JP3832104B2 - String-like structure for direct sowing of rice - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a string-like structure for direct sowing of rice made of a novel material.
[0002]
[Prior art]
Rice cultivation is a typical industry unique to Japan and is one of the few self-sufficiency crops. However, rice cultivation will be maintained in the future due to the recent liberalization of the global market, domestic economic conditions, and successor status. It is also an industry that is seen as very difficult. In addition, due to the shortage of workers and the rapid decrease in young workers in the agricultural management, the situation has been forced to mechanize, and for small and medium-sized farmers, the burden of payment of machinery has become very heavy and stable and continuous. Management is difficult.
[0003]
In order to maintain rice cultivation, direct sowing has been attempted as a way of introducing mechanization / automation and farming methods by consolidating large-scale farmland, but it has not been effective enough. In particular, these problems are becoming more and more serious in farms that are difficult to scale up, and the aging of farmers and farming away from farms without successors are progressing. In addition, it has become difficult to obtain original good-tasting rice in a large-scale agriculture. On the other hand, in order to increase the yield, the use of agricultural chemicals and fertilizers is increasing more and more, and it is one factor that promotes contamination of groundwater and downstream water areas and environmental destruction along with cost increase.
[0004]
[Problems to be solved by the invention]
As a result of intensive studies, the present inventors have completed the present invention. That is, an object of the present invention is to propose a breakthrough direct sowing string-like structure industrially easily and inexpensively that enables simplification and labor saving of the current farming method.
[0005]
[Means for Solving the Problems]
The present invention is essentially composed of a biodegradable material, where high strength retention portions and low strength portions in the soil are alternately present in the length direction, and high strength retention portions in the soil. A string-like fiber structure for direct sowing of rice, which is a cylindrical fiber structure having a height of 3 mm at most and includes at least one rice bran in a portion having a high strength retention rate.
[0006]
The cylindrical fiber structure used for the portion having a high strength retention rate in the soil of the present invention includes a cylindrical woven fabric, a cylindrical (circular knitted) knitted fabric, a product obtained by forming a normal woven knitted fabric into a cylindrical shape, and a braided shape. A structure or a non-woven fabric such as spunbond formed into a cylindrical shape can be used. The inside diameter of the cylindrical fiber structure may be such that it can be fixed with rice paddies, but is preferably at most 3 mm, more preferably at most 2 mm, particularly preferably at most 1.5 mm, It is preferable to be somewhat tight. Particularly, a tubular woven fabric, a tubular knitted fabric, and a braided structure are preferable because a natural fastening force is generated.
[0007]
When manufacturing parts with high and low strength retention in the soil continuously, the size will be the same, but parts with high and low strength retention will be made separately and connected later The size of each cylinder is not particularly limited. However, in view of workability, cost, and decomposability in the soil, it is preferable to be equal to or smaller than a portion having a high strength retention rate.
[0008]
The size of the cylindrical material in the part where the strength retention rate is high in the soil must be the size necessary to hold the rice paddy in it, and the roots will come out from the rice paddy. It is necessary to open it to a size that does not prevent the buds from appearing. Usually, it is at most 3 mm, preferably at most 2 mm, more preferably 0.2 to 1.5 mm. If the mesh size is wider than 3 mm, rice paddies may fall off, and sparrows, crows and other birds may stick to the rice paddies in the string. In addition, when the mesh is thinner than 0.2 mm, it is not preferable because there are obstacles in germination and rooting. The term “mesh” used herein refers to the size of the mesh at the portion where the rice paddy is added to the cylindrical structure.
[0009]
The part with high strength retention in the soil is inherently biodegradable, but it has a relatively high strength retention in the soil, and the physical properties of the fiber, ease of manufacture, and price, etc. And fibers mainly composed of polylactic acid are preferred.
[0010]
The polylactic acid used in the present invention refers to a lactic acid copolymer containing a lactic acid polymer and a comonomer, and preferably has a molecular weight of 80,000 or more, more preferably a molecular weight of 100,000 or more, and particularly preferably a molecular weight of 10 to 250,000. is there.
[0011]
Polylactic acid may be a single polymer, but can be copolymerized with other monomers, oligomers and the like. For example, (a) hydroxyalkyl carboxylic acids such as glycolic acid and hydroxybutyl carboxylic acid, (b) aliphatic lactones such as glycolide, lactide, butyrolactone and caprolactone, (c) ethylene glycol, propylene glycol, butanediol, hexane Aliphatic diols such as diols, (d) oligomers of polyalkylene ethers such as diethylene glycol, triethylene glycol, ethylene / propylene glycol, dihydroxyethylbutane, polyalkylene glycols such as polyethylene glycol, polypropylene recall, polybutylene ether (E) Polypropylene carbonate, polybutylene carbonate, polyhexane carbonate, polyoctane carbonate, polydecane Components derived from aliphatic polyester polymerization raw materials, such as polyalkylene carbonate glycols such as nates and oligomers thereof, and (f) aliphatic dicarboxylic acids such as succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, and decanedicarboxylic acid , Ie, 50% by weight or more (especially 60% or more) of aliphatic polyester homopolymer, aliphatic polyester block or / and random copolymer, and other components in aliphatic polyester, For example, aromatic polyester, polyether, polycarbonate, polyamide, polyurea, polyurethane, polyorganosiloxane, etc., 40% by weight or less, preferably 30% by weight (block or / and random) copolymerized and / or mixed All For free.
[0012]
A small amount of D-lactic acid may be contained in L-lactic acid. In particular, the amount of D-form is preferably 0.5% or more, more preferably D-form for the purpose of imparting flexibility to the fiber, adjusting the melting point, adjusting the degradability, and adjusting the spinning temperature. The amount of is 0.7 to 1.5%.
[0013]
When polylactic acid is melted, lactide (monomer) and its low polymerization degree (oligomer) remain in the polymer, but this residual monomer and low molecular weight oligomer are the operability during fiber production and the physical properties of the obtained fiber. The amount is preferably 10% by weight or less, more preferably 5% by weight or less, and most preferably 1% by weight or less.
However, although the reason for the residual monomers and oligomers is unknown, an effect is seen in promoting the germination and rooting of plants, and it is particularly preferable that 0.1 to 0.7% by weight remain in the fiber.
[0014]
In order to increase the stability of the obtained polylactic acid, an antioxidant can be additionally mixed, for example, about 0.1 to 3% by weight when the polymerization of the polylactic acid proceeds. As the antioxidant, hindered phenol, hindered amine, and other known ones are used. The addition rate is preferably about 10 to 30000 ppm, particularly 50 to 10000 ppm. If necessary, a light-resistant agent such as an ultraviolet absorber, a matting agent such as titanium oxide and magnesium oxide, and various organic and inorganic pigments such as carbon black can also be added.
[0015]
These matting agents and pigments can be added either at the time of polymerization of polylactic acid or at the time of spinning, but it is more preferable to add them immediately before spinning. In particular, by coloring the polylactic acid fiber in black, brown, brown, or gray, which is close to the color of the soil, even if it remains after it is harvested at the time of installation in the rice field or at the time of harvest, it is particularly uncomfortable. There is no.
[0016]
As other additives, heat stabilizers, light stabilizers, water repellents, hydrophilizing agents, lubricants, and the like can be appropriately added depending on the purpose and application. In particular, water repellents and hydrophilizing agents are important in terms of biodegradability control.
[0017]
The polylactic acid fiber may be a monofilament composed of a single fiber or a multifilament composed of a plurality of fibers. The fineness of the polylactic acid fiber is not particularly limited, but is usually 100 denier or more, preferably 200 denier or more, and more preferably 300 to 1000 denier. When it is thinner than 100 denier, workability and yield are poor in manufacturing a string-like structure with knitting. On the other hand, if it is larger than 1000, not only is the material used more than necessary, but the string-like structure becomes stiff and it becomes somewhat difficult when rice paddies are inserted therein, which is not economically preferable.
[0018]
The fineness of each filament constituting the multifilament is usually at least 1 denier, preferably at least 1.5 denier, more preferably at least 3 denier. When the denier is less than 1 denier, not only the fiber productivity is lowered, but also unfavorable influence on the germination and rooting of rice.
[0019]
In a multifilament, it is preferable to twist a little so that each filament may not fall apart. As the number of twists, a sweet twist degree expressed by a normal multifilament is sufficient, but a medium twist or a strong twist may be used. For example, if the number is 200 denier and the number of twists is at most 2 to 500 turns / m, the object can be sufficiently achieved. That is, one standard is a twist number × denier number of about 100,000 at most. It should be noted that it is possible to adopt more or less if it meets the purpose.
[0020]
The polylactic acid fiber is produced by a conventional monofilament or multifilament production method. Preferably, the heat of fusion indicating the crystallinity of the obtained fiber is at least 15 joules / g, preferably 20 joules / g. g, more preferably 25 Joules / g. If the heat of fusion is less than 15 joules / g, the crystallinity of the fiber is insufficient and the strength and strength retention are not sufficient. In particular, when manufacturing a string-like structure by knitting, workability and yield are lowered, and the form stability and thermal stability of the string-like structure are lowered, which becomes an obstacle at the time of germination and rooting of rice.
[0021]
The fiber having a low strength retention rate in the soil may be any fiber that is retained in the soil for 6 months and has a strength retention rate lower than that of the polylactic acid fiber. Preferably, the retention rate is at most 80% of the polylactic acid fiber. More preferably, it is at most 70%, particularly preferably at most 60%. When the retention rate is higher than 80%, the string-like structure of the present invention remains after harvesting, which becomes an obstacle when the field is dug up by a tiller or the like. In other words, if the string containing rice paddies remains strong in the length direction, it will wrap around the rotating teeth of the tiller or cause troubles when digging up with the tiller.
[0022]
As the fiber having a low strength retention rate in the soil used in the present invention, the strength retention rate after standing in the soil for 6 months is preferably at most 80% of the strength retention rate of the polylactic acid fiber used in the present invention. Biologically produced PHB, PH (V / B) (for example, Monsanto Biopol), polybutylene succinate, polyethylene succinate adipate (for example, Showa High Polymer Bioonole), polycaprolactone (for example, UCC) Tone), rayon, acetate, polyvinyl alcohol, polyvinyl alcohol derivatives and the like, and one or more of them can be used. The shape of the fiber is not particularly limited as long as it is the same as the polylactic acid fiber described above.
[0023]
When used in combination with natural fibers, it is preferable from the viewpoint of cost reduction and control of degradability. Especially, the use of blended yarns made of short fibers can make the degradability critical. It is preferable in that it can be done. When short fibers are used, the thickness of the fibers is set to a thickness corresponding to the above-mentioned denier.
[0024]
The strength of the string-like structure is sufficient as long as it can be pulled by a human or machine, and is preferably at least 0.5 kg, more preferably at least 1 kg.
[0025]
【Example】
Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not particularly limited thereto. In the examples, unless otherwise specified,%, part indicates% by weight and part by weight.
[0026]
<Example 1>
L-lactic acid / D-lactic acid = 99.5 / 0.5, polylactic acid having a weight average molecular weight (Mw) of 135,000, melt spinning at a spinning temperature of 220 ° C., and 200d / 12f multifilament Got. The strength was 3.3 g / d and the elongation was 35%. Moreover, it spun at 210 degreeC using commercially available aliphatic polyester (SUNKYONG INDUSTRIES company SG1111), and obtained the multifilament of 150d / 36f. The strength was 3.1 g / d, and the elongation was 41%.
Each filament was twisted 350 times / m. Using each yarn, a cylindrical woven fabric having a warp / weft density of 150 mesh (150 pieces / inch) and a diameter of 2 mm was produced.
[0027]
Next, the cylindrical woven fabric using polylactic acid fibers was cut to a length of 10 cm, and the cylindrical woven fabric using aliphatic polyester fibers was cut to a length of 10 cm. In the present invention, a single rice paddy is attached to the center of a cylindrical woven fabric using polylactic acid fibers, and then the cylindrical woven fabric and a cylindrical woven fabric using aliphatic polyester fibers are alternately connected to form a long string. A string-like fiber structure for direct sowing of rice was produced.
[0028]
The string-like fiber structure was stretched on the surface of the soil, and water was laid on the surface so as to have a depth of 1 cm. The water was changed once every two days. After 6 months, the fiber structure was taken out and the strength was measured. As a result, the polylactic acid fiber portion was 91% of the initial strength and the aliphatic polyester fiber portion was 58% of the initial strength.
[0029]
<Example 2>
The tubular woven fabric using the polylactic acid fiber of Example 1 was cut into a length of 10 cm. In addition, the aliphatic polyester fiber of Example 1 was made into three twisted yarns, and the tubular woven fabric was continuously bound so that rice paddies entered at intervals of 12 cm.
Similarly to Example 1, the strength of each part was measured after being left for 6 months. The polylactic acid fiber portion was 90% of the initial strength, and the aliphatic polyester fiber portion was 57% of the initial strength.
[0030]
<Example 3>
Spinning with polylactic acid having a composition of L-lactic acid / D-lactic acid / polyethylene glycol (number average molecular weight 12000) = 91.7 / 0.3 / 8.0 and having a weight average molecular weight (Mw) of 125,000 Melt spinning was performed at a temperature of 215 ° C. to obtain a 300d / 1f monofilament by a conventional method. The strength was 3.5 g / d and the elongation was 30%. Moreover, it spun at 210 degreeC using commercially available aliphatic polyester (SUNKYONG INDUSTRIES Co., Ltd. SG1111), and obtained the multifilament of 100d / 18f. The strength was 3.0 g / d, and the elongation was 43%. The filament was twisted 400 times / m.
[0031]
Using each yarn, a cylindrical woven fabric having a warp / weft density of 150 mesh (150 pieces / inch) and a diameter of 1.5 mm was produced.
Next, the cylindrical woven fabric using polylactic acid fibers was cut to a length of 10 cm, and the cylindrical woven fabric using aliphatic polyester fibers was cut to a length of 10 cm. In the present invention, a single rice paddy is attached to the center of a cylindrical woven fabric using polylactic acid fibers, and then the cylindrical woven fabric and a cylindrical woven fabric using aliphatic polyester fibers are alternately connected to form a long string. A string-like fiber structure for direct sowing of rice was produced.
In the same manner as in Example 1, the strength after 6 months passed was measured. The polylactic acid fiber monofilament remained 85% of the initial strength, and the aliphatic polyester fiber portion was 55% of the initial strength.
[0032]
【The invention's effect】
By using the string-like structure of the present invention, it is possible to completely change the concept of the conventional farming method and to sow seeds that are extremely efficient and labor-saving. Moreover, since the string has fissures in the string, there is no outflow or unevenness of the lines, and the string is excellent in the uprightness of the rice. It is possible to germinate and grow very stably.
In addition, by using this string structure, there is a case where the growth of rice is somewhat improved although the reason is unknown. That is, by using the string structure of the present invention, it is possible to save labor, but it is relatively durable against wind and water damage after the germination of rice, and is effective in improving growth and harvesting.
[Brief description of the drawings]
FIG. 1 String structure according to the present invention (woven fabric + woven fabric)
FIG. 2 String structure according to the present invention (woven fabric + string)
FIG. 3 String structure according to the present invention (woven fabric + nonwoven fabric)
[Explanation of symbols]
1 Part with high strength retention 2 Part with low strength retention 3 Joint

Claims (4)

It consists essentially of a biodegradable material, where high strength retention portions and low strength portions in the soil exist alternately in the length direction, and high strength retention portions in the soil have a mesh size of at most 3 mm. A string-like fiber structure for direct sowing of rice in which at least one rice bran is included in a portion having a high strength retention. The string-like fiber structure according to claim 1, wherein the portion having a high strength retention rate in the soil is a fiber mainly composed of polylactic acid. The parts with low strength retention in the soil are polyhydroxybutyrate, polyhydroxy (butyrate valate), polybutylene succinate, polyethylene (succinate adipate), polycaprolactone, rayon, acetate, polyvinyl alcohol, polyvinyl alcohol derivatives The string-like fiber structure according to claim 1, wherein the string-like fiber structure is at least one kind of fibers. The string-like fiber structure according to claim 2, wherein the portion of the polylactic acid fiber is colored brown, black or brown.

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