Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G9/00—Developers
  • G03G9/08—Developers with toner particles
  • G03G9/087—Binders for toner particles
  • G03G9/08742—Binders for toner particles comprising macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • G03G9/08755—Polyesters

Definitions

• the present invention relates to a toner for electrophotography. More specifically, it relates to a toner for electrophotography, which has hydrolyzability and biodegradability and permits facile deinking (removal of ink) with an existing deinking system, and which can be easily waste-treated.
• waste paper In recent years, with a view to both environmental protection and waste treatment, i.e., the protection of forest resources and the prevention of global warming, it is actively promoted worldwide to use waste paper.
• waster paper For promoting the use of waster paper, there are methods in which the content of a deinked pulp in reclaimed paper is increased and the process of incorporating a deinked pulp into woodfree paper and paper for information industry is developed. For this purpose, it is required to improve the quality of a deinked pulp obtained from waster paper from printed matter such as newspaper, magazines, and the like, by increasing the deinking ratio and dustproof ratio of the deinked pulp.
• biodegradable resins for medical materials have been put to practical use to a considerable extent.
• biodegradable materials are practically used as multifiles, sustained-releasable agrochemicals, fertilizers and gardening tools.
• fishing lines, fishing tackle and tees for golfing are practically produced from biodegradable materials.
• packaging materials for daily necessities such as containers are practically produced from biodegradable materials.
• JP-A-4-179967 discloses a toner containing a specific polyester-based biodegradable binder resin.
• this toner is with high humidity absorption properties and unstable in chargeability, and it further has a problem in that it has insufficient deinking properties due to its insolubility in an alkali solution.
• a conventional toner for electrophotography is generally produced as follows.
• a binder resin, a colorant, an offset preventer and other optional additives as components for the toner are mixed in advance.
• the resultant mixture is kneaded while the binder resin is melted by heating the mixture, to obtain a mass, and the mass is pulverized to obtain a toner having a desired particle diameter.
• the dispersibility of the additives in the binder resin is poor when the mixture is kneaded while the binder resin is melted. It is therefore required to employ very severe conditions for the melt-kneading.
• the toner sometimes has a problem in properties for practical use such as uniform chargeability and offset prevention properties.
• a toner for electrophotography which contains, as a binder resin, a lactic acid-based resin of the formula (1), H-[-O-CH(CH3)-CO-] n -OR (1) wherein R is hydrogen, alkyl, an alkali metal or an alkaline earth metal, and n is an integer of 10 to 20,000.
• a process for the production of a toner for electrophotography which comprises the step of polymerizing a monomer which is to form a lactic acid-based resin of the formula (1), H-[-O-CH(CH3)-CO-] n -OR (1) wherein R is hydrogen, alkyl, an alkali metal or an alkaline earth metal, and n is an integer of 10 to 20,000, as a component for the toner for electrophotography, in the presence of at least one additive selected from the group consisting of a colorant, a charge control agent and an offset preventer.
• a lactic acid obtained by the lactic acid fermentation of glucose is directly dehydratively condensed, or a cyclic dimer of lactic acid (lactide) is ring-opening polymerized, to prepare a lactic acid-based resin, and this lactic acid-based resin is incorporated into a toner as a binder, whereby the toner can be imparted with hydrolyzability and biodegradability.
• the so-obtained hydrolyzable and biodegradable toner can achieve the above objects.
• the cyclic dimer of lactic acid (lactide) is obtained by concentrating a lactic acid aqueous solution to obtain a lactic acid polycondensate and allowing the lactic acid polycondensate to react under heat (140 to 200°C) in the presence of a catalyst.
• the reaction product is distilled, recrystallized and dried, and the resultant cyclic dimer of lactic acid (lactide) is used as a monomer for the ring-opening polymerization.
• the ring-opening polymerization of the lactide is preferably carried out in the presence of a tin compound.
• the lactic acid-based resin is produced with an apparatus such as an extruder, a pressure kneader or a Banbury mixer.
• the lactic acid-based resin is available, for example, as a product supplied by SHIMADZU CORPORATION in the trade name of "Lacty".
• a lactic acid-based resin is easily hydrolyzable in the presence of an alkali solution, and it has an advantage in that a toner containing a colorant such as carbon black can be effectively removed from used copying paper.
• the colorant used in the present invention includes carbon black, a monoazo red pigment, a diazo yellow pigment, a quinacridone magenta pigment and an anthraquinone pigment.
• the charge control agent includes a Nigrosine dye, a quaternary ammonium salt and a monoazo metal complex dye.
• the offset preventer preferred is an polyolefin having a weight average molecular weight of approximately 1,000 to 45,000.
• the polyolefin is required to have high dispersibility in lactic acid monomer or dimer or the lactic acid-based resin, and it increases the fusion temperature of the toner if it has too high a melting point. In view of these points, it is preferred to use a polyolefin having a proper molecular weight.
• the weight average molecular weight of the polyolefin is particularly preferably about 2,000 to 6,000.
• the softening point of the polyolefin is preferably 100 to 180°C, particularly preferably 130 to 160°C.
• polystyrene resin examples include polyethylene, polypropylene and polybutylene. Of these polyolefins, polypropylene is particularly preferred.
• the offset preventer which can be used effectively can be further selected from fatty acid metal salts such as zinc salt, barium salt, lead salt, cobalt salt, calcium salt and magnesium salt of stearic acid, zinc salt, manganese salt, iron salt and lead salt of olefinic acid and zinc acid, cobalt salt and magnesium salt of palmitic acid; higher fatty acids having at least 16 carbon atoms; higher alcohols having at least 16 carbon atoms, esters of polyhydric or monohydric alcohols; natural or synthetic paraffins; fatty acid esters or partial saponification products thereof; and ethylene-bisstearoylamides.
• fatty acid metal salts such as zinc salt, barium salt, lead salt, cobalt salt, calcium salt and magnesium salt of stearic acid, zinc salt, manganese salt, iron salt and lead salt of olefinic acid and zinc acid, cobalt salt and magnesium salt of palmitic acid
• higher fatty acids having at least 16 carbon atoms higher alcohols having at least 16 carbon atoms
• the above offset preventers may be used alone or in combination.
• the amount of the offset preventer per 100 parts by weight of the binder resin or the monomer to constitute the binder resin is generally 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight.
• the toner for electrophotography may contain other thermoplastic resin as a binder resin in combination with the lactic acid-based resin.
• the "other" thermoplastic resin includes polystyrene, polyacrylic acid ester, a styrene-acrylate copolymer, polyvinyl chloride, polyvinyl acetate, polyvinylidene chloride, a phenolic resin, an epoxy resin and a polyester resin.
• the amount of the "other" thermoplastic resin based on the total weight of the binder reins is preferably 80 % by weight or less, particularly preferably 50 % by weight or less.
• the amount of the "other" thermoplastic resin exceeds 80 % by weight, the bonding strength thereof to a paper surface is too high, and the toner shows decreased deinking properties.
• the toner of the present invention is used as a biodegradable toner, it is preferred not to incorporate the "other" thermoplastic resin.
• the toner for electrophotography is obtained by a method in which the lactic acid-based resin as a binder, the colorant, the charge control agent, the offset preventer and other additive are mixed, the mixture is melt-kneaded, the kneaded mixture is cooled to solidify it and the solidified mixture is pulverized and classified.
• the toner of the present invention is obtained by a method in which the additives such as the colorant, the charge control agent, the offset preventer, etc., are added, as required, to the lactic acid-based resin prepared by the polymerization in the presence of at least one additive selected from the colorant, the charge control agent and the offset preventer, the mixture is melt-kneaded, the kneaded mixture is cooled to solidify it and the solidified mixture is pulverized and classified.
• the additives such as the colorant, the charge control agent, the offset preventer, etc.
• the latter method has an advantage in that the additives such as the colorant, the charge control agent, the offset preventer, etc., can be contained in the binder resin in a state where these additives are remarkably uniformly dispersed in the binder resin. That is because, by polymerizing the monomer which is to give the binder resin in a state where the additives are mixed with the monomer, the additives are mixed with the monomer in a liquid state before the completion of the polymerization of the monomer. That is, when the monomer itself is in a liquid state (or it may be in a solution state), the additives can be fully uniformly dispersed in the monomer. As a result, the additives are fully uniformly dispersed among molecular chains of the resin.
• the toner When the colorant, carbon black in particular, is uniformly dispersed in the binder resin, the toner shows a decreased intrinsic volume resistance, and the toner for electrophotography exhibits stable chargeability. This is also the case with the charge control agent.
• the offset preventer When the offset preventer is uniformly dispersed in the binder resin, there can be obtained a toner for electrophotography which has non-offset properties effective for practical use and which can be fixed with a hot roller.
• a fluidization agent such as hydrophobic silica or colloidal silica and a magnetic powder may be incorporated into the toner for electrophotography, provided by the present invention, in order to impart the toner with fluidity.
• These additives may be used in a state where the toner particle surfaces are covered with particles of these additives.
• the toner for electrophotography may be mixed with a carrier comprising an iron powder, ferrite or granulated magnetite for the use of the mixture as a two-component developer. Further, when a magnetic material is incorporated into the toner, the toner can be used as a one-component developer without mixing it with any carrier.
• Tin octylate (Cosmos 29" supplied by TH. GOLDSCHMIDT AG., catalyst for ring-opening polymerization) 0.2 part
• a raw material having the above composition was fed to the raw material feeding port of a twin-screw kneading extruder.
• the cylinder temperature was set at 190°C, and the screw rotation was set at 60 rpm in one direction.
• a nitrogen gas was introduced through a feeding port.
• the average residence time in the twin-screw kneading extruder was 15 minutes.
• the resultant polymer was extruded through a nozzle having an opening diameter of 2 mm, and the extrudate was cooled to solidify it, and the solidified polymer was cut to give chips of a lactic acid-based resin.
• the so-obtained chips had a weight average molecular weight of 100,000.
• This resin had the formula (1) in which n was 1,400 and R was dodecyl.
• Polyolefin wax ("NP-105", supplied by MITSUI PETROCHEMICAL INDUSTRIES, LTD.) 2 parts
• a raw material having the above composition was mixed with a super mixer and melt-kneaded under heat with a twin-screw kneader, and the kneaded mixture was pulverized with a jet mill. Then, the pulverized product was classified with a dry-method flush classifier to give negatively chargeable toner particles having an average particle diameter of 12 ⁇ m. 100 Parts of the so-obtained toner particles and 0.3 part of hydrophobic silica ("R972", supplied by Nippon Aerosil Co., Ltd.) were stirred with a Henschel mixer for 1 minute to allow the hydrophobic silica to adhere to the toner particles, whereby a toner (A) for electrophotography was obtained.
• R972 hydrophobic silica
• a toner (B) for electrophotography was obtained in the same manner as in Example 1 except that the amount of the lactic acid-based resin was changed to 50 parts and that 50 parts of a styrene/acrylate copolymer resin ("NC-6550" supplied by Nippon Carbide Industries Co., Inc.) was added.
• a styrene/acrylate copolymer resin ("NC-6550" supplied by Nippon Carbide Industries Co., Inc.) was added.
• a toner (C) for electrophotography was obtained in the same manner as in Example 1 except that the lactic acid-based resin was replaced with 100 parts of the same styrene/acrylate copolymer resin as that used in Example 2.
• Polyolefin wax ("NP-105", supplied by MITSUI PETROCHEMICAL INDUSTRIES, LTD.) 2 parts
• Tri-iron tetroxide (average particle diameter: 0.2 ⁇ m) 40 parts
• a toner (D) for electrophotography was obtained from a raw material having the above composition in the same manner as in Example 1.
• a toner (E) for electrophotography was obtained in the same manner as in Example 3 except that the lactic acid-based resin was replaced with 100 parts of the same styrene/acrylate copolymer resin as that used in Example 2.
• Tin octylate (Cosmos 29" supplied by TH. GOLDSCHMIDT AG., catalyst for ring-opening polymerization) 0.2 part
• a raw material having the above composition was fed to the raw material feeding port of a twin-screw kneading extruder.
• the cylinder temperature was set at 190°C, and the screw rotation was set at 60 rpm in one direction.
• a nitrogen gas was introduced through a feeding port.
• the average residence time in the twin-screw kneading extruder was 15 minutes.
• the resultant polymer was extruded through a nozzle having an opening diameter of 2 mm, and the extrudate was cooled to solidify it, and the solidified polymer was cut to give chips of a lactic acid-based resin.
• the so-obtained chips had a weight average molecular weight of 110,000.
• This resin had the formula (1) in which n was 1,500 and R was dodecyl.
• Polyolefin wax ("NP-105", supplied by MITSUI PETROCHEMICAL INDUSTRIES, LTD.) 2 parts
• a raw material having the above composition was mixed with a super mixer and melt-kneaded under heat with a twin-screw kneader, and the kneaded mixture was pulverized with a jet mill. Then, the pulverized product was classified with a dry-method flush classifier to give negatively chargeable toner particles having an average particle diameter of 12 ⁇ m. 100 Parts of the so-obtained toner particles and 0.3 part of hydrophobic silica ("R972", supplied by Nippon Aerosil Co., Ltd.) were stirred with a Henschel mixer for 1 minute to allow the hydrophobic silica to adhere to the toner particles, whereby a toner (F) for electrophotography was obtained.
• R972 hydrophobic silica
• Tin octylate (Cosmos 29" supplied by TH. GOLDSCHMIDT AG., catalyst for ring-opening polymerization) 0.2 part
• a raw material having the above composition was fed to the raw material feeding port of a twin-screw kneading extruder.
• the cylinder temperature was set at 190°C, and the screw rotation was set at 60 rpm in one direction.
• a nitrogen gas was introduced through a feeding port.
• the average residence time in the twin-screw kneading extruder was 15 minutes.
• the resultant polymer was extruded through a nozzle having an opening diameter of 2 mm, and the extrudate was cooled to solidify it, and the solidified polymer was cut to give chips of a lactic acid-based resin.
• the so-obtained chips had a weight average molecular weight of 110,000.
• This resin had the formula (1) in which n was 1,500 and R was dodecyl.
• Polyolefin wax ("NP-105", supplied by MITSUI PETROCHEMICAL INDUSTRIES, LTD.) 2 parts
• a raw material having the above composition was mixed with a super mixer and melt-kneaded under heat with a twin-screw kneader, and the kneaded mixture was pulverized with a jet mill. Then, the pulverized product was classified with a dry-method flush classifier to give negatively chargeable toner particles having an average particle diameter of 12 ⁇ m. 100 Parts of the so-obtained toner particles and 0.3 part of hydrophobic silica ("R972", supplied by Nippon Aerosil Co., Ltd.) were stirred with a Henschel mixer for 1 minute to allow the hydrophobic silica to adhere to the toner particles, whereby a toner (G) for electrophotography was obtained.
• R972 hydrophobic silica
• Tin octylate (Cosmos 29" supplied by TH. GOLDSCHMIDT AG., catalyst for ring-opening polymerization) 0.2 part
• Polyolefin wax ("NP-105", supplied by MITSUI PETROCHEMICAL INDUSTRIES, LTD.) 2 parts
• a raw material having the above composition was fed to the raw material feeding port of a twin-screw kneading extruder.
• the cylinder temperature was set at 190°C, and the screw rotation was set at 60 rpm in one direction.
• a nitrogen gas was introduced through a feeding port.
• the average residence time in the twin-screw kneading extruder was 15 minutes.
• the resultant polymer was extruded through a nozzle having an opening diameter of 2 mm, and the extrudate was cooled to solidify it, and the solidified polymer was cut to give chips of a lactic acid-based resin.
• the so-obtained chips had a weight average molecular weight of 100,000.
• This resin had the formula (1) in which n was 1,400 and R was dodecyl.
• a raw material having the above composition was mixed with a super mixer and melt-kneaded under heat with a twin-screw kneader, and the kneaded mixture was pulverized with a jet mill. Then, the pulverized product was classified with a dry-method flush classifier to give negatively chargeable toner particles having an average particle diameter of 12 ⁇ m. 100 Parts of the so-obtained toner particles and 0.3 part of hydrophobic silica ("R972", supplied by Nippon Aerosil Co., Ltd.) were stirred with a Henschel mixer for I minute to allow the hydrophobic silica to adhere to the toner particles, whereby a toner (H) for electrophotography was obtained.
• R972 hydrophobic silica
• Tin octylate (Cosmos 29" supplied by TH. GOLDSCHMIDT AG., catalyst for ring-opening polymerization) 0.2 part
• Polyolefin wax ("NP-105", supplied by MITSUI PETROCHEMICAL INDUSTRIES, LTD.) 2 parts
• a raw material having the above composition was fed to the raw material feeding port of a twin-screw kneading extruder.
• the cylinder temperature was set at 190°C, and the screw rotation was set at 60 rpm in one direction.
• a nitrogen gas was introduced through a feeding port.
• the average residence time in the twin-screw kneading extruder was 15 minutes.
• the resultant polymer was extruded through a nozzle having an opening diameter of 2 mm, and the extrudate was cooled to solidify it, and the solidified polymer was cut to give chips of a lactic acid-based resin.
• the so-obtained chips had a weight average molecular weight of 120,000.
• This resin had the formula (1) in which n was 1,650 and R was dodecyl.
• a raw material composed of the lactic acid-based resin obtained in Synthesis Example 5 was mixed with a super mixer and melt-kneaded under heat with a twin-screw kneader, and the kneaded mixture was pulverized with a jet mill. Then, the pulverized product was classified with a dry-method flush classifier to give negatively chargeable toner particles having an average particle diameter of 12 ⁇ m.
• a white toner (J) having an average particle diameter of 12 ⁇ m was obtained from a raw material having the above composition in the same manner as in Example 1.
• a white toner (K) having an average particle diameter of 12 ⁇ m was obtained in the same manner as in Comparative Example 1 except that no carbon black was used.
• the toners for electronphotography obtained in Examples 1 to 7 and Comparative Examples 1 and 2 were used for forming test images having a black and white ratio of 6 % on surfaces of paper sheets having a weight of 75 g/m2 to pare test sheets. Then, hand-made paper sheets were prepared from these test sheets under the following conditions.
• Defibering An aqueous dispersion containing 5.0 % of the test sheet, 0.7 % of NaOH, 3.0 % of sodium silicate, 3.0 % of H2O2 and 0.2 % of a deinking agent ("Liptol" S2800, supplied by LION CORPORATION) was stirred in a beaker at 50°C for 20 minutes.
• a deinking agent "Liptol" S2800, supplied by LION CORPORATION
• Dilution-Dehydration-Kneader treatment Water was added to the aqueous dispersion such that the aqueous dispersion had a solid content of 5 %, and the mixture was centrifugally dehydrated. Further, pulp, sodium silicate, etc., were added such that the mixture had a pulp content of 20 %, a sodium silicate content of 3.0 % and an NaOH content of 0.5 %, and these components were disaggregated with a kneader.
• the disaggregation mixture was aged at 50°C for 2 hours.
• Floatation Water was added to the aged product to prepare a dispersion having a pulp concentration of 1 %, and fine air bubbles were introduced into the dispersion for 7 minutes to allow the bubbles to adsorb the toner. The bubbles adsorbing the toner went upward and floated on the water surface, whereby the toner and the water were separated.
• Preparation of hand-made sheet A hand-made sheet having a basis weight of 100 g.m2 was prepared with a TAPPI sheet machine.
• Table 1 shows the above test results. Each value in Table 1 shows the number of remaining toner spots. Table 1 60 - 100 ⁇ m Number More than 100 ⁇ m Number Total Number Example 1 9 6 15 Example 2 10 10 20 Example 3 9 4 13 Example 4 8 6 14 Example 5 10 5 15 Example 6 10 4 14 Example 7 8 5 13 Comparative Example 1 34 28 62 Comparative Example 2 28 25 53
• Table 1 clearly shows that the toner for electrophotography, provided by the present invention, shows excellent deinking properties.
• test toners (A), (B), (D), (F), (G), (H), (I) and (J) and the comparative toners (C), (E) and (K) was separately melt-molded into a film having a thickness of about 50 ⁇ m, and allowed to remain in soil for 6 months.
• Example 1 The kneaded mixture (not pulverized) obtained in Examples 1, 2, 4 and 7 were cut to a thickness of 0.5 ⁇ m, and their cross sections were observed through an optical microscope (400 times).
• Table 2 shows the number of dispersed carbon black particles in the field of microscopic vision. Headings in Table 2 show the diameters of the carbon black particles and numbers of carbon black particles having these diameters. Table 2 Over 10 ⁇ m 10 - 5 ⁇ m Below 5 ⁇ m Example 1 7 21 Abundant Example 2 6 13 Abundant Example 4 0 4 Abundant Example 7 0 3 Abundant
• Table 2 shows that the dispersion state of the colorant in each of Examples 1, 2, 4 and 7 had no problem in practical use, and that the dispersion states in Examples 4 and 7 were excellent.
• Table 3 shows the image quality of the initial copy and 5,000th copy.
• Triboelectric charge Measured with a blow-off frictional charge measuring apparatus supplied by Toshiba Chemical Co., Ltd.
• Image density Measured with a reflection densitometer "RD-914" supplied by Macbeth.
• Table 3 shows that the toners obtained in Examples 1, 2, 4, 5, 6 and 7 had no problem in practical use, and the toners obtained in Examples 4 and 7 gave excellent images free of background.
• Example 3 25 Parts of the toner obtained in Example 3 was mixed with 75 parts of magnetite carrier having an average particle diameter of 60 ⁇ m to prepare a two-component developer.
• the so-obtained developer was evaluated with a printer ("KX-P4430", supplied by Matsushita Electric Industrial Co., Ltd.) to give excellent images free of density nonuniformity or background.
• Table 4 shows the image properties of the initial print and the 5,000th print.
• the toner for electrophotography composed mainly of a lactic acid-based resin, provided by the present invention, reacts with water in an alkaline aqueous solution, and the resin molecules are hydrolyzed to decrease the bonding strength. Therefore, it can permit the facile deinking with an existing deinking system. As a result, the recycling of used copying paper is advantageously advanced. Further, the toner of the present invention is biodegradable, and has advantages in that a recovered toner can be disposed of without any problem and that waste paper can be disposed of without any problem.
• R may be alkyl, suitably C2 ⁇ 20, preferably C6 ⁇ 16, more preferably C10 ⁇ 14, for example dodecyl.
• the value of n is from 10 to 20,000, preferably from 500 to 10,000, more preferably from 800 to 5,000, most preferably from 1,000 to 2,500.
• the toner of the invention comprises, as binder resin, a lactic acid-based resin of the formula (1) above, and may further comprise at least one of a colourant, a charge control agent or an offset preventer.
• the toner comprises a colourant, a charge control agent and an offset preventer.

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• Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Spectroscopy & Molecular Physics (AREA)
• General Physics & Mathematics (AREA)
• Developing Agents For Electrophotography (AREA)
• Biological Depolymerization Polymers (AREA)

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Citations (2)

• 1994
  • 1994-08-02 JP JP6200250A patent/JP2909873B2/ja not_active Expired - Fee Related
  • 1994-08-30 EP EP19940306341 patent/EP0640882B1/fr not_active Expired - Lifetime
  • 1994-08-30 DE DE1994616470 patent/DE69416470T2/de not_active Expired - Lifetime

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