Preform and bottle

Abstract

Provided is a method for manufacturing a preform (1). The method includes injecting into a cavity of a mold through the gate: (i) a first colored resin (R1) for a first predetermined time period, and (ii) a second colored resin (R2), having a color different from that of the first colored resin, for a second predetermined time period.

Claims

1. A method for manufacturing a synthetic resin preform, the preform comprising: (i) a base material layer made of a first colored resin, (ii) a colored layer that is made of a second colored resin having a color different from that of the first colored resin and forms a gradation region on an outer circumferential side of the base material layer, wherein a layer thickness of the gradation region gradually decreases upward, and (iii) a coating layer, made of the first colored resin, on an outer circumferential side of the colored layer, the method comprising: filling the first colored resin in a gate disposed in correspondence with a middle of a bottom of the preform, injecting into a cavity of a mold through the gate: (i) the first colored resin for a first predetermined time period, and (ii) the second colored resin material, having a color different from that of the first colored resin, for a second predetermined time period, wherein: (i) a starting time point of the first predetermined time period is set to be between a starting time point of the second predetermined time period and a finishing time point of the second predetermined time period, (ii) a finishing time point of the first predetermined time period is set to be after the finishing time point of the second predetermined time period, and (iii) an injection rate of the second colored resin is set to be faster than an injection rate of the first colored resin, so that: (i) the second colored resin penetrates a center portion of the first colored resin under a state in which a region on an outer circumferential surface of the cavity is coated with the first colored resin, where the region corresponds to the gradation region, and then (ii) the first colored resin penetrates a center portion of the second colored resin located inside the cavity of the mold, such that the first colored resin is caused to flow while stretching the second color resin, so as to form: (a) the colored layer on the outer circumferential side of the base material layer, and (b) the coating layer on the outer circumferential side of the colored layer.

2. The method for manufacturing the preform according to claim 1, wherein the first colored resin has an IV in the range from 0.5 to 0.63.

3. A method for manufacturing a bottle, comprising: biaxially stretch blow molding the preform manufactured by the method according to claim 1, and decorating with gradations associated with color density that are caused to appear by the colored layer.

4. A method for manufacturing a bottle, comprising: biaxially stretch blow molding the preform manufactured by the method according to claim 2, and decorating with gradations associated with color density that are caused to appear by the colored layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the accompanying drawings:

(2) FIG. 1 is a partial sectional side view, with some portions thereof enlarged, of a preform according to one of embodiments of the present disclosure;

(3) FIG. 2 illustrates an example of an injection pattern used to mold a preform illustrated in FIG. 1;

(4) FIGS. 3A to 3D illustrate the process of filling molten resin into a cavity of a mold according to an injection pattern illustrated in FIG. 2;

(5) FIG. 4 is a side view of a bottle obtained by biaxially stretch blow molding a preform illustrated in FIG. 1;

(6) FIG. 5 is a side view of a modification of a preform according to one of embodiments of the present disclosure; and

(7) FIG. 6 is a side view of a bottle obtained by biaxially stretch blow molding a preform illustrated in FIG. 5.

DETAILED DESCRIPTION

(8) The following describes a preform 1 and a bottle 8 according to one of embodiments of the present disclosure in more detail by way of illustration with reference to FIGS. 1 to 4.

(9) Herein, the upward and the downward direction refers to a direction extending along the axis of the preform 1. The term upward refers to a direction extending from a bottom 2 to a mouth 4 of the preform 1, and the term downward refers to a direction opposite thereto.

(10) As illustrated in FIG. 1, the synthetic resin preform 1 according to the present embodiment has a bottomed cylindrical shape including the bottom 2, a trunk 3, and the mouth 4, and the preform 1 has been molded by co-injecting two types of colored resin. In detail, the preform 1 includes a base material layer 5, which is made of a first colored resin R1 (preferably, PET in which a white coloring agent is added). On the outer circumferential side of the base material layer 5, there is also formed an outer colored layer 6a, which is made of a second colored resin R2 (preferably, PET in which a coloring agent in any color other than white is added) having a color different form that of the first colored resin R1 and which forms a gradation region Gr in which a layer thickness gradually decreases upward. Furthermore, a coating layer 7, which is made of the first colored resin R1, is formed on the outer circumferential side of the outer colored layer 6a.

(11) Moreover, an inner colored layer 6b, which is made of the second colored resin R2, is formed on the inner circumferential side of the base material layer 5. Thus, the preform 1 has, in the gradation region Gr, a four-layer structure including the coating layer 7 (the first colored resin R1)/the outer colored layer 6a (the second colored resin R2)/the base material layer 5 (the first colored resin R1)/the inner colored resin 6b (the second colored resin R2) from the outer circumferential side to the inner circumferential side. Additionally, the preform 1 according to the present embodiment is used to obtain a beverage bottle having a weight of 22 g and may be biaxially stretch blow molded to form a bottle of, for example, 266 ml, 542 ml, or 579 ml.

(12) The preform 1 with the above configuration may be produced according to the following outline. That is to say, the preform 1 is molded, from the state where the first colored resin R1 is filled in a gate disposed in correspondence with the middle of a bottom 2 of the preform 1, by injecting the first colored resin R1 into a cavity of a mold through the gate for a first predetermined time period and by injecting the second colored resin material R2 for a second predetermined time period, with use of a two-layer gate nozzle. For instance, as illustrated in FIG. 2, a starting time point T1s of the first predetermined time period is behind a starting time point T2s of the second predetermined time period, and a finishing time point T1f of the first predetermined time period is behind a finishing time point T2f of the second predetermined time period. Furthermore, an injection rate of the second colored resin R2 is faster than an injection rate of the first colored resin R1.

(13) Herein, the first predetermined time period may be 7 seconds, the second predetermined time period may be 0.68 second, and a delay time period of the starting time point T1s of the first predetermined time period with respect to the starting time point T2s of the second predetermined time period may be 0.1 second. The injection rate of the second colored resin R2 may be 80 mm/s, and the injection rate of the first colored resin R1 may be 6 mm/s.

(14) By co-injection molding the first colored resin R1 and the second colored resin R2 at the injection timing and injection rates as described above, the resins R1 and R2 are flown as illustrated in FIGS. 3A to 3D, and thus, the preform 1 is obtained. That is to say, as illustrated in FIG. 3A, at a time point Ta, which is behind the start of the injection of the second colored resin R2 from the state where the first colored resin R1 is filled in the gate and ahead of the start of the injection of the first colored resin R1, the second colored resin R2 flows inside the cavity of the mold while extruding the first colored resin R1 filled in the gate. Then, at a time point T2f, when the injection of the second colored resin R2 is finished, as illustrated in FIG. 3B, the second colored resin R2 penetrates a center portion of the first colored resin R1, with a region on an outer circumferential surface of the cavity that corresponds to the gradation region Gr being coated with the first colored resin R1. Furthermore, at a time point Tb, as illustrated in FIG. 3C, the first colored resin R1 penetrates a center portion of the colored resin R2 and flows while stretching the second colored resin R2. At a time point T1f, when the injection of the first colored resin R1 is finished, as illustrated in FIG. 3D, the aforementioned layer structure of the preform 1 is achieved.

(15) According to the preform 1 of the present embodiment described above, the bottle 8, which is decorated with gradations associated with color density that are caused to appear by the outer colored layer 6a as illustrated in FIG. 4, is obtained by biaxially stretch blow molding the preform 1. According to the bottle 8 of the present embodiment, since the outer colored layer 6a, which is made of the second colored resin R2 having a color different from that of the first colored resin R1, is formed on the outer circumferential side of the base material layer 5, which is made of the first colored resin R1, a gradation pattern Gm is emphasized. Furthermore, since the coating layer 7, which is made of the first colored resin R1, is formed on the outer circumferential side of the outer colored layer 6a, transition in density of the gradation pattern Gm is obscured with the thin coating layer 7 covering the outer colored layer 6a. Thus, the favorable gradation pattern Gm is achieved.

(16) Additionally, to achieve the favorable gradation pattern Gm, an intrinsic viscosity (IV) of the first colored resin R1 is preferably in the range from 0.5 to 0.63 and more preferably in the range from 0.6 to 0.63.

(17) Although the preform 1 and the bottle 8 according to the embodiment has been described to be used in beverage application, as a modification, those used in toiletry application as illustrated in FIGS. 5 and 6 may also be considered. A bottle 8′ according to the present modification is obtained, for example, by biaxially stretch blow molding a preform 1′ having a weight of 50 g, and the bottle 8′ has a capacity of, for example, 550 ml. In this case also, similarly to the above embodiment, the favorable gradation pattern Gm is achieved.

(18) The description above is considered to be merely illustrative of one of embodiments of the present disclosure, and various changes may be made within the scope of the claims. For example, one or both of the first colored resin R1 and the second colored resin R2 may be polypropylene (PP) instead of PET. Furthermore, the first colored resin R1 and the second colored resin R2 does not need to be colorless and transparent and may be colored and transparent depending on purposes.

REFERENCE SIGNS LIST

(19) 1, 1′ Preform 2 Bottom 3 Trunk 4 Mouth 5 Base material layer 6a Outer colored layer (colored layer) 6b Inner colored layer 7 Coating layer 8, 8′ Bottle R1 First colored resin R2 Second colored resin Gr Gradation region T1s Starting time point of first predetermined time period T2s Starting time point of second predetermined time period T1f Finishing time point of first predetermined time period T2f Finishing time point of second predetermined time period Ta, Tb Time point Gm Gradation pattern