JP2005000166A - Mulching sheet made of black paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mulching sheet made of paper with large area per unit mass, capable of laying in a large area of paddy field in installing as a mulching roll conforming to a rated dimension of a device especially installed on a paddy field transplanter, free from breaking in transplanting, excellent in visible light shielding property, workability and weeding property, and not requires recovering from paddy field. <P>SOLUTION: The mulching sheet is obtained by forming a black layer comprising active carbon and a biodegradable resin, on one side of a paper base made of cellulose fibers. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a black paper mulch (hereinafter sometimes simply referred to as “multi”), and more particularly to a mulch that can reduce the amount of agricultural chemicals used in rice cultivation and reduce labor.

  In rice cultivation, weeds are prosperous, and the removal of the weeds affects the yield of rice. Therefore, weeding is required as the rice grows. Weeding methods include extraction with human power or a weeder, spraying herbicides, spraying activated carbon, sowing rice bran, and using duckweed, all of which require heavy labor. There is a problem that the herbicidal effect is not sufficiently improved due to adverse effects on the human body and the environment.

  As a means for solving such problems, a method of preventing the growth of weeds by laying a plastic film mulch in rice farming is known in the same way as in field cropping. When the mulch is laid, the mulch has no air permeability to the methane gas generated from the paddy field, and the mulch floats on the water surface and is washed away by the wind, covering the rice and stopping the growth of the rice. Moreover, since the conventional mulch is made of plastic that is not biodegradable, there is a problem that it is necessary to collect the mulch when harvesting rice.

  The use of biodegradable plastic films has also been proposed as plastic films, but in addition to the same problems as ordinary plastic films, these biodegradable plastic films can be completely There is a problem that the mulch that is partly biodegraded and subdivided remains in the paddy field and is mixed into the harvested rice.

  It has also been proposed to use a paper mulch instead of the plastic film. The paper mulch is a mulch suitable for paddy fields because of its breathability and quick decomposition. However, when the mulch is laid on a paddy field, the strength of the mulch is reduced when the mulch gets wet with water The paper mulch may also be insufficient (visible light shielding property).

  As countermeasures for the above problems, proposals have been made to use thick and bulky paper as a paper mulch or to increase the content of fillers for strengthening paper spacing (Patent Document 1). When the mulch is cardboard and bulky, when laying the mulch and planting rice with the rice planting machine, the roll length of the mulch wound in one roll is shortened, and as a result, the work of replacing the mulch with respect to the rice planting machine is reduced. Frequently, the workability of rice planting is reduced. Also, in a paper mulch containing a large amount of filler, there is a time difference for water to penetrate the entire mulch, and immediately after laying in a paddy field, the mulch curls on the outer surface, and it is said that there is wind during work. Since the mulch is drowned, there is a disadvantage that the work cannot be performed when there is wind.

JP-A-6-78659

  Therefore, the object of the present invention is to solve the above-mentioned problems of the conventional paper mulch, and the area per unit mass is large. It is to provide a paper mulch that is not torn at the time of rice planting, has excellent visible light shielding properties, has excellent workability and herbicidal properties, and does not require collection from paddy fields.

The above object is achieved by the present invention described below. That is, the present invention provides a mulch characterized in that a black layer made of activated carbon and a biodegradable resin is provided on at least one surface of a paper substrate made of cellulose fibers. In the mulch, the paper substrate is preferably a thin paper having a basis weight of 25 to 65 g / m ² and a thickness of 35 to 80 μm; and the visible light shielding rate is preferably 70% or more.

  According to the present invention, a biodegradable resin as a binder, and a mulch formed with a black layer with a paint containing activated carbon is excellent in preventing the growth of weeds by shielding visible light, and can be wound in a roll shape, The laying workability of the mulch is good, and the binder is biodegradable, so there is no need to collect the mulch from the paddy field after use.

  Next, the present invention will be described in more detail with reference to preferred embodiments. The present invention solves the problems of the prior art paper mulch. In other words, in the work of laying a mulch in a paddy field with a rice planting machine, the more the number of attachment (replacement) of the mulch rice planting machine, the more the number of times the rice planting machine is stopped, and the workability of rice planting is reduced. There is a demand to reduce the number of installation operations.

The conventional paper mulch has a basis weight of 35 to 160 g / m ² , a thickness of 80 to 300 μm, and an optimum basis weight of 90 to 120 g / m ² . As a result of investigating the density obtained by dividing the basis weight of the paper by the value of thickness in the normally available paper, the density of the conventional paper mulch is 0.60 to 0.80 g / m ³ , The value according to Patent Document 1 is 0.44 to 0.67 g / m ³ . From this, it can be said that the paper mulch described in Patent Document 1 uses bulky special paper. This is because, for the purpose of obtaining a high visible light shielding property, the paper is manufactured using paper that is bulky with respect to the basis weight of the paper (that is, low-density paper).

  In the present invention, paper having a low basis weight (thin paper) equivalent to normally available paper is used as a paper base for paper mulch, and activated carbon and biodegradation are used on at least one surface of the paper base. By forming a black layer made of a functional resin, high visible light shielding properties are obtained, and a long roll paper mulch that can be accommodated in a roll installation device of a rice transplanter is used. By increasing the area that can be laid, rice planting work can be made efficient.

As a result of investigating paper multi-rolls that the present inventors have already put on the market, these paper multis are made of bulky special paper in order to obtain visible light shielding properties and wet strength, and have a basis weight of 120 g / m. The mulch of ² was 100 m, and the mulch having a basis weight of 90 g / m ² was 125 m. On the other hand, in the present invention, a thin paper which is not bulky is used as a multi-paper substrate, and a black layer is formed on the multi-paper substrate to make multi. This multi has excellent visible light shielding properties and has a roll winding length of 2 to 4 times the same roll diameter as the conventional paper multi, and the number of times the multi is attached to the rice planting machine is the case of the conventional paper multi. It becomes 1 / 2-1 / 4, the stop time of the rice planting machine for exchanging a roll decreases, and the work efficiency of rice planting improves.

  The mulch of the present invention is obtained by providing a black layer made of activated carbon and a biodegradable resin on at least one surface of a paper base made of cellulose fiber, and the black layer comprises activated carbon and a biodegradable resin. It is formed by applying and drying a paint containing it. The activated carbon used here does not adversely affect the human body and the environment, and the biodegradable resin that makes up the black layer is biodegraded in the same way as paper after the mulch is laid on the paddy field. Will not remain and will not adversely affect the environment.

  In the present invention, cellulose paper having a basis weight lower than that of paddy paper mulches already marketed is used as the paper base, but the biodegradable resin (binder) in the coating applied to the paper base is a paper base. By penetrating into the fiber structure of the material, the water resistance and wettability of the paper base material is improved, and even when laying in paddy fields using a rice planting machine, rice planting work is performed without causing paper breakage. Can do. Further, when the black layer has a visible light shielding rate of 70% or more, a substantial weed growth prevention effect appears, and when it is 90% or more, a remarkable weed growth prevention effect is seen.

The paper base material used in the present invention is preferably a thin paper having a basis weight of 25 to 65 g / m ² and a thickness of 35 to 80 μm. For such thin paper, the time required for water penetration is faster than for thick paper, and the curl caused by the paper stretching due to water wetting is minimized, and the influence of wind when laying the multi is considered. No need to plant rice. As a general rule, a mulch made of paper coated with resin is easy to repel water, and when the mulch is laid in a paddy field, the mulch floats on the water surface immediately after laying, but activated carbon is used as a black layer pigment. Since the surface of the black layer of the present invention using the porous layer is porous, water permeation from the surface of the black layer also occurs easily, and the multi can be laid in a form following the paddy field immediately after laying.

  In the laying operation of the mulch by the rice planting machine, the mulch is attached to the rice planting machine, and the rice is planted simultaneously with the laying of the mulch. Although the roll diameter of the multi-roll attached to the rice planting machine is limited, the use of the long roll multi-roll of the present invention reduces the work of replacing the multi-roll in the rice planting work, and the work area per hour is reduced. Can be raised.

  The activated carbon used in the present invention preferably has an average particle size of 0.2 to 20 μm, and more preferably 0.2 to 10 μm, in order to increase the coloring power. It is very difficult to make the average particle size less than 0.2 μm. On the other hand, if the average particle size exceeds 20 μm, the amount of activated carbon used increases, which is uneconomical, dispersibility is poor, coloring power is low, and when a mulch is made with a paint containing the activated carbon, The activated carbon does not enter between the fibers of the paper, and the activated carbon tends to fall off due to paddy water or rainwater, and high visible light shielding properties cannot be maintained.

  The activated carbon is not particularly limited, and activated carbon made from sawdust, coconut husk, coal, etc. and activated by chemicals or steam can be used. In addition to activated carbon commercially available as powdered coal, granular coal is pulverized. Can also be used. Activated carbon has a long history of use in the food and beverage industry, including water treatment in waterworks, purification of beer, liquor and soy sauce in breweries, purification of pharmaceuticals, and decolorization of refined sugar, and its safety has been confirmed.

In addition, the true density of the activated carbon is about 2 g / cm ³ , and it does not easily fall out and flow out from the mulch, has numerous fine pores, and adsorbs various molecules due to its large surface area. Fertilizers and useful microorganisms can be adsorbed and retained, and their effects can be sustained over a long period of time. In contrast, carbon black has the advantage of good dispersibility in the paint, but if a mulch made using carbon black is laid in a paddy field, carbon black can easily fall off and flow into the river Since the carbon black is not a food additive approved product, there is also a health and safety concern.

  The paint used in the present invention preferably contains 1 to 40% by mass of activated carbon, and more preferably 5 to 30% by mass. When the activated carbon content is less than 1% by mass, when a paint is applied to a paper substrate and used as a mulch, the visible light shielding property is insufficient and the effect of preventing the generation of weeds is not sufficient. On the other hand, when the content of the activated carbon exceeds 40% by mass, the dispersion stability of the activated carbon during preparation of the coating tends to decrease.

  Examples of biodegradable resins used in the present invention include polycaprolactone made from petroleum-based materials, various polyester resins such as a polymer of succinic acid and glycol, a polymer of adipic acid and glycol, polyethylene glycol, polyvinyl Polyurethane resin, polyurethane / urea resin, etc. made from alcohol, biodegradable polyol as raw material, rosin and its modified product, oil and fat and its modified product, shellac and its modified product made from natural product or modified product of natural product Products, cellulose acetate, starch, calcined starch, modified starch, caseins, polylactic acid, and modified products based on polylactic acid.

  It is preferable that content of the said biodegradable resin in the coating material used by this invention is 1-40 mass%. If the content of the biodegradable resin is less than 1% by mass, the effect of dispersing the activated carbon is inferior, and the activated carbon may aggregate or settle in the coating material. On the other hand, when the content of the biodegradable resin exceeds 40% by mass, no further improvement in the dispersion effect on the activated carbon is seen for the content, which is rather disadvantageous economically. Moreover, it is preferable that the usage-amount of biodegradable resin is 30-200 mass parts per 100 mass parts of activated carbon.

  The coating material used in the present invention can be prepared by uniformly dispersing activated carbon in a dispersion medium containing a biodegradable resin. As the dispersion medium, water, an organic solvent, or a mixture of water and an organic solvent can be used. As the biodegradable resin, it is preferable to use a water-insoluble material in order to improve the strength of the mulch when used in paddy fields and prevent the activated carbon from dropping off. It is preferable to use general-purpose solvents such as alcohols such as methanol and ethanol that can dissolve the resin, ketones such as acetone and methyl ethyl ketone, and esters such as ethyl acetate.

  There is no restriction | limiting in particular in the method to disperse | distribute activated carbon in a dispersion medium, For example, it can carry out using dispersers, such as a sand mill and a speed line mill. In the activated carbon dispersion step, it is desirable to sufficiently disperse the activated carbon until the average particle size of the activated carbon becomes 0.2 to 20 μm, preferably 0.2 to 10 μm.

  The mulch of the present invention is obtained by applying and drying the black paint on one surface of a paper substrate. As a method for applying the paint, any conventionally known method such as roll coating, gravure coating, bar coating, spray coating, or the like may be used. The coating amount of the coating is such that the resulting multi-visible light shielding property is 70% or more, preferably 90% or more, and more preferably 95% or more. If the amount is less than the above range, sufficient visible light shielding property is obtained. Multi with

  A cross section of the black paper mulch of the present invention is schematically shown in FIG. As shown in the figure, a significant part of the activated carbon has entered the paper base tissue together with the biodegradable resin, and the activated carbon is fixed in the paper base by the sizing agent and the biodegradable resin in the paper base. ing. Therefore, even if the mulch encounters paddy field water, rainwater, etc., some activated carbon may fall off, but at least half of the activated carbon is retained on the paper base for several months, generating weeds and Growth can be prevented. Such a mulch of the present invention is useful not only as a paddy field mulch but also as a field action mulch.

  Next, the present invention will be described more specifically with reference to examples and comparative examples. In the text, “part” or “%” is based on mass unless otherwise specified.

[Example 1]
As a biodegradable resin, a mixture of 15 parts of starch fatty acid ester resin (esterification rate: 90%, weight average molecular weight of about 30,000), 20 parts of charcoal powder activated carbon and 65 parts of ethyl acetate is dispersed by a horizontal sand mill. Produced. 5 parts of ethyl acetate are added per 10 parts of the paint to dilute, and the diluted paint is applied to unbleached kraft paper having a basis weight of 50 g / m ² and a thickness of 72 μm at 0.5, ¹ , ² , 3 and 5 g / m. The mulch of the present invention was obtained by coating and drying at a coating amount of ² (dry).

[Example 2]
A mixture of 10 parts of polycaprolactone resin (weight average molecular weight of about 50,000), 20 parts of charcoal powder activated carbon and 70 parts of ethyl acetate as a biodegradable resin was dispersed in a horizontal sand mill to prepare a coating material. 5 parts of ethyl acetate are added per 10 parts of the paint to dilute, and the diluted paint is applied to unbleached kraft paper having a basis weight of 50 g / m ² and a thickness of 72 μm at 0.5, ¹ , ² , 3 and 5 g / m. The mulch of the present invention was obtained by coating and drying at a coating amount of ² (dry).

[Example 3]
A coating material was prepared by dispersing a mixture of 15 parts of unbleached shellac resin, 20 parts of charcoal-based powdered activated carbon and 65 parts of ethanol as a biodegradable resin with a horizontal sand mill. 5 parts of ethanol is diluted per 10 parts of the paint, and the diluted paint is applied to unbleached kraft paper having a basis weight of 50 g / m ² and a thickness of 72 μm at 0.5, ¹ , ² , 3, and 5 g / m ^2. The mulch of the present invention was obtained by coating and drying at a coating amount of (dry).

[Example 4]
A coating material was prepared by dispersing a mixture of 3 parts of cellulose acetate resin, 13 parts of charcoal powder activated carbon, 30 parts of methyl ethyl ketone and 54 parts of acetone as a biodegradable resin with a horizontal sand mill. 5 parts of ethyl acetate are added per 10 parts of the paint to dilute, and the diluted paint is applied to unbleached kraft paper having a basis weight of 50 g / m ² and a thickness of 72 μm at 0.5, ¹ , ² , 3 and 5 g / m. The mulch of the present invention was obtained by coating and drying at a coating amount of ² (dry).

[Example 5]
As a biodegradable resin, a mixture of 15 parts of starch fatty acid ester resin (esterification rate: 90%, weight average molecular weight of about 30,000), 20 parts of charcoal powder activated carbon and 65 parts of ethyl acetate is dispersed by a horizontal sand mill. Produced. 5 parts of ethyl acetate is added per 10 parts of the paint to dilute, and the diluted paint is applied to an unbleached kraft paper having a basis weight of 30 g / m ² and a thickness of 45 μm at a coating amount of 3 g / m ² (dry) and dried. Thus, the mulch of the present invention was obtained.

[Comparative Example 1]
A coating material was prepared by dispersing 15 parts of starch fatty acid ester (esterification rate: 90%, weight average molecular weight of about 30,000), 10 parts of carbon black and 75 parts of ethyl acetate as a biodegradable resin using a horizontal sand mill. 5 parts of ethyl acetate are added per 10 parts of the paint to dilute, and the diluted paint is applied to unbleached kraft paper having a basis weight of 50 g / m ² and a thickness of 72 μm at 0.5, ¹ , ² , 3 and 5 g / m. ^It was coated and dried at a coating amount of ² (dry) to obtain a mulch of a comparative example.

[Comparative Example 2]
Unbleached kraft paper (paper substrate) having a basis weight of 50 g / m ² and a thickness of 72 μm.

[Comparative Example 3]
White colored paddy paper mulch with a basis weight of 120 g / m ² already on the market.

[Comparative Example 4]
A mulch made of black-colored paddy paper with a basis weight of 90 g / m ² that is already on the market.

[Working efficiency]
As a result of winding the mulch of the above examples and comparative examples on a paper tube having an outer diameter of 35 mm at a winding diameter of 165 mm and examining the winding length, the comparative example 3 (basis weight 120 g / m ² ) was 100 m, and comparative example 4 ( With a basis weight of 90 g / m ² ), the winding length is 125 m. The winding length of the mulch of the present invention with a coating amount of 3 g / m ² (dry) is 470 m when the basis weight is 30 g / m ² and the thickness is 45 μm (Example 5), and the basis weight is 50 g / m ^2. In the case of a thickness of 72 μm (Example 1), it is 280 m.

  The thickness of the mulch is the same regardless of the coating amount of the paint forming the black layer, and the same amount of winding length can be obtained at any coating amount. This is because the paint does not affect the thickness of the mulch because the paint permeates and dries near the coated surface of the paper substrate. The mulch of the present invention is an operation of laying the mulch in a paddy field, and can be laid in a large area with one roll. The number of stoppages of rice planting machines for exchanging the plant will be reduced, and the efficiency of rice planting will be improved.

[Visible light shielding]
The multi-visible light shielding property increases as the amount of the black paint applied to the paper substrate increases. The visible light shielding property was 50% for a paper substrate (Comparative Example 2) having a basis weight of 50 g / m ² and a thickness of 72 μm as measured by using a spectrophotometer after dipping the mulch in water for 24 hours. In Examples 1 to 3, the coating amount was 0.5 g / m ² (dry), 80%, the coating amount 1 g / m ² (dry), 93%, the coating amount 2 g / m ² (dry), 97%, and coating. 99% in an amount 3g / m ² (dry), 99.8% in the coating amount of 5g / m ² (dry).

In Example 4, the application amount was 0.5 g / m ² (dry), 70%, the application amount 1 g / m ² (dry), 90%, the application amount 2 g / m ² (dry), 93%, and the application amount 3 g / m. ² (dry) is 96%, and the coating amount is 5 g / m ² (dry). Comparative Example 1 has a visible light shielding rate equivalent to that of Examples 1 to 3, but is a multi using carbon black as a black pigment, and carbon black may contain a small amount of a carcinogenic substance. It is an unfavorable material. Comparative Example 3 has a visible light shielding rate of 90%, and Comparative Example 4 has a visible light shielding rate of 97%.

[Weed growth prevention effect]
The weed growth prevention effect increases as the visible light shielding rate increases, but this effect was confirmed by the following test. The test paddy field was a fallow paddy field that was left untreated for 2 years. In December, the grass was cut and withered by leaving the paddy field, and the dead weeds were not removed.

Under the above conditions, the weed growth prevention rate based on the amount of weeds without multi-use is 70% for the paper substrate itself having a basis weight of 50 g / m ² and a thickness of 72 μm, and the coating amount is 0.5 g / m ² (dry). 80-90% for multi, and 94-97% for multi with a coating amount of 1 g / m ² (dry), 95-99% for multi with a coating amount of 2 g / m ² (dry), 3 g / m ² (dry) ) To 5 g / m ² (dry) multi is 99% or more.
Therefore, the preferable coating amount of the black paint is 2 g / m ² or more, but this is the case where the coating material of the example is used, and the preferable coating amount depends on the concentration and dispersion state of the powdered activated carbon. When the concentration of the powdered activated carbon is low or the coating material with poor dispersion of the activated carbon is used, a large amount of coating is required. If a powdered activated carbon is used in a high concentration or a paint in which powdered activated carbon is highly dispersed, the coating amount of the paint can be reduced.

[Multi adhesion]
The adhesion of the mulch to the paddy field when the mulch is laid on the paddy field is affected by the amount of black paint applied to the paper substrate. Usually, when the coating amount of black paint increases, the resin in the paint has the same effect as the sizing agent, penetrates the entire paper base, and forms a black layer that includes voids in the paper base. However, when this ratio increases, the specific gravity of the black layer becomes greater than that of water, but the water permeability to the black layer is poor and the adhesion of the mulch to the paddy field is poor (floating on the water surface stretched on the paddy field). . This phenomenon was observed in the mulch using the carbon black of Comparative Example 1, and there was no effect on the adhesiveness up to a coating amount of 3 g / m ² with an unbleached kraft paper (paper base material) having a basis weight of 50 g. When the amount is 5 g / m ² , there are mulch floating on the surface of the paddy field where there is much water filling, and there is a movement of mulch under the influence of water flow and wind. It can be seen. However, in the mulch of the present invention using powdered activated carbon as the black pigment, paddy field adhesion is not affected by the amount of paint applied to the paper substrate. This is because the powdered activated carbon is porous, so that it has water permeability from the surface of the black layer, and water permeation rapidly occurs inside the paper substrate.

[Biodegradability]
Since the resin (binder) used in the paint is contaminated with the soil if the resin (binder) remains in the paddy field as a result of using the mulch, the biodegradable resin is used in the present invention as a method for avoiding the resin remaining in the paddy field. In the examples, the test was performed using starch fatty acid ester, polycaprolactone and shellac resin as biodegradable resins. However, between the paper substrate and the mulch using the paper substrate, the biodegradation rate in paddy fields was reduced. There was no difference, and both disappeared in the paddy field in about two months.

[Tensile strength]
In rice planting, a multi roll is attached to a rice planting machine, and seedlings are planted while laying the mulch on a paddy field. At this time, the mulch is subjected to tensile stress in a wet state. As a result of measuring the tensile strength of the mulch in the wet state, in the present invention, the tensile strength in the mulch wet state was improved by forming the black layer. The tensile strength was measured by immersing the mulch in water for 1 hour and using a tensile tester in the flow direction of the mulch paper.

For a paper substrate having a basis weight of 50 g / m ² and a thickness of 72 μm, 1 N / 15 mm, a coating amount of 0.5 g / m ² (dry) multi is 1 N / 15 mm, and a coating amount of 1 g / m ² (dry) multi is 1 .2 N / 15 mm, multi coating amount 2 g / m ² (dry) multi 1.3 N / 15 mm, multi coating amount 3 g / m ² (dry) multi 1.4 N / 15 mm, coating amount 5 g / m ² (dry) It is 1.5N / 15mm in the multi. There was no difference in performance among the resins (starch fatty acid ester, polycaprolactone, shellac, cellulose acetate) used in the paint, and the values were almost the same. The strength of the mulch was a value proportional to the thickness of the black layer. As an example, the mulch of Example 5 using a paper substrate with a basis weight of 30 g / m ² and a thickness of 45 μm has a tensile strength of 0.6 N / 15 mm and was laid on a paddy field using a rice planting machine. Was not seen.
Multi-tensile strength is achieved by forming a black layer as in the present invention even on paper with lower performance than the paper used in the examples such as lowering the basis weight of the paper base to be used or less mixing of long fibers. It can be easily estimated that even if the paper base material alone is not suitable for use, it can be used as a multi due to the performance improvement effect due to the formation of the black layer.

  As described above, according to the present invention, the mulch in which a biodegradable resin is used as a binder and the black layer is formed with a paint containing activated carbon is excellent in preventing the growth of weeds by shielding visible light, and is wound in a roll shape. As a result, the laying workability of the mulch at the time of rice planting is good, and since the binder is biodegradable, there is no need to collect the mulch from the paddy field after use.

The figure which shows the state which the coating material osmose | permeated the vicinity of the application | coating surface of the paper base material, and dried in manufacture of the mulch of this invention.

Claims (3)

  A black paper mulch characterized in that a black layer made of activated carbon and a biodegradable resin is provided on at least one surface of a paper substrate made of cellulose fibers. The black paper mulch according to claim 1, wherein the paper base material is a thin paper having a basis weight of 25 to 65 g / m ² and a thickness of 35 to 80 μm. The black paper mulch according to claim 1, wherein the visible light shielding ratio is 70% or more.

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