JP2020040690A - Foamed container and manufacturing method of foamed container - Google Patents

Abstract

To provide a foamed container which is a container of foam molding and which has a flange part at an opening part, and to provide a manufacturing method of the same.SOLUTION: A foamed container includes a bottom part and a side part 10c. The foamed container has a flange part 10e peripherally provided in the container outside direction of an opening end of the side part. The flange part has a flat surface on an upper surface. A curvature radius R1 in a first curve surface part formed from a container inside surface of the side part to the upper surface of the flange part is equal to or greater than 0.5 mm, and a shortest distance A from an intersection point between a straight line along the container inside surface of the side part and a straight line along the upper surface of the flange part to an open end of the flange part upper surface is larger than the curvature radius R1 of the first curve surface part.SELECTED DRAWING: Figure 3

Description

The present invention relates to a foam container and a method for manufacturing a foam container. More specifically, the present invention relates to a foamed container having a flange and a method for manufacturing the same.

The foam molded article has features such as light weight, reduced amount of material used, and excellent heat insulation. A foam molded article can be generally produced by molding a resin composition filled in a mold while foaming the resin composition. As a foaming method, for example, a method of decomposing a foaming agent in a resin composition and a method of injecting a gas into the resin composition are known. In recent years, a method of injecting a fluid in a supercritical state (hereinafter, also referred to as “supercritical fluid”) into a resin composition has been developed. For example, molding is performed using injection molding as in Patent Documents 1 and 2. It is known.

Further, when used as a food container in which food is stored inside the foamed molded product, a lid is provided to hygienically protect the food stored therein. The lid is heat-sealed to the flange at the opening of the container. In order to heat-seal the lid more firmly, the upper surface of the flange is preferably flat.

JP-A-2002-067111 JP 2006-056008 A Japanese Patent No. 6232170 Japanese Patent No. 55333546

However, as described in Patent Literature 1, in foam injection molding, a bulge portion (a portion where the thickness is increased) is formed in a projection portion such as a boss or a rib of a molded product and a support portion of a flange portion. However, there is a problem that a relatively large number of bubble cells (expanded particles) are generated. In the foam molding process, internal cooling occurs due to cooling of the molten resin in the cavity, but foaming starts from a portion where the gas foaming pressure becomes larger than the resin internal pressure. Since the amount of internal shrinkage accompanying cooling is likely to increase in the flesh portion, many bubble cells are formed in the flesh portion. In addition, the cell size tends to be large in the fillet portion, and in the protrusions such as bosses and ribs protruding from the resin main body and the support portion of the flange portion, many cell cells may be generated or the cell may grow large. Was.

The present inventors have studied the use of a foam molded article for a food container, and when the support portion extends over the entire container, such as a flange portion provided around the food container opening, the thickness becomes uneven. I found it easy. If the thickness of the flange portion is not uniform, heat sealing cannot be performed in a state where the entire upper surface of the flange portion is in uniform contact with the lid, and depending on the degree of unevenness, a product defect may occur. There is.

Patent Literatures 3 and 4 disclose injection-molded resin-made cup containers, each of which has a flange portion provided around the opening of the container, and the upper surface of the flange portion is positioned with respect to the lid. Although it has a flat surface capable of uniformly contacting, none of the documents discloses a food container of a foam molded product.

The present invention has been made in view of the above situation, and relates to a foamed container which is a container for a foamed molded product, which has a flange portion at an opening, and a method for producing the same.

The present inventors have analyzed the shape of the flange portion provided around the opening end of the foaming container from various angles, and as a result, determined the shape of the foam container from the inner side surface of the side portion of the foam container to the upper surface of the flange portion. It has been found that the curved shape suppresses the growth of foamed particles in the molten resin and forms a flange portion having a flat surface on the upper surface.

One embodiment of the present invention is a foamed container having a bottom portion and a side portion, wherein the foamed container has a flange portion provided in a container outer direction at an opening end of the side portion, and the flange portion is Has a flat surface on the upper surface, a radius of curvature R1 in a first curved surface portion formed from the inner side surface of the side portion to the upper surface of the flange portion is 0.5 mm or more, and the inner side surface of the side portion of the container. The shortest distance A from the intersection of the straight line along the upper surface of the flange portion to the open end of the upper surface of the flange portion is larger than the radius of curvature R1 of the first curved surface portion. Container.

The foaming container preferably has a radius of curvature R2 of 0.2 mm or more in a second curved surface portion formed from the container outer surface of the side portion to the lower surface of the flange portion.

The thickness of the flange portion is preferably 0.5 mm or more and 8.0 mm or less.

It is preferable that the inclination of the plane on the upper surface of the flange portion be within ± 30 ° with respect to a virtual plane parallel to the ground plane of the foam container.

Another aspect of the present invention is a method of manufacturing a foamed container manufactured by injection molding, comprising: filling a cavity in a mold having a concave mold and a convex mold with a molten resin; and filling the cavity with the molten resin. Before the solidified molten resin ends, moving at least one of the concave mold and the convex mold to increase the volume of the cavity, wherein the cavity forms the bottom of the foam container. A first region, a second region for molding the side portion, and a third region for molding the flange portion, a ventilation groove for bleeding the air in the cavity, the ventilation groove for the cavity from the third region. A method for manufacturing a foamed container, wherein 16 or more are provided toward the outside, and a position where the concave mold and the convex mold are aligned is located near a lower surface of the flange portion in the third region. .

ADVANTAGE OF THE INVENTION According to the foaming container of this invention and the manufacturing method of a foaming container, the foaming container in which the flange which has a flat surface on the upper surface was provided in the opening end part of the foaming container is obtained.

It is the perspective view which showed an example of the foaming container of this invention. FIG. 2 is a schematic cross-sectional view illustrating an XY cross section of the foam container of FIG. 1. FIG. 3 is a partially enlarged view illustrating the vicinity of a flange portion in FIG. 2. It is a plane schematic diagram of the foaming container shown in FIG. FIG. 3 is a schematic cross-sectional view showing an enlarged cross-section of FIG. 2. It is a schematic diagram explaining an example of the method of manufacturing a foaming container using a supercritical injection molding apparatus. FIG. 7 is an enlarged schematic cross-sectional view showing the periphery of a cavity of a mold in FIG. 6 for explaining a core back which is an example of a method for manufacturing a foamed container, and FIG. 6A shows an initial state before the core back. , (B) shows the expanded state after core back. FIG. 7 is an enlarged schematic cross-sectional view illustrating an example of a mold used in the supercritical injection molding apparatus shown in FIG. 6. It is a schematic diagram which expands and demonstrates the flange part vicinity of FIG. 8-1. It is the plane schematic diagram which looked at the metallic mold shown in Drawing 8-1 from the resin injection port side. FIG. 7 is a schematic cross-sectional view illustrating another example of a mold used in the supercritical injection molding apparatus shown in FIG. 6 in an enlarged manner. FIG. 11 is a schematic plan view of the mold illustrated in FIG. 10 as viewed from a resin injection port side. FIG. 11 is a schematic plan view of the mold 30 as viewed from the back side of the resin injection port, and is a diagram illustrating a ventilation groove extending from the cavity 33 of the mold illustrated in FIGS. 8A and 10 to the outside of the cavity 33. It is an enlarged view of the metal mold | die 30 which shape | molds the 3rd area | region of a cavity, (a) shows the initial state before core back, (b) shows the expansion state after core back. It is a photograph at the time of a swelling having arisen in the flange part upper surface of a foaming container.

Hereinafter, the foam container 10 of the present invention will be described. FIG. 1 is a perspective view showing an example of the foam container of the present invention, and FIG. 2 is a schematic cross-sectional view illustrating an XY cross section of the foam container of FIG. The foam container 10 includes a bottom portion 10a and a side portion 10c, and a bottom curved surface portion 10b disposed between the bottom portion 10a and the side portion 10c. The bottom portion 10a is a portion that is grounded when the foam container 10 is used, and may be depressed toward the inside of the foam container. With such a shape, the foam container 10 can be easily held. The side part 10c has a straight line part. A draft line indicating the water level in the container may be formed inside the side part 10c. The bottom curved surface portion 10b corresponds to a portion where the side portion 10c rises from the bottom portion 10a, and is curved toward the outside of the foam container 10. Further, the foam container 10 includes a flange portion 10e and a flange-side curved surface portion 10d disposed between the side portion 10c and the flange portion 10e. The flange portion 10e is a portion to which the lid is attached, and the upper surface of the flange portion 10e has a flat surface. With such a shape, the adhesion to the lid can be further strengthened.

FIG. 3 is a partially enlarged view illustrating the vicinity of the flange portion in FIG. As shown in FIG. 3, the first curved surface portion formed from the inner side surface of the container of the side portion 10c to the upper surface of the flange portion 10e is formed such that the radius of curvature R1 is an arc of 0.5 mm or more. . Note that the first curved surface portion is the upper surface side of the flange-side curved surface portion 10d.

The curvature radius R1 is more preferably 0.7 mm or more, and further preferably 1.0 mm or more. The radius of curvature R1 is preferably equal to or less than 3.0 mm, and more preferably equal to or less than 2.0 mm.

The flange portion 10e is provided in the outer direction of the container at the opening end of the side portion 10c, and the flange portion 10e and the side portion 10c form an angle. Conventional molds have a shape in which the flange portion and the side portion form an angle, so that the resin flowing from the side portion forms the flange portion when filling the molten resin to produce a foamed container. It collided with the surface and the flow was easily disrupted. As a result, there is a problem in that a collision between the resins occurs at the flange portion, resulting in a weld and a reduction in strength. Conventionally, at the boundary between the side portion and the flange portion, the foamed particles tend to grow excessively, and the upper surface of the flange portion swells and no flat surface is formed. FIG. 14 shows a photograph in the case where the upper surface of the flange portion is swollen and a predetermined plane is not formed.

On the other hand, in the present invention, the boundary between the side portion 10c and the flange portion 10e is a curved surface portion (flange-side curved surface portion 10d), so that the flow of the resin is stabilized, the collision between the resins is suppressed, and the weld is suppressed. Can be suppressed. Thereby, a decrease in the strength of the flange portion 10e can be suppressed. Further, by providing the flange-side curved surface portion 10d, it is possible to suppress the foamed particles from growing excessively at the boundary portion between the side portion 10c and the flange portion 10e, and to form a flat surface on the upper surface of the flange portion 10e.

When the radius of curvature R1 of the first curved surface portion is 0.5 mm or more, the thickness from the side portion 10c to the flange portion 10e is formed so as to gradually increase. Therefore, the side portion 10c, the flange-side curved surface portion 10d, and the flange portion are formed. In 10e, there is no place where the amount of internal shrinkage of the resin is significantly different. It is considered that this is because generation and growth of expanded particles inside the resin filled in the flange side curved surface portion 10d are suppressed. Further, when the radius of curvature R1 of the first curved surface portion is 0.5 mm or more, the area of the first curved surface portion can be set to a certain area or more. This is because the cooling speed at the first curved surface portion is substantially equal to the cooling speed at the inner side surface of the container of the adjacent side portion 10c and the cooling speed at the upper surface of the flange portion 10e, and the solidification at the resin surface proceeds rapidly. It is. Thereby, it is considered that deformation according to the generation and growth of the foamed particles inside the resin does not occur.

Also, as shown in FIG. 3, the shortest distance A from the intersection of the straight line along the container inner side surface of the side portion 10c and the straight line along the upper surface of the flange portion 10e to the open end of the upper surface of the flange portion 10e is , Larger than the radius of curvature R1. Since the shortest distance A is larger than the radius of curvature R1, a surface for heat sealing the lid is secured on the upper surface of the flange portion 10e, and the adhesiveness with the lid can be improved.
The shortest distance A is preferably larger than the radius of curvature R1 by 0.2 mm or more.

Further, as shown in FIG. 3, the second curved surface portion formed from the outer surface of the side portion 10c to the lower surface of the flange portion 10e preferably has a radius of curvature R2 of 0.2 mm or more.
When the radius of curvature R2 of the second curved surface portion is 0.2 mm or more, the thickness from the side portion 10c to the flange portion 10e can be gradually increased, and the flow of the molten resin can be stabilized during injection. Furthermore, when the lid is heat-sealed to the flange portion 10e, pressure is concentrated on the boundary portion from the outer surface of the container of the side portion 10c to the lower surface of the flange portion 10e, so that destruction is likely to occur. Therefore, by providing the second curved surface portion having R2 of 0.2 mm or more, the strength of the flange portion 10e can be improved.
Note that the radius of curvature R2 is preferably 3 mm or less. If the radius of curvature R2 is larger than 3 mm, the second curved surface portion of the foam container may be caught on a pedestal used when heat-sealing the lid to the flange portion 10e, which may cause breakage. That's why.
Further, the radius of curvature R2 is more preferably 0.3 mm or more and 2 mm or less, and even more preferably 0.4 mm or more and 1.2 mm or less. The second curved surface is a lower surface of the flange-side curved surface 10d.

Further, it is preferable to have a third curved surface portion from the open end upper surface to the open end side surface of the flange portion 10e. The radius of curvature R3 of the third curved surface portion is preferably from 0.2 mm to 1 mm, more preferably from 0.3 mm to 0.6 mm.
The open end of the flange portion 10e corresponds to the filling end of the foam container 10. In the process of flowing the molten resin from the gate of the mold cavity to the filling end, since the pressure of the leading molten resin is released, foaming occurs inside the molten resin and grows. As a result, relatively large expanded particles are present inside the molten resin reaching the filling end. And, due to the core back, relatively large expanded particles tend to grow further. For this reason, at the open end (filled end) of the flange portion 10e, there is a possibility that poor appearance due to swelling may occur. On the other hand, when the foaming container of the present invention has the third curved surface portion, further growth of relatively large foamed particles inside the resin filled in the open end of the flange portion 10e is suppressed, and the flange portion 10e Shape deformation due to poor swelling from the open end upper surface to the open end side surface can be suppressed.

The thickness Te of the flange portion 10e is preferably 0.5 mm or more and 8.0 mm or less, and more preferably 2.5 mm or more and 5.0 mm or less. Here, the thickness Te refers to the maximum thickness of the flange portion when the foam container 10 is cut along a plane perpendicular to the ground surface of the foam container 10.
When the thickness Te is smaller than 0.5 mm, when the lid is heat-sealed to the flange portion 10e, the pressure is not applied uniformly over the entire circumference, and the sealing performance may be uneven. On the other hand, if Te is larger than 8.0, the solidification rate inside the flange becomes slow, so that the deformation amount due to the foaming pressure is large, and it may be difficult to make the shape uniform.

The thickness Tc of the side portion 10c is preferably 1.2 mm or more and 3.5 mm or less, and more preferably 1.4 mm or more and 2.2 mm or less. If the thickness Tc of the side portion 10c is smaller than 1.2 mm, the heat insulating property may be deteriorated. If the thickness Tc exceeds 3.5 mm, the thickness when the foamed containers are stacked increases, which may affect the transportation cost.

The thickness (Te / Tc) of the flange portion 10e with respect to the thickness of the side portion 10c is preferably 1 to 3 times, and more preferably 1.5 to 2 times. This is because the smaller the difference in thickness between the side portion 10c and the flange portion 10e and the smaller the difference in the degree of foaming inside the resin, the more sufficient mechanical properties such as deformation suppression, strength and impact resistance are secured.

Further, the inclination of the plane on the upper surface of the flange portion 10e is preferably within ± 30 °, more preferably within ± 20 °, and ± 10 ° with respect to a virtual plane parallel to the ground plane of the foam container 10. More preferably, it is within °. The case where the upper surface of the flange 10e is inclined in the opening direction of the foam container 10 with respect to the virtual plane is defined as plus (+), and the upper surface of the flange 10e is inclined in the direction of the bottom 10a of the foam container 10. Is defined as minus (-).
A flat surface substantially parallel to the ground surface of the foam container 10 is formed on the upper surface of the flange portion 10e, so that when the cover is attached to the foam container 10, the cover can be brought into uniform contact with the flange portion. Thus, the hermeticity of the foam container 10 can be ensured.

Further, in the foam container 10, an angle θ1 (see FIG. 2) formed by a straight line along the container outer surface of the side portion 10c and a straight line along the lower surface of the flange portion 10e is, for example, 95 ° to 135 °.

As the shape of the foam container 10, the shape of the opening may be circular when viewed from above. The inner diameter (diameter of the opening) Φ1 (see FIG. 4) of the foam container 10 is, for example, 80 mm to 180 mm. Further, the height H1 of the foam container 10 (see FIG. 2) is, for example, 35 mm to 100 mm. Here, the height H1 is a height vertically connecting the ground surface of the bottom portion 10a of the foam container 10 to the maximum height of the upper surface of the flange portion 10e. It is preferable that each of the side portion 10c and the bottom portion 10a has a straight line portion, and the angle θ2 between the straight line along the container outer surface of the side portion 10c and the straight line along the ground surface of the bottom portion 10a is, for example, 95 ° to 135 °. The angle θ2 may be the same angle as the angle θ1. The bottom curved surface portion 10b preferably has a curvature radius R0 of 10 mm or more and 50 mm or less. The foaming container 10 may have a side portion 10c, and the size of the side portion 10c is not particularly limited. For example, a shallow bowl-shaped foaming container may be used.

Note that the height H1 is preferably uniform over the entire circumference of the flange portion 10e of the foam container 10. In the present invention, when the difference between the minimum value and the maximum value of the height H1 is 2 mm or less, the heights H1 are equal.

In addition, the thickness of the bottom curved surface portion 10b or the side portion 10c when the foam container 10 is cut at a predetermined height from the ground surface of the foam container 10 at a plane parallel to the ground surface is a maximum value over the entire circumference. Is preferably 2 mm or less.

FIG. 5 is a schematic cross-sectional view showing the cross section of FIG. 2 in an enlarged manner. The foam container 10 shown in FIG. 5 has a structure in which a foam layer 12 is sandwiched by a skin layer (skin layer) 11 located on the surface of the foam container 10. The foam layer 12 refers to a region that contains a large number of bubbles (foam particles) in the resin, and the skin layer 11 refers to a region that does not contain bubbles. The foam container 10 has high strength due to the presence of the non-foamed skin layer 11 on the surface, and the surface of the mold is transferred as it is. The presence of the foam layer 12 in the center of the foam container 10 not only reduces the weight, but also makes it difficult for heat to be transmitted, and thus is excellent in heat insulation. The foam container 10 shown in FIG. 5 is an example of the foam container manufactured according to the present invention. The structure of the foam container manufactured according to the present invention is not limited to the three-layer structure of skin layer 11 / foam layer 12 / skin layer 11.

When the cross section of the foamed container 10 is observed, the foamed layer 12 preferably has 100 or more foamed particles in a range of 1 mm × 1 mm of the foamed layer 12, and an average particle of 100 arbitrarily selected foamed particles. The diameter is preferably 100 μm or less. The measurement of the expanded particles can be performed with a scanning electron microscope (SEM), and for example, “S-4800” manufactured by Hitachi High-Technologies Corporation can be used.

The foamed container 10 is not particularly limited as long as it is a foamed molded product having a foamed layer and skin layers formed on both sides of the foamed layer. For example, a molten resin containing a foaming agent and a resin composition is made of gold. It is formed by a method such as injection molding in a cavity in a mold.

The MFR of the molten resin is preferably from 5 to 50 g / 10 minutes, more preferably from 10 to 35 g / 10 minutes. When the MFR of the molten resin is lower than 10 g / 10 min, the injection moldability (flowability) is deteriorated, and the foaming property is also deteriorated. On the other hand, when the MFR is higher than 35 g / 10 min, the air in the cavity 33 is forced out. Resin leakage (burr) from the ventilation groove for pulling out increases. The MFR is a value measured at a temperature of 230 ° C. and a load of 21.2 N according to JIS K7210.

As the foaming agent, a chemical foaming agent or a physical foaming agent may be used. Examples of the chemical foaming agent include sodium hydrogen carbonate, dinitrosopentamethylenetetramine (DPT), azodicarbonamide (ADCA), and the like. Examples of the physical foaming agent include a supercritical fluid. As the supercritical fluid, for example, a supercritical fluid of an inert gas such as carbon dioxide, nitrogen, argon, and helium is used. Among them, a supercritical fluid of carbon dioxide or nitrogen is preferred. A supercritical fluid of nitrogen is more preferable because of its excellent foamability.

The resin composition is not particularly limited, but preferably contains a thermoplastic resin as a main component. Examples of the thermoplastic resin include polyolefins such as polypropylene (PP) and polyethylene, polylactic acid (PLA), polystyrene (PS), polyphenylene ether (PPE), polybutylene succinate (PBS), and polybutylene succinate adjuvant. (PBSA), polycaprolactone (PCL), polyacetal (POM), polyamide (PA) and the like. These may be used alone or in combination of two or more. Among them, polypropylene, polylactic acid, polybutylene succinate and the like are preferable. The content of the thermoplastic resin with respect to the entire resin composition is, for example, 50% by weight or more.

The thermoplastic resin may further contain an acid-modified polyolefin or the like. Examples of the acid-modified polyolefin include those obtained by subjecting a polyolefin to an addition reaction with an unsaturated carboxylic acid, an ester of an unsaturated carboxylic acid, or an anhydride of an unsaturated carboxylic acid. Examples of the unsaturated carboxylic acid include maleic acid, fumaric acid, and itaconic acid. Examples of the esters of unsaturated carboxylic acids include monomethyl maleate, monoethyl maleate, diethyl maleate, and monomethyl fumarate. Examples of the anhydride of the unsaturated carboxylic acid include itaconic anhydride and maleic anhydride. As the acid-modified polyolefin, maleic anhydride-modified polyolefins such as maleic anhydride-modified polypropylene and maleic anhydride-modified polyethylene, and glycidyl methacrylate-modified polyolefin are preferably used. The acid-modified polyolefins may be used alone or in combination of two or more.

As the resin composition, a mixture of polyolefin and polylactic acid is preferable. Since polyolefin and polylactic acid are incompatible polymers that do not dissolve in each other, they do not dissolve in each other even when mixed, and an interface is formed. Therefore, in foaming using a supercritical fluid, the interface can be used as a foam starting point (foam nucleus). On the other hand, in order to produce a foamed container made of a foamed product that has been foamed uniformly, it is required to uniformly disperse the resin composition before foaming. For this reason, a mixture of polyolefin, polylactic acid and acid-modified polyolefin is more preferable as the resin composition. By adding an acid-modified polyolefin, polyolefin and polylactic acid are made compatible and dispersibility is improved. Thereby, a large number of fine air bubbles (foamed particles having a small particle diameter) can be uniformly present inside the foamed molded article forming the foamed container, and excellent properties such as heat insulating properties, strength, and lightness are excellent. A foam container can be manufactured.

The melt viscosity (220 ° C.) of the polyolefin is preferably 150 Pa · S or more and 400 Pa · S or less. A more preferred lower limit of the melt viscosity of the polyolefin is 200 Pa · S, and a more preferred upper limit is 300 Pa · S. The above-mentioned melt viscosity can be measured using, for example, “Flow Tester CFT-500D” manufactured by Shimadzu Corporation. Specifically, the resin to be measured is heated and fluidized to a predetermined temperature, and extruded from a cylinder by a piston having a predetermined surface pressure of 1 MPa through a capillary die (inner diameter Φ2 mm, length 10 mm), and the amount of movement of the piston is determined. The viscosity characteristics can be evaluated based on the time taken.

The content of the polyolefin with respect to the entire resin composition is preferably 30% by weight or more and 80% by weight or less. If the content is less than 30% by weight, the fluidity and the solidification rate of the resin composition may decrease, and the moldability may deteriorate. When the content is more than 80% by weight, the foaming property is deteriorated, the surface of the obtained foamed container has irregularities, the appearance is impaired, and the resin composition is mixed when the resin composition and the supercritical fluid are mixed. May be difficult to impregnate with a supercritical fluid. A preferred lower limit of the content of the polyolefin to the entire resin composition is 35% by weight, and a preferred upper limit is 70% by weight.

The polylactic acid is a homopolymer of L-lactic acid, a homopolymer of D-lactic acid, a copolymer of L-lactic acid and D-lactic acid, or a mixture thereof. Polylactic acid obtained by changing the method of producing lactic acid, such as adjusting the enantiomeric ratio of lactic acid, copolymerizing the enantiomers (random, block, graft, etc.), adding a nucleating agent, etc. Crystallinity can be adjusted.

The melt viscosity (220 ° C.) of the polylactic acid is preferably 150 Pa · S or more and 400 Pa · S or less. A more preferred lower limit of the melt viscosity of the polylactic acid is 200 Pa · S, and a more preferred upper limit is 300 Pa · S. The melt viscosity of the polylactic acid can be measured in the same manner as the melt viscosity of the polyolefin.

The content of the polylactic acid in the entire resin composition is preferably 3% by weight or more and 40% by weight or less. If the content is less than 3% by weight, the foamability of a foamed container formed by foaming the resin composition may be insufficient. If the content exceeds 40% by weight, the fluidity and the solidification rate of the resin composition may decrease, and the moldability may deteriorate. A more preferred lower limit of the content of the polylactic acid to the entire resin composition is 8% by weight, and a more preferred upper limit is 30% by weight.

The fluidity of the resin composition is adjusted by setting the content of the polyolefin in the range of 30% by weight to 80% by weight and the content of the polylactic acid in the range of 3% by weight to 40% by weight. Properties can be improved.

Further, the difference in melt viscosity between the polyolefin and the polylactic acid is preferably 200 Pa · S or less. When the melt viscosity difference is 200 Pa · S or less, both components are easily mixed. A more preferred upper limit of the above melt viscosity difference is 150 Pa · S.

In the above resin composition, the content of the modified polyolefin containing a carbonyl group in the molecule, based on the entire resin composition, is preferably 1% by weight or more and 20% by weight or less. Within this range, an interface is formed between the incompatible polyolefin and polylactic acid, and the dispersibility of both components can be effectively improved. If the content is less than 1% by weight, the foaming properties of the resulting foamed container may be reduced. When the content exceeds 20% by weight, generation of odor, coloring, deterioration of moldability, increase in water absorption, and the like may be caused. A more preferred lower limit of the content of the modified polyolefin containing a carbonyl group in the molecule with respect to the entire resin composition is 3% by weight, and a more preferred upper limit is 12% by weight.

The resin composition may contain, in addition to the thermoplastic resin, a layered silicate such as talc, mica, and montmorillonite; and a filler such as calcium carbonate, glass fiber, and cellulose fiber. By including a filler, it is possible to improve the shearing force at the time of mixing the thermoplastic resin, among which, the resin composition preferably contains an inorganic filler such as talc, kaolin, montmorillonite, mica, The content of the inorganic filler is preferably 10% by weight or more and 40% by weight or less. If the content is less than 10% by weight, the effect of improving the shearing force during mixing may not be sufficiently obtained. If the content exceeds 40% by weight, the moldability of the resin composition may be reduced. A more preferred lower limit of the content of the layered silicate to the entire resin composition is 15% by weight, and a more preferred upper limit is 35% by weight.

The foam container may be provided with a decoration such as a pattern, a color or a character on the surface or the like. When such a decoration is provided, a pigment filler, a color masterbatch, or the like may be added to the resin composition.

Next, a method of manufacturing a foamed container according to another embodiment of the present invention will be described.
The present invention is a method for producing a foam container by injection molding, wherein a step of filling a cavity in a mold composed of a concave mold and a convex mold with a molten resin, and the molten resin filled in the cavity is solidified. Before finishing, a step of moving at least one of the concave mold and the convex mold to increase the volume of the cavity, wherein the cavity has a first region for molding the bottom of the foam container, and the side portion. And a third region for molding the flange portion, and 16 or more ventilation grooves for bleeding air from the cavity are provided from the third region toward the outside of the cavity. And a method of manufacturing a foamed container, characterized in that a position where the concave mold and the convex mold are aligned is located near a lower surface of the flange portion in the third region.

In the injection molding, it is preferable to perform injection molding of a molten resin containing a foaming agent and a resin composition, and injection molding of a molten resin containing a supercritical fluid and a resin composition (hereinafter, simply referred to as “molten resin”). More preferably, it is supercritical injection molding. Examples of the molten resin used in the supercritical injection molding include, for example, a molten resin composition containing a supercritical fluid, and a single-phase solution of the resin composition and the supercritical fluid. Is preferred. Such a molten resin can be produced by injecting a supercritical fluid generated by a conventionally known supercritical fluid generator into a molten resin composition under high pressure and further stirring. The resin composition for impregnating the supercritical fluid will be described later in detail.

In the supercritical injection molding, after filling the molten resin into the cavity of the mold, by cooling and solidifying, a molded product having a precise shape corresponding to the shape of the cavity in the mold, and various shapes. Can be manufactured. In addition, when the pressure of the molten resin is reduced during injection molding, the supercritical fluid undergoes a phase transition to gas, so that the molten resin foams and a foaming container containing fine bubbles is obtained. By having a large number of foaming starting points (foam nuclei) uniformly present in the molten resin, the amount of bubbles can be increased.

In the method for producing a foamed container of the present invention, a step of moving a part of the mold to increase the volume of the cavity (hereinafter, referred to as a “core”) before the molten resin filled in the cavity is completely solidified. Back). By forcibly expanding the cavity while part or all of the molten resin is molten, a sudden pressure decrease is caused, and the foaming amount can be greatly increased. Thereby, air bubbles can be formed over the entire inside of the molten resin filled in the cavity. The mold usually has a male mold having a convex shape and a female mold having a concave shape, and a gap formed in a state where the male mold and the female mold are fitted becomes a cavity filled with the molten resin. . When expanding the volume of the cavity, at least a part of the male mold and / or the female mold may be moved. For example, when the male mold is on the movable side and the female mold is on the fixed side, the entire male mold may be moved or only a part thereof may be moved.

It is preferable that the core back is started immediately after filling of the molten resin into the cavity (0 second after completion of filling) to within 5 seconds after completion of filling. The moving speed of the mold (core back speed) is preferably 0.1 mm / sec or more. The amount of expansion of the gap distance of the mold by the core back (core back amount) is preferably 0.5 mm to 10 mm, more preferably 0.5 mm to 8 mm.

Producing a molten resin containing a supercritical fluid and a resin composition, and molding while foaming the molten resin is, for example, supercritical injection molding in which an injection molding machine and a supercritical fluid generator are connected. It can be performed using an apparatus. As the supercritical injection molding apparatus, for example, a MuCell injection molding machine ("MuCell" is a registered trademark of Trexel.co. Ltd.) is exemplified.

FIG. 6 is a schematic diagram illustrating an example of a method of manufacturing a foam container using a supercritical injection molding device. In the supercritical injection molding apparatus 20 shown in FIG. 6, an injection molding machine including a hopper 21, a heating cylinder 22, a screw 23, and a nozzle 24 is provided with a cylinder 25, a supercritical fluid generation unit 26, and a supercritical fluid injection control unit 27. A fluid generator is connected.

The hopper 21 includes a container for storing the charged resin material, and causes the resin material to drop into the heating cylinder 22 from an openable / closable opening at the bottom of the container. An appropriate amount of the resin material is transferred and melted in the heating cylinder 22 by rotating the screw 23. Examples of the resin material to be put into the hopper 21 include pellets of a resin composition produced by melting and kneading a mixture of a plurality of types of raw materials using an extruder. The extruder is not particularly limited, and various types of single-screw or multi-screw extruders can be used. For example, a twin-screw extruder having a set temperature of 200 ° C. or more is preferable. As a kneading method, all the raw materials may be kneaded at once, or after kneading arbitrary raw materials, the remaining raw materials may be added and kneaded. The heating cylinder 22 can heat the inside of the cylindrical space, and can melt the resin material.

The cylinder 25 is filled with an inert gas serving as a raw material of a supercritical fluid. The inert gas is sent from the cylinder 25 to the supercritical fluid generator 26, where it becomes a supercritical fluid. The supercritical fluid is injected into the heating cylinder 22 from the supercritical fluid generator 26 via the injection controller 27. The injection control unit 27 controls the filling amount of the supercritical fluid into the resin material melted in the heating cylinder 22.

The screw 23 is configured to be movable while rotating inside the heating cylinder 22, and extrudes toward the tip of the heating cylinder 22 while mixing the molten resin material and the supercritical fluid. By this mixing, a single-phase solution (molten resin) of the molten resin material and the supercritical fluid is formed. The molten resin containing the supercritical fluid and the resin composition is extruded by the screw 23, conveyed to the nozzle 24 side, and injected into the mold 30 from the nozzle 24 by an appropriate amount.

The mold 30 has a male mold 31 having a convex shape and a female mold 32 having a concave shape, and a cavity 33 is formed between the male mold 31 and the female mold 32. The molten resin injected from the nozzle 24 passes through the runner 34 and fills the cavity 33 from the resin injection port 35. Due to the pressure loss in the mold 30, the supercritical fluid undergoes a phase transition to a gas when it reaches the critical pressure, and bubbles are generated in the molten resin. Further, as shown in FIG. 7, before the cooling and solidification of the molten resin proceeds, the male mold 31 is retracted, and a core back is performed to expand the cavity 33, thereby accelerating the pressure drop and melting in the cavity 33. It can promote foaming of the resin. FIG. 7 is an enlarged schematic cross-sectional view showing the periphery of the mold cavity of FIG. 6 for explaining a core back which is an example of a method for manufacturing a foamed container. 4B shows an initial state, and FIG. 4B shows an expanded state after core back.

FIG. 8A is a schematic cross-sectional view illustrating an example of a mold used in the supercritical injection molding apparatus shown in FIG. 6 in an enlarged manner. FIG. 8B is a schematic view of the flange of the cavity 33 shown in FIG. It is a schematic diagram which expands and demonstrates a part vicinity. FIG. 9 is a schematic plan view of the mold shown in FIG. 8A when viewed from the resin injection port side. FIG. 10 is a schematic cross-sectional view illustrating another example of the mold used in the supercritical injection molding apparatus shown in FIG. 6 in an enlarged manner. FIG. 11 shows the mold shown in FIG. It is the plane schematic diagram seen from. FIGS. 8A and 8B are schematic diagrams of a mold in which the resin injection port 35 is formed in the male mold 31. FIGS. 10 and 11 show a mold in which the resin injection port 35 is formed in the female mold 32. FIG. 9 and 11 are plan views of the mold as viewed from the resin injection port side. As shown in FIG. 8A and FIGS. 9 to 11, it is preferable that the number of the resin injection ports 35 communicating with the cavity 33 is one for each cavity 33. As a result, the molten resins injected from the different injection ports do not collide with each other in the cavity 33, so that it is possible to more effectively prevent swelling and poor foaming of the molded product surface from occurring over a wide range. The resin injection port 35 is preferably provided at a position corresponding to the bottom as shown in FIGS. Thereby, the molten resin can be diffused from the resin injection port 35 to the entire inside of the cavity 33 at a uniform radial speed, so that wrinkles and swelling on the surface of the foam container 10 can be more effectively prevented. . More preferably, the resin injection port 35 is provided at a position corresponding to the center of the bottom.

The cavity 33 is formed with a grounding portion 33a, which is a first region for molding the bottom of the foam container, toward the end of the cavity 33 farthest from the resin injection port 35 (hereinafter, simply referred to as “flow end E”). It has a side curved surface portion 33b, has a second region 33c for molding a side portion, and has a flange side curved surface portion 33d and a flange portion 33e as a third region for molding a flange portion. As illustrated in FIGS. 8A and 8B, the first region 33 a may be planar, or may be wholly or partially curved toward the male mold 31. For example, the center of the curved portion 33 a in the first region may be the same as the center of the resin injection port 35 of the male mold 31. The third region in the cavity 33 is a flange portion arranged at an angle from the side portion toward the flow end E from the side portion. The angle θ3 between the second region 33c and the third region 33e is, for example, 95 ° to 135 °. Preferably, the distance from the resin inlet 35 to the flow end E is substantially equal at any flow end E in the cavity 33.

As shown in FIGS. 8A and 10B, the male mold 31 has a convex diameter φ2 of, for example, 80 mm to 180 mm. The diameter Φ2 corresponds to the diameter Φ1 of the opening of the obtained foam container 10 (see FIG. 4). The convex height H2 of the male mold 31 (see FIGS. 8 and 10) is, for example, 35 mm to 100 mm. The height H2 corresponds to the height H1 of the obtained foam container 10 (see FIG. 2). The height H1 of the obtained foam container 10 tends to be higher than the height obtained by adding the thickness of the bottom portion 10a of the foam container 10 to the height H2. It is preferable that each of the first region 33a and the second region 33c has a straight line portion. The angle θ4 between the straight line along the first region 33a and the straight line along the second region 33c is, for example, 95 ° to 135 °. 33b in the first region preferably has a radius of curvature R0 of 10 mm or more and 50 mm or less. The angle θ4 may be the same angle as the angle θ3.

According to the study of the present inventors, the foamed container 10 in which the resin composition is foamed by supercritical injection molding is likely to be deformed due to swelling at the flange side curved surface portion 10d and the flange portion 10e. Therefore, it is preferable to provide the male mold facing the flange side curved surface portion 33d of the cavity corresponding to the flange side curved surface portion 10d of the foam container 10 with the curved surface M1. The curvature radius mR1 of the curved surface M1 is preferably set according to the resin used for forming the foamed container and the radius of curvature of the first curved surface portion of the foamed container.

Further, from the intersection of the straight line along the male mold facing the cavity second region 33c and the straight line along the male mold facing the flange 33e in the third region, the male facing the flow end E of the flange 33e. The shortest distance mA to the mold is preferably larger than the radius of curvature mR1.

Further, it is preferable that the female mold facing the flange side curved surface portion 33d of the cavity corresponding to the flange side curved surface portion 10d of the foam container 10 is provided with the curved surface F1. The radius of curvature mR2 of the curved surface F1 is preferably set according to the resin used to form the foam container and the radius of curvature of the second curved surface portion of the foam container.

In addition, it is preferable that the male mold facing the flow end E of the cavity corresponding to the open end side surface from the open end upper surface of the flange portion 10e of the foam container 10 has a curved surface M2. The curvature radius mR3 of the curved surface M2 is preferably set according to the resin used for forming the foamed container and the radius of curvature of the third curved surface portion of the foamed container.

When filling the molten resin (before the core back), the minimum value of the gap distance W of the mold 30 forming the cavity 33 is preferably 0.2 mm or more. In the cavity 33 that defines the shape of the foam container 10, the gap distance W between the molds 30 defines the thickness of the foam container 10. If the gap distance of the mold is less than 0.2 mm, the molten resin cannot be sufficiently foamed, and a non-foamed portion without bubbles may be formed. In a non-foamed portion or a portion that is not sufficiently foamed, sufficient heat insulating properties cannot be obtained. In addition, the appearance of the uncolored foam container 10 usually looks white due to scattering of light by air bubbles, but a non-foamed portion or a portion that does not sufficiently foam looks transparent, so that a non-foamed portion is formed. And the appearance of the foaming container 10 becomes uneven.

The minimum value of the gap distance between the molds 30 corresponding to the third regions 33d and 33e in the cavity before the core back is preferably 0.6 mm or more. Since the flange portion 10e of the foam container 10 formed by filling the third region with the molten resin is a position where the lid is heat-sealed after the food is stored, the flange portion 10e can withstand the pressure during heat sealing. As described above, it is preferable that the thickness is thicker than other portions of the foam container.
The gap distance of the third region in the cavity before the core back is preferably 0.6 mm or more and 2.0 mm or less, and more preferably 0.7 mm or more and 1.2 mm or less.

In addition, it is preferable that the upper limit of the gap distance W between the molds 30 corresponding to the first region and the second region in the cavity before the core back is 3.0 mm. In the first region and the second region close to the resin injection port 35, the cooling and solidifying time is long in the portion where the gap distance W exceeds 3.0 mm. There is a possibility that the foaming container 10 may be deformed due to (the portion where the foaming power remains and the solidification of the resin is insufficient). Therefore, it is preferable that the gap distance W between the molds 30 corresponding to the first region and the second region of the cavity is in the range of 0.2 to 3.0 mm.

FIG. 12 is a schematic plan view of the mold 30 as viewed from the back side of the resin injection port, and illustrates a ventilation groove 41 extending from the cavity 33 of the mold shown in FIGS. It is. The mold 30 forming the cavity 33 has a ventilation groove 41 extending from the cavity 33 to the outside of the cavity 33 in at least one of the male mold and the female mold corresponding to the third region of the cavity. It is preferable that a total of 16 or more ventilation grooves are formed. The ventilation groove is for bleeding air from the cavity, and may be provided on the surface corresponding to the third region.

Further, the ventilation grooves 41 are preferably formed in a eccentric shape with the resin injection port 35 as a center, and are preferably arranged at equal intervals. This is because air in the cavity is easily exhausted.
Further, the ventilation groove 41 may be configured to communicate the air or gas in the cavity 33 to the outside of the cavity 33 via the gas discharge line 42.

FIG. 13 is an enlarged view of a mold 30 for molding the third region of the cavity, and illustrates a position where the male mold 31 and the female mold 32 are aligned. The male mold 31 and the female mold 32 of the mold 30 used in the present invention have matching positions near the lower surface of the flange 33e in the third region of the cavity. FIG. 13A is a diagram illustrating an initial state of the third region before core back, and FIG. 13B is a diagram illustrating an expanded state of the third region after core back.

The flow end side surface 33f of the flange portion 33e in the third region of the cavity 33 is preferably formed parallel to the moving direction of the core back. In addition, "parallel to the moving direction of the core back" means that it is parallel to the moving direction in the step of moving a part of the mold to increase the volume of the cavity, and is parallel to the moving direction. The angle may be within ± 5 ° with respect to the virtual axis.

Further, it is preferable that the flow end side surface 33f of the flange portion 33e has a shape in which the foam container 10 is hard to be detached from the mold 30 at the time of core back. Specifically, the end portion 33f ₁ in core back movement direction of the flow end side 33f, it is preferably located in the cavity inside direction than opposite end 33f _2. That is, it is preferable that the flow end side surface 33f is formed such that the cylindrical shape formed from the entire circumference of the flow end side surface 33f tapers toward the core back moving direction and becomes tapered. Further, it is preferable that the flow end side surface 33f has an inclination within a range of more than 0 ° and within 3 ° with respect to an imaginary axis parallel to the core back moving direction. By having such an inclination, the foam container 10 is easily caught by the mold 30, the mold transferability is maintained even during foam molding by the core back, and the shape accuracy of the flange portion 10e in the foam container 10 is improved ( The shape over the entire circumference of the flange portion 10e and the shape of each foam container 10 can be made uniform). In the foam container 10 manufactured using such a mold 30, the open end side of the flange portion 10e is larger than 0 and within 3 ° with respect to an axis perpendicular to the ground surface of the foam container 10. With a slope.

In the mold 30, it is preferable that the surface of the third region of the cavity 33 that faces the flow end side surface 33f of the flange portion 33e be provided with an uneven shape (texture). Thereby, the foam container 10 is easily caught by the mold that does not move at the time of core back, and the mold transferability can be maintained even at the time of core back foam molding, the shape accuracy can be maintained, and the appearance defect can be suppressed.
Furthermore, by performing the graining process, in a region where the surface of the cavity has an uneven shape, the molten resin is easily convected, the surface area of the cavity is increased, and the outer surface of the foam container 10 (for example, a skin layer) In the above, it is considered that the deformation caused by the occurrence of swelling can be suppressed by increasing the solidification rate of the molten resin.

In the mold 30, it is preferable that the surface of the third region of the cavity 33 facing the lower surface of the flange portion 33e has an uneven shape (texture). Thereby, excessive foaming at the time of core back foam molding can be suppressed, and deformation of the flange portion 10e of the foam container 10 into a rounded shape due to bulging of the body can be suppressed, and the flange portion 10e is directed upward. Deformation can be suppressed. The uneven shape is formed in order to make the surface of the mold facing the cavity of the mold 30 rough, and is formed by, for example, fine unevenness that can be visually confirmed to a matte degree. Examples of the method of forming the uneven shape include a method in which a region of the mold where the uneven shape is not applied is masked and formed by sandblasting, laser processing, or the like.

The mold temperature is preferably set so as to improve the releasability, transferability of the mold surface, and fluidity of the molten resin in a well-balanced manner. The mold temperature is not particularly limited, but is preferably lower than the molten resin temperature and a temperature difference from the molten resin temperature is 100 ° C or more and 200 ° C or less. The mold temperature is not particularly limited, but is, for example, 30 ° C or more and 85 ° C or less. By increasing the mold temperature, the solidification of the flange can be slowed, the foaming property can be increased, and the mold transferability during core-back foam molding can be improved.

The foamed container manufactured by the method for manufacturing a foamed container of the present invention is excellent in heat resistance and heat insulation, and is lightweight. The heat resistance of the foamed container can be adapted to the 7.4 heat resistance test (display heat resistance temperature of 120 ° C.), the 7.10 microwave oven high frequency adequacy test, and the 7.11 microwave oven durability test of JIS S2029. it can. Therefore, the foaming container may be used for heating or cooking by a microwave oven.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to only these Examples.

<Preparation of resin composition>
The raw materials and amounts of the resin compositions used for producing the foam containers in the following Examples and Comparative Examples are as follows.
Resin composition: PP (40 wt%) / PLA (25 wt%) / talc (25 wt%) / modified PP (10 wt%)
PP: "J106G" manufactured by Prime Polymer
PLA: "Terramac TE-2000" manufactured by Unitika Ltd.
Talc: "MS" manufactured by Nippon Talc Co., Ltd.
Modified PP: "ZP648" manufactured by Prime Polymer
The above blended raw materials were dry-blended in the above blended amounts and kneaded at a temperature of 220 ° C. using a twin screw extruder (“TEX30” manufactured by Nippon Steel Works, Ltd.) to obtain a pellet-shaped resin composition for foaming. .

(Example 1)
<Formation of foam molding>
The obtained pellet-shaped resin composition for foaming was charged into an injection molding machine (manufactured by Toshiba Machine Co., Ltd.) equipped with a supercritical generator. While melting the resin composition for foaming in a cylinder set at a temperature of 200 ° C., a supercritical fluid of nitrogen (N ₂ ) was mixed under the conditions of a filling amount of 0.5% by weight and a filling pressure of 16 MPa. The filling amount (unit:% by weight) of the supercritical fluid can be calculated by the following equation (1).
Filling amount of supercritical fluid (unit: wt%) = [(flow rate of supercritical fluid x inflow time of supercritical fluid x conversion factor 27.8) / weight of resin composition for foaming] x 100 (1)

The molten resin obtained by mixing the supercritical fluid was injected into a cavity in a mold whose mold temperature was set to 60 ° C. under the conditions of a filling peak pressure of 140 MPa and a screw back pressure of 15 MPa. The minimum value of the gap distance between the molds in the cavity before the core back was 0.8 mm. The mold temperature was 60 ° C. The core back was performed at a timing immediately after the filling of the cavity with the molten resin was completed. Specifically, foaming of the molten resin was promoted by retracting the male mold of the mold by 1.5 mm to increase the volume of the cavity. After the solidification of the molten resin was completed, the foaming container was taken out.

(Examples 2 to 7 and Comparative Examples 1 and 2)
The moving distance of the foaming agent and the core back is changed as shown in Table 1 below, and the cavity of the mold is formed such that the first curved surface and the second curved surface in the flange side curved surface portion shown in Table 1 below are formed. Except for adjusting the shape, foamed containers of Examples 2 to 7 and Comparative Examples 1 to 3 were obtained in the same manner as in Example 1 above.

The radius of curvature R1 on the first curved surface formed from the inner surface of the container to the upper surface of the flange portion of the obtained foamed container and the radius of curvature R2 on the second curved surface formed from the outer surface of the container to the lower surface of the flange portion are measured. did. In addition, the shortest distance A from the intersection of the straight line along the container inner side surface on the side of the obtained foamed container and the straight line along the upper surface of the flange portion to the open end of the upper surface of the flange portion was measured. The results of each measurement are shown in Table 1 below.

With respect to the obtained foamed container, the following heat insulation properties, the swelling or inclination of the plane above the flange, and the flange strength were evaluated. The evaluation results obtained are shown in Table 1 below.

(Thermal insulation properties)
Put boiling water (about 100 ° C.) immediately after boiling into the obtained foaming container up to 20 cm from the top of the container, and lift the container with boiling water with bare hands so as to touch the bottom and sides, and the time until it can be held. Was measured and evaluated according to the following evaluation criteria.
◎: What was held for 20 seconds or more ：: What was held for 15 seconds to less than 20 seconds △: What was held for 10 seconds to less than 15 seconds ×: What was held for less than 10 seconds

(Swelling / tilting of the plane above the flange)
The obtained foamed container is cut into 12 equal parts so as to pass through the center of the foamed container and the end of the flange, the cross section of the upper surface of the flange is observed with a microscope, the inclination angle is measured from the microscope image, and the average value is measured. Is the inclination of the upper surface of the flange. The swelling of the upper surface of the flange was visually confirmed.

(Flange strength)
The obtained foamed container is placed with the opening facing upward (that is, with the flange facing upward), and a flat plate having a larger outer diameter than the flange is pressed against the upper surface of the flange until the flange breaks. The strength was measured and evaluated according to the following evaluation criteria.
◎: Pressure at break is 0.2 MPa or more ：: Pressure at break is 0.15 MPa to less than 0.2 MPa Δ: Pressure at break is 0.1 MPa to less than 0.15 MPa x: Pressure at break is 0. Less than 1MPa

As can be seen from Table 1, the foamed containers obtained in Examples 1 to 7 all have a curvature radius R1 of the first curved surface of 0.5 mm or more and satisfy R1 <distance A. Deformation was suppressed, the inclination of the plane on the upper surface of the flange portion was smaller than 20 °, and no swelling of the upper surface of the flange portion was observed. A foamed container having a flange portion with a uniform shape was obtained. Further, in the foamed containers obtained in Examples 1 to 6, since R2 is 0.2 mm or more, the flange portion has excellent strength, and all of the pressure when the lid is heat-sealed. It had a strength to withstand. Furthermore, the foamed containers obtained in Examples 1 to 7 all had good heat insulating properties.
On the other hand, in the foamed container obtained in the comparative example, since either the curvature radius R1 of the first curved surface or the relationship between R1 and the distance A does not satisfy the predetermined range, swelling occurs on the upper surface of the flange portion. Also, a large inclination exceeding 30 ° occurred.

(Example 8 and Comparative Examples 3 to 5)
Except that the moving distance of the foaming agent and the core back was changed as shown in Table 2 below, and the cavity shape of the mold corresponding to the shape of the flange-side curved surface portion of the foaming container was changed, the same as in Example 1 above. Thus, foamed containers of Example 8 and Comparative Examples 3 to 5 were obtained.

As can be seen from Table 2, in the foamed container obtained in Example 8, the curvature radius R1 of the first curved surface is 0.5 mm or more, and R1 <distance A, so that the inclination and / or Or, deformation such as swelling was suppressed, and a uniform-shaped foam container having a flat surface on the upper surface of the flange portion could be obtained.
On the other hand, in the foamed containers obtained in Comparative Examples 3 to 5, since the radius of curvature R1 of the first curved surface does not satisfy the predetermined range, foamed particles grow in the resin, or a large number of foamed particles are generated in the resin. In addition, swelling and inclination on the upper surface of the flange portion, or swelling on the lower surface of the flange portion have occurred.

Reference Signs List 10 foam container 10a bottom 10b bottom curved surface 10c side 10d flange curved surface 10e flange 11 skin layer (skin layer)
12 foam layer 20 supercritical injection molding device 21 hopper 22 heating cylinder 23 screw 24 nozzle 25 cylinder 26 supercritical fluid generating unit 27 injection control unit 30 mold 31 male mold 32 female mold 33 cavities 33a, 33b first area 33c second Regions 33d, 33e Third region 33f Flow end surface 33f ₁ Core back moving direction end 33f at the flow end side ₂ End opposite to flow end side 34 Runner 35 Resin inlet 41 Vent groove 42 Gas external discharge line

Claims (5)

A foam container having a bottom and side portions,
The foamed container has a flange portion which is provided in the outer direction of the container at the open end of the side portion,
The flange portion has a flat surface on an upper surface,
The radius of curvature R1 in the first curved surface portion formed from the container inner side surface of the side portion to the upper surface of the flange portion is 0.5 mm or more,
The shortest distance A from the intersection of the straight line along the container inner surface of the side portion and the straight line along the upper surface of the flange portion to the open end of the upper surface of the flange portion is calculated from the radius of curvature R1 of the first curved surface portion. A foam container characterized by having a large size. 2. The foam container according to claim 1, wherein a radius of curvature R2 of a second curved surface portion formed from the outer surface of the side container to the lower surface of the flange portion is 0.2 mm or more. 3. The foam container according to claim 1, wherein a thickness of the flange portion is 0.5 mm or more and 8.0 mm or less. The foam container according to any one of claims 1 to 3, wherein an inclination of a plane on an upper surface of the flange portion is within ± 30 ° with respect to a virtual plane parallel to a ground plane of the foam container. A method for producing a foamed container according to any one of claims 1 to 3 by injection molding,
A step of filling the cavity in the mold composed of a concave mold and a convex mold with a molten resin,
Before the molten resin filled in the cavity is completely solidified, a step of moving at least one of the concave mold and the convex mold to increase the volume of the cavity,
The cavity includes a first region for molding the bottom portion of the foam container, a second region for molding the side portion, and a third region for molding the flange portion,
Vent grooves for removing air in the cavity are provided 16 or more from the third region toward the outside of the cavity,
A method of manufacturing a foamed container, wherein a position where the concave mold and the convex mold are aligned is located near a lower surface of the flange portion in the third region.

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