JPH0820772B2 - Static charge control agent - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrostatic charge control agent.

[Prior Art] Conventionally, in electrophotography, electrostatic recording paper, etc., for the purpose of imparting a charge of toner used for developing an electrostatic charge image,
It is known that a negative or positively charged electrostatic charge control agent is used for toner by means of internal addition or external addition.

As the positively charged electrostatic charge control agent, an azine dye such as nigrosine and a quaternary ammonium salt such as decyltrimethylammonium bromide are used.

[Problems to be Solved by the Invention] However, azine dyes are difficult to use in color toners because they are colored, and their properties are not constant because they are complex mixtures. Quaternary ammonium salt derivatives are humidity dependent. Many of them have a high chargeability and a small absolute amount of electrification,
In addition, since it has low heat resistance, there is a problem that it is difficult to obtain stable quality due to separation in the processing step.

[Means for Solving Problems] The inventors of the present invention have conducted extensive studies to obtain an electrostatic charge control agent that can be used in color toners and has good charging stability and high heat resistance. The present invention has been reached.

That is, the present invention has the general formula (In the formula, R ₁ and R ₃ are each independently a optionally substituted C _{1 to} C ₂₄ hydrocarbon group, and R ₂ is hydrogen or an optionally substituted C _{1 to} C ₂₄ hydrocarbon group. R ₄ and R ₅ each independently represent hydrogen or an optionally substituted C _{1 to} C ₈ hydrocarbon group, and optionally R ₄ and R ₅ are linked to each other to form an aromatic ring. A-represents an anion).
The electrostatic charge control agent is characterized by comprising an imidazolium salt represented by:

In the general formula (1), the C _{1 to} C ₂₄ hydrocarbon group of R ₁ and R ₃ is an alkyl group (methyl group, ethyl group, propyl group, pentyl group, octyl group, nonyl group, decyl group,
Undecyl group, dodecyl group, tetradecyl group, heptadecyl group, etc.), aryl group (phenyl group, etc.), aralkyl group (benzyl group, etc.), cycloalkyl group (cyclohexyl group, etc.), etc .; Substituted C ₁ -C ₂₄ carbon Examples of the hydrogen group include 4-hydroxybutyl group and nitrobenzyl group.

 Of these, preferred is a benzyl group.

The carbon hydrogen group optionally substituted with a C ₁ -C ₂₄ of R ₂ include the same groups as R ₁ and R _3. Preferably,
It is hydrogen.

The hydrocarbon group of R ₄ and R ₅ is an alkyl group (methyl group, ethyl group, propyl group, pentyl group, octyl group, etc., aryl group (phenyl group, etc.), aralkyl group (benzyl group, etc.), cycloalkyl group (Cyclohexyl group, etc.), etc .; Examples of the aromatic ring formed by connecting R ₄ and R ₅ to each other include a benzene ring or a nitro group adduct thereof.

Of these, preferred is a benzene ring formed by connecting R ₄ and R ₅ to each other.

As the anionic counterion A ⁻ , the halogen ion (C
l ^-, Br ^-, I ^-, etc.), alkyl sulfate ion (CH ₃
OSO _3- , C ₂ H ₅ OSO _3-, etc.), BF _4- , BPh _4- , MoO _42- , W
O ₄₂₋ , CH ₃ C ₆ H ₄ SO _{3 −} , CH ₃ SO _{3 −} , hydroxynaphthosulfonate ion and the like can be mentioned. Preferable among these, BF _4-, Cl ^- and MoO _42- and the like.

Examples of the compound represented by the general formula (1) include 1,3-dimethylimidazolium chloride, 1-methyl-3-butylimidazolium bromide, 1,3-dibenzyl-2-methylimidazolium tetrafluoroborate and 1,3-dimethyl. -4,5-diphenylimidazolium-p-toluenesulfonate, 1,3-dibenzylbenzimidazolium chloride, 1,3-dibenzylbenzimidazolium tetrafluoroborate, 1-methyl-2-dodecyl-3-benzyl Benzimidazolium ethosulfate, 1,3-
Dimethyl-2-phenylimidazolium-p-toluenesulfonate, 1-benzyl-2,3-dimethylbenzimidazolium molybrate, 1,3-dibenzylbenzimidazolium molybrate, 1,3-dimethyl-2- Examples thereof include phenylbenzimidazolium iodoato, 1,3-dibutyl-2-laurylbenzimidazolium tetrafluoroborate, and 1,2,3-trimethyl-5 (6) nitrobenzimidazolium neville wintate.

Preferred are 1,3-dibenzylbenzimidazolium tetrafluoroborate, 1,3-dibenzylbenzimidazolium chloride and 1-benzyl2,3-dimethylbenzimidazolium molybrate.

The compound of general formula (1) can be prepared by several methods, for example, by synthesizing a 1,3-unsubstituted (benzo) imidazole and then alkylating the 1,3-position with an alkylating agent, and finally It can be obtained by exchanging the counter anion.

Although various kinds of 1,3-unsubstituted imidazoles are commercially available, they can also be obtained, for example, by reacting a 1,2-dicarbonyl compound with aldehyde and ammonia.

Glyoxal as the 1,2-dicarbonyl compound,
Examples thereof include methylglyoxal, dimethylglyoxal and benzyl.

Examples of the aldehyde include formaldehyde, acetaldehyde, benzaldehyde and the like.

Examples of the ammonia source include alcoholic ammonia and a method using ammonium acetate in glacial acetic acid.

1,3-Unsubstituted benzimidazoles are obtained by heating o-phenylenediamines and carboxylic acids.

[X represents an alkyl group (a methyl group, an ethyl group, etc.), a nitro group, an acetoxyl group, or the like. Examples of o-phenylenediamines include o-phenylenediamine, 3,4-diaminotoluene, and 3,4-diaminonitrobenzene.

Examples of the carboxylic acid include fatty acids (formic acid, acetic acid, propionic acid, stearic acid, etc.) and aromatic carboxylic acids (benzoic acid, p-hydroxybenzoic acid, etc.).

The reaction is usually carried out in dilute hydrochloric acid, but it may sometimes give a sufficient yield in the absence of solvent or in water.

The reaction temperature is usually 80 to 100 ° C, but in the case of an aromatic carboxylic acid, a high temperature of 150 to 200 ° C is often required.

The (benzo) imidazolium salts can be obtained by reacting the 1,3-unsubstituted (benzo) imidazoles obtained as described above with an alkylating agent.

Alkylation can be performed by reacting imidazoles with an equimolar amount of an alkylating agent to alkylate only the 1-position, or by reacting with a 2-fold molar amount of an alkylating agent to simultaneously alkylate the 1-position and the 3-position.

Examples of the alkylating agent include alkyl halides (methyl chloride, butyl bromide, benzyl chloride, xylylene dichloride, etc.), dialkyl sulfates (dimethyl sulfate, diethyl sulfate, etc.), trialkyl phosphates (trimethyl phosphate, etc.) and the like.

Examples of the reaction solvent include alcohols such as methanol and isopropanol; aprotic polar solvents such as dimethylformamide and dimethylacetamide; hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as chloroform, carbon tetrachloride, dichloroethane, tetrachloroethane, etc. , And mixed solvents thereof are preferable, but alcohols and mixed solvents thereof are preferable from the viewpoint of solubility of raw materials, products, and reaction yield.

The reaction temperature is usually 0 ° C to 150 ° C. When only the 1-position is alkylated, the reaction is stopped at 50 ° C or lower to stop the reaction, and the 3-position is reacted at 50 ° C or higher to be alkylated.

In addition, a strong alkali (NaOH, KOH, etc.) can coexist for the purpose of neutralizing hydrogen halide formed in the reaction system. From the viewpoint of yield, it is preferable to coexist with a strong alkali.

The negative counterion of the imidazolium salt obtained by the above method is a strong alkali salt (sodium p-toluenesulfonate, sodium hydroxynaphthosulfonate, potassium tetrafluoroborate, sodium tetraphenylborate, sodium molybdate, It is also possible to change to a structure other than the counterion obtained by the reaction with the alkylating agent by reacting with sodium tungstate or the like).

The electrostatic charge control agent of the present invention is usually a slightly yellow to colorless solid and has a melting point of 100 ° C. to 200 ° C. or higher. According to a known method, it is usually used in a state where it is pulverized in a toner manufacturing process by mixing and melting it in a toner resin together with a coloring agent, a fluidizing agent and the like. In use, the fact that the preparation agent of the present invention is dispersed in the toner in a reasonably uniform manner is important for showing its effect.

It is also possible to prepare a resin containing a high concentration of an electrostatic charge adjusting agent in advance by a masterbatch method, and then dilute it to a predetermined concentration so that it can be used in a uniformly dispersed state.

The electrostatic charge control agent of the present invention may be added in advance in a toner resin production process such as a polymerization process, mixed in the toner resin and used in a more uniformly dispersed form.

The preparation agent of the present invention can also be used by adding it together with a fluidizing agent after pulverizing it into a toner.

As the toner resin, generally, a styrene- (meth) acrylic acid ester copolymer type resin, a polyester type resin, an epoxy type resin and the like can be mentioned.

The amount used is 0.1 per 100 parts by weight of toner resin.
From 10 to 10. It is preferably 0.5 to 5 parts.

Some colorants have an effect as an electrostatic charge adjusting agent, and examples thereof include carbon black, aniline blue, chrome yellow, DuPont oil red, quinoline yellow, malachite green oxalate and other metal dyes.

Examples of the fluidizing agent include silica derivatives, fatty acid metal salts, metal aluminum and the like.

EXAMPLES Hereinafter, the present invention will be further described with reference to Examples, but the present invention is not limited thereto.

Example 1 and Comparative Example 1 Example 1 (Synthesis of Static Charge Controlling Agent) 108 parts of o-phenylenediamine and 77 parts of formic acid were placed in a three-necked flask equipped with a stirrer and a cooling tube and heated at 100 ° C. for 2 hours. Stir to react. After cooling to room temperature, 10
It was neutralized with an aqueous sodium hydroxide solution until the pH became -7. The precipitated crystals were separated by filtration and recrystallized from water to obtain benzimidazole.

The obtained benzimidazole (35.3 parts), benzyl chloride (75.6 parts), potassium hydroxide (19.7 parts) and isopropanol (300 parts) were placed in an autoclave and heated at 50 ° C. for 3 hours and then at 120 ° C. for 6 hours. After cooling, the precipitated crystals were separated by filtration, washed with isopropanol and then washed with water.
3-Dibenzylbenzimidazolium chloride was obtained. The appearance was colorless crystals. This is designated as regulator I.

(Preparation of evaluation toner) Styrene-acrylic acid butyl ester copolymer resin (80 parts styrene, 20 parts acrylic acid butyl ester, weight average molecular weight 110,000), carbon black # 40 (manufactured by Mitsubishi Kasei), VISCOL 660P (Sanyo Chemical Co., Ltd.) Manufactured) and the above adjusting agent I
And were premixed in the sample mill in the mixing ratios shown in Table 1.

The pre-mixed sample was kneaded using a Labo Plastomill (manufactured by Toyo Seiki) at 140 ° C x 30 rpm for 10 minutes, and the resulting kneaded product was jet mill PJM100 (manufactured by Nihon Pneumatic).
Was finely pulverized. Powder having a particle size of 5 to 20 μm was obtained from the finely pulverized product using an air flow classifier MDS (manufactured by Nippon Pneumatic Co., Ltd.), and designated as Toners I-1, I-2, and I-3, respectively.

Comparative Example 1 A toner was prepared in the same manner as in Example 1 except that the electrostatic charge adjusting agent was not added, and a comparative toner 1 was obtained.

Test Example 1 (Measurement of electrification amount) 0.5 part of the toner prepared above and carrier 25 made of iron powder
The parts and parts were collected in a wide-mouthed bottle with a stopper, and the temperature and humidity were adjusted to 25 ° C and 65% RH. The mixture was mixed under the same conditions for 30 seconds, 1 minute, 5 minutes and 15 minutes with a turbula shaker mixer, and then the charge amount was measured at the same temperature and humidity using a blow-off charge amount measuring device (manufactured by Toshiba Chemical). The results are shown in Table 2.

Example 2 and Comparative Example 2 (Synthesis of Static Charge Controlling Agent) 50 parts of 1,3-dibenzylbenzimidazolium chloride obtained in Example 1 was dissolved in 200 parts of methanol. This solution was added dropwise to 2000 parts of a 1% sodium tetrafluoroborate aqueous solution, and the precipitated crystals were separated by filtration to obtain 1,3-dibenzylbenzimidazolium fluoroborate.

 This is designated as Conditioning Agent II.

(Preparation of Evaluation Toner) Toner II was obtained in the same manner as in Toner I-2 of Example 1, except that the adjusting agent II was used in place of the adjusting agent II.

Similarly, a comparative toner 2 was obtained by using cetyltrimethylammonium bromide (colorless positively charging electrostatic charge regulator) instead of the regulator I.

Test Example 2 (Pyrolysis temperature) Thermobalance (TG-D manufactured by Rigaku Denki Co., Ltd.) according to the thermogravimetry method.
The starting temperature was measured using a TA device).

The thermal decomposition temperature of the adjusting agent II of the present invention was 335 ° C, but that of cetyltrimethylammonium bromide was 200 ° C.

(Measurement of Charge Amount) Toner II and Comparative Toner 2 were processed in the same manner as in Test Example 1.
At 25 ° C., the humidity was adjusted to 40% RH, 65% RH and 90% RH, the mixture was stirred for 10 minutes with a carrier, and the charge amount was measured. Table 3 shows the results. The humidity dependence of the charge amount of Toner II was smaller than that of the comparative toner.

(Running Change in Charge Amount) Toner II and Comparative Toner 2 were stirred in a Turbula shaker mixer for 10 minutes and 180 minutes in an environment of 25 ° C. and 65% RH. Table 4 shows the change in the charge amount at that time.

Example 3 and Comparative Example 3 (Synthesis of Static Charge Controlling Agent) 108 parts of o-phenylenediamine, 90 parts of acetic acid and 200 parts of 4N hydrochloric acid were reacted in the same manner as in Example 1 to obtain 2-methylbenzimidazole.

66 parts of 2-methylbenzimidazole obtained, 63 parts of benzyl chloride, 62 parts of potassium hydroxide and methanol
300 parts was placed in a three-necked flask equipped with a stirrer and a condenser, and reacted at 30 ° C. for 4 hours and then at 50 ° C. for 2 hours.

The reaction mixture is transferred to an autoclave and methyl iodide is added.
85 parts and 200 parts of methanol were added and reacted at 150 ° C. for 4 hours. Then, unreacted methyl iodide was distilled off. 5% aqueous solution of sodium molybdate 11
Crystals precipitated by dropping in 00 parts were filtered off and 1-benzyl-2,3
-Dimethylbenzimidazolium molybdate was obtained.

 This is designated as regulator III.

(Preparation of Toner for Evaluation) 100 parts of styrene / acrylic acid-2-ethylhexyl ester copolymer resin (81 parts of styrene, 19 parts of acrylic acid-2-ethylhexyl ester, weight average molecular weight of 200,000) and 1 part of the above regulator III Was converted into a toner in the same manner as in Example 1 to obtain Toner III.

Comparative Toner 3 was obtained in the same manner except that 1 part of nigrosine was used instead of the regulator III.

Toner III was colorless, while Comparative Toner 3 was black purple.

Test Example 3 (Measurement of Charge Amount) Table 5 shows the results of measuring the charge amount of Toner III and Comparative Toner 3 in the same manner as in Test Example 1.

Example 4 and Comparative Example 4 (Synthesis of Static Electricity Modifier) 144 parts of commercially available 2-phenylimidazole, 355 parts of methyl iodide, 62 parts of potassium hydroxide and 500 parts of methanol were placed in an autoclave and the mixture was heated at 150 ° C. for 4 hours. Reacted for hours. Then, unreacted methyl iodide was distilled off. This methanol solution is a 10% aqueous solution of sodium p-toluenesulfonate.
Crystals deposited by dropping into 2000 parts were separated by filtration to obtain 1,3-dimethyl-2-phenylimidazolium-p-toluenesulfonate.

 This is designated as a regulator IV.

(Preparation of Evaluation Toner) Toner IV was obtained as toner in the same manner as in Example 1 except that 1 part of the adjusting agent IV was used in place of the adjusting agent I.

Comparative Toner 4 was obtained in the same manner as above except that 3 parts of nigrosine was used instead of the regulator IV.

Test Example 4 Toner IV and Comparative Toner 4 were copied by an electrophotographic copying machine for positively chargeable toner using an OPC photoconductor, and toner IV gave an image with very little fog, but comparative toner 4 had fog. Occurred.

EFFECTS OF THE INVENTION The electrostatic charge control agent of the present invention is 1. Since it is colorless, it can be used for color toners.

2. The structure is uniform, so the properties are constant and the charging is stable.

3. Despite having the structure of a quaternary ammonium salt, the charge rises quickly, maintains a high charge, and has low humidity dependence.

4. Since it has high heat resistance, stable quality is maintained without thermal decomposition in the resin kneading process.

It has effects such as.

Claims (1)

[Claims] 1. A general formula (In the formula, R ₁ and R ₃ are each independently a optionally substituted C _{1 to} C ₂₄ hydrocarbon group, and R ₂ is hydrogen or an optionally substituted C _{1 to} C ₂₄ hydrocarbon group. R ₄ and R ₅ each independently represent hydrogen or an optionally substituted C _{1 to} C ₈ hydrocarbon group, and optionally R ₄ and R ₅ are linked to each other to form an aromatic ring. A-represents an anion).
An electrostatic charge control agent comprising an imidazolium salt represented by: