JP2007131688A - Thermally expandable microcapsule - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermally expandable microcapsule without releasing inflammable gas on heating, also capable of optionally adjusting its expanding temperature and having extremely high safety/exapndability. <P>SOLUTION: This thermally expandable microcapsule is provided by having a non-volatile fluid substance (C) and a solid material (D) releasing gas by thermal decomposition in a polymer shell (B) consisting of a thermoplastic polymer (A), without releasing the inflammable gas on expansion or being used at a high temperature and having an extremely high safety. Also, by adjusting the thermal decomposition temperature of the encapsulated solid (D), it is possible to regulate the expansion temperature exactly. Therefore, a thermally peelable adhesive using the thermally expandable microcapsules is extremely stable and can hold its bonding strength on using, and it is possible to heat the adhesive for peeling off at an optional temperature on wishing to peel it off. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a thermally expandable microcapsule.

Thermally expandable microcapsules are microcapsules having a core made of a volatile liquid such as pentane and a shell made of a thermoplastic polymer, and are particles that expand to a volume of several tens of times when heated (Patent Document 1). 2). Because of its unique feature of expanding when heated, it is used in expandable inks and heat-peelable adhesives.
JP 2000-024488 JP-A-2005-105181

Conventional heat-expandable microcapsules soften the shell polymer by heating, and at the same time, gasify the volatile liquid and expand the particles using the vapor pressure of the generated gas. As the volatile liquid, a low boiling point flammable liquid such as pentane is used, and thus a large amount of flammable gas is released during the heat treatment. Therefore, it is necessary to sufficiently confirm that there is no fire in the vicinity when the particles expand, which poses a serious problem in safety.
In addition, the conventional thermally expandable microcapsules use a volatile liquid having a low boiling point in order to increase the expansion ratio. However, when the temperature becomes high during storage or use (for example, 60 to 80 ° C.), the volatile liquid is used. This causes problems such as gasification and leakage. For example, a heat-releasable adhesive is an adhesive to which a heat-expandable microcapsule is added, and when it is desired to peel off, the heat-expandable microcapsule is heated to expand the heat-expandable microcapsule to reduce the adhesive surface and peel off. However, if the gas leaks at about 60 ° C. and the adhesive strength decreases, it cannot be used as an adhesive for automobiles or daily necessities.
That is, an object of the present invention is to provide an extremely safe thermally expandable microcapsule in which a combustible gas is not released by heating and the expansion temperature can be adjusted to an arbitrary temperature.

  The heat-expandable microcapsule of the present invention has a non-volatile flowable substance (C) and a solid (D) that generates gas by thermal decomposition in a polymer shell (B) made of a thermoplastic polymer (A). The point is summarized.

  The thermally expandable microcapsule of the present invention is extremely safe because no flammable gas is released during expansion or high temperature use. Further, the expansion temperature can be strictly controlled by adjusting the thermal decomposition temperature of the solid (D) to be included. Therefore, the heat-peelable adhesive using the present heat-expandable microcapsules can be extremely stable at the time of use and can maintain the adhesive strength, and can be peeled off by heating at an arbitrary temperature when it is desired to peel off.

As the thermoplastic polymer (A), any polymer that can be softened by heating 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 polymer can be arbitrarily controlled according to the purpose for which the thermally expandable microcapsules are used. When used for a heat-peelable adhesive, the softening temperature (° C.) of the polymer is preferably 110 to 250, more preferably 120 to 220, and particularly preferably 130 to 200. 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 non-volatile flowable substance (C) means a substance having a high boiling point or no boiling point and not solid at the polymerization temperature of the thermoplastic polymer (A). More specifically, the boiling point is preferably 100 ° C. or higher and the pour point is 45 ° C. or lower.
More preferably, the boiling point is 150 to 400 ° C. or no boiling point. Further, the pour point is more preferably 35 ° C. or less, and particularly preferably 25 ° C. or less.
Here, the pour point means the lowest temperature at which the substance flows and is measured according to JISK2269.
The flowable substance (C) is hydrophobic and is preferably dissolved in the monomer constituting the thermoplastic polymer (A). Here, the hydrophobic property means that it is difficult to dissolve in water. Specifically, the solubility in water is preferably 1 g / 100 g or less of water, more preferably 0 to 0.5 g / 100 g of water, and particularly preferably 0 to 0.1 g / 100 g of water. When the solubility of the fluid substance (C) in water is within this range, the fluid substance (C) is phase-separated inside the particles as the polymerization of the monomer proceeds, as will be described later.
As the non-volatile fluid substance (C), higher hydrocarbons, higher alcohols, silicone oils, vegetable oils (olive oil, rapeseed oil, coconut oil, etc.), ionic liquids and the like can be used.

The higher hydrocarbon is preferably a hydrocarbon having an average carbon number of 7 to 40, more preferably 15 to 35, and may be a linear structure or a branched structure, or a mixture thereof. Furthermore, not only aliphatic hydrocarbons but also alicyclic hydrocarbons or aromatic hydrocarbons, or mixtures thereof can be used.
Examples of the aliphatic hydrocarbon include heptane, octane, decane, tetradecane, nonadecane, and liquid paraffin.
Examples of the alicyclic hydrocarbon include cyclohexane, cycloheptane, cyclooctane, and methylcyclohexane.
Aromatic hydrocarbons include toluene, xylene, naphthalene, and the like.
Among these, from the viewpoint of safety, an aliphatic hydrocarbon is preferable, more preferably an aliphatic hydrocarbon having an average carbon number of 10 to 50, and particularly preferably an aliphatic hydrocarbon having an average carbon number of 15 to 40 or less. (Nonadecane, liquid paraffin, etc.).

As the higher alcohol, a hydrocarbon having an average carbon number of 3 to 40 can be used, and it may be a linear structure or a branched structure, or a mixture thereof.
Specific examples include pentyl alcohol, isopentyl alcohol, hexyl alcohol, octyl alcohol, dodecyl alcohol, octadecyl alcohol, cyclohexanol, benzyl alcohol, diphenylmethanol and the like.
Among these, from the viewpoint of safety, higher alcohols having an average carbon number of 5 to 40 are preferable, and higher alcohols having an average carbon number of 8 to 15 (octyl alcohol, dodecyl alcohol, etc.) are more preferable.

  As the non-volatile fluid substance (C), it is preferable to use higher hydrocarbons, higher alcohols, silicone oils, vegetable oils, and more preferably higher carbonization from the viewpoints of safety and phase separation during polymerization. Hydrogen, silicone oil, particularly preferable are aliphatic hydrocarbons and silicone oils having an average carbon number of 15 to 40.

The thermally expandable microcapsule of the present invention preferably contains 1 to 50% by weight of the flowable substance (C) based on the weight of the thermally expandable microcapsule in the polymer shell (PS), more preferably It is 3 to 40% by weight, particularly preferably 5 to 20% by weight.
Within this range, thermally expandable microcapsules with good expandability can be obtained.

  The solid (D) that generates gas by pyrolysis means a solid that decomposes by heating to generate gas. The temperature at which gas is decomposed by heating can be arbitrarily controlled according to the purpose of using the thermally expandable microcapsule by selecting the solid (D), and is 100 ° C. or higher and 200 ° C. or lower. Is more preferable, and it is 130 degreeC or more and 190 degrees C or less.

As the solid (D), an organic compound, an inorganic compound, a mixture thereof, or the like can be used.
Organic 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 - (benzene sulfonyl semicarbazide), etc.), triazole (5-morpholyl-1,2,3,4-thiatriazole, etc.) and the like.
Examples of the inorganic compound include sodium hydrogen carbonate (bicarbonate), ammonium hydrogen carbonate, ammonium carbonate, potassium hydrogen tartrate, sodium fumarate, and the like.
As foaming aids, zinc oxide, zinc nitrate, lead phthalate, lead carbonate, tribasic phosphate, tribasic lead sulfate and other inorganic salts, zinc fatty acid soap, lead fatty acid soap, cadmium fatty acid soap, etc. Metal soaps, acids such as boric acid, oxalic acid, succinic acid, adipic acid, urea, biurea, ethanolamine, glycol, glycerin and the like can be mixed and used.
Of these, organic compounds are preferable from the viewpoint of controllability of expansion temperature, and the like, more preferably azo compounds, sulfohydrazide compounds, and nitroso compounds, and particularly preferably azo compounds.

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

The surface of the solid (D) that generates gas by thermal decomposition is preferably treated with a treatment agent (E) that is a hydrophobic substance. The solid (D) needs to move into the particles together when the fluid substance (C) phase-separates into the particles as the polymerization proceeds. Therefore, it is necessary to increase the affinity with the fluid substance (C), and when this affinity is high, the solid (D) can easily move into the particles. On the other hand, when this affinity is low, the solid (D) does not move inside the particles but is embedded in the polymer shell or discharged outside the particles, and the expansion ratio is lowered.
The treating agent (E) preferably has a solubility in water of 1 g / 100 g or less of water, more preferably 0.5 g / 100 g or less of water, and particularly preferably 0.1 g / 100 g or less of water. Furthermore, what does not flow is preferable at the polymerization temperature (20 ° C. to 90 ° C.) of the thermoplastic polymer (A).

Specifically, higher fatty acids having an average carbon number of 10 to 80 or salts thereof (capric acid, lauric acid, palmitic acid, stearic acid, magnesium stearate, etc.), higher alcohols having an average carbon number of 10 to 80 (dodecyl alcohol, tetra Decyl alcohol, hexadecyl alcohol, octadecyl alcohol, diphenylmethanol, etc.), higher hydrocarbons having an average carbon number of 10-80 (pentadecane, hexadecane, heptadecane, octadecane, nonadecane, natural wax (petroleum wax), synthetic wax, etc.), fatty acid amide And oxidized polyethylene wax.
Among these, those which melt at a temperature not lower than the polymerization temperature of the thermally expandable microcapsule and not higher than the decomposition temperature of the solid (D) are preferable. Specifically, higher fatty acids having 10 to 60 carbon atoms or salts thereof, average carbon Higher hydrocarbons of several 10 to 60 are preferable, and petroleum wax having an average carbon number of 20 to 50 and magnesium stearate are particularly preferable.
As a surface treatment method with the treatment agent (E), first, the (E) is heated and melted, and the melted (E) and solid (D) are mixed using a planetary mixer or the like and then cooled. The method of depositing and coating (E) on the surface of solid (D) is mentioned.

  Various additives may be used in the heat-expandable microcapsules of the present invention as needed. For example, antioxidants (such as hindered phenol, phosphorus and lactone), ultraviolet absorbers (such as benzotriazole) Further, an antibacterial agent (such as phenyl ether) and an antistatic agent (such as a polyamide copolymer) can be added.

1-100 are preferable, as for the volume average particle diameter (micrometer) of a thermally expansible microcapsule, More preferably, it is 5-75, Most preferably, it is 10-50.
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.).

As a method for producing the thermally expandable microcapsule of the present invention, a non-volatile fluid substance (C) is dissolved in a monomer, and then a solid (D) that generates gas by thermal decomposition is dispersed in the solution. There is a method in which an oil phase is formed, and this is emulsified and dispersed in an aqueous phase containing water as a main component and then polymerized.
Emulsification and dispersion can be performed by applying a mechanical shear force to the mixture of the oil phase and the aqueous phase. Examples of the method for applying a mechanical shearing force include stirring with a stirring blade, dispersion with an ultrasonic disperser, dispersion with a membrane emulsifier (manufactured by Chilling Industries). When stirring with a stirring blade, a special disperser such as a (continuous) homomixer (manufactured by Special Machinery Co., Ltd.) can be used.
In the emulsification dispersion, a surfactant or a dispersion stabilizer can be used to improve dispersibility.

When the monomer is a vinyl monomer, the polymerization can be performed by adding a polymerization initiator and heating, and the heating temperature and the polymerization time are determined depending on the type of the polymerization initiator used.
On the other hand, when the monomer is an isocyanate or an acid chloride and a polyurethane or polyamide is synthesized, polymerization is performed at the interface of the emulsified and dispersed oil phase by adding a reactant such as amine or polyol from the aqueous phase side. Can do.
In either case, as the polymerization proceeds, the fluid substance (C) is not dissolved in the monomer and phase-separated into the particles. In the phase separation process, the solid (D) also moves into the particles together with the fluid substance (C).
When the monomer and the flowable substance (C) are not compatible with each other, a compatibilizing agent such as a surfactant or an organic solvent can be used. Also in this case, it is necessary to phase-separate the fluid substance (C) into the particles as the polymerization proceeds. As a compatibilizing agent, dimethylformamide, tetrahydrofuran, methyl ethyl ketone, acetone, ethyl acetate, butyl acetate, etc. can be used. However, from the viewpoint of safety, etc., it should be removed by depressurization after emulsification dispersion or polymerization. Is preferred.

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.

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.

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.

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).

As the expansion method of the thermally expandable microcapsule, a known method can be applied. An air flow dryer, a forward air dryer and a Nauta mixer (manufactured by Hosokawa Micron), solid air (manufactured by Hosokawa Micron), a universal mixer (Dalton) It is possible to carry out the heating by using, for example.
The heating temperature (° C.) is preferably {softening temperature of polymer (A) (NT) −20 to (NT) +70} ° C. (90 to 350 ° C.), more preferably 100 to 330, particularly preferably 120 to 250. Most preferably, it is 130-220.
The heating time is preferably 1 minute to 60 minutes, more preferably 5 to 30 minutes, and particularly preferably 0.5 to 15 minutes.

The specific gravity (g / cm ³ ) of the hollow resin particles obtained by expanding the thermally expandable microcapsule is preferably 0.6 to 0.008, more preferably 0.5 to 0.01, and particularly preferably 0.4. ~ 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, and the lower the specific gravity of the hollow resin particles, the higher the expansion ratio of the thermally expandable microcapsules. To do.
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).

A heat-peelable adhesive containing a heat-expandable microcapsule is an adhesive in which a heat-expandable microcapsule is added to an adhesive composition. It is an adhesive that can be easily peeled by decreasing or can be peeled naturally. Moreover, sealants and adhesive tapes are also included as usage forms.
Here, the adhesive composition includes thermoplastic resins (vinyl acetate resin, ethylene vinyl acetate resin, vinyl chloride resin, acrylic resin, polyamide resin, cellulose resin, olefin resin, etc.), thermosetting resins (urea resin, melamine resin). Phonol resin, urethane resin, epoxy resin, resorsilanol resin, polyester resin, etc.) and elastomer (chloroprene rubber, nitrile rubber, styrene butadiene rubber, polysulfide, butyl rubber, urethane rubber, acrylic rubber, silicone rubber, etc.) It is done. Among these, a thermoplastic resin or an elastomer is preferable from the viewpoint of improving heat peelability.
The blending amount of the heat-expandable microcapsule is preferably 1 to 70% by weight, more preferably 3 to 60% by weight, based on the adhesive composition, from the viewpoint of achieving both adhesive strength and heat peelability. Particularly preferred is 5 to 40% by weight.
The preferred range of the thermal peeling temperature varies depending on the use, but is generally preferably 100 ° C. or higher and 200 ° C. or lower, more preferably 130 ° C. or higher and 190 ° C. or lower. The thermal peeling temperature can be controlled by adjusting the thermal decomposition temperature of the solid (D) that generates gas by thermal decomposition.

EXAMPLES Hereinafter, although an Example demonstrates this invention further, this invention is not limited to this.
<Example 1>
After uniformly mixing 340 parts by weight of deionized water, 17.6 parts by weight of 20% colloidal silica, 1.0 part by weight of adipic acid-diethanolamine condensate and 110 parts by weight of sodium chloride, 83 parts by weight of acrylonitrile, methacrylic acid, 10 parts by weight of acid, 14 parts by weight of methyl methacrylate, 23 parts by weight of liquid paraffin (average carbon number 34, Sanko Chemical Industries 260-S) (C-1) and 0.5 part by weight of azobisisobutyronitrile The solution was treated with an azodicarbonamide [ADCA (D-1) (ADC-1 (D-1) (E-1), the surface of which was treated with a treating agent, petroleum wax (average carbon number 40, linear hydrocarbon, Nippon Seiro Co., Ltd., HNP-9) (E-1)]. Sankyo Chemical Co., Ltd.)] 10 parts by weight were added, and the mixture was stirred for 2 minutes using a homomixer (ROBOMICS, 4000 rpm, produced by Special Machinery Co., Ltd.) to obtain a suspension. The surface treatment of ADCA (D-1) with petroleum wax (surface treatment agent) is carried out by melting 10 parts by weight of petroleum wax at 70 ° C., mixing 10 parts by weight of ADCA (D-1), and then planetary. This was carried out by stirring for 15 minutes with a mixer.
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.

<Example 2>
Thermally expandable microcapsules in the same manner as in Example 1 except that N, N-dinitropentamethylenetetramine (DPT) (D-2) (manufactured by Sankyo Kasei) was used instead of ADCA (D-1). Was synthesized and evaluated.

<Example 3>
The surface treatment agent is changed from petroleum wax to magnesium stearate, ADCA is increased by 5 parts by weight to 8 parts by weight, and liquid paraffin is changed to silicone oil (KF-54 manufactured by Shin-Etsu Silicone) (E-2). In the same manner as in Example 1, the thermally expandable microcapsules were synthesized and evaluated.

<Example 4>
A thermally expandable microcapsule was synthesized and evaluated in the same manner as in Example 3 except that 23 parts by weight of liquid paraffin was changed to 26 parts by weight of silicone oil.

<Example 5>
The structural units of the thermoplastic polymer (A) are as shown in Table 1, and the thermal expansion microcapsules were synthesized and evaluated in the same manner as in Example 2 except that 23 parts by weight of liquid paraffin was changed to 26 parts by weight of silicon oil. went.

<Example 6>
The structural unit of the thermoplastic polymer (A) is as shown in Table 1, and in the same manner as in Example 2 except that sodium bicarbonate (D-3) (manufactured by Sankyo Kasei) is used instead of ADCA, Swellable microcapsules were synthesized and evaluated.

<Example 7>
340 parts by weight of deionized water, 17.6 parts by weight of 20% colloidal silica, 1.0 part by weight of polyvinyl alcohol and 110 parts by weight of polyethylene terephthalate (PET) having a weight average molecular weight of 30,000 A suspension was obtained in the same manner as in Example 1 except that an oil phase consisting of parts by weight and 23 parts by weight of liquid paraffin was used.
Ethyl acetate was completely removed from this suspension using an evaporator (manufactured by Ishii Scientific Instruments Co., Ltd.) under conditions of 3 mmHg and 40 ° C. Subsequently, after filtering this, it was made to dry at 60 degreeC for 5 hours, and the thermally expansible microcapsule was obtained.
The thermal expansion microcapsules were evaluated in the same manner as in Example 1.

<Example 8>
340 parts by weight of deionized water, 17.6 parts by weight of 30% calcium carbonate suspension, 220 parts by weight of an aqueous phase and a urethane prepolymer solution (prepoly) in which 1.0 part by weight of sodium polyacrylate is uniformly mixed, an amine system A suspension was obtained in the same manner as in Example 1 except that an oil phase consisting of 5 parts by weight of a curing agent and 23 parts by weight of liquid paraffin was used.
Ethyl acetate was completely removed from this suspension using an evaporator (manufactured by Ishii Scientific Instruments Co., Ltd.) under conditions of 3 mmHg and 40 ° C. Subsequently, after filtering this, it was made to dry at 60 degreeC for 5 hours, and the thermally expansible microcapsule was obtained.
The thermal expansion microcapsules were evaluated in the same manner as in Example 1.
The urethane prepolymer was synthesized by the following method. In a reaction vessel equipped with a stirrer and a dehydrator, 681 parts of bisphenol A / EO 2 mol adduct, 81 parts of bisphenol A / PO 2 mol adduct, 275 parts of terephthalic acid, 7 parts of adipic acid, 22 parts of trimellitic anhydride, dibutyl 2 parts of tin oxide was added, and after 5 hours of dehydration reaction at normal pressure and 230 ° C., the dehydration reaction was performed for 5 hours under a reduced pressure of 3 mmHg. 407 parts of this, 54 parts of IPDI, and 485 parts of ethyl acetate were added and reacted in a sealed state at 100 ° C. for 5 hours to obtain a urethane prepolymer solution having an isocyanate group at the molecular end.
The amine-based curing agent should be removed after 50 parts of isophoronediamine and 300 parts of methyl ethyl ketone are placed in a reaction vessel equipped with a stirrer, a solvent removal device, and a thermometer, and reacted at 50 ° C. for 5 hours. Was synthesized.

<Comparative Example 1>
Thermally expandable microcapsules were synthesized and evaluated in the same manner as in Example 5 except that pentane was used as an expanding agent instead of (C), (D) and the treating agent.

<Comparative example 2>
Thermally expandable microcapsules were synthesized and evaluated in the same manner as in Example 1 except that pentane was used as an expanding agent instead of (C), (D) and the treating agent.

  About the heat | fever expansible microcapsule of Examples 1-6 and Comparative Examples 1-2, the heat resistant storage stability, expansibility, flammability, and volume average particle diameter were evaluated by the following method. The results are shown in Table 1 or Table 2.

<Heat resistant storage stability (weight loss)>
The heat-resistant storage stability was evaluated by analyzing the weight loss when 100 parts by weight of thermally expandable microcapsules were treated at 80 ° C. for 300 hours. A smaller weight loss means better heat resistant storage stability. As the thermally expandable microcapsules, those having a water content of 0.1% by weight or less as measured in accordance with the method for obtaining the non-volatile content of JISK6828-1 synthetic resin emulsion are used.

<Expandability (specific gravity of hollow resin particles)>
The thermally expandable microcapsules were heated at 165 ° C. for 5 minutes using an electric furnace (manufactured by the company) to obtain hollow resin particles. The specific gravity of the hollow resin particles is determined according to 2. of JIS Z8807-1976 “Solid Specific Gravity Measurement Method”. It measured based on the measuring method (liquid; methanol) by a specific gravity bottle. A smaller specific gravity means superior expansibility.

<Flash point>
The flash point of the thermally expandable microcapsule was measured in the range of 50 to 150 ° C. using a Clement ground flash point measuring device (COC).

<Volume average particle diameter>
In accordance with JIS Z8825-1: 2001, 0.1 g of a measurement sample is dispersed in 100 ml of methyl alcohol and measured using a laser scattering particle size distribution analyzer LA-920 (25 ° C., manufactured by Horiba, Ltd.). did.

The pyrolysis temperature of the solid (D) used, the boiling point of the fluid substance (C), the pour point, and the solubility in water are as follows.
Thermal decomposition temperature of solid (D)
ADCA; 150 ° C
DPT; 190 ° C
Sodium bicarbonate; 130 ° C
Boiling point, pour point, solubility in water of liquid substance (C) Liquid paraffin Boiling point: 390 ° C (first run)
Pour point: -7.5 ° C or lower Solubility in water; Insoluble in water (0.1 g / 100 g or less of water)
Silicone oil Boiling point; 300 ° C or more Pour point; -10 ° C or less Solubility in water; Insoluble in water (0.1g / 100g or less of water)

  None of the thermally expandable microcapsules of the examples has a flash point and is extremely safe. Further, when treated at 80 ° C. for 300 hours, there is almost no weight loss and the heat-resistant storage stability is extremely high. On the other hand, the expandability is equal to or greater than that of the comparative example, and the thermally expandable microcapsules of the examples are thermally expandable microcapsules that satisfy both expandability, safety, and heat-resistant storage stability.

  The thermally expandable microcapsule of the present invention maintains the conventional level of expandability, and does not release flammable gas when expanded or used at high temperatures, and is extremely safe. Therefore, according to the present heat-expandable microcapsule, it is possible to use the heat-expandable microcapsule that has been conventionally used more safely in almost all applications. Moreover, since expansion temperature is easy to control, it is suitable for a heat-peelable adhesive.

Claims (8)

A thermally expandable microcapsule having a non-volatile flowable substance (C) and a solid (D) that generates gas by thermal decomposition in a polymer shell (B) made of a thermoplastic polymer (A). 2. The thermally expandable microcapsule according to claim 1, wherein the pyrolysis temperature of the solid (D) that generates gas by pyrolysis is 100 ° C. or higher and 200 ° C. or lower. The thermally expandable microcapsule according to claim 1 or 2, wherein the solid (D) that generates gas by thermal decomposition is an organic compound. The boiling point of the non-volatile flowable substance (C) is 100 ° C or higher, the pour point is 45 ° C or lower, and the solubility in water is 1 g / 100 g or less of water. The heat-expandable microcapsule described in 1. The thermal expansion according to any one of claims 1 to 4, wherein the non-volatile fluid substance (C) is at least one selected from the group consisting of higher hydrocarbons having an average carbon number of 7 to 40 and silicone oil. Microcapsules. The thermally expandable microcapsule according to any one of claims 1 to 5, wherein the solid (D) that generates gas by thermal decomposition is surface-treated with a hydrophobic substance. The thermally expandable microcapsule according to any one of claims 1 to 6, wherein the thermoplastic polymer (A) comprises at least a cyano group-containing vinyl monomer as a constituent unit. A heat-peelable adhesive containing the heat-expandable microcapsule according to claim 1.