Body coated by multi-layer polymer, and method for cultivating plant

Abstract

The present invention provides a body coated by a multi-layer polymer that can be germinated under an increased air temperature condition after dormancy, even when sown during autumn which is an agricultural off-season. Provided is a body coated by a multi-layer polymer coating which is a coated body obtained by coating at least two layers of polymer onto a coating target body, said body coated by a multi-layer polymer coating being characterized in that an outer coating layer including at least one inner coating layer on an inner side is formed from a polymer exhibiting lower limit critical temperature (LCST) characteristics after being subjected to a phase transition at a temperature lower than the softening temperature of the polymer forming the inner coating layer.

Description

Coating body made of a plurality of layers of polymers and method for cultivating plants

[0001] The present invention relates to a coating body made of a plurality of layers of polymers that can block a coating layer coated inside from the external environment until a specific temperature condition is reached in an environment where the ambient temperature changes, and expose the inner coating layer to the external environment when the specific temperature condition is reached.

[0002] As an object that requires the coated body protected by the coating layer to be blocked from the external environment and the coating layer to be removed and exposed to the outside under specific temperature conditions, for example, the seeds of the plants shown below can be mentioned.

[0003] From the perspective of food security, sustainable domestic food production is an important issue. Onions and beets, which are widely cultivated in cold regions such as Hokkaido, are transplanted and cultivated by sowing in a vinyl house around February and raising seedlings, and transplanting them to the field around May to June.

[0004] On the other hand, due to the aging of farmers, which has been worsening year by year, and the labor shortage accompanying the decrease in the agricultural working population, labor-intensive transplanting cultivation has been regarded as a problem. This transplanting cultivation requires, for example, transplanting seedlings raised in a house for two months with a machine and then replanting them manually, which is time-consuming and requires a lot of costs for houses and transplanting machines, and is a heavy burden for individual farmers. Furthermore, due to the increase in the number of farmers leaving agriculture, the cultivated area per farm has increased, and "improvement of productivity" is desired.

[0005] A method of direct seeding in the spring season is also considered, but spring is the sowing time for many crops, and since agricultural operations overlap, it cannot be an effective solution for farmers with the above-mentioned aging and labor shortage.

[0006] By the way, in cold regions, after the harvest in autumn, there is a relatively idle period with less work. Therefore, if direct seeding can be done during the idle period, the work will be dispersed and the above-mentioned problems can be solved. However, if direct seeding is done in autumn, the temperature is still relatively high, so the seeds will germinate and then wither due to the cold in winter that follows. Also, it is extremely difficult to carry out seeding work in winter due to freezing and snow accumulation in the field.

[0007] Therefore, there is a need for technology that allows seeds sown in the autumn, the off-season for farming, to germinate in the spring after overwintering.

[0008] Patent Document 1 describes a technique for delaying the germination time of seeds by sealing the outer surface of the seeds with biodegradable plastic and isolating the seeds from the outside air and water for a certain period of time.

[0009] Patent Document 2 discloses a multi-coated seed having an inner coating that slowly penetrates water, an intermediate coating that is semi-permeable to water, and an outer coating that is substantially impermeable to moisture but capable of nuclear fission at frost temperatures.

[0010] Patent Document 3 discloses that coated seeds have a coating layer formed of a polymer material that has temperature-dependent permeability to materials such as water. The polymer material used in the manufacture of the coating is relatively impermeable to materials such as water at low temperatures (below the optimal growth or germination temperature) and relatively permeable at high temperatures (above the optimal growth or germination temperature), and it has been shown that the variable permeability of the coating prevents absorption at low temperatures and allows absorption at high temperatures.

[0011] Japanese Patent Publication No. Hei 8-21, U.S. Patent No. 3,545,129, U.S. Patent No. 5,829,180

[0012] Namikoshi, T. Hashimoto, T. Urushisaki, M. ,Synthesis of poly(vinilether) plastics for optical use by cationic copolymerization of tricyclodecyl vinyl ether with n-butyl vinyl ether, Journal of Polymer Science, Part a: Polymer Chemistry, 45(18), 4389-4393 (2007) Sugihara, Shinji. , Hashimoto, Kiyotaka. , Matsumoto, Yuko. , Kanaoka, Shokyoku. , Aoshima, Sadahito. , Thermosensitive polyalcohols: Synthesis via living cationic polymerization of vinyl ethers with a silyloxy group, Journal of Polymer Science, Part A: Chemistry, 41(21), 3300-3312, (2003)

[0013] The technology disclosed in Patent Document 1 is a technology in which the start of seed germination depends on the decomposition action of a coating layer (biodegradable resin) by microorganisms. If soil conditions are not constant in different areas of the sowing field, and if the decomposition activity is uneven due to factors such as the density of microorganisms or temperature conditions, differences in the timing of germination may occur in different areas of the field, which could lead to an increase in subsequent differences in growth.

[0014] Examples of synthetic or natural plastic materials used as outer coatings for seeds, as described in Patent Document 2, include polystyrene, beeswax, acrylic resin, polyvinyl chloride, cellulose nitrate, polyethylene, and shellac. Winter jackets are described as preferably having synthetic plastic materials that decompose under freezing conditions as the main component, along with plasticizers and solvents, but the mechanism of decomposition under freezing conditions is not clearly explained.

[0015] The polymer material used in the manufacture of the coating described in Patent Document 3 is described as being relatively impermeable to materials such as water at low temperatures (below the optimal growth or germination temperature) and relatively permeable at high temperatures (above the optimal growth or germination temperature), exhibiting water permeability under relatively high temperature conditions. For this reason, even if seeds are sown in the autumn and intended to overwinter, they germinate before winter, making it difficult to control the germination time.

[0016] This invention has been made in view of the above problems, and aims to provide a multi-layer polymer coated seed that can germinate even when sown in the autumn, which is the off-season for farming, under the rising temperature conditions after overwintering, and a cultivation method using said seed.

[0017] In other words, the above problems are solved by the following configuration of the present invention. (1) The multi-layer polymer coated body of the present invention is a coated body in which at least two or more layers of polymer are coated on a body to be coated, and the outer coating layer having at least one inner coating layer on the inside is characterized in that it is formed of a polymer that undergoes a phase transition at a temperature lower than the softening temperature of the polymer forming the inner coating layer and exhibits lower critical temperature (LCST) characteristics (hereinafter referred to as "the first multi-layer polymer coated body of the present invention").

[0018] In the first multi-layer polymer coating of the present invention, the outer coating layer is formed of a polymer that undergoes a phase transition at a temperature lower than the softening temperature of the polymer forming the inner coating layer, exhibiting lower critical temperature (LCST) characteristics. Therefore, the outer coating layer peels off only when exposed to low temperatures in winter, thus protecting the coated object from the relatively warm temperatures of autumn. For example, if seeds are coated, germination in autumn can be prevented, allowing sowing to take place during the off-season in autumn, reducing the labor of farmers and improving productivity.

[0019] (2) Furthermore, in the first multi-layer polymer coating of the present invention, the polymer exhibiting the lower critical temperature (LCST) characteristic is characterized by having hydrophilic groups (hereinafter referred to as the "second multi-layer polymer coating of the present invention").

[0020] (3) Furthermore, in the first multi-layer polymer coating of the present invention, the polymer exhibiting lower critical temperature (LCST) characteristics is formed from a polyvinyl ether having a hydroxyl group (hereinafter referred to as the "third multi-layer polymer coating of the present invention").

[0021] In the second and third multi-layer polymer coatings of the present invention, by using polymers having hydrophilic groups, more specifically hydroxyl groups, in their side chains, it is possible to easily exhibit lower critical temperature (LCST) characteristics.

[0022] (4) Furthermore, in the second multilayer polymer coated seed of the present invention, the polyvinyl ether is a polyhydroxypropylpropenyl ether represented by the following formula (1) (hereinafter referred to as the "fifth multilayer polymer coated body of the present invention"). In equation (1), n ​​represents an integer greater than or equal to 2.

[0023] Fourth, with respect to the multi-layer polymer coating of the present invention, a synthesis method has been established, making it possible to reliably obtain a polymer having lower critical temperature (LCST) characteristics.

[0024] (5) In addition, in the first multi-layer polymer coated body of the present invention, the inner coating layer is characterized in that it is a polymer with a softening temperature of 1°C or higher, a viscosity of 30 to 300 Pa·s at 25°C, and a number average molecular weight of 800 to 15000 (hereinafter referred to as "the fifth multi-layer polymer coated body of the present invention").

[0025] The fifth aspect of the present invention, a multi-layer polymer coating, is formed from a polymer with a softening temperature of 1°C or higher, a viscosity of 30 to 300 Pa·s at 25°C, and a number-average molecular weight of 800 to 15000. For example, when seeds are coated, the inner coating layer peels off from the seeds during periods of rising temperatures, allowing them to germinate.

[0026] (6) Furthermore, in the fifth multi-layer polymer coating body of the present invention, the inner coating layer is characterized in that it is a vinyl ether copolymer (hereinafter referred to as the sixth multi-layer polymer coating body of the present invention).

[0027] The sixth aspect of the present invention, a coating body made of multiple polymer layers, allows for relatively easy control of the softening temperature.

[0028] (7) In addition, in the sixth multilayer polymer coating of the present invention, the vinyl ether copolymer is characterized in that it consists of repeating units represented by the following formula (2) (hereinafter referred to as the seventh multilayer polymer coating of the present invention). In formula (2), R1 represents an alkyl group having 3 to 10 carbon atoms, R2 represents a cyclic hydrocarbon group with an alicyclic group having 10 to 15 carbon atoms as its basic skeleton, p represents an integer from 3 to 95, q represents an integer from 2 to 38, and p and q satisfy the ratio p:q = 5.8:4.2 to 7.2:2.8, and m represents the number of alkylene groups, which is an integer of 0 or 1.

[0029] The seventh aspect of the present invention, the multi-layer polymer coating, can be synthesized relatively easily in large quantities.

[0030] (8) In addition, in the first or second multilayer polymer coated body of the present invention, the coated body is characterized in that it is a plant seed (hereinafter referred to as the eighth multilayer polymer coated body of the present invention).

[0031] (9) Furthermore, in the method for cultivating plants of the present invention, seeds coated with the eighth multilayer polymer are sown in the autumn, overwintered, and then germinated in the spring (hereinafter referred to as "the eighth multilayer polymer coated body of the present invention").

[0032] According to the eighth multi-layer polymer coating body and the plant cultivation method of the present invention, sowing can be performed in the autumn, which is the off-season for farming, thus reducing the burden on farmers and contributing to increased productivity.

[0033] The multi-layer polymer coating of the present invention, when applied to seeds, has the advantage of enabling germination in the spring after overwintering, even when sown in the autumn. Furthermore, the cultivation method of the present invention has the advantage of enabling work during the off-season, thereby reducing the burden on farmers.

[0034] Figure 3B is a contrast-adjusted version of Figure 3A. Schematic diagram showing theoretical Tg values ​​according to Fox's formula for copolymers with varying composition ratios of n-butyl vinyl ether (NBVE) and tricyclodecane vinyl ether (TCDVE). Schematic diagram showing equipment for measuring softening temperature. Graph showing temperature dependence of transmittance at 500 nm of a 0.25 wt% poly HPPE aqueous solution: heating rate and cooling rate (0.1°C / min). Graph showing temperature dependence of transmittance at 500 nm of a 0.25 wt% poly HPPE aqueous solution: heating rate and cooling rate (0.1°C / min). Figure 3B is a contrast-adjusted version of Figure 3A. Schematic diagram showing the synthesis conditions and procedure for the copolymer. Schematic diagram showing the synthesis conditions and procedure for the copolymer. Figure 4B is a contrast-adjusted version of Figure 4A. Image showing 30 seeds of the invention sample and 30 seeds of a comparison sample sown in a seedling tray with 7 x 13 pods used for germination testing. Image showing 30 seeds of the invention sample and 30 seeds of the comparison sample sown in a seedling tray with 7 x 13 pots used for the germination test. Figure 5B is a drawing with adjusted contrast from Figure 5A. Schematic diagram showing the schedule of the germination test. Image showing the state of the invention sample and comparison sample on day 14 of the germination test. Image showing the state of the invention sample and comparison sample on day 14 of the germination test. Figure 7B is a drawing with adjusted contrast from Figure 7A. Image showing the state of the invention sample from day 20 onwards of the germination test. Image showing the state of the invention sample from day 20 onwards of the germination test. Figure 8B is a drawing with adjusted contrast from Figure 8A.

[0035] Hereinafter, one embodiment of the present invention (hereinafter referred to as "this embodiment") will be described.

[0036] (Outer coating material) The outer coating material consists of a polymer that has the function of covering and protecting the inner coating material until the ambient temperature drops under predetermined temperature conditions, in order to prevent the inner coating material from detaching before winter.

[0037] As a polymer having the above characteristics, we can mention a polymer that undergoes a phase transition at a temperature lower than the softening temperature of the polymer forming the inner coating layer and exhibits lower critical temperature (LCST) characteristics.

[0038] For the polymer exhibiting LCST characteristics, the temperature Tps representing the solubility in water is lower than the softening temperature of the polymer forming the inner coating layer, preferably equal to or lower than the softening temperature - 1°C. For example, when the softening temperature of the polymer forming the inner coating layer is set higher than 7°C, for the polymer exhibiting LCST characteristics that undergoes phase transition at low temperature, the temperature Tps representing the solubility in water is 7°C or lower, preferably 6°C or lower, more preferably 5°C or lower. In cold regions such as Hokkaido, it may be adjusted to 4°C or lower. The lower limit value is the temperature at which water undergoes phase transition and solidifies, usually 0°C, but it may be lower than this within a range that does not cause practical problems, such as - 5°C etc.

[0039] For the phase transition temperature of the polymer, for example, an aqueous solution of an LCST polymer can be prepared, and the temperature at which the transmittance of light (500 nm) passing through the sample cell rapidly decreases when using a visible ultraviolet near-infrared spectrophotometer can be taken as the phase separation temperature (Tps) LCST temperature.

[0040] As the polymer exhibiting LCST characteristics, a polymer having a hydrophilic group is preferred, and for example, polyvinyl ether having a hydroxy group can be cited. Such a polymer preferably has a molecular weight Mn of about 8000 - 16000, a glass transition temperature Tg of 60 - 80°C, and a thermal decomposition temperature Td of 250 - 350°C.

[0041] More specifically, the polyvinyl ether is preferably polyhydroxypropyl propenyl ether represented by the following formula (1). In formula (1), n represents an integer of 2 or more.

[0042] Since the compound represented by the above formula (1) is not commercially available, it is usually synthesized and used. Generally, when cationic polymerization of vinyl ether having a hydroxy group is carried out, the hydroxy group rich in electrons nucleophilically attacks the carbocation, resulting in the formation of a polymer having an acetal bond or a cyclic oligomer. Therefore, the synthesis of poly(vinyl ether) having a hydroxy group on one side chain is extremely difficult.

[0043] However, a poly(vinyl ether) having a hydroxy group in the side chain can be synthesized by polymerizing a vinyl ether in which the hydroxy group is protected with a protecting group and then deprotecting the resulting polymer.

[0044] In recent years, living cationic polymerization of vinyl ethers having a protecting group has been achieved using a t-butyldimethylsiloxy group (BMSi) as the protecting group, and synthesis of poly(vinyl ether) having a hydroxy group in the side chain with a narrow molecular weight distribution by deprotecting the resulting polymer has been reported (Non-Patent Document 2).

[0045] The above polyhydroxypropyl propenyl ether can also be synthesized by this method.

[0046] (Coating method for the outer coating material) Since poly(HPPE) is solid at room temperature, it is difficult to form a coating layer as it is. As a method for forming the coating layer, a gel method in which it is dissolved in a solvent and applied, and the solvent is distilled off to form a layer is preferable.

[0047] As another coating method, a method of dissolving the polymer by heating and applying it is conceivable. However, when attempting a two-layer coating using the heating method, the first-layer copolymer, which is the inner layer, softens due to heat and it becomes difficult to form a layer. Therefore, for the two-layer coating seeds of the present invention, a method of applying them to the seeds by the gel method is preferable.

[0048] As the solvent used in the gel method, various alcohols such as methanol and ethanol are preferable in view of ease of handling, price, ease of availability, etc. Also, lower alcohols with low boiling points are preferable.

[0049] (Inner coating material) The inner coating material consists of a polymer that inhibits water absorption by the coated seeds until a predetermined temperature is reached after the outer coating material has detached. In other words, the coating material is a material that does not dissolve or disintegrate due to moisture, a hydrophobic material (also called a hydrophobic polymer), and maintains a solidified state until a predetermined temperature is reached, thereby preventing water from passing through the coating layer and penetrating to the seeds. In this specification, "hydrophobic polymer" means a polymer with low affinity for water.

[0050] (Softening Temperature) Water absorption, which triggers germination, occurs when the coating layer, consisting of an inner coating material covering the seed, softens at a predetermined temperature, causing it to peel away from the seed. The temperature at which the coating layer softens, that is, the temperature at which the solidified coating material becomes fluid and turns into a liquid state, causing the peeling of the coating layer covering the seed to begin and progress, is defined as the "softening temperature."

[0051] The softening temperature is the temperature at which the coating layer detaches from the seed, and can be used as an indicator of the temperature conditions for initiating germination. However, in this application, it is used as a separate concept from the optimal temperature for seed germination.

[0052] The appropriate softening temperature for the inner coating layer is a temperature that prevents the coated seeds from germinating during the coldest period and allows them to germinate at a temperature suitable for germination in early spring, and must be at least 0.5°C. Furthermore, although it depends on the cold tolerance of the seedlings that germinate, a temperature of 3°C or higher is preferable, 4°C or higher is more preferable, and 5°C or higher is even preferable, in order to suppress stagnation of growth and / or a decrease in survival rate due to exposure to cold air after germination.

[0053] The softening temperature can generally be measured by the method described in JIS K7206 (Plastics - Thermoplastics - Method for determining the Vicat softening temperature (VST)) (ISO 306:2013), but in the present invention, for convenience, the temperature measured by the following method is treated as the softening temperature.

[0054] First, fill an aluminum pan (for example, a crimp cell for DSC measurement) (Φ5.8 mm x height 1.5 mm) with a coating material (polymer). If necessary, heat the polymer to a molten state and fill the aluminum pan with it. At this time, fill the aluminum pan completely with polymer up to the top edge.

[0055] Next, the aluminum pan is placed on a temperature control unit set to -20°C, and a roughly Y-shaped stainless steel rod is inserted into the center of the polymer inside the aluminum pan, so as to be in contact with the bottom of the pan, leaving the stainless steel rod upright. The roughly Y-shaped stainless steel rod used here has a mass of 0.21 g, an overall length of 2.1 cm, a handle length of 0.9 cm, a bottom surface of the handle of 1.0 mm x 0.7 mm (roughly rectangular), a length from the fork of the branched section to the top surface of the branched section of 1.2 cm, a thickness of the branched section of 0.7 mm, and a distance of 0.85 cm between the top surfaces of the branched sections. The rod is inserted into the polymer so that the branched section faces upwards.

[0056] Next, the temperature is gradually increased from -2.0°C, and the surface temperature of the polymer in the aluminum pan at the moment when the stainless steel rod is completely tilted (when the entire stainless steel rod is in contact with the polymer) is measured using an infrared radiation thermometer, and this surface temperature is defined as the softening temperature.

[0057] (Viscosity, number-average molecular weight) Setting the softening temperature is the main factor in controlling the detachment of the inner coating layer from the seed, but the viscosity and number-average molecular weight of the coating material can also be considered as secondary factors. For example, in order for the coating layer to detach from the seed, it is desirable that the coating material has appropriate viscosity when softened. That is, even if the coating material (polymer) reaches the glass transition temperature (Tg) described later, if its viscosity is high, its fluidity will be low, which can hinder the detachment of the coating material from the seed.

[0058] The viscosity at 25°C can be used as an indicator of the viscosity at which the softened inner coating layer can be peeled off the seed. Specifically, the viscosity of the coating material (polymer) should be 30 to 300 Pa·s (value measured with a vibrating viscometer at 25°C), more preferably 35 to 250 Pa·s, and even more preferably 38 to 200 Pa·s.

[0059] Generally, the viscosity of a polymer increases as its molecular weight increases. Therefore, for a coating material to have an appropriate viscosity, the number-average molecular weight (Mn) of the polymer used as the coating material is preferably, for example, 800 to 15000, more preferably 1000 to 14000, and even more preferably 1200 to 13000.

[0060] Furthermore, if the number-average molecular weight (Mn) is 18,000 or higher, the viscosity will be high, which may make it difficult for the coating layer to detach from the seeds under germination-compatible temperature conditions. In other words, as a general trend, lowering the molecular weight to reduce viscosity makes it possible to control the temperature difference between Tg and the softening temperature to be small, while increasing the molecular weight to increase viscosity makes it possible to control the temperature difference between Tg and the softening temperature to be large.

[0061] Thus, one method for adjusting the viscosity of the inner coating material is to control the molecular weight of the polymer. For example, molecular weight control can be achieved by using living cationic polymerization, which allows for molecular weight control during polymer preparation. In other words, the polymer of the coating material according to the present invention can be a living cationic polymer. Of course, when preparing the polymer, commonly used polymerization methods such as anionic polymerization, living anionic polymerization, cationic polymerization, free radical polymerization, and living radical polymerization can be used.

[0062] The inner coating material (polymer) preferably has a molecular weight distribution (hereinafter sometimes referred to as molecular weight dispersion) (Mw / Mn) of 2.0 or less, more preferably 1.5 or less, and even more preferably 1.2 or less. The above number-average molecular weight (Mn) and molecular weight distribution (Mw / Mn) can be the values ​​obtained in terms of polystyrene, a standard sample, by gel permeation chromatography (GPC).

[0063] If the molecular weight distribution (Mw / Mn) is 2.0 or less, the molecular weights are concentrated within a certain range, and the upper and lower limits of viscosity are also within a certain range. If the molecular weight distribution (Mw / Mn) exceeds the aforementioned range, polymers with higher molecular weights may increase the overall viscosity.

[0064] (Glass Transition Temperature) The glass transition temperature (Tg) is the freezing temperature of the micro-Brownian motion of the polymer backbone, that is, the temperature at which the coating material begins to change from a glassy state to a viscous state, and is a physical property value that serves as an indicator of how easily the polymer softens. It is assumed that the inner coating material goes through a state of release from a solidified state (frozen state) (viscous state) before reaching the "softened" state (where the peeling of the coating layer progresses). In other words, for the solidified coating material (polymer) to soften and peel off from the seed, it is desirable that at least the polymer, which is the inner coating material, has reached its glass transition temperature and transitioned from a frozen state to a viscous state.

[0065] From this perspective, when considering the glass transition temperature (Tg) of the polymer used as the inner coating material, the lower limit should be at least -35°C, preferably -10°C or higher, more preferably -3°C or higher, and even more preferably 0°C or higher. Furthermore, the upper limit of Tg should be 10°C or lower, preferably 7°C or lower, and more preferably 5°C or lower, from the viewpoint of allowing peeling to proceed at a temperature suitable for germination in early spring when temperatures rise.

[0066] Furthermore, considering the risk of frost damage, and taking into account that young crop seedlings have low resistance to frost damage even during the germination period, the upper limit of Tg can be determined by considering the temperature of the environment in which sowing takes place. For example, if the goal is to germinate when the soil temperature reaches 10-15°C, such as in early May in the Tokachi region of Hokkaido, the upper limit of Tg can be set to 13°C.

[0067] The glass transition temperature (θ) of a copolymer composed of two or more monomers can be theoretically determined according to a formula. For example, in the case of a copolymer composed of two monomers, it can be theoretically determined using Fox's equation below, based on the Tg (θ1, θ2) of the homopolymers (conjugates) of each copolymer monomer A and B and the composition ratio (C1, C2) of each copolymer monomer: 1 / θ = c1 / θ1 + c2 / θ2

[0068] In other words, the glass transition temperature of a copolymer of a vinyl ether having an alkyl group in its backbone (monomer A) and a vinyl ether having a cyclic hydrocarbon (monomer B), as described later, can be calculated from the Tg(A) of the homopolymer of monomer A, the Tg(B) of the homopolymer of monomer B, and the composition ratio of monomer A to monomer B.

[0069] For example, as shown in Figure 1, it has been reported that the Tg of a copolymer obtained by copolymerizing poly(n-butyl vinyl ether) (poly(NBVE): Tg = -56°C) and poly(tricyclodecane vinyl ether) (poly(TCDVE): Tg = 105°C) can be controlled by the TCDVE fraction (or NBVE fraction) according to the above Fox formula (Non-Patent Literature 1).

[0070] In Figure 1, the black circles (●) indicate the theoretical value of Tg calculated using mole fraction, and the white circles (〇) indicate the theoretical value of Tg calculated using mass fraction.

[0071] According to the formula, for NBVE:TCDVE = 5.8:4.2 to 7.2:2.8 (molar ratio), the theoretical Tg of the copolymer is in the range of -10.2°C to 12.5°C. Furthermore, for a copolymer of poly(n-decyl vinyl ether) (NDVE): Tg = -62°C and poly(tricyclodecane vinyl ether) (TCDVE): Tg = 105°C, the theoretical Tg is -33.0°C to -15.1°C for NDVE:TCDVE = 5.8:4.2 to 7.2:2.8.

[0072] On the other hand, while Tg is one indicator of the transition to a state where the coating layer can be detached from the seed, it is not a temperature that indicates the fluidity of the polymer. As an indicator of the coating layer detaching from the seed at a predetermined temperature, the softening temperature mentioned above is more direct. Furthermore, Tg and the aforementioned softening temperature do not necessarily correlate. Differential scanning calorimetry (DSC) or TMA can be used to measure Tg.

[0073] (Type of polymer) The polymer used as the inner coating material is a so-called hydrophobic polymer. When the seed is covered and solidified (polymer layer), it prevents water from penetrating into the polymer layer and allows the seed to absorb water. When the polymer layer softens at a predetermined temperature... It is not particularly limited as long as it possesses the property of peeling off the coated seeds by having a certain viscosity (fluidity).

[0074] As mentioned above, "hydrophobic polymers" refer to polymers with low affinity for water, and can include polymers having a hydrophobic structure. Examples of such hydrophobic structures include nonpolar groups and nonpolar skeletons, and in particular, hydrocarbon groups, cyclic hydrocarbon groups, and hydrocarbon main chains. Copolymers that use monomers having a hydrophobic structure (hydrophobic monomers) as constituent units can also be included in the category of hydrophobic polymers.

[0075] (Hydrophobic polymer) As a hydrophobic polymer having the above properties, a vinyl ether copolymer consisting of two types of repeating units shown in formula (2) below can be used.

[0076] In the formula, p is 2 to 9.5, q is 2 to 3.8, and m is the number of alkylene groups, representing an integer from 0 to 1 (i.e., a single bond or a methylene group). Furthermore, p and q satisfy the condition p:q = 5.8:4.2 to 7.2:2.8, and preferably can be in the range of p:q = 6:4 to 7:3.

[0077] In formula (2), R1 is an alkyl group having 3 to 10 carbon atoms, and specifically can represent linear alkyl groups such as m-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, and n-decyl group, as well as branched alkyl groups such as isopropyl group, isobutyl group, t-butyl group, isopentyl group, neopentyl group, isohexyl group, isoheptyl group, isooctyl group, 2-ethylhexyl group, isononyl group, and isodecyl group.

[0078] In formula (2), R2 is not particularly limited as long as it is a cyclic hydrocarbon group with an alicyclic group having 10 to 15 carbon atoms as its basic skeleton, and is represented by the following tricyclo[5.2.1.0. ２，６ A decyl group, a tricyclodecenyl group represented by formula (4) or formula (5), or a pentacyclopentadecyl group represented by formula (6) or formula (7) can be preferably used. In each formula, * represents a bond.

[0079] The vinyl ether copolymer described above can be produced by polymerizing a vinyl ether having R1 (alkyl group) (monomer A) and a vinyl ether having R2 (alicyclic group) (monomer B) in a solvent.

[0080] One method of polymerization is living cationic polymerization, in which polymerization is carried out in an aromatic hydrocarbon solvent such as toluene or xylene, or a halogenated hydrocarbon such as methylene chloride, to dissolve each monomer and polymer. Living cationic polymerization allows for easy control of the degree of polymerization and is useful as a method for obtaining polymers with a narrow molecular weight distribution. This makes it possible to control the molecular weight of the copolymer and easily adjust the viscosity of the coating material. In addition, commonly used polymerization methods such as anionic polymerization, living anionic polymerization, cationic polymerization, free radical polymerization, and living radical polymerization can be used.

[0081] Monomer A is not particularly limited as long as it is a vinyl ether having an alkyl group with 3 to 10 carbon atoms. Examples include vinyl ethers having linear alkyl groups such as n-propyl vinyl ether, n-butyl vinyl ether, n-pentyl vinyl ether, n-hexyl vinyl ether, n-heptyl vinyl ether, n-octyl vinyl ether, n-nonyl vinyl ether, and n-decyl vinyl ether, as well as vinyl ethers having branched alkyl groups such as isopropyl vinyl ether, isobutyl vinyl ether, t-butyl vinyl ether, isopentyl vinyl ether, neopentyl vinyl ether, isohexyl vinyl ether, isoheptyl vinyl ether, isooctyl vinyl ether, 2-ethylhexyl vinyl ether, isononyl vinyl ether, and isodecyl vinyl ether.

[0082] Monomer B is not particularly limited as long as it is a vinyl ether having a cyclic hydrocarbon group with an alicyclic group as its basic skeleton, for example, 8-tricyclo[5.2.1.0. ２，６ ] Decane vinyl ether (formula (3-1)), 8-tricyclo[5.2.1.0. ２，６Examples include decane monomethyl vinyl ether (formula (3-2)), 8-tricyclodecene vinyl ether (formula (4-1), formula (5-1)), 8-tricyclodecene monomethyl vinyl ether, 8-pentacyclopentadecane vinyl ether (formula (6-1), formula (7-1)), 8-pentacyclopentadecane monomethyl vinyl ether (formula (6-2), formula (7-2)), 8-pentacyclopentadecane vinyl ether, and 8-pentacyclopentadecane vinyl ether tricyclodecene monomethyl vinyl ether. These vinyl ethers can be synthesized according to the method described in Japanese Patent No. 4136886.

[0083] (Coated Seeds) The seeds used in this invention are not particularly limited and include those derived from angiosperms and gymnosperms. Examples include seeds of vegetables, flowers, pasture grasses, grains and industrial crops, and trees. Furthermore, the seeds in this invention include plant spores. For example, spores from vascular plants (so-called ferns), bryophytes, and algae that can be coated are included. More specifically, the following are examples.

[0084] Examples of vegetable seeds include those of the Cucurbitaceae family, such as cucumbers, melons, and pumpkins; those of the Solanaceae family, such as eggplants and tomatoes; those of the Fabaceae family, such as peas and green beans; those of the Liliaceae family, such as onions and leeks; those of the Brassica genus, such as turnips, Chinese cabbage, cabbage, broccoli, and radishes; those of the Apiaceae family, such as carrots and celery; those of the Asteraceae family, such as burdock, lettuce, and garland chrysanthemum; those of the Lamiaceae family, such as perilla; and those of the Amaranthaceae family, such as sugar beets and spinach. Among these, vegetables suitable for cultivation in cold regions, such as onions and sugar beets, are preferred.

[0085] Examples of flowering plant seeds include those of the Brassicaceae family such as ornamental cabbage, stock, and alyssum; those of the Campanulaceae family such as lobelia; those of the Asteraceae family such as aster, zinnia, and sunflower; those of the Ranunculaceae family such as delphinium; those of the Scrophulariaceae family such as snapdragon; those of the Primulaceae family such as primrose; those of the Begoniaceae family such as begonia; those of the Lamiaceae family such as salvia; those of the Violaceae family such as pansy and viola; those of the Solanaceae family such as petunia; and those of the Gentianaceae family such as eustoma.

[0086] Examples of forage grass seeds include timothy grass, Italian ryegrass, Bermuda grass, oat hay, Sudan grass, crengrass, fescue, and orchardgrass.

[0087] Examples of cereal seeds include rice, barley, wheat, soybeans, foxtail millet, buckwheat, barnyard millet, and proso millet.

[0088] Examples of seeds used in industrial crops include seeds of the Amaranthaceae family, such as sugar beets; seeds of the Solanaceae family, such as tobacco; seeds of the Brassicaceae family, such as rapeseed; and seeds of the Poaceae family, such as rushes.

[0089] Examples of tree seeds include those of Japanese laurel, sawtooth oak, Japanese cedar, Japanese cypress, Japanese oak, beech, pine, and azaleas.

[0090] The method for producing coated seeds according to the present invention is not particularly limited, and seeds can be coated using methods such as dipping, spraying, or coating.

[0091] Furthermore, for mass production, known devices such as granulators can be used. Specifically, the seeds can be made into a fluid state using a fluidizing device or a jetting device, or the seeds can be made into a rolling state using a rolling device such as a rotating pan or rotating drum, and the molten liquid or solution of the coating material according to the present invention can be added to the surface of the seeds by dropping, spraying, or other methods.

[0092] After the coating process, drying is performed to remove the solvent as needed. Heating may be used during this process, provided it does not adversely affect the seeds or the coating resin.

[0093] Since the seeds coated with the multi-layer polymer of the present invention have at least two layers, an inner coating layer and an outer coating layer, the coating treatment of the seeds must be performed at least twice. Alternatively, the same type of coating layer may be formed multiple times.

[0094] The thickness of each coating layer is not particularly limited, as long as it can perform the required function, has sufficient strength to prevent peeling from the seed under external forces such as sowing, and can peel off the seed when the function is being performed. For example, it can be adjusted within the range of 10 μm to 1 mm, but since it will be affected by the size and shape of the seed, it is best to set the thickness to the optimal level for the purpose of coating.

[0095] The method for sowing coated seeds of the present invention is not particularly limited, as long as sowing is performed at a temperature below the softening temperature of the outer coating material, preferably below Tg, from the viewpoint of obtaining the effects of the present invention, that is, from the viewpoint of preventing the coating material from peeling off the seeds during sowing.

[0096] Specifically, methods include sowing seeds only on the soil surface, sowing seeds on the soil surface and then covering them with soil, sowing seeds on the soil surface and then mixing them with soil, and sowing seeds in seedling pots such as paper tubes filled with soil and then covering them with soil. Furthermore, the type of soil is not particularly limited as long as it is the type that the above-mentioned seeds are generally suited to.

[0097] The present invention will be further illustrated in detail below with reference to examples. However, the present invention is not limited in any way by these examples and comparative examples.

[0098] [Manufacturing Example 1] Preparation of the outer polymer In this example, a polymer that exhibits LCST properties at low temperatures was used as the outer polymer. Below, a vinyl ether compound having a hydroxyl group is described as a typical polymer exhibiting LCST properties.

[0099] The following materials were prepared and used in the synthesis described below: Allyl bromide (Aldrich), sodium hydroxide (Wako Pure Chemical Industries), tetra-n-butylammonium bromide (TBAB; Wako Pure Chemical Industries), sodium sulfate (Wako Pure Chemical Industries, special grade), methanol (Wako Pure Chemical Industries, super-dehydrated), dichlorotris(triphenylphosphine)ruthenium(II) (RuCl2(PPh3)3; Wako Pure Chemical Industries), sodium carbonate (Kishida Chemical Industries, special grade), imidazole (Wako Pure Chemical Industries), dimethylformamide (DMF; Wako Pure Chemical Industries, super-dehydrated), t-butyldiphenylchloro Rosilane (Aldrich), ethyl acetate (Kanto Chemical, Grade 1), hexane (Kanto Chemical, Grade 1), calcium hydride (Aldrich), deuterated chloroform (CDCl3, Merck), deuterated chloroform (CDCl3; containing TMS, Merck), triethylamine (Wako Pure Chemical Industries, Special Grade), methanol (Kanto Chemical, Grade 1), tetrahydrofuran (THF; Kanto Chemical, Grade 1), isopropanol (Wako Pure Chemical Industries), tetrabutylammonium fluoride (TBAF; 1.0 M THF solution, Wako Pure Chemical Industries), dimethylformamide (DMF; Wako Pure Chemical Industries), deuterated dimethyl sulfoxide (DMSO-d6; containing TMS, Wako Pure Chemical Industries), toluene (Wako Pure Chemical Industries, Super-dehydrated), 1,3-propenediol (Wako Pure Chemical Industries, Special Grade).

[0100] Ethyl aluminum sesquichloride (Et 1.5 AlCl 1.5 Commercially available nitriles (SnCl4; manufactured by Aldrich, 1.0 M dichloromethane solution) were divided into ampoules and stored in a freezer.

[0101] Isobutyl ethyl acetate (IBEA) was synthesized according to the literature and then repackaged into ampoules. Ethyl acetate (AcOEt; manufactured by Wako Pure Chemical Industries, super-dehydrated) was similarly repackaged from commercially available ethyl acetate into ampoules. Toluene (manufactured by Wako Pure Chemical Industries, super-dehydrated), dichloromethane (manufactured by Wako Pure Chemical Industries, super-dehydrated), and diethyl ether (manufactured by Wako Pure Chemical Industries, super-dehydrated) were purified using an organic solvent purification apparatus (GlassContour; manufactured by NIKKO HANSEN & CO., LTD) before use.

[0102] <Synthesis of Monomers> [Synthesis of Hydroxypropyl Allyl Ether] Hydroxypropyl allyl ether was synthesized by the reaction of 1,3-propenediol with allyl bromide.

[0103] A 200 ml two-necked flask containing sodium hydroxide (4.4 g, 0.11 mol) and TBAB (0.7 g, 2.2 mmol) was fitted with a reflux condenser and purged with nitrogen. Toluene (30 ml), 1,3-propenediol (7.97 ml, 0.11 mol), and allyl bromide (9.585 ml, 0.11 mol) were added, and the mixture was reacted at 70°C for 10 hours. After the reaction, the solvent was removed by distillation to obtain a colorless, transparent liquid.

[0104] [Synthesis of Hydroxypropylpropenyl Ether] Hydroxypropylpropenyl ether was synthesized by the reaction of hydroxypropyl allyl ether with methanol using a ruthenium catalyst.

[0105] The hydroxypropyl allyl ether (9.67 g, 0.083 mol) obtained above, methanol (10.1 ml, 0.249 mol), sodium carbonate (0.44 g, 4.15 mmol), and RuCl2(PPh3)3 (0.8 g, 0.83 mmol) were placed in a pressure vessel, and the mixture was purged with nitrogen and reacted at 120°C for 3 hours. The reaction mixture was filtered by suction to remove the sodium carbonate and RuCl2(PPh3)3. Subsequently, vacuum distillation was performed under calcium hydride to obtain a colorless, transparent liquid. <Synthesis of poly (HPPE)>

[0106] [Synthesis of t-butyldiphenylsiloxypropylpropenyl ether (TBDPSiPPE)] TBDPSiPPE was synthesized by the reaction of the hydroxypropylpropenyl ether obtained above with t-butyldiphenylchlorosilane. Imidazole (8.5 g) was placed in a 300 ml three-necked flask equipped with a reflux condenser and dropping funnel, and nitrogen was purged. After nitrogen purging, the hydroxypropylpropenyl ether obtained above (6.14 g, 0.053 mol) and DMF (12 ml) were added, and t-butyldiphenylchlorosilane obtained above (13.6 ml, 0.053 mol) was dissolved in DMF (12 ml) and added dropwise, and the reaction was allowed to proceed at room temperature for 6 hours. After the reaction, diethyl ether was added to the reaction mixture and washed with water.

[0107] Subsequently, the solution was dehydrated with sodium sulfate, and the solvent was removed by distillation. TBDPSiPPE was isolated by column chromatography using hexane and ethyl acetate (20 / 1, v / v), and a colorless, transparent liquid was obtained by vacuum distillation under calcium hydride.

[0108] Polymerization procedure: A pear-shaped flask and test tube fitted with a three-way stopcock were baked with a heat gun while nitrogen was flowed through them. Under a nitrogen atmosphere, the monomer solution, initiator solution, and activator solution obtained above were adjusted to desired concentrations in the baked pear-shaped flask. The monomer and initiator solution (IBEA / Et) were then added to a test tube fitted with a three-way stopcock. １．５ AlCl １．５ After adding the SnCl4 initiator system and cooling to the polymerization temperature, the initiator solution and activator solution were added in that order, and polymerization was carried out with 5 ml of the polymerization solution. Polymerization was stopped by adding 2 ml of methanol with a small amount of triethylamine added.

[0109] [Desilylation] The synthesized polymer was desilylated using TBAF. The purified polymer and TBAF (1.0 M THF solution) were placed in a round-bottom flask and reacted at room temperature for 6 hours. The amount of TBAF used in the reaction was 1.2 equivalent moles, which is the number of moles of silyl protecting groups expected to be present in the side chains of the polymer.

[0110] [Purification] The obtained poly (TBDPSiPPE) was dissolved in a small amount of THF and reprecipitationd in a large amount of isopropanol. Polyhydroxypropylpropenyl ether [poly (HPPE)] was purified by dialysis in methanol for one week (Fisherbrand® Regenerated Cellulose Dialysis Tubing: MWCO 3500).

[0111] (Test Example 1) Confirmation of Phase Transition State As shown below, the obtained poly(HPPE) exhibited LCST-type phase separation behavior in water. At low temperatures around 0°C, the poly(HPPE) was a clear aqueous solution, but at room temperature, the solution was clearly cloudy. Therefore, the temperature was increased from 0°C (0.1°C / min), and the transmittance of the solution at each temperature was measured. This phase separation behavior was observed using the transmittance at 500 nm.

[0112] As shown in Figures 3A and 3B, the transmittance decreased sharply as the solution temperature increased, indicating that phase separation is very sensitive (Tps = 6°C). Furthermore, the solution that underwent phase separation returned to a homogeneous solution upon cooling, and this reversible phase transition occurred repeatedly. However, the behavior from phase separation to becoming a homogeneous solution differed significantly from the behavior when the solution underwent phase separation. The transmittance gradually increased from a temperature higher than the temperature at which the solution underwent phase separation, and the solution became homogeneous at a temperature lower than Tps.

[0113] (Test Example 2) Confirmation of water absorption rate by temperature Obtained poly (HPPE): Two solid samples of the same volume, mass, and shape were prepared and immersed in petri dishes filled with water at 20°C and 4°C, respectively. They were left for 24 hours while maintaining the temperature, and then removed and the water absorption rate was measured from the increase in mass.

[0114] As a result, the water absorption rate of the sample immersed in 20°C water was 7%, while the water absorption rate of the sample immersed in 4°C water was partially dissolved, making it impossible to measure. This indicated that it was a water-soluble polymer with a water absorption rate of less than Tps.

[0115] [Manufacturing Example 2] Preparation of Inner Polymers In order to prepare polymers with different viscosities, four copolymers with different molecular weights—target molecular weights of 1000, 5000, 10000, and 10000 or more—were prepared using the following procedure.

[0116] Furthermore, to ensure that the Tg of the copolymer is 5 to 10°C, the copolymer composition was determined to be NBVE (n-butyl vinyl ether):TCDVE (tricyclodecane vinyl ether) = 6:4 based on the relationship between TCDVE fraction and Tg shown in Figure 1, and the copolymer was prepared according to the following procedure.

[0117] <Synthesis of Copolymers> n-butyl vinyl ether (NBVE, liquid monomer, Fujifilm Wako Pure Chemical Industries, Ltd.), tricyclodecane vinyl ether (TCDVE, liquid monomer, Maruzen Petrochemical Co., Ltd.), boron trifluoride diethyl ether (BF3OEt2 (liquid)), and hydrogen chloride solution (HCl; Aldrich, 4.0 M 1,4-dioxane solution) were each divided into ampoules, stored in a refrigerator, and used in the following manufacturing process.

[0118] Furthermore, commercially available zinc chloride solution (ZnCl2; Aldrich, 1.0 M diethyl ether solution), diethyl ether ((C2H5)2O, Fujifilm Wako Pure Chemical Industries, Ltd., super-dehydrated), and toluene (C6H5CH3, Fujifilm Wako Pure Chemical Industries, Ltd., super-dehydrated) were used, and the water was removed and purified using an organic solvent purification apparatus before being used in the following manufacturing process.

[0119] The number-average molecular weight (Mn) and molecular weight distribution (Mw / Mn) of polymers were calculated using gel permeation chromatography (GPC) and a calibration curve created from standard polystyrene (molecular weights: 96400, 37900, 18100, 9100, 5870, 2670, 1050, 500).

[0120] Gel permeation chromatography (GPC) Pump: HITACHI 17100 Differential refractometer: TOSOH RI-8020 UV-Vis spectrometer: SHIMAZU SPD-10a Columns: Shodex LF-802, Shodex LF-804 (3) Solvent: THF Flow rate: 1.0 ml / min (40.0℃)

[0121] Random polymerization was carried out under the conditions shown in Figures 4A and 4B for copolymerization. The NBVE was 0.12 M / TCDVE was 0.08 M, and trifluoromethanesulfonic acid (TfOH) was 0.04 M and 0.01 M, with flow rates F of 9 / 12 and 6 / 9 ml / min, and reaction times of 0.44 / 0.33 sec and 0.65 / 0.33 sec. The temperature was -50 and -50 / -75°C, the reactor inner diameter was 1000 μm, and a T250 mixer was used.

[0122] The monomer / initiator (equivalent), polymerization temperature, flow rate, molecular weight (Mn), and molecular weight dispersion (PDI) are shown in Table 1 below.

[0123] As shown in Table 1, polymerization was carried out at a monomer / initiator equivalent (eq) of 10 and -50°C, yielding a polymer with a molecular weight (Mn) of approximately 2000 and a molecular weight dispersion (PDI) of 1.34. When the monomer / initiator equivalent (eq) was increased to 40, polymers with a molecular weight (Mn) of 3500 were obtained at -50°C, and polymers with a molecular weight (Mn) in the high 2000s and a molecular weight dispersion (PDI) in the 1.3 range were obtained at -75°C, showing a steady increase in molecular weight (Mn).

[0124] <Large-scale synthesis of random copolymers> Next, large-scale synthesis of random copolymers was carried out. As shown in Table 2 below, the concentrations of the monomer solution, initiator solution, and termination solution were increased by 2, 3, etc., and conditions were investigated to prevent reactor clogging due to freezing of polymers and TfOH, and continuous operation at high concentrations was performed. Note that since it is dangerous if the TfOH concentration becomes too high, the initiator flow rate was also adjusted to F, which is 0.06 M at 3 times the concentration and 0.08 M at 4 times the concentration.

[0125] Table 2 shows that yields increased with increasing concentrations of monomer solution, initiator solution, and termination solution. (The decrease in yield at double the concentration is due to halving the flow rate to reduce the pressure in the system; at the same flow rate, the yield would likely be double, or 90 mg.) Furthermore, continuous operation for 1322 seconds at four times the concentration yielded 8250 mg. This yield is comparable to that obtained when polymerization is carried out in a 100 ml flask, but at a high speed.

[0126] <Polymerization Procedure> A round-bottom flask fitted with a three-way stopcock rubber septum was baked with a heating gun while vacuuming and argon displacement were performed approximately three times. Baking was carried out for at least one minute to ensure the entire round-bottom flask was heated, and argon displacement was performed while it was still hot.

[0127] Under an argon atmosphere, monomer solutions, initiator solutions, and termination solutions were adjusted to desired concentrations. A flow microreactor pathway was assembled by combining polytetrafluoroethylene (Teflon™) tubing, a mixer, and a reactor using a wrench or spanner. Additionally, solutions were placed in gas-tight syringes and connected to the reactor.

[0128] Next, an acetone bath or water bath was prepared and adjusted to the desired temperature using dry ice. The reactor was placed in the bath and operated at the desired flow rate. Initially, the reactor was run for approximately 30 seconds (depending on the flow rate and route) until the solution in the reactor was replaced three times to stabilize it, and sampling was performed for a desired amount of time using a sample tube containing approximately 2 ml of NaHCO3.

[0129] The molecular weight, glass transition temperature, and softening temperature of the obtained polymer were measured according to the following procedure.

[0130] (Test Example 3) Measurement of the Glass Transition Temperature (Tg) of the Polymer The glass transition temperature (Tg) of the obtained polymer was determined by differential scanning calorimetry (DSC). A SHIMADZU DSC-60 was used as the apparatus, and measurements were taken in an aluminum sample pan under a nitrogen atmosphere. The first heating and cooling rate was 10°C / min, and the second heating and cooling rate was 5°C / min. The data from the second heating midpoint was used for analysis.

[0131] (Test Example 4) Measurement of Polymer Softening Temperature The obtained polymer was packed into a crimp cell (aluminum pan Φ5.8 mm × height 1.5 mm) for DSC measurement, filling it to the brim. Polymers that were liquid at the time of filling were left as is, while polymers that were solid or had high viscosity at the time of filling were heated to approximately 60°C before being packed into the crimp cell.

[0132] This was placed on a temperature control unit (TOB1000, Hayashi Repic Co., Ltd.) set to -20°C, and a roughly Y-shaped stainless steel rod with a mass of 0.21 g was inserted into the center of the polymer so that it was in contact with the bottom of the cell, with the Y-shape facing upwards (see Figure 2). The roughly Y-shaped stainless steel rod had an overall length of 2.1 cm, a handle length of 0.9 cm, a bottom surface of the handle of 1.0 mm x 0.7 mm (roughly rectangular), a length from the fork of the branched section to the top surface of the branched section of 1.2 cm, a thickness of the branched section of 0.7 mm, and a distance of 0.85 cm between the top surfaces of the branched sections.

[0133] The temperature of the temperature control unit was gradually increased from -20°C, and at the moment the stainless steel rod was completely bent and in contact with the polymer, the surface temperature of the polymer in the aluminum pan was measured with an infrared radiation thermometer (SK-8900, Sato Keiryoki Mfg. Co., Ltd.) and defined as the softening temperature.

[0134] The softening temperature of the obtained polymer was between 6°C and 8°C.

[0135] Furthermore, it has been confirmed that copolymers with similar compositions obtained by other synthesis methods can be obtained with glass transition temperatures Tg = 2.9–4.3°C and softening temperatures in the range of 0.5–12.5°C.

[0136] [Example 1] Preparation of coated seeds At room temperature, the NBVE:TCVE copolymer obtained in Production Example 2 was placed in a sample bottle, and 30 uncoated onion seeds were added thereto. The mixture was stirred with a spatula and the seeds were removed. The removed seeds were left at a low temperature (-20°C) to harden the polymer and obtain seeds with an inner layer coating.

[0137] At room temperature, 1 g of poly (HPPE) obtained in Production Example 1 was placed in a sample bottle, and 2 ml of methanol was added and stirred to dissolve it, thereby preparing the outer layer coating solution.

[0138] Thirty seeds with the inner layer coating described above were added to the mixture, stirred with a spatula, and the seeds were removed. The removed seeds were left at room temperature to remove the methanol solvent, yielding two-layer coated seeds with the outer layer coating the inner layer.

[0139] (Test Example 5) Germination Test A seedling tray with 7 x 13 pods was prepared, and a germination test was conducted using 6 x 5 pods at both ends of this tray. The soil used for seedling cultivation was a general seedling growing medium that did not contain solidifying agents.

[0140] As shown in Figures 5A and 5B, uncoated onion seeds (comparative sample: commercially available variety) were sown in 6x5 pots on the left side of the seedling tray, and the two-layer coated seeds of the present invention (inventive sample: commercially available variety) were sown in 6x5 pots on the right side.

[0141] After sowing each seed in the soil, the temperature was controlled in an incubator, and assuming a scenario where the seeds were sown in the fall and then overwintered, germination was confirmed while breeding according to the following schedule, as shown in Figure 6.

[0142] 4 days at 15°C → 21 days at 3°C ​​→ 20 days at -20°C → 6 days at 3°C ​​→ 7 days at 7°C → 10 days at 15°C → 14 days at 20°C.

[0143] First, to confirm that polymer-coated seeds would not germinate at autumn temperatures, the incubator was set to 15°C and seedlings of each type of seed were grown. As shown in Figures 7A and 7B, 24 uncoated seeds germinated two weeks after sowing (germination rate 80%). At this time, no germination was observed in the coated seeds. Therefore, it was found that at autumn temperatures, the polymer inhibits water absorption in coated seeds, thus controlling germination.

[0144] Subsequently, when the seedling temperature was lowered to 3°C, five more uncoated seeds germinated within three weeks, resulting in a germination rate of 97%. On the other hand, no germination was observed in the coated seeds at this time.

[0145] When the seedling temperature was further lowered to -20°C, all the seedlings that had germinated so far withered and died. Meanwhile, no germination of coated seeds was observed during this period.

[0146] After raising seedlings at -20°C for 20 days, the seedling temperature was gradually increased to 3°C (6 days), 7°C (7 days), and 15°C. At 15°C, germination of the coated seeds was first observed on the 4th day. Further increasing the seedling temperature from 15°C to 20°C resulted in gradual germination as shown in Figure 8, ultimately achieving a germination rate of 40%.

[0147] From the above, it was found that the coated seeds peel off gradually at each temperature, allowing for controllable germination. The reason for the low germination rate of the coated seeds is thought to be that the thickness of the polymer coating on the onion seeds was not uniform, which may have resulted in uneven germination timing for the coated seeds.

[0148] In the above embodiment, plant seeds were used as an example of the material to be coated, but the present invention is not limited to plant seeds and can be applied to a variety of materials as long as the material to be coated can be coated with the two layers.

[0149] Multilayer polymer coatings are not limited to plant seeds; they can also be used to coat fertilizers or pesticides, allowing them to be applied at the optimal time. Furthermore, their applications extend beyond agriculture to include pharmaceuticals, industrial products, and building materials.

Claims

A coated body in which at least two or more layers of polymer are coated onto the object to be coated, A multi-layer polymer coated body characterized in that the outer coating layer, having at least one inner coating layer on the inside, is formed of a polymer that undergoes a phase transition at a temperature lower than the softening temperature of the polymer forming the inner coating layer and exhibits lower critical temperature (LCST) characteristics. The polymer exhibiting the lower critical temperature (LCST) characteristic is a coating body made of multiple layers of polymer according to claim 1, wherein the polymer has hydrophilic groups. The coating body made of multiple layers of polymer according to claim 1, characterized in that the polymer exhibiting the lower critical temperature (LCST) characteristic is formed from a polyvinyl ether having a hydroxyl group. The coating body made of a plurality of polymers according to claim 3, wherein the polyvinyl ether is polyhydroxypropyl propenyl ether represented by the following formula (1). In equation (1), n ​​represents an integer greater than or equal to 2. The coated body made of multiple polymer layers according to claim 1, characterized in that the inner coating layer is a polymer having a softening temperature of 1°C or higher, a viscosity of 30 to 300 Pa·s at 25°C, and a number average molecular weight of 800 to 15000. The coated body made of multiple polymer layers according to claim 5, characterized in that the inner coating layer is a vinyl ether copolymer. The coating body made of a multi-layer polymer according to claim 5, characterized in that the vinyl ether copolymer consists of repeating units represented by the following formula (2). In equation (2), R1 represents an alkyl group having 3 to 10 carbon atoms. R2 represents a cyclic hydrocarbon group whose basic skeleton is an alicyclic group with 10 to 15 carbon atoms. p represents an integer from 3 to 95, q represents an integer from 2 to 38, and p and q satisfy p:q = 5.8:4.2 to 7.2:2.

8. m represents the number of alkylene groups and is an integer of 0 or 1. The coated body is a plant seed, and the coated body is made of multiple layers of polymer as described in item 1 or 2. A method for cultivating plants by direct sowing, in which seeds coated with the multi-layer polymer described in claim 8 are sown in the fall, overwintered, and then germinated in the spring.

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