HEAT-FIXABLE ELECTROPHOTOGRAPHIC TONER

Abstract: A heat-flexible electrophotographic toner composition comprising (A) a graft modified polyolefin composed of 100 parts by weight of a polyolefin having an intrinsic viscosity, measured in decalin at 135°C, of from 0.04 to 1.2 dl/g, and grafted thereto a monomer selected from the group consisting of (a) 1.0 to 100 parts by weight of acrylonitrile or methacrylonit­ rile, (b) 3 to 200 parts by weight of an aromatic carboxylic acid vinyl ester and (c) 2 to 43 parts by weight of an unsaturated carboxylic acid ester, and (B) a coloring agent.

Description: This invention relates to an electrophotographic toner composition, and more specifically, to a heat-fixable electrophotographic toner composition having a reduced tendency to adhesion to fixing rollers during heat fixing. The electrophotographic toner composition, known as an electrostatic toner, is an image-forming material used in a step following charging and exposure in an electrophotographic process. It is a chargeable fine powder composed of a resin and carbon black or a pigment dispersed therein. Generally, electrostatic toners are classified into dry two-component toners used with carriers such as an iron powder or glass particles, wet toners dispersed in organic solvents such as isoparaffins, and dry one-component toners having a fine powder of a magentic material dispersed therein. The image obtained on a photosensitive plate by development with the electrostatic toner is transferred to a receptor sheet and fixed with heat or a solvent vapor. The image directly developed on paper coated with a photosensitive layer is directly subjected to the fixing treatment. Fixation by hot rollers which involves direct contact with the toner image is preferred because it has a high thermal efficiency, the toner image can be accurately fixed by a heat source of relatively low temperatures, and moreover, it is suitable for high-speed copying. However when the image is fixed by contact with a heated body such as hot rollers, a so-called offset phenomenon occurs in which a part of the electrostatic toner adheres to the heating body and is transferred to the image area of a copy that subsequently reaches the fixing heated body. In particular, in high-speed copying, the heated body is kept at a high temperature so as to increase the effect and speed of fixing, and the increased temperatures result in a greater tendency to the offset phenomenon. Accordingly, when, for example, an image formed by using a one-comonent electrostatic toner is to be fixed by hot rollers, attempts are made to obviate the offset phenomenon by, for example, impregnating the roller surface with a silicone oil or supplying it to the roller surface. This may give rise to another problem such as the soiling of the rolls. Examples of the thermoplastic resin as a main component of the electrostatic toner include styrene resins such as polystyrene, styrene/(meth)acrylate copolymers and styrene/(meth)acrylic acid copolymers, ketone resins, maleic acid resins, coumarone resin, phenolic resins, polyester resins, epoxy resins, terpene resins, polyvinylbutyral, and poly(butyl methacrylate). Among these, the styrene resins are most frequently used because they have good chargeability and suitable softening points (90 to 160°C) and thus good fixability, low moisture absorption, and good miscibility with carbon black as a coloring material, and is easy to pulverize, and the photosensitive plate contaminated with the toner can be easily cleaned. In spite of these superior practical characteristics, the styrene resins tend to undergo offset in high-speed copying. It has been desired to develop an electrostatic toner which does not undergo offset. There are two possible methods of solving the aforesaid problem, namely (i) improvement of the thermoplastic resin itself which is the main component of the electrostatic toner, and (ii) the addition of a releasing agent capable of avoiding the offset phenomenon while the thermoplastic resin as the main component of the electrostatic toner is left intact. Techniques of adding polyolefin waxes as releasing agents to styrene polymers in an attempt to solve the above problem by the method (ii) are proposed in JP-B-3304/1977, JP-B-3305/1977, JP-B-52574/1982, JP-B-58,664/1983, and JP-A-59455/1983. In these techniques, too, the compatibility of the polyolefin waxes with the styrene resin component is still insufficient. Hence, the properties of the polyolefin waxes as a releasing agent cannot be fully exhibited, and the toner tends to agglomerate during storage or during a copying operation. Furthermore, since the wax is liable to leave the toner, it tends to soil the photosensitive drum, etc. Another disadvantage is that the fixed image obtained by using the toner has poor bending resistance. JP-A-90642/1982 discloses a toner for pressure fixation comprising a homopolymer of ethylene and a graft copolymer of an aromatic vinyl compound and acrylonitrile. JP-B-17109/1985 discloses a low-molecular-weight propylene polymer. US-A-4385107 discloses a toner comprising a graft copolymer comprising a crystalline polymer derived from at least one of ethylene, propylene and vinyl acetate and an amorphous polymer derived from at least one vinyl monomer such as styrenes, monocarboxylic acid esters, vinyl esters, (meth)acrylic acid derivatives, vinyl ethers and ketones and N-vinyl compounds. According to this invention there is provided a heat-fixable electrophotographic toner composition comprising (A) a graft modified polyolefin composed of 100 parts by weight of a polyolefin having an intrinsic viscosity, measured in decalin at 135°C, of from 0.04 to 1.2 dl/g, and grafted thereto 2 to 43 parts by weight of an unsaturated dicarboxylic acid ester, (B) a coloring agent, and optionally (C) a polymer binder. A heat-fixable electrophotographic toner should have excellent bondability to paper and excellent releasability from hot rollers without being transferred thereto when an image directly developed with the developer material on paper. It has been found that the graft modified polyolefins used in this invention give developer materials having excellent bondability and releasability. The trunk polyolefin used in this invention has an intrinsic viscosity, measured in decalin at 135°C, of from 0.04 to 1.2 dl/g. The polyolefin may be a homopolymer or copolymer of alpha-olefins such as ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene and 1-decene. Linear or branched alpha-olefins having 2 to 10 carbon atoms are preferably used. Examples of the aforesaid polyolefin of relatively low molecular weights include polyolefins obtained by producing polyolefins of relatively high molecular weights by the high-pressure process or by the medium or low pressure process using transition metal compound catalysts and thermally decomposing the resulting polyolefins; high-pressure polyethylene obtained by radical polymerization of ethylene under high pressures; polymers obtained by medium or low pressure polymerization of ethylene or ethylene with the aforesaid alpha-olefins in the presence of transition metal compound catalysts, such as polyethylene and ethylene/alpha-olefin copolymers; polypropylene wax; propylene/1-butene copolymer; poly-1-butene; poly(4-methyl-1-pentene); and propylene/4-methyl-1-pentene copolymer. The polyolefins, as referred to herein, include oxidized polyolefins usually containing less than 10% of oxygen. Among the above exemplified polyolefins, polyethylene, polypropylene, ethylene/propylene copolymer, ethylene/1-butene copolymer, ethylene/4-methyl-1-pentene, propylene/1-butene copolymer, and poly-1-butene are preferred. The starting polyolefins may be solid, liquid or waxy, but the waxy polyolefins are preferred. The graft modified polyolefin used in this invention is obtained by grafting an unsaturated di-carboxylic acid ester to the aforesaid polyolefin (trunk polymer) having a relatively low molecular weight. The grafting may, for example, be carried out by directly melting the trunk polyolefin or dissolving it in a solvent, and grafting the grafting monomer in the presence or absence of a radical initiator. Useful radical initiators include organic peroxides and organic peresters such as benzoyl peroxide, dichlorobenzoin peroxide, dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(peroxybenzoate)hexyne-3, 1,4-bis(tert-butylperoxyisopropyl)benzene, lauroyl peroxide, tert-butyl peracetate, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, tert-butyl benzoate, tert-butylperphenylacetate, tert-butyl perisobutyrate, tert-butyl per-sec-octoate, tert-butyl perpivalate, cumyl perpivalate and tert-butyl perdiethylacetate; and azo compounds such as azobisisobutyronitrile and dimethyl azoisobutyrate. Preferred among these are dialkyl peroxides such as dicumylperoxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, 2,5-di-methyl-2,5-di(tert-butylperoxy)hexane, and 1,4-bis(tert-butylperoxyisopropyl)benzene. The temperature at which the grafting reaction is carried out is usually 130 to 350°C, preferably 135 to 300°C. Examples of the unsaturated dicarboxylic acid esters include monoethyl maleate, diethyl maleate, monopropyl maleate, dipropyl maleate, monobutyl maleate, dibutyl maleate, di(2-ethylhexyl) maleate, monoethyl fumarate, diethyl fumarate, dibutyl fumarate, di(2-ethylhexyl) fumarate, monoethyl itaconate, diethyl itaconate, monobutyl itaconate, di(2-ethylhexyl) itaconate, monoethyl citraconate, diethyl citraconate, dibutyl citraconate and di(2-ethylhexyl) citraconate. Such unsaturated dicarboxylic acid esters may be used singly or in combination. The polyolefin for the production of the graft modified polyolefin preferably has an intrinsic viscosity of 0.07 to 0.6 dl/g, especially 0.08 to 0.5 dl/g. If the intrinsic viscosity of the polyolefin is below the lower limit, a toner composition prepared by using a graft modified polyolefin obtained from the above polyolefin has too low a melt viscosity, and does not produce a sufficient releasing effect nor give a clear image. Furthermore, the toner tends to agglomerate or to soil the photosensitive plate in a copying machine. If, on the other hand the intrinsic viscosity of the polyolefin exceeds the upper limit, a graft polyolefin obtained from the trunk polyolefin has poor compatibility with a binder resin such as a styrene resin, and a toner composition prepared from the grafted polyolefin has so high a melt viscosity that it fails to show a sufficient releasing effect, nor does it have sufficient fixability to paper. The amount of the unsaturated dicarboxylic acid ester grafted is 2 to 43 parts by weight, preferably 3 to 33 parts by weight, per 100 parts by weight of the trunk polymer. If the amount of the grafting monomer exceeds the above-specified upper limit, the compatibility of the modified polyolefin with a binder resin such as a styrene resin becomes too high, and at the time of fixation, the modified polyolefin in the toner has difficulty in migrating to the surface of the molten toner and thus has a reduced effect as a releasing agent. Consequently, the adhesion of the toner to heat fixing rollers occurs. On the other hand, if the amount of grafted monomer falls below the above-specified lower limit, the modified polyolefin has poor compatibility with the binder resin, and the resulting toner has reduced releasability, agglomeration resistance, photosensitive drum soiling resistance and bending resistance which are usually improved with an increase in compatibility. Furthermore, the dispersion of the coloring agent in the resin becomes poor, and the fixability of the toner to paper becomes insufficient. The modified polyolefin grafted with the unsaturated dicarboxylic acid ester preferably has an intrinsic viscosity of 0.05 to 0.8 dl/g, more preferably 0.08 to 0.5 dl/g. The graft modified polyolefin (A) can be used as a releasing agent or as a binder in a heat-fixable electrophotographic toner composition. The graft modified polyolefins (A), if desired, may have other monomers (those which are different from the unsaturated dicarboxylic acid ester) grafted thereto in an amount of less than 70 mole%, particularly less than 50 mole%, based on the total amount of the grafting monomers. Examples of such other grafting monomers include styrene, alpha-methylstyrene, vinyltoluene, acrylonitrile, methacrylonitrile, N-methylolacrylamide, vinyl acetate, vinyl chloride, vinyl pyrolidone, vinyl pyridine, vinyl carbazole, vinyl butyral, vinyl acetate, acrylic acid, methacrylic acid, and maleic anhydride. The heat-fixable electrophotographic toner composition of this invention comprises the graft modified polyolefin (A) and the coloring agent (B). If it is desired to have the graft modified polyolefin exhibit a releasing action, a binder resin (C) is further incorporated. The binder resin may preferably be a homopolymer of a styrene-type monomer or a copolymer of a styrene-type monomer such as styrene, alpha-methylstyrene, beta-methylstyrene, o-, m- or p-methylstyrene and o-, m- or p-chloro-styrene and another vinyl-type monomer, for example. Such a polymer or copolymer is known per se , and is described, for example, in JP-B-6,895/1980. Examples of the other vinyl monomer include p-chlorostyrene; vinylnaphthalene; unsaturated monolefins such as ethylene, propylene, butylene and iosobutylene; vinyl halides such as vinyl chloride, vinyl bromide and vinyl fluoride; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate; esters of alpha-methylene aliphatic monocarboxylic acids such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutylacrylate, n-octyl acrylate, dodecyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl alphachloroacrylate, methyl methacrylate, ethyl methacrylate and n-butyl methacrylate; acrylonitrile; methacrylonitrile; acrylamide; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone; and N-vinyl compounds such as N-vinylpyrrole, N-vinylcarbazole, N-vinylindole and N-vinylpyrrolidone. One or more of these other vinyl monomers can be copolymerized with the styrene monomer. The styrene polymer preferably has a number average molecular weight of at least about 2,000, especially preferably 3,000 to 30,000. Preferably, the styrene component content of the polymer is at least 25% by weight based on the entire weight of the styrene-type polymer. Other thermoplastic resins which can be used in this invention as a binder, excepting the styrene-type polymers indicated above, include polyester resins, ketone resins, maleic acid resins, coumarone resin, phenolic resins, epoxy resins, terpene resins, polyvinylbutyral, poly(butyl methacrylate), polyvinyl chloride, polyethylene, polypropylene, polybutadiene and ethylene/vinyl acetate copolymer. Among the above binder resins, the styrene-type polymers and polyester resins are preferred. Advantageously, in the toner composition in which the graft modified polyolefin (A) is required to exhibit a releasing action, the proportion of the binder resin is 80 to 99% by weight, especially 90 to 98% by weight, based on the total weight of the binder resin and the graft modified polyolefin. When the graft modified polyolefin (A) itself is used as a binder, it is not necessary to use another releasing agent since the modified polyolefin (A) itself has excellent releasability as stated above. When the other binder resin is used in combination, its proportion is desirably less than 75% by weight, especially less than 50% by weight, based on the total weight of the graft modified polyolefin and the other binder resin. The coloring agent (B) used in the toner composition of this invention preferably contain at least one pigment or dye, such as carbon black, Phthalocyanine Blue, Aniline Blue, Algol Oil Blue, Chrome Yellow, Ultramarine Blue, Quinoline Yellow, Lamp Black, Rose Bengale, Diazo Yellow, Rhodamine B Lake, Carmine 6B and quinacridone derivatives. As required, oil-soluble dyes such as azine-type nigrosine dyes, induline, azo dyes, anthraquinonic dyes, triphenylmethane dyes, xanthene-type dyes and phthalocyanine dyes may be used together for the purpose of color adjustment or charge control. The toner composition of this invention may contain other components which do not reduce the effects of this invention. For examples charge controlling agents, plasticizers, and other toner additives may be incorporated. The amounts of these are arbitrary. The toner composition of this invention may be used either as a toner for a two-component developer or a one-component developer. When the toner composition of this invention is used for a two-component developer, it is prepared by mixing the graft modified polyolefin (A), the coloring agent (B) and as required the thermoplastic binder resin (C) by known methods, for example by using a ball mill or an attriter, then kneading the mixture by a hot two roll mill, a hot kneader or an extruder, cooling and solidifying the mixture, coarsely pulverizing it with a hammer mill or a crusher, and then finely pulverizing it in a jet mill or a vibratory mill, or in the presence of water, in a ball mill or an attriter to prepare a powder having an average particle diameter of 5 to 35, µm. The resulting toner composition is used in combination with a carrier. The carrier used may include, for example, silica sand, glass beads or iron balls having a diameter of 200 to 700 µms, or a powder of a magnetic material such as iron, nickel, or cobalt. When the toner composition of this invention is to be used as a one-component developer, the modified polyolefin (A), the coloring agent (B), the thermoplastic resin (C) as an optional component, and a magnetic powder are mixed in the same way as in the preparation of the toner for the two-component developer. Usually, a fine magnetite powder having a particle diameter of not more than 1 µm is used as the magnetic powder to be added to the toner composition. There can also be used powders of metals such as cobalt, iron and nickel, alloys and oxides thereof, ferrites, and mixtures of these. In the one-component developer, the proportion of the magnetic material is usually 40 to 70 parts by weight per 100 parts by weight of the thermoplastic resin including the modified polyolefin (A), and the magnetic material. If the proportion of the magnetic material is excessively large, the electric resistance of the developer decreases, and the electrostatic toner has poor ability to hold a charge. This may result in blurring of the resulting image. Furthermore, the softening point of the electrostatic toner becomes high, and proper fixation may become dificult. On the other hand, when the proportion of the magnetic material is too small, the function of the electrostatic toner may be lost and it fails to gain the required chargeability. Furthermore, the toner is liable to scatter. Known charge controlling agents may be added to such a one-component or two-component developers. As stated above, the grafted modified polyolefin (A) can be used as a releasing agent or as a binder to give a heat-fixable toner composition having excellent releasability from hot rolls or the like at high temperatures, which therefore does not undergo offset even at high roll temperatures and an increased fixing speed and is suitable for high-speed copying. Furthermore, since the toner composition of this invention has excellent fixability to paper and can be fixed satisfactorily even at low roll temperatures, it is very suitable for copying with reduced energy consumption. In addition, the toner composition of this invention has little tendency to agglomeration and excellent development characteristics, and after fixation shows excellent bending resistance. The graft modified polyolefin (A) when used as a releasing agent not only has excellent compatibility with binder resins such as styrene-type polymer, but also shows excellent compatibility or affinity with various additives such as pigments, dyes, charge controlling agents, and plasticizers. Accordingly, it increases the dispersibility of these additives in the binder resins and the physical uniformity, such as charge controllability, of the toner, and thus improves the functional properties of the toner composition as a developer. The following Examples illustrate the present invention are specifically. All parts in these examples are by weight unless otherwise specified. EXAMPLE 1 (1) Preparation of an unsaturated dicarboxylate-grafted polyolefin wax:- Five hundred grams of a polyethylene wax (homopolymer) having an intrinsic viscosity of 0.11 dl/g, a propylene content of 1.6 mole% and obtained by polymerization with Ziegler catalyst was charged into a 1.5-liter glass reactor, and melted at 160°C. Then, 70 g of diethyl itaconate, 70 g of vinyl toluene and 11.5 g of di-t-butyl peroxide (DTBPO) were added, and the mixture was heated for 3 hours. While the mixture was in the molten state, it was subjected to a deaerating treatment for 1 hour in vacuum at 1.3 kPa (10 mmHg) to remove the volatile components. The residue was then cooled and 20 g of it was dissolved in 200 ml of p-xylene. The solution was added with stirring to 600 ml of methyl ethyl ketone. The solid portion that precipitated was washed twice with 500 ml of methyl ethyl ketone, and dried. The resulting solid portion was subjected to ¹H-NMR to determine its diethyl itaconate and vinyl toluene contents. The amounts grafted, so determined, were 11.4 parts of diethyl itaconate and 12.0 parts of vinyl toluene by weight per 100 parts by weight of the grafted polyethylene wax. The resulting grafted polyethylene wax is designated as MW-1. (2) Preparation of a toner and a copying test Eighty-five parts of styrene/n-butyl methacrylate copolymer (Himer SBM-600, made by Sanyo Chemical Industry Co., Ltd.), 4 parts of MW-1, 9 parts of carbon black (Diablack SH, a product of Mitsubishi Chemical Co., Ltd.) and 2 parts of a gold-containing dye (Zapon Fast Black B made by BASF) were mixed in a ball mill for 24 hours, and then kneaded with a hot roll. After cooling, the mixture was pulverized and classified to form an electrostatic toner having a particle diameter of 13 to 15 micrometers. The electrostatic toner (2 parts) was mixed with 100 parts of an iron powder carrier having an average particle diameter of 50 to 80 micrometers to form a developer. By a conventional electrophotographic process, a latent electrostatic image was formed on a selenium photosensitive drum and developed with the resulting developer. The resulting toner image is transferred to a receptor sheet and heat-fixed by hot rolls at 200°C. Even after 5000 copies were continuously produced, clear soil-free copied images could be obtained without the offset phenomenon as in the early stage of the copying process. No soiling of the hot rollers and the photosensitive drum was observed. EXAMPLE 2 By the same procedure as in Example 1, (1), a diethyl maleate/styrene-grafted polyethylene wax (designated as MW-2) containing 9.7 parts of diethyl maleate and 11.2 parts of styrene grafted thereto was prepared by adding 60 g of diethyl maleate, 65 g of styrene and 10.0 g of DTBPO to 500 g of a polypropylene wax homopolymer having an intrinsic viscosity of 0.22 dl/g and obtained by polymerization with a Ziegler catalyst and heating the mixture at 170°C for 3 hours. A toner was prepared, and a copying test as performed, in the same way as in Example 1 except that MW-2 was used instead of MW-1. Even after 3000 cycles of copying, clear soil-free copies images were obtained without the offset phenomenon as in the early stage of copying. No soiling of the hot rollers and the photosensitive drum was observed. The flowability of the toner with temperature changes was examined. The toner was put onto a Petri dish, and its flowability was visually examined. It was found that a toner sample kept at 50°C for 48 hours had slightly lower flowability than a toner sample kept at room temperature for 48 hours, but that it did not produce agglomerates and had no problem in practical toner applications. COMPARATIVE EXAMPLE 1 (1) By the same procedure as in Example 1, (1), a diethyl maleate-grated polypropylene wax (designated as MW-3) containing 0.9 parts of diethyl maleate grafted thereto was prepared by adding 5.0 of diethyl maleate and 0.5 g of DTBPO to 500 g of a polypropylene wax (homopolymer) having an intrinsic viscosity of 0.22 dl/g obtained by polymerization with a Ziegler catalyst and heating the mixture at 170°C for 2 hours. A toner was prepared from 7 parts of MW-3, 82 parts of Himer SBM-600, 9 parts of Diablack SH and 2 parts of Zapon Fast Black and a copying test was performed, in the same way as in Example 1. In about the 4000th cycle of copying, the clearness of the images began to decrease. At the same time, a film of the polypropylene wax was seen to form partly on the surface of the photosensitive drum and the surfaces of the iron carrier particles (filming phenomenon). After the fixing, a solid image area was subjected to 500 cycles of bending, and the degree of fixation was visually evaluated by peeling with an adhesive tape before and after the bending. The toner peeled markedly from the receptor sheet along the bended line. COMPARATIVE EXAMPLE 2 Three hundred grams of polypropylene having an intrinsic viscosity of 1.36 dl/g and an ethylene content of 3.2 mole% was charged into a 1-liter autoclave and thermally decomposed at 340°C for 2.2 hours while passing a minute nitrogen into the autoclave. The resulting polypropylene wax had an intrinsic viscosity of 0.10 dl/g. A toner was prepared, and a copying test was performed, in the same way as in Comparative Example 1 except that the resulting polypropylene wax was used instead of MW-3. The clearness of the toner image began to decrease approximately in the 3500th cycle of copying, and at the same time, a film of the polypropylene wax was seen to form partly on the surface of the photosensitive drum and the surfaces of the iron carrier particles (filming phenomenon). The flowability of the toner with temperature changes was examined in the same way as in Example 2. A sample of the toner kept at 50°C developed agglomerated particles having a size of about 5 mm at one side, and the toner had very poor flowability unsuitable for practical toner application. EXAMPLE 3 (1) Preparation of an unsaturated carboxylate-grafted polyolefin wax:- A 1.5-liter glass reactor was charged with 500 g of an ethylene/propylene copolymer wax having a propylene content of 1.6 mole % having an intrinsic viscosity of 0.11 dl/g, and melted in an atmosphere of nitrogen. Then, diethyl itaconate, vinyltoluene and DTBPO were continuously fed into the reaction system (at 160°C) over 4 hours. The mixture was heated further for 2 hours, and while the reaction mixture was in the molten state, it was subjected to a deaeration treatment in vacuum at 1.3 kPa (10 mmHg) for 1 hour to remove the volatile components. The residue was cooled, and 20 g of the cooled product was dissolved in p-xylene. The solution was added with stirring to 600 ml of methyl ethyl ketone. The precipitated solid portion was washed twice with 500 ml of methyl ethyl ketone, and dried. The resulting solid portion was analyzed by ¹H-NMR for its diethyl itaconate and vinyl toluene contents. The amounts of diethyl itaconate and vinyl toluene grafted, so determined, were 23.5 and 8.7 parts, respectively per 100 parts by weight of the grafted wax. The grafted wax is designated as EW-1. (2) Preparation of a toner and a copying test Forty parts of the modified wax (EW-1), 60 parts of a styrene/n-butyl methacrylate copolymer (Himer SBM-600, a product of Sanyo Chemical Industry Co., Ltd., 5 parts of carbon black ( Diablack SH, a product of Mitsubishi Chemical Industry Co., Ltd.) and 2 parts of a gold-containing dye (Zapon Fast Black, a product of BASF) were mixed in a ball mill for 24 hours. The mixture was kneaded by a hot roll, cooled, pulverized and classified to prepare an electrostatic toner having a particle diameter of 13 to 15 micrometers. The electrostatic toner (120 parts) was mixed with 100 parts of an iron powder carrier having an average particle diameter of 50 to 80 micrometers to form a developer. By a conventional electrophotographic process, a latent electrostatic image was formed on a selenium photosensitive drum and developed with the developer. The toner image was transferred to a receptor sheet and heat-fixed by hot rollers at 200°C. Even after 5000 cycles of copying, clear soil-free copied images were obtained without the offset phenomenon as in the early stage of the copying process. No soiling of the hot rollers and the photosensitive drum was noted. The flowability of the toner was examined in the same way as in Example 2. It was found that the flowability of a toner sample kept at 50°C for 48 hours was little different from that of a toner sample kept at room temperature for 48 hours, and that the toner had excellent flowability even at high temperatures. EXAMPLE 4 (1) By the same procedure as in Example 3, a diethyl maleate/styrene-grafted polypropylene wax (designated as EW-2) containing 40.1 parts of a diethyl maleate component and 5 parts of styrene grafted thereto was prepared by using a polypropylene wax having an intrinsic viscosity of 0.22 dl/g as a starting material. A toner was prepared in the same way as in Example 3 from 100 parts of EW-2, 7 parts of the same carbon black as used in Example 3 and 4 parts of the same gold-containing dye as used in Example 3. A copying test was performed by using the resulting toner in the same way as in Example 3. Even after 5,000 cycles of copying, clear soil-free copied images were obtained without the offset phenomenon as in the early stage of the copying process. No soiling of the hot rollers and the photosensitive drum was noted. The same bending test as in Comparative Example 1 was carried out. The degree of fixing of the toner image remained substantially unchanged after the bending test, and the fixed image was found to have excellent bending resistance.

Claims: A heat-fixable electrophotographic toner composition comprising (A) a graft modified polyolefin composed of 100 parts by weight of a polyolefin having an intrinsic viscosity, measured in decalin at 135°C, of from 0.04 to 1.2 dl/g, and grafted thereto 2 to 43 parts by weight of an unsaturated di-carboxylic acid ester, (B) a coloring agent, and optionally (C) a polymer binder. A toner composition according to claim 1 wherein the graft modified polyolefin is composed of 100 parts by weight of a polyolefin having an intrinsic viscosity of 0.07 to 0.6 dl/g and grafted thereto 2 to 43 parts by weight of the unsaturated di-carboxylic acid ester. A toner composition according to claim 2 wherein the polyolefin has grafted thereto 3 to 33 parts by weight of the unsaturated di-carboxylic acid ester. A toner composition according to claim 2 or 3 wherein the polyolefin has an intrinsic viscosity of 0.08 to 0.5 dl/g. Use of a graft modified polyolefin as defined in any one of the preceding claims as a releasing agent or as a binder in a heat-fixable electrophotographic developer. Use of a graft modified polyolefin as defined in any one of claims 1 to 4 having an acid number of 6 to 200 mg-KOH/g as a releasing agent in a heat-fixable electrophotographic toner composition.

Inventors: SAGANE, TOSHIHIRO, UEDA, TAKASHI
Applicants: MITSUI PETROCHEMICAL INDUSTRIES, LTD.
Application year: 1985
Main classification: G03G9
IPC codes: G03G9, C08F255