JP6919335B2 - Agricultural sheet - Google Patents

Description

This disclosure relates to agricultural sheets.

Agricultural sheets are used, for example, as members for covering soil and agricultural products, members for agricultural houses, and the like. Agricultural sheets imparted with light reflectivity can be used, for example, for solving a shortage of light rays in a house, promoting coloring of harvested products, controlling soil temperature, controlling weeds, and the like.

Patent Document 1 describes an agricultural sheet provided with a sheet base material and a light reflecting layer provided on one surface of the sheet base material, and the sheet base material has an average diameter of 1 μm to 50 μm. It is a porous thermoplastic resin sheet having voids in the range of, having a porosity in the range of 35% to 60%, and having a thickness in the range of 30 μm to 90 μm, and further, of the light reflecting layer thereof. Agricultural sheets with thicknesses in the range of 0.5 μm to 4 μm are disclosed.

Japanese Unexamined Patent Publication No. 2014-233206

For example, when the agricultural sheet is used as a member for covering the soil, the agricultural sheet may be trampled when performing agricultural work. There is a problem that the agricultural sheet is damaged as a result of repeated trampling of the agricultural sheet. In addition, the property of suppressing damage due to trampling of an agricultural sheet may be described simply as durability.

The present disclosure has been made in view of the above circumstances, and the main purpose of the present disclosure is to provide an agricultural sheet having good durability.

In the present disclosure, a polyethylene sheet containing a polyethylene resin and an inorganic filler is provided, and the content of the inorganic filler in the polyethylene sheet is 50% by mass or more and 80% by mass or less with respect to the polyethylene resin. When a steel wool reciprocating wear test was performed on the surface of the polyethylene sheet using a steel wool reciprocating wear tester to reciprocate the steel wool 2000 times under the condition of a load of 300 g, after the steel wool reciprocating wear test. Provided is an agricultural sheet in which the reduction in haze of the above polyethylene sheet is 10% or less.

The agricultural sheet of the present disclosure has the effect of having good durability.

It is the schematic sectional drawing which shows an example of the agricultural sheet of this disclosure. It is the schematic sectional drawing which shows the other example of the agricultural sheet of this disclosure. It is a schematic process diagram which shows an example of the manufacturing method of the agricultural sheet of this disclosure.

Hereinafter, the agricultural sheet of the present disclosure will be described in detail.

FIG. 1 is a schematic cross-sectional view showing an example of the agricultural sheet of the present disclosure. The agricultural sheet 10 in FIG. 1 has a polyethylene sheet 1 and a reinforcing sheet 2. Further, the content of the inorganic filler in the polyethylene sheet is 50% by mass or more and 80% by mass or less with respect to the polyethylene-based resin. Further, when a steel wool reciprocating wear test in which steel wool is reciprocated 2000 times under a load of 300 g is performed on the surface of the polyethylene sheet using a steel wool reciprocating wear tester, the polyethylene after the steel wool reciprocating wear test is performed. The reduction in sheet haze is less than 10%. The thickness of the polyethylene sheet is, for example, the distance indicated by reference numeral t in FIG.

For example, when the agricultural sheet is used as a member for covering the soil, the agricultural sheet may be trampled when performing agricultural work. If the agricultural sheet is repeatedly trampled, the agricultural sheet is rubbed, and as a result, the agricultural sheet is damaged. Conventionally, no particular study has been made on such damage caused by trampling the agricultural sheet.
In this disclosure, the damage caused by trampling the agricultural sheet was examined. As a result, it was found that the damage caused by trampling the agricultural sheet was caused by the agricultural sheet being worn away by trampling the agricultural sheet. Therefore, in the present disclosure, the damage caused by trampling the agricultural sheet is examined by conducting a steel wool test using a steel wool reciprocating wear tester and measuring the haze after the test.
As a result, it was found that the damage caused by trampling the agricultural sheet can be suppressed by setting the content of the inorganic filler in the polyethylene sheet to a predetermined value or more. That is, in the present disclosure, the agricultural sheet has a polyethylene sheet containing a polyethylene resin and an inorganic filler, and a steel wool reciprocating wear tester is used to load steel wool on the surface of the polyethylene sheet at a load of 300 g. When the steel wool reciprocating wear test of reciprocating 2000 times is performed under the steel wool reciprocating wear test, the haze reduction of the polyethylene sheet after the steel wool reciprocating wear test can be reduced to 10% or less, and the agricultural sheet has good durability. Can be done.

Hereinafter, the agricultural sheet of the present disclosure will be described for each configuration.

1. 1. Polyethylene sheet The polyethylene sheet in the present disclosure is a white sheet containing a polyethylene-based resin and an inorganic filler, and exhibits light reflectivity. Further, the polyethylene sheet is preferably a non-stretched sheet, and specifically, a dense sheet. Here, the "dense sheet" means a sheet in which the polyethylene sheet is not a porous sheet. The specific porosity of the polyethylene sheet, which is a dense sheet, is, for example, preferably 5% or less, particularly preferably 3% or less, and particularly preferably 0%. The porosity indicates the ratio of voids in the polyethylene sheet, and can be calculated from the following formula.
Density of each layer = ^{Mass per m 2 of} each laminated layer / Thickness of each laminated layer Porosity = (1-Density of each layer / Density of polyethylene sheet that does not form voids) × 100

In the present disclosure, when a steel wool reciprocating wear test is performed by using a steel wool reciprocating wear tester to reciprocate steel wool 2000 times on the surface of a polyethylene sheet under a load of 300 g, after the steel wool reciprocating wear test. The reduction in haze of the polyethylene sheet is 10% or less. In the present disclosure, the reduction in haze is preferably 5% or less. In the present disclosure, good durability can be obtained when the decrease in haze of the polyethylene sheet after the steel wool test is within the above range.

Here, as the steel wool reciprocating wear tester used for the steel wool reciprocating wear test on the surface of the polyethylene sheet, for example, a paperboard abrasion resistance tester (manufactured by Kumagai Riki Kogyo Co., Ltd.) can be used.

The grade of steel wool used in the steel wool reciprocating wear test is # 0000 (ultra-fine) to # 0 (fine), and it is preferable to use # 000 (ultra-fine), particularly # 0000 (ultra-fine). Is preferably used.

The haze in the present disclosure can be measured using, for example, Nippon Denshoku Industries Haze Meter NDH7000.

The polyethylene sheet may have a single-layer structure or a multi-layer structure. When the polyethylene sheet has a multi-layer structure, the polyethylene sheet may have a two-layer structure or a three-layer structure.

The thickness of the polyethylene sheet may be, for example, 150 μm or less, 100 μm or less, or 80 μm or less. If the polyethylene sheet is too thick, the mass of the agricultural sheet may increase and the handleability may decrease. On the other hand, the thickness of the polyethylene sheet is, for example, 25 μm or more, 30 μm or more, or 40 μm or more. If the polyethylene sheet is too thin, it can be weak. In addition, since the amount of resin used is large, the manufacturing cost of agricultural sheets is also high.

The polyethylene sheet preferably has a high visible light reflectance. The average reflectance of visible light (wavelength 380 nm or more and 780 nm or less) is, for example, 70% or more, preferably 80% or more, and more preferably 90% or more. The measurement conditions for the average reflectance of visible light will be described in detail in Examples. The polyethylene sheet has a total reflectance at a wavelength of 600 nm, for example, 70% or more, 80% or more, or 90% or more.

The polyethylene sheet preferably has high smoothness. Specifically, the arithmetic mean height Sa of the polyethylene sheet surface is, for example, 1 μm or less, preferably 0.7 μm or less, and more preferably 0.5 μm or less. Further, the polyethylene sheet preferably has high antifouling property. Specifically, the contamination grade (JIS-L-1919) on the surface of the polyethylene sheet is preferably 3 grade or higher.

(1) Polyethylene-based resin The polyethylene sheet contains a polyethylene-based resin. Examples of the polyethylene-based resin include high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), and ultra-low-density polyethylene (VLDPE). These may be used alone or in combination of two or more.

Among these, high-density polyethylene and linear low-density polyethylene are preferable, and high-density polyethylene is more preferable. This is because the high-density polyethylene is excellent in weather resistance and tensile strength, and the sheet containing the high-density polyethylene has no slack even in a long roll and is less likely to cause an appearance defect due to whitening during bending.

The polyethylene-based resin preferably has a melt flow rate (temperature 230 ° C., load 2.16 kg) measured in accordance with JIS K 7210 of 0.1 g / 10 min or more and 4.0 g / 10 min or less, and is 0. It is more preferably .4 g / 10 min or more and 2.0 g / 10 min or less. When the melt flow rate (MFR) is in the above range, it is particularly suitable for sheet forming by calendar processing.

The polyethylene sheet may contain a polyethylene-based resin as a main component of the resin component. The ratio of the polyethylene-based resin to the total amount of the resin components is, for example, 50% by mass or more, and may be 70% by mass or more.

(2) Inorganic filler The polyethylene sheet contains titanium oxide as an inorganic filler in order to enhance whiteness and light reflectivity. Further, the polyethylene sheet includes calcium carbonate, talc, titanium oxide, antimony oxide, nickel oxide solid solution and the like, if necessary. These may be used alone or in combination of two or more.

The content of the inorganic filler in the polyethylene sheet may be, for example, 30% by mass or more, 40% by mass or more, or 50% by mass or more with respect to the polyethylene-based resin. If the content of the inorganic filler is too low, the whiteness and light reflectivity of the polyethylene sheet may be reduced. On the other hand, the content of the inorganic filler is, for example, 80% by mass or less, 75% by mass or less, or 70% by mass or less with respect to the polyethylene-based resin. If the content of the inorganic filler is too high, the flexibility of the polyethylene sheet may be reduced.

(3) Light Stabilizer The polyethylene sheet may contain a light stabilizer, if necessary. Examples of the light stabilizer include a hindered amine light stabilizer, and among them, a NOR type hindered amine light stabilizer is preferable. Agricultural sheets may be exposed to acidic environments such as acid rain, pesticide spraying, and sulfur fumigation, but NOR-type hindered amine-based light stabilizers have good acid resistance and weather resistance is greatly improved.

The NOR-type hindered amine-based light stabilizer is a light stabilizer having excellent acid resistance. As an example of the NOR type hindered amine light stabilizer, a compound containing a group represented by the general formula (1) can be mentioned.

In the general formula (1), R is a substituted or unsubstituted hydrocarbon group or acyl group. Examples of R include alkyl groups, alkenyl groups, alkylene groups, cycloalkyl groups, bicycloalkyl groups, phenyl groups, naphthyl groups, phenylalkyl groups, alkyl group-substituted phenyl groups, hydroxyl group-substituted alkyl groups, acyl groups, and alkoxy-substituted alkyls. Examples include groups, thioalkoxy group-substituted alkyl groups and the like. Note that * and ** in the general formula (1) indicate a state in which they can be combined with other elements.

Other examples of the NOR-type hindered amine-based light stabilizer include compounds represented by the general formula (2) or the general formula (3).

In the general formula (2), R ¹ and R ² are independently substituted or unsubstituted hydrocarbon groups or acyl groups, respectively, as in R in the general formula (1) described above. Among them, ^{it is preferable that R 1} and R ² are independently alkyl groups having 4 or more and 20 or less carbon atoms.

In the general formula (3), R ³ and R ⁴ are independently substituted or unsubstituted hydrocarbon groups or acyl groups, respectively, as in R in the general formula (1) described above. Among them, ^{it is preferable that R 3} and R ⁴ are independently alkyl groups having 4 or more and 20 or less carbon atoms. Also, R ⁵ is an alkylene group having 1 to 8 carbon atoms.

Specific examples of the NOR-type hindered amine-based light stabilizer include ADEKA STAB LA-81 manufactured by Adeka and Tinubin 123 manufactured by BASF (bis decanedioate (2,2,6,6-tetramethyl-1- (octyloxy)). ) -4-piperidinyl) ester) and the like.

The content of the light stabilizer in the polyethylene sheet is, for example, 0.05% by mass or more, 0.1% by mass or more, or 0.15% by mass or more, based on the polyethylene resin. good. If the content of the light stabilizer is too low, the weather resistance of the polyethylene sheet may not be improved. On the other hand, the content of the light stabilizer in the polyethylene sheet is, for example, 10.0% by mass or less, 9.0% by mass or less, or 8.0% by mass or less, based on the polyethylene resin. You may. If the content of the light stabilizer is too high, the manufacturing unit price may increase.

(4) Additives The polyethylene sheet may contain at least one of an antioxidant and an ultraviolet absorber. Since it is presumed that the deterioration of the antioxidant and the ultraviolet absorber is caused by the reaction with the protons in the acidic solution, the antioxidant and the ultraviolet absorber are preferably materials having high acid resistance.

(A) Antioxidants Examples of the antioxidants include phenolic antioxidants and phosphorus-based antioxidants. Examples of the phenolic antioxidant include pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propinate], 2,6-di-t-butyl-4-methylphenol, and the like. 4,4'-Methylene-bis (2,6-di-t-butyl) phenol, 4,4'-butylidene-bis (6-t-butyl-3-methyl) phenol, 2,2-methylene-bis (2,2-methylene-bis) 6-t-butyl-3-methyl) phenol, 2,2-methylene-bis (4-methyl-6-t-butyl) phenol, 4,4'-thiobis (2-methyl-6-t-butyl) phenol , 4,4'-thiobis (3-methyl-2-t-butyl) phenol, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4hydroxybenzyl) Examples thereof include benzene, 3,5-t-butyl-4-hydroxy-α-hydroxybenzene, n-octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate and the like.

On the other hand, as phosphorus-based antioxidants, for example, trisnonylphenyl phosphite, tris (2,4-dithiary butylphenyl) phosphite, tris [2-third butyl-4- (three-third butyl-) 4-Hydroxy-5-methylphenylthio) -5-methylphenyl] phosphite, tridecylphosphite, octyldiphenylphosphite, di (decyl) monophenylphosphite, di (tridecyl) pentaerythritol diphosphite, distearyl Pentaerythritol diphosphite, di (nonylphenyl) pentaerythritol diphosphite, bis (2,4-ditertiary butylphenyl) pentaerythritol diphosphite, bis (2,6-ditertiary butyl-4-methylphenyl) ) Pentaerythritol diphosphite, bis (2,4,6-triterone butylphenyl) pentaerythritol diphosphite, tetra (tridecyl) isopropyridene diphenol diphosphite, tetra (tridecyl) -4,4'-n -Butylidenebis (2-tertiary butyl-5-methylphenol) diphosphite, hexa (tridecyl) -1,1,3-tris (2-methyl-4-hydroxy-5-third butylphenyl) butanetriphosphite, tetrakis ( 2,4-Ditertiary Butylphenyl) Biphenylenediphosphonite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, tris (2-[(2,4,8,10) -Tetraxyl tertiary butyldibenzo [d, f] [1,3,2] dioxaphosfepine-6-yl) oxy] ethyl) amine and the like can be mentioned.

The content of the antioxidant in the polyethylene sheet is, for example, 0.05% by mass or more, 0.1% by mass or more, or 0.4% by mass or more, based on the polyethylene resin. good. If the content of the antioxidant is too low, the weather resistance of the polyethylene sheet may not be improved. On the other hand, the content of the antioxidant in the polyethylene sheet is, for example, 5.0% by mass or less, may be 3.0% by mass or less, or 1.0% by mass or less, based on the polyethylene resin. You may. Too much antioxidant content can lead to poor appearance due to bleed-out.

(B) Ultraviolet absorbers Examples of the ultraviolet absorbers include benzotriazole-based ultraviolet absorbers, triazine-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, salicylate-based ultraviolet absorbers, and cyanoacrylate-based ultraviolet absorbers. Further, examples of the benzotriazole-based ultraviolet absorber include 2- (2-hydroxy-5-methylphenyl) benzotriazole, 2- (2-hydroxy-3,5-ditertiary butylphenyl) benzotriazole, 2-. (2-Hydroxy-3,5-ditertiary butylphenyl) -5-chlorobenzotriazole, 2- (2-hydroxy-3-3rd butyl-5-methylphenyl) -5-chlorobenzotriazole, 2-( 2-Hydroxy-3-tertiary butyl-5-carboctoxyethylphenyl) benzotriazole, 2- (2-hydroxy-5-third octylphenyl) benzotriazole, 2- (2-hydroxy-3,5-diku) Examples thereof include 2-hydroxyphenylbenzotriazole compounds such as milphenyl) benzotriazole and 2,2'-methylenebis (4-third octyl-6-benzotriazolylphenol).

The content of the ultraviolet absorber in the polyethylene sheet is, for example, 0.05% by mass or more, 0.1% by mass or more, or 0.4% by mass or more, based on the polyethylene resin. good. If the content of the UV absorber is too low, the weather resistance of the polyethylene sheet may not be improved. On the other hand, the content of the ultraviolet absorber in the polyethylene sheet is, for example, 5.0% by mass or less, may be 3.0% by mass or less, or 1.0% by mass or less, based on the polyethylene resin. You may. If the content of the UV absorber is too high, it may lead to poor appearance due to bleed-out, and depending on the type of UV absorber, poor appearance due to coloring.

(C) Heavy metal inactivating agent The polyethylene sheet may contain a heavy metal inactivating agent. When the polyethylene sheet comes into contact with, for example, an iron pipe, the polyethylene-based resin may be decomposed due to the influence of heavy metal elements (for example, Fe element) contained in the iron pipe. Specifically, heavy metal elements form oxides, and the catalytic action of the oxides may decompose the polyethylene-based resin. Examples of heavy metal elements include Fe element, Cu element, Mn element, Zn element and the like.

Heavy metal deactivators are known as copper damage inhibitors. The heavy metal deactivator is not particularly limited, and examples thereof include an oxalic acid derivative, a salicylic acid derivative, and a hydrazide derivative. , CDA-6 (manufactured by Adeka Corporation), Cel-180, Inganox MD 1024 (manufactured by BASF) and the like can be exemplified. In addition, Japanese Patent Publication No. 37-14484, Japanese Patent Publication No. 39-9072, Japanese Patent Publication No. 39-12454, Japanese Patent Publication No. 39-19541, Japanese Patent Publication No. 40-12293, Japanese Patent Publication No. 40-18852, Tokusho 42-4356, Tokusho 42-4596, Tokusho 42-13247, Tokusho 43-6538, Tokusho 43-18606, Tokusho 47-27624, Tokukousho 48-36837, 49-154666, 52-2834, 54-43537, 54-90343, US Pat. No. 3,357,944, US Pat. No. 3,376,907. It may be exemplified in the specification, the French Patent No. 148105, the French Patent No. 1495830, and the like.

The content of the heavy metal deactivator in the polyethylene sheet is, for example, 0.05% by mass or more, 0.1% by mass or more, or 0.4% by mass or more, based on the polyethylene resin. May be good. If the content of the heavy metal inactivating agent is too low, copper damage may not be sufficiently suppressed. On the other hand, the content of the heavy metal deactivator in the polyethylene sheet is, for example, 5.0% by mass or less, may be 3.0% by mass or less, or 1.0% by mass or less, based on the polyethylene resin. There may be. If the content of the heavy metal inactivating agent is too high, it may lead to poor appearance due to poor dispersion.

(D) Other Additives The polyethylene sheet contains an appropriate amount of known additives such as other lubricants, heat stabilizers, pigments, modifiers, flame retardants, antistatic agents, reinforcing agents, and fungicides. May be good.

(5) Method for producing polyethylene sheet The method for producing a polyethylene sheet is not particularly limited as long as it is a method for obtaining a target polyethylene sheet, and for example, a polyethylene resin, a light stabilizer, and an inorganic filler are used. Examples thereof include a manufacturing method including a step of producing a resin composition containing the resin composition and a step of forming the resin composition into a sheet (filming) to prepare a polyethylene sheet.

The method for producing the resin composition is not particularly limited, but a method for producing the resin composition by melting and kneading a predetermined amount of each raw material is preferable. Examples of the apparatus used for melt kneading include a continuous kneader, a Banbury mixer, a kneader, an extruder and the like. The heating temperature for melt-kneading is, for example, 150 ° C. or higher and 200 ° C. or lower.

Examples of the method for forming the resin composition into a sheet include known molding methods such as extrusion stretching processing, calendar processing, and extrusion molding. Due to the structure of the molding machine, calendar processing is suitable because it is easy to handle sizes and types of resins, and it is easy to handle small lots. Further, for example, when a resin composition having a high content of an inorganic filler is used, it is preferable to mold it by calendar processing. When a large amount of inorganic filler is contained, for example, when molding is performed by extrusion molding, the surface of the obtained sheet becomes rough and the sheet is easily torn, but molding by calendar processing does not cause such inconvenience and the surface is smooth. Sheet can be manufactured. Further, the superiority of calendar processing when a resin composition having a high content of an inorganic filler is used is particularly remarkable when the thickness of the polyethylene sheet is as thin as, for example, about 30 μm or more and 70 μm or less.

(6) Others In the present disclosure, a dense sheet may be used instead of the polyethylene sheet regardless of the type of resin. Here, the "dense sheet" means a sheet in which the polyethylene sheet is not a porous sheet. Since the specific porosity of the polyethylene sheet, which is a dense sheet, can be the same as the content described in the above section "1. Polyethylene sheet", the description here is omitted.

2. Reinforcing Sheet The agricultural sheet of the present disclosure may further have a reinforcing sheet. In the present disclosure, better durability can be obtained by further having the reinforcing sheet in the agricultural sheet. This is because the agricultural sheet has a reinforcing sheet, so that the surface of the polyethylene sheet follows the surface of the reinforcing sheet having an uneven structure, and when a steel wool test is performed on the surface of the polyethylene sheet, the surface of the polyethylene sheet and steel It is considered that this is due to the fact that the contact surface with wool can be reduced. Therefore, when the agricultural sheet further has a reinforcing sheet, it is considered that the decrease in haze of the polyethylene sheet after the steel wool test can be suppressed more effectively.

The reinforcing sheet is a member arranged on one surface of the polyethylene sheet. The reinforcing sheet is a sheet that reinforces the polyethylene sheet. The agricultural sheet may have another layer between the polyethylene sheet and the reinforcing sheet, or may be in contact without the other layer.

The reinforcing sheet in the present disclosure may be any member as long as it can impart a predetermined strength to the agricultural sheet, and examples thereof include non-woven fabrics and woven fabrics. Among the thermoplastic resins, the material of the non-woven fabric or the woven fabric is preferably a polyethylene-based resin, an ester-based resin, or an amide-based resin. Examples of non-woven fabrics include fiber orthogonal non-woven fabrics, long-fiber non-woven fabrics, short-fiber non-woven fabrics, wet non-woven fabrics, dry non-woven fabrics, air-laid non-woven fabrics, card-type non-woven fabrics, parallel non-woven fabrics, cloth-type non-woven fabrics, random non-woven fabrics, spunbonded non-woven fabrics, and melt blown non-woven fabrics. , Flash-spun non-woven fabric, chemical bond non-woven fabric, water flow entanglement non-woven fabric, needle punch non-woven fabric, stitch bond non-woven fabric, thermal bond non-woven fabric, burst fiber non-woven fabric, tow open fiber non-woven fabric, split fiber non-woven fabric, composite non-woven fabric, laminated non-woven fabric, coated non-woven fabric, laminated non-woven fabric, etc. Can be mentioned.

A cloth-type non-woven fabric is preferably used as an example of the reinforcing sheet. For example, the polyolefin mesh cloth disclosed in Japanese Patent Application Laid-Open No. 2007-259734 can be mentioned. The polyolefin mesh cloth is made of polyethylene and is preferably used in consideration of adhesiveness in extrusion molding. Since the content of the polyolefin mesh cloth can be the same as that described in the above publication, the description here is omitted.

The reinforcing sheet preferably contains a resin. The resin may be a thermoplastic resin or a thermosetting resin, but the former is preferable. In particular, the resin used for the reinforcing sheet is preferably a polyethylene resin. That is, in the present disclosure, the reinforcing sheet is preferably a cloth-type non-woven fabric containing a polyethylene-based resin. This is because the reinforcing sheet contains a polyethylene resin, which is excellent in heat resistance, water resistance, chemical resistance, and cost.

Examples of the polyethylene-based resin include high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), and ultra-low-density polyethylene (VLDPE). Among these, low-density polyethylene, high-density polyethylene, and linear low-density polyethylene are preferable. These may be used alone or in combination of two or more.

Further, the polyethylene resin has a melt flow rate (temperature 230 ° C., load 2.16 kg) measured in accordance with JIS K 7210 of 0.1 g / 10 minutes or more and 4.0 g / 10 minutes or less. It is preferably 0.4 g / 10 minutes or more and 2.0 g / 10 minutes or less.

Further, as the thermoplastic resin, other polyolefin resins, acrylic resins, styrene resins, vinyl fluoride resins, amide resins, ester resins and the like can be used. Examples of other polyolefin resins include polypropylene resins and the like. Examples of the acrylic resin include polymethyl acrylate, polymethyl methacrylate, ethylene-ethyl acrylate copolymer and the like. Examples of the styrene resin include a butadiene-styrene copolymer, an acrylonitrile-styrene copolymer, polystyrene, a styrene-butadiene-styrene copolymer, a styrene-isoprene-styrene copolymer, a styrene-acrylic acid copolymer, and the like. Can be mentioned. Examples of the vinyl fluoride resin include vinyl chloride resin, polyvinyl fluoride, polyvinylidene fluoride and the like. Examples of the amide resin include 6-nylon, 6,6-nylon, 12-nylon and the like. Examples of the ester resin include polyethylene terephthalate and polybutylene terephthalate. Further, as the thermoplastic resin, polycarbonate, polyphenylene oxide, polyacetal, polyphenylene sulfide, silicone resin, thermoplastic urethane resin, polyether ether ketone, polyetherimide, thermoplastic elastomer and the like may be used.

The thermoplastic resin contained in the reinforcing sheet and the thermoplastic resin contained in the polyethylene sheet described above may be the same or different.

The thickness of the reinforcing sheet is not particularly limited, but is, for example, 5 μm or more and 150 μm or less, preferably 30 μm or more and 100 μm or less, and more preferably 50 μm or more and 80 μm or less.

The reinforcing sheet in the present disclosure may have a single-layer structure or a multi-layer structure. As an agricultural sheet having a single-layer structure reinforcing sheet, for example, as shown in FIG. 2A, an agricultural sheet 10 having a polyethylene sheet 1, an adhesive layer 3, and a single-layer structure reinforcing sheet 2 in this order. Can be mentioned.

On the other hand, as an agricultural sheet having a multi-layered reinforcing sheet, for example, as shown in FIG. 2B, agriculture having a polyethylene sheet 1, an adhesive layer 3, and a multi-layered reinforcing sheet 2 in this order. Sheet 10 can be mentioned. The reinforcing sheet 2 having a multi-layer structure has a first reinforcing sheet 2a, an adhesive layer 4 for reinforcing sheets, and a second reinforcing sheet 2b in this order. Although not shown, the plurality of reinforcing sheets may be in contact (for example, fused) without interposing an adhesive layer. The type of the adhesive layer for the reinforcing sheet is not particularly limited, and may be the same as the content described in the section "3. Adhesive layer" described later.

The thickness of the reinforcing sheet is not particularly limited, but is preferably, for example, 10 μm or more and 200 μm or less, and 20 μm or more and 180 μm or less. When the reinforcing sheet has a multi-layer structure, the thickness of each layer constituting the reinforcing sheet is preferably within the above-mentioned range. Further, the agricultural sheet may have a reinforcing sheet on the outermost surface or may have a reinforcing sheet inside.

3. 3. Adhesive layer In the agricultural sheet, the polyethylene sheet and the reinforcing sheet may be laminated through the adhesive layer, or may be directly laminated without the adhesive layer. The adhesive layer is composed of an adhesive or an extruded coating. The adhesive layer is not particularly limited, but is preferably an extruded coating.

In the extruded coating, resins that can be melted by heat and fused to each other can be used. Specifically, for example, low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear (linear) low-density polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ionoma-resin, ethylene-acrylic acid copolymer weight. Combined, ethylene-ethyl acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer, ethylene-propylene copolymer, methylpentene polymer, polybutene polymer, polyolefin such as polyethylene or polypropylene Acid-modified polyolefin resin, polyvinyl acetate resin, poly (meth) acrylic resin obtained by modifying the based resin with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, and itaconic acid. , Polyvinyl chloride resin, and other resins can be used.

These may be used alone or in combination of two or more. Among these, polyethylene-based resins are suitable, low-density polyethylene, linear low-density polyethylene are preferable, and low-density polyethylene is more preferable. Low-density polyethylene has excellent processability, excellent adhesion to polyethylene non-woven fabric, and is inexpensive.

The polyethylene-based resin preferably has a melt flow rate (temperature 230 ° C., load 2.16 kg) measured in accordance with JIS K 7210 of 0.1 g / 10 min or more and 4.0 g / 10 min or less, and is 0. It is more preferably .4 g / 10 min or more and 2.0 g / 10 min or less. When the melt flow rate (MFR) is in the above range, it is particularly suitable for extrusion coating.

Further, in order to strengthen the adhesion of the polyethylene sheet, an anchor coating agent may be coated on the polyethylene sheet to provide an anchor coating agent layer. Examples of the anchor coating agent forming the anchor coating agent layer include an organic titanium-based anchor coating agent such as alkyl titanate, an isocyanate-based anchor coating agent, a polyethyleneimine-based anchor coating agent, a polybutadiene-based anchor coating agent, and the like. .. In the present disclosure, similarly to the above, the anchor coating agent is coated with, for example, roll coating, gravure coating, knife coating, dip coating, spray coating, or other coating method, and the solvent, diluent, etc. are dried. , Anchor coating agent layer can be formed. In the above, the coating amount of the anchor coating agent is preferably 0.1 g / m ² or more and 5 g / m ² or less (dry state).

In the present disclosure, examples of the laminating adhesive forming the anchor coating agent include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and polymethylene polyphenylene polyisocyanate, or hexamethylene diisocyanate. , Polyether polyurethane resin, polyester obtained by reaction of polyfunctional isocyanate such as aliphatic polyisocyanate such as xylylene diisocyanate with hydroxyl group-containing compound such as polyether polyol, polyester polyol, polyacrylate polyol, etc. It is preferable to use a polyurethane-based resin or a laminating adhesive containing a polyacrylate polyurethane-based resin as a main component.

The anchor coating agent layer can form a thin film that is soft, has abundant flexibility, and has abundant flexibility, and can improve the degree of tensile elongation thereof. In addition, it acts as a film having flexibility, flexibility, etc. on the polyethylene sheet, improves the polyethylene sheet processing suitability at the time of laminating, and can prevent peeling failure at the time of use.

The anchor coating agent layer in the present disclosure preferably has a tensile elongation of 100% or more and 300% or less based on JIS standard K7113. The tensile elongation of the anchor coating agent layer can improve the tight adhesion between the polyethylene sheet and the reinforcing sheet. Therefore, the lamination strength between the polyethylene sheet and the reinforcing sheet can be increased.

The thickness of the adhesive layer formed by the extruded coating is not particularly limited, but is preferably thinner from the viewpoint of handleability of the agricultural sheet. The thickness of the adhesive layer is preferably 10 μm or more and 20 μm or less.

Further, the agricultural sheet may be produced by using the dry laminating method. For example, in the dry laminating method, it is preferable to perform laminating in a temperature environment in which the polyolefin sheet is not thermally deformed. In the dry laminating method, for example, it is not necessary to heat the polyolefin sheet at the time of laminating, but heating may be performed as long as the polyolefin sheet is not thermally deformed.

4. Agricultural sheet The agricultural sheet has the polyethylene sheet described above. The agricultural sheet preferably has a polyethylene sheet on the outermost surface. The agricultural sheet preferably has a tear strength of 1.4 N or more according to the Elmendorf tear method. The tear strength of the agricultural sheet by the Elmendorf tearing method is, for example, 1.4 N or more, preferably 2.5 N or more. On the other hand, the tear strength of the agricultural sheet is, for example, 15 N or less, and may be 10 N or less.

In addition, agricultural sheets have high visible light reflectance. The average reflectance of visible light (wavelength 380 nm or more and 780 nm or less) is, for example, 70% or more, preferably 80% or more, and more preferably 90% or more. The measurement conditions for the average reflectance of visible light will be described in detail in Examples.

The agricultural sheet may or may not have a light reflecting layer. When the light reflecting layer is provided, the visible light reflectance can be made higher, the coloring of fruits can be promoted, and the rise in soil temperature can be suppressed. The light reflecting layer contains, for example, a white powder and a resin component. Examples of the white powder include anatase-type or rutile-type titanium oxide, titanium oxide whose surface is treated with a metal oxide such as Al or Si, calcium carbonate, barium sulfate and the like. Examples of the resin component include polyurethane-based resin and polyester-based resin. Examples of the polyurethane-based resin include polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, and polycarbonate polyurethane. The location of the light reflecting layer is not particularly limited, and may be the outermost surface of the agricultural sheet or the inside. Further, it is preferable that the light reflecting layer is provided on the side opposite to the reinforcing sheet with the porous substrate sheet as a reference. The thickness of the light reflecting layer is, for example, 0.5 μm or more and 4 μm or less.

Agricultural sheets preferably have high UV reflectance. This is because it can exert a pest repellent effect. The average reflectance of ultraviolet rays (wavelength 300 nm or more and 380 nm or less) on the surface of the agricultural sheet on the reinforcing sheet side is, for example, preferably 35% or more, preferably 60% or more, and preferably 80% or more. More preferred. The “surface on the reinforcing sheet side of the agricultural sheet” refers to the surface on the side opposite to the polyethylene sheet side with respect to the reinforcing sheet.

The thickness of the agricultural sheet is not particularly limited, but is preferably, for example, 50 μm or more and 200 μm or less, and 80 μm or more and 150 μm or less. The agricultural sheet may have a plurality of through holes penetrating from one surface to the other. The ratio of through holes is, for example, 10,000 / m ² or more and 1 million / m ² or less, and ^{preferably 100,000 / m 2} or more and 700,000 / m ² or less.

5. Agricultural Sheet Manufacturing Method The agricultural sheet manufacturing method is not particularly limited as long as the target agricultural sheet can be obtained, and for example, a method of heat-sealing a polyethylene sheet and a reinforcing sheet, a polyethylene sheet and a reinforcing sheet, etc. Examples thereof include a method of laminating through an adhesive layer and a method of laminating a polyethylene sheet and a reinforcing sheet via an adhesive layer composed of an extruded coating. In the agricultural sheet of the present disclosure, a non-woven fabric is suitable as the reinforcing sheet, and therefore, as a method for producing the agricultural sheet, a method of laminating via an adhesive layer composed of an extruded coating is preferable.

FIG. 3 is a schematic cross-sectional view showing an example of a method for manufacturing an agricultural sheet, and specifically shows a method for manufacturing an agricultural sheet by extruded coating. In FIG. 3, an anchor coating agent is applied to the surface of the polyethylene sheet 1 to form an anchor coating agent layer 5 (FIG. 3A). Next, the adhesive composition 3x is applied to the surface of the anchor coating agent layer 5 (FIG. 3 (b)). Next, the adhesive composition 3x is dried to form the adhesive layer 3 (FIG. 3 (c)). Next, the polyethylene sheet 1 and the reinforcing sheet 2 are laminated via the adhesive layer 3 (FIG. 3 (d)). As a result, an agricultural sheet 10 having a polyethylene sheet 1, an anchor coating agent layer 5, an adhesive layer 3 and a reinforcing sheet 2 in this order can be obtained (FIG. 3 (e)).

The adhesive composition may further contain a solvent in addition to the adhesive. The adhesive is as described above. On the other hand, as the solvent, for example, alcohols such as isopropyl alcohol and normal propyl alcohol, esters such as methyl acetate, ethyl acetate, butyl acetate, propyl acetate, ethyl lactate and ethylene glycol acetate, and ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone. , Diethylene glycol methyl ether, ethers such as tetrahydrofuran and dioxane, aromatics such as toluene and xylene, halogenated hydrocarbons and the like.

Examples of the coating method of the adhesive composition include general coating methods such as roll coating, gravure coating, kiss coating, knife coating, dip coating, and spray coating. The temperature at which the adhesive composition is dried varies depending on the type of polyethylene sheet and solvent, but is, for example, 90 ° C. or lower, preferably 70 ° C. or lower. Further, vacuum drying or other vacuum drying may be performed. The drying time is appropriately selected according to the type of adhesive.

When the polyethylene sheet 1 and the reinforcing sheet 2 are bonded together by extruded coating, it is preferable to control the pressure by tension. In this case, it is preferable to control the polyethylene sheet of the first paper feed at, for example, 100 N or more and 300 N or less, and more preferably 150 N or more and 250 N or less. The reinforcing sheet for the second paper feed is preferably controlled at, for example, 100 N or more and 180 N or less, and more preferably 120 N or more and 150 N or less in order to prevent curling of the entire sheet.

The present invention is not limited to the above embodiment. The above embodiment is an example, and any one having substantially the same configuration as the technical idea described in the claims of the present invention and exhibiting the same effect and effect is the present invention. It is included in the technical scope of the invention.

[Example 1]
(Making polyethylene sheet)
HDPE film as a polyethylene resin (high density polyethylene (HDPE, melting point 130 ° C, MFR (190 ° C, 2160 g): 0.5 g / 10 min) 100 parts by mass, 2 (2'-hydroxy-5'-tert) as an ultraviolet absorber -Octylphenyl) benzotriazole 0.1 parts by mass, NOR type hindered amine light stabilizer (Adecastab LA-81) (bis (1-undecanooxy-2,2,6,6-tetramethylpiperidin-4) -Il) carbonate) 0.4 parts by mass, as a phenolic antioxidant, pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propinate] 0.1 parts by mass, inorganic filling 20 parts by mass of calcium carbonate as agent 1 (heavy calcium carbonate (PE master batch with 60% filling rate): PE master batch contains 8 parts by mass of PE in addition to calcium carbonate ), 40 parts by mass of titanium pigment as inorganic filler 2. Parts (PE master batch with a filling rate of 80%: PE master batch contains 8 parts by mass of PE in addition to the titanium pigment ) were mixed and melt-kneaded at 180 ° C. using a Banbury mixer.

The total amount of the polyethylene-based resin contained in the obtained kneaded product is 116 parts by mass, and the content of the NOR-type hindered amine-based light stabilizer with respect to the polyethylene-based resin is 0.34% by mass. The content of the inorganic fillers 1 and 2 with respect to the polyethylene resin is 51.7% by mass.

Next, the obtained kneaded product is supplied to a 12-inch diameter x 30 L common head type mixing roll (rotation speed: 18 rpm) and rolled at a roll temperature of 165 ° C. or higher and 190 ° C. or lower to obtain a polyethylene sheet having a thickness of 60 μm. Manufactured.

(Preparation of agricultural sheet)
As a reinforcing sheet, a polyethylene cloth (thickness 65 μm) made of polyethylene resin is prepared, and a urethane-based anchor coating agent is coated on the polyethylene sheet to provide an anchor coating agent having a thickness of 0.5 g / m ² (dry state). A layer was formed. Further, low density polyethylene (LDPE, MI = 8.0, density = 0.92) is extruded and coated on the above anchor coating agent layer to a thickness of 15 μm while being subjected to ozone treatment, and attached to a reinforcing sheet. Together, an agricultural sheet was prepared. The molten resin temperature of LDPE was 320 ° C.

[Example 2]
Agricultural sheets were prepared in the same manner as in Example 1 except that linear low density polyethylene (L-LDPE, melting point 125 ° C., MFR (190 ° C., 2160 g): 2.0 g / 10 min) was used as the polyethylene resin. Manufactured.

[Example 3]
Agricultural sheets were produced in the same manner as in Example 1.

[Example 4]
An agricultural sheet was produced in the same manner as in Example 1 except that the reinforcing sheet was not provided.

[Comparative Example 1]
(Preparation of porous polypropylene sheet)
As the resin composition constituting the inner layer of the sheet, 65.5% by mass of propylene homopolymer (manufactured by Japan Polychem Corporation, trade name "Novatec PP: MA-8", melting point 164 ° C.), high density polyethylene (Japan) Made by Polychem Corporation, trade name "Novatec HD: HJ580", melting point 134 ° C., density 0.960 g / cm ³ ) is 6.5% by mass, and calcium carbonate powder with an average particle size of 1.5 μm is 28% by mass. A non-stretched sheet was obtained from a resin composition consisting of% by using an extruder. Next, this unstretched sheet was stretched four times in the longitudinal direction to obtain a uniaxially stretched sheet.

On the other hand, as the resin composition constituting the outer layer of the sheet, using the same material as above, the propylene homopolymer was 51.5% by mass, the high-density polyethylene was 3.5% by mass, and the average particle size was 1.5 μm. 42% by mass of calcium carbonate powder, 3% by mass of titanium oxide powder having an average particle size of 0.8 μm, and 0.1 part by mass of 2 (2'-hydroxy-5'-tert-octylphenyl) benzotriazole as an ultraviolet absorber. , NOR type hindered amine light stabilizer (Adecastab LA-81, manufactured by Adeca) (bis (1-undecaneoxy-2,2,6,6-tetramethylpiperidine-4-yl) carbonate) 0.4 parts by mass, As a phenolic antioxidant, a resin composition consisting of 0.1 parts by mass of pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propinate] was prepared using another extruder. It was melt-kneaded and extruded from dies on both sides of the surface of the uniaxially stretched sheet to obtain a laminated sheet having a layer structure of an outer layer, an inner layer, and an outer layer.

Next, by stretching this laminated sheet 7 times in the lateral direction and slitting the selvage portion, the thickness is 70 μm, and the layer structure of the outer layer (15 μm), the inner layer (40 μm), and the outer layer (15 μm) is fine. A porous polypropylene sheet containing voids was obtained.

(Preparation of agricultural sheet)
An agricultural sheet was produced in the same manner as in Example 1 except that the obtained porous polypropylene sheet was used as the polyolefin sheet.

[evaluation]
(Haze after steel wool test)
Using a steel wool reciprocating wear tester, the polyethylene sheet surfaces obtained in Examples 1 to 4 and Comparative Example 1 were subjected to Steel Wool # 0000 in Examples 1 and 2 and Comparative Example 1 and in Example 3. Performed a steel wool reciprocating wear test in which # 0 was reciprocated 2000 times under the condition of a load of 300 g. Next, the haze of the polyethylene sheet at that time was measured, and the degree of decrease in haze before and after the steel wool test was evaluated. The results are shown in Table 1. The result of the decrease in haze was rounded off to the nearest whole number.

(Visible light reflectance measurement)
Visible light reflectance was measured on the agricultural sheets obtained in Examples 1 to 7 and Comparative Example 1. In the visible light reflectance measurement, using an ultraviolet / visible / near-infrared spectrophotometer (Shimadzu Seisakusho UV-3600) and an integrating sphere attachment (ISR-3100), the visible region is 380 nm or more and 780 nm or less at an incident angle of 8 °. The reflectance (total reflectance) of the above was measured, and the average reflectance was obtained. As a standard plate, Spectralon (manufactured by Teflon (registered trademark)) manufactured by Lovesphere Inc. of the United States was used. The measurement surface was the surface of the agricultural sheet on the polyethylene sheet side. The results are shown in Table 1.

(Appearance after steel wool test)
The agricultural sheets obtained in Examples 1 to 7 and Comparative Example 1 were visually evaluated for appearance after the steel wool test. Specifically, when there is no rubbing on the surface of the polyethylene sheet and there is no particular problem, it is evaluated as ○, and when the surface of the polyethylene sheet is worn out and there is damage such as partial tearing, it is evaluated as ×. bottom.

1 ... Polyethylene sheet 2 ... Reinforcing sheet 3, 4 ... Adhesive layer 5 ... Anchor coating agent layer 10 ... Agricultural sheet

Claims (4)

It further has a polyethylene sheet containing a polyethylene resin and an inorganic filler, and a reinforcing sheet.
The content of the inorganic filler in the polyethylene sheet is 50% by mass or more and 80% by mass or less with respect to the polyethylene-based resin.
When a steel wool reciprocating wear test in which steel wool is reciprocated 2000 times under a load of 300 g was performed on the surface of the polyethylene sheet using a steel wool reciprocating wear tester, the polyethylene after the steel wool reciprocating wear test was performed. Agricultural sheet with a reduction in sheet haze of 10% or less. The agricultural sheet according to claim 1, wherein the grade of the steel wool is # 0000 (ultra-fine) to # 0 (fine). The agricultural sheet according to claim 1 or 2 , wherein the polyethylene-based resin is high-density polyethylene or linear low-density polyethylene. The agricultural sheet according to any one of claims 1 to 3, wherein the reinforcing sheet contains a polyethylene-based resin.

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