JP2018134632A - Microcapsule and method for producing microcapsule - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microcapsule having an ultrafine material as a core material, and a method for producing the microcapsule.SOLUTION: The present invention provides a microcapsule obtained by coating a surface of an ultrafine material with a polymer. The ultrafine material is an inorganic nitride particle, and the polymer contains at least one monomer unit selected from styrene, (meth) acrylate, vinyl acetate, polyvinyl chloride and acrylonitrile.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a microcapsule and a method for producing the microcapsule.

  Conventionally, a microcapsule in which a predetermined substance is included as a core substance is known.

  Such microcapsules have been proposed for various uses in a wide variety of fields, such as sustained release bodies of aromatic components and elastomer modifiers.

  For example, as shown in Patent Document 1 described below, microcapsules encapsulating a silicon nitride ultrafine substance as a core substance are used as a useful means for improving the problem of scorch that occurs in the production of elastomers.

International Publication No. 2016/204272

  However, the above-described conventional microcapsules still have room for improvement in terms of the stability of the core material encapsulated, the improvement of the content rate, and the yield of microcapsule preparation. There has been a demand for a microcapsule that can be encapsulated in a more stable and high content state when the fine particle substance is used as a core substance, and a preparation method for obtaining an improved yield of the microcapsule.

  This invention is made | formed in view of the said present condition, Comprising: It aims at providing the microcapsule which used the ultrafine particle substance as the core substance, and its manufacturing method.

  In order to solve the above conventional problems, in the microcapsule according to the present invention, (1) the surface of the ultrafine particle material is encapsulated with a polymer.

In addition, the microcapsule according to the present invention is also characterized by the following points.
(2) The ultrafine substance is inorganic nitride particles.
(3) The polymer contains at least one monomer unit selected from styrene, (meth) acrylic acid ester, vinyl acetate, vinyl chloride and acrylonitrile.

  In the method for producing a microcapsule according to the present invention, (4) a solvent or mixed solvent composed of at least one selected from alcohol, benzene, and toluene and containing substantially no water, an ultrafine substance, a monomer, Dispersions for preparing two types of dispersions, a dispersion liquid phase 1 containing an ultrafine substance in which a dispersing agent and a polymerization initiator are dispersed, and a dispersion liquid phase 2 in which a dispersing agent is dissolved and mixed in a solvent or a mixed solvent From the preparation step, the slurry preparation step in which the dispersion phase 1 and the dispersion phase 2 obtained in the dispersion preparation step are mixed and the monomer is dispersed and polymerized to obtain a slurry, and the slurry obtained in the slurry preparation step And a recovery step of recovering the microcapsules.

  According to the microcapsule according to the present invention, since the surface of the ultrafine substance is encapsulated with the polymer, when the ultrafine substance is used as the core substance, it can be encapsulated in a more stable state.

  In addition, according to the method for producing a microcapsule according to the present invention, a solvent or mixed solvent composed of at least one selected from alcohol, benzene, and toluene and containing substantially no water, an ultrafine substance, a monomer, Dispersion preparation for preparing two types of dispersions: a dispersion liquid phase 1 containing an ultrafine substance in which a dispersant and a polymerization initiator are dispersed, and a dispersion liquid phase 2 in which a dispersant is dissolved and mixed in a solvent or a mixed solvent. A slurry preparation step in which the dispersion phase 1 and the dispersion phase 2 obtained in the dispersion preparation step are mixed and the monomer is dispersed and polymerized to obtain a slurry, and a slurry is obtained from the slurry obtained in the slurry preparation step. Manufacturing a microcapsule that can be included in a more stable state when an ultrafine substance is used as a core substance. It is possible to provide a capability way.

It is explanatory drawing which showed the stability data of the silicon nitride particle included in the microcapsule. It is explanatory drawing which shows the examination result of the recovery rate of silicon nitride. It is explanatory drawing which shows the examination result of the particle size distribution of a microcapsule. It is explanatory drawing which shows the examination result of the silicon nitride content rate and microencapsulation rate of a microcapsule. It is explanatory drawing which shows the examination result of the residual monomer amount and the residual amount of alcohol.

  The present invention provides a microcapsule in which the surface of an ultrafine substance is encapsulated with a polymer.

  In this embodiment, the ultrafine material constituting the microcapsule is not particularly limited, but particles such as silicon nitride (Si3N4), lithium nitride, titanium nitride, aluminum nitride, boron nitride, vanadium nitride, zirconium nitride, etc. can give. Among these, silicon nitride particles are preferable from the viewpoint that nano-sized fine particles can be supplied and that they do not contain metals that are hated in the semiconductor manufacturing process. These nitride particles may be used in combination of two or more.

  The ultrafine substance preferably has a particle size of 1000 nm or less, more preferably 300 nm or less, and even more preferably 100 nm or less. The lower limit is not particularly limited but is preferably 5 nm.

  The polymer constituting the microcapsule may be a polymer produced by causing a polymerization reaction of a monomer in a solvent described later, or may be a polymer prepared in advance.

  For example, the polymer constituting the microcapsule corresponding to the former example may be a polymer of a monomer having a vinyl group and radical polymerization, such as styrene, (meth) acrylic acid ester, vinyl acetate, vinyl chloride, and the like. A polymer containing at least one monomer unit selected from the group consisting of acrylonitrile, preferably a polymer containing at least one monomer unit selected from the group consisting of styrene, (meth) acrylic acid ester and vinyl acetate It is more preferable that

  In particular, the (meth) acrylic acid ester is preferably at least one selected from the group consisting of methyl methacrylate, ethyl methacrylate, butyl methacrylate and butyl acrylate.

  The polymer constituting the microcapsule corresponding to the latter example is composed of polystyrene, styrene copolymer, polymethacrylic acid ester, methacrylic acid ester copolymer, polyvinyl acetate, polyvinyl chloride and polyacrylonitrile. It is preferably at least one selected from the group, more preferably at least one selected from the group consisting of polystyrene, polymethacrylic acid ester and polyvinyl acetate.

  The polymer produced by the monomer polymerization reaction in the solvent preferably has a number average molecular weight of about 10,000 to 1,000,000 on the surface of the ultrafine substance. The molecular weight can be measured by a method using liquid chromatography or a precipitation method.

  The microcapsule preferably contains 1 to 90% by mass of silicon nitride, for example, when the ultrafine material is silicon nitride.

  The microcapsules preferably have a particle size of 1 to 100 μm.

  In the microcapsule preparation method according to this embodiment, the microcapsule is preferably obtained by polymerizing a monomer in a dispersion liquid in which an ultrafine substance is dispersed.

  The above microcapsules can be produced by a known method (for example, a method described by Hayato Tanaka “Key Points for Nano / Microcapsule Preparation”, Techno System Publishing Co., Ltd., May 6, 2008).

  The microcapsules can be produced by dispersion polymerization. In particular, in the method for producing a microcapsule according to the present embodiment, an ultrafine substance, a monomer, and a dispersion are formed in a solvent or mixed solvent that includes at least one selected from alcohol, benzene, and toluene and does not substantially contain moisture. Dispersion Preparation Step for Preparing Two Dispersions of Dispersion Phase 1 Containing Ultrafine Particles Dispersed in Dispersing Agent and Polymerization Initiator and Dispersion Phase 2 of Dispersing Dispersant in Solvent or Mixed Solvent A slurry preparation step of mixing the dispersion phase 1 and the dispersion phase 2 obtained in the dispersion preparation step to disperse polymerize the monomers to obtain a slurry, and a microcapsule from the slurry obtained in the slurry preparation step And a recovery step for recovering.

  In particular, the dispersion liquid preparation process will be described in more detail. The dispersion liquid phase 1 is obtained by adding an ultrafine substance to a dispersion liquid 1 preparation solution obtained by dissolving and mixing a dispersant in a solvent or a mixed solvent. An adsorbent layer encapsulant in which an adsorbent layer is formed by adsorbing a dispersing agent on the surface of the adsorbent layer and the adsorption layer of the adsorbent layer encapsulant is absorbed with a monomer and a polymerization initiator to form an absorption adsorbent layer on the surface of the ultrafine material. It is prepared through an absorption adsorbing layer forming step for obtaining an absorbed layer encapsulating body.

  Then, in the slurry preparation step, by adding the dispersion liquid phase 2 to the dispersion liquid phase 1 containing the absorbent layer encapsulant obtained through the absorption adsorption layer forming step, the dispersion liquid phase 1 in the dispersion liquid phase 1 is added. The absorbent of the dispersion liquid phase 2 is adsorbed to the absorption / adsorption layer in the absorption layer encapsulant to improve the dispersion stability and further promote the growth and formation of the absorption / adsorption layer. It is effective and contributes to stable shell formation.

  The solvent used in the dispersion preparation step is preferably a solvent that does not substantially contain water. Here, a solvent that does not substantially contain water means that there is no water intentionally added in the preparation of microcapsules, and moisture originally contained in the chemical solution or moisture absorption from the atmosphere. It should be understood that the solvent having moisture and the like contained by doing so corresponds to a solvent that does not substantially contain moisture.

  The monomer used for dispersion polymerization in the microcapsule preparation method according to the present embodiment may be any monomer that has a vinyl group and undergoes radical polymerization, such as styrene, (meth) acrylic acid ester, vinyl acetate, vinyl chloride, and the like. At least one monomer selected from the group consisting of acrylonitrile is preferable, and at least one monomer selected from the group consisting of styrene, (meth) acrylic acid ester and vinyl acetate is more preferable.

  The weight ratio of the ultrafine substance to the monomer (superfine substance / monomer) is preferably 20/80 to 70/30.

  The dispersant is preferably at least one selected from the group consisting of polyvinyl pyrrolidone, saponified polyvinyl alcohol and hydroxypropyl cellulose, and more preferably polyvinyl pyrrolidone.

  The polymerization initiator is preferably at least one selected from the group consisting of azo compounds and peroxides, and more preferably azo compounds. Examples of the azo compound include 2,2′-azobis-2,4-dimethylvaleronitrile and 2,2′-azobisisobutyronitrile.

  The solvent is preferably at least one selected from the group consisting of alcohol, benzene and toluene, and more preferably at least one selected from the group consisting of alcohol. As said alcohol, C1-C5 alcohol is preferable and methanol, ethanol, or butanol is more preferable.

  In order to disperse each component in a solvent, known means such as ultrasonic waves, a homogenizer, and a vibro mixer may be used.

  The polymerization of the monomer performed in the slurry preparation step can be initiated by a polymerization initiator. The polymerization temperature is usually from 30 to 100 ° C. The polymerization time is usually 1 to 24 hours.

  When the polymerization is completed, a slurry containing the microcapsules and the solvent is generated. A method for recovering the microcapsules from the slurry in the recovery step is performed by a known centrifugation method or the like. In addition, the microcapsules are dried after collection.

  As described above, in the method of manufacturing a microcapsule according to the present embodiment, the microcapsule includes a step of dispersing a superfine substance, a monomer, a dispersant, and a polymerization initiator in the solvent to obtain a dispersion, and in the dispersion It can be manufactured by a manufacturing method including a step of obtaining a slurry by dispersion polymerization of monomers and a step of recovering microcapsules from the slurry.

  Hereinafter, specific preparation examples will be described with reference to the drawings. The following description should not be construed as limiting the present invention to such preparation examples.

[1. Preparation of microcapsules
First, weigh 6390 ± 20g of n-butanol and 250g of polyvinylpyrrolidone (hereinafter abbreviated as PVP), add it to a 15L reactor (φ240mm), and stir until the PVP is no longer visible. went.

  Of the total amount of the PVP solution thus prepared, 2 L was dispensed into a beaker to prepare a PVP solution for preparing the dispersion liquid phase 1, and the remainder was the dispersion liquid phase 2.

  Next, 2 L of the prepared PVP solution for preparing the dispersion phase 1 was added to 300 g of silicon nitride, 664 g of methyl methacrylate (hereinafter abbreviated as MMA), 105 g of azobisdimethylvaleronitrile (hereinafter abbreviated as ADVN), azobisisobutyrate. A mixed solution for dispersion phase 1 was prepared by adding 40 g of nitrile (hereinafter abbreviated as AIBN).

  Next, the mixed solution for dispersion liquid phase 1 was fed into a vibro mixer at a flow rate of 1000 ml / min, and silicon nitride was dispersed in the solution to obtain dispersion liquid phase 1 (dispersion liquid preparation step). The vibromixer was set to 25 Hz, and the solution was mixed for 60 (± 5) minutes.

  Specifically, a PVP adsorption layer is formed by adsorbing PVP on the surface of silicon nitride in the PVP solution for preparation of dispersion liquid phase 1, and MMA, ADVN and AIBN are effectively absorbed by the PVP adsorption layer on the surface of silicon nitride. The PVP adsorption layer is used as an absorption adsorption layer (absorption adsorption layer forming step).

  Next, Dispersion Phase 1 and Dispersion Phase 2 are added to a 15 L reactor, and mixing is started at a speed of 150 (± 10) rpm using a 6-blade inclined paddle (φ120 mm), taking about 1 hour. The temperature of the solution was raised to 70 (± 5) ° C., and then a dispersion polymerization reaction was performed for 15 hours (slurry preparation step).

  In particular, by adding the dispersion liquid phase 2 to the dispersion liquid phase 1, as described above, the dispersant of the dispersion liquid phase 2 is adsorbed to the absorption adsorbing layer in the absorbent layer encapsulant in the dispersion liquid phase 1. And further promoting the growth and formation of the absorption / adsorption layer, a stable dispersion polymerization reaction is performed.

  Next, the solution and the microcapsule were separated using a centrifugal sedimentator. At this time, in order to prevent aggregation of unreacted MMA, treatment was performed so that the temperature of the solution at the time of recovery did not fall below 40 ° C.

  Next, the microcapsules attached to the wall of the centrifugal sedimentator were peeled off and added to a 3 L absolute ethanol centrifuge weighed in a beaker. After leaving still for 30 minutes, the microcapsules recovered by separating the capsules with a centrifuge were washed. In addition, this washing | cleaning can be performed in multiple times (for example, twice) as needed.

  Next, the microcapsules are allowed to stand for 48 hours or more in a dryer set at 40 ° C. and dried, and the dried microcapsules are visually ground using a mortar (φ70 × 100) until the aggregates disappear. A microcapsule according to this embodiment was obtained.

  The obtained microcapsules had a configuration in which silicon nitride particles were dispersed in polymethyl metaacrylate. The particle diameter of the microcapsule measured by a laser diffraction particle size distribution analyzer was 1 to 100 μm, and the average particle diameter was 20.3 μm.

[2. (Evaluation of ammonia generation behavior)
Next, the microcapsules according to the present embodiment were tested to confirm the stability of the encapsulated ultrafine substance, that is, silicon nitride particles.

Specifically, the above-mentioned [1. According to the preparation shown in Table 1 below, Preparation Samples 1 to 5 as microcapsules according to this embodiment were prepared according to the formulation shown in Table 1 below, and the stability of these samples was confirmed. Moreover, silicon nitride particles that were not microencapsulated were used as comparative samples.

  In addition, in the stability test, 50 mg of each sample was taken, immersed in 100 ml of 0.0001N hydrochloric acid aqueous solution for 1 hour, and ΔpH changed by ammonia generated when water contained in the hydrochloric acid aqueous solution reacted with silicon nitride was confirmed. I went there. The result is shown in FIG.

  As can be seen from FIG. 1, the non-microencapsulated silicon nitride particles as a comparative sample had a high ΔpH of about 5.8, while the working samples 1 to 5 that are microcapsules according to this embodiment were ΔpH was less than 1.

  This is because the silicon nitride particles contained in the working samples 1 to 5 are firmly protected by the structure of the microcapsule according to the present embodiment and the generation of ammonia is prevented, and is contained in a very stable state. It was shown that.

[3. Evaluation of silicon nitride recovery rate
Next, the ratio of the silicon nitride added as a raw material to be accommodated in the microcapsules, that is, the silicon nitride recovery rate was examined. The test was performed 6 times under different conditions (Run 1 to Run 6). The examination result is shown in FIG.

  As can be seen from FIG. 2, it was confirmed that all of them had a relatively good recovery rate. In particular, in Run5 and Run6, the yield exceeded 50%, and it was confirmed that the yield was extremely good. Moreover, it was shown that even if the solvent was changed from ethanol to n-butanol, the recovery rate of the silicon nitride contained was not affected.

  In particular, the microcapsule preparation method according to the present embodiment is a method suitable for mass production as compared with the conventional microcapsule production method, and therefore this excellent recovery rate greatly contributes to the microcapsule production business. It is thought to bring about a contribution.

[4. Study on particle size distribution of microcapsules]
Next, the particle size distribution of the microcapsules was examined for Run 4 to Run 6 shown in FIG. The result is shown in FIG.

  As can be seen from FIG. 3, even when the polymerization time was extended from 8 hours (Run 4) to 15 hours (Run 5 and Run 6), no significant difference was observed in the particle size distribution.

[5. Study of microencapsulation rate
Next, with respect to Run 4 to Run 6 shown in FIG. 2, the silicon nitride content and microencapsulation rate of the microcapsules were examined. The result is shown in FIG.

  As can be seen from FIG. 4, even when the polymerization time was extended from 8 hours (Run 4) to 15 hours (Run 5 and Run 6), no significant difference was observed in the Si 3 N 4 content and the encapsulation rate.

[6. Examination of residual monomer amount and alcohol residual amount)
Next, with respect to Run4 shown in FIG. 2, the remaining monomer amount and the remaining alcohol amount were examined for Run5 and Run6. The result is shown in FIG.

  As shown in FIG. 5, a double bond (C = O) of carbon and oxygen existing in both methyl methacrylate (MMA) in a monomer state and polymethyl methacrylate formed by polymerization of the same monomer. ) And a second peak derived from a carbon double bond (C = C) peculiar to methyl methacrylate in the monomer state were observed in any of Run 4 to Run 6.

  Here, with regard to these first and second peaks, focusing on Run5 and Run6 with reference to Run4, the area ratio of the second peak to the first peak is that of both Run5 and Run6 compared to Run4. It was shown that it was reduced to about 1/2.

  That is, it was shown that the unreacted residual monomer decreased by increasing the polymerization time (about twice) as compared with the Run4 preparation method.

  As for the third peak derived from the hydroxy group of the alcohol, focusing on Run6 based on Run4, in Run6, although n-butanol was used as a solvent, a significant difference was confirmed compared to Run4. There wasn't. From this, it was shown that there was no significant difference in the residual amount of solvent even when the solvent was changed to n-butanol.

  Finally, the description of each embodiment described above is an example of the present invention, and the present invention is not limited to the above-described embodiment. For this reason, it is a matter of course that various modifications can be made in accordance with the design and the like as long as they do not depart from the technical idea according to the present invention other than the embodiments described above.

Claims (4)

  A microcapsule in which the surface of an ultrafine substance is encapsulated with a polymer.   The microcapsule according to claim 1, wherein the ultrafine substance is inorganic nitride particles.   The microcapsule according to claim 1 or 2, wherein the polymer contains at least one monomer unit selected from styrene, (meth) acrylic acid ester, vinyl acetate, vinyl chloride, and acrylonitrile. . An ultrafine substance in which an ultrafine substance, a monomer, a dispersant, and a polymerization initiator are dispersed in a solvent or mixed solvent consisting essentially of at least one selected from alcohol, benzene, and toluene. A dispersion liquid preparation step of preparing two kinds of dispersion liquid: a dispersion liquid phase 1 and a dispersion liquid phase 2 in which a dispersant is dissolved and mixed in a solvent or a mixed solvent;
A slurry preparation step of mixing the dispersion phase 1 and the dispersion phase 2 obtained in the dispersion preparation step to disperse polymerize the monomer to obtain a slurry;
A recovery step of recovering the microcapsules from the slurry obtained in the slurry preparation step.