JP3813938B2

JP3813938B2 - Dimensional stabilization treatment method for wood

Info

Publication number: JP3813938B2
Application number: JP2003088622A
Authority: JP
Inventors: 治郎西尾; 高志木村; 友加里瀬戸
Original assignee: Eidai Co Ltd
Current assignee: Eidai Co Ltd
Priority date: 2003-03-27
Filing date: 2003-03-27
Publication date: 2006-08-23
Anticipated expiration: 2016-09-20
Also published as: JP2003245907A

Description

【０００１】
【発明の属する技術分野】
本発明は木質材の寸法安定化処理方法に関し、特に、木質材の内部に高圧水蒸気を供給することにより木質材の寸法安定性を向上させるようにした木質材の処理方法の改良に関する。
【０００２】
【従来の技術】
木材は水分の吸放出により膨潤又は収縮する。このことは無垢の挽き板、木材薄板（厚さ０．２ｍｍ〜１０ｍｍ程度）やパーチクルボード、ＭＤＦ、ＯＳＢ、合板等でも同様である。建築用あるいは家具用材料として木質材を用いる場合には、環境により木質材が膨潤又は収縮することは好ましくなく、環境に左右されない寸法安定性を持つことが望まれる。
【０００３】
そのための対策として、プレス盤で木質材を上下に挟持してオートクレーブ内に入れ、高圧水蒸気で数分間処理して木質材の寸法安定化を図る方法等が行われている。しかし、この方法は設備が大がかりであることに加え、木質材内部（中央部）への高圧水蒸気の浸透が難しく、木質材の中央部と周辺部での処理状態が異なる場合が生じる。
【０００４】
本出願人は、その不都合を解消すべく、従来の木材処理で用いられる熱盤を持つ平盤プレスの熱盤間に、自然乾燥状態にある木質材を配置し、その周囲に弾性シリコン材等の弾性密封材料を配置して密封状態とした後、上下の熱盤に設けた蒸気供給孔から高圧水蒸気を供与して、木質材に含まれる水分を水蒸気化させ、木質材の寸法安定化を図る方法を提案した（特開平６−２３８６１６号公報）。この処理方法は、通常の熱盤を持つ平盤プレスを用いて木質材の寸法安定化処理を行うことから、処理が簡素化される利点がある。また、この処理において、本発明者らの実験によれば、約１５０℃〜２３０℃に近い温度の高圧水蒸気（飽和水蒸気又は過熱水蒸気）を密封空間内に供給し、木質材を約１８０℃〜２００℃に近い温度まで昇温させて、木質材の含水率分の水分を水蒸気化させることにより有効に処理が進行することを経験している。
【０００５】
上記した高圧水蒸気による木質材の寸法安定化処理は、木質材に高い寸法安定性をもたらすと共に、フェノールやホルマリンのような薬剤を使わず、処理後も薬剤が残らないクリーンな処理方法であることからも有用なものである。
【０００６】
本発明者らは、一層均質に安定化処理が施された木質材を得るべくさらに研究を行い、寸法安定化処理に際して、木質材を収容した密封空間内を減圧し、そこに高圧水蒸気を導入することが有効であることを知覚し、それに基づき、さらに改良された木質材の寸法安定化処理方法を提案している（特願平８−４５１７３号）。この方法を取ることにより、高圧水蒸気が木質材内部にまで確実に透過しかつ均一に供給され、処理木質材に一層均質でかつ高い寸法安定性を付与することができることを確認した。
【０００７】
さらに、これまでの木質材の高圧水蒸気処理では、常温、常態にある木質材、すなわち、含水率が低くても７％〜１０％程度であり、温度が１５℃〜２５℃程度である自然乾燥状態にある木質材をそのまま熱盤プレス間等に形成された密封空間に配置して処理を行うようにしており、当該木質材に含まれる水分が水蒸気化する温度までに木質材を昇温させ、かつ、高い含水率の水分を高圧水蒸気化するのに、前記のように約１５０℃〜２３０℃程度の高圧水蒸気の持つエネルギーを主として使用しており、この高圧水蒸気の製造に高い製造コストを必要としていること、また、木質材の昇温に長い時間を要していることに着目し、それを解消するものとして、処理すべき木質材に対して別途用意した乾燥施設により加熱乾燥処理を施し、自然乾燥状態による含水率より低い含水率とし、該加熱乾燥処理が施された木質材を密封空間内に収容し、該密封空間内に高圧水蒸気を供給することにより該木質材に寸法安定化処理を施すようにした方法も提案している（特願平８−１９２４２６号参照）。
【０００８】
この処理方法によれば、従来法に比較して、短い高圧水蒸気処理時間で従来品と同等の処理効果を上げることができ、高圧水蒸気の製造にかかるコストを低減でき、処理単価を下げることが可能となる。
【０００９】
【発明が解決しようとする課題】
すでに提案している上記の方法は、エネルギーコストの低減に資するものであり有効なものであるが、前記のように、処理すべき木質材に対して予め加熱乾燥処理を施すことを必要とし、そのために乾燥施設を別途用意する必要がある。また、乾燥済みの木質材を乾燥施設から高圧水蒸気処理施設へ移動する必要があり、移動の手間と共に一時保管場所等も必要となる。
【００１０】
そのような設備的また場所的制約を受けることを配慮しつつ、木質材の高圧水蒸気処理についてさらに研究と実験を継続する過程において、自然乾燥状態の木質材を高圧水蒸気処理施設の密封空間内に置き、そこで、高圧水蒸気導入と圧解放とを１サイクルとする処理を同じ密封空間内において複数回繰り返すことにより、木質材を予備加熱乾燥しなくても、短い処理時間で予備加熱乾燥をした場合と同等の処理効果を上げることができることを知覚した。
【００１１】
【課題を解決するための手段】
本発明の木質材の寸法安定化処理方法は、上記知覚に基づくものであり、基本的に、木質材を密封空間内に収容し、該密封空間内への高圧水蒸気の導入及び該密封空間内の圧開放とからなるサイクルを、同じ密封空間内において連続して、少なくとも２回以上繰り返すことにより該木質材の寸法安定化を図ることを特徴とする。
【００１２】
本発明において、処理すべき木質材に特に制限はなく、単板等の無垢材や合板だけでなく、中質繊維板（ＭＤＦ）、配向性ボード（ＯＳＢ）やパーチクルボード（ＰＢ）等の木質加工材料も処理可能である。木質加工材料の場合に、プレス盤により加圧圧縮を施しながら本発明の処理を行なうことは、圧密化処理と共に寸法安定化処理を行うことができることから、特に有効である。また、本発明において用いる処理木質材は自然乾燥状態のものであってよく、特別の加熱乾燥施設による予備乾燥処理は必要としない。
【００１３】
前記木質材は密封空間内に収容される。該密封空間は、高圧水蒸気の導入と圧解放が可能であり、また、好ましくは密封空間内の減圧が可能であることを条件に、従来用いられている木質材処理用の耐圧型圧力容器による密封空間であってもよく、木質材の圧締や複合材の製造に従来用いられる平盤プレスに装着されるプレス盤の間に形成される密封空間であってもよい。
【００１４】
密封空間内の減圧が可能である場合には、好ましくは、第１回目の高圧水蒸気の導入に先立って、密封空間内の減圧を行う。本発明者らの実験によれば、予め減圧された空間内に高圧水蒸気を導入することにより、圧解放後の木質材の含水率低下は促進され、かつ、木質材の中央部まで寸法安定化処理が均一に施されることを確認した。減圧は７００ｍｍＨｇ〜７５０ｍｍＨｇ程度が好ましく、本発明者らの実験によれば、７５０ｍｍＨｇ程度の減圧で十分な効果が得られた。なお、この減圧は、各サイクルでの高圧水蒸気導入に先立って行うようにしてもよく、その場合には、より少ない高圧水蒸気供給量で（すなわち、より短い高圧水蒸気処理時間で）処理効果が期待できる利点がある。
【００１５】
前記耐圧型圧力容器又はプレス盤は、熱源を有するもの、有しないものいずれであってもよいが、熱源を有するものが特に推奨される。熱源としては、耐圧型圧力容器あるいはプレス盤に組み込まれたヒーターあるいはバンドヒーター等の電気的加熱手段、加熱蒸気、マイクロウェーブを含む高周波加熱、等任意であり、該熱源によって予め昇温状態とされた密封空間内に木質材を収容する。昇温温度は、好ましくは、高圧水蒸気による寸法安定化処理が木質材において進行する温度範囲（１８０℃〜２００℃程度）である。
【００１６】
木質材を収容した密封空間内に好ましくは１５０℃〜２３０℃程度の飽和水蒸気又は過熱水蒸気（飽和水蒸気より高い温度の水蒸気）である高圧水蒸気を導入する。高圧水蒸気の圧力は、処理すべき木質材の種類等によって相違するが、数ｋｇｆ／ｃｍ²〜３０ｋｇｆ／ｃｍ²であってよい。
【００１７】
密封空間への高圧水蒸気の供給及び必要な場合の前記密封空間内の減圧の方法は任意であるが、例えば、密封空間がプレス盤の間に形成され、かつ、プレス盤が外部に連通する多数の細孔を有するものである場合には、一方のプレス盤の該細孔を従来公知の高圧水蒸気発生源に適宜の配管及び弁手段等を介して接続し、他方のプレス盤の細孔を従来公知の好ましくは耐熱性の真空ポンプあるいは吸引ブロアー等の真空引き源にやはり適宜の配管及び弁手段等を介して接続することにより可能である。
【００１８】
高圧水蒸気の供給及び減圧の他の方法として、上下のプレス盤と木質材との間に、多数の細孔を有しかつ耐圧性、耐熱性を有する別部材を配置して行なうようにしてもよい。その場合には、一方の前記別部材を高圧水蒸気発生源に接続し、他方の前記別部材を真空引き源に接続する。それにより、前記別部材の細孔を介して木質材に高圧水蒸気を供給し、かつ真空引きすることが可能となる。この種の別部材の好ましい態様は処理すべき木質材を収容できる内部空間を持つ箱状部材と該内部空間を密閉する蓋部材とから構成される。
【００１９】
密封空間内の減圧を行う場合には、噴出する高圧水蒸気は、噴出力に加えて吸引力の作用を受け、運動エネルギーが増大する。それにより、従来法よりも短時間で木質材の内部にまで確実に透過し、かつ等しくかつ均一に行き渡る。その結果、寸法安定化処理が速やかにかつ全域にわたり迅速に進行する。
【００２０】
第１サイクルの高圧水蒸気導入を所要時間行った後、密封空間内の圧解放を行う。高圧水蒸気導入時間は、高圧水蒸気による寸法安定化処理が進行する温度（１８０℃〜２００℃程度）にまで当該木質材が昇温するまでは少なくとも継続して行うことが好ましい。圧解放は所定の温度に昇温した後に直ちに行ってもよく、高圧水蒸気の導入を停止してしばらく放置した後に行うようにしてもよい。
【００２１】
圧解放後、直ちに、又は１分〜２分間程度放置して解圧バルブを締めた後、再び、第１サイクル目と同じ処理を同じ密封空間において繰り返す。その際に、第２サイクル目以降においても、「密封空間内の減圧」処理は任意であり、行う場合には高圧水蒸気処理時間を短くできる利点がある。また、第２サイクル目以降での「密封空間内への高圧水蒸気の導入」処理時間は第１サイクル目でのそれよりも長い時間とすることが好ましい。それは、本発明者の実験によれば、第１サイクル目（あるいは、３サイクル以上行う場合での初期段階での数回のサイクル）は、高含水率かつ常温の木質材が密封空間内で加圧条件下で１８０℃〜２００℃程度までの昇温を受け、次の圧解放により、供給された水蒸気と共に木質材内部の水分も外部に放出されてその含水率を３％程度にまで低下させる段階であり、木質材の昇温には長い時間を必要としないことによる。また、含水率が低下した後に木質材に対して従来と同様の高圧水蒸気処理が施す場合に、比較的長時間に亘って、連続して高温高圧条件におくことが効果的であることを知覚したことによる。
【００２２】
前記のようにして処理サイクルを繰り返し、所要の寸法安定化処理が達成された時点で処理を終了し、密封空間から処理済み木質材を取り出す。
本発明者らの実験によれば、上記の方法により処理された木質材は、無処理のものと比較して高い寸法安定性が得られ、前記サイクルを繰り返さないで処理したものと比較してより短い処理時間で同程度の寸法安定性が得られ、また、予め含水率を低下させた木質材を用いて処理する場合と比較して、同程度の高圧水蒸気処理時間でありながら同程度の寸法安定性が得られた。
【００２３】
本発明の方法により上記のような効果が得られる理由は必ずしも明らかでないが、（必要に応じて行う減圧）→高圧水蒸気導入→圧解放、を１サイクルとする処理を複数回繰り返すことは、木質材に対して、高圧水蒸気の過度の流動と圧の上下変動を反復して与えることとなり、そのために、処理すべき木質材の木質エレメント中の壁孔が破壊されて、処理効果が迅速にかつ中央部にまで及ぶことによると解される。事実、実験では、エレメントの大きな材料（無垢材、ブロックボード、合板等において、特に高い処理効果が得られている。
【００２４】
【発明の実施の形態】
以下、図面を参照しつつ本発明をさらに詳細に説明する。図１は本発明の木質材の寸法安定化処理方法を実施する装置の一例である。図において、１ａ、１ｂは、従来の木材処理で用いられる平板プレスに装着されると同様のプレス盤であり、それぞれに熱源としてのヒータ２ａ、２ｂが設けられ、さらに、処理すべき木質材Ｗと衝接することとなる表面部分には多数の細孔３ａ、３ｂが形成されている。上方のプレス盤１ａに形成された細孔３ａは配管４ａ及び開閉弁Ｖを介して高圧水蒸気発生源Ｓに接続しており、下方のプレス盤１ｂに形成された細孔３ｂは配管４ｂを介して真空ポンプＶＰに接続している。配管４ｂには三方弁Ｖ_Tを介して分岐管４ｃが接続しており、該分岐管４ｃの他端は大気に解放している。真空ポンプに変えてブロアー（図１には示されない）を用いてもよい。
【００２５】
この装置を用いて本発明による処理方法を実施するに際しては、先ず、処理すべき平板状の木質材Ｗを、下方のプレス盤１ｂの該細孔３ｂが形成されている位置に載置する。一方、上方のプレス盤１ａには前記木質材Ｗを収容できる位置にステンレス材等からなる方形状の厚さ規制治具１０をネジ止め（図示されない）等により固定する。図中、１１は厚さ規制治具１０の下端縁に取り付けた弾性シール材である。この厚さ規制治具１０は下方のプレス盤１ｂに固定的に取り付けてもよい。
【００２６】
次に、プレス盤１ａ、１ｂを該厚さ規制治具１０により規制されるまで接近させ、停止させる。図示しないが、前記のように木質材Ｗの周囲に密封材料を配置して、プレス盤１ａ、１ｂの間に密封空間を形成するようにしてもよい。実施例に示すように、形成される密封空間は、処理すべき木質材Ｗの当初厚みよりもわずかに広い高さを持つ密封空間としてもよい。
【００２７】
その状態で、高圧水蒸気発生源Ｓ側の配管４ａに設けた開閉弁Ｖを閉じ、真空ポンプＶＰ（又は、ブロアー）を作動し、かつ三方弁Ｖ_Tを操作して、下方のプレス盤１ｂに形成した細孔３ｂから真空引きを行なう。所定圧に減圧した時点で、三方弁Ｖ_Tを操作して配管４ｂを閉鎖する。次に、高圧水蒸気発生源Ｓ側の配管４ａに設けた開閉弁Ｖを開き、プレス盤１ａに形成した細孔３ａから高圧水蒸気を密封空間内に噴出する。細孔３ａから木質材Ｗに向けてあるいは密封空間に向けて噴出する水蒸気は、噴出力に加えて吸引力による力を受け、木質材の木質材Ｗの内部にまで容易にかつ均一に到達し、木質材Ｗは内部水分が水蒸気化する温度に達する。
【００２８】
所望量の高圧水蒸気の噴出を終えた後、三方弁Ｖ_Tを操作して密封空間を分岐管４ｃを介して大気に解放し、圧の解放を行う。解圧により、供給した水蒸気と共に木質材の内部水分も放出されて、木質材の含水率は低下する。これで、１回目のサイクルは終了する。圧解放後、好ましくは１分〜５分程度経過した後に、２回目のサイクルとして、再び、三方弁Ｖ_Tを操作して密封空間を真空ポンプＶＰ側に接続し、密封空間内の減圧を行う。木質材の含水率が所定値（３％程度）になるまで、以下同様の操作を必要回数繰り返す。その際に、高圧水蒸気導入処理の時間を次第に長くしていくことは有効である。
【００２９】
木質材が所定の含水率となった時点で、再度、前記サイクルを反復する。但し、この場合には、これまでよりも長い時間高圧水蒸気の供給を行うことが望ましい。また、２回目以降のサイクルにおいて最初の減圧操作を行うことは必ずしも必要ない。必要回数だけ上記サイクルを繰り返し、所定の寸法安定処理が達成された時点で、必要に応じて冷却工程を行ないながら、木質材を取り出し、本発明による木質材の寸法安定化処理方法は終了する。
【００３０】
図２は本発明の木質材の寸法安定化処理方法を実施する装置の他の例を示している。この例は、プレス盤に外部に連通する細孔が設けられていない平板プレスを本発明の処理方法に用いる場合に好適な例であり、蒸気噴出用の細孔２３ａを有する平板状の第１の別部材２０ａがネジ２１ａを用いて上方のプレス盤１ａに固定され、さらに、真空引き用の細孔２３ｂを有する平板状の第２の別部材２０ｂがネジ２１ｂを用いて下方のプレス盤１ｂに固定されている。そして、それぞれの細孔２３ａ、２３ｂは、図１に示した装置の場合と同様に、高圧水蒸気発生源Ｓ及び真空ポンプＶＰに接続している。この装置の使用方法は図１の場合と実質的に同じである。この場合でも、実施例に示すように、形成される密封空間は、処理すべき木質材Ｗの当初厚みよりもわずかに広い高さを持つ密封空間としてもよい。
【００３１】
【実施例】
以下、実施例に基づき本発明を説明する。
〔実施例１〕
寸法が１５×３００×１８００ｍｍで、常温での含水率７．７％であるＭＤＦを、ヒーター加熱により前もって１９５℃に加温した寸法１６×３３０×１８５０ｍｍの耐圧容器内に配置した。この容器内を密封し、容器内を１サイクル目、７５０ｍｍＨｇまで減圧した後、容器内部に１５ｋｇｆ／ｃｍ²、１９５℃の飽和水蒸気を３分間導入した。解圧弁を開いて容器内部を解圧した。解圧後のＭＤＦの含水率は３．３％であった。１分後に、解圧弁を閉じ内部を密封した後、２サイクル目として、同じ飽和水蒸気を６分間導入した。その後、再度解圧弁を操作して常圧に戻し、処理済のＭＤＦを取り出した。
【００３２】
〔比較例１〕
寸法が１５×３００×１８００ｍｍで、常温での含水率７．７％であるＭＤＦを、熱風温度１５０℃、風速２５ｍのジェットドライヤーによって、ボード温度１３６℃、ボード含水率３．５％にまで下げた後に、ヒーター加熱により１９５℃に加熱した寸法１６×３３０×１８５０ｍｍの耐圧容器内に配置した。この容器内を密封し、７５０ｍｍＨｇまで減圧した後、容器内部に１５ｋｇｆ／ｃｍ²、１９５℃の飽和水蒸気を１０分間導入した。処理後に解圧弁を操作して容器内部を常圧に戻し、処理済のＭＤＦを取り出した。
【００３３】
〔比較例２〕
寸法が１５×３００×１８００ｍｍで、常温での含水率７．７％であるＭＤＦを、ヒーター加熱により前もって１９５℃に加温した寸法１６×３３０×１８５０ｍｍの耐圧容器内に配置した。この容器内を密封し７００ｍｍＨｇまで減圧した後、容器内部に１５ｋｇｆ／ｃｍ²、１９５℃の飽和水蒸気を２０分間導入した。蒸気の供給を停止した後、解圧弁を開いて常圧に戻し、処理済の木質材を取り出した。
【００３４】
〔実施例２〕
寸法が１５×３００×１８００ｍｍで、常温での含水率７．７％であるパーチクルボードを、ヒーター加熱によって前もって１９５℃に加温した寸法１６×３３０×１８５０ｍｍの耐圧容器内に配置した。この容器内を密封し、容器内を１サイクル目、７００ｍｍＨｇまで減圧した後、容器内部に１７．５ｋｇｆ／ｃｍ²、２０５℃の飽和水蒸気を１分間導入した。その後、解圧弁を開いて容器内部を解圧した。１分後に、２サイクル目として、解圧弁を閉じ密封した後、容器内部を７００ｍｍＨｇまで減圧し、その後に容器内部に同じ飽和水蒸気を２分間導入した。解圧後のパーチクルボードの含水率は３．５％であった。
次に、３サイクル目として、容器内を密封し、７００ｍｍＨｇまで減圧した後、容器内部に１５ｋｇｆ／ｃｍ²、２０５℃の飽和水蒸気を１０分間導入した。処理後に解圧弁を操作して容器内部を常圧に戻し、処理済のパーチクルボードを取り出した。
【００３５】
〔比較例３〕
寸法が１５×３００×１８００ｍｍで、常温での含水率７．７％であるパーチクルボードを高周波加熱によってボード温度１４６℃、含水率３．７％にした後、蒸気加熱によって前もって２０５℃に加温した寸法が１６×３３０×１８５０ｍｍの耐圧容器内に配置した。この容器内を密封し、７００ｍｍＨｇまで減圧した後、容器内部に１７．５ｋｇｆ／ｃｍ²、２０５℃の飽和水蒸気を１５分間導入した。その後、解圧弁を開いて容器内部を解圧し、処理済のパーチクルボードを取り出した。
【００３６】
〔比較例４〕
寸法が１５×３００×１８００ｍｍで、常温での含水率７．７％であるパーチクルボードを、蒸気加熱によって前もって２０５℃に加温した寸法が１６×３３０×１８５０ｍｍの耐圧容器内に配置した。この容器内を密封し、７００ｍｍＨｇまで減圧した後、容器内部に１７．５ｋｇｆ／ｃｍ²、２０５℃の飽和水蒸気を２５分間導入した。その後、解圧弁を開いて容器内部を解圧し、処理済のパーチクルボードを取り出した。
【００３７】
〔評価試験〕
前記の実施例１、２、比較例１〜４、及び、実施例及び比較例で用いた木質材であって無処理のものについて、厚さ膨張率及び剥離強さ（ｋｇｆ／ｃｍ²）を測定した。その結果を表１に示す。
なお、厚さ膨張率は（Ｔ₁−Ｔ₀）／Ｔ₀×１００であり、ここで、Ｔ₀＝絶乾時の厚さ、Ｔ₁＝飽水時の厚さ。また、剥離試験は、５ｃｍ角試験片を剥離試験治具に取り付け、試験片の内部剥離試験を行って内部剥離力を求め、その値を試験片面積２５ｃｍ²で割って１ｃｍ²当たりの内部剥離応力を求めた。
【００３８】
【表１】

【００３９】
〔考察〕
表１に示されるように、本発明品では、（減圧→）高圧水蒸気導入→圧解放、を１サイクルとする処理を２回又は３回繰り返すことにより、無処理のもの比較して高い寸法安定性が得られ、前記サイクルを繰り返さないで処理したもの（比較例２、４）と比較してより短い処理時間で同程度の寸法安定性が得られ、また、予め含水率を低下させた木質材を用いて処理したもの（比較例１、３）と比較して、同程度の高圧水蒸気処理時間でありながら同程度の寸法安定性が得られることが分かる。
【００４０】
【発明の効果】
本発明による木質材の寸法安定化処理方法によれば、従来法に比較して、短い高圧水蒸気処理時間で同等の処理効果を上げることができる。それにより、高圧水蒸気の製造にかかるコストを低減でき、処理単価を下げることができる。また、処理木質材に対して予備乾燥を施す必要がないことから、乾燥施設に要する経費や設置場所が不要であり、また、予備乾燥後に高圧水蒸気処理にいたるまでの間に木質材が吸湿してしまうことにより生じるロスも回避される。
【図面の簡単な説明】
【図１】木質材の寸法安定化処理方法を実施する装置の一例を示す図。
【図２】木質材の寸法安定化処理方法を実施する装置の他の例を示す図。
【符号の説明】
１ａ、１ｂ…プレス盤、２ａ、２ｂ…ヒータ、３ａ…高圧水蒸気導入用細孔、３ｂ…真空引き用細孔、４ａ…高圧水蒸気供給用配管、５ｂ…真空引き用配管、１０…厚さ規制治具、Ｗ…木質材、Ｓ…高圧水蒸気供給源、Ｖ…開閉弁、Ｖ_T…三方弁、ＶＰ…真空ポンプ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a timber material dimensional stabilization method, and more particularly to an improvement in a timber material processing method in which high-pressure steam is supplied into the timber material to improve the dimensional stability of the timber material.
[0002]
[Prior art]
Wood swells or shrinks due to moisture absorption and release. The same applies to a solid saw board, a thin wood board (thickness of about 0.2 mm to 10 mm), a particle board, MDF, OSB, and plywood. When a wood material is used as a building or furniture material, it is not preferable that the wood material swells or shrinks depending on the environment, and it is desirable to have dimensional stability that is not influenced by the environment.
[0003]
As a countermeasure for this, a method has been used in which a wooden material is sandwiched up and down by a press board and placed in an autoclave and treated with high-pressure steam for several minutes to stabilize the size of the wooden material. However, in this method, in addition to the large-scale equipment, it is difficult for high-pressure water vapor to penetrate into the wood material (center portion), and the processing state at the center portion and the peripheral portion of the wood material may be different.
[0004]
In order to eliminate the inconvenience, the present applicant arranges a wood material in a naturally dry state between the heat plates of a flat plate press having a heat plate used in conventional wood processing, and elastic silicon material or the like around it. After the elastic sealing material is placed and sealed, high-pressure steam is supplied from the steam supply holes provided in the upper and lower heating plates to vaporize the moisture contained in the wood material and stabilize the size of the wood material. A method has been proposed (JP-A-6-238616). This processing method has an advantage that the processing is simplified because the timber dimensional stabilization processing is performed using a flat plate press having a normal hot platen. In this treatment, according to the experiments of the present inventors, high-pressure steam (saturated steam or superheated steam) having a temperature close to about 150 ° C. to 230 ° C. is supplied into the sealed space, and the wood material is about 180 ° C. to It has been experienced that the processing proceeds effectively by raising the temperature to a temperature close to 200 ° C. and steaming the moisture content of the wood material.
[0005]
The above-mentioned dimensional stabilization treatment of wood using high-pressure steam brings high dimensional stability to the wood, and does not use chemicals such as phenol or formalin. Is also useful.
[0006]
The present inventors have further studied to obtain a wood material that has been subjected to a more uniform stabilization treatment, and in the dimension stabilization treatment, the inside of the sealed space containing the wood material is decompressed, and high-pressure steam is introduced therein. Based on this, a further improved method for stabilizing the size of a wood material has been proposed (Japanese Patent Application No. 8-45173). By adopting this method, it was confirmed that the high-pressure water vapor surely permeates the inside of the wood material and is uniformly supplied, and can impart more uniform and high dimensional stability to the treated wood material.
[0007]
Furthermore, in the conventional high-pressure steam treatment of the wood material, the wood material at normal temperature and in the normal state, that is, the dryness is about 7% to 10% even at a low moisture content, and the temperature is about 15 ° C. to 25 ° C. The wood material in a state is placed in a sealed space formed between hot platen presses as it is, and the treatment is performed, and the temperature of the wood material is raised to a temperature at which the moisture contained in the wood material is steamed. In addition, as described above, the energy of high-pressure steam of about 150 ° C. to 230 ° C. is mainly used to convert high moisture content into high-pressure steam. Focusing on the fact that it takes a long time to raise the temperature of the wooden material, and as a solution to this, heat drying treatment is performed using a separate drying facility for the wooden material to be processed. Alms, nature A moisture content lower than that in a dry state is set, and the wood material subjected to the heat drying treatment is accommodated in a sealed space, and the wood material is subjected to dimensional stabilization treatment by supplying high-pressure steam into the sealed space. There is also a method proposed (see Japanese Patent Application No. 8-192426).
[0008]
According to this treatment method, compared with the conventional method, the treatment effect equivalent to that of the conventional product can be increased in a short high-pressure steam treatment time, the cost for the production of high-pressure steam can be reduced, and the processing unit price can be reduced. It becomes possible.
[0009]
[Problems to be solved by the invention]
The above-mentioned method that has already been proposed is effective because it contributes to the reduction of energy costs, but as described above, it is necessary to pre-heat and dry the wood material to be treated, Therefore, it is necessary to prepare a drying facility separately. In addition, it is necessary to move the dried wood material from the drying facility to the high-pressure steam treatment facility, and a temporary storage place and the like are required together with the labor of movement.
[0010]
In consideration of such equipment and location restrictions, in the process of further research and experiment on high-pressure steam treatment of wood materials, naturally dried wood materials are placed in the sealed space of the high-pressure steam treatment facility. If the wood material is preheated and dried in a short treatment time without repeating preheat drying, the process of introducing high-pressure steam and releasing the pressure one cycle is repeated several times in the same sealed space. It was perceived that the same processing effect can be achieved.
[0011]
[Means for Solving the Problems]
The wood material dimensional stabilization processing method of the present invention is based on the above perception. Basically, the wood material is accommodated in the sealed space, the introduction of high-pressure steam into the sealed space, and the sealed space. The wood material is dimensionally stabilized by repeating a cycle comprising the pressure release of at least twice continuously in the same sealed space.
[0012]
In this invention, there is no restriction | limiting in particular in the wood material which should be processed, not only solid materials, such as a single board, and a plywood, but wood processing, such as a medium density fiber board (MDF), an orientation board (OSB), and a particle board (PB) Materials can also be processed. In the case of a woody processed material, it is particularly effective to perform the treatment of the present invention while applying pressure and compression with a press board, because the dimensional stabilization treatment can be performed together with the consolidation treatment. Further, the treated wood material used in the present invention may be in a naturally dried state and does not require a preliminary drying treatment by a special heat drying facility.
[0013]
The wooden material is accommodated in a sealed space. The sealed space is a pressure-resistant pressure vessel for treating a wood material that has been conventionally used on condition that high-pressure steam can be introduced and pressure-released, and preferably that the pressure in the sealed space can be reduced. It may be a sealed space, or may be a sealed space formed between press plates mounted on a flat plate press conventionally used for pressing a wooden material or manufacturing a composite material.
[0014]
When the pressure in the sealed space can be reduced, the pressure in the sealed space is preferably reduced prior to the first introduction of high-pressure steam. According to the experiments of the present inventors, by introducing high-pressure steam into a space that has been previously depressurized, the moisture content of the wood material after pressure release is reduced, and dimensional stabilization is achieved up to the center of the wood material. It was confirmed that the treatment was uniformly applied. The reduced pressure is preferably about 700 mmHg to 750 mmHg, and according to experiments by the present inventors, a sufficient effect was obtained with a reduced pressure of about 750 mmHg. This decompression may be performed prior to the introduction of high-pressure steam in each cycle, and in that case, a treatment effect is expected with a smaller amount of high-pressure steam supply (that is, with a shorter high-pressure steam treatment time). There are advantages you can do.
[0015]
The pressure-resistant pressure vessel or press panel may be either one having a heat source or one having no heat source, but one having a heat source is particularly recommended. As the heat source, an electric heating means such as a pressure-type pressure vessel or a heater or a band heater incorporated in a press panel, heating steam, high-frequency heating including microwaves, etc. are arbitrary, and the temperature is raised in advance by the heat source. A wooden material is accommodated in the sealed space. The temperature rise is preferably in the temperature range (about 180 ° C. to 200 ° C.) in which the dimensional stabilization treatment with high-pressure steam proceeds in the wood material.
[0016]
High-pressure steam, which is preferably saturated steam or superheated steam (steam having a temperature higher than saturated steam) at about 150 ° C. to 230 ° C., is introduced into the sealed space containing the wood material. The pressure of the high pressure steam, which varies depending on the type of wood material to be processed may be a number ^{^{kgf / cm 2 ~30kgf / cm 2}} .
[0017]
The method of supplying high-pressure steam to the sealed space and reducing the pressure in the sealed space when necessary is arbitrary. For example, a sealed space is formed between the press machines, and the press machine communicates with the outside. If there is a pore of the other press plate, connect the pore of one press plate to a conventionally known high-pressure steam generation source through appropriate piping, valve means, etc. It is possible to connect to a vacuum source such as a heat-resistant vacuum pump or a suction blower known in the art through appropriate piping and valve means.
[0018]
As another method of supplying high-pressure steam and reducing pressure, another member having a large number of pores and having pressure resistance and heat resistance may be disposed between the upper and lower press panels and the wood material. Good. In that case, one said another member is connected to a high pressure steam generation source, and the other said other member is connected to a vacuum suction source. This makes it possible to supply high-pressure steam to the wood material through the pores of the separate member and to evacuate it. A preferred embodiment of this type of separate member is composed of a box-shaped member having an internal space capable of accommodating a wood material to be processed and a lid member for sealing the internal space.
[0019]
When decompressing the sealed space, the high-pressure steam that is ejected is subjected to the action of a suction force in addition to the jet power, and the kinetic energy increases. Thereby, it penetrates into the inside of the wood material in a shorter time than the conventional method, and spreads equally and uniformly. As a result, the dimensional stabilization process proceeds promptly and throughout the entire area.
[0020]
After introducing the high-pressure steam in the first cycle for the required time, the pressure in the sealed space is released. The high-pressure steam introduction time is preferably continued at least until the temperature of the wood material is increased to a temperature (about 180 ° C. to 200 ° C.) at which the dimensional stabilization treatment with high-pressure steam proceeds. The pressure release may be performed immediately after the temperature is raised to a predetermined temperature, or may be performed after the introduction of high-pressure steam is stopped and left for a while.
[0021]
Immediately after releasing the pressure, or after letting it stand for about 1 to 2 minutes and tightening the pressure release valve, the same processing as in the first cycle is repeated again in the same sealed space. At that time, the "depressurization in the sealed space" process is optional even after the second cycle, and when it is performed, there is an advantage that the high-pressure steam treatment time can be shortened. Moreover, it is preferable that the processing time for “introducing high-pressure steam into the sealed space” after the second cycle is longer than that for the first cycle. According to the inventor's experiment, the first cycle (or several cycles in the initial stage when three or more cycles are performed) is applied with high moisture content and room temperature wood in the sealed space. Under a pressure condition, the temperature rises to about 180 ° C. to 200 ° C., and the next release of pressure releases the moisture inside the wood material together with the supplied water vapor to reduce its moisture content to about 3%. This is because it does not require a long time to raise the temperature of the wood material. In addition, it is perceived that it is effective to continuously maintain high temperature and high pressure conditions for a relatively long time when the high pressure steam treatment similar to the conventional one is applied to the wood material after the moisture content is lowered. It depends on.
[0022]
The processing cycle is repeated as described above, and when the required dimensional stabilization processing is achieved, the processing ends, and the processed wood material is taken out from the sealed space.
According to the experiments by the present inventors, the wood material treated by the above method has a higher dimensional stability compared to the untreated material, compared with the treated material without repeating the cycle. Similar dimensional stability can be obtained in a shorter processing time, and compared with the case of processing using a wood material whose moisture content has been reduced in advance, the same level of high-pressure steam processing time but the same level Dimensional stability was obtained.
[0023]
The reason why the above-described effects can be obtained by the method of the present invention is not necessarily clear, but repeating a process of (depressurization performed as necessary) → high-pressure steam introduction → pressure release one cycle a plurality of times The material will be repeatedly subjected to excessive flow of high-pressure steam and fluctuations in the pressure up and down, so that the wall hole in the wood element of the wood material to be treated is destroyed, and the treatment effect is quickly and It is understood that it extends to the central part. In fact, in experiments, particularly high processing effects have been obtained for materials with large elements (solid materials, block boards, plywood, etc.).
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 shows an example of an apparatus for carrying out the method for stabilizing a size of a wood material of the present invention. In the figure,

reference numerals

1a and 1b denote press machines similar to those mounted on a flat plate press used in conventional wood processing, respectively provided with

heaters

2a and 2b as heat sources, and further a wood material W to be processed. A large number of

pores

3a and 3b are formed on the surface portion that comes into contact with the surface. The pore 3a formed in the upper press panel 1a is connected to the high-pressure steam generation source S through the pipe 4a and the on-off valve V, and the pore 3b formed in the lower press panel 1b is connected through the pipe 4b. Connected to the vacuum pump VP. The pipe 4b is branched pipe 4c is connected via a three-way valve V _T, the other end of the branch pipe 4c is open to the atmosphere. A blower (not shown in FIG. 1) may be used instead of the vacuum pump.
[0025]
In carrying out the treatment method according to the present invention using this apparatus, first, the flat wooden material W to be treated is placed at a position where the pores 3b of the lower press board 1b are formed. On the other hand, a square-shaped thickness regulating jig 10 made of stainless steel or the like is fixed to the upper press panel 1a by screws (not shown) or the like at a position where the wood material W can be accommodated. In the figure, reference numeral 11 denotes an elastic sealing material attached to the lower end edge of the thickness regulating jig 10. The thickness regulating jig 10 may be fixedly attached to the lower press board 1b.
[0026]
Next, the

press panels

1a and 1b are brought close to each other until they are regulated by the thickness regulating jig 10 and stopped. Although not shown, a sealing material may be disposed around the wood material W as described above to form a sealed space between the

press panels

1a and 1b. As shown in the embodiment, the sealed space to be formed may be a sealed space having a height slightly larger than the initial thickness of the wood material W to be processed.
[0027]
In this state, the on-off valve V provided in the pipe 4a on the high-pressure steam generation source S side is closed, the vacuum pump VP (or blower) is operated, and the three-way valve _VT is operated, so that the lower press panel 1b Vacuuming is performed from the formed pores 3b. When the pressure was reduced to a predetermined pressure, by operating the three-way valve V _T to close the pipe 4b. Next, the on-off valve V provided in the pipe 4a on the high-pressure steam generation source S side is opened, and high-pressure steam is jetted into the sealed space from the pores 3a formed in the press panel 1a. The water vapor spouted from the pores 3a toward the wooden material W or toward the sealed space is easily and uniformly reached inside the wooden material W of the wooden material under the force of suction force in addition to the jet power. The wood material W reaches a temperature at which the internal moisture is steamed.
[0028]
After finishing the ejection of the desired amount high pressure steam, the sealed space via the branch pipe 4c by operating the three-way valve V _T is released to the atmosphere, it releases the pressure. The internal pressure of the wood material is released together with the supplied water vapor by the decompression, and the moisture content of the wood material is lowered. This completes the first cycle. After pressure release, preferably after a lapse of about 1 to 5 minutes, as the second cycle, again, by operating the three-way valve V _T connects the sealed space to a vacuum pump VP side, performs decompression of the sealed space . The same operation is repeated as many times as necessary until the moisture content of the wood material reaches a predetermined value (about 3%). At that time, it is effective to gradually increase the time of the high-pressure steam introduction treatment.
[0029]
When the wood material reaches a predetermined moisture content, the cycle is repeated again. However, in this case, it is desirable to supply the high-pressure steam for a longer time than before. Further, it is not always necessary to perform the first decompression operation in the second and subsequent cycles. The above cycle is repeated as many times as necessary, and when a predetermined dimensional stabilization process is achieved, the wooden material is taken out while performing a cooling process as necessary, and the dimensional stabilization processing method for the wooden material according to the present invention ends.
[0030]
FIG. 2 shows another example of an apparatus for carrying out the method for stabilizing the size of a wood material according to the present invention. This example is a suitable example in the case where a flat plate press in which a fine hole communicating with the outside is not provided in the press plate is used in the processing method of the present invention, and is a flat plate-like first having a vapor discharge fine hole 23a. The separate member 20a is fixed to the upper press platen 1a using screws 21a, and the flat plate-like second separate member 20b having the vacuum evacuation pores 23b is used to press the lower press platen 1b using screws 21b. It is fixed to. And each

pore

23a, 23b is connected to the high pressure steam generation source S and the vacuum pump VP similarly to the case of the apparatus shown in FIG. The method of using this device is substantially the same as in FIG. Even in this case, as shown in the embodiment, the formed sealed space may be a sealed space having a height slightly larger than the initial thickness of the wood material W to be processed.
[0031]
【Example】
Hereinafter, the present invention will be described based on examples.
[Example 1]
MDF having a size of 15 × 300 × 1800 mm and a moisture content of 7.7% at room temperature was placed in a pressure-resistant container having a size of 16 × 330 × 1850 mm, which was heated to 195 ° C. in advance by heating with a heater. The inside of the container was sealed, and the inside of the container was depressurized to 750 mmHg in the first cycle, and then 15 kgf / cm ² and saturated steam at 195 ° C. were introduced into the container for 3 minutes. The pressure relief valve was opened to decompress the inside of the container. The moisture content of the MDF after decompression was 3.3%. After 1 minute, the pressure relief valve was closed and the inside was sealed, and then the same saturated water vapor was introduced for 6 minutes as the second cycle. Thereafter, the pressure relief valve was operated again to return to normal pressure, and the processed MDF was taken out.
[0032]
[Comparative Example 1]
MDF with dimensions of 15x300x1800mm and moisture content of 7.7% at room temperature is reduced to a board temperature of 136 ° C and a board moisture content of 3.5% by a jet dryer with hot air temperature of 150 ° C and wind speed of 25m. After that, it was placed in a pressure-resistant container having a size of 16 × 330 × 1850 mm heated to 195 ° C. by heating with a heater. After sealing the inside of the container and reducing the pressure to 750 mmHg, 15 kgf / cm ² and saturated steam at 195 ° C. were introduced into the container for 10 minutes. After the treatment, the pressure relief valve was operated to return the inside of the container to normal pressure, and the treated MDF was taken out.
[0033]
[Comparative Example 2]
MDF having a size of 15 × 300 × 1800 mm and a moisture content of 7.7% at room temperature was placed in a pressure-resistant container having a size of 16 × 330 × 1850 mm, which was heated to 195 ° C. in advance by heating with a heater. After sealing the inside of the container and reducing the pressure to 700 mmHg, 15 kgf / cm ² , saturated steam at 195 ° C. was introduced into the container for 20 minutes. After stopping the supply of steam, the pressure relief valve was opened to return to normal pressure, and the treated wood material was taken out.
[0034]
[Example 2]
A particle board having dimensions of 15 × 300 × 1800 mm and a moisture content of 7.7% at room temperature was placed in a pressure-resistant container having dimensions of 16 × 330 × 1850 mm, which was heated to 195 ° C. in advance by heating with a heater. The inside of the container was sealed, and the inside of the container was depressurized to 700 mmHg in the first cycle, and then 17.5 kgf / cm ² , saturated steam at 205 ° C. was introduced into the container for 1 minute. Thereafter, the pressure relief valve was opened to decompress the inside of the container. One minute later, as the second cycle, the pressure relief valve was closed and sealed, and then the inside of the container was decompressed to 700 mmHg, and then the same saturated water vapor was introduced into the container for 2 minutes. The moisture content of the particle board after decompression was 3.5%.
Next, as the third cycle, the inside of the container was sealed and the pressure was reduced to 700 mmHg, and then 15 kgf / cm ² , saturated steam at 205 ° C. was introduced into the container for 10 minutes. After the treatment, the pressure relief valve was operated to return the inside of the container to normal pressure, and the treated particle board was taken out.
[0035]
[Comparative Example 3]
A particle board having dimensions of 15 × 300 × 1800 mm and having a moisture content of 7.7% at room temperature was heated to 205 ° C. by steam heating after the board temperature was 146 ° C. and the moisture content was 3.7% by high frequency heating. It arrange | positioned in the pressure-resistant container whose dimension is 16x330x1850mm. After sealing the inside of the container and reducing the pressure to 700 mmHg, 17.5 kgf / cm ² and saturated steam at 205 ° C. were introduced into the container for 15 minutes. Thereafter, the pressure relief valve was opened to decompress the inside of the container, and the treated particle board was taken out.
[0036]
[Comparative Example 4]
A particle board having a size of 15 × 300 × 1800 mm and a moisture content of 7.7% at room temperature was placed in a pressure-resistant container having a size of 16 × 330 × 1850 mm, which was previously heated to 205 ° C. by steam heating. The inside of the container was sealed, and the pressure was reduced to 700 mmHg, and then 17.5 kgf / cm ² , saturated steam at 205 ° C. was introduced into the container for 25 minutes. Thereafter, the pressure relief valve was opened to decompress the inside of the container, and the treated particle board was taken out.
[0037]
〔Evaluation test〕
For the wood materials used in Examples 1 and 2 and Comparative Examples 1 to 4 and Examples and Comparative Examples, the thickness expansion coefficient and the peel strength (kgf / cm ² ) were determined. It was measured. The results are shown in Table 1.
The thickness expansion coefficient is (T ₁ −T ₀ ) / T ₀ × 100, where T ₀ = thickness when absolutely dry and T ₁ = thickness when saturated. In the peel test, a 5 cm square test piece is attached to a peel test jig, an internal peel test of the test piece is performed to determine an internal peel force, and the value is divided by a test piece area of 25 cm ² to obtain an internal peel per 1 cm ^2. The stress was determined.
[0038]
[Table 1]

[0039]
[Discussion]
As shown in Table 1, in the product of the present invention, the dimensional stability is higher than that of the non-treated product by repeating the treatment of (depressurization →) high-pressure steam introduction → pressure release as one cycle twice or three times. Wood, whose dimensional stability of the same degree is obtained in a shorter processing time compared to those processed without repeating the cycle (Comparative Examples 2 and 4), and whose moisture content has been reduced in advance. It can be seen that the same level of dimensional stability can be obtained while having the same level of high-pressure steam treatment time as compared with those processed using the material (Comparative Examples 1 and 3).
[0040]
【The invention's effect】
According to the method for stabilizing the size of a wood material according to the present invention, the same treatment effect can be achieved in a short high-pressure steam treatment time as compared with the conventional method. Thereby, the cost concerning manufacture of high pressure steam can be reduced, and a processing unit price can be lowered. In addition, since it is not necessary to pre-dry the treated wood material, the cost and installation location required for the drying facility are unnecessary, and the wood material absorbs moisture before the high-pressure steam treatment after the pre-drying. Loss caused by this is also avoided.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of an apparatus for carrying out a method for stabilizing a size of a wood material.
FIG. 2 is a view showing another example of an apparatus for carrying out a dimensional stabilization processing method for a wood material.
[Explanation of symbols]
DESCRIPTION OF

SYMBOLS

1a, 1b ... Press board, 2a, 2b ... Heater, 3a ... High pressure steam introduction pore, 3b ... Vacuum suction pore, 4a ... High pressure steam supply pipe, 5b ... Vacuum suction pipe, 10 ... Thickness regulation Jig, W ... wood material, S ... high-pressure steam supply source, V ... open / close valve, V _T ... three-way valve, VP ... vacuum pump

Claims

木質材を密封空間内に収容し、該密封空間内を減圧した後に、該減圧された密封空間内へ１５０℃〜２３０℃の高圧水蒸気を導入して該木質材の高圧水蒸気処理による寸法安定化を図ることを特徴とする木質材の寸法安定化処理方法。Dimensional stabilization by high-pressure steam treatment of the wood material by accommodating the wood material in the sealed space and, after decompressing the sealed space, introducing high-pressure steam at 150 ° C. to 230 ° C. into the decompressed sealed space A method for stabilizing the dimension of a wood material, characterized by:

木質材を該処理すべき木質材の当初厚みよりも広い高さを持つ密封空間内に収容し、該密封空間内を減圧した後に、該減圧された密封空間内へ１５０℃〜２３０℃の高圧水蒸気を導入して該木質材の高圧水蒸気処理による寸法安定化を図ることを特徴とする木質材の寸法安定化処理方法。The wooden material is accommodated in a sealed space having a height wider than the initial thickness of the wooden material to be treated, and after the pressure in the sealed space is reduced, a high pressure of 150 ° C. to 230 ° C. is introduced into the reduced sealed space. A method for dimensional stabilization of a wood material, characterized by introducing water vapor to stabilize the size of the wood material by high-pressure steam treatment.