Seedling growing tray and use thereof

Abstract

To provide a raising seedling tray excellent in workability (culture soil-keeping property) when taking out raised seedlings from a pot.SOLUTION: A seedling growing tray (10) includes a tray body (1), and the tray body (1) includes a synthetic resin foam having a glass transition temperature of 110 °C or higher and an expansion ratio of 5 times to 50 times.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a seedling tray and its use. [Background technology]

[0002] Conventionally, non-foam trays made of vinyl chloride resin, polystyrene resin, etc. have been used as seedling raising trays for agricultural crop seedlings. However, such seedling raising trays are prone to cracking during handling and are difficult to handle.

[0003] To address this issue, non-foamed trays made of polypropylene resin have been proposed. However, the injection molding dies required to produce these trays are expensive, making them less economical. Furthermore, poor insulation properties mean that seedling roots are prone to rot during high temperatures.

[0004] Therefore, seedling trays have been constructed from polystyrene foam molded products, which are lightweight and have excellent heat insulation properties. Such seedling trays are disclosed, for example, in Patent Document 1, and are expected to have the effect of retaining heat in winter and providing heat insulation in summer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 7-327508 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, a method has become known for manufacturing seedling trays with soil, in which soil is filled into the seedling pot portion of the tray body, the filled soil is solidified by steam treatment at approximately 100°C, and then seeds are sown in the solidified soil.

[0007] When the above-mentioned method for manufacturing seedling trays with soil was used, seedling trays made of molded polystyrene foam, such as those in Patent Document 1, had room for improvement in terms of ease of use (soil shape retention) when removing grown seedlings from pots.

[0008] An object of one aspect of the present invention is to provide a seedling raising tray that is excellent in workability (soil shape retention) when removing raised seedlings from pots, and to realize use of the same. [Means for solving the problem]

[0009] In order to solve the above problems, one aspect of the present invention is as follows.

[0010] <1> A seedling tray comprising a tray body, the tray body comprising a synthetic resin foam having a glass transition temperature of 110°C or higher and an expansion ratio of 5 to 50 times.

[0011] <2> The tray body has a pot portion for forming a seedling pot, and the pot portion has a dimensional change rate of 2% or less before and after heating with steam at 100°C for 2 hours. <1> Seedling tray.

[0012] <3> The pot portion has an inner wall portion and an outer wall portion, and the expansion ratio of the inner wall portion is smaller than the expansion ratio of the outer wall portion. <2> Seedling tray.

[0013] <4> The inner wall portion of the pot portion has an inclined surface that is inclined so that the distance between the opposing inner surfaces becomes smaller as it goes from the top to the bottom, and at least one protrusion extending from the top to the bottom is formed on the inclined surface. <2> or <3> Seedling tray.

[0014] <5> the synthetic resin is any one resin selected from the group consisting of polycarbonate-based resins, heat-resistant polystyrene-based resins, and polyphenylene ether-based resins; <1> ~ <4> Seedling trays.

[0015] <6> A method for manufacturing a seedling tray, which comprises a tray body, the tray body comprising a synthetic resin foam having a glass transition temperature of 110°C or higher and an expansion ratio of 5 to 50 times, the method comprising: a filling step of filling a mold with pre-expanded particles of the synthetic resin; and an expansion step of expanding the pre-expanded particles of the synthetic resin to manufacture the tray body.

[0016] <7> <1> ~ <5> A seedling raising tray treatment method comprising a heating step of heat treating any one of the seedling raising trays.

[0017] <8> <1> ~ <5> A method for manufacturing a seedling tray with culture soil, comprising: a filling step of filling the pot portion of the tray body with culture soil in any one of the seedling trays above; and a solidification step of treating the culture soil filled in the filling step with steam to solidify the culture soil. [Effects of the Invention]

[0018] According to one aspect of the present invention, a seedling raising tray that is excellent in workability (soil shape retention) when removing raised seedlings from pots can be realized. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a perspective view showing a schematic configuration of a seedling raising tray according to an embodiment of the present invention. [Figure 2] 1 is a cross-sectional view showing a schematic configuration of a seedling raising tray according to an embodiment of the present invention. [Figure 3] FIG. 2 is a cross-sectional view illustrating the ridges formed in the pot portion of the seedling tray according to the embodiment of the present invention. [Figure 4] FIG. 2 is a top view illustrating the ridges formed in the pot portion of the seedling tray according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] The following describes embodiments of the present invention with reference to the drawings, but the present invention is not limited thereto. The present invention is not limited to the respective configurations described below, and various modifications are possible within the scope of the claims. Furthermore, embodiments or examples obtained by combining the technical means disclosed in different embodiments or examples are also included in the technical scope of the present invention. Furthermore, new technical features can be created by combining the technical means disclosed in each embodiment. All academic and patent documents described in this specification are incorporated herein by reference. Unless otherwise specified, "A to B" representing a numerical range means "A or more (including A and greater than A) and B or less (including B and less than B)." In the drawings of this application, "HD" refers to the vertical direction, "HDa" refers to the upper side, which is one side of the vertical direction, and "HDb" refers to the lower side, which is the other side of the vertical direction.

[0021] <Technical philosophy> As described above, conventional seedling raising trays made of molded polystyrene foam, such as those in Patent Document 1, have poor workability (soil shape retention) when removing raised seedlings from pots. Therefore, the present inventors have conducted extensive research into the cause of this poor workability (soil shape retention). As a result, the present inventors have newly discovered that the poor workability (soil shape retention) is caused by dimensional changes in the seedling raising tray.

[0022] The inventors of the present invention believed that the dimensional changes in the seedling raising trays were due to the sterilization of the seedling raising soil and the heating (high-temperature steam treatment) used to solidify the seedling raising soil. Therefore, the present invention was completed by manufacturing seedling raising trays using a synthetic resin foam that is dimensionally stable and can withstand high-temperature steam treatment.

[0023] Hereinafter, one embodiment of the present invention will be described in detail.

[0024] <Configuration of seedling tray according to this embodiment> Fig. 1 is a perspective view showing a schematic configuration of a seedling raising tray 10 according to this embodiment. Fig. 2 is a cross-sectional view showing a schematic configuration of the seedling raising tray 10 according to this embodiment.

[0025] As shown in Figures 1 and 2, the seedling raising tray 10 according to this embodiment includes a tray body 1. The tray body 1 includes a synthetic resin foam, and is preferably made of a synthetic resin foam. The foam of the tray body 1 is not particularly limited, but is preferably an in-mold foamed body of synthetic resin foam particles. In the seedling raising tray 10, the tray body 1 is preferably for sowing seeds.

[0026] The tray body 1 has a rectangular appearance in a plan view, and includes a plurality of pot portions 2 and a plate-like portion 3. The pot portions 2 are intended to form seedling pots. In the tray body 1, the pot portions 2 are arranged at predetermined intervals in the width and length directions. The plate-like portion 3 has a flat plate shape and forms the rectangular external shape of the tray body 1. The pot portions 2 and the plate-like portion 3 may be separable from each other, or may be molded integrally. Preferably, the pot portions 2 and the plate-like portion 3 are molded integrally.

[0027] The number of pot parts 2 is not particularly limited and can be set appropriately depending on the number of seedlings to be raised, the size of the tray body 1, etc. In consideration of the efficiency of raising seedlings, the number of pot parts 2 per tray body 1 is preferably 50 to 300.

[0028] The pot portion 2 has a bottomed cylindrical shape that extends in the HD direction and protrudes toward the HDb side relative to the plate-like portion 3. The end face of the pot portion 2 on the HDa side, which has an opening, is flush with the HDa-side surface of the plate-like portion 3. A seedling pot is constructed by filling the pot portion 2 with a seedling raising material, such as culture soil, and sowing seeds into the seedling raising material.

[0029] The walls of the pot portion 2 include an inner wall portion 21 and an outer wall portion 22. The inner wall portion 21 is composed of an inner side surface 21a and an inner bottom surface 21b. The outer wall portion 22 is composed of an outer side surface 22a and an outer bottom surface 22b. The inner wall portion 21 of the pot portion 2 has an inclined surface that is inclined so that the distance between the opposing inner side surfaces 21a becomes smaller as it moves from the HDa side to the HDb side. In other words, the inner side surfaces 21a are tapered surfaces that become narrower from the HDa side to the HDb side.

[0030] Furthermore, the pot portion 2 has ridges formed on the inner surface 21a. Figures 3 and 4 are diagrams illustrating the ridges 23 of the pot portion 2, with Figure 3 being a cross-sectional view and Figure 4 being a top view. As shown in Figures 3 and 4, four ridges 23 are formed on the inner surface 21a, which is an inclined surface. The ridges 23 extend from the HDa side to the HDb side. When viewed from the side of the central axis O of the pot portion 2, each ridge 23 extends in a stripe-like manner in the HD direction (vertical direction). In other words, the ridges 23 are configured as follows: in the plan view shown in Figure 4, a straight line passing through the end 23a of the ridge 23 on the HDa side and the end 23b of the ridge 23 on the HDb side intersects with the central axis O.

[0031] In this way, the inner surface 21a of the inner wall portion 21 of the pot portion 2 is an inclined surface, and the ridges 23 are formed on this inclined surface, thereby improving the ease of removing seedlings grown in the pot portion 2. In the configuration shown in Figures 3 and 4, the number of ridges 23 is four. However, the number of ridges 23 is not limited to four, and can be set to any number as long as it makes it easy to remove seedlings.

[0032] Furthermore, when the seedling raising trays 10 are not in use, they are usually stored in a stacked state. The seedling raising trays 10 may shrink or expand due to changes in temperature, humidity, etc., making it difficult to remove the seedling raising trays 10 from the stacked storage state. According to the above configuration, even if the seedling raising trays 10 shrink or expand due to changes in temperature, humidity, etc., the ridges 23 provided on the inner surface 21a of the pot portion 2 interfere with each other, making it easier to remove the seedling raising trays 10 from the storage state.

[0033] Furthermore, in the pot portion 2, the expansion ratio of the inner wall portion 21 is smaller than the expansion ratio of the outer wall portion 22. Preferably, the expansion ratio of the synthetic resin foam particles that make up the inner wall portion 21 is smaller than the expansion ratio of the synthetic resin foam particles that make up the outer wall portion 22. This further improves the ease of removing the seedlings grown in the pot portion 2.

[0034] From the viewpoint of ease of removal of seedlings, the difference between the expansion ratio of the inner wall portion 21 and the expansion ratio of the outer wall portion 22 is preferably 3 times or more, and more preferably 5 times or more. The expansion ratio of the inner wall portion 21 is not particularly limited as long as it is 5 times to 50 times, but is preferably 5 times to 25 times, and more preferably 5 times to 20 times. The expansion ratio of the outer wall portion 22 is not particularly limited as long as it is 5 times to 50 times, but is preferably 5 times to 30 times, and more preferably 5 times to 25 times.

[0035] (Adjustment of the foaming ratio of the inner wall portion 21 of the pot portion 2) One example of a method for adjusting the expansion ratio of the inner wall 21 of the pot portion 2 to be smaller than that of the outer wall 22 is adjusting the cracking gap in the molding space of the mold that corresponds to the wall of the pot portion 2 during in-mold foam molding of synthetic resin foam beads. That is, the expansion ratio of the inner wall 21 of the pot portion 2 can be made smaller than that of the outer wall 22 by a method including the following steps: a filling step in which the mold is clamped so that the portion of the molding space corresponding to the wall of the pot portion 2 is larger by an amount corresponding to the cracking gap, and this molding space is filled with pre-expanded synthetic resin beads; and a molding step in which, after the filling step, the mold is completely clamped and the pre-expanded beads are heated and expanded to form the foamed molded article. In this method, during the filling step, the pre-expanded beads flow into the portion of the mold that corresponds to the wall of the pot portion 2 by an amount corresponding to the cracking gap. In this state, by completely clamping the mold in the molding step, the compression ratio of the pre-expanded particles increases in the portion of the wall of the pot portion 2 that corresponds to the inner wall portion 21, resulting in a higher density of the pre-expanded particles. In this state, by heating and expanding the pre-expanded particles, the expansion ratio of the inner wall portion 21 can be made smaller than that of the outer wall portion 22. The cracking gap can be appropriately set depending on the difference between the desired expansion ratios of the inner wall portion 21 and the outer wall portion 22. As long as the expansion ratio of the inner wall portion 21 can be made smaller than that of the outer wall portion 22, the cracking gap is not particularly limited, but is preferably 60% to 400%, and more preferably 60% to 150%, of the thickness of the pot portion 2.

[0036] In addition to the above methods, the expansion ratio of the inner wall 21 can be reduced by thermally fusing the inner surface 21a and the inner bottom surface 21b of the inner wall 21 of the pot part 2. Examples of such thermal fusing methods include contacting a hot plate with the inner surface 21a and the inner bottom surface 21b, or performing hot air treatment. Furthermore, the (apparent) expansion ratio of the inner wall 21 can also be reduced by laminating a film to the inner surface 21a and the inner bottom surface 21b.

[0037] <Tray body 1> As described above, in the seedling raising tray 10 according to this embodiment, the tray body 1 includes a synthetic resin foam. The foam has a glass transition temperature of 110° C. or higher and an expansion ratio of 5 to 50 times.

[0038] In the method of producing potted seedlings using seedling trays, culture soil is placed in the pots and exposed to high-temperature steam at about 100°C to solidify and sterilize the culture soil in the pots. Seedling trays made of molded polystyrene resin foam beads, such as those described in Patent Document 1, are prone to deformation due to insufficient heat resistance to high-temperature steam, making repeated use difficult.

[0039] Furthermore, the heat history caused by the high-temperature steam causes the gaps between the foam particles (hexagonal pattern) in the pot to widen, allowing the roots of the seedlings to penetrate into these gaps. As a result, the release properties of the potting soil when removing the seedlings from it deteriorate with increasing frequency of use, impairing the soil's shape retention and damaging the roots.

[0040] According to the seedling raising tray 10 of this embodiment, the tray body 1 comprises a synthetic resin foam having a glass transition temperature of 110°C or higher and an expansion ratio of 5 to 50 times. Therefore, the tray body 1 has good heat resistance against high-temperature steam, and is excellent in heat insulation and light weight. Therefore, according to the seedling raising tray 10 of this embodiment, the seedlings can be easily released when removed from the pot portion 2. Therefore, the seedling raising tray 10 of this embodiment has the effect of providing excellent workability (soil shape retention) when removing the raised seedlings from the pot portion 2.

[0041] Considering the above effects, the glass transition temperature of the foam of the tray body 1 is preferably 110° C. or higher, and more preferably 115° C. or higher. There is no particular upper limit to the glass transition temperature, but it is preferably 180° C. or lower, and more preferably 160° C. or lower.

[0042] In the seedling raising tray 10 according to this embodiment, the dimensional change rate of the pot portion 2 before and after heating with steam at 100°C for two hours is preferably 2% or less, and more preferably 1% or less. If the dimensional change rate is within the above range, the dimensional stability of the pot portion 2 is very high. Therefore, the dimensional change of the pot portion 2 is sufficiently suppressed even in an environment where it is exposed to high-temperature steam.

[0043] In the seedling tray 10 according to this embodiment, it is sufficient that the dimensional change rate of at least the pot portion 2 of the tray body 1 is within the above-mentioned numerical range. From the viewpoint of ease of manufacturing the foam of the tray body 1, it is preferable that the dimensional change rate of the entire tray body 1 is within the above-mentioned numerical range.

[0044] (synthetic resin foam) Although there are no particular limitations on the synthetic resin that constitutes the foam of the tray body 1, it is preferably a thermoplastic resin. Any resin can be used as the thermoplastic resin as long as it has a base resin with a glass transition temperature of 110°C or higher.

[0045] Examples of the thermoplastic resin include polycarbonate resin; methacrylic acid-modified polystyrene resins such as styrene-acrylic acid copolymer and styrene-methacrylic acid copolymer; heat-resistant polystyrene resins such as styrene-maleic anhydride copolymer and styrene-itaconic acid copolymer; and polyphenylene ether resins such as styrene-phenylene ether copolymers, such as blends of polystyrene or heat-resistant polystyrene with polyphenylene ether, and styrene graft polymers of polyphenylene ether.

[0046] In particular, the synthetic resin is preferably selected from the group consisting of polycarbonate-based resins, heat-resistant polystyrene-based resins, and polyphenylene ether-based resins. Hereinafter, polycarbonate-based resins may be referred to as PC-based resins, and polyphenylene ether-based resins may be referred to as PPE-based resins.

[0047] Any foam can be used for the tray body 1 as long as it is a foam that uses the above-mentioned thermoplastic resin as a base resin. Preferably, the foam is a thermoplastic resin foam bead molded product. The thermoplastic resin foam bead molded product can be produced by in-mold molding of pre-expanded beads obtained by pre-expanding expandable thermoplastic resin beads (hereinafter referred to as expandable resin beads).

[0048] (PC resin) PC resins have a polyester structure of carbonic acid and glycol or dihydric phenol, and those containing aromatic groups are particularly preferred. Examples of PC resins containing aromatic groups include aromatic polycarbonates derived from bisphenols, such as 2,2-bis(4-oxyphenyl)propane, 2,2-bis(4-oxyphenyl)butane, 1,1-bis(4-oxyphenyl)cyclohexane, 1,1-bis(4-oxyphenyl)butane, 1,1-bis(4-oxyphenyl)isobutane, and 1,1-bis(4-oxyphenyl)ethane. These PC resins are preferred because of their excellent heat resistance.

[0049] Furthermore, without departing from the object and effect of the present invention, the tray body 1 may be formed from a resin foam containing polycarbonate resin and other resins, such as polypropylene resin, acrylic resin, saturated polyester resin, acrylonitrile butadiene styrene (ABS) resin, polystyrene resin, polyphenylene oxide resin, etc.

[0050] (heat-resistant polystyrene resin) Any foam of heat-resistant polystyrene resin can be used as long as it is a foam using a heat-resistant polystyrene resin as a base resin. The heat-resistant polystyrene resin is, for example, a (meth)acrylic acid-modified styrene resin having a structural unit derived from (meth)acrylic acid. In the (meth)acrylic acid-modified polystyrene resin, the structural unit (monomer unit) derived from (meth)acrylic acid is preferably 3.0% by weight to 30% by weight, more preferably 5.0% by weight to 25% by weight, in order to suppress deformation of the synthetic resin foam. However, the total amount of the (meth)acrylic acid-modified polystyrene resin is taken as 100% by weight.

[0051] In the above preferred embodiment, the heat-resistant styrene resin is not limited to a (meth)acrylic acid-modified polystyrene resin, but may be any styrene resin other than 100% styrene homopolymer. Examples of such styrene resins include an alloy of styrene homopolymer / diene rubber-reinforced polystyrene and a polyphenylene ether resin.

[0052] In the above preferred embodiment, in order to suppress deformation of the foam of the tray body 1, the glass transition temperature (Tg) of the heat-resistant styrene resin constituting the foam is preferably 110°C to 135°C, more preferably 115°C to 130°C.

[0053] (PPE resin) Specific examples of PPE resins include poly(2,6-dimethylphenylene-1,4-ether), poly(2-methyl-6-ethylphenylene-4-ether), poly(2,6-diethylphenylene-1,4-ether), poly(2,6-diethylphenylene-1,4-ether), poly(2-methyl-6-n-propylphenylene-1,4-ether), poly(2-methyl-6-n-butylphenylene-1,4-ether), poly(2-methyl-6-chlorophenylene-1,4-ether), poly(2-methyl-6-bromophenylene-1,4-ether), and poly(2-ethyl-6-chlorophenylene-1,4-ether), and these may be used alone or in combination of two or more.

[0054] Specific examples of styrene-based monomers to be polymerized, preferably graft-polymerized, onto PPE-based resins include styrene, α-methylstyrene, 2,4-dimethylstyrene, monochlorostyrene, dichlorostyrene, p-methylstyrene, and ethylstyrene. These may be used alone or in combination of two or more. Among these, styrene is preferred from the viewpoints of versatility and cost.

[0055] The PPE resin used for the foam of the tray body 1 may be a blend of a PPE resin with a polystyrene resin such as polystyrene or heat-resistant polystyrene. Examples of polystyrene resins that form a mixed resin with a PPE resin include resins whose main component is styrene or a derivative thereof, such as α-methylstyrene, 2,4-dimethylstyrene, monochlorostyrene, dichlorostyrene, p-methylstyrene, or ethylstyrene. Therefore, the polystyrene resin is not limited to a homopolymer consisting of only styrene or a styrene derivative, but may also be a copolymer obtained by copolymerizing it with other monomers.

[0056] The base resin (blend) used in the foam of the tray body 1 is typically preferably 10-70% by weight of PPE resin and 90-30% by weight of polystyrene resin, more preferably 20-60% by weight of PPE resin and 80-40% by weight of polystyrene resin, and even more preferably 25-50% by weight of PPE resin and 75-60% by weight of polystyrene resin. If the PPE resin content in the blend is less than 10% by weight, heat resistance tends to be poor, while if the PPE resin content exceeds 70% by weight, viscosity increases during heating and flow, making foam molding difficult.

[0057] (Method of manufacturing the seedling raising tray 10 according to this embodiment) The seedling raising tray manufacturing method according to this embodiment is a method for manufacturing a seedling raising tray 10 comprising a tray body 1, the tray body 1 comprising a synthetic resin foam having a glass transition temperature of 110°C or higher and an expansion ratio of 5 to 50. The manufacturing method includes a filling step of filling a mold with pre-expanded synthetic resin particles, and an expansion step of expanding the pre-expanded synthetic resin particles to manufacture the tray body 1.

[0058] First, the pre-expanded particles to be filled in the filling step are produced by pre-expanding expandable resin particles. The expandable resin particles can be produced by a known production method, but either the following first or second production method is preferred from the viewpoint of ease and stability of production.

[0059] The first method for producing expandable resin particles comprises the following steps (1) to (3): (1) Using an extruder, a thermoplastic resin component, a blowing agent, and, if necessary, additives are melt-kneaded. (2) The molten mixture is extruded into a cutter chamber filled with pressurized circulating water through a die having many small holes attached after the extruder. (3) Immediately after extrusion, the molten mixture is cut by a rotating cutter in contact with the die and cooled and solidified by the pressurized circulating water.

[0060] The second method for producing expandable resin particles is as follows: Resin particles containing a thermoplastic resin component and, if necessary, additives are suspended in water, and a blowing agent is supplied to the resin particles to incorporate the blowing agent into the resin particles, thereby obtaining expandable resin particles.

[0061] In terms of simplicity of equipment and ease of production, the first method for producing expandable resin particles is more preferred.

[0062] (foaming agent) The blowing agent may be a volatile blowing agent and / or an inorganic blowing agent. Specific examples of volatile blowing agents include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, aliphatic alcohols, aliphatic ketones, and halogenated hydrocarbons. Aliphatic hydrocarbons include propane, n-butane, i-butane, n-pentane, i-pentane, and hexane. Alicyclic hydrocarbons include cyclobutane, cyclopentane, and cyclohexane. Aromatic hydrocarbons include benzene, toluene, and xylene. Aliphatic alcohols include methanol, ethanol, and propanol. Aliphatic ketones include acetone and methyl ethyl ketone. Halogenated hydrocarbons include 1-chloro-1,1-difluoroethane, pentafluoroethane, 1,1,1,2-tetrafluoroethane, and 1,1-difluoroethane. Inorganic blowing agents include inorganic gases such as carbon dioxide (CO2), nitrogen gas (N2), and air. In this embodiment, the foaming agents listed above can be used alone or in combination of two or more types. For example, different types of foaming agents, such as an inorganic foaming agent and a volatile foaming agent, can be used in combination. The amount of foaming agent used is appropriately determined depending on the type of foaming agent and the desired expansion ratio. When the amount of foaming agent used is determined depending on the desired expansion ratio, the density of the in-mold foam molded product is determined by the expansion ratio, so the amount of foaming agent used is determined mainly by the desired density of the in-mold foam molded product.

[0063] (pre-foamed) The pre-expanding method for the expandable resin particles can be any known method. For example, the expandable resin particles are expanded to a desired expansion ratio with heated steam to form pre-expanded particles, which are then cured for a certain period of time as necessary. The obtained pre-expanded particles are used for in-mold molding.

[0064] (Foaming process) In the expansion step, the pre-expanded particles are expanded to produce the tray body 1. Specifically, the obtained pre-expanded particles are in-mold molded by steam heating under normal molding conditions using a conventional molding machine to produce the tray body 1. A preferred method for molding the tray body 1 is to fill a molding die with pre-expanded particles and further expand them by steam heating to fuse and integrate the pre-expanded particles together to form an in-mold foamed article. The reasons for this are as follows: (1) even complex shapes can be produced relatively easily, and (2) the density uniformity in the in-mold foamed article is excellent, making it easy to obtain relatively uniform mechanical properties. As a result, when comparing foamed articles of the same density, it is easier to achieve high compressive stress and high energy absorption performance compared to methods other than the in-mold molding method.

[0065] (Other additives) In this embodiment, the in-mold foamed article may contain additives such as antioxidants, weather resistance improvers, antistatic agents, colorants, flame retardancy improvers, and conductivity improvers, as needed.

[0066] These additives may be conventionally known additives that can be used in the production of in-mold foam molded articles. There are no limitations on the colorants listed as examples of additives. The in-mold foam molded article can be natural in color without the addition of a colorant, but a desired color can also be achieved by adding a colorant such as blue, red, or black to impart design features or to make stains that may occur over time less noticeable.

[0067] (Expansion ratio of the foam of the tray body 1) As described above, the expansion ratio of the foam of the tray body 1 is 5 to 50. The expansion ratio of the synthetic resin foam is calculated by calculating the density of the synthetic resin foam using a submersion method and dividing the density of the synthetic resin used by the calculated value.

[0068] If the expansion ratio is less than 5 times, the lightweight property of the tray body 1 is lost. In addition, the expansion ratio is 50 times or less in view of the closed cell ratio of the foam and mechanical properties such as rigidity.

[0069] The lower limit of the expansion ratio of the foam of the tray body 1 may be 5 or more, preferably 10 or more, and more preferably 15 or more. The upper limit of the expansion ratio of the foam of the tray body 1 may be 50 or less, preferably 45 or less, and more preferably 40 or less.

[0070] <Seedling pots> In the seedling raising tray 10 according to this embodiment, the seedling raising pots can have a conventionally known configuration as long as they are made up of the pot portion 2 of the tray body 1. The seedling raising pots that can be used in the seedling raising tray 10 include a configuration that includes culture soil, such as a configuration in which culture soil and seeds or seedlings are filled in the pot portion 2, or a configuration in which culture soil and seeds or seedlings are filled in a nonwoven bag and the nonwoven bag is contained in the pot portion 2.

[0071] The seedling raising tray 10 according to this embodiment can also be applied to hydroponic cultivation. In this case, the seedling raising pot has a configuration in which only seeds or young seedlings are housed in the pot portion 2.

[0072] <Method for treating seedling tray 10 according to this embodiment> The method for treating the seedling raising tray 10 according to this embodiment includes a heating step for heat treating the seedling raising tray 10. The treatment method is mainly aimed at sterilizing the seedling raising tray 10, and the seedling raising tray 10 is sterilized by the heating step.

[0073] In the heating step, the heat treatment is not particularly limited as long as it is a treatment that can sterilize the seedling raising tray 10. Examples of the heat treatment include steam heating treatment and air heating treatment.

[0074] The heated steam used in the steam heating treatment may be any steam capable of sterilization, such as saturated steam, supersaturated steam, unsaturated steam, superheated steam, etc. The amount of heated steam used in the heat treatment can be appropriately set depending on the degree of sterilization.

[0075] <Method of manufacturing the seedling raising tray 10 with culture soil according to this embodiment> The seedling raising tray 10 according to this embodiment can be manufactured with culture soil. That is, the method for manufacturing the seedling raising tray with culture soil according to this embodiment includes a filling step of filling the pot portion 2 of the tray body 1 with culture soil in the seedling raising tray 10 according to this embodiment, and a solidification step of treating the culture soil filled in the filling step with steam to solidify the culture soil.

[0076] The culture medium filled in the pot portion 2 is not particularly limited as long as it has the property of solidifying when treated with steam. This culture medium is a type that can be physically solidified by special fiber processing, known as solidified culture medium. The solidified culture medium contains heat-fusible fibers. In solidified culture medium, the heat-fusible fibers melt or soften when treated with steam, bonding the fibers together or bonding the fibers with other components, forming a three-dimensional mesh-like reinforcing structure, thereby solidifying the culture medium. Examples of such solidified culture medium include Excelsoil (manufactured by Minoru Sangyo Co., Ltd.) and PlantPlug (registered trademark, manufactured by Sakata Seed). Excelsoil is a mixture of culture medium materials such as peat moss, coco peat, perlite, and vermiculite with heat-fusible plastic fibers. PlantPlug (registered trademark) contains peat moss and coco fiber as culture medium materials.

[0077] In the solidification step, the steam used to solidify the soil is not particularly limited as long as it can solidify the soil, but steam at 100° C. or higher is preferred. Examples of steam at 100° C. or higher include saturated steam and superheated steam.

[0078] The seedling raising tray 10 used in the method for manufacturing a seedling raising tray with culture soil according to this embodiment has a tray body 1 made of a synthetic resin foam with a glass transition temperature of 110°C or higher and an expansion ratio of 5 to 50. As a result, the tray body 1 has good heat resistance to high-temperature steam of 100°C or higher, and is excellent in heat insulation and lightweight. This means that the seedling raising tray with culture soil has good releasability when removing seedlings raised in the culture soil from the pot portion 2. Therefore, the method for manufacturing a seedling raising tray with culture soil according to this embodiment can manufacture a seedling raising tray with culture soil that has excellent workability (shape retention of the culture soil) when removing raised seedlings from the pot portion 2.

[0079] The method for manufacturing a seedling tray with culture soil according to this embodiment may further include a sowing step of sowing seeds in the culture soil solidified in the solidification step. [Example]

[0080] Examples and comparative examples are given below, but the present invention is not limited to these.

[0081] The measurement and evaluation methods used in the following examples and comparative examples are as follows.

[0082] <Measurement and evaluation methods> [Measurement of glass transition temperature (Tg)] Films were produced from expandable resin particles, pre-expanded particles of the expandable resin particles, or foamed molded products of the pre-expanded particles using a press heated to 210°C. Test pieces measuring 2-4 mg were cut from the films and subjected to differential scanning calorimetry (DSC) analysis. DSC measurements were performed in accordance with JIS K 7121 (1987) using a TA Instruments DSC measuring device, Model Q1000 DSC. The midpoint glass transition temperature of the DSC curve obtained at a heating rate of 10°C / min was then determined.

[0083] [Bulk expansion ratio of pre-expanded particles] The bulk expansion ratio of the pre-expanded particles was calculated by placing the pre-expanded particles in a measuring cylinder so that the volume was 1,000 cc, measuring the weight, and using the following formula. Bulk expansion ratio (cc / g) = 1,000 cc / [weight of pre-expanded particles (g)]...(1).

[0084] [density] The density of the expanded bead molding was calculated according to the following formula in accordance with JIS K 7222:2005. Density (Kg / m 3 ) = Weight of foamed bead molding (Kg) / Volume of foamed bead molding (m 3 )…(2).

[0085] [Expansion ratio] The expansion ratio of the expanded bead molding was calculated from the above density using the following formula. Expansion ratio (times) = Density of resin used (Kg / m 3 ) / density(Kg / m 3 ) …(3) The densities of the resins used are as follows: PC resin: 1,200Kg / m 3 , heat-resistant polystyrene resin or polystyrene resin: 1,060 kg / m 3 , PPE resin: 1,080Kg / m 3 , PP resin: 910Kg / m 3 .

[0086] [Steam heat resistance] The seedling tray (tray body) was placed in a heated steamer (steamer) directly connected to a boiler, and the dimensional change rate was measured before and after heating at 100°C for 2 hours. In measuring the dimensional change rate, the tray body was exposed to a saturated steam environment at 100°C for 2 hours.

[0087] Dimensional change rate (%) = (dimension before heating - dimension after heating) / (dimension before heating) × 100... (4).

[0088] The dimensional change rate was calculated by measuring the dimensions of the seedling tray in three directions, i.e., width, length, and thickness, and then calculating the average value of the three directions.

[0089] The dimensional change rate was evaluated as follows.

[0090] A: 2% or less, B: More than 2% but less than 8%, C: More than 8%.

[0091] [Lightweight] The seedling tray was held in one hand and the weight was evaluated by sensory evaluation.

[0092] ◎: Very light, ○: Light, △: Slightly heavy, ×:Heavy.

[0093] [Rigidity (bending deflection)] The seedling tray was held at both ends in the length direction and vibrated vertically, and the degree of deflection was evaluated by sensory evaluation.

[0094] ◎: Rigid and very little deflection ○: Somewhat rigid with little deflection △: The rigidity is slightly poor and it bends. ×: Poor rigidity and large deflection.

[0095] [Ease of removing seedlings] The pot portion of the tray body was filled with Excel soil (solidified soil), which was then heated with steam at 100°C for 1 hour and then cooled and solidified. The ease of removing seedlings from the solidified Excel soil was then evaluated sensorily as follows: ◯ and △ were considered acceptable, and × was considered unacceptable.

[0096] ○: Easy to extract, △: Some parts are stuck, ×: Difficult to extract.

[0097] Example 1 [Formation of expandable resin particles] 80 parts by weight of polycarbonate resin (manufactured by Mitsubishi Engineering Plastics Corporation; NOVAREX M7027BF), 20 parts by weight of polycarbonate resin (manufactured by Mitsubishi Engineering Plastics Corporation; LUPILON H-4000), and 0.5 parts by weight of talc (manufactured by Hayashi Kasei Co., Ltd.; Talcan Powder TP-20) were fed into a 40 mm diameter co-meshing twin-screw extruder (first extruder) at a total feed rate of 50 kg / hr. The cylinder temperature after the raw material feed section of the twin-screw extruder was set to 260°C, and the feed materials were melt-kneaded. Next, 4.0 parts by weight of ethyl chloride and 4.0 parts by weight of cyclopentane as foaming agents were injected into the cylinder after the raw material feed section of the twin-screw extruder, per 100 parts by weight of the melt obtained by melt-kneading, and further melt-kneaded.

[0098] The resulting melt (melt impregnated with the blowing agent) was then supplied to a 90 mm diameter single-screw extruder (second extruder) through a continuation pipe set at 220°C. A gear pump set at 210°C and a diverter valve were connected to the tip of the single-screw extruder. A die was connected downstream of the diverter valve. The die had 55 small holes with a diameter of 0.65 mm and a land length of 5.0 mm and was set at a temperature of 270°C. The cylinder temperature of the single-screw extruder was then set at 210°C to knead the melt, and the melt obtained by melt kneading was extruded through the die connected to the tip of the single-screw extruder at an extrusion (discharge) rate of 54 kg / hr into pressurized water at a temperature of 94°C and a water pressure of 1.3 MPa.

[0099] Immediately after that, a rotary cutter having four blades was used to cut the melt into particles by rotating the cutter at a rotation speed of 2000 rpm, thereby forming expandable resin particles for in-mold molding.

[0100] [Formation of pre-expanded particles] The resulting expandable resin particles were placed in a pre-expanding machine and expanded by introducing steam at 0.16 MPa for 150 seconds. This resulted in the formation of pre-expanded particles. The bulk expansion ratio of the resulting pre-expanded particles was 30 times (cc / g).

[0101] [Production of in-mold foamed synthetic resin (PC foamed molded product)] The obtained pre-expanded particles were filled into a mold (in-mold molding - mold for seedling trays) attached to a foamed polypropylene molding machine, and steam at 0.24 MPa was introduced for 30 seconds to cause in-mold foaming. The mold was then cooled with water until the pressure of the resin foam molding in the mold pressing against it reached 0.015 MPa (gauge pressure), producing a PC foam molded sample. The cracking gap was adjusted so that the thickness of the side wall of the pot section was thinner than the thickness of other parts, and the degree of compression of the side wall was increased compared to other parts, thereby reducing the expansion ratio of the side wall. The sample had an average density of 40.2 kg / m 3 (Expansion ratio 29.8 times), inner wall density of side wall 119 kg / m 3 (Expansion ratio 10 times), outer wall density of side wall 82 kg / m3 It is a rectangular PC-based resin foam molded body (96 seedling pot holes) with an expansion ratio of 15 times, a closed cell ratio of 75% in the side wall, a sloped inner surface of the pot, and protrusions on four points on the inner surface.

[0102] The obtained samples were evaluated for steam heat resistance, light weight, bending deflection, and ease of extracting seedlings from the seedling raising pot. The measurement and evaluation results are shown in Table 1.

[0103] Example 2 [Preparation of expandable resin particles] 100 parts by weight of methacrylic acid-modified heat-resistant polystyrene resin (G9001, manufactured by PS Japan Co., Ltd., 8% by weight methacrylic acid) and 0.5 parts by weight of talc (Talcan Powder TP-20, manufactured by Hayashi Kasei Co., Ltd.) were fed into a 40 mm diameter co-rotating intermeshing twin-screw extruder (first extruder). The cylinder temperature after the raw material feed section of the twin-screw extruder was set to 200°C, and the fed materials were melt-kneaded. Next, 8.0 parts by weight of mixed pentane (a mixture of 80% by weight of n-pentane and 20% by weight of isopentane (manufactured by SK Sangyo Co., Ltd.)) serving as a blowing agent was injected into the cylinder after the raw material feed section of the twin-screw extruder, and further melt-kneaded relative to 100 parts by weight of the melt obtained by melt-kneading.

[0104] The resulting thermoplastic resin melt (the thermoplastic resin melt impregnated with the blowing agent) was then fed to a 90 mm diameter single-screw extruder (second extruder) through a continuation pipe set to 190°C. A gear pump set to 180°C and a diverter valve were connected to the tip of the single-screw extruder, and a die set to 250°C and containing 60 small holes with a diameter of 0.65 mm and a land length of 5.0 mm was connected downstream of the diverter valve. The cylinder temperature of the single-screw extruder was then set to 180°C to knead the thermoplastic resin melt. The melt obtained by melt kneading was then extruded through the die connected to the tip of the single-screw extruder at an extrusion rate (discharge) of 60 kg / hr into pressurized water at a temperature of 80°C and a water pressure of 1.2 MPa.

[0105] Immediately after that, the molten material was cut into particles using a rotary cutter with a blade, thereby forming expandable resin particles for in-mold molding. The average particle weight of the resulting expandable resin particles was 1 mg.

[0106] [Formation of pre-expanded particles] The obtained expandable resin particles were placed in a pre-expanding machine and expanded by introducing steam at 0.1 MPa. This resulted in the formation of pre-expanded particles. The bulk expansion ratio of the obtained pre-expanded particles was 30 times (cc / g).

[0107] [Production of in-mold foamed synthetic resin products (heat-resistant polystyrene-based resin foamed products)] The obtained pre-expanded particles were filled into a mold (in-mold molding - mold for seedling trays) attached to a polystyrene foam molding machine, and 0.12 MPa of steam was introduced to cause in-mold foaming. The resin foam molded body in the mold was then water-cooled until the pressure pressing the mold down to 0.015 MPa (gauge pressure), producing a sample of a heat-resistant polystyrene resin foam molded body. The cracking gap was adjusted so that the thickness of the side wall of the pot section was thinner than the thickness of other parts, and the degree of compression of the side wall was increased compared to other parts, thereby reducing the expansion ratio of the side wall. The sample had an average density of 29.4 kg / m 3 (Expansion ratio 36 times), inner wall density of side wall 106 kg / m 3 (Expansion ratio 10 times), outer wall density of side wall 71 kg / m 3 It is a rectangular heat-resistant polystyrene resin foam molded body (96 seedling pot holes) with an expansion ratio of 15 times, a closed cell ratio of 83% in the side wall, a sloped inner surface of the pot, and protrusions on four points on the inner surface.

[0108] The obtained sample was evaluated in the same manner as in Example 1. The measurement results and evaluation results are shown in Table 1.

[0109] Example 3 [Formation of expandable resin particles] 71.43 parts by weight of polystyrene resin (680 manufactured by PS Japan Co., Ltd.), 28.57 parts by weight of polyphenylene ether resin (NORYL PKN4752 manufactured by SABIC Innovative Plastics IP BV), and 0.4 parts by weight of talc (TALCAN Powder PK-S manufactured by Hayashi Kasei Co., Ltd.) were fed into a 40 mm diameter co-rotating intermeshing twin-screw extruder (first extruder) at a total feed rate of 50 kg / hr. The cylinder temperature after the feed section of the twin-screw extruder was set to 280 °C, and the feed materials were melt-mixed. Next, 8.0 parts by weight of mixed pentane (a mixture of 80 wt% n-pentane and 20 wt% isopentane manufactured by SK Sangyo Co., Ltd.) was injected into the cylinder after the feed section of the twin-screw extruder and further melt-mixed per 100 parts by weight of the melt obtained after melt-mixing. The resulting melt (melt impregnated with the blowing agent) was then fed to a 90 mm diameter single-screw extruder (second extruder) through a continuation pipe set at 250°C. A gear pump set at 210°C and a diverter valve were connected to the tip of the single-screw extruder, and a die set at 290°C and having 54 small holes with a diameter of 0.65 mm and a land length of 5.0 mm was connected downstream of the diverter valve. The cylinder temperature of the single-screw extruder was then set to 210°C to knead the melt, and the melt obtained by melt kneading was extruded through the die connected to the tip of the single-screw extruder at an extrusion (discharge) rate of 54 kg / hr into pressurized water at a temperature of 80°C and a water pressure of 1.0 MPa.

[0110] Immediately after that, the melt was cut into particles using a six-blade rotary cutter at 3450 rpm, forming expandable resin particles for in-mold molding. The average particle weight of the resulting expandable resin particles was 2.2 mg.

[0111] [Formation of pre-expanded particles] The resulting expandable resin particles were placed in a pre-expander and expanded by introducing steam at 0.1 MPa for 150 seconds. This resulted in the formation of pre-expanded particles. The bulk expansion ratio of the resulting pre-expanded particles was 30 times (cc / g).

[0112] [Production of in-mold foamed synthetic resin products (PPE-based resin foamed products)] The obtained pre-expanded particles were filled into a mold (in-mold molding - mold for seedling trays) attached to a foamed polypropylene molding machine, and 0.12 MPa of steam was introduced for 60 seconds to cause in-mold foaming. The mold was then cooled with water until the pressure of the resin foam molding in the mold reached 0.015 MPa (gauge pressure), producing a sample of a PPE-based resin foam molding. The cracking gap was adjusted so that the thickness of the side wall was thinner than the thickness of other parts, and the degree of compression of the side wall of the pot part was increased compared to other parts, thereby reducing the expansion ratio of the side wall. The sample had an average density of 35.9 kg / m 3 (Expansion ratio 30 times), density of inner wall of side wall 108 kg / m 3 (Foaming ratio: 10 times), outer wall density of side wall: 72 kg / m 3 It is a rectangular PPE-based resin foam molded body (96 seedling pot holes) with an expansion ratio of 15 times, a closed cell ratio of 81% in the side wall, a sloped inner surface of the pot, and protrusions on four points on the inner surface.

[0113] The obtained sample was evaluated in the same manner as in Example 1. The measurement results and evaluation results are shown in Table 1.

[0114] Example 4 Average density of synthetic resin foam molding: 119.8 kg / m 3 (Expansion ratio 10 times), inner wall density of side wall 240 kg / m 3 (Expansion ratio 5 times), outer wall density of side wall 150 kg / m 3 A sample of a PC resin foam molded article was prepared and evaluated in the same manner as in Example 1, except that the expansion ratio was 8 times and the closed cell ratio of the side wall was 85%. The evaluation results are shown in Table 1.

[0115] Example 5 Average density of synthetic resin foam molding: 40.2 kg / m 3 (Expansion ratio 29.8 times), density of inner and outer wall of side wall 40.2 kg / m 3A sample of a PC resin foam molded article was prepared and evaluated in the same manner as in Example 1, except that the expansion ratio was the same (29.8 times) and the closed cell ratio of the side wall was 75%. The evaluation results are shown in Table 1.

[0116] Example 6 A sample of a PC resin foam molded article was prepared and evaluated in the same manner as in Example 1, except that no ridges were provided on the inner surface of the pot portion. The evaluation results are shown in Table 1.

[0117] Example 7 A sample of a PC resin foam molded article was prepared and evaluated in the same manner as in Example 1, except that a mold having a shape such that the upper and lower inner areas of the pot portion were the same was used. The seedling raising tray of Example 7 does not have a slope on the inner surface of the pot portion. The measurement results and evaluation results are shown in Table 1.

[0118] (Comparative Example 1) Except for changing the synthetic resin to a polypropylene-based resin (PP-based resin), a sample of a PP-based resin expansion molded article was produced and evaluated in the same manner as in Example 1. The measurement results and evaluation results are shown in Table 1.

[0119] (Comparative Example 2) A sample of a polystyrene resin foam molded article was prepared and evaluated in the same manner as in Example 2, except that the methacrylic acid-modified polystyrene resin (G9001 manufactured by PS Japan Co., Ltd.) was replaced with a polystyrene resin (680 manufactured by PS Japan Co., Ltd.). The measurement and evaluation results are shown in Table 1.

[0120] (Comparative Example 3) Average density of synthetic resin foam molding: 21.8 kg / m 3 (Expansion ratio: 55 times), density of inner and outer wall of side wall: 21.8 kg / m 3 A sample of a PC resin foam molded article was prepared and evaluated in the same manner as in Example 5, except that the expansion ratio was the same as that of Example 5 (55 times) and the closed cell ratio of the side wall was 75%. The measurement and evaluation results are shown in Table 1.

[0121] [Table 1] [Industrial Applicability]

[0122] The present invention can be used, for example, in seedling raising trays that require heat resistance. [Explanation of symbols]

[0123] 1 Tray body 2 Pot section 3 Plate-shaped part 10 seedling trays 21 Inner wall 21a Inside surface 21b Inner bottom surface 22 Exterior wall 22a External surface 22b Outer bottom surface 23 Convex strip

Claims

1. Equipped with a tray body, The seedling tray comprises a tray body made of a synthetic resin foam having a glass transition temperature of 110°C or higher and an expansion ratio of 5 to 50 times.

2. The tray body has a pot portion for forming a seedling pot, 2. The seedling raising tray according to claim 1, wherein the pot portion has a dimensional change rate of 2% or less before and after heating with steam at 100°C for 2 hours.

3. The pot portion has an inner wall portion and an outer wall portion, The seedling raising tray according to claim 2 , wherein the foaming ratio of the inner wall portion is smaller than the foaming ratio of the outer wall portion.

4. The inner wall portion of the pot portion has an inclined surface that is inclined so that the distance between the inner surfaces facing each other becomes smaller as the surface goes from the top to the bottom, 4. The seedling raising tray according to claim 2, wherein the inclined surface has at least one protruding ridge extending from the top to the bottom.

5. 3. The seedling tray according to claim 1, wherein the synthetic resin is any one resin selected from the group consisting of polycarbonate-based resins, heat-resistant polystyrene-based resins, and polyphenylene ether-based resins.

6. A method for manufacturing a seedling tray, comprising: a tray body; and the tray body comprising a synthetic resin foam having a glass transition temperature of 110°C or higher and an expansion ratio of 5 to 50 times, a filling step of filling a mold with the pre-expanded particles of the synthetic resin; and a foaming step of foaming the pre-foamed synthetic resin particles to produce the tray body.

7. A method for treating a seedling tray, comprising a heating step of heat-treating the seedling tray according to any one of claims 1 to 3.

8. A filling step of filling the pot portion of the tray body with culture soil in the seedling tray according to any one of claims 1 to 3; A method for manufacturing a seedling tray with culture soil, comprising: a solidification step of treating the culture soil filled in the filling step with steam to solidify the culture soil.

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