JP4991057B2 - Method for producing porous ceramic filter - Google Patents
Method for producing porous ceramic filter Download PDFInfo
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- JP4991057B2 JP4991057B2 JP2001204725A JP2001204725A JP4991057B2 JP 4991057 B2 JP4991057 B2 JP 4991057B2 JP 2001204725 A JP2001204725 A JP 2001204725A JP 2001204725 A JP2001204725 A JP 2001204725A JP 4991057 B2 JP4991057 B2 JP 4991057B2
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- polymer particles
- porous ceramic
- monomer
- ceramic filter
- hollow polymer
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B38/00—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof
- C04B38/06—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof by burning-out added substances by burning natural expanding materials or by sublimating or melting out added substances
- C04B38/063—Preparing or treating the raw materials individually or as batches
- C04B38/0635—Compounding ingredients
- C04B38/0645—Burnable, meltable, sublimable materials
- C04B38/065—Burnable, meltable, sublimable materials characterised by physical aspects, e.g. shape, size or porosity
- C04B38/0655—Porous materials
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D39/00—Filtering material for liquid or gaseous fluids
- B01D39/14—Other self-supporting filtering material ; Other filtering material
- B01D39/20—Other self-supporting filtering material ; Other filtering material of inorganic material, e.g. asbestos paper, metallic filtering material of non-woven wires
- B01D39/2068—Other inorganic materials, e.g. ceramics
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
- C04B2111/00793—Uses not provided for elsewhere in C04B2111/00 as filters or diaphragms
Description
【０００１】
【発明の属する技術分野】
本発明は、高気孔率と高耐熱性を有する多孔質セラミックフィルタの製造方法に関するものである。
【０００２】
【従来の技術】
近年、多孔質のセラミックフィルタとして、炭化珪素（ＳｉＣ）粉末を焼結せしめたハニカム構造体の隔壁を多孔質構造となし、このような隔壁を通過せしめることにより、ガス等の流体に対してフィルタ機能を持たせた多孔質ハニカムフィルタが種々提案され、例えばディーゼル車から排出される排ガスの微粒子捕集用フィルタ（ディーゼルパティキュレートフィルタ）として実用されている。
【０００３】
このような多孔質ハニカムフィルタにおいては、多孔質の平均細孔径（以下細孔径と呼ぶ）及び気孔率がフィルタの性能を決定するための非常に重要な因子であり、ディーゼルパティキュレートフィルタの如き多孔質セラミックフィルタにあっては、微粒子の捕集効率、圧損、捕集時間の関係から、細孔径が大きく、気孔率の大きいフィルタが望まれている。
【０００４】
従来より、セラミックフィルタ細孔径の制御は、原料となるセラミック組成物の骨材粒子径を適宜選択することにより行われてきた。フィルタ性能を改善するために、細孔径を制御する方法としては、例えば、セラミック組成物に有機高分子を添加する方法などが提案されている（特開２０００−２８８３２５号公報）。一方、気孔率を向上させる方法としては、例えば、特開平３−２１５３７４号公報に、平均粒径が１００〜１５０μｍで、平均粒径の±２０％以内に９０重量％以上が存在する粒度分布を有するＳｉＣ粉末を、その表面部分が潰れて相互に連結し、かつその内部は潰れずに成形体中に残存するように成形圧縮した後、焼成する方法が提案されている。
【０００５】
しかしながら、これらの方法では、多孔質体を構成するＳｉＣ粒子の結合が、ＳｉＣ微粒子の粒子成長のみによるものであるから、気孔率が高くなると機械的強度が小さくなり、気孔率と強度特性を両立させるのが難しいという問題があった。また、グラファイト等の造孔剤を添加する方法も一般的であるが、気孔率をさらに向上させようとして、造孔剤を多量に使用すると、焼成時間が延長して製造工程に長時間を要すると共に、特に焼成温度の高いＳｉＣ組成物の場合、燃焼熱の増加により成形体に大きな歪みがかかり、成形体にクラックが生じるという問題があった。従って、低熱膨張性及び耐熱衝撃性を付与すると共に、気孔率を向上させることが可能な多孔質フィルタの製造方法が要望されている。
【０００６】
【発明が解決しようとする課題】
本発明の目的は、上記問題点に鑑み、低熱膨張性及び耐熱衝撃性を付与すると共に、気孔率を向上させた多孔質セラミックフィルタの製造方法を提供することにある。
【０００７】
【課題を解決するための手段】
上記課題を解決することを目的として、本発明者らはそれら各種の問題点に関し、充分に満足できるような多孔質セラミックフィルタの製造方法について鋭意検討を重ねてきた結果、炭化珪素粉末を主成分とし、中空ポリマー粒子を造孔剤として用いたセラミック組成物から所定の成形体を賦形した後焼成することにより、熱変形なく気孔率を向上させた多孔質セラミックフィルタが得られることを見いだし、本発明を完成するに至った。
【０００８】
即ち、本発明は、炭化珪素粉末を主成分とし、造孔剤として複数個の中空孔を有する中空ポリマー粒子を含有するセラミック組成物から所定の成形体を成形した後、該成形体を焼成することを特徴とする。
【０００９】
以下、本発明をさらに詳しく説明する。
本発明では多孔質セラミックフィルタを得るために、炭化珪素（ＳｉＣ）粉末を主成分とし、造孔剤として中空ポリマー粒子を含有するセラミック組成物が用いられる。上記セラミック組成物において、中空ポリマー粒子の添加量は、特に限定されないが、少なすぎると十分な気孔率が得られず、多すぎると焼成後のセラミック成形体の強度が低下するため、該組成物中１０〜５０重量％とするのが好ましい。
【００１０】
上記中空ポリマー粒子としては、平均粒径５〜１００μｍ、１０％圧縮強度１．５ＭＰａ以上であるものが好ましい。
平均粒径が５μｍより小さくなると、得られる多孔質セラミックフィルタの細孔径が小さくなり、フィルタの圧力損失が増大して捕集時間が短くなる。一方、平均粒径が１００μｍより大きくなると、セラミックフィルタの細孔径が大きくなり、フィルタの圧力損失は減少するが捕集効率は低下する。
【００１１】
また、セラミック組成物を所定の成形体に賦形する段階で、機械的剪断力により中空ポリマー粒子が破壊するのを防ぐため、１０％圧縮強度が１．５ＭＰａ以上であることが好ましい。
【００１２】
さらに、同じ空隙率の中空粒子においても、複数の空孔からなるハニカム状のモルホロジーを有する中空粒子が圧縮強度に優ることを見出し、複数孔を有する中空ポリマー粒子を造孔剤として用いることにより、フィルタの成形過程で破壊される粒子が減少し、気孔率を向上させることができる。
【００１３】
上記中空ポリマー粒子を製造する方法としては、特に限定されないが、下記の懸濁重合および脱溶剤の２つの工程からなる製造方法が好ましい。
即ち、親水性モノマー、多官能性モノマー及びその他のモノマーからなる混合モノマーに、非重合性有機溶剤を混合してモノマー溶液を調製し、このモノマー溶液を極性溶媒に懸濁せしめた後モノマー成分を重合し、上記非重合性有機溶剤を内包するポリマー粒子を得る第１の工程と、ポリマー粒子中の有機溶剤を除去することにより中空ポリマー粒子を得る第２の工程から構成される。
上記製造方法において、重合方法は特に限定されないが、粒子径の制御が容易で、かつ有効な空隙を内包する粒子を形成し易いことから懸濁重合法を用いるのが好ましい。
【００１４】
上記モノマー成分を構成する親水性モノマーは、有機溶剤に比べて極性溶媒に対する親和性が高いため、モノマー溶液の懸濁油滴中において油滴界面に局在すると考えられ、結果的に重合により中空ポリマー粒子の外壁面を形成する。
上記親水性モノマーとしては水に対する溶解度が１重量％以上であるものが好ましく、例えば、メチル（メタ）アクリレート、（メタ）アクリロニトリル、（メタ）アクリルアミド、（メタ）アクリル酸、グリシジル（メタ）アクリレート、２−ヒドロキシエチルメタクリレート、２−ヒドロキシプロピルメタクリレート、ビニルピリジン、２−アクリロイルオキシエチルフタル酸、イタコン酸、フマル酸、ジメチルアミノメチルメタクリレート等が挙げられ、好ましくは、メチルメタクリレート、（メタ）アクリル酸、２−ヒドロキシエチルメタクリレート等である。これらは単独あるいは２種以上を組み合わせて用いることができる。
【００１５】
上記親水性モノマーの使用量は、少なすぎると中空ポリマー粒子外壁面が十分に形成されず、中空ポリマー粒子の空隙率が低下するため、モノマー成分において１０〜９９．９重量％使用されるのが好ましく、より好ましくは３０〜９９．９重量％である。
【００１６】
上記モノマー成分を構成する多官能性モノマーは、粒子の耐圧縮強度を改善する目的で添加され、ジ（メタ）アクリレート、トリ（メタ）アクリレート等が好適に用いられる。上記ジ（メタ）アクリレートとしては、例えば、エチレングリコールジ（メタ）アクリレート、ジエチレングリコールジ（メタ）アクリレート、トリエチレングリコールジ（メタ）アクリレート、1,6-ヘキサンジオールジ（メタ）アクリレート、トリメチロールプロパンジ（メタ）アクリレート等が挙げられる。上記トリ（メタ）アクリレートとしては、例えば、トリメチロールプロパントリ（メタ）アクリレート、エチレンオキサイド変性トリメチロールプロパントリ（メタ）アクリレート、ペンタエリスリトールトリ（メタ）アクリレート等が挙げられる。
【００１７】
また、上記以外の多官能性モノマーとしては、例えば、ペンタエリスリトールテトラ（メタ）アクリレート、ジペンタエリスリトールヘキサ（メタ）アクリレート、ジアリルフタレート、ジアリルマレート、ジアリルフマレート、ジアリルサクシネート、トリアリルイソシアヌレート等のジもしくはトリアリル化合物、ジビニルベンゼン、ブタジエン等のジビニル化合物などが挙げられる。
【００１８】
これらの多官能性モノマーは、単独または２種類以上を組み合わせて用いることができる。
【００１９】
上記多官能性モノマーの使用量は、少なすぎると中空ポリマー粒子の耐圧縮強度が十分でなく、多すぎると重合中に粒子の凝集が発生するため、モノマー成分において０．１〜３０重量％使用されるのが好ましく、より好ましくは０．３〜５重量％である。
【００２０】
上記モノマー成分を構成するその他のモノマーは、機械的強度、耐薬品性及び成形性を改善する目的で添加され、特に種類は限定されないが、例えば、エチル（メタ）アクリレート、プロピル（メタ）アクリレート、ブチル（メタ）アクリレート、クミルメタクリレート、シクロヘキシル（メタ）アクリレート、ミスチリル（メタ）アクリレート、パルミチル（メタ）アクリレート、ステアリル（メタ）アクリレート等のアルキル（メタ）アクリレート；スチレン、α−メチルスチレン、ｐ−メチルスチレン、ｐ−クロロスチレン等の芳香族ビニルモノマー；酢酸ビニル、プロピオン酸ビニル等のビニルエステル；塩化ビニル、塩化ビニリデン等のハロゲン含有モノマー；エチレン、プロピレン、ブタジエン等が挙げられる。これらは単独または２種類以上を組み合わせて用いることができる。
【００２１】
上記その他のモノマーの使用量は、多すぎるとモノマー成分の親水性を低下させ、中空ポリマー粒子の外壁が形成されるのを阻害するため、モノマー成分において８９．９重量％以下が好ましく、より好ましくは６９．９重量％以下である。
【００２２】
上記モノマー成分に添加される非重合性有機溶剤は、モノマー溶液の懸濁油滴中において油滴中心部に局在することが望ましく、水に対する溶解度が０．２重量％以下の疎水性を示すことが好ましく、その種類は特に限定されないが、例えば、ブタン、ペンタン、ヘキサン、シクロヘキサン、トルエン、キシレン等が好適に用いられる。中でも、揮発性の高いブタン、ペンタン、ヘキサン、シクロヘキサンがより好ましい。
【００２３】
上記非重合性有機溶剤の添加量は、少なすぎると粒子の空隙率が低くなり、多すぎると空隙率が高くなりすぎて粒子の強度が低下するため、モノマー成分１００重量部に対して１〜４００重量部が好ましく、より好ましくは１０〜２００重量部である。
【００２４】
本発明の多孔質セラミックフィルタの製造方法において、まず、ＳｉＣ粉末に、無機質結合材としてタルク、焼タルク等のタルク粉末成分、非晶質シリカにて代表されるシリカ粉末、造孔剤、カオリン、仮焼カオリン、酸化硼素、アルミナ、水酸化アルミニウム等を適宜配合して、ＳｉＣ粉末を主成分とするセラミック組成物を調製する。上記ＳｉＣ粉末に対する無機質結合材の配合量は特に限定されず、中空ポリマー粒子の品質等によって適宜決定される。
【００２５】
このように調製されたセラミック組成物には、従来法と同様に可塑剤や粘結剤等が加えられて可塑化され、賦形可能な押出成形用原料となされる。
この原料を用いて、所定形状のハニカム成形体等に押出成形した後乾燥し、次いで、その乾燥物を１６００〜２２００℃の温度で焼成することにより、目的とする多孔質セラミックフィルタを製造する。
【００２６】
（作用）
本発明の製造方法では、セラミック組成物に造孔剤として中空ポリマー粒子を配合することにより、多孔質セラミックフィルタに低熱膨張性を付与すると共に、気孔率及び耐熱衝撃性の向上を図ることができ、高捕集効率を維持しつつ、圧力損失の上昇を抑制し、捕集時間の効果的な延長が可能なフィルタを与え得る。
即ち、従来の造孔剤である有機粒子を同重量の中空ポリマー粒子に置き換えることによって、造孔剤が占める体積は増大し、気孔率の向上を図ることができる。また、同体積の中空ポリマー粒子で置き換えた場合、焼成時における粒子の燃焼熱は減少し、セラミック成形品にかかる歪みが小さくなるため、低熱膨張性が付与されると共に耐熱衝撃性が向上する。
【００２７】
【発明の実施の形態】
以下、本発明の実施例について説明するが、下記の例に限定されるものではない。
・中空ポリマー粒子の調製
表１に示した配合量の、モノマー成分、非重合性有機溶剤及び重合開始剤を混合・撹拌してモノマー溶液を調製した後、イオン交換水（全使用量の５０重量％）及び分散剤を添加し、ホモジナイザーにて撹拌して懸濁モノマー溶液を調製した。一方、撹拌機、ジャケット、還流冷却器及び温度計を備えた２０リットルの重合器に、残りのイオン交換水、表１に示した配合量の塩化ナトリウム、亜硝酸ナトリウム、塩酸及び水酸化ナトリウムを投入して、撹拌を開始した。
次いで、重合器内を減圧して容器内の脱酸素を行った後、窒素を注入して圧力を大気圧まで戻し、内部を窒素雰囲気とした後、上記懸濁モノマー溶液を一括して添加し、重合器を８０℃まで昇温し重合を開始した。５時間で重合を終了し、引き続き１時間の熟成期間をおいた後、重合器を室温まで冷却した。
スラリーをセントルにて脱水した後真空乾燥により有機溶剤を除去し、中空ポリマー粒子（ａ）〜（ｅ）を得た。
【００２８】
・中実ポリマー粒子（ｆ）
発泡性粒子（松本油脂社製「Ｆ−８５Ｄ」）を１７０℃にて１分間加熱し、発泡させた中実のポリマー粒子を使用した。
【００２９】
上記中空ポリマー粒子（ａ）〜（ｅ）及び中実粒子（ｆ）について、下記性能評価を行い、その結果を表１に示した。
（１）平均粒径
堀場製作所社製レーザー回折粒度分布計「ＬＡ−９１０」を使用して、中空ポリマー粒子の体積平均粒径を測定した。粒子の任意の場所から３ケ所サンプリングし、その平均値を用いた。
【００３０】
（２）内部モルホロジー
中空ポリマー粒子の赤道断面を薄膜にカットし、透過型電子顕微鏡にて内部モルホロジーを観察した。
【００３１】
（３）比（＝中空孔径／粒子外径）
任意に選んだ１０個の粒子について中空孔径（粒子中の全ての中空孔について、最長径および最短径の平均値を計測し、その平均値を用いた）を計測し、粒子外径（上記平均粒径を用いた）に対する比（＝中空孔径／粒子外径）を計算した。
【００３２】
（４）空隙率
アムコ社製ポロシメーター「２０００」を使用して、中空ポリマー粒子の空隙率を測定した。封入水銀圧力は２，０００ｋｇ／ｃｍ2とし、任意の場所から０．５ｇサンプリングした中空ポリマー粒子サンプルを評価に用いた。
【００３３】
（５）耐圧縮強度
島津製作所社製微小圧縮試験機「ＭＣＴＭ−５００」を使用して、中空ポリマー粒子の１０％圧縮強度を測定した。
【００３４】
【表１】
表１中で使用した成分は下記の通りである。
ＭＭＡ：メチルメタクリレート、ＭＡＣ：メタクリル酸
ＩＢＭ：イソブチルメタクリレート
ＴＭＰ：トリメチロールプロパントリアクリレート
ＤＰＥ：ジペンタエリスリトールヘキサアクリレート
ＡＩＢＮ：アゾビスイソブチロニトリル
ＰＶＰ：ポリビニルピロリドン
コロイダルシリカ、リン酸カルシウム：２０重量％水溶液
塩酸：３５重量％水溶液
【００３６】
（実施例１〜３、参考例１、比較例１）
ＳｉＣ９０重量％、酸化硼素５重量％、カオリン２重量％及びアルミナ３重量％からなる無機混合物７０重量部に対して、表２に示した中空ポリマー粒子３０重量部を加えて混合したセラミック組成物１００重量部に対して、メチルセルロース１５重量部及び添加水を加えて混練し、押出成形可能な坏土とした。次いで、得られた各坏土を公知の押出成形法により賦形して、リブ厚：４３０μｍ、セル数：１６個／ｃｍ2 を有する直径：１１８ｍｍ、高さ：１５２ｍｍの円筒形ハニカム構造体を作製した。次に、このハニカム構造体を乾燥した後、昇温速度４０℃／時で５００℃に昇温して１時間脱脂工程を行い、さらに不活性ガス雰囲気下２１００℃で２時間保持して焼成し、多孔質セラミックフィルタを得た。
【００３７】
（比較例２）
造孔剤として、中実のポリマー粒子（ｆ）を使用したこと以外は、実施例２と同様にして多孔質セラミックフィルタを得た。
【００３８】
上記実施例、参考例及び比較例で得られた多孔質セラミックフィルタについて、下記の性能評価を行い、その結果を表２に示した。
（５）熱膨張係数
セイコーインスツルメンツ社製「ＴＭＡ１００」を用いて、高さ方向（Ａ軸）及び円筒直径方向（Ｂ軸）の熱膨張係数を測定した。測定温度は４０〜８００℃、昇温速度は４０℃／時とした。
【００３９】
（６）気孔率
空隙率と同様の方法で測定した。サンプルは得られたフィルタをそのまま使用した。
【００４０】
【表２】
【発明の効果】
本発明の多孔質セラミックフィルタの製造方法は、上述の構成であり、造孔剤として中空ポリマー粒子を用いることにより、気孔率が高く、耐熱衝撃性の高い多孔質セラミックフィルタを得ることができる。
従って、得られた多孔質セラミックフィルタは、特にディーゼルパティキュレートフィルタとして好適に使用される。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a porous ceramic filter having high porosity and high heat resistance.
[0002]
[Prior art]
2. Description of the Related Art In recent years, as a porous ceramic filter, a partition wall of a honeycomb structure in which silicon carbide (SiC) powder is sintered has a porous structure, and by passing through such a partition wall, a filter against a fluid such as a gas is obtained. Various porous honeycomb filters having a function have been proposed and put into practical use, for example, as a filter for collecting particulates of exhaust gas discharged from a diesel vehicle (diesel particulate filter).
[0003]
In such a porous honeycomb filter, the average pore diameter (hereinafter referred to as the pore diameter) and the porosity of the porous honeycomb filter are very important factors for determining the performance of the filter, and the porous honeycomb filter such as a diesel particulate filter is used. In the case of a porous ceramic filter, a filter having a large pore diameter and a large porosity is desired from the relationship of the collection efficiency of fine particles, pressure loss, and collection time.
[0004]
Conventionally, the control of the pore size of the ceramic filter has been performed by appropriately selecting the aggregate particle size of the ceramic composition as a raw material. In order to improve the filter performance, as a method for controlling the pore diameter, for example, a method of adding an organic polymer to a ceramic composition has been proposed (Japanese Patent Laid-Open No. 2000-288325). On the other hand, as a method for improving the porosity, for example, JP-A-3-215374 discloses a particle size distribution in which an average particle size is 100 to 150 μm and 90% by weight or more exists within ± 20% of the average particle size. There has been proposed a method in which the SiC powder having the surface thereof is crushed and connected to each other, and is molded and compressed so as to remain in the molded body without being crushed.
[0005]
However, in these methods, the bonding of the SiC particles constituting the porous body is only due to the particle growth of the SiC fine particles, so that the mechanical strength decreases as the porosity increases, and both the porosity and strength characteristics are compatible. There was a problem that it was difficult to make. In addition, a method of adding a pore-forming agent such as graphite is also common, but if a large amount of the pore-forming agent is used to further improve the porosity, the firing time is extended and the manufacturing process takes a long time. At the same time, particularly in the case of a SiC composition having a high firing temperature, there is a problem that a large distortion is applied to the molded body due to an increase in combustion heat, and cracks are generated in the molded body. Therefore, there is a demand for a method for producing a porous filter that can provide low thermal expansion and thermal shock resistance and improve the porosity.
[0006]
[Problems to be solved by the invention]
In view of the above problems, an object of the present invention is to provide a method for producing a porous ceramic filter having low thermal expansion and thermal shock resistance and improved porosity.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventors have made extensive studies on a method for producing a porous ceramic filter that can be sufficiently satisfied with respect to these various problems. And, after forming a predetermined molded body from the ceramic composition using the hollow polymer particles as a pore-forming agent and firing, it was found that a porous ceramic filter with improved porosity without thermal deformation was obtained, The present invention has been completed.
[0008]
That is, the present invention forms a predetermined molded body from a ceramic composition containing silicon carbide powder as a main component and hollow polymer particles having a plurality of hollow holes as a pore- forming agent, and then firing the molded body. It is characterized by that.
[0009]
Hereinafter, the present invention will be described in more detail.
In the present invention, in order to obtain a porous ceramic filter, a ceramic composition containing silicon carbide (SiC) powder as a main component and hollow polymer particles as a pore former is used. In the ceramic composition, the amount of the hollow polymer particles added is not particularly limited. However, if the amount is too small, sufficient porosity cannot be obtained. If the amount is too large, the strength of the ceramic molded body after firing is lowered. The content is preferably 10 to 50% by weight.
[0010]
The hollow polymer particles are preferably those having an average particle size of 5 to 100 μm and a 10% compressive strength of 1.5 MPa or more.
When the average particle diameter is smaller than 5 μm, the pore diameter of the obtained porous ceramic filter becomes small, the pressure loss of the filter increases, and the collection time becomes short. On the other hand, when the average particle diameter is larger than 100 μm, the pore diameter of the ceramic filter is increased, and the pressure loss of the filter is reduced, but the collection efficiency is lowered.
[0011]
Further, in order to prevent the hollow polymer particles from being destroyed by mechanical shearing force at the stage of shaping the ceramic composition into a predetermined molded body, the 10% compressive strength is preferably 1.5 MPa or more.
[0012]
Furthermore, even in hollow particles having the same porosity, the hollow particles having a honeycomb-like morphology composed of a plurality of pores are found to have excellent compressive strength, and by using the hollow polymer particles having a plurality of pores as a pore-forming agent, Particles destroyed during the filter forming process are reduced, and the porosity can be improved.
[0013]
Although it does not specifically limit as a method to manufacture the said hollow polymer particle, The manufacturing method which consists of two processes of the following suspension polymerization and solvent removal is preferable.
That is, a monomer solution is prepared by mixing a non-polymerizable organic solvent with a mixed monomer composed of a hydrophilic monomer, a polyfunctional monomer, and other monomers, and then suspending the monomer solution in a polar solvent, It comprises a first step of polymerizing to obtain polymer particles encapsulating the non-polymerizable organic solvent, and a second step of obtaining hollow polymer particles by removing the organic solvent in the polymer particles.
In the above production method, the polymerization method is not particularly limited, but it is preferable to use the suspension polymerization method because it is easy to control the particle diameter and easily form particles enclosing effective voids.
[0014]
The hydrophilic monomer that constitutes the monomer component has a higher affinity for a polar solvent than an organic solvent. Therefore, it is considered that the hydrophilic monomer is localized at the oil droplet interface in the suspended oil droplet of the monomer solution. Form the outer wall of the polymer particles.
The hydrophilic monomer preferably has a water solubility of 1% by weight or more. For example, methyl (meth) acrylate, (meth) acrylonitrile, (meth) acrylamide, (meth) acrylic acid, glycidyl (meth) acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, vinyl pyridine, 2-acryloyloxyethyl phthalic acid, itaconic acid, fumaric acid, dimethylaminomethyl methacrylate, and the like, preferably methyl methacrylate, (meth) acrylic acid, 2-hydroxyethyl methacrylate and the like. These can be used alone or in combination of two or more.
[0015]
If the amount of the hydrophilic monomer used is too small, the outer wall surface of the hollow polymer particles will not be sufficiently formed, and the porosity of the hollow polymer particles will decrease, so that 10 to 99.9% by weight is used in the monomer component. Preferably, it is 30 to 99.9% by weight.
[0016]
The polyfunctional monomer constituting the monomer component is added for the purpose of improving the compression strength of the particles, and di (meth) acrylate, tri (meth) acrylate and the like are preferably used. Examples of the di (meth) acrylate include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and trimethylolpropane. Examples include di (meth) acrylate. Examples of the tri (meth) acrylate include trimethylolpropane tri (meth) acrylate, ethylene oxide-modified trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, and the like.
[0017]
Other polyfunctional monomers other than those described above include, for example, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, diallyl phthalate, diallyl malate, diallyl fumarate, diallyl succinate, triallyl isocyanurate And divinyl compounds such as divinyltriall, divinylbenzene and butadiene.
[0018]
These polyfunctional monomers can be used alone or in combination of two or more.
[0019]
If the amount of the polyfunctional monomer used is too small, the compressive strength of the hollow polymer particles is not sufficient, and if too large, the particles are aggregated during polymerization. Preferably, it is 0.3 to 5% by weight.
[0020]
Other monomers constituting the monomer component are added for the purpose of improving mechanical strength, chemical resistance and moldability, and the type is not particularly limited. For example, ethyl (meth) acrylate, propyl (meth) acrylate, Alkyl (meth) acrylates such as butyl (meth) acrylate, cumyl methacrylate, cyclohexyl (meth) acrylate, mistyryl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate; styrene, α-methylstyrene, p- Aromatic vinyl monomers such as methylstyrene and p-chlorostyrene; vinyl esters such as vinyl acetate and vinyl propionate; halogen-containing monomers such as vinyl chloride and vinylidene chloride; ethylene, propylene, butadiene and the like. These can be used alone or in combination of two or more.
[0021]
When the amount of the other monomer used is too large, the hydrophilicity of the monomer component is lowered and the outer wall of the hollow polymer particles is prevented from being formed. Therefore, the amount of the monomer component is preferably 89.9% by weight or less. Is 69.9% by weight or less.
[0022]
The non-polymerizable organic solvent added to the monomer component is desirably localized in the center of the oil droplet in the suspended oil droplet of the monomer solution, and exhibits a hydrophobicity of 0.2% by weight or less in water. The type is not particularly limited, but for example, butane, pentane, hexane, cyclohexane, toluene, xylene and the like are preferably used. Of these, highly volatile butane, pentane, hexane, and cyclohexane are more preferable.
[0023]
When the amount of the non-polymerizable organic solvent is too small, the porosity of the particles is low, and when it is too large, the porosity is too high and the strength of the particles is reduced. 400 parts by weight is preferred, more preferably 10 to 200 parts by weight.
[0024]
In the method for producing a porous ceramic filter of the present invention, first, SiC powder, talc powder components such as talc and baked talc as an inorganic binder, silica powder represented by amorphous silica, pore former, kaolin, A ceramic composition mainly composed of SiC powder is prepared by appropriately blending calcined kaolin, boron oxide, alumina, aluminum hydroxide and the like. The blending amount of the inorganic binder with respect to the SiC powder is not particularly limited, and is appropriately determined depending on the quality of the hollow polymer particles.
[0025]
The ceramic composition thus prepared is plasticized by adding a plasticizer, a binder or the like in the same manner as in the conventional method, and becomes a formable material for extrusion molding.
Using this raw material, extrusion molding into a honeycomb molded body or the like having a predetermined shape is performed, followed by drying. Then, the dried product is fired at a temperature of 1600 to 2200 ° C. to produce a target porous ceramic filter.
[0026]
(Function)
In the production method of the present invention, by blending hollow polymer particles as a pore-forming agent in the ceramic composition, low thermal expansion can be imparted to the porous ceramic filter, and the porosity and thermal shock resistance can be improved. Further, it is possible to provide a filter capable of suppressing the increase in pressure loss and effectively extending the collection time while maintaining high collection efficiency.
That is, by replacing the organic particles that are conventional pore-forming agents with hollow polymer particles having the same weight, the volume occupied by the pore-forming agent is increased and the porosity can be improved. Further, when replaced with hollow polymer particles of the same volume, the heat of combustion of the particles during firing is reduced and the strain applied to the ceramic molded article is reduced, so that low thermal expansion is imparted and thermal shock resistance is improved.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the present invention will be described below, but the present invention is not limited to the following examples.
-Preparation of hollow polymer particles The monomer components, non-polymerizable organic solvent and polymerization initiator of the blending amounts shown in Table 1 were mixed and stirred to prepare a monomer solution, and then ion-exchanged water (all used) 50% by weight of the amount) and a dispersing agent were added and stirred with a homogenizer to prepare a suspended monomer solution. Meanwhile, in a 20 liter polymerization vessel equipped with a stirrer, a jacket, a reflux condenser and a thermometer, the remaining ion-exchanged water, sodium chloride, sodium nitrite, hydrochloric acid and sodium hydroxide in the amounts shown in Table 1 were added. Stirring was started.
Then, after depressurizing the inside of the polymerization vessel and deoxidizing the inside of the container, nitrogen was injected to return the pressure to atmospheric pressure, and the inside was made into a nitrogen atmosphere, and then the suspension monomer solution was added all at once. The polymerization apparatus was heated to 80 ° C. to initiate polymerization. The polymerization was completed in 5 hours, and after a aging period of 1 hour, the polymerization vessel was cooled to room temperature.
The slurry was dehydrated with a centle, and then the organic solvent was removed by vacuum drying to obtain hollow polymer particles (a) to (e).
[0028]
-Solid polymer particles (f)
Expandable particles (“F-85D” manufactured by Matsumoto Yushi Co., Ltd.) were heated at 170 ° C. for 1 minute to use solid polymer particles that were foamed.
[0029]
The following performance evaluation was performed on the hollow polymer particles (a) to (e) and the solid particles (f), and the results are shown in Table 1.
(1) Average particle diameter The volume average particle diameter of the hollow polymer particles was measured using a laser diffraction particle size distribution analyzer “LA-910” manufactured by Horiba, Ltd. Three points were sampled from arbitrary locations of the particles, and the average value was used.
[0030]
(2) Internal morphology The equator cross section of the hollow polymer particles was cut into a thin film, and the internal morphology was observed with a transmission electron microscope.
[0031]
(3) Ratio (= hollow pore diameter / particle outer diameter)
For 10 particles selected arbitrarily, the hollow pore diameter (the average value of the longest diameter and the shortest diameter was measured for all the hollow holes in the particles, and the average value was used) was measured, and the particle outer diameter (the above average) The ratio (= hollow pore diameter / particle outer diameter) was calculated.
[0032]
(4) Porosity The porosity of hollow polymer particles was measured using a porosimeter “2000” manufactured by AMCO. The enclosed mercury pressure was 2,000 kg / cm 2, and a hollow polymer particle sample sampled 0.5 g from an arbitrary place was used for evaluation.
[0033]
(5) Compressive strength The 10% compressive strength of the hollow polymer particles was measured using a micro compression tester “MCTM-500” manufactured by Shimadzu Corporation.
[0034]
[Table 1]
The components used in Table 1 are as follows.
MMA: methyl methacrylate, MAC: methacrylic acid IBM: isobutyl methacrylate TMP: trimethylolpropane triacrylate DPE: dipentaerythritol hexaacrylate AIBN: azobisisobutyronitrile PVP: polyvinylpyrrolidone colloidal silica, calcium phosphate: 20 wt% aqueous hydrochloric acid: 35% by weight aqueous solution [0036]
(Examples 1 to 3, Reference Example 1 , Comparative Example 1)
Ceramic composition 100 obtained by adding 30 parts by weight of hollow polymer particles shown in Table 2 to 70 parts by weight of an inorganic mixture composed of 90% by weight of SiC, 5% by weight of boron oxide, 2% by weight of kaolin and 3% by weight of alumina, and mixing them. 15 parts by weight of methylcellulose and added water were added and kneaded with respect to parts by weight to obtain a kneaded clay. Next, each of the obtained clays was shaped by a known extrusion molding method to obtain a cylindrical honeycomb structure having a rib thickness: 430 μm, a cell number: 16 cells / cm 2 , a diameter: 118 mm, and a height: 152 mm. Produced. Next, after drying this honeycomb structure, the temperature was increased to 500 ° C. at a temperature increase rate of 40 ° C./hour to perform a degreasing process for 1 hour, and further, held at 2100 ° C. for 2 hours in an inert gas atmosphere and fired. A porous ceramic filter was obtained.
[0037]
(Comparative Example 2)
A porous ceramic filter was obtained in the same manner as in Example 2 except that solid polymer particles (f) were used as the pore former.
[0038]
The following performance evaluation was performed on the porous ceramic filters obtained in the above Examples , Reference Examples and Comparative Examples, and the results are shown in Table 2.
(5) Thermal expansion coefficient The thermal expansion coefficient of the height direction (A axis) and the cylindrical diameter direction (B axis) was measured using "TMA100" manufactured by Seiko Instruments Inc. The measurement temperature was 40 to 800 ° C., and the heating rate was 40 ° C./hour.
[0039]
(6) Measured by the same method as the porosity porosity. The sample used the obtained filter as it was.
[0040]
[Table 2]
【Effect of the invention】
The method for producing a porous ceramic filter of the present invention has the above-described configuration. By using hollow polymer particles as a pore-forming agent, a porous ceramic filter having high porosity and high thermal shock resistance can be obtained.
Therefore, the obtained porous ceramic filter is particularly preferably used as a diesel particulate filter.
Claims (3)
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001204725A JP4991057B2 (en) | 2001-07-05 | 2001-07-05 | Method for producing porous ceramic filter |
| PCT/JP2002/006658 WO2003004132A1 (en) | 2001-07-05 | 2002-07-01 | Method for manufacturing porous ceramic filter |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001204725A JP4991057B2 (en) | 2001-07-05 | 2001-07-05 | Method for producing porous ceramic filter |
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| JP2003010617A JP2003010617A (en) | 2003-01-14 |
| JP4991057B2 true JP4991057B2 (en) | 2012-08-01 |
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| JP2001204725A Expired - Fee Related JP4991057B2 (en) | 2001-07-05 | 2001-07-05 | Method for producing porous ceramic filter |
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| JP (1) | JP4991057B2 (en) |
| WO (1) | WO2003004132A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP4224368B2 (en) * | 2003-08-12 | 2009-02-12 | 積水化学工業株式会社 | Method for producing hollow resin particles and hollow resin particles |
| JP4183603B2 (en) * | 2003-11-19 | 2008-11-19 | 積水化学工業株式会社 | Method for producing hollow resin particles and hollow resin particles |
| JP2005145937A (en) * | 2003-11-19 | 2005-06-09 | Sekisui Chem Co Ltd | Pore-forming agent for molding porous ceramic filter and oil-absorbing or water-absorbing particle for cosmetic |
| US7387829B2 (en) | 2004-01-13 | 2008-06-17 | Ibiden Co., Ltd. | Honeycomb structure, porous body, pore forming material for the porous body, and methods for manufacturing the pore forming material, the porous body and the honeycomb structure |
| WO2005068398A1 (en) * | 2004-01-13 | 2005-07-28 | Ngk Insulators, Ltd. | Process for producing ceramic structure |
| JP4745964B2 (en) * | 2004-04-22 | 2011-08-10 | 日本碍子株式会社 | Porous honeycomb structure manufacturing method and porous honeycomb structure |
| JP4630696B2 (en) * | 2005-03-08 | 2011-02-09 | 積水化学工業株式会社 | Method for producing bell structure resin particles |
| CA2596294A1 (en) | 2005-03-23 | 2006-09-28 | Sekisui Chemical Co., Ltd. | Thermally disappearing resin particle |
| JP4668654B2 (en) * | 2005-03-23 | 2011-04-13 | 積水化学工業株式会社 | Heat extinguishing hollow resin particles and method for producing heat extinguishing hollow resin particles |
| JP2007073946A (en) * | 2005-08-10 | 2007-03-22 | Sekisui Chem Co Ltd | Manufacturing method of anode body for solid electrolytic capacitor |
| JP5596611B2 (en) * | 2011-03-31 | 2014-09-24 | 日本碍子株式会社 | Manufacturing method of honeycomb structure |
| JP6943714B2 (en) * | 2017-01-27 | 2021-10-06 | 積水化学工業株式会社 | Solid oxide fuel cell electrode pore-forming agent resin fine particles |
| US11230503B2 (en) * | 2017-06-27 | 2022-01-25 | General Electric Company | Resin for production of porous ceramic stereolithography and methods of its use |
| JP6513273B1 (en) * | 2018-08-31 | 2019-05-15 | 三井化学株式会社 | Resin particles |
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| JPS59174561A (en) * | 1983-03-18 | 1984-10-03 | 三井造船株式会社 | Manufacture of porous ceramics |
| DE3529075A1 (en) * | 1985-08-14 | 1987-02-19 | Man Technologie Gmbh | METHOD FOR PRODUCING POROUS OBJECTS |
| JPH02290211A (en) * | 1989-04-28 | 1990-11-30 | Kanebo Ltd | Ceramic filter and manufacture thereof |
| US5198001A (en) * | 1991-09-13 | 1993-03-30 | Calgon Carbon Corporation | Apparatus and process for removing organic compounds from a gas stream |
| JP2728838B2 (en) * | 1993-02-04 | 1998-03-18 | 鐘紡株式会社 | Method for producing porous sintered body |
| JP3387266B2 (en) * | 1995-05-31 | 2003-03-17 | 松下電器産業株式会社 | Exhaust gas filter and manufacturing method thereof |
| JPH11128639A (en) * | 1997-10-31 | 1999-05-18 | Asahi Glass Co Ltd | Ceramic filter and its production |
| JP4394329B2 (en) * | 2001-03-01 | 2010-01-06 | 日本碍子株式会社 | Manufacturing method of ceramic structure |
| KR20030089702A (en) * | 2001-03-14 | 2003-11-22 | 세키스이가가쿠 고교가부시키가이샤 | Hollow polymer particles, method for preparing hollow polymer particles, porous ceramic filter, and method for preparing porous ceramic filter |
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| WO2003004132A1 (en) | 2003-01-16 |
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