JPWO2006095567A1 - Recovery method of inclusion substance and novel microspheres obtainable by the method - Google Patents

Abstract

The method for recovering the encapsulating substance comprises a contact step of contacting a microsphere composed of an outer shell made of a thermoplastic resin and an encapsulating substance contained therein with a boiling point not higher than the softening point of the thermoplastic resin, and a solvent. It is a method that includes. The novel microspheres can be obtained after the contacting step in the above-mentioned encapsulation substance recovery method, and use the thermoplastic resin as the outer shell.

Description

  The present invention relates to a method for recovering an encapsulated substance from a microsphere composed of an outer shell made of a thermoplastic resin and an encapsulated substance contained therein, and a novel microsphere obtainable by carrying out the method.

In recent years, along with the tightening of regulations on chemical substances, promotion of resource recycling from used electric appliances and automobiles, etc., there has been a demand for recovery of substances and useful substances that affect the natural environment.
In particular, CFCs (chlorofluorocarbons) are substances that cause the destruction of the ozone layer and global warming. When they are released into the atmosphere and reach the stratosphere, they are decomposed by strong ultraviolet rays from the sun, and the chlorine radicals generated at that time are generated in the stratosphere. It destroys the ozone layer, causes ozone holes, etc., and deteriorates the environmental conditions in the stratosphere. Also, CFCs remaining in the troposphere of the earth are stable compounds that are extremely difficult to decompose, so they are not decomposed and cause the greenhouse effect like carbon dioxide, which promotes global warming and is suitable for the survival of living things. Aggravate the global environment. Therefore, the release of CFCs into the atmosphere has an enormous adverse effect on all living things on earth and humankind.
At present, the recovery of CFC gas has become a global issue to be addressed by humankind, and a technique for recovering CFC gas from a resin material or the like containing CFC gas as a foaming agent is drawing attention.
For example, in Patent Document 1, a crushing material in which fragments of a thermosetting urethane resin containing fluorocarbon gas and a thermoplastic resin are mixed is supplied to a vent type extruder, and the crushing material is finely crushed or melted in a barrel, After collecting the CFC gas separated from the crushed material at the vent part, the crushed material from which the CFC gas has been removed is pushed out from the nozzle connected to the barrel, and the separated CFC gas is separated by a separator in communication with the vent section. A method for recovering CFC gas is disclosed.
Further, in Patent Document 2, the outer plate or inner plate of a heat insulating box body such as a refrigerator filled with foamed heat insulating material is peeled off, and the foamed heat insulating material is crushed by a peeling device and peeled off from the outer plate or inner plate, and a peeling device. The separator and the separated foam insulation used in the above are separated by a separator, and the separated foam insulation is crushed by a crusher to release the CFCs enclosed in the air bubbles inside and released. A method is disclosed in which CFCs are liquefied and recovered by a CFC recovery device to recover CFC gas in a foamed heat insulating material.
All of these methods require a large-scale device because CFCs are collected using physical means such as crushing and melting. In addition, since it is difficult to maintain the airtightness due to the nature of the device, there is a problem that a high recovery rate cannot be expected.
Thermally expandable microcapsules are known as a kind of resin material containing the above-mentioned foaming agent, and have a structure in which a thermoplastic resin is used as an outer shell and an encapsulating substance as a foaming agent is enclosed therein. ing. When such a heat-expandable microcapsule is heated, a part or all of the encapsulating material is vaporized and the volume of the entire encapsulating material is expanded, and further, the outer shell softened by heating is caused by the volume expansion of the encapsulating material. The pressure causes the particles to be pushed outwards, resulting in lightweight hollow particles.
Patent Document 3 discloses a novel heat-expandable microcapsule that eliminates the drawbacks of CFC gas. This heat-expandable microcapsule is characterized by containing, as a foaming agent, a fluorine-containing ether compound which has a small load on the environment, instead of CFC gas.
JP-A-2002-192524 JP, 2000-102923, A International Publication No. 2004/074396 Pamphlet

  Since the fluorine-containing ether compound is more expensive than CFC gas, recovery and reuse are desired from the viewpoint of resource recycling. Further, conventionally, it has not been considered that the heat-expandable microcapsules or the inclusion substances encapsulated in the hollow particles have a great influence on the natural environment. However, now that volatile organic compounds (VOCs) are listed as the causative substances of urban air pollution, it is possible to establish regulations for recovery and reuse of substances that are suspected of having a slight adverse effect on the global environment. I can't deny sex. For these reasons, there is an urgent need to establish a method for recovering any type of entrapped substance.

An object of the present invention is to provide a method for easily and efficiently recovering an encapsulated substance from a microsphere composed of an outer shell made of a thermoplastic resin and an encapsulated substance contained therein. Another object of the present invention is to provide novel microspheres that can be obtained after recovering the encapsulated substance.
When the methods disclosed in Patent Documents 1 and 2 are applied to microspheres, the device is large and difficult to operate, a high recovery rate of the inclusion substance cannot be expected, and physics that consumes a large amount of energy such as crushing and melting. It is expected that there will be problems such as indispensable means.
As a result of various investigations with these problems in mind, the present inventors have found that (1) the microspheres are already in the form of fine particles and have a large surface area. , It is possible to efficiently transfer the encapsulated substance inside the outer shell to the solvent outside the outer shell by utilizing the concentration gradient without damaging the outer shell, and (2) the microspheres that can be obtained after collection are novel microspheres. The present invention has been achieved by finding that it is a sphere.
That is, the method for recovering the encapsulating material according to the present invention is a microsphere composed of an outer shell made of a thermoplastic resin and an encapsulating material contained therein and having a boiling point not higher than the softening point of the thermoplastic resin, and a solvent. Is a method including a contacting step of contacting. The method for recovering the encapsulated substance of the present invention is preferably a method further including a separation step of recovering the encapsulated material from the mixture obtained in the contacting step, and more preferably performing the separating step together with the contacting step.
The novel microspheres according to the present invention can be obtained after the contacting step in the above-mentioned encapsulation substance recovery method, and use the thermoplastic resin as an outer shell.

（式中、ｓは粒子径の標準偏差、＜ｘ＞は平均粒子径、ｘ_ｉはｉ番目の粒子径、ｎは粒子の数である。）
熱膨張性微小球は、外殻および内包物質以外の成分によって付加や修飾等されたものであってもよい。たとえば、熱膨張性微小球においてその外殻の外表面に微粒子充填剤を付着させて用いることが、使用時における分散性の向上及び流動性改善の観点から、好ましい。
微粒子充填剤は、有機系及び無機系充填剤のいずれでもよく、その種類及び量は、使用目的に応じて適宜選定される。
有機系充填剤としては、たとえば、ステアリン酸マグネシウム、ステアリン酸カルシウム、ステアリン酸亜鉛、ステアリン酸バリウム、ステアリン酸リチウム等の金属セッケン類；ポリエチレンワックス、ラウリン酸アミド、ミリスチン酸アミド、パルミチン酸アミド、ステアリン酸アミド、硬化ひまし油等の合成ワックス類；ポリアクリルアミド、ポリイミド、ナイロン、ポリメタクリル酸メチル、ポリエチレン、ポリテトラフルオロエチレン等の樹脂粉体等が挙げられる。
無機系充填剤としては、層状構造を有するもの、たとえば、タルク、マイカ、ベントナイト、セリサイト、カーボンブラック、二硫化モリブデン、二硫化タングステン、弗化黒鉛、弗化カルシウム、窒化ホウ素等；その他、シリカ、アルミナ、雲母、炭酸カルシウム、水酸化カルシウム、リン酸カルシウム、水酸化マグネシウム、リン酸マグネシウム、硫酸バリウム、二酸化チタン、酸化亜鉛、セラミックビーズ、ガラスビーズ、水晶ビーズ等が挙げられる。
これらの微粒子充填剤は、１種または２種以上を併用してもよい。
外殻の外表面に付着する微粒子充填剤は、上記のうち、融点９０℃以上（好ましくは１００℃以上、より好ましくは１１０℃以上、さらに好ましくは１２０℃以上、特に好ましくは１５０℃以上、最も好ましくは２００℃以上の融点を有する）の有機化合物又は層状構造を有する無機化合物（好ましくはカーボンブラック、二硫化モリブデン、二硫化タングステン、弗化黒鉛および窒化ホウ素から選ばれた少なくとも１種）、つまり、熱融着防止剤であることが好ましい。ここで、熱融着防止剤は、熱膨張性微小球および／または熱膨張した微小球の外殻樹脂の熱融着を防止し、さらに、加熱膨張時にも隣接する熱膨張性微小球および／または熱膨張した微小球との熱融着を防止し、発泡性能を損なわない働きをするものとする。これにより、例えば、熱膨張性微小球を膨張させて得られ、再膨張できる余力を有する熱膨張した微小球を、タイヤとリムとの組立体内部に充填した場合、タイヤが受傷してタイヤ内圧が低下したとしても、速やかにタイヤ受傷部を封止し、高いタイヤ内圧付与機能を発揮させることができ、その結果、受傷したタイヤでも、必要な距離を走行させることができる。この効果は、特に、発泡剤が含弗素化合物を含む場合に顕著である。
また、ニトリル系単量体とカルボキシル基含有単量体とを必須成分として含む単量体混合物を重合して得られる熱可塑性樹脂を外殻に用いた熱膨張性微小球の場合には、耐熱性、難燃（不燃）性において良好な性能を発揮させることができるとともに、熱膨張性微小球を膨張させて得られ、再膨張できる余力を有する熱膨張した微小球に対して、９０℃以上（好ましくは１００℃以上、さらに好ましくは１２０℃以上）の温度で再膨張開始させることができ、上記効果が顕著となる。
微粒子充填剤の平均粒子径は、付着前の熱膨張性微小球の平均粒子径の１／１０以下であることが好ましい。ここで、平均粒子径とは、一次粒子における平均粒子径を意味する。
熱膨張性微小球への微粒子充填剤の付着量は、特に限定はないが、微粒子充填剤による機能を十分に発揮でき、熱膨張性微小球の真比重の大きさ等を考慮すると、付着前の熱膨張性微小球に対して好ましくは０．１〜９５重量％、さらに好ましくは０．５〜６０重量％、特に好ましくは５〜５０重量％、最も好ましくは８〜３０重量％である。
熱膨張性微小球の外表面への微粒子充填剤の付着は、熱膨張性微小球と微粒子充填剤とを混合することによって行うことができる。混合については、特に限定はなく、容器と攪拌バネといった極めて簡単な機構を備えた装置を用いて行うことができる。また、一般的な揺動または攪拌を行える粉体混合機を用いてもよい。粉体混合機としては、たとえば、リボン型混合機、垂直スクリュー型混合機等の揺動攪拌または攪拌を行える粉体混合機を挙げることができる。また、近年、攪拌装置を組み合わせたことにより効率のよい多機能な粉体混合機であるスーパーミキサー（株式会社カワタ製）及びハイスピードミキサー（株式会社深江製）、ニューグラムマシン（株式会社セイシン企業製）等を用いてもよい。
なお、熱膨張性微小球は、例えば、そのままタイヤとリムとの組立体内部に充填し、熱膨張性微小球の膨張開始温度以上の温度で加熱することにより膨張させて、体積保持材として使用することができる。また、そのまま、自動車等の塗料の軽量化充填剤、壁紙や衣服装飾用の発泡インク用発泡粒子、樹脂組成物軽量化のための発泡材等の用途に使用してもよい。
次に、熱膨張した微小球について説明する。
ｂ．熱膨張した微小球
熱膨張した微小球は、上記で説明した熱膨張性微小球を熱膨張させて得られる。熱膨張した微小球を製造する方法については、熱膨張性微小球を加熱して熱膨張させる工程を含む製造方法であれば特に限定はなく、従来公知の方法を適用することができるが、なかでも、以下に示す２つの方法を好ましい方法として挙げることができる。
（Ａ）上記で説明した熱膨張性微小球（原料）を含む気体流体を、出口に分散ノズルを備え且つ熱風流の内側に設置された気体導入管に流し、前記分散ノズルから噴射させる工程（噴射工程）と、前記気体流体を前記分散ノズルの下流部に設置された衝突板に衝突させ、熱膨張性微小球を前記熱風気流中に分散させる工程（分散工程）と、分散した熱膨張性微小球を前記熱風気流中で膨張開始温度以上に加熱して膨張させる工程（膨張工程）とを含む製造方法。
（Ｂ）上記で説明した熱膨張性微小球（原料）を含む気体流体を、出口に分散ノズルを備え且つ熱風流の外部に設置された少なくとも１つの気体導入管に流し、前記分散ノズルから噴射させ、熱膨張性微小球を前記熱風流中に分散させる工程（分散工程）と、分散した熱膨張性微小球を前記熱風流中で膨張開始温度以上に加熱して膨張させる工程（膨張工程）とを含む製造方法。
上記製造方法においては、エネルギー効率が高く、温度制御が容易で、原料であるどの熱膨張性微小球に対してもほぼ同一の熱履歴を連続的に与えることができ、気流中での分散性が高い。このため、膨張前後における粒度分布の変動係数の変化が小さく、得られた熱膨張した微小球の品質（特に、粒子径分布および真比重の分布）の均一性が高い。すなわち、得られた熱膨張した微小球に含まれる凝集微小球の生成をできるだけ抑制することができ、しかも、原料やわずかに膨張した微小球の含有率を極めて小さくすることができる。
また、上記の製造方法において、膨張条件を制御することによって、得られる熱膨張した微小球が再膨張開始温度を有するようにも、有しないようにもすることができる。なお、微小球が再膨張開始温度を有するとは、一旦製造された熱膨張した微小球がなお熱膨張する性質を有しており、熱膨張した微小球を加熱すると、再び加熱膨張する現象が見られることを意味する。そして、その加熱膨張し始める温度を再膨張開始温度と称する。また、熱膨張した微小球が再膨張開始温度を有することは、最大（再）膨張温度における膨張倍率が１００％超であることと同義である。一方、微小球が再膨張開始温度を有しないとは、微小球がほぼ完全に熱膨張したことを意味する。
膨張条件の制御については、特に限定はない。たとえば、まず、原料供給量、熱風流量や原料分散気体量等のパラメーターを一定に固定し、熱風流の温度（以下、「熱風温度」ということがある。）を変化させる。次に、熱風温度を段階的に変化させ、かつ、他のパラメーターを一定に固定しながら各温度で原料微小球を膨張させ、得られた微小球の真比重を測定し、熱風温度（ｘ軸）と真比重（ｙ軸）の関係をプロットしたグラフを作成する。このグラフにおいて、最低真比重（グラフにおける極小値）に対応する温度領域を熱風温度に設定することによって、得られる熱膨張した微小球が再膨張開始温度を有しないように製造することができる。
また、所望の真比重を有する膨張した微小球を製造する場合は、そのグラフにおいて所望の真比重に対応する熱風温度に設定する。これにより、膨張条件の制御が行われ、所望の再膨張できる余力を有する熱膨張した微小球を製造することができる。
さらに、原料供給量および／または原料分散気体量を変化させる場合、熱風気流により供給される熱量や原料である熱膨張性微小球の全熱容量等を考慮して、熱風温度等を変化させて、膨張条件を制御する。例えば、原料供給量および原料分散気体量を増加させる場合は、熱風温度を上げる。原料供給量および原料分散気体量を減少させる場合は、熱風温度を低くする。
上記製造方法においては、エネルギー効率が高く、温度制御が容易で、原料であるどの熱膨張性微小球に対してもほぼ同一の熱履歴を連続的に与えることができ、気流中での分散性が高い。このため、膨張前後における粒度分布の変動係数の変化が小さく、得られた熱膨張した微小球の品質（特に、粒子径分布および真比重の分布）の均一性が高い。すなわち、得られた熱膨張した微小球に含まれる凝集微小球の生成をできるだけ抑制することができ、しかも、原料やわずかに膨張した微小球の含有率を極めて小さくすることができる。
このようにして得られた熱膨張した微小球は、たとえば、ランフラットタイヤの主要部材として利用できる。すなわち、タイヤとリムとの組立体内部に熱膨張した微小球を充填することにより、タイヤが受傷して、タイヤ内圧が低下した際に、タイヤ受傷部封止材および／またはタイヤ内圧付与材として使用することができる。
熱膨張した微小球の平均粒子径は、特に限定はされず、用途に応じて自由に設計することができる。例えば、外殻による発泡剤の内包保持率、熱膨張した微小球の耐久性等を考慮すると、好ましくは１〜１０００μｍ、さらに好ましくは５〜８００μｍ、特に好ましくは１０〜５００μｍである。
熱膨張した微小球中に含まれる真比重０．７９ｇ／ｃｃ以上の微小球の含有率（２５℃）は、真比重の均一性を考慮し、内包物質を高い効率で回収し、形状の良好な新規な微小球を得るためには、５重量％以下であることが好ましく、より好ましくは３重量％以下、さらに好ましくは２重量％以下、特に好ましくは１重量％以下である。０．７９ｇ／ｃｃ以上の微小球の含有率は、イソプロピルアルコール（２５℃における比重：０．７９）を用いた比重差分離後の沈降成分の定量により測定される。また、本発明において真比重の測定は、たとえば、試料０．５〜２．０ｇについて、温度２５℃においてイソプロピルアルコールを用いた液置換法（アルキメデス法）により行う。なお、ここでいう真比重は、熱膨張した微小球の１個について真比重を測定した値ではなく、熱膨張した微小球の集合体について真比重を測定した値であり、平均真比重を意味する。
熱膨張した微小球の外殻の厚みについても、特に限定はないが、内包物質を高い効率で回収し、形状の良好な新規な微小球を得るためには、好ましくは０．１〜２０μｍ、より好ましくは０．２〜１０μｍ、さらに好ましくは０．２〜５μｍ、特に好ましくは０．２〜１μｍである。外殻の厚みは、熱膨張した微小球の平均粒子径、発泡剤の内包率、前記液置換法（アルキメデス法）によって測定された真比重から算出される。その算出方法は、以下に示すとおりである。
（１）まず、平均粒子径を有する熱膨張した微小球１粒について考え、その総体積を平均粒子径から算出し、その総重量を真比重から算出し、得られた総重量と発泡剤の内包率から発泡剤ガス重量を算出する。
（２）次いで、総重量と発泡剤ガス重量との差を外殻の重量とし、この外殻の重量と外殻の比重から外殻の体積を算出する。
（３）さらに、総体積と外殻の体積との差を外殻内部の体積とし、この外殻内部の体積から外殻内部の半径を算出する。
（４）最後に、平均粒子径を２で割って平均粒子半径を算出し、この平均粒子半径と外殻内部の半径との差を算出し、外殻の厚みが計算される。
熱膨張した微小球は、再膨張開始温度を有していなくてもよいし、有していてもよい。特に、熱膨張した微小球が再膨張開始温度を有しない場合や、再膨張開始温度を有していても、熱膨張した微小球の再膨張倍率が１００〜５００％の範囲にある場合は、外殻を構成する熱可塑性樹脂の厚みが薄くて、内包物質が外殻を透過しやすくなり、内包物質を高効率で回収できる。
本発明で用いる微小球は、以上説明した熱膨張性微小球や熱膨張した微小球をそのまま使用しても良いが、資源の回収、再利用の観点からは、熱膨張性微小球や熱膨張した微小球をある用途に使用した使用済の微小球が好ましい。
上記用途としては、熱膨張性微小球や熱膨張した微小球が有する種々の特性を利用した用途であれば特に限定はない。上記特性としては、たとえば、意匠性、多孔性、嵩高性、スリッップ防止性、収縮防止性（寸法安定性）、軽量化（コストダウン）、断熱性（保温性、保冷性）、衝撃吸収性（反発弾性）、防音性、制振性、剛性、表面改質性（艶消し、ソフト感付与）、隠蔽性、易剥離性、目止性等を挙げることができる。具体的な用途としては、ランフラットタイヤの主要部材（タイヤとリムとの組立体内部に熱膨張した微小球を充填することにより、タイヤが受傷して、タイヤ内圧が低下した際に、タイヤ受傷部封止材および／またはタイヤ内圧付与材として使用）、ゴムや樹脂の内部添加剤（ゴムや樹脂に添加し、たとえば、加熱成形時に発泡させ、得られる部材の軽量化剤として使用）等を挙げることができる。
次に、以上で説明した微小球中の内包物質を回収する方法を詳しく説明する。
［内包物質の回収方法］
本発明の内包物質の回収方法は、上記で説明した微小球と溶媒とを接触させる接触工程を含む方法である。
この接触工程で使用する溶媒としては、液体であれば特に限定はないが、通常、溶媒の極性の程度、微小球の外殻を構成する熱可塑性樹脂の種類、後述する分離工程における操作性等を考慮して選定される。
溶媒としては、たとえば、水；メタノール、エタノール、プロパノール、エチレングリコール、グリセリン等のアルコール類；プロピルエーテル、ブチルエーテル、ペンチルエーテル、ヘキシルエーテル等のエーテル類；ギ酸メチル、ギ酸エチル、ギ酸プロピル、ギ酸ブチル、酢酸メチル、酢酸エチル、酢酸プロピル、酢酸ブチル、プロピオン酸メチル、プロピオン酸エチル、プロピオン酸プロピル、プロピオン酸ブチル等のエステル類；アセトン、メチルエチルケトン、シクロヘキサノン、ピナコリン、メシチルオキシド等のケトン類；ヘキサン、ヘプタン、オクタン、ノナン、デカン、ウンデカン、ドデカン、シクロヘキサン、メチルシクロヘキサン等の脂肪族炭化水素；ベンゼン、トルエン、キシレン、エチルベンゼン、フェニルアセチレン等の芳香族炭化水素；アセトニトリル、プロピオニトリル等のニトリル類；ジメチルホルムアミド（ＤＭＦ）等のアミド類；ジメチルスルホキサイド（ＤＭＳＯ）等のスルホキサイド類等を挙げることができる。これらの溶媒は、１種または２種以上を併用してもよい。
本発明の回収方法においては、極性溶媒を用いると、内包物質を高効率で回収できるため好ましい。極性溶媒としては、たとえば、水、アルコール類、エーテル類、エステル類、ケトン類、ニトリル類、アミド類、スルホキサイド類等を挙げることができる。これらの極性溶媒の内でも、水、アルコール類が好ましく、また、本発明の回収方法で得られる新規な微小球が良好な形状を保持し、内包物質の単離が容易であるという観点からは、水がさらに好ましい。
極性溶媒はさらに酸性やアルカリ性を示す溶媒であってもよいが、微小球の外殻を構成する熱可塑性樹脂が、カルボキシル基含有単量体等の酸性単量体を含む単量体混合物を重合して得られる場合は、極性溶媒がアルカリ性を示すと好ましく、極性溶媒がアルカリ性を示す水および／またはアルコール類（特にエタノール等）であるとさらに好ましく、本発明の回収方法で得られる新規な微小球が良好な形状を保持し、内包物質の単離が容易であるという観点からは、アルカリ性を示す水が特に好ましい。極性溶媒がアルカリ性を示す場合、極性溶媒のｐＨについては、特に限定はないが、９〜１４が好ましく、１１〜１３がさらに好ましい。
接触工程においては、微小球と溶媒とを混合して接触させる。微小球と溶媒との混合比率については、特に限定はないが、回収効率の向上や、経済性等を考慮すると、溶媒１Ｌ当たりの微小球が０．１〜３０００ｇであると好ましく、１０〜２０００ｇであるとさらに好ましく、１００〜１０００ｇであると特に好ましい。
接触工程における微小球と溶媒との接触時間は、溶媒、内包物質、微小球の外殻を構成する熱可塑性樹脂や、作業性等を考慮して適宜設定され、特に限定はないが、たとえば０．１〜１０００時間である。
接触工程における微小球と溶媒との接触温度は、接触時間と同様に適宜設定され、特に限定はない。しかし、余りにも低い温度で両者を接触させることは操作上有利ではないことや、内包物質の沸点が通常室温あるいはそれよりもやや高い温度である場合が多いことを考慮すると、接触温度は、たとえば−５０〜１００℃である。また、接触温度は内包物質の沸点以下が好ましい。
接触工程における接触時間および接触温度は、微小球の外殻の厚みを考慮して適宜設定してもよい。
微小球の外殻の厚みが２μｍ以上の場合（たとえば、微小球が熱膨張性微小球の場合）、内包物質の回収効率の向上を考慮すると、接触工程における接触時間は、１〜１０００時間であると好ましく、１０〜１０００時間であるとさらに好ましく、１００〜１０００時間であると特に好ましい。接触工程における接触温度は、３０〜１００℃であると好ましく、５０〜１００℃であるとさらに好ましく、７０〜１００℃であると特に好ましい。この場合に使用する溶媒としては、微小球と溶媒との接触温度以上の沸点を持つものが望ましく、上記で例示した溶媒のうちでも、沸点５０℃以上の溶媒を挙げることができる。
次に、微小球の外殻の厚みが２μｍ未満の場合（たとえば、微小球が熱膨張した微小球の場合）、内包物質の回収効率の向上を考慮すると、接触工程における接触時間は、０．１〜５００時間であると好ましく、０．１〜１００時間であるとさらに好ましい。接触工程における接触温度は、０〜８０℃であると好ましい。この場合に使用する溶媒としては、微小球と溶媒との接触温度以上の沸点を持つものが望ましく、上記で例示した溶媒のうちでも、沸点２０℃以上の溶媒を挙げることができる。
本発明の内包物質の回収方法においては、微小球と溶媒とを接触させることによって、微小球に内包された内包物質を回収することができる。その作用については、確証はないが、外殻を構成する熱可塑性樹脂が溶媒によって膨潤や変質し、内包された内包物質が濃度勾配にしたがって溶媒中に透過、拡散するものと推測される。
本発明の内包物質の回収方法は、分離工程をさらに含むと好ましい。分離工程は、前記接触工程で得られた微小球および溶媒を含む混合物から前記内包物質を回収する工程である。
分離工程は、接触工程とともに行ってもよく、接触工程後に行ってもよいが、分離工程を接触工程とともに行うことによって、内包物質を短時間で分離回収することができる。
分離工程を行う具体的な手段については、特に限定はなく、たとえば、内包物質の蒸留分離、抽出分離、遠心分離、吸着分離等を挙げることができる。
蒸留分離は、内包物質と溶媒との沸点差を利用して内包物質を分離回収する方法である。沸点差は、作業効率を上げるために沸点差を大きくする方が好ましい。沸点差は、たとえば、５℃以上が好ましく、１０℃以上がさらに好ましく、２０℃以上が特に好ましい。蒸留分離においては、内包物質を一旦蒸気化させ冷却装置で液化して分離するが、内包物質の沸点が通常室温あるいはそれよりもやや高い温度である場合が多いことを考慮して、冷却装置や液化した内包物質の貯蔵器等に用いる冷媒の温度を低めに制御することが好ましい。冷媒の温度と内包物質の沸点との温度差は、たとえば、３０℃以上が好ましく、５０℃以上がさらに好ましく、１００℃以上が特に好ましい。
抽出分離および遠心分離は、いずれも内包物質と溶媒とが相分離する性質を利用して分離回収する方法である。抽出分離や遠心分離を行う場合、溶媒としては、内包物質と混合した場合に相分離する性質を有するものが好ましい。溶媒としては、たとえば、水；メタノール、エタノール等のアルコール類等を挙げることができる。抽出分離で容易に相分離しない場合、遠心分離を行って内包物質と溶媒とを相分離させてもよい。抽出分離や遠心分離によって相分離させた内包物質は、デカンテーション等の分液操作を経て、分離回収される。
吸着分離は、気化した物質を活性炭などの吸着剤を用いた吸着ユニットにより捕捉して回収する方法である。吸着ユニットに捕捉された物質は蒸気により脱着されて再生され、深冷凝縮によって液化回収される。
上記接触工程および分離工程において、微小球および溶媒を含む混合物を攪拌してもよいし、攪拌しなくてもよいが、攪拌した場合は、微小球および溶媒の接触効率が高まると考えられる。前記攪拌に用いる攪拌機については、特に限定はなく、たとえば、ホモミキサーやラインミキサー等の一般的な攪拌機を挙げることができる。攪拌速度についても特に限定はない。
上記接触工程および分離工程を行うにあたり、その圧力雰囲気についても特に限定はなく、減圧下、常圧下、加圧下のいずれの圧力下で行ってもよい。
次に、接触工程後に得ることができる新規な微小球について説明する。
［新規な微小球］
本発明の新規な微小球（以下、微小球ａということがある。）は、上記回収方法における接触工程後に得ることができ、熱可塑性樹脂を外殻としている微小球である。
微小球ａは、その外殻に内包物質に代わって溶媒が内包されており、新規な微小球である。微小球ａでは少なくとも溶媒が内包されているが、回収されずに残った内包物質が溶媒とともに内包されていてもよい。
接触工程後の混合物から溶媒を除去して乾燥した微小球ａを単離してもよいが、凝集や融着が生じない点を考慮すると、微小球ａを液体で湿潤された状態で取扱う方が好ましい。
上記液体としては、上記回収方法で説明した溶媒をそのまま用いることができるが、微小球ａの用途に応じて、ジブチルフタレート、ジイソオクチルフタレート、ジオクチルアジベート、トリクレジルホスフェート、トリエチルシトレート、アセチルトリブチルシトレート、オクチルアルコール等の可塑剤（プラスチック、エラストマー、シーラント、塗料等に用いる場合）；ジシクロペンタジエンやスチレン等の単量体（軽量発泡成形体や接着剤用に用いる場合）；非イオン界面活性剤、アルキレングリコール、ポリアルキレングリコール、グリセリン、シリコーンオイル、流動パラフィン、油脂類等を、液体として用いてもよい。接触工程後の混合物中の溶媒を、液体に置換することによって微小球ａを液体で湿潤された状態にすることができる。
微小球ａの平均粒子径については、特に限定はないが、微小球ａが湿潤された状態の場合、好ましくは１〜１０００μｍ、さらに好ましくは５〜８００μｍ、特に好ましくは１０〜５００μｍ、最も好ましくは１〜１５０μｍである。
微小球ａの真比重については、特に限定はないが、微小球ａが乾燥された状態の場合、好ましくは０．００１〜１．５ｇ／ｃｃ、さらに好ましくは０．００１〜１．０ｇ／ｃｃ、特に好ましくは０．００１〜０．８ｇ／ｃｃである。
微小球ａの用途については、前述の熱膨張性微小球や熱膨張した微小球が有する種々の特性を利用した用途や、微小球ａが微小な粒子状であることを利用した用途であれば特に限定はない。微小球ａを、樹脂等の有機材料、無機材料等の充填材として利用してもよく、例えば、押出しセメント成形品やシーリング剤のフィラー、樹脂粘土のフィラー、窯業サイディングの補強フィラー、木質繊維板の補強フィラー、手洗い石鹸や業務用洗剤の研磨剤、ブロッキング防止剤、平滑性付与剤、軽量骨材の代替物、多孔化付与剤、流動化剤、粉塵防止剤、緑化促進剤、法面侵食防止剤等が挙げられる。First, the microspheres containing the inclusion substance used in the present invention will be described.
[Microsphere]
The microspheres used in the present invention are microspheres composed of an outer shell made of a thermoplastic resin and an encapsulated substance contained therein and having a boiling point not higher than the softening point of the thermoplastic resin.
The encapsulation rate of the encapsulating substance contained in the microspheres is not particularly limited, but from the viewpoint of improving the work efficiency in recovering the encapsulating substance, preferably 5% or more, more preferably 15% or more, particularly preferably Is 30% or more.
The encapsulation rate of the encapsulation substance (hereinafter, also referred to as the encapsulation rate of the foaming agent) is a value expressed as a percentage of the weight of the encapsulation substance encapsulated in the microspheres with respect to the weight of the microspheres.
The microspheres used in the present invention are roughly classified into thermally expandable microspheres and thermally expanded microspheres (obtained by thermally expanding the thermally expandable microspheres). These will be described in detail below.
a. Thermally expandable microsphere
The heat-expandable microspheres are composed of an outer shell made of a thermoplastic resin and an encapsulating substance that is included in the outer shell and has a boiling point not higher than the softening point of the thermoplastic resin. The encapsulating substance acts as a foaming agent. , The heat-expandable microspheres exhibit heat-expandability as a whole microsphere (the property that the whole microsphere expands by heating). In the following description, the inclusion substance and the foaming agent are used synonymously.
The foaming agent is not particularly limited as long as it has a boiling point not higher than the softening point of the thermoplastic resin, and examples thereof include hydrocarbons having 1 to 12 carbon atoms and their halides; fluorine-containing compounds; tetraalkylsilanes; azodicarbons. Examples thereof include compounds that are thermally decomposed by heating an amide or the like to generate gas. These foaming agents may be used alone or in combination of two or more.
Examples of the hydrocarbon having 1 to 12 carbon atoms include propane, cyclopropane, propylene, butane, normal butane, isobutane, cyclobutane, normal pentane, cyclopentane, isopentane, neopentane, normal hexane, isohexane, cyclohexane, heptane, cycloheptane. , Octane, isooctane, cyclooctane, 2-methylpentane, 2,2-dimethylbutane, petroleum ether and the like. These hydrocarbons may be linear, branched or alicyclic and are preferably aliphatic.
Examples of the hydrocarbon halide having 1 to 12 carbon atoms include methyl chloride, methylene chloride, chloroform and carbon tetrachloride. These halides are preferably the above-mentioned hydrocarbon halides (fluoride, chloride, bromide, iodide, etc.).
The fluorine-containing compound is not particularly limited, and for example, a compound having an ether structure, containing no chlorine atom and bromine atom, and having 2 to 10 carbon atoms is preferable. Specifically, C _Three H _Two F ₇ OCF _Two H, C _Three HF ₆ OCH _Three , C _Two HF _Four OC _Two H _Two F _Three , C _Two H _Two F _Three OC _Two H _Two F _Three , C _Four HF ₈ OCH _Three , C _Three H _Two F ₅ OC _Two H _Three F _Two , C _Three HF ₆ OC _Two H _Two F _Three , C _Three H _Three F _Four OCHF _Two , C _Three HF ₆ OC _Three H _Two F ₅ , C _Four H _Three F ₆ OCHF _Two , C _Three H _Three F _Four OC _Two HF _Four , C _Three HF ₆ OC _Three H _Three F _Four , C _Three F ₇ OCH _Three , C _Four F ₉ OCH _Three , C _Four F ₉ OC _Two H ₅ , C ₇ F ₁₅ OC _Two H ₅ And other hydrofluoroethers. The (fluoro)alkyl group of the hydrofluoroether may be linear or branched.
The foaming agent may be composed of, for example, the entire amount of a fluorine-containing compound, but a substance other than the fluorine-containing compound having a boiling point not higher than the softening point of the thermoplastic resin may be used together with the fluorine-containing compound. .. Such a substance is not particularly limited, and for example, it can be selected and used from those exemplified as the above-mentioned foaming agent. The substance other than the fluorine-containing compound can be appropriately selected according to the thermal expansion temperature range of the thermally expandable microspheres.
In the foaming agent, the weight ratio of the fluorine-containing compound is preferably more than 50% by weight, more preferably more than 80% by weight, particularly preferably more than 95% by weight, based on the whole blowing agent. As the weight ratio of the fluorine-containing compound in the foaming agent is higher, the physical properties of the fluorine-containing compound are reflected in the heat-expandable microspheres, and the heat-expandable microspheres can be given physical properties such as flame retardancy and nonflammability. it can.
The heat-expandable microspheres are composed of, for example, a thermoplastic resin obtained by polymerizing a monomer mixture containing a radical-polymerizable monomer, and by appropriately adding a polymerization initiator to the monomer mixture, heat An outer shell of expandable microspheres can be formed.
The radical-polymerizable monomer is not particularly limited, and examples thereof include nitrile-based monomers such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile, and fumaronitrile; acrylic acid, methacrylic acid, and itaconic acid. Carboxyl group-containing monomers such as maleic acid, fumaric acid and citraconic acid; vinylidene chloride; vinyl acetate; methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, (Meth)acrylic acid ester-based monomers such as t-butyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, β-carboxyethyl acrylate; styrene, α-methylstyrene , Styrene-based monomers such as chlorostyrene; acrylamide-based monomers such as acrylamide, substituted acrylamide, methacrylamide, and substituted methacrylamide; N-phenylmaleimide, N-(2-chlorophenyl)maleimide, N-cyclohexylmaleimide, N And maleimide-based monomers such as lauryl maleimide. Regarding the carboxyl group-containing monomer, some or all of the carboxyl groups may be neutralized during polymerization.
These radically polymerizable monomers may be used alone or in combination of two or more. Among these, the monomer mixture was selected from nitrile-based monomers, (meth)acrylic acid ester-based monomers, carboxyl group-containing monomers, styrene-based monomers, vinyl acetate and vinylidene chloride. It is preferably a monomer mixture containing at least one radically polymerizable monomer. In particular, when the monomer mixture is a monomer mixture containing a nitrile monomer as an essential component, heat resistance can be imparted, which is preferable. The weight ratio of the nitrile-based monomer is preferably 80% by weight or more, more preferably 90% by weight or more, particularly preferably 95% by weight or more, in consideration of heat resistance with respect to the monomer mixture. Is.
Further, when the monomer mixture is a monomer mixture containing a carboxyl group-containing monomer as an essential component together with a nitrile monomer, heat resistance can be imparted, and by expanding the heat-expandable microspheres. The resulting heat-expanded microspheres can be manufactured so as to have a re-expansion capacity, and re-expansion is initiated at a temperature of 90° C. or higher (preferably 100° C. or higher, more preferably 120° C. or higher). Since it can be set as follows, it is more preferable. The weight ratio of the nitrile-based monomer is such that the encapsulation retention rate and the foamability of the encapsulating foaming agent, further adjusting the re-expansion start temperature of the thermally expanded microspheres, usually considering the internal pressure high-speed running performance evaluation and the like. It is preferably 20 to 95% by weight, more preferably 20 to 80% by weight, further preferably 20 to 60% by weight, and particularly preferably 20 to 50% by weight, based on the monomer mixture. And most preferably 20 to 40% by weight. Further, the weight ratio of the carboxyl group-containing monomer is such that the re-expansion start temperature of the thermally expanded microspheres is adjusted, the normal internal pressure high-speed running performance evaluation, and the inclusion retention rate and the foamability of the encapsulated foaming agent, etc. Considering the above, it is preferably 5 to 80% by weight, more preferably 20 to 80% by weight, still more preferably 40 to 80% by weight, and particularly preferably 50 to 80% by weight based on the monomer mixture. % By weight, most preferably 60-80% by weight.
When the monomer mixture contains a carboxyl group-containing monomer as an essential component, it reacts with the carboxyl group of the carboxyl group-containing monomer as a monomer other than the carboxyl group-containing monomer contained in the monomer component. It may contain a monomer. Examples of the monomer that reacts with the carboxyl group of the carboxyl group-containing monomer include N-methylol (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth). Acrylate, magnesium mono(meth)acrylate, zinc mono(meth)acrylate, vinyl glycidyl ether, propenyl glycidyl ether, glycidyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy Butyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate and the like can be mentioned. The weight ratio of the monomer that reacts with the carboxyl group of the carboxyl group-containing monomer is preferably 0.1 to 10% by weight, more preferably 1 to 8% by weight, based on the monomer mixture. , And most preferably 3 to 5% by weight.
The monomer mixture may contain a polymerizable monomer (crosslinking agent) having two or more polymerizable double bonds in addition to the above radical polymerizable monomer. By polymerizing with a cross-linking agent, the content of aggregated microspheres contained in the thermally expanded microspheres obtained by this production method becomes smaller, and the retention of the encapsulated foaming agent after thermal expansion (inclusion retention) Rate) is suppressed, and thermal expansion can be effectively performed.
In the present invention, the encapsulation retention rate (%) of the foaming agent after thermal expansion is the encapsulation rate of the foaming agent encapsulated in the heat-expandable microspheres before expansion by G ₁ And the encapsulation rate of the foaming agent contained in the thermally expanded microspheres obtained by thermal expansion is G _Two Then, G _Two /G ₁ It is defined as ×100.
The cross-linking agent is not particularly limited, and examples thereof include aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; allyl methacrylate, triacrylic formal, triallyl isocyanate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth). Acrylate, triethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, PEG#200. Di(meth)acrylate, PEG#400 di(meth)acrylate, PEG#600 di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol di( (Meth)acrylate, 1,9-nonanediol di(meth)acrylate, trimethylolpropane trimethacrylate, glycerine dimethacrylate, dimethylol-tricyclodecane diacrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetraacrylate, di Pentaerythritol hexaacrylate, neopentyl glycol acrylic acid benzoate, trimethylolpropane acrylic acid benzoate, 2-hydroxy-3-acryloyloxypropyl methacrylate, hydroxypivalic acid neopentyl glycol diacrylate, ditrimethylolpropane tetra Examples thereof include di(meth)acrylate compounds such as acrylate and 2-butyl-2-ethyl-1,3-propanediol diacrylate. These cross-linking agents may be used alone or in combination of two or more.
The weight ratio of the cross-linking agent is not particularly limited, but considering the degree of cross-linking, the encapsulation retention rate of the foaming agent encapsulated in the outer shell, the heat resistance and the thermal expansion property, it is preferable for the monomer mixture. Is 0.01 to 5% by weight, and more preferably 0.05 to 3% by weight.
The polymerization initiator is not particularly limited, and known polymerization initiators can be used. For example, t-butylperoxyisobutyrate, t-butylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, 2,5-dimethyl-2,5-bis(2 -Ethylhexanoylperoxy)hexane, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, t-butylperoxypivalate, t-hexylperoxypivalate, t-butylper Oxyneodecanoate, t-hexylperoxyneodecanoate, 1-cyclohexyl-1-methylethylperoxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, Kumi Ruperoxy neodecanoate, di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, bis(4-t-butylcyclohexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, di-2 -Ethoxyethyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, di-3-methoxybutyl peroxydicarbonate 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearyl Peroxides such as peroxides, succinic acid peroxides, benzoyl peroxides; 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, Azo compounds such as 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylpropionate) and 2,2'-azobis(2-methylbutyronitrile) Can be mentioned. The polymerization initiator is preferably an oil-soluble polymerization initiator that is soluble in the radically polymerizable monomer.
The heat-expandable microspheres can be manufactured by various methods used in the conventionally known methods for manufacturing heat-expandable microcapsules.
That is, a monomer mixture containing a radically polymerizable monomer as an essential component and optionally a cross-linking agent, a polymerization initiator, and a foaming agent are mixed, and the resulting mixture is mixed with an aqueous suspension containing an appropriate dispersion stabilizer. It is a method of suspension polymerization in a suspension.
As the dispersion stabilizer in the aqueous system, colloidal silica, colloidal calcium carbonate, magnesium hydroxide, calcium phosphate, aluminum hydroxide, ferric hydroxide, calcium sulfate, sodium sulfate, calcium oxalate, calcium carbonate, barium carbonate, magnesium carbonate, alumina sol. Etc. The dispersion stabilizer is preferably used in a proportion of 0.1 to 20% by weight based on the monomer mixture. In addition, as a dispersion stabilizing aid, a condensation product of diethanolamine and an aliphatic dicarboxylic acid, gelatin, polyvinylpyrrolidone, methylcellulose, polyethylene oxide, a high molecular type dispersion stabilizing aid such as polyvinyl alcohol, alkyltrimethylammonium chloride, dialkyldimethyl chloride. Various emulsifiers such as cationic surfactants such as ammonium, anionic surfactants such as sodium alkylsulfate, amphoteric surfactants such as alkyldimethylaminoacetic acid betaine and alkyldihydroxyethylaminoacetic acid betaine may be used. The dispersion stabilizing aid is preferably used in a proportion of 0.05 to 2% by weight with respect to the monomer mixture.
The aqueous suspension containing the dispersion stabilizer is prepared by mixing the dispersion stabilizer, the dispersion stabilization auxiliary agent and the like with water (for example, ion-exchanged water). The pH of the aqueous suspension at the time of polymerization is appropriately determined depending on the type of dispersion stabilizer and dispersion stabilization aid used. Further, a water-soluble reducing agent may be added to the aqueous suspension, which suppresses the formation of aggregated microspheres during polymerization. Examples of the water-soluble reducing agent include alkali metal nitrites such as sodium nitrite and potassium nitrite, stannous chloride, stannic chloride, ferrous chloride, ferric chloride, ferrous sulfate, and water-soluble ascorbin. Examples thereof include acids. Among these, alkali metal nitrite is preferable from the viewpoint of stability in water. The addition amount thereof is preferably 0.0001 to 1% by weight, more preferably 0.0003 to 0.1% by weight, based on the monomer mixture.
The polymerization temperature is freely set depending on the type of the polymerization initiator, but is preferably controlled in the range of 40 to 100°C, more preferably 45 to 90°C, and particularly preferably 50 to 85°C. The initial polymerization pressure is a gauge pressure of 0 to 5.0 MPa, more preferably 0.1 to 3.0 MPa, and particularly preferably 0.2 to 2.0 MPa.
The obtained heat-expandable microspheres have good foaming performance, can be filled in an assembly of a tire and a rim, and can exhibit sufficient performance when used as a tire internal pressure imparting material. From the viewpoint that the thickness of the thermoplastic resin, which is the outer shell of the sphere, can ensure the encapsulation retention rate of the enclosing foaming agent, the foaming agent is 2 to 85% by weight, preferably 5% by weight of the entire heat-expandable microspheres. -60% by weight, more preferably 7-50% by weight. In particular, when the foaming agent contains a fluorine-containing compound, it is preferably 10 to 60% by weight, more preferably 15 to 50% by weight.
The average particle size of the heat-expandable microspheres is not particularly limited because it can be freely designed according to the application, and is preferably 1 to 100 μm, more preferably 2 to 80 μm, and particularly preferably 5 to 60 μm. is there.
The coefficient of variation CV of the particle size distribution of the heat-expandable microspheres is not particularly limited, but is preferably 30% or less, more preferably 27% or less, and particularly preferably 25% or less. The coefficient of variation CV is calculated by the following calculation formulas (1) and (2).

(In the formula, s is the standard deviation of the particle size, <x> is the average particle size, x _i Is the i-th particle diameter, and n is the number of particles. )
The heat-expandable microspheres may be added or modified by a component other than the outer shell and the inclusion substance. For example, in the thermally expandable microspheres, it is preferable to use a fine particle filler attached to the outer surface of the outer shell from the viewpoint of improving dispersibility and fluidity during use.
The fine particle filler may be either an organic filler or an inorganic filler, and the type and amount thereof are appropriately selected according to the purpose of use.
Examples of the organic filler include metal soaps such as magnesium stearate, calcium stearate, zinc stearate, barium stearate and lithium stearate; polyethylene wax, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid. Examples include synthetic waxes such as amides and hydrogenated castor oil; resin powders such as polyacrylamide, polyimide, nylon, polymethylmethacrylate, polyethylene, and polytetrafluoroethylene.
Inorganic fillers having a layered structure, for example, talc, mica, bentonite, sericite, carbon black, molybdenum disulfide, tungsten disulfide, graphite fluoride, calcium fluoride, boron nitride, etc.; and others, silica , Alumina, mica, calcium carbonate, calcium hydroxide, calcium phosphate, magnesium hydroxide, magnesium phosphate, barium sulfate, titanium dioxide, zinc oxide, ceramic beads, glass beads, crystal beads and the like.
These fine particle fillers may be used alone or in combination of two or more.
Among the above, the fine particle filler adhering to the outer surface of the outer shell has a melting point of 90° C. or higher (preferably 100° C. or higher, more preferably 110° C. or higher, further preferably 120° C. or higher, particularly preferably 150° C. or higher, and most preferably An organic compound having a melting point of preferably 200° C. or higher) or an inorganic compound having a layered structure (preferably at least one selected from carbon black, molybdenum disulfide, tungsten disulfide, graphite fluoride and boron nitride), that is, It is preferably a heat fusion inhibitor. Here, the heat fusion preventing agent prevents heat fusion of the outer shell resin of the heat-expandable microspheres and/or the heat-expanded microspheres, and further, even at the time of heat expansion, Alternatively, it should prevent thermal fusion with the thermally expanded microspheres, and should not impair the foaming performance. Thereby, for example, when the thermally expanded microspheres obtained by expanding the thermally expandable microspheres and having thermally expanded microspheres having a surplus capacity for re-expansion are filled inside the assembly of the tire and the rim, the tire is damaged and the tire internal pressure is reduced. Even if the tire is deteriorated, the damaged portion of the tire can be quickly sealed, and a high tire internal pressure imparting function can be exerted. As a result, even a damaged tire can travel a required distance. This effect is particularly remarkable when the foaming agent contains a fluorine-containing compound.
Further, in the case of heat-expandable microspheres using a thermoplastic resin obtained by polymerizing a monomer mixture containing a nitrile-based monomer and a carboxyl group-containing monomer as an essential component, heat resistance 90°C or more against heat-expanded microspheres that have a surplus capacity that can be re-expanded while being able to exhibit good performance in heat resistance and flame retardancy (noncombustible) The re-expansion can be started at a temperature (preferably 100° C. or higher, more preferably 120° C. or higher), and the above effect becomes remarkable.
The average particle size of the fine particle filler is preferably 1/10 or less of the average particle size of the heat-expandable microspheres before adhesion. Here, the average particle diameter means the average particle diameter of the primary particles.
The amount of the fine particle filler adhered to the heat-expandable microspheres is not particularly limited, but the function of the fine particle filler can be sufficiently exerted, and in consideration of the true specific gravity of the heat-expandable microspheres, etc. It is preferably 0.1 to 95% by weight, more preferably 0.5 to 60% by weight, particularly preferably 5 to 50% by weight, and most preferably 8 to 30% by weight, based on the heat-expandable microspheres.
The adhesion of the fine particle filler to the outer surface of the heat expandable microspheres can be performed by mixing the heat expandable microspheres and the fine particle filler. The mixing is not particularly limited, and the mixing can be performed using a device equipped with an extremely simple mechanism such as a container and a stirring spring. Moreover, you may use the powder mixer which can perform a general rocking|fluctuation or stirring. Examples of the powder mixer include a powder mixer capable of rocking stirring or stirring such as a ribbon mixer and a vertical screw mixer. In recent years, a super mixer (made by Kawata Co., Ltd.), a high-speed mixer (made by Fukae Co., Ltd.) and a new-gram machine (Seishin Enterprise Co., Ltd.), which are efficient and multifunctional powder mixers by combining a stirring device. Manufactured) or the like may be used.
The heat-expandable microspheres are used, for example, as a volume-holding material by directly filling the inside of an assembly of a tire and a rim and expanding the heat-expandable microspheres by heating at a temperature equal to or higher than the expansion start temperature of the heat-expandable microspheres. can do. Further, as it is, it may be used as a filler for reducing the weight of paints for automobiles, expanded particles for expanded ink for wallpaper and clothes decoration, and a foam material for reducing the weight of a resin composition.
Next, the thermally expanded microspheres will be described.
b. Thermally expanded microspheres
The thermally expanded microspheres are obtained by thermally expanding the thermally expandable microspheres described above. The method for producing the heat-expanded microspheres is not particularly limited as long as it is a production method including a step of heating the heat-expandable microspheres to thermally expand, and a conventionally known method can be applied. However, the following two methods can be mentioned as preferable methods.
(A) A step of causing a gas fluid containing the heat-expandable microspheres (raw material) described above to flow through a gas introduction pipe provided with a dispersion nozzle at the outlet and installed inside a hot air flow, and ejected from the dispersion nozzle ( (Injecting step), a step of causing the gaseous fluid to collide with a collision plate installed in the downstream portion of the dispersion nozzle to disperse the thermally expandable microspheres in the hot air flow (dispersing step), and the dispersed thermal expandability A step of expanding the microspheres by expanding the microspheres in the hot air stream at a temperature not lower than the expansion start temperature (expansion step).
(B) The gas fluid containing the heat-expandable microspheres (raw material) described above is caused to flow through at least one gas introduction pipe provided with a dispersion nozzle at the outlet and provided outside the hot air flow, and jetted from the dispersion nozzle. And a step of dispersing the heat-expandable microspheres in the hot air flow (dispersion step), and a step of heating the dispersed heat-expandable microspheres in the hot air flow to an expansion start temperature or higher to expand (expansion step) And a manufacturing method including.
In the above manufacturing method, energy efficiency is high, temperature control is easy, almost the same thermal history can be continuously given to any of the heat-expandable microspheres as a raw material, and the dispersibility in the air flow is improved. Is high. Therefore, the variation in the coefficient of variation of the particle size distribution before and after expansion is small, and the quality of the thermally expanded microspheres obtained (particularly, the particle size distribution and the true specific gravity distribution) is highly uniform. That is, generation of aggregated microspheres contained in the obtained thermally expanded microspheres can be suppressed as much as possible, and the content of the raw material and slightly expanded microspheres can be made extremely small.
Further, in the above-mentioned manufacturing method, the thermally expanded microspheres obtained may or may not have the re-expansion start temperature by controlling the expansion conditions. It should be noted that the fact that the microspheres have a re-expansion start temperature means that the once-produced thermally expanded microspheres still have the property of thermal expansion. Means being seen. The temperature at which the heat begins to expand is called the re-expansion start temperature. Further, the fact that the thermally expanded microspheres have the re-expansion start temperature is synonymous with the expansion ratio at the maximum (re)expansion temperature of more than 100%. On the other hand, the fact that the microspheres do not have the re-expansion start temperature means that the microspheres have almost completely thermally expanded.
The control of the expansion condition is not particularly limited. For example, first, parameters such as the raw material supply amount, the hot air flow rate, and the raw material dispersed gas amount are fixed, and the temperature of the hot air flow (hereinafter, also referred to as “hot air temperature”) is changed. Next, the hot air temperature was changed stepwise, and the raw material microspheres were expanded at each temperature while fixing other parameters constant, and the true specific gravity of the obtained microspheres was measured to determine the hot air temperature (x-axis). ) And true specific gravity (y axis) are plotted. In this graph, by setting the temperature region corresponding to the lowest true specific gravity (minimum value in the graph) to the hot air temperature, the obtained thermally expanded microspheres can be manufactured so as not to have the reexpansion start temperature.
Further, when manufacturing expanded microspheres having a desired true specific gravity, the hot air temperature corresponding to the desired true specific gravity is set in the graph. As a result, the expansion conditions are controlled, and the thermally expanded microspheres having a desired reserve capacity for reexpansion can be manufactured.
Furthermore, when changing the raw material supply amount and/or the raw material dispersed gas amount, the hot air temperature and the like are changed in consideration of the heat amount supplied by the hot air flow and the total heat capacity of the heat-expandable microspheres that are the raw materials. Control expansion conditions. For example, when increasing the raw material supply amount and the raw material dispersed gas amount, the hot air temperature is raised. When reducing the amount of raw material supplied and the amount of raw material dispersed gas, the hot air temperature is lowered.
In the above manufacturing method, energy efficiency is high, temperature control is easy, almost the same thermal history can be continuously given to any of the heat-expandable microspheres as a raw material, and the dispersibility in the air flow is improved. Is high. Therefore, the variation in the coefficient of variation of the particle size distribution before and after expansion is small, and the quality of the thermally expanded microspheres obtained (particularly, the particle size distribution and the true specific gravity distribution) is highly uniform. That is, generation of aggregated microspheres contained in the obtained thermally expanded microspheres can be suppressed as much as possible, and the content of the raw material and slightly expanded microspheres can be made extremely small.
The thermally expanded microspheres thus obtained can be used, for example, as a main member of a run flat tire. That is, by filling the thermally expanded microspheres inside the assembly of the tire and the rim, when the tire is damaged and the tire internal pressure is reduced, as a tire damaged portion sealing material and/or a tire internal pressure applying material. Can be used.
The average particle size of the thermally expanded microspheres is not particularly limited and can be freely designed according to the application. For example, considering the encapsulation retention rate of the foaming agent by the outer shell and the durability of the thermally expanded microspheres, the range is preferably 1 to 1000 μm, more preferably 5 to 800 μm, and particularly preferably 10 to 500 μm.
The content rate of microspheres with a true specific gravity of 0.79 g/cc or more contained in the thermally expanded microspheres (25°C) takes into consideration the homogeneity of the true specific gravity, highly efficiently recovers the encapsulated substance, and has a good shape. In order to obtain such novel microspheres, the content is preferably 5% by weight or less, more preferably 3% by weight or less, further preferably 2% by weight or less, and particularly preferably 1% by weight or less. The content of microspheres of 0.79 g/cc or more is measured by quantifying the sedimentation component after specific gravity difference separation using isopropyl alcohol (specific gravity at 25° C.: 0.79). Moreover, in the present invention, the true specific gravity is measured, for example, for a sample of 0.5 to 2.0 g at a temperature of 25° C. by a liquid replacement method (Archimedes method) using isopropyl alcohol. The true specific gravity here is not a value obtained by measuring the true specific gravity of one of the thermally expanded microspheres, but a value obtained by measuring the true specific gravity of an aggregate of the thermally expanded microspheres, which means the average true specific gravity. To do.
The thickness of the outer shell of the thermally expanded microspheres is also not particularly limited, but in order to recover the encapsulated substance with high efficiency and obtain novel microspheres having a good shape, preferably 0.1 to 20 μm, The thickness is more preferably 0.2 to 10 μm, still more preferably 0.2 to 5 μm, and particularly preferably 0.2 to 1 μm. The thickness of the outer shell is calculated from the average particle diameter of the thermally expanded microspheres, the encapsulation rate of the foaming agent, and the true specific gravity measured by the liquid replacement method (Archimedes method). The calculation method is as follows.
(1) First, consider one thermally expanded microsphere having an average particle diameter, calculate the total volume from the average particle diameter, calculate the total weight from the true specific gravity, and obtain the total weight and the foaming agent The foaming agent gas weight is calculated from the inclusion rate.
(2) Next, the difference between the total weight and the blowing agent gas weight is taken as the weight of the outer shell, and the volume of the outer shell is calculated from the weight of the outer shell and the specific gravity of the outer shell.
(3) Furthermore, the difference between the total volume and the volume of the outer shell is taken as the volume inside the outer shell, and the radius inside the outer shell is calculated from the volume inside this outer shell.
(4) Finally, the average particle diameter is divided by 2 to calculate the average particle radius, the difference between this average particle radius and the inner radius of the outer shell is calculated, and the outer shell thickness is calculated.
The thermally expanded microspheres may or may not have a re-expansion start temperature. In particular, when the thermally expanded microspheres do not have a reexpansion start temperature, or even when the thermally expanded microspheres have a reexpansion magnification of 100 to 500%, Since the thickness of the thermoplastic resin forming the outer shell is thin, the encapsulated substance can easily pass through the outer shell, and the encapsulated substance can be recovered with high efficiency.
As the microspheres used in the present invention, the heat-expandable microspheres and the heat-expanded microspheres described above may be used as they are, but from the viewpoint of resource recovery and reuse, the heat-expandable microspheres and the heat-expandable microspheres may be used. Used microspheres obtained by using the microspheres for a certain purpose are preferable.
The above application is not particularly limited as long as it is an application utilizing various characteristics of the heat-expandable microspheres and the heat-expanded microspheres. Examples of the above-mentioned characteristics include designability, porosity, bulkiness, slip prevention, shrinkage prevention (dimensional stability), weight reduction (cost reduction), heat insulation (heat retention, cold retention), shock absorption ( Impact resilience), soundproofing, vibration damping, rigidity, surface modification (matting, softness imparting), concealing property, easy peeling property, sealing property and the like. As a specific application, a main member of a run-flat tire (filling the inside of an assembly of a tire and a rim with thermally expanded microspheres causes the tire to be injured when the tire is injured and the internal pressure of the tire is reduced, Used as a part sealing material and/or a tire internal pressure imparting material), an internal additive of rubber or resin (added to rubber or resin, for example, foamed at the time of heat molding, and used as a weight reducing agent for the obtained member), etc. Can be mentioned.
Next, the method for recovering the encapsulated substance in the microspheres described above will be described in detail.
[Recovery method of inclusion substance]
The method for recovering the encapsulated substance of the present invention is a method including the contact step of contacting the microspheres and the solvent described above.
The solvent used in this contact step is not particularly limited as long as it is a liquid, but normally, the degree of polarity of the solvent, the type of thermoplastic resin that constitutes the outer shell of the microspheres, operability in the separation step described below, etc. Will be selected.
Examples of the solvent include water; alcohols such as methanol, ethanol, propanol, ethylene glycol and glycerin; ethers such as propyl ether, butyl ether, pentyl ether, hexyl ether; methyl formate, ethyl formate, propyl formate, butyl formate, Esters such as methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate; ketones such as acetone, methyl ethyl ketone, cyclohexanone, pinacholine, mesityl oxide; hexane, Aliphatic hydrocarbons such as heptane, octane, nonane, decane, undecane, dodecane, cyclohexane and methylcyclohexane; aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene and phenylacetylene; nitriles such as acetonitrile and propionitrile; Examples thereof include amides such as dimethylformamide (DMF); sulfoxides such as dimethyl sulfoxide (DMSO). These solvents may be used alone or in combination of two or more.
In the recovery method of the present invention, it is preferable to use a polar solvent because the encapsulated substance can be recovered with high efficiency. Examples of the polar solvent include water, alcohols, ethers, esters, ketones, nitriles, amides, sulfoxides and the like. Among these polar solvents, water and alcohols are preferable, and from the viewpoint that the novel microspheres obtained by the recovery method of the present invention retain a good shape and the inclusion substance is easily isolated. , Water is more preferred.
The polar solvent may be a solvent which further shows acidity or alkalinity, but the thermoplastic resin constituting the outer shell of the microspheres polymerizes a monomer mixture containing an acidic monomer such as a carboxyl group-containing monomer. When it is obtained by the above method, it is preferable that the polar solvent is alkaline, and it is further preferable that the polar solvent is water and/or alcohols (especially ethanol etc.) that shows alkaline. Water showing alkalinity is particularly preferable from the viewpoint that the sphere retains a good shape and the inclusion substance is easily isolated. When the polar solvent is alkaline, the pH of the polar solvent is not particularly limited, but is preferably 9 to 14, and more preferably 11 to 13.
In the contacting step, the microspheres and the solvent are mixed and brought into contact with each other. The mixing ratio of the microspheres and the solvent is not particularly limited, but in view of improvement of recovery efficiency and economic efficiency, the microspheres per 1 L of the solvent are preferably 0.1 to 3000 g, and 10 to 2000 g. Is more preferable, and 100 to 1000 g is particularly preferable.
The contact time between the microspheres and the solvent in the contacting step is appropriately set in consideration of the solvent, the encapsulating substance, the thermoplastic resin forming the outer shell of the microspheres, workability, etc., and is not particularly limited, but may be 0, for example. 1 to 1000 hours.
The contact temperature between the microspheres and the solvent in the contact step is appropriately set similarly to the contact time and is not particularly limited. However, considering that it is not operationally advantageous to contact them at a temperature that is too low, and that the boiling point of the inclusion substance is usually room temperature or a temperature slightly higher than that, the contact temperature is, for example, It is -50 to 100°C. Further, the contact temperature is preferably not higher than the boiling point of the inclusion substance.
The contact time and the contact temperature in the contact step may be appropriately set in consideration of the thickness of the outer shell of the microsphere.
When the thickness of the outer shell of the microspheres is 2 μm or more (for example, when the microspheres are heat-expandable microspheres), the contact time in the contacting step is 1 to 1000 hours, considering the improvement of the recovery efficiency of the inclusion substance. It is preferable, it is more preferable that it is 10 to 1000 hours, and it is particularly preferable that it is 100 to 1000 hours. The contact temperature in the contact step is preferably 30 to 100°C, more preferably 50 to 100°C, and particularly preferably 70 to 100°C. The solvent used in this case preferably has a boiling point not lower than the contact temperature between the microspheres and the solvent, and among the above-exemplified solvents, those having a boiling point of 50° C. or higher can be mentioned.
Next, when the thickness of the outer shell of the microspheres is less than 2 μm (for example, when the microspheres are thermally expanded microspheres), the contact time in the contact step is 0. It is preferably 1 to 500 hours, more preferably 0.1 to 100 hours. The contact temperature in the contact step is preferably 0 to 80°C. The solvent used in this case preferably has a boiling point not lower than the contact temperature between the microspheres and the solvent, and among the solvents exemplified above, those having a boiling point of 20° C. or higher can be mentioned.
In the method for recovering the encapsulated substance of the present invention, the encapsulated substance encapsulated in the microspheres can be recovered by bringing the microspheres into contact with the solvent. Although its action is not confirmed, it is presumed that the thermoplastic resin forming the outer shell swells or deteriorates by the solvent, and the encapsulated substance permeates and diffuses in the solvent according to the concentration gradient.
It is preferable that the method for recovering the encapsulated substance of the present invention further includes a separation step. The separation step is a step of recovering the inclusion substance from the mixture containing the microspheres and the solvent obtained in the contact step.
The separation step may be performed together with the contact step or after the contact step, but by performing the separation step together with the contact step, the inclusion substance can be separated and recovered in a short time.
The specific means for performing the separation step is not particularly limited, and examples thereof include distillation separation, extraction separation, centrifugation, adsorption separation of the inclusion substance.
Distillation separation is a method of separating and collecting the inclusion substance by utilizing the boiling point difference between the inclusion substance and the solvent. Regarding the boiling point difference, it is preferable to increase the boiling point difference in order to improve work efficiency. The boiling point difference is, for example, preferably 5° C. or higher, more preferably 10° C. or higher, particularly preferably 20° C. or higher. In the distillation separation, the entrapped substance is once vaporized and liquefied in the cooling device to be separated, but in consideration of the fact that the boiling point of the entrapped substance is usually room temperature or slightly higher than that, a cooling device or It is preferable to control the temperature of the refrigerant used for the reservoir of the liquefied inclusion substance to be low. The temperature difference between the temperature of the refrigerant and the boiling point of the inclusion substance is, for example, preferably 30°C or higher, more preferably 50°C or higher, and particularly preferably 100°C or higher.
Both extraction separation and centrifugation are methods of separating and recovering by utilizing the property that the inclusion substance and the solvent are phase-separated. In the case of performing extraction separation or centrifugation, the solvent preferably has a property of phase separation when mixed with the inclusion substance. Examples of the solvent include water; alcohols such as methanol and ethanol. When phase separation is not easily carried out by extraction separation, centrifugation may be carried out to separate the inclusion substance and the solvent into phases. The encapsulated substance that has been phase-separated by extraction separation or centrifugation is separated and recovered through a liquid separation operation such as decantation.
The adsorption separation is a method of capturing and recovering a vaporized substance by an adsorption unit using an adsorbent such as activated carbon. The substance captured by the adsorption unit is desorbed by steam and regenerated, and is liquefied and recovered by deep-condensation.
In the contacting step and the separating step, the mixture containing the microspheres and the solvent may or may not be stirred, but it is considered that the contact efficiency of the microspheres and the solvent is improved when the mixture is stirred. The stirrer used for the stirring is not particularly limited, and examples thereof include general stirrers such as a homomixer and a line mixer. The stirring speed is also not particularly limited.
In carrying out the contacting step and the separating step, the pressure atmosphere is not particularly limited, and may be performed under any of reduced pressure, normal pressure and increased pressure.
Next, the novel microspheres that can be obtained after the contacting step will be described.
[New microsphere]
The novel microspheres of the present invention (hereinafter sometimes referred to as microspheres a) are microspheres that can be obtained after the contacting step in the above-mentioned recovery method and have a thermoplastic resin as an outer shell.
The microsphere a is a novel microsphere in which the solvent is contained in the outer shell instead of the inclusion substance. At least the solvent is encapsulated in the microspheres a, but the encapsulated substance remaining without being recovered may be encapsulated together with the solvent.
The solvent may be removed from the mixture after the contacting step to isolate the dried microspheres a, but considering that no aggregation or fusion occurs, it is preferable to handle the microspheres a wet with a liquid. preferable.
As the liquid, the solvent described in the recovery method can be used as it is, but depending on the use of the microsphere a, dibutyl phthalate, diisooctyl phthalate, dioctyl adipate, tricresyl phosphate, triethyl citrate, Acetyltributyl citrate, plasticizers such as octyl alcohol (when used in plastics, elastomers, sealants, paints, etc.); Monomers such as dicyclopentadiene and styrene (when used in lightweight foam moldings and adhesives); Non Ionic surfactants, alkylene glycols, polyalkylene glycols, glycerin, silicone oils, liquid paraffin, fats and oils may be used as the liquid. By replacing the solvent in the mixture after the contacting step with a liquid, the microsphere a can be made wet with the liquid.
The average particle size of the microspheres a is not particularly limited, but when the microspheres a are in a wet state, preferably 1 to 1000 μm, more preferably 5 to 800 μm, particularly preferably 10 to 500 μm, and most preferably It is 1 to 150 μm.
The true specific gravity of the microsphere a is not particularly limited, but when the microsphere a is in a dried state, it is preferably 0.001 to 1.5 g/cc, more preferably 0.001 to 1.0 g/cc. And particularly preferably 0.001 to 0.8 g/cc.
Regarding the use of the microsphere a, if the use is made of various characteristics of the heat-expandable microspheres or the heat-expanded microspheres described above, or if the microspheres a are fine particles, There is no particular limitation. The microspheres a may be used as a filler such as an organic material such as a resin or an inorganic material, for example, a filler for an extrusion cement molded product or a sealing agent, a filler for resin clay, a reinforcing filler for ceramic siding, a wood fiber board. Reinforcing fillers, abrasives for hand-washing soaps and commercial detergents, anti-blocking agents, smoothing agents, substitutes for lightweight aggregates, porosity-imparting agents, superplasticizers, dust inhibitors, greening accelerators, slope erosion Examples include inhibitors.

The present invention will be described in detail with reference to the following examples and comparative examples, but the present invention is not limited to these examples.
(Measurement method and definition)
[Measurement of average particle size and particle size distribution]
As a measuring device, a laser diffraction type particle size distribution measuring device (HEROS & RODOS manufactured by SYMPATEC) was used. The dispersion pressure of the dry dispersion unit was 5.0 bar, the degree of vacuum was 5.0 mbar, and the dry measurement method was used to measure the D50 value as the average particle size.
[Measurement of true specific gravity]
The true specific gravity was measured at a temperature of 25° C. by a liquid displacement method (Archimedes method) using isopropyl alcohol.
[Measurement of water content of thermally expandable microspheres]
A Karl Fischer moisture meter (MKA-510N type, manufactured by Kyoto Electronics Manufacturing Co., Ltd.) was used as a measuring device.
[Measurement of Encapsulation Rate of Foaming Agent Enclosed in Thermally Expandable Microspheres]
1.0 g of the heat-expandable microspheres were placed in a stainless steel evaporation dish having a diameter of 80 mm and a depth of 15 mm, and the weight (W ₁ ) thereof was measured. After 30 ml of acetonitrile was added and uniformly dispersed, the mixture was allowed to stand at room temperature for 30 minutes, heated at 120° C. for 2 hours, and the weight (W ₂ ) after drying was measured. The inclusion rate of the foaming agent is calculated by the following formula.
Encapsulation rate (wt%)=(W ₁ −W ₂ )(g)/1.0(g)×100−(water content) (wt%)
(In the formula, the water content is measured by the above method.)
[Internal retention rate]
The encapsulation retention rate of the foaming agent is the ratio of the encapsulation rate (G ₂ ) of the foaming agent after expansion to the encapsulation rate (G ₁ ) of the foaming agent before expansion, and is calculated by the following formula.
Encapsulation retention rate (%)=G ₂ /G ₁ ×100
[Measurement of (re)expansion start temperature and maximum (re)expansion temperature]
As a measuring device, DMA (DMA Q800 type, manufactured by TA instruments) was used. 0.5 mg of heat-expandable microspheres (or heat-expanded microspheres) was placed in an aluminum cup with a diameter of 6.0 mm and a depth of 4.8 mm, and an aluminum lid with a diameter of 5.6 mm and a thickness of 0.1 mm was placed on it. A sample was prepared. The sample height (H ₁ ) was measured while a force of 0.01 N was applied to the sample from above with a pressurizer. With the force of 0.01 N applied by the presser, the pressure was heated from 20 to 300° C. at a temperature rising rate of 10° C./min, and the amount of displacement of the presser in the vertical direction was measured. The displacement start temperature in the positive direction was taken as the (re)expansion start temperature, and the temperature at which the maximum displacement amount (H ₂ ) was shown was taken as the maximum (re)expansion temperature. The (re)expansion ratio (E) at the maximum (re)expansion temperature is calculated by the following formula.
E(%)=H ₂ /H ₁ ×100
[Production Example 1]
To 500 g of ion-exchanged water, 150 g of sodium chloride, 3.0 g of adipic acid-diethanolamine condensate, 20 g of colloidal silica (amount of active ingredient: 20%) and 0.15 g of sodium nitrite were added and mixed uniformly. The water phase was used.
200 g of acrylonitrile, 45 g of methacrylonitrile, 75 g of methacrylic acid, 1.2 g of trimethylolpropane trimethacrylate, 2.0 g of azobisisobutyronitrile and 150 g of C ₃ F ₇ OCH ₃ (encapsulating material, foaming agent) are mixed and stirred, It was dissolved and this was the oil phase.
The water phase and the oil phase were mixed, premixed with a homomixer at 3,000 rpm for 2 minutes, and stirred at 10,000 rpm for 2 minutes to prepare a suspension. This was transferred to a reactor and purged with nitrogen, and then polymerized at 61° C. for 20 hours while stirring. After the polymerization, the polymerization product was filtered and dried to obtain the heat-expandable microspheres as microspheres 1. The ignition source was brought close to the heat-expandable microspheres, but it did not burn.
[Production Example 2]
The microspheres 1 obtained in Production Example 1 were heated and expanded by the method for producing thermally expanded microspheres described above (Production Method (A) to produce thermally expanded microspheres. Was used as a member of a run-flat tire by filling the hollow portion of the tire-rim assembly with a run-flat tire. (Hereinafter, may be simply referred to as microspheres 2), and its physical properties were measured. The average particle diameter was 90 μm, the true specific gravity was 0.028 g/cc, the encapsulation rate was 32%, the encapsulation retention rate was 98%, and re-expansion started The content (25° C.) of microspheres having a temperature of 132° C., a maximum re-expansion temperature of 202° C., a re-expansion ratio of 211%, and a true specific gravity of 0.79 g/cc or more was 0.8% by weight.
[Production Example 3]
Microspheres 3 were heat-expandable microspheres obtained by polymerization in the same manner as in Production Example 1 except that 64 g of isopentane was used as the inclusion substance instead of 150 g of C ₃ F ₇ OCH ₃ in Production Example 1.
[Production Example 4]
The microspheres 3 obtained in Production Example 3 were heated and expanded in the same manner as in Production Example 2 to produce thermally expanded microspheres (microspheres 4).
[Production Example 5]
The microspheres 1 obtained in Production Example 1 and carbon black (manufactured by Lion Corporation, product name: Ketjen Black ECP600JD, average particle diameter: 34 nm) were mixed at a weight ratio of 9:1 with a super mixer (manufactured by Kawata Corporation). ) Was used for uniform mixing to obtain thermally expanded microspheres having carbon black attached to the outer surface. The obtained heat-expandable microspheres were heated and expanded in the same manner as in Production Example 2 to produce heat-expanded microspheres (microspheres 5).
[Example 1]
0.05 g of the microspheres 2 obtained in Production Example 2 was weighed and mixed and dispersed in 20 mL of ethanol. The resulting mixture was left in the refrigerator overnight and then extracted with hexane. When the obtained hexane phase was analyzed by gas chromatography (GC17A manufactured by Shimadzu Corporation), C ₃ F ₇ OCH ₃ was detected.
The ethanol used above was replaced with acetonitrile, toluene, dimethylformamide, weak alkaline water (pH 9) and strong alkaline water (pH 12), and the same operation as above was performed. In each, C ₃ F ₇ OCH ₃ was detected.
[Example 2]
40 g of the microspheres 2 obtained in Production Example 2 were weighed, and 1 L of ethanol was mixed and dispersed for 10 minutes using a homomixer. The obtained mixture was supplied to a round-bottomed flask having a volume of 2 L, and the heat source for heating the flask was set to 40° C. to carry out atmospheric distillation. This distillation operation was performed for 30 minutes, and the distillate (7.7 mL) collected in the cooling tube cooled with liquid nitrogen was analyzed by gas chromatography to confirm that it was C ₃ F ₇ OCH ₃ , and the recovery rate was confirmed. Was 90%. After collection, new microspheres were obtained.
[Example 3]
C ₃ F ₇ OCH ₃ was recovered in the same manner as in Example 2 except that strong alkaline water (pH 12) was used instead of ethanol in Example 2. The recovery rate was 90%. The new microspheres obtained after the collection retained the spherical shape, and the strong alkaline water was contained in the outer shell.
[Example 4]
40 g of the microspheres 3 obtained in Production Example 3 were weighed, and 1 L of ethanol was mixed and dispersed for 10 minutes using a homomixer. The obtained mixture was supplied to a round-bottomed flask having a volume of 2 L, and the heat source for heating the flask was set to 30° C. to carry out atmospheric distillation. This distillation operation was performed for 30 minutes, and the distillate (22 mL) collected in the cooling tube cooled with liquid nitrogen was analyzed by gas chromatography to confirm that it was isopentane, and the recovery rate was 91%. After collection, new microspheres were obtained.
[Example 5]
Isopentane was recovered in the same manner as in Example 4 except that strong alkaline water (pH 12) was used in place of ethanol in Example 4 above. The recovery rate was 91%. The new microspheres obtained after the collection retained the spherical shape, and the strong alkaline water was contained in the outer shell.
[Example 6]
200 g of the microspheres 1 obtained in Production Example 1 were weighed, and strong alkaline water (pH 12) was mixed and dispersed for 10 minutes using a homomixer. The obtained mixture was supplied to a round-bottomed flask having a volume of 2 L, and the heat source for heating the flask was set to 80° C. to perform atmospheric distillation. This distillation operation was performed for 120 minutes, and the distillate (37 mL) collected in the cooling tube cooled with liquid nitrogen was analyzed by gas chromatography to confirm that it was C ₃ F ₇ OCH ₃ , and the recovery rate was 88. %Met. The new microspheres obtained after the collection retained the spherical shape, and the strong alkaline water was contained in the outer shell.
[Example 7]
200 g of the microspheres 3 obtained in Production Example 3 were weighed, and strong alkaline water (pH 12) was mixed and dispersed for 10 minutes using a homomixer. The obtained mixture was supplied to a round-bottomed flask having a volume of 2 L, and the heat source for heating the flask was set to 80° C. to perform atmospheric distillation. This distillation operation was performed for 120 minutes, and the distillate (90 mL) collected in the cooling tube cooled with liquid nitrogen was analyzed by gas chromatography to confirm that it was C ₃ F ₇ OCH ₃ , and the recovery rate was 90. %Met. The new microspheres obtained after the collection retained the spherical shape, and the strong alkaline water was contained in the outer shell. The novel microspheres were dried at 40° C. for 20 hours, and the true specific gravity of the crushed flakes was measured, and it was 0.97 g/cc.
[Example 8]
40 g of the microspheres 5 obtained in Production Example 5 were weighed, and 1 L of ethanol was mixed and dispersed for 10 minutes using a homomixer. The obtained mixture was supplied to a round-bottomed flask having a volume of 2 L, and the heat source for heating the flask was set to 40° C. to carry out atmospheric distillation. This distillation operation was performed for 30 minutes, the distillate (7.7 mL) collected in the cooling tube cooled with liquid nitrogen was analyzed by gas chromatography, and it was confirmed that it was C ₃ F ₇ OCH ₃ , and the recovery rate was confirmed. Was 90%. After collection, new microspheres were obtained.
[Example 9]
C ₃ F ₇ OCH ₃ was recovered in the same manner as in Example 2 except that strong alkaline water (pH 12) was used in place of ethanol in Example 8. The recovery rate was 91%. The new microspheres obtained after the collection retained the spherical shape, and the strong alkaline water was contained in the outer shell.

INDUSTRIAL APPLICABILITY The encapsulating substance recovery method of the present invention can easily and efficiently recover the encapsulating substance from the microspheres composed of the outer shell made of a thermoplastic resin and the encapsulating substance included therein.
The novel microspheres of the present invention are new microspheres that have not been heretofore known and can be obtained after recovering the encapsulated substance in the above-mentioned recovery method.

Claims (18)

A method for recovering an encapsulated substance, comprising a step of contacting a microsphere composed of an outer shell made of a thermoplastic resin and an encapsulated substance contained therein with a boiling point not higher than the softening point of the thermoplastic resin, and a solvent. .. The method for recovering an encapsulated substance according to claim 1, further comprising a separation step of recovering the encapsulated substance from the mixture containing the microspheres and the solvent obtained in the contacting step. The method for recovering an encapsulated substance according to claim 2, wherein the separating step is performed together with the contacting step. The method for recovering an encapsulated substance according to claim 2 or 3, wherein the separation step is a step of separating the encapsulated substance by distillation. The method for recovering an encapsulated substance according to claim 2, wherein the separation step is a step of extracting and separating the encapsulated substance from the mixture. The method for recovering an encapsulated substance according to any one of claims 1 to 5, wherein the microspheres are further composed of a fine particle filler attached to the outer surface of the outer shell. The method for recovering an encapsulated substance according to any one of claims 1 to 6, wherein an entrapment ratio of the encapsulated substance is 5% or more. Recovery of the inclusion substance according to any one of claims 1 to 7, wherein the content of microspheres contained in the microspheres and having a true specific gravity at 25°C of 0.79 g/cc or more is 5% by weight or less. Method. The thermoplastic resin is at least one radical selected from nitrile monomer, (meth)acrylic acid ester monomer, carboxyl group-containing monomer, styrene monomer, vinyl acetate and vinylidene chloride. The method for recovering an encapsulated substance according to any one of claims 1 to 8, which is a resin obtained by polymerizing a monomer mixture containing a polymerizable monomer. The method for recovering an encapsulated substance according to claim 9, wherein the thermoplastic resin is a resin obtained by polymerizing a monomer mixture containing a nitrile monomer and a carboxyl group-containing monomer as essential components. The method for recovering an encapsulating substance according to any one of claims 1 to 10, wherein the encapsulating substance has at least a fluorine-containing compound having an ether structure and containing no chlorine atom or bromine atom and having 2 to 10 carbon atoms. The method for recovering an encapsulated substance according to claim 1, wherein the solvent is a polar solvent. The method for recovering an encapsulated substance according to claim 12, wherein the polar solvent is ethanol and/or water. The method for recovering an encapsulated substance according to claim 12 or 13, wherein the polar solvent is a solvent showing alkalinity. The method for recovering an encapsulated substance according to any one of claims 1 to 14, wherein the microspheres are microspheres filled in a hollow portion of a tire-rim assembly. The method for recovering an encapsulated substance according to any one of claims 1 to 15, which is a novel microsphere that can be obtained after the contacting step and has the thermoplastic resin as an outer shell. The novel microsphere according to claim 16, wherein the solvent is encapsulated in the outer shell. The novel microsphere according to claim 16 or 17, which is in a state of being wet with a liquid.