JP2000025729A - Preform for blow molding and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of a wrinkle in a bottom part and the existence of a gate residue, enable even and uniform stretch molding for the bottom part of a blow-molded item, and improvement in the impact resistance of the bottom part, by compression-molding a thermoplastic-resin fused-object by means of a male die and a female die that move relatively. SOLUTION: A resin for molding fused and kneaded in an extrusion machine main body 11 is supplied to a nozzle 16 by a fixed quantity and extruded cylindrically. In a cutting/supplying device 2, it is cut into cylindrical fused clumps with a cutter, and without substantially decreasing their temperatures they are thrown into the female dies 32 of a molding compression device, which comprises a large number of female dies 32 and male dies 33 arranged around a rotary turret 31. Subsequently, the male dies 33 on the same axes as the female dies 32 are lowered by a lifting/lowering drive mechanism 42, and the fused resins in the female dies 32 are compression-molded into performs for molding, each having a bottomed body part and a mouth part. At the same time as the start of the compression molding, air in the female dies 32 is discharged outside at once from vent parts made in the bottom parts of them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a preform for blow molding and a method for producing the same, and more particularly to a preform for blow molding, which is formed by compression molding of a thermoplastic resin melt and has no gate portion and no wrinkles. The present invention relates to a preform for blow molding having a closed bottom and a method for producing the same.

[0002]

2. Description of the Related Art Stretch-blow molded plastic containers, particularly polyester containers, are nowadays commonplace. Due to their excellent transparency and moderate gas barrier properties, liquid detergents,
In addition to liquid products such as shampoo, cosmetics, soy sauce and sauce, carbonated beverages such as beer, cola and cider, fruit juice,
It is widely used in other beverage containers such as mineral water, dessert cups, miso containers, cup products and the like.

[0003] In molding a polyester container, a preform with a bottom having a size considerably smaller than that of the final container and an amorphous polyester is preliminarily formed by injection molding of the polyester, and the preform is preheated to its stretching temperature. In addition, a method is used in which the film is stretched in the axial direction in the blow mold and is stretched in the circumferential direction.

[0004] The shape of the bottomed preform includes a mouth-neck portion corresponding to the mouth-neck portion of the container and a bottomed cylindrical portion to be stretch-blow-molded. Tubular ones are common. The mouth and neck are provided with, for example, a sealing opening end and a means for engaging with a lid. In addition, a gate protruding outward from the center of the bottom is necessarily formed at the bottom due to the necessity of injection molding.

It is also known to produce a bottomed preform by compression molding of a resin.
No./32706, prepare a compression mold having a closed bottom and a cavity forming a preform shape, mold a thermoplastic resin into a precursor and put the precursor into the compression mold,
Here, the precursor is fixed and adhered entirely in the cavity, and the precursor is not completely filled in the compression mold, but before being compressed into the final shape, the cavity of the compression mold is compressed. A preform having a shape such that it is supported in a predetermined manner within the preform, and heating the precursor prior to putting the precursor into the compression mold, and compression-molding the heated precursor in the compression mold. Are described.

[0006]

However, the gate portion formed on the bottomed preform by injection molding has many problems in terms of productivity, manufacturing cost, and characteristics of the final blow molded product. I have. In other words, a special cutting step is required to cut this gate portion, which is one of the factors that lowers the productivity. In addition, the cut gate portion becomes scrap resin, which wastes resources. Furthermore, the remaining gate tends to cause crystallization and whitening of the final blow-molded product, which causes deterioration in appearance characteristics, and also causes orientation during stretch blow molding due to flow orientation at the time of molding and distortion at the time of cutting. This causes unevenness and unevenness of the structure, and also causes a bottom crack due to a drop impact or the like.

In addition, in injection molding, a large shear force acts during molding, so that molding at a high temperature is required, and there is a problem in that the heat history causes thermal degradation (thermal degradation) of the resin. For this reason, in the production of a conventional PET (polyethylene terephthalate) container, PET having a high intrinsic viscosity by a solid-state polymerization method must be used in anticipation of a decrease in the intrinsic viscosity that occurs at the time of injection molding. Has brought. Furthermore, since not only the cooling of the injected resin but also the flow of the resin is required for the mold at the same time, the degree of freedom in setting the mold temperature is small, and the injection molding time becomes longer. There are also problems.

[0008] The molding of the preform by the above-mentioned compression molding method has an advantage that the thermal degradation of the resin due to the injection molding can be reduced. Thermoforming into a body, heating this precursor again and feeding it to the injection mold, and re-forming for compression molding in addition to thermoforming, such as the heated precursor having to be compression molded in the injection mold. There is still something to be improved in that heating is required.

[0009] Furthermore, compression molding has the advantage that the flow of resin in the compression mold does not require much consideration and the molding pressure can be relatively low, but wrinkles are formed on the closed bottom of the preform to be molded. Such a preform has a problem that a bottle having poor impact resistance is formed.

Therefore, an object of the present invention is to form a thermoplastic resin melt by compression molding without wrinkles at the bottom,
Another object of the present invention is to provide a blow-molded preform and a method for producing the same, which have no gate residue and allow uniform and uniform stretch-forming to the bottom of the blow-molded product and improvement in impact resistance of the bottom. Another object of the present invention is to provide a method for producing a preform for blow molding in which compression molding is possible by one heating for melting the resin, and as a result, thermal deterioration of the resin is remarkably suppressed. To be.

[0011]

According to the present invention, a step of extruding a thermoplastic resin melt and cutting it into a substantially fixed amount of molten mass is provided.
A step of supplying the molten mass into the mold without substantially lowering the temperature; and, while discharging residual air at or near the bottom in the mold, compression molding into a molded article having a bottomed body and a mouth. And a step of cooling and solidifying the compression molded product and discharging the molded product out of the mold. In the production method of the present invention: The thermoplastic resin melt is extruded in parallel with the axial direction of the male mold and the female mold, and the cut molten mass is maintained substantially in a parallel state, and the portion forming the preform bottom of the molten mass is formed. 1. feeding into the female mold without cooling; 2. the molten mass has a cylindrical shape or a shape close to a cylindrical shape; 3. gripping the molten mass at a position higher than its center of gravity and feeding it into the mold; 4. a mold having a fine gap or a plurality of pores at the bottom of the mold or in the vicinity thereof; The male mold is composed of a core mold, and a driven mold provided coaxially and openably and closably around the core mold, and forming a tapered portion having a bottom with the core mold and the female mold. 5. Perform molding of the mouth with the core mold and the driven mold. It is preferable to immediately discharge the residual air at or near the bottom when the molten mass is formed by a mold. According to the present invention, also in a blow molding preform formed from a thermoplastic resin, formed by compression molding of a thermoplastic resin melt, a mouth having a shape and dimensions corresponding to the mouth of the final molded body. A preform for blow molding, characterized in that it has a bottomed body to be blow molded and has no closed bottom wrinkles and no gate residue. Preferably, the closed bottom of the preform has no whitened portion.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a male mold and a female mold are relatively movably arranged, and a molten mass of resin supplied to the mold is compression-molded. Cutting into a fixed amount of molten mass, feeding the molten mass into the mold without substantially lowering the temperature, and compressing the supplied molten mass substantially immediately, while discharging the residual air in the mold; It is characterized in that it is compression-molded into a molded article having a portion and a bottomed body.

It has already been pointed out that compression molding can be performed at a relatively low temperature, unlike injection molding. However, in the present invention, pre-molding for blow molding is performed by one heat melting and compression molding. Since a product is obtained, the degree of thermal degradation of the resin is small, and a blow-molded product excellent in physical properties can be manufactured.

That is, in order to produce blow molded products having the same physical properties (strength and impact resistance), it is possible to use a cheaper resin, and when using the same raw material resin, it is necessary to produce a blow molded product having more excellent physical properties. Can be done. In addition, preforms for large blow molded products that require high impact resistance can be easily molded into preforms for blow molding, even if the resin viscosity is high and resin materials unsuitable for injection molding are required. It is also possible to get

In the one-stage compression molding method of the present invention, the amount of heat of the molten mass of the resin during the melt extrusion of the resin is effectively used, and the local cooling of the mass is prevented as much as possible.
In particular, the preform having a homogeneous internal structure and excellent stretch blow moldability should not be cooled, and the movement of the resin on the surface of the mold during compression molding should not be restricted during the compression molding. It is important for manufacturing things.

For this purpose, the method according to the invention comprises feeding a substantially fixed amount of molten mass formed by cutting the extrudate into a female mold without substantially lowering the temperature, The mass is immediately compression molded in a mold. Also, at the time of compression molding, compression molding is performed into a molded article having a bottomed body and a mouth while quickly discharging residual air in the mold.

In the single-stage compression molding method, the temperature of the resin decreases after cutting into a molten mass and before charging into a mold.
This has a significant effect on the uniformity of the structure of the bottomed body to be blow-molded and the stretch orientation of the preform, as well as on the physical properties of the final blow-molded product, especially impact resistance. The effect of this temperature drop is particularly pronounced in the lower part of the molten mass that forms the bottom of the preform (the bottom of the final blow molded product). That is, when the lower part of the molten resin mass is locally cooled, the degree of distortion at the bottom of the preform becomes large, which causes poor appearance and reduced impact resistance in the final blow molded product ( See Comparative Examples 1 and 2 described later). In the present invention, after cutting into a molten mass, suppressing a substantial temperature decrease of the resin molten mass before being put into a mold, particularly suppressing a temperature decrease within the above-described time of the lower portion of the molten resin mass. Thus, the above trouble can be effectively solved.

As described above, in order to suppress a decrease in the temperature of the molten mass, after cutting into the molten mass and before putting it into the mold, for example, except for the gripping portion, the molten mass and the other members are separated. Contact should be avoided, especially contact between the lower part of the molten mass and other members should be avoided as much as possible.

In a preferred embodiment of the present invention, for this purpose, a thermoplastic resin melt is extruded in parallel with the axial direction of the male mold and the female mold, and the cut molten mass is substantially brought into a parallel state. Supply it into the mold while maintaining it.

It is preferable to supply the molten mass of the resin in a cylindrical shape or a shape close to a cylindrical shape so that the molten mass can be supplied in a substantially quantitative state and the lower portion can be cooled as much as possible. Furthermore, for the purpose of avoiding the temperature drop in the lower part of the molten mass as much as possible, and for the purpose of stably supplying the molten mass, that is, preventing the molten mass from falling down, the molten mass is placed at a portion above the center of gravity of the molten mass. It is preferable to grip, move from the cutting position to the mold position, and feed the mold.

In order to avoid the cooling of the molten mass, it is preferable that the injection from the cutting into the mold and the start of molding after the injection into the mold be performed in as short a time as possible. It is recommended that the process be performed within 1 second, and within 0.5 seconds from the time of injection into the mold until the start of molding.

In the single-stage compression molding method of the present invention, it is extremely important to perform compression molding while eliminating residual air at the bottom of the mold or in the vicinity thereof. That is, under the condition that air remains in the mold, wrinkles tend to be generated in a portion attached to the mold or in the vicinity thereof. On the other hand, if the air is removed immediately after the molding is started, the occurrence of wrinkles can be effectively prevented. It is considered that wrinkles are caused by the minute gap between the close contact part and the non-contact part on the mold surface, and this is believed to be a phenomenon peculiar to compression molding. Then, it is considered that the mold surface and the resin are re-adhered to each other, and a container wall without wrinkles is formed.

In order to eliminate the residual air on the surface of the female mold, it is sufficient to form a way for the residual air to escape from the molding site to the outside. The means is not particularly limited. It is preferable to use a mold having a fine gap or a porous portion. It is particularly effective to forcibly remove residual air with an external vacuum pump or the like at the start of molding.

In the single-stage compression molding method of the present invention, the shapes and structures of the female mold and the male mold are not particularly limited as long as they can form the bottomed body and the mouth. Uses a core mold and a driven mold which is provided around the core mold so as to be coaxial and openable and closable as the male mold. The core mold and the female mold (cavity mold) are used. It is desirable to form a tapered portion with a bottom in the above, and to form a mouth portion with a core mold and a driven mold. In this case, the driven mold is reciprocally driven together with the core mold, but the driven mold is always biased toward the female mold by biasing means such as a spring. In, the core mold and the driven mold are always kept in a constant contact state. For this reason, even when the amount of molten resin mass fluctuates slightly, preforming always has a constant height (height from the inner surface of the bottom to the top of the mouth), and the shape of the mouth important for sealing is always constant. An object will be formed. Further, the variation in the amount of the molten resin mass can be absorbed by the engagement between the core mold and the female mold (cavity mold), that is, the thickness of the bottomed body of the formed preform.

The molten resin mass can be supplied almost quantitatively by melt-extruding the resin through an extruder or a gear pump and cutting the resin at a predetermined timing. It is inevitable that variations in the range will occur. In the above-mentioned molding method of the present invention, this variation can be easily absorbed.

The one-stage compression molding method of the present invention has an advantage that the molding force itself generally needs to be considerably small even if a certain pressure is required for preventing sinking during molding. Therefore, there is an advantage that the size of the device itself can be considerably reduced and the cost of the device can be reduced as compared with the injection molding device.

The blow molded preform of the present invention is formed by compression molding of a thermoplastic resin melt, and has a mouth having a shape and dimensions corresponding to the mouth of the final molded body, and a bottomed portion to be blow molded. It has a body portion, but has a feature that the closed bottom portion has no wrinkles and no gate portion.

It has already been pointed out that the gate part present in the bottomed preform of the injection molding poses many problems in terms of productivity, production cost and characteristics of the final blow molded product. In the preform of the present invention, since this gate does not exist at all, the cutting step is unnecessary, there is no generation of scrap resin, and the bottom center is also smooth and uniform, which causes crystallization and whitening. There is an advantage that there is no such thing.

Further, the preform for blow molding of the present invention is characterized in that there is no wrinkle at the bottom or in the vicinity thereof due to the above-mentioned strict temperature control and the fact that the molding is performed under the condition of eliminating residual air. have.

When the preform for blow molding of the present invention is used, there is no gate at the bottom and no wrinkles are generated, and the smoothness and the uniformity of the structure are remarkably excellent. The blow-molded article has an advantage that the bottom has remarkably excellent appearance characteristics and impact resistance.

Further, in this preformed product, the degree of thermal deterioration of the resin is small as described above, and the tensile strength, pressure strength,
It has the advantage that a blow-molded article having excellent physical properties such as impact resistance and heat resistance can be produced.

[Single-Stage Compression Molding Apparatus] In FIGS. 1 (plan view) and 2 (side view) showing the overall arrangement of the apparatus used in the single-stage compression molding method of the present invention, this apparatus is roughly described The apparatus comprises an apparatus 1 for extruding a plastic resin, an apparatus 2 for cutting and supplying a molten mass, and an apparatus 3 for compression molding into a preform.

The extruder 1 has an extruder main body 11 for melting and kneading the resin, and an inlet side of the main body has an extruder.
Vacuum hopper 1 for holding powder or pellets of thermoplastic resin to be molded in a dry state and supplying it to the extruder body
A suction vent 13 for sucking and removing decomposed gas and the like in the resin and a die head 14 for receiving the extruded molten resin are provided on the outlet side of the main body. The die head 14 is connected to an extruder nozzle 16 via a pipe 15. A gear pump 17 for supplying a fixed amount of molten resin is provided between the die head 14 and the extruder nozzle 16.
Should be provided. In FIG. 2, the gear pump 17 is omitted to avoid complication.

As shown in FIGS. 3 (plan view) and 4 (side view), the cutting and feeding device 2 for the molten mass is provided with a cutter 22 provided on a rotary turret 21 and an external device for gripping the molten mass. It consists of a combination of a gripping member 23 and an inner gripping member 24. The cutter 22 is a turret 21
And the resin melt 18 extruded from the extruder nozzle 16 can be cut in a direction perpendicular to the extrusion direction with the rotation of the turret 21. The outer gripping member 23 includes a portion extending in the radial direction of the turret and an outer portion extending in the circumferential direction, and is fixed to the turret 21. On the other hand, the inner gripping member 2
Reference numeral 4 is provided so as to be movable in the radial direction of the turret with respect to the outer gripping member 23.

The rotating turret 21 of the cutting and feeding device 2
Is provided so as to pass below the extruder nozzle 16 of the extrusion device 1 and above the female mold 32 of the compression molding device 3,
Under the extruder nozzle 16, the holding of the melt 18 by the holding members 23 and 24 and the cutting by the cutter 22 are performed,
The molten mass 19 in the gripping state by the gripping members 23 and 24
Of the molten mass 18 into the female mold 32 by releasing the gripping members 23 and 24.

As shown in FIGS. 2 and 4, in this single-stage compression molding apparatus, the thermoplastic resin melt 18 is mixed with the male mold 33 and the female mold 3.
2. The molten mass 19 is extruded in parallel with the axial direction of 2, and the cut molten mass 19 is supplied into the female mold 32 while substantially maintaining the parallel state. The molten mass 18 is supplied by the gear pump 17 in a substantially constant state. Then, the molten mass 19 of the resin is supplied in a shape of a cylinder or a column, and the molten mass 19 is gripped by the gripping members 23 and 24 at a position above the center of gravity, and the die is cut from the cutting position C. It is clear that it has moved to the position M and is being fed into the mold 32.

The compression molding apparatus 3 generally comprises a combination of a rotating turret 31 and a number of female dies 32 and male dies 33 disposed around the rotating turret. The rotating turret 31 is provided with a mechanism for cutting and supplying the molten mass, which has already been pointed out, and is also provided with a mechanism 34 for taking out the formed preform for blow molding.

The rotary turret 31 is rotatably supported by a vertical axis 36 on a machine base 35 in a horizontal direction and is rotatably driven by a motor 37 and a drive transmission mechanism 38. A combination (set) of the female mold 32 and the male mold 33 is fixedly provided on the outer peripheral upper surface of the rotating turret 31. That is, the female mold 32 is
On the other hand, the male mold 33 is provided coaxially with the female mold 32 so as to be able to move up and down by a lifting drive mechanism 42 such as a hydraulic mechanism via a vertical support member 40 and a horizontal support member 41. Have been.

5 and 6, which show the detailed structure of the female mold 32 and the male mold 33 and the molding process in steps, FIG.
Has a cavity 43, and at the bottom thereof, a vent portion 44 for removing residual air and a vent portion 45 at a connection portion between the bottom portion and the tapered portion are provided. A small upward protrusion 46 is formed around the upper portion of the cavity 43. The operation will be described later. Further, a ring-shaped driven member 47 slidable coaxially with the female mold is provided around the female mold 32.
7 has a shaft 48 extending downward, and a stopper 49 is formed at the lower end thereof.
It is housed in the lower recess 50 of the female mold 32. Thus, it will be appreciated that the stopper 49 can be raised and lowered between the upper and lower surfaces of the lower recess 50. The stopper 49 is biased upward by means such as a spring (not shown). Furthermore, on the upper inner peripheral surface of the driven member 47,
An engagement taper portion 51 whose diameter increases upward is formed.

On the other hand, the male mold 33 has a core mold 53 fixed to a support member 52 which can move up and down. The core mold 53 has a portion 54 for forming the top surface of the mouth of the preform, a portion 55 for forming the inner peripheral surface of the mouth, and a portion 55 for forming the inner surface of the bottomed tapered body. And a portion 56.

A driven mold 57 is provided around the core mold 33 coaxially with the core mold 33 so as to be openable and closable.
The driven mold 57 is fixed to a driven support member 58, and although not shown, the support member 52 and the driven support member 5
A push spring is provided between the rollers 8 to urge the driven mold downward. The lower inner peripheral surface of the driven mold 57 is provided with a portion 59 that forms the mouth inner peripheral surface of the preform, while the lower outer peripheral surface is formed with an engagement taper portion 60 whose diameter decreases downward. ing.

In the compression molding apparatus shown in FIGS. 5 and 6, the pressing force (absolute value) of each member is set as follows in order to perform each operation smoothly. The pressing force of the male mold 33> the pressing force of the driven member 47> the driven mold 5
Pressing force of 7

The molding operation by the above device is performed as follows. (A) Melt extrusion step: The molding resin such as thermoplastic polyester is supplied to the vacuum hopper 12 of the extruder 1 and the extruder body 1 is cut off in a vacuum while moisture absorption from outside air is shut off.
When it is separated in 1, it is melted and kneaded by a screw, and is fixedly supplied to a nozzle 16 by a gear pump 17 via a die head 14 and a pipe 15, and is extruded from the nozzle 16 into a cylindrical shape.

(B) Cutting and Supplying Step: The resin stream 18 melt-extruded from the nozzle 16 is cut by a cutter 22 into a molten mass 19 having a columnar or nearly cylindrical shape.
The molten mass 19 is gripped by the gripping members 23 and 24 and moves with the rotation of the turret from the cutting position C to the supply position M to the female die 32 without substantially lowering the temperature. It is thrown in.

(C) Compression molding step: In the approach step shown in FIG. 5I, the cavity mold 43 and the core mold 53 are used.
Is still open, and the molten mass 19 is stored in the cavity 43 in an upright state. The core mold 53 has begun to descend.

In the cavity mold clamping step II shown in FIG. 5, the core mold 53 descends into the cavity, and the molten resin 19 ′ is substantially filled in the space defined by the cavity 43 and the core 53. At the same time as the start of the compression molding, the residual air in the cavity is quickly released to the outside via the vent portions 44 and 45. At the same time, the driven mold 57 descends and comes into contact with the driven member 47, but there is still a gap between the upper surface of the driven supporting member 58 and the lower surface of the male supporting member 52.

In the core mold clamping step III shown in FIG. 5, the core mold 53 further descends, and the upper surface of the driven support member 58 and the lower surface of the male support member 52 come into contact. Along with this, the molten resin 19 ′ in the cavity flows into the space defined by the core mold 53 and the driven mold 57.

In the solidification step at a high temperature shown by IV in FIG. 5, the core mold 53 further descends slightly, and the driven member 47 also descends accordingly, and the cavity 43, the core mold 53 and the driven mold 57 Will be filled with resin.

In the solidification process at a low temperature shown in FIG. 5V, a decrease in the resin temperature causes volume shrinkage of the resin, that is, sinking. The distortion due to the volume shrinkage is caused by a male mold (core 53). Can be absorbed by applying a compressive force. In this case, the core mold 53 and the cavity 4
It is naturally necessary to move so as to mesh with the driven mold 5.
By engaging with No. 7, it is possible to obtain a preform for blow molding which absorbs volume shrinkage and has no distortion.

The step of removing the compression-molded preform is shown by steps I to V in FIG. Step I shows the stage when the molding is completed. In steps II and II, the core mold 53 starts to rise, and mold opening is started. In Step III, the core mold 53 is raised before the driven mold 57, and the core is removed from the formed preform 60. In step IV, the core mold 53 is further raised, and the preform 60 is taken out of the cavity 43. In Step V, the driven mold 57 moves to a position outside the diameter (the position indicated by the dotted line) at the re-elevated position of the core mold,
The held blow molding preform 60 is released.

[Resin Raw Material] As the raw material resin for forming the preform for blow molding of the present invention, any moldable thermoplastic resin can be used. Such resins include polyethylene terephthalate (PET) and polybutylene terephthalate (PB).
T), thermoplastic polyesters such as polyethylene naphthalate (PEN), copolymerized polyesters mainly composed of these ester units or blends thereof; polycarbonates; acrylic-butadiene-styrene copolymer (ABS resin); polyacetal resin Nylons such as nylon 6, nylon 66, and their copolymerized nylons;
Acrylic resins such as polymethyl methacrylate; isotactic polypropylene; polystyrene and the like, as well as low-, medium-, or high-density polyethylene, ethylene-propylene copolymer, ethylene-butene-1 copolymer, styrene-butadiene Examples thereof include a thermoplastic elastomer. Various additives such as a colorant, an ultraviolet absorber, a release agent, a lubricant, and a nucleating agent can be added to these plastics as long as the quality of the product is not impaired.

In particular, it is preferable to use a polyester as the thermoplastic resin. In this case, the intrinsic viscosity (η) of the polyester is at least 0.5 dl / g, particularly in the range of 1.3 to 0.7 dl / g. Those are preferred. Also,
As the polyester, those having a diethylene glycol unit content of 1.60% by weight or less, particularly 1.50% by weight or less are suitably used.

[Molding conditions] The melt extrusion temperature (die head temperature) of the thermoplastic resin differs depending on the resin.
Generally, Tm is determined based on the melting point (Tm) of a thermoplastic resin.
+ 100 ° C to Tm + 10 ° C, especially Tm + 40 ° C to T
It is preferably in the range of m + 20 ° C. At a temperature lower than the above range, the shear rate may be too high to form a uniform melt extrudate, while at a temperature higher than the above range, the degree of thermal degradation of the resin may increase. In the case of polyester or polyester, the drawdown tends to be too large.

The weight of the molten mass to be cut, that is, the basis weight is naturally determined by the final blow molded product.
An appropriate value is preferably selected from the range of 0 to 2 g, particularly 40 to 10 g, depending on the required strength.

It is advantageous in terms of handling that the molten mass has a columnar shape or a shape close to a column, but the ratio (H / D) of the diameter (D) to the height (H) of the molten mass is generally The range of 0.8 to 4 is advantageous in that the temperature of the molten mass can be prevented from lowering as much as possible and the molten mass can be easily put into the female mold. That is, when the H / D is outside the above range, the surface area of the molten mass becomes large, and the temperature tends to be easily lowered.

An arbitrary cutter is used for cutting the molten resin block, but a cutter which can prevent the resin from sticking is preferable. For example, surface treatment such as shot blasting is particularly effective.

As a gripping member for moving the molten resin mass, a member made of a material having good heat conductivity is used.
A resin having a minimum contact area with the resin is preferably used. From the cutting of the molten resin mass to the injection into the mold, it is preferable to perform the process promptly and within the time already indicated.

As the compression molding die, one having a fine gap or a porous portion formed at the bottom or in the vicinity thereof is used. The fine gap is obtained by dividing the bottom or the vicinity of the female mold into several pieces, It can be formed by forming a minute gap for excluding air between these pieces or by forming a hole for excluding air in a mold. Further, the porous portion can be used by processing a component such as a sintered metal.

The surface temperature of the compression mold may be any temperature at which solidification of the molten resin occurs. For example, in the case of polyester, a temperature range of 65 to 30 ° C. is appropriate. In order to maintain the surface temperature of the mold within the above range, it is preferable to pass a medium such as cooling water or temperature-controlled water through the mold.

One of the features is that the molding force required for compression molding can be considerably small. The specific molding force varies considerably depending on the type of resin and the size of the preform for blow molding, but generally, 800 to 50 kg.
f, especially a forming force of 600 to 150 kgf is suitable.

According to the present invention, by one-stage compression molding,
Since a preform for blow molding that does not require any gate portion or any other trimming operation is obtained, this preform can be used as it is in the stretch blow molding process,
It has many advantages in terms of process simplicity and productivity.

[Blow Molding Preform] In FIG. 7 showing the blow molding preform of the present invention, the preform 60 is roughly divided into a mouth portion 61 and a tapered bottomed body portion 62.
It consists of The mouth portion 61 serves as a mouth portion of a bottle which is a final molded product. On the outer periphery of the mouth portion 61, a locking portion 63 of the lid and a support ring 64 necessary for sealing with the lid are formed. The bottomed body portion 62 is a portion to be stretch blow-molded, and includes a tapered side wall portion 65 and a downwardly convex bottom portion 66 smoothly connected thereto.
As noted above, there are no gate remnants or wrinkles at bottom 66. The mouth portion 61 and the bottomed body portion 62 are smoothly connected via a connection portion 67.

The tapered side wall portion 65 and the bottom portion 66 have a certain preferable range in terms of their size and shape in terms of compression moldability and moldability at the time of final stretch blow. Generally, the outer surface of the side wall portion 65 is a frustoconical surface, and the outer surface of the bottom portion 66 is preferably a partially spherical surface smoothly connected to the frustoconical surface in terms of moldability. It is a shape and can be used. On the other hand, the inner surface of the side wall portion 65 is also a frustoconical surface connected from the inner periphery of the connection portion via an inclined portion 66 having an increased thickness. The taper angle (θ) of the outer surface of the side wall is preferably 0.5 to 89.5 ° from the viewpoint of moldability. 9 shows a cross section of the blow molding preform of the present invention at a taper angle of 0.8 °, and FIG. 10 shows a cross section of the blow molding preform of the present invention at a taper angle of 45 °. I have. The thickness of the side wall portion 65 and the bottom portion 66 may be a uniform thickness except for the above-described inclined portion 67, and may vary in thickness. For example, the thickness of the side wall portion increases toward the bottom portion. May have such a distribution that the size increases.

The preform can be used as it is for stretch blow molding, and the mouth of the preform is crystallized by heat treatment at the stage of the preform in order to impart heat resistance and rigidity to the mouth of the preform. After the preform is formed into a bottle by biaxial stretch blow molding described below, the mouth of the obtained plastic bottle is crystallized,
It may be whitened.

[Stretch Blow Molding] The preform is heated to a stretching temperature, and the preform is stretched in the axial direction and blow-stretched in the circumferential direction to produce a bottle.

Prior to stretch blow molding, the preform is preheated to a suitable stretching temperature by means such as hot air, an infrared heater, or high frequency induction heating. The temperature range is 85 to 120 ° C. for polyester, especially 95 to 11 ° C.
It is preferably in the range of 0 ° C.

The preform is fed into a stretch blow molding machine known per se, set in a mold, stretched in the axial direction by pushing a stretching rod, and circumferentially stretched by blowing a fluid. Blow stretching is performed.

The stretching ratio in the final bottle is suitably 1.5 to 25 times in area ratio, and among these, the axial stretching ratio is 1.2 to 6 times, and the circumferential stretching ratio is 1.times.
It is good to make it 2 to 4.5 times.

In FIG. 8 (side view) showing an example of a bottle manufactured from the preform for blow molding of the present invention, this bottle 70 has a mouth 61, a frustum-shaped shoulder 71, and an upper trunk 72. , A lower body 73 and a bottom 74. The structure and dimensions of the mouth 61 are exactly the same as those of the preform.

The bottom part 74 is formed of a ground part 75 and an upper bottom 76 which rises upward from the ground part. A panel (mirror) 77 for absorbing reduced-pressure deformation is formed on the upper body 72 of the bottle via a rib 78. In addition, a peripheral concave bead 79 for reinforcement is formed at a connection portion between the lower trunk portion 73 and the shoulder portion 71 and the upper trunk portion 72.

The bottle produced from the preform for blow molding of the present invention has excellent shape and structure expression (molding) and remarkably excellent properties such as strength and impact resistance. It has the advantage that.

[0072]

[Embodiment 1] The present invention will be described with reference to the following examples. A polyethylene terephthalate resin EFS-7H manufactured by Kanebo Gosen Co., Ltd. is dried by a dryer, and is extruded vertically from a nozzle having a diameter of 22 mm using an extruder having a diameter of 65 mm and an L / D of 27, and is horizontally rotated. The resin in the molten state is cut horizontally to form a molten mass with a weight of 20 g, immediately conveyed, dropped vertically onto the female mold in the molding machine rotating in synchronization with the rotation of the cutter, and the mold is quickly removed. Compression molding is performed while closing and simultaneously discharging the residual air in the mold.
After cooling and solidifying for a time, the mold was opened to obtain a preform for blow molding having a diameter of 38 mm, a height of 63 mm, an average thickness of 3 mm and a weight of 20 g. There was no wrinkle or whitening at the bottom of the preform and its vicinity, and although it was observed after the residual air discharge portion, the gate had a very smooth surface with no gate residue. When the bottom of the preform was observed by polarized light,
The strain was extremely low. This preform was heated to 110 ° C. in a stretch blow molding machine for testing, stretched in a blow mold in the longitudinal direction, and then blow-molded with high-pressure air at 35 atm. 6
A bottle having a size of 7.5 mm and a capacity of 380 cc was obtained. The appearance of the bottle was beautiful without wrinkles or streaks. Place 350 cc of water in a bottle, seal with a cap,
When the bottle was dropped from a height of m, the bottle did not crack even after repeated 15 times.

[Comparative Example 1] A preform for blow molding was obtained under the same conditions as in the example except that the compression molding was carried out without discharging the residual air in the mold. Wrinkles and whitening due to some crystallization were observed at and near the bottom of the preform. This preform was heated to 110 ° C. in a stretch blow molding machine for testing, stretched in a blow mold in the longitudinal direction, and then blow-molded with high-pressure air at 35 atm. A bottle having a capacity of 67.5 mm and a content of 380 cc was obtained. The bottle had no commercial value with wrinkles and streaks around the bottom. 35 bottles of water
When 0 cc was added, the bottle was sealed with a cap and dropped from a height of 1.2 m. When the container was repeated seven times, cracks occurred from around the bottom of the bottle.

[Comparative Example 2] A preform for blow molding was obtained under the same conditions as in the example except that the cut molten mass was once subjected to a rough mold, and then transferred into a mold and then subjected to compression molding. Extremely large wrinkles were observed at the bottom of the preform and in the vicinity thereof. This preform was heated to 110 ° C. in a stretch blow molding machine for testing, stretched in a blow mold in the longitudinal direction, and then blow-molded with high-pressure air at 35 atm. 67.5m
m, a bottle with a content of 380 cc was obtained. The appearance of the bottle was of no commercial value, with large wrinkles and streaks from the periphery of the bottom to the trunk. The bottle was filled with 350 cc of water, sealed with a cap, and dropped from a height of 1.2 m. As a result, cracks occurred around the bottom of the bottle in three repetitions.

[0075]

According to the present invention, the temperature of the molten resin block is prevented from lowering as much as possible, and the compression molding is carried out while eliminating the residual air, so that one heating for melting the resin can be performed. Compression molding becomes possible, and as a result, it is possible to provide a preform for blow molding in which thermal degradation of the resin is significantly suppressed. This preform for blow molding has no wrinkles at the bottom and no gate residue, so that uniform and uniform stretch forming on the bottom of the blow molded product and improvement of impact resistance at the bottom are possible. It is.

[Brief description of the drawings]

FIG. 1 is a plan view showing an overall arrangement of an apparatus used for a one-stage compression molding method of the present invention.

FIG. 2 is a side view of the apparatus of FIG.

FIG. 3 is a plan view of a device for cutting and supplying a molten mass.

FIG. 4 is a side view showing each stage of the apparatus of FIG. 3;

FIG. 5 is a side sectional view for explaining each stage of a compression molding process.

FIG. 6 is a side sectional view for explaining each stage of a step of taking out a preform after compression molding.

FIG. 7 is a sectional view of a preform for blow molding according to the present invention.

FIG. 8 is a side view showing an example of a bottle manufactured from the preform of FIG.

FIG. 9 is a cross-sectional view of another blow molding preform according to the present invention.

FIG. 10 is a sectional view of another blow molding preform according to the present invention.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3E033 AA01 BA13 BA14 BA17 BB04 CA01 CA16 CA18 DA02 DA03 DA08 DB01 DD05 EA01 EA04 EA05 FA02 FA03 GA02

Claims (10)

[Claims] 1. A step of extruding a thermoplastic resin melt and cutting it into a substantially fixed amount of molten mass, a step of disposing a male mold and a female mold so as to be relatively movable, and supplying the molten mass into the mold. ,
A step of compression-molding a molded article having a bottomed body and a mouth while discharging residual air in the mold; and a step of cooling and solidifying the compressed molded article and discharging the molded article out of the mold. A method for producing a preform for blow molding. 2. The thermoplastic resin has an intrinsic viscosity of 1.3 to 0.1.
2. The process according to claim 1, which comprises up to 50 thermoplastic polyesters. 3. The thermoplastic resin melt is extruded in parallel with the axial direction of the male mold and the female mold, and the cut molten mass is supplied into the female mold while substantially maintaining the parallel state.
3. The production method according to any one of claims 1 to 2. 4. The method according to claim 1, wherein a portion forming the bottom of the preform of the molten mass is not cooled. 5. The method according to claim 1, wherein the molten mass is gripped at a position higher than the center of gravity and supplied into the mold. 6. The method according to claim 1, wherein a minute gap or a hole is formed in a mold portion forming a bottom of the preform.
6. The method according to any one of claims 1 to 5, 7. The male mold comprises a core mold and a driven mold provided around the core mold so as to be coaxial with and openable with the core mold. The core mold and the female mold are provided. The manufacturing method according to any one of claims 1 to 6, wherein the bottom body is formed, and the mouth is formed by the core mold and the driven mold. 8. A blow molding preform formed from a thermoplastic resin, comprising: a mouth formed by compression molding of a thermoplastic resin melt, having a shape and dimensions corresponding to a mouth of a final molded body; A blow molding preform having a bottomed body to be molded and no gate at the closed bottom. 9. The preform for blow molding according to claim 8, wherein the closed bottom has no whitened portion. 10. The preform is a thermoplastic polyester having an intrinsic viscosity of 1.295 to 0.495.
A preform for blow molding according to any one of claims 1 to 9.