JPH0113098B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a powder toner used for electrophotographic development. Electrophotography uses selenium,
An electrical latent image is formed on a photoreceptor made of a photoconductive material such as zinc oxide or cadmium sulfide, and this is developed with a powder developer and transferred to paper, sheet, etc., followed by heating and solvent treatment. It is fixed by pressure, etc. Such a powder developer consists of a powder toner, iron powder called a carrier, and glass beads, and the powder toner is generally made by dispersing a coloring agent in a binder resin and pulverizing it. Traditionally, the so-called oven fixing method, in which the powder toner transferred to paper or sheet is melted and fixed in an oven, was the mainstream, but in recent years, from the standpoint of increasing copying speed and saving energy, a method of fixing using a heated roll has been adopted. is becoming mainstream. In the conventional oven fixing method, it is necessary to melt quickly in the oven, so a resin in the molecular weight range called oligomer with a molecular weight of 10,000 or less is used as the binder resin for powder toner. be done. However, in the method of fixing with a heated roll, powder toner that uses oligomers as a binder suffers from significant offset during roll fixing.
This results in staining of the roll, making it unusable for practical use. In order to prevent offset, release liquid such as silicone oil is applied to the roll, but
Uniform application is mechanically difficult, and it is difficult to completely prevent stains on copy paper. In order to prevent offset from the viewpoint of the binder resin, it is effective to increase the molecular weight of the resin, and in the case of polystyrene, which is often used as a binder resin,
If the average molecular weight is 50,000 or more, preferably 100,000 or more, it will not be offset at all by a hot roll made of silicone, Teflon, or the like. However, powder toner using a high molecular weight binder resin has the disadvantage that its fixability to paper is extremely weak, and the fixed image easily peels off due to bending or friction. An object of the present invention is to provide a new powder toner that solves the problems that occur in fixing systems using heated rolls. That is, the present invention relates to a powder toner that has excellent fixing properties to paper at relatively low temperatures and is suitable for a heated roll fixing system that does not offset up to considerably high temperatures. The feature of the present invention is that at least 50% by weight of aromatic vinyl is contained in 2 to 50 parts by weight of polyester with a molecular weight of 500 to 10,000 containing 0.2 to 10% by weight of aliphatic unsaturated dibasic acid as a binder resin for powder toner. One or more vinyl monomers containing 98 to 50
The purpose is to use a graft polymer having a molecular weight of 50,000 or less obtained by graft polymerizing parts by weight. Balancing the offset property and the fixability to paper is the most technical point in the binder resin for heat roll toner. A method of adding a mold release agent such as paraffin to the polymer has been proposed. The present inventors have discovered that a polymer obtained by grafting a vinyl monomer onto an unsaturated polyester has a relatively low molecular weight (50,000 or less), has extremely excellent offset properties, and does not impair the fixability to paper. completed the invention. Furthermore, the binder resin of the present invention is also characterized by good negative chargeability. The acid polyester, which is the first component of the graft polymer of the present invention, is obtained by polycondensation of a dibasic acid and a glycol, and must contain 0.2 to 10% by weight of an aliphatic dibasic acid as an essential component. Typical examples of these aliphatic dibasic acids are maleic acid, maleic anhydride, fumaric acid, itaconic acid,
Examples include citraconic acid. The remaining dibasic acid components include aromatic dibasic acids such as phthalic anhydride, phthalic acid, isophthalic acid, terephthalic acid, hexahydrophthalic anhydride, and tetrahydrophthalic anhydride, malonic acid, succinic acid, glutaric acid, adipic acid, Examples include aliphatic dibasic acids such as azelaic acid and sebacic acid. Next, as glycol components, ethylene glycol, 1,2-propylene glycol, 1,3-
Butylene glycol, 1,4-butylene glycol, 1,6-hexanediol, neobentyl glycol, 3,3,5-trimethyl, 2,4-pentanediol, dipropylene glycol, dipropylene glycol, and hydrogenated bisphenol A, bisphenol A propylene oxide adduct, bisphenol A ethylene oxide adduct, and the like. In addition to these components, trifunctional compounds such as trimellitic anhydride, glycerin, trimethylolethane, and trimethylolpropane may also be used in combination as long as the polyester does not gel. Furthermore, monofunctional compounds such as benzoic acid, paratertiary butylbenzoic acid, and cyclohexanol can also be used as appropriate as molecular weight regulators. It is suitable for the molecular weight of polyester to be in the range of 500 to 10,000, but if the molecular weight exceeds 10,000 and becomes too large, it will tend to gel during graft polymerization.
A suitable graft polymer cannot be obtained. The content of aliphatic unsaturated dibasic acid, which is an important component in the sense that it serves as a graft active site during graft polymerization and introduces a partially crosslinked structure into the graft polymer, is If it is less than 0.2% by weight, it becomes difficult to carry out graft polymerization, and if it is more than 10% by weight, gelation tends to occur during graft polymerization. The preferred content varies depending on the molecular weight of the polyester, but the optimal content is 0.5 to 7% by weight, and the optimal component is maleic anhydride. The polyesterification reaction is carried out by a conventional method at an OH excess of 0 to 10% in an inert gas stream without a solvent or in the presence of a solvent at a temperature of 150 to 250°C. The reaction is tracked by measuring the acid value and hydroxyl value, and the molecular weight is calculated from both, and the reaction is terminated when the desired molecular weight is obtained. A graft polymer is obtained by graft polymerizing a polymerizable monomer to the polyester thus obtained. Examples of the aromatic vinyl which is an essential component of the polymerizable monomer include styrene, vinyltoluene, α-methylstyrene, orthochlorostyrene, and styrene is most suitable. Other polymerizable monomers used in combination with these include:
Examples include methyl methacrylate, ethyl methacrylate, butyl methacrylate, methyl acrylate, and dibutyl fumarate. For graft modification of polyester, 98 to 50 parts by weight of the above polymerizable monomer is used for 2 to 50 parts by weight of polyester;
Parts by weight are preferred. The graft reaction can be suitably produced by solution polymerization or suspension polymerization. In the former method, a polymerizable monomer and a polymerization initiator are added to a solution of polyester in a solvent such as xylene or toluene, and the mixture is dissolved in a stream of inert gas.
The reaction is continued at a temperature of 60 to 150°C until the polymerization rate substantially reaches 90% or more. In this case, a polymerization component or a catalyst may be added dropwise to the polyester resin solution. Preferred polymerization catalysts include benzoyl peroxide, lauroyl peroxide, and t-butyl perbenzoate. Furthermore, a chain transfer agent such as dodecylmercabutane or thiophenol can also be used for the purpose of adjusting the molecular weight of the graft polymer. The desired toner can be obtained by melt-kneading the thus obtained graft polymer and a coloring pigment such as carbon black in a conventional manner, and after cooling, pulverizing the mixture using a hammer mill, jet mill, etc. EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples. Example 1 Isophthalic acid was added to a four-necked flask equipped with a stirrer, condenser, inert gas inlet tube, and thermometer.
1660g, maleic anhydride 49g, bisphenol A
3,793 g of 2 mole adduct of propylene oxide of
15mgKOH/g, hydroxyl value 35mgKOH/g molecular weight approx.
2200 unsaturated polyester was obtained. 50 g of this polyester was dissolved in 450 g of styrene to form a solution. Charge 1000g of pure water and 0.5g of polyvinyl alcohol into a reaction vessel equipped with a stirrer, thermometer, condenser, and nitrogen gas blowing tube, raise the temperature to 70℃, and then add 500g of the styrene solution of the above polyester and azobisisobutyronitrile. 0.25g was added dropwise over 1 hour. After reaction at 70°C for 1 hour, the temperature was raised to 80°C in 30 minutes, and the reaction was completed in 10 hours. After removing the suspending agent by washing with water, a dry granular graft polymer was obtained. The number average molecular weight of this polymer by GPC was 23,500, and the softening point by the ring and ball method was 140°C. 90 parts by weight of this polymer and 10 parts by weight of carbon black ("Morgan A" manufactured by CABOT) were melt-kneaded at 180°C, cooled and solidified, and then finely pulverized with a jet mill to obtain powder toner A with an average particle size of 10 microns. . Example 2 In the same manner as in Example 1, from 125 g of unsaturated polyester obtained in Example 1 and 375 g of styrene,
A graft polymer was obtained with a number average molecular weight of 19,500 by GPC and a softening point of 154°C by the ring and ball method. 90 parts by weight of the obtained polymer and 10 parts by weight of carbon black (Morgan A) were melt-kneaded at 190°C, cooled and solidified, and then finely pulverized with a jet mill to obtain powder toner B having an average particle size of 10 microns. Example 3 A polymerizable solution consisting of 50 g of the unsaturated polyester obtained in Example 1, 400 g of styrene, and 50 g of butyl acrylate was prepared. The number average molecular weight was determined by the same polymerization method as in Example 1.
A graft polymer with a softening point of 128°C was obtained by the 20400 ring and ball method. Powder toner C having an average particle size of 10 microns was obtained in the same manner as in Example 1. Example 4 A four-necked flask equipped with a stirrer, condenser, inert gas inlet tube, and thermometer was charged with 1660 g of terephthalic acid, 1144 g of 2,2-dimethyl-1,3-propanediol, and 14 g of dibutyltin oxide. The temperature was raised from 150° to 240°C over 6 hours in a nitrogen stream, and after further reaction at 240°C for 6 hours, the temperature was raised to 180°C.
30g of maleic anhydride was added and reacted at 180°C for 1 hour to give an acid value of 18mgKOH/g and a hydroxyl value of 43.
An unsaturated polyester of mgKOH/g was obtained. A flask equipped with a stirrer, a condenser, an inert gas inlet tube, and a thermometer was charged with 350 g of the above unsaturated polyester, 650 g of styrene, 500 g of toluene, and 500 g of butyl acetate. At the same time, 5 g of benzoyl peroxide was added and dissolved, followed by a nitrogen stream. Raise the temperature to 90℃ in the middle, hold it for 1 hour, then raise it to 100℃.
After 15 hours of reaction, 1 g of hydroquinone was added and distillation of toluene and butyl acetate was started under reduced pressure.
The temperature is raised to 200°C to complete distillation. The obtained polymer had a molecular weight of 10,300 and a ring and ball softening point of 118°C. Powder toner D was obtained from this polymer in the same manner as in the example. Example 5 A polymer having a molecular weight of 12,300 and a ring and ball softening point of 105° C. was obtained under the same polymerization conditions as in Example 4 from 100 g of the unsaturated polyester obtained in Example 4, 800 g of styrene, and 100 g of butyl acrylate. Powder toner E having an average particle size of 10 microns was obtained from 70 parts by weight of this polymer, 20 parts by weight of a commercially available polystyrene homopolymer having a molecular weight of 48,000, and 10 parts by weight of carbon black (Morgan A). Comparative Example 1 90 parts by weight of a commercially available polystyrene homopolymer with a molecular weight of 48,000 and a ring and ball softening point of 190°C and 10 parts by weight of carbon black (Morgan A) were melt-kneaded at 250°C.
After cooling, it was finely pulverized with a jet mill to obtain a powder toner with an average particle size of 10 microns. Comparative Example 2 90 parts of a commercially available polystyrene homopolymer with a molecular weight of 25,000 and a ring and ball softening point of 160°C and 10 parts by weight of carbon black (Morgan A) were melt-kneaded at 180°C, cooled, and pulverized with a jet mill to obtain an average particle size of 10 microns. Powder Tonaro was obtained. Comparative Example 3 A powder toner was obtained in the same manner as in Comparative Example 2 from 90 parts by weight of a commercially available polystyrene homopolymer having a molecular weight of 4000 and a ring and ball softening point of 125° C. and 10 parts by weight of carbon black (Morgan A). Comparative Example 4 60 parts by weight of a commercially available polystyrene homopolymer with a molecular weight of 48,000 and a ring and ball softening point of 190°C and 30 parts by weight of a polystyrene homopolymer with a molecular weight of 4,000 and a ring and ball softening point of 125°C.
A powdered toner was obtained from 10 parts by weight of carbon black (Morgan A) in the same manner as in Comparative Example A. Comparative Example 5 Terephthalic acid was placed in a four-necked flask equipped with a stirrer, condenser, nitrogen gas inlet tube, and thermometer.
166 g, 2,2-dimethyl-1,3-propanediol 208 g dibutyltin oxide 1.5 g and sodium acetate 0.1 g were charged, and nitrogen gas was blown into the reactor.
The reaction was carried out at ℃, and when the acid value reached 3 mgKOH/g or less, an additional 130 g of terephthalic acid was added to the reaction.
The reaction was further continued at a reaction temperature of 250℃, and the acid value was 5.1mg.
KOH/g, hydroxyl value 10.3mgKOH/g, softening point
A polyester at 140°C was obtained. A toner was obtained in the same manner as in Example 1. Comparative Example 6 The same method as in Comparative Example 1 was prepared from 60 parts by weight of a commercially available polystyrene homopolymer with a molecular weight of 48,000 and a ring and ball softening point of 190°C, 30 parts by weight of the polyester obtained in Comparative Example 5, and 10 parts by weight of carbon black (Morgan A). A powder toner was obtained by the method. Test Examples The toners obtained in the above Examples and Comparative Examples were subjected to the following tests. The results are shown in Table-1. (1) Offset property: As shown in Fig. 1, an electrophotographic copy paper 2 is placed on a heat plate (koffler hot bench) 1 having a thermal gradient, and then a toner 3 is sprinkled on it and heated to form a toner. The temperature at which the film was fixed on the paper was measured using a surface thermometer and was defined as the fixing temperature. Furthermore, the temperature of the heat plate is set to the lowest fixing temperature, and the temperature difference is approximately
After heating the temperature to 120℃, place several pieces of 1mm thick silicone rubber (TC tape, manufactured by Shin-Etsu Chemical Co., Ltd.) 4 with 100g weights 5 on them at equal intervals, leave it for 3 minutes, and then peel off the silicone rubber to remove the toner from the copy paper. The temperature at which the film no longer peels off was measured and was defined as the offset temperature. (2) Fragility: Evaluated based on the degree of coarse particle contamination after crushing. (3) Blocking resistance: 3 g of toner with an average size of 10 microns was collected in a hard glass viscosity tube, sealed, heated in an oven at 50° C. for 24 hours, and then the degree of aggregation was checked. (4) Charge amount: Measured by blow-off method. The heated roll fixing type electrophotographic toners of Examples 1 to 5 based on the present invention exhibited a fixing temperature of about 100°C, and also had a very high offset temperature, which could not be obtained in Comparative Examples 1 to 5. It exhibited good offset properties. Furthermore, it has excellent fixability to paper, and as for the crushability, although Toner A is somewhat hard, this problem could be solved by copolymerizing a soft component like Toner E. In addition, the amount of charge by the blow-off method is clearly better than that of polystyrene toner, and furthermore, the powder toner composition can be adjusted in both N polarity and P polarity by changing the copolymer composition. It is a thing.

[Table] Moderate.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the state when examining the offset property of toner for electrophotography, in which copy paper 2 is placed on a heat plate 1, toner 3 is placed on top of it, and
Furthermore, a 1 mm thick silicone rubber 4 on which a 100 g weight 5 is placed is placed.

Claims (1)

[Claims] 1 0.2 aliphatic unsaturated dibasic acids as essential components
By graft polymerizing 98 to 50 parts by weight of one or more vinyl monomers containing at least 50% by weight of aromatic vinyl to 2 to 50 parts by weight of a polyester with a molecular weight of 500 to 10,000 containing ~10% by weight. An electrophotographic toner composition for heating roll fixing, characterized in that the obtained graft polymer is used as a binder resin.