JP2934409B2 - Multilayer blow molding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer blow molding apparatus, and more particularly to a multi-layer blow molding apparatus capable of saving raw materials at the time of resin change or color change and reducing the thickness of a multilayer hollow parison without generating weld lines. The present invention relates to a controllable multilayer blow molding apparatus.

[0002]

2. Description of the Related Art When a bottle or the like is formed by using different types of resins in a multilayer shape, a resin in consideration of gas barrier properties is used for a layer inside the container, and a resin outside the container is used. In the layer (1), a resin considering the surface glossiness is used to achieve both gas barrier properties and surface glossiness. Thus, when blow molding a multilayer container utilizing the properties of the resin to be used, the hollow parison is formed in a multilayer shape, and after sandwiching the multilayer hollow parison in a mold, air is blown, It is manufactured by taking out after cooling. As a device for forming a multilayer hollow parison, devices described in JP-A-55-107429 and JP-A-52-12273 are known.

[0003] The device described in JP-A-55-107429 is
It has a plurality of so-called side feed resin supply paths for supplying the resin from a direction perpendicular to the extrusion direction of the hollow parison. After the molten resin supplied from the supply path hits a mandrel for forming the hollow portion of the hollow parison, the molten resin wraps around the mandrel along an annular flow path formed around the mandrel and is opposed to the supply path. The resin flows merge on the side and flow downward. Then, the other resin flows that have flowed in the same manner merge at the respective merging points, and the hollow parison formed in a multilayer shape is extruded from the tip of the die. The thickness of the hollow parison is controlled by moving the mandrel in the vertical direction and adjusting the gap between the core pin at the end of the mandrel and the die.

However, in the apparatus described in Japanese Patent Application Laid-Open No. 55-107429, since the molten resin is supplied from the side, a flow path design for uniformly distributing the molten resin in the circumferential direction is provided. However, there is a problem that unevenness is generated in the layer thickness distribution in the circumferential direction, and a molding defect called a weld line is easily generated on the opposite side of the supply path. Also, at the time of resin change or color change to change the type or color of the resin, the hollow parison must be extruded with new resin to remove the old resin from inside the die, but since the above device is a side feed system, There is also a problem that the resin flow on the opposite side of the supply path tends to stagnate, requiring a lot of time when changing the resin or changing the color, and increasing the amount of wasted resin.

Further, in the apparatus described in Japanese Patent Application Laid-Open No. 52-12273, the outermost layer is formed in the same direction on the same axis as the extrusion direction of the hollow parison, in addition to the side feed type resin supply path as described above. It also has a so-called center feed type resin supply path for supplying the resin to be formed. Since the molten resin supplied by the center feed method is uniformly guided in an annular flow path like an umbrella and supplied downward, by using both methods together, a weld line can be generated on the surface of the container after molding. In addition, resin change and color change can be performed in a short time, and wasteful resin can be reduced. Note that it is not realistic to use all the resin supply paths as the center feed method due to structural restrictions, and only one of the plurality of resin supply paths can be used as the center feed method.

However, in the above-described apparatus described in Japanese Patent Application Laid-Open No. 52-12273, a resin feed path by a center feed method is provided, and a mechanism for raising and lowering a core pin at the tip of a mandrel cannot be provided. For this reason, there is a problem that the thickness of the hollow parison cannot be controlled by adjusting the gap amount between the core pin and the die. For this reason, there has been a problem that it is not possible to reduce the amount of resin used to change the wall thickness in accordance with the shape of the bottle or the like to be molded, and to mold an article such as a bottle with a light weight and a short cooling time. Further, even if a shaft for raising and lowering the core pin can be arranged, the shaft impedes the resin flow supplied by the center feed method, and the advantage of the center feed method cannot be obtained.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a multilayer blow molding method which can save the raw materials at the time of resin change or color change and can control the thickness of a multilayer hollow parison without generating weld lines. It is to provide a device.

[0008]

According to the present invention, a mandrel for forming a hollow portion of a hollow parison is provided.
9, an inner annular flow path 4 surrounding the mandrel 19;
Upper part 1a having an inner sleeve 13 interposed therebetween, and an outer sleeve 14 interposed with the outer annular flow path 7 so as to surround the inner sleeve 13.
And a lower die part 1b having a die 17 at the lower end thereof, from which the hollow parison is extruded, wherein the lower end of the inner sleeve 13 is located above the lower end of the outer sleeve 14. , Above
Inner annular flow path 4 and outer ring at lower end of side sleeve 13
Inner annular channel 4 and outer annular channel 4
At the confluence of the converging annular channel 8 formed by merging with the channel 7
That channel width and is widened, the die lower part 1b is formed in a separate body and the die upper part 1a, the mandrel 1
9 is slidably disposed so as to surround the lower portion of the die 9 and contact the outer surface of the outer sleeve 14.
The above object has been attained by providing a multilayer blow molding apparatus characterized in that the gap 10 between the tip 7 and the core pin 21 at the tip of the mandrel 19 is adjusted.

According to a second aspect of the present invention, in the first aspect, the circular cross-sectional diameter of the mandrel 19 on the side of the lower end of the outer sleeve 14 is larger than the circular cross-sectional diameters above and below the mandrel 19. The present invention also provides a multilayer blow molding apparatus characterized in that the mandrel 19 is formed in a drawn shape so as to reduce the size.

[0010] The invention described in claim 3 is the invention according to claim 1 or 2.
Wherein the method of supplying the molten resin to the inner annular flow path 4 is a center feed method, and the method of supplying the molten resin to the outer annular flow path 5 is a side feed method. To provide a multi-layer blow molding apparatus.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the multilayer blow molding apparatus of the present invention will be described below with reference to the drawings.
1 and 2 show a multilayer blow molding apparatus of the present embodiment. FIG. 1 is a sectional view of a die head for extruding a parison of the present embodiment. FIG. 2 is an enlarged view showing the vicinity of a sliding portion between an outer sleeve and a die body. It is sectional drawing.

The multilayer blow molding apparatus according to the present embodiment is shown in FIG.
As shown in FIG. 2, a mandrel 19 for forming a hollow portion of the hollow parison, an inner sleeve 13 disposed around the inner annular flow path 4 so as to surround the mandrel 19,
A die upper part 1a having an outer sleeve 14 disposed so as to surround the inner sleeve 13 with an outer annular flow path 7 interposed therebetween; and a die lower part 1b having a die 17 at the lower end of the die 17 from which the hollow parison is extruded. And
These configurations are the same as those of the conventional device.

Thus, in the multilayer blow molding apparatus according to the present embodiment, the lower end of the inner sleeve 13 is connected to the outer sleeve 1.
4, the lower part 1b of the die is formed separately from the upper part 1a of the die, and surrounds the lower part of the mandrel 19;
4 is arranged so as to be slidable in contact with the outer surface thereof, so as to adjust the gap 10 between the tip of the die 17 and the core pin 21 at the tip of the mandrel 19.

Further, in the multilayer blow molding apparatus of the present embodiment, the circular cross-sectional diameter of the mandrel 19 on the side of the lower end of the outer sleeve 14 is smaller than the circular cross-sectional diameters above and below the mandrel 19. The mandrel 19 is formed in a constricted shape, the method of supplying the molten resin to the inner annular flow path 4 is a center feed method, and the method of supplying the molten resin to the outer annular flow path 5 is a side feed method. It is a feed system.

The multilayer blow molding apparatus according to the present embodiment will be described in more detail. The multilayer blow molding apparatus of this embodiment has a die head 1 as shown in FIG. 1 for forming a hollow parison having two layers, an inner layer and an outer layer. The die head 1 includes the upper die portion 1a and the lower die portion 1b, and the lower die portion 1b is slidably disposed at the lower end of the upper die portion 1a.

The upper die portion 1a comprises a die main body 11, the inner sleeve 13, the outer sleeve 14, the mandrel 19, and the ring-shaped engaging portion 12, and the mandrel 19 is provided below the die main body 11. The ring-shaped locking portion 12, the inner sleeve 13, and the outer sleeve 14, which are connected to a plurality of bolts 23, are sequentially arranged.
(Only one is shown in FIG. 1).

The die body 11 has a supply path 2 for supplying a molten resin for an inner layer. The supply path 2 is formed in a horizontal direction from a barrel (not shown), and is then pushed out of the center of a hollow parison. It is bent along the axis A and communicates with the umbrella channel 3.

The upper end of the mandrel 19 is formed in a conical shape and forms the umbrella-shaped flow path 3. The lower part of the mandrel 19 is formed in a columnar shape. The core pin 21 is formed further below. The mandrel 19 and the ring-shaped engaging portion 12 are provided with a plurality of spiders 18, 18,... Protruding radially from the outer surface of the mandrel 19.
Are connected by The mandrel 19 is arranged so that its central axis coincides with the axis A.

The inner sleeve 13 has a substantially cylindrical shape, and has a flange-shaped portion formed thereon for locking the ring-shaped locking portion 12 and for attaching to the die body 11. ing. The inner diameter of the cylindrical portion of the inner sleeve 13 is larger than the outer diameter of the cylindrical portion of the mandrel 19, and the inner sleeve 13 forms the inner annular flow path 4 between the inner sleeve 13 and the mandrel 19. is there. A groove 6 is formed diagonally on the outer peripheral surface of the inner sleeve 13, and the groove 6 is communicated at its uppermost portion with the supply path 5 for supplying the molten resin for the outer layer. The thickness of the cylindrical portion of the inner sleeve 13 is formed so that the portion below the groove 6 is thinner than the portion above the groove 6. The lower end of the cylindrical portion of the inner sleeve 13 is formed so as to be narrow and thin.

The outer sleeve 14 has a substantially cylindrical shape, and a portion serving as an attachment portion to the die body 11 is formed on an upper portion thereof. The inner diameter of the cylindrical portion of the outer sleeve 14 is equal to the outer diameter of the portion of the inner sleeve 13 above the groove 5, and the outer sleeve 14 is located below the groove 5 of the inner sleeve 13. The outer annular flow path 7 is formed between the outer annular flow path 7 and the portion. The lower end of the cylindrical portion of the outer sleeve 14 is formed so as to be narrowed and thinner, like the inner sleeve 13.

The inner annular flow path 4 and the outer annular flow path 7 join at the lower end of the inner sleeve 13 to form a combined annular flow path 8. In addition, the above-mentioned mandrel 1
The concave groove 20 formed on the outer peripheral surface of the outer sleeve 14 is located on the side of the lower end of the outer sleeve 14. For this reason, the merging annular channel 8 has a wider channel width than the inner annular channel 4 (or the outer annular channel 7) above the merging annular channel 8.

The die lower part 1b is provided with a die body 1
5, a die holder 16 and the dice 17, and the die holder 1 is provided below the dice body 15.
6. The dies 17 are arranged in order, and are integrally fastened together by a plurality of bolts 24 (only one is shown in FIG. 1). A shaft 22 parallel to the axis A is attached to the die lower part 1b, and the shaft 22 is connected to a servo motor (not shown) through the die upper part 1a.

The die body 15 has a hole formed in the center thereof at the lower part of the mandrel 19, and the inner diameter of the center of the hole is equal to the outer diameter of the lower end of the outer sleeve 14. The merging annular flow path 8 is formed between the converging annular flow path 8 and the mandrel 19. The lower part of the hole is narrowed, and accordingly, the width of the merging annular flow path 8 is narrowed toward the lower part. The die holder 16 is attached to the die body 15 so as to sandwich the die 17 in a hole formed in the center thereof.

The die 17 has a substantially cylindrical shape, and a flange-shaped portion serving as a locking portion to the die holder 16 is formed at an upper portion thereof. The die 17 has a hole in the center thereof through which the core pin 21 at the lower end of the mandrel 19 is inserted. The inner diameter of the hole is slightly higher than the hole so as to be continuous from the hole of the die body 15. The die land 9 is formed to be narrowed and fixed at the center thereof and forms a die land 9 with the core pin 21, and is slightly widened at the lower end thereof to form the gap 10 between the lower end of the core pin 21 and the die land 9. The dies 17 are mounted on the dies holder 1
6, the position of the core pin 21 can be finely adjusted by an adjustment screw (not shown).
The gap 10 is adjusted so as not to be biased.

Next, a procedure for forming a multilayer hollow parison using the multilayer blow molding apparatus of the present embodiment will be briefly described.

The molten resin for the inner layer, which is melted in a barrel (not shown) and supplied to the supply path 2 by a screw (not shown), is supplied to the umbrella-shaped flow path 3 along the supply path 2. In the umbrella-shaped flow path 3, the molten resin for the inner layer is uniformly distributed without unevenness, and passes through the plurality of the spiders 18.
Supplied to

Similarly, at the same time, the molten resin for the outer layer melted in a barrel (not shown) and supplied to the supply path 5 by a screw (not shown) is supplied to the side surface of the mandrel 19 when the resin leaves the supply path 5. , And are joined along the opposite side of the supply path 5 to be supplied to the lower outer annular flow path 7 below.

The inner layer molten resin that has traveled through the inner annular flow path 4 and the outer layer molten resin that has traveled through the outer annular flow path 7 merge at the lower end of the inner sleeve 13. It is supplied to the annular flow path 8. The width of the merging annular channel 8 at the merging portion is increased, and the thickness of the merged multilayer resin flow is reduced by the merging annular channel 8 that narrows downward. ,
It is supplied to the die land 9.

In the die land 9, the shape of the hollow parison to be extruded is adjusted, and the resin flow passing through the die land 9 is extruded as a multilayer hollow parison through the gap 10. At this time, the thickness of the hollow parison is adjusted by moving the lower part 1b of the die up and down by a servomotor via the shaft 22 to change the amount of the gap 10.

In the present embodiment, the tip of the inner sleeve 13 is located above the tip of the outer sleeve 14, but the tip of the inner sleeve 13 is located above the tip of the outer sleeve 14. 4, the portion corresponding to the sliding movement of the die lower portion 1b on the outer surface of the hollow parison composed of the inner layer I and the outer layer O extruded from the gap 10 has a flaw X as shown in FIG. May occur. This is because the molten resin is pulled when the lower die portion 1b slides,
This is probably because the flow at the boundary between the inner layer and the outer layer is disturbed at the tip of the inner sleeve 13 and the tip of the outer sleeve 14.

In the present embodiment, the tip of the inner sleeve 13 is positioned above the tip of the outer sleeve 14 so that the inner sleeve 13 is already slid at the portion where the outer sleeve 14 and the die body 15 slide. The resin and the outer layer resin are merged so that the flow at the junction of the inner layer and the outer layer at the tip of the inner sleeve 13 is not affected by the sliding of the die body 15. In the present embodiment, the width of the merging annular flow path 8 on the side of the sliding portion between the outer sleeve 14 and the die body 15 is further increased to increase the thickness of the outer resin layer. The flow at the boundary of the multilayer flow at the tip of the outer sleeve 14 is not affected by the sliding of the die body 15.

The sliding speed of the die body 15 is higher, the flow rate of the resin is larger, and the viscosity of the outer layer resin is higher.
Since the pulling force of the slide of the die body 15 is increased, a scratch X as shown in FIG. 4 is easily generated on the outer surface of the hollow parison. Further, the smaller the thickness of the outer resin layer, the more easily the slide body 15 is affected by the slide, so that the above-mentioned scratches X are more likely to occur.

The multilayer blow molding apparatus of the present embodiment is configured as described above. According to the multilayer blow molding apparatus of the present embodiment, it is possible to save raw materials at the time of resin change or color change, and to reduce a weld line. Without causing
The thickness of the multilayer hollow parison can be controlled.

The multilayer blow molding apparatus of the present invention is not limited to the above embodiment. For example, in the present embodiment, the mandrel 19 is formed with the concave groove 20 so that the converging tubular flow path 8 is formed. Although the width of the flow path was further expanded,
As shown in FIG. 3, the converging tubular flow path 8 'may be formed without forming a concave groove in the mandrel 19'. Further, in the multilayer blow molding apparatus of the present embodiment, two hollow parisons are formed by the above-described die head 1, but the multilayer blow molding apparatus of the present invention forms three or more multilayer parisons. In this case, the lower end of the outer sleeve (that is, the outermost sleeve) that slides with the lower portion of the die may be located below the lower end of the inner sleeve (that is, the innermost sleeve). An inner resin layer may be further joined inside the inner sleeve. Other points can be appropriately changed without departing from the spirit of the present invention.

[0035]

According to the first aspect of the present invention, in the die head for multilayer blow molding, the molten resin is merged upstream of the sliding portion between the outer sleeve 14 and the die body 15 and the die lower portion 1b is formed. By sliding
It is possible to adjust the wall thickness of the parison, and it is possible to form a thin-walled, light-weight, short-cooling time, good-looking article such as a bottle that satisfies physical properties such as compressive strength and ESCR. The width of the merging annular flow path 8 at the merging portion
The outer sleeve 14 and the die
Resin flow (particularly outer layer)
Resin flow), the flow at the interface of the multilayer flow
Not be affected by the slide of the chair body 15
By doing so, it is difficult to generate scratches on the surface of the hollow parison , so that the sliding speed of the die body 15 can be increased, and also in this respect, productivity can be improved.

According to the invention described in claim 2, according to claim 1
In addition to the above-described effects according to the invention described in the above, the mandrel 19 is squeezed so that the circular cross-sectional diameter of the mandrel 19 on the side of the lower end portion of the outer sleeve 14 is smaller than the circular cross-sectional diameters above and below it. The outer sleeve 14 and the die body 1 are formed into a shape, that is, by forming a concave groove 20 on the outer surface of the mandrel 19.
5, the thickness of the resin flow (especially the outer layer resin flow) is increased by widening the flow width of the converging tubular flow path 8 on the side of the sliding portion with the 5, and the outer surface of the formed hollow parison is further damaged. Can be difficult.

According to the invention described in claim 3, according to claim 1
Or, in addition to the above-described effects according to the invention described in 2 above, since the molten resin is supplied by using both the center feed method and the side feed method, the stagnant portion of the resin is small, and the resin change and color change are performed in a short time. In addition, it is possible to save raw materials, and it is possible to form articles such as bottles having an excellent appearance and a uniform layer thickness distribution without generating weld lines on the resin surface (particularly, the outer resin surface). .

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a multilayer blow molding apparatus of the present invention.

FIG. 2 is an enlarged sectional view showing the vicinity of a sliding portion between an outer sleeve and a die body in one embodiment of the multilayer blow molding apparatus of the present invention.

FIG. 3 is an enlarged sectional view showing the vicinity of a sliding portion between an outer sleeve and a die body in another embodiment of the multilayer blow molding apparatus of the present invention.

FIG. 4 is an explanatory sectional view showing a scratch generated on the outer surface of the hollow parison.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Die head 1a Die upper part 1b Die lower part 2 Supply path (for inner layer resin) 3 Umbrella-shaped flow path 4 Inner tubular path 5 Supply path (for outer layer resin) 6 Groove 7 Outer tubular flow path 8 Merging tubular flow path 9 Die land Reference Signs List 10 gap 11 die body 12 ring-shaped locking portion 13 inner sleeve 14 outer sleeve 15 dice body 16 dice holder 17 dice 18 spider 19 mandrel 20 concave groove 21 core pin 22 shaft 23, 24 bolt

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B29C 49/00-49/80

Claims (3)

(57) [Claims] 1. A mandrel 19 for forming a hollow portion of a hollow parison, an inner sleeve 13 provided with an inner annular flow path 4 surrounding the mandrel 19, and an inner sleeve 13 surrounding the inner sleeve 13. A die upper part 1a having an outer sleeve 14 disposed with an outer annular flow path 7 interposed therebetween; and a die 17 from which the hollow parison is extruded.
And a lower die part 1b having a lower end of the inner sleeve 13, wherein a lower end of the inner sleeve 13 is located above a lower end of the outer sleeve 14, and an inner annular shape at a lower end of the inner sleeve 13. Channel 4
The inner annular flow path 4 and the outer annular flow path 4
Converging part of merging annular channel 8 formed by merging with side annular channel 7
, The die lower portion 1b is formed separately from the die upper portion 1a, surrounds the lower portion of the mandrel 19, and contacts the outer surface of the outer sleeve 14. The tip of the die 17 and the mandrel 19
A multilayer blow molding apparatus characterized in that a gap (10) with a core pin (21) at the tip is adjusted. 2. The mandrel 19 is formed in a drawing shape such that the circular cross-sectional diameter of the mandrel 19 on the side of the lower end of the outer sleeve 14 is smaller than the circular cross-sectional diameters above and below the mandrel. Claim 1
2. The multilayer blow molding apparatus according to item 1. 3. A method for supplying the molten resin to the inner annular flow path 4 is a center feed method, and a method for supplying the molten resin to the outer annular flow path 5 is a side feed method. 2. The multilayer blow molding apparatus according to item 1.