【０００１】
【発明の属する技術分野】本発明は、木質材料に化学処理を施して強度を向上させる為の木質材料の強化方法に関する。
【０００２】
【従来の技術】わが国においては、木質材料は建築その他に多用されている。木材は、再生産可能な資源であるうえに、加工性、風合い、美観等も良好であるために、建築材料としては好適である。しかしながら、我が国でも豊富に産生する生産性の良いスギやヒノキの様な針葉樹は、材が軟質であり、使用が限定される。これらの問題を解決するために、従来は、▲１▼ＷＰＣと称される樹脂を注入する方法や、▲２▼ポリエステル系樹脂等の塗料を基材表面に厚塗りし、厚さ０．１〜１ｍｍ程度の強靭な塗膜を形成する方法、或いは、▲３▼熱プレス、もしくは、熱圧ロールにより木材を圧縮強化する方法も提案されている。
【０００３】しかしながら、▲１▼のＷＰＣでは樹脂の注入は木質材料を減圧や加圧注入装置内に仕込み、減圧や加圧或いはその両方を行い、樹脂液を装置内で木質材料に注入するバッチシステムで行われるため、注入に時間がかかり、しかも注入後の木質材料はべたつくため取り扱いが面倒であるなどの問題点を有する。更に、注入は木質材料全体にされるため、木質材料が厚いと樹脂量が多くなり、コストアップとなるほか、注入樹脂のために加工がしずらく、重量が大となるため搬送が困難などの欠点を示す。又、木としての風合いもなくなり、プラスチック様になってしまう。
【０００４】▲２▼の塗料の厚塗りは、通常の塗装の１０倍以上の厚さに塗布するため、塗布むらが生じたり、乾燥・硬化に時間がかかるほか、塗膜硬化時の樹脂の収縮等の歪みによる基材面からの剥離ならびに基材の反りなどに注意しなければならないなどの問題点を有する。また、基材がスギやヒノキ等の軟質材では塗膜をより厚くしなければならないなどの問題も有する。更に、塗装の場合には、あらかじめ素地調整を行う場合が多いので、樹脂成分が木質材料の内部にまで浸透出来なくなっており、単に表層に付着しているに過ぎない。従って、表層のみが堅くなるので、丁度、柔らかいスポンジの上に堅いが薄いプラスチック板を固定した様な形となり、塗装された堅い塗膜の破壊強度を超える力が加わると、塗膜の割れが生じ、その部分に陥没などが生じたりする為、著しく美観を損ねてしまう。
【０００５】▲３▼の圧縮木材の場合には、物理的に圧縮されただけなので、そのままでは、空気中の湿気等の影響を受け、元のサイズ並びに元の強度に戻り、強度面での低下のみならず、寸法安定性に関しても問題があった。
【０００６】▲２▼の改良法としては、木質材料の表面の繊維組織内に無溶剤型熱硬化性樹脂液を高圧で噴射注入する方法（特開２００１−１７９７０８）もあるが、噴射圧力は、８０〜１００ｋＰａ必要であり、樹脂浸透深さは、せいぜい１〜２ｍｍ程度であり、且つ、樹脂噴射後、ヒートロールにより加熱加圧することにより表面強化された板材を得るが、加圧噴射装置やヒートロール等高価な設備が必要である。更に加圧噴射するので、処理速度は、１〜４ｍ／分程度と遅い。又、ロールプレスなどにより木質材料を高温高圧下で圧縮後、硬化性樹脂を塗布し、圧縮後の木質材料の復元力により該樹脂を浸透させ、次いで該樹脂を硬化することにより圧縮された形状を固定する方法（特開平９−１７４５１４）がある。更にこの硬化性樹脂に薬剤を混入したものを用いる方法（特開平９−２７７２０８）も有るが、これらの方法では、強度は木質材料を圧縮処理することにより得られるのであり、樹脂による処理は単に圧縮強化された状態の保持という目的のために使用するものであり、木質材料そのものの強度保持が目的ではない。更に、設備的にも▲３▼と同様に高価なロールプレス機械が必要である。
【０００７】木材圧縮による強化は、強度を大きくするために圧縮率をを上げると、木質材料の柔らかい部分が優先的に圧縮される。堅い部分は圧縮されにくく、そのままの厚さを保つため、うづくりの様になり、表面に凸凹が生じてしまい、平滑な表面が得られにくい。又、強度を上げるために圧縮率を上げると、木質材料自体が割れる場合があり、歩留まりが悪くなる。更に大きな欠点としては、平面状の板状の素材に対してしか有効でなく、立体構造物では適用出来ない。
【０００８】
【発明が解決しようとする課題】
木質材料は樹種、その基材により、部分的に性質が異なり、表面硬度や素材としての強度的にも非常にムラがあり、使いにくかった。我が国で豊富な原材料であるスギやヒノキは材質が柔らかく、強度的に弱く、単なる塗装のみでは十分な強度が得られず、押し傷を生じることが多く、そのままでは家具や建材など、特にテーブルの天板や床材として利用することが出来なかった。例えば下塗り塗料を木質材料の表面に塗布した後、中塗り塗料を塗布したものでは、上記のように柔らかい基材では塗装後も基材が強靭にならなかった。又、硬化後、塗膜自体のヤセが起こり、平滑な塗面が得られない場合が多かった。更に、導管の大きい木質材料では、下塗り塗料の１回の塗布では導管をシールする事が出来ず、中塗り塗料を塗装しても、木質材料中に含まれている空気と置換するために、時には泡が発生し、平滑な塗面が得られない場合が多かった。そのために、表面の硬度を上げることと平滑にするための工夫が種々なされてきたが、特に下地処理に付いては、実用的なコスト範囲内に於いて浸漬用の特殊な槽も必要としない木質材料の強化方法による解決が課題となっていた。
【０００９】
【課題を解決するための手段】本発明者らは、木質材料の表面処理方法について種々研究した結果、木質材料の処理すべき表面に、該木質材料の温度以下の温度の反応硬化性樹脂液（以下樹脂液という）を塗布することにより、高い温度で塗布された場合に生じやすい導管等から発生する泡が抑えられる。又、予め木質材料が樹脂液の温度より高い温度設定されているので、樹脂液の温度が木質材料の温度により昇温するため、樹脂液の粘度が低下し、その結果、浸透し易くなり、導管などから発生する泡はより抑えられ、均一な塗布が可能となる。一方、樹脂液の浸透性は、吸い込みやすい部分、即ち柔らかい部分に樹脂液がより多く浸透されるので、柔らかい部分、即ち、強度的に弱い部分が優先的に補強され、表面強度がより均一化された木質材料が得られることを見出して本発明を完成した。
【００１０】
【発明の実施の形態】本発明において、木質材料としては特に限定されない。例えば、針葉樹、広葉樹の柱や板等の無垢材、集成材、突き板用単板、或いは／及び、ＭＤＦ、パーティクルボード等の木材チップを樹脂で固化した加工材、或いは／及び、突き板、合板、ＬＶＬ等の積層材等いずれのものであってもよい。或いは／及び、合板、ＬＶＬ等の積層材を基材とし、その表面に樹脂処理すべき単板を積層したものなどを用いることもできる。
【００１１】本発明で使用する浸透用の樹脂としては、浸透に適する液状であるものが好ましく、低粘度で流動性のあるものが好ましい。樹脂液の粘度は、樹脂の種類および塗布温度によって異なるが、２，０００ｍＰａ・ｓ以下が好ましい。
【００１２】本発明の浸透させる為の樹脂液処理は、木質材料表面に塗布浸透後硬化させてもよく、また適当な段階まで予備反応させたプレポリマーを用いてもよい。
【００１３】流動性を得るために必要ならば樹脂液を、樹脂処理される木質材料の温度以下の温度に予め加熱してもよい。この場合には、木質材料を樹脂液の温度以上の温度に予じめ加熱（以下、予熱と称する）しておくことが必要である。
【００１４】これらの樹脂液には、必要に応じ、硬化剤、硬化促進剤、架橋剤、着色剤、浸透助剤、防腐剤、防黴剤、香料、難燃剤等を配合することもできる。
【００１５】樹脂液の成分としては、無溶剤型又はハイソリッド型の常温又は加熱硬化性樹脂が好ましく、更に、硬化時の収縮が小さい樹脂が好ましい。樹脂液としては、エポキシ系樹脂、不飽和ポリエステル系樹脂、フェノール系樹脂、メラミン系樹脂、ユリア系樹脂、アクリル系樹脂、ウレタン系樹脂及びこれらの樹脂の組み合わせからなる樹脂液等が挙げられるが、エポキシ系樹脂が低収縮性ならびに密着性に優れるので特に好ましい。
【００１６】樹脂液として、エマルションやＮＡＤ（非水分散系）の様なポリマー微粒子を媒体に分散された系は、木質材料に浸透する際、強度を上げてくれるはずのポリマー粒予が木質材料の表面で濾過され、木質材料の表面に残り、奥深くまでは浸透できず、その結果、強度発現の期待は少ないし、又、樹脂濃度を高濃度にすることが困難なため、望ましくない。
【００１７】本発明における樹脂液浸透によって木質材料表面に効率よく注入される理由については下記のメカニズムによるものと思われる。木質材料の温度以下の温度の樹脂液を木質材料に塗布すると、木質材料の導管部分の空気が樹脂液により冷却されるため減圧状態となる。その結果、導管内部の空気は体積が減少するため、減圧状態となり、従って、外へ出て泡になるよりも、逆に樹脂液を吸引して木質材料の内部に樹脂液を導入することが出来る。この際、木質材料の温度をあらかじめ予熱しておくと、木質材料と樹脂液の温度差を大きく出来るので、その効果は更に大となり、効率的である。
【００１８】この場合には、予熱によりの導管内部の空気が膨張し、その結果、導管内部の空気は押し出される。次いで予熱による木質材料の表面温度よりも低い樹脂液が塗布されることにより、表面温度が低下し、導管内部の空気が収縮する。同時に予熱された木質材料により樹脂液の温度が上がり、樹脂液の粘度が低下し、浸透しやすくなる。これらの相乗効果により、樹脂液は木質材料に吸引され浸透する。木質材料に樹脂液が塗布された後、次の硬化工程に入るが、この間に浸透した樹脂液は硬化反応が進み、樹脂液は増粘し、流動性が減少する。次いで硬化乾燥炉、或いは加熱乾燥炉に導入されて、硬化は完了する。なお、硬化時間を十分にとれる場合には、特に加熱乾燥炉に入れる必要はなく常温で硬化させても良い。加熱炉では、基本的には表面から加熱されてゆくので、表面がまず硬化する。その結果、表面がまず硬化されるので、加熱炉の温度が高すぎない限り、導管内部に存在していた空気は、出口を封じられ、泡吹きはかなり抑制される。従って、硬化させるための炉の温度は、はじめの予熱温度より高くても問題にならない場合が多い。
【００１９】本発明の方法により、木質材料の吸い込み易さの度合いや温度条件、樹脂液の粘度などに大きく依存するが、木質材料の表面部分に０．１〜２ｍｍ程度の深さに樹脂液を浸透させ、樹脂層を形成することができ、ＷＰＣと同程度又はそれ以上の表面強度を得ることができる。
【００２０】この方法は、加圧、減圧等による強制的な浸透と異なり、木質材料そのものの吸い込み特性を利用しているので、柔らかい部分は吸い込みやすく、従って、浸透される樹脂量は多くなり、その結果、その部分は堅くなる。一方、堅い部分は吸い込みにくく、浸透される樹脂量は少ない。その結果、柔らかい部分は、より堅く、一方、はじめから堅い部分は、不必要に堅くなることがない。つまり、木質材料の強度並びに表面硬度が均一化するというメリットも生ずる。更に、木質材料そのものの吸い込み特性によるので、木質材料表面ほど、樹脂の含有量が高く、従って表面の方が内部よりも高い高度が得られやすい。その結果、表面は堅く、一方、内部は柔らかさを保持出来るので、木質材料の素材としての材質感を損なうことが少ない。
【００２１】一般の塗料でも、若干の樹脂分は木質材料に浸透させることは可能であるが、塗装の場合には、浸透すると、目ヤセが生じ、商品価値が落ちるので、極力浸透しないように、あらかじめ目止めなどの操作を行う場合が多く、内部まで堅くすることは困難である。
【００２２】更に、一般の塗料では、表面状態、即ち見栄えを重視するため、表面の平滑性に充填を置くため、塗料の粘度は低く、更に、不揮発分も少ない場合が多い。たとえ、不揮発分が高いものであっても、作業性重視の為、硬化速度の速いものを好む故に、樹脂分が木質材料に浸透できる時間も短かく、樹脂液の浸透深さ及び浸透量も十分では無く、従って強度の向上も期待できない。
【００２３】
【発明の詳細】本発明は、処理すべき木材等の木質材料に、該木質材料の温度以下の温度の反応硬化性の樹脂液を塗布し、木質材料に浸透させ、その後、塗布浸透された樹脂液を硬化させる事を特徴とするが、木質材料と樹脂液との温度差が大きい方が有利である。この際、木質材料を加温しない場合には、樹脂液を冷却することが必要となるが、冷却操作はそれ自身コストが掛かる上に樹脂液粘度が増粘し浸透性が落ちる為、効果的ではない。従って、処理すべき木質材料を予熱することが好ましい。この予熱処理は熱風や遠赤外線等による乾燥炉等の加熱炉内で行っても良く、スチーム、マイクロ波、熱盤加熱等によってもよい。予熱温度は特には限定されないが、木質材料を変形したりしない限り高温度で処理するのが望ましい。一般的には、３０〜１２０℃であり、この内、特に望ましい温度は、４５〜８０℃である。この温度では木質材料の変形や劣化が少なく、かつ、次の工程で用いられる樹脂液の粘度の低下並びに樹脂液の硬化反応の促進に有効であり、更に、導管内の水分や空気の除去にも効果が期待できるので有効である。
【００２４】予熱処理した木質材料に、予熱された温度と同じかそれ以下の温度に制御された樹脂液を塗布し、浸透させる。木質材料は予め加温されているが、より低温度の該樹脂液が接することにより表面温度が低下し、その結果、導管内部の空気層が冷却され、空気層の体積が減少する。この減少により減圧となり、木質材料の毛細管現象にプラスして、この吸引力により樹脂液は木質材料に浸透してゆく。更に、表面温度が樹脂液温度よりも高いために、樹脂液自体の温度が上昇し、その結果、樹脂液の粘度が低下し、浸透性を増すので、浸透には有効な力として相乗的に働く。
【００２５】樹脂液の塗布方法としては、スプレー、ロールコーター、フローコーター、ナイフコーター、刷毛、モップ、へら、しごき、ワイピング等、何れの方法も適用可能である。この内、ロールコーター、刷毛、モップ、へら、しごき、ワイピング等の塗布方法は、木質材料表面での吸い込みムラを減少出来るので好適である。
【００２６】浸透した樹脂液の硬化は、木質材料を１枚または多段に積み重ねて上下から加圧、圧締もしくは圧縮して加熱炉内等で加熱硬化させても良いし、又、ライン上で乾燥炉に入れて１枚ずつ硬化させても良い。また更に、加熱ロール間を通して加熱硬化させることもできる。硬化時間を十分にとれる場合には、室温で硬化しても良い。しかしながら、室温では、硬化時間を長くとれるので、浸透させる時間は長くできるが、作業時間も長くなるし、更に、加温による樹脂液の粘度の低下、ひいては、浸透性の向上という効果が期待できないので、必ずしも好ましくはない。
【００２７】浸透に使用される反応硬化性を有する樹脂液としては、熱硬化性樹脂、ラジカル等の開始剤による付加重合タイプの樹脂、硬化剤との反応による常温硬化型樹脂など、木質材料に浸透されて硬度、耐摩耗性等の強化効果を発揮するものであれば使用できる。例えば、エポキシ系樹脂、不飽和ポリエステル系樹脂、フェノール系樹脂、メラミン系樹脂、ユリア系樹脂、アクリル系樹脂、ウレタン系樹脂及びこれらの樹脂の組み合わせからなる樹脂液を挙げることができる。
【００２８】これらの樹脂は、無溶剤型樹脂液として使用してもよく、また、浸透を容易にするためや、付加的な性能を付与させるため、例えば抗菌組成物等の混入のために、若干の溶剤を含ませることもできる。
【００２９】樹脂液の不揮発分としては６０％以上が望ましく、更に望ましくは、８０％以上が好ましい。不揮発分が少ないと、硬度や強度が出ないばかりか、硬化後の溶剤等の蒸発により、硬化樹脂の体積収縮が生じ、木質材料の変形にも繋がるからである。
【００３０】樹脂液の成分としては、硬化時に木質材料の成分と接着性が良く、木質材料中のセルロース等の繊維素等とのＦＲＰ（繊維強化プラスチック）化が図れるものが望ましく、更に、硬化時の体積収縮率の低い樹脂が更に望ましい。これらの条件からは、上記樹脂の中では、エポキシ系樹脂が特に望ましい。
【００３１】
【実施例】以下に本発明の実施例について説明するが、本発明はこれらに限定されるものではない。
【００３２】実施例１
木質材料として針葉樹の内で中程度の軟質材であるスギの乾燥板材（幅４５５×長さ９１０×厚さ２４ｍｍ）を試片として用い、予め木質材料を６０℃の雰囲気下におき、木質材料の表面温度が５５〜６０℃になるまで加熱した。ついで、室温（２５℃）のエポキシ樹脂液（三精塗料工業株式会社製 低粘度エポキシ樹脂−脂肪族アミン系硬化剤の組み合わせによる木材強化剤 「ＤＳ−４５」、配合比率は主剤：硬化剤＝２：１、硬化時間＝１２０分（５０ｇポット ２０℃）、混合粘度＝１１０ｍＰａ・ｓ（２０℃）、硬化物の硬度（ショワーＤ）＝８３）を、ロールコーター塗装により塗布量が１５ｇ／尺２となるように塗布した。セッティング時間１０分経過中に樹脂液は木質材料の温度により加熱され、低粘度化し、同時に、樹脂液により表面温度が４５℃まで下がったため、導管内部の空気が体積収縮し、大部分の樹脂が吸引された。更に、予熱による木質材料の温度により、樹脂液は一部反応硬化した。次いで、５５℃の乾燥炉に入れ、４０分間加熱した。導管表面の樹脂は表面が高温に曝されるため、表面から硬化したので、導管からの発泡は殆ど認められなかった。この間にハンドリング可能な程度まで硬化した。樹脂液の浸透量は、厚さ０．５ｍｍで、従来のＷＰＣと同等の表面強度を有していた。
【００３３】実施例２
実施例１で、木質材料の予熱を行わず、室温のまま（２５℃）で、同じ温度の樹脂液（実施例１と同じ樹脂液）でロールコーターにより塗布量が１０ｇ／尺２塗布した。セッティング時間３０分間放置後、５０℃の乾燥炉に入れ、４５分間加熱した。導管部分の空気の出入りは殆ど無く、泡吹きも少なかった。樹脂液の浸透量は、厚さ０．３ｍｍであった。
【００３４】比較例１
木質材料は室温（２５℃）のままで、一方、実施例１と同じ樹脂液を温度を５０℃として刷毛により塗布量を１０ｇ／尺２で塗布した。塗布直後は樹脂液自体が低粘度化しているので吸い込みは良く、浸透したが室温で放置中に導管から数多くの泡が出、このまま硬化した。一方、浸透厚さは０．２ｍｍであり、表面の見栄えも悪く、強度的にも不満足であった。
【００３５】比較例２
樹脂液として、実施例１で用いたＤＳ−４５をエポキシシンナーで樹脂固形分として５０％に希釈して用いた以外は実施例と同じ方法で行った。泡吹きは無く、且つ、樹脂液が低粘度であるため、浸透性は大きく、厚さ２ｍｍまで浸透していることが認められたが、２ヶ月経過後、塗布された側が収縮し、凹状に変形した。更に、強度的にも不満足であった。
【００３６】本実施例や比較例で得られた表面処理木質材料と処理前の木質材料の表面硬度の比較を表１に示す。それぞれについての処理前後の硬度を示す。ここで、硬度評価はバーコル硬度計（針式）による。〔値の大きい方が硬い〕
【００３７】
【００３８】
【発明の効果】本発明の表面強化方法は、従来の各種樹脂浸透強化方法に比べて以下の点で優れている。
▲１▼連続生産が可能である。処理すべき木質材料を連続して流せるので、長大材等にも加工が可能である。
▲２▼装置が小型、簡便、且つ安価である。基本的には、塗装機及び硬化乾燥炉があればよく、更に望ましくは予熱炉としての加温炉があれば良いので、極めて安価かつ簡単な装置で済む。なお、予熱炉と硬化乾燥炉とは共に木質材料を加熱加温出来れば良いので、両者を同じ設備で共用できることもメリットとして上げられる。
▲３▼安全性が高い。破裂の危険性がある圧力容器を使用する必要がない。
▲４▼表面からの一定深度までの樹脂浸透が可能である。表面から０．１〜２ｍｍ程度の深さであれば、強化用樹脂液を浸透できる。強化用樹脂液の他、着色剤等の浸透も容易である。一般に樹脂液の浸透は深さ０．２ｍｍ程度以上が確保されれば、ほぼムラなく均一に見えるので、充分な注入量が確保できる。従って、不必要な大量の樹脂は不要であり、コスト的に優れる。
▲５▼木質材料の表面だけの強化が可能であるので、ＷＰＣの様なプラスチック感は生じない。更に、特に柔らかい部分は、樹脂液の吸い込み性が高いため、より大くの樹脂液を浸透するため、堅さがより増し、一方、既に堅い部分は一般に吸い込み性が低いため、樹脂液をあまり吸い込まず、従って過多さの増し方は少ないため、堅さや強度が均一化される。
▲６▼化粧単板等の化粧材を基材に貼着した状態での強化も可能である。
▲７▼仕上がり感が良好である。従来の「塗料の厚塗り品」と比べ、樹脂が木質材料内に浸透されているため不自然さがなく、また、「樹脂液塗布による熱圧処理品」に比べて樹脂液が十分な深さに注入されているため、樹脂ムラもない。以上述べたように、本発明によれば従来のＷＰＣ等では実施できない樹脂加工が可能である。本発明で使用する樹脂は必ずしも、高硬度、高強度の得られる樹脂である必要はなく、木質材料の加工、例えば切削等を容易にする樹脂等でもよく、塗布も２段に分けて行うなど、任意の形態で実施してよい。
▲８▼高価且つ複雑な設備が不要であり、平面状のもの以外に、どの様な形状の製品にも適用が可能である。[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for strengthening a woody material for improving its strength by chemically treating the woody material.
[0002]
2. Description of the Related Art In Japan, wood materials are widely used for construction and the like. Wood is suitable as a building material because it is a reproducible resource and has good workability, texture, aesthetics, and the like. However, conifers such as cedar and cypress, which are abundantly produced in Japan and have high productivity, are soft in wood and their use is limited. Conventionally, in order to solve these problems, (1) a method of injecting a resin called WPC, or (2) a paint such as a polyester-based resin is thickly applied on the surface of the base material so as to have a thickness of 0.1%. A method of forming a tough coating film of about 1 mm or (3) a method of compressing and strengthening wood with a hot press or a hot-press roll has also been proposed.
[0003] However, in the WPC of (1), the resin is injected into a batch in which the wood material is charged into a decompression or pressurization injection device, depressurized and / or pressurized, and the resin liquid is injected into the wood material in the device. Since the injection is carried out in the system, it takes a long time to inject the wood material, and the wood material after the injection is sticky, so that there is a problem that the handling is troublesome. Furthermore, since the injection is performed on the entire wood material, if the wood material is thick, the amount of resin increases and the cost increases.In addition, the injection resin makes processing difficult and the weight increases, making transport difficult. The disadvantages of In addition, the texture of the wood is lost, and it becomes plastic-like.
[0004] Thick coating of (2) is applied to a thickness 10 times or more that of a normal coating, so that uneven coating occurs, it takes time to dry and harden, and the resin is hardened when the coating is hardened. There are problems such as the need to pay attention to peeling from the substrate surface due to distortion such as shrinkage and warping of the substrate. Further, if the base material is a soft material such as cedar or cypress, the coating film must be made thicker. Further, in the case of painting, since the substrate adjustment is often performed in advance, the resin component cannot penetrate into the interior of the wooden material, and merely adheres to the surface layer. Therefore, only the surface layer becomes hard, so it has a shape like a hard but thin plastic plate fixed on a soft sponge, and when a force exceeding the breaking strength of the hard film is applied, the coating cracks. This causes a depression or the like in that portion, which significantly impairs the appearance.
[0005] In the case of compressed wood of (3), since it is only physically compressed, it returns to its original size and original strength under the influence of moisture in the air as it is, and the strength in terms of strength is reduced. There was a problem not only in reduction but also in dimensional stability.
[0006] As an improvement method of (2), there is a method of injecting a solventless thermosetting resin liquid at a high pressure into a fiber structure on the surface of a wood material (Japanese Patent Application Laid-Open No. 2001-179708). , 80 to 100 kPa is required, the resin penetration depth is at most about 1 to 2 mm, and after the resin is injected, a sheet material whose surface is reinforced by heating and pressing with a heat roll is obtained. Expensive equipment such as a heat roll is required. Further, since the pressure is injected, the processing speed is as low as about 1 to 4 m / min. Also, after compressing the wood material under high temperature and high pressure by a roll press or the like, applying a curable resin, penetrating the resin by the restoring force of the compressed wood material, and then curing the resin to form a compressed shape. (Japanese Patent Laid-Open No. 9-174514). Furthermore, there is a method using a mixture of a curable resin and a chemical (Japanese Patent Application Laid-Open No. 9-277208), but in these methods, the strength is obtained by compressing a woody material, and the treatment with the resin is simply performed. It is used for the purpose of maintaining a state of being compressed and strengthened, and not for maintaining the strength of the woody material itself. Furthermore, an expensive roll press machine is required in terms of equipment as in (3).
In the strengthening by wood compression, when the compression ratio is increased to increase the strength, the soft portion of the wood material is compressed preferentially. The hard part is hard to be compressed and the thickness is maintained as it is, so it is like making, and the surface becomes uneven, and it is difficult to obtain a smooth surface. In addition, when the compression ratio is increased to increase the strength, the wood material itself may be cracked, and the yield is reduced. As a further major disadvantage, it is effective only for a flat plate-shaped material, and cannot be applied to a three-dimensional structure.
[0008]
[Problems to be solved by the invention]
The woody material has partially different properties depending on the tree species and its base material, and has very uneven surface hardness and strength as a material, making it difficult to use. Japanese cedar and cypress, which are abundant raw materials in Japan, are soft and weak in strength. It could not be used as a top plate or flooring. For example, when the undercoat was applied to the surface of the wooden material and then the intermediate coat was applied, the base material did not become tough even after coating with the soft base material as described above. Further, after curing, the coating film itself was frayed, and a smooth coated surface was often not obtained. Furthermore, in the case of wood material having a large conduit, it is not possible to seal the conduit with a single application of the undercoat paint, and even if the intermediate paint is applied, the paint is replaced with air contained in the wood material. Occasionally, bubbles were generated and a smooth coated surface could not be obtained in many cases. For this purpose, various measures have been taken to increase the hardness of the surface and to make it smooth, but especially for the surface treatment, a special tank for immersion is not required within a practical cost range. The solution by the method of strengthening the woody material has been an issue.
[0009]
Means for Solving the Problems The present inventors have conducted various studies on a method for treating the surface of a wooden material. As a result, a reaction-curable resin solution having a temperature equal to or lower than the temperature of the wooden material is applied to the surface of the wooden material to be treated. By applying (hereinafter, referred to as a resin liquid), bubbles generated from a conduit or the like which are likely to be generated when applied at a high temperature can be suppressed. In addition, since the temperature of the wood material is previously set higher than the temperature of the resin solution, the temperature of the resin solution is increased by the temperature of the wood material, so that the viscosity of the resin solution decreases, and as a result, the resin material easily penetrates, Bubbles generated from a conduit or the like are further suppressed, and uniform application becomes possible. On the other hand, the permeability of the resin liquid is such that the resin liquid penetrates more into the easy-to-suction part, that is, the soft part, so that the soft part, that is, the weak part is preferentially reinforced, and the surface strength is made more uniform. The present inventors have found that a wood material obtained can be obtained and completed the present invention.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, wood materials are not particularly limited. For example, softwood, solid wood such as pillars and boards of hardwood, laminated wood, veneer veneer or / and MDF, processed material obtained by solidifying wood chips such as particle board with resin, or / and veneer, Any material such as a plywood or a laminated material such as LVL may be used. Alternatively, it is also possible to use a laminated material such as plywood or LVL as a base material, on which a single plate to be resin-treated is laminated.
The resin for permeation used in the present invention is preferably a liquid suitable for permeation, and preferably a resin having low viscosity and fluidity. The viscosity of the resin liquid varies depending on the type of resin and the application temperature, but is preferably 2,000 mPa · s or less.
The resin liquid treatment for infiltration according to the present invention may be carried out after application and infiltration onto the surface of the wooden material, or may be carried out using a prepolymer preliminarily reacted to an appropriate stage.
If necessary to obtain fluidity, the resin liquid may be preheated to a temperature lower than the temperature of the wood material to be resin-treated. In this case, it is necessary to heat the woody material in advance to a temperature equal to or higher than the temperature of the resin liquid (hereinafter, referred to as preheating).
If necessary, a curing agent, a curing accelerator, a crosslinking agent, a coloring agent, a penetrating aid, a preservative, a fungicide, a fragrance, a flame retardant, and the like can be added to these resin liquids.
As a component of the resin liquid, a non-solvent type or high solid type room temperature or heat curable resin is preferable, and further, a resin having a small shrinkage upon curing is preferable. Examples of the resin liquid include an epoxy resin, an unsaturated polyester resin, a phenol resin, a melamine resin, a urea resin, an acrylic resin, a urethane resin and a resin liquid composed of a combination of these resins. Epoxy resins are particularly preferred because of their low shrinkage and excellent adhesion.
In a system in which polymer particles such as an emulsion or NAD (non-aqueous dispersion system) are dispersed in a medium as a resin solution, the polymer particles which should increase the strength when penetrating into the wood material are made of wood material. And remains on the surface of the woody material, and cannot penetrate deeply. As a result, there is little expectation of developing strength, and it is difficult to increase the resin concentration, which is not desirable.
The reason why the resin solution is efficiently injected into the surface of the woody material by the permeation of the resin solution in the present invention is considered to be due to the following mechanism. When a resin liquid having a temperature equal to or lower than the temperature of the wood material is applied to the wood material, the air in the conduit portion of the wood material is cooled by the resin liquid, and the pressure is reduced. As a result, since the volume of the air inside the conduit is reduced, the pressure is reduced.Therefore, it is possible to suck the resin liquid and introduce the resin liquid into the wood material, rather than go out and foam. I can do it. At this time, if the temperature of the wood material is preheated in advance, the temperature difference between the wood material and the resin liquid can be increased, so that the effect is further increased and the efficiency is improved.
In this case, the air inside the conduit expands due to the preheating, and as a result, the air inside the conduit is pushed out. Next, by applying a resin liquid lower than the surface temperature of the woody material due to preheating, the surface temperature decreases, and the air inside the conduit contracts. At the same time, the preheated wood material raises the temperature of the resin liquid, lowers the viscosity of the resin liquid, and facilitates penetration. Due to these synergistic effects, the resin liquid is sucked and permeated by the wood material. After the resin liquid is applied to the wood material, the next curing step is started. During this time, the resin liquid that has permeated undergoes a curing reaction, the resin liquid increases in viscosity, and the fluidity decreases. Next, it is introduced into a curing / drying oven or a heating / drying oven to complete the curing. If a sufficient curing time can be taken, it is not particularly necessary to put the composition in a heating and drying oven, and the composition may be cured at room temperature. In a heating furnace, since the surface is basically heated from the surface, the surface is first hardened. As a result, since the surface is first hardened, as long as the temperature of the heating furnace is not too high, the air present inside the conduit is sealed at the outlet, and bubble blowing is considerably suppressed. Therefore, there is often no problem even if the temperature of the furnace for curing is higher than the initial preheating temperature.
The method of the present invention greatly depends on the degree of ease of sucking the wood material, the temperature conditions, the viscosity of the resin solution, etc., but the resin solution is formed to a depth of about 0.1 to 2 mm on the surface of the wood material. And a resin layer can be formed, and a surface strength equivalent to or higher than that of WPC can be obtained.
In this method, unlike the forced infiltration by pressurization, decompression, etc., the suction property of the woody material itself is used, so that the soft part is easy to suck in, so that the amount of permeated resin increases, As a result, the part becomes stiff. On the other hand, the hard part is difficult to suck, and the amount of permeated resin is small. As a result, the soft parts are stiffer, while the stiff parts from the start do not become unnecessarily stiff. That is, there is an advantage that the strength and the surface hardness of the wood material are made uniform. Furthermore, because of the suction properties of the wood material itself, the resin content is higher on the wood material surface, and therefore the surface is more likely to have a higher altitude than the interior. As a result, the surface is hard and the inside can be kept soft, so that the woody material is hardly spoiled.
Even with a general paint, it is possible to infiltrate a small amount of resin into the woody material. However, in the case of paint, if it penetrates, it will cause fouling and reduce the commercial value. In many cases, operations such as filling are performed in advance, and it is difficult to harden the inside.
Further, in the case of general paints, the viscosity of the paint is low and the non-volatile content is also low in many cases because the surface state, that is, the appearance is emphasized and the filling is placed on the surface smoothness. Even if the non-volatile content is high, the workability is emphasized, and because the hardening speed is preferred, the time for which the resin component can penetrate the wood material is short, and the penetration depth and the penetration amount of the resin liquid are also low. It is not sufficient, so that improvement in strength cannot be expected.
[0023]
DETAILED DESCRIPTION OF THE INVENTION According to the present invention, a wood-based material such as wood to be treated is coated with a reaction-curable resin liquid at a temperature equal to or lower than the temperature of the wood-based material, penetrated into the wood-based material, and then applied and permeated. It is characterized in that the resin liquid is cured, but it is advantageous that the temperature difference between the wood material and the resin liquid is large. In this case, if the wood material is not heated, it is necessary to cool the resin liquid, but the cooling operation itself is costly, and the viscosity of the resin liquid increases, and the permeability decreases. is not. Therefore, it is preferable to preheat the wood material to be treated. This pre-heat treatment may be performed in a heating furnace such as a drying furnace using hot air or far-infrared rays, or may be performed by steam, microwaves, heating on a hot platen, or the like. The preheating temperature is not particularly limited, but it is desirable to treat at a high temperature unless the woody material is deformed. Generally, it is 30 to 120C, and a particularly desirable temperature is 45 to 80C. At this temperature, there is little deformation or deterioration of the woody material, and it is effective for lowering the viscosity of the resin liquid used in the next step and accelerating the curing reaction of the resin liquid, and for removing moisture and air in the conduit. Is also effective because it can be expected.
[0024] A resin liquid controlled at a temperature equal to or lower than the preheated temperature is applied to the preheat-treated woody material and is allowed to penetrate. Although the woody material is pre-heated, the surface temperature is reduced by the contact of the lower temperature resin liquid, and as a result, the air layer inside the conduit is cooled, and the volume of the air layer is reduced. Due to this decrease, the pressure is reduced, and in addition to the capillary action of the wood material, the resin liquid permeates the wood material by this suction force. Furthermore, since the surface temperature is higher than the resin liquid temperature, the temperature of the resin liquid itself rises, and as a result, the viscosity of the resin liquid decreases and the permeability increases. work.
As a method for applying the resin liquid, any method such as spraying, roll coater, flow coater, knife coater, brush, mop, spatula, ironing, wiping and the like can be applied. Among them, a coating method such as a roll coater, a brush, a mop, a spatula, an iron, an wiping, and the like are preferable because uneven suction on the surface of the woody material can be reduced.
The infiltrated resin liquid may be cured by heating or curing in a heating furnace by pressing, pressing or compressing one or more wooden materials from above and below, or from a line. It may be placed in a drying oven and cured one by one. Still further, it can be heated and cured by passing between heating rolls. If the curing time is sufficient, curing may be performed at room temperature. However, at room temperature, the curing time can be extended, so that the infiltration time can be extended, but the working time is also increased, and further, the effect of lowering the viscosity of the resin liquid by heating and, consequently, improving the permeability cannot be expected. Therefore, it is not always preferable.
Examples of the resin liquid having a reaction curability used for infiltration include wood-based materials such as a thermosetting resin, an addition polymerization type resin with an initiator such as a radical, and a room temperature curing type resin by a reaction with a curing agent. Any material can be used as long as it can be penetrated and exert a reinforcing effect such as hardness and wear resistance. For example, a resin liquid composed of an epoxy resin, an unsaturated polyester resin, a phenol resin, a melamine resin, a urea resin, an acrylic resin, a urethane resin, and a combination of these resins can be used.
These resins may be used as a solvent-free resin liquid, and are used for facilitating penetration and for imparting additional performance, for example, for mixing an antibacterial composition or the like. Some solvent may be included.
The nonvolatile content of the resin liquid is preferably at least 60%, more preferably at least 80%. If the non-volatile content is small, not only the hardness and strength are not obtained, but also the volume of the cured resin is reduced due to the evaporation of the solvent and the like after the curing, which leads to the deformation of the woody material.
As a component of the resin liquid, a resin which has good adhesiveness to the components of the woody material at the time of curing and can be converted into a fiber reinforced plastic (FRP) with cellulose or the like in the woody material is desirable. A resin having a low volumetric shrinkage at the time is more desirable. From these conditions, among the above resins, an epoxy resin is particularly desirable.
[0031]
EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples.
Embodiment 1
As a wood material, a dry board material of cedar (width 455 x length 910 x thickness 24 mm), which is a soft material of a moderate degree in softwood, is used as a test piece, and the wood material is previously placed in an atmosphere of 60 ° C, Was heated until the surface temperature reached 55 to 60 ° C. Next, a room temperature (25 ° C.) epoxy resin liquid (manufactured by Sansei Paint Industry Co., Ltd., a wood reinforcing agent “DS-45” by a combination of a low-viscosity epoxy resin and an aliphatic amine-based curing agent), and the compounding ratio is as follows: 2: 1, curing time = 120 minutes (50 g pot 20 ° C.), mixed viscosity = 110 mPa · s (20 ° C.), hardness of cured product (Shoir D) = 83) 2 was applied. During the setting time of 10 minutes, the resin liquid is heated by the temperature of the woody material to lower the viscosity, and at the same time, the surface temperature is lowered to 45 ° C. by the resin liquid, so that the air inside the conduit contracts in volume, and most of the resin is removed. Aspirated. Further, the resin liquid partially reacted and hardened due to the temperature of the woody material due to preheating. Then, it was placed in a 55 ° C. drying oven and heated for 40 minutes. The resin on the surface of the conduit was hardened from the surface because the surface was exposed to a high temperature, and almost no foaming from the conduit was observed. During this time, it was cured to the extent that it could be handled. The permeation amount of the resin liquid was 0.5 mm in thickness, and had a surface strength equivalent to that of a conventional WPC.
Embodiment 2
In Example 1, the wood material was not preheated, and the coating amount was 10 g / scale 2 with the same temperature resin solution (the same resin solution as in Example 1) using a roll coater at room temperature (25 ° C.). After leaving for 30 minutes for the setting time, it was placed in a drying oven at 50 ° C. and heated for 45 minutes. There was almost no inflow and outflow of air in the conduit, and there was also little foam blowing. The permeation amount of the resin liquid was 0.3 mm in thickness.
Comparative Example 1
The wood material was kept at room temperature (25 ° C.), while the same resin liquid as in Example 1 was applied at a temperature of 50 ° C. with a brush at an application amount of 10 g / scale 2 . Immediately after the application, the resin liquid itself had a low viscosity, so that the suction was good, and the resin liquid permeated. However, many bubbles came out of the conduit during standing at room temperature, and the resin cured as it was. On the other hand, the permeation thickness was 0.2 mm, the surface appearance was poor, and the strength was unsatisfactory.
Comparative Example 2
A resin liquid was used in the same manner as in Example 1, except that DS-45 used in Example 1 was diluted to 50% as a resin solid content with an epoxy thinner. Since there is no bubble blowing and the resin liquid has a low viscosity, the permeability is large and it has been recognized that the resin liquid has penetrated to a thickness of 2 mm. However, after 2 months, the coated side shrinks and becomes concave. Deformed. Further, the strength was not satisfactory.
Table 1 shows a comparison of the surface hardness between the surface-treated wood material obtained in this example and the comparative example and the wood material before the treatment. The hardness before and after each treatment is shown. Here, the hardness evaluation is based on a Barcol hardness meter (needle type). [The higher the value, the harder]
[0037]
[0038]
The surface strengthening method of the present invention is superior to the conventional various resin penetration strengthening methods in the following points.
(1) Continuous production is possible. Since the woody material to be treated can be continuously flowed, it can be processed into long woods and the like.
(2) The device is small, simple, and inexpensive. Basically, a coating machine and a curing / drying furnace may be used, and more preferably, a heating furnace as a preheating furnace may be used. In addition, since both the preheating furnace and the curing / drying furnace need only be able to heat and heat the woody material, there is an advantage that both can be shared by the same equipment.
(3) High safety. There is no need to use pressure vessels that are at risk of rupture.
{Circle around (4)} Permeation of resin to a certain depth from the surface is possible. If the depth is about 0.1 to 2 mm from the surface, the reinforcing resin liquid can penetrate. In addition to the reinforcing resin liquid, it is easy to penetrate a coloring agent or the like. In general, if the depth of the resin liquid is about 0.2 mm or more, the resin liquid can be seen almost uniformly without unevenness, so that a sufficient injection amount can be ensured. Therefore, an unnecessary large amount of resin is not required, and the cost is excellent.
(5) Since only the surface of the wooden material can be reinforced, a plastic feeling unlike WPC does not occur. Furthermore, the particularly soft part has a high suction property of the resin liquid, so that a larger amount of the resin liquid penetrates, so that the hardness is further increased. Since it is not sucked in, and thus the excess is not increased, the hardness and strength are made uniform.
{Circle around (6)} It is also possible to reinforce a decorative material such as a decorative veneer attached to a base material.
(7) Finish feeling is good. Compared with the conventional “thick paint product”, there is no unnaturalness because the resin penetrates into the wood material, and the resin liquid has a sufficient depth compared to the “heat-pressure treated product with resin liquid application”. There is no resin unevenness because it is injected into the substrate. As described above, according to the present invention, resin processing that cannot be performed by conventional WPC or the like is possible. The resin used in the present invention does not necessarily need to be a resin having high hardness and high strength, but may be a resin or the like that facilitates the processing of woody material, for example, cutting, etc., and the application is performed in two stages. , May be implemented in any form.
(8) No expensive and complicated equipment is required, and the present invention can be applied to products of any shape other than planar products.
