WO2003000402A1

WO2003000402A1 - Process for producing heat-expandable microcapsule

Info

Publication number: WO2003000402A1
Application number: PCT/JP2002/006209
Authority: WO
Inventors: Yasuhiro Kawaguchi; Takahiro Omura; Toshiharu Furukawa
Original assignee: Sekisui Chemical Co., Ltd.; Tokuyama Sekisui Co., Ltd.
Priority date: 2001-06-21
Filing date: 2002-06-21
Publication date: 2003-01-03
Also published as: JP2003001099A

Abstract

A process for efficiently and easily producing heat-expandable microcapsules which combine excellent heat resistance with excellent solvent resistance, are less apt to shrink or break even when heated at a high temperature for long, and highly stably heat-expand (foam stably). The process is characterized in that monomer ingredients comprising 55 to 75 wt.% acrylonitrile, 20 to 40 wt.% methacrylonitrile, 1 to 10 wt.% vinyl acetate, and 0.1 to 1 wt.% crosslinking agent having a functionality of 4 or higher and a volatile expanding agent which gasifies at a temperature not higher than the softening point of the polymer to be obtained from the monomer ingredients are polymerized while being pressurized with nitrogen and that the resultant polymer is formed into microcapsules.

Description

Specification

Method for producing heat-expandable microcapsules

Technical field

The present invention relates to a method for producing a heat-expandable microcapsule, particularly a heat-expandable microcapsule having excellent heat resistance and solvent resistance. BACKGROUND ART A method for producing a heat-expandable microcapsule by using a thermoplastic polymer as a wall material and microencapsulating a volatile expanding agent that becomes gaseous at a temperature lower than the softening point of the polymer is known.

For example, Japanese Patent Publication No. 42-26524 discloses that a liquid foaming agent such as a low-boiling aliphatic hydrocarbon is added to a monomer, and an oil-soluble polymerization initiator is mixed with the monomer component. The heat-expandable microcapsules for producing spherical particles containing the above-mentioned liquid foaming agent by adding the above-mentioned monomer components to an aqueous dispersion medium containing a dispersion stabilizer while stirring and performing suspension polymerization. Is disclosed. However, the heat-expandable microcapsule obtained by the production method disclosed in the above publication is not excellent in heat resistance and solvent resistance, and expands and expands at a low temperature of about 80 to 130 ° C, There was a problem that the foaming ratio was reduced under heating conditions of high temperature and long time.

To cope with such a problem, for example, the Kokoku 5-1 5 4 9 9 JP, nitrile-based monomer 8 0 wt ^_0/0 or more, the non-nitrile-based monomer 2 0% by weight and Cross-linking agent Using a polymer obtained from a monomer component containing 0.1 to 1% by weight, a heat-expandable microcapsule for converting a volatile expander which becomes gaseous at a temperature equal to or lower than the softening point of the polymer into a micro force. Is disclosed. The heat-expandable microcapsules obtained by this manufacturing method are superior in heat resistance to the heat-expandable microcapsules obtained by the conventional manufacturing method. Is also excellent. However, microcapsules are liable to shrink or break when heated at high temperatures for long periods of time. There is a problem that the stability at the time of foaming is insufficient. Summary of the Invention

An object of the present invention is to provide a combination of excellent heat resistance and excellent solvent resistance, hardly cause shrinkage and bubble breakage even under high temperature and long-time heating conditions, and excellent heat expansion stability (foaming stability). An object of the present invention is to provide an efficient and simple method for producing expandable microcapsules. The present invention, acrylonitrile 5 for 5-7 5 weight ^_0/0, methacrylonitrile 2 0-4 0 wt%, vinyl acetate 1-1 0% by weight and tetrafunctional or more crosslinking agents from 0.1 to 1 weight

%, And a volatile expander which becomes gaseous at a temperature lower than the softening point of the polymer obtained from the monomer component, is polymerized under nitrogen pressure to form a microcapsule. It is a manufacturing method of a capsule. Detailed Disclosure of the Invention

Hereinafter, the present invention will be described in detail.

The monomer component used in the method for producing a heat-expandable microcapsule of the present invention contains 55 to 75% by weight of acrylonitrile and 20 to 40% by weight of methacrylic nitrile as nitrile monomers. When the content of acrylonitrile in the monomer component is less than 55% by weight and / or the content of metall-tolyl is less than 20% by weight, heat-expandable microcapsules (hereinafter also referred to as microcapsules)耐熱) The solvent resistance becomes insufficient, and conversely, the content of acrylonitrile in the monomer component exceeds 75% by weight and / or the content of methacrylonitrile becomes 40% by weight. If it exceeds, the glass transition temperature of the microcapsules becomes too high, and the thermal expansion (foamability) is impaired.

The monomer component used in the method for producing a thermally expandable microcapsule of the present invention contains 1 to 10% by weight of vinyl acetate as a non-nitrile monomer. By containing the butyl acetate having a high radical reactivity in a small amount of 1 to 10% by weight in the monomer component, it is possible to effectively promote the reaction of methacrylonitrile having a remarkably low growth radical reactivity. As a result, methacryloni It becomes possible to increase the polymerization rate of toril, and the microcapsules exhibit remarkably excellent heat resistance and solvent resistance. If the content of vinyl acetate in the monomer component is less than 1% by weight, it is not possible to sufficiently promote the growth radical reactivity of metathalonitrile, and conversely, the content of vinyl acetate in the monomer component is reduced. If it exceeds 10% by weight, the glass transition temperature of the polymer becomes too low, and the heat resistance and the solvent resistance of the microcapsule become insufficient.

The monomer component used in the method for producing a heat-expandable micro force cell of the present invention contains 0.1 to 1% by weight of a crosslinking agent having four or more functional groups as a crosslinking agent. By including 0.1 to 1% by weight of a crosslinking agent having four or more functional groups in the monomer component, the degree of crosslinking of the polymer obtained from the mixed monomer comprising acrylonitrile, methacrylic acid-tolyl, and butyl acetate can be sufficiently increased. The microcapsules are less likely to shrink or break even under high temperature and long heating conditions.

Examples of the crosslinker having four or more functionalities include, for example, pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, dipentaerythritol hexaatalylate, and dipentaerythritol hexamethacrylate, which are preferably used. These crosslinkers having four or more functionalities may be used alone or in combination of two or more.

If the content of the cross-linking agent having four or more functionalities in the monomer component is less than 0.1% by weight, the degree of cross-linking of the polymer is not sufficiently improved, and conversely, the cross-linking agent having four or more functionalities in the monomer component is Even if the content exceeds 1% by weight, the degree of crosslinking of the polymer is no longer improved.

The monomer component used in the manufacturing method of the heat-expandable micro power capsule of the present invention may optionally within a range that does not inhibit the assignment achievement of the present invention, for example, alpha-Kuroruakuri Ronitorinore, _alpha - ethoxyacrylonitrile, such Fumaronitorinore Nitrile monomers other than acrylonitrile and methacrylonitrile, acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, dicyclopentenyl acrylate, etc., methyl methacrylate, ethyl methacrylate, and butyrate methacrylate. Methacrylates such as isobonyl methacrylate, and vinyl acetate such as styrene. And a non-nitrile-based monomer other than toluene. These nitrile-based monomers other than atarilonitrile and methacrylonitrile and non- nitrile-based monomers other than butyl acetate may be used alone or in combination of two or more.

The wall material of the microcapsule produced by the method for producing a thermally expandable microcapsule of the present invention comprises a monomer component comprising the above-mentioned acrylonitrile, methacrylonitrile, biel acetate, and a tetrafunctional or more cross-linking agent; It is prepared by blending as appropriate.

Examples of the polymerization initiator include various known polymerization initiators generally used in this field, and are preferably used. Among them, oil-soluble polymerization initiators soluble in acrylonitrile, methacrylonitrile and vinyl acetate are preferred. Agents are particularly preferably used. Examples of the oil-soluble polymerization initiator include dialkyl peroxide, diacyl peroxide, peroxyester, peroxydicarbonate, and azo compound. More specifically, dialkyl peroxides such as methylethyl peroxide, di-tert-butyl peroxide, and dicumyl peroxide; isoptyl peroxide, benzoin peroxide , 2,4-diclo-benzoylperoxide, 3,5,5-dimethyl peroxide such as trimethylhexanoyl peroxide; t-butyl benzoyl oxyvalate, t-hexyl oxy valiva, t-Butyl peroxy sineodecanoate, t-hexyloxy neodecanoate, 1-cyclohexyl-1- 1-methylethyl peroxy neodecanoate, 1,1,3,3-tetramethyl Peroxyesters such as butyl peroxy neodecanoate, cumyl peroxy neodecanoate, (α, α-bis-neodecanyl baroxy) diisopropylbenzene Bis (4-t-butylcyclohexyl) peroxydicarbonate, di-n-propyloxydicarbonate, disopropylperoxydicarbonate, di (2-ethylethylperoxy) dicarbonate, dimethoxy Peroxydicarbonates such as siptyl baroxydicarbonate and di (3-methyl-3-methoxybutylperoxy) dicarbonate; 2,2'-azobisisobutyronitrile, 2,2,1-azobis (4-methoxy) 1, 2, 4-dimethylvale Azo compounds such as lonitrinole, 2,2′-azobis (2,4-dimethinorevaleronitrile), and 1,1′-azobis (1-cyclohexanecarbonitrile) and the like are mentioned, and are preferably used. These oil-soluble polymerization initiators may be used alone or in combination of two or more.

The volatile swelling agent used in the method for producing a thermally expandable microcapsule of the present invention and contained in the microcapsule is a substance which becomes gaseous at a temperature equal to or lower than the softening point of the polymer obtained from the monomer component. If the volatile expanding agent is a substance which becomes gaseous at a temperature exceeding the softening point of the polymer, the microcapsules tend to contract or break during thermal expansion (foaming).

Examples of the volatile swelling agent include a low-boiling organic solvent and a compound which is thermally decomposed by heating and becomes gaseous, and is preferably used. Among them, a low-boiling organic solvent is particularly preferably used. . These volatile swelling agents may be used alone or in combination of two or more.

Examples of the low-boiling organic solvent include ethane, ethylene, propane, propylene, n-butane, isobutane, n-butene, isobutene, n-pentane, isopentan, neopentane, n-hexane, heptane, petroleum Low-molecular-weight carbon such as ether; hydrogen such as CC13F, CC12F2, CC1F3, CC1F2-CC12F2; and chlorofluorocarbon such as CC12F2; tetramethylenosilane, trimethylethyl Examples thereof include tetraalkylsilanes such as silane, trimethylisopropyl silane, and trimethyl_n-propyl silane, which are preferably used. Among them, n-butane, isobutane, n-pentane, isopentane, n-hexane and Petroleum ether is particularly preferably used. These low-boiling organic solvents may be used alone or in combination of two or more.

In the method for producing a thermally expandable microcapsule according to the present invention, the monomer component and the volatile expander are polymerized under nitrogen pressure to form a microcapsule.

The pressure value at the time of pressurizing the nitrogen is not particularly limited, but is preferably 0.1 to 2.0 MPa. If the pressure value at the time of pressurizing nitrogen is less than 0. IMP a, the radical reactivity of atarilonitrile / methacrylonitrile will deteriorate and the bulk specific gravity will decrease. Microcapsules with low bulk density may have poor thermal expansion stability (foaming stability) under high temperature and long-time heating conditions, causing shrinkage and foam breakage. The pressure value when pressurizing nitrogen

2. Even if it exceeds OMPa, the thermal expansion stability (foaming stability) of the microcapsules no longer improves.

The method of polymerizing the monomer component and the volatile swelling agent under nitrogen pressure of preferably 0.1 to 2.0 OMPa to microencapsulate is not particularly limited. good. A particularly preferred method is described in, for example,

As described in No. 524, a monomer component is mixed with a volatile swelling agent and a polymerization initiator, and the mixture is mixed in an aqueous dispersion medium containing an appropriate dispersion stabilizer, co-stabilizer and the like. This is a suspension polymerization method.

The suspension polymerization is usually carried out in an aqueous dispersion medium containing a dispersion stabilizer, an auxiliary stabilizer and the like.

Examples of the dispersion stabilizer include silica such as colloidal silica, calcium phosphate, magnesium hydroxide, aluminum hydroxide, ferric hydroxide, barium sulfate, calcium sulfate, sodium sulfate, calcium oxalate, calcium carbonate, and the like. It includes potassium carbonate, magnesium carbonate and the like, and is preferably used. These dispersion stabilizers may be used alone or in combination of two or more. The amount of the dispersion stabilizer used is not particularly limited, but is preferably 0.1 to 20 parts by weight based on 100 parts by weight of the monomer component. Examples of the co-stabilizer include condensation products such as condensation products of diethanolamine and aliphatic dicarbonic acid and condensation products of urea and formaldehyde; polybutylpyrrolidone and polyethyleneimine; A water-soluble nitrogen-containing compound of the following; polyethylene oxide, tetramethylammonium hydroxide, gelatin, methyl alcohol, polyvinyl alcohol, octyl sulfosuccinate, sorbitan ester, various emulsifiers, and the like. Used for These co-stabilizers may be used alone or in combination of two or more.

The aqueous dispersion medium used for the suspension polymerization is prepared by blending the above-mentioned dispersion stabilizer and auxiliary stabilizer in deionized water. The pH of the aqueous phase during suspension polymerization is used It is appropriately determined depending on the type of the dispersion stabilizer, the auxiliary stabilizer and the like. For example, when silica such as colloidal silica is used as the dispersion stabilizer, suspension polymerization is performed in an acidic aqueous phase. To make the aqueous phase acidic, the pH of the aqueous phase may be adjusted to 3 to 6 by adding an acid such as hydrochloric acid as needed. When calcium phosphate, magnesium hydroxide, or the like is used as a dispersion stabilizer, suspension polymerization is performed in an alkaline aqueous phase. To make the aqueous phase alkaline, the pH of the aqueous phase may be adjusted to 8 to 11 by adding a base such as caustic soda as needed.

An example of a preferred combination of the dispersion stabilizer and the co-stabilizer includes a combination of colloidal silica (dispersion stabilizer) and a condensation product (co-stabilizer). As the above condensation product, a condensation product of diethanolamine and an aliphatic dicarboxylic acid is preferable, and among them, a condensation product of diethanolamine and adipic acid and a condensation product of diethanolamine and itaconic acid are preferable. Particularly preferred. These condensation products may be used alone or in combination of two or more. Further, when an inorganic salt such as sodium chloride / sodium sulfate is added, microcapsules having a more uniform particle shape can be easily obtained.

The amount of the above-mentioned colloidal silica may be adjusted depending on the particle size, and is not particularly limited.However, it may be 1 to 20 parts by weight of the colloidal silica with respect to 100 parts by weight of the monomer component. Preferably, it is more preferably 2 to 10 parts by weight. The amount of the condensation product used may be adjusted depending on the kind thereof, and is not particularly limited. However, the amount of the condensation product is 0.0 with respect to 100 parts by weight of the monomer component.

Preferably it is 5 to 2 parts by weight. Further, the amount of the inorganic salt to be used may be adjusted depending on the type thereof, and is not particularly limited. However, the amount of the inorganic salt is 100 parts by weight or less based on 100 parts by weight of the monomer component. Is preferred.

Another example of a preferable combination of the dispersion stabilizer and the co-stabilizer is a combination of colloidal silica (dispersion stabilizer) and a water-soluble nitrogen-containing compound (co-stabilizer). Examples of the water-soluble nitrogen-containing compound include polybutylpyrrolidone, polyethyleneimine, polyoxyethylenealkylamine, polydimethylaminoethyl acrylate, and polydialkylaminoalkyl represented by polydimethylaminoethyl methacrylate. Meta) atarilate, polydimethyla Minopropylacrylamide: polydialkylaminoalkyl (meth) acrylamide represented by polydimethylaminopropylmethacrylamide, polyatarylamide, polycationic acrylamide, polyaminesulfone, polyallylamine, etc. Among them, polyvinylpyrrolidone is particularly preferably used. These water-soluble nitrogen-containing compounds may be used alone or in combination of two or more. In the case of the above combination, in order to adjust the particle size of the microcapsules, the amount of colloidal silica used is preferably fixed to 1 to 20 parts by weight of colloidal silica with respect to 100 parts by weight of the monomer component, and It is preferable to adjust by changing the amount of don used.

Further, another preferred example of the combination of the dispersion stabilizer and the co-stabilizer includes a combination of calcium phosphate or magnesium hydroxide (dispersion stabilizer) with an emulsifier (co-stabilizer).

The order of mixing each component in the aqueous dispersion medium is arbitrary and not particularly limited.However, usually, deionized water, a dispersion stabilizer and, if necessary, an auxiliary stabilizer are charged into a polymerization vessel, and the dispersion is stabilized. An aqueous dispersion medium containing the agent is prepared. If necessary, compounds such as alkali metal nitrite, stannous chloride, stannic chloride and potassium dichromate are added. The monomer component and the volatile swelling agent may be individually added to an aqueous dispersion medium to form an oily mixture in the aqueous dispersion medium. Prepare and add the oily mixture to the aqueous dispersion medium. The polymerization initiator may be added to the oily mixture in advance, or may be added after stirring and mixing the aqueous dispersion medium and the oily mixture in a polymerization vessel. Alternatively, the aqueous dispersion medium and the oily mixture may be mixed in a separate container in advance and mixed by stirring, and then charged into the polymerization vessel.

The particle diameter of the microcapsules obtained by the method for producing thermally expandable microcapsules of the present invention is not particularly limited, but is about 5 to 50 / zm in a state before thermal expansion (unfoamed state). Preferably, there is. The amount of the volatile swelling agent included in the microcapsules is not particularly limited, but is preferably about 10 to 20% by weight. According to the method for producing a heat-expandable microcapsule of the present invention, the amount ratio of acrylonitrile, methacrylonitrile, butyl acetate, and a tetrafunctional or higher crosslinking agent constituting the monomer component is controlled within the above-described specific amounts. Various types of microcapsules exhibiting thermal expansion behavior (foaming behavior) according to the intended use can be manufactured by selecting the type of volatile expanding agent.

The microcapsule produced by the method for producing a heat-expandable microcapsule of the present invention is a polymer obtained from a monomer component containing acrylonitrile, methacrylonitrile, vinyl acetate and a specific amount of a tetrafunctional or higher crosslinker. The wall material is composed of a volatile expander which becomes gaseous at a temperature lower than the softening point of the polymer, and has excellent heat resistance and excellent solvent resistance. Shrinkage and foam breakage are unlikely to occur even under heating conditions, and the expansion ratio does not decrease. In particular, by including vinyl acetate having a high radical reactivity in a small amount of 1 to 10% by weight in the monomer component, it is possible to effectively promote the reaction of methacrylonitrile having a remarkably low growth radical reactivity. . As a result, it becomes possible to increase the polymerization rate of metatarilonitrile, which has high heat resistance, and the microcapsules exhibit remarkably excellent heat resistance and solvent resistance. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to only these Examples.

(Example 1)

220 parts by weight of acrylonitrile, 990 parts by weight of metathallonitrile, 100 parts by weight of vinyl acetate, 5 parts by weight of dipentaerythritol hexatalylate, 64 parts by weight of n-pentane and azobisisop 17 parts by weight of thyronitrile were uniformly stirred and mixed to prepare an oily mixture. Also, 7300 parts by weight of deionized water, silica dispersion (solid content: 20% by weight), 126 parts by weight, potassium dichromate (2.5% by weight aqueous solution) 45 parts by weight, polybutyl Pyrrolidone 8 parts by weight, sodium chloride 220 Parts by weight and 8.5 parts by weight of hydrochloric acid were uniformly stirred and mixed to prepare an aqueous dispersion medium. Next, the obtained oil-based mixture and aqueous dispersion medium are stirred and mixed with a homogenizer, and then charged into a nitrogen-substituted pressure polymerization reactor (20 liters in internal volume), and pressurized with nitrogen at a pressure value of 0.2 MPa. The polymerization was carried out at 60 ° C. for 16 hours. Next, the obtained polymer product was repeatedly filtered and washed with water, and then dried to produce microcapsules having an average particle size of 22 / m.

(Examples 2 and 3),

The oil-based mixtures were each prepared with the composition shown in Table 1, and the average particle diameter was 20 μππι in the same manner as in Example 1 except that the aqueous dispersion medium prepared in Example 1 was used as the aqueous dispersion medium. (Example 2) and 2 / im (Example 3) microcapsules were produced.

(Comparative Examples 1 and 2)

Each of the oily mixtures was prepared with the composition shown in Table 1, and the average particle size was 30 / X by the same method as in Example 1 except that the aqueous dispersion medium prepared in Example 1 was used as the aqueous dispersion medium. m (Comparative Example 1) and 25 μm (Comparative Example 2) microcapsules were produced.

The expansion ratio of the microcapsules obtained in Examples 1 to 3 and Comparative Example 2 was measured by the following method.

The results are shown in Table 1.

(Method of measuring expansion ratio)

Microcapsules and 0 g were placed in a gear oven and heated under the following heating conditions to foam. Next, each of the obtained foams was placed in a measuring cylinder, the volume after foaming was measured, and the foamed volume was divided by the volume when not foamed to obtain a foaming ratio (times). Heating temperature: 140 ° C, 160 ° C, 170 ° C and 180 ° C

Heating time: 1 minute, 2 minutes, 3 minutes and 4 minutes at each of the above heating temperatures ^ atrial from ¹ frfe

Example 1 Actual ^ l

JS example 2 Actual IE example 3 Comparative example 1 Comparative example 2 Acryloni: ethanol 2220 2220 2270 2220 221 0 Oil methacrylonitrile 9 Q 0 820 gg 0 820 700 Properties Vinyl dioxylate 100 1 00 5 O 400 Blended methacryl Methyl acid 1 6 5 2 β 5

To *

Object n pentane R 4. Π R A Π β n R A H fi Λ Π azo'bisiza α nitrile 1 7 1 7

Heat 1 1 π 1 n »* +

Hour 2 1 O 15 ク Q heating temperature

140 C

3 1Rov

Departure

4 Q n Q

Bubbles

Heat 1 2 2 2 5 i o Q Body heat

Hour 2 25 28 25 25 1 6 Heating temperature

of

1 Between 60 ° C

3 25 28 25 23 1 6 departures

4 25 26 23 22 1 5 Foam

Heat 1 40 4 o 3 o 3 o 18 times heat

Hour 2 40 40 30 25 1 5 Heating temperature

Ratio

170 ° C

3 38 35 30 1 8 1 2 minutes

4 36 33 30 1 5 10 times

Heat 1 43 35 28 25 1 5 Heat

Hour 2 4 3 3 3 2 8 2 0 1 3 Heating temperature

while

1 80 ° C

3 40 33 28 1 8 10 minutes

4 40 30 26 1 6 8 According to Table 1, all of the microcapsules produced in Example 13 foamed smoothly at a heating temperature of 160 ° C or higher, and even when heated at a heating temperature of 180 ° C, Little decrease was recognized, and excellent heat resistance and thermal expansion stability (foaming stability) were exhibited. Replacement paper (Rule 26) In contrast, in the microcapsules of Comparative Example 1 in which no beer acetate was contained in the monomer component, a decrease in the expansion ratio was observed at a heating temperature of 170 ° C or more, and the heat resistance and thermal expansion stability ( (Foaming stability) was inferior. In addition, the microcapsules of Comparative Example 2 in which the content of the butyl acetate in the monomer component exceeded 10% by weight had poor heat resistance, and started thermal expansion (foaming) even at 140 ° C. Moreover, at a heating temperature of 160 ° C. or more, shrinkage and foam breakage occurred, and a good foam could not be obtained.

Industrial applicability

ADVANTAGE OF THE INVENTION According to this invention, it has excellent heat resistance and excellent solvent resistance, and it is hard to shrink or break even under high-temperature and long-time heating conditions, and has excellent thermal expansion stability (foaming stability). An efficient and simple method for producing an inflatable microphone-mouth capsule can be provided.

Claims

The scope of the claims

1. acrylonitrile 55-75 wt ^_0/0, and methacrylonitrile Roni Turin les 20-40 wt%, acetic acid Bulle 1-10 wt% and tetrafunctional or more monomer components you a crosslinking agent from 0.1 to 1 wt% A method for producing heat-expandable microcapsules, comprising polymerizing a volatile expander which becomes gaseous at a temperature equal to or lower than the softening point of a polymer obtained from the monomer component under nitrogen pressure to microencapsulate the polymer. .