JP2007191614A - Method for producing hollow resin particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing hollow resin particles, which produces hollow resin particles having low specific gravity without a process for drying hollow resin particles having difficulty in handling. <P>SOLUTION: The method for producing hollow resin particles comprises continuously feeding thermally expandable microcapsules from a supply port of one end upper part to an indirect heating type stirring dryer (B) that has a constitution that a stirring blade (A) for renewing the surface of powder is installed in the inside of a casing having a jacket (C) and on a shaft in parallel with the casing and horizontally and a heating medium is introduced to at least one selected from the group consisting of the jacket (C), the stirring blade (A) and the shaft and has the heat transfer area/effective volume of ≥10 m<SP>-1</SP>and continuously discharging hollow resin particles from the discharge port of the other end lower part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a method for producing a hollow resin particle by thermally expanding a thermally expandable microcapsule.

Thermally expandable microcapsules are particles that expand to a volume several tens of times when heated. As a method of expanding the heat-expandable microcapsules by heating, a method of heating with high-temperature steam (hereinafter referred to as a wet method) is the mainstream. The wet method has an advantage that the specific gravity of the obtained hollow resin particles becomes uniform because the temperature applied to the microcapsules is extremely uniform. Also, if the product temperature of the microcapsules can be quickly raised to the expansion temperature, the hydrocarbon encapsulated as the expansion agent will not be unnecessarily released and the expansion ratio will be improved. Since the product temperature quickly reaches the expansion temperature, a high expansion ratio can be obtained. (For example, see Patent Document 1 and Patent Document 2)
JP-A-2005-82718 JP-A-2005-254213

While the wet method has the advantages as described above, the hollow resin particles to be obtained contain a large amount of moisture, and when dry hollow resin particles are required, the hollow resin particles having a very low specific gravity must be dried. There is a disadvantage of having to. In normal applications, dry hollow resin particles are often required, and this drying step is a major cause of high cost. There are also problems such as contamination of the work environment due to dust and high moisture content in terms of quality, making it difficult to use for resins that react with water or that use water as a catalyst.
On the other hand, JP-A-4-9319 exemplifies a dry expansion method using a continuous Ladige mixer, but the Ladige mixer is not only high in heating efficiency but also has a low expansion ratio. Since the controllability is poor, it is necessary to add inorganic fine particles to prevent coalescence of the thermally expandable microcapsules. Therefore, hollow resin particles having a small specific gravity could not be obtained by this method.
That is, an object of the present invention is to provide a method for producing hollow resin particles that does not have a step of drying hollow resin particles that are difficult to handle and that can obtain hollow resin particles having a small specific gravity.

A feature of the method for producing hollow resin particles of the present invention is that a stirring blade (A) capable of renewing the surface of a powder inside a casing having a jacket (C) is disposed parallel and horizontally to the casing. The heat transfer area / effective volume capable of introducing a heat medium into at least one selected from the group consisting of a jacket (C), a stirring blade (A) and a shaft is 10 m ⁻¹ or more. The point is that the thermally expandable microcapsules are continuously supplied to the indirectly heated agitating dryer (B) from the supply port at the top of one end, and the hollow resin particles are continuously discharged from the discharge port at the bottom of the other end. To do.

  According to the heating and expanding method of the present invention, since it is a dry heating and expanding method, there is no step of drying the hollow resin particles obtained as in the wet method. Problems such as contamination do not occur. In addition, the resulting hollow resin particles have a low water content, and can be used without any problem for resins that react with water or use water as a catalyst. Furthermore, it is possible to obtain hollow resin particles having the same expansibility as the wet method and having a small specific gravity as in the wet method.

  In the present invention, the jacket (C) of the indirectly heated agitating / drying machine (B) means a metallic cover having a cavity inside and capable of introducing a heat medium or refrigerant made of gas or liquid. . It is located outside the casing and has a function of heating or cooling the casing by introducing a heat medium or a refrigerant.

In the present invention, the casing means a body portion of an apparatus in which a stirring blade, a jacket, a supply port, a discharge port, and the like are installed.
The stirring blade is disposed inside the casing, and the jacket is installed outside. The casing and the jacket may be manufactured as a single unit.
The supply port is installed at one upper end of the casing, and the discharge port is installed at one lower end of the casing. The thermally expandable microcapsules supplied from the supply port are heat-treated in the casing and discharged from the discharge port. That is, the inside of the casing serves as a processing chamber for thermally expandable microcapsules.
As the material of the casing, any material having high thermal conductivity and durability can be used, but SUS304, SUS316, and SUS316L are preferable.

As the stirring blade (A) capable of renewing the surface of the powder, those having various shapes can be used, and examples thereof include a circular shape, a triangular shape, a fan shape, a rectangular shape, and a cylindrical shape.
The stirring blade (A) is installed on a shaft that is arranged parallel and horizontally to the casing from the viewpoint of improving the heat transfer area and ease of maintenance. By providing the shaft and installing the stirring blade (A) on the shaft, a large space in the center of the casing is filled with the shaft and the stirring blade (A), and the effective volume is reduced. If the heat medium is also introduced into the shaft and the stirring blade (A), the heat transfer area is also greatly improved.

  Here, the surface of the powder can be renewed means that the powder can be moved, and the moving direction can be either the supply port side or the discharge port side, or the upper or lower side. . By this surface update, the heat-expandable microcapsules are brought into contact with a portion where the heat medium such as the inner wall of the casing and the stirring blade is introduced and heat treated, and the heat medium is introduced into the hollow resin particles obtained after the heat treatment is completed Separate from site. When the movement of the powder by renewal of the surface is other than the direction of the discharge port, the powder is moved to the discharge port side by gravity flow by tilting the piston flow by the raw material supply or the angle of the device itself to the discharge port side. be able to.

  In the present invention, the heat medium is a medium for heating the apparatus, and steam, heat-resistant oil or the like is used. The temperature of the heat medium to be introduced is preferably 5 to 50 ° C., more preferably 10 to 40 ° C. higher than the softening temperature of the thermoplastic polymer described later. Specifically, the temperature is preferably 120 to 200 ° C, more preferably 130 to 180 ° C. Within this range, the expansion ratio is further improved.

In the present invention, the heat transfer area is the total area of the portion where heat can be applied to the powder, which is the portion where the powder in the casing can come into contact, and can be heated by a heat medium. It means the area of the part. Therefore, for example, when a heat medium can be introduced into the jacket and the stirring blade, the surface area of the jacket and the stirring blade inside the casing that can be contacted with the powder becomes the heat transfer area. Further, when a heat medium can be introduced into any of the jacket, the stirring blade, and the shaft, the surface area of the jacket, the stirring blade, and the shaft inside the casing that can be contacted with the powder becomes the heat transfer area.
In the indirect heating type agitation dryer (B), the part into which the heat medium is introduced is at least one selected from the group consisting of a jacket, a stirring blade and a shaft, but it is preferably introduced into all of the jacket, the stirring blade and the shaft.

The effective volume means an effective volume inside the casing, which is obtained by subtracting a volume such as a stirring blade or a shaft from the total volume inside the casing. Therefore, even if the casing is large, the effective volume is small when the volume occupied by the stirring blades is large. When the effective volume is small, that is, when a large space in the center of the casing is filled with the shaft and the stirring blade (A), the diffusion distance of the thermally expandable microcapsules becomes small. Therefore, the frequency with which the heat-expandable microcapsules come into contact with the heat transfer surface by stirring increases, and the expansion ratio becomes good.
The heat transfer area / effective volume is an index of heat transfer efficiency, and its unit is m ⁻¹ . The larger this value, the better the heat transfer efficiency, and the temperature of the powder can be raised rapidly. In order to ensure high expandability by rapidly raising the temperature of the thermally expandable microcapsule to the expansion temperature, the heat transfer area / effective volume (m ⁻¹ ) needs to be 10 or more, It is preferably 15 to 100, more preferably 20 to 100, and particularly preferably 30 to 100. When the heat transfer area / effective volume (m ⁻¹ ) is less than 10, the temperature rise of the thermally expandable microcapsule becomes extremely gradual, and a large amount of expander (low boiling point) is reached before reaching the softening temperature of the thermoplastic polymer shell. Solvent etc.) diffuses, and the expansion ratio is greatly reduced. On the other hand, from the viewpoint of improving the expandability, it is preferable that the heat transfer area / effective volume (m ⁻¹ ) is large, but there is no commercially available indirect heating type agitation dryer (or improved model) exceeding about 100. This is because the design of the apparatus is impossible or extremely difficult, and the upper limit of the heat transfer area / effective volume (m ⁻¹ ) is naturally about 100.

The time from the supply of the heat-expandable microcapsules to the discharge of the hollow resin particles can be arbitrarily controlled, and is adjusted according to the heat medium temperature, the softening temperature of the thermoplastic polymer, and the like. From the viewpoint of expandability, productivity, etc., it is preferably 0.5 to 15 minutes, more preferably 0.6 to 12 minutes, and particularly preferably 0.8 to 10 minutes.
The time from the supply of the heat-expandable microcapsules to the discharge of the hollow resin particles is mainly determined by the rotation speed of the stirring blade (A) and the supply speed of the heat-expandable microcapsules. The rotational speed varies depending on the capacity of the apparatus, but in the case of an apparatus having an effective volume of 5 to 100 m ³ , 20 to 80 rpm is appropriate, and preferably 30 to 50 rpm. The supply rate of the heat-expandable microcapsules varies depending on the capacity of the apparatus, but in the case of an apparatus having an effective volume of 5 to 100 m ³ , 5 to 50 kg / hour is appropriate, and preferably 10 to 40 kg / hour.

As an indirect heating type agitation dryer, it can be used as long as the above conditions are satisfied, and even an existing dryer can be used as long as it satisfies the above conditions.
Here, the indirect heating type is a method in which the powder is heated when it comes into contact with a portion where a heating medium such as a jacket, a stirring blade and a shaft is introduced, and the powder is heated directly by a flame, steam, or the like. Differentiated from direct heating type.
Examples of indirect heating type stirrers include paddle dryers (manufactured by Nara Machinery Co., Ltd.), continuous kneaders, CD dryers (manufactured by Kurimoto Iron Works), inner tube rotary (manufactured by Okawara Seisakusho Co., Ltd.), rotary kilns (Kurimoto Iron Works) , Manufactured by Takasago), solid air, thermoprocessor (manufactured by Hosokawa Micron), and the like.
Of these, from the viewpoints of expandability, productivity, etc., paddle dryers (manufactured by Nara Machinery Co., Ltd.), continuous kneaders, CD dryers (manufactured by Kurimoto Iron Works), inner tube rotary (manufactured by Okawara Seisakusho), solid air A thermoprocessor (manufactured by Hosokawa Micron Corporation) is preferable, more preferably a paddle dryer (manufactured by Nara Machinery Co., Ltd.), a continuous kneader, a CD dryer (manufactured by Kurimoto Iron Works Co., Ltd.), particularly preferably a paddle dryer (manufactured by Nara Machinery Co., Ltd.), CD dryer (manufactured by Kurimoto Iron Works).
As a method of continuously supplying the thermally expandable microcapsules from the supply port at the upper end, a method of supplying using a quantitative feeder is appropriate from the viewpoint of stabilizing the quality. As the quantitative feeder, an accurate feeder (Mu Seiki Co., Ltd.), a heaton feeder (Lasa Industrial Co., Ltd.) or the like can be used.

  In the present invention, the heat-expandable microcapsule is a particle whose volume expands several times to several tens of times when heated, and a low-boiling solvent or sublimable solid is an expansion agent in a polymer shell made of a thermoplastic polymer. Is included.

As the thermoplastic polymer constituting the polymer shell, any polymer that softens when heated can be used, and examples thereof include polyurethane, polyamide, polyester, polyether, and vinyl polymer. Moreover, even if it is a polymer generally called thermosetting, such as an epoxy resin and a silicone resin, any polymer that is softened by heating can be used.
The softening temperature of the thermoplastic polymer constituting the polymer shell can be arbitrarily controlled depending on the purpose for which the heat-expandable microcapsules are used. In general, the temperature is preferably 100 to 180 ° C, more preferably 110 to 170. ° C, particularly preferably 120 to 160 ° C. The softening temperature is measured in accordance with JISK5601-2-2: 1999 5.1 powder method (measurement sample is heated at 50 ° C. and 0.1 to 3 torr for 90 minutes).
Of these, polymers having high gas barrier properties are preferable from the viewpoint of expansibility, specifically, polyamides and vinyl polymers are preferable, and vinyl polymers are particularly preferable.

Here, the vinyl polymer is a polymer having a vinyl monomer as a structural unit, and preferably having a cyano group-containing vinyl monomer as a structural unit. As a vinyl monomer, in addition to a cyano group-containing vinyl monomer, (meth) acrylate, a carboxyl group-containing vinyl monomer, an aromatic vinyl hydrocarbon having 8 to 12 carbon atoms, an aliphatic vinyl hydrocarbon having 2 to 18 carbon atoms, a carbon number 5-15 alicyclic vinyl hydrocarbons, (meth) acrylamides having 3-22 carbon atoms, vinyl sulfonic acids having 2-10 carbon atoms, vinyl ethers having 3-10 carbon atoms, vinyl ketones having 4-11 carbon atoms, crosslinkability Monomers and the like can be used.
Among these, from the viewpoint of expansion property and expansion temperature control, in addition to the cyano group-containing vinyl monomer, (meth) acrylate, carboxyl group-containing vinyl monomer, aromatic vinyl hydrocarbon, (meth) acrylamide may be used in combination. More preferably, it is a combined use of (meth) acrylate and a carboxyl group-containing vinyl monomer.

As the cyano group-containing vinyl monomer, any vinyl polymer having a cyano group can be used without limitation. (Meth) acrylonitrile, α-chloro (meth) acrylonitrile, α-ethoxy (meth) acrylonitrile, fumaronitrile, maleoylnitrile, cyano Examples thereof include styrene and a mixture thereof. Among these, from the viewpoint of gas barrier properties, (meth) acrylonitrile, α-chloro (meth) acrylonitrile and α-ethoxy (meth) acrylonitrile are preferable, (meth) acrylonitrile is more preferable, and acrylonitrile is particularly preferable.
In addition, in this specification, (meth) acryl ... means acryl ... and methacryl ...

As the (meth) acrylate, an alkyl (meth) acrylate having 4 to 24 carbon atoms can be used, and methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (Meth) acrylate, dodecyl (meth) acrylate, isobornyl (meth) acrylate and the like can be mentioned.

As (meth) acrylate, in addition to alkyl (meth) acrylate, (meth) acrylate having various functional groups can be used. For example, hydroxyalkyl (meth) acrylate (C2-C20 of alkyl group: 2-hydroxyethyl (meth) acrylate (HEMA), hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, etc. The same)), aminoalkyl (meth) acrylate (aminoethyl (meth) acrylate, aminoisopropyl (meth) acrylate, aminobutyl (meth) acrylate, aminohexyl (meth) acrylate, etc.), isocyanatoalkyl (meth) acrylate (isocyanate) Natoethyl (meth) acrylate, isocyanatopropyl (meth) acrylate, isocyanatobutyl (meth) acrylate and isocyanatohexyl (meth) acrylate), glycidyl methacrylate (GMA), polyethylene glycol (weight average molecular weight 100 to 10000) mono (meth) acrylate, polyethylene / polypropylene glycol (weight average molecular weight 200 to 10000, oxyethylene content 10 to 90% by weight) mono (meth) acrylate and polypropylene Examples include glycol (weight average molecular weight 100 to 10,000) mono (meth) acrylate.
Of these, (meth) acrylates having 4 to 15 carbon atoms are preferable from the viewpoint of improving expansibility, and more preferable are methyl methacrylate, isobornyl methacrylate, and 2-hydroxyethyl methacrylate, and particularly preferable is methyl methacrylate. It is.

As the carboxy group-containing vinyl monomer, a vinyl carboxylic acid having 3 to 20 carbon atoms or the like is used. (Meth) acrylic acid, (anhydrous) maleic acid, maleic acid monoalkyl ester (alkyl having 1 to 20 carbon atoms: maleic acid) Monoethyl ester, maleic acid monobutyl ester, maleic acid monohexyl ester, etc. (the same applies to alkyl), fumaric acid, fumaric acid monoalkyl ester, crotonic acid, itaconic acid, itaconic acid monoalkyl ester, itaconic acid glycol mono Ethers (2-20 carbon atoms of glycol: ethylene glycol, propylene glycol, hexene glycol, etc.), citraconic acid, citraconic acid monoalkyl ester and cinnamic acid, etc., and alkali metal (sodium and potassium) salts, alkaline earth Metal (calcium and magnesium) salts, amines (C3-20: trimethylamine, triethylamine, butyl dimethylamine and triethanolamine) salts and ammonium salts.
Among these, from the viewpoints of expandability and heat resistance (improvement of expansion start temperature, expansibility at high temperature, etc., the same applies hereinafter) and the like, vinyl carboxylic acids having 3 to 10 carbon atoms are preferable, and ( (Meth) acrylic acid, (anhydrous) maleic acid and maleic acid monoalkyl ester, particularly preferably (meth) acrylic acid.

Examples of the aromatic vinyl hydrocarbon having 8 to 12 carbon atoms include styrene, α-methyl styrene, vinyl toluene, 2,4-dimethyl styrene, ethyl styrene, isopropyl styrene, butyl styrene, phenyl styrene, cyclohexyl styrene, benzyl styrene, Examples include tilbenzene, hydroxystyrene, vinyl naphthalene, vinyl pyridine, chlorostyrene, aminostyrene, and dichlorostyrene.
Examples of the aliphatic vinyl hydrocarbon having 2 to 18 carbon atoms (D2) include ethylene, propylene, butene, isobutylene, pentene, heptene, octene, dodecene, octadecene 1-buten-3-ol and 2-buten-1-ol. Is mentioned.
Examples of the alicyclic vinyl hydrocarbon having 5 to 15 carbon atoms include vinylcyclohexane, cyclohexene, pinene, limonene and indene.

  Examples of the (meth) acrylamide having 3 to 22 carbon atoms include (meth) acrylamide, N-alkyl (meth) acrylamide (N-methyl (meth) acrylamide, N-butyl (meth) acrylamide, N-benzyl (meth) acrylamide and the like. ), N, N-dialkyl (meth) acrylamide (N, N-dimethyl (meth) acrylamide and N, N-dipropyl (meth) acrylamide), N-hydroxyalkyl (meth) acrylamide (N-hydroxymethyl (meth)) In addition to acrylamide and N-hydroxyethyl (meth) acrylamide), and aminoalkyl (meth) acrylamide (dimethylaminoethyl (meth) acrylamide, diethylaminoethyl (meth) acrylamide, etc.), N-vinyl lactam (N − Nirupiroridon, etc.) and the like can also be used.

  Examples of the vinyl sulfonic acid having 2 to 10 carbon atoms include vinyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, α-methylstyrene sulfonic acid, (meth) acryloxypropyl sulfonic acid, (meth) acryloxyethane sulfonic acid, 3 -(Meth) acryloyloxy-2-hydroxypropanesulfonic acid and propylallylsulfosuccinic acid, and alkali metal (sodium and potassium) salts, alkaline earth metal (calcium and magnesium) salts, amine salts, ammonium salts, etc. Is mentioned.

  Examples of the vinyl ether having 3 to 10 carbon atoms include vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, vinyl butyl ether, vinyl 2-ethylhexyl ether, vinyl phenyl ether, vinyl 2-methoxyethyl ether, vinyl 2-butoxyethyl ether, 2 -Butoxy-2'-vinyloxydiethyl ether, vinyl 2-ethylmercaptoethyl ether, etc. are mentioned.

  Examples of the vinyl ketone having 4 to 11 carbon atoms include vinyl methyl ketone, vinyl ethyl ketone, vinyl phenyl ketone, and vinyl 2-ethylhexyl ketone.

As the crosslinkable monomer, a monomer having at least two vinyl groups can be used, and a diene having 4 to 10 carbon atoms, bis (meth) acrylamide having 8 to 12 carbon atoms, poly (2 to 10 carbon atoms) poly ( A (meth) acrylate, a C6-C9 polyallylamine, a C6-C17 polyallyl ether, a C9-C14 diallyl ester, etc. can be used.
Examples of the diene include butadiene, pentadiene, hexadiene, cyclopentadiene, ethylidene norbornene, divinylbenzene, divinyltoluene, divinylxylene, and diallylcarbinol.
Examples of bis (meth) acrylamide include N, N′-methylenebis (meth) acrylamide, N, N′-ethylenebis (meth) acrylamide, and N, N′-propylenebis (meth) acrylamide.
Poly (meth) acrylates of polyols include polyol di (meth) acrylate {ethylene glycol di (meth) acrylate, poly (degree of polymerization 2-5) ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate and glycerin. Di (meth) acrylate, etc.} and polyol tri or tetra (meth) acrylate {glycerin tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, diglycerin tetra (meth) acrylate, etc.} and the like.
Examples of polyallylamine include diallylamine and triallylamine.
Examples of the polyvinyl ether include divinyl ether, diallyl ether {diallyl ether, diallyloxymethane, diaryloxyethane, pentaerythritol diallyl ether, etc.} and tri- or tetra-allyl ether {tetraallyloxyethane, pentaerythritol triallyl ether. And pentaerythritol tetraallyl ether, etc.}.
Examples of diallyl esters include diallyl phthalate, diallyl malonate, diallyl succinate, and diallyl adipate.

When the structural unit is a cyano group-containing vinyl monomer and at least one vinyl monomer selected from the group consisting of other vinyl monomers, the content (mol%) of the cyano group-containing vinyl monomer unit is the structural unit. Based on the total number of moles of the vinyl monomer, 50 to 99.5 is preferable, more preferably 60 to 96, and particularly preferably 70 to 93. Within this range, the gas barrier properties can be sufficiently exerted and the expansibility can be further improved.
The content (mol%) of at least one vinyl monomer unit selected from the group consisting of vinyl monomers other than cyano group-containing vinyl monomers is 0.5 to 50 based on the total number of moles of vinyl monomers as constituent units. Is more preferable, 4 to 40 is more preferable, and 7 to 30 is particularly preferable. Within this range, the expansibility and heat resistance are further improved.
When (meth) acrylate or a carboxyl group-containing vinyl monomer is included as a structural unit, the content (mol%) is preferably 0.5 to 50, more preferably based on the total number of moles of vinyl monomer as a structural unit. Is from 2 to 30, particularly preferably from 5 to 20.
When the crosslinkable vinyl monomer is included as a constituent unit, the content (mol%) is preferably 0.01 to 10, more preferably 0.05 to 5, based on the total number of moles of the vinyl monomer as the constituent unit. Especially preferably, it is 0.09-1. Within this range, the expansibility and heat resistance are further improved.

  The weight average molecular weight (Mw) of the thermoplastic polymer (A) is preferably from 5,000 to 1,000,000, more preferably from 10,000 to 500,000, particularly preferably from 20,000 to 300,000. Mw is measured by gel permeation chromatography using polystyrene as a standard substance.

The volatile liquid and / or sublimable solid (SL) is not particularly limited as long as it does not dissolve the constituent components of the polymer shell (PS), and known ones can be used, including hydrocarbons, halogenated hydrocarbons, Alcohols, ethers, ketones and sublimable compounds are included.
Examples of the hydrocarbon include hydrocarbons having 3 to 15 carbon atoms, such as propane, butane, pentane, n-hexane, isohexane, heptane, benzene, toluene, xylene, cyclohexane, cyclopentane, and methylcyclohexane.
Examples of the halogenated hydrocarbon include halides having 1 to 4 carbon atoms such as ethyl chloride, methyl chloride, methyl bromide, chloroform, dichlorobutane, and trichloroethane.
As alcohol, C1-C20 alcohol etc. are used, and methanol, ethanol, butanol, cyclohexanol, t-butanol, etc. are mentioned.
As ether, C2-C15 ether etc. are used, and dimethyl ether, diethyl ether, dibutyl ether, diethylene glycol, dioxane, tetrahydrofuran, etc. are mentioned.
As a ketone, a C3-C13 ketone etc. are used, and acetone, methyl isobutyl ketone, methyl ethyl ketone, benzophenone, dicyclohexyl ketone, etc. are mentioned.
Sublimable compounds include azo compounds (azoisobutyronitrile (AIBN), azodicarbonamide (ADCA), barium azodicarboxylate, 1,1'-azobis-1-cyclohexanenitrile, diazoaminobenzene, etc.), sulfo Hydrazide compounds (diphenylsulfone-3,3′-disulfohydrazide, 4,4′-hydroxy-bis- (benzenesulfohydrazide), trihydrazinotriazine, aryl-bis- (sulfohydrazide), p-toluenesulfonylhydrazide, 4,4′-oxybenzenesulfonylhydrazide, etc.), nitroso compounds (N, N′-dinitrosopentamethylenetetramine, N, N-dimethyl-N, N′-dinitrosophthalamide, etc.), semicarbazide (p-tolylene) Sulfonyl semicarbazide, 4,4 ' Hydroxy-bis- (benzenesulfonyl semicarbazide), etc.), triazole (5-morpholyl-1,2,3,4-thiatriazole, etc.), sodium bicarbonate (bicarbonate), ammonium bicarbonate, ammonium carbonate, potassium hydrogen tartrate, fumarate Examples include sodium acid.

Of these, hydrocarbons and azo compounds are preferred from the viewpoint of expansibility, etc., more preferably hydrocarbons, and particularly preferably pentane, n-hexane, cyclohexane and isohexane.
The content (% by weight) of the volatile liquid and / or sublimable solid (SL) is preferably 1 to 50, more preferably 5 to 20, particularly preferably 10 to 10% based on the weight of the polymer shell (PS). 15.

The thermally expandable microcapsule of the present invention preferably contains 1 to 50% by weight (SL) based on the weight of the thermally expandable microcapsule in the polymer shell (PS), more preferably 2 to 40%. % By weight, particularly preferably 3 to 20% by weight.
Within this range, thermally expandable microcapsules with good expandability can be obtained.

The thermally expandable microcapsule of the present invention can be produced by a known method. For example, acrylonitrile, methacrylic acid, (meth) acrylate and optionally other monomers, a volatile liquid (SL), and a polymerization initiator are used. The mixture can be produced by suspension polymerization in an aqueous medium containing a surfactant and / or a dispersion stabilizer (Japanese Patent Publication No. 42-26524).
The polymerization temperature (° C.) is preferably 40 to 120, more preferably 45 to 90, and particularly preferably 50 to 80. The polymerization may be performed under atmospheric pressure, but is preferably performed under pressure (atmospheric pressure +0.1 to 1 MPa) so as not to make the volatile liquid or the like (SL) gaseous.
The suspension polymerization is preferably performed in a sealed state using a pressure vessel. Moreover, after suspending with a disperser etc., it may transfer to a pressure-resistant container and suspension polymerization may be carried out, and you may make it suspend in a pressure-resistant container.
After completion of the polymerization, solid-liquid separation and / or washing may be performed by a known method (such as centrifugation or filtration). On the other hand, the product can be produced in a state dispersed in water or in a solvent or the like without performing solid-liquid separation.
In the case of solid-liquid separation and / or washing, it may be dried and / or pulverized below the softening temperature of the polymer shell (PS). Drying and pulverization can be performed by a known method, and an air flow dryer, a normal air dryer, a Nauter mixer (manufactured by Hosokawa Micron), or the like can be used. Further, drying and pulverization can be simultaneously performed by a pulverization dryer or the like.

Although it does not specifically limit as a polymerization initiator, The oil-soluble initiator soluble in a monomer is preferable and a well-known peroxide initiator, an azo initiator, etc. can be used. Of these, azo initiators are preferred, and 2,2′-azobisisobutyronitrile, 1,1′-azobiscyclohexane 1-carbonitrile, and 2,2′-azobis-4-methoxy-2 are more preferred. , 4-dimethylvaleronitrile and 2,2′-azobis-2,4-dimethylvaleronitrile, particularly preferably 2,2′-azobisisobutyronitrile.
When a polymerization initiator is used, the amount used (% by weight) is preferably 0.01 to 5, more preferably 0.05 to 2, particularly preferably 0, based on the total weight of the vinyl monomer as a constituent unit. .1-1.

Examples of the surfactant include anionic surfactants (sodium lauryl sulfate, (poly) oxyethylene (degree of polymerization 1 to 100) sodium lauryl sulfate and (poly) oxyethylene (degree of polymerization 1 to 100) lauryl sulfate triethanolamine, etc. ), Cationic surfactants (stearyltrimethylammonium chloride, diethylaminoethylamide stearate lactate, dilaurylamine hydrochloride and oleylamine lactate, etc.), nonionic surfactants (diethanolamine adipic acid condensate, lauryldimethylamine oxide, Glyceryl monostearate, sorbitan monolaurate and diethylaminoethylamide lactate stearate) and amphoteric surfactants (coconut oil fatty acid amidopropyldimethylaminoacetic acid betaine, lauryl hydroxysulfobe Included in and β- laurylamino sodium propionate, etc.), in addition to these surfactants, it is possible to use a polymer type dispersant (polyvinyl alcohol, starch and carboxymethyl cellulose).
Of these, cationic, nonionic and amphoteric surfactants and their combined use with polymeric dispersants are preferred, and more preferred are nonionic active agents and nonionic active agents with polymeric dispersants. Particularly preferred are nonionic active agents.
When a surfactant is used, the amount used (% by weight) is preferably 0.01 to 10, more preferably 0.05 to 5, based on the total weight of the monomer and the volatile liquid (SL). Most preferably, it is 0.1-2.

As the dispersion stabilizer, silica (such as colloidal silica), calcium carbonate, calcium phosphate, aluminum hydroxide, barium carbonate, magnesium hydroxide, or the like is used, and two or more kinds can be used in combination.
Of these, colloidal silica is preferable from the viewpoint of dispersion stability.
When a dispersion stabilizer is used, the amount used (% by weight) is preferably 0.01 to 30, more preferably 0.1 to 20, based on the total weight of the monomer and the volatile liquid (SL). Especially preferably, it is 0.5-10.

The volume average particle size (μm) of the thermally expanded microcapsule is preferably 0.1 to 100, more preferably 0.5 to 60, and particularly preferably 1 to 30.
In addition, when used for lightening materials, such as resin, 10-100 micrometers is preferable, More preferably, it is 20-60 micrometers. Moreover, when using for the coating materials for motor vehicles etc., 0.5-60 micrometers is preferable, More preferably, it is 1-20 micrometers. The volume average particle size is measured by a laser diffraction type particle size distribution measuring apparatus having a measurement principle {light scattering method (25 ° C.)} described in JIS Z8825-1: 2001 {for example, LA-920 manufactured by Horiba, Shimadzu Manufactured by SALD-1100, etc.).
The volume average particle diameter can be controlled by a known method. The type and amount of the surfactant (decreases as the amount increases), the type and amount of the dispersion stabilizer (decreases as the amount increases), the dispersion condition (conditions It can be arbitrarily controlled by, for example, decreasing when tightened).
The shape of the thermally expandable microcapsule may be a needle shape or a flat shape, but is preferably spherical from the viewpoint of expandability. The thickness of the shell varies depending on the volume average particle diameter and the like, but is usually about 0.5 to 75 μm, and can be adjusted by the amount of (SL) (decreasing as the amount is increased).

Hollow resin particles can be obtained by heat-treating thermally expandable microcapsules.
The volume average particle diameter (μm) of the hollow resin particles is preferably 0.1 to 200, more preferably 0.5 to 150, and particularly preferably 1 to 100.
The volume average particle size is measured by a laser diffraction type particle size distribution measuring apparatus having a measurement principle {light scattering method (25 ° C.)} described in JIS Z8825-1: 2001 {for example, LA-920 manufactured by Horiba, Shimadzu Manufactured by SALD-1100, etc.).
The volume average particle size can be adjusted by controlling the particle size of the thermally expandable microcapsules, and can be arbitrarily controlled by the heating expansion temperature and time of the thermally expandable microcapsules.

The specific gravity (g / cm ³ ) of the hollow resin particles is preferably 0.6 to 0.008, more preferably 0.5 to 0.01, and particularly preferably 0.4 to 0.02.
Here, the specific gravity of the hollow resin particles means the specific gravity (apparent density) of the whole particle including the hollow portion.
The specific gravity is described in 2. of JIS Z8807-1976 “Method for Measuring Solid Specific Gravity”. It is measured according to a measurement method using a specific gravity bottle (liquid; distilled water or methanol).

EXAMPLES Hereinafter, although an Example demonstrates this invention further, this invention is not limited to this.

<Specific gravity of hollow resin particles>
2. JIS Z8807-1976 “Method of measuring solid specific gravity” It measured based on the measuring method (liquid; methanol) by a specific gravity bottle. A smaller specific gravity means that the expandability of the thermally expandable microcapsule is superior.

<Water content of hollow resin particles>
Measured according to JISK6828-1 synthetic resin emulsion non-volatile content. In addition, the heating temperature at the time of moisture content measurement shall be 80 degreeC.

<Example 1>
After uniformly mixing 340 parts by weight of deionized water, 17.6 parts by weight of a 20% colloidal silica aqueous solution, 1.0 part by weight of adipic acid-diethanolamine condensate and 110 parts by weight of sodium chloride, 83 parts by weight of acrylonitrile, Add a solution consisting of 10 parts by weight of methacrylic acid, 14 parts by weight of methyl methacrylate, 23 parts by weight of pentane and 0.5 parts by weight of azobisisobutyronitrile, and using a homomixer (ROBOMICS, 4000 rpm, manufactured by Special Machinery Co., Ltd.). Stir for 2 minutes to obtain a suspension.
This suspension was transferred to a pressure-resistant reaction vessel and polymerized at a gauge pressure of 0.25 MPa and 60 ° C. for 20 hours. Next, the polymerization solution was filtered and dried at 60 ° C. for 5 hours to obtain thermally expandable microcapsules.
The thermally expandable microcapsules shown in FIG. 1 were subjected to the indirect heating type agitation dryer (L; 0.5 m, W; 0.2 m, heat transfer area; 0.35 m ² , effective volume; 0.005 m ³ , heat transfer) Area / effective volume: 70 m ⁻¹ , the heat medium was introduced into the jacket, the stirring blade and the shaft) and subjected to heat treatment (time from supply to discharge for 3 minutes) to obtain hollow resin particles. The supply speed from the quantitative feeder was set to 10 kg / hour. As the heat medium, steam at 170 ° C. was used.

<Example 2>
Hollow resin particles are obtained in the same manner as in Example 1 except that the heat medium is introduced and used only in the jacket of the indirectly heated stir dryer shown in FIG. 1 (heat transfer area / effective volume; 20 m ⁻¹ ). It was.

<Example 3>
In the same manner as in Example 1, except that 83 parts by weight of acrylonitrile, 10 parts by weight of methacrylic acid, and 14 parts by weight of methyl methacrylate were used, 83 parts by weight of acrylonitrile, 15 parts by weight of methacrylic acid, and 9 parts by weight of methyl methacrylate were used. Resin particles were obtained.

<Example 4>
Instead of 83 parts by weight of acrylonitrile, 10 parts by weight of methacrylic acid and 14 parts by weight of methyl methacrylate, 85 parts by weight of acrylonitrile, 7 parts by weight of methacrylic acid, 14 parts by weight of methyl methacrylate, 1 part by weight of N, N-dimethylacrylamide were used. And it is the same as in Example 1 except that a heat medium is introduced and used only for the stirring blade and shaft of the indirectly heated stirrer and dryer shown in FIG. 1 (heat transfer area / effective volume; 50 m ⁻¹ ). Hollow resin particles were obtained.

<Example 5>
Example 1 is used except that 83 parts by weight of acrylonitrile, 10 parts by weight of methacrylic acid, and 14 parts by weight of methyl methacrylate are used, and 83 parts by weight of acrylonitrile, 20 parts by weight of methyl methacrylate, and 3 parts by weight of N, N-dimethylacrylamide are used. Thus, hollow resin particles were obtained.

<Example 6>
The heat transfer area etc. are (L; 0.5 m, W; 0.35 m, heat transfer area; 0.10 m ² , effective volume; 0.01 m ³ , heat transfer area / effective volume; 10 m ⁻¹ ) FIG. Hollow resin particles were obtained in the same manner as in Example 1 except that the heat medium was introduced and used only in the jacket of the indirect heating type agitating dryer described in 1.

<Comparative Example 1>
Indirect heating type agitating dryer shown in FIG. 2 (L; 0.5 m, W; 0.3 m, heat transfer area; 0.47 m ³ , effective volume; 0.07 m ³ , heat transfer area / effective volume; 7 m ^{− 1} , hollow resin particles were obtained in the same manner as in Example 1 except that the heating medium was introduced only into the jacket.

<Comparative example 2>
The expansion process of the thermally expandable microcapsule is performed according to the method described in Example 2 of Patent 2927933.
The thermally expandable microcapsule produced in Example 1 was adjusted to an aqueous dispersion containing 15% by weight, and this dispersion was treated with the apparatus shown in FIG. 3 to obtain a hollow fine particle composition. The dispersion liquid is sent from the slurry introduction pipe (13) to the foaming pipe (diameter 36 mm, length 600 mm, made of SUS304TP) (5) at a flow rate of 35 kg / hour, and the water in the tank (6) is further transferred to the heat exchanger (7). The mixture was heated to 160 ° C. and supplied to the introduction part (14) of the heat exchanger (5) at a flow rate of 150 kg / hour, and mixed with the slurry. The temperature in the foamed tube at this time was set to 140 ° C. After introducing normal temperature water at 250 kg / hour into the foam slurry liquid flowing out from the foam pipe discharge part (9), the slurry liquid is cooled to 60 ° C. or lower, and then drained by the suction dehydrator (10). Hollow resin particles containing 85% water were obtained.

  Regarding the hollow resin particles of Examples 1 to 6 and Comparative Examples 1 and 2, the softening temperature, specific gravity, and moisture of the polymer shell were measured, and the results are shown in Table 1.

  In any of the hollow resin particle production methods of Examples, the specific gravity of the obtained hollow resin particles is small. It can be seen that the expansion ratio of the thermally expandable microcapsule is high. Further, the hollow resin particles obtained have almost no moisture and do not contain a large amount of moisture unlike the wet method.

  The hollow resin particles obtained by the production method of the present invention have a low specific gravity equivalent to that of the wet method, and have a low water content, and can be used without any problem for resins that react with water or use water as a catalyst. Can do. Therefore, it can be used for all uses of hollow resin particles obtained by a wet method, and is particularly suitable for resins that require strict moisture management, such as urethane resins and epoxy resins.

Indirect heating type agitating dryer -2 axis type Indirect heating type agitating dryer-shaftless type Wet expansion device (patent 2927933, cited from Drawing 1)

Explanation of symbols

A: Stirring blade C: Jacket S: Shaft FI: Supply port F: Metering feeder EX: Discharge port

Claims (3)

A stirring blade (A) capable of renewing the surface of the powder inside the casing having the jacket (C) is installed on a shaft arranged parallel and horizontally to the casing, and the jacket (C) is stirred. The heat transfer area / effective volume capable of introducing a heat medium into at least one selected from the group consisting of blades (A) and shafts is connected to an indirect heating type agitation dryer (B) having an effective volume of 10 m ^-1 or more. A method for producing hollow resin particles, comprising continuously supplying thermally expandable microcapsules from a supply port and continuously discharging hollow resin particles from a discharge port at a lower end of the other end.   The method for producing hollow resin particles according to claim 1, wherein the temperature of the heat medium to be introduced is 120 to 200 ° C. The method for producing hollow resin particles according to claim 1 or 2, wherein the softening temperature of the polymer shell constituting the thermally expandable microcapsule to be supplied is 100 to 180 ° C.