JPH01203478A - Agent for improving fluidity of negatively charging resin powder - Google Patents

Abstract

PURPOSE:To obtain an agent for improving fluidity of negatively charging resin powder imparted with a property to be charged negative when exposed to the friction with magnetic powder such as iron (oxide) powder, by treating fine silica powder with a mixture of specific organic silicon compounds. CONSTITUTION:Fine silica powder is made to be hydrophobic and negatively chargeable, by treating the surface of (A) fine silica powder with (B) (i) an organic silicon compound having one or more hydrolyzable groups or silanol groups directly bonded to silicon atom and one or more (substituted) univalent hydrocarbon groups (excluding amino-substituted univalent hydrocarbon group) directly bonded to silicon atom through C-Si bond in one molecule and (ii) an organic silicon compound having one or more hydrolyzable groups or silanol groups directly bonded to silicon atom and one or more amino-substituted univalent hydrocarbon groups bonded to silicon atom through C-Si bond in one molecule.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a fluidity improver for negatively charged resin powder, and more specifically, it relates to a fluidity improver for negatively charged resin powder, and more specifically, for fluidity improvers that are exposed to friction with magnetic powders such as iron powder or iron oxide powder. Sometimes, it relates to a fluidity improver that is a hydrophobic silica-based fine powder that has been given the property of being negatively charged.

[Conventional technology]

Silica-based fine powders have been used in many industrial fields to prevent powder solidification and increase fluidity.

Examples of these uses include resin powders that are used by imparting an electrostatic charge, such as dry toner for electrophotographic copying machines, and in this case, the charging properties of additives also become a problem.

That is, an electrophotographic copying machine using Ss or CdS as a photosensitive medium requires a negatively chargeable toner, and additives for improving the fluidity thereof are also preferably negatively chargeable.

Hydrophobic silica fine powder treated with dimethyldichlorosilane has been used as an additive to improve the fluidity of negatively charged toner (Japanese Patent Publication No. 54-16219, Japanese Patent Publication No. 54-16220). The fluidity improver is
Since it was hydrophobized with dimethyldichlorosilane, it had the advantage that the fluidity improvement effect was less likely to deteriorate due to moisture absorption even after long-term storage. It also had the property of becoming negatively charged when exposed to friction with magnetic powder such as iron powder or iron oxide powder.

[Problem to be solved by the invention]

However, since the amount of charge is as large as about -520 μC/g, it is necessary to add a suitable amount (approximately 0.0 μC/g) to improve the fluidity of the toner.
25 to about 1% by weight), there is a drawback that the amount of charge of the toner varies greatly. Therefore, the range of toners to which this hydrophobic silica fine powder can be added as a fluidity improver is limited.

Therefore, the present inventor conducted extensive research to develop a fluidity improver for negatively chargeable resin powder such as negatively chargeable toner that does not have these drawbacks, and as a result, the present invention was achieved.

It is an object of the present invention to have a negligibly small effect on the amount of negative charge when added to a negatively chargeable resin powder, and to greatly improve the fluidity of the negatively chargeable resin powder. The object of the present invention is to provide a fluidity improver that can maintain improved fluidity for a long period of time.

[Means for solving problems and their effects]

The object of the present invention described above is to combine silica-based fine powder with (a) at least one hydrolyzable group or silanol group directly bonded to a silicon atom in one molecule and an unsubstituted or silanol group directly bonded to a silicon atom through a carbon-silicon bond; an organosilicon compound having at least one substituted monovalent hydrocarbon group (excluding amino group-substituted monovalent hydrocarbon groups); and (b) at least one hydrolyzable group or silanol group directly bonded to a silicon atom in one molecule. Hydrophobic and negatively chargeable silica-based fine powder surface-treated with an organosilicon compound having at least one amino group-substituted monovalent hydrocarbon group bonded to silicon atoms through carbon-silicon bonds is 6. Silica-based fine powders used to produce the fluidity improver of the present invention include fumed silica, silica aerogel, precipitated silica, and silicon tetrachloride. Examples include fine composite powders of silica and other metal oxides, which are produced in combination with other metal halides such as aluminum trichloride and titanium tetrachloride, but fumed silica is the most preferred.

The silica-based fine powder preferably has a BET specific surface area of 40 to 400 rrr/g in view of its performance as a fluidity improver for negatively charged resin powder.

It is preferable for the silica-based fine powder to contain some moisture rather than to be completely anhydrous in order to improve the treatment effect, and for this purpose, the preferable water content of the silica-based fine powder is 0.3 ~5% by weight. It is thought that this moisture promotes the condensation reaction between the hydrolyzable groups of the organosilicon compound and the silanol groups on the surface of the silica, which will be described later.

Among such silica-based fine powders, fumed silicate powders are commercially available under the following trade names, for example.

Aerosil 90, A manufactured by Nippon Aerosil Co., Ltd.
erosi1130, Aerosil 200, Aer
osil 300, Aerosil 380, Aero
sil 0X50, Aerosil MOX80, Ae
rosil MOX170, C manufactured by Cabot, USA
ab・0・Sil M-5, Cab・0・Sil MS
-7, Cab-0-3il MS-75, Cab・0・
Sil 15-5, Cab・O・Sil EH-5, HDKN20.1 (DK V
15. HDK T2O, ) IDK T2O, etc.

Among the two types of organosilicon compounds used to treat silica-based fine powder, representative examples of the above-mentioned organosilicon compound (a) have the general formula (R), 5L(X)4-, (
1) [wherein R is an unsubstituted or substituted monovalent hydrocarbon group,
(However, an amino group-bonded monovalent hydrocarbon group is excluded), or a hydrolyzable group or a hydroxyl group, and m is 1, 2 or 3].

Examples of unsubstituted monovalent hydrocarbon groups include alkyl groups such as methyl, ethyl, butyl, and decyl groups, phenyl groups, benzyl groups, and vinyl groups; examples of substituted monovalent hydrocarbon groups include 1- Examples include chloromethyl group, 3-chloropropyl group, 3,3.3-trifluoropropyl group, and 3-methacryloxypropyl group. When two or three R's exist in one molecule, R may be the same group or different groups. Examples include a hydrogen atom; a halogen atom such as a chlorine atom or a bromine atom; an alkoxy group such as a methoxy group or an ethoxy group; an acyloxy group such as an acetoquito group or a propionoxy group; an oximo group such as a methylethylketoxime group. .

Specific examples of the organosilane represented by the general formula (I) include trimethylchlorosilane, triethylchlorosilane, trimethylmethoxysilane, trimethylethoxysilane,
Dimethylphenylchlorosilane, methylvinylphenylchlorosilane, dimethyldichlorosilane, dimethyljethoxysilane.

Methylphenyldimethoxysilane, methylvinyldimethoxysilane, methylhexyldiacetoxysilane, dimethylhydrodienechlorosilane, methyltrichlorosilane, ethyltrichlorosilane, methyltrimethoxysilane, propyltriethoxysilane, decyltrimethoxysilane, vinyltrimethoxy Silane, phenyltriethoxysilane, methyltri(methylethylketoxime)
These include silane, trimethylsilanol, and diphenylsilanediol.

Other specific examples of the organosilicon compound (a) include hexamethyldisilazane, divinyltetramethyldisilazane, and octamethylcyclotetrasilazane.

Among the two types of organosilicon compounds used to treat silica-based fine powder, a typical example of the above-mentioned organosilicon compound (b) is A-3i(X)n (wherein A is an amino group-substituted monovalent carbide). It is an organosilane represented by a hydrogen group or 2).

Here, as the amino group-substituted monovalent hydrocarbon group, amino group-substituted alkyl groups such as 1-aminomethyl group, 2-aminoethyl group, 3-aminopropyl group, and 4-aminobutyl group; 1-(N-methyl N-alkylamino group-substituted alkyl groups such as amino)methyl group, 2-(N-propylamino)ethyl group, 3-(N-ethylamino)propyl group, and 3-(N-butylamino)propyl group; 1 -(N, N-
dimethylamino)methyl, 2-(N,N-diethylamino)ethyl, 3-(N-methyl,N-ethylamino)propyl, 3-(N,N-dibutylamino)propyl, etc. N,N-dialkylamino group-substituted alkyl group; p-aminophenyl group, p-aminobenzyl group are exemplified, and the alkyl group of R1 is a methyl group,
Examples include an ethyl group, a propyl group, and a xyl group. Examples of the X6-H#-hydrolyzable group include the same groups as those exemplified as the compound in general formula (I).

A specific example of the organosilane (b) represented by the general formula (n) is HzNCIIzSl (OCR3)3 1%NCH2CH25l(oc2Fls)3H3 82MCII2CH,CI(□Si (O et al Hs)zH
2NCHzCH, HNCHL, CH2CH2Si (O
CR,).

H,NGst(OCR,)2 CiH’y　　　　”” ;NCII□CHzCHzSl(OCHa)zCH.

C, H, \,. H2S1(..R3)21I' and those in which the alkoxy group of these organosilanes are substituted with the hydrolyzable group or hydroxyl group of Iya have the following properties.

Among these, organosilicon compounds having a monovalent hydrocarbon group bonded to a tertiary amino group are preferable to a primary amino group or a secondary amino group because they make the silica-based fine powder more hydrophobic.

Such organosilicon compounds (a) and organosilicon compounds (
(b) is a silicon atom-bonded hydrolyzable or silanol group that undergoes a condensation reaction with the surface silanol group of the silica-based fine powder,
The silicon-oxygen-silicon bond chemically bonds with the silicon atom on the surface of the silica-based fine powder.

The amount of organosilicon compound (a) required to sufficiently hydrophobize the silica-based fine powder is determined by the specific surface area of the silica-based fine powder, the silanol group density on the surface of the silica-based fine powder, and the hydrolysis in the organosilicon compound (a). Although it is not particularly limited as it may vary depending on the nature or the content of silanol groups, it is usually in the range of 1 to 50 parts by weight, preferably 5 to 30 parts by weight, based on 100 parts by weight of the silica-based fine powder.

When hydrophobic silica-based fine powder treated with organosilicon compound (a) alone is exposed to friction with magnetic powder such as iron powder or iron oxide powder, it has a large negative charge amount of several hundred μC/g. show.

This amount of negative charge is significantly reduced by the combined treatment with an organosilicon compound (b).

The amount of organosilicon compound (b) required to reduce this negative charge is not particularly limited, as it varies depending on the specific surface area of the silica-based fine powder, the density of silanol groups, the type of organosilicon compound (a), etc. However, the amount is usually in the range of 0.1 to 4.5 parts by weight per 100 parts by weight of the fine silica powder. When treating silica-based fine powder, the ratio of organosilicon compound (a) to organosilicon compound (b) is (4 to 1
00): 1 is preferred.

This is because if it is out of this range, it may tend to become positively chargeable or become too negatively chargeable.

In order to treat a silica-based fine powder with such an organosilicon compound (a) and an organosilicon compound (b), for example, the organosilicon compound (a) and the organosilicon compound (b) are added to the silica-based fine powder to make it uniform. Mix until heated through.

Alternatively, the organosilicon compound (a) and the organosilicon compound (b) may be added while mixing the silica-based fine powder under heating. Alternatively, either the organosilicon compound (a) or the organosilicon compound (b) may be added to the silica-based fine powder in advance and heated while being mixed, and then the other may be added and heated while being mixed.

In particular, when the hydrolyzable group of the organosilicon compound (a) is an acidic group such as a halogen atom or an acyloxy group, the acid by-produced by the condensation reaction with the silanol group on the surface of the silica-based fine powder must be sufficiently removed. After setting the organosilicon compound (
On the other hand, when the hydrolyzable groups of the organosilicon compound (a) and the organosilicon compound (b) are the same group such as an alkoxy group, it is preferable to treat both organosilicon compounds (a) and (b) in advance. The compound may be mixed, then added to the silica-based fine powder, and then heat treated.

A preferable temperature range during the heating is 100° C. or higher. This is because if the temperature is less than 100°C, the condensation reaction between the silica-based fine powder and the organosilicon compound will be difficult to complete.

Organosilicon compounds (a) and organosilicon compounds (b)
The silica-based fine powder surface-treated by A substituted monovalent hydrocarbon group is attached. When the organosilicon compound (a) or organosilicon compound (b) has two or three silicon-bonded hydrolyzable groups or hydroxyl groups in the molecule, the respective silicon atoms are bonded to each other via an oxygen atom. Organosilicon compounds (a), organosilicon compounds (b) together, or organosilicon compounds (a) and organosilicon compounds (b) condense to form an organopolysiloxane, and the surface of the silica-based fine powder It may be covered.

The unsubstituted monovalent hydrocarbon group derived from the organosilicon compound (a) and the substituted monovalent hydrocarbon group as described above contribute to imparting negative chargeability and hydrophobicity.

The amino group-substituted monovalent hydrocarbon group derived from the organosilicon compound (b) contributes to imparting positive chargeability, but the monovalent hydrocarbon group derived from the organosilicon compound (a) contributes to the mitigation of negative chargeability. It only contributes to

When the amino group in the amino group-substituted monovalent hydrocarbon is a primary amino group and the amino group content is large, it contributes to imparting hydrophilicity; It becomes hydrophobic as a whole due to the hydrophobicity imparting effect of the hydrocarbon group.

When the amino group in the amino group-substituted monovalent hydrocarbon group is a secondary amino group or tertiary amino group, or even if it is a primary amino group, when the amino group content is small, it is extremely difficult to impart hydrophobicity. Contribute.

Therefore, the silica-based fine powder surface-treated with the organosilicon compound (a) and the organosilicon compound (b) is negatively charged as a whole, smaller than 0, and -10
The degree of resistance is relaxed, such as 0 μC/g or more, and the overall hydrophobicity is large. Therefore, it becomes negatively charged when it is rubbed against magnetic powder such as iron powder or iron oxide powder. Since the amount of charge is kept small, when it is added to a negatively chargeable resin powder as a fluidity improver, it has little effect on the negatively chargeable property of the resin powder.

Organosilicon compounds (a) and organosilicon compounds (b)
Since the silica-based fine powder surface-treated with is hydrophobic, when added to negatively charged resin powder, it significantly improves the fluidity of the resin powder, and the improved fluidity is maintained even after a long period of time. . Note that examples of the negatively chargeable resin powder include negatively chargeable toner and anion exchange resin powder.

As a negatively charged toner, polystyrene and styrene-n-
Toner is a toner made by finely pulverizing a thermoplastic resin such as butyl methacrylate copolymer with a pigment, dye, or charge control agent such as carbon black dispersed to a particle size of 1 to 40 mm, and also a magnetic material such as magnetite. A one-component toner containing body particles is exemplified. The negatively chargeable toner usually has a negative charge amount smaller than O and larger than -40 μC/g. The appropriate amount of the fluidity improver of the present invention added to the negatively chargeable resin powder is 0.1 to 5% by weight.

〔Example〕

Examples and comparative examples of the present invention are shown below.

In Examples and Comparative Examples, parts mean parts by weight.

(2) The fluidity of the powder and the powder mixed with a fluidity improver was determined by measuring the angle of repose.

■The degree of hydrophobicity was determined as follows.

0.2 g of the treated silica-based fine powder was collected in a 100 mQ beaker, and 50 ml of pure water was added (if the silica-based fine powder is sufficiently hydrophobic, it will float on the liquid surface).The inside of the beaker was stirred using a magnetic stirrer. While stirring, methanol was added below the liquid surface, and the end point was the point at which the silica-based fine powder was no longer observed on the liquid surface, and the degree of hydrophobicity was calculated from the amount of methanol required up to that point using the following formula.

X: Amount of methanol used (tQ) ■ The amount of charge is the amount of contact charge with iron oxide powder, and was measured using a blow-off powder charge amount measuring device manufactured by Toshiba Chemical.

(a) Carbon content and nitrogen content were determined by organic organic analysis.

Example 1 100 g of commercially available hydrophobic fumed silica that had been hydrophobized with dimethyldichlorosilane was placed in a 5Q separable flask. The fumed silica has a carbon content of about 1% by weight and a specific surface area of about 130rrr/g, so the number of dimethylsiloxy groups bonded to silicon atoms on the silica surface is There are 1.9 pieces. The hydrophobic fumed silica had approximately 3 silanol groups per 100 silanes on the untreated surface. Therefore, in the hydrophobic fumed silane group, about 64 mol% of the hydrogen atoms of the silanol groups were substituted with dimethylsilyl groups, and the remaining 36 mol% remained as silanol groups. It is thought that the dimethylsilyl group is bonded with one hand to the silicon atom on the silica surface via oxygen, and the other hand is bonded to another dimethylsilyl group via oxygen.

While mixing 100 g of this hydrophobic fumed silica,
The following silane 2. Og CH3 (C4H,) 2 N (CH,)3 Sl (OCH
3)! was added dropwise and mixed for 1 hour. Then, the temperature was raised to 150° C. while stirring, and nitrogen gas was flowed until methanol, a reaction by-product, was no longer generated. The nitrogen content of the hydrophobic fumed silicone obtained was 0.1% by weight. Therefore, about 0.3 aminopropyl group-bonded silicon atoms per 100 persons on the surface of the fine silica powder are bonded to silicon atoms on the surface of the fine silica powder via oxygen atoms.

The characteristics of the obtained treated hydrophobic fumed silicon were that the degree of hydrophobicity was 40% and the amount of charge was -20 μC/g.

Consisting of 97% by weight styrene-butyl methacrylate-divinylbenzene copolymer and 3.0% by weight carbon black, average particle size 20. When 1.0 part of the treated hydrophobic fumed silica was added to 100 parts of the negatively chargeable toner and mixed using a turbular mixer, the charge amount of the toner remained unchanged at -20 μC/g. , the angle of repose is 5
The flowability was improved by decreasing from 0° to 39°. Even after this toner mixed powder was left in an atmosphere of a temperature of 25° C. and a humidity of 70% RH for one month, there was no change in both the amount of charge and the angle of repose.

Comparative Example 1 The characteristics of the commercially available hydrophobic fumed silicone itself in Example 1 were a degree of hydrophobicity of 40% and a charge amount of -530 μC/g.

When 1.0 part of this hydrophobic fumed silica was added to 100 parts of the toner used in Example 1 and mixed using a turbular mixer, the angle of repose decreased from 50'' to 40@, and the fluidity improved. I could see it.

The amount of charge changed from 120 μC/g to 25 μC/g. Therefore, it has become difficult to use this product as it is as a toner.

Example 2 100 g of fumed silica having a specific surface area of 200 rrr/g and a water content of 3% by weight was placed in a 5Q separable flask, and 23 g of dimethyldimethoxysilane and the following silane CH3(c4os)2N(cua)isi(oc2Hs) were added. )2(
m ) 2.0 g was added dropwise and mixed for 1 hour.

Next, the temperature was raised to 150° C. while stirring, and nitrogen gas was flowed until methanol and ethanol, which were reaction by-products, were no longer generated to obtain a hydrophobic fumed silica.

The characteristics of the obtained hydrophobic fumed silicate force are as follows: degree of hydrophobicity 5
0%, charge amount -30tt C/g, carbon content was 2.1% by weight, and nitrogen content was 0.1% by weight.

When 0.7 parts of this hydrophobic fumed silica was added to 100 parts of the toner used in Example 1 and mixed using a turbular mixer, a similar improvement in fluidity was observed, and the angle of repose increased from 50' to 38'. It decreased to @. Further, the charge amount of the toner remained unchanged at -20 μC/g.

The angle of repose and charge amount of the toner are at a temperature of 25°C and a humidity of 70% R.
There was no change even after leaving it for one month in an H atmosphere.

Comparative Example 2 Fumed silane treatment was carried out under the same conditions as in Example 2, except that 2.0 g of dimethyldimethoxysilane was added instead of the silane represented by formula (m) used in Example 2. The characteristics of the obtained hydrophobic fumed silicone are as follows: carbon content: 2.1% by weight, nitrogen content: 0
% by weight, degree of hydrophobization was 50%, and charge amount was -400 μC/g.

When 0.7 parts of this hydrophobic fumed silica was mixed with 100 parts of toner in the same manner as in Example 2, a similar improvement in fluidity was observed, and the angle of repose decreased from 50' to 38°. The amount of charge is from -20μC/g to -23μ
It changed to C/g. Therefore, it has become difficult to use this product as it is as a toner.

Example 3 100 g of fumed silica having a specific surface area of 130 rrr/g and a water content of 2% by weight was placed in a 5Q separable flask, and the butyltrimethoxysilane Log was added.

3-7 Add 1.0 g of minopropyltrimethoxysilane and mix for 1 hour, then raise the temperature to 150°C and flush with nitrogen gas while stirring until no reaction by-products are generated. The hydrophobic fumed silicate force was obtained.

The properties of the obtained hydrophobic fumed silica were that the carbon content was 2.0% by weight, the nitrogen content was 0.08% by weight, the degree of hydrophobicity was 50%, and the amount of charge was -35 μC/g.

Based on the nitrogen content, 3-aminopropylsilyl groups are chemically bonded to silicon atoms on the silica fine powder via oxygen atoms at a density of about 0.2 per 100 2 on the silica fine powder surface. , from the carbon content, the butylsilyl group is 1
This means that they exist in similar chemical bonds at a density of about 1.7 per 2 people.

When 0.6 part of this hydrophobic fumed silica was added to 100 parts of the toner used in Example 1 and mixed using a turbular mixer, a similar improvement in fluidity was observed, and the angle of repose increased from 50° to 39°. On the other hand, the charge amount of the toner remained unchanged at -20 μC/g.

〔Effect of the invention〕

The fluidity improver of the present invention is obtained by surface-treating silica-based fine powder with an organosilicon compound (a) and an organosilicon compound (b). Since it is a hydrophobic and negatively chargeable silica-based fine powder, when added to a negatively chargeable resin powder, the effect on the negative chargeability is negligible, and the fluidity of the negatively chargeable resin powder is minimized. It has the remarkable effect of being able to greatly improve the fluidity and maintain the improved fluidity for a long period of time.

Claims (1)

[Scope of Claims] 1 Silica-based fine powder (a) has at least one hydrolyzable group or silanol group directly bonded to a silicon atom in one molecule, and unsubstituted or substituted silica group directly bonded to a silicon atom through a carbon-silicon bond. An organosilicon compound having at least one monovalent hydrocarbon group (excluding amino-substituted monovalent hydrocarbon groups), and (b) at least one hydrolyzable group or silanol group directly bonded to a silicon atom in one molecule. A hydrophobic and negatively charged silica-based fine powder surface-treated with an organosilicon compound having at least one amino group-substituted monovalent hydrocarbon group bonded to a silicon atom through a carbon-silicon bond. A fluidity improver for negatively charged resin powder. 2. The fluidity improver according to claim 1, wherein the silica-based fine powder is fumed silica. 3 The organosilicon compound (a) has the general formula (R)_mSi(X)_4_-_m(I) [wherein R is an unsubstituted or substituted monovalent hydrocarbon group (excluding amino group-substituted monovalent hydrocarbon groups). ), X is a hydrolyzable group or a hydroxyl group, and m is 1, 2 or 3], and the organosilicon compound (b) has the general formula ▲ mathematical formula, chemical formula, table, etc. ▼(II) (In the formula, R^1 is a monovalent hydrocarbon group, R^2 is an amino group-substituted monovalent hydrocarbon group, Y is a hydrolyzable group or a hydroxyl group, and n is 0 , 1 or 2). 4 R in the general formula (I) is an alkyl group, X is a chlorine atom or an alkoxy group, and R in the general formula (II)
The fluidity improver according to claim 3, wherein ^1 is an alkyl group, R^2 is an amino group-substituted alkyl group, and Y is an alkoxy group. 5. The fluidity improver according to claim 4, wherein the amino group-substituted alkyl group is an N,N-dialkylaminoalkyl group. 6. The fluidity according to claim 1, wherein the contact charge amount with the iron oxide powder is -100 to 0 (not including 0) μC/g, and the negatively chargeable resin powder is a negatively chargeable toner. improver.