Pulp molded container

Abstract

A pulp molded container (10) is provided with a container body (11) and a synthetic resin layer (11) formed by coating at least one surface of the container body (11) with a synthetic resin. The synthetic resin layer (12) is composed of a plurality of unit resin layers (12a, 12b) in multiple layers. The innermost resin layer (12a) does not contain an organic substance that melts at a temperature of 250°C or lower, and the outermost resin layer (12b) contains an anti-blocking material.

Description

Pulp molded container

[0001] This invention relates to a pulp molded container, and more particularly to a pulp molded container having a synthetic resin layer formed on the inner and outer surfaces of the container body by coating with synthetic resin.

[0002] As containers for storing food and other items, plastic containers made from molded synthetic resin materials and paper containers made by folding and gluing together blanks of cardboard are well known. These are widely used because they are lightweight, inexpensive, and disposable, but plastic containers cannot be disposed of as combustible waste, and paper containers have the disadvantage that the adhesive will peel off due to the heat of the contents.

[0003] Therefore, pulp molded containers are also used, which are made from pulp materials such as reeds, sugarcane, and wood, and molded using a mold. Unlike plastic containers, pulp molded containers can be disposed of as combustible waste, and unlike paper containers, they are molded as a single piece, so there is no risk of the adhesive coming undone.

[0004] Unlike plastic containers, these pulp molded containers have poor water resistance, and if the surface is rubbed, paper dust derived from the raw materials may be generated. For this reason, for containers that store contents containing a lot of moisture, such as food, it is common to form a water-resistant layer by laminating a thermoplastic film on the inner surface, as shown in Patent Document 1. When forming a water-resistant layer on the inner surface of a pulp molded container in this way, the usual method is as shown in Patent Document 1, in which the pulp molded container is set in a mold with many suction holes, a thermoplastic film is supplied between the mold and a heater placed above it, and the thermoplastic film heated by the heater is drawn toward the inner surface of the pulp molded container by the suction force of the suction holes in the mold and welded to it.

[0005] Such a suction method utilizes the fact that the pulp mold itself has air permeability. However, when a water-resistant layer is formed on the inner surface of the container, its air permeability will be lost. Therefore, when it is desired to form a water-resistant layer on the outer surface of the container as well in order to further improve water resistance and suppress paper dust generation, the suction method cannot be used. Regarding the outer surface of the pulp mold container, it is possible to use other methods such as manually attaching a film, but this is laborious and increases the manufacturing cost.

[0006] On the other hand, instead of attaching films to the inner and outer surfaces of the pulp mold container, there is also a technique of applying a synthetic resin to the inner and outer surfaces of the pulp mold container as in Patent Document 2. According to such a technique, it is relatively easy to form a film made of synthetic resin on both the inner and outer surfaces of the pulp mold container.

[0007] By the way, when forming a film made of synthetic resin on the inner and outer surfaces of the pulp mold container as in Patent Document 2, the film may contain a wax such as olefin wax. When such a wax is contained in the film, even when the containers are separated and used after being packed or stored in a stacked state (also referred to as a stacking state), it is possible to prevent the containers from sticking to each other (also referred to as blocking). That is, the wax functions as an anti-blocking material. In addition, due to the water-repellent action of the wax itself, when the pulp mold container is used as a food storage container, even when storing a food with a lot of moisture in the container, it also has the effect of suppressing the penetration of moisture into the container.

[0008] Japanese Unexamined Patent Application Publication No. 2012-158160, Japanese Unexamined Patent Application Publication No. 2001-114247

[0009] However, such waxes have the property of being easily melted by heating, and thus have the following problems. For example, as a food storage container, when a container body made of a pulp mold is provided with a coating of a synthetic resin on both the inner and outer surfaces thereof and the coating contains a wax such as an olefin-based wax, if food is stored in this container immediately after heat cooking, the wax in the coating may be melted by heat. The same problem also occurs when heat cooking is performed on the production line with food stored in this container, or when heating with a microwave oven from a state where the food is cooled in a frozen or refrigerated state.

[0010] When the wax in the coating is melted by heat in this way, the wax escapes from the coating, and a large number of fine defect portions, that is, pores that are not visible, are formed as traces of the wax escaping from the coating. Then, oil and the like penetrate into the container body made of a pulp mold through these pores, resulting in stains and a deterioration in the appearance (design) of the container. In severe cases, oil and the like may penetrate from the inner surface to the outer surface of the container body, and there is a risk of contaminating the production line used when storing food in the container or soiling fingers and clothing during consumption by general consumers.

[0011] On the other hand, for the purpose of preventing the penetration of such oil and the like into the container body, an organic compound containing fluorine or a resin containing fluorine may be added to the container body itself or the coating. With such a configuration, even if there are problems such as wax escaping from the coating due to heating or defects due to pinholes in the coating itself, it is possible to prevent the penetration of oil into the container body.

[0012] However, regarding organic substances containing fluorine such as PFAS (a general term for perfluoroalkyl compounds and polyfluoroalkyl compounds among organic fluorine compounds), regulations on their usage amounts and bans on their use have been initiated due to their effects on the human body such as carcinogenicity. Therefore, it has become difficult to use them in the container body or the coating.

[0013] The present invention was made to solve the above-mentioned problems, and aims to suppress the penetration of oil and other substances into the container body of a pulp molded container equipped with a synthetic resin layer formed by coating with synthetic resin, even when heat is applied.

[0014] To achieve the above objective, the pulp molded container according to the invention comprises a container body made of pulp mold and a synthetic resin layer formed by coating of synthetic resin on at least one of the inner or outer surfaces of the container body, wherein the synthetic resin layer is composed of multiple unit resin layers, and the innermost resin layer in contact with the container body does not contain organic matter that melts at a temperature of 250°C or lower. The organic matter that melts in a predetermined temperature range and is not contained in the innermost resin layer may be a wax containing either natural wax or synthetic wax. More preferably, the wax used as the organic matter that melts in a predetermined temperature range and is not contained in the innermost resin layer is a polyolefin-based wax, and among these, a polyethylene-based wax.

[0015] With this configuration, the innermost resin layer does not contain organic matter that melts within a predetermined temperature range, making it less likely for minute defects to occur due to heating. In other words, the innermost resin layer can maintain a dense structure even after heating, which makes it possible to suppress the penetration of oil and other substances into the pulp molded container body.

[0016] In the pulp molded container according to the invention, neither the container body nor the synthetic resin layer may contain organic substances containing fluorine (F), particularly organofluorine compounds.

[0017] This configuration makes it possible to suppress the penetration of oil and other substances into the pulp molded container body, and also creates a safe pulp molded container that does not pose a risk of adverse effects on the human body due to organic matter containing fluorine (F).

[0018] In the pulp molded container according to the invention, the outermost resin layer of the synthetic resin layer may contain an antiblocking material. The content of the antiblocking material is not particularly limited, but it is preferably 0.5% to 30% by weight as solid content in the outermost resin layer, and more preferably 5% to 30% by weight. Within this range, the desired antiblocking properties can be achieved. The antiblocking material may contain a wax that includes either a natural wax or a synthetic wax, and the synthetic wax may include a polyolefin-based wax, and the polyolefin-based wax may include a polyethylene-based wax. In addition to these waxes, other examples include ionomer resins such as ionomer resins of ethylene unsaturated carboxylic acid copolymers.

[0019] This configuration makes it possible to suppress the penetration of oil and other substances into the pulp molded container body, and also to create a pulp molded container with excellent anti-blocking properties. In other words, the pulp molded container body has a dense innermost resin layer that is less prone to damage even when heat is applied, and the outermost layer is designed to suppress blocking when the containers are stacked on top of each other. Thus, it is possible to achieve both suppression of oil and other substances penetration into the container body and anti-blocking properties.

[0020] Furthermore, in order to achieve the above objectives, another embodiment of the pulp molded container according to the invention comprises a container body made of pulp mold and a synthetic resin layer formed by coating a synthetic resin on at least one of the inner or outer surfaces of the container body, wherein the synthetic resin layer is composed of a plurality of unit resin layers, and the number of pinholes penetrating from the outermost resin layer to the innermost resin layer in contact with the surface of the container body is 0 / cm. ２ 0.2 pieces / cm or more ２ The following is the result.

[0021] With this configuration, the number of pinholes penetrating from the outermost resin layer to the innermost resin layer in contact with the surface of the container body is 0 / cm. ２0.2 pieces / cm or more ２ For the reasons described below, it is possible to suppress the penetration of oil and other substances into the pulp molded container body. In particular, even when a wax that is easily melted by heating is used as an antiblocking material to impart antiblocking properties to the synthetic resin layer, the number of pinholes penetrating the synthetic resin layer is small, which makes it possible to suppress the penetration of oil and other substances into the pulp molded container body.

[0022] As the present invention is configured as described above, it is possible to provide a pulp molded container in which the penetration of oil and other substances into the container body is suppressed even when heat is applied to the pulp molded container.

[0023] A longitudinal cross-sectional view of the pulp molded container according to the first embodiment. A schematic diagram showing the manufacturing method of the pulp molded container according to the first embodiment. A schematic diagram showing the manufacturing method of the pulp molded container according to the first embodiment. A schematic diagram showing the manufacturing method of the pulp molded container according to the first embodiment. A schematic diagram showing the manufacturing method of the pulp molded container according to the first embodiment. A schematic diagram of the dipping method. A schematic diagram of the dipping method. A schematic diagram of the dipping method. A schematic diagram of the dipping method.

[0024] The first embodiment of the present invention will be described below with reference to the drawings. Note that the drawings schematically represent embodiments of the present invention, and the shapes, proportions, thicknesses, etc., do not accurately reflect the content of the invention.

[0025] Figure 1 is a longitudinal cross-sectional view of a pulp molded container according to the first embodiment. Referring to Figure 1, the pulp molded container 10 has a multilayer structure consisting of a container body 11 and a synthetic resin layer 12 in the thickness direction. The pulp molded container 10 is also composed of a bottom, a side wall rising from the outer edge of the bottom, and a flange 13 extending almost horizontally from the upper edge of the side wall, and the storage space partitioned by the bottom and side wall opens upward.

[0026] The container body 11 is made of a pulp mold formed from wood pulp using wood materials such as coniferous trees and broad-leaved trees, non-wood pulp using non-wood materials obtained from reeds and sugarcane, or a mixed pulp of wood pulp and non-wood pulp. Here, it is preferable that the container body 11 does not contain organic substances containing fluorine (F), particularly organic fluorine compounds. With this configuration, it is possible to obtain a safe pulp mold container 10 that is not likely to have an adverse effect on the human body due to organic substances containing fluorine (F). Note that if the container body 11 is configured not to contain organic fluorine compounds or the like, there is a risk that oil and the like may penetrate as it is. However, by configuring the synthetic resin layer 12 as described below, the penetration of oil and the like into the container body 11 is suppressed, so there is no problem.

[0027] The synthetic resin layer 12 is formed on the entire inner and outer surfaces of the container body 11, excluding the synthetic resin non-coated portion 13a at the outer end of the flange portion 13. With this configuration, when a moisture-containing content such as food is stored in the pulp mold container 10, the moisture of the food or the like does not penetrate into the container body 11, and the generation of paper dust from the container body 11 can be suppressed.

[0028] The resin used in the synthetic resin layer 12 is not particularly limited. For example, acrylic, styrene-acrylic, ethylene-vinyl acetate, styrene-butadiene rubber, polyvinyl alcohol, vinylidene chloride silicone resins, copolymers thereof, and combinations thereof can be exemplified. Among them, synthetic resin emulsions and water-soluble resins that can use an aqueous solvent are preferable.

[0029] Further, as in the embodiment described below, the synthetic resin layer 12 is composed of multiple unit resin layers in multiple layers, and includes at least two layers, namely the innermost resin layer 12a and the outermost resin layer 12b. The innermost resin layer 12a preferably has a dry coating amount of 5 g / m ２ or more and 50 g / m ２ or less, more preferably a dry coating amount of 10 g / m ２ or more and 40 g / m ２ or less, and even more preferably a dry coating amount of 15 g / m ２ or more and 30 g / m２ It is even more preferable to form it as follows: The outermost resin layer 12b has a dry coating amount of 0.5 g / m². ２ 20g / m or more ２ It is preferable to form it as follows, with a dry coating amount of 1.0 g / m². ２ 10g / m or more ２ It is more preferable to form it as follows, with a dry coating amount of 2.0 g / m². ２ 8.0g / m or more ２ It is even more preferable to form it as follows: By forming the innermost resin layer 12a and the outermost resin layer 12b within this range of dry coating amounts, it is possible to effectively suppress the penetration of oil and other substances into the pulp molded container body. When the synthetic resin layer 12 is composed of two layers, the innermost resin layer 12a and the outermost resin layer 12b, the total dry coating amount for both layers is 6.0 g / m². ２ 70.0g / m or more ２ It is preferable to form it as follows, with a dry coating amount of 12.0 g / m². ２ 60.0g / m or more ２ It is more preferable to form it as follows, with a dry coating amount of 17.0 g / m². ２ 48g / m or more ２ It is even more preferable to form them as follows. By setting the range in this way, the functions of each layer, the innermost resin layer 12a and the outermost resin layer 12b, can be effectively expressed. Also, in this case, the ratio of the dry coating amount of the outermost resin layer 12b to the dry coating amount of the innermost resin layer 12a ("dry coating amount of outermost resin layer 12b g / m") ２ "÷ "Dry coating amount of innermost resin layer 12a g / m ２ The ratio is preferably 0.4 or less, more preferably 0.3 or less, and even more preferably 0.2 or less. This range allows the functions of each layer, the innermost resin layer 12a and the outermost resin layer 12b, to be effectively expressed. The lower limit of this ratio is preferably 0.1 or more, and within this range, the function of the outermost resin layer 12b is sufficiently expressed.

[0030] Furthermore, it is preferable that the dry coating amount of the outermost resin layer 12b is smaller than the dry coating amount of the innermost resin layer 12a. By maintaining this relationship, for example, when imparting antiblocking properties to the outermost resin layer 12b as described later, although in extreme cases the antiblocking properties only need to be applied to the surface of the outermost resin layer 12b, typically the entire outermost resin layer 12b will contain antiblocking properties. In that case, if the dry coating amount of the outermost resin layer 12b is large, the amount of antiblocking material added to the outermost resin layer 12b will also increase proportionally, and there is a risk that the cost of the final pulp molded container will increase even if the antiblocking properties do not change. Also, since the innermost resin layer 12a provides a certain degree of barrier performance, the dry coating amount of the outermost resin layer 12b can be made smaller than that of the innermost resin layer 12a. Note that if one or more other resin layers are formed as unit resin layers between the innermost resin layer 12a and the outermost resin layer 12b, the dry coating amount of the resin layer can be formed within the same range as that of the outermost resin layer 12b. Furthermore, the dry coating amount for the innermost resin layer 12a can be determined by measuring the weight of the container body 11 before and after the formation of the innermost resin layer 12a, and dividing the difference in weight by the area to which the innermost resin layer 12a is coated (usually the surface area of ​​the container body 11). For the outermost resin layer 12b, the weight of the container body 11 with the innermost resin layer 12a (or the unit resin layer to which the outermost resin layer 12b directly contacts if another unit resin layer is formed between the outermost resin layer 12b and the innermost resin layer 12a) formed before the formation of the outermost resin layer 12b, and the weight of the pulp molded container 10 after the formation of the outermost resin layer 12b can be determined by measuring the difference in weight and dividing the area to which the outermost resin layer 12b is coated (usually approximately the same as the surface area of ​​the container body 11). However, when calculating the dry coating amount of each layer from a pulp molded container after the formation of the synthetic resin layers, the calculation method is not limited to the above method.

[0031] The presence of the uncoated synthetic resin portion 13a means that when the pulp molded container 10 is used as a food container for frozen foods or the like and heated in a microwave oven, the water vapor generated from inside the container body 11 containing moisture is discharged to the outside through the uncoated synthetic resin portion 13a without accumulating, thus suppressing the formation of blisters. In particular, if the opening of the pulp molded container 10 is sealed with a sealant film, if blisters form on the flange portion 13 during microwave heating, the sealant film fused to the flange portion 13 may peel off unintentionally, potentially causing leakage of contents and resulting burns to the hands. This is suppressed by the uncoated synthetic resin portion 13a.

[0032] Furthermore, the synthetic resin layer 12 is composed of multiple unit resin layers, as in the embodiment described later, and comprises at least two layers: an innermost resin layer 12a and an outermost resin layer 12b. The presence of the outermost resin layer 12b makes it possible to suppress paper peeling (a condition in which a part of the container body 11 peels off together with the sealant film in the portion of the pulp molded container 10 where the sealant film is formed) when the sealant film is peeled off. Paper peeling is undesirable because it makes it difficult to separate and dispose of the pulp molded container 10 and the sealant film. The reason why the presence of the outermost resin layer 12b suppresses paper peeling is not clear, but in the case of a single resin layer, if the resin layer penetrates the container body 11 and adheres firmly, the resin layer will peel off together with the sealant film when it is peeled off, and consequently the pulp fibers of the pulp molded container 10 will also peel off together with the resin layer. On the other hand, in the present invention, the presence of an outermost resin layer 12b and an innermost resin layer 12a (or another unit resin layer if there is one between the outermost resin layer 12b and the innermost resin layer 12a) means that the outermost resin layer 12b acts as an interference layer, mitigating the direct transmission of the peeling force of the sealant film to the pulp molded container 10. Furthermore, even if the adhesion between the sealant film's sealing layer and the outermost resin layer 12b is strong and the outermost resin layer 12b peels off together when the sealant film is removed, it is presumed that the peeling will be limited to only the outermost resin layer 12b.

[0033] Preferably, the proportion of the uncoated synthetic resin portion 13a to the surface area of ​​the flange portion 13 is 1% or more and 10% or less. In this case, since most of the surface area of ​​the flange portion 13 is covered with the synthetic resin layer 12, it is possible to sufficiently suppress the penetration of moisture from food etc. into the container body 11 and suppress the generation of paper dust, while also suppressing the occurrence of blisters and appearance defects in a balanced manner. In this embodiment, an uncoated synthetic resin portion 13a is formed, but it is also possible to not form an uncoated synthetic resin portion 13a on the pulp molded container 10, for example, by forming the synthetic resin layer 12 on the outer end of the flange portion 13.

[0034] In the first embodiment, the synthetic resin layer 12 in the pulp molded container 10 is composed of a multilayer structure made up of multiple unit resin layers of different types. In Figure 1, the synthetic resin layer 12 consists of two layers, an innermost resin layer 12a and an outermost resin layer 12b, with the innermost resin layer 12a in contact with the container body 11.

[0035] The innermost resin layer 12a has a layer structure that does not contain organic matter that melts at temperatures below 250°C. Furthermore, it is preferable that the innermost resin layer 12a has a layer structure that does not contain organic matter that melts at temperatures between 60°C and 250°C, and it is even more preferable that the innermost resin layer 12a has a layer structure that does not contain organic matter that melts at temperatures between 60°C and 150°C. Examples of organic matter that melts at temperatures below 250°C include waxes containing either natural waxes or synthetic waxes, or fine particles of synthetic resin (such fine particles may be dispersed in a solution during compounding). In the case of synthetic waxes, polyolefin waxes are an example, and among them, polyethylene waxes are a particular example. By making the innermost resin layer 12a a layer that does not contain organic matter that melts at such a predetermined temperature, it becomes less likely that fine defects will occur due to heating. In other words, since the innermost resin layer 12a can maintain a dense layer even after heating, it is possible to suppress the penetration of oil and other substances into the container body 11.

[0036] On the other hand, the outermost resin layer 12b is configured to include an antiblocking material. The amount of antiblocking material is not particularly limited, but it is preferable that it be contained in the outermost resin layer 12b as solid content of 0.5% to 30% by weight, and more preferably 5% to 30% by weight. Within this range, the desired antiblocking properties can be achieved. Examples of this antiblocking material include wax containing either natural wax or synthetic wax, fine particles of synthetic resin (such fine particles may be dispersed in a solution during compounding), or inorganic powders such as talc, diatomaceous earth, calcium carbonate, feldspar, or quartz. Among these, synthetic wax is preferred, and among synthetic waxes, those containing polyolefin-based wax are more preferred because they disperse well in the outermost resin layer, and those containing polyethylene-based wax as polyolefin-based wax are even more preferred. With this configuration, it is possible to suppress the penetration of oil and other substances into the container body 11, and a pulp molded container 10 with excellent antiblocking properties can be obtained.

[0037] Thus, in the pulp molded container 10 of the first embodiment, the synthetic resin layer 12 has an innermost resin layer 12a that is dense and resistant to damage even when heat is applied, and an outermost resin layer 12b that can suppress blocking when containers are stacked. In other words, both suppression of oil penetration into the container body 11 and anti-blocking properties are achieved. It should be noted that each resin layer constituting the synthetic resin layer 12 may have defects due to microscopic pinholes in some parts. However, even if such pinholes occur, it is extremely rare for them to penetrate all the resin layers constituting the synthetic resin layer from top to bottom into the container body 11. In addition, as described above, since the innermost resin layer 12a is a dense layer even when affected by heat, it is possible to significantly suppress the penetration of oil into the container body compared to conventionally known pulp molded containers with a coating. In this embodiment, the pulp molded container 10 has the above-described configuration, and the number of pinholes penetrating from the outermost resin layer 12b to the innermost resin layer 12a is 0 / cm. ２ 0.2 pieces / cm or more ２ The following is observed, and in fact, oil penetration is suppressed to an extremely high degree.

[0038] Furthermore, it is preferable that, similar to the container body 11, neither the innermost resin layer 12a nor the outermost resin layer 12b of the synthetic resin layer 12 contains organic matter containing fluorine (F), and in particular does not contain organofluorine compounds. With this configuration, it is possible to suppress the penetration of oil and other substances into the container body 11, and a safe pulp molded container 10 can be made without the risk of adverse effects on the human body due to organic matter containing fluorine (F).

[0039] Figures 2A and 2B show an outline of the manufacturing method for the pulp molded container 10 of the first embodiment. First, as shown in Figure 2A, a container connecting body 11' is prepared, in which container bodies 11 made of at least two or more pulp molds are connected. In the container connecting body 11', the flange portions 13 of adjacent container bodies 11 are integrally connected, and this connected portion constitutes the connecting portion. In the container connecting body 11', the manner in which the container bodies 11 are connected is not limited to those shown, as long as there are multiple container bodies 11, but examples include four connected in a single row, or a total of eight connected in four horizontal rows and two vertical rows.

[0040] The container connector 11' can be prepared by a known process of forming a pulp mold. For example, the process may consist of a pulp suspension preparation step of preparing a pulp suspension, a papermaking step of papermaking pulp from the pulp suspension using a mesh die, and a heating and pressing step of forming the container connector 11', which is made of pulp mold, using a first press die provided at the bottom of the mesh die and a second press die located in the opposite direction from the first press die, while heating the papermaking material obtained in the papermaking step.

[0041] Next, as shown in Figure 2B, a synthetic resin solution that will become the innermost resin layer 12a of the synthetic resin layer 12 is applied to both the inner and outer surfaces of the container connector 11'. This process forms the innermost resin layer 12a of the synthetic resin layer 12 on both the inner and outer surfaces of the container connector 11'.

[0042] The application method for forming the innermost resin layer 12a is not particularly limited and can include spraying, brushing, or dipping. The process of applying the synthetic resin solution that will become the innermost resin layer 12a preferably includes a drying step in which the synthetic resin solution applied to the container connector 11' is dried to form a dry coating that will become the innermost resin layer 12a, and it is even more preferable that the drying step be heat drying. This drying step makes the innermost resin layer 12a a dense layer. In particular, if the synthetic resin solution uses an aqueous solvent, it takes a long time for the synthetic resin solution to air dry after application, which may reduce the productivity of pulp molded containers, so it is preferable to include a drying step. If the inside of the innermost resin layer 12a is not sufficiently dried, it will be difficult for the innermost resin layer 12a to become a dense layer, and moisture or solvent will remain inside the innermost resin layer 12a when the next outermost resin layer 12b is formed. Therefore, when food or other items are placed in the final pulp molded container and heated, moisture and solvents inside the innermost resin layer 12a may turn into vapor, potentially causing partial swelling or peeling of the synthetic resin layer 12, which is known as blistering.

[0043] Furthermore, as shown in Figure 2C, a synthetic resin solution that will become the outermost resin layer 12b of the synthetic resin layer 12 is applied to both the inner and outer surfaces of the container connector 11' on which the innermost resin layer 12a is laminated. This process forms the outermost resin layer 12b of the synthetic resin layer 12 on both the inner and outer surfaces of the container connector 11'. Here, the innermost resin layer 12a and the outermost resin layer 12b have different layer structures. As described above, the entire synthetic resin layer 12 is formed by the sequential lamination of the innermost resin layer 12a and the outermost resin layer 12b.

[0044] The application method for forming the outermost resin layer 12b is not particularly limited and can include spraying, brushing, or dipping. It is preferable that the process of applying the synthetic resin solution that will become the outermost resin layer 12b also includes a drying process to dry the synthetic resin solution after application to form a dry coating film of the outermost resin layer 12b. This drying process ensures that the outermost resin layer 12b is a homogeneous layer. In particular, if the synthetic resin solution uses an aqueous solvent, natural drying of the synthetic resin solution after application may take a long time, potentially reducing the productivity of pulp molded containers. If the outermost resin layer 12b is not sufficiently dried, and if it contains antiblocking material, the antiblocking material may settle during the long natural drying period. Therefore, the proportion of antiblocking material on the surface of the outermost resin layer 12b may decrease, potentially preventing the desired antiblocking properties from being properly achieved. Furthermore, if the inside of the outermost resin layer 12b is not sufficiently dried, moisture or solvent will remain inside the outermost resin layer 12b. As a result, when food or other items are placed in the final pulp molded container and heated, the moisture or solvent inside the outermost resin layer 12b will turn into vapor, which may cause partial swelling or peeling of the synthetic resin layer 12, known as blistering.

[0045] Next, as shown in Figure 2D, the container connector 11' on which the synthetic resin layer 12 is formed is cut using a cutter C or other appropriate means in the middle of the connecting portion that connects adjacent container bodies 11. This separates the multiple pulp molded containers 10 from a connected state into individual containers. At the same time, the outer edge of the flange portion 13 is cut, so that each pulp molded container 10 has at least one cut surface on the flange portion 13, and this cut surface becomes an uncoated synthetic resin portion 13a where the synthetic resin layer 12 is not formed.

[0046] For the sake of convenience in describing the embodiment, the individual pulp molded containers 10 were cut from the container connector 11' as described above. However, a pulp molded container 10 may also be made by preparing a single container body 11 and then forming the synthetic resin layer 12 described above on it. In this case, the synthetic resin layer 12 may also be formed on the outer end of the flange portion 13 of the pulp molded container 10.

[0047] Furthermore, in a second embodiment of the present invention, the container body is made of pulp mold and comprises a synthetic resin layer formed by coating a synthetic resin on at least one surface of the container body, wherein the synthetic resin layer is composed of a plurality of unit resin layers, and in the unit resin layer, the number of pinholes penetrating from the outermost resin layer furthest from the surface of the container body to the innermost resin layer in contact with the surface of the container body is 0 / cm. ２ 0.2 pieces / cm or more ２ The following pulp molded containers are examples. This embodiment corresponds to the description in paragraph 0021 of the means for solving the invention described herein.

[0048] In the second embodiment, the same configuration as in the first embodiment can be adopted, except that the configuration of the synthetic resin layer 12 is different from that of the first embodiment. In the second embodiment as well, the configuration of the synthetic resin layer 12 consists of two layers, an innermost resin layer 12a and an outermost resin layer 12b, and the innermost resin layer 12a is in contact with the container body 11. However, unlike the first embodiment, the innermost resin layer 12a can have the same configuration as the outermost resin layer 12b. That is, the innermost resin layer 12a can also have a configuration that includes an antiblocking material, similar to the outermost resin layer 12b.

[0049] In the second embodiment, if the synthetic resin layer 12 is configured in this way, for example, if the innermost resin layer 12a also contains a wax such as an olefin-based wax as an antiblocking material, the wax in the innermost resin layer 12a may also melt when heated, and the wax may escape from the innermost resin layer 12a, potentially forming numerous fine defects, i.e., invisible holes, in the coating as traces of the wax loss. However, in the second embodiment, unlike conventionally known pulp molded containers, the synthetic resin layer 12 consists of two layers: an innermost resin layer 12a and an outermost resin layer 12b. Therefore, even if such holes are formed in the innermost resin layer 12a and the outermost resin layer 12b, it is rare for the holes formed in each layer to penetrate both the innermost resin layer 12a and the outermost resin layer 12b at the same location.

[0050] Furthermore, the number of pinholes penetrating from the outermost resin layer 12b to the innermost resin layer 12a is 0 / cm. ２ 0.2 pieces / cm or more ２ The configuration is as follows. With this configuration, even in the second embodiment, oil penetration can be suppressed to a higher level compared to conventionally known pulp molded containers with a coating. The type and content of the antiblocking material in the innermost resin layer can be the same as that of the outermost resin layer.

[0051] In the second embodiment, it is preferable that the container body 11 and the synthetic resin layer 12 do not contain organic matter containing fluorine (F), and in particular do not contain organofluorine compounds, as is the case in the first embodiment. Also, in the second embodiment, the method for manufacturing the pulp molded container 10 is the same as in the first embodiment.

[0052] The present invention will be further clarified by the following examples and comparative examples. Pulp molded containers, which are Examples 1 to 8 and Comparative Examples 1 to 6, were manufactured as described below. Examples 1 to 3 and Examples 7 and 8 correspond to the first embodiment, and Examples 4 to 6 correspond to the second embodiment.

[0053] (Example 1) A container assembly was prepared, consisting of multiple container bodies made of pulp mold, each having a bottom and side walls rising from the bottom, with a substantially flat flange extending around the entire circumference at the upper end of the side walls. The adjacent container bodies were molded with their respective flanges connected. The dimensions of each individual container body are as follows: Container body: 20 cm wide (including flange) x 15 cm long (including flange) x 5 cm high Container body storage area: 17.5 cm wide x 12.5 cm long x 5 cm high Flange width: 1.5 cm (including connecting part) Container body cross-sectional thickness: approximately 1 mm

[0054] Next, synthetic resin layers were formed on the inner and outer surfaces of the container connector. The synthetic resin layer consisted of two layers: an outermost resin layer and an innermost resin layer. Both layers contained 15% by weight of polyethylene-based wax as a solid component as an antiblocking material. The unit resin layers of the synthetic resin layer were applied by dipping, as shown in Figures 3A and 3C, by sequentially immersing the entire container connector 11' in coating solution tanks B1 and B2 containing synthetic resin solutions S1 and S2, respectively, and then removing it. As shown in Figures 3B and 3D, any excess synthetic resin solutions S1 and S2 adhering to the container connector 11' was removed by tilting it to an appropriate angle when it was removed from the coating solution tanks B1 and B2. Here, the process shown in Figures 3B and 3D includes a drying step for the synthetic resin solution adhering to the container connector.

[0055] In Figures 3A and 3C, the synthetic resin solutions S1 and S2 were prepared by diluting a styrene-acrylic copolymer (55% by mass of acrylic resin component, 45% by mass of styrene resin component, 38% by mass of solids, with the remaining percentage being mainly water solvent and trace amounts of additives) with water. Polyethylene wax was added to this synthetic resin solution in the proportions described above, along with 2% by weight of other additives such as dispersants (equivalent to the solids content in the synthetic resin layer). The synthetic resin layer, consisting of the outermost and innermost layers, had a total dry coating weight (dry coating amount) of approximately 10 g / m². ２ It was formed in such a way.

[0056] Subsequently, the container assembly with the synthetic resin layer formed on it was cut at the central part (connecting section) where the flange portions of the individual container bodies were connected, thereby separating them into individual pulp molded containers. In the separated pulp molded containers, the synthetic resin layer was not formed on the outer end of the flange portion where it was cut at the connecting section. Through the above steps, the pulp molded container of Example 1 of the present invention was obtained.

[0057] (Example 2) For the synthetic resin layer, the total weight of the coating film after drying (dry coating amount) of the outermost and innermost resin layers was approximately 18 g / m². ２ A pulp molded container of Example 2 of the present invention was obtained in the same manner as in Example 1, except that it was formed in such a manner.

[0058] (Example 3) For the synthetic resin layer, the total weight of the coating film after drying (dry coating amount) of the outermost and innermost resin layers combined was approximately 25 g / m². ２ A pulp molded container of Example 3 of the present invention was obtained in the same manner as in Example 1, except that it was formed in the manner described above. (Example 4) In Example 4, the preparation of the container connector was carried out in the same manner as in Example 1. The synthetic resin layer consisted of two layers: an outermost resin layer and an innermost resin layer. The outermost resin layer contained 15% by weight of polyethylene-based wax as a solid component as an antiblocking material, while the innermost resin layer did not contain polyethylene-based wax as an antiblocking material. Therefore, the same synthetic resin container as in Example 1 was used as the synthetic resin solution S2 for forming the outermost resin layer shown in Figure 3C. However, the synthetic resin solution S1 for forming the innermost resin layer shown in Figure 3A used a styrene-acrylic copolymer (55% by weight of acrylic resin component, 45% by weight of styrene resin component, and 38% by weight of solid component) diluted with water as the synthetic resin. In addition, 2% by weight of other additives such as a dispersant (equivalent to the solid component in the synthetic resin layer) was added to the synthetic resin solution without adding polyethylene-based wax. The synthetic resin layer consists of two layers: the outermost resin layer and the innermost resin layer. The total weight of the dried coating (dry application amount) is approximately 10 g / m². ２ It was formed in such a manner. (Example 5) For the synthetic resin layer, the total weight of the coating film after drying (dry coating amount) of the outermost resin layer and the innermost resin layer was approximately 18 g / m². ２A pulp molded container of Example 5 of the present invention was obtained in the same manner as in Example 4, except that it was formed in the manner described above. (Example 6) For the synthetic resin layer, the total weight of the coating film after drying (dry coating amount) of the outermost resin layer and the innermost resin layer was approximately 25 g / m². ２ A pulp molded container of Example 6 of the present invention was obtained in the same manner as in Example 4, except that it was formed in the manner described above. (Example 7) For the synthetic resin layer, the total weight of the coating film after drying (dry coating amount) of the outermost resin layer and the innermost resin layer was approximately 8 g / m². ２ A pulp molded container of Example 7 of the present invention was obtained in the same manner as in Example 1, except that it was formed in the manner described above. (Example 8) For the synthetic resin layer, the total weight of the coating film after drying (dry coating amount) of the outermost resin layer and the innermost resin layer was approximately 30 g / m². ２ A pulp molded container of Example 8 of the present invention was obtained in the same manner as in Example 1, except that it was formed in such a manner.

[0059] (Comparative Examples 1 to 6) Multiple container bodies made of the same pulp mold as in Example 1 were connected to each other to prepare a container assembly. Unlike Example 1, only one synthetic resin layer was used, and the weight of the coating film after drying (dry coating amount) of the synthetic resin layer was approximately 10 g / m² in Comparative Example 1. ２ In comparative example 2, the amount was approximately 18 g / m². ２ In comparative example 3, the amount was approximately 25 g / m². ２ In Comparative Example 4, the amount was approximately 10 g / m². ２ In Comparative Example 5, the amount was approximately 18 g / m². ２ In comparative example 6, the amount was approximately 25 g / m². ２ It was formed in such a manner. Similar to Example 1, the container joint with the synthetic resin layer was cut to obtain a pulp molded container.

[0060] Oil resistance tests were conducted on the pulp molded containers of Examples 1 to 8 and Comparative Examples 1 to 6. In the oil resistance test, an amount of oil heated to 80°C sufficient to cover the entire bottom was poured into the pulp molded container, and it was left for 10 minutes. After 10 minutes, the state of oil penetration into the container was observed visually, and it was evaluated as follows: ◎ if there was no oil stain, ○ if there was a slight oil stain but no oil seepage, △ if there was both oil stain and oil seepage, and × if there was oil stain and oil seepage throughout.

[0061] Similarly, blocking tests were conducted on the pulp molded containers of Examples 1 to 8 and Comparative Examples 1 to 6. In the blocking test, 100 pulp molded containers of the same specifications (same example, same comparative example) were stacked in the same orientation, left to stand at 60°C for 24 hours, then returned to room temperature and left for 1 hour. After that, the pulp molded containers were separated by hand to check whether blocking occurred. No blocking was evaluated as ○, and blocking occurred as ×.

[0062] Furthermore, for the pulp molded containers of Examples 1 to 8 and Comparative Examples 1 to 6, the condition of the coating surface after drying of the synthetic resin layer was visually observed and evaluated for the presence or absence of drip marks.

[0063] Furthermore, tests were conducted to confirm the presence and number of pinholes penetrating the synthetic resin layer from top to bottom for the pulp molded containers of Examples 1 to 8 and Comparative Examples 1 to 6 (pinhole test). Specifically, to confirm the presence and number of pinholes, room temperature (approximately 25°C) oil was poured into the pulp molded container in an amount sufficient to cover the entire bottom, and left for 30 minutes. After 30 minutes, the state of oil penetration into the container was visually observed, and the presence or absence of oil stains and, if oil stains occurred, the number of oil stains were counted as the number of pinholes. More specifically, if there were pinholes, small, dark-colored, dot-like oil stains appeared at the pinholes, and light-colored oil stains that had penetrated the container body appeared, spreading from the pinholes outwards. The number of dark-colored oil stains, which were the pinholes, was counted. The number of pinholes present at the bottom of the pulp molded container, as confirmed in this way, was divided by the area of ​​the bottom to determine the number of pinholes per unit area (pinholes / cm²). ２ The following was calculated. The results for each example are shown in Table 1, and the results for each comparative example are shown in Table 2.

[0064]

[0065]

[0066] (Example 9) Regarding the synthetic resin layer, the outermost resin layer (dry coating amount: approximately 4 g / m²) ２ ) and the innermost resin layer (dry coating amount: approximately 21 g / m²) ２ The total dry coating amount for the two layers is approximately 25 g / m². ２ A pulp molded container of Example 9 of the present invention was obtained in the same manner as in Example 1, except that it was formed in the manner described above. Note that the dry coating amount ratio (dry coating amount of the outermost resin layer g / m) ２ ÷ Dry coating amount of the innermost resin layer g / m ２ ) was approximately 0.19. (Example 10) In Example 10, the preparation of the container connector was carried out in the same manner as in Example 1. The synthetic resin layer consisted of two layers: an outermost resin layer and an innermost resin layer. The outermost resin layer contained 15% by weight of polyethylene-based wax as a solid component as an antiblocking material, while the innermost resin layer did not contain polyethylene-based wax as an antiblocking material. Therefore, the same synthetic resin container as in Example 1 was used as the synthetic resin solution S2 for forming the outermost resin layer shown in Figure 3C. However, the synthetic resin solution S1 for forming the innermost resin layer shown in Figure 3A used a styrene-acrylic copolymer (55% by mass of acrylic resin component, 45% by mass of styrene resin component, and the remaining % mainly consisting of water solvent with trace amounts of additives; solid content concentration 38% by mass) diluted with water as the synthetic resin. In addition, 2% by weight of other additives such as dispersants (equivalent to the solid content in the synthetic resin layer) was added to the synthetic resin solution without adding polyethylene-based wax. The synthetic resin layer is the outermost resin layer (dry coating amount: approximately 1.5 g / m²). ２ ) and the innermost resin layer (dry coating amount: approximately 8.5 g / m²) ２ The combined weight of the two layers after drying (dry coating amount) is approximately 10 g / m². ２ It was formed in such a manner. Note that the dry coating amount ratio (dry coating amount of the outermost resin layer g / m) ２ ÷ Dry coating amount of the innermost resin layer g / m ２ ) was approximately 0.18. (Example 11) For the synthetic resin layer, the outermost resin layer (dry coating amount: approximately 2 g / m²) ２ ) and the innermost resin layer (dry coating amount: approximately 16 g / m²) ２ The combined weight of the two layers after drying (dry coating amount) is approximately 18 g / m². ２A pulp molded container of Example 11 of the present invention was obtained in the same manner as in Example 10, except that it was formed in such a manner. Note that the dry coating amount ratio (dry coating amount of the outermost resin layer g / m) ２ ÷ Dry coating amount of the innermost resin layer g / m ２ ) was approximately 0.13. (Example 12) For the synthetic resin layer, the outermost resin layer (dry coating amount: approximately 4 g / m²) ２ ) and the innermost resin layer (dry coating amount: approximately 21 g / m²) ２ The combined weight of the two layers after drying (dry coating amount) is approximately 25 g / m². ２ A pulp molded container of Example 12 of the present invention was obtained in the same manner as in Example 10, except that it was formed in the manner described above. Note that the dry coating amount ratio (dry coating amount of the outermost resin layer g / m) ２ ÷ Dry coating amount of the innermost resin layer g / m ２ ) was approximately 0.19. (Example 13) For the synthetic resin layer, the outermost resin layer (dry coating amount: approximately 1 g / m²) ２ ) and the innermost resin layer (dry coating amount: approximately 7 g / m²) ２ The combined weight of the two layers after drying (dry coating amount) is approximately 8 g / m². ２ A pulp molded container of Example 13 of the present invention was obtained in the same manner as in Example 1, except that it was formed in the manner described above. Note that the dry coating amount ratio (dry coating amount of the outermost resin layer g / m) ２ ÷ Dry coating amount of the innermost resin layer g / m ２ The ratio was approximately 0.14.

[0067] (Example 14) Regarding the synthetic resin layer, the outermost resin layer contained 15% by weight of an ionomer resin of ethylene unsaturated carboxylic acid copolymer (Mitsui Chemicals, ChemiPearl S500, average particle size 0.7 μm by microtrac method) as a solid content, instead of polyethylene-based wax, as an antiblocking material. This was the same procedure as in Example 12 to obtain the pulp molded container of Example 14 of the present invention. Note that the dry coating ratio (dry coating amount of the outermost resin layer g / m) ２ ÷ Dry coating amount of the innermost resin layer g / m ２The ratio was approximately 0.19. (Example 15) Regarding the synthetic resin layer, the outermost resin layer contained 15% by weight of an ionomer resin of ethylene unsaturated carboxylic acid copolymer (Mitsui Chemicals, ChemiPearl S300, average particle size 0.5 μm by microtrac method) as a solid content, instead of polyethylene wax, as an antiblocking material. This was the same procedure as in Example 12 to obtain the pulp molded container of Example 15 of the present invention. Note that the dry coating amount ratio (dry coating amount of the outermost resin layer g / m) ２ ÷ Dry coating amount of the innermost resin layer g / m ２ The ratio was approximately 0.19.

[0068] For the pulp molded containers obtained in Examples 9 to 15, oil resistance tests, blocking tests, visual inspection of the coating surface after drying of the synthetic resin layer to evaluate the presence or absence of drip marks, and pinhole tests were performed, as in Examples 1 to 8. The results are shown in Table 3. Note that the dry coating amount ratios in Table 3 have been rounded to the third decimal place.

[0069]

[0070] The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the claims and is intended to include all modifications and variations within that scope.

[0071] In this embodiment, the synthetic resin layer 12 consists only of the innermost resin layer 12a and the outermost resin layer 12b, but it is not limited to this, and one or more intermediate resin layers can be interposed between the innermost resin layer 12a and the outermost resin layer 12b. The interposition of intermediate resin layers further suppresses the penetration of the aforementioned pinholes into the container body 11. Furthermore, when an intermediate resin layer is provided, it is preferable that the entire synthetic resin layer 12, including the intermediate resin layer, does not contain organic substances containing fluorine (F), and in particular does not contain organofluorine compounds.

[0072] In this embodiment, the uncoated synthetic resin portion 13a is provided on the flange portion 13, but it is not limited to this, and it can also be provided on the side wall portion other than the flange portion 13, or on the bottom portion. Furthermore, the method for forming the uncoated synthetic resin portion 13a is not limited to this embodiment, and for example, it is possible to perform masking, or to form the synthetic resin layer 12 on only a part of the outer surface of the container body 11 using appropriate means such as spraying or brushing, and leave the remaining portion as the uncoated synthetic resin portion 13a. It is also possible to cover the entire container body 11 with the synthetic resin layer 12 so that there is no uncoated synthetic resin portion 13a.

[0073] In this embodiment, the container body 11 consists of a bottom and a side wall to which a flange portion 13 is attached. However, the shape of the container body 11 is not limited to this; the flange portion 13 may be omitted, or the bottom and side wall may be curved and not clearly separated. The storage space of the container body 11 is not limited to a single space, but may be divided into multiple sections by partitions or the like. The plan view shape of the container body 11 is also not particularly limited, and examples include circular, elliptical, and polygonal shapes.

[0074] 10 Pulp molded container 11 Container body 12 Synthetic resin layer 12a Innermost resin layer 12b Outermost resin layer 13 Flange section 13a Uncoated synthetic resin section 11' Container connector C Cutter S1, S2 Synthetic resin solution B1, B2 Coating solution tank

Claims

1. A pulp molded container comprising a container body made of pulp mold, and a synthetic resin layer formed by coating with synthetic resin on at least one surface of the container body, wherein the synthetic resin layer is composed of multiple unit resin layers, and the innermost resin layer of the unit resin layers that is in contact with the container body does not contain organic matter that melts at a temperature of 250°C or less.

2. A pulp molded container comprising a container body made of pulp mold, and a synthetic resin layer formed by coating of synthetic resin on at least one surface of the container body, wherein the synthetic resin layer is composed of multiple unit resin layers, and the innermost resin layer of the unit resin layers that is in contact with the container body does not contain natural wax or synthetic wax.

3. A pulp molded container comprising a container body made of pulp mold, and a synthetic resin layer formed by coating with a synthetic resin on at least one surface of the container body, wherein the synthetic resin layer is composed of multiple unit resin layers, and the innermost resin layer of the unit resin layers that is in contact with the container body does not contain polyolefin-based wax.

4. A pulp molded container comprising a container body made of pulp mold, and a synthetic resin layer formed by coating at least one surface of the container body with a synthetic resin, wherein the synthetic resin layer is composed of multiple unit resin layers, and the innermost resin layer of the unit resin layers that is in contact with the container body does not contain polyethylene-based wax.

5. The pulp molded container according to any one of claims 1 to 4, wherein neither the container body nor the synthetic resin layer contains organic matter containing fluorine (F).

6. The pulp molded container according to any one of claims 1 to 5, wherein neither the container body nor the synthetic resin layer contains an organofluorine compound.

7. The pulp molded container according to any one of claims 1 to 6, wherein the outermost resin layer of the unit resin layers constituting the synthetic resin layer contains an antiblocking material.

8. The pulp molded container according to claim 7, wherein the antiblocking material is a wax containing either a natural wax or a synthetic wax.

9. The pulp mold container according to claim 8, wherein the synthetic wax is a polyolefin-based wax.

10. The pulp molded container according to claim 9, wherein the polyolefin wax is a polyethylene wax.

11. A container body made of pulp mold, and a synthetic resin layer formed on at least one surface of the container body by coating with synthetic resin, wherein the synthetic resin layer is composed of a plurality of unit resin layers, and the number of pinholes penetrating from the outermost resin layer furthest from the surface of the container body to the innermost resin layer in contact with the surface of the container body is 0 / cm. ２ 0.2 pieces / cm or more ２ The following is a pulp molded container.

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