaller than the molecular weight of I. There is a method.

The present invention employs the latter method. The reason for this is that the so-called casting method, which uses a mold, tends to produce a polymer with a small molecular weight. Further, in the present invention, if the number average molecular weight of the polymer is larger than that of Polymer 1, the heat fixability will be lowered and a good toner resin will not be obtained. Next, in the present invention, the force ζ that defines the ratio of the weight average molecular weight to the number average molecular weight of the copolymer, this ratio indicates the breadth of the molecular weight distribution, and when this ratio is 4 or less, the offset resistance is Sexuality becomes insufficient.

A particularly preferred range is a range in which the polymer contains 50 to 95% by weight of a vinyl polymer having a number average molecular weight of 6,000 or less, and the ratio of the weight average molecular weight to the number average molecular weight of the polymer H is 5 or more. Furthermore, since the toner resin according to the present invention is used in a powdered developer and needs to be solid at room temperature, the monomer resin is used so that its glass transition temperature is 30°C or higher. Adjust the combination of

Here, solid means excluding those that are fluid, semi-fluid, or viscoelastic at room temperature. The resin prepared by the above method Q) is usually mixed with a coloring agent such as carbon black and a charge control agent in a Banbury mixer, an extruder,
The mixture is kneaded using a melt kneader such as a heated roll, and after cooling, it is finely pulverized to an average particle size of 50 μm or less to form a toner product for electrophotography.

In the method of the present invention, when producing a resin with a desirable molecular weight distribution for use as a toner, a polymerization method that does not use a surfactant, such as a suspension polymerization method or an emulsion polymerization method, is adopted.
In addition, we have adopted a polymerization method that achieves a desired molecular weight distribution by appropriately adjusting the molecular weight of the vinyl polymer 1 as a raw material, the polymerization initiator, and the polymerization temperature without using a molecular weight regulator. Even if the polymerization temperature is adjusted to the required temperature on a large scale, runaway reactions can be suppressed and resins of constant quality can be produced. Adopts polymerization method.

As a result of these effects, the resin for electrophotographic toners obtained by the method of the present invention is easier to heat fix than conventional products and is less likely to cause offset phenomenon. The resulting electrophotographic images have significantly clearer image quality. Hereinafter, the present invention will be specifically explained with reference to Examples.

Example (1) 800 g of styrene, 800 g of methyl methacrylate, and 400 g of hydroxyethyl acrylate were charged into an autoclave with an internal volume of 4 tons equipped with a stirrer, heated at 120°C for 2 hours, and then immediately cooled. A mixture of polymer and monomer was obtained.

The copolymer content in this mixture was 23% by weight, with the remaining 7% by weight.
7% by weight was monomer. The GPC measurement result of the number average molecular weight of the obtained copolymer was 35,000. 70 g of benzoyl peroxide and 10 g of cumene hydroperoxide were dissolved in this syrupy liquid and injected between two glass plate slits glued together with Teflon packing (inner volume: 300 x - 600 x 1011). Thereafter, it was immersed in warm water at 80°C for 4 hours, and then left in a hot air dryer at 125°C for 2 hours to complete polymerization.

After cooling, the glass plate was removed to obtain a plate-shaped resin (the number average molecular weight of this resin was 8,500, which was smaller than the number average molecular weight of the initially existing copolymer, and the weight average molecular weight was lower than the number average molecular weight). The ratio was 6.9.
00g, carbon black 100g, and chargeability regulator Nigrosine 10g were charged into a Banbury mixer.
The mixture was kneaded in a molten state at 0° C. for 30 minutes, cooled, and then pulverized using a hammer-type pulverizer, and the material that passed through 300 meshes of gold steel was collected to obtain a toner for electrophotography.

The obtained toner has excellent heat fixing properties and no offset phenomenon even when used in a high-speed copying machine that prints 100 copies per minute.
It gave a clear image without showing.

Example (2) 1,600 g of ethyl methacrylate, 200 g of 2-ethylhexyl methacrylate, 200 g of acrylonitrile, 2 g of di-t-butyl peroxide as a polymerization initiator, and 4 g of n-dodecyl mercaptan as a molecular weight regulator were placed in an autoclave with an internal volume of 4 tons equipped with a stirrer. After heating at 110° C. for 1.5 hours, the mixture was immediately cooled to obtain a syrup-like liquid mixture of copolymer and monomer.

The content of copolymer in this mixture was 30% by weight, and the remaining 70% by weight was monomer. The number average molecular weight of the obtained copolymer was 21,000. Dissolve 60g of azobisisobutyronitrile in this syrupy liquid, inject it between the slits of two glass plates glued together in the same manner as in Example (1), and soak in warm water at 60°C for 5 hours. 12 more
The mixture was left in a hot air dryer at 5° C. for 2 hours, and after cooling, the glass plate was removed to obtain a resin plate.

The number average molecular weight of this resin was 7,200, which was lower than the number average molecular weight of the initially existing copolymer, and the ratio of weight average molecular weight to number average molecular weight was 5.8. An electrophotographic toner was obtained using the above resin in the same manner as in Example (1).

Even when this toner was used in a high-speed copying machine capable of printing 100 copies per minute, it had excellent heat fixing properties and gave clear images without exhibiting any offset phenomenon. Example (3) 200 g of a copolymer with a number average molecular weight of 45,000 consisting of 70% by weight of styrene and 30% by weight of butyl methacrylate obtained by a suspension polymerization method was mixed with 400 g of metal methacrylate, 200 g of isobutyl acrylate, and 1,100 g of vinyl toluene.
g1 Dissolved in 100 g of methacrylic acid monomer mixture, and further added 50 g of polymerization initiator t-butyl peroctoate.
g, 20 g of lauroyl peroxide, and 1 g of cobalt naphthenate as a polymerization initiation accelerator were added to obtain a syrup-like liquid.

This liquid was injected between the slits of two glass plates glued together in the same manner as in Example (1), immersed in hot water at 70°C for 5 hours, and then left in a hot air dryer at 125°C for 2 hours. After cooling, the glass plate was removed to obtain a resin plate. The number average molecular weight of this resin was 6,800, which was lower than the number average molecular weight of the initially existing copolymer, and the ratio of weight average molecular weight to number average molecular weight was 7.0. A toner for electrophotography was obtained using the above resin in the same manner as in Example (1).

This toner had excellent heat fixing properties even when used in a high speed copying machine capable of printing 100 copies per minute, and gave clear images without exhibiting any offset phenomenon. Example (4) Content selection 4: 1400 g of styrene, 180 g of dibutyl fumarate, and 20 g of diethyl and minoethyl methacrylate.
The mixture was placed in an autoclave equipped with a stirrer, heated at 130°C for 3 hours, and then cooled immediately.

Copolymer contained in the produced syrupy liquid? The ratio is 4
0% by weight, and its number average molecular weight was 28,000. Add to this syrupy liquid 250 g of styrene, 100 g of cyclohexyl methacrylate, 50 g of dimethylacrylamide, and 50 g of azobisvaleronitrile as a polymerization initiator.
The syrup-like liquid was readjusted by adding 10 g of the molecular weight regulator thioglycolic acid (copolymer 32% by weight, monomer 68% by weight), and two sheets were glued together in the same manner as in Example (1). The resin was injected between the slits of a glass plate, immersed in hot water at 70°C for 4 hours, and left in a hot air dryer at 125°C for 2 hours. After cooling, the glass plate was removed to obtain a resin plate.
The number average molecular weight of this resin was 8,500, which was lower than the number average molecular weight of the initially existing copolymer, and the ratio of weight average molecular weight to number average molecular weight was 6.3.

A toner for electrophotography was obtained using the above resin in the same manner as in Example 1).

Even when this toner was used in a high-speed copying machine capable of printing 100 copies per minute, it had excellent heat fixability and gave clear images without exhibiting any offset phenomenon. Comparative Example (1) Dissolve 55 g of benzoyl peroxide and 10 g of cumene hydroperoxide in a monomer mixture of 800 g of styrene, 800 g of methyl methacrylate, and 400 g of hydroxyethyl acrylate, and pour it into the mold used in Example (1). After that, it was immersed in warm water at 80°C for 4 hours, and then left in a hot air dryer at 125°C for 2 hours to complete polymerization.

After cooling, the glass plate was removed to obtain a plate-shaped resin for comparative evaluation. The number average molecular weight of this resin was 8,700, and the ratio of the weight average molecular weight to the number average molecular weight was 3.5. 1000 g of the above resin, 100 g of carbon black, and 10 g of nigrosine as a charge control agent were charged into a Banbury mixer, and kneaded in a molten state at 130 ° C. for 30 minutes.
After cooling, it was pulverized using a hammer-type pulverizer, and the material that passed through 300 bushes of wire mesh was collected to obtain a toner for electrophotography.

Claims (1)

[Claims] 1 Vinyl polymer with number average molecular weight of 10,000 or more (1)
A syrupy liquid consisting of 5 to 50% by weight and 95 to 50% by weight of one or more vinyl monomers that can dissolve this polymer (I) and polymerize to give a solid polymer at room temperature. is injected into a releasable mold, and the mold is heated from the outside to polymerize the monomer, and the number average molecular weight of the resulting vinyl copolymer (II) is equal to the number of the vinyl polymer (I). 1. A method for producing a resin for electrophotographic toners, which comprises controlling polymerization conditions so that the resin is smaller than the average molecular weight and the ratio of the weight average molecular weight to the number average molecular weight of the vinyl polymer (II) is 4 or more.