【発明の詳細な説明】[Detailed description of the invention]
［産業上の利用分野］
本発明は土壌中のような湿潤環境下でも強度を
保ち、一定期間後土壌微生物の作用により分解す
ることによつて、植物の根の伸長を自由とする多
孔性の農業用シート状造形物の製法に関するもの
である。具体的には育苗移植用ポツト、苗床用シ
ート、水耕栽培用床等の農業用シート造形物に適
用される。
［従来技術］
プラスチツクや紙パルプ製品で作られた育苗移
植用ポツトは従来から広く利用されている。ポツ
トに必要な性質は、根の伸長のため透水性・通気
性があることのほか畑に移植するまでの間強度を
保ち、隣接するポツト間の根が絡み合わず、移植
時に容易に分離すること、また移植後は根の伸長
を妨げないようすみやかに分解することであり、
さらに分解物が苗の成長を促進すれば理想的であ
る。
従来のプラスチツク製のものは土中で分解せず
根の伸長を妨げるため、移植にあたつて取り外す
必要がある。この際伸長しかけた根を傷める恐れ
と、取り外して廃棄する手間がかかり作業能率が
低下する欠点があつた。また紙パルプ製のものは
土中で強度を保たせるため防腐剤や強度増加剤を
含浸させるのが一般的であるが、その量が多過ぎ
ると通気、透水性を損ない、また少ないと安定し
た紙力が得られない等の問題点があつた。パルプ
とプラスチツク繊維を混抄する形式のポツトもあ
るが、移植後もプラスチツク繊維部分がちみつな
構造のまま残るため、やはり根の伸長が妨げられ
ることと、プラスチツク繊維のコストが高い欠点
があつた。
またポツト以外の育苗シート等に用いる場合に
も移植まで強度を保ち、移植後すみやかに分解し
て根の伸長を助ける点でポツトと同様な性質を具
備する必要があるが、従来の素材では上記のよう
な欠点があつた。
［発明が解決しようとする問題点］
本発明は天然パルプを主成分とし、キトサンが
バインダーであるシート素材を用いることによ
り、これら従来の欠点を排除しながら十分な紙力
を持ち、移植後作物の根を自由に伸長させ且つ養
分も供給する、安価で性能の優れた苗移植用ポツ
ト等に用いられる農業用シート及びその製造方法
を提供するものである。
［問題点を解決するための手段］
本発明者らは木材非木材等の天然パルプ繊維と
キトサンとの混抄あるいはパルプ繊維シートへの
キトサンの塗布について鋭意研究を行つた結果、
パルプ繊維シートへのキトサンの塗布は育苗移植
用ポツト等の農業用シート素材として適切な性質
を具備していることを見い出し、本発明を完成さ
せるに至つた。
本発明に用いる天然パルプは特に制限されるも
のではなく、針葉樹、広葉樹の樹木及び非木材植
物から得られるもののほか、古紙パルプ等も用い
ることができる。またその叩解度についても特に
制限はないが、多孔質のシートが好ましい用途に
はカナダ標準ろ水度500〜700mlが適当であり、密
で薄いシートが必要な用途には100〜300mlが適当
である。
キトサンは蟹殻、海老殻、あるいは菌糸体等か
ら採取したキチンに化学的あるいは生物学的処理
を加えて脱アセチル化したものである。キトサン
は日本各地の畑土中に普遍的に存在するカン状菌
等による分解され、窒素栄養源として植物体の生
育を助長する。キトサンはパルプ繊維間のバイン
ダーの効果を持ち、キトサンを塗布し乾燥したパ
ルプシートは乾燥時のみならず、湿潤時にも一定
の強度を保つ。この塗布材料であるキトサンはそ
の原料を特に制限するものではなく、蟹殻、海老
殻、あるいは菌糸体等、いずれから調製したもの
でも良い。得られるキトサンの分子量、脱アセチ
ル化度は高い方がシート強度が良いが、これも特
に制限するものではなく、脱アセチル化度60％以
上であれば良い。塗布量に関しては対パルプ１〜
10％が適当である。
本発明は天然パルプを抄紙して得られたシート
に、キトサン水溶液をキトサン１〜10％（対パル
プ）となるよう塗布し、乾燥さす製造法を特徴と
する。シートへの塗布は約２％酢酸に溶解させた
１〜３％キトサン水溶液で行う。
抄紙は円網、長網等の通常の抄紙機によつて行
うことができる。得られたシートをドライヤーマ
シンで半乾燥した後、塗布機あるいは塗工機を用
いてキトサン水溶液をシートに含浸させ、再びド
ライヤーで十分乾燥させることによつて本発明の
農業用シートが得られ、これをさらに成形しポツ
ト等にすることができる。
この農業用シートを育苗用ポツトに用いると、
育苗期間中は十分な強度を保ち、移植後は徐々に
強度低下するとともに腐食分解して栄養源となり
植物の育成を助けることとなり、前記従来のポツ
トにみられた不都合が解決されるのである。
またポツト以外の農業用シートに用いる場合に
もパルプのカナダ標準ろ水度やシートの坪量を変
えることで、目的に合うように分解時期やシート
の多孔性を調整することができる。
［作用と実施例］
次に本発明の実施方法について実験結果を例に
あげて説明する。
実施例 １
叩解度約150ml（CSF）の針葉樹砕木パルプを
坪量約50ｇ／m2に抄紙し、半乾燥させた後、１〜
３％キトサン水溶液をパルプ当たりキトサンが１
〜10％となるよう塗布して乾燥させた。乾燥は
105℃で送風乾燥した。キトサンは海老殻から調
製された脱アセチル化度約95％のものを２％酢酸
で溶解して用いた。得られたシートを約50％水分
の湿潤土壌中（25℃、相対湿度95％）に３週間及
び２ケ月埋没した後、その湿潤強度をJIS Ｐ−
8113に従つて測定した。その結果を第１表に示
す。
[Industrial Application Field] The present invention is a porous material that maintains its strength even in a humid environment such as soil, and decomposes after a certain period of time through the action of soil microorganisms, thereby allowing plant roots to grow freely. The present invention relates to a method for producing agricultural sheet-shaped objects. Specifically, it is applied to agricultural sheet structures such as pots for raising and transplanting seedlings, sheets for seedbeds, and beds for hydroponic cultivation. [Prior Art] Pots for raising and transplanting seedlings made of plastic or paper pulp products have been widely used. Pots need to have water permeability and air permeability for root growth, maintain strength until transplanted into the field, prevent roots from intertwining between adjacent pots, and be easily separated when transplanted. Also, after transplanting, it should be decomposed quickly so as not to hinder root growth.
Furthermore, it would be ideal if the decomposed product promoted the growth of seedlings. Conventional plastic ones do not decompose in the soil and prevent root growth, so they must be removed before transplanting. At this time, there was a risk of damaging the roots that were beginning to grow, and there was a drawback that work efficiency was reduced because it took time and effort to remove and discard. In addition, paper pulp products are generally impregnated with preservatives and strength-increasing agents to maintain their strength in the soil, but if the amount is too large, it will impair ventilation and water permeability, and if there is too little, it will not be stable. There were problems such as not being able to obtain paper strength. There are pots that mix pulp and plastic fibers, but the plastic fibers remain in a tight structure even after transplanting, which hinders root elongation, and the disadvantages are that the plastic fibers are expensive. In addition, when using materials other than pots, such as seedling-raising sheets, they must have properties similar to those of pots in that they maintain their strength until transplanting, quickly decompose after transplanting, and support root elongation. There were drawbacks such as: [Problems to be Solved by the Invention] The present invention uses a sheet material containing natural pulp as a main component and chitosan as a binder, thereby eliminating these conventional drawbacks and having sufficient paper strength, which allows crops to be easily grown after transplantation. An object of the present invention is to provide an agricultural sheet for use in pots for transplanting seedlings, etc., which is inexpensive and has excellent performance, allowing roots to freely extend and supplying nutrients, and a method for manufacturing the same. [Means for Solving the Problems] The present inventors have conducted intensive research on mixing chitosan with natural pulp fibers such as wood and non-wood fibers, or on applying chitosan to pulp fiber sheets.
It was discovered that the application of chitosan to a pulp fiber sheet has properties suitable for use as an agricultural sheet material such as pots for raising and transplanting seedlings, leading to the completion of the present invention. The natural pulp used in the present invention is not particularly limited, and in addition to those obtained from coniferous trees, broad-leaved trees, and non-wood plants, waste paper pulp and the like can also be used. There is also no particular limit to its freeness, but Canadian standard freeness of 500 to 700 ml is appropriate for applications where a porous sheet is preferred, and 100 to 300 ml is appropriate for applications that require a dense and thin sheet. be. Chitosan is made by deacetylating chitin collected from crab shells, shrimp shells, or mycelium through chemical or biological treatment. Chitosan is decomposed by camp-shaped bacteria that are ubiquitous in field soil throughout Japan, and serves as a nitrogen nutrient source to promote plant growth. Chitosan acts as a binder between pulp fibers, and pulp sheets coated with chitosan and dried maintain a certain level of strength not only when dry but also when wet. There are no particular restrictions on the raw material for chitosan, which is the coating material, and it may be prepared from any of crab shells, shrimp shells, mycelium, and the like. The higher the molecular weight and degree of deacetylation of the obtained chitosan, the better the sheet strength, but this is not particularly limited either, as long as the degree of deacetylation is 60% or more. Regarding the amount of application, it is 1 to 1 for pulp.
10% is appropriate. The present invention is characterized by a manufacturing method in which a chitosan aqueous solution is applied to a sheet obtained by papermaking from natural pulp so that the amount of chitosan is 1 to 10% (based on the pulp), and the sheet is dried. The sheet is coated with a 1-3% chitosan aqueous solution dissolved in about 2% acetic acid. Paper making can be carried out using a conventional paper machine such as a cylinder or Fourdrinier machine. After semi-drying the obtained sheet with a dryer machine, the sheet is impregnated with an aqueous chitosan solution using a coating machine or a coating machine, and the agricultural sheet of the present invention is obtained by sufficiently drying it again with a dryer. This can be further molded into pots and the like. When this agricultural sheet is used in a pot for raising seedlings,
It maintains sufficient strength during the seedling-raising period, and after transplanting, the strength gradually decreases and it corrodes and decomposes, becoming a source of nutrients and aiding the growth of plants, solving the disadvantages of conventional pots. Furthermore, when used in agricultural sheets other than pots, by changing the Canadian standard freeness of the pulp and the basis weight of the sheet, the decomposition time and porosity of the sheet can be adjusted to suit the purpose. [Operations and Examples] Next, the method of carrying out the present invention will be explained using experimental results as examples. Example 1 A softwood groundwood pulp with a freeness of about 150 ml (CSF) was made into paper with a basis weight of about 50 g/ m2 , and after semi-drying,
3% chitosan aqueous solution with 1 chitosan per pulp
It was applied to a concentration of ~10% and dried. Drying is
It was air-dried at 105°C. Chitosan was prepared from shrimp shells and had a degree of deacetylation of approximately 95%, and was dissolved in 2% acetic acid. After burying the obtained sheet in moist soil with about 50% moisture (25℃, 95% relative humidity) for 3 weeks and 2 months, its wet strength was determined according to JIS P-
8113. The results are shown in Table 1.
【表】
実施例 ２
古紙パルプを使用し、抄紙したシートに２％キ
トサン水溶液を塗布し、加熱送風乾燥した。この
シートを移植用ポツトに成型し、トウモロコシの
種子を播種して潅水を行い、３週間後ポツトごと
露地移植を行つた。この移植時点でのシートへの
根の貫通はなく、ポツト強度も十分に移植に耐え
た。その後、２ケ月後には根はシートを貫通して
生育しており、茎の成長はポツトを使用しない場
合と同程度であつた。
実施例 ３
叩解度500mlの粗砕砕木パルプを厚み約２mmに
抄造し、25x25cmのシートとして西洋芝の種子を
懸濁させた３％キトサンを塗布し、30℃で送風乾
燥した。このシートマツトに潅水を行い、種子を
発芽させた。発芽後、シートマツトを露地に移植
して生育状態を観察したが、生育は良好であり、
またシートマツトは６ケ月後には土壌と識別が困
難な程度に分解していた。
［発明の効果］
本発明の方法で得られる農業用シートは湿潤状
態下で強度、通水性及び通気性を保ち、一定期間
後に土壌中で分解するため、作物の根の生育媒体
及び支持体として最適である。また分解物は何ら
作物に害を及ぼすことなく、むしろ栄養分となる
ため理想的である。[Table] Example 2 A 2% chitosan aqueous solution was applied to a paper-made sheet using waste paper pulp, and the sheet was dried with heating and blowing air. This sheet was molded into a pot for transplanting, corn seeds were sown and watered, and three weeks later the pot was transplanted into open ground. At the time of transplantation, there were no roots penetrating the sheet, and the pot strength was sufficient to withstand transplantation. Two months later, the roots had grown through the sheet, and the growth of the stems was at the same level as when no pots were used. Example 3 Coarse crushed wood pulp with a beating degree of 500 ml was made into a sheet with a thickness of about 2 mm, a sheet of 25 x 25 cm was coated with 3% chitosan in which western grass seeds were suspended, and dried with air at 30°C. This sheet pine was irrigated to germinate the seeds. After germination, the sheet pine was transplanted to open ground and its growth status was observed, and the growth was good.
Moreover, after six months, the sheet pine had decomposed to such an extent that it was difficult to distinguish it from soil. [Effects of the Invention] The agricultural sheet obtained by the method of the present invention maintains strength, water permeability, and air permeability under moist conditions, and decomposes in the soil after a certain period of time, so it can be used as a growth medium and support for crop roots. Optimal. Furthermore, decomposed products are ideal because they do not cause any harm to crops, but rather serve as nutrients.