Method for producing binder for image formation material

Abstract

To provide a binder for an image formation material that exhibits excellent chargeability and grindability, and has a wide fixing width and scratch resistance.SOLUTION: A method for producing a binder for an image formation material that includes a polyester resin (A), comprises: a step of depolymerizing a polyethylene terephthalate resin (B) by reacting the polyethylene terephthalate resin (B) with a diol (b) having 2 to 5 carbon atoms and a carboxylic acid component (c) at 180°C to 250°C to obtain a depolymerized product (bx); and a step of obtaining the polyester resin (A) by polycondensing the depolymerized product (bx) with an alcohol component and a carboxylic acid component. The carboxylic acid component (c) includes a carboxylic acid component (c1) having a salt of an acidic group.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a binder for an image-forming material. [Background technology]

[0002] In recent years, advances in electrophotography have led to efforts to expand the application of electrophotography to commercial and industrial printing. Commercial and industrial printing require stable, high-speed printing, which requires a certain level of low-temperature fixability and hot offset resistance, i.e., a wide fixation range. Other requirements include durability against shear and compression caused by agitation within the toner cartridge to prevent the generation of fine powder, and maintaining charging performance to enable stable mass printing of images of the same quality. The image forming material used in the toner etc. has a significant effect on the toner properties as described above, and known materials include polystyrene resin, styrene-acrylic resin, polyester resin, epoxy resin, polyurethane resin, polyamide resin, etc., but polyester resin has attracted particular attention because it is easy to achieve a balance between fixability and chargeability. For example, a toner binder that has excellent fixing and charging properties and contains a polyester resin containing an aliphatic diol having 2 to 4 carbon atoms as a main component has been disclosed (Patent Documents 1 and 2). However, it cannot be said that they have sufficient chargeability, wide fixing width, pulverizability, and abrasion resistance to be used as toners for commercial printing and industrial printing, and improvements in these areas are desired. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-141966 [Patent Document 2] Japanese Patent Application Publication No. 9-278873 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a binder for an image-forming material which has excellent chargeability and pulverizability, a wide fixing width and abrasion resistance. [Means for solving the problem]

[0005] The present inventors have conducted extensive research and have arrived at the present invention. That is, the present invention is a method for producing a binder for an image-forming material containing a polyester resin (A), comprising the steps of: reacting a polyethylene terephthalate resin (B) with a diol (b) having 2 to 5 carbon atoms and a carboxylic acid component (c) at 180°C to 250°C to depolymerize the polyethylene terephthalate resin (B) to obtain a depolymerized product (bx); and polycondensing the depolymerized product (bx) with an alcohol component and a carboxylic acid component to obtain the polyester resin (A), wherein the carboxylic acid component (c) is a carboxylic acid component containing a carboxylic acid component (c1) having a salt of an acidic group. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide a binder for an image-forming material which is excellent in chargeability and pulverizability, has a wide fixing width and abrasion resistance. DETAILED DESCRIPTION OF THE INVENTION

[0007] The method for producing the image-forming material of the present invention will be described in detail below.

[0008] The method for producing a binder for an image-forming material of the present invention is a method for producing a binder for an image-forming material containing a polyester resin (A), and includes the steps of: reacting a polyethylene terephthalate resin (B) with a diol (b) having 2 to 5 carbon atoms and a carboxylic acid component (c) at 180°C to 250°C to depolymerize the polyethylene terephthalate resin (B) to obtain a depolymerized product (bx); and polycondensing the depolymerized product (bx) with an alcohol component and a carboxylic acid component to obtain the polyester resin (A), wherein the carboxylic acid component (c) is a carboxylic acid component containing a carboxylic acid component (c1) having a salt of an acidic group.

[0009] The binder for the image-forming material in the present invention contains a polyester resin (A).

[0010] The polyester resin (A) is a polyester resin obtained by reacting a polyethylene terephthalate resin (B) with a diol (b) having 2 to 5 carbon atoms and a carboxylic acid component (c) to depolymerize the polyethylene terephthalate resin (B) to obtain a depolymerized product (bx), and then polycondensing the depolymerized product (bx) with an alcohol component and a carboxylic acid component.

[0011] The polyethylene terephthalate resin (B) is a polyethylene terephthalate (hereinafter also referred to as PET) resin, for example, a recycled PET resin, and its raw material is PET products collected from the market (hereinafter also referred to as recycled PET products), such as PET bottles and PET films.

[0012] Examples of the diol (b) having 2 to 5 carbon atoms include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, and diethylene glycol, which may be used alone or in combination of two or more. Of these diols (b) having 2 to 5 carbon atoms, from the viewpoint of low-temperature fixability and heat-resistant storage stability, diols having 2 to 4 carbon atoms are preferred, ethylene glycol and propylene glycol are more preferred, and ethylene glycol is even more preferred.

[0013] The carboxylic acid component (c) is a carboxylic acid containing a carboxylic acid component (c1) having a salt of an acid group. It is an ingredient. Examples of the carboxylic acid component (c1) having a salt of an acidic group include a dicarboxylic acid component (c11) having a sulfonate group, a dicarboxylic acid component (c12) having a sulfamate group, a dicarboxylic acid component (c13) having a phosphate group, and ester-forming derivatives thereof. Here, the ester-forming derivative means a carboxylic acid anhydride, an alkyl (having 1 to 24 carbon atoms such as methyl, ethyl, butyl and stearyl, preferably having 1 to 4 carbon atoms) ester, and a partial alkyl ester.

[0014] Examples of the dicarboxylic acid component (c11) having a sulfonate group include 4-sulfoisophthalate, 5-sulfoisophthalate, 2-sulfoterephthalate, and sulfosuccinate. Examples of ester-forming derivatives of (c11) include dialkyl isophthalate-5-sulfonate (e.g., dimethyl isophthalate-5-sulfonate). Examples of the dicarboxylic acid component (c12) having a sulfamate group include N-[1,3-dicarboxyphenyl]sulfamate, N-[2,3-dicarboxyphenyl]sulfamate, and N-[2,4-dicarboxyphenyl]sulfamate. Examples of the dicarboxylic acid component (c13) having a phosphate group include a compound obtained by reacting a dicarboxylic acid having a hydroxyl group with a phosphoric acid compound. Examples of the phosphoric acid compound include a salt of a phosphate and an acidic phosphoric acid ester (a phosphoric acid mono- or diester having an alkyl group having 1 to 12 carbon atoms). Of these, from the viewpoint of charging properties (charge retention rate), preferred are the dicarboxylic acid component (c11) having a sulfonate group, the dicarboxylic acid component (c12) having a sulfamate group, and the dicarboxylic acid component (c13) having a phosphate group, more preferred are the dicarboxylic acid component (c11) having a sulfonate group, even more preferred are aromatic dicarboxylic acid components having a sulfonate group, particularly preferred are dialkyl isophthalate-5-sulfonate, and most preferred is dimethyl isophthalate-5-sulfonate.

[0015] Examples of the salt constituting the carboxylic acid component (c1) having a salt of an acidic group include salts with tertiary amines having 3 to 30 carbon atoms (such as triethylamine) and salts with alkali metals (such as lithium, sodium, and potassium). Of these, from the viewpoint of chargeability (charge retention rate), alkali metal salts are preferred, sodium salts and potassium salts are more preferred, and sodium salts are even more preferred.

[0016] The carboxylic acid component (c1) may contain a carboxylic acid component other than the carboxylic acid component (c1) having a salt of an acidic group. Examples of the carboxylic acid component other than the carboxylic acid component (c1) include the carboxylic acid component (y) constituting the polyester resin (A) described below.

[0017] The content of the carboxylic acid component (c1) having a salt of an acidic group is preferably 10 mol % or more, more preferably 30 mol % or more, even more preferably 50 mol % or more, particularly preferably 80 mol % or more, and most preferably 100 mol %, based on the number of moles of the carboxylic acid component (c), from the viewpoint of chargeability (charge retention rate).

[0018] In the present invention, polyethylene terephthalate resin (B) is reacted with diol (b) having 2 to 5 carbon atoms and carboxylic acid component (c) to depolymerize the polyethylene terephthalate resin (B) to obtain depolymerized product (bx). The reaction of polyethylene terephthalate resin (B) includes transesterification and depolymerization. The depolymerized product (bx) includes a bishydroxyalkyl terephthalate ester and a bishydroxyalkyl ester of the carboxylic acid component (c), and further includes a polyethylene terephthalate oligomer and a polyethylene terephthalate oligomer in which at least one terminal ethylene glycol residue has been substituted with a diol residue having 2 to 5 carbon atoms. The weight average molecular weight of the depolymerized product (bx) is preferably 300 or less from the viewpoint of chargeability (charge retention rate).

[0019] The depolymerized product (bx) preferably contains 60% by weight or more, more preferably 80% by weight or more, and particularly preferably 90% by weight or more of terephthalic acid bishydroxyalkyl ester based on the total weight of the depolymerized product (bx) from the viewpoint of chargeability (charge retention rate). By containing 60% by weight or more of terephthalic acid bishydroxyalkyl ester, it is presumed that the crystalline structure derived from the polyethylene terephthalate resin (B) is disrupted, and when a toner containing a binder for an image-forming material is prepared, leakage does not occur and chargeability (charge retention rate) is improved.

[0020] The molar ratio (alcohol component / carboxylic acid component) of the alcohol component to the carboxylic acid component contained in the depolymerized product (bx) (considering both those contained as constituent monomers and those contained as compounds) is preferably 1.00 or more, more preferably 1.02 or more, and particularly preferably 1.04 or more, from the viewpoint of chargeability (charge retention rate). The upper limit is preferably 4.0, more preferably 3.5, and particularly preferably 3.0. The molar ratio (alcohol component / carboxylic acid component) in the depolymerized product (bx) can be calculated from the amounts of the diol (b) having 2 to 5 carbon atoms, the carboxylic acid component (c), and the terephthalic acid and ethylene glycol constituting the polyethylene terephthalate resin (B) during the reaction. Specifically, the number of moles of the diol (b) can be calculated as the sum of the number of moles of the diol (b) having 2 to 5 carbon atoms used during the reaction (charge amount / molecular weight) and the number of moles of ethylene glycol constituting the polyethylene terephthalate resin (B) (charge amount of polyethylene terephthalate resin (B) / 192). The number of moles of terephthalic acid can be calculated as the number of moles of terephthalic acid constituting the polyethylene terephthalate resin (B) (charge amount of polyethylene terephthalate resin (B) / 192).

[0021] The depolymerization step will be described. In the step of obtaining the depolymerized product (bx), the polyethylene terephthalate resin (B) is mixed with the diol (b) having 2 to 5 carbon atoms and the carboxylic acid component (c), and the mixture is heated to react at 180°C to 250°C, whereby the polyethylene terephthalate resin (B) is efficiently depolymerized to obtain the depolymerized product (bx). For example, polyethylene terephthalate resin (B), diol (b) having 2 to 5 carbon atoms, and carboxylic acid component (c) are added, and the mixture is stirred in an esterification reaction apparatus at 180°C to 250°C, and depolymerized at a molar ratio ((b) / (terephthalic acid + carboxylic acid component (c))) of 1.0 or more for preferably 0.1 to 30 hours, to obtain a depolymerized product (bx). By setting the molar ratio ((b) / (terephthalic acid + carboxylic acid component (c)) to be 1.0 or more under these conditions, the bishydroxyalkyl terephthalate can be easily contained in an amount of 60% by weight or more based on the total weight of the depolymerized product (bx), which is preferable from the viewpoint of chargeability (charge retention rate). Furthermore, from the viewpoints of productivity and chargeability (charge retention rate), the number of moles of the diol (b) having 2 to 5 carbon atoms relative to the number of moles of the repeating unit of the polyethylene terephthalate resin (B) is preferably 1 to 3, and more preferably 1 to 2. From the viewpoint of chargeability (charge retention rate), the number of moles of the carboxylic acid component (c) relative to the number of moles of the repeating unit of the polyethylene terephthalate resin (B) is preferably 0.01 to 0.05, and more preferably 0.01 to 0.03. Here, the weight proportion of the bishydroxyalkyl terephthalate contained in the depolymerized product (bx) can be analyzed using, for example, a liquid chromatograph mass spectrometer. In order to accelerate the progress of the depolymerization step, a known ester catalyst may be added as necessary. In order to melt the polyethylene terephthalate resin (B) and promote the depolymerization reaction, the reaction temperature is preferably 200°C or higher and 250°C or lower, and particularly preferably 220°C or higher and 240°C or lower. If the temperature exceeds 250°C, a thermal decomposition reaction of the depolymerized product (bx) occurs, causing quality problems such as a decrease in the degree of polymerization when polycondensed again. If the temperature is lower than 180°C, the depolymerization reaction proceeds slowly, which is a problem in practical production.

[0022] The depolymerization step improves the chargeability (charge retention rate) and grindability of the binder for image-forming materials, resulting in a wider fixation width. While the detailed mechanism is unclear, it is believed that depolymerization using a diol (b) having 2 to 5 carbon atoms disrupts the crystalline structure derived from the polyethylene terephthalate resin (B), resulting in improved chargeability (charge retention rate) and no leakage when a toner containing the binder for image-forming materials is produced. Furthermore, the combined use of a carboxylic acid component (c1) having a salt of an acidic group results in a binder for image-forming materials having a salt of an acidic group in its structure, which is believed to result in excellent chargeability (charge retention rate). The carboxylic acid component (c1) is not incorporated into the polyester resin (A) even when used in the process for obtaining the polyester resin (A). This is believed to be because the carboxylic acid component (c1) is poorly compatible with the polyethylene terephthalate resin (B) and thus is less susceptible to transesterification. However, as depolymerization progresses, compatibility increases, resulting in transesterification. Therefore, in order to obtain excellent charging properties, it is necessary to use it in the depolymerization step. Regarding grindability, it is presumed that by breaking down the crystalline structure derived from polyethylene terephthalate resin (B), the intermolecular interactions are weakened, thereby improving grindability. Regarding fixability, it is presumed that by breaking down the crystalline structure, the sharp melting properties of polyester resin (A) due to the crystalline structure are reduced, and the hot offset temperature is increased, thereby widening the fixation width. Regarding abrasion resistance, it is presumed that the binder for image-forming materials, which uses a carboxylic acid component (c1) having a salt of an acidic group and has the resulting salt of an acidic group in its structure, has high cohesive force and is strong, and that when made into a toner containing the binder for image-forming materials, the abrasion resistance is improved.

[0023] This depolymerized product (bx) may be polycondensed again, if necessary, to control the viscosity. By controlling the viscosity, the degree of polymerization is controlled, and a depolymerized product containing a polyester diol having a desired melt viscosity can be obtained.

[0024] In the present invention, the polyester resin (A) is obtained by polycondensing the depolymerized product (bx), an alcohol component, and a carboxylic acid component. The alcohol component may contain a polyol component (x) other than the alcohol component contained in the depolymerized product (bx). Examples of the polyol component (x) include a diol (x1) having 2 to 5 carbon atoms, a diol (x2) other than the diol (x1) having 2 to 5 carbon atoms, and a trihydric or higher polyol (x3). These may be used alone or in combination of two or more.

[0025] Examples of the diol (x1) having 2 to 5 carbon atoms include the same as those listed for the diol (b) having 2 to 5 carbon atoms, and the preferred examples are also the same.

[0026] Examples of the diol (x2) include alkylene glycols having 6 to 36 carbon atoms (3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, and 1,12-dodecanediol), alkylene ether glycols having 6 to 36 carbon atoms (dipropylene glycol, polyethylene glycol, polypropylene glycol, and polypropylene glycol), and the like. Examples of the alkylene oxide adduct include alicyclic diols having 6 to 36 carbon atoms (1,4-cyclohexanedimethanol, hydrogenated bisphenol A, etc.), (poly)alkylene oxide adducts of the above alicyclic diols (preferably having an average number of moles added of 1 to 30), aromatic diols [monocyclic dihydric phenols (e.g., hydroquinone, etc.) and bisphenols, etc.] and alkylene oxide adducts of the above aromatic diols (preferably having an average number of moles added of 2 to 30).

[0027] The alkylene oxide adducts of the bisphenols can be obtained by adding alkylene oxide (hereinafter, "alkylene oxide" may be abbreviated as AO) to the bisphenols.

[0028] Examples of bisphenols include those represented by the following general formula (1). HO-Ar-P-Ar-OH (1) [In the formula, P represents an alkylene group having 1 to 3 carbon atoms, -SO2-, -O-, -S-, or a direct bond, and Ar represents a phenylene group in which a hydrogen atom may be substituted with a halogen atom or an alkyl group having 1 to 30 carbon atoms.]

[0029] Specific examples of bisphenols include bisphenol A, bisphenol F, bisphenol B, bisphenol E, bisphenol S, trichlorobisphenol A, tetrachlorobisphenol A, dibromobisphenol F, 2-methylbisphenol A, 2,6-dimethylbisphenol A, and 2,2′-diethylbisphenol F, and two or more of these can also be used in combination.

[0030] Examples of alkylene oxides to be added to bisphenols include alkylene oxides having 2 to 30 carbon atoms, such as ethylene oxide (hereinafter, "ethylene oxide" may be abbreviated as EO), propylene oxide (hereinafter, "propylene oxide" may be abbreviated as PO), butylene oxide, tetrahydrofuran, and combinations of two or more of these.

[0031] Of these diols (x2), from the viewpoints of low-temperature fixability and heat-resistant storage stability, alkylene glycols having 6 to 36 carbon atoms and alkylene oxide adducts of aromatic diols are preferred, alkylene glycols having 6 to 10 carbon atoms and alkylene oxide adducts of bisphenols (average number of added moles is preferably 2 to 5) are more preferred, alkylene glycols having 3 to 6 carbon atoms and alkylene oxide adducts of bisphenol A (average number of added moles is preferably 2 to 5) are even more preferred, and EO and / or PO adducts of bisphenol A (average number of added moles is preferably 2 to 3) are particularly preferred.

[0032] Furthermore, the alcohol component constituting the polyester resin (A) preferably contains an alkylene oxide adduct of bisphenol A, and more preferably contains an EO and / or PO adduct of bisphenol A (the average number of moles added is preferably 2 to 3). When the alcohol component constituting the polyester resin (A) contains an alkylene oxide adduct of bisphenol A, the durability of the toner state is improved compared to when this adduct is not contained.

[0033] Examples of the trivalent or higher polyol (x3) include aliphatic polyhydric alcohols having 3 to 36 carbon atoms and having a valence of 3 or more, sugars and derivatives thereof, alkylene oxide adducts of aliphatic polyhydric alcohols (the average number of moles added is preferably 1 to 30), alkylene oxide adducts of trisphenols (trisphenol PA, etc.) (the average number of moles added is preferably 2 to 30), and alkylene oxide adducts of novolak resins (including phenol novolak and cresol novolak, etc., having an average degree of polymerization of preferably 3 to 60) (the average number of moles added is preferably 2 to 30).

[0034] Examples of the aliphatic polyhydric alcohol having 3 to 36 carbon atoms and a valence of 3 or more include alkane polyols and their intramolecular or intermolecular dehydration products, such as glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, sorbitol, sorbitan, polyglycerin, and dipentaerythritol. Furthermore, examples of sugars and their derivatives include sucrose and methyl glucoside.

[0035] Among these trivalent or higher polyols (x3), from the viewpoint of achieving both low-temperature fixability and hot offset resistance, preferred are trivalent or higher aliphatic polyols having 3 to 36 carbon atoms, and alkylene oxide adducts (average number of added moles is preferably 2 to 30) of novolak resins (including phenol novolak and cresol novolak, etc., with an average degree of polymerization preferably of 3 to 60), more preferred are trivalent aliphatic polyols having 3 to 8 carbon atoms, and particularly preferred is trimethylolpropane.

[0036] Furthermore, the alcohol component constituting the polyester resin (A) may contain a mono-ol component, if necessary. Examples of the mono-ol include linear or branched alkyl alcohols having 1 to 30 carbon atoms (e.g., methanol, ethanol, isopropanol, 1-decanol, dodecyl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, arachidyl alcohol, behenyl alcohol, and lignoceryl alcohol).

[0037] Of these monools, from the viewpoints of image strength and heat-resistant storage stability, linear or branched alkyl alcohols having 8 to 24 carbon atoms are preferred, linear alkyl alcohols having 8 to 24 carbon atoms are more preferred, and dodecyl alcohol, stearyl alcohol, arachidyl alcohol, behenyl alcohol, and lignoceryl alcohol are even more preferred.

[0038] In the present invention, the polyester resin (A) may contain a carboxylic acid component (y) other than the carboxylic acid component contained in the depolymerized product (bx). The carboxylic acid component (y) includes dicarboxylic acids (y1) and trivalent or higher polycarboxylic acids (y2), etc. These may be used alone or in combination of two or more.

[0039] Examples of dicarboxylic acids (y1) include aromatic dicarboxylic acids having 8 to 36 carbon atoms (such as terephthalic acid, isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid), aliphatic dicarboxylic acids having 2 to 50 carbon atoms (such as oxalic acid, malonic acid, succinic acid, adipic acid, lepargic acid, and sebacic acid), alicyclic dicarboxylic acids having 6 to 40 carbon atoms (such as dimer acids (dimerized linoleic acid)), and alkene dicarboxylic acids having 4 to 36 carbon atoms (such as alkenylsuccinic acids such as dodecenylsuccinic acid, maleic acid, fumaric acid, citraconic acid, and mesaconic acid), as well as ester-forming derivatives thereof. Here, the term "ester-forming derivatives" refers to carboxylic acid anhydrides, alkyl (such as methyl, ethyl, butyl, and stearyl having 1 to 24 carbon atoms, preferably those having 1 to 4 carbon atoms) esters, and partial alkyl esters.

[0040] Among these dicarboxylic acids (y1), from the viewpoint of achieving both low-temperature fixability, hot offset resistance, and heat-resistant storage stability, aromatic dicarboxylic acids having 8 to 36 carbon atoms, aliphatic dicarboxylic acids having 2 to 50 carbon atoms, and alkene dicarboxylic acids having 4 to 36 carbon atoms are preferred, terephthalic acid, isophthalic acid, adipic acid, succinic acid, maleic acid, and fumaric acid are more preferred, terephthalic acid, isophthalic acid, adipic acid, fumaric acid, and succinic acid are particularly preferred, and terephthalic acid, isophthalic acid, adipic acid, and succinic acid are most preferred. Furthermore, anhydrides and lower alkyl esters of these acids may also be used.

[0041] Examples of the trivalent or higher polycarboxylic acid (y2) include trivalent or higher aromatic polycarboxylic acids having 9 to 20 carbon atoms (trimellitic acid, pyromellitic acid, etc.), aliphatic (including alicyclic) tricarboxylic acids having 6 to 36 carbon atoms (hexanetricarboxylic acid, decanetricarboxylic acid, etc.), and ester-forming derivatives thereof.

[0042] Among these trivalent or higher polycarboxylic acids (y2), from the viewpoint of achieving both low-temperature fixability and hot offset resistance, aromatic polycarboxylic acids having 9 to 20 carbon atoms are preferred, and trimellitic acid and pyromellitic acid are more preferred. Furthermore, anhydrides and lower alkyl esters of these acids may also be used.

[0043] Furthermore, the carboxylic acid component constituting the polyester resin (A) may contain a monocarboxylic acid component, if necessary. Examples of the monocarboxylic acid include aromatic monocarboxylic acids having 7 to 37 carbon atoms (such as benzoic acid, toluic acid, 4-ethylbenzoic acid, and 4-propylbenzoic acid), and aliphatic (including alicyclic) monocarboxylic acids having 2 to 50 carbon atoms (such as acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, and behenic acid).

[0044] Of these monocarboxylic acids, aromatic monocarboxylic acids having 7 to 37 carbon atoms are preferred, and benzoic acid is more preferred, from the viewpoint of image strength and heat-resistant storage stability.

[0045] The acid value of the polyester resin (A) is preferably 0 to 50 mgKOH / g, more preferably 0.1 to 30 mgKOH / g, from the viewpoints of low-temperature fixability, chargeability (charge retention rate) and durability of print quality. The acid value can be measured by the method specified in JIS K0070.

[0046] The glass transition temperature of the polyester resin (A) is preferably from 50 to 75°C, more preferably from 55 to 70°C, from the viewpoint of heat-resistant storage stability and low-temperature fixability. The glass transition temperature (Tg) of the polyester resin (A) can be determined by the method (DSC method) specified in ASTM D3418-82. For measuring the glass transition temperature (Tg), for example, a DSC Q20 manufactured by TA Instruments can be used. The glass transition temperature (Tg) can be measured under the following conditions. <Measurement conditions> (1) Heat from 30°C to 150°C at 20°C / min (2) Hold at 150°C for 10 minutes (3) Cool to -35°C at 20°C / min (4) Keep at -35°C for 10 minutes (5) Heat up to 150°C at 20°C / min (6) The differential scanning calorimetry curve measured in the step (5) is analyzed, and the position of the inflection point is determined as the glass transition temperature.

[0047] The weight average molecular weight of the polyester resin (A) is preferably 3,000 to 100,000, more preferably 5,000 to 50,000, from the viewpoints of low-temperature fixability, heat-resistant storage stability, and pulverizability.

[0048] In the present invention, the weight average molecular weight and peak top molecular weight of the polyester resin (A) and the depolymerized product (bx) can be measured by gel permeation chromatography (GPC) under the following conditions. Device (example): Tosoh Corporation HLC-8120 Column (example): 2 TSK GEL GMH6 columns [manufactured by Tosoh Corporation] Measurement temperature: 40℃ Sample solution: 0.25 wt% THF solution Solution injection volume: 100μL Detector: Refractive index detector Standard substance: 12 standard polystyrenes (TSKstandard POLYSTYRENE) manufactured by Tosoh Corporation (molecular weight: 500, 1,050, 2,800, 5,970, 9,100, 18,100, 37,900, 96,400, 190,000, 355,000, 1,090,000, 2,890,000) For measuring the molecular weight, a sample is dissolved in tetrahydrofuran (THF) to a concentration of 0.25% by weight, and the insoluble matter is filtered off using a PTFE filter with an aperture of 220 nm to obtain a sample solution.

[0049] In the present invention, the polyester resin (A) contains, as a constituent carboxylic acid component, preferably 50 to 99.0 mol %, and more preferably 60 to 95 mol % of terephthalic acid, from the viewpoints of fixability and grindability. In the present invention, the polyester resin (A) contains, as a constituent carboxylic acid component, preferably 0.1 to 5.0 mol %, more preferably 0.3 to 3.0 mol %, of a carboxylic acid component (c1) having a salt of an acidic group, from the viewpoints of chargeability (charge retention rate), grindability, and fixability. In view of the chargeability (charge retention rate) and fixability, the polyester resin (A) of the present invention preferably contains 0.1 to 48 mol %, more preferably 1 to 38 mol %, of an acid other than terephthalic acid and the carboxylic acid component (c1) having a salt of an acidic group as the constituent carboxylic acid component.

[0050] In the present invention, the polyester resin (A) contains, as a constituent alcohol component, preferably 40 to 100 mol %, more preferably 50 to 100 mol %, of a diol (b) having 2 to 5 carbon atoms, from the viewpoints of chargeability (charge retention rate) and fixability. From the viewpoint of fixability, the constituent alcohol component of the polyester resin (A) in the present invention preferably contains 0 to 60 mol %, more preferably 0 to 50 mol %, of an alcohol component other than the diol (b) having 2 to 5 carbon atoms.

[0051] The process for obtaining the polyester resin (A) will be described. The polyester resin (A) can be obtained by carrying out a polycondensation reaction of the depolymerized product (bx), an alcohol component, and a carboxylic acid component in the presence of a polymerization catalyst.

[0052] Specifically, the polyester resin (A) can be produced, for example, as follows: For example, the depolymerized product (bx), an alcohol component, and a carboxylic acid component are subjected to a polycondensation reaction in an inert gas (nitrogen gas, etc.) atmosphere at a reaction temperature of preferably 150 to 280°C, more preferably 160 to 250°C, and even more preferably 170 to 235°C, from the viewpoints of suppressing thermal decomposition reaction and increasing reaction rate.

[0053] In this case, an esterification catalyst can be used as needed. Examples of esterification catalysts include tin-containing catalysts (e.g., dibutyltin oxide), antimony trioxide, titanium-containing catalysts (e.g., titanium alkoxides (tetrabutoxytitanate), potassium oxalate titanate, titanium terephthalate, titanium terephthalate alkoxides, catalysts described in JP 2006-243715 A (titanium diisopropoxybis(triethanolaminate), titanium dihydroxybis(triethanolaminate), titanium monohydroxytris(triethanolaminate), titanyl bis(triethanolaminate) and their intramolecular polycondensates, etc.), and catalysts described in JP 2007-11307 A (titanium tributoxyterephthalate, titanium triisopropoxyterephthalate, titanium diisopropoxyditerephthalate, etc.), zirconium-containing catalysts (e.g., zirconyl acetate), and zinc acetate. Among these, titanium-containing catalysts are preferred.

[0054] A stabilizer may be added to the polyester to ensure stable polymerization, and examples of the stabilizer include hydroquinone, methylhydroquinone, and hindered phenol compounds.

[0055] The binder for the image-forming material in the present invention may contain, in addition to the polyester resin (A), a resin such as a vinyl resin, an epoxy resin, a polyurethane resin, a polycarbonate resin, or a polyester resin other than the polyester resin (A). These resins may be amorphous or crystalline.

[0056] Examples of polyester resins other than the polyester resin (A) include polyester resins obtained by polycondensation of an alcohol component and a carboxylic acid component that does not contain the carboxylic acid component (c1). Except for not containing the carboxylic acid component (c1), the alcohol component and the carboxylic acid component may be the same as those for the polyester resin (A), and the preferred examples are also the same.

[0057] Of the resins other than the polyester resin (A), from the viewpoint of the fixing width of the toner, vinyl resins and polyester resins other than the polyester resin (A) are preferred, polyester resins other than the polyester resin (A) are more preferred, and amorphous polyester resins other than the polyester resin (A) are particularly preferred.

[0058] When the binder for an image-forming material of the present invention contains a resin other than the polyester resin (A), the weight proportion of the polyester resin (A) is preferably 10% by weight or more, and more preferably 20% by weight or more, based on the total weight of the binder for an image-forming material (100% by weight), from the viewpoint of the fixing width of the toner. Furthermore, the weight proportion of resins other than the polyester resin (A) is preferably 90% by weight or less, and more preferably 80% by weight or less, based on the total weight of the binder for the image-forming material (100% by weight), from the viewpoint of the fixing width of the toner.

[0059] The image-forming material of the present invention may contain, in addition to the binder for image-forming materials, one or more known additives selected from colorants, release agents, charge control agents, fluidizing agents, and the like, if necessary.

[0060] As the colorant, any dye or pigment used as a toner colorant can be used. Examples include carbon black, iron black, Sudan Black SM, Fast Yellow G, Benzidine Yellow, Pigment Yellow, India First Orange, Irgasin Red, paranitroaniline red, toluidine red, Carmine FB, Pigment Orange R, Lake Red 2G, Rhodamine FB, Rhodamine B Lake, Methyl Violet B Lake, Phthalocyanine Blue, Pigment Blue, Brilliant Green, Phthalocyanine Green, Oil Yellow GG, Kayaset YG, Orazol Brown B, and Oil Pink OP. The colorant may be any one of these alone or a mixture of two or more. If necessary, magnetic powder (powder of ferromagnetic metals such as iron, cobalt, or nickel, or compounds such as magnetite, hematite, or ferrite) can be added to function as a colorant.

[0061] Examples of the release agent include aliphatic hydrocarbon waxes such as low molecular weight polypropylene, low molecular weight polyethylene, low molecular weight polypropylene / polyethylene copolymer, polyolefin wax, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax, and oxides thereof; carnauba wax, montan wax, sazol wax, and deacidified waxes thereof; ester waxes such as fatty acid ester wax; fatty acid amides; fatty acids; higher alcohols; fatty acid metal salts; and mixtures thereof.

[0062] Examples of polyolefin waxes include (co)polymers of olefins (such as ethylene, propylene, 1-butene, isobutylene, 1-hexene, 1-dodecene, 1-octadecene, and mixtures thereof) [including those obtained by (co)polymerization and thermally degradable polyolefins], oxides of olefin (co)polymers with oxygen and / or ozone, maleic acid modified olefin (co)polymers [for example, modified products of maleic acid and its derivatives (maleic anhydride, monomethyl maleate, monobutyl maleate, dimethyl maleate, etc.)], copolymers of olefins and unsaturated carboxylic acids [(meth)acrylic acid, itaconic acid, maleic anhydride, etc.] and / or unsaturated carboxylic acid alkyl esters [(meth)acrylic acid alkyl (C1 to C18) esters and alkyl maleates (C1 to C18) esters, etc.], and Sasol wax.

[0063] The higher alcohols include aliphatic alcohols having 30 to 50 carbon atoms, such as triacontanol, and the fatty acids include aliphatic alcohols having 30 to 50 carbon atoms, such as triacontanol.

[0064] Examples of the charge control agent include nigrosine dyes, triphenylmethane dyes containing a tertiary amine as a side chain, quaternary ammonium salts, polyamine resins, imidazole derivatives, polymers containing a quaternary ammonium base, metal-containing azo dyes, copper phthalocyanine dyes, metal salicylate salts, boron complexes of benzilic acid, sulfonic acid group-containing polymers, fluorine-containing polymers, and halogen-substituted aromatic ring-containing polymers. Specific examples of charge control agents include T-77 (azo-iron complex manufactured by Hodogaya Chemical Co., Ltd.).

[0065] Examples of the fluidizing agent include colloidal silica, alumina powder, and titanium oxide powder.

[0066] The weight proportion of the polyester resin (A) is preferably from 10 to 87% by weight, more preferably from 20 to 76% by weight, and even more preferably from 25 to 65% by weight, based on the weight of the image-forming material. The weight proportion of resins other than the polyester resin (A) is preferably from 10 to 87% by weight, more preferably from 20 to 76% by weight, and even more preferably from 25 to 65% by weight, based on the weight of the image-forming material. The total weight of the binder for the image-forming material is preferably 30 to 97% by weight, more preferably 40 to 95% by weight, and even more preferably 45 to 92% by weight, based on the weight of the image-forming material. The content of the colorant is preferably 0.05 to 60% by weight, more preferably 0.1 to 55% by weight, and even more preferably 0.5 to 50% by weight, based on the weight of the image-forming material. The content of the release agent is preferably 0 to 30% by weight, more preferably 0.5 to 20% by weight, and even more preferably 1 to 10% by weight, based on the weight of the image-forming material. The content of the charge control agent is preferably 0 to 20% by weight, more preferably 0.1 to 10% by weight, and even more preferably 0.5 to 7.5% by weight, based on the weight of the image-forming material. The content of the fluidizing agent is preferably 0 to 10% by weight, more preferably 0 to 5% by weight, and even more preferably 0.1 to 4% by weight, based on the weight of the image-forming material. The total content of the additives is preferably 3 to 70% by weight, more preferably 4 to 58% by weight, and even more preferably 5 to 50% by weight, based on the weight of the image-forming material. By setting the composition ratio of the image-forming material within the above range, it is possible to easily obtain an image-forming material that has good low-temperature fixing properties, hot offset resistance, chargeability (charge retention rate), durability of print quality, and durability of the image-forming material.

[0067] The image-forming material may be obtained by any of known methods such as kneading and pulverization, emulsion phase inversion, and polymerization. For example, when an image-forming material is obtained by a kneading and pulverizing method, the components constituting the image-forming material, excluding the fluidizing agent, are dry-blended, melt-kneaded, then coarsely pulverized, and finally pulverized using a jet mill pulverizer or the like, and further classified to obtain fine particles having a volume average particle size (D50) of preferably 5 to 20 μm, and then the fluidizing agent is mixed therein to produce the image-forming material. The volume average particle size (D50) is measured using a Coulter counter (for example, Multisizer III (trade name, manufactured by Beckman Coulter, Inc.)).

[0068] When the image-forming material is obtained by the emulsion phase inversion method, the components constituting the image-forming material except for the fluidizing agent are dissolved or dispersed in an organic solvent, and then emulsified by adding water, etc., and if necessary, the resulting mixture is subjected to aggregation, etc., followed by separation and classification, whereby the image-forming material can be produced. The volume average particle size of the image-forming material is preferably 3 to 15 μm.

[0069] In the case of toner applications, the toner is mixed with carrier particles such as iron powder, glass beads, nickel powder, ferrite, magnetite, and ferrite coated with resin (acrylic resin, silicone resin, etc.) as needed to be used as a developer for electric latent images. When carrier particles are used, the weight ratio of toner to carrier particles is preferably 1 / 99 to 99 / 1. Alternatively, an electric latent image can be formed by friction with a member such as a charging blade instead of carrier particles. The toner does not necessarily contain carrier particles.

[0070] The image-forming material is fixed to a support (paper, polyester film, etc.) by a copier, printer, etc. to form a recording material. As a method for fixing to a support, known methods such as a heat roll fixing method and a flash fixing method can be used.

[0071] The image-forming material is used for developing electrostatic images or magnetic latent images in electrophotography, electrostatic recording, electrostatic printing, etc. More specifically, it is used for developing electrostatic images or magnetic latent images particularly suitable for full color applications.

[0072] The present specification discloses the following:

[0073] The present disclosure (1) is a method for producing a binder for an image-forming material containing a polyester resin (A), the method comprising the steps of: reacting a polyethylene terephthalate resin (B) with a diol (b) having 2 to 5 carbon atoms and a carboxylic acid component (c) at 180°C to 250°C to depolymerize the polyethylene terephthalate resin (B) to obtain a depolymerized product (bx); and polycondensing the depolymerized product (bx) with an alcohol component and a carboxylic acid component to obtain the polyester resin (A), wherein the carboxylic acid component (c) is a carboxylic acid component containing a carboxylic acid component (c1) having a salt of an acidic group.

[0074] The present disclosure (2) is a method for producing a binder for an image-forming material according to the present disclosure (1), wherein the carboxylic acid component (c1) having a salt of an acidic group is a dicarboxylic acid component having at least one group selected from the group consisting of a sulfonate group, a sulfamate group, and a phosphate group.

[0075] The present disclosure (3) is a method for producing a binder for an image-forming material according to the present disclosure (1) or (2), wherein the polyethylene terephthalate resin (B) is a recycled PET resin. [Example]

[0076] The present invention will be further explained below with reference to examples and comparative examples, but the present invention is not limited to these.

[0077] Example 1 Synthesis of Polyester Resin (A1), a Binder for Image-Forming Materials A pressurizable reaction vessel was charged with 152 parts by weight (2.00 mol) of propylene glycol, 192 parts by weight of recycled PET resin (IV value: 0.6) (the number of moles of each of the constituent monomers, terephthalic acid and ethylene glycol, was 1.00 mol), and 6.33 parts by weight (0.0214 mol) of sodium 5-sulfoisophthalate dimethyl ester. The mixture was stirred at 220°C and 0.1 to 0.3 MPaG for 5 hours to carry out a depolymerization reaction (closed transesterification reaction). It was confirmed that the weight-average molecular weight (Mw) of the depolymerized product was 300 or less, yielding a depolymerized product (bx-1). Next, the depolymerized product (bx-1) was cooled to 180 ° C., and 10.4 parts by weight (0.0879 mol) of succinic acid and 0.6 parts by weight of tetrabutoxy titanate as a condensation catalyst were added. The temperature was raised to 220 ° C., and the pressure was reduced to 0.5 to 2.5 kPa to remove ethylene glycol, propylene glycol, methanol, and water. When the weight average molecular weight (Mw) reached 10,500, 7.2 parts by weight (0.0375 mol) of trimellitic anhydride was added, and esterification was carried out at 180 ° C. for 1 hour under normal pressure, followed by removal from the reactor to obtain polyester resin (A1). The amounts of ethylene glycol, propylene glycol, methanol, and water recovered by distillation were 37.6 parts by weight, 92.4 parts by weight, 1.4 parts by weight, and 3.2 parts by weight, respectively.

[0078] Example 2 Synthesis of Polyester Resin (A2), a Binder for Image-Forming Materials A pressurizable reaction vessel was charged with 124 parts by weight (2.00 mol) of ethylene glycol, 192 parts by weight of recovered PET resin (IV value: 0.6) (the number of moles of the constituent monomers, terephthalic acid and ethylene glycol, each being 1.00 mol), and 7.46 parts by weight (0.0252 mol) of sodium 5-sulfoisophthalate dimethyl ester. The mixture was stirred at 200°C and 0.1 to 0.3 MPaG for 5 hours to carry out a depolymerization reaction (closed transesterification reaction). It was confirmed that the weight-average molecular weight (Mw) of the PET resin had reached 300 or less, yielding a depolymerized product (bx-2). Next, the depolymerized product (bx-2) was cooled to 180°C, and 73.9 parts by weight (0.212 mol) of bisphenol A propylene oxide 2-mol adduct and 0.7 parts by weight of tetrabutoxy titanate as a condensation catalyst were added. The temperature was raised to 220°C while the pressure was reduced to 0.5 to 2.5 kPa to remove ethylene glycol and methanol. When the weight average molecular weight (Mw) reached 11,000, 8.43 parts by weight (0.044 mol) of trimellitic anhydride was added, and esterification at normal pressure for 1 hour at 180°C was carried out, followed by removal from the reactor to obtain polyester resin (A2). The amounts of ethylene glycol and methanol recovered by distillation were 130 parts by weight and 1.6 parts by weight, respectively.

[0079] Example 3: Synthesis of polyester resin (A3) A pressurizable reaction vessel was charged with 103 parts by weight (1.665 mol) of ethylene glycol, 30.3 parts by weight (0.337 mol) of 1,4-butanediol, 192 parts by weight of recycled PET resin (IV value: 0.6) (the number of moles of the constituent monomers, terephthalic acid and ethylene glycol, each being 1.00 mol), and 9.59 parts by weight (0.0324 mol) of sodium 5-sulfoisophthalate dimethyl ester. The mixture was stirred at 250°C and 0.1 to 0.3 MPaG for 5 hours to carry out a depolymerization reaction (closed transesterification reaction). It was confirmed that the weight-average molecular weight (Mw) of the PET resin had reached 300 or less, yielding a depolymerized product (bx-3). Next, the depolymerized product (bx-3) was cooled to 180°C, and 159 parts by weight (0.457 mol) of bisphenol A propylene oxide 2-mol adduct and 0.9 parts by weight of tetrabutoxy titanate as a condensation catalyst were added. The temperature was raised to 220°C while the pressure was reduced to 0.5 to 2.5 kPa to remove ethylene glycol, 1,4-butanediol, and methanol. When the weight-average molecular weight (Mw) reached 11,000, 10.9 parts by weight (0.0568 mol) of trimellitic anhydride was added, and esterification was carried out at 180°C for 1 hour under normal pressure. The polyester resin (A3) was obtained. The amounts of ethylene glycol, 1,4-butanediol, and methanol recovered by distillation were 130 parts by weight, 20 parts by weight, and 2.1 parts by weight, respectively.

[0080] Example 4: Synthesis of polyester resin (A4) A pressurizable reaction vessel was charged with 152 parts by weight (2.00 mol) of propylene glycol, 192 parts by weight of recycled PET resin (IV value: 0.6) (the number of moles of the constituent monomers, terephthalic acid and ethylene glycol, each being 1.00 mol), and 6.07 parts by weight (0.0214 mol) of sodium N-[1,3-dicarboxyphenyl]sulfamate, and a depolymerization reaction (closed transesterification reaction) was carried out at 180°C and 0.1 to 0.3 MPaG for 5 hours while stirring. It was confirmed that the weight-average molecular weight (Mw) was 300 or less, and a depolymerized product (bx-4) was obtained. Next, 10.4 parts by weight (0.0879 mol) of succinic acid and 0.6 parts by weight of tetrabutoxy titanate as a condensation catalyst were added to the depolymerized product (bx-4), and the mixture was heated to 220°C while the pressure was reduced to 0.5 to 2.5 kPa to remove ethylene glycol, propylene glycol, and water. When the weight-average molecular weight (Mw) reached 10,000, 7.2 parts by weight (0.0375 mol) of trimellitic anhydride was added, and esterification was carried out at 180°C for 1 hour under normal pressure, followed by removal from the reaction vessel to obtain polyester resin (A1). The amounts of ethylene glycol, propylene glycol, and water recovered by distillation were 37.6 parts by weight, 92.4 parts by weight, and 3.2 parts by weight, respectively.

[0081] Example 5: Synthesis of polyester resin (A5) A pressurizable reaction vessel was charged with 103 parts by weight (1.665 mol) of ethylene glycol, 35.1 parts by weight (0.337 mol) of 1,5-pentanediol, 192 parts by weight of recycled PET resin (IV value: 0.6) (the number of moles of the constituent monomers, terephthalic acid and ethylene glycol, each being 1.00 mol), and 10.71 parts by weight (0.0362 mol) of sodium 5-sulfoisophthalate dimethyl ester. The mixture was stirred at 220°C and 0.1 to 0.3 MPaG for 5 hours to carry out a depolymerization reaction (closed transesterification reaction). It was confirmed that the weight-average molecular weight (Mw) of the PET resin had reached 300 or less, yielding a depolymerized product (bx-5). Next, the depolymerized product (bx-5) was cooled to 180°C, and 203 parts by weight (0.584 mol) of bisphenol A propylene oxide 2-mol adduct and 0.9 parts by weight of tetrabutoxy titanate as a condensation catalyst were added. The temperature was raised to 220°C while the pressure was reduced to 0.5 to 2.5 kPa to remove ethylene glycol, 1,5-pentanediol, and methanol. When the weight-average molecular weight (Mw) reached 11,000, 12.1 parts by weight (0.0632 mol) of trimellitic anhydride was added, and esterification was carried out at 180°C for 1 hour under normal pressure. The resulting mixture was then discharged to obtain polyester resin (A5). The amounts of ethylene glycol, 1,5-pentanediol, and methanol recovered by distillation were 137.4 parts by weight, 23.1 parts by weight, and 2.3 parts by weight, respectively.

[0082] Comparative Example 1 Synthesis of Polyester Resin (A'1) A reaction vessel was charged with 152 parts by weight (2.00 mol) of propylene glycol, 192 parts by weight of recycled PET resin (IV value: 0.6) (the number of moles of the constituent monomers terephthalic acid and ethylene glycol each being 1.00 mol), 6.33 parts by weight (0.0214 mol) of 5-sulfoisophthalic acid dimethyl ester sodium, 10.4 parts by weight (0.0879 mol) of succinic acid, and 0.6 parts by weight of tetrabutoxy titanate as a condensation catalyst. The mixture was stirred at 170°C under a nitrogen stream at atmospheric pressure, and the reaction was carried out for 15 hours while distilling off ethylene glycol, propylene glycol, methanol, and water. The reaction was then carried out under a reduced pressure of 2.5 to 5.0 kPa. When the weight-average molecular weight (Mw) reached 10,000, 7.2 parts by weight (0.0375 mol) of trimellitic anhydride was added, and the mixture was esterified at 170°C for 1 hour under atmospheric pressure, after which the mixture was removed to obtain polyester resin (A'1). The amounts of ethylene glycol, propylene glycol, methanol and water recovered by distillation were 37.6 parts by weight, 92.4 parts by weight, 1.4 parts by weight and 3.2 parts by weight, respectively.

[0083] Comparative Example 2: Synthesis of polyester resin (A'2) A pressurizable reaction vessel was charged with 236 parts by weight (2.00 mol) of 1,6-hexanediol and 192 parts by weight of recovered PET resin (IV value: 0.6) (the number of moles of the constituent monomers, terephthalic acid and ethylene glycol, each being 1.00 mol), and the depolymerization reaction (closed transesterification reaction) was carried out at 260°C and 0.1 to 0.3 MPaG for 5 hours while stirring. It was confirmed that the weight average molecular weight (Mw) of the PET resin had reached 300 or less, yielding a depolymerized product (bx'-1). Next, the depolymerized product (bx'-1) was cooled to 180°C, and 280 parts by weight (0.805 mol) of bisphenol A propylene oxide 2-mol adduct and 1.1 parts by weight of tetrabutoxy titanate as a condensation catalyst were added, and 1,6-hexanediol was removed. When the weight average molecular weight (Mw) reached 10,000, 13.9 parts by weight (0.0724 mol) of trimellitic anhydride was added, and esterification was carried out at 180°C for 1 hour under atmospheric pressure, followed by removal from the reactor to obtain polyester resin (A'2). The amounts of ethylene glycol and 1,6-hexanediol recovered by distillation were 48.8 parts by weight and 222.7 parts by weight, respectively.

[0084] Comparative Example 3: Synthesis of polyester resin (A'3) Polyester resin (A'3) was obtained in the same manner as in Example 1, except that the reaction temperature of the depolymerization reaction in Example 1 was changed from 220°C to 160°C, and the depolymerized product (bx-1) was heated to 180°C instead of being cooled to 180°C. The amounts of ethylene glycol, propylene glycol, methanol, and water recovered by distillation were 37.6 parts by weight, 92.4 parts by weight, 1.4 parts by weight, and 3.2 parts by weight, respectively.

[0085] The physical properties of polyester resins (A1) to (A5) and polyester resins (A'1) to (A'3) are shown in Tables 1 and 2. In the tables, the amount of terephthalic acid is the amount calculated by multiplying the amount of recycled PET resin by 132 / 192. The number of moles of recycled PET resin means the number of moles of the repeating unit of polyethylene terephthalate.

[0086] [Table 1]

[0087] [Table 2]

[0088] <Production Example 1> Synthesis of polyester resin (C1) A reactor was charged with 140 parts by weight of bisphenol A·PO 2-mol adduct, 600 parts by weight of bisphenol A·PO 3-mol adduct, 32 parts by weight of trimethylolpropane, 176 parts by weight of terephthalic acid, 17 parts by weight of trimellitic anhydride, and 1 part by weight of tetrabutoxy titanate as a condensation catalyst. The mixture was reacted at 220°C under a nitrogen stream for 4 hours while distilling off the water produced, followed by 2 hours of reaction under a reduced pressure of 0.5 to 2.5 kPa. Next, 90 parts by weight of trimellitic anhydride was added at 210°C, and the mixture was reacted for 1 hour under normal pressure, followed by 10 hours of reaction under a reduced pressure of 0.5 to 5 kPa. The resulting resin was cooled to room temperature, crushed, and granulated to obtain polyester resin (C1).

[0089] <Production Example 2> Synthesis of polyester resin (C2) A reactor equipped with a condenser, stirrer, and nitrogen inlet tube was charged with 715 parts by weight of propylene glycol, 740 parts by weight of terephthalic acid, 35 parts by weight of adipic acid, and 1 part by weight of tetrabutoxy titanate as a polymerization catalyst. The mixture was reacted at 180°C under a nitrogen stream for 12 hours while distilling off the water produced. The temperature was then gradually increased to 230°C, and the mixture was reacted for 4 hours under a nitrogen stream while removing the water produced. The mixture was then further reacted under a reduced pressure of 0.7 to 2.7 kPa and cooled when the softening point reached 88°C. 325 parts by weight of propylene glycol was recovered. The mixture was then cooled to 180°C, and 50 parts by weight of trimellitic anhydride was added. The mixture was reacted for 2 hours under a sealed condition, then reacted at 220°C under a reduced pressure of 2.7 to 5.3 kPa and discharged at the specified softening point. The resulting resin was cooled to room temperature, pulverized, and granulated to obtain polyester resin (C2).

[0090] Table 3 shows the physical properties of the polyester resin (C1) and the polyester resin (C2).

[0091] [Table 3]

[0092] <Examples 6 to 10> Using a Henschel mixer [Mitsui Miike Chemical Engineering Co., Ltd., FM10B], polyester resin (A) and polyester resin (C) were premixed as binders for image-forming materials with colorants, release agents, and charge control agents according to the blending ratios (parts by weight) in Table 4, and then kneaded in a twin-screw kneader [Ikegai Corporation, PCM-30]. The resulting mixture was then finely pulverized using a supersonic jet mill, Labojet [Nippon Pneumatic Mfg. Co., Ltd.], and classified using an air classifier [Nippon Pneumatic Mfg. Co., Ltd., MDS-I] to obtain toner particles with a particle size D50 of 7 μm. Next, 100 parts by weight of the toner particles were mixed with 0.5 parts by weight of colloidal silica [Aerosil R972, Nippon Aerosil Co., Ltd.] using a sample mill to obtain toners (T1) to (T5) containing binders for image-forming materials.

[0093] <Comparative Examples 4 to 6> Comparative polyester resins (A') and (C) were premixed as binders for image-forming materials with colorants, release agents, and charge control agents in the formulation ratios (parts by weight) shown in Table 4 using a Henschel mixer (FM10B, manufactured by Mitsui Miike Chemical Engineering Co., Ltd.). The mixture was then kneaded in a twin-screw kneader (PCM-30, manufactured by Ikegai Corporation). The resulting mixture was then finely pulverized using a supersonic jet mill (Labjet, manufactured by Nippon Pneumatic Mfg. Co., Ltd.) and classified using an air classifier (MDS-I, manufactured by Nippon Pneumatic Mfg. Co., Ltd.) to obtain toner particles with a particle size D50 of 7 μm. Next, 100 parts by weight of the toner particles were mixed with 0.5 parts by weight of colloidal silica (Aerosil R972, manufactured by Nippon Aerosil Co., Ltd.) using a sample mill to obtain toners (T'1) to (T'3) containing binders for image-forming materials.

[0094] The toners (T1) to (T5) and the toners (T′1) to (T′3) were evaluated by the following methods, and the results are shown in Table 4. The colorants, release agents, and charge control agents in Table 4 are as follows: Colorant: Carbon black MA-100 [Mitsubishi Chemical Corporation] Release agent: Carnauba wax [Toyo Adle Co., Ltd.] Charge control agent: T-77 [Hodogaya Chemical]

[0095] [Evaluation method] <Charge retention rate> (1) 0.5 g of toner and 20 g of ferrite carrier (F-150, manufactured by Powder Tech Co., Ltd.) were placed in a 50 mL glass bottle, and the bottle was conditioned at 23° C. and a relative humidity of 50% for 8 hours or more. (2) The mixture was stirred by friction at 50 rpm for 10 minutes and 60 minutes using a Turbula shaker mixer, and the charge amount at each time was measured using a blow-off charge amount measuring device (manufactured by Kyocera Chemical Corporation). Using the obtained values, "charge amount after 60 minutes of friction / charge amount after 10 minutes of friction" was calculated, and this was taken as the charge stability index. A larger charge stability index indicates a better charge retention rate. Under these evaluation conditions, a charge stability index of 0.8 or more is preferred.

[0096] <Fixing width> Toner is applied to the paper at 1.00 mg / cm 2 The powder was applied evenly to the paper surface using a printer with the thermal fixing unit removed. The paper was passed through a soft roller at a fixing speed (heating roller peripheral speed) of 213 mm / sec, and at a heating roller temperature ranging from 90 to 230°C in 5°C increments. The fixed image was then visually inspected for cold offset, and the temperature at which cold offset occurred (MFT) and the temperature at which hot offset occurred were measured. The difference between the low temperature fixing temperature and the hot offset resistance temperature was taken as the fixing width. The wider the fixing width, the better the toner is. Under these evaluation conditions, a temperature of 80° C. or higher is preferred.

[0097] <Crushability> To 85 parts by weight of each binder for image-forming materials used in toners (T1) to (T5) and (T'1) to (T'3), 8 parts by weight of the pigment carbon black MA-100 [manufactured by Mitsubishi Chemical Corporation], 4 parts by weight of the release agent carnauba wax, and 2 parts by weight of the charge control agent T-77 [manufactured by Hodogaya Chemical Industry Co., Ltd.] were added, and the mixture was premixed using a Henschel mixer [manufactured by Mitsui Miike Chemical Engineering Co., Ltd., FM10B]. The mixture was then kneaded in a twin-screw kneader [manufactured by Ikegai Corporation, PCM-30]. The resulting mixture was cooled and then pulverized to sizes ranging from 8.6 mesh pass to 30 mesh on. This was used as particles for evaluating pulverizability. These particles for pulverizability evaluation were then finely pulverized using a supersonic jet pulverizer, Labojet [manufactured by Nippon Pneumatic Mfg. Co., Ltd.] under the following conditions: Crushing pressure: 0.5 MPa Grinding time: 10 minutes Adjuster ring: 15mm Louver size: Medium The volume average particle size (μm) of the finely pulverized particles for evaluation of grindability was measured without classification using a Coulter Counter-TAII (manufactured by Coulter Electronics, Inc., USA), and grindability was evaluated according to the following criteria: Under these conditions, a particle size of less than 7 μm is preferable.

[0098] <Abrasion resistance> The image fixed at 150°C used in the measurement of the fixing width was used as a test piece to conduct an abrasion resistance test using a Gakushin-type abrasion fastness tester. A 60mm x 60mm cotton cloth (Kanakin No. 3) was attached to the abrader, and the abrasion resistance was performed 50 times with a load of 100g. The image retention rate was determined visually from the fixed image after the test, and the abrasion resistance of the toner was evaluated according to the following criteria. ◎: Image retention rate is 70-100% ○: Image retention rate is 50-69% ×: Image retention rate is less than 50% In this evaluation, a rating of ◎ or higher is desirable.

[0099] [Table 4] [Industrial Applicability]

[0100] The image-forming material of the present invention has excellent chargeability and pulverizability, a wide fixing width and abrasion resistance, and therefore can be suitably used as a toner for developing electrostatic images used in electrophotography, electrostatic recording, electrostatic printing, etc. Furthermore, it can be suitably used as a surface modifier for inkjet recording media.

Claims

1. A method for producing a binder for an image-forming material containing a polyester resin (A), the method comprising the steps of: reacting a polyethylene terephthalate resin (B) with a diol (b) having 2 to 5 carbon atoms and a carboxylic acid component (c) at 180°C to 250°C to depolymerize the polyethylene terephthalate resin (B) to obtain a depolymerized product (bx); and polycondensing the depolymerized product (bx) with an alcohol component and a carboxylic acid component to obtain the polyester resin (A), wherein the carboxylic acid component (c) is a carboxylic acid component containing a carboxylic acid component (c1) having a salt of an acidic group.

2. 2. The method for producing a binder for an image-forming material according to claim 1, wherein the carboxylic acid component (c1) having a salt of an acidic group is a dicarboxylic acid component having at least one group selected from the group consisting of a sulfonate group, a sulfamate group, and a phosphate group.

3. 3. The method for producing a binder for an image-forming material according to claim 1, wherein the polyethylene terephthalate resin (B) is a recycled PET resin.

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