JPH01134A - Porous hollow particles and their manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention has a structure in which a hollow body made of a crosslinked polymer has a plurality of holes communicating with the hollow part in its shell, and has excellent uniformity in particle size. The present invention relates to porous hollow particles useful as microcapsules and a method for producing the same.

Conventional technology Fine polymer particles with uniform particle size are widely used in various fields such as opacifying materials, matting materials, organic pigments or fillers, thickness and gap adjustment materials, carriers for chromatography, ion exchange resins, etc. There is.

Generally, these polymer particles have various functions added to them based on the uniformity of particle size, and are used for various purposes based on their characteristics.

For example, if the polymer particles are hollow particles with a porous shell, they are useful as microcapsules, and can be used to prepare sustained-release drugs that gradually release the drug by sealing the drug in the microcapsules. Can be used. In this case, conventional sustained-release agents have been hollow bodies made of natural polymers such as polylactic acid, polyglycolic acid, and cellulose derivatives, and synthetic polymers such as polyvinyl alcohol, polyvinyl and lolidone, and polyhydroxyethyl methacrylate. However, since the uniformity of the particle size was poor and the controllability of the sustained release rate was difficult, polymer fine particles having the above characteristics are highly useful as they can improve the controllability of the sustained release rate. .

Means for Solving the Problems The present invention provides porous hollow particles that are made of hollow particles having porous grains and have excellent uniformity in particle size.

That is, the present invention is a hollow body made of a crosslinked polymer of a non-crosslinkable monomer and a crosslinkable monomer, whose shell has a plurality of pores communicating with the hollow part, and whose particle size is 2 to 30 um. (A) porous hollow particles consisting of fine particles with a coefficient of variation of particle size distribution of 10% or less; In molecular fine particles.
(B) obtaining a precursor of porous hollow particles by absorbing a non-crosslinking monomer, a crosslinking monomer, and a pore regulating agent and copolymerizing them in an aqueous medium; (B) obtaining a precursor of porous hollow particles; The gist of the present invention is a method for producing the porous hollow particles, which comprises a step of extracting a solvent-soluble substance from a precursor of the porous hollow particles.

In the method of the present invention, first, a non-crosslinkable monomer, a crosslinkable monomer, and a pore control agent are absorbed into non-crosslinked polymer fine particles obtained by a seed polymerization method, and then copolymerized in an aqueous medium. A precursor of porous hollow particles is obtained by processing (Step A).

At that time, the particle size is determined by repeating seed polymerization using a non-crosslinking monomer as the non-crosslinking polymer fine particles and a water-soluble polymerization initiator such as potassium persulfate or ammonium persulfate. The grown ones are used. This achieves the uniformity of the particle size in the present invention and enables the production of hollow bodies. The object of the present invention cannot be achieved by a seed polymerization method using an oil-soluble polymerization initiator.

In the present invention, a non-crosslinked polymer or the like in an emulsion obtained by processing a non-crosslinkable monomer by a conventional emulsion polymerization method is used as the initial seed particle, and the particle size of this seed particle is determined by the seed polymerization method. Those grown sequentially are preferably used. At that time, the amount of non-crosslinking monomer added is 2000 parts by weight or less, especially 100 parts by weight per 100 parts by weight of the seed particles.
It is desirable that the amount be 0 parts by weight or less in order to make the particle size uniform.

The non-crosslinked polymer fine particles used in step A have a particle size of 0.5 to 20μI and a standard deviation of particle size distribution of 0.1u.
The thickness is preferably 0.05 um or less, especially 0.05 um or less.

The treatment for using non-crosslinked polymer fine particles as a precursor of porous hollow particles involves making non-crosslinked polymer fine particles absorb a non-crosslinkable monomer, a crosslinkable monomer, and a pore control agent. This is carried out by copolymerizing this in the state. It is appropriate to copolymerize particles whose particle size has increased by about 8 to 100 times due to absorption. Note that it is preferable to mix the non-crosslinkable monomer and the crosslinkable monomer and add them in the form of a monomer mixture, from the viewpoint of homogeneity of the resulting particles.

The process of absorbing (infiltrating) the monomer and the pore control agent into non-crosslinked polymeric particles involves adding to an aqueous dispersion of non-crosslinking polymeric particles, particularly an aqueous dispersion as an emulsion polymerization liquid. A common method is to add a monomer mixture and a pore control agent and stir. This method has the advantage that a series of copolymerization treatments can be performed using a preparation liquid of non-crosslinked polymer fine particles. however,
The method is not limited to this (as long as an absorption state is formed as a result). Yo(,
You may use these together. Therefore, the monomer mixture and the pore-adjusting agent may exist in a mixed and integrated state in the non-crosslinked polymer fine particles, or they may not (or may not). Heating may be applied to increase the speed, or a water-soluble solvent such as acetone or ethanol may be added.Furthermore, the monomer mixture and pore control agent may be emulsified beforehand and added. In the method used, it is preferable to remove the solvent before starting polymerization.

The amount of non-crosslinkable monomer and crosslinkable monomer used is 100 to 3 parts by weight, respectively, per 100 parts by weight of non-crosslinked polymer fine particles.
000 parts by weight is suitable. The amount used is 1o each
If it is less than 1 part by weight, the resulting porous hollow particles will have insufficient solvent resistance, and if it exceeds 3,000 parts by weight, polymerization outside the non-crosslinked polymer particles will tend to proceed, which is undesirable.

The appropriate ratio of the non-crosslinking monomer to the crosslinking monomer is 10 to 90% by weight of the non-crosslinking monomer and 90 to 10% by weight of the crosslinking monomer. When the proportion of crosslinkable monomer used exceeds 90% by weight, the crosslinking density of the crosslinked polymer becomes excessive,
If it is less than 10% by weight, the crosslinking density will be too low, making it difficult to achieve the object of the present invention.

In the present invention, monomers which themselves or their polymers are poorly soluble or insoluble in water are preferably used. If it is easily dissolved in water, polymerization will proceed in water, making it difficult for the particle size of seed particles to grow, creating new particles (or forming them), or absorbing them into non-crosslinked polymer fine particles. It's undesirable because it looks like it's going to be hard.

Preferred non-crosslinking monomers include styrene monomers such as styrene, methylstyrene, and ethylstyrene, butyl acrylate, butyl methacrylate,
Examples include ester monomers of acrylic acid and methacrylic acid having an alkyl group having 4 or more carbon atoms, such as 2-ethylhexyl acrylate and 2-ethylhexyl methacrylate.

Examples of crosslinkable monomers that can be preferably used include monomers having two or more ethylenic double bonds, such as trimethylolpropane trimethacrylate, diethylene glycol dimethacrylate, and divinylbenzene.

The number of non-crosslinkable monomers and crosslinkable monomers may be one, or two or more.

Determined according to the intended use of the object.

The appropriate amount of the pore regulator used is 100 to 3000 parts by weight per 100 parts by weight of non-crosslinked polymeric particles.

If the amount used is outside the above range, the object of the present invention will not be achieved.

As the pore adjusting agent, one that can be removed as a solvent-soluble substance in the subsequent extraction process is used. - In general, those having a solubility in water of 1% by weight or less at room temperature (water-insoluble) and soluble in the non-crosslinking monomer or crosslinking monomer used are used.

If the solubility exceeds 1% by weight, it will not be absorbed into the non-crosslinked polymer fine particles and will remain in the aqueous medium, not contributing to the formation of porosity or hollow bodies, or inhibiting the stability of the reaction system. There may be cases where you do so.

Specific examples of pore control agents include saturated hydrocarbons such as hexane, heptane, and isooctane, aromatic hydrocarbons such as toluene, xylene, and ethylbenzene, and n-hexyl alcohol, n-octyl alcohol, and 2-ethylhexyl alcohol. Examples include linear polymers such as alcohols, polystyrene, and liquid paraffin. Only one type of pore adjusting agent may be used, or two or more types may be used in combination.

The copolymerization treatment of the non-crosslinked polymer fine particles that have absorbed the monomer and the pore control agent can be carried out under usual polymerization treatment conditions using an aqueous medium. As the polymerization initiator, an ordinary oil-soluble radical initiator is preferably used. If it is water-soluble, new particles may be generated, which may cause problems. Note that it is desirable to use the oil-soluble polymerization initiator dissolved in the monomer mixture in an amount of 0.1 to 5% by weight in order to smoothly carry out the polymerization in the non-crosslinked polymer fine particles.

Incidentally, during the copolymerization treatment, it is desirable to stabilize the particles using an emulsifier or a polymerization stabilizer.

It is appropriate that the amount used is such that no new particles are generated other than the precursor of the porous hollow particles.

By performing the copolymerization treatment as described above, the particle size of the seed particles consisting of non-crosslinked polymer fine particles grows with the crosslinked polymer based on the non-crosslinkable monomer and the crosslinkable monomer and the pore control agent. A precursor of porous hollow particles having such a structure, a particle size of 2 to 30 um, a standard deviation of particle size distribution of 1 or less, and generally excellent sphericity can be obtained.

In the method of the present invention, the porous hollow particle precursor obtained in the above step is then subjected to a step of extracting a solvent-soluble substance (step B). This imparts porosity as well as hollowness.

Extraction of solvent-soluble substances can be performed, for example, by the following method.

That is, water as a dispersion medium in the aqueous dispersion containing the porous hollow particle precursor obtained in step A above was gradually replaced with a less polar medium as necessary. The medium is replaced with a medium having a similar SP value (solubility parameter) to that of the non-crosslinking monomer or its polymer or the pore control agent, and washing is repeated with this medium to extract the solvent-soluble substances in the precursor.

As the substitution medium, a volatile low boiling point solvent is generally preferably used since it is desired that the medium be ultimately removed from the fine particles. Typical examples thereof include alcohols such as methanol and ethanol, ketones such as acetone, acetonitrile, chloroform, tetrahydro-7, benzene, toluene, xylene, and ethylbenzene. The displacement medium may be a hot medium with water or a hot medium using two or more types of solvents.

In some cases, it is efficient to perform the extraction process by dispersing a precursor of porous hollow particles in a replacement medium. In that case, it is also possible to apply a dispersion method using ultrasonic waves, for example.

The weight loss of the components extracted by the extraction process after the process is approximately equal to the total weight of the non-crosslinked polymer fine particles and the pore control agent used as the seed particles. We believe that the main components are non-crosslinked polymer fine particles and pore control agents.

The substitution medium remaining in the porous hollow particles after the extraction process can be easily removed by, for example, a vacuum drying method, a spray dryer, or the like.

As described above, a hollow body made of a crosslinked polymer of a non-crosslinkable monomer and a crosslinkable monomer, whose shell is porous and has a plurality of pores communicating with the hollow part, and whose particle size is is 2~30μ
11 Preferably 2 to 20 μI, coefficient of variation of particle size distribution 1
Porous hollow particles having a standard deviation of 0% or less, preferably 1 μm or less, particularly 0.5 μm or less, are obtained. Incidentally, the degree of porosity and the size of the hollow part of the porous hollow particles can be adjusted by appropriately changing the copolymerization treatment conditions such as the amount of the pore regulator used.

The porous hollow particles of the present invention have excellent solvent resistance as well as particle size uniformity, and can be applied to various uses. Suitable microcapsules for sustained-release drugs have a hollow space of 10 to 90% of the particle volume and a specific surface area of 30 to 500 J/g, particularly 50 to 500 J/g.

Effects of the Invention The porous hollow particles of the present invention have excellent uniformity in particle size, and since they are extracted products of solvent-soluble substances, they have excellent solvent resistance and a large specific surface area.

In addition, the shell is porous and has a large number of holes communicating with the hollow part.

On the other hand, according to the method of the present invention, porous hollow particles having the above-mentioned characteristics can be obtained in a high yield in a state that can be used for practical purposes without performing a classification process.

Examples Reference Examples Sodium lauryl sulfate 0.6 parts (parts by weight, the same applies hereinafter)
After dispersing 30 parts of styrene in 65 parts of ion-exchanged water, the temperature was raised to 70°C under a nitrogen stream while stirring, and then 5 parts of ion-exchanged water with 0.03 parts of potassium persulfate dissolved therein. The mixture was heated to 70° C. for 8 hours to obtain an aqueous dispersion of a non-crosslinked polymer as initial seed particles. The particle size of this non-crosslinked polymer was 0.045 mm, and the standard deviation of the particle size distribution was 0.011 mm.

Next, 10 parts of the aqueous dispersion of the obtained initial seed particles and 65 parts of ion-exchanged water were mixed and the temperature was raised to 70°C. 27 parts of styrene was added and stirred for 1 hour, followed by 0.5 parts of potassium persulfate. Add 5 parts of ion exchange water in which 1 part was dissolved and make 70
℃ for 8 hours to obtain an aqueous dispersion of secondary seed particles with a particle diameter of 0.162 mm and a standard deviation of particle size distribution of 0.014 μm. Then, according to the above procedure, 3 mL of secondary seed particles were obtained. Secondary seed particles were prepared in order from the tertiary seed particles to the 4th seed particles, from the 4th seed particles to the 5th seed particles, and from the 5th seed particles to the 6th seed particles with the compositions shown in the table.

Example The sixth seed particles obtained in the reference example were used as non-crosslinked polymer fine particles, and 10 parts of an aqueous dispersion as a preparation liquid, 100 parts of ion-exchanged water, and 10 parts by weight of polyvinyl alcohol with a degree of saponification of 88% were added. After adding 8 parts of % aqueous solution and stirring uniformly, 28% by weight of styrene and 72% by weight of divinylbenzene were added.
0.2 parts of benzoyl peroxide was dissolved in a mixture of 2.8 parts of the monomer mixture and 3.3 parts of toluene, and 120 parts of ion-exchanged water and 0.015 parts of sodium lauryl sulfate were mixed therewith and subjected to ultrasonication. An emulsified solution was added to the treated solution, and copolymerization was carried out at 80° C. under a nitrogen stream for 8 hours while stirring to obtain an aqueous dispersion containing a precursor of porous hollow particles. What is the particle size of this precursor? , the standard deviation of the 79ums particle size distribution is 0.3in.
Met.

Next, the dispersion medium in this aqueous dispersion was changed from water to methanol, ethanol, acetone, acetone/toluene (1/l
) and toluene to prepare a toluene dispersion, which was then heated at its boiling point temperature for 40 hours. Thereafter, fine particles were separated from the toluene dispersion and further washed with toluene, and then the dispersion medium was replaced in the reverse order to prepare an aqueous dispersion.

The porous hollow particles after the extraction treatment were separated from the obtained aqueous dispersion and dried under reduced pressure.

The obtained porous hollow particles have a particle size of 7.79 μm1
The standard deviation of particle size distribution is 0.31 μm, and its coefficient of variation is 3.
．． It was 98%, which was the same as in the case of the precursor described above. In addition, the weight reduction due to the extraction process is 40%.
Met. This value is almost comparable to the total amount of the solid content of the non-crosslinked polymer fine particles used as the sixth seed particles and the amount of toluene added as a pore control agent. Furthermore, B,
The specific surface area determined by the E,T method (nitrogen gas adsorption) is 11
2.5j/g, and observation of its cross section using an electron microscope revealed that it was a hollow body with a porous shell and a plurality of pores communicating with the hollow part. It also had excellent sphericity.

[Brief explanation of the drawing]

The figure shows the cross section of the porous hollow particles obtained in the example at a magnification of 7500.
This is an electron micrograph taken at magnification. Patent applicant Nitto Electric Industry Co., Ltd.

Claims (1)

[Claims] 1. A hollow body made of a crosslinked polymer of a non-crosslinkable monomer and a crosslinkable monomer, whose shell has a plurality of pores communicating with the hollow part, and whose particle size is 2. The coefficient of variation of particle size distribution is 10 at ~30 μm.
Porous hollow particles consisting of fine particles of less than %. 2. The particle according to claim 1, wherein the size of the hollow portion is 10 to 90% of the particle volume. 3. The particles according to claim 1, which are made of a polymer of water-insoluble monomers. 4. (A) Non-crosslinkable monomers, crosslinkable monomers, and pores are contained in non-crosslinked polymer fine particles obtained by growing the particle size by a seed polymerization method using a water-soluble polymerization initiator. A step of absorbing a conditioning agent and copolymerizing it in an aqueous medium to obtain a precursor of porous hollow particles; (B) Extracting a solvent-soluble substance from the precursor of porous hollow particles obtained in the above step; It is a hollow body made of a crosslinked polymer of a non-crosslinkable monomer and a crosslinkable monomer, and its shell has a plurality of pores communicating with the hollow part, and the particle size is 2 to 30 μm. A method for producing porous hollow particles comprising fine particles having a coefficient of variation in particle size distribution of 10% or less. 5. The method according to claim 4, wherein the non-crosslinkable monomer and the crosslinkable monomer are added as a monomer mixture to the aqueous medium. 6. The method according to claim 4 or 5, wherein the pore regulating agent is insoluble in water and soluble in a non-crosslinkable monomer, a crosslinkable monomer, or a monomer mixture. . 7. 100 to 3000 parts by weight of non-crosslinkable monomer, 100 parts by weight of crosslinkable monomer per 100 parts by weight of non-crosslinked polymer fine particles
5. The method of claim 4, using .about.3000 parts by weight and 100 to 3000 parts by weight of a pore control agent. 8. The method according to claim 4, wherein the non-crosslinking monomer, the crosslinking monomer, and the pore regulator are added in an emulsified state to an aqueous medium.