GB2070031A - A toner composition for electrophotography and a method for manufacturing the same - Google Patents

Abstract

Toner compositions for electrophotographic use can be obtained by polymerizing a monomer with a reactive prepolymer (especially a butadiene type polymer e.g. polybutadiene glycol). A coloring agent is incorporated before or after polymerization. Preferably polymerization is carried out in the presence of an olefin polymer of molecular weight from 1,000 to 45,000. The toner compositions do not exhibit the so-called offset and twinning phenomena.

Description

SPECIFICATION A toner composition for electrophotography and a method for manufacturing the same The present invention relates to a toner composition for electrophotography, electrostatic printing and an electrostatic recording method and a method for manufacturing such toner.

Generally, an electrostatic image formed on a photo-conductive plate is developed by the use of colored powder, toner and thus formed toner image is fixed directly thereon or after being transferred onto a transfer paper or the like. As a fixing method, among others, heat-fixing method is well known and used from a practical point of view, and in particular, a contact type heat-fixing method by the use of a pair of heat-fixing rollers is widely utilized because of its high heat efficiency with relatively low temperature and because according to this method, fixing at high speed becomes possible.

In the contact type heat-fixing method, however, there is often occured a so-called "off-set" phenomenon, wherein melted or half-melted toner adheres to the surface of the heat-fixing roller and thus deposited toner is thereafter transferred onto the paper coming into contact with it succeedingly.

This off-set phenomenon tends to occur when viscoelasticity of the toner is not proper and, especially, when it is too small.

In order to prevent the occurrence of such "off-set" phenomenon, various proposals have been offered, however, there still remains a big room for improvement in this field of the art.

Thus, the primary object of the present invention is to provide a novel toner composition for developing an electrostatic image which possesses excellent anti-offset property and it makes possible to accomplish fixing at low temperature.

Another object of the present invention is to provide a toner composition for electrophotography which has improved resistance against impulsive force, that is, anti-impact property.

Further object of the present invention is to provide a method for manufacturing such toner composition.

Thus the present invention relates, more precisely, to a toner composition for electrophotography comprising a polymer having been prepared by polymerizing a monomer and a reactive prepolymer, and a coloring agent, and a method for preparing the same.

According to one preferable embodiment of the present invention, above-mentioned polymerization of the monomer with the prepolymer, of which meaning is given hereinafter, is conducted in the presence of a cross-linking agent.

According to one other preferable embodiment of the present invention, said polymerization is conducted in the presence of a so-called "anti-offset" agent, which can effectively prevent the occurrence of the off-set phenomenon.

According to still further preferable embodiment of the present invention, said polymerization is conducted in the presence of a coloring agent such as carbon black.

According to still further preferable embodiment of the present invention, said polymerization is conducted in the presence of any mixture of above-mentioned cross-linking agent, anti-offset agent and coloring agent as well as, if necessary, other known additives for the toner, such as so-called charge controlling agent.

According to still further preferable embodiment of the present invention, said polymerization is conducted so that toner particles prepared by a method of the present invention may have an average diameter of 1 to 50 microns.

According to still further preferable embodiment of the present invention, the toner particles thus formed by the polymerization may be subject to other conventionally known process, if necessary or appropriate, for the purpose of, for example, incorporating into thus prepared polymer component other additives such as mentioned hereinbefore.

In the present invention, the polymer may be prepared by any known polymerization process including suspension polymerization, block polymerization, emulsification polymerization and solution polymerization, and on carrying out the polymerization process, any optionally selected catalyzer or initiator may be used.

According to the present invention, it is possible to prepare toner composition which consists of fine spherically shaped grains having desirably selected grain size by appropriately selecting the conditions of the polymerization. In this case, it is possible to prepare the toner of the present invention through single polymerization process by using other necessary additives, such as a coloring agent, electric charge controlling agent and adding them to a solution containing the monomer either before or during the polymerization. For this purpose suspension polymerization is preferably applied.

According to another embodiment of the present invention, it is also possible for the polymer thus prepared by above-mentioned polymerization to be subject to other processes such as fusing, kneading and crushing processes to prepare toner particles, and in this case such other additives may not be added before or during polymerization step but they may be added to the polymer component during any subsequent step, preferably, during fusing or kneading step.

In the case the polymer is prepared by suspension polymerization, since the polymerization is carried out in such a manner that a liquid composition containing the monomer of the present invention is dispersed in the form of suspension in a dispersion medium such as water so that dispersed particles have desirable size, for the purpose of preventing the particles from coagulating and becoming too large grains, due to the increase in tackiness of the solution during polymerization, the use of a suspension stabilizer may be preferable.

Such suspension stabilizer used for this purpose may be generally classified roughly into water soluble high molecular substance and fine powder of less soluble inorganic compound and in the former, gelatin, starch, polyvinylalcohol and others are included and in the latter, less soluble salt such as barium sulfate, calcium sulfate, barium carbonate, calcium carbonate and calcium phosphate or the like and inorganic high molecular substance such as talc, clay, cilicic acid and diatomaceous earth or the like and powder of a metallic oxide and others are included, In case dispersed grains are charged in one kind of polarity either positive or negative when polymeric composed substance is dispersed in water with polymeric composed substance containing ionic substance such as nitrogen-containing polymeric monomer for example or cationic substance like less water soluble amine or anionic substance, ionic dispersing agent that will be charged, when dispersed in water, in the polarity on the other side such as negatively-charged colloidal silica or positively-charged aluminium oxide etc. can be effectively used as suspension stabilizer.

In this suspension polymerization, stirring conditions of the suspension are important and they may well influence on the grain size of the product and the stability of the polymerization. In order to obtain polymer particles having desirable grain size, which is 1 to 50 microns in diameter, although the size of the particles is affected by various other factors such as viscosity or surface tension of the suspension, it is generally preferable to stir the suspension with the sheering force of 103 to 106 dyne/cm2.

As polymeric monomers that can be used in the present invention, styrene monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, a-methylstyrene, p-ethylstyrene, 2,4dimethylstyrene, p-n-butylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-nnonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, pchlorostyrene and 3,4-dichlorostyrene etc. are given as a preferable one.In addition to this, ethylene unsaturated monoolefin such as ethylene, propylene, butylene and isobutylene etc., vinyl halide such as vinyl chloride, vinylidene chloride, vinyl bromide and vinyl fluoride etc., vinylester such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate etc., ez-methylene aliphatic monocarboxylic acid ester such as acrylic acid methyl, acrylic acid ethyl, acrylic acid n-butyl, acrylic acid isobutyl, acrylic acid propyl, acrylic acid n-octyl, acrylic acid dodecyl, acrylic acid lauryl, acrylic acid 2-ethylhexyl, acrylic acid stearyl, acrylic acid 2-chloroethyl, acrylic acid phenyl, ez-chloroacrylic acid methyl, metacrylic acid methyl, metacrylic acid ethyl, metacrylic acid propyl, metacrylic acid n-butyl, metacrylic acid isobutyl, metacrylic acid n-octyl, metacrylic acid dodecyl, metacrylic acid lauryl, metacrylic acid 2-ethyl hexyl, metacrylic acid stearyl, metacrylic acid phenyl, metacrylic acid dimethyl amino ethyl and metacrylic acid diethylaminoethyl etc., acrylic acid derivative or metacrylic acid derivative such as acrylonitrile, metacrylonitrile, acrylamido etc., vinylether such as vinylmethylether, vinylethylether and vinylisobutylether etc., vinylketone such as vinylmethylketone, vinylhexylketone and methylisopropenylketone etc., N-vinyl compound such as N-vinylpyrrole, N-vinylcarbazole, N-vinylindole and N-vinylpyrolidone etc., vinylnaphthalene and others are given, for example. These monomers can be used either independently or in combination of plural monomers and further, the combination that has polymerization and gives copolymers is also possible.

As reactive prepolymers to be used in the present invention, polybutadiene prepolymers such as butadiene polymer, a,co-polybutadienehomopolymer, ,sI)-polybutadieneglycol, ,- polybutadienedicarboxylic acid, maleic polybutadiene, terminal acryl denatured polybutadiene and terminal half ester denatured polybutadiene etc. can be given as a preferable one and these can be used either independently or in combination thereof.

Any of these polybutadiene prepolymers has, from its own structural feature, a nature of polyolefin and therefore toners obtained therefrom are given an anti-coking property.

Such reactive prepolymers are to be contained in polymeric composed substance within a range of 140% in weight and preferably 520% in weight against polymeric monomers.

As for polymerizing initiators which may be used for the present invention, any of ordinary use may be utilized within appropriate temperature range. As the examples, benzoyl peroxide, 2,2' azobisisobutylonitrile, 2,2'-azobis-(2,4-dibutylvaleronitrile), lauryl peroxide, orthochloro benzoyl peroxide and orthomethoxy benzoyl peroxide can be mentioned.

In the present invention, the polymerization can be effected under either ordinary or high pressure.

In the present invention, it is preferable to effect the aforementioned polymerization in the presence of a cross-linking agent which is a compound having two or more polymerizable double bonds in it, of which examples are given as such aromatic divinyl compounds as divinyl benzene, divinyl naphthalene and the derivatives thereof, e.g.: diethylene carboxylic acid type esters such as diethylene glycol acrylate, diethylene glycol methacrylate, triethylene glycol methacrylate, trimethylol propane triacrylate, allylmethacrylate, t-butylaminoethyl methacrylate, tetraethylene glycol dimethacrylate, 1,3butanediol dimethacrylate, ethyleneglycol dimethacrylate, and tetramethylolmethane tetraacrylate; every divinyl compound such as N,N-divinyl aniline, divinyl ether, divinyl sulfide and divinyl sulfone; and compounds having three or more vinyl radicals; every one of which can be used singly or mixedly. The mixing ratio of the cross linking agents against polymeric monomers is within the range of 0.00520% by weight, preferably 0.15% by weight.

Further in the present invention, it is preferable to use a low molecular polyolefin for the purpose of further improving the anti-offset property of the toner. As the low molecular polyolefin compound, those having relatively low melting point and a weight average molecular weight of 1 ,000 to 45,000 can be mentioned. Especially those having softening point of 100 to 1800 C, and more preferably, 130 to 1 600C can suitably be used.

As concrete examples of such polyolefin, polyethylene, polypropylene, polybutylene or the like can be given and among these, polypropylene is particularly preferable.

In low molecular polyolefin to be used for the prevention of offset in the present invention, low molecular olefin copolymer is included. Such low molecular olefin copolymer is an olefin copolymer wherein only olefin is contained as monomer component, or is an olefin copolymer wherein the one other than olefin is contained as monomer component and the molecular weight thereof is relatively small.

Olefin as monomer component includes, ethylene, propylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1, nonene-1 and decene-1 and their isomer wherein the position of unsaturated bond is different for example and 3-methyl-1 -butene, 3-methyl-2-pentene, 3-propyl-5-methyl-2-hexene etc. having branch chains made of alkyl group for example and all other olefins therein.

As a monomer other than oiefin that makes up copolymer together with olefin, vinylether such as vinylmethylether, vinyl-n-butylether and vinylphenylether etc. for example, vinylester such as vinylacetate and vinylbutylate for example, haloolefins such as vinyl fluoride, vinylidene fluoride, tetrafluoroethylene, vinyl chloride, vinylidene chloride and tetrachloroethylene etc. for example, ester acrylate or ester methacrylate such as methylacrylate, ethylacrylate, n-butylacrylate, methylmethacrylate, ethylmethacrylate, n-butylmethacrylate, stearylmethacrylate, N,Ndimethylaminoethylmethacrylate and t-butylaminoethylmethacrylate etc. for example, derivative acrylate such as acrylonitrile and N,N-dimethylacrylamide etc. for example, organic acid such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid etc., and various other compounds such as diethylefumarate and p-pinene can be mentioned.

Consequently, low molecular olefin copolymer that can be used in the present invention as low molecular polyolefin includes olefin copolymer made of only olefin that contains at least 2 kinds of above-mentioned olefin as monomer component, such as ethylene-propylene copolymer, ethylenebutenecopolymer, ethylene-pentene copolymer, propylene-butene copolymer, propylene-pentene copolymer, ethylene-3-methyl-1 -butene copolymer and ethylene-propylene-butene copolymer etc. for example, or olefin copolymer containing at least one kind of above-mentioned olefin and at least one kind of monomer other than above-mentioned olefin as monomer component such as ethylenevinylacetate copolymer, ethylene-vinylmethylether copolymer, ethylene-vinyl chloride copolymer, ethylene-methylacrylate copolymer, ethylene-methylmethacrylate copolymer, ethylene-acrylic acid copolymer, propylene-vinylacetate copolymer, propylene-vinylethylether copolymer, propyleneethylacrylate copolymer, propylene-methacrylic acid copolymer, butene-vinylmethylether copolymer, butene-methylmethacrylate copolymer, pentene-vinylacetate copolymer, hexene-vinylbutylate copolymer, ethylene-propylene-vi nylacetate copolymer and ethylene-vinylacetate-vinylmethylether copolymer etc. for example.

In case of olefin copolymer containing monomer other than olefin as its monomer component among low molecular olefin copolymer mentioned above, the one containing much olefin component therein is preferable. The reason for this is that in such copolymers, the releasing property is generally low, causing less effect as an offset prevention agent when the containing amount of olefin is small and there is a tendency that the characteristics such as fluidity and image forming property etc. of the toner obtained are deteriorated. Therefore, in case of aforesaid copolymers, the one containing much olefin is more desirable and particulariy the one containing olefin component of more than about 50 mol ,6 is advantageous as an offset prevention agent to be used in the present invention.

When using polyolefin having its average molecular weight of less than 1,000, the softening point of toners being obtained thereby is lowered and cohesion of toner grains is apt to occur and accordingly, stains on photosensitive substance or carrier become more serious when the aforesaid toners are applied to electrophotographic process, and on the other hand, when the average molecular weight thereof is over 45,000, the softening point of toners thus obtained becomes too high, so that it is impossible to obtain an offset prevention effect successfully.

Polyolefin serving as the abovementioned offset preventive is to be used at the ratio of 1-20 parts by weight, preferably 3-1 5 parts by weight against 100 parts of monomers of polymerized composite. When the ratio is less than 1 part by weight, the offset prevention effect becomes insufficient and unreliable, and when over 20 parts thereof, the fluidity of the toners thus obtained will become lower.

Further in the present invention, metallic salts of fatty acid such as zinc salt, barium salt, lead salt, cobalt salt, calcium salt and magnecium salt of stearic acid; zinc salt, manganese salt, iron salt and lead salt of oleic acids; and zinc salt, cobalt salt and magnecium salt of palmitic acids; and, higher fatty acids having more than 1 7 carbon atom numbers, higher alcohols having the same as above, esters of polyhydric alcohol, natural or synthesized paraffins, fatty acid esters and the partially saponified matters thereof, alkylene bis fatty acid amido such as ethylene bis stearoylamido, and other matters effective for offset prevention, can be used jointly with the aforesaid polyolefins having a low molecular weight.

The application of the aforementioned polyolefin compound to the toner composition itself has been heretofore known, however, in the known method where polymer and coloring agent are fused and kneaded at high temperature to make a mixture, in which the coloring agent is dispersed in the polymer, and then thus prepared mixture is ground or crushed into fine powders, there is a great disadvantage that because of rather poor miscibility of the polyolefin with the polymer, it has been rather difficult to incorporate the polyolefin into the polymer at high concentration, or uniformly.As the result of this fact, higher proportion of the polyolefin often exist on the surface of the polymer grains than in the grain, which leads to poor fluidity of the toner and which is the cause of so-called "tonerfilming" phenomenon, and thereby proper development with satisfactory image quality becomes difficult. Due to such a problem it has been difficult to use the polyolefin compound in such an amount as to sufficiently prevent the off-set phenomenon. Also, this fact has made it difficult to solve so-called "twining" problem in which the transfer paper winds around a fixing-roller.

According to the present invention, however, these disadvantages can be greatly improved since in the present invention the polyolefin compound can be incorporated at higher proportion and uniformly in the polymer grains. In this respect it is more preferable in the present invention that the low molecular polyolefin compound is made present at the time of polymerizing the monomer of the invention.

As for the coloring agents to be used for the present inventiqn, any suitable pigment or dye may optionally be used, for example, they are given as carbon black, nigrnsine dye (C.I. No. 5041 SB), aniline blue (C.l. No. 50405), chalcoil blue (C.I. No. azoee blue 3), chrome yellow (C.I. No. 14090), ultramarine blue (C.l. No. 77103), Du Pont oil red (C.l. No. 26105), Orient oil red #330 (C.l. No. 60505), quinoline yellow (C.l.No. 47005), methylene blue chloride (C.l. No.52015), phthalocyanine blue (C.l. No. 74160), malachite green oxalate (C.I. No. 42000), lamp black (C.l. No. 77266), rose bengal (C.I. No. 45435), oil black and azo oil black, each of which may be used singly or by mixing with each other. The coloring agents may be held in toners which are as the ultimate product, at such a ratio that the coloring agent can be held in at about 3-20% by weight of the toner. And in the case that magnetic powders of which are described hereinafter are to be utilized, the magnetic powders may be utilized as a coloring agent.

Further in the present invention, a so-called "single-component" type magnetic toner may also be obtainable by incorporating in the polymer component of the toner suitable magnetic substances. The magnetic substance in this invention means a substance which is capable of being strongly magnetized in a magnetic field and which has, more perferably, in black and is chemically stable. In the present invention it is preferable that the magnetic substance is in the form of fine powder having the average grain size of less than 1 micron, and in the above-mentioned respects magnetite (triiron tetraoxide) is most preferable.As examples of such magnetic substances, metals such as cobalt, iron and nickel; metallic alloys or mixtures of, for example, aluminium, cobalt, copper, iron, magnesium, nickel, tin, zinc, antimony, berylium, bithmuth, cadmium, calcium, manganese, selenium, titanium, tungsten and vanadium; metallic compound including metal oxide such as aluminium oxide, iron oxide, copper oxide, nickel oxide, zinc oxide, titanium oxide and magnecium oxide; refractory nitride such as vanadium nitride and chromium nitride; carbide such as silica carbide; and ferrite and a mixture thereof can be mentioned. It is preferable that fine powder of the aforementioned magnetic substance have the average grain diameter of 0.01 to 1 micron.The magnetic substance may be incorporated into the toner at the proportion of 50 to 300 parts by weight based on 100 parts by weight of polymer component of the toner, preferably 50 to 200 parts by weight, and particularly, 90 to 1 50 parts by weight based on the polymer component of the toner. The magnetic substance can either be present at the time of polymerization of the monomer of the present invention or be added to the polymer component after the polymerization, i.e., during fusing or kneading step.

The present invention is thus as described above and as is obvious from the examples and the descriptions thereof to be mentioned hereinafter the toners relating to the invention has an excellent anti-offset property and, in addition, it is possible to achieve the satisfactory fixing at a low fixing temperature.

As the reasons why such excellent effect can be obtained, the polymerization of polymeric monomer in a polymerized composite is made in the presence of reactive prepolymer, therefore, in the process of the aforesaid polymerization, a polymeric intermediate will come to partial cross-linkage to the aforementioned reactive prepolymer, and consequently, it can be considered that thus obtained polymer produces a part having a high molecular weight therein, by which anti-offset property may be obtained, and that the fixability, i.e., the fixing possibility at a low temperature, may be obtained by unreacted polymers and a part having a comparatively low molecular weight therein.

When the cross-linking agent is used in the present invention, the anti-impact property of the toner will be improved and, therefore the toner of the present invention is less likely to be pulverized by stirring of the toner before development, for the purpose of inducing the toner to bear electric charge, and, thus the toner-filming caused by the existence of toner particles of extremely fine grain size will be reduced.

Further in the case where the low molecular polyolefin compound is employed in the present invention, since according to the manufacturing method of the present invention, uniform incorporation of the compound at higher concentration is possible, improved fluidity of the toner will be obtainable, and furthermore such nuisance as the winding of the paper around the fixing roller can effectively be prevented.

The present invention is further illustrated hereinafter with reference to examples. In the examples, the term "part" or "parts" is expressed in terms of part or parts by weight.

EXAMPLE 1 Styrene 70 parts n-butyl methacrylate 30 parts Carbon black "Raven 1250" (mfd. by Columbian Co.) 5 parts "Oil Black BW" (mfd. by Orient Chem. Co., Electric charge 0.2 parts control agent) Azo bisisobutylonitrile 3 parts a,-polybutadiene glycol "NISSO-PB G-1000" (mfd. by Nihon 10 parts Soda Co., molecular weight 1000) The above mentioned substances are mixed and dispersed to prepare a composition for polymerization.This composition is added into 0.6 weight % solution of polyvinyl alcohol in a separable flask whose capacity is two liters, and the mixture is heated up to the temperature of 900C while stirring and is then polymerized in keeping it for eight hours time at the same degree of temperature, and after cooling, a solid is separated therefrom, centrifugally dehydrated, dried up and then pulverized, and thereby toner in the form of fine powder having the average grain size of 13 microns for two-component type developer, which is hereinafter referred to as Sample 1, is obtained.

EXAMPLE 2 Toner for two-component type developer, having the average grain size of 1 3 microns was prepared in the same manner as Example 1 except that in this example 1 part of Diethyleneglycol methacrylate was added to the composition of Example 1. This toner is hereinafter referred to as Sample 2.

EXAMPLE 3 Toner for two-component type developer, having the same grain size as Example 1 was prepared in the same manner as Example 1 except that in this example 5 parts of VISCOL 550P (a low molecular weight polypropylene, product of Sanyo Kasei Co., Ltd.) was added to the composition. This toner is hereinafter referred to as Sample 3.

EXAMPLE 4 Toner for two-component type developer, having the same grain size as Example 1 was prepared in the same manner as Example 2 except that in this example 5 parts of VISCOL 550P was added to the composition. This toner is hereinafter referred to as Sample 4.

EXAMPLE 5 Toner for two-component type developer having the average grain size of 1 3 microns was prepared by effecting a polymerization to the composition of Example 1 in the same manner as Example 1 (except that, however, in this example carbon black and electric charge controlling agent are excluded from the composition) and then by fusing, kneading and pulverizing a mixture consisting of 50 parts of polymer thus obtained by the polymerization, 3 parts of carbon black (Raven 1250) and 1 part of electric charge controlling agent (Oil Black BW). This toner is hereinafter referred to as Sample 5.

EXAMPLE 6 Toner having the same average grain size was prepared in the same manner as Example 5, except that in this example, 1 part of Diethylene glycol was added to the composition of Example 5. This toner is hereinafter referred to as Sample 6.

EXAMPLE 7 Toner having the same average grain size was prepared in the same manner as Example 5, except that in this example, 5 parts of VISCOL 550P was added to the composition of Example 5. This toner is hereinafter referred to as Sample 7.

EXAMPLE 8 Toner having the same average grain size was prepared in the same manner as Example 6, except that in this example, 5 parts of VISCOL 550P was added to the composition of Example 6. This toner is hereinafter referred to as Sample 8.

EXAMPLE 9 Styrene 90 parts n-butylacrylate, "Mitsubishi Carbon Black #2300" 5 parts (mfd. by Mitsubishi Kasei Kogyo Co.) "Oil Black BW" 0.1 part Diethyl amino ethyl methacrylate (cationic polymeric 4 parts monomer) 2,2'-azobis-(2,4-dimethyl valeronitrile) 2 parts ct,w-polybutadiene glycol "NISSO-PB G-1000" 10 parts A composition for polymerization was prepared by mixing the substances shown above. This composition was put into a 2-liter separable flask in which is 0.8 parts of colloidal silica, "Aerosil 200" (Product of Degussa) in distilled water contained. Then the temperature of the mixture was raised up to 650C while stirring said mixture by using TK Homomixer (Product of Tokushu Kika Kogyo Co., Ltd.) at 3000 r.p.m. and the temperature of the mixture was maintained at 650C.The average diameter of the thus dispersed grains after 30 minutes' stirring at 650C was within the range of 10 to 1 5 microns.

Thereafter, while stirring the suspension thus formed by using a common mixer at 100 r.p.m., polymerization was carried out for 6 hours. After the polymerization was complete no substantial change in the average grain size was observed. The solid part of the suspension thus prepared was then filtrated and dried up, to obtain toner for two-component type developer having the average grain size of 13 microns in the powder form. This toner is hereinafter referred to as Sample 9.

EXAMPLE 10 In this example, toner was prepared in the same manner as Example 9, except that in this example, 0.5 parts of trimethylolpropane triacrylate was added to the composition for polymerization of Example 9. This toner is hereinafter referred to as Sample 10.

EXAMPLE 11 In this example, toner was prepared in the same manner as Example 9, except that in this example, 5 parts of VISCOL 550P was added to the composition of Example 9. This toner is hereinafter referred to as Sample 11.

EXAMPLE 12 In this example, toner was prepared in the same manner as Example 9, except that in this example, 0.5 parts of trimethylolpropane triacrylate and 5 parts of VISCOL 550P were added to the composition of Example 9. This toner is hereinafter referred to as Sample 12.

EXAMPLE 13 Styrene 70 parts Methylmethacrylate 20 parts n-butylmethacrylate 10 parts "Mitsubishi Carbon Black MA-600" (mfd. by Mitsubishi 5 parts Kasei Kogyo Co.) "Azo Oil Black (R)" (mfd. by National Aniline Co. 0.3 part Electric Charge Controlling Agent) Lauroyl peroxide 2 parts ,-polybutadiene glycol "NISSO-PS G-3000" 10 parts (mfd. by Nihon Soda Co. molecular weight 3000) A composition for polymerization consisting of the substances shown above was prepared in the same manner as Example 9. This composition was then poured into a 2-liter separable flask which contains therein 1.25% by weight of polyvinyl alcohol solution. Then the mixture was treated in the same manner as Example 9, to obtain toner for two-component type having the average grain size of 13 microns, in the powder form.

This toner is hereinafter referred to as Sample 13.

EXAMPLE 14 In this example, toner was prepared in the same manner as Example 13, except that in this example, 2 parts of triethyleneglycol methacrylate was added to the composition for polymerization of Example 1 3. This toner is hereinafter referred to as Sample 14.

EXAMPLE 1 5 In this example, toner was prepared in the same manner as Example 13, except that in this example, 10 parts of low molecular weight ethylene-propylene copolymer was added to the composition of Example 1 3. This toner is hereinafter referred to as Sample 1 5.

EXAMPLE 16 In this example, toner was prepared in the same manner as Example 13, except that in this example, 2 parts of triethyleneglycol methacrylate and 1 0 parts of low molecular weight ethylenepropylene copolymer were added to the composition of Example 13. This toner is hereinafter referred to as Sample 1 6.

EXAMPLE 17 Methyl methacrylate 100 parts Triiron tetraoxide powders "Mapico Black BL-100" 60 parts (mfd. by Titan Kogyo Co.) Triiron tetraoxide powders, "Toda Color-EPT-1 000" 40 parts (mfd, by Toda Kogyo Co.) "Nigrosine Base EX" (mfd. by Orient Kogyo Co. 0.2 part Electric Charge Controlling Agent) Dicocoamine (cationic, less water soluble amine) 1.2 parts Azobisisobutylonitrile 1 part )-polybutadiene glycol "NISSO-PB G-1 000" 1 5 parts A composition consisting of the substances shown above was prepared in the same manner as Example 13. This composition was then poured into a 2-liter separable flask which contains therein 1.2 parts of colloidal silica "Arosil Mox 1 70", as a cathionic inorganic dispersing agent, distilled in water.

Then the mixture was treated in the same manner as Example 13 for polymerization, thereby to obtain toner, in the form of fine powder having the average grain size of 13 microns, for one-component type developer. This toner is hereinafter referred to as Sample 1 7.

EXAMPLE 18 In this example, toner was prepared in the same manner as Example 17, except that in this example 1.5 parts of diethyleneglycol methacrylate was added to the composition for polymerization of Example 17. This toner is hereinafter referred to as Sample 18.

EXAMPLE 19 In this example, toner was prepared in the same manner as Example 17, except that in this example, 5 parts of VISCOL 550P was added to the composition of Example 17. This toner is hereinafter referred to as Sample 1 9.

EXAMPLE 20 In this example, toner was prepared in the same manner as Example 17, except that in this example, 1.5 parts of diethyleneglycol methacrylate and 5 parts of VISCOL 550P were added to the composition of Example 1 7. This toner is hereinafter referred to as Sample 20.

COMPARATIVE EXAMPLE 1 Toner was prepared in the same manner as Example 9, except that in this example, Qo)- polybutadieneglycol was excluded from the composition of Example 9. This toner is hereinafter referred to as Comparative Sample 1.

COMPARATIVE EXAMPLE 2 Toner was prepared in the same manner as Example 10, except that in this example, Qw- polybutadieneglycol was excluded from the composition of Example 10. This toner is hereinafter referred to as Comparative Sample 2.

COMPARATIVE EXAMPLE 3 Toner was prepared in the same manner as Example 11, except that in this example, a'w- polybutadiene was excluded from the composition of Example 11. This toner is hereinafter referred to as Comparative Sample 3.

COMPARATIVE EXAMPLE 4 In this example, toner was prepared in the same manner as Example 12, except that ,- polybutadieneglycol was excluded from the composition of Example 12.

The above mentioned samples and comparison samples have been put to the tests, of which results are illustrated as follows: OFFSET TEST In the tests with respect to Samples 1-4 and Comparison Samples 1-3, each electrostatically charged images having been formed by an electrophotocopier, [U-Bix V] (mfd. by Konishiroku Photo Int.

Co.), are developed by making use of the developing agents respectively prepared by mixing five parts each of the above samples with 95 parts each of [Iron powdered carrier, D B P], (mfd. by Dowa Iron Powder Ind. Co.); and, with respect to Sample 5, an electrostatically charged image formed by an electrophotocopier, [U-Bix T] (mfd. by Konishiroku Photo Ind.Co.), is developed by making use of the sample toner, as it is, as a developing agent by each of which the each toner image respectively formed is transferred onto transfer paper having the weight of 64 g/m2 and the transferred image is fixed at the line speed of 150 mm/sec, by the fixing device comprising a heat roller of which surface layer is of Teflon (mfd. by Du Pont, Tetrafluoroethylene) and a pressure roller, and then blank transfer paper without having any toner image is processed under the similar conditions and in the similar manner, and the checking operations are made on whether or not there is any stain on the transfer paper due to offset phenomenon, by setting at a variety of degrees of the temperature of the aforesaid heat roller, by which the lowest temperature to cause such offset phenomenon is obtained. The results thereof are shown in the Table below.

II. TESTS OF FIXING TEMPERATURE In the tests, taking in the similar manner to that in the above mentioned offset tests, the transferred image which is formed on the similar transfer paper by making use of each Sample and Comparison Sample, can be completely fixed on the said transfer paper by a heat roller for which the lowest temperature thereof (that is called as "Complete Fixation Temperature") is obtained. The results thereof are shown in the Table below.

III. TWINING TESTS In the tests, making use of the similar apparatuses and transfer paper under the similar conditions to those of the offset tests, a solid black toner image of 3 cm wide is formed in front portion of a transfer paper and is made fix, then various degrees of temperature of the heat roller of fixing device are set, by which the lowest temperature not to cause any twining of transfer paper is obtained.The results thereof are shown in the table below: TABLE Temperature at Temperature at which Offset Complete Fixation which twining Sample No. occurred (OC) Temperature (OC) occurred (OC) 1 200* 150 2 220* 155 3 210* 150 170* 4 240* 150 170* 5 190* 150 6 210* 155 7 200* 150 170* 8 230* 150 170* 9 200* 150 10 220* 150 11 210* 150 170* 12 240* 150 170* 13 200* 150 14 220* 155 15 210* 150 170* 16 240* 150 170* 17 190* 160 18 210* 160 19 200* 160 170* 20 240* 160 170* Comparative Sample 1 130 180 Comparative Sample 2 210 200 Comparative Sample 3 200 180 170* Comparative Sample 4 240* 200 170* Note: Asterisks in the Table means that no off-set phenomenon was observed at the respective temperatures.

From the above results, it is obvious that the toners prepared according to the present invention (Samples 1 to 20) have excellent anti-offset property, fixability at low temperature, and when the low molecular polyolefin is added, excellent anti-twining property.

As compared thereto, Comparative Samples are inferior to the sample of the present invention in view of either anti-offset property, fixability at low temperature or anti-twining property.

Claims (14)

1. A toner composition for electrophotography which comprises a polymer obtained by polymerizing a monomer and a reactive prepolymer, and a coloring agent.

2. A toner composition as claimed in Claim 1, wherein the polymer is obtained by polymerization in the presence of a cross-linking agent.

3. A toner composition as claimed in Claim 1 or 2, wherein the polymer is obtained by polymerization in the presence of a low molecular olefin polymer having a weight average molecular weight of 1,000 to 45,000.

4. A toner composition as claimed in any preceding Claim wherein the reactive prepolymer is a butadiene type prepolymer.

5. A toner composition as claimed in any preceding Claim which comprises particles having an average diameter of 1 to 50 microns.

6. A toner composition as claimed in Claim 1 and substantially as hereinbefore described with reference to any of Example 1 to 20.

7. A method for manufacturing a toner composition for electrophotography which comprises polymerizing a monomer and a reactive prepolymer.

8. A method as claimed in Claim 7, wherein polymerization is effected in the presence of a crosslinking agent.

9. A method as claimed in Claim 8, wherein the cross-linking agent is present in an amount from 0.005 to 20 percent by weight, based on monomer.

10. A method as claimed in any of Claims 7 to 9, wherein the reactive prepolymer is present in an amount from 1 to 40 percent by weight, based on monomer.

11. A method as claimed in any of Claims 7 to 10, wherein the reactive prepolymer is a butadiene type prepolymer.

12. A method as claimed in any of Claims 7 to 11, wherein polymerization is effected in the presence of a low molecular polyolefin having a weight average molecular weight of 1,000 to 45,000.

13. A method as claimed in any of Claims 7 to 12, wherein polymerization is effected in the presence of a coloring agent.

14. A method as claimed in any of Claims 7 to 12, wherein the polymer resulting from polymerizing the monomer and the reactive prepolymer is mixed with a coloring agent.

1 5. A method as claimed in any of Claims 7 to 14, wherein polymerization is carried out in suspension.

1 6. A method as claimed in Claim 7 and substantially as hereinbefore described with reference to any of Examples 1 to 20.