JPS63189413A - Production of crosslinked polymer particle - Google Patents

Abstract

PURPOSE:To obtain the titled highly crosslinked particle having easily controllable particle diameter and useful as an assistant for toner for electrophotography, using a reaction system having excellent polymerization stability, by absorbing a polymerizable monomer in a specific seed polymer and polymerizing the monomer. CONSTITUTION:The objective particle can be produced by mixing (A) an aqueous dispersion containing (i) 1pt.wt. of seed polymer particle having a weight- average molecular weight of 500-10,000 with (B) 2-500pts. of polymerizable monomers containing (ii) >=3wt.% crosslinkable monomer and polymerizing the component B absorbed in the component (i). The amount of the component B is preferably 4-19pts. per 1pt. of the component (i). The component (i) can be produced e.g. by the emulsion polymerization process using a relatively large amount of a mercaptan-based molecular weight modifier.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for making crosslinked polymer particles, and in particular to a method for making highly crosslinked polymer particles.

[Prior art]

Methods for polymerizing polymer particles are broadly classified into emulsion polymerization, soap-free polymerization, and suspension polymerization. Among these, according to emulsion polymerization method or soap-free polymerization method,
The obtained polymer particles have a relatively narrow particle size distribution, but the particle size is usually about 0.5 nm or less, and even under special conditions it is about several nanometers or less, and it is difficult to obtain polymer particles with a large particle size. Have difficulty. Furthermore, according to the suspension polymerization method, it is possible to obtain polymer particles with a large particle size of several meters or more, but the resulting polymer particles have a very wide particle size distribution, and it is difficult to control the particle size. It is.

By the way, in order to obtain polymer particles with excellent hardness, strength, heat resistance, or solvent resistance, crosslinked polymer particles may be obtained by polymerizing a polymerizable monomer containing a considerable proportion of crosslinkable heptamers. However, when producing crosslinked polymer particles by the conventionally known emulsion polymerization method or soap-free polymerization method, if the proportion of crosslinkable monomer in the monomer exceeds 3% by weight, the stability of the polymerization reaction system becomes extremely poor. For this reason, a large amount of coagulum is produced, resulting in extremely low production efficiency of crosslinked polymer particles, or the polymerization reaction product solidifies (gels) during polymerization, making it difficult to actually produce the desired crosslinked polymer particles. The problem is that it can't be done.

In the polymerization mechanism in these methods, particle nuclei are formed at the beginning of polymerization (first stage of Smith-Ebert theory), and monomers are absorbed into these particle nuclei and polymerized (second and third stages of Smith-Ebert theory). ). However, in a polymerization reaction system in which the proportion of cross-linking monomer is large, the particle nuclei formed have almost no monomer absorption capacity for the cross-linking monomer, and therefore, in practice, the reaction does not proceed until the second stage of polymerization or later. Without this, only small polymer particles with an average particle diameter of about 0.05 μm or less are formed in large quantities, and the surface area of the particles in the polymerization reaction system becomes excessive and the colloidal chemical stability of the system is lost. It will be destroyed.

As described above, the emulsion polymerization method or the soap-free polymerization method cannot increase the proportion of crosslinkable monomer in the monomer, and as a result, it is difficult to produce highly crosslinked polymer particles. This is an essential problem caused by the particle formation mechanism.

On the other hand, when polymerizable monomers containing a large amount of crosslinkable monomers are polymerized by the suspension polymerization method, although there is no problem with polymerization stability, the crosslinked polymer particles formed are particles with a particle size of several grams or more. Moreover, it is difficult to control the particle size, and furthermore, the particle size distribution becomes extremely wide, making it impossible to produce practically useful crosslinked polymer particles.

[Problem that the invention seeks to solve]

In this way, the particle diameter of polymer particles obtained by emulsion polymerization method or soap-free polymerization method is within the range of a number n to 0.1n.
To produce highly cross-linked polymer particles having a particle size in the range of It has been difficult to industrially advantageously produce polymer particles that have a large diameter and are highly crosslinked.

The present invention provides industrially advantageous production of highly cross-linked polymer particles having a particle size precisely controlled to a specific target particle size within the range of 0.1 to 100 nm, and having a narrow particle size distribution. The present invention provides a method for producing crosslinked polymer particles that can be produced.

[Structure of the invention]

The method for producing crosslinked polymer particles of the present invention involves polymerization containing 3% by weight or more of a crosslinkable heptamer in an aqueous dispersion containing 1 part by weight of seed polymer particles having a weight average molecular weight within the range of 500 to 10,000. The method is characterized in that 2 to 500 parts by weight of a polymerizable monomer is added, and the seed polymer particles absorb the polymerizable monomer and polymerize.

The present invention will be specifically explained below.

The method of the present invention has the greatest feature in that polymer particles having a weight average molecular weight within a specific range are used as so-called seed polymer particles. That is, the seed polymer particles used in the present invention have a weight average molecular weight of 50
It needs to be 0 to ooo, preferably 700 to 7,000, more preferably 1,000 to 6,000.

In the present invention, the "weight average molecular weight" of polymer particles refers to the weight average molecular weight measured by a conventional method such as viscosity measurement of a solution of the polymer particles or gel permeation chromatography (polystyrene equivalent) based on viscosity measurement. It is molecular weight.

When the weight average molecular weight of the seed polymer particles exceeds 10,000, the monomer absorption capacity of the seed polymer particles is small, and the monomer independently polymerizes without being absorbed by the seed polymer particles, resulting in a particle size different from the intended one. In addition, a large amount of polymer particles are produced, and the stability of the polymerization reaction system is deteriorated due to these foreign particles, and a large amount of coagulum is generated during polymerization.

Further, when the weight average molecular weight of the seed polymer particles is less than 500, the molecular weight is too small and the monomer absorption capacity is also small, resulting in the same problem as above.

In addition, the particle size and particle size distribution of the seed polymer particles are
Since this will affect the particle size and particle size distribution of the crosslinked polymer particles to be produced, it is preferable to use seed polymer particles with uniform particle sizes that are controlled as much as possible and have a narrow particle size distribution. Specifically, the particle size is 0
．． 2-0. Seed polymer particles of F1a irises with a narrow particle size distribution, for example, those with a variation coefficient of 10% or less, are preferably used.

The composition of the seed polymer particles is not particularly limited as long as it dissolves or swells in the monomer used for polymerization, but
It is preferable that the monomer is of the same type as the monomer used for polymerization, and specifically, polystyrene or other polymer particles are preferably used.

The method for obtaining such seed polymer particles is not particularly restricted or restricted, but examples include synthesis using an emulsion polymerization method using a relatively large amount of a mercaptan-based molecular weight modifier or a soap-free polymerization method. Can be done.

Also in the production of the seed polymer particles, it is preferable to use a seed polymerization method using seed particles in order to control the particle size.

In the present invention, the crosslinkable monomer includes two or more, preferably non-conjugated divinyl compounds such as divinylbenzene, or polyvalent acrylate compounds such as trimethylolpropane trimethacrylate and trimethylolpropane triacrylate. A compound having two copolymerizable double bonds can be preferably used.

Examples of polyvalent acrylate compounds that can be used in the present invention include the following compounds.

Diacrylate human polyethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,6-hexane glycol diacrylate, neopentyl glycol diacrylate, polyethylene glycol diacrylate (oxyprobyloxyphenyl) propane 5.2,2°- Bis(4-acryloxyjethoxyphenyl)propane triacrylate Trimethylolpropane triacrylate, trimethylolethane triacrylate, tetramethylolmethane triacrylate 1
Ratehi A Ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, l,3-butylene glycol dimethacrylate, 1
．． 4-Butylene glycol dimethacrylate, 1.6-
Hexane glycol diacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 2,2゛-bis(4-methacryloxyjethoxyphenyl)propane trimethacrylate human trimethylolpropane trimethacrylate, trimethylol Among the above ethane trimethacrylates, it is particularly preferable to use divinylbenzene, ethylene glycol dimethacrylate or trimethylolpropane trimethacrylate, and these crosslinking monomers are
It is also possible to use a mixture of more than one species.

In the present invention, it is necessary that the proportion of the crosslinkable polymer is 3 to 100% by weight, preferably 5 to 100% by weight, and more preferably 10 to 100% by weight based on the total monomers.

If the proportion of the crosslinking monomer is less than 3% by weight, problems arise in the hardness, strength, heat resistance, or solvent resistance of the resulting polymer particles.

In the present invention, the polymerizable monomers used together with the above-mentioned crosslinking polymer include aromatic monovinyl compounds such as styrene, α-methylstyrene, fluorostyrene, and vinylpyrine, vinyl cyanide compounds such as acrylonitrile and methacrylonitrile, and butyl Acrylate, 2
-ethylhexyl acrylate, methyl acrylate,
Acrylic acid ester monomers such as 2-hydroxyethyl acrylate, glycidyl acrylate, N,N'-dimethylaminoethyl acrylate, butyl methacrylate, 2-ethylhexyl methacrylate, methyl methacrylate, 2-hydroxyethyl methacrylate,
Methacrylic acid ester monomers such as glycidyl methacrylate, N,N'-dimethylaminoethyl methacrylate, mono- or dicarboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid and acid anhydrides of dicarboxylic acids, acrylamide, methacrylamide, etc. An amide monomer can be used. In addition, within the allowable range in terms of polymerization rate and polymerization stability,
Conjugated double bond compounds such as butadiene and isoprene, vinyl ester compounds such as vinyl acetate, 4-methyl-1
-Pentene and other α-olefin compounds can also be used. Two or more types of these may be used.

Methods for adding monomers include a method of adding the monomer to the seed polymer particles all at once, and a method of adding the monomer in parts or continuously while polymerizing. In the present invention, when polymerization starts, the seed polymer It is necessary for the seed polymer particles to absorb monomer before substantial crosslinking occurs in the particles.

If a monomer is added after the middle stage of polymerization, the monomer will not be absorbed into the polymer particles, resulting in a large amount of microparticles, resulting in poor polymerization stability and inability to maintain the polymerization reaction. All monomers are added before the start of polymerization or the polymerization yield is 30%.
In the present invention, it is particularly preferable to start polymerization after all the monomers have been absorbed into the seed polymer particles.

In the present invention, the amount of monomer used per 1 part by weight of seed polymer particles is 2 to 500 parts by weight, preferably 3 parts by weight.
~100 parts by weight, more preferably 4 to 19 parts by weight.

If the amount of this monomer used is less than 2 parts by weight, the proportion of soft seed polymer particles to the total will be high, making it difficult to ensure that the final crosslinked polymer particles have sufficient hardness and strength. However, due to phase separation occurring within the seed polymer particles, the crosslinked polymer particles finally obtained have an irregular shape, making it impossible to obtain truly spherical crosslinked polymer particles.

Furthermore, if the amount of monomer used exceeds 500 parts by weight, the monomer absorption capacity of the seed polymer particles is insufficient and the amount of monomer that is not absorbed by the seed polymer particles increases, making it difficult to control the particle size.

In the present invention, the particle diameter of the finally obtained crosslinked polymer particles can be controlled by adjusting the amount of seed polymer particles and the amount of monomer. Specifically, if the weight of the seed polymer particles is W3, the number average particle diameter is 8, the amount of monomer is M, and the polymerization conversion rate is X (%), then the number average seed diameter of the resulting crosslinked polymer particles is is calculated using the following formula, and is achieved with relatively high accuracy in practice.

However, dll is the specific gravity of the seven-dimensional polymer, and d is the specific gravity of the crosslinked polymer particles.

In the present invention, a general water-soluble radical polymerization initiator or an oil-soluble radical polymerization initiator can be used as the polymerization initiator, but monomers that are not absorbed into the seed polymer particles may initiate polymerization in the water phase. It is preferable to use an oil-soluble polymerization initiator.

Examples of the oil-soluble polymerization initiator used in the present invention include benzoyl peroxide, α, α1-azobisisobutyronitrile, t-butylperoxy-2-ethylhexanoate, 3. Examples include S,S-)limethylhexanoyl peroxide. In addition, in the polymerization reaction, it is preferable to add a small amount of a water-tI polymerization inhibitor such as potassium dichromate, ferric chloride, or hydroquinone, since this can suppress the generation of fine particles.

In the polymerization reaction, a suspension protectant or a surfactant may be used to increase the stability of the polymerization reaction system.

However, when using a surfactant, microparticles may be generated and the polymerization stability may be reduced, so it is preferable to use as little amount as possible, especially when polymerization is carried out using a water-soluble polymerization initiator. In some cases, the concentration of the surfactant must be below the critical micelle formation concentration (C, M, C,).

On the other hand, when polymerizing using an oil-soluble polymerization initiator, if the water solubility of the monomer and the oil-soluble polymerization initiator is sufficiently low, the amount of surfactant used can be at a concentration of C, M, C, or higher. It is possible to carry out polymerization even if there is

In the present invention, common surfactants can be used, and examples include anionic emulsifiers such as sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium dialkylsulfosuccinate, and formalin condensate of naphthalenesulfonic acid. Can be done.

Furthermore, polyoxyethylene nonylphenyl ether,
It is also possible to use nonionic surfactants such as polyethylene glycol monostearate and sorbitan monostearate.

Preferable protective agents that can be used in the present invention include polyvinyl alcohol, carboxymethyl cellulose, sodium polyacrylate, and finely powdered inorganic compounds.

The crosslinked polymer particles obtained by the method of the present invention have a high degree of crosslinking (therefore, crosslinked polymer particles with extremely high hardness, strength, heat resistance or solvent resistance are obtained).

These crosslinked polymer particles can be used in various fields by taking advantage of such properties.

Examples of uses of crosslinked polymer particles according to the invention include:
Sliding materials, spacers, anti-blocking agents, powder fluidity improvers, powder lubricants, cosmetic particles, abrasives, rubber compounding agents, plastic pigments, filter media and filter aids, gelling agents, flocculants, paints These include additives for plastics, gloss modifiers, mold release agents, column fillers for chromatography, particles for microcapsules, particles for adding synthetic fibers, etc.

The crosslinked polymer particles prepared by the method of the present invention are particularly effective as an auxiliary agent for electrophotographic toners. For example, 1 to 10% by weight of the crosslinked polymer particles prepared by the method of the present invention are added together with the base resin and various toner additives during toner production. When melted and crushed, the crushability is improved, so the energy required for crushing is reduced, and the crushed product has a narrow particle size distribution, which reduces the burden of classification.

Further, it is possible to improve the balance between fixing properties and anti-blocking properties as a toner. Furthermore, when the crosslinked polymer particles according to the present invention are blended into a toner in a proportion of 1 to 20% by weight by dry mixing, the toner has improved anti-blocking properties, improved fluidity, reduced contamination of the photosensitive drum, and improved capri. Also, it is possible to prevent a decrease in image density due to deterioration of toner over time.

〔Example〕

The present invention will be explained in detail below. In addition, in the following description, "parts" are parts by weight.

Example 1 Styrene 98 parts Methacrylic acid 2 parts t-Dodecylmercaptan 10 parts Sodium dodecylbenzenesulfonate 0.05 parts Potassium persulfate 0.4 parts Water
More than 200 parts of the substance was placed in a flask with a volume of 21 cm, and the temperature was raised to 70° C. in nitrogen gas while stirring, and polymerization was carried out for 6 hours.

As a result, seeded polymer particles A were obtained with a polymerization yield of 98%, a particle diameter of 0.45 n, and a standard deviation value of particle diameter of 0.015 ps. The particle diameter here is the average value of values measured for 100 polymer particles using transmission electron micrographs. This seed polymer particle A has a toluene-soluble content of 9
8%, and the molecular weight measured by gel permeation chromatography is weight average molecular weight (Mw) = 5. The QOO number average molecular fi (Mn) = 3,100.

Next, Seed polymer particles A (solid content equivalent) 8 parts Sodium lauryl sulfate 0.2 parts Potassium persulfate 0.5 parts Water
500 parts styrene
Mix 80 parts of divinylbenzene and 20 parts of divinylbenzene and heat at 30℃ for 10 minutes.
Stir for a minute to allow the seed polymer particles to absorb the monomer.

Next, when the temperature was raised to 70°C and polymerization was carried out for 3 hours, the polymerization yield was 99%, and the polymerized coagulum remaining on the 200 mesh filter was 0.02% (based on polymerized solid content).
Crosslinked polymer particles with high polymerization stability were obtained.

The crosslinked polymer particles had an average particle diameter of 1.02 nm and were perfectly spherical.

Differential thermal analysis and thermobalance analysis were performed on these crosslinked polymer particles, and it was found that they did not melt or soften from room temperature to 450°C until ashing, and that the amount of heat M up to 400°C was 2.
It was less than % by weight.

Examples 2 to 4 and Comparative Examples 1 to 3 t in the production of seed polymer particles in Example 1
- The amount of dodecyl mercaptan used is 0 parts, 2 parts, 5 parts,
The same procedure was applied to the seed polymer particles except that the weight average molecular weight was changed to 20 parts, 50 parts, and 100 parts, respectively, and the weight average molecular weight was 120 parts.
,000.15,000.8,900.3,050.7
10 and 320 seed polymer particles B-
G was synthesized.

Crosslinked polymer particles were produced in the same manner as in Example 1, except that each of these seed polymer particles was used in advance.

Table 1 shows the ratio of polymerized coagulates and polymerization yields in each of the above polymerization reactions, as well as the average particle diameter and standard deviation of the obtained crosslinked polymer particles.

As is clear from Table 1, Comparative Example 1 and Comparative Example 3
In Comparative Example 2, the reaction system gelled during polymerization, and although polymerization was achieved in Comparative Example 2, the amount of coagulated material produced was excessive, and the obtained polymer particles had a particle size of about 0.8n, which was close to the target particle size. A large number of microparticles with a particle size of 0.05 to 0.1n and monomer droplets that are not absorbed by the seed polymer particles are polymerized as they are, resulting in a particle size of 10 to 100n.
It was a mixture of three types of μ particles, and had a very broad particle size distribution.

Example 5 8 parts of seed polymer particles A of Example 1 as solid content,
40 parts of styrene and 10 parts of divinylbenzene as monomers
Polymerization was carried out in the same manner as in Example 1, except that 20% of the polymer was used, and crosslinked polymer particles were obtained.

Example 6 8 parts of the seed polymer particles A of Example 1 as solid content,
60 parts of styrene and 40 parts of divinylbenzene
Polymerization was carried out in the same manner as in Example 1, except that 20% of the polymer was used, and crosslinked polymer particles were obtained.

Example 7 8 parts of seed polymer particles A of Example 1 as solid content,
Polymerization was carried out in the same manner as in Example 1, except that 80 parts of methyl methacrylate was used in place of styrene and 20 parts of ethylene glycol dimethacrylate was used in place of divinylbenzene, to obtain crosslinked polymer particles.

Examples 8 to 18 and Comparative Examples 4 to 6 Example 10 Seed polymer particles A as seed polymer particles and benzoyl peroxide (BP) as a polymerization initiator.
O) is dissolved in a monomer and sodium lauryl sulfate or polyvinyl alcohol (rGM-
Polymerizations of Examples 8 to 18 and Comparative Examples 4 to 6 were carried out in the same manner as in Example 1, except that the formulations shown in Table 2 were made using 154 (manufactured by Nippon Gosei Kagaku ■). The results are shown in Table 2.

Examples 8 and 9 are systems using BPO as a polymerization initiator and sodium lauryl sulfate as a stabilizer, and Example 10 is a system using BPO as a polymerization initiator and sodium lauryl sulfate as a stabilizer.
Systems using PO as a polymerization initiator and polyvinyl alcohol as a stabilizer, Examples 8, 11 and 12, and Comparative Example 4 are systems in which the amount of divinylbenzene as a crosslinking additive was changed, Examples 13 to 18 and comparative examples 5 and 6,
This is a system in which the ratio of monomer to seed polymer particles is changed.

In Table 2, the "amount of coarse particles" refers to the amount of coarse particles after the completion of the polymerization reaction.
After filtration with a 00 mesofiltration filter and measuring the amount of coagulated matter, the ratio of particles having a particle diameter of 1 nm or more to the total particles was determined by measuring with a Coulter counter.

In addition, the "solvent resistance" of crosslinked polymer particles was determined by mixing 10 g of dry particles with 30 g of toluene and sealing the mixture.
Judgment was made by examining the condition after being left at 0°C for 24 hours. In Table 2, rXJ indicates that particles are partially dissolved or sticky, "Δ" indicates that particles are slightly sticky, and rOJ indicates that no signs of dissolution are observed.

Reference Experiment The following experiment was conducted to demonstrate that it is difficult to carry out emulsion polymerization with a polymerizable monomer containing too much crosslinking monomer.

Using an emulsion polymerization system using 500 parts of water, 0.5 parts of potassium persulfate as an initiator, sodium dodecylbenzenesulfonate as an emulsifier, and a total of 100 parts of styrene, divinylbenzene and acrylic acid as monomers, in a nitrogen atmosphere, The operation of polymerizing under the conditions of polymerization at 70'C for 6 hours was repeated by changing the amount of emulsifier and the ratio of monomer components. Table 3 shows the proportion of polymerized coagulum and the polymerization yield in this polymerization reaction.

In Reference Examples 1 to 6, the ratio of styrene and divinylbenzene was changed, but if the amount of divinylbenzene used exceeds 3 parts, the polymerization stability deteriorates and the amount of coagulated product formed becomes excessive, or the reaction The system gels. In Reference Example 7 and Reference Example 8, the amount of emulsifier used was increased while keeping the amount of divinylbenzene used at 3 parts, but the amount of foreign particles newly generated during polymerization increased, and this actually worsened the polymerization stability. It got worse. In Reference Example 9 and Reference Example 10, an attempt was made to improve the stability of the particles by using a growth factor in combination, but no significant effect was observed.

As mentioned above, it is difficult to carry out emulsion polymerization when a polymerizable monomer with a large number of crosslinkable heptamers is used.

〔Effect of the invention〕

The method of the present invention has excellent polymerization stability in the polymerization reaction system for producing polymer particles, and the particle size can be easily controlled, and crosslinked polymer particles of any particle size and narrow particle size distribution can be produced. can be manufactured. Furthermore, since the obtained crosslinked polymer particles are highly crosslinked, they have excellent hardness, strength, heat resistance, and solvent resistance, and the particle size is uniform, and particles of any size can be selected. Therefore, it is expected that the properties expected in various applications will be well exhibited, and that it will also be successfully used in new applications.

Claims (1)

[Scope of Claims] 1) An aqueous dispersion containing 1 part by weight of seed polymer particles having a weight average molecular weight within the range of 500 to 10,000;
Polymerizable monomer 2 containing 3% by weight or more of a crosslinking monomer
A method for producing crosslinked polymer particles, which comprises adding 500 parts by weight of a polymerizable monomer to the seed polymer particles, and polymerizing the polymerizable monomer by absorbing the polymerizable monomer into the seed polymer particles. 2) The amount of polymerizable monomer used is 1
The method for producing crosslinked polymer particles according to claim 1, wherein the amount is 4 to 19 parts by weight.