JP2006262723A - Paper agricultural sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper agricultural sheet and a protection layer-forming composition for being applied to the paper agricultural sheet. <P>SOLUTION: The protection layer-forming composition for the paper agricultural sheet comprises the following: (A) synthetic resin latex; (B) a mixture of styrene-acrylic emulsified polymer and emulsified-dispersion substance obtained by using α,βunsaturated polybasic acid-added synthetic carbon hydride resin, paraffinic wax, natural and/or synthetic wax, a straight chain nonionic surface active agent and an oily nonionic surface active agent, and using inorganic alkali and/or organic alkali to be emulsified and dispersed; and (C) paper sludge charcoal, calcium carbonate or zeolite. The paper agricultural sheet is obtained by applying the protection layer-forming composition on at least one side of a paper material. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a paper agricultural sheet and a protective layer forming composition for application to the paper agricultural sheet. More specifically, it has water repellency, dimensional stability, and light-shielding properties. It can cut off the growth of weeds, etc. Also, since the sheet itself decays at the harvest time, there is no need for disposal. It is related to the sheet.

  Conventional agricultural sheets include a colorless, transparent, silvery, and black low-density polyethylene film sheet (for example, Tyvek: registered trademark) having light shielding properties. However, these agricultural sheets can sufficiently exhibit light-shielding properties, water repellency, and dimensional stability, but at the time of harvesting, the sheets must be discarded, resulting in the problem of dust that has become a problem in recent years. For this reason, there is a sheet using a biodegradable polymer and having improved biodegradability, but it takes time to decompose and is expensive, so the economic burden is large.

  There were also paper multi-sheets with high biodegradability. However, these paper multi-sheets have to be embossed or creped to prevent tearing due to expansion and contraction, which increases the number of processing steps and costs.

Furthermore, it has a moisture-proof layer formed from a pigment and a synthetic resin latex, and the moisture-proof layer contains a hydrocarbon oligomer that is liquid at room temperature selected from polybutene, polyisobutylene, and butyl rubber, or a rosin ester, a terpene resin, and a petroleum resin. Agricultural paper multi-sheet containing at least one kind of a hydrophobic polymer that is solid at room temperature at a softening point of 180 ° C. or lower selected from (see Patent Document 1). However, the synthetic resin latex only gives the film flexibility and followability, and has only a function of suppressing moisture and water intrusion from the bent portion, and it has only a protective function of moisture protection. In addition, the composition as described herein requires a coating amount of 20 to 30 g / m ^{2 and} is expensive. Furthermore, the performance cannot be maintained unless high-temperature drying at 150 ° C. or higher is performed, and the performance is extremely inferior at temperatures below 150 ° C. For this reason, there are cases where it is necessary to apply more than the optimum coating amount and to perform drying more than necessary so that the drying can be sufficiently performed. Further, with such a composition, water repellency cannot be expected at all.

  On the other hand, as a method for producing a moisture-proofing agent for paper or paperboard, a softening point obtained by polymerizing a fraction having a boiling range of -20 to 250 ° C by-produced during naphtha decomposition by Friedel-Craft type reaction is 40 to 90 ° C. Synthetic hydrocarbon resin of 92 to 98% by weight (based on α, β unsaturated polybasic acid addition synthetic hydrocarbon resin) and 2 to 8% by weight of α, β unsaturated polybasic acid (α, β unsaturated polybasic) Acid-added synthetic hydrocarbon resin standard) to form α-, β-unsaturated polybasic acid-added synthetic hydrocarbon resin 40-88% by weight (based on emulsion A), and then a wax having a melting point of 50-80 ° C. 10 to 50% by weight (based on emulsion A) and 2 to 10% by weight of nonionic surfactant (based on emulsion A), and further emulsified and dispersed by adding an inorganic alkali and / or organic alkali, and the resulting emulsion A, 50-80 weight % (Based on moisture-proofing agent for paper or paperboard) and 20-50% by weight (based on moisture-proofing agent for paper or paperboard, solid conversion) (see Patent Document 2) . However, Patent Document 2 does not teach or suggest that the moisture-proofing agent obtained here can be applied to agricultural sheets.

  Furthermore, as a method for producing a moisture-proofing agent for paper or paperboard, A. Based on the total weight of the polymerization reaction mixture, as emulsion polymerization monomers, a) 10-30 parts by weight of stearyl acrylate and / or stearyl methacrylate; b) 20-50 parts by weight of hydrophobic monomer; and c) acrylic 20 to 50 parts by weight of alkyl acid and / or alkyl methacrylate; and d) an alkali salt of a resin obtained by bulk polymerization of styrene-acrylic acid and stearyl methacrylate or stearyl acrylate as a dispersant for emulsion polymerization. E) emulsion polymerization using an anionic surfactant and / or nonionic surfactant as an auxiliary for emulsion polymerization to obtain an emulsion polymer; Separately, an α, β-unsaturated polybasic acid addition synthetic hydrocarbon resin, a wax and a nonionic surfactant, an inorganic alkali and / or an organic alkali are added and emulsified to obtain an emulsified dispersion. There was a method including mixing and dispersing the emulsion polymer of A and the emulsion dispersion of B (see Patent Document 3). However, Patent Document 3 neither teaches nor suggests that the moisture-proofing agent obtained here can be applied to agricultural sheets.

JP-A-10-84789 (Claims 1, 2, [0007] to [0008], [0017], etc.) Japanese Patent Laid-Open No. 5-262956 (Claim 1 etc.) JP-A-8-239407 (Claim 1 etc.)

  The object of the present invention is that there is no problem of dust seen in the conventional agricultural sheet made of the above-mentioned low density polyethylene film sheet, water repellency, dimensional stability, light-shielding property, and the growth of weeds and the like can be stopped. It is also possible to provide a paper agricultural sheet that does not need to be disposed of because the sheet itself decays at the harvest time.

  Furthermore, an object of the present invention is to provide a paper agricultural sheet which eliminates the disadvantages of the conventional agricultural multi-sheet comprising the pigment and the synthetic resin latex described above, and exhibits sufficient performance even at low temperature drying below 150 ° C. There is.

  Another object of the present invention is to provide a protective layer forming composition for protecting a paper agricultural sheet.

  As a result of diligent research to solve the above-mentioned problems, the present inventors have found that a synthetic resin latex has a styrene-acrylic emulsion polymer and a α, β unsaturated polybasic basic composition as a moisture-proof layer forming composition. Using acid addition synthetic hydrocarbon resin, paraffin wax, natural and / or synthetic wax, linear nonionic surfactant and oily nonionic surfactant, emulsified and dispersed using inorganic alkali and / or organic alkali. An agricultural sheet comprising a combination of a mixture with an emulsified dispersion and further coated with a composition containing paper sludge charcoal, calcium carbonate, or zeolite on paper is a conventional agricultural multi-sheet comprising a pigment and a synthetic resin latex. Conventionally made of low-density polyethylene film sheet that eliminates defects and exhibits sufficient performance even at low-temperature drying below 150 ° C. The present invention has been completed by finding that there is no drawback of the agricultural sheet of the present invention, it is excellent in water repellency, dimensional stability and light-shielding property, and the sheet itself decays at the harvest time, so that it is not necessary to dispose of it.

That is, the present invention provides A synthetic resin latex;
B Styrene-acrylic emulsion polymer, α, β unsaturated polybasic acid addition synthetic hydrocarbon resin, paraffin wax, natural and / or synthetic wax, linear nonionic surfactant and oily nonionic surfactant And a mixture with an emulsified dispersion obtained by emulsifying and dispersing using an inorganic alkali and / or an organic alkali; and C-paper sludge charcoal, calcium carbonate or zeolite.

  Furthermore, the present invention provides A synthetic resin latex; B styrene-acrylic emulsion polymer, α, β unsaturated polybasic acid addition synthetic hydrocarbon resin, paraffin wax, natural and / or synthetic wax, linear system A mixture with an emulsified dispersion obtained by emulsifying and dispersing using a nonionic surfactant and an oily nonionic surfactant with an inorganic alkali and / or an organic alkali; and C paper sludge charcoal, calcium carbonate or zeolite It exists in the paper-made agricultural sheet | seat formed by apply | coating the composition for protective layer formation to the at least single side | surface of paper material.

  Since the agricultural sheet | seat which apply | coated the composition for protective layer formation of this invention to the paper material is excellent in water repellency, dimensional stability, and light-shielding property, it can stop growth of weeds. Furthermore, since the sheet itself decays at the harvest time, it shows a remarkable effect that does not require disposal. Also, paper sludge charcoal, which is a wood fiber carbide that can be used as the C component, is inexpensive and has an excellent light-shielding property because it is coated on the paper surface, and can prevent the growth of weeds and the like. Furthermore, paper sludge charcoal can be used as a soil conditioner when it decays.

The composition for forming a protective layer for the paper agricultural sheet of the present invention,
A synthetic resin latex;
B) Based on the case where the solid content of the emulsion polymer is 100 parts by weight a) One or more components selected from the group consisting of styrene, α-methylstyrene, and (meth) acrylic acid alkyl ester 10 to 40 parts by weight (emulsion polymerization dispersant) of an alkali salt of polymerized (meth) acrylic acid and
b) An emulsion polymer obtained by emulsion polymerization using 60 to 90 parts by weight of one or more components selected from the group consisting of styrene and alkyl (meth) acrylate;
B) Based on the case where the solid content of the emulsified dispersion is 100 parts by weight a) 50 to 80 parts by weight of α, β-unsaturated polybasic acid addition synthetic hydrocarbon resin,
b) 10 to 40 parts by weight of paraffin wax,
c) 3-15 parts by weight of natural (synthetic) wax,
d) 1-8 parts by weight of a linear nonionic surfactant, and e) 3-10 parts by weight of a specific oily nonionic surfactant, and emulsified and dispersed using an inorganic alkali and / or an organic alkali. And a paper sludge charcoal, calcium carbonate or zeolite which is a carbide of wood fiber.

  The mixing ratio of each component of the composition for forming a protective layer is that the A component is 30 to 60 parts by weight, preferably 35 to 55 parts by weight, most preferably, when the total weight of the A and B components is 100 parts by weight. 40 to 50 parts by weight, B component is 40 to 70 parts by weight, preferably 45 to 65 parts by weight, and most preferably 50 to 60 parts by weight. C component is 20 parts per 100 parts by weight of the total weight of A and B components. To 50 parts by weight, preferably 25 to 45 parts by weight, most preferably 30 to 40 parts by weight.

  The synthetic resin latex used in the present invention mainly gives flexibility and followability to the protective film formed, and can prevent moisture and water from entering from a bent portion when the sheet is bent, for example. Synthetic resin latex that can be used in the present invention includes styrene butadiene latex (SBR), methyl methacrylate butadiene latex (MBR), acrylonitrile butadiene latex (NBR), etc. Latex is preferred. As for synthetic resin latex, for example, SBR latex can be obtained as A-6130, A-6925, A-6950 manufactured by Asahi Kasei Kogyo Co., Ltd.

The styrene-acrylic emulsion polymer of component B (1) used in the present invention improves compatibility with the emulsified dispersion of component B (2) and can form a uniform moisture barrier film. it can.
The dispersant for emulsion polymerization used for emulsion polymerization to obtain a styrene-acrylic emulsion polymer is one or more components selected from the group consisting of styrene, α-methylstyrene, and (meth) acrylic acid alkyl ester ( Alkaline salts obtained by polymerizing meth) acrylic acid are suitable, and ammonium salts are particularly preferred. The total weight of each component can be 10 to 40 parts by weight, preferably 10 to 30 parts by weight, more preferably 15 to 25 parts by weight per 100 parts by weight of the solid content in the emulsion polymer.

  The monomer that can be used in the emulsion polymerization of the present invention includes one or more monomers selected from the group consisting of styrene and (meth) acrylic acid alkyl ester, and the amount of the monomer is 100 parts by weight of solid content in the emulsion polymer. The total weight of each component can be 60 to 90 parts by weight, preferably 70 to 90 parts by weight, and more preferably 75 to 85 parts by weight. The use range of each monomer component can be arbitrarily set, but the relative ratio of styrene to (meth) acrylic acid alkyl ester is generally 30 to 70:70 to 30, preferably 35 to 65:65 on a weight basis. ~ 35, most preferably 40-60: 60-40.

  Examples of the (meth) acrylic acid alkyl ester that can be used in the present invention include methyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tertiary butyl (meth) acrylate, (meth) Examples include 2-ethylhexyl acrylate. Considering the film properties and flexibility of the emulsion polymer to be produced, n-butyl acrylate and 2-ethylhexyl acrylate are preferred.

  The glass transition point of the emulsion polymer of the present invention is -15 to 35 ° C, preferably -5 to 25 ° C, and most preferably 5 to 15 ° C. When the glass transition point exceeds 35 ° C., it is expected that the coating surface temperature does not exceed the glass transition point in a low temperature (for example, 130 ° C.) drying treatment, and there is a possibility that film formation cannot be sufficiently performed. Moreover, even if it dry-processes at high temperature (for example, 150 degreeC), a film | membrane tends to crack and performance cannot be maintained. By employing a glass transition point in the above range, the glass transition point is exceeded even at a low temperature (for example, 130 ° C.), and a sufficient film can be formed. If the glass transition point is less than −15 ° C., a film can be formed, but the film becomes sticky, and when the protective layer-forming composition is applied to one side of the paper material sheet and wound, There is a possibility of blocking on the work surface.

  As a polymerization method of the dispersant for emulsion polymerization used in the composition for forming a protective layer of the present invention, a method known in the art can be used. For example, (meth) acrylic acid, which is an essential component in the polymerization reaction vessel, and one or more selected from styrene, α-methylstyrene, and (meth) acrylic acid alkyl ester (the use range of each monomer component is arbitrarily set) And, with additional surfactant and water, warm to about 60-65 ° C. with stirring. While maintaining the above temperature, a catalyst such as ammonium persulfate is added and maintained at 70-80 ° C. for 70-80 minutes. Further, a catalyst such as ammonium persulfate is added and maintained at the same temperature for 40 to 50 minutes to complete the reaction, and an alkali is added and emulsified.

  As a polymerization method of the emulsion polymer, a method known in the art can be used. For example, a dispersant for emulsion polymerization and water are placed in a polymerization reaction vessel and heated to 78 to 85 ° C. with stirring. As the dispersant for emulsion polymerization, it is preferable to use the dispersant for emulsion polymerization specified above. While maintaining the above temperature, a catalyst such as ammonium persulfate is added, a predetermined amount of styrene separately prepared, and (meth) acrylic acid alkyl ester (one or more) can be used. The range can be set arbitrarily) and the mixture is added dropwise over about 2-3 hours. After dropping, the reaction is terminated by maintaining at the same temperature for about 2 to 2.5 hours.

  The emulsified dispersion (B (2) component) used in the present invention has a softening point of 40 to 40 obtained by polymerizing a fraction having a boiling point range of −20 to 250 ° C. by-produced during naphtha decomposition by Friedel-Craft reaction. Synthetic hydrocarbon resin at 90 ° C. of 92 to 98% by weight (based on α and β unsaturated polybasic acid addition synthetic hydrocarbon resin) and α and β unsaturated polybasic acid of 2 to 8% by weight, preferably 3 to 5% After adding 50% by weight to produce 50 to 80 parts by weight of α, β unsaturated polybasic acid addition synthetic hydrocarbon resin (based on the solid content of the emulsified dispersion being 100 parts by weight), melting point 50 10 to 40 parts by weight of paraffin wax at -80 ° C (based on the solid content of the emulsified dispersion as 100 parts by weight), 3 to 15 parts by weight of natural (synthetic) wax (100% by weight of the solid content of the emulsified dispersion) Parts) and linear nonionic surfactant 1 8 parts by weight (based on the solid content of the emulsified dispersion being 100 parts by weight), and 3 to 10 parts by weight of a specific oily nonionic surfactant (the solid content of the emulsified dispersion is 100 parts by weight) And adding an inorganic alkali and / or an organic alkali to neutralize and emulsify and disperse to obtain an emulsified dispersion.

  The α, β unsaturated polybasic acid used in the present invention can be selected from at least one selected from maleic acid, fumaric acid, itaconic acid and maleic anhydride. The wax can be selected from at least one selected from paraffin wax, oxidized paraffin wax, natural wax, hydrogenated petroleum resin, hydrogenated rosin and the like. As the paraffin wax, a wax having a melting point of 50 to 80 ° C. can be arbitrarily selected, and the natural wax can be arbitrarily selected from carnauba wax, montan wax, candelilla wax, rice wax and the like. As described above, the amount of paraffin wax used is in the range of 10 to 40 parts by weight (based on the solid content of the emulsified dispersion being 100 parts by weight), and the amount of natural (synthetic) wax used is 3 to 15 parts. It is a range of parts by weight (based on the case where the solid content of the emulsified dispersion is 100 parts by weight).

  The linear nonionic surfactant used in the present invention is a polyoxyethylene alkylphenol ether, a polyoxyethylene higher alcohol ether or the like based on the solid dispersion of 100 parts by weight based on 1 to 8 parts by weight. Add parts by weight, preferably 2-5 parts by weight.

  Specific oily nonionic surfactants of the present invention include hexastearic acid POE (6) sorbit, monolauric acid POE (6) sorbit, tetrahexastearic acid POE (60) sorbit, tetraoleic acid POE (6) sorbit, Examples include tetraoleic acid POE (30) sorbit, tetraoleic acid POE (40) sorbit, tetraoleic acid POE (60) sorbit, and the like. Unlike the general hydrophilic surfactant, the oily nonionic surfactant has a feature that it can be emulsified without impairing moisture resistance and water repellency. Considering the water repellency and emulsifying property of the produced emulsified dispersion, hexastearic acid POE (6) sorbit is preferable.

  Examples of the alkali that can be used in the emulsified dispersion of the present invention include potassium hydroxide and sodium hydroxide as inorganic alkali, and examples of the organic alkali include triethanolamine, diethanolamine, morpholine, aminoalcohol, and dimethylamine.

  The mixing ratio of the emulsion polymer of component B and the emulsified dispersion is 40 to 90:10 to 60, preferably 45 to 85:15 to 55, and most preferably 50 to 80, based on 100 parts by weight of the mixture. : It is the range of 20-50.

  The paper sludge charcoal that can be used in the present invention is a wood fiber carbide. The particle size is desirably 100 μm or less. If it is more than that, the concealing property is deteriorated and sufficient light shielding property cannot be obtained. Paper sludge charcoal can be obtained as PS charcoal from Kagoshima Kasei Co., Ltd., for example. Calcium carbonate, zeolite, etc. can also be used. Paper sludge charcoal etc. can use 20-50 weight part with respect to 100 weight part of mixture of A and B component. If it is less than 20 parts by weight, sufficient light shielding properties cannot be obtained. If it exceeds 50 parts by weight, sufficient moisture resistance cannot be obtained.

  The composition for forming a protective layer of the present invention simply mixes the above-described synthetic resin latex, a mixture of a styrene-acrylic emulsion polymer and an emulsion dispersion, and each component of paper sludge charcoal, calcium carbonate, or zeolite. Can only be manufactured. Moreover, the mixture of the styrene-acrylic emulsion polymer and the dispersion can be mixed individually or uniformly.

Paper materials that can be used in the agricultural sheet of the present invention include bleached kraft paper, unbleached kraft paper, liner paper, and newsprint. In order to adjust the strength and weight according to the use of the agricultural sheet and the type of paper material, the basis weight can be varied. In general, it can set the basis weight to 50 to 120 / ^{m 2,} preferably in 60 to 100 / ^{m 2,} most preferably, be set to 65~85g / ^{m 2.}

The agricultural sheet of the present invention can be produced by applying the protective layer forming composition to one or both sides of a paper material. Examples of the coating apparatus for coating include an air knife, a blade coater, a reversible coater, a curtain coater, and a roll coater. Coating amount is can vary by local weather conditions, etc., used period or agricultural sheets want to protect agricultural sheeting, generally in the range of 5 to 20 g / m ^2, preferably from 10~18g / m ^2, most preferably in the range of 15~18g / ^{m 2.}

  Hereinafter, the present invention will be further described by examples.

(Reference Example 1 Production of Dispersant for Emulsion Polymerization)
In a reaction vessel, 60 g of styrene, 60 g of methacrylic acid, 5 g of n-butyl methacrylate, 15 g of α-methylstyrene, 9 g of n-dodecyl mercaptan, 449 g of ion-exchanged water, and 2 g of sodium dioctylsulfosuccinate (70%) were added and stirred at 60 ° C. Warmed to. After adding 0.8 g of ammonium persulfate as a catalyst to this, 70 minutes at 75 ° C., then 0.3 g of ammonium persulfate was added, and the reaction was carried out at 65 ° C. for 50 minutes. After completion of the reaction, the reaction mixture was cooled, and 400 g of ion-exchanged water and 48 g of aqueous ammonia (25%) were added to obtain a dispersant for emulsion polymerization having a solid content of 15%, pH 9.0, and a viscosity of 250 mPa · s.

(Reference Example 2 Production of Emulsion Polymerized Product) -Production of B (1) Component-
The dispersion agent for emulsion polymerization obtained in Example 1 and 313 g of ion-exchanged water were added to a four-necked flask and heated to 80 ° C. with stirring. To this was added 1.6 g of ammonium persulfate as a catalyst, and then a monomer mixture consisting of 148 g of styrene, 59 g of n-butyl acrylate, 104 g of 2-ethylhexyl acrylate, and 4 g of n-dodecyl mercaptan was added dropwise over 2 hours. After adding 0.6 g of ammonium persulfate, the mixture was aged for 2 hours while stirring at 80 ° C. and then cooled to obtain an emulsion polymer having a solid content of 37%, pH 9.0, and a viscosity of 450 mPa · s.

(Reference Example 3 Production of Emulsified Dispersion) -Production of B (2) Component-
96.5 g of a synthetic hydrocarbon resin having a softening point of 64 ° C. obtained by polymerizing a fraction having a boiling point range of −20 to 250 ° C. produced as a by-product during naphtha decomposition by Friedel-Crafts reaction, was heated and melted, The system temperature was adjusted to 180 to 190 ° C., 3.5 g of maleic anhydride was added, the temperature was gradually raised with stirring, and the reaction was carried out at 200 to 210 ° C. for 5 hours. Next, 60 g of the resulting maleated synthetic hydrocarbon resin (per 100 g of the total amount charged), 30 g of paraffin wax having a melting point of 62.7 ° C., 5 g of polyoxyethylene cetyl ether, and 5 g of hexastearic acid POE (6) sorbit are emulsified. Place in a kettle and heat melt at 100-120 ° C. After adjusting the system temperature to 100 to 110 ° C., 4.3 g of potassium hydroxide (49%) is further added. Next, 70-80 degreeC warm water was added gradually and the emulsion of 40% of solid content was obtained. Let the obtained emulsion be an emulsified dispersion.

Example 1
Synthetic resin latex (component A), mixture of emulsion polymer and emulsion dispersion obtained by the above method (component B), and paper sludge charcoal or calcium carbonate (component C) shown in Table 1 Part) to obtain a protective layer forming composition of the present invention.

  A-6950 made by Asahi Kasei Co., Ltd. is used for the synthetic resin latex, PS coal made by Kagoshima Kasei Co., Ltd. is used for the paper sludge charcoal, and the average particle size is adjusted to 10 μm by dry pulverization. BF300 was used.

The above composition was applied to a paper material using the following materials and conditions to obtain a paper agricultural sheet.
Base paper: Unbleached kraft paper Basis weight 60g / m ²
Coating amount: 10, 15 g / m ² (solid)
Coating method: Bar coater Drying conditions: Drying at 130 ° C for 20 seconds (hot air drying)

[performance test]
Regarding the performance of the paper agricultural sheet according to the present invention, the black low-density polyethylene film sheet (manufactured by Sekisui Film Kyushu Co., Ltd., trade name: Agricultural Poly Black Multi) has a light-shielding property, water repellency, dimensional stability, and decay properties. , And uncoated unbleached kraft paper sheet as a comparative example.

(Light shielding test)
The light-shielding property test conformed to JIS L 1055 “Method for testing curtain light-shielding property”.
(Water repellency test)
The water repellency test conformed to JIS P 8137 “Testing method for water repellency of paper and paperboard”.

(Water immersion elongation test)
In order to evaluate the dimensional stability, the immersion elongation test was conducted. The water immersion elongation test is described in J.A. According to TAPPI paper pulp test method No. 27A “Paper and paperboard water immersion elongation test method”. The test paper after the measurement of water immersion elongation was left to dry in a constant temperature and humidity chamber adjusted to 23 ° C.-65% for 24 hours, and the elongation after drying on the basis of before water immersion was also confirmed. Furthermore, the same process was performed again, and the repeated water immersion elongation and the elongation after repeated drying were also confirmed.

(Tensile strength test, wet tensile strength test)
In order to evaluate the strength, a tensile strength test and a wet tensile strength test were performed. The tensile strength test and the wet tensile strength test were in accordance with JIS P 8113 “Paper and board tensile strength test method” and JIS P 8135 “Paper and paperboard wet tensile strength test method”, respectively. The water immersion time was 60 minutes, and the water-treated test paper was allowed to stand in a constant temperature and humidity chamber adjusted to 23 ° C.-65% for 24 hours and dried, and the tensile strength was also confirmed after drying.

(Degradability test)
Place the soil for gardening on the planter, and insert the coated paper or uncoated paper into the half of it. The planter was placed outdoors, and water was soaked that the soil surface was moistened every 3 days. The decayability of the plugged portion over time (after 30 days, 90 days, and 120 days) was confirmed.

(Disaggregation test)
After cutting 20 g of paper stock into a 3 cm square, it was put into a home mixer (100 V) together with 780 ml of fresh water and disaggregated for 5 minutes. The slurry after disaggregation is diluted to 8 liters, hand-made with a basis weight of 50 g / m ² with a round paper machine, and the degree of disaggregation is visually determined. Judgment was good when the pulp was uniformly dispersed and made, and the case where the pulp was partially agglomerated and made unevenly was judged as poor.

  The reason for conducting this test is to evaluate the ease of recycling non-paper, which becomes garbage generated when cutting into agricultural sheets of a predetermined size by slitting, as waste paper.

[Test results]
Tables 2 to 6 and FIGS. 1 to 7 show the test results.
(Light shielding test)

From the above results, it was found that 20 g / m ² (solid) of Formulation Examples-1 and 2 using paper sludge charcoal had a light shielding property equivalent to that of the polyethylene film sheet.
(Water repellency test)

From the above results, it was found that all the formulation examples showed R10 (water droplets completely rolled down) and were good.
(Water immersion elongation test)

From the above results, it was found that in all coating conditions, there was almost no expansion and contraction in both length and width and the dimensional stability was excellent.
(Tensile strength test, wet tensile strength test)

From the above results, it was found that the strength was remarkably increased compared to uncoated paper.
(Degradability test)
The photograph which compared the test result by 10 g / m < ² > (solid) with the non-coating in the compounding example-1 was shown as FIGS.
From the results of the decay test, it was found that the uncoated paper decayed in 90 days, but the coated paper was in the form of paper even in 120 days.
(Disaggregation test)

Good disaggregation 5⇔1 Poor disaggregation From the above results, disaggregation was good.

It is a photograph before the start of the decay test of the agricultural sheet of the present invention. It is the photograph at the time of 30-day progress of the decay property test of the agricultural sheet | seat of this invention. It is the photograph at the time of 90-day progress of the decay property test of the agricultural sheet | seat of this invention. It is the photograph at the time of 120-day progress of the decay property test of the agricultural sheet | seat of this invention. It is the photograph before the start of the decay test of the uncoated paper sheet used for comparison. It is the photograph at the time of 30-day progress of the decay property test of an uncoated paper sheet. It is the photograph at the time of 90-day progress of the decay property test of an uncoated paper sheet.

Claims (2)

A protective layer forming composition for a paper agricultural sheet,
A synthetic resin latex;
B Styrene-acrylic emulsion polymer, α, β unsaturated polybasic acid addition synthetic hydrocarbon resin, paraffin wax, natural and / or synthetic wax, linear nonionic surfactant and oily nonionic surfactant A composition for forming a protective layer, comprising a mixture with an emulsified dispersion obtained by emulsifying and dispersing using an inorganic alkali and / or an organic alkali; and C paper sludge charcoal, calcium carbonate or zeolite.   A paper agricultural sheet obtained by applying the protective layer-forming composition according to claim 1 to at least one surface of a paper material.