JP5360981B2 - Method for producing positively chargeable acrylic polymer particles and positively chargeable acrylic polymer particles obtained by the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing positively chargeable acrylic polymer particles, and to provide the positively chargeable acrylic polymer particles obtained by the method. <P>SOLUTION: The method for producing positively chargeable acrylic polymer particles includes a process for absorbing a polymerizable monomer in seed particles in the presence of the seed particles and a cationic surfactant in an aqueous medium, and performing seed emulsion polymerization to produce the acrylic polymer particles. In the method, the seed particles are vinyl-based polymer particles, the polymerizable monomer is a mixture comprising 20-100 wt.% of a (meth)acryl ester-based monomer and 0-80 wt.% of a vinyl-based polymerizable monomer copolymerizable with the (meth)acryl ester-based monomer, the number of carbon atoms in a substituent of the ester portion of the (meth)acryl ester-based monomer is 4-10, and the passing rate of the acrylic polymer particles through a sieve having a mesh opening of 45 &mu;m is 80-99%. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a method for producing positively chargeable acrylic polymer particles, and particles obtained by the method. More specifically, the present invention is obtained by seed emulsion polymerization by absorbing (meth) acrylic ester monomer in the presence of seed particles and a cationic surfactant, and passing through a sieve having an opening of 45 μm. The present invention relates to a method for producing positively chargeable acrylic polymer particles, characterized in that the rate is 80% to 99%, and particles obtained by the method.

Acrylic polymer resin particles are widely used as paint additives, adhesives, cosmetic additives, toner additives, light diffusing agents, liquid crystal spacers, binders, rheology modifiers, extenders, coating film performance improvers, etc. Yes. Furthermore, it has a wide range of application fields such as paints, civil engineering top coats, sealers, ink jet recording materials, and electrodeposition paints, and its utility value is high. Such polymer resin particles prevent blocking between toners, improve toner fluidity, and do not cause fusion, aggregation, cracking or chipping due to mechanical external force or heat. Since it does not damage parts such as printers, it is suitably used as a toner additive (hereinafter referred to as a toner external additive).
Conventionally, as such fine particles, fine particles made of an inorganic material such as silica or an organic material such as an acrylic resin have been generally used. However, fine particles made of an inorganic material have problems that the hardness is too high and the photosensitive drum is easily damaged, and that the average particle diameter is limited to a small one of about 100 nm or less.

JP 2001-163985 A JP 2005-82765 A

Patent Document 1 discloses a method of improving fluidity by particles having an average particle diameter of 0.3 μm or less and a gel fraction adjusted by an emulsion polymerization method. However, the particles obtained by the above method have a problem that sufficient fluidity cannot be imparted. In addition, the fluidity of a positively charged particle having a large number of carbon atoms in the ester portion, such as isobutyl methacrylate, becomes worse. Further, in the above method, sufficient fluidity was not obtained with the positively chargeable acrylic system.
On the other hand, Patent Document 2 discloses that fine particles made of an organic-inorganic composite material can impart fluidity. However, since organic solvents are used and the reaction time is long, production efficiency is not good. There is.

  Thus, in the present invention, as a result of studying to solve the above problems, it was found that positively charged acrylic polymer particles capable of imparting excellent fluidity can be obtained by performing seed emulsion polymerization at a specific monomer ratio. Invented.

Thus, in the present invention, in the presence of seed particles and a cationic surfactant in an aqueous medium, the acrylic particles are absorbed into the seed particles, and seed emulsion polymerization is performed to produce acrylic polymer particles. Including steps,
The seed particles are vinyl acrylic polymer particles, the acrylic polymerizable monomer is 20 to 100% by weight of (meth) acrylic ester monomer, and vinyl copolymerizable with the (meth) acrylic monomer. A mixture of 0 to 80% by weight of a polymerizable monomer,
The number of carbon atoms of the substituent of the ester portion of the (meth) acrylic ester monomer is 4 or more and 10 or less, and the acrylic polymer particle has a sieve passage rate of 45% to 80% to 99%. A method for producing positively chargeable acrylic polymer particles and particles obtained by the method are provided.

The positively chargeable acrylic polymer particles of the present invention are characterized by excellent fluidity, with a sieve passage rate of 45 to 80 μm and 80 to 99%. Therefore, it can be used as an external additive for toners used in electrostatic image development (used as an external additive for electrophotographic toners), paint additives, adhesives, cosmetic additives, toner additives, light It is suitable as a diffusing agent, a liquid crystal spacer, a binder, a rheology modifier, an extender, a coating film performance improvement and the like.
Moreover, in the present invention, the use of an aqueous medium and the reaction time can be significantly shortened compared to the above-described method, so that the desired positively chargeable acrylic polymer particles can be obtained with high production efficiency.

  The present invention absorbs an acrylic polymerizable monomer containing 20 to 100% by weight of a (meth) acrylic ester monomer having 4 to 10 carbon atoms in the ester portion in vinyl acrylic polymer particles as seed particles. And obtained by seed emulsion polymerization. It is a particle obtained by the method for producing positively chargeable acrylic polymer particles characterized by having a sieve passage rate of 80 to 99% with an opening of 45 μm, and the method. Here, “(meth) acryl” means acrylic or methacrylic.

(Seed particles)
The seed particle used in the present invention is a polymer obtained by polymerizing a vinyl monomer. Specifically, aromatic vinyl monomers such as styrene and α-methylstyrene, methyl (meth) acrylate, ethyl (meth) acrylate, (meth) acrylic ester monomers such as butyl (meth) acrylate, vinyl acetate, etc. Or a block, random or graft copolymer of these with a homopolymer or a monomer copolymerizable therewith. In addition, the polymer containing a (meth) acrylic ester monomer is preferable in that the absorbability of the acrylic polymerizable monomer is excellent.

The method for producing the seed particles is not particularly limited, and a method such as emulsion polymerization, soap-free emulsion polymerization or suspension polymerization can be used. In view of the uniformity of the seed particle size and the simplicity of the production method, emulsion polymerization and soap-free emulsion polymerization are preferred.
The number average molecular weight of the seed particles of the present invention is not particularly limited, but is preferably 10,000 or more, more preferably 12,000 to 500,000, as measured by gel permeation chromatography. Such seed particles preferably have a uniform particle size in order to make the resulting acrylic polymer particles have a uniform particle size.
If the average particle size of the seed particles of the present invention is too small, the absorption of the acrylic polymerizable monomer into the seed particles may be insufficient, and the polymerization stability may be significantly reduced, and if too large, the use of the acrylic polymerizable monomer is too large. Since it is necessary to reduce the amount and productivity is lowered, 0.05 to 0.4 μm is preferable.
If the amount of seed particles used is small, polymerization may proceed on the seed particles or other than in the seed particles, and many fine particles and coarse particles may be generated. May fall. In addition, if the amount of seed particles used is large, the particles may be deformed due to phase separation from the polymer forming the seed particles, and the sphericity of the acrylic polymer particles may be reduced. The amount is preferably 1 to 50 parts by weight, more preferably 3 to 30 parts by weight, and particularly preferably 5 to 15 parts by weight with respect to 100 parts by weight of the monomer.

(Acrylic polymerizable monomer)
The acrylic polymerizable monomer used in the present invention is 20 to 100% by weight of a (meth) acrylic ester monomer having 4 to 10 carbon atoms in the substituent of the ester portion, and the (meth) acrylic ester monomer. Is a blend of 0 to 80% by weight of a vinyl polymerizable monomer copolymerizable with the polymer.

In the present invention, a (meth) acrylic ester monomer having 4 to 10 carbon atoms in the substituent of the ester moiety is used. When the number of carbon atoms of the substituent of the ester portion is 3 or less, although the stability at the time of polymerization is good, the sieve passing rate is lowered. Moreover, when carbon number of the substituent of an ester part is 11 or more, stability at the time of superposition | polymerization may deteriorate and a particle diameter may become large. Further, the passing rate of the obtained particles is also lowered. More specifically, examples of the (meth) acrylic ester monomer having 4 to 10 carbon atoms in the substituent of the ester moiety used in the present invention include n-butyl (meth) acrylate and (meth) acrylic acid. Examples include isobutyl, t-butyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, and the like. In particular, isobutyl (meth) acrylate, t-butyl (meth) acrylate, cyclohexyl (meth) acrylate, and isobornyl (meth) acrylate are more preferable in that high fluidity can be imparted. These (meth) acrylic ester monomers may be used alone or in combination of two or more.
If the amount of the (meth) acrylic ester monomer used is small, the polymerization stability is good but the sieve passing rate is lowered, so that it is 20 to 100% by weight with respect to the total polymerizable monomer, and 50 to 50%. 100% by weight is more preferred.

Examples of the monomer copolymerizable with the (meth) acrylic ester monomer having 4 to 10 carbon atoms in the substituent of the ester portion of the present invention include aromatic vinyl monomers such as styrene and α-methylstyrene, (meth) Examples include (meth) acrylic ester monomers such as methyl acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate, vinyl acetate, and the like, and methyl (meth) acrylate is particularly preferable.
The amount of the vinyl polymerizable monomer copolymerizable with the (meth) acrylic ester monomer having 4 to 10 carbon atoms in the substituent of the ester moiety used in the present invention is the same for the same reason. 0 to 80% by weight, preferably 0 to 50% by weight, based on the functional monomer.

  A chain transfer agent may be added to the acrylic polymerizable monomer. Specific examples of the chain transfer agent include alkyl mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, α-methylstyrene dimer, 2,6-di- Examples thereof include phenolic compounds such as t-butyl-4-methylphenol and styrenated phenol, allyl compounds such as allyl alcohol, halogenated hydrocarbon compounds such as dichloromethane, dibromomethane, and carbon tetrachloride. It is preferable to use 0.1 to 5 parts by weight with respect to parts by weight. More preferably, it is 0.3-3 weight part.

Other monomers and additives may be added to the acrylic polymerizable monomer as long as the effects of the present invention are not impaired.
Examples of the other monomer include aromatic vinyl compounds such as styrene, α-methylstyrene, vinyl toluene, and chlorostyrene.
Still other monomers include bifunctional polymerizable vinyl monomers. Specific examples include allyl (meth) acrylate, divinylbenzene, alkylene glycol dimethacrylate (alkylene preferably has 2 to 4 carbon atoms). The mixing ratio of the bifunctional polymerizable vinyl monomer is preferably 50 parts by weight or less, more preferably 40 parts by weight or less with respect to 100 parts by weight of the (meth) acrylic ester monomer.
Examples of other additives include light stabilizers, ultraviolet absorbers, pigments, dyes, antifoaming agents, thickeners, heat stabilizers, leveling agents, lubricants, antistatic agents, and the like.

(Aqueous medium)
Emulsion polymerization is performed in an aqueous medium. Although it does not specifically limit as an aqueous medium, The mixture of water, water, and a water-soluble organic solvent (for example, lower alcohol) etc. are mentioned. Of these, water with less wastewater treatment problems is preferred.

(Seed emulsion polymerization)
The acrylic polymerizable monomer is subjected to seed emulsion polymerization in the presence of seed particles in an aqueous medium.
In the present invention, when the acrylic polymerizable monomer as described above is absorbed into the seed particles and seed emulsion polymerization is performed, the acrylic polymerizable monomer is mixed and stirred with a cationic surfactant as described later and an aqueous medium. Then, it is preferably emulsified to obtain an emulsion dispersion (O / W emulsion) in which an acrylic polymerizable monomer is dispersed in an aqueous medium, and an aqueous dispersion of seed particles is added to the emulsion dispersion.
The use ratio (parts by weight / parts by weight) of the polymerizable monomer and the aqueous medium when adjusting the emulsified dispersion is preferably in the range of 1:20 to 1: 2. When the ratio of the acrylic polymerizable monomer blend is less than 1:20, productivity may be deteriorated, which is not preferable. When the ratio of the acrylic polymerizable monomer compound is more than 1: 2, the stability of the particles during polymerization is deteriorated and aggregates of the acrylic polymer particles after polymerization may be generated, which is not preferable. A more preferable use ratio (parts by weight / parts by weight) is 1:15 to 1: 3.
The time for absorbing the acrylic polymerizable monomer in the seed particles is not particularly limited, but is preferably 10 minutes to 3 hours.

The cationic surfactant that can be used in the present invention is not particularly limited, and any known cationic surfactant can be used. For example, alkylamine or a salt thereof, ammonium salt having polyalkylene oxide, pyridinium salt, amino alcohol fatty acid derivative, polyamine fatty acid derivative, imidazoline, alkyltrimethylamine, or ammonium salt thereof, dialkyldimethylamine or ammonium salt thereof, alkyldimethylbenzyl Examples include amines, ammonium salts thereof, pyridinium salts, alkylisoquinolinium salts, and benzethonium chloride. Of these, ammonium salts such as ammonium hydrochloride, ammonium sulfate, ammonium sulfonate, ammonium paratoluene sulfonate, and ammonium acetate are preferable. For example, lauryltrimethylammonium hydrochloride, stearyltrimethylammonium hydrochloride, cetylmethylammonium hydrochloride, and distearyldimethylammonium chloride N-polyoxyalkylene-N, N, N-trialkylammonium paratoluenesulfonate are more preferable. . These may be used alone or in combination of two or more.
If the amount of the cationic surfactant used is too small, absorption of the acrylic polymerizable monomer into the seed particles may be insufficient, and the polymerization stability may be significantly reduced. If the amount is too large, polymerization in the aqueous phase is likely to occur, and a large amount of fine particles are generated, which may reduce the yield of the target acrylic acrylic polymer particles. It is preferable that it is 0.01-0.5 weight part, and 0.02-0.2 weight part is more preferable.

Instead of the cationic surfactant that can be used in the present invention, a cationic water-soluble polymer may be used. Specific examples include amino group-modified polyvinyl alcohol, polydiallyldimethylammonium chloride, and cationized hydroxyethyl cellulose. Amino group-modified polyvinyl alcohol and polydiallyldimethylammonium chloride are particularly preferable. These may be used alone or in combination of two or more.
If the amount of the cationic water-soluble polymer used is too small, the acrylic polymerizable monomer may not be sufficiently absorbed by the seed particles, and the polymerization stability may be significantly reduced. If the amount is too large, polymerization in the aqueous phase is likely to occur and a large amount of fine particles may be generated, and the yield of the target polymer particles may decrease. The amount is preferably 0.01 to 0.5 parts by weight, more preferably 0.02 to 0.2 parts by weight, based on 100 parts by weight of the monomer blend.

As the polymerization initiator in the present invention, either a water-soluble polymerization initiator or an oil-soluble polymerization initiator can be used. A water-soluble polymerization initiator is preferable from the viewpoint of polymerization stability.
As the water-soluble polymerization initiator that can be used in the present invention, a cationic water-soluble polymerization initiator can be preferably used. Specific examples of the cationic water-soluble polymerization initiator used in the present invention include 2,2-azobis (2-amidinopropane) hydrogen dichloride, 2,2-azobis [2- (2-imidazolin-2-yl). Propane] disulfide dihydrate, 2,2-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate, 2,2-azobis {2- [1- (2-hydroxyethyl) ) -2-imidazolin-2-yl] propane} hydrogen dichloride, 2,2-azobis [2- (2-imidazolin-2-yl) propane], 2,2-azobis (1-imino-1-pyrrolidino- 2-ethylpropane) hydrogen dichloride, 2,2-azobis {2-methyl-N [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propionamide}, 2,2-azobis [2-methyl- N- (2-Hide Xylethyl) propionamide], 2,2-azobis (N-hydroxyethylisobutyramide), 4,4-azobis (4-cyanopentanoic acid), azobisisobutyronitrile, azobis (2,4-dimethylvaleronitrile) And other azo compounds. The persulfates and organic peroxides include sodium sulfooxylate formaldehyde, sodium bisulfite, ammonium bisulfite, sodium thiosulfate, ammonium thiosulfate, hydrogen peroxide, sodium hydroxymethanesulfinate, L-ascorbic acid, And redox initiators using a reducing agent such as a salt thereof, a cuprous salt, and a ferrous salt in combination with a polymerization initiator.

Examples of the oil-soluble polymerization initiator include benzoyl peroxide, t-butyl peroxide, lauryl peroxide, t-butyl hydroxy peroxide, cumene hydroxy peroxide, t-butyl perbenzoate, t-butyl peroxyisopropyl carbonate, Examples thereof include peroxides such as methyl ethyl ketone peroxide, isopropyl peroxycarbonate, dioctanoyl peroxide, and azo compounds such as azobisisobutyronitrile, azobisisovaleronitrile, and azobiscyclohexanecarbonitrile.
Although the usage-amount of a polymerization initiator changes with kinds, it is preferable to use 0.1-5 weight part with respect to 100 weight part of acrylic polymerizable monomer compounds. More preferably, it is 0.3 to 3 parts by weight.

The number of stirring rotations of the polymerization system is not particularly limited. For example, when a reactor having a capacity of 5 liters is used, it is preferably 100 to 500 rpm. Moreover, although superposition | polymerization temperature changes with kinds of the monomer and polymerization initiator to be used, it is preferable that it is 30-100 degreeC, and it is preferable that superposition | polymerization time is 2 to 10 hours.
In addition, the acrylic polymer particles can be isolated from the aqueous medium by a known method, such as a spray drying method typified by a spray dryer, or a dry attached to a heated rotating drum typified by a drum dryer. It can be carried out by a method such as lyophilization. Furthermore, it is desirable that the dried acrylic polymer particles be crushed by a pulverizer or a pulverizer.

  The positively chargeable acrylic polymer particles of the present invention have an average particle size of 0.1 to 1.0 μm. When the average particle size is less than 0.1 μm, the cohesive force of the acrylic polymer particles is increased, so that the sieve passing rate is decreased, which is not preferable. Moreover, when exceeding 1.0 micrometer, since the specific surface area of an acrylic polymer particle becomes small and a sieve passage rate falls, it is unpreferable. A more preferable average particle diameter is 0.15 to 0.8 μm. In addition, the measuring method of an average particle diameter is described in the Example column.

  Furthermore, the positively chargeable acrylic polymer particles of the present invention have a sieve passage rate of 80 to 99% with an opening of 45 μm. If it is less than 80%, for example, when it is used as an additive for a toner used for developing an electrostatic image, the fluidity is not sufficiently imparted.

  The positively chargeable acrylic polymer particles of the present invention are positively chargeable acrylic polymer particles excellent in fluidity, and can be used for desired applications. For such applications, it can be used as an additive for toners used in electrostatic image development, as well as additives for paints, ink adhesives, adhesives, artificial marble, paper processing agents, cosmetics. It is suitable as a packing material for use, a column packing material for chromatography, an antiblocking agent for film, a light diffusing agent and the like.

  Hereinafter, although an example and a comparative example explain the present invention, the present invention is not limited to this. In addition, the measuring method of the average particle diameter in an Example and a comparative example and a sieve passage rate is described below.

(Average particle size)
The average particle diameter here means a particle diameter measured using a method called a dynamic light scattering method or a photon correlation method. That is, the aqueous dispersion of positively chargeable acrylic polymer particles adjusted to 0.1 vol% is irradiated with laser light at 25 ° C., and the scattered light intensity scattered from the acrylic polymer particles is changed over time in microseconds. Measure with It is an average particle size obtained by a cumulant analysis method for calculating an average particle size by applying a scattering intensity distribution caused by the detected polymer resin particles to a normal distribution. This type of average particle diameter can be easily measured with a commercially available measuring apparatus. In this example, “Zeta Sizer Nano ZS” commercially available from Malvern is used for measurement.
The above-described commercially available measurement apparatus is equipped with data analysis software, and can automatically analyze measurement data.

(Polymerization stability)
The polymerization stability referred to here is obtained by passing the total amount of the aqueous dispersion of the positively chargeable acrylic polymer particles obtained through a stainless steel sieve having an opening of 100 μm and drying the residue on the sieve at 50 ° C. for 24 hours. Weigh the residue. This value (Wa) is calculated as an aggregate formation rate (Equation (1)), and when the obtained value is less than 5%, the polymerization stability is very excellent (）) at 5 to 10%. In some cases, the polymerization stability was excellent (◯), and when it was 10% or more, the polymerization stability was judged to be poor (x).

Aggregate production rate = (Wa / polymerizable monomer use amount) × 100

(Measurement of sieve passage rate)
a. External Addition Treatment A mixture of 15 g of particles having an average particle size of 10 μm, which is a styrene-butyl methacrylate copolymer produced by a synthesis method described later, and 0.45 g of measurement data is mixed with a mill mixer (National product number MX-X57-Y fiber mixer). The mixture was mixed for 5 seconds, and then allowed to stand for 1 minute. The mixture was mixed again for 5 seconds and kept still for 1 minute, and this was performed 5 times in total. The positively charged acrylic polymer particles to be measured are externally added to styrene-acrylic polymer particles produced by a synthesis method described later, and are used as a pseudo toner.

b. Screening rate The degree of aggregation was measured by using a powder tester made by Hosokawa Micron. The measurement was carried out using a single-stage sieve having a metal opening of 45 μm in a powder tester. 2 g of pseudo toner subjected to the external addition treatment by the method described above is placed on a first stage sieve, a 7.2 V rheostat voltage is applied to the powder tester, and the first stage sieve is vibrated for 93 seconds to remain on a 45 μm sieve. The weight of the powder was measured, and the value calculated by the following formula is shown as the degree of aggregation. Convert to sieve pass rate and calculate.
Aggregation degree (%) = (powder weight remaining on upper stage screen) / 2 g × 100
Sieve passing rate (%) = 100-coagulation degree (%)

<Synthesis example>
The production of styrene-acrylic polymer particles used for the measurement of the sieve passing rate will be described. In a 5 L autoclave, 26 parts by weight of magnesium pyrophosphate is dispersed in 2600 parts by weight of water, and 0.13 parts by weight of sodium nitrite and 1.3 parts by weight of phosphanol LO-529 (manufactured by Toho Chemical Co., Ltd.) are dissolved. It was. A mixed solution of 10.4 parts by weight of azobisisobutyronitrile, 910 parts by weight of styrene and 390 parts by weight of butyl methacrylate in which 3.9 parts by weight of t-butylperoxy-2-ethylhexanoate was dissolved. In addition, the mixture was emulsified with a homogenizer at 4000 rpm, and then treated with a nanomizer system LA-33 (manufactured by Nanomizer Co., Ltd.) at a treatment pressure of 0.5 MPa to obtain a dispersion. The resulting dispersion was heated at 60 ° C. for 6 hours while stirring at a stirring speed of 450 rpm. Thereafter, 1.3 parts by weight of sulfamic acid and 100 parts by weight of water in which 2.6 parts by weight of sodium dodecylbenzenesulfonate were dissolved were added, and the mixture was heated to 110 ° C. and further polymerized while continuing stirring for 1 hour. Thereafter, the mixture was cooled to room temperature and dehydrated and dried to obtain styrene-acrylic polymer particles. The average particle diameter of the obtained styrene-acrylic polymer particles was 10 μm.

(Synthesis method 1 of seed particles used in Examples 1 to 6 and Comparative Examples 2 and 3)
To a 5 L autoclave, 3600 parts by weight of water, 1.429 parts by weight of a 28% aqueous solution of stearyltrimethylammonium chloride (Coatamine 86W manufactured by Kao Corporation), 400 parts by weight of methyl methacrylate, 8 parts by weight of normal octyl mercaptan, The mixture was heated to 70 ° C. while stirring at a stirring rotational speed of 250 rpm. Next, 2 parts by weight of 2,2′-azobis (2-amidinopropane) dihydrochloride (V-50 manufactured by Wako Pure Chemical Industries, Ltd.) was supplied, stirred at 70 ° C. for 3 hours, and then up to 80 ° C. The emulsion polymerization was carried out while heating and further stirring for 1 hour. Thereafter, the emulsion was cooled to room temperature to obtain an aqueous dispersion of acrylic polymer particles. The average particle diameter of the acrylic polymer particles in the obtained aqueous dispersion was 0.12 μm. The weight average molecular weight was 36,900.

Example 1
In a 5 L autoclave, 2740 parts by weight of water, 0.571 parts by weight of a 28% aqueous solution of stearyltrimethylammonium chloride (Coatamine 86W manufactured by Kao Corporation), 240 parts by weight of methyl methacrylate, 560 parts by weight of isobutyl methacrylate, normal dodecyl mercaptan 8 parts by weight was supplied, and after emulsifying and stirring with a homogenizer at a stirring speed of 7000 rpm for 10 minutes, 400 parts by weight of an aqueous dispersion of acrylic polymer particles produced by Synthesis Method 1 was supplied, and then for 1 hour. Stir at room temperature. Thereafter, the mixture was heated to 70 ° C., 2 parts by weight of 2,2′-azobis (2-amidinopropane) dihydrochloride (V-50 manufactured by Wako Pure Chemical Industries, Ltd.) was supplied and stirred for 3 hours. Emulsion polymerization was carried out while continuing stirring at 1 ° C. for 1 hour. Thereafter, the emulsion was cooled to room temperature to obtain an aqueous dispersion of positively chargeable acrylic polymer particles. The average particle diameter of the positively chargeable acrylic polymer particles in the obtained aqueous dispersion was 0.28 μm. Further, the aqueous dispersion of the positively chargeable acrylic polymer particles obtained is treated with a spray dryer at an air supply temperature of 105 ° C. and an exhaust temperature of 55 ° C., and then treated with a jet mill to thereby obtain a positively chargeable acrylic polymer. A powder of particles was obtained. After the positively chargeable acrylic polymer particles were externally added by the above-described method, the passing rate of the pseudo toner having a sieve opening of 45 μm was 83%, and the fluidity was excellent.

(Example 2)
The procedure was the same as in Example 1 except that tertiary butyl methacrylate (TBMA; carbon number of ester part 4) (manufactured by Kyoeisha Chemical Co., Ltd .; light ester TB) was used instead of isobutyl methacrylate.
The average particle diameter of the positively chargeable acrylic polymer particles in the obtained aqueous dispersion was 0.32 μm. After the positively chargeable acrylic polymer particles were externally treated by the above-described method, the passing rate of the pseudo toner having a mesh opening of 45 μm was 95%, and the fluidity was extremely excellent.

(Example 3)
The procedure was the same as Example 1 except that cyclohexyl methacrylate (CHMA; ester part carbon number 6) (manufactured by Kyoeisha Chemical Co., Ltd .; light ester CH) was used instead of isobutyl methacrylate.
The average particle diameter of the positively chargeable acrylic polymer particles in the obtained aqueous dispersion was 0.36 μm. The positively charged acrylic polymer particles after the external addition treatment by the above-described method had a sieve passing rate of 85% and excellent fluidity.

Example 4
The same procedure as in Example 1 was performed except that 240 parts by weight of methyl methacrylate was replaced with 560 parts by weight, and 240 parts by weight was replaced with 560 parts by weight of isobutyl methacrylate.
The average particle diameter of the positively chargeable acrylic polymer particles in the obtained aqueous dispersion was 0.28 μm. After the positively chargeable acrylic polymer particles were externally added by the above-described method, the passing rate of the pseudo toner was 81%, and the fluidity was excellent.

(Example 5)
The same procedure as in Example 1 was performed, except that 80 parts by weight instead of 240 parts by weight of methyl methacrylate and 720 parts by weight instead of 560 parts by weight of isobutyl methacrylate.
The average particle diameter of the positively chargeable acrylic polymer particles in the obtained aqueous dispersion was 0.34 μm. After the positively chargeable acrylic polymer particles were externally added by the above-described method, the passing rate of the pseudo toner was 90%, and the fluidity was very excellent.

(Example 6)
The same procedure as in Example 1 was carried out except that isobornyl methacrylate (IBOA; ester part carbon number 10) (manufactured by Kyoeisha Chemical Co., Ltd .; light ester IB-XA) was used instead of isobutyl methacrylate.
The average particle diameter of the acrylic polymer particles in the obtained aqueous dispersion was 0.35 μm. After the acrylic polymer particles were externally added by the above-described method, the passing rate of the pseudo toner was 81%, and the fluidity was excellent.

(Comparative Example 1)
The same procedure as in Example 1 was performed except that emulsion polymerization was performed without using seed particles.
The average particle diameter of the positively chargeable acrylic polymer particles in the obtained aqueous dispersant was 0.32 μm. After the positively chargeable acrylic polymer particles were externally added by the above-described method, the passing rate of the pseudo toner was 66%, and the fluidity was not excellent.

(Comparative Example 2)
The same procedure as in Example 1 was performed except that 720 parts by weight instead of 240 parts by weight of methyl methacrylate and 80 parts by weight instead of 560 parts by weight of isobutyl methacrylate were used.
The average particle diameter of the positively chargeable acrylic polymer particles in the obtained aqueous dispersant was 0.26 μm. After the positively chargeable acrylic polymer particles were externally added by the above-described method, the passing rate of the pseudo toner was 68%, and the fluidity was not excellent.

(Comparative Example 3)
The procedure was the same as in Example 1 except that 560 parts by weight of isostearyl acrylate (STMA; ester part carbon number 18) (manufactured by Kyoeisha Chemical Co., Ltd .; light ester ST) was used instead of 560 parts by weight of isobutyl methacrylate.
The average particle diameter of the positively chargeable acrylic polymer particles in the obtained aqueous dispersion was 1.85 μm, which was not a desired size. After the positively chargeable acrylic polymer particles were externally added by the above-described method, the passing rate of the pseudo toner was 70%, and the fluidity was not excellent.

  The acrylic polymer particles of the present invention are characterized in that the average particle diameter of the acrylic polymer particles is 0.1 to 1.0 μm and excellent in positive chargeability. Therefore, it can be used as an additive for toners used in electrostatic image development, as well as additives for paints, ink adhesives, adhesives, artificial marble, paper processing agents, cosmetics, etc. It can be used as a material, a chromatographic column filler, a toner additive or carrier coating agent used for electrostatic charge image development, a film antiblocking agent, a light diffusing agent, and the like.

Claims (4)

In the presence of seed particles and a cationic surfactant in an aqueous medium, the seed particles are allowed to absorb an acrylic polymerizable monomer and perform seed emulsion polymerization to produce acrylic polymer particles,
The seed particles are vinyl polymer particles;
The acrylic polymerizable monomer is a blend of 30 to 90% by weight of a (meth) acrylic ester monomer and 10 to 70% by weight of a vinyl polymerizable monomer copolymerizable with the (meth) acrylic ester monomer. ,
The carbon number of the substituent of the ester part of the (meth) acrylic ester monomer is 4 or more and 10 or less,
The acrylic polymer particles have an average particle size of 0.1 to 1.0 μm,
A method for producing positively chargeable acrylic polymer particles, characterized by being used as an external additive for toner used in electrostatic image development . The substituent of the ester part of the (meth) acrylic ester monomer is one or more of isobutyl, t-butyl, benzyl, cyclohexyl group, and isobornyl group. A method for producing positively chargeable acrylic polymer particles. The positively chargeable acrylic polymer particles according to claim 1 or 2, wherein the vinyl polymerizable monomer copolymerizable with the (meth) acrylic ester monomer is methyl (meth) acrylate. Way . When a pseudo-toner is obtained by externally adding the positively chargeable acrylic polymer particles to styrene-acrylic polymer particles having an average particle size of 10 μm, the sieve passing rate with an opening of 45 μm is 80% to 99%. The method for producing positively chargeable acrylic polymer particles according to any one of claims 1 to 3, wherein: