JPH0447310B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a toner binder. More specifically, the present invention relates to a toner binder that has a wide molecular weight distribution and is suitable for electrophotography. [Prior Art] In electrophotography, a method using a heat roller is widely used to fix an electrostatic latent image visualized with toner. In this method, it is desirable that the minimum fixing temperature (hereinafter abbreviated as MF) is low.
In addition, it is desirable that the temperature at which offset to the heat roll occurs (hereinafter abbreviated as HO) is high. In general, when a polymer with a low molecular weight is used as a toner binder, the MF is low, but the HO is also low. On the other hand, if a polymer with a high molecular weight is used as a binder, the problem arises that although the HO becomes high, the MF also becomes high. In order to meet these mutually contradictory demands, a polymer with a wide molecular weight distribution, which is a blend of a high molecular weight polymer and a low molecular weight polymer, is used as a binder for toner. [Problems to be solved by the invention] However, the binders obtained by these technologies cannot
Inadequate in terms of HO and MF. Furthermore, it is desirable for toners to have easy control of charging characteristics and low environmental dependence, but residues of the polymerization initiator used during polymerization have an adverse effect on these aspects, making it difficult to control charging and the environment. Problems also arise in terms of dependencies. [Means for Solving the Problems] The present inventors have developed a binder made of a polymer with a wide molecular weight distribution that has favorable properties in terms of HO and MF (a binder that provides a toner with low MF and high HO), and As a result of extensive research into binders with less environmental dependence, the present invention was arrived at. That is, the present invention refers to styrene monomers and (meth)acrylic monomers (acrylic monomers and/or methacrylic monomers) among styrene polymers having a molecular weight of 5,000 to 50,000.
(hereinafter this expression will be used) from the temperature at which thermal polymerization substantially starts to a temperature that is 50°C or more higher and 250°C or lower depending on the temperature, substantially the absence of a polymerization initiator. A method for producing a binder for electrophotographic toner comprising a polymer with a wide molecular weight distribution, which is thermally polymerized under the following conditions. In the present invention, styrenic polymers include homopolymers of styrene monomers and copolymers of styrene monomers and other monomers. Styrenic monomers include styrene, alkylstyrene (e.g. α-methylstyrene, p-
methylstyrene), etc. Preferably it is styrene. Other monomers include (meth)acrylic monomers, vinyl esters, and aliphatic hydrocarbon vinyl monomers. Examples of (meth)acrylic monomers include alkyl (meth)acrylates [alkyl having 1 to 18 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate , lauryl (meth)acrylate, stearyl (meth)acrylate, etc.], hydroxyl group-containing (meth)acrylates [hydroxylethyl (meth)acrylate, etc.], amino group-containing (meth)acrylates [dimethylaminoethyl (meth)acrylate,
diethylaminoethyl (meth)acrylate, etc.], nitrile group-containing (meth)acrylic compounds [acrylonitrile, etc.], and (meth)acrylic acid. Examples of the vinyl ester include vinyl acetate and vinyl propionate, and examples of the aliphatic hydrocarbon vinyl monomer include butadiene. Among these, preferred are (meth)acrylic monomers, particularly preferred are methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (meth)acrylic acid, and the like. It is a mixture of two or more. The amount of monomers constituting this styrenic polymer is usually 100 to 50% by weight.
Preferably 100-70% by weight, other monomers 0-70% by weight
50% by weight, preferably 0-30% by weight. The molecular weight of styrenic polymers is usually 5×10 ³ ~
5×10 ⁴ , preferably 6×10 ³ to 2×10 ⁴ .
If the molecular weight is less than 5×10 ³ , the glass transition temperature (Tg) will decrease and blocking properties will deteriorate;
If it exceeds 10 ⁴ , the MF becomes too high. The molecular weight was determined by gel permeation chromatography (hereinafter referred to as GPC) using tetrahydrofuran (hereinafter referred to as THF) as a solvent.
It can be converted to standard polystyrene and expressed as a weight average. This polymer can be obtained by polymerizing the monomer by any method such as thermal polymerization, radical polymerization, or ionic polymerization, but when using a polymerization initiator, one with a particularly low boiling point (for example, boron trifluoride in cationic polymerization) is used. , di-t in radical polymerization
-butyl peroxide, etc.) is preferably used. Examples of the styrene monomer and (meth)acrylic monomer used in thermal polymerization include those described in the polymer section above, and preferred ones are also the same. In addition to styrene monomers and acrylic monomers, other monomers (vinyl esters, aliphatic vinyl monomers, etc.)
Can also be used together. In order to obtain higher molecular weight polymers during thermal polymerization, polyfunctional monomers having at least two polymerizable double bonds [e.g. di- or polyvinyl compounds (divinylbenzene, divinyltoluene, ethylene glycol diacrylate, 1,6-hexanediol di- acrylate, etc.)] can be added. Preferably divinylbenzene and 1,
6-hexanediol diacrylate. The amount of monomers to be thermally polymerized is that the styrene monomer is usually 95 to 55% by weight, preferably 90 to 60% by weight, and the (meth)acrylic monomer is usually 5 to 45% by weight, preferably 10% by weight, based on the weight of all monomers.
~40% by weight, polyfunctional monomers 3% or less, preferably 1% or less, other monomers usually 10% or less,
Preferably it is 5% or less. When the amount of the polyfunctional monomer exceeds 3 mol %, gelation tends to occur during polymerization. The amount of the styrenic polymer and all monomers [styrenic monomer, (meth)acrylic monomer, polyfunctional monomer, and other monomers] added during thermal polymerization is the styrene unit and (meta)
The amount of acrylic monomer units is selected to fall within the range shown in Table 1 below.

[Table] The amount of styrenic monomer units is less than 65% and the amount of (meth)acrylic monomer units is 35%
If it exceeds 100%, the HO of the toner becomes low, the blocking properties deteriorate, and the pulverizability of the binder also deteriorates. Conversely, if each amount exceeds 95% and is less than 5%, the MF of the toner becomes too high. The weight ratio of the styrene polymer to all monomers is usually 30:70 to 70:30, preferably 40:60 to 60:
It is 40. When the polymer ratio is less than 30, it becomes difficult to control the thermal polymerization reaction, and MF
It also becomes more expensive. On the other hand, if the polymer ratio exceeds 70
HO becomes low. Examples of the compositions and blending ratios of the styrenic polymers, styrene monomers and (meth)acrylic monomers, and monomer compositions in the blends of polymers and monomers are shown in Table 2.

[Table] In the present invention, in addition to the above-mentioned components, a low molecular weight polyolefin can also be used in a uniformly dispersed state. For electrophotographic toners for which the present binder is used, it is preferable that the low molecular weight polyolefin is uniformly dispersed, since a better mold release effect can be obtained. For this reason, it is desirable that the low molecular weight polyolefin be added to the system during thermal polymerization of the styrene monomer and (meth)acrylic monomer. The weight average molecular weight of the low molecular weight polyolefin is usually 1000 to 100000, preferably 5000 to 60000.
(a): Polyethylene, polypropylene, ethylene-
α-olefin (3 to 8 carbon atoms) copolymer (e.g. ethylene 50wt% or more, especially 70wt% or more), (b) Maleic acid derivatives (maleic anhydride, maleic acid dimethyl ester, maleic acid diethyl ester) , maleic acid di-2-ethylhexyl ester, etc.) adducts, (c): oxides of (i), (d): ethylenically unsaturated carboxylic acids ((meth)acrylic acid, itaconic acid, etc.) and/or their Esters (such as alkyl (C1-C18) esters) and ethylenically unsaturated hydrocarbons (ethylene,
copolymers with propylene, butene-1, etc.) and mixtures of two or more thereof. Among the above low molecular weight polyolefins, (a) is a high molecular weight polyolefin (the molecular weight is usually 10,000 ~
2,000,000), or by monopolymerizing or copolymerizing olefin. (B) can be obtained by subjecting a low molecular weight polyolefin to an addition reaction with a maleic acid derivative in the presence of a peroxide catalyst or in the absence of a catalyst.
(C) can be obtained by oxidizing low molecular weight polyolefin with oxygen or oxygen-containing gas (air), or by oxidizing it with ozone-containing oxygen or ozone-containing gas (air). The acid value of the oxide is usually 100 or less, preferably 50 or less. (d) is an ethylenically unsaturated carboxylic acid and/or its alkyl ester (C ₁
~ _C18 ) and an ethylenically unsaturated hydrocarbon. The amount of ethylenically unsaturated carboxylic acid and/or its alkyl ester is usually not more than 30%, preferably not more than 20% by weight. The amount of low molecular weight polyolefin is usually less than 30% by weight, preferably less than 20% by weight, based on the total weight of styrenic polymer and monomer. If it exceeds 30% by weight, dispersion will be insufficient. The molecular weight of the low molecular weight polymer olefin is
Using o-dichlorobenzene as a solvent in GPC
Can be measured at 135℃. Thermal polymerization can be carried out with or without a solvent. As the solvent, it is preferable to use a solvent with a high boiling point such as cumene or dibenzyl ether. However, when a solvent is used, a step of desolvation is required after polymerization, and from the viewpoint of production efficiency, no solvent is preferable. The atmosphere is preferably an inert gas such as nitrogen. Moreover, the system can be either an open system or a closed system. Thermal polymerization substantially starts from the temperature at which thermal polymerization starts.
The temperature is 50℃ or more higher than that temperature and 250℃
It is carried out by raising the temperature to a certain temperature below. The temperature at which thermal polymerization substantially starts as described herein is the temperature at which a meaningful polymerization rate for binder production (for example, a polymerization rate of 2%/hr) is obtained, and is usually 80 to 130°C and preferably. is 100-120
It is ℃. The upper limit temperature for thermal polymerization is in the range from 50°C higher than the above-mentioned starting temperature to 250°C, usually in the range of 170 to 250°C, preferably in the range of 180 to 200°C. If it is less than 80°C, the rate of thermal polymerization is slow and is not practical. Furthermore, if the temperature exceeds 250°C, thermal decomposition of the polymer will occur. The polymerization time to achieve a polymerization rate of 90% or more depends on the polymerization temperature, but is usually 10~
It is 24 hours. The temperature may be raised continuously or stepwise within this range, but from the viewpoint of controlling the molecular weight distribution, it is preferable to raise the temperature stepwise. Table 3 shows an example of the relationship between temperature increase method and polymerization rate.

[Table] The polymerization rate is determined by quantifying the amount of monomer remaining in the reaction solution using gas chromatography. Molecular weight distribution of the binder obtained by thermal polymerization [ratio of weight average molecular weight to number average molecular weight (Mw/
Mn) is usually 30 or more, preferably 35 or more for binders for electrophotographic toners. If the molecular weight distribution is less than 30, the balance between HO and MF will be poor. Also, the glass transition point is usually 40 to 80
℃, preferably 45-70℃. glass transition point
If it is less than 40°C, the toner will have poor storage stability, and if it exceeds 80°C, the MF will be high and it will not be practical as a toner. Furthermore, the binder produced by the polymerization method of the present invention has a larger amount of double bonds than binders produced by other polymerization methods (for example, radical polymerization method).
As a result, it has the advantage that the MF is low and the dispersibility of the coloring material of the toner is excellent. The electrophotographic toner to which the binder of the present invention is used usually has a binder content of 50 to 95% based on toner polymerization.
%, known coloring materials (carbon black, iron black,
Benzidine yellow, quinacridone, rhodamine B, phthalocyanine, etc.) is usually used in an amount of 5 to 10%, and magnetic powder (ferromagnetic metal powder such as iron, cobalt, nickel, etc. or compounds such as magnetite, hematite, ferrite, etc.) is usually used in an amount of 0 to 50%. Consists of what was given. Furthermore, various additives [charge control agents (metal complexes,
nigrosine, etc.), lubricants (such as polytetrafluoroethylene, low molecular weight polyolefins, fatty acids, or metal salts or amides thereof), etc.). The amount of these additives is typically 0-5% based on toner weight. Electrophotographic toner is produced by dry blending the above components, then melt-kneading, then coarsely pulverizing, finally pulverizing using a jet pulverizer, etc., and further classifying to obtain fine particles with a particle size of 5 to 20 microns. . The electrophotographic toner is mixed with carrier particles such as iron powder, glass beads, nickel powder, ferrite, etc., if necessary, and used as a developer for electrostatic latent images. Further, hydrophobic colloidal silica fine powder can also be used to improve the fluidity of the powder. The electrophotographic toner is used by being fixed on a support (paper, polyester film, etc.), and a known hot roll fixing method can be used as a fixing method. [Examples] The present invention will be further explained below with reference to Examples.
The present invention is not limited thereby. In the examples, all parts represent parts by weight. Moreover, the conditions for molecular weight measurement by GPC are as follows. Equipment: Toyo Soda HLC-802A Column: 2 TSK gel GMH6 (Toyo Soda) Measurement temperature: 25℃ Sample solution: 0.5% by weight THF solution Solution injection amount: 200 μl Detection device: Refractive index detector Molecular weight calibration curve is made using standard polystyrene. Synthesis example 1 2500 g of xylene in a 10 liter sealed reaction vessel equipped with a stirring device
The tank was replaced with nitrogen. After sealing the container and reducing the pressure inside the system to 100 mmHg, the liquid temperature was brought to 155°C. While maintaining the temperature at 155°C, a mixed solution of 2700 parts of styrene and 300 parts of butyl acrylate, and a mixed solution of 210 parts of di-t-butyl peroxide (volatile radical polymerization initiator) and 1200 parts of xylene were introduced under pressure over a period of 4 hours. Polymerized. The temperature was further maintained at the same temperature for 2 hours to complete the polymerization. After the polymerization was completed, xylene was distilled off under reduced pressure. The polymerization average molecular weight of the obtained polymer is
It was 6000. This polymer will be referred to as Polymer (1). Synthesis Example 2 4,000 parts of ethylene dichloride was charged into a 10-liter reaction vessel equipped with a reflux condenser and a stirring device, and the atmosphere was replaced with nitrogen, followed by 6 parts of acetic anhydride and a 50% solution of boron trifluoride in diethyl ether (initiator for volatile cationic polymerization). I put in 4 copies. After raising the temperature to 60°C, 4000 parts of styrene was added dropwise over 4 hours while maintaining the system at 60°C. The system was kept at 60°C for an additional 3 hours to complete polymerization. After the polymerization was completed, ethylene dichloride was distilled off under reduced pressure. The weight average molecular weight of the obtained polymer is 10000
When the amount of boron trifluoride remaining in the polymer was determined by the Alftsson method, it was found to be a trace amount of less than 5 ppm. This polymer will be referred to as Polymer (2). Example 1 Styrene 1980 was placed in the same sealed reaction vessel as in Synthesis Example 1.
495 parts of butyl acrylate and 275 parts of methyl methacrylate, and further added 2250 parts of polymer (1).
I joined the club. After replacing the inside of the system with nitrogen, the system was sealed and the mixture was uniformly dissolved. The temperature inside the system was raised to 110°C, and thermal polymerization was carried out at the same temperature for 4 hours. The polymerization rate is 12
It was %. Next, thermal polymerization was carried out at 120°C for 6 hours.
The polymerization rate reached 45%. Further, thermal polymerization was carried out at 130°C for 2 hours to obtain a polymerization rate of 60%. Finally, the temperature was raised to 185°C and thermal polymerization was carried out for 2 hours to reach a polymerization rate of 95%. After this, the pressure is reduced and the remaining monomer is distilled off to form a binder.
I got (A). Binder (A) has a weight average molecular weight
110,000, molecular weight distribution of 35, and glass transition point of 65°C. Example 2 Styrene 2050 was placed in the same sealed reaction vessel as in Example 1.
parts, butyl acrylate 600 parts, 1,6-hexanediol diacrylate 1.3 parts and polymer (2)
2,350 copies were sold. This was thermally polymerized stepwise in the same manner as in Example 1 at 110°C for 4 hours, 120°C for 9 hours, 130°C for 4 hours, and 180°C for 2 hours, and then the remaining monomer was distilled off. A binder (B) was obtained. The binder (B) had a weight average molecular weight of 200,000, a molecular weight distribution of 45, and a glass transition point of 60°C. Example 3 Styrene 1550 was placed in the same sealed reaction vessel as in Example 1.
650 parts of butyl methacrylate, 250 parts of stearyl methacrylate, 50 parts of methacrylic acid, 0.8 parts of divinylbenzene, 2500 parts of polymer (1), and 75 parts of Viscol 550P (low molecular weight polypropylene manufactured by Sanyo Chemical Industries, Ltd.) was introduced. This was heated at 110°C for 3 hours, at 120°C for 6 hours, and at 160°C in the same manner as in Example 1.
After thermal polymerization was carried out stepwise at 180°C for 1 hour and 2 hours at 180°C, the remaining monomers were distilled off to obtain a binder (C). Binder (C) has a weight average molecular weight
120,000, molecular weight distribution was 40, and glass transition point was 55°C. Comparative Example 1 1250 parts of toluene and 2000 parts of polymer (1) were put into the same reaction vessel as in Synthesis Example 2, the system was made into a nitrogen atmosphere, and the temperature was raised while stirring to obtain a solution of polymer (1). Styrene while keeping the system under reflux at 120°C.
2,460 parts of a polymerization initiator solution of a mixed solution of 2,460 parts of butyl acrylate, 540 parts of butyl acrylate, and 25 parts of divinylbenzene, 25 parts of azobisisobutyronitrile, and 750 parts of toluene.
The mixture was added dropwise over a period of time to perform radical polymerization. After the completion of the dropwise addition, the system was further maintained at the same temperature, and 150 parts of a 3% toluene solution of azobisisobutyronitrile was added 1.5 and 3.0 hours later to complete the polymerization. Toluene was distilled off under reduced pressure from this polymerization solution to obtain a binder (D). Binder (D) has a weight average molecular weight of 120,000 parts,
The molecular weight distribution was 30 and the glass transition point was 60°C. Use Examples 1 to 3 and Comparative Use Example 1 Electrophotographic toners were prepared by the following method using binders (A) to (D), and further, an electrophotographic developer was prepared. Toner production method Binder 90 parts Viscoel 660P (low molecular weight polypropylene manufactured by Sanyo Chemical Industries, Ltd.) 3 parts Carbon Black MA-100 (Mitsubishi Chemical Industries, Ltd.)
6 parts Eisenspiro Black TRH (Hodogaya Chemical Industry Co., Ltd.)
(manufactured by Nippon Neumatics Co., Ltd.) 1 part The above-mentioned mixture was powder-blended and kneaded for 10 minutes at 140° C. and 30 rpm using a laboplast mill, and the resulting kneaded product was pulverized using a jet mill PJM100 (manufactured by Nippon Neumatic Co., Ltd.). Using an air classifier MDS (manufactured by Nippon Neumatics Co., Ltd.), the finely ground material is separated into 5μ
The following fine powder was cut. To 1000 parts of the obtained powder, 3 parts of Aerosil R972 (manufactured by Nippon Aerosil Co., Ltd.) were uniformly mixed to obtain a toner. Developer Preparation Method An electrophotographic developer was obtained by mixing 1000 parts of carrier iron powder for electrophotography (F-100 manufactured by Nippon Tetsuko Co., Ltd.) with 25 parts of the above toner. Evaluation Results The evaluation results are shown in Tables 4 and 5.

[Table] Measured.

【table】

【table】

[Table] The binders (A) to (C) of the present invention have a wider temperature range between MF and HO than binder (D), and have thermal properties preferable as a toner. Furthermore, it was confirmed that it has excellent charge controllability and environmental dependence. [Effects of the Invention] The binder of the present invention is made of a polymer with a wide molecular weight distribution and satisfies both HO and MF, which are originally contradictory to each other. Furthermore, it is a binder that can be easily controlled in charge and has little environmental dependence, making it extremely useful.

Claims (1)

[Scope of Claims] 1. Among styrenic polymers having a molecular weight of 5,000 to 50,000, styrene monomers and (meth)acrylic monomers are heated at a temperature 50°C or more higher than the temperature at which thermal polymerization substantially starts. and
A method for producing a binder for an electrophotographic toner comprising a polymer with a wide molecular weight distribution, characterized by carrying out thermal polymerization in the substantial absence of a polymerization initiator while raising the temperature to a temperature of 250° C. or lower. 2. Among styrenic polymers and low molecular weight polyolefins with a molecular weight of 5,000 to 50,000, styrene monomers and (meth)acrylic monomers are heated from the temperature at which thermal polymerization substantially starts to 50° below that temperature.
A binder for an electrophotographic toner comprising a polymer with a wide molecular weight distribution, which is thermally polymerized in the substantial absence of a polymerization initiator while raising the temperature to a temperature higher than ℃ and lower than 250℃. manufacturing method. 3 Based on the weight of total monomers, 95% to 55% styrenic monomer, 5% to 55% (meth)acrylic monomer
45%, polyfunctional monomer 3% or less, other monomers
The method for producing a binder according to claim 1 or 2, wherein 10% or less of the binder is thermally polymerized.