JP3372063B2 - Binder resin for toner - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner for use in electrophotography and electrostatic printing which is excellent in non-offset properties, fixing properties and image density stability. It relates to a binder resin. 2. Description of the Related Art In a typical image forming process by electrophotography or electrostatic printing, a photoconductive insulating layer is uniformly charged, the insulating layer is exposed, and then the exposed portion is exposed. A developing step of forming an electric latent image by dissipating the above electric charge, and visualizing the latent image by attaching a fine powder toner having the electric charge to the latent image; It comprises a transfer step of transferring to a transfer material, and a fixing step of permanently fixing by heating or pressing. Various performances are required for the toner and the binder resin for the toner used in the electrophotographic method or the electrostatic printing method in each of the above steps. For example, in the development process, the toner and the binder resin for the toner maintain a charge amount suitable for a copying machine without being affected by the surrounding environment such as temperature and humidity in order to attach the toner to the electric latent image. I have to do it. Also,
In the fixing step by the heat roller fixing method, the non-offset property that does not adhere to the heat roller and the fixability to paper must be good. Further, it is required to have a blocking resistance so that the toner does not block during storage in a copying machine. Conventionally, styrene acrylic resins have been frequently used as toner resins, and linear resins and crosslinked resins have been used. As the linear type resin, a resin in which a high molecular weight polymer and a low molecular weight polymer are mixed to improve the fixing property, the non-offset property, and the like is known. Further, in a crosslinked type resin, the molecular weight distribution is widened by crosslinking, and the fixing property and the non-offset property are improved. In particular, research on linear resin has been progressing,
JP-B-63-32182 and JP-A-62-9356.
As described in Japanese Patent Application Laid-Open Publication No. H10-163, attempts have been made to improve the fixing property and the non-offset property by controlling the high molecular weight and low molecular weight regions and the molecular weight of the resin. [0005] However, in the toner using such a resin, although the balance between the fixing property and the non-offset property is improved, there is a problem in the image density stability. are doing. In particular, with the increase in size and speed of copiers and printers, the number of prints is increasing, and long-life toners with little change in image density are required even when printing many sheets. ing. Therefore, an object of the present invention is to provide a binder resin for toner which is excellent in balance between fixing property and non-offset property and has excellent image density stability with little change in image density even when printing a large number of sheets. . In view of such circumstances, the inventors of the present invention have conducted intensive studies on binder resins for toner, and as a result, it has been found that a specific resin subjected to alkali treatment has a high image density stability. Have been found, and the present invention has been achieved. That is, the binder resin for a toner of the present invention is a styrene-acrylic resin composed of a high molecular weight polymer component and a low molecular weight polymer component, and the high molecular weight polymer and the low molecular weight polymer contain a carboxylic acid component. Together with the carboxylic acid contained in the high molecular weight polymer
Component content (W _H ) and low molecular weight polymer
The content of the carboxylic acid component _{(W L)} is Seki _{W H} ≧ _{W L}
It is characterized by being subjected to an alkali treatment . The binder resin for a toner of the present invention comprises a high molecular weight polymer component and a low molecular weight polymer component, and it is important that both polymers contain a carboxylic acid component. Examples of the polymer containing a carboxylic acid component include a carboxylic acid group-containing vinyl monomer as an essential component and a copolymer composed of a styrene monomer or another copolymerizable vinyl monomer. Can be The monomer used is not particularly limited as long as it is polymerizable. For example, carboxylic acid-containing vinyl polymers include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid and cinnamic acid, unsaturated dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid, monomethyl maleate and maleic acid. And unsaturated monocarboxylic acid monoesters such as monoethyl, monobutyl maleate, monomethyl fumarate, monoethyl fumarate and monobutyl fumarate. Of these, unsaturated monocarboxylic acids and unsaturated monocarboxylic acid monoesters are preferred. As the styrene monomer, styrene, o
-Methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene,
2,4-dimethylstyrene, pn-butylstyrene,
p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-densyl styrene, pn-dodecyl styrene, p-phenyl styrene, 3, 4-dicrosylstyrene and the like. Among them, styrene is preferred. [0010] Other copolymerizable vinyl monomers include ethyl acrylate, methyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, and metaaryl. Acrylic acid, ethyl methacrylate, methyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, propyl methacrylate, 2-ethylhexyl methacrylate, unsaturated monocarboxylic acid esters such as stearyl methacrylate, And unsaturated dicarboxylic acid diesters such as dimethyl maleate, diethyl maleate, butyl maleate, dimethyl fumarate, diethyl fumarate and dibutyl fumarate. The copolymerization ratio of these monomers is not particularly limited, but it is preferable to use them in a range where the glass transition temperature of the obtained resin is 50 ° C. or higher. This is because if the glass transition temperature of the resin is less than 50 ° C., the storage stability may be extremely reduced when the toner is formed. The monomer components of the high molecular weight polymer and the low molecular weight polymer may be the same or different as long as both polymers contain a carboxylic acid component. When only one of the high molecular weight polymer or the low molecular weight polymer contains a carboxylic acid component,
This is not preferable because sufficient image density stability cannot be obtained. When the content (W _H ) of the carboxylic acid component contained in the high molecular weight polymer exceeds the content (W _L ) of the carboxylic acid component contained in the low molecular weight polymer, the image density becomes stable. In some cases, W _H ≧ W _L
It is required to be in the relation of (% by weight). Further, when the content of the carboxylic acid component is extremely large, there may occur a problem of environment dependence of charging under high temperature and high humidity, and the carboxylic acid component may be contained in both the high molecular weight polymer and the low molecular weight polymer. The content of the acid component is preferably in the range of 0.5 to 5% by weight. The high molecular weight polymer constituting the toner binder resin of the present invention has a weight average molecular weight of 1 × 10
It is preferably in the range of ⁵ to 1 × 10 ⁶ . this is,
If the weight average molecular weight of the high molecular weight polymer is less than 1 × 10 ⁵ , the non-offset property decreases, and if it exceeds 1 × 10 ⁶ , the fixing property decreases. Further, the low molecular weight polymer preferably has a weight average molecular weight of 3 × 10 ³ to 8 × 10 ⁴ . This is because, if the weight average molecular weight of the low molecular weight polymer is less than 3 × 10 ³ , the mechanical strength of the resin is reduced, and the toner is excessively pulverized at the time of electrification, causing fog on the image. This is because if it exceeds 8 × 10 ⁴ , the fixability will decrease. Further, the ratio between the high molecular weight polymer component and the low molecular weight polymer component is not particularly limited, but the high molecular weight polymer component is
Those contained in the range of 0% by weight are preferred. This is because if the high molecular weight polymer component is less than 10% by weight, the non-offset property is poor, and if it exceeds 50% by weight, the fixing property is poor. [0014] In the binder resin for toner of the present invention is the image density stability is further improved by alkali treatment. Examples of the alkali compound used for the alkali treatment include hydroxides of alkali metals and alkaline earth metals such as lithium, sodium, potassium, magnesium and calcium. However, when an alkaline earth metal hydroxide is used, the carboxylic acid group in the resin is cross-linked with the metal, which may increase the softening temperature of the resin and cause poor fixing. It is preferable to use an object. Among them, potassium hydroxide and sodium hydroxide are particularly preferred. The alkali treatment is performed at a temperature equal to or higher than the glass transition temperature of the resin, preferably at a temperature equal to or higher than 90 ° C., and is preferably performed so that the pH of the waste liquid after the treatment becomes 7 or higher. this is,
If the treatment is performed at a temperature lower than the glass transition temperature of the resin, the effect of the alkali treatment may not be sufficiently exerted and may not contribute to the improvement of the image density stability. Similarly, when the pH of the waste liquid after the treatment is less than 7, This is because there is a case where a sufficient effect of improving the image density stability cannot be obtained. The binder resin for toner of the present invention can be produced, for example, by synthesizing a high molecular weight polymer by an emulsion polymerization method and synthesizing a low molecular weight polymer by a suspension polymerization method in the presence of the emulsion. In the present invention,
The method for producing the resin is not limited to this, and each of the synthesized high-molecular-weight polymer and low-molecular-weight polymer may be mixed and melt-kneaded with an extruder, a kneader, a mixer, or the like. It may be produced by a polymerization method such as a suspension polymerization method, a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, or a combination thereof. In the present invention, in order to adjust the molecular weight, α-methylstyrene dimer, n-dodecylmercaptan, 2-ethylhexyl thioglycolate,
-A chain transfer agent such as octyl mercaptan, an emulsifier, a dispersant, a dispersing aid, and an initiator in emulsion polymerization and suspension polymerization can be appropriately used. Hereinafter, the present invention will be described in detail with reference to examples. In Examples, the weight average molecular weight (Mw) is a value measured by gel permeation chromatography, and using tetrahydrofuran as a solvent, HC
It was measured according to L-8020 and determined in terms of polystyrene. The image density stability was measured by using a Macbeth densitometer to measure the change in image density by performing a running test of 50,000 sheets with a copier,
The change in image density of the tenth sheet was calculated according to the following equation 1. If this rate of change is within 5%, good image density stability is obtained. {(D ₁ −D ₅₀₀₀₀ ) / D ₁ } × 100 (1) (where D ₁ is the image density of the first sheet, and D _50,000 is the image density of the 50,000 sheet. Example 1 79% by weight of styrene and 20% by weight of n-butyl acrylate
And 1% by weight of methacrylic acid have a weight average molecular weight of 8 ×
167 parts by weight of 10 ⁵ high molecular weight polymer emulsion (solid content 15% by weight) were charged into a reaction vessel, and 100 parts by weight of water in which 0.7% by weight of partially saponified polyvinyl alcohol was dissolved under stirring was further added. 75 parts by weight of a mixed solution for low molecular weight polymer composed of 79% by weight of styrene, 20% by weight of n-butyl acrylate and 1% by weight of methacrylic acid and 7 parts by weight of benzoyl peroxide were added and uniformly dispersed at 85 ° C. For 12 hours. Next, 25 parts by weight of water in which 1.3% by weight of sodium hydroxide was dissolved were added, and alkali treatment was performed at 95 ° C. for 1 hour.
The pH of the waste liquid was 7 or more. Thereafter, it was sufficiently washed with water and dried to obtain a binder resin for toner. The weight average molecular weight of the obtained resin is shown in Table 1. 93% by weight of the obtained resin, 4% by weight of carbon black, 1% by weight of a negatively charged static control agent and 2% by weight of a polyolefin wax were mixed and melt-kneaded at 145 ° C. Thereafter, the mixture was pulverized using a jet mill pulverizer and classified to obtain a toner having an average particle diameter of 13 μm.
Table 1 shows the measurement results of the image density change of the obtained toner. Example 2 78% by weight of styrene, 20% by weight of n-butyl acrylate
And 2% by weight of methacrylic acid having a weight average molecular weight of 7.
8 × 10 ⁵ high molecular weight polymer emulsion (solid content 15
167 parts by weight), 100 parts by weight of water in which 0.7% by weight of partially saponified polyvinyl alcohol is dissolved, and 79% by weight of styrene and 20% by weight of n-butyl acrylate. % Of methacrylic acid and 1 part by weight of methacrylic acid, 75 parts by weight of a mixed solution for low molecular weight polymer and 7 parts by weight of benzoyl peroxide were charged and uniformly dispersed, and polymerized at 85 ° C. for 12 hours. Then, water 25 containing 1.3% by weight of sodium hydroxide was dissolved.
Parts by weight were charged, and alkali treatment was performed at 95 ° C. for 1 hour. The pH of the waste liquid was 7 or more. Thereafter, it was sufficiently washed with water and dried to obtain a binder resin for toner.
The weight average molecular weight of the obtained resin is shown in Table 1. 93% by weight of the obtained resin, 4% by weight of carbon black, 1% by weight of a negatively charged static control agent and 2% by weight of a polyolefin wax were mixed and melt-kneaded at 145 ° C. Thereafter, the mixture was pulverized using a jet mill pulverizer and classified to obtain a toner having an average particle diameter of 13 μm.
Table 1 shows the measurement results of the image density change of the obtained toner. Example 3 75% by weight of styrene, 20% by weight of n-butyl acrylate
And methacrylic acid having a weight average molecular weight of 7% by weight.
5 × 10 ⁵ high molecular weight polymer emulsion (solid content 15
167 parts by weight) into a reaction vessel, 100 parts by weight of water in which 0.7% by weight of partially saponified polyvinyl alcohol is dissolved under stirring, and 78% by weight of styrene and 20% by weight of n-butyl acrylate % And a mixture of 2% by weight of methacrylic acid and 75 parts by weight of a mixed solution for a low molecular weight polymer and 7 parts by weight of benzoyl peroxide were uniformly dispersed and polymerized at 85 ° C. for 12 hours. Then, water 25 containing 1.3% by weight of sodium hydroxide was dissolved.
Parts by weight were charged, and alkali treatment was performed at 95 ° C. for 1 hour. The pH of the waste liquid was 7 or more. Thereafter, it was sufficiently washed with water and dried to obtain a binder resin for toner.
The weight average molecular weight of the obtained resin is shown in Table 1. 93% by weight of the obtained resin, 4% by weight of carbon black, 1% by weight of a negatively charged static control agent and 2% by weight of a polyolefin wax were mixed and melt-kneaded at 145 ° C. Thereafter, the mixture was pulverized using a jet mill pulverizer and classified to obtain a toner having an average particle diameter of 13 μm.
Table 1 shows the measurement results of the image density change of the obtained toner. Comparative Example 4 79% by weight of styrene, 20% by weight of n-butyl acrylate
And 1% by weight of methacrylic acid have a weight average molecular weight of 8 ×
10 ⁵ of the high molecular weight polymer emulsion (solid content 15 wt%) 167 parts by weight were charged in a reaction vessel was charged with 100 parts by weight of water having dissolved therein 0.7 wt% partially saponified polyvinyl alcohol under stirring, further 75 parts by weight of a mixture for a low molecular weight polymer composed of 75% by weight of styrene, 20% by weight of n-butyl acrylate and 5% by weight of methacrylic acid and 7 parts by weight of benzoyl peroxide were charged and uniformly dispersed at 85 ° C. For 12 hours. Next, 25 parts by weight of water in which 1.3% by weight of sodium hydroxide was dissolved were added, and alkali treatment was performed at 95 ° C. for 1 hour.
The pH of the waste liquid was 7 or more. Thereafter, it was sufficiently washed with water and dried to obtain a binder resin for toner. The weight average molecular weight of the obtained resin is shown in Table 1. 93% by weight of the obtained resin, 4% by weight of carbon black, 1% by weight of a negatively charged static control agent and 2% by weight of a polyolefin wax were mixed and melt-kneaded at 145 ° C. Thereafter, the mixture was pulverized using a jet mill pulverizer and classified to obtain a toner having an average particle diameter of 13 μm.
Table 1 shows the measurement results of the image density change of the obtained toner. Comparative Example 1 80% by weight of styrene and 20% by weight of n-butyl acrylate
167 parts by weight of a high molecular weight polymer emulsion having a weight average molecular weight of 9.8 × 10 ⁵ (solid content 15% by weight) is charged into a reaction vessel, and 0.7% by weight of partially saponified polyvinyl alcohol is dissolved under stirring. 100 parts by weight of the obtained water, 75 parts by weight of a low-molecular-weight polymer mixture comprising 78% by weight of styrene, 20% by weight of n-butyl acrylate and 2% by weight of methacrylic acid, and 7 parts by weight of benzoyl peroxide. And dispersed uniformly, 85
Polymerization was performed at 12 ° C. for 12 hours. Next, 25 parts by weight of water in which 1.3% by weight of sodium hydroxide were dissolved were added, and
For one hour. The pH of the waste liquid was 7 or more. Thereafter, it was sufficiently washed with water and dried to obtain a binder resin for toner. The weight average molecular weight of the obtained resin is shown in Table 1. 93% by weight of the obtained resin, 4% by weight of carbon black, 1% by weight of a negatively charged static control agent and 2% by weight of a polyolefin wax were mixed and melt-kneaded at 145 ° C. Thereafter, the mixture was pulverized using a jet mill pulverizer and classified to obtain a toner having an average particle diameter of 13 μm.
Table 1 shows the measurement results of the image density change of the obtained toner. Comparative Example 2 78% by weight of styrene, 20% by weight of n-butyl acrylate
And 2% by weight of methacrylic acid having a weight average molecular weight of 7.
8 × 10 ⁵ high molecular weight polymer emulsion (solid content 15
167 parts by weight) into a reaction vessel, 100 parts by weight of water containing 0.7% by weight of partially saponified polyvinyl alcohol dissolved therein under stirring, and further 80% by weight of styrene and 20% by weight of n-butyl acrylate. % Of a mixture for low-molecular-weight polymer and 7 parts by weight of benzoyl peroxide, and the mixture was uniformly dispersed and polymerized at 85 ° C. for 12 hours. Then, sodium hydroxide 1.
25 parts by weight of water in which 3% by weight is dissolved are added.
Alkaline treatment was performed for hours. The pH of the waste liquid was 7 or more. Thereafter, it was sufficiently washed with water and dried to obtain a binder resin for toner. The weight average molecular weight of the obtained resin is shown in Table 1. 93% by weight of the obtained resin, 4% by weight of carbon black, 1% by weight of a negatively charged static control agent and 2% by weight of a polyolefin wax were mixed and melt-kneaded at 145 ° C. Thereafter, the mixture was pulverized using a jet mill pulverizer and classified to obtain a toner having an average particle diameter of 13 μm.
Table 1 shows the measurement results of the image density change of the obtained toner. Comparative Example 3 80% by weight of styrene and 20% by weight of n-butyl acrylate
167 parts by weight of a high molecular weight polymer emulsion having a weight average molecular weight of 9.8 × 10 ⁵ (solid content 15% by weight) is charged into a reaction vessel, and 0.7% by weight of partially saponified polyvinyl alcohol is dissolved under stirring. 100 parts by weight of the obtained water, and a mixed solution 75 for a low molecular weight polymer composed of 80% by weight of styrene and 20% by weight of n-butyl acrylate.
Parts by weight and 7 parts by weight of benzoyl peroxide were charged and uniformly dispersed, and polymerized at 85 ° C. for 12 hours.
Next, water 2 containing 1.3% by weight of sodium hydroxide was dissolved.
5 parts by weight were charged, and alkali treatment was performed at 95 ° C. for 1 hour. The pH of the waste liquid was 7 or more. Thereafter, it was sufficiently washed with water and dried to obtain a binder resin for toner.
The weight average molecular weight of the obtained resin is shown in Table 1. 93% by weight of the obtained resin, 4% by weight of carbon black, 1% by weight of a negatively charged static control agent and 2% by weight of a polyolefin wax were mixed and melt-kneaded at 145 ° C. Thereafter, the mixture was pulverized using a jet mill pulverizer and classified to obtain a toner having an average particle diameter of 13 μm.
Table 1 shows the measurement results of the image density change of the obtained toner. As is evident from Table 1, all of the toners of Examples 1 to 3 using the binder resin of the present invention exhibited excellent image density stability with an image density change rate of less than 3.5 %. . On the other hand, in the toner of Comparative Example 3 using the binder resin containing no carboxylic acid component , the image density change rate exceeds 50%, and only one of the high molecular weight polymer and the low molecular weight polymer has carboxylic acid. In the toners of Comparative Examples 1 and 2 using the binder resin containing the components , the image density change rate exceeds 10%,
The content of the carboxylic acid component contained in the high molecular weight polymer is
From the content of the carboxylic acid component contained in the low molecular weight polymer
Comparative Example 4 using less binder resin
Indicates that the image density change rate is 7.3%, and none of the toners shows sufficient image density stability. [Table 1] The symbols of the compositions shown in Table 1 indicate the following compounds, respectively. St: styrene n-BA: n-butyl acrylate MAA: BPO methacrylate: benzoyl peroxide The binder resin for a toner according to the present invention is composed of a high molecular weight polymer and a low molecular weight polymer. By containing a carboxylic acid component, respectively, it is possible to provide a toner excellent in fixing property and non-offset property of the toner and excellent in image density stability with little change in image density even when copying many sheets.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-235069 (JP, A) JP-A-62-29356 (JP, A) JP-A-3-113463 (JP, A) JP-A-3-3 288158 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 9/00-9/087

Claims (1)

(57) Claims 1. A styrene-acrylic resin comprising a high molecular weight polymer component and a low molecular weight polymer component, wherein the high molecular weight polymer and the low molecular weight polymer are carboxylic acid components. And the calories contained in the high molecular weight polymer.
Bonic acid component content (W _H ) and low molecular weight polymer
The content (W _L ) of the carboxylic acid component is W _H ≧ W _L
And a binder resin for toner that has been subjected to an alkali treatment .