Toner and method for producing the same

Abstract

This invention relates to a method for preparing a low-temperature fixing toner for electrostatic image development, comprising a composite flocculation step, wherein the composite flocculant is a combination of organic polymers, inorganic substances, and modified natural polymers. The resulting toner has a particle size of 5 to 8 μm, a particle size distribution range ≤ 1.5, a sphericity ≥ 0.92, and exhibits good low-temperature fixing performance and thermal storage stability.

Description

Technical Field

[0001] This invention relates to the field of electronic photographic products technology, and more specifically, to an electronic photographic toner for printing and copying and its preparation method. Background Technology

[0002] Toner is a core consumable for office imaging equipment such as laser printers and electrostatic copiers. Its performance directly affects the image quality of printing / copying, fixing effect, and equipment lifespan.

[0003] Emulsion polymerization / flocculation methods have been developed for preparing toners in existing technologies. However, existing flocculation methods for preparing chemical toners typically use a single flocculant (such as aluminum salts, iron salts, or cationic polymers), which suffers from the following technical drawbacks: First, the flocculation behavior of a single flocculant in a complex multi-component system is difficult to coordinate synchronously, easily leading to selective or excessive particle aggregation, resulting in a wide toner particle size distribution and affecting development uniformity and imaging resolution. Second, the flocculant has poor compatibility with resin, pigment, and wax dispersions, easily causing surface defects in the toner. Third, it is difficult to simultaneously achieve low-temperature fixing performance and thermal storage stability. To overcome these drawbacks of single flocculants, some research has attempted to use composite flocculant systems; however, existing composite flocculants struggle to consistently produce toner products with narrow particle size distribution, high sphericity, and excellent overall performance.

[0004] Furthermore, in the selection of resin binders, using a blend of crystalline and amorphous polyester resins as the bonding system can balance low-temperature fixing performance and thermal storage stability. However, existing technical solutions using blends of crystalline and amorphous polyesters lack systematic optimization and matching of the key physical properties of the two resins. The melting point of crystalline polyester resin directly affects its low-temperature melting behavior and compatibility with other components in the system; the glass transition temperature and acid value of amorphous polyester resin determine the stability of the resin emulsion and its interaction with components such as flocculants, pigments, and waxes. If these parameters are not properly selected, it will lead to uneven particle agglomeration and a wide particle size distribution during flocculation, as well as difficulties in balancing fixing performance and storage stability. Therefore, how to synergistically optimize the key physical properties of crystalline and amorphous polyester resins to obtain toner products with excellent particle morphology is one of the technical problems to be solved in this field.

[0005] In summary, developing a colorant and its preparation process that can solve the above problems through the optimization of resin physical parameters and the synergistic optimization of composite flocculants has certain practical value. Summary of the Invention

[0006] To address the problems existing in the prior art, the first aspect of the present invention provides a method for preparing a low-temperature fixing toner for electrostatic image development, comprising the following steps:

[0007] S1: Raw material pretreatment: Add non-crystalline polyester resin and crystalline polyester resin to deionized water, stir and emulsify to prepare resin emulsion; mix pigment and dispersant with deionized water, and disperse by high-speed shearing to prepare pigment dispersion; mix polyethylene wax, emulsifier and deionized water, stir and emulsify to prepare wax dispersion.

[0008] S2: Mixing and Dispersion: Add resin emulsion, pigment dispersion, wax dispersion and charge control agent to the reaction vessel, stir and mix to obtain a uniform mixed dispersion;

[0009] S3: Composite flocculation: Dilute the composite flocculant with deionized water, and slowly add it dropwise to the mixed dispersion while stirring. After the addition is complete, continue stirring, adjust the pH value, keep warm and flocculate to form the initial shape of the colorant particles.

[0010] The composite flocculant is a combination of organic polymers, inorganic substances, and natural polymer modifiers;

[0011] Furthermore, the organic polymer is selected from cationic polyacrylamide, polydimethyldiallylammonium chloride, and polyethyleneimine, preferably cationic polyacrylamide; the inorganic material includes polyaluminum chloride, polyferric sulfate, and polyferric chloride, preferably polyaluminum chloride; the natural polymer modifier includes modified starch, chitosan, and carboxymethyl starch, preferably modified starch;

[0012] Furthermore, the degree of substitution of the modified starch is 0.3 to 0.6, and preferably the degree of substitution of the modified starch is 0.45 to 0.55;

[0013] Furthermore, the mass ratio of the organic polymer, inorganic material, and natural polymer modifier is 2~4:1~3:0.5~1.5;

[0014] Furthermore, the flocculant is used at a concentration of 5 to 10 wt%;

[0015] Furthermore, the crystalline polyester resin has a melting point of 80 to 100°C; the amorphous polyester resin has a glass transition temperature of 55 to 65°C and an acid value of 15 to 30 mg KOH / g.

[0016] Furthermore, the crystalline polyester resin includes a polyadipate diol copolymer system and a fumarate diol copolymer system, and the amorphous polyester resin includes a bisphenol A epoxy alkyl adduct copolymer system and an isophthalic acid trimellitic anhydride modified copolymer system.

[0017] Further, the crystalline polyester resin is 15 to 25 parts by weight, and the amorphous polyester resin is 40 to 60 parts by weight;

[0018] Furthermore, in step S3, the pH value is adjusted to 4.5 to 6.0, and the temperature for heat preservation and flocculation is 55 to 65°C.

[0019] A second aspect of the present invention provides a toner obtained by the preparation method according to the first aspect of the present invention, wherein the toner has a particle size of 5 to 8 μm, a particle size distribution range of ≤1.5, and a sphericity of ≥0.92.

[0020] Beneficial effects:

[0021] (1) A composite flocculant composed of organic polymers, inorganic substances, and natural polymer modifiers was used to achieve precise control over the particle size, particle size distribution range, and sphericity of the colorant particles. Further limiting the degree of substitution of modified starch and the ratio of organic polymers, inorganic substances, and natural polymer modifiers can further control the particle size, particle size distribution range, and sphericity of the colorant particles.

[0022] (2) By using crystalline polyester resin and amorphous polyester resin with specific parameters in synergy, a balance between low-temperature fixing performance and thermal storage stability is achieved. Further limiting the mass fraction of amorphous polyester resin in the crystalline polyester resin can further regulate the low-temperature fixing performance and thermal storage stability. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Low temperature fixing toner

[0025] The low-temperature fixing toner for electrostatic image development of this invention has an usable temperature range of 150 to 170°C. The toner comprises crystalline polyester resin and amorphous polyester resin as binders. The crystalline polyester resin has a melting point of 80 to 100°C; the amorphous polyester resin has a glass transition temperature of 55 to 65°C and an acid value of 15 to 30 mg KOH / g. These two resins complement each other in terms of their physical properties: the crystalline polyester resin has a lower melting point, allowing it to melt rapidly at the fixing temperature, significantly reducing the fixing temperature of the toner and meeting the requirements of low-temperature fixing. The amorphous polyester resin has a higher Tg (55~65°C), effectively inhibiting the agglomeration of toner particles and providing excellent thermal storage stability; its acid value of 15~30 mg KOH / g provides the resin emulsion with a suitable negative charge density, ensuring both the dispersion stability of the emulsion and providing a controllable basis for charge neutralization during subsequent flocculation. The synergistic matching of the two resins in key physical properties balances low-temperature fixing and thermal storage stability.

[0026] Furthermore, by controlling the glass transition temperature of the crystalline resin to 45 to 52°C and the number-average molecular weight to 10,000 to 30,000, and the number-average molecular weight of the amorphous polyester resin to 30,000 to 50,000, appropriate fluidity during melting can be further ensured, and the stability of low-temperature fixing and thermal storage can be further considered.

[0027] Crystalline polyester resins include polyadipate diol copolymer systems and fumarate diol copolymer systems, such as poly(ethylene adipate glycol) copolyester, poly(1,4-butanediol adipate) copolyester, and poly(1,4-butanediol fumarate) copolyester. Amorphous polyester resins include bisphenol A epoxy alkyl adduct copolymer systems and isophthalic acid trimellitic anhydride modified copolymer systems. Examples include bisphenol A propylene oxide-terephthalic acid copolyester, bisphenol A ethylene oxide-isophthalic acid copolyester, and isophthalic acid-ethylene glycol-trimeric anhydride copolyester.

[0028] The crystalline polyester resin comprises 15 to 25 parts by weight, and the amorphous polyester resin comprises 40 to 60 parts by weight. Controlling the ratio of crystalline to amorphous polyester resin within this range can further improve low-temperature fixing and thermal storage stability. For crystalline polyester resin, if its dosage is too high (too large a proportion), thermal storage stability decreases; if its dosage is too low (too small a proportion), the low-temperature fixing effect is not significant. For amorphous polyester resin, if its dosage is too high (too large a proportion), it leads to increased fixing temperature and low-temperature fixing failure; if its dosage is too low (too small a proportion), the particle shell strength is insufficient, and pigments and waxes easily migrate from the surface, affecting image quality.

[0029] Toners also contain conventional components such as pigments, waxes, and charge control agents. Pigments are selected from carbon black, phthalocyanine blue, azo red, or permanent yellow, among others. Examples of cyan colorants include Pigment Blue 15:3 and Pigment Blue 15:4; yellow colorants include Pigment Yellow 74, Pigment Yellow 93, Pigment Yellow 94, Pigment Yellow 155, Solvent Yellow 162, Pigment Yellow 180, and Pigment Yellow 185; magenta colorants include Pigment Red 31, Pigment Red 122, Pigment Red 150, Pigment Red 184, Pigment Red 185, Pigment Red 57:1, Pigment Red 238, and Pigment Red 269; black colorants include carbon black and magnetite. Waxes are selected from hydrocarbon waxes such as polyethylene wax, maleic anhydride-modified polyethylene wax, polypropylene wax, copolyolefin wax, paraffin wax, oxidized paraffin wax, and microcrystalline wax; natural waxes such as docosuccinate, octadecanoate, carnauba wax, and beeswax; and higher fatty acid amides such as oleamide and stearamide.

[0030] Preparation method of toner

[0031] The preparation method includes the following steps:

[0032] S1: Raw material pretreatment: Add non-crystalline polyester resin and crystalline polyester resin to deionized water, stir and emulsify to prepare resin emulsion; mix pigment and dispersant with deionized water, and disperse by high-speed shearing to prepare pigment dispersion; mix polyethylene wax, emulsifier and deionized water, stir and emulsify to prepare wax dispersion.

[0033] S2: Mixing and Dispersion: Add resin emulsion, pigment dispersion, wax dispersion and charge control agent to the reaction vessel, stir and mix to obtain a uniform mixed dispersion;

[0034] S3: Composite flocculation: The composite flocculant is diluted with deionized water and slowly added dropwise to the mixed dispersion while stirring. After the addition is complete, stirring is continued, the pH value is adjusted, and the mixture is kept warm to form the initial shape of the colorant particles.

[0035] The composite flocculant is a combination of organic polymers, inorganic substances, and natural polymer modifiers. The organic polymers are selected from cationic polyacrylamide, polydimethyldiallylammonium chloride, and polyethyleneimine; the inorganic substances include polyaluminum chloride, polyferric sulfate, and polyferric chloride; and the natural polymer modifiers include modified starch, chitosan, and carboxymethyl starch. Preferred composite flocculants are cationic polyacrylamide (CPAM), polyaluminum chloride (PAC), and modified starch. The three flocculants each play a distinct role and work synergistically during the flocculation process: Organic polymers, as polymeric flocculants, can form a "bridging" effect between multiple resin particles with their long molecular chains, promoting the effective aggregation of primary particles. At the same time, their cationic groups can neutralize the negative charge on the surface of resin particles, reducing the electrostatic repulsion barrier between particles and providing driving force for flocculation. Inorganic substances, as inorganic flocculants, have a high positive charge density, which can quickly neutralize the negative charge on the surface of dispersion particles such as pigments and waxes, allowing these components that are difficult to flocculate alone to be effectively incorporated into the flocculation system. At the same time, their hydrolysis products can also be adsorbed on the particle surface to form a protective film, preventing excessive aggregation in the later stages of flocculation. Natural polymer modified products, with their hydrophobic framework, can generate affinity adsorption on the surface of organic particles such as resins and waxes. At the same time, their steric hindrance effect also helps to maintain the dispersion stability of the system. The three components address the shortcomings of existing single flocculants in coordinating the flocculation behavior of multiple components simultaneously, enabling resin, pigment, wax and other particles to achieve synchronous and uniform co-flocculation, avoiding selective or excessive agglomeration, thereby improving the particle size, particle size distribution range and sphericity of the colorant particles.

[0036] The degree of substitution of the modified starch is 0.3 to 0.6, with a preferred degree of substitution of 0.45 to 0.55. By controlling the degree of substitution within the above range, the modified starch can provide an appropriate amount of positive charge, which enhances the binding force with anionic particles while avoiding excessive flocculation due to its moderate degree of substitution.

[0037] The mass ratio of organic polymers, inorganic substances, and natural polymer modifiers is 2~4:1~3:0.5~1.5. Organic polymers promote the aggregation of primary particles through molecular chain bridging; an excessively high proportion leads to over-bridging and the formation of loose aggregates, while an insufficient proportion results in insufficient bridging and the retention of fine particles. Inorganic substances neutralize the negative charge on the particle surface through high positive charge density; an excessively high proportion leads to charge reversal and flocculation, while an insufficient proportion results in insufficient charge neutralization and the inability to incorporate pigments and waxes. Natural polymer modifiers have both compatibility and stabilizing effects; an excessively high proportion coats particles and hinders bridging, while an insufficient proportion fails to inhibit the separation of the crystalline and amorphous phases.

[0038] The flocculant concentration is 5 to 10 wt% during use. When the flocculant concentration is below 5 wt%, the molecular chain spacing is too large, the effective collision frequency is insufficient, the flocculation reaction is slow, and the amount of fine particle residue increases. When the concentration is above 10 wt%, the polymer chains become entangled, inorganic matter hydrolyzes too quickly to form precipitation, and the local positive charge density increases sharply, leading to particle redispersion, all of which cause uneven flocculation. A concentration of 5-10 wt% combined with a dropping acceleration rate allows the flocculant to gradually extend and be adsorbed in an orderly manner during dynamic dilution, achieving controllable flocculation and ensuring uniform particle size distribution and sphericity.

[0039] In S3, the pH value is adjusted to 4.5 to 6.0, and the temperature for heat preservation and flocculation in S3 is 55 to 65℃. Under the action of the above-mentioned composite flocculant, combined with the precise control of the heat preservation and flocculation temperature of 55~65℃ and the pH value of 4.5~6.0, carbon powder particles with a particle size of 5 to 8 μm, a particle size distribution range of ≤1.5, and a sphericity of ≥0.92 can be stably obtained, thus achieving precise control over the morphology of carbon powder particles.

[0040] The above and other advantages of the present invention can be better understood through the following embodiments, but the following embodiments are not intended to limit the scope of the present invention.

[0041] Example

[0042] The following embodiments illustrate the present invention, but the present invention is not limited to the following embodiments.

[0043] Preparation Example 1: Synthesis of poly(1,4-butanediol adipate) copolyester a1

[0044] 100 parts by weight of adipic acid, 60 parts by weight of 1,4-butanediol, and 5 parts by weight of cycloalkyl dihydroxypropyl ether monomer were used as copolymerizing modifiers. 0.12 parts by weight of tetrabutyl titanate were added as esterification and polycondensation catalysts, and 0.3 parts by weight of triphenyl phosphite were added as a high-temperature antioxidant. All materials were added to a polymerization reactor, and under a nitrogen inert atmosphere, the mixture was stirred and heated to 170°C to ensure thorough melting and homogenization. The temperature was then raised to 195°C for atmospheric pressure esterification, and fractionation was continuously carried out to remove byproducts. Moisture was produced, and the esterification time was controlled at 4.5 h. Then, the system was slowly heated to 220 °C while the vacuum degree was gradually increased to ≤80 Pa. Under these conditions, the polycondensation reaction was maintained for 2.5 h. After the polycondensation was completed, nitrogen gas was introduced, and the molten product was cooled and shaped in a water-cooling tank. Then, it was coarsely crushed, ground into powder, and passed through an 80-mesh sieve to obtain poly(1,4-butanediol adipate) copolyester powder resin a1. The resin was tested and found to have a melting point of 82 °C, a glass transition temperature (Tg) of 45 °C, and a number-average molecular weight of 12000.

[0045] Preparation Example 2: Synthesis of poly(1,4-butanediol fumarate) copolyester a2

[0046] 100 parts by weight of fumaric acid, 67 parts by weight of 1,4-butanediol, 10 parts by weight of ethylene glycol, and 3 parts by weight of cycloalkyl dihydroxypropyl ether monomer were used as copolymerizing modifiers. 0.15 parts by weight of tetraisopropyl titanate was added as an esterification polycondensation catalyst, and 0.4 parts by weight of triphenyl phosphite was added as a high-temperature antioxidant. All materials were added to a polymerization reactor, and under a nitrogen inert atmosphere, the mixture was stirred and heated to 170°C to melt and mix evenly. The temperature was then raised to 200°C and carried out under normal pressure. The esterification reaction was carried out, and the by-product moisture was removed by continuous fractionation. The esterification time was controlled at 5h. Then, the temperature was slowly raised to 230℃ and the system was evacuated to a vacuum degree of ≤100Pa. Under these conditions, the polycondensation reaction was carried out for 3h. After the polycondensation was completed, nitrogen gas was introduced. The molten product was cooled and pelletized in a water-cooling tank, then crushed and passed through an 80-mesh sieve to obtain polyfuric acid 1,4-butanediol copolyester powder resin a2. The resin was tested and found to have a melting point of 98℃, a glass transition temperature Tg of 51℃, and a number average molecular weight of 28000.

[0047] Preparation Example 3: Synthesis of Bisphenol A Ethylene Oxide-Isophthalic A Copolyester b1

[0048] Take 100 parts by weight of isophthalic acid, 180 parts by weight of bisphenol A ethylene oxide adduct (average molecular weight of about 340, i.e., an average of 2.2 to 2.6 ethylene oxide units added per mole of bisphenol A molecule, with a hydroxyl value of 330 to 350 mg KOH / g), 4 parts by weight of trimellitic anhydride, and add 0.10 parts by weight of monobutyltin oxide as an esterification polycondensation catalyst and 0.3 parts by weight of triphenyl phosphite as a high-temperature antioxidant. Add all materials to a polymerization reactor, stir and heat to 180°C under a nitrogen inert atmosphere to melt and mix the materials evenly, and then heat to 210°C under normal pressure to carry out esterification. The esterification reaction was carried out, and the by-product moisture was continuously removed by fractionation. The esterification time was controlled at 5.5 h. Then, the temperature was slowly raised to 235 °C and the system was evacuated to a vacuum degree of ≤80 Pa. Under these conditions, the polycondensation reaction was carried out for 3.5 h. During the polycondensation process, the acid value was measured at regular intervals to monitor the reaction progress. When the acid value dropped to 16 mg KOH / g, nitrogen gas was introduced. The molten product was cooled and shaped in a water-cooling tank, and then coarsely crushed, ground, and passed through an 80-mesh sieve to obtain bisphenol A ethylene oxide-isophthalic acid copolyester powder resin b1. The glass transition temperature Tg of this resin was found to be 56 °C, the acid value was 16 mg KOH / g, and the number average molecular weight was 32000.

[0049] Preparation Example 4: Synthesis of isophthalic acid-ethylene glycol-trimethoxytriacrylic anhydride copolyester b2

[0050] 100 parts by weight of isophthalic acid, 60 parts by weight of ethylene glycol, and 5 parts by weight of trimellitic anhydride were added, along with 0.12 parts by weight of dibutyltin oxide as an esterification polycondensation catalyst. All materials were added to a polymerization reactor, and under a nitrogen inert atmosphere, the mixture was stirred and heated to 180°C to ensure thorough melting and homogenization. The temperature was then raised to 215°C and subjected to esterification under normal pressure. Byproducts were continuously removed by fractional distillation, with the esterification time controlled to 5 hours. Subsequently, the system was slowly heated to 245°C and gradually increased... Under high vacuum conditions ≤80Pa, the polycondensation reaction was carried out for 4.5 hours. During the polycondensation process, the acid value was measured at regular intervals to monitor the reaction progress. When the acid value dropped to 29mgKOH / g, nitrogen gas was introduced. The molten product was cooled and pelletized in a water-cooling tank, then crushed and passed through an 80-mesh sieve to obtain isophthalic acid-ethylene glycol-trimeric anhydride copolyester powder resin b2. The glass transition temperature Tg of this resin was found to be 64℃, the acid value was 29mgKOH / g, and the number average molecular weight was 48000.

[0051] Example 1

[0052] 20 parts by weight of crystalline polyester resin a1 and 50 parts by weight of amorphous polyester resin b1 were added to 105 parts by weight of deionized water and emulsified by stirring at 78°C and 400 rpm to prepare a resin emulsion with a solid content of 35%. 2.2 parts by weight of carbon black, 0.8 parts by weight of polycarboxylate dispersant, and 9.0 parts by weight of deionized water were mixed and dispersed by high-speed shearing at 9000 rpm for 20 min to prepare a pigment dispersion. 1.9 parts by weight of polyethylene wax, 0.4 parts by weight of polyoxyethylene octylphenol ether, and 5.7 parts by weight of deionized water were mixed and emulsified by stirring at 85°C for 25 min to prepare a wax dispersion. The resin emulsion, pigment dispersion, wax dispersion, and charge control agent were added to a reaction vessel and stirred and mixed at 68°C and 500 rpm for 35 min to obtain a homogeneous mixed dispersion.

[0053] The composite flocculant is composed of cationic polyacrylamide, polyaluminum chloride, and cationic etherified starch in a mass ratio of 3:2:1, with the degree of substitution of the cationic etherified starch being 0.45. 3.5 parts by mass of the composite flocculant were diluted with deionized water to prepare an 8% flocculant solution. This solution was then slowly added dropwise to the mixed dispersion at a rate of 1.5 mL / min while stirring (350 rpm). After the addition was complete, stirring was continued for 20 minutes. The pH of the system was then adjusted to 5.2 with dilute hydrochloric acid, and the mixture was kept at 60°C for 45 minutes to form preliminary colorant particles. The flocculated system was then heated to 80°C and kept at this temperature for 25 minutes to allow the particles to agglomerate and solidify, yielding colorant particles T-1.

[0054] Example 2

[0055] In Example 1, crystalline polyester resin a1 was replaced with crystalline polyester resin a2, and amorphous polyester resin b1 was replaced with amorphous polyester resin b2, while keeping everything else the same as in Example 1, to obtain toner particles T-2.

[0056] Example 3

[0057] The amount of crystalline polyester resin a1 in Example 1 was changed to 10 parts by mass, and the amount of non-crystalline polyester resin b1 was changed to 70 parts by mass, while other aspects remained the same as in Example 1, to obtain toner particles T-3.

[0058] Example 4

[0059] The degree of substitution of the cationic etherified starch in Example 1 was changed to 0.20, while other aspects remained the same as in Example 1, to obtain colorant particles T-4.

[0060] Example 5

[0061] The mass ratio of cationic polyacrylamide, polyaluminum chloride and cationic etherified starch in Example 1 was changed to 3:5:3, while other aspects remained the same as in Example 1, to obtain colorant particles T-5.

[0062] Example 6

[0063] The composite flocculant in Example 1 was diluted with deionized water to a flocculant solution with a mass concentration of 15%, while keeping other aspects consistent with Example 1, to obtain colorant particles T-6.

[0064] Comparative Example 1

[0065] In Example 1, 20 parts by weight of crystalline polyester resin a1 and 50 parts by weight of amorphous polyester resin b1 were replaced with 70 parts by weight of amorphous polyester resin b1, while keeping everything else the same as in Example 1, to obtain toner particles Ta.

[0066] Comparative Example 2

[0067] The cationic etherified starch in Example 1 was replaced with starch, while other aspects remained the same as in Example 1, to obtain toner particles Tb.

[0068] Comparative Example 3

[0069] The composite flocculant in Example 1 was replaced with a mixture of cationic polyacrylamide and polyaluminum chloride in a mass ratio of 1:1, while other aspects remained the same as in Example 1, to obtain colorant particles Tc.

[0070] Comparative Example 4

[0071] The composite flocculant in Example 1 was replaced with polyaluminum chloride, while other aspects remained the same as in Example 1, to obtain toner particles Td.

[0072] The particle size, particle size distribution span, and sphericity of the toner particles in the test examples and comparative examples were measured using a FIFA 3000 detector and a Xerox 5575 detector, and the data are shown in Table 1.

[0073] Table 1

[0074] Particle size (μm) Particle size distribution span sphericity Example 1 6.0 1.203 0.96 Example 2 6.2 1.248 0.98 Example 3 6.3 1.184 0.97 Example 4 6.8 1.458 0.95 Example 5 5.9 1.560 0.92 Example 6 7.2 1.328 0.93 Comparative Example 1 6.4 1.825 0.89 Comparative Example 2 6.9 1.960 0.91 Comparative Example 3 6.7 1.785 0.88 Comparative Example 4 6.5 1.883 0.87

[0075] The toner particles from Examples 1 to 3 and Comparative Example 1 were vacuum filtered and washed with deionized water to remove residual flocculants and impurities. They were then dried at 35°C to a moisture content of 0.3%. Finally, they were sieved through a 100-mesh sieve and surface modified by adding 0.5 parts of silane coupling agent to obtain a low-temperature fixing toner.

[0076] The fixing and thermal storage properties of the toners in the above embodiments and comparative embodiments were tested:

[0077] Fixing performance: Add 1.0 part by weight of hydrophobic silica to 100 parts by weight of the toner in each example and comparative example, mix thoroughly, print using a Xerox 5575 machine, and test its density value. After rubbing with standard accessories 5 times, measure the density value again. The density value after rubbing / density value before rubbing × 100% = fixing value.

[0078] Agglomeration temperature: Add 1.0 part by weight of hydrophobic silica to 100 parts by weight of the toner in each embodiment and comparative example, mix evenly, place in a constant temperature oven for 24 hours, observe and press to see if there are any hard lumps. If there are no problems, increase the temperature by 1°C each time until hard lumps appear. This temperature is the agglomeration temperature.

[0079] The results are shown in Table 2 below:

[0080] Table 2

[0081] Fixability (%) Agglomeration temperature (°C) Example 1 99 56 Example 2 98 56 Example 3 99 55 Comparative Example 1 90 60

[0082] As shown in Table 2, compared with Comparative Example 1, Examples 1-3 used a combination of crystalline polyester resin and non-crystalline polyester resin, which greatly improved the low-temperature fixing performance within an acceptable range of agglomeration temperature.

[0083] It should be noted that, based on the explanations and descriptions in the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some equivalent modifications and alterations to the present invention should also be within the scope of protection of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the invention.

Claims

1. A method for preparing a low-temperature fixing toner for electrostatic image development, characterized in that, Includes the following steps: S1: Raw material pretreatment: Add non-crystalline polyester resin and crystalline polyester resin to deionized water, stir and emulsify to prepare resin emulsion; mix pigment and dispersant with deionized water, and disperse by high-speed shearing to prepare pigment dispersion; mix polyethylene wax, emulsifier and deionized water, stir and emulsify to prepare wax dispersion. S2: Mixing and Dispersion: Add resin emulsion, pigment dispersion, wax dispersion and charge control agent to the reaction vessel, stir and mix to obtain a uniform mixed dispersion; S3: Composite flocculation: Dilute the composite flocculant with deionized water, and slowly add it dropwise to the mixed dispersion while stirring. After the addition is complete, continue stirring, adjust the pH value, keep warm and flocculate to form the initial shape of the colorant particles. The composite flocculant is a combination of organic polymers, inorganic substances, and natural polymer modifiers.

2. The preparation method according to claim 1, characterized in that, The organic polymer is selected from cationic polyacrylamide, polydimethyldiallylammonium chloride, and polyethyleneimine, preferably cationic polyacrylamide; the inorganic material includes polyaluminum chloride, polyferric sulfate, and polyferric chloride, preferably polyaluminum chloride; the natural polymer modifier includes modified starch, chitosan, and carboxymethyl starch, preferably modified starch.

3. The preparation method according to claim 2, characterized in that, The degree of substitution of the modified starch is 0.3 to 0.6, and preferably the degree of substitution of the modified starch is 0.45 to 0.

55.

4. The preparation method according to claim 1, characterized in that, The mass ratio of the organic polymer, inorganic material and natural polymer modifier is 2 ~ 4:1 ~ 3:0.5 ~ 1.

5.

5. The preparation method according to claim 1, characterized in that, The flocculant is used at a concentration of 5 to 10 wt%.

6. The preparation method according to claim 1, characterized in that, The crystalline polyester resin has a melting point of 80 to 100°C; the amorphous polyester resin has a glass transition temperature of 55 to 65°C and an acid value of 15 to 30 mg KOH / g.

7. The preparation method according to claim 6, characterized in that, The crystalline polyester resin includes a polyadipate diol copolymer system and a fumarate diol copolymer system, while the amorphous polyester resin includes a bisphenol A epoxy alkyl adduct copolymer system and an isophthalic acid trimellitic anhydride modified copolymer system.

8. The preparation method according to claim 1, characterized in that, The crystalline polyester resin is 15 to 25 parts by weight, and the amorphous polyester resin is 40 to 60 parts by weight.

9. The preparation method according to claim 1, characterized in that, In step S3, the pH value is adjusted to 4.5 to 6.0, and the temperature for heat preservation and flocculation is 55 to 65°C.

10. A toner prepared according to any one of claims 1 to 9, wherein the toner has a particle size of 5 to 8 μm, a particle size distribution span of ≤1.5, and a sphericity of ≥0.92.