JP4116534B2 - Magnetic toner - Google Patents

Description

  The present invention relates to a magnetic toner used for developing a latent image formed in electrophotography, electrostatic recording method, electrostatic printing method and the like.

  In recent years, in order to cope with downsizing of devices and higher printing speeds, polyester with excellent low-temperature fixability is the main component of the binder resin, and from the standpoint of compensating for its offset resistance, a magnetic material containing wax. Many one-component toners are used. However, magnetic powder has low dispersibility with respect to polyester and wax, and toner with a non-uniform dispersion state of magnetic powder tends to have insufficient charging stability in a one-component development system in which charging is performed by a single friction with a blade or the like.

Therefore, in order to solve such a problem, for example, a toner containing magnetic powder having a hydroxyl group specific polyester and carbon black adsorbed on the surface (see Patent Document 1), a toner containing magnetic fine particles with a titanate coupling agent (See Patent Document 2) and the like are known, but further improvement is desired.
JP 2001-296689 A (Claim 1) Japanese Patent Laid-Open No. 4-124681 (Claims 1 and 2)

  An object of the present invention is to provide a magnetic toner having good charging stability and excellent offset resistance.

  The present invention is a magnetic toner comprising a binder resin, wax and magnetic powder, wherein the binder resin is a monovalent aliphatic carboxylic acid compound having 10 to 24 carbon atoms and 1 having 10 to 24 carbon atoms. The present invention relates to a magnetic toner comprising a polyester resin having as a structural unit at least one monovalent aliphatic compound selected from the group consisting of divalent aliphatic alcohols.

  Since the magnetic toner of the present invention contains wax and the magnetic powder is uniformly dispersed in the toner, it has an effect that it is excellent in both charging stability and offset resistance.

  The magnetic toner of the present invention contains a binder resin containing a polyester resin having a monovalent aliphatic compound having 10 to 24 carbon atoms as a structural unit, a wax, and magnetic powder. In the present invention, since a long-chain alkyl group of a monovalent aliphatic compound is introduced at the terminal of the polyester resin contained as the binder resin, the dispersibility of the wax is improved, so that the magnetic powder can be made uniform. As a result, both offset resistance and charging stability are achieved.

  The monovalent aliphatic compound is at least one selected from the group consisting of a monovalent aliphatic carboxylic acid compound having 10 to 24 carbon atoms and a monovalent aliphatic alcohol having 10 to 24 carbon atoms.

  As the aliphatic compound, an aliphatic carboxylic acid compound is preferable, and the aliphatic compound may have either a straight chain structure or a branched chain structure, but in order to further enhance the desired effect of the present invention. It preferably has a linear structure, and the carbon number thereof is preferably 12-18. Therefore, in the present invention, as the monovalent aliphatic compound, an aliphatic carboxylic acid compound having 12 to 18 carbon atoms is more preferable, and an aliphatic carboxylic acid compound having a linear structure having 12 to 18 carbon atoms is more preferable.

  Examples of the monovalent aliphatic carboxylic acid compound having 10 to 24 carbon atoms include decanoic acid, undecanoic acid, lauric acid, palmitic acid, stearic acid, oleic acid, behenic acid, anhydrides and alkyls of these acids (carbon number 1 -3) Esters may be mentioned, and these may be used alone or in admixture of two or more, and among these, stearic acid is preferred from the viewpoint of the effect of the present invention. The content of stearic acid is preferably 50% by weight or more, more preferably 80 to 100% by weight, and particularly preferably 100% by weight in the aliphatic carboxylic acid compound. When the aliphatic carboxylic acid compound is an alkyl ester of an aliphatic carboxylic acid, the carbon number of the alkyl group in the alkyl ester portion is not included in the above carbon number.

  Examples of the monovalent aliphatic alcohol having 10 to 24 carbon atoms include 1-dodecanol, pentadecanol, hexadecanol, octadecanol (stearyl alcohol) and the like.

  The polyester resin has the monovalent aliphatic compound in all the structural units, preferably 0.1 to 20 mol%, more preferably 0.5 to 10 mol%, and still more preferably 1 to 5 mol%. It is desirable that In the present invention, the proportion of the structural unit can be determined from the content in all the monomers when the polyester is completely hydrolyzed. It is equal to the content obtained from

  As the monomer, a polyhydric alcohol component composed of a divalent or higher alcohol and a polyvalent carboxylic acid component composed of a divalent or higher carboxylic acid compound are further used.

  Examples of the divalent alcohol include polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane and polyoxyethylene (2.2) -2,2-bis (4-hydroxyphenyl) propane. Formula (I):

(Wherein R is an alkylene group having 2 or 3 carbon atoms, x and y are positive numbers, and the sum of x and y is 1 to 16, preferably 1.5 to 5.0)
An alkylene oxide adduct of bisphenol A represented by: ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, neopentyl glycol, polyethylene glycol, polypropylene glycol, hydrogenated bisphenol A and the like.

  Examples of the trihydric or higher polyhydric alcohol include sorbitol, pentaerythritol, glycerin, trimethylolpropane and the like.

  From the viewpoint of charge retention, the alcohol component is preferably an alkylene oxide adduct of bisphenol A represented by the formula (I), preferably 50 mol% or more, more preferably 80 to 100 mol%, still more preferably 100 mol. % Content is preferable.

  Divalent carboxylic acid compounds include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid; oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, Aliphatic dicarboxylic acids such as succinic acid substituted with alkyl groups having 1 to 20 carbon atoms or alkenyl groups having 2 to 20 carbon atoms such as adipic acid, dodecenyl succinic acid, octyl succinic acid; anhydrides of these acids and their Examples thereof include alkyl (C1-C3) esters of acids. Of these, aromatic dicarboxylic acid compounds are preferred from the viewpoint of charge retention.

  The content of the aromatic dicarboxylic acid compound is preferably 50 to 100 mol%, more preferably 80 to 100 mol% in the divalent carboxylic acid component.

  Examples of the trivalent or higher polyvalent carboxylic acid compound include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, pyromellitic acid and acid anhydrides thereof, and lower alkyl. (C1-C3) ester etc. are mentioned.

  The content of the trihydric or higher polyhydric alcohol and / or polyhydric carboxylic acid compound, preferably the polyhydric carboxylic acid compound, is preferably 15 mol% or less in all monomers.

The polyester is obtained, for example, by subjecting a monomer mixture comprising an alcohol component and a carboxylic acid component to a condensation polymerization at 150 to 280 ° C. in an inert gas atmosphere, if necessary, in the presence of an esterification catalyst. The monovalent aliphatic compound may be added to the reaction system from the beginning of polymerization or may be added during the reaction. Furthermore, after performing the condensation polymerization of monomers other than the monovalent aliphatic compound, the monovalent aliphatic compound may be added and the reaction may be continued.
By the above reaction, a polyester having a monovalent aliphatic compound at the molecular end is obtained.

  The polyester resin in the present invention includes not only polyester but also its modified resin. Examples of the polyester-modified resin include urethane-modified polyester in which polyester is modified with a urethane bond, epoxy-modified polyester in which polyester is modified with an epoxy bond, and a hybrid resin having two or more resin components including a polyester component. It is done. As the hybrid resin, for example, a resin in which a polyester described in JP-A-7-98517 and an addition polymerization resin such as a vinyl polymerization resin are partially chemically bonded is preferable, and two or more kinds of resins are obtained as raw materials. In order to obtain a hybrid resin efficiently, two or more kinds of resins may be used. Those obtained from a mixture of raw material monomers are preferred.

  The polyester and its modified resin may be either one or both may be used together, but it is preferable that the polyester is contained rather than the modified resin.

  The binder resin may further contain a polyester resin other than the polyester resin obtained using the monovalent aliphatic compound, a styrene-acrylic resin, an epoxy resin, a polycarbonate, a polyurethane, and the like. The total content of the polyester resin is preferably 30 to 100% by weight, more preferably 80 to 100% by weight, and particularly preferably 100% by weight of the polyester resin obtained by using the monovalent aliphatic compound. The content is preferably 30 to 100% by weight, more preferably 70 to 100% by weight, and particularly preferably 100% by weight in the total amount of the polyester resin.

  The softening point of the polyester resin is preferably 80 to 165 ° C, more preferably 95 to 155 ° C, and the glass transition point is preferably 50 to 85 ° C.

  From the viewpoint of obtaining a wider fixing area, it is preferable that resins having different softening points are used in combination. The softening point of the resin having the higher softening point (high softening point resin) is preferably 130 to 160 ° C., more preferably 140 to 150 ° C., and the softening of the resin having the lower softening point (low softening point resin). A point becomes like this. Preferably it is 80-120 degreeC, More preferably, it is 90-110 degreeC. The high softening point resin / low softening point resin (weight ratio) is preferably 10/90 to 90/10, more preferably 30/70 to 70/30. The high softening point resin is preferably a polyester-based resin obtained using the monovalent aliphatic compound.

  As waxes, polyolefin waxes such as polypropylene wax, polyethylene wax, and polypropylene polyethylene copolymer wax, carnauba wax, ester waxes such as haze wax, beeswax, whale wax, and montan wax, and amides such as fatty acid amide waxes Wax etc. are mentioned, Among these, polyolefin wax is preferred. Normally, polyolefin waxes have high hardness and high durability, but have a large SP (solubility parameter) value difference from polyester and low dispersibility with respect to polyester. However, in the present invention, even such a polyolefin wax is well dispersed in the polyester.

  The content of the polyolefin wax is preferably 50% by weight or more, more preferably 80 to 100% by weight, and particularly preferably 100% by weight in the total amount of the wax.

  The melting point of the wax is preferably 60 to 120 ° C, more preferably 100 to 120 ° C, from the viewpoint of offset resistance and durability.

  The content of the wax is preferably 0.5 to 20 parts by weight and more preferably 2 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

Magnetic powder includes ferromagnetic materials such as cobalt, iron and nickel, alloys of metals such as cobalt, iron, nickel, aluminum, lead, magnesium, zinc and manganese, Fe ₃ O ₄ , γ-Fe ₃ O ₄ , cobalt Examples thereof include metal oxides such as added iron oxide, various ferrites such as Mn—Zn ferrite and Ni—Zn ferrite, magnetite and hematite. Furthermore, those surfaces may be treated with a surface treatment agent such as a silane coupling agent or a titanate silane coupling agent, or may be polymer-coated.

  The primary average particle diameter of the magnetic powder is preferably 0.05 to 0.5 μm, more preferably 0.1 to 0.3 μm from the viewpoint of dispersibility.

  The content of magnetic powder is preferably binder resin / magnetic powder (weight ratio), preferably 80/20 to 30/70, more preferably 50/50 to 70/30.

  The toner of the present invention further includes a charge control agent, a colorant, a conductivity modifier, an extender pigment, a reinforcing filler such as a fibrous substance, an antioxidant, an anti-aging agent, a fluidity improver, and a cleaning property improver. Such additives may be appropriately contained.

  Charge control agents include nigrosine dyes, triphenylmethane dyes containing tertiary amines as side chains, quaternary ammonium salt compounds, polyamine resins, imidazole derivatives and other positively chargeable charge control agents and metal-containing azo dyes, copper Examples include negatively chargeable charge control agents such as phthalocyanine dyes, metal complexes of alkyl derivatives of salicylic acid, and boron complexes of benzylic acid.

  As the colorant, the magnetic powder can be used as a colorant, but all of the dyes and pigments used as toner colorants can also be used. Carbon black, phthalocyanine blue, permanent brown FG , Brilliant First Scarlet, Pigment Green B, Rhodamine-B Base, Solvent Red 49, Solvent Red 146, Solvent Blue 35, Quinacridone, Carmine 6B, Disazo Yellow, etc. These may be used alone or in combination of two or more. The toner of the present invention may be any of black toner, color toner, and full color toner. The content of these coloring agents such as dyes and pigments is preferably 1 to 40 parts by weight and more preferably 3 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  The method for producing the magnetic toner of the present invention may be any conventionally known method such as a kneading pulverization method, a phase inversion emulsification method, an emulsion dispersion method, a suspension polymerization method, etc. A kneading and pulverizing method is preferred. For example, in the case of pulverized toner by the kneading and pulverizing method, binder resin, wax, magnetic powder, etc. are uniformly mixed with a mixer such as a Henschel mixer and then melt-kneaded with a closed kneader or a single or twin screw extruder. Then, it can be manufactured by cooling, pulverizing and classifying. The weight average particle diameter of the toner is preferably 3 to 15 μm.

  Since the magnetic toner of the present invention is excellent in charging stability of the toner itself, the magnetic toner of the present invention is used as a magnetic one-component developing toner rather than a two-component developing toner capable of adjusting the chargeability by a carrier. The effect of is exhibited more remarkably.

[Softening point of resin (Tm)]
Using a Koka type flow tester (manufactured by Shimadzu Corporation, CFT-500), a 1 g sample was heated at a heating rate of 6 ° C./min, a load of 1.96 MPa was applied by a plunger, a diameter of 1 mm, A nozzle with a length of 1 mm is pushed out, and this draws a plunger drop amount (flow value) -temperature curve of the flow tester. When the height of the S-shaped curve is h, the temperature corresponding to h / 2 (resin The temperature at which half of the effluent flowed out) is taken as the softening point.

[Glass transition point (Tg) of resin and melting point of wax]
Using a differential scanning calorimeter (Seiko Denshi Kogyo Co., Ltd., DSC210), the temperature was raised to 200 ° C., and the sample cooled from that temperature to 0 ° C. at a temperature lowering rate of 10 ° C./min was measured at a temperature rising rate of 10 ° C./min. When a wax is used as a sample, the maximum peak temperature is taken as the melting point. When a resin is used as a sample, the glass transition point is defined as the temperature at the intersection of the base line extension below the maximum peak temperature and the tangent showing the maximum slope from the peak rising portion to the peak apex.

Example of resin production The raw material monomer shown in Table 1 and 4 g of dibutyltin oxide were placed in a 5-liter four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer, and a thermocouple, and reacted at 230 ° C for 12 hours. I let you. Furthermore, it was made to react until it obtained the predetermined softening point at 8.3 kPa, and resin AD was obtained.

Examples 1 to 4, Comparative Examples 1 and 2
Binder resin and wax shown in Table 2, magnetic powder “MTS106HD” (manufactured by Toda Kogyo Co., Ltd.) 66 parts by weight, charge control agent “T-77” (manufactured by Hodogaya Chemical Co., Ltd.) 0.5 part by weight in a Henschel mixer After thorough mixing, the mixture was melt kneaded using a co-rotating twin screw extruder having a total length of 1560 mm, a screw diameter of 42 mm, and a barrel inner diameter of 43 mm. The heating temperature in the roll was 140 ° C., the roll rotation speed was 150 rotations / minute, the mixture supply speed was 20 kg / hour, and the average residence time was about 18 seconds.
The obtained kneaded material was rolled with a cooling roller, mechanically pulverized, and classified to obtain a powder having a weight average particle diameter of 6 μm.

  To 100 parts by weight of the obtained powder, 2 parts by weight of hydrophobic silica “R-972” (manufactured by Nippon Aerosil Co., Ltd.) and strontium titanate “ST” (manufactured by Fuji Titanium, primary average particle size: 0) .97 μm) 1 part by weight was added and mixed with a Henschel mixer to obtain a magnetic toner.

Test example 1
A magnetic one-component developing device “Laser Jet 4200” (manufactured by HP) was loaded with 250 g of magnetic toner to obtain an unfixed image (2 cm × 12 cm) with a toner adhesion amount of 0.6 mg / cm ² .
The obtained unfixed image was converted to 100 using a fixing machine (fixing speed: 200 mm / sec) improved so that the fixing machine of the copying machine “AR-505” (manufactured by Sharp Corporation) can be fixed off-line. The fixing test was performed while gradually increasing from 10 ° C. to 240 ° C. by 10 ° C., and the occurrence of offset was visually observed, and the offset resistance was evaluated according to the following evaluation criteria. The paper used for the fixing test is “CopyBond SF-70NA” (manufactured by Sharp Corporation, 75 g / m ² ). The results are shown in Table 2.

〔Evaluation criteria〕
Non-offset region is ◎: 60 ° C or higher ○: 20 ° C or higher and lower than 60 ° C △: 10 ° C or higher and lower than 20 ° C ×: Not observed

Test example 2
250 g of magnetic toner was mounted on a magnetic one-component developing device “Laser Jet 4200” (manufactured by HP), and 500 images with a printing rate of 5% were printed in an environment of a temperature of 40 ° C. and a relative humidity of 90%. The image density (optical reflection density) was measured 10 times in total for every 50 sheets printed using a reflection densitometer “RD-915” (manufactured by Macbeth), and the image density stability was evaluated according to the following evaluation criteria. The results are shown in Table 2.

〔Evaluation criteria〕
A: The image density of 8 to 10 times is in the range of 1.4 ± 0.1.
A: The image density of 3 to 7 times is in the range of 1.4 ± 0.1.
X: The image density of 0 to 2 times is in the range of 1.4 ± 0.1.

  From the above results, the magnetic toners of Examples 1 to 4 are excellent in both offset resistance and image density stability, whereas the toner of Comparative Example 1 that does not use wax has offset resistance. It can be seen that the toner of Comparative Example 2 which uses a monovalent aliphatic compound having a long-chain alkyl group as a binder resin and a polyester not using a raw material monomer lacks in image density stability.

  The magnetic toner of the present invention is used for developing a latent image formed in electrophotography, electrostatic recording method, electrostatic printing method and the like.

Claims (5)

A magnetic toner comprising a binder resin, wax and magnetic powder, wherein the binder resin comprises a polyester having a softening point of 130 to 160 ° C. and a polyester having a softening point of 80 to 120 ° C .; At least one of the structural units is at least one monovalent aliphatic compound selected from the group consisting of a monovalent aliphatic carboxylic acid compound having 10 to 24 carbon atoms and a monovalent aliphatic alcohol having 10 to 24 carbon atoms. Magnetic toner which is polyester having as.   The magnetic toner according to claim 1, wherein the monovalent aliphatic compound is an aliphatic carboxylic acid compound. Monovalent polyester Le having aliphatic compound as a constituent unit, a monovalent aliphatic compound, in all the structural units, the magnetic toner according to claim 1 or 2, wherein a 0.1 to 20 mol%.   The magnetic toner according to claim 1, wherein the wax is a polyolefin wax.   The magnetic toner according to claim 1, wherein the magnetic toner is a magnetic one-component developing toner.