MOLD INSERT FOR INJECTION MOLDED PLASTIC CONTAINERS AND MOLD ASSEMBLY INCLUDING THE MOLD INSERT

Abstract

MOLD INSERT FOR INJECTION MOLDED PLASTIC CONTAINER AND MOLD ASSEMBLY COMPRISING THE MOLD INSERT. The present invention relates to a mold insert (100) for injection molding a plastic container, the mold insert (100) comprising a top, an outer wall, and a bottom, a groove (104) for housing a hot runner nozzle being constructed in the mold insert (100), the groove (104) being open outwards at the top of the mold insert (100), and a gate (103) and a molding cavity (102) being constructed at the bottom of the mold insert (100), the shape of the molding cavity (102) corresponding to the shape of the bottom of the plastic container to be molded, in which the groove (104) is connected to the molding cavity (102) through the gate (103), and a cooling channel. (105) for the flow of the cooling medium is constructed in the mold insert (100),and the inlet (106) and outlet (107) of the cooling channel (105) are respectively constructed on the outer wall of the mold insert (100), wherein at least a partial section of the cooling channel (105) extends into the area of ​​the bottom of the mold insert (100) adjacent to the door (103). Figure for the abstract: none,

Description

Title of the invention: MOLD INSERT FOR INJECTION MOLDING OF A PLASTIC CONTAINER AND MOLD ASSEMBLY INCLUDING THE MOLD INSERT FIELD OF INVENTION

[0001] The invention relates to a mold insert for the injection molding of a plastic container and a mold assembly comprising the mold insert. BACKGROUND OF THE INVENTION

[0002] The development of eco-responsible and environmentally friendly solutions, designed and developed with environmental considerations in mind, is becoming a major objective in efforts to address global challenges. It is therefore essential to design more sustainable products that can replace existing materials with greener alternatives and utilize recyclable materials to reduce the carbon footprint of products.

[0003] In this context, it is important to replace materials with those that have a better environmental footprint, particularly by reducing the use of petrochemical raw materials. The objective is to offer eco-responsible materials and to use recyclable materials in order to limit the environmental impact of packaging from its manufacture to its end of life.

[0004] Thick-walled, transparent plastic containers are common in the cosmetics industry. Today, most thick-walled, transparent plastic containers are made from PETG using injection molding technology. However, because PETG is difficult to recycle, post-consumer recycled PET, namely PCR PET, is increasingly being used to replace PETG in the manufacture of thick-walled plastic containers.

[0005] PCR PET includes mechanically recycled PET and chemically recycled PET. Mechanical recycling involves cutting and crushing discarded PET materials, then separating impurities such as high-density polyethylene, aluminum, adhesives, and paper from the discarded products. The PET fragments are then washed, dried, and pelletized to complete the recycling process. Chemical recycling involves depolymerizing discarded PET into compounds such as terephthalic acid (TPA), dimethyl terephthalate (DMT), and ethylene glycol (EG).

[0006] However, the inventors of the present application have discovered that the use of chemically recycled PET in the injection molding process of thick-walled transparent plastic containers can lead to a problem whereby Opaque, mushroom-shaped defects are easily generated at the bottom of plastic containers, caused by the crystallization of the plastic material. Therefore, there is a need to prevent the crystallization of the plastic material at the bottom of the container and to eliminate these opaque, mushroom-shaped defects. Summary of the invention

[0007] To solve the above problem, according to a first aspect of the present invention, a mold insert for the injection molding of plastic containers is proposed, the mold insert comprising a top, an outer wall and a bottom, a groove for receiving a hot runner nozzle being constructed in the mold insert, the groove being open outwards at the top of the mold insert, and a door and a molding cavity being constructed at the bottom of the mold insert, the shape of the molding cavity corresponding to the shape of the bottom of the plastic container to be molded, in which the groove is connected to the molding cavity via the door, and a cooling channel for the flow of the cooling medium is constructed in the mold insert, the inlet and outlet of the cooling channel being respectively constructed on the outer wall of the mold insert,in which at least a partial section of the cooling channel extends into the area of ​​the bottom of the mold insert adjacent to the door.

[0008] The expression "adjacent to" in this context refers to the shortest distance among the distances from any point on the central curve of the cooling channel to the central point of the door. The shortest distance must be in the range of 6 mm to 30 mm.

[0009] The basic inventive concept of the present invention consists of arranging the cooling channel as close as possible to the door when the structural strength of the mold insert allows, thereby improving the cooling conditions at the door so that the temperature at the door can be reduced as quickly as possible during the cooling process. This is conducive to the suppression of crystallization defects in the container base.

[0010] The arrangement of the cooling channel must ensure that the thinnest thickness of material around the cooling channel is at least 2 mm. The material thickness refers to the distance from the periphery of the cooling channel to the inner surface of the groove or the bottom of the mold insert.

[0011] In the prior art, since the central area of ​​the container base near the door cools more slowly than the peripheral area, the cooling rate of the container base is uneven, which easily leads to crystallization of the plastic material in the central area of ​​the container base. By improving the cooling conditions at the door, the central area of ​​the container base can also be cooled rapidly during the solidification process, and the cooling of the container bottom is uniform in the central and peripheral areas, thus significantly reducing or even eliminating crystallization defects in the container bottom.

[0012] Preferably, at least a partial section of the cooling channel extends along the contour of the mold insert. The mold insert generally has a cylindrical outer contour. The cooling channel is usually constructed within the cylindrical outer wall of the mold insert. In the prior art, the cooling channel is usually processed by drilling, thus allowing the construction of several straight cooling channels in the outer wall of the mold insert. On the one hand, straight cooling channels compromise the structural strength of the mold insert, as they are often too close to the groove in the central area of ​​the mold insert.In contrast, straight cooling channels are not conducive to uniform cooling, since the distances from the groove and the gate to each position of the cooling channel vary. The central area of ​​the cooling channels is closer to the groove and the gate, while the two ends of the cooling channels are further away from the groove and the gate. Conversely, by constructing the cooling channel to extend along the contour of the mold insert, not only is the structural strength of the material near the cooling channel improved, but the cooling effect of the channel is also uniform.

[0013] Preferably, at least a partial section of the cooling channel extends around the door, so that the door is sufficiently cooled in all directions, thus further improving cooling efficiency and uniformity.

[0014] Preferably, at least a partial section of the cooling channel extends in a plane orthogonal to the longitudinal axis of the mold insert in the area adjacent to the door, whereby the cooling channel has a constant distance from the molding cavity or the bottom of the container in the area adjacent to the door, thus improving the uniformity of the cooling of the bottom of the container.

[0015] Preferably, the inlet and outlet of the cooling channel are arranged opposite each other at an angle of approximately 180° on the outer wall of the mold insert, thereby improving the flow characteristics of the coolant in the cooling channel. The term "approximately" in this context is equivalent to "±15°", preferably "±10°", more preferably "±5°".

[0016] Preferably, two subsections of the cooling channel extend on both sides of the door, and the cooling medium has a symmetrical flow direction in both subsections, thus achieving a uniform cooling effect on both sides of the door and improving cooling efficiency. If the two subsections of the cooling channel are arranged symmetrically with respect to the door, the cooling uniformity can be further improved.

[0017] Preferably, the door is located in the center of the bottom of the mold insert, whereby sufficient structural space can be left in the bottom of the mold insert to arrange the cooling channel.

[0018] Preferably, at least a partial section of the cooling channel extends axially into the outer wall of the mold insert, according to which the inlet and outlet of the cooling channel can be arranged at any position of the outer wall of the mold insert, thus improving the flexibility of the cooling channel arrangement.

[0019] Preferably, the internal contour shape of the groove corresponds to the external contour shape of the hot runner nozzle. In injection molding, the hot runner nozzle enters the groove and aligns the hot runner with the gate at the bottom of the groove, thus pushing the molten plastic directly into the gate.

[0020] Preferably, the cooling medium is water. The cooling medium may also be other suitable fluids.

[0021] Preferably, the mold insert is used for transparent PET plastic containers, preferably PET PCR, particularly preferably PET PCR. The mold insert can also be used for transparent PET PCR mechanical plastic containers.

[0022] Compared to mechanically recycled PET, chemically recycled PET is more suitable for manufacturing thick-walled transparent plastic containers because of its better transparency.

[0023] Preferably, the mold insert is used for plastic containers with a base thickness of at least 5 mm, preferably 5-10 mm, more preferably 6-9 mm, and even more preferably 7-8 mm. When thick-bottomed plastic containers are produced using PET PCR, crystallization defects can occur, so the mold insert according to the invention is particularly suitable.

[0024] Preferably, the mold insert is manufactured using a metal 3D printing process. The metal 3D printing process can be used to process a cooling channel of any shape within the mold insert. In the prior art, drilling-processed cooling channels only have a straight shape, and it is It is difficult to construct a cooling channel extending along the contour shape of the mold insert.

[0025] According to a second aspect of the present invention, a mold assembly for the injection molding of plastic containers is proposed, the mold assembly comprising at least one slide and at least one mold insert according to the first aspect of the present invention, wherein the shape of the mold cavity in the slide corresponds to the shape of the container wall. The slide(s) and the mold insert(s) together constitute a mold assembly for the injection molding of plastic containers. The mold insert has a mold cavity corresponding to the shape of the container base, and the slide has a mold cavity corresponding to the shape of the container wall. The molten plastic flows into the mold cavities above through the gate of the mold insert.

[0026] Other features and advantages of the present invention will become apparent from the following more detailed description of the illustrative embodiment, taken together with the accompanying drawings which illustrate, by way of example, the principles of the invention. Brief description of the drawings

[0027] [Fig-1] [Fig.1] shows a perspective view of a mold insert according to a mode preferred embodiment of the present invention;

[0028] [Fig.2] Fig.2 shows a cross-sectional view of a mold insert according to the mode of preferred embodiment of the present invention;

[0029] [Fig. 3] Fig. 3 shows a perspective view of a cooling channel of a mold insert according to the preferred embodiment of the present invention;

[0030] [Fig.4] Figure [Fig.4] shows a mold assembly according to a preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0031] Figure 1 shows a perspective view of a mold insert 100 according to the present invention. In a preferred embodiment, the mold insert 100 has a substantially cylindrical external contour. The mold insert 100 has a top, an outer wall, and a bottom. The mold insert 100 is arranged with a flange 101 at the top for engagement with an accessory of an injection molding system.

[0032] The base of the mold insert 100 has a molding cavity 102, the shape of which corresponds to the shape of the base of the container to be treated. In this embodiment, the molding cavity 102 of the mold insert 100 is constructed in an approximately rectangular shape to treat a container, in particular a cosmetic container, with a rectangular cross-section. A door 103 is provided In the central area of ​​the mold cavity 102, the gate 103 connects the groove 104 in the mold insert 100 to the mold cavity 102. During the injection molding process, the hot runner nozzle is inserted into the groove 104 of the mold insert 100, and the hot runner in the nozzle is aligned with the gate. The molten plastic is forced into the mold cavity 102 through the gate 103 and then flows to other positions within the mold.

[0033] A cooling channel 105 is also configured in the mold insert 100, and its inlet 106 and outlet 107 are arranged on the outer wall of the mold insert 100. In this embodiment, the inlet 106 and outlet 107 of the cooling channel 105 are arranged approximately at a median position along the height direction of the mold insert 100, and are arranged opposite each other in a plane orthogonal to the longitudinal axis L at an angle of approximately 180°. During the injection molding process, a cooling medium, such as water, flows into the mold insert 100 from the inlet 106 of the cooling channel 105 and flows out of the mold insert 100 from the outlet 107 of the cooling channel 105, thus enabling the mold insert 100 to be cooled.

[0034] Figure 2 shows a cross-sectional view of the mold insert 100 of Figure 1. As can be clearly seen in Figure 2, a substantially cylindrical groove 104 is constructed in the mold insert 100, and the shape of the internal contour of the groove 104 corresponds to the shape of the hot runner nozzle, so that the hot runner nozzle is accommodated in the groove 104 during the injection molding process. The groove 104 includes a cylindrical portion 1041 of a larger diameter and a tapered portion 1042 of a smaller diameter. The cylindrical portion 1041, with a larger diameter, is near the top of the mold insert 100, and the tapered portion 1042, with a smaller diameter, is near the bottom of the mold insert 100. A stepped transition portion 1043 is formed between the cylindrical portion 1041 and the tapered portion 1042. The groove 104 is open in a direction towards the top of the mold insert 100 to allow the entry of the hot runner nozzle.The groove 104 is almost closed in the direction towards the bottom of the mold insert 100, and is connected only to the molding cavity 102 located outside the bottom of the mold insert 100 through the door 103 located at the bottom of the groove 104.

[0035] Figure 2 also shows the direction of extension of the cooling channel 105 in the mold insert 100. The inlet 106 of the cooling channel 105 is located in the middle position along the height direction of the mold insert 100. After the inlet 106, the cooling channel 105 extends vertically downwards directly along the longitudinal direction towards the bottom of the mold insert 100. After passing the transition portion 1043 of the groove 104, the channel Cooling channel 105 begins to deviate towards the gate 103 and continues to extend downwards. Without affecting structural strength, particularly when the minimum wall thickness requirement is met, the cooling channel 105 should extend as close as possible to the gate 103 to achieve optimal cooling. The direction of the cooling channel 105 near the gate 103 will be discussed in detail below in conjunction with [Fig. 3]. The cooling channel 105 has a symmetrical structure on its outlet side compared to its inlet side. The outlet 107 and the inlet 106 of the cooling channel 105 are arranged in the same horizontal plane orthogonal to the longitudinal axis L of the mold insert 100. Upstream of the outlet 107, the cooling channel 105 extends obliquely upwards before the transition portion 1043 of the mold insert 100.After passing the transition portion 1043, the cooling channel 105 extends vertically upwards parallel to the longitudinal axis L of the mold insert 100 and merges into the outlet 107 of the cooling channel 105.

[0036] Figure 3 shows a perspective view of a cooling channel of the mold insert according to Figures 1 and 2. It should be noted that the cooling channel 105 is a hole formed directly in the base body of the mold insert 100. The cooling channel 105 is not a separate component installed in the mold insert 100. Figure 3 shows the cooling channel 105 separately only for clarity, but this does not mean that the cooling channel 105 can be an independent component of the base body of the mold insert 100.

[0037] As can be seen in [Fig.3], the cooling channel 105 is mainly composed of five sections, namely, the inlet section 1060, the inlet guide sections 1061 and 1062, the sections 1051 and 1052 near the gate, the outlet guide sections 1071 and 1072, and the outlet section 1070. The inlet section 1060 and the outlet section 1070 have a larger diameter than the other sections, in particular a diameter twice the diameter of the other sections, thus ensuring that a sufficient cooling medium always flows through each section of the cooling channel and that the cooling medium can be smoothly discharged. The inlet guide sections 1061 and 1062 are respectively arranged on both sides of the inner end of the inlet section 1060, and their extension directions have been described above in relation to [Fig.2].Before the transition portion 1043 of the mold insert 100, the inlet guide sections 1061 and 1062 extend vertically downwards parallel to the longitudinal axis L of the mold insert 100. After passing the transition portion 1043, the inlet guide sections 1061 and 1062 begin to deviate towards the gate 103. Providing two inlet guide sections 1061 and 1062 avoids the need for a vertically extending channel with a relatively large diameter in . the outer wall of the mold insert 100, which would negatively affect the structural strength of the outer wall of the mold insert 100. In addition, the arrangement of the two inlet guide sections 1061 and 1062 also fully exploits the structural space under the transition portion 1043, so that the sections 1051 and 1052 near the subsequent door can be closer to the door 103 without affecting the structural strength, thus allowing a better cooling effect.

[0038] The sections 1051 and 1052 adjacent to the door exit respectively from the inlet guide sections 1061 and 1062, and extend around both sides of the door 103. The sections 1051 and 1052 adjacent to the door together constitute an annular cooling zone. In the present embodiment, the sections 1051 and 1052 adjacent to the gate extend in a plane orthogonal to the longitudinal axis L. The cooling medium enters the sections 1051 and 1052 adjacent to the gate respectively via the inlet section 1060, the inlet guide sections 1061 and 1062, so that the cooling medium has a symmetrical flow direction in the sections 1051 and 1052 adjacent to the gate, thus ensuring a symmetrical cooling effect on both sides of the gate 103. This is also conducive to the suppression of crystallization defects.Furthermore, the shapes of sections 1051 and 1052 adjacent to the door also correspond to the contour shape of the mold insert 100, thus ensuring a uniform wall thickness near sections 1051 and 1052 adjacent to the door.

[0039] It is also conceivable that, in addition to the sections 1051 and 1052 adjacent to the door located near the door 103, other cooling channel sections extending along the contour shape of the mold insert 100 are provided in the mold insert 100. Such cooling channel sections can be, for example, cooling channel sections extending in a spiral shape in the wall of the mold insert 100, which allows for cooling of the wall of the mold insert 100, thus further accentuating the cooling effect at the door 103.

[0040] The output guide sections 1071 and 1072 and the output section 1070 adopt a symmetrical arrangement to the input section 1060 and to the input guide sections 1061 and 1062.

[0041] The structure of the cooling channel 105 can be easily manufactured using a metal 3D printing process.

[0042] Figure 4 shows a mold assembly according to a preferred embodiment of the present invention, which has a mold insert 100 according to Figure 1 and Figure 2 and a corresponding slide 200. The slide 200 is composed of two sub-slides that can be opened and closed during the molding process. Once the injection molding process is complete, the molded container is removed by opening the two sub-slides. In [Fig. 4], only one of the sub-slides is shown for clarity. A mold cavity 201 is constructed in the slide 200, and the shape of the mold cavity 201 of the slide 200 corresponds to the shape of the container wall. An insert 202 is also arranged inside the slide 200. The external surface of the insert 202, the internal surface of the mold cavity 201 of the slide 200, and the internal surface of the mold cavity 102 of the mold insert 100 together define a mold chamber 300 for the injection molding process of the container.During the injection molding process, the molten plastic flows into the molding chamber 300 through the gate 103 of the mold insert 100, then fills the molding chamber 300 and cools and solidifies to complete the container molding process. A cooling channel (not shown) is also formed in the slide 200, which is independent of the cooling channel 105 in the mold insert 100.

[0043] Although the invention has been described with reference to preferred embodiments, those skilled in the art will understand that various changes can be made and that equivalents can replace elements without departing from the spirit and scope of the invention as defined in the accompanying claims. Those skilled in the art will appreciate that the invention can be used with numerous modifications of structure, arrangement, proportions, sizes, materials, and components, and otherwise employed in the practice of the invention, which are particularly suited to specific environments and operational requirements without departing from the principles of the present invention.The embodiments currently disclosed should therefore be considered in all respects as illustrative and non-restrictive, the scope of the invention being defined by the attached claims, and not limited to the description or the preceding embodiments. LIST OF DIGITAL REFERENCES

[0044] 100 mold insert

[0045] 101 bridle

[0046] 102 molding cavity of the mold insert

[0047] 103 door

[0048] 104 groove

[0049] 1041 cylindrical portion

[0050] 1042 tapered portion

[0051] 1043 transition portion

[0052] 105 cooling channel

[0053] 1051 section adjacent to the door

[0054] 1052 section adjacent to the door

[0055]

[0056]

[0057]

[0058]

[0059]

[0060]

[0061]

[0062]

[0063]

[0064]

[0065]

[0066] 106 Cooling channel inlet 1060 Inlet section 1061 Inlet guide section 1062 Inlet guide section 107 Cooling channel outlet 1070 Outlet section 1071 Outlet guide section 1072 Outlet guide section 200 Slide 201 Slide molding cavity 202 Insert 300 Molding chamber

Claims

Demands

1. A mold insert (100) for injection molding a plastic container, the mold insert (100) comprising a top, an outer wall, and a bottom, a groove (104) for housing a hot runner nozzle being constructed in the mold insert (100), the groove (104) being open outwards at the top of the mold insert (100), and a gate (103) and a molding cavity (102) being constructed in the bottom of the mold insert (100), the shape of the molding cavity (102) corresponding to the shape of the bottom of the plastic container to be molded, wherein the groove (104) is connected to the molding cavity (102) through the gate (103), and a cooling channel (105) for the flow of the cooling medium is constructed in the mold insert (100), and the inlet (106) and outlet (107) of the cooling channel (105) are respectively constructed on the outer wall of the mold insert (100),characterized in that at least a partial section of the cooling channel (105) extends into the area of ​​the bottom of the mold insert (100) adjacent to the door (103).

2. Mold insert (100) according to claim 1, characterized in that at least a partial section of the cooling channel (105) extends into the area adjacent to the door (103) in a plane orthogonal to the longitudinal axis (L) of the mold insert (100).

3. Mold insert (100) according to claim 1, characterized in that the inlet (106) and outlet (107) of the cooling channel (105) are arranged opposite each other at an angle of about 180° on the outer wall of the mold insert (100).

4. Mold insert (100) according to claim 1, characterized in that the door (103) is located in the center of the bottom of the mold insert (100).

5. Mold insert (100) according to claim 1, characterized in that the shape of the internal contour of the groove (104) corresponds to the shape of the external contour of the hot runner nozzle.

6. Mold insert (100) according to claim 1, characterized in that the mold insert (100) is used for a transparent PET plastic container, preferably PET PCR, particularly preferably chemical PET PCR.

7. Mold insert (100) according to claim 1, characterized in that the mold insert (100) is used for a plastic container

8.

9.

10. including a container base with a thickness of at least 5 mm, preferably 5-10 mm, more preferably 6-9 mm, even more preferably 7-8 mm. Mold insert (100) according to claim 1, characterized in that the mold insert (100) is manufactured using a metal 3D printing process. Mold insert (100) according to claim 1, characterized in that the mold insert (100) is constructed in the form of a cylindrical body. Mold assembly for injection molding of plastic containers, comprising at least one slide (200) and at least one mold insert (100) according to any one of the preceding claims, wherein the shape of the molding cavity (201) of the slide (200) corresponds to the shape of the container wall.