【発明の詳細な説明】[Detailed description of the invention]
本発明は、育苗用発泡尿素樹脂成型品の改良に関するも
のである。
近年稲作における田植用機械の急速な普及に伴ない、田
植時期においては機械田植用苗の確保に懸命な努力がな
されている。
すなわち、機械田植用苗は苗代で生育される苗と違って
、木箱またはプラスチック箱を使用し一定規格（長さ６
０肌、幅３瓜流）のマット苗に仕上げられるが、前記箱
には１箱当り３．５ｋｇの土壌が必要であり、ｌｈａに
要する苗を栽培するには０．７〜１．０屯の土壌が必要
である。また、農家若し〈は育苗センター等が前記の量
の土壌を確保できたとしても、田植の忙しい時期に前記
土壌について、更に斑調整、殺菌、肥料混入等の繁雑な
作業が必要との理由から、育苗用人工塔土の需要が年々
増加の傾向にある。前記育苗用人工培土は、稲作の機械
田植用苗の栽培に限らず、施設園芸、畑作、家庭園芸の
培地としても使用されており、また士壌改良剤としても
使用されているが、水稲育苗用に使用されるためには下
記のような性質を具備する必要がある。
すなわち、｛１）吸水性が良好であること。
健全な苗を生育させるには、５７６側×２７５側×１６
．５肋の体積の人工培士に約１．８そ以上の水が吸収で
きるものでなければならない。
｛２’保水性が良好であること。
（３｝ 容易に植物根の侵入できるものであること。The present invention relates to improvements in foamed urea resin molded products for raising seedlings. With the rapid spread of rice transplanting machines in rice cultivation in recent years, efforts are being made to secure seedlings for machine rice transplanting during the rice planting season. In other words, unlike seedlings that are grown using seedlings, seedlings for mechanical rice transplanting use wooden boxes or plastic boxes and are kept to a certain standard (length 6
However, each box requires 3.5 kg of soil, and 0.7 to 1.0 ton of soil is required to grow the seedlings required for lha. of soil is required. In addition, even if farmers or seedling centers are able to secure the above amount of soil, the reason is that during the busy rice planting season, complicated work such as patch adjustment, sterilization, and mixing of fertilizers is necessary for the soil. Therefore, the demand for artificial tower soil for raising seedlings is increasing year by year. The artificial soil for raising seedlings is used not only for the cultivation of rice seedlings for mechanical rice planting, but also as a medium for greenhouse horticulture, field cultivation, and home horticulture, and is also used as a soil improver. In order to be used for this purpose, it must have the following properties. That is, {1) good water absorption. To grow healthy seedlings, 576 sides x 275 sides x 16
．． It must be able to absorb approximately 1.8 or more water per 5 ribs of artificial culture. {2' Good water retention. (3) It must be easily penetrated by plant roots.
【４１土壌中で速やかに分解するものであること。育苗
時間（２０〜２５日）は培士としての形状を維持し、田
植または移植後数ケ月で土壌中で分解するものであるこ
と。
‘５’人工培土中には発根あるいは植物の生育を阻害す
る成分が含まれていないこと。
本発明者等は、上記知見にもとずき水稲育苗用人工培士
としての尿素樹脂発泡体について改良を重ねた結果、本
発明を開発しここに提案するものである。
本発明の水稲育苗用発泡尿素樹脂成型品は、乾燥時の高
比重が０．０１０〜０．０１３５夕／めであり、且つ組
成がホルムアルデヒド１モルに対し尿素０．６〜０．９
モルであることを特徴とする。
本発明においては、育苗用発泡尿素樹脂成型品（以下樹
脂成型品という）の乾燥時の高比重が０．０１３５夕／
塊以上になると、吸水性および植物根の侵入が不良にな
るとともに土壌中における分解性も悪くなるので、０．
０１３５夕／塊以下に限定した。
なお、乾燥時の高比重が０．０１３５夕／均以上になる
と、樹脂成型品組成中に遊離ホルムアルデヒドが多くな
り、植物根の生育を阻害するので好ましくない。また、
乾燥時の高比重が０．０１０夕／球以下になると、強度
が低下し成型品としての使用に耐え得ないものとなるの
で、０．０１０夕／嫌以上に限定した。
なお、成型品とは、板状、立方体状等使用目的に応じて
、各種の形、大きさに成型した発泡尿素樹脂をいう。次
に、樹脂成型品の組成がホルムアルデヒド１モルに対し
尿素が０．６モル以下になると、樹脂成型品中に遊離ホ
ルムアルデヒドの含有量が多くなり、前記の如く植物根
の生育が阻害されるとともに植物根の樹脂成型品への侵
入の不良ならびに土壌中における分解性も悪くなるので
、ホルムアルデヒド１モルに対し尿素０．６モル以上に
限定した。
なお、樹脂成型品の組成がホルムアルデヒド１モルに対
し尿素が１．０モル以上になると、強度が低下し板とし
ての使用に耐え得ないものとなるので、ホルムアルデヒ
ド１モルに対し尿素１．０モル以下に限定した。
上記組成の本発明の樹脂成型品を得るには〜各種の製造
法により得ることができ、例えば図の工程図で示すよう
に、尿素ーホルムアルデヒド初期縮合溶液に尿素、発泡
剤および固化剤（燐酸）等の溶液、圧縮空気等を導入し
て発泡尿素樹脂ブロックを製造し、該ブロックを室温で
２〜３日間乾燥・固化させた後一定の形状、大きさに切
断して発泡尿素樹脂成型品とする。
この発泡尿素樹脂成型品の製造は、乾燥時の高比重を測
定したとき０．０１〜０．０１３５夕／地の範囲となる
ような条件を選択して製造し、該樹脂成型品にはァルキ
レングリコール類および無機塩類の溶液を含浸させて吸
水性を付与する。
更に、前記樹脂成型品組成中のホルムアルデヒドに対す
る尿素のモル比を測定し、尿素０．６〜０．９モルのも
のを選択する。なお、樹脂成型品中の遊離のホルムアル
デヒドを測定し、ホルムアルデヒドの含有量の少ないも
のを選ぶ必要がある。以下吸水性試験、遊離ホルムアル
デヒド測定試験によって、本発明の樹脂成型品（以下の
試験例、実施例においては、板状に成型したものを使用
した。
）の乾燥時の高比重およびホルムアルデヒド‘こ対する
尿素モル比を限定した理由を、試験例によって具体的に
説明する。試験例 １
０ 樹脂板の吸水試験
ホルムアルデヒドと尿素のモル比および嵩比重の異なる
樹脂板（寸法：２７５肋×５７５側×１６．５帆）表面
にポリエチレングリコール２．５夕および硝酸アンモニ
ウム２．５夕を水２５のこ溶解した液を均一に塗布し、
塗布後一日養生させて各種の試験試料を調製したｏ前記
試験試料を５比吻×５物帆×１６．５肋の大きさに切り
、試験片とした。
次に、前記試験片の薬液塗布面を水面に向けて水槽内に
浮べ、１２硯酸間浮上させた後試験片を秤量し、この重
量から水に投下前の試験片の重量を差し引いて吸水量を
求め、この値を６３．升音して樹脂板（寸法：２７５側
×５７５柳×１６．５柳）１枚当りの吸水量を算出した
。
試験の結果を第１表に示す。
第１表樹自動坂の蜜り的性試験（単位：多／枚）（言主
）モル比＊，．．下段のホルムアルデヒド１モルに対し
、上段に尿素のモル比を示した。
高比重＊＊．．．ポリエチレングリコールと硝酸アンモ
ニウムとの溶液塗布前の高比重である。
第１表よりして、本発明による樹脂板は、高比重が０．
０１３５（夕／塊）以下でなければ吸水性を満足し得な
いことが判った。
試験例 ２
樹脂板の遊離ホルムアルデヒド含有量測定試験試験例１
と同機にして得られた試験片を、蒸溜水中で粉砕して細
片とするとともに充分吸水させた後ヌツチェで吸引炉遇
し、炉液中のホルムアルデヒド量をアセチルアセトン法
だ比色定量した。
測定結果を第２表に示した。第２表
横月罰阪の遊離ホルムァルデヒトｔ含有量額垢疋】山岸
脇験（単位：ＣＨ２０略〆板−の試験例 ３
樹脂板の強度試験
試験例１と同様にして得られた試験試料（寸法：２７５
肌×５７５側×１６．５側）について、第２図に側面図
および第３図に平面図で示すようにして、樹脂板取扱い
時の強度を測定した。
図に示すように、樹脂板１の中央部が測定台２の端部に
来るように、樹脂板１を保持した後、重量（夕）の異な
る分銅３を載遣し、樹脂板１上に保持しうる分銅３の最
大値（夕）を求めた。
なお分銅１４０タ以下は不可である。測定の結果を第３
表に示す。
第３表 樹脂板の強度試験 （単位：ｇ）第３表よ
りして、樹脂板の乾燥時の嵩比重が０．００８のように
、本発明の限定範囲以外の場合は強度が著しく低下する
こと、およびホルムアルデヒド１モルに対し尿素のモル
比が本発明の限定範囲以外の１．０モル以上の場合強度
が著しく低下することが判った。
次に、本発明を実施例によって具体的に説明する。
試験例 １
樹脂板への植物根の侵入測定試験
大きさ５７５肋×２７５柳×１６．５肌とした以外は、
すべて試験例と同機にして調製した樹脂板を、育苗箱中
に入れ、１箱当り１．８その水（必要量の肥料を含有さ
せた。
）を吸収させた後、わずかに発芽した水稲種子（品種：
日本晴）２００夕を播種し、洪積±で覆土した。上記育
苗箱を、３２０の育苗器中で４斑時間保持した後取出し
、約５００ｃｃの水を港した後１５〜２０ｑ０の温室内
で２日間保持し、水稲の根の樹脂板への侵入状況および
最長根長を測定した。なお、根の生育の良、不良は、第
４図の説明図に示すように、稲の主根４が樹脂板（１６
．５肌）の厚さに達し冠根５が５本程度に発根した最良
の状態Ａを◎印、主綾４が樹脂板の厚さの中央部に達し
冠根５が５本程度に発根した状態Ｂを○印、主板４およ
び冠根５が短かく発不良の状態を△印、根ならびに芽の
発育の悪い状態ＤをＸ印であらわした。測定結果を第４
表に示す。
第 ４ 表 樹脂板への植物根の侵入測定試験試
験例 ５実施例４のようにして生育した２．９庭期（播
種後約２０日）の水稲苗を本田に移植し、移植６ケ月後
に樹脂板の分解状態を下記判定規準に従い肉眼観察した
。
・判定基準
一…本田中に樹脂板が認められない。
十…本田中に樹脂板がわずかに認められる。
日・・・本田中に樹脂板が可成認められる。川・・・本
田中に樹脂板が多く認められる。観察の結果を第５表に
示す。第５表 本田中における横月轍扮解試験
以下の如く、本発明の育苗用発泡尿素樹脂板は、吸水性
および植物根の侵入が良好であるとともに±穣中におけ
る分解性を良好であって、樹脂板の分解によって生成さ
れる窒素分は植物の生育を助長する等の利点を有する。
なお、本発明の樹脂板は遊離ホルムアルデヒドの含有量
が少なく植物の生育を阻害することがないので、本発明
の価値は極めて大きなものである。[41 It must be something that decomposes quickly in soil. The seedlings must maintain their original shape during the growing time (20 to 25 days) and decompose in the soil several months after planting or transplanting. '5' Artificial soil does not contain any ingredients that inhibit rooting or plant growth. Based on the above knowledge, the present inventors have repeatedly improved the urea resin foam as an artificial cultivator for raising paddy rice seedlings, and as a result, they have developed the present invention and propose it here. The foamed urea resin molded product for raising paddy rice seedlings of the present invention has a high specific gravity of 0.010 to 0.0135 m/m when dry, and a composition of urea of 0.6 to 0.9 per mole of formaldehyde.
Characterized by being molar. In the present invention, a foamed urea resin molded product for seedling raising (hereinafter referred to as a resin molded product) has a high specific gravity of 0.0135 m/m when dried.
If it becomes larger than a lump, water absorption and penetration by plant roots will be poor, and decomposition in the soil will also be poor, so 0.
0135 evening/Limited to lumps or less. It should be noted that if the high specific gravity when dried is 0.0135 m/y or more, free formaldehyde will increase in the composition of the resin molded product, which will inhibit the growth of plant roots, which is not preferable. Also,
If the high specific gravity during drying is less than 0.010 g/bulb, the strength will decrease and it will not be able to withstand use as a molded product, so it was limited to 0.010 g/bulb or more. Note that the molded product refers to foamed urea resin molded into various shapes and sizes depending on the purpose of use, such as a plate shape or a cube shape. Next, when the composition of the resin molded product is 0.6 mole or less of urea per 1 mole of formaldehyde, the content of free formaldehyde in the resin molded product increases, which inhibits the growth of plant roots as described above. Since the intrusion of plant roots into the resin molded article and the decomposition in the soil would be poor, the amount of urea was limited to 0.6 mole or more per 1 mole of formaldehyde. If the composition of the resin molded product is 1.0 mole or more of urea per 1 mole of formaldehyde, the strength will decrease and the product will not be able to withstand use as a board. Limited to the following. The resin molded product of the present invention having the above composition can be obtained by various manufacturing methods. For example, as shown in the process diagram in the figure, urea, a blowing agent, and a solidifying agent (phosphoric acid) are added to a urea-formaldehyde initial condensation solution. ), compressed air, etc. are introduced to produce a foamed urea resin block, and the block is dried and solidified at room temperature for 2 to 3 days, and then cut into a certain shape and size to produce a foamed urea resin molded product. shall be. This foamed urea resin molded product is manufactured by selecting conditions such that when the high specific gravity when dry is measured, it is in the range of 0.01 to 0.0135 m/g. It is impregnated with a solution of alkylene glycols and inorganic salts to impart water absorption properties. Furthermore, the molar ratio of urea to formaldehyde in the composition of the resin molded product is measured, and one containing 0.6 to 0.9 mole of urea is selected. Note that it is necessary to measure the free formaldehyde in the resin molded product and select one with a low formaldehyde content. The water absorption test and free formaldehyde measurement test were conducted to determine the high specific gravity and formaldehyde content of the resin molded product of the present invention (in the following test examples and examples, a plate molded product was used) when dried. The reason for limiting the urea molar ratio will be specifically explained using test examples. Test Example 1 0 Water absorption test for resin plates Resin plates with different molar ratios of formaldehyde and urea and bulk specific gravity (dimensions: 275 ribs x 575 sides x 16.5 sails) 2.5 liters of polyethylene glycol and 2.5 liters of ammonium nitrate were applied to the surface of the resin plates. Dissolve 25 ml of water and apply a solution uniformly.
After application, various test samples were prepared by curing for one day. The test samples were cut into pieces of 5 ratio x 5 lengths x 16.5 ribs to obtain test pieces. Next, the test piece is floated in a water tank with the chemical-coated side facing the water surface, and after floating for 12 minutes, the test piece is weighed, and the weight of the test piece before being dropped into the water is subtracted from this weight. Find the amount and set this value as 63. The amount of water absorbed per resin board (dimensions: 275 side x 575 willow x 16.5 willow) was calculated. The test results are shown in Table 1. Table 1: Tree-automatic slope test (unit: many/sheet) (subject) molar ratio*,. ．． The molar ratio of urea is shown in the upper row to 1 mole of formaldehyde in the lower row. High specific gravity**. ．． ．． High specific gravity before application of solution of polyethylene glycol and ammonium nitrate. According to Table 1, the resin plate according to the present invention has a high specific gravity of 0.
It was found that the water absorbency could not be satisfied unless the water absorbency was 0135 (evening/lump) or less. Test example 2 Free formaldehyde content measurement test of resin plate Test example 1
A test piece obtained using the same machine was crushed into small pieces in distilled water, thoroughly absorbed, and then placed in a Nutsche suction furnace, and the amount of formaldehyde in the furnace liquid was determined colorimetrically using the acetylacetone method. The measurement results are shown in Table 2. Table 2: Free formaldehyde t content of Yokozuki Penisaka] Yamagishiwaki test (Unit: CH20 omitted) Test example 3 Resin board strength test Test sample obtained in the same manner as Test example 1 ( Dimensions: 275
The strength of the resin plate during handling was measured as shown in a side view in FIG. 2 and a plan view in FIG. 3. As shown in the figure, after holding the resin plate 1 so that the center of the resin plate 1 is at the end of the measuring table 2, weights 3 of different weights (weights) are placed on the resin plate 1. The maximum value (evening) of weight 3 that can be held was determined. Note that weights of 140 ta or less are not allowed. The third measurement result
Shown in the table. Table 3 Strength test of resin plate (Unit: g) According to Table 3, when the dry bulk specific gravity of the resin plate is outside the limited range of the present invention, such as when the bulk specific gravity is 0.008, the strength decreases significantly. In addition, it has been found that when the molar ratio of urea to 1 mol of formaldehyde is 1.0 mol or more, which is outside the limited range of the present invention, the strength is significantly reduced. Next, the present invention will be specifically explained using examples. Test Example 1 Test for measuring the penetration of plant roots into a resin board Except for the size: 575 ribs x 275 willow x 16.5 skins.
All the resin plates prepared using the same machine as the test example were placed in seedling boxes, and each box absorbed 1.8 ml of water (containing the required amount of fertilizer), and then slightly germinated paddy rice seeds were obtained. (Variety:
Seeds were sown at 200 p.m. (Nippon Sei) and covered with soil. The above-mentioned seedling raising box was kept in a 320 seedling nursery for 4 hours and then taken out, and after pouring about 500 cc of water into it, it was kept in a greenhouse of 15 to 20 q0 for 2 days, and the situation of invasion of paddy rice roots into the resin board and The longest root length was measured. In addition, whether the root growth is good or bad is determined by the fact that the main root 4 of the rice is covered with a resin plate (16
．． The best condition A is marked ◎, where the thickness of the resin board has reached the thickness of the resin plate and about 5 crown roots 5 have grown. Rooted state B is indicated by ○, state where the main plate 4 and crown root 5 are short and poorly developed is indicated by Δ, and state D where roots and buds are poorly developed is indicated by X. The measurement results are shown in the fourth
Shown in the table. Table 4 Test example for measuring penetration of plant roots into resin plates 5 Rice seedlings grown in the manner described in Example 4 at the 2.9 garden stage (approximately 20 days after sowing) were transplanted to Honda, and 6 months after transplantation, The state of decomposition of the resin plate was visually observed according to the following criteria.・Judgment Criteria 1: No resin plate is found inside the Honda. 10... A slight resin plate is observed inside the Honda. Japan: Resin plates were found in Honda. River: Many resin plates can be seen in Honda. The results of the observations are shown in Table 5. Table 5 Yokozuki rutting test at Honda Naka As shown below, the foamed urea resin board for raising seedlings of the present invention has good water absorption and penetration of plant roots, as well as good decomposition during ripening. The nitrogen content generated by the decomposition of the resin plate has advantages such as promoting the growth of plants. Note that the resin board of the present invention has a small content of free formaldehyde and does not inhibit the growth of plants, so the value of the present invention is extremely large.
【図面の簡単な説明】[Brief explanation of the drawing]
第１図は本発明の樹脂板の製造過程を示す工程図、第２
図は試験例３における樹脂板の強度測定法を説明するた
めの側定図、第３図は同上の平面図、第４図は実施例１
における樹脂板への植物根の侵入測定試験の判定基準の
説明図、である。
図中、１……樹脂板、２…・・・測定台、３…・・・分
銅、４・・・・・・主線、５・・・・・・冠根、Ａ〜Ｄ
・・・・・・判定基準、をあらわす。第２図第３図
第１図
第４図FIG. 1 is a process diagram showing the manufacturing process of the resin plate of the present invention, and FIG.
The figure is a side view for explaining the strength measurement method of the resin plate in Test Example 3, Figure 3 is a plan view of the same, and Figure 4 is Example 1.
FIG. 3 is an explanatory diagram of the criteria for a test to measure the penetration of plant roots into a resin board in FIG. In the figure, 1...resin plate, 2...measuring table, 3...weight, 4...main line, 5...crown, A to D
・・・・・・Represents the judgment criteria. Figure 2 Figure 3 Figure 1 Figure 4