Container with synthetic resin window, preform, and preform injection molding apparatus

Abstract

A biaxially stretch blow molded container is formed with a clearly transparent window portion in a longitudinal strip shape by preventing mixture and cut-in of a colored resin to the window portion. In a predetermined range extending from an upstream end to a downstream position of a flow path including a cylindrical flow path and a reduced-diameter flow path formed in a nozzle portion, a pair of guiding ribs in the form of longitudinal ridges is linearly arranged partitioning the flow path in a circumferential direction, and a longitudinal groove flow path is formed between the guiding ribs. A molten B resin is supplied to the longitudinal groove flow path, and a molten A resin is supplied to the cylindrical flow path excluding the longitudinal groove flow path. The longitudinal strip-shaped flow path of the B resin interrupts the cylindrical flow path of the A resin in the circumferential direction.

Claims

1. A synthetic resin container with a window that is produced by biaxially stretch blow molding a test-tube-shaped preform, the synthetic resin container with a window comprising a circumferential wall including a longitudinal strip-shaped portion that is made of a transparent or a semi-transparent B resin and that is formed in a longitudinal strip shape penetrating the circumferential wall in a circumferentially predetermined position in the circumferential wall over a predetermined height range, a remaining portion of the circumferential wall excluding the longitudinal strip-shaped portion being made of an A resin that is obtained by coloring a synthetic resin and that is adhesive to the B resin, and the longitudinal strip-shaped portion serving as a window portion, wherein a portion of the B resin constituting the longitudinal strip-shaped portion flows around to a side opposite to the circumferentially predetermined position in which the longitudinal strip-shaped portion is formed, to be laminated in vicinity of a portion of the circumferential wall made of the A resin that is close to an inner circumferential surface of the circumferential wall.

2. The synthetic resin container with the window of claim 1, further comprising a bottom portion, wherein the longitudinal strip-shaped portion is formed over an entire height range measured from a bottom wall of the bottom portion.

3. The synthetic resin container with the window of claim 1, wherein, in a bottom wall of a bottom portion, the longitudinal strip-shaped portion is arranged from a peripheral edge toward a center and beyond a center position of the bottom wall.

4. The synthetic resin container with the window of claim 2, wherein, in a bottom wall of a bottom portion, the longitudinal strip-shaped portion is arranged from a peripheral edge toward a center and beyond a center position of the bottom wall.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the accompanying drawings:

(2) FIG. 1 is a perspective view illustrating a container with a window according to one embodiment;

(3) FIG. 2A is a sectional plan view taken along a line A-A in FIG. 1, and FIG. 2B is a bottom view of FIG. 1;

(4) FIG. 3 is a perspective view of a preform according to one embodiment;

(5) FIG. 4A is a sectional plan view of the preform taken along a line B-B in FIG. 3, and FIG. 4B is a bottom view of the preform illustrated in FIG. 3;

(6) FIG. 5A is a side view illustrating a longitudinal section of a part of an injection molding apparatus according to one embodiment taken along a line C-C in FIG. 6, and FIG. 5B is an enlarged view of a front end portion of a shut-off pin illustrated in FIG. 5A;

(7) FIG. 6 is a plan view of the injection molding apparatus illustrated in FIG. 5;

(8) FIG. 7 is an enlarged front view of a partial longitudinal section of a part of the vicinity of a nozzle portion of the injection molding apparatus illustrated in FIG. 5 taken along a line C2-C2 in FIG. 6;

(9) FIG. 8A is a sectional plan view flows in the longitudinal strip taken along a line N1-N1 in FIG. 7, FIG. 8B is a sectional plan view taken along a line N2-N2 in FIG. 7, FIG. 8C is a sectional plan view taken along a line N3-N3 in FIG. 7, all of which illustrate flow path shapes, and FIG. 8D is a sectional plan view of columnar resin melts taken along a line N4-N4 in FIG. 7, and FIG. 8E is another exemplary sectional plan view of columnar resin melts;

(10) FIG. 9 is a schematic view of how resins flow in the side view of FIG. 5A;

(11) FIGS. 10A to 10C are front views of three variations of an inner mandrel; and

(12) FIGS. 11A to 11C are side views of three variations in shapes of a front end portion of a shut-off pin.

REFERENCE SIGNS LIST

(13) 1 mold 2 cavity 3 pin gate 11 nozzle portion 12a introduction path (of A resin) 12b introduction path (of B resin) 13a supply start position (of A resin) 13b supply start position (of B resin) 14 manifold 15 cylindrical flow path 16 reduced-diameter flow path 17 longitudinal groove flow path 17a upstream longitudinal groove flow path 19 joining flow path 20 shut-off pin 20t conical front end portion 20tp front end 21 inner mandrel 21g guiding rib 22 outer mandrel 101 preform 102 mouth tubular portion 103 neck ring 105 trunk portion 106 bottom portion 107 gate mark 112 longitudinal strip-shaped portion 201 container 202 mouth tubular portion 203 neck ring 204 shoulder portion 205 trunk portion 206 bottom portion 212 longitudinal strip-shaped portion 212w window portion Ax central axis Axc central axis (of conical front end portion) center position Hc cylindrical region Ht tapered region Ra A resin Rb B resin Sa resin supply unit (of A resin) Sb resin supply unit (of B resin) W flow path width

DETAILED DESCRIPTION

(14) A biaxially stretch blow molded synthetic resin container with a window, a preform, and an injection molding apparatus according to embodiments will be described below with reference to the drawings.

(15) FIGS. 1 and 2 illustrate one embodiment of the container with a window. FIG. 1 is an overall perspective view of the container, FIG. 2A is a sectional plan view taken along a line A-A in FIG. 1, and FIG. 2B is a bottom view of FIG. 1.

(16) A container 201 is made of a PET resin and has a bottle shape formed by biaxial stretch blow molding. The container 201 includes a mouth tubular portion 202, a shoulder portion 204 having a tapered tubular shape, a trunk portion 205 having a cylindrical shape, and a bottom portion 206. The mouth tubular portion 202 is provided on a circumference thereof with a neck ring 203. The trunk portion 205 has a diameter of 55 mm and an overall height of 190 mm.

(17) The container 201 is formed with the A resin Ra, which is obtained by coloring a PET resin opaque white, and the B resin Rb, which is an uncolored PET resin. Substantially the entire container 201 is made of the opaque A resin Ra, and a longitudinal strip-shaped portion 212, which is made of the transparent B resin Rb, is located in a circumferentially predetermined position in a circumferential wall of the container 201 over the entire height range measured from un upper end of the mouth tubular portion 202 to a bottom wall of the bottom portion 206. The longitudinal strip-shaped portion 212 is utilized as a window portion 212w through which an inside of the container 201 is visible and through which the amount of a remaining content is identified.

(18) In the sectional plan view as illustrated in FIG. 2A, substantially the entire circumferential wall is made of the A resin Ra, and the longitudinal strip-shaped portion 212 made of the B resin Ra is laminated along the circumferential direction in the form of a slit penetrating through the circumferential wall in such a manner as to interrupt the A resin Ra portion.

(19) The longitudinal strip-shaped portion 212 has a horizontal width that varies according to respective stretch (draw) ratios of portions in the horizontal direction.

(20) With reference to a bottom view in FIG. 2B, as illustrated in the figure, in the bottom wall of the bottom portion 206, the longitudinal strip-shaped portion 212 extends from a peripheral edge to a center position Cx, and further to a position beyond the center position Cx.

(21) The longitudinal strip-shaped portion 212 also has a fan shape arising from an increased width from the center position to the peripheral edge as a result of the biaxial stretch blow molding.

(22) FIG. 2A also includes an additional enlarged view of a part of the section of the circumferential wall. As illustrated in the enlarged view, a portion of the B resin Rb constituting the longitudinal strip-shaped portion 212 has flowed around the opposite side of the circumferentially predetermined position in which the longitudinal strip-shaped portion 212 is formed, to be laminated in the vicinity of a portion of the circumferential wall made of the A resin that is close to an inner circumferential surface of the circumferential wall.

(23) With the portion of the B resin Rb flowing around the opposite side of the longitudinal strip-shaped portion 212, as described later with respect to our molding apparatus, the clearly transparent window portion 212w, which is obtained by the longitudinal strip-shaped portion 212, is formed to penetrate through the circumferential wall of the container.

(24) Meanwhile, even when the transparent B resin flows around close to the inner circumferential surface of the circumferential wall made of the A resin as illustrated in the enlarged view of FIG. 2A, the transparent B resin will be covered by the colored A resin from the outer side thereof, and appearance properties will not be deteriorated.

(25) Next, FIGS. 3 and 4 illustrate a preform according to one embodiment. A preform 101 is a precursor of the container 201 according to the above embodiment. FIG. 3 is a perspective view, FIG. 4A is a sectional plan view taken along a line B-B in FIG. 3, and FIG. 4B is a bottom view of FIG. 3.

(26) The preform 101 is made of a PET resin and has a test tubular shape formed by injection molding. The preform 101 includes a mouth tubular portion 102, a trunk portion 105 having a cylindrical shape, and a bottom portion 106. The mouth tubular portion 102 is provided on a circumference thereof with a neck ring 103.

(27) The preform 101 is formed with the A resin Ra, which is obtained by coloring the PET resin opaque white, and the B resin Rb, which is the uncolored PET resin. Substantially the entire preform 101 is made of the opaque A resin Ra, and a longitudinal strip-shaped portion 112, which is made of the transparent B resin Rb, is formed in a circumferentially predetermined position in a circumferential wall of the preform 101 over the entire height range measured from un upper end of the mouth tubular portion 102 to a bottom wall of the bottom portion 106.

(28) In the sectional plan view as illustrated in FIG. 4A, substantially the entire circumferential wall is made of the A resin Ra, and the longitudinal strip-shaped portion 112 made of the B resin Ra is laminated along the circumferential direction in the form of a slit completely penetrating the circumferential wall in such a manner as to interrupt the A resin Ra portion.

(29) Furthermore, a portion of the B resin Rb constituting the longitudinal strip-shaped portion 112 flows around the opposite side of the circumferentially predetermined position in which the longitudinal strip-shaped portion 112 is formed, to be laminated in the vicinity of a portion of the circumferential wall made of the A resin that is close to an inner circumferential surface of the circumferential wall.

(30) With reference to a bottom view in FIG. 4B, as illustrated in the figure, in the bottom wall of the bottom portion 106, the longitudinal strip-shaped portion 112 extends from a peripheral edge to the center position Cx, and further to a position beyond the center position Cx. There is also a gate mark 107 located in a middle of the bottom wall.

(31) Next, FIGS. 5 to 8 illustrate the injection molding apparatus according to one embodiment. The injection molding apparatus is used for injection molding the preform 101 according to the above embodiment.

(32) FIG. 5A is a side view illustrating a longitudinal section taken along a line C1-C1 in FIG. 6, and FIG. 5B is an enlarged view of a front end portion of a shut-off pin 20 illustrated in FIG. 5A, FIG. 6 is a plan view, and FIG. 7 is an enlarged front view of a partial longitudinal section of a part of the vicinity of a nozzle portion 11 taken along a line C2-C2 in FIG. 6.

(33) FIGS. 8A to 8E illustrate plane sectional shapes of flow paths in the nozzle portion 11.

(34) The injection molding apparatus includes resin supply units Sa and Sb that supply the A resin Ra and the B resin Rb in their molten states, a nozzle portion 11 that laminates these resins in the circumferential direction, and a mold 1 that shapes the preform (refer to FIG. 5A).

(35) A basic structure of the nozzle portion 11 includes the cylindrical inner mandrel 21 and an outer mandrel 22 that are coaxially arranged, and a columnar shut-off pin 20 that is inserted and arranged in the inner mandrel 21 in a manner such that the shut-off pin 20 may slidably move forward and backward. The shut-off pin 20 serves to release and shut off flows of the molten resins in a front end portion of the nozzle portion 11.

(36) With reference to the enlarged view of the vicinity of the front end portion of the shut-off pin 20 in FIG. 5B, as illustrated in the enlarged view, the front end portion of the shut-off pin 20 has a conical shape, and this conical front end portion 20t is positioned to protrude from a front end of the inner mandrel 21 in a releasing position of the shut-off pin 20.

(37) In the present embodiment, a central axis Axc of the conical front end portion 20t is inclined to a front end thereof toward a (left) direction that is opposite to a circumferential position (on the right in FIG. 5) in which a longitudinal groove flow path 17 is formed, and a front end 20tp of the conical front end portion 20t diverges to the direction that is opposite to the circumferential position in which the longitudinal groove flow path 17 is formed to be eccentrically positioned.

(38) In the present embodiment, the front end 20tp of the conical front end portion 20t has an eccentricity of 0.4 mm.

(39) As illustrated in FIG. 7, the inner mandrel 21 and the outer mandrel 22 each include a cylindrical region He and a tapered region Ht.

(40) Between the inner mandrel 21 and the outer mandrel 22, a cylindrical flow path 15 is formed in the cylindrical region He, and a reduced-diameter flow path 16 in communication with the cylindrical flow path 15 is formed in the tapered region. The reduced-diameter flow path 16 is configured by a cylindrical flow path tapered to have a reduced diameter toward downstream. Furthermore, on the downstream of a front end of the reduced-diameter flow path 16, there is formed a columnar joining flow path 19 in which the molten resins in cylindrical forms join into a columnar form.

(41) The cylindrical flow path 15 is formed by cutting an outer circumferential surface of the inner mandrel 21 in a lower half region of the inner mandrel 21.

(42) During the cutting process of the cylindrical flow path 15, upper end portions of the cylindrical flow path 15 are left unprocessed to form a pair of guiding ribs 21g in the form of longitudinal ridges.

(43) As illustrated in FIG. 8B, the pair of guiding ribs 21g in the form of longitudinal ridges partitions the cylindrical flow path 15 in the circumferential direction, and the longitudinal groove flow path 17, in which the B resin Rb flows, is formed between the pair of guiding ribs 21g.

(44) Furthermore, on the upstream of the cylindrical flow path 15, the outer circumferential surface of the inner mandrel 21 is engraved with an upstream longitudinal groove flow path 17a (refer to FIG. 8A) which is in communication with the aforementioned longitudinal groove flow path 17.

(45) Herein, the upstream longitudinal groove flow path 17a and the longitudinal groove flow path 17 each include a flow path width of 2 mm and a groove depth of 1 mm.

(46) The cylindrical flow path 15, in which the A resin Ra flows, also has a groove depth of 1 mm.

(47) In the following, a description is given of molding processes of the preform 101 illustrated in FIGS. 3 and 4 using the injection molding apparatus (refer to FIGS. 5 to 8).

(48) Firstly, the A resin Ra, which is obtained by coloring the PET resin white, is supplied from the resin supply unit Sa to an A resin introduction path 12a and caused to flow into the cylindrical flow path 15 via a supply start position 13a and the manifold 14.

(49) On the other hand, the B resin Rb, which is the uncolored PET resin, is supplied from the resin supply unit Sb to a B resin introduction path 12b and caused to flow to the upstream longitudinal groove flow path 17a and the longitudinal groove flow path 17 via a supply start position 13b (refer to FIGS. 5 and 7).

(50) The supply start position 13b of the B resin Rb is located further upstream of the supply start position 13a of the A resin.

(51) As the resin supply units Sa and Sb, various devices, such as a screw extruder or an accumulator including a plunger attached to a front end of an extruder, may be used.

(52) Then, the molten A resin Ra is shaped into a cylindrical form by the cylindrical flow path 15, and in the upper end portion of the cylindrical flow path 15, the molten B resin Rb flows across the longitudinal groove flow path 17 to interrupt the A resin Ra in the circumferential direction. However, the longitudinal groove flow path 17 is formed between the pair of guiding ribs 21g and 21g (refer to FIG. 8B), and therefore, the A resin is prevented from mixing with or cutting into the B resin.

(53) In a region extending from a lower half region of the cylindrical flow path 15 to the reduced-diameter flow path 16, the guiding ribs 21g and 21g are not arranged any more, that is to say, the longitudinal groove flow path 17 is not formed any more. Accordingly, the B resin Rb is in direct contact with the A resin Ra to interrupt the flow of the A resin Ra in the cylindrical form.

(54) Thus, the longitudinal groove flow path 17 does not need to be formed in the overall ranges of the cylindrical flow path 15 and the reduced-diameter flow path 16. As in the present embodiment, by simply forming the longitudinal groove flow path 17 in the upper end portion of the cylindrical flow path 15, the B resin Rb is allowed to interrupt the flow of the A resin Ra in the cylindrical form penetratingly.

(55) Additionally, suppose that the longitudinal groove flow path 17 is formed in the overall ranges of the cylindrical flow path 15 and the reduced-diameter flow path 16. Although this ensures that the B resin Rb may interrupt the A resin Ra, the B resin comes into the direct contact with the A resin Ra with a delay and is prevented from coming into the contact until the B resin reaches the columnar joining flow path 19 that is located in the end portion of the nozzle portion 11 on the downstream thereof, resulting in negative effects such as occurrence of flow turbulence at an interface between the A resin Ra and the B resin Rb. Accordingly, the extent of the longitudinal groove flow path may be determined as appropriate in consideration of the width of the longitudinal strip-shaped portion desired to be formed and properties, such as penetrability and clarity, of the longitudinal strip-shaped portion 112 formed in the preform 101.

(56) After passing through the reduced-diameter flow path 16, the A resin Ra and the B resin Rb in the cylindrical forms pass through the columnar joining flow path 19 to be joined into a molten resin lump in a columnar form in which the B resin is laminated in the A resin in the form of a slit. Thus obtained columnar molten resin lump is injected and filled into a cavity 2 via a pin gate 3 located in a position of the cavity 2 of the mold 1 that corresponds to the middle of the bottom portion 106 of the preform 101 (refer to FIG. 5).

(57) Herein, as illustrated in the sectional plan view of FIG. 8C, in the cylindrical flow path 15 and the reduced-diameter flow path 16, the B resin Rb remains laminated in the form of a slit to interrupt the ring-shaped A resin Ra in the circumferential direction. Eventually, however, the B resin Rb is shaped into the columnar form in the joining flow path 19.

(58) Upon the joining, the A resin and the B resin collide with each other in the vicinity of a center position of the junction flow path. At this collision time, the A resin sometimes pushes the B resin to a direction of the peripheral portion and prevents a tip of the slit-shaped B resin Rb portion from reaching the center position Cx as illustrated in FIG. 8E.

(59) When the molten resin lump in the laminated state as illustrated in FIG. 8E is injected and filled into the cavity 2 via the pin gate 3 of the mold 1 to inject mold the preform 1 illustrated in FIGS. 3 and 4, the A resin Ra, which is colored white, cuts into a portion of the longitudinal strip-shaped portion 112, which is made of the transparent B resin Rb, for example, a portion of the longitudinal strip-shaped portion 112 that is located on the inner circumferential surface side. Accordingly, when the preform 1 is biaxially stretch blow molded into the container 1 with a window as illustrated in FIGS. 1 and 2, various problems of defects such as a portion of the window portion 112w being colored white and a border between the window portion 212w and the adjacent white circumferential wall being unclear. As a result, usability of the container 1 as a product is ruined.

(60) In view of the above, the injection molding apparatus illustrated in FIGS. 5A, 5B, and 7 includes the shut-off pin 20 including, in the front end portion thereof, the eccentric conical front end portion 20t, thereby reliably solving the aforementioned problems.

(61) FIG. 9 is a schematic view of how the A resin Ra and the B resin Rb flow in the side view of FIG. 5A. The eccentric conical front end portion 20t in the front end portion of the shut-off pin 20 provides an advantageous effect of enhancing flowability of the B resin Rb in the direction of the central axis Ax (in a left lateral direction in FIG. 9).

(62) This results in the B resin Rb portion being laminated in the form of a slit extending sufficiently to reach the center position Cx, or even in the form of a slit extending beyond the center position Cx, in the flow path 19 as illustrated in the sectional view of the columnar molten resin lump in FIG. 8D.

(63) Consequently, a portion (denoted by reference numeral Rbs in FIG. 9) of the B resin Rb flowing into the cavity 2 from the gate 3 flows around the opposite side of the circumferentially predetermined position in which the longitudinal strip-shaped portion 112 is formed.

(64) By achieving the laminated state as illustrated in FIG. 8D and letting the portion of the B resin Rb flow around the opposite side of the circumferentially predetermined position in which the longitudinal strip-shaped portion 112 is formed, the longitudinal strip-shaped portion 112 is formed in the preform 101 in such a manner as to further ensure that the longitudinal strip-shaped portion 112 penetrates the circumferential wall. Biaxial stretch blow molding of the preform 101 provides the container with a window including the transparent and clear window portion of an even higher quality.

(65) Thus, as illustrated in FIG. 8D, the longitudinal strip-shaped portion 112 is laminated from the peripheral edge toward the center of the bottom wall, and further to a position beyond the center position Cx of the bottom wall. Furthermore, a portion of the B resin Rb flows around the opposite side of the circumferentially predetermined position in which the longitudinal strip-shaped portion 112 is formed, resulting in the laminated structure as illustrated in FIG. 4A where the B resin Rb layer is laminated in the vicinity of a portion of the circumferential wall made of the A resin that is close to an inner circumferential surface of the circumferential wall on the opposite side of the circumferentially predetermined position in which the longitudinal strip-shaped portion 212 is formed. The preform 101 may have at least one of the above features.

(66) Although the synthetic resin container with a window, the preform, and the injection molding apparatus of the preform according to the embodiments have been described above, this disclosure is not limited to these embodiments.

(67) For example, although in the above embodiments the container is a round bottle made of a PET resin, any other synthetic resin such as a polypropylene resin that may be subjected to biaxial stretch blow molding may be used. Furthermore, the shape of the container may be any other shape such as a square.

(68) Furthermore, even when a PET resin is used for each of the A resin and the B resin, a molecular weight or the like of the A resin may be differentiated from that of the B resin in consideration of flowability behavior of each resin.

(69) By determining the molecular weight and supply temperature of each resin as appropriate, relative flowability behaviors of the A resin and the B resin may be adjusted, and fine adjustments of properties, such as the penetrability of the longitudinal strip-shaped portion and the degree of clarity of the window portion formed in the container, are accomplished.

(70) Moreover, as the resin material of the window portion 212w, a colored transparent resin may also be used.

(71) Moreover, in the above embodiment of the container with a window (refer to FIGS. 1 and 2), the window portion 212w is formed over the entire height range. However, the window portion 212w may also be formed over a predetermined height range of the trunk portion 205 by providing opening and closing means for the flow paths.

(72) Moreover, in the above embodiment, the window portion 212w formed in the trunk portion 205 has a straight shape having a constant width over the entire height range. However, depending on the shape of the longitudinal groove flow path 17 and the injection pressure of the B resin, for example, the width of the window portion 212w may be increased downward in the lower end portion of the trunk portion 205.

(73) The shape, such as the groove width, the groove depth, and the extent, of the longitudinal groove flow path 17, as well as the shape of the front end portion of the shut-off pin 20, may be determined as appropriate by checking the width of the longitudinal strip-shaped portion desired to be formed and the properties, such as the degree of clarity and uniformity of the width, of the window portion formed in the container.

(74) FIGS. 10A to 10C are front views of three variations of the inner mandrel 21. FIG. 10A illustrates the inner mandrel 21 used in the above embodiment, and the extent of the longitudinal strip-shaped flow path 17 reaches the upper end portion of the cylindrical flow path 15. The longitudinal strip-shaped flow path 17 has a groove width W of 2 mm.

(75) In FIG. 10B, the extent of the longitudinal strip-shaped flow path 17 is extended to the vicinity of a border between the cylindrical flow path 15 and the reduced-diameter flow path 16. The longitudinal strip-shaped flow path 17, on an upstream side thereof, has a groove width W of 4 mm and, on a downstream side thereof, a groove width W of 3 mm.

(76) In FIG. 10C, the extent of the longitudinal strip-shaped flow path 17 is extended to a lower end of the reduced-diameter flow path 16, and the longitudinal strip-shaped flow path 17 has a groove width W of 1.5 mm.

(77) FIGS. 11A to 11C are side views of three variations in shapes of the conical front end portion 20t of the shut-off pin 20. FIG. 11A illustrates the conical front end portion 20t having no eccentricity, FIG. 11B illustrates the one having an eccentricity d of 0.2 mm, and FIG. 11C illustrates the one used in the above embodiment that has an eccentricity d of 0.4 mm.

INDUSTRIAL APPLICABILITY

(78) The container with a window that is produced by biaxially stretch blow molding the preform molded by the injection molding apparatus according to this disclosure includes a longitudinal strip-shaped clearly transparent window portion that is conventionally considered difficult to form, and such a container is expected to be used in a wide range of applications.