JP7228446B2 - Manufacturing method for crystalline resin foam container - Google Patents

Description

The present invention relates to a method for manufacturing a crystalline resin foam container.

It is generally known that a crystalline resin foam container formed by molding a crystalline resin foam sheet is excellent in heat resistance. For this reason, the crystalline resin foam container is widely used as a container for foods to be heat-processed in a microwave oven or an oven.
As a method for obtaining a crystalline resin foam container, a molding method of molding a crystalline resin foam sheet in multiple stages is often adopted.
A multi-stage molding die includes a heated die heated to 160 to 180°C and a cooled die cooled to 20 to 60°C. The molds are arranged in the order of heating molds and cooling molds (see Patent Document 1, for example).

The crystalline resin foam container is obtained by heating and molding a crystalline resin foam sheet with a heating mold until it is sufficiently crystallized, and then cooling it with a cooling mold.
However, when the foam-molded sheet molded in the hot mold is transported to the cooling mold, the molded part of the foam-molded sheet is out of position due to shrinkage, stretching, etc. during the time from the completion of the hot molding to the cooling mold. may cause If a foam-molded sheet that has been misaligned is pressed with a cooling mold, misalignment will occur, and the edge line when molding with the heating mold and the edge line when molding with the cooling mold will be doubled. formed. If the crystalline resin foam container is obtained by trimming the foam-molded sheet with the misaligned shape, the appearance of the crystalline resin foam container deteriorates.

To address these problems, Patent Document 2 proposes a method for forming a crystalline resin foam sheet in which a foam-molded sheet molded with a heated mold is allowed to cool without using a cooling mold. In the method of Patent Document 2, the use of a cooling mold is intended to prevent mold displacement of the foam-molded sheet.

JP-A-2000-117826 JP-A-2000-117827

However, the crystalline resin foam container manufactured by the method of Patent Document 2 is fragile and easily damaged by dropping or vibration in a low temperature (eg, -15°C) environment.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for producing a crystalline resin foam container that has a good appearance, excellent heat resistance, and resistance to breakage at low temperatures.

As a result of intensive studies, the present inventors have found that when a foam-molded sheet molded with a heating mold is allowed to cool without using a cooling mold, the crystallinity of the crystalline resin increases too much during cooling. It was found that the crystalline resin foam container became brittle. Therefore, the present inventors have found that by controlling the cooling rate during cooling, the degree of crystallinity of the crystalline resin foam container can be controlled and the brittleness of the crystalline resin foam container can be improved, leading to the completion of the present invention.

That is, the present invention has the following aspects.
[1] A molding step of obtaining a foam-molded sheet by heat-molding the shape of a container on the foam sheet while transferring the long foam sheet in its longitudinal direction, and cooling the foam-molded sheet at a rate of 10 ° C./sec. A method for producing a crystalline resin foam container, comprising an air cooling step of air cooling as described above and a trimming step of cutting out a container from the air-cooled foam molded sheet.
[2] A molding step of obtaining a foam-molded sheet by heat-molding the shape of a container on the foam sheet while transferring the long foam sheet in its longitudinal direction, and cooling the foam-molded sheet at a rate of 10 ° C./sec. and a trimming step of cutting out a container from the air-cooled foam-molded sheet, wherein the air-cooling step is performed while regulating the width direction length of the foam-molded sheet, A method for manufacturing a resin foam container.
[3] The method for producing a crystalline resin foam container according to [2], wherein in the air-cooling step, the length of the foam-molded sheet in the width direction is regulated by chain rails.
[4] The method for producing a crystalline resin foam container according to any one of [1] to [3], wherein the air-cooling step passes the foam-molded sheet through a space adjusted to an arbitrary temperature.

According to the method for producing a crystalline resin foam container of the present invention, a crystalline resin foam container that has a good appearance, excellent heat resistance, and is resistant to breakage at low temperatures can be obtained.

1 is a side view showing an example of a manufacturing apparatus for a crystalline resin foaming container; FIG. FIG. 2 is a plan view of the manufacturing apparatus of FIG. 1; It is a sectional view showing an example of a foam sheet. FIG. 2 is a flow chart showing an example of a process for producing a plant-derived polyester-based resin. FIG. 2 is a flow chart showing an example of a process for producing a plant-derived polyester-based resin. FIG. 2 is a flow chart showing an example of a process for producing a plant-derived polyester-based resin. 1 is a plan view showing an example of a crystalline resin foaming container; FIG. FIG. 8 is a cross-sectional view taken along the line AA of FIG. 7;

[Method for producing crystalline resin foam container]
In the method for producing a crystalline resin foam container (hereinafter also referred to as a "foam container") of the present invention, a long foam sheet is transported in its longitudinal direction, and the shape of the container is thermally formed on the foam sheet. , to obtain a foam container.
The method for manufacturing a foam container of the present invention has a molding step, an air cooling step, and a trimming step.
A method for manufacturing a foam container according to one embodiment of the present invention will be described below.

The method for manufacturing a foam container according to the present embodiment includes a lamination process, a preheating process, a molding process, an air cooling process, and a trimming process.
FIG. 1 shows an example of a foaming container manufacturing apparatus according to the present embodiment. FIG. 2 shows a plan view of the manufacturing apparatus of FIG.

The apparatus 100 for manufacturing a crystalline resin foam container shown in FIG. , a cooling bath 160 , a cutting machine 170 , and a sheet conveying machine 180 . The X direction in FIG. 1 is the longitudinal direction of the long foam sheet.
As shown in FIG. 2, the sheet conveyors 180 are positioned at both ends in the width direction (Y direction) of the foam sheet. The width direction of the foam sheet is a direction orthogonal to the longitudinal direction of the foam sheet.

The foam sheet roll 110 is a roll around which a long foam sheet 101 as a raw material for a crystalline resin foam container (hereinafter also simply referred to as a "foam container") is wound. As the foamed sheet 101, a single-layer sheet made of a foamed layer obtained by foaming a resin that crystallizes by heating (crystalline resin) can be used. The crystalline resin will be described later.

The first film roll 120 is a roll around which a long first resin film 102, which is the raw material of the foaming container, is wound. The first resin film 102 may be a non-foamed film containing a crystalline resin.
The second film roll 122 is a roll around which the elongated second resin film 103, which is the raw material of the foaming container, is wound. As the second resin film 103, the same film as the first resin film 102 can be used.

The laminator 130 is a device that thermally bonds the foamed sheet 101 to the first resin film 102 and the second resin film 103 . The laminator 130 includes a device that includes a pair of heated rolls.

The heater tank 140 is a device for preheating the laminated foam sheet 104 obtained from the foam sheet 101 and the first resin film 102 and the second resin film 103 . As the heater tank 140, a known heating device can be used.

The molding die 150 is a device for thermoforming the secondary foam sheet 105 obtained by preheating the laminated foam sheet 104 . The molding die 150 includes a device that includes a male mold 152 and a female mold 154 .

The cooling tank 160 is a device for air-cooling the foam-molded sheet 106 obtained by heat-molding the secondary foam sheet 105 . As the cooling tank 160, an upper cooling tank 160A is positioned above the foam-molded sheet 106 and blows air onto the foam-molded sheet 106, and an upper cooling tank 160A is positioned below the foam-molded sheet 106 and blows air onto the foam-molded sheet 106. and a lower cooling bath 160B.

The cutting machine 170 is a device for cutting out the foam-molded sheet 106 . As the cutting machine 170, there is a device provided with a cutting blade (knife) having an arbitrary size according to the shape of the container.

The sheet transporter 180 is a device capable of transporting the laminated foam sheet 104, the secondary foam sheet 105, or the foam-molded sheet 106 (hereinafter also referred to as "the laminated foam sheet 104, etc." in this paragraph). As the sheet conveying machine 180, there is a device capable of conveying the laminated foam sheet 104 or the like while gripping the edges of the laminated foam sheet 104 or the like at both ends in the width direction. Examples of the sheet transporter 180 include chain rails. As a chain rail, for example, a chain attached with a plurality of spike-shaped members is wound around the edge of the laminated foam sheet 104 or the like, and the spike-shaped member is pierced into the edge to extend the laminated foam sheet 104 or the like along with the circumference of the chain. A chain rail that can be transported and a clamp member that can realize a clamped state and a non-clamped state are attached to the chain, and the chain is rotated while realizing a clamped state at the edge of the laminated foam sheet 104 etc. A chain rail or the like that can transport the
The sheet conveying machine 180 grips both edges of the laminated foam sheet 104 or the like in the width direction and applies tension to the laminated foam sheet 104 or the like in the width direction, thereby increasing the length of the laminated foam sheet 104 or the like in the width direction. A chain rail that can regulate the

<Lamination process>
The lamination step is a step of forming the foam sheet 101 into the laminated foam sheet 104 .
First, the foam sheet 101 is fed out from the foam sheet roll 110 .
Next, the first resin film 102 is unwound from the first film roll 120 and overlaid on one side of the foam sheet 101 . Also, the second resin film 103 is unwound from the second film roll 122 and overlaid on the other surface of the foam sheet 101 .
A laminate obtained by stacking the first resin film 102 and the second resin film 103 on the foam sheet 101 is supplied to the laminator 130 . The laminated body is sandwiched between a pair of heating rolls and heated at an arbitrary temperature, and the foamed sheet 101 and the first resin film 102 and the second resin film 103 are pressure-bonded to form a laminated foamed sheet 104 . The temperature for crimping the laminate is preferably 80 to 150.degree. C., more preferably 90 to 140.degree.
Through the lamination process, a laminated foam sheet 104 having non-foamed layers on both sides of the foamed layer is obtained.

<Preheating process>
The preheating step is a step of supplying the laminated foam sheet 104 to the heater tank 140 and preheating it to soften the laminated foam sheet 104 . The softened laminated foam sheet 104 becomes the secondary foam sheet 105 .
In this embodiment, the laminated foam sheet 104 is supplied to the heater tank 140 by the sheet conveyor 180 . The sheet transporter 180 may be one that moves continuously at a constant speed, or one that moves intermittently according to the heat molding time in the molding process.
The width of the sheet conveyor 180 is set to the width of the foam sheet 101 fed from the foam sheet roll 110 at the entrance of the heater tank 140 . The width of the sheet transporter 180 is constant inside the heater tank 140 .
Even if the laminated foam sheet 104, which tends to shrink due to heating inside the heater tank 140, is slackened at the entrance of the heater tank 140, the sheet is "stretched" by heating, so that the sheet conveying machine 180 does not expand the width of the sheet. , the sheet can be conveyed while keeping the width interval of .
In the case of a laminated foam sheet that draws down (softens and hangs down) due to preheating inside the heater tank 140, it may be conveyed while expanded in the width direction (Y direction).
By expanding the width of the sheet conveyor 180 inside the heater tank 140 in this way, the softened secondary foam sheet 105 can be flattened, and the shape of the container can be easily molded in the molding process. .
The expansion ratio of the laminated foam sheet 104 is preferably 2 to 6% of the width dimension of the laminated foam sheet 104, for example. When the expansion rate of the laminated foam sheet 104 is 2% or more of the width dimension of the laminated foam sheet 104, the sheet surface of the secondary foam sheet 105 can be easily flattened. When the expansion ratio of the laminated foam sheet 104 is 6% or less of the width dimension of the laminated foam sheet 104, it is possible to suppress the secondary foam sheet 105 from being excessively extended. Therefore, it is possible to prevent the thickness of the obtained foam container 107 from becoming uneven.

The temperature of the heater bath 140 is preferably 90 to 180.degree. C., more preferably 100 to 170.degree. C., and even more preferably 105 to 160.degree. The moldability of the secondary foam sheet 105 can be enhanced by setting the temperature of the heater tank 140 to the above lower limit or higher. Excessive crystallization of the crystalline resin can be suppressed by setting the temperature of the heater tank 140 to the upper limit value or less.
At this time, the surface temperature of the laminated foam sheet 104 is preferably 105 to 140.degree. C., more preferably 110 to 135.degree. C., even more preferably 115 to 130.degree. By making the surface temperature of the laminated foam sheet 104 equal to or higher than the above lower limit, the laminated foam sheet 104 can be sufficiently softened, and the moldability of the secondary foam sheet 105 can be enhanced. By setting the surface temperature of the laminated foam sheet 104 to the upper limit value or less, excessive crystallization of the crystalline resin can be suppressed, and the moldability of the secondary foam sheet 105 can be enhanced.
The preheating time of the laminated foam sheet 104 in the preheating step is preferably 10 to 90 seconds, more preferably 20 to 85 seconds, even more preferably 30 to 80 seconds. By making the preheating time equal to or longer than the above lower limit, the laminated foam sheet 104 can be sufficiently softened, and the moldability of the secondary foam sheet 105 can be enhanced. By setting the preheating time to the above upper limit or less, excessive crystallization of the crystalline resin can be suppressed, and the moldability of the secondary foam sheet 105 can be enhanced.

In the preheating process, it is preferable to use a mechanism that can change the width interval of the sheet conveying machine 180 .
In the preheating step, the preheating softens the secondary foam sheet 105 and causes a dimensional change. This dimensional change is adjusted by changing the width interval of the sheet conveying machine 180, and the length of the secondary foam sheet 105 in the width direction is regulated.
More specifically, the width interval of the sheet conveying machine 180 is provisionally set to the sheet width of the laminated foam sheet 104, and the dimensional change due to the softening of the secondary foam sheet 105 is confirmed by test operation. If there is a discrepancy between the confirmed dimensional change and the tentatively set width interval of the sheet conveying machine 180, the tentatively set width interval of the sheet conveying machine 180 is changed. By adjusting in this way, the deviation between the actual dimensional change and the width interval of the sheet conveying machine 180 can be eliminated.
By eliminating the deviation between the actual dimensional change and the width interval of the sheet conveying machine 180, a container having a desired size and shape can be thermoformed.
The preheated secondary foam sheet 105 is supplied to the molding die 150 by the sheet conveyor 180 .

<Molding process>
The molding step is a step of heat-molding the secondary foam sheet 105 with a molding die 150 to obtain a foam molded sheet 106 .
The forming method in the forming step includes, for example, vacuum forming or pressure forming, and among them, pressure forming is preferable. Vacuum forming or pressure forming includes plug forming, free drawing forming, plug and ridge forming, matched mold forming, straight forming, drape forming, reverse draw forming, air slip forming, plug assist forming, and plug assist reverse draw forming. etc.

In the molding process, the temperature of the mold 150 is preferably 130 to 200.degree. C., more preferably 140 to 195.degree. C., even more preferably 160 to 190.degree. The degree of crystallinity of the crystallized resin can be increased by setting the temperature of the molding die 150 to the above lower limit or higher. Excessive crystallization of the crystallized resin can be suppressed by keeping the temperature of the molding die 150 at or below the upper limit.
In the molding step, the heat molding time is preferably 4 to 15 seconds, more preferably 5 to 13 seconds, and even more preferably 6 to 12 seconds. The degree of crystallinity of the crystallized resin can be increased by making the heat molding time equal to or longer than the above lower limit. The productivity of the foam container can be increased by setting the heat molding time to the above upper limit or less.

In the case of air pressure molding, a male mold 152 and a female mold 154 heated to 160 to 200° C. are used as the mold 150, and compressed air is supplied from the male mold 152 side to form the secondary foam sheet 105 into the female mold 154 four times. It is preferable to keep them in close contact for ~15 seconds.
By bringing the secondary foam sheet 105 into close contact with the female mold 154, the crystallinity of the crystallized resin can be sufficiently increased.
From the viewpoint of sufficiently increasing the degree of crystallinity of the crystallized resin of the secondary foam sheet 105, the temperature of the molding die 150 in the molding process is preferably higher than the temperature of the heater tank 140 in the preheating process.

From the molding process to the air cooling process, a mechanism for changing the width interval of the sheet conveying machine 180 is provided.
The width of the sheet conveying machine 180 is set to the width of the secondary foam sheet 105 at the entrance of the molding die 150 . The width of the sheet conveyor 180 is such that the foam-molded sheet 106 moves in the width direction (Y-direction) as the foam-molded sheet 106 moves in the conveying direction (X-direction) from the exit of the molding die 150 to the entrance of the cooling tank 160. installed in an extended width.
The foam-molded sheet 106 heat-molded in the molding process undergoes a dimensional change. This dimensional change is adjusted by changing the width interval of the sheet conveyor 180, and the length of the foam-molded sheet 106 in the width direction is regulated.
The foam-molded sheet 106 shrinks while being transported from the molding process to the trimming process. For this reason, the size of the molding die is made large in advance in consideration of the expected shrinkage rate for the punching blade for trimming. However, the shrinkage rate of the foam-molded sheet 106 may differ from the expected shrinkage rate, and this may cause a positional deviation called a removal deviation in the trimming process. In order to prevent this misalignment, the width of the sheet conveying machine 180 is adjusted by widening or narrowing from the molding process to the air cooling process. By adjusting in this way, the deviation between the actual dimensional change and the assumed shrinkage rate can be eliminated.
By eliminating the difference between the actual dimensional change and the assumed shrinkage rate, it is possible to thermoform a container having a desired size and shape.
The foam-molded sheet 106 in which a container having a desired size and shape has been heat-molded is supplied to the cooling tank 160 by the sheet conveying machine 180 .

<Air cooling process>
The air-cooling step is a step of air-cooling the foam-molded sheet 106 . In the air-cooling process, the foam-molded sheet 106 is supplied into a space (cooling tank 160) adjusted to an arbitrary temperature, and passed through the foam-molded sheet 106 to cool the surface temperature of the foam-molded sheet 106 to below the softening point of the crystalline resin. do. The softening point of the crystalline resin is, for example, 70° C. when the crystalline resin is PET.
The cooling rate in the air cooling step is 10° C./sec or more, preferably 10 to 100° C./sec, more preferably 15 to 80° C./sec, and even more preferably 20 to 60° C./sec.
In addition, in this specification, the "cooling rate" is represented by the following formula (1).
Cooling rate (°C/sec) = {(Surface temperature of the foam-molded sheet immediately after exiting the mold)-(Softening point of the crystalline resin) (°C)}/(When the foam-molded sheet exits the mold to the time required for the surface temperature of the foam-molded sheet to reach the softening point of the crystalline resin (sec)) (1)
When the cooling rate is equal to or higher than the above lower limit, excessive crystallization of the crystalline resin can be suppressed, and the brittleness of the foam-molded sheet 106 can be easily improved. When the brittleness of the foam-molded sheet 106 is good, the foam container 107 is less likely to break at low temperatures. When the cooling rate is equal to or lower than the upper limit, the load applied to the foam-molded sheet 106 can be reduced.
In the air-cooling process, by increasing the cooling rate, excessive crystallization of the crystalline resin can be suppressed as compared with the case where the foam-molded sheet 106 is allowed to cool. Therefore, the brittleness of the foam-molded sheet 106 can be easily improved, and the foam container 107 that is less likely to break at low temperatures can be obtained.
Further, since no cooling mold is used in the air-cooling process, formation of double lines due to misalignment with the molding mold 150 can be prevented. Therefore, the foam container 107 with good appearance without double lines can be obtained.

The arbitrary temperature (adjusted temperature) of the cooling bath 160 is not particularly limited, but is preferably -50 to 30°C, more preferably -20 to 30°C, and even more preferably 0 to 30°C. When the adjusted temperature is equal to or higher than the above lower limit, the load applied to the foam-molded sheet 106 can be reduced. When the adjustment temperature is equal to or lower than the above upper limit, excessive crystallization of the crystalline resin can be easily suppressed.

In the air-cooling step, the foam-molded sheet 106 may be cooled using a gas such as air until the surface temperature of the foam-molded sheet 106 becomes equal to or lower than the softening point of the crystalline resin, and the method of cooling the foam-molded sheet 106 is not particularly limited. As a method for air-cooling the foam-molded sheet 106, in addition to the method of supplying the foam-molded sheet 106 into the cooling tank 160 described above and allowing the foam-molded sheet 106 to pass through, a method of blowing cooled air onto the foam-molded sheet 106, a method of A method of blowing cooled nitrogen gas onto the formed sheet 106 and the like can be used.
From the viewpoint of being able to cool the foam-molded sheet 106 more efficiently, the method of air-cooling the foam-molded sheet 106 is preferably a method of blowing cooled air onto the foam-molded sheet 106 .
As a method of blowing cooled air onto foam-molded sheet 106, a method of blowing cooled air in the X direction along the conveying direction of foam-molded sheet 106 is more preferable. A method of blowing cooled air in the X direction along the conveying direction from both sides is more preferable. When cooled air is blown onto the foam-molded sheet 106 from both the upper cooling tank 160A and the lower cooling tank 160B, the temperature of the air blown from the upper cooling tank 160A is lower than the temperature of the air blown from the lower cooling tank 160B. Adjustment is particularly preferred. By adjusting the temperature of the air blown from the upper cooling tank 160A to be lower than the temperature of the air blown from the lower cooling tank 160B, the foam-molded sheet 106 can be cooled more efficiently by the air convection inside the cooling tank 160. .
The cooling rate in the air cooling process can be adjusted by controlling the adjustment temperature, the temperature of the blown air, the volume of the blown air, and the like.

In the air-cooling step, it is preferable to air-cool while restricting the length of the foam-molded sheet 106 in the width direction. In the air-cooling process, the heated foam-molded sheet 106 is rapidly cooled, resulting in dimensional change due to shrinkage. This dimensional change is adjusted by changing the width interval of the sheet conveyor 180, and the length of the foam-molded sheet 106 in the width direction is regulated.
More specifically, the width interval of the sheet conveying machine 180 is provisionally set, and the dimensional change due to shrinkage of the foam-molded sheet 106 is confirmed by test operation. If there is a discrepancy between the confirmed dimensional change and the tentatively set width interval of the sheet conveying machine 180, the tentatively set width interval of the sheet conveying machine 180 is changed. By adjusting in this way, the deviation between the actual dimensional change and the width interval of the sheet conveying machine 180 can be eliminated.
By air-cooling the foam-molded sheet 106 while regulating the length in the width direction in this manner, the foam-molded sheet 106 is cooled and hardened while maintaining the adjusted width interval. Therefore, the deviation between the dimensions of the molding die and the position of the punching blade of the cutting machine 170 can be eliminated. In addition, the crystallization of the foam-molded sheet 106 is stopped, making it easier to obtain the foam container 107 having the desired degree of crystallinity.
The foam-molded sheet 106 air-cooled in the air-cooling process is supplied to the cutting machine 170 by the sheet conveying machine 180 .

<Trimming process>
The trimming step is a step of cutting out a container from the air-cooled foam-molded sheet 106 . The trimming process provides the foam container 107 with the desired shape.
Foam sheet 106 fed to cutter 170 has the shape of a thermoformed container. The punching blade of the cutter 170 cuts out the shape of the thermoformed container. As described above, air cooling is performed while restricting the length of the foam-molded sheet 106 in the width direction, so that the shape of the heat-molded container does not shift from the position of the punching blade of the cutting machine 170 . Therefore, it is easy to obtain a foaming container 107 having a desired shape. In addition, since the crystallization of the foam-molded sheet 106 is stopped by the air-cooling process, excessive crystallization of the crystalline resin can be suppressed, brittleness is improved, and the foam container 107 that is hard to break at low temperatures can be obtained.
The sheet from which the foam container 107 is cut is wound up by a winder (not shown) and discarded. The sheet from which the foam container 107 is cut may be reused as a raw material for the foam sheet 101 .

In the trimming step, one foam container may be obtained by one cutting operation, or two or more foam containers may be obtained by one cutting operation. As shown in FIGS. 1 and 2, in this embodiment, six foam containers are obtained in one cutting operation.
The number of foamed containers obtained by one cutting operation is, for example, preferably 2 to 20, more preferably 3 to 15, and even more preferably 4 to 10.
When the number of foamed containers obtained in one cutting operation is at least the above lower limit value, the productivity of foamed containers can be enhanced. When the number of foamed containers obtained by one cutting operation is equal to or less than the above upper limit, it is easy to improve the appearance of the foamed container.

Through the above steps, the foamed container 107 having a desired shape, a desired size, and a desired degree of crystallinity can be obtained.

Next, the foam sheet used in the method for manufacturing the foam container of the present embodiment will be described.

[Foam sheet]
FIG. 3 is a cross-sectional view showing an example of a foam sheet. The foamed sheet 200 of FIG. 3 includes a first non-foamed layer 20 located on one side of the foamed layer 10 and a second non-foamed layer 22 located on the other side of the foamed layer 10 . That is, the foam sheet 200 of the present embodiment is a laminated foam sheet in which non-foam layers are provided on both sides of the foam layer 10 .
In the foam sheet 200, the foam layer 10 is formed from the foam sheet 101, the first non-foam layer 20 is formed from the first resin film 102, and the second non-foam layer 22 is formed from the second resin film 103. be done.

The thickness T ₂₀₀ of the foam sheet 200 is, for example, preferably 0.3 to 5.0 mm, more preferably 0.4 to 4.5 mm, even more preferably 0.5 to 4.0 mm. When the thickness T200 of the foam sheet ₂₀₀ is at least the above lower limit, the strength of the foam container can be further increased. When the thickness T200 of the foam sheet ₂₀₀ is equal to or less than the above upper limit, the degree of crystallinity of the foam container can be easily increased, and as a result, the heat resistance of the foam container can be further enhanced.
In addition, the thickness _T200 of the foam sheet 200 is a value obtained by the following method. The thickness of ten arbitrary points in the width direction of the foam sheet 200 is measured with a microgauge. The thickness _T200 of the foam sheet 200 is obtained by averaging the measured values at 10 points.

The basis weight of the foam sheet 200 is preferably 100-1200 g/m ² , more preferably 200-1000 g/m ² , and even more preferably 300-800 g/m ² . When the basis weight of the foam sheet 200 is at least the above lower limit, the strength of the foam container can be further increased. When the basis weight of the foam sheet 200 is equal to or less than the above upper limit, the moldability of the foam sheet 200 is easily improved.
In addition, the basis weight of the foam sheet 200 can be measured by the following method.
Ten pieces of 10 cm×10 cm are cut out at equal intervals in the width direction except for 20 mm at both ends in the width direction of the foam sheet 200, and the mass (g) of each piece is measured to the nearest 0.001 g. The basis weight (g/m ² ) of the foam sheet 200 is obtained by converting the average value of the mass (g) of each section into the mass per 1 m ² .

<Foam layer>
The foam layer 10 is formed from a resin composition containing a crystalline resin and a foaming agent. The foam sheet 200 is provided with the foam layer 10 and thus has excellent heat insulation and impact resistance.
The cells in the foam layer 10 may be individually independent closed cells or open cells in which cells are connected to each other. From the viewpoint of improving the moldability of the foam sheet 200, the cells in the foam layer 10 are preferably closed cells.

The closed cell ratio of the foam layer 10 is preferably 70% or more, more preferably 80% or more, still more preferably 90% or more, and may be 100%. The closed cell rate of the foam layer 10 can be measured by the method described in JIS K7138:2006 "Rigid foamed plastics - Determination of open cell rate and closed cell rate".

The foaming ratio of the foam layer 10 is, for example, preferably 1.5 to 15 times, more preferably 2 to 10 times, and even more preferably 3 to 8 times. When the foaming ratio of the foamed layer 10 is equal to or higher than the above lower limit, the thermal insulation of the foamed container can be further enhanced. When the expansion ratio of the foam layer 10 is equal to or less than the above upper limit value, the moldability of the foam sheet 200 can be easily improved.
The expansion ratio of the foam layer 10 is a value obtained by dividing 1 by "the apparent density of the foam layer 10".

The average cell diameter of the foam layer 10 is preferably 80 to 450 μm, for example. The average cell diameter of the foam layer 10 can be measured according to the method described in ASTM D2842-69.

The crystalline resin forming the foam layer 10 may be any resin that crystallizes when heated. Examples of crystalline resins include polyolefin-based resins, polyester-based resins, polyamide-based resins, and the like. As the crystalline resin forming the foam layer 10, a polyester-based resin is preferable from the viewpoint of excellent heat resistance.

Polyester-based resins include polyethylene terephthalate resin (PET), polybutylene terephthalate resin, polyethylene naphthalate resin, polyethylene furanoate resin (PEF), polybutylene naphthalate resin, polytrimethylene terephthalate resin (PTT), terephthalic acid and ethylene. Examples include copolymers of glycol and cyclohexanedimethanol, mixtures thereof, and mixtures of these with other resins. Also, a plant-derived polyethylene terephthalate resin, a plant-derived polyethylene furanoate resin, or a plant-derived polytrimethylene terephthalate resin may be used. One of these polyester-based resins may be used alone, or two or more thereof may be used in combination. A particularly preferred polyester resin is polyethylene terephthalate resin.

The polyester-based resin may be a plant-derived polyester-based resin such as so-called bio-PET.
Plant-derived polyester resins are polymers derived from plant raw materials such as sugar cane and corn. "Derived from plant material" includes polymers synthesized or extracted from plant material. Further, for example, the phrase “derived from plant raw materials” includes polymers obtained by polymerizing monomers synthesized or extracted from plant raw materials. "Monomers synthesized or extracted from plant materials" include monomers synthesized using compounds synthesized or extracted from plant materials as raw materials. Plant-derived polyester-based resins include those in which a part of the monomers is "derived from plant raw materials".

PET and PEF will be described as examples of plant-derived polyester resins.

The synthesis reaction of PET is shown in Formula (I). PET is synthesized by a dehydration reaction of nmoles of ethylene glycol and nmoles of terephthalic acid (Benzen-1,4-dicarboxylic Acid). The stoichiometric mass ratio in this synthesis reaction is ethylene glycol:terephthalic acid=30:70 (mass ratio).

［（Ｉ）式中、ｎは化学量論係数である。］

[In formula (I), n is a stoichiometric coefficient. ]

Ethylene glycol is produced industrially by oxidizing and hydrating ethylene. Moreover, terephthalic acid is industrially produced by oxidizing paraxylene.
Here, as shown in FIG. 4, ethylene is obtained by a dehydration reaction of plant-derived ethanol (bioethanol), and ethylene glycol synthesized from this ethylene (ethylene glycol derived from bioethanol) and terephthalate derived from petrochemicals are synthesized. When synthesizing PET from an acid, the PET produced is 30% by mass of plant-derived PET.
Further, as shown in FIG. 5, paraxylene is obtained by a dehydration reaction of plant-derived isobutanol (bioisobutanol), and PET is synthesized from terephthalic acid synthesized from this paraxylene and ethylene glycol derived from bioethanol. In this case, the PET produced is 100% by mass plant-derived PET.

The synthesis reaction of PEF is shown in formula (II). PEF is synthesized by a dehydration reaction of nmoles of ethylene glycol and nmoles of furandicarboxylic acid (2,5-Furandicarboxylic Acid).

［（ＩＩ）式中、ｎは化学量論係数である。］

[(II) where n is a stoichiometric coefficient. ]

Furandicarboxylic acid (FDCA) is obtained, for example, by dehydrating plant-derived fructose or glucose to obtain hydroxymethylfural (HMF) and oxidizing HMF.
As shown in FIG. 6, when both FDCA and ethylene glycol are plant-derived, the produced PEF is 100% by weight plant-derived PEF.

The resin composition may contain other resins than the crystalline resin. When the resin composition contains a resin other than the crystalline resin, the content of the other resin is preferably less than 50% by mass, more preferably less than 30% by mass, more preferably less than 10% by mass, based on the total mass of the crystalline resin. Less than mass % is more preferred.

The weight average molecular weight of the crystalline resin forming the foam layer 10 is, for example, preferably 100,000 to 500,000, more preferably 150,000 to 450,000, and even more preferably 200,000 to 400,000. When the weight-average molecular weight of the crystalline resin forming the foam layer 10 is within the above numerical range, the brittleness of the foam sheet 200 is easily improved. When the foam sheet 200 has good brittleness, the foam container is less likely to break at low temperatures.
In the present specification, the weight average molecular weight is a value measured by gel permeation chromatography (GPC) using the product names "STANDARD SM-105" and "STANDARD SH-75" manufactured by Showa Denko Co., Ltd. as standard samples. It is a value converted based on the calibration curve obtained by

The limiting viscosity (IV value) of the crystalline resin is, for example, preferably 0.50 to 1.50 dl/g, more preferably 0.90 to 1.10 dl/g. When the IV value of the crystalline resin is equal to or higher than the above lower limit, foaming is facilitated, and the foamed sheet 200 is easily obtained by extrusion. When the IV value of the crystalline resin is equal to or less than the above upper limit, it becomes easier to obtain a smooth foamed sheet 200 .
The IV value can be measured according to the method described in JIS K7367-5:2000.

The thickness T ₁₀ of the foam layer 10 is, for example, preferably 0.25 to 4.5 mm, more preferably 0.35 to 4.0 mm, even more preferably 0.45 to 3.5 mm. When the thickness _T10 of the foam layer 10 is at least the above lower limit, the strength of the foam container can be further increased. When the thickness T10 of the foam layer ₁₀ is equal to or less than the above upper limit, the heat resistance of the foam container can be further enhanced.
The thickness T ₁₀ of the foam layer 10 is determined by the same method as the thickness T ₂₀₀ of the foam sheet 200 .

The basis weight of the foam layer 10 is, for example, preferably 250-900 g/m ² , more preferably 250-800 g/m ² , even more preferably 300-700 g/m ² . When the basis weight of the foam layer 10 is at least the above lower limit, the strength of the foam container can be further increased. When the basis weight of the foam layer 10 is equal to or less than the above upper limit, the moldability of the foam sheet 200 is likely to be improved.
The basis weight of the foam layer 10 is determined by the same method as that for the foam sheet 200 .

The resin composition forming foam layer 10 contains a foaming agent. Examples of foaming agents include saturated aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane and hexane, ethers such as dimethyl ether, methyl chloride, 1,1,1,2-tetrafluoroethane, 1 , 1-difluoroethane, monochlorodifluoromethane, carbon dioxide, nitrogen and the like, preferably dimethyl ether, propane, normal butane, isobutane, carbon dioxide and nitrogen.
A foaming agent may be used individually by 1 type, and may use 2 or more types together.

The content of the foaming agent is not particularly limited, but is preferably, for example, 0.1 to 10 parts by mass with respect to 100 parts by mass of the crystalline resin.

The foam layer 10 may contain other components (optional components) in addition to the crystalline resin.
Examples of optional components include resin components other than crystalline resins, foam control agents, surfactants, colorants, shrinkage inhibitors, flame retardants, lubricants, and deterioration inhibitors.
Talc, tetrafluoroethylene resin, etc. are mentioned as a cell regulator.

<Non-foam layer>
The first non-foamed layer 20 is a layer in which substantially no bubbles are formed.
By including the first non-foamed layer 20 located on one side of the foamed layer 10, the foamed sheet 200 hides the unevenness of the surface of the foamed layer 10, thereby easily improving the appearance. In addition, it is easy to form a printed layer (not shown) on the surface of the first non-foamed layer 20, and by forming the printed layer, the foamed sheet 200 can be colored and decorated, so that it is easy to improve the appearance.

Examples of the crystalline resin forming the first non-foamed layer 20 include the same type of crystalline resin as the crystalline resin forming the foamed layer 10 .
The crystalline resin forming the first non-foamed layer 20 is preferably the same kind of crystalline resin as the crystalline resin forming the foamed layer 10 from the viewpoint of preventing delamination.
The crystalline resin forming the first non-foamed layer 20 and the crystalline resin forming the foamed layer 10 may be different types of crystalline resin.

The thickness T ₂₀ of the first non-foamed layer 20 is, for example, preferably 10-300 μm, more preferably 10-200 μm, even more preferably 20-100 μm. When the thickness T20 of the first non-foamed layer ₂₀ is equal to or greater than the above lower limit, the appearance of the foamed sheet 200 is likely to be good. When the thickness T20 of the first non-foamed layer ₂₀ is equal to or less than the above upper limit, the formability of the foamed sheet 200 is likely to be improved.
The thickness _T20 of the first non-foamed layer 20 is obtained by, for example, observing a cut surface of the foamed sheet 200 in the thickness direction with a microscope and averaging the measured values obtained by measuring the thickness of arbitrary 10 points. can be done.

The second non-foamed layer 22 is a layer in which substantially no bubbles are formed.
By providing the second non-foamed layer 22 on the other side of the foamed layer 10, the foamed sheet 200 hides the unevenness of the surface of the foamed layer 10, thereby easily improving the appearance. In addition, the foam sheet 200 includes the first non-foam layer 20 and the second non-foam layer 22 on both sides of the foam layer 10, so that flatness can be easily maintained and warping can be suppressed. Easy to improve.

As the crystalline resin forming the second non-foamed layer 22, the same type of crystalline resin as the crystalline resin forming the first non-foamed layer 20 can be used.
The crystalline resin forming the second non-foamed layer 22 is preferably the same kind of crystalline resin as the crystalline resin forming the foamed layer 10 from the viewpoint of preventing delamination.
The crystalline resin forming the second non-foamed layer 22 and the crystalline resin forming the foamed layer 10 may be different types of crystalline resin.
The crystalline resin that forms the second non-foamed layer 22 and the crystalline resin that forms the first non-foamed layer 20 may be the same type of crystalline resin or different types of crystalline resin. .

The thickness T ₂₂ of the second non-foamed layer 22 is similar to the thickness T ₂₀ of the first non-foamed layer 20 .
The thickness _T22 of the second non-foamed layer 22 can be measured in the same manner as the thickness _T20 of the first non-foamed layer 20.

The foam sheet 200 includes the first non-foam layer 20 and the second non-foam layer 22 on both sides of the foam layer 10, but the form of the foam sheet is not limited to this.
The foamed sheet may have a non-foamed layer on only one side of the foamed layer, or may be a single-layer sheet having only a foamed layer.
The foamed sheet preferably has a non-foamed layer on both sides of the foamed layer from the viewpoint of excellent moldability and easy appearance.

[Method for manufacturing foam sheet]
A foamed sheet is obtained by foaming and curing a resin composition containing a crystalline resin and a foaming agent.
As a suitable method for producing such a foamed sheet, a known method for producing a foamed sheet can be employed.

[Crystalline resin foam container]
Next, the foam container obtained by the method for manufacturing the foam container of the present embodiment will be described.
The foam container is obtained by thermoforming the foam sheet of the present embodiment described above.
The shape of the foaming container is not particularly limited. Various containers such as a container, a container with a lid such as a container for natto (fermented soybeans), and a lid attached to a container body can be used.
Applications of these foamed containers include, for example, home electric appliance packaging containers, machine parts packaging containers, food packaging containers, and the like.
These foam containers are particularly useful as food packaging containers. Since the foamed container obtained by the manufacturing method of the foamed container of the present embodiment is excellent in heat resistance, it is preferable to use the foamed container heated in a microwave oven or an oven.
Furthermore, since the foamed container obtained by the method for producing a foamed container of the present embodiment is less likely to break at low temperatures, it is baked like gratin or lasagna, distributed in a refrigerator or freezer, and then heated in a microwave oven or oven. It is particularly preferable as a freezer microwave container for foods to be eaten after being heated.
It should be noted that "freezer microwave up" refers to heating and cooking frozen food in a microwave oven or an oven.

An example of the foam container will be described with reference to FIG.
As shown in FIG. 7, the foaming container 107 has an elliptical bottom wall 1 in a plan view, and a substantially cylindrical side wall 2 rising from the peripheral edge of the bottom wall 1 and surrounding the bottom wall 1. It comprises a container body 8 formed with an opening 7 bounded at its upper end. Side wall 2 narrows from opening 7 toward bottom wall 1 . The opening 7 has an elliptical shape with its long side in the X1 direction and its short side in the Y1 direction in a plan view.
In this embodiment, the upper end of the side wall 2 has a flange portion 3 projecting outward from the opening 7 . The flange portion 3 encircles the opening portion 7, and a knob portion 3A projecting on both sides in the longitudinal direction X1 is formed.
Moreover, in the center of the bottom wall 1, it has the elliptical bottom wall reinforcement part 4 by planar view. The side wall 2 has a side wall reinforcing portion 5 having a wavy cross-sectional shape.
The foaming container 107 contains gratin or the like and is used as a microwave-up container for foods that are heated in a microwave oven or an oven and eaten.

In the foaming container 107, the length L1 in the longitudinal direction is preferably 215-230 mm. The length W1 in the lateral direction is preferably 130-150 mm. The height H1 is preferably 30-45 mm.

FIG. 8 is a cross-sectional view of foaming container 107 of FIG. 7 taken along line AA. As shown in FIG. 8, the corner portion 6 between the bottom wall 1 and the side wall 2 preferably has an arcuate cross-sectional shape.
As shown in FIGS. 7 and 8, the bottom wall reinforcing portion 4 has an elliptical shape in plan view with a central portion depressed. The outer peripheral portion of the elliptical bottom wall 1 is concave like the bottom wall reinforcing portion 4 and is in contact with the installation surface like the bottom wall reinforcing portion 4 .
The height h1 from the bottom wall reinforcing portion 4 to the bottom wall 1 is preferably 4 to 7 mm. The bottom wall reinforcing portion 4 does not have to be in contact with the ground surface.
The side wall reinforcing portion 5 may be formed continuously as shown in FIG. 7, or may be formed in a divided manner. The cross section of the side wall reinforcing portion 5 is preferably wavy.

In addition, although the foaming container 107 of the present embodiment has an elliptical shape in plan view, the present invention is not limited to this. The plan view shape of the foaming container may be a perfect circle or a polygon.

In the foam container 107, the crystallinity of the foam layer 10 is preferably 21% to 30%, more preferably 21% to 27%, for example. When the crystallinity of the foam layer 10 is equal to or higher than the above lower limit, the heat resistance of the foam container 107 is enhanced. When the degree of crystallinity of the foam layer 10 is equal to or less than the above upper limit value, the foam container 107 that is more resistant to breakage at low temperatures can be obtained.
The degree of crystallinity can be calculated by the following formula (2).
Crystallinity (%) = {(absolute value of heat of fusion (J/g) - absolute value of heat of crystallization (J/g)) / heat of complete crystallization (J/g)} x 100 (2 )
Here, the heat of fusion and the heat of crystallization can be obtained from a differential scanning calorimetry (DSC) curve measured according to JIS K7122:2012 "Method for measuring heat of transition of plastics".

The crystallinity calculated herein means the difference between the heat of fusion (J/g) determined from the area of the heat fusion peak and the heat of crystallization (J/g) determined from the area of the crystallization peak, It is a value obtained by dividing by the theoretical heat of fusion of a perfect crystal of the resin. The heat of fusion and the heat of crystallization can be calculated using analysis software attached to the DSC device.
The heat quantity for complete crystallization represents the heat quantity for 100% crystallization. The heat quantity for complete crystallization of polyethylene terephthalate (PET) is 140.1 J/g.
The crystallinity of the foam container 107 can be adjusted by the molding conditions of the laminated foam sheet 104 .

EXAMPLES The present invention will be described in detail below with reference to Examples, but the present invention is not limited by the following description.

(Manufacture of foam sheet)
100 parts by mass of PET resin having an IV value of 1.04 as a crystalline resin, 1.0 parts by mass of talc as a cell control agent, and 0.2 parts by mass of pyromellitic anhydride (manufactured by Daicel Corporation) as a cross-linking agent. C. for 4 hours. The raw material after drying was put into an extruder with a diameter of 90 mm, and was kneaded by injecting nitrogen gas into the extruder. The PET resin was melted at a temperature of 285° C. (set temperature), extruded through a circular die with a diameter of φ135 mm, and cut with a mandrel while being cooled to obtain a single-layer foamed sheet. The resulting foamed sheet had a thickness of 0.75 mm, a basis weight of 330 g/m ² and an expansion ratio of 2.27.

(Manufacture of laminated foam sheet)
A PET film having a thickness of 25 μm was laminated as a non-foamed layer on both sides of the resulting foamed sheet, and the layers were thermally laminated at 120° C. at 2.0/min to obtain a laminated foamed sheet.

[Example 1, Comparative Examples 1 and 2]
The obtained laminated foam sheet was heated with a heater at 150° C. for 90 seconds to set the surface temperature of the laminated foam sheet to 125° C. (secondary foam sheet). Compressed air was supplied from the male mold side to bring the secondary foam sheet into close contact with the female mold. After that, the male mold and the female mold were closed for 6 seconds, and vacuum pressure molding was performed at 180° C. to obtain a foam-molded sheet. The resulting foam-molded sheet was cooled under the cooling conditions shown in Table 1 and trimmed to obtain a foam container of each example.
The shape of the resulting foaming container was similar to that of the foaming container 107 in FIG. The size of the resulting foam container was 222 mm in L1 in FIG. 7, 140 mm in W1 in FIG. 7, and 37 mm in H1 in FIG.

The resulting foamed container was evaluated for moldability, heat resistance, and low-temperature brittleness according to the following evaluation methods. Table 1 shows the results.

[Evaluation of moldability]
The appearance of the surface of the resulting foamed container was visually observed, and moldability was evaluated based on the following evaluation criteria. If the appearance is good, the moldability is excellent.
"Evaluation criteria"
◯: The surface of the foamed container has no wrinkles or double lines, and the appearance is good.
x: There are wrinkles and double lines on the surface of the foaming container.

[Evaluation of heat resistance]
The length of the obtained foam container (L1 in FIG. 7) was measured with a vernier caliper, and then baked by heating in an oven at 200° C. for 10 minutes. After that, the container was taken out, the dimension of the major axis was measured again, and the dimensional change before and after heating was calculated by the following formula (3). The obtained value was taken as the dimensional change rate (%) after firing, and heat resistance was evaluated based on the following evaluation criteria. The smaller the absolute value of the dimensional change rate, the more excellent the heat resistance of the foam container.
Dimensional change rate after firing (%)={(major axis dimension after heating)−(major axis dimension before heating)}/(major axis dimension before heating)×100 (3)
"Evaluation criteria"
○: Absolute value of dimensional change rate is 2.0% or less.
Δ: The absolute value of the dimensional change rate is more than 2.0% and 3.0% or less.
x: The absolute value of the dimensional change rate is over 3.0%.

[Evaluation of low temperature embrittlement]
200 g of water was added to the obtained foam container, and the container was cured and frozen for 12 hours in a freezing room at -25°C to obtain a test sample. The test piece was horizontally dropped onto a steel plate surface with the bottom wall facing down in a freezer compartment, and the drop height (damage height) at which the foam container was damaged was confirmed, and low-temperature brittleness was evaluated based on the following evaluation criteria. The heights at which the specimens were dropped horizontally were 10 cm, 20 cm, 30 cm, 40 cm, 50 cm, and 60 cm. The higher the break height, the better the low temperature brittleness of the foam container. A foamed container with good low-temperature brittleness is less likely to break at low temperatures.
"Evaluation criteria"
○: Damage height is 50 cm or more.
Δ: Damage height is 40 cm or more and less than 50 cm.
x: Damage height is less than 40 cm.

In Example 1 to which the present invention was applied, all of the evaluations of moldability, heat resistance, and low-temperature brittleness were "good".
On the other hand, in Comparative Example 1 using a cooling mold, the moldability was "poor". Comparative Example 2, in which the cooling rate was outside the scope of the present invention, was rated "x" for low-temperature embrittlement.

From these results, it was found that according to the method for producing a crystalline resin foamed container of the present invention, a crystalline resin foamed container with good appearance, excellent heat resistance, and resistant to breakage at low temperatures can be obtained.

100 foam container manufacturing apparatus 101, 200 foam sheet 102 first resin film 103 second resin film 104 laminated foam sheet 105 secondary foam sheet 106 foam molded sheet 107 foam container 110 foam sheet Roll, 120 first film roll, 122 second film roll, 130 laminator, 140 heater tank, 150 molding die, 152 male mold, 154 female mold, 160 cooling tank, 170 cutting machine, 180 sheet conveying machine

Claims (3)

a forming step of obtaining a foam-molded sheet by heat-molding the shape of a container on the foam sheet while transferring the long foam sheet in its longitudinal direction;
an air-cooling step of blowing cooled air onto the foam-molded sheet to cool the foam-molded sheet at a cooling rate of 10° C./sec or more until the surface temperature of the foam-molded sheet becomes equal to or lower than the softening point of the crystalline resin without using a cooling mold; ,
and a trimming step of cutting out a container from the foam-molded sheet that has been air-cooled,
The air-cooling step is performed while regulating the length in the width direction of the foam-molded sheet.
A method for manufacturing a crystalline resin foam container. 2. The method of manufacturing a crystalline resin foam container according to claim 1 , wherein in the air cooling step, the length of the foam-molded sheet in the width direction is regulated by a chain rail. The air cooling step includes an upper cooling tank positioned above the foam-molded sheet and blowing air onto the foam-molded sheet, and a lower cooling tank positioned below the foam-molded sheet and blowing air onto the foam-molded sheet. 3. The crystalline resin foaming container according to claim 1 or 2, wherein the temperature of the air blown from the upper cooling tank is adjusted to be lower than the temperature of the air blown from the lower cooling tank using a cooling device comprising a tank. manufacturing method.

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