JP3746431B2 - Method for producing resin particles - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing resin particles. More specifically, the present invention relates to a method for efficiently recovering resin particles dispersed in a suspension in a method for producing resin particles.
[0002]
[Prior art and problems to be solved by the invention]
Resin particles are used in applications such as matting agents for paints, light diffusing agents, cosmetic slipperiness imparting agents, toners, and anti-blocking agents for plastic films. One method for producing resin particles is a suspension polymerization method, which is widely adopted. The particles produced by the suspension polymerization method must be separated from the suspension. As a separation method, a centrifugal sedimentation method or a method of aggregating or precipitating using a flocculant is used.
However, recently, the diameter of particles obtained by suspension polymerization has been reduced to about several μm, and separation with existing separation methods has become difficult, such as requiring strong centrifugal force for centrifugal sedimentation. Yes. Further, when particles obtained by solid-liquid separation using a general flocculant are used as, for example, an electrophotographic toner, the flocculant may affect performance such as moisture resistance.
[0003]
On the other hand, JP-A-5-40366 discloses a method for facilitating solid-liquid separation by agglomerating spherical resin particles by adding water-insoluble fine particles or an organic solvent to the suspension. In JP-A-5-1000048, after suspension polymerization, the resin particles are aggregated by treatment at a temperature equal to or higher than the glass transition temperature to remove the dispersion stabilizer, and then the aggregates are crushed, A method for obtaining a toner comprising amorphous resin particles is disclosed.
However, these conventional methods require a step of crushing the aggregates into particles after the drying step.
Accordingly, an object of the present invention is to provide a method that makes it possible to more efficiently separate and recover resin particles in a suspension. More specifically, in the present invention, the aggregate of resin particles (hereinafter also referred to as primary particles) is brought into the state of the original primary particles without being substantially subjected to a crushing step after the drying step, that is, An object of the present invention is to provide a method for efficiently separating resin particles.
[0004]
[Means for Solving the Problems]
Thus, according to the present invention, the resin particles obtained by suspension polymerization, suspension stability may be degraded by an acid substance, the hardly water-soluble phosphate salt is selected from magnesium hydroxide and aluminum hydroxide A water-soluble acidic substance selected from succinic acid, acetic acid, ascorbic acid and sulfamic acid or an aqueous solution thereof is added to an aqueous suspension containing an inorganic suspension stabilizer to lower the pH by 1 to 5 and It is made into the range of 3.5-7, Then, it heat-processes under the temperature 10-100 degreeC higher than the temperature at the time of suspension polymerization , and consists of obtaining a resin particle by performing solid-liquid separation and drying after this, substantially In particular, a method for producing resin particles is provided that does not include a crushing step.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a water-soluble acidic substance such as an inorganic acid is added to an aqueous suspension of primary particles containing at least an inorganic suspension stabilizer whose suspension stability is lowered by an acidic substance, followed by heating treatment. Thus, the primary particles can be once aggregated and separated from the suspension efficiently and easily, and the state of the original primary particles can be easily obtained without being substantially subjected to the crushing step. It is a method to make.
The resin particles in the present invention are not particularly limited as long as they are particles that can be suspended by an inorganic suspension stabilizer. Moreover, the shape may be spherical or indefinite. Of these, the method of the present invention is preferably applied to spherical resin particles.
[0006]
The resin particles in the present invention preferably have a weight average particle diameter of 1 to 10 μm, and more preferably 1 to 4 μm. When the weight average particle size is larger than 10 μm, it is not preferable because aggregation hardly occurs. Particles smaller than 1 μm are not preferred because they are difficult to produce by general suspension polymerization and are difficult to obtain. In addition, particles larger than 4 μm may be separated by other methods, but particles of 1 to 4 μm are particularly useful because they are difficult by other methods.
[0007]
The resin particles may be made of any resin as long as it has the above properties. For example, styrene monomers such as styrene, α-methylstyrene, p-methylstyrene, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate , Obtained by polymerizing monomers having a vinyl group such as acrylic acid or methacrylic acid monomers such as n-butyl methacrylate and isobutyl methacrylate, ethylene, propylene, plaques, vinyl chloride, vinyl acetate and acrylonitrile. Resin. Moreover, the resin which polymerized these monomers individually or in combination of 2 or more types may be used. Furthermore, the resin may be crosslinked.
[0008]
The resin particles in the present invention may contain colorants such as dyes and pigments, magnetic powder, antistatic agents, fillers and the like.
Colorants include carbon black, nigrosine dye, aniline blue, calco oil blue, chrome yellow, ultramarine blue, oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malakide green oxalate, lamp black, oil black, Examples include azo oil black and rose bengal.
Examples of the magnetic powder include iron, cobalt, nickel, magnetite, hematite, and ferrite.
[0009]
The suspension stabilizer contains at least an agent whose suspension stability is lowered by an acidic substance. Examples of such suspension stabilizers include poorly water-soluble phosphates such as calcium phosphate and magnesium pyrophosphate, magnesium hydroxide, and aluminum hydroxide. Here, the decrease in suspension stability means that the suspension stabilizer is decomposed by an acidic substance, neutralized, or the like so that the amount of the resin decreases to form an aggregate with each other. It means that.
[0010]
Furthermore, the suspension stabilizer may contain other suspension stabilizer that does not decrease the stability as long as it contains at least an agent that decreases the suspension stability due to the acidic substance. Other suspension stabilizers include water-soluble polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, and methyl cellulose, anionic surfactants such as sodium oleate, sodium lauryl sulfate, and sodium dodecylbenzene sulfonate, lauryl amine acetate, and lauryl trimethyl. Examples thereof include cationic surfactants such as ammonium chloride and nonionic surfactants such as polyoxyethylene alkyl ether and polyoxyethylene alkylphenyl ether. In addition, other suspension stabilizer has the effect | action which can make the weight average particle diameter of the resin particle obtained become a predetermined magnitude | size by adjusting the composition and usage-amount suitably.
[0011]
However, if the above-mentioned other suspension stabilizer is used in an excessive amount, the suspension stability does not decrease even when a water-soluble acidic substance is added, and the effects of the present invention may be impaired. Therefore, it is necessary to adjust the amount of other suspension stabilizers used.
The solvent of the suspension is preferably an aqueous medium composed of water alone or a mixture of water and a water-soluble organic solvent such as alcohol.
[0012]
The resin particles used in the present invention are preferably particles obtained by a suspension polymerization method. The suspension polymerization method is a method of obtaining resin particles in a suspended state by polymerizing the monomer in an aqueous medium using a polymerization initiator in the presence of a suspension stabilizer. As the aqueous medium and suspension stabilizer that can be used in this suspension polymerization method, the same ones as described above can be used.
When using a crosslinked body for the resin particles, a crosslinking agent is usually added to the monomer. Examples of the crosslinking agent include trimethylolpropane triacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, divinylbenzene, divinylnaphthalene and the like.
[0013]
As the polymerization initiator, an oil-soluble peroxide-based or azo-based initiator usually used for suspension polymerization can be used. Examples of peroxide polymerization initiators include benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, cumene hydroperoxide, t-butyl hydroperoxide, and the like. 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), and the like.
Here, the following method is mentioned as a method of obtaining the spherical resin particle of 1-4 micrometers suitable for applying the method of this invention.
First, water in which a suspension stabilizer is dissolved or suspended is mixed with a polymerizable monomer containing a polymerization initiator, and the mixture is subjected to mechanical shearing to give O / O having a desired droplet size. A W-type emulsion is prepared and then polymerized.
[0014]
A dispersion device with adjustable shear strength can be used without limitation to adjust the droplet size of the emulsion. Among the devices, in particular, the primary suspension is a device for obtaining a secondary suspension by simply injecting the liquid from a nozzle without causing the liquids or liquids to collide with a predetermined plane under pressure. The apparatus is divided into a plurality of streams under pressure, the plurality of streams collide with each other, and a suspension is crushed by impact to obtain a secondary suspension, or a primary suspension is added. It is preferable to use an apparatus that obtains a secondary suspension by pressing and causing the liquid to collide with a predetermined plane. When a secondary suspension is obtained by these methods, a primary suspension is required, and a dispersion apparatus necessary for obtaining the primary suspension is particularly a dispersion apparatus capable of adjusting the shear strength. Can be used without limitation. In addition, it is preferable that the liquid suitable diameter of the primary suspension for forming a spherical resin particle of 1-4 micrometers is about 5-20 micrometers.
[0015]
In the method of the present invention, the suspension stabilizer is partially decomposed or neutralized with a water-soluble acidic substance, and heated to reduce the suspension stability to cause aggregation of primary particles. This will be specifically described below.
In the present invention, a water-soluble acidic substance is first added to an aqueous suspension.
Here, as the aqueous suspension of the resin particles using the inorganic suspension stabilizer in the present invention, a solution after suspension polymerization containing the inorganic suspension stabilizer may be used as it is. Examples of the suspension stabilizer used for suspension polymerization include poorly water-soluble phosphates such as calcium phosphate and magnesium pyrophosphate, magnesium hydroxide, and aluminum hydroxide. The suspension stabilizer varies depending on the type and type of the resin particles, but is preferably used in a ratio of 1 to 100 parts by weight with respect to 100 parts by weight of the resin particles.
[0016]
Examples of the water-soluble acidic substance include organic acidic substances such as succinic acid, acetic acid and ascorbic acid, and inorganic acidic substances such as sulfamic acid and potassium persulfate. These water-soluble acidic substances are preferably used in amounts so that the pH of the aqueous suspension is lowered by 1 to 5. If it is too low, it is not preferred because excessive aggregation or fusion may occur during the heating treatment. When the decrease is smaller than 1, aggregation is insufficient, which is not preferable. Furthermore, it is preferable that pH at the time of adding a water-soluble acidic substance is 3.5-7. When the pH is lower than 3.5, it is not preferable because it may cause adverse effects such as excessive agglomeration and fusion during the heating treatment, and corrosion of the polymerization tank. On the other hand, when the pH is higher than 7, aggregation is insufficient, which is not preferable.
The water-soluble acidic substance varies depending on the type, resin particles and suspension stabilizer, but it may be used at a ratio of 0.1 to 10 parts by weight with respect to 100 parts by weight of the suspension stabilizer. preferable.
[0017]
Next, the particles are slightly agglomerated by holding for a predetermined time while stirring at an appropriate temperature. The temperature is preferably 10 to 100 ° C. higher than that during suspension polymerization. A temperature lower than 10 ° C. is not preferable because aggregation is insufficient. A temperature higher than 100 ° C. is not preferable because excessive aggregation or fusion may occur.
Furthermore, it is preferable to perform a heating process at 70-150 degreeC. By performing in this range, more optimal aggregation can be realized. Moreover, when the resin particles have a glass transition temperature, it is preferable to keep the temperature 5 to 50 ° C. lower than that temperature. If the temperature is higher than the glass transition temperature of the particles, the particles may be fused, which is not preferable. Moreover, when a resin particle does not have a glass transition temperature, it is preferable to hold | maintain at 70-150 degreeC.
In addition, it is preferable that processing time is 0.5 to 5 hours. When the time is shorter than 0.5 hours, aggregation is insufficient, which is not preferable. On the other hand, when the time is longer than 5 hours, excessive aggregation or fusion may occur, which is not preferable.
[0018]
The particles that have been agglomerated by the method of the present invention can be easily separated from the suspension using a general solid-liquid separation device such as suction filtration or centrifugal separation. Subsequently, it is preferable to wash away acidic substances by performing a washing step. The particles that have undergone the solid-liquid separation and washing steps are already in the state of primary particles from the aggregated state. For this reason, the substantial crushing process after drying (namely, the process using a well-known crusher) is unnecessary, and there is very little possibility that an aggregated particle will mix in a final product.
The primary particles after the solid-liquid separation and washing process are aggregated due to a decrease in suspension stability of the aggregates before the solid-liquid separation, and very fine aggregates in which the particles are not fused together. Therefore, it is considered that the primary particles return to the primary particles by stimulation during the washing process and the drying process.
[0019]
【Example】
EXAMPLES Hereinafter, the present invention will be specifically described by way of examples. However, these examples do not limit the present invention in any way. In addition, the average particle diameter after particle | grain drying in an Example shows a weight average particle diameter, and measured it with the Coulter counter (made by Coulter company).
[0020]
(Example 1)
In a 2 liter polymerization vessel equipped with a stirrer and a thermometer, 1250 g of water in which 1 g of sodium lauryl sulfate was dissolved was placed, and 125 g of tribasic calcium phosphate was dispersed therein. A mixed solution in which 1.5 g of benzoyl peroxide and 1.5 g of azobisisobutyronitrile were dissolved in 200 g of methyl methacrylate and 50 g of ethylene glycol dimethacrylate prepared in advance was added thereto. Put T. The droplet diameter was adjusted to about 3 to 4 μm with a K homomixer (manufactured by Special Machine Industries). Next, suspension polymerization was performed while heating and stirring the polymerization vessel at 65 ° C. to obtain a suspension of primary particles.
[0021]
Polymerization subsequently added to the polymerization vessel of 10% aqueous solution of potassium persulfate 20g, a pH6.7 was measured pH, 1.5 pH before the addition was reduced. Subsequently, after heating at 100 ° C. for 1 hour, the suspension was cooled and taken out.
When this suspension was observed with a microscope, it was confirmed that the particles were aggregated. Subsequently, the aggregated particle suspension was suction filtered to take out the particles and dried in an oven to obtain spherical particles having an average particle diameter of 3.5 μm. When the obtained particles were observed with a microscope, no aggregation was observed and the particles were in a primary particle state.
[0022]
(Comparative Example 1)
After carrying out to suspension polymerization like Example 1, it heat-processed at 100 degreeC for 1 hour, without adding anything. When the suspension after cooling was observed with a microscope, the particles were not aggregated and were dispersed in the form of primary particles. Next, when this suspension was subjected to suction filtration using the same filter paper as in Example 1, particles were also observed in the filtrate, and the filtration time required more than twice that of Example 1.
[0023]
(Comparative Example 2)
When the same procedure as in Example 1 was performed except that the droplet diameter was adjusted to about 15 μm, the particles in the suspension were not aggregated.
[0024]
(Example 2)
600 g of water in which 1 g of sodium dodecylbenzenesulfonate was dissolved was placed in a 1 liter polymerization vessel equipped with a stirrer and a thermometer, and 16 g of metathesis magnesium pyrophosphate was dispersed therein. A mixture of 1 g of benzoyl peroxide and 1 g of 2,2′-azobis (2,4-dimethylvaleronitrile) dissolved in 180 g of styrene and 20 g of divinylbenzene prepared in advance was added thereto. Put T. The droplet diameter was adjusted to about 3 to 4 μm with a K homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.). Next, suspension polymerization was performed while heating and stirring the polymerization vessel at 60 ° C. to obtain primary particles.
[0025]
Subsequent to the polymerization, 10 g of a 10% aqueous sulfamic acid solution was added to the polymerization vessel, and the pH was measured to find that it was pH 3.9, which was 1.7 lower than before the addition. Subsequently, the mixture was heated at 110 ° C. for 2 hours and then cooled to take out the suspension.
When this suspension was observed with a microscope, it was confirmed that the particles were aggregated. Subsequently, the aggregated particle suspension was subjected to suction filtration to take out the particles, followed by drying in an oven. As a result, spherical particles having an average particle size of 3.9 μm were obtained. When the obtained particles were observed with a microscope, no aggregation was observed and the particles were in a primary particle state.
[0026]
(Comparative Example 3)
After the suspension polymerization was carried out in the same manner as in Example 2, 10 g of a 10% aqueous sulfamic acid solution was added to the polymerization vessel and maintained at the same temperature (60 ° C.) for 1 hour. When the suspension after cooling was observed with a microscope, the particles were not aggregated.
[0027]
(Comparative Example 4)
After up to suspension polymerization in the same manner as in Example 2, was added into a 10% aqueous solution of sulfamic acid 30g polymerizer, a pH3.2 was measured pH, 2.6 pH before the addition was reduced . Subsequently, the mixture was heated at 110 ° C. for 2 hours and then cooled to take out the suspension. When this suspension was observed with a microscope, it was confirmed that the particles were aggregated. Moreover, rust was seen in a part of the polymerization tank. Subsequently, this agglomerated particle suspension was suction filtered to take out particle components and dried in an oven. However, spherical particles were agglomerated and the average particle size of primary particles could not be measured.
[0028]
(Example 3)
80 g of tribasic calcium phosphate was dispersed in 800 g of water in which 1.6 g of sodium lauryl sulfate was dissolved. To this was added a polymerizable monomer component of 175 g of styrene dissolved with 1 g of benzoyl peroxide and 25 g of divinylbenzene (80% pure). A droplet diameter was adjusted to about 10 μm with a K homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to obtain a primary suspension.
Next, a nanomizer processor LD-500 (manufactured by Nanomizer) is connected to Nanomizer LA-33 (manufactured by Nanomizer), and the primary suspension is treated at a treatment pressure of 800 kg / cm ^2. A 2 μm secondary suspension was obtained.
Next, this secondary suspension was put into a 2 liter polymerization vessel equipped with a stirrer and a thermometer, and the polymerization was performed while heating and stirring the polymerization vessel at 80 ° C. to obtain primary particles.
[0029]
Polymerization subsequently added to the polymerization vessel of 10% aqueous solution of sulfamic acid 20g, a pH5.8 was measured pH, 2.0 pH before the addition was reduced. Subsequently, the mixture was heated at 110 ° C. for 2 hours and then cooled to take out the suspension.
When this suspension was observed with a microscope, it was confirmed that the particles were aggregated. Subsequently, the aggregated particle suspension was suction filtered to take out the particles and dried in an oven to obtain spherical particles having an average particle size of 2.2 μm. When the obtained particles were observed with a microscope, no aggregation was observed and the particles were in a primary particle state.
[0030]
(Example 4)
30 g of metathesis magnesium pyrophosphate was dispersed in 1200 g of water in which 1.2 g of sodium lauryl sulfate was dissolved. To this was added a polymerizable monomer component of 280 g of methyl methacrylate in which 1 g of azobis-N, N-dimethylvaleronitrile was dissolved and 120 g of trimethylolpropane trimethacrylate. The droplet diameter was adjusted to about 7 μm with a K homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to obtain a primary suspension.
Next, a nozzle type processor LNP-20 / 300 (manufactured by Nanomizer) is connected to Nanomizer LA-33 (manufactured by Nanomizer), and the primary suspension is treated at a treatment pressure of 300 kg / cm ² to produce droplets. A secondary suspension having a diameter of about 3 μm was obtained.
Next, this secondary suspension was put into a 2 liter polymerization vessel equipped with a stirrer and a thermometer, and the polymerization was carried out while heating and stirring the polymerization vessel at 60 ° C. to obtain primary particles.
[0031]
Subsequent to the polymerization, 12 g of a 10% aqueous sulfamic acid solution was added to the polymerization vessel, and the pH was measured. The pH was 4.6, which was 1.1 before the addition. Subsequently, the mixture was heated at 100 ° C. for 3 hours and then cooled to take out the suspension.
When this suspension was observed with a microscope, it was confirmed that the particles were aggregated. Subsequently, this aggregated particle suspension was filtered by suction to take out the particles and dried in an oven to obtain spherical particles having an average particle size of 2.8 μm. When the obtained particles were observed with a microscope, no aggregation was observed and the particles were in a primary particle state.
[0032]
【The invention's effect】
According to the present invention, an acid substance is added to a suspension of resin particles and heated to obtain an aggregate of the resin particles, and the aggregate is obtained using a general solid-liquid separator. Can also be efficiently separated from the suspension. In the method of the present invention, since aggregation is eliminated after drying, primary particles can be obtained without the need for a substantial crushing step, and productivity can be improved.

Claims (1)

And resin particles obtained by suspension polymerization, suspension stability by acid substances can decrease, poorly water-soluble phosphate, a suspension stabilizer inorganic selected from magnesium hydroxide and aluminum hydroxide A water-soluble acidic substance selected from succinic acid, acetic acid, ascorbic acid and sulfamic acid or an aqueous solution thereof is added to the aqueous suspension containing the solution to lower the pH by 1 to 5, and the pH is in the range of 3.5 to 7 , then warmed treated with 10 to 100 ° C. higher temperatures than the temperature of the suspension polymerization, consists of obtaining the resin particles by performing a solid-liquid separation and drying after this, it is substantially free of crushing step The manufacturing method of the resin particle characterized by the above-mentioned.