JP6485690B2 - Resin tray and resin tray manufacturing method - Google Patents

Description

  The present invention relates to a resin tray manufactured by blow molding, and a method for manufacturing the resin tray.

  As a method for manufacturing a resin storage tray, vacuum molding or press molding in which a resin sheet is placed on a mold and the resin sheet is shaped into a shape along the surface of the mold by pressurization is known. ing. Patent Document 1 is a conventional example of a tray made of a resin material. This tray is vacuum-molded by sucking a sheet made of a resin material such as polypropylene into a cavity formed in a mold and transferring the molding surface shape of the mold to the sheet.

Japanese Patent No. 5470060

  By the way, in the manufacturing method by vacuum molding or press molding, after placing the resin sheet on the mold, preheating is performed to soften the resin sheet to an extent suitable for molding. However, this preheating requires a certain amount of time, and it is necessary to perform preheating every time it is molded, so that the productivity is low.

  An object of the present invention is to provide a tray that can be manufactured with higher productivity than vacuum forming and press forming, and a method of manufacturing the tray.

  The tray of the present invention is a resin tray that includes a bottom wall portion and an annular peripheral wall portion that rises from a peripheral portion of the bottom wall portion, and forms a storage space by the bottom wall portion and the peripheral wall portion, The resin constituting the resin tray is a thermoplastic resin containing 5 to 50% by weight of polypropylene and 50 to 95% by weight of polyethylene, having the polypropylene as an island part and a sea-island structure having the polyethylene as a sea part, The upper end surface of the peripheral wall portion is formed from an internal hollow blow-molded product in which one side corresponding to one mold and the other side corresponding to the other mold are joined along a parting line. It is the surface which peeled along the line, It is characterized by the above-mentioned.

  According to this invention, when an internal hollow blow-molded product is peeled along the parting line, it is separated into one side and the other side to form two resin trays. A blow-molded product is one in which one side corresponding to one mold and the other side corresponding to the other mold are joined along a parting line, but the thermoplastic resin used as a material is polypropylene and Since polyethylene forms a sea-island structure at a predetermined ratio, the bonding strength is not so high, and it can be easily agglomerated and peeled along the parting line. Since this blow-molded product is obtained by blow-molding a molten cylindrical parison that is sequentially fed out, preheating necessary for vacuum forming and press-molding is unnecessary.

  According to the present invention, two trays can be manufactured simultaneously from one blow-molded product. Blow-molded products can be molded one after another from the melted parisons that are sequentially sent out, so preheating is not required for each molding. For this reason, compared with the case of vacuum forming or press molding, the manufacturing method of the resin-made tray and resin-made tray with favorable productivity can be provided.

It is a perspective view of the resin-made trays of the embodiment of the present invention. It is a schematic sectional drawing explaining the blow molding machine used by embodiment of this invention. It is sectional drawing in the radial direction of a parison when the metal mold | die of embodiment of this invention is opened. It is sectional drawing in the radial direction of a parison when the metal mold | die of embodiment of this invention is clamped. It is a perspective view of the blow molded product taken out from the metal mold | die of embodiment of this invention. It is a partial cross section figure of the blow molded product of embodiment of this invention. It is explanatory drawing explaining the process of separating the blow molded product of embodiment of this invention into one side part and the other side part. It is a disassembled perspective view of the metal mold | die for protrusion for forming the 1st protrusion of embodiment of this invention. It is a disassembled perspective view of the metal mold | die for protrusion for forming the 1st protrusion of the other shape of embodiment of this invention. It is a disassembled perspective view of the metal mold | die for protrusion for forming the 1st protrusion of the other shape of embodiment of this invention. It is a perspective view of the metal mold | die for protrusion for forming the 2nd protrusion of embodiment of this invention. It is a partial cross section figure of the state where the metal mold | die for protrusion of embodiment of this invention was attached to one metal mold | die. It is a side view when the resin tray of the embodiment of the present invention is nested. It is a partial expanded sectional view when the resin tray of embodiment of this invention is nested. It is a side view when stacking the resin tray of the embodiment of the present invention. It is a partially expanded sectional view when stacking the resin tray of the embodiment of the present invention.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a perspective view of a resin-made resin tray 10 according to the present embodiment. The resin tray 10 includes a bottom wall portion 11 having a substantially flat plate shape, and an annular peripheral wall portion 12 that rises upward from the entire periphery of the peripheral edge portion of the bottom wall portion 11, and the bottom wall portion 11 and the peripheral wall portion 12. A space surrounded by and forms a storage space.

  The bottom wall portion 11 has a shape in which four corners of a rectangular flat plate are cut out. A plurality of protrusions are provided at predetermined positions on the surface (upper surface) of the bottom wall portion 11 on the storage space side. In the present embodiment, first protrusions 21, 22, and 23 for positioning the object to be stored with respect to the bottom wall portion 11 by fitting a concave portion (not shown) of the object to be stored, and the plurality of resin trays 10 are provided. A second protrusion 24 that supports the bottom surface of the tray immediately above when stacking, and minute protrusions 25 that are formed in a matrix at predetermined intervals on the entire top surface of the bottom wall portion 11 are provided. The upper ends of the first protrusions 21, 22, 23 and the minute protrusion 25 are lower than the upper end surface of the peripheral wall portion 12, and the upper end of the second protrusion 24 is substantially the same as the upper end surface of the peripheral wall portion 12. ing.

  Below, the technical idea of this invention is demonstrated using the manufacturing method of the resin-made trays 10. FIG. FIG. 2 is a schematic cross-sectional view illustrating a blow molding machine used in the present embodiment. The blow molding machine includes a molding die 30 and an extrusion device (not shown) for supplying the parison P in a molten state.

  The mold 30 includes a pair of molds 31 and 32 that can contact and separate from each other. Formed on the opposing surfaces of the molds 31 and 32 are concave molding surfaces 33 that are symmetrical with each other. On each of the molding surfaces 33, irregularities corresponding to the shape of the resin tray 10 are formed, and the resin tray 10 is shaped along the molding surface 33. Further, annular pinch-off portions 31a and 32a are provided on the entire outer peripheral edge of the molding surface 33 of the molds 31 and 32, and notches 31b and 32b are formed on the outer peripheral sides of the pinch-off portions 31a and 32a. Yes.

  In addition, the molds 31 and 32 are conventionally known so that a blow pressure can be applied in a sealed space formed by the molds 31 and 32 when the molds 31 and 32 are clamped. No blow pin is installed.

  The extrusion apparatus (not shown) is a conventionally known type, and detailed description thereof is omitted, but the thermoplastic resin pellets charged from the hopper are melted and kneaded in the cylinder by the rotation of the screw by the hydraulic motor. The molten resin is transferred to the accumulator chamber and stored in a certain amount, and the molten resin is sent toward the head by driving the plunger, through a die gap formed by an annular space formed between the head die and the core. A continuous cylindrical parison P is extruded. The thermoplastic resin forming the resin tray 10 of the present invention has a sea-island structure in which polypropylene is dispersed in an island shape with respect to polyethylene. Can be adjusted. That is, by decreasing the kneading degree of the thermoplastic resin, the polypropylene islands become large, and cohesive peeling at the parting line becomes easy.

  The die gap is arranged vertically downward, and the molten parison P extruded from the die gap is sent vertically downward in a form that hangs down from the die gap as it is, and a die 31 disposed below the die gap. 32 is arranged between them.

  A method for manufacturing the resin tray 10 using the blow molding machine having the above configuration will be described. 3 is a sectional view in the radial direction of the parison P when the molds 31 and 32 are opened, and FIG. 4 is a sectional view in the radial direction of the parison P when the molds 31 and 32 are clamped. FIG. 5 is a perspective view of the blow molded product 60 taken out from the molds 31 and 32, and FIG. 6 is a partial cross-sectional view of the blow molded product 60.

  First, a thermoplastic resin material that is a mixture of polypropylene and polyethylene is stored in an extrusion apparatus in a molten state. Then, by intermittently extruding the stored thermoplastic resin from the die gap at a predetermined extrusion rate per unit time, the molten cylindrical parison P is extruded at a predetermined extrusion speed so as to hang downward. The extruded cylindrical parison P is sequentially supplied between the molds 31 and 32 opened as shown in FIG. Thereby, according to the opening / closing timing of the dies 31, 32, a predetermined area (hereinafter referred to as a molding area) to be molded of the cylindrical parison P is positioned between the dies 31, 32. Become.

  Next, as shown in FIG. 4, the molds 31 and 32 are clamped. The molding area is configured to be slightly larger than the area surrounded by the pinch-off portions 31a and 32a of the molds 31 and 32. That is, the diameter of the cylindrical parison P is slightly larger than the area surrounded by the pinch-off portions 31a and 32a, and the lower end of the cylindrical parison P is positioned below the pinch-off portions 31a and 32a. As a result, when the molds 31 and 32 are clamped, the molding region of the cylindrical parison P is crushed and held between the pinch-off portions 31a and 32a, and over the entire circumference of the pinch-off portions 31a and 32a. The burr | flash part 64 of the state which the parison P protruded outside is formed.

  In this state, air is injected into the interior sealed by the pinch-off portions 31a and 32a of the parison P via blow pins (not shown), and the parison P is expanded by this air pressure to form the molding surfaces 33 of the molds 31 and 32. Adhere closely. Thereby, the parison P is shape | molded in the shape of a complementary relationship with each shaping | molding surface of the metal mold | dies 31 and 32. FIG. After the parison P is cooled and solidified, the mold 31 and the mold 32 are opened, and the blow molded product 60 made of a hollow body is taken out between the mold 31 and the mold 32.

  FIG. 5 is a perspective view of the blow molded product 60. The blow molded product 60 is formed with a burr 64 along the parting line 63. Since the burr 64 is formed on the end side of the molding region of the cylindrical parison P, one end 64a that is substantially parallel to the radial direction of the parison P is open and substantially parallel to the axial direction. The other side end portion 64b has a bag shape. In addition, the blow molded product 60 shown in FIG. 5 shows the state separated from the parison P by a cutter or the like.

  Next, the burr part 64 is cut and removed from the blow molded product 60 with a cutter or the like. FIG. 6 is a partial cross-sectional view of the blow molded product 60 from which the burr 64 is cut and removed. As a result, an internal hollow blow-molded product 60 in which the one side 61 corresponding to one mold 31 and the other side 62 corresponding to the other mold 32 are symmetrically joined to each other along the parting line 63. It becomes. The one side portion 61 and the other side portion 62 exhibit a shape that is plane-symmetric with respect to a plane that passes through the parting line 63.

  FIG. 7 is an explanatory diagram illustrating a process of separating the blow molded product 60 into one side portion 61 and the other side portion 62. First, one side 61 of the blow molded product 60 is supported by the jig 70. A supporting recess 71 is formed on the upper surface of the jig 70. The supporting recess 71 has a shape that fits to the outer peripheral surface of the one side portion 61 of the blow molded product 60, and can hold the one side portion 61 with the other side portion 62 exposed.

  After fitting one side 61 of the blow-molded product 60 into the supporting recess 71 of the jig 70, an impact is applied to the other side 62 by a hammer (not shown) or the like. When this impact is applied to the parting line 63 of the blow molded product 60, the blow molded product 60 is peeled along the parting line 63 and separated into one side portion 61 and the other side portion 62. The separated one side portion 61 and the other side portion 62 each constitute a resin tray 10, and two resin trays 10 having the same shape as shown in FIG. . That is, the upper end surface of the peripheral wall portion 12 of the resin tray 10 corresponding to the one side portion 61 and the upper end surface of the peripheral wall portion 12 of the resin tray 10 corresponding to the other side portion 62 part the blow molded product 60. The surface is peeled along the line P.

  Here, the thermoplastic resin which is the material of the blow molded product 60 contains 5 to 50% by weight of polypropylene and 50 to 95% by weight of polyethylene, and has a sea-island structure in which polypropylene is an island part and the polyethylene is a sea part. ing. For this reason, the one side part 61 and the other side part 62 of the blow molded product 60 are fused at the portion where the polypropylene and the polyethylene are in contact with each other, but are not fused at the portion where the polypropylene and the polyethylene are in contact with each other. The strength (fusion strength) is not so great. Thereby, the one side part 61 and the other side part 62 can be cohesively peeled along the parting line 63, and can be easily separated by an appropriate impact.

  Further, in the internal space of the blow molded product 60, the protrusions on the one side portion 61 and the other side portion 62 are located facing each other. Among the plurality of protrusions, the second protrusion 24 has the same height as the peripheral wall portion 12, and therefore, the top portions facing each other contact each other (see FIG. 6). However, the bonding strength of the top portion of the second protrusion 24 is not large due to the above-described sea-island structure, and the cohesive separation can be easily performed. On the other hand, since the first protrusions 21, 22, 23 and the minute protrusions 25 are lower than the peripheral wall part 12 and have a gap between the opposing top parts (see FIG. 4), they do not hinder peeling.

  In each of the resin trays 10 thus agglomerated and peeled, the surface shape of the upper end surface 12 a of the peripheral wall portion 12 becomes a rough surface rougher than the outer peripheral surface of the peripheral wall portion 12. For this reason, after peeling off, the end surface 28a of the peripheral wall 28 may be subjected to a flame treatment process to form a smooth surface. Similarly, the top of the second protrusion 24 may be subjected to flame treatment to form a smooth surface.

  As described above, in the method for manufacturing the resin tray 10 according to the present embodiment, the thermoplastic resin as the material is sequentially arranged in the molds 31 and 32 as the melted parison P, so that preheating for each molding is unnecessary. In addition, since the two resin trays 10 can be simultaneously manufactured by one molding, the productivity is better than the case of manufacturing by vacuum molding or press molding.

  Moreover, in the manufacturing method of the resin tray 10 of the present embodiment, it is easy to change the shape and position of the protrusions 21, 22, 23, 24, 25 provided on the bottom wall portion 11. For this reason, as shown in FIGS. 2 and 4, the molding surfaces 33 of the molds 31 and 32 used in the present embodiment are provided with projections corresponding to the projections 21, 22, 23, 24, and 25. However, these protrusions are detachable from the molding surfaces 33 of the dies 31 and 32.

  In the present embodiment, since the first protrusions 21, 22, and 23 are three types of protrusions having different shapes, the protrusion molds for forming the protrusions have shapes corresponding to the respective protrusions. 8 is an exploded perspective view of the projection mold 41 for forming the first projection 21, and FIG. 9 is an exploded perspective view of the projection mold 42 for forming the first projection 22. FIG. 4 is an exploded perspective view of a protrusion mold 43 for forming a first protrusion 23. Since the first protrusions 21, 22, 23 are provided with a truncated cone-shaped protrusion on a flat base, the protrusion molds 41, 42, 43 are flat plate members 41 a, 42 a corresponding to the base. , 43a, and truncated cone members 41b, 42b, 43b corresponding to the truncated cone-shaped protrusions. A small hole is provided at substantially the center of the flat plate members 41a, 42a, and 43a, and a screw portion provided on the lower surface of the truncated cone portion of the truncated cone members 41b, 42b, and 43b can be inserted.

  FIG. 11 is a perspective view of a protrusion mold 44 for forming the second protrusion 24. Since the second projection 24 has a truncated cone shape, the projection mold 44 also has a truncated cone shape, and a screw portion is provided on the lower surface of the truncated cone portion. Although not shown in the drawing, since the minute protrusion 25 has a hemispherical shape, the protrusion mold for forming the minute protrusion has a hemispherical shape, and is formed on the lower surface of the hemispherical portion like the other protrusion molds. A threaded portion is provided.

  A plurality of screw holes (not shown) are provided in a matrix shape on the molding surfaces of the two dies 31 and 32, and these protrusion dies are screwed into the screw holes. Can be attached. FIG. 12 is a partially enlarged cross-sectional view of the state in which the projection molds 42 and 44 are attached to the mold 31. Thereby, the positions and shapes of the protrusions of the molds 31 and 32 can be freely changed, and various variations of trays can be easily manufactured.

  Further, the resin tray 10 of the present embodiment can be nested and stacked. 13 is a side view when the resin tray 10 is nested, and FIG. 14 is a partially enlarged sectional view thereof. 15 is a side view when the resin tray 10 is stacked, and FIG. 16 is a partially enlarged sectional view thereof.

  Here, nesting refers to the storage or transport of empty trays, etc., when the trays are stacked in a state in which no objects are stored, and the tray directly above partially enters the tray immediately below. This is an aspect that enables space saving, and stacking is an aspect in which the stacked state is stabilized when the trays are stacked in a state in which the objects to be stored are stored.

  First, the nesting state will be described. On the back surface of the bottom wall portion 11 of the resin tray 10, back surface side recesses are provided at positions corresponding to the protrusions 21, 22, 23, 24, and 25. Further, the peripheral wall portion 12 gradually expands to the outer peripheral side as the lower side portion moves upward from the bottom wall 11 side, the upper side portion is erected vertically on the lower side portion, and the upper end side is the bottom wall portion 11. It has a shape that expands to the outer peripheral side rather than the side.

  For this reason, when a plurality of resin trays 10 are stacked in the same posture (hereinafter referred to as a predetermined nesting posture), the lower portion of the resin tray 10 positioned immediately above is loosely fitted to the resin tray 10 positioned immediately below. . A second protrusion 24 having a high height is provided on the bottom wall portion 11 of the resin tray 10, but a back surface-side recess corresponding to the second protrusion 24 is provided on the back surface of the bottom wall portion 11 of the resin tray 10. 26 is formed, and the second protrusion 24 is loosely fitted in the back surface recess 26 of the resin tray 10 immediately above. In the present embodiment, only the second projection 24 having a high height is loosely fitted in the concave portion 26 on the back surface (see FIG. 14), and the other projections 21, 22, 23, and 25 having a low height are directly above the resin. It will be positioned below without reaching the back of the tray 10. With this configuration, when a plurality of resin trays 10 are nested, the height becomes lower than when stacking, and space saving is achieved in transporting and storing empty resin trays 10.

  Next, the stacking state will be described. The upper end surface of the second protrusion 24 is located at the same height as the upper end surface of the peripheral wall portion 12. In addition, when the resin tray 10 directly above the resin tray 10 directly below is alternately superposed in a posture rotated 180 degrees in the horizontal direction (hereinafter referred to as a predetermined stacking posture), the resin tray 10 directly below is formed. The second protrusion 24 of the tray 10 is configured to support an area other than the back-side recess 26 corresponding to the second protrusion 24 of the resin tray 10 immediately above. In the present embodiment, the second protrusion 24 supports the outer peripheral side region of the back surface side concave portion corresponding to the minute protrusion 25 of the resin tray 10 immediately above.

  For this reason, when the objects to be stored are stored in the resin tray 10 and overlapped in a predetermined stacking posture, the second protrusion 24 of the resin tray 10 directly below is an outer peripheral side region of the recess on the back surface side of the resin tray 10 immediately above. And a space is formed between the resin tray 10 immediately below and the resin tray 10 directly above. Since the upper end surface of the second protrusion 24 is located at the same height as the upper end surface of the peripheral wall portion 12 and the region supported by the second protrusion 24 constitutes the lowermost surface of the resin tray 10, Thus, a sufficient space is formed between the resin tray 10 immediately below and the resin tray 10 immediately above. Thereby, a plurality of resin trays 10 can be stacked.

  As described above, according to the present embodiment, the resin tray 10 can be switched between the nesting posture and the stacking posture by rotating the resin tray 10 in the horizontal direction, so that convenience is improved.

  In nesting and stacking, the space formed between adjacent resin trays 10 may be designed according to the size of the object to be stored, and at least the height when nesting is It should be lower than the height.

  As mentioned above, although embodiment which applied this invention has been described, it cannot be overemphasized that this invention is not what is limited to the above-mentioned embodiment, A various change can be added in the range which does not deviate from the summary of this invention. It is.

  For example, the bottom wall portion of the tray can be formed in another shape such as a circle, a square, or a polygon, and the peripheral wall portion can be formed in another shape.

  Further, the function, shape, and position of the protrusion formed on the upper surface of the bottom wall portion of the tray are not limited to the above embodiment, and can be changed as appropriate. What is necessary is just to design suitably the metal mold | die for protrusion attached to two metal mold | die according to each protrusion of a bottom wall part upper surface.

  Further, the switching between nesting and stacking may be such that the horizontal rotation angle is other than 180 degrees. For example, the horizontal rotation angle may be 90 degrees or other angles. In this case, if the overall shape of the tray, the position of each protrusion, etc. are designed so that nesting and stacking are possible at the set rotation angle good.

DESCRIPTION OF SYMBOLS 10 Resin tray 11 Bottom wall part 12 Peripheral wall part 21,22,23 1st protrusion 24 2nd protrusion 25 Minute protrusion 26 Back surface side recessed part 30 corresponding to 2nd protrusion Mold 31, 32 Mold 31a, 32a Pinch-off part 41 , 42, 43, 44, 45 Protrusion mold 60 Blow molding 61 One side portion 62 corresponding to one side die 62 The other side portion 63 corresponding to the other side die 63 Parting line 64 Burr portion 70 Jig P Parison

Claims (7)

A resin tray comprising a bottom wall and an annular peripheral wall rising from a peripheral edge of the bottom wall, and forming a storage space by the bottom wall and the peripheral wall;
The resin contains 5 to 50% by weight of polypropylene and 50 to 95% by weight of polyethylene, and is a thermoplastic resin having a sea-island structure with the polypropylene as an island and the polyethylene as a sea.
The upper end surface of the peripheral wall portion is formed from an internal hollow blow-molded product in which one side corresponding to one mold and the other side corresponding to the other mold are joined along a parting line. A resin tray characterized by being a surface peeled along a line.   2. The resin tray according to claim 1, wherein a first protrusion having a height lower than that of the peripheral wall portion is formed on a surface of the bottom wall portion on the storage space side.   The tray according to claim 1 or 2, wherein a surface shape of an upper end surface of the peripheral wall portion is a rough surface rougher than an outer peripheral surface of the peripheral wall portion.   The tray according to claim 1 or 2, wherein an upper end surface of the peripheral wall portion is made a smooth surface by flame treatment. The peripheral wall portion has an upper end side that extends to the outer peripheral side rather than the bottom wall portion side,
A plurality of second protrusions are provided on the surface of the bottom wall portion on the storage space side,
A plurality of back side concave portions are provided at positions corresponding to the second protrusions on the back surface of the bottom wall portion,
When the resin tray directly below and the resin tray directly above are stacked in the same posture, the second protrusion of the resin tray directly below is loosely fitted into the recess on the back surface of the resin tray directly above, and the nesting state And
When the resin tray directly above is alternately overlapped with the resin tray directly below in a posture rotated by a predetermined angle in the horizontal direction, the second protrusions of the resin tray directly below are placed on the tray directly above. The resin tray according to any one of claims 1 to 4, wherein the bottom wall portion is in a stacking state by supporting an area other than the back surface recess. A resin tray manufacturing method comprising a bottom wall part and an annular peripheral wall part rising from a peripheral part of the bottom wall part, and forming a storage space by the bottom wall part and the peripheral wall part,
Polypropylene is contained in an amount of 5 to 50% by weight and polyethylene is contained in an amount of 50 to 95% by weight. A cylindrical Paris having a sea-island structure in which the polypropylene is used as an island and the polyethylene is used as a sea, and a predetermined region of the Paris is paired. Placing between the molds,
Clamping a pair of molds, sandwiching the predetermined area of the parison with a pinch-off part of the mold, and forming a burr part in a state where the parison protrudes from the entire outer periphery of the pinch-off part; ,
Supplying a gas to the inside of the parison located in the pair of molds clamped, and molding an internal hollow blow-molded product in which a parting line is formed along the burr portion;
Cutting and removing the burr part from the blow molded product taken out from the mold;
Separating the blow molded product from which the burr portion has been cut and removed along the parting line, thereby obtaining the resin tray in which the separation surface is the upper end surface of the peripheral wall portion; and
A method for producing a resin tray, comprising:   The tray manufacturing method according to claim 6, further comprising a step of performing a flame treatment on the peeled surface peeled along the parting line to form a smooth surface.

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