JP3690388B2 - Compression molding method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present inventionThe final molded bodyA preform for blow molding having a mouth portion having a shape and size corresponding to a mouth portion of a container and a bottomed body portion to be blow-molded.Compression molding methodAbout.
[0002]
[Prior art]
Stretch blow molded plastic containers, especially polyester containers, are now commonplace, and because of their excellent transparency and moderate gas barrier properties, beer is used in addition to liquid products such as liquid detergents, shampoos, cosmetics, soy sauce and sauces. It is widely used in carbonated beverages such as cola and cider, other beverage containers such as fruit juice and mineral water, dessert cups, miso containers and cup products.
[0003]
When molding a polyester container, a preform having a size considerably smaller than that of the final container and having an amorphous polyester is formed in advance by injection molding of the polyester, and the preform is preheated to its stretching temperature and blown. A method is employed in which the film is stretched in the axial direction in the mold and blown in the circumferential direction.
[0004]
As the shape of the preform, a mouth portion corresponding to the mouth portion of the container and a bottomed body portion to be stretch blow molded are generally used, and the shape as a whole is generally a test tube for a vertically long container. Is. In the mouth portion, for example, an engagement means with an opening end for sealing or a lid is formed. In addition, a gate portion that protrudes outward from the center of the bottom portion is necessarily formed on the bottom portion because of the necessity of injection molding.
[0005]
It is also known to produce a preform by compression molding of a resin. For example, in WO 97/32706, a compression mold having a cavity for forming a preform is prepared, and a thermoplastic resin is used as a precursor. The body is molded and the precursor is placed in a compression mold, where the precursor is generally fixed and intimately seated in the cavity and the precursor does not completely fill the compression mold, It must have a shape that is supported in a predetermined manner within the cavity of the compression mold before being compressed to the final shape, and the precursor is heated prior to placing the precursor in the compression mold, and the heated precursor Is compression-molded in a compression mold.
[0006]
[Problems to be solved by the invention]
However, the gate portion formed in the preform by injection molding has many problems in terms of productivity, manufacturing cost, and final blow-molded product characteristics. That is, in order to cut the gate portion, a special cutting process is required, which is one factor for reducing productivity. Moreover, the cut | disconnected gate part becomes scrap resin and is a waste of resources. Furthermore, the remaining gate is liable to cause crystallization and whitening of the final blow-molded product, which causes deterioration in appearance characteristics, and orientation during stretch blow molding due to flow orientation during molding and generation of distortion during cutting. It causes unevenness and non-uniformity of the structure, and causes a bottom crack due to a drop impact.
[0007]
In injection molding, since a large shearing force acts during molding, molding at a high temperature is required, and this thermal history causes a problem of heat degradation (thermal degradation) of the resin. For this reason, in the manufacture of conventional PET (polyethylene terephthalate) containers, it is necessary to use a PET with a high intrinsic viscosity by a solid-phase polymerization method in anticipation of a decrease in intrinsic viscosity that occurs during injection molding, which increases costs. Has brought. Furthermore, since not only cooling of the injected resin but also the flow of the resin is required at the same time, the degree of freedom in setting the mold temperature is small and the injection molding time is inevitably long. There is also a problem.
[0008]
Molding of a preform by the above-described compression molding method has the advantage that the thermal degradation of the resin accompanying injection molding can be reduced, but in order to avoid excess or deficiency of resin supply to the compression mold, the resin is temporarily used as a precursor. In addition to thermoforming, reheating for compression molding is required, such as thermoforming, this precursor must also be heated and fed to the compression mold, and the heated precursor must be compression molded in the compression mold. There is still a point to be improved in that it is necessary.
[0009]
  Therefore, the technical problem of the present invention is that the resin does not need to be once molded into a precursor, and is caused by the volume shrinkage of the resin due to a decrease in the resin temperatureVariation of the shape and size to be generated is generated in a predetermined portion, that is, the blow molding portion, and the variation of the shape and size in the mouth portion is avoided., Preforms for blow moldingNew and superior method for compression moldingIs to provide.
[0010]
[Means for Solving the Problems]
  As a method for achieving the above technical problem, according to the present invention, a preform for blow molding having a mouth portion having a shape and a dimension corresponding to the mouth portion of a container and a bottomed body portion to be blow-molded is compressed. In a molding process, a molten mass of thermoplastic resin is fed into the female cavity, then the male mold is moved relative to the female mold to compress the molten mass into the required shape, and further against the female mold. The volume of the resin shrinks due to a decrease in the resin temperature by moving the male moldWithout changing the shape and dimensions of the mouthVariations in the shape and dimensions of the blow molded partAt leastA method of absorbing is provided.
[0011]
  In the method of the present invention, after the molten mass of the thermoplastic resin is compressed into the required shape resin, the required shape resin is further compressed to absorb the volume shrinkage of the resin due to the decrease in the resin temperature. Variations in shape or dimensions due to volume shrinkage as well as errors in the molten mass suppliedIs generated in a specific part, that is, a blow-molded part, thus avoiding shape and dimension variations due to volume shrinkage in the mouth defining the mouth of the container to be finally formed.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0013]
[Configuration of the entire device]
In FIG. 1 (plan view) and FIG. 2 (side view) showing the overall arrangement of a molding apparatus including a compression molding apparatus that can be suitably used to perform the compression molding method of the present invention, Roughly speaking, it comprises a thermoplastic resin extrusion device 1, a molten lump cutting and feeding device 2, and a compression molding device 3 into a preform.
[0014]
The extrusion apparatus 1 includes an extruder main body 11 for melting and kneading a resin, and a thermoplastic resin powder or pellet to be molded is held in a dry state on the inlet side of the main body. A vacuum hopper 12 for supplying is provided, and on the outlet side of the main body, there are provided a suction vent 13 for sucking and removing decomposition gas in the resin and a die head 14 for receiving the molten resin to be pushed out. The die head 14 is connected to the extruder nozzle 16 via a pipe 15, and a gear pump 17 for supplying a fixed amount of molten resin may be provided between the die head 14 and the extruder nozzle 16. In FIG. 2, the gear pump 17 is omitted to avoid complication.
[0015]
As shown in FIG. 3 (plan view) and FIG. 4 (side view), the molten lump cutting and feeding device 2 includes a cutter 22 provided on the rotating turret 21 and an outer gripping member 23 for gripping the molten lump. The inner gripping member 24 is combined. The cutter 22 is provided so as to be inclined with respect to the radial direction of the turret 21 and, as the turret 21 rotates, the resin melt 18 extruded from the extruder nozzle 16 can be cut in a direction perpendicular to the extrusion direction. ing. 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 24 is provided so as to be movable with respect to the outer gripping member 23 in the radial direction of the turret.
[0016]
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. The molten material 18 is gripped by 23 and 24 and cut by the cutter 22, and the molten mass 19 is moved upward in the gripping state by the gripping members 23 and 24 and melted by releasing the gripping members 23 and 24. The lump 19 is put into the female mold 32.
[0017]
2 and 4, in the illustrated embodiment, the thermoplastic resin melt 18 is extruded in parallel with the axial direction of the male mold 33 and the female mold 32, and the cut molten mass 19 is substantially in a parallel state. Being supplied into the female mold 32 while being maintained above, the melt 18 being supplied in a substantially quantitative state by the gear pump 17, and the molten mass 19 of the resin being supplied in a shape close to a cylinder, or It is apparent that the molten mass 19 is gripped by the gripping members 23 and 24 at a position above the center of gravity, moved from the cutting position C to the mold position M, and supplied into the mold 32.
[0018]
The compression molding apparatus 3 is roughly composed of a combination of a rotating turret 31 and a large number of female molds 32 and male molds 33 arranged around the rotating turret. The rotary turret 31 is provided with the previously described melt lump cutting and feeding mechanism 2 and also with a blow-molding preform take-out mechanism 34.
[0019]
The rotating turret 31 is supported by a vertical shaft 36 in a horizontal direction and rotatably with respect to the machine base 35, and is driven and rotated by a motor 37 and a drive transmission mechanism 38. A large number of combinations (sets) of the female mold 32 and the male mold 33 are provided on the outer peripheral upper surface of the rotating turret 31. That is, the female mold 32 is fixed on the gantry 39, while the male mold 33 is coaxial with the female mold 32 by a vertical drive member 42 and a horizontal support member 41 by a lift drive mechanism 42 such as a hydraulic mechanism. And can be moved up and down.
[0020]
In FIG. 5 and FIG. 6 showing the detailed structure of the female mold 32 and the male mold 33 and the molding process step by step, the female mold 32 has a cavity 43, and in order to eliminate residual air at the bottom thereof. The vent portion 45 is also provided at the vent portion 44 and the connecting portion between the bottom portion and the tapered portion. An upward small 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 die is provided around the female die 32. The driven member 47 has a shaft 48 extending downward, and a stopper is provided at the lower end thereof. 49 is formed, and the stopper 49 is accommodated 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). Further, an engagement taper portion 51 whose diameter increases upward is formed on the upper inner peripheral surface of the driven member 47.
[0021]
On the other hand, the male mold 33 includes a core mold 53 fixed to a support member 52 that can move up and down. The core mold 53 has a portion 54 for forming the mouth top surface of the preform, a portion 55 for forming the inner peripheral surface of the mouth, and an inner surface of the bottomed tapered body portion. And a portion 56.
[0022]
Around the core mold 33, a driven mold 57 provided coaxially with the core mold 33 so as to be openable and closable is positioned. The driven mold 57 is fixed to a driven support member 58. Although not shown, a push spring is provided between the support member 52 and the driven support member 58 so that the driven mold is moved downward. Energized. The lower inner peripheral surface of the driven mold 57 is provided with a portion 59 that forms the outer peripheral surface of the mouth of the preform, while the lower outer peripheral surface is formed with an engagement taper portion 60 whose diameter decreases downward. ing.
[0023]
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 smoothly perform each operation.
The pressing force of the male mold 33> the pressing force of the driven member 47> the pressing force of the driven mold 57
[0024]
The molding operation by the above apparatus is performed as follows.
(A) Melt extrusion process:
Molding resin such as thermoplastic polyester is supplied to the vacuum hopper 12 of the extruder 1 and melted and kneaded by a screw when it is blown in the extruder body 11 in a state where moisture absorption from the outside air is blocked in vacuum. A fixed amount is supplied to the nozzle 16 by the gear pump 17 through the die head 14 and the pipe 15, and is extruded from the nozzle 16 into a cylindrical shape.
[0025]
(B) Cutting and feeding process:
The resin stream 18 melt-extruded from the nozzle 16 is cut into a molten lump 19 having a cylindrical shape or a shape close to a cylinder by a cutter 22, and the molten lump 19 is held by holding members 23 and 24, and is cut from a cutting position C. It moves along with the rotation of the turret without causing a substantial temperature drop to the supply position M to the female mold 32 and is put into the female mold 32.
[0026]
(C) Compression molding process:
5, the cavity mold 43 and the core mold 53 are still open, and the molten mass 19 is stored in the cavity 43 in an upright state. The core mold 53 is starting to descend.
[0027]
In the cavity mold clamping step shown in II of FIG. 5, the core mold 53 is lowered into the cavity, and the molten resin 19 ′ is almost filled in the space defined by the cavity 43 and the core 53. Simultaneously with the start of compression molding, the residual air in the cavity is quickly released to the outside through the vent portions 44 and 45. At the same time, the driven mold 57 is also lowered and contacts the driven member 47, but there is still a gap between the upper surface of the driven support member 58 and the lower surface of the male support member 52.
[0028]
5, the core mold 53 is further lowered, and the upper surface of the driven support member 58 and the lower surface of the male support member 52 are in contact with each other. Accordingly, the molten resin 19 ′ in the cavity flows into a space defined by the core mold 53 and the driven mold 57.
[0029]
In the solidification process at a high temperature shown in IV of FIG. 5, the core mold 53 is further lowered slightly, and the driven member 47 is also lowered accordingly, and is defined by the cavity 43, the core mold 53 and the driven mold 57. The space to be filled is filled with resin, and the resin is compressed into a predetermined shape.
[0030]
  In the solidification process at a low temperature indicated by V in FIG.RikiFat volume shrinkage (sink) occurs, but the distortion caused by this volume shrinkage is absorbed by applying a compressive force to the male mold (core 53).TheIn this case, it is naturally necessary to move the core mold 53 and the cavity 43 so as to mesh with each other, but the upward small protrusion 46 of the cavity 43 is meshed with the driven mold 57.By sliding the bodyAbsorbs product shrinkage.As clearly understood by comparing IV and V in FIG. 5, the volumetric shrinkage of the resin due to the decrease in the resin temperature is absorbed by the variation in the shape and size of the specific portion, that is, the blow molded part. The shape and dimensions of the mouth are not fluctuated.
[0031]
The process of taking out the compression-molded preform is shown in steps I to V of FIG. Step I shows the stage where molding is completed. In Step II, the core mold 53 starts to rise and mold opening is started. In Step III, the core mold 53 is raised prior to the driven mold 57, and the core is removed from the molded 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 radially outward position (position indicated by a dotted line) at the re-raising position of the core mold, and the held blow molding preform 60 is released.
[0032]
[Resin raw materials]
In the present invention, as a raw material resin for forming a preform for blow molding, any resin can be used as long as it is a moldable thermoplastic resin. Examples of such resins include thermoplastic polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), copolymerized polyesters mainly composed of these ester units, or blends thereof; polycarbonates Acrylic-butadiene-styrene copolymer (ABS resin); polyacetal resin; nylon 6, nylon 66, nylons such as those copolymerized nylon; acrylic resin such as polymethyl methacrylate; isotactic polypropylene; polystyrene, etc. Other examples include low-, medium-, or high-density polyethylene, ethylene-propylene copolymer, ethylene-butene-1 copolymer, and styrene-butadiene thermoplastic elastomer. These plastics can be blended with various additives such as a colorant, an ultraviolet absorber, a release agent, a lubricant, and a nucleating agent within a range not impairing the quality of the product.
[0033]
In particular, it is preferable to use polyester as the thermoplastic resin. In this case, it is preferable that the intrinsic viscosity (η) of the polyester is 0.5 dl / g or more, particularly 1.3 to 0.7 dl / g. It is. As the polyester, those having a diethylene glycol unit content in the range of 1.60% by weight or less, particularly 1.50% by weight or less are preferably used.
[0034]
[Molding condition]
The melt extrusion temperature of the thermoplastic resin (die head temperature) varies depending on the resin, but is generally in the range of Tm + 100 ° C. to Tm + 10 ° C., particularly Tm + 40 ° C. to Tm + 20 ° C., based on the melting point (Tm) of the thermoplastic resin. Is preferred. If the temperature is lower than the above range, the shear rate may become too high to form a uniform melt extrudate, whereas if the temperature is higher than the above range, the degree of thermal degradation of the resin will increase. Or in the case of polyester, the drawdown tends to be too large.
[0035]
The weight of the molten mass to be cut, that is, the basis weight, is naturally determined by the final blow-molded product. Generally, an appropriate value is selected from the range of 100 to 2 g, particularly 40 to 10 g depending on the required strength. Good.
[0036]
In addition, it is advantageous in terms of handling that the molten mass is cylindrical or a shape close to it, but the ratio (H / D) of the diameter (D) to the height (H) of the molten mass is generally 0.8. The range of 4 to 4 is advantageous in that the temperature reduction of the molten mass is prevented 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 tends to increase, and the temperature tends to decrease.
[0037]
An arbitrary cutter is used for cutting the molten resin lump, but one that can prevent the resin from sticking is suitable. For example, surface treatment such as shot blasting is particularly effective.
[0038]
As the gripping member for moving the molten resin lump, a member made of a material having good thermal conductivity and having a contact area with the resin as small as possible is preferably used. The process from cutting the molten resin mass to putting it into the mold should be performed promptly and within the time already pointed out.
[0039]
As the compression mold, one having a fine gap or porous part formed at the bottom or in the vicinity thereof is used, and the fine gap divides the bottom of the female mold or the vicinity into several pieces, and these pieces are used. It can be formed by forming a fine gap for excluding air between them or by forming a hole for excluding air in the mold. The porous portion can be used by, for example, processing a sintered metal or the like.
[0040]
The surface temperature of the compression mold may be a temperature at which the molten resin is solidified. 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, a medium such as cooling water or conditioned water may be passed through the mold.
[0041]
One of the features is that the molding force required for compression molding may be quite small. The specific molding force varies considerably depending on the type of resin and the size of the preform for blow molding, but generally a molding force of 800 to 50 kgf, particularly 600 to 150 kgf is appropriate.
[0042]
According to the present invention, a one-stage compression molding yields a preform for blow molding that does not require any gate part or other trimming operation, so this preform can be used as it is in the stretch blow molding process. It has many advantages in terms of process simplification and productivity.
[0043]
[Preforms for blow molding]
In FIG. 7 showing the preform for blow molding in the present invention, the preform 60 is roughly composed of a mouth portion 61 and a tapered bottomed body portion 62. The mouth portion 61 is a mouth portion of a bottle that is a final molded product, and a lid locking portion 63 and a support ring 64 necessary for sealing with the lid are formed on the outer periphery of the mouth portion 61. The bottomed body portion 62 is a portion to be stretch blow molded, and includes a tapered side wall portion 65 and a downward convex bottom portion 66 smoothly connected thereto. As already pointed out, the bottom 66 has no gate residue or wrinkles. The mouth part 61 and the bottomed body part 62 are smoothly connected via a connection part 67.
[0044]
The tapered side wall portion 65 and the bottom portion 66 have a certain preferable range with respect to their dimensions and shape in terms of compression moldability and formability at the time of final stretch blow. In general, the outer surface of the side wall portion 65 is a truncated cone surface, and the outer surface of the bottom portion 66 is preferably a partial spherical surface that is smoothly connected to the truncated cone surface in terms of moldability. The shape is acceptable. On the other hand, the inner surface of the side wall portion 65 is also a truncated cone surface connected via an inclined portion 66 whose thickness increases from the inner periphery of the connection portion. The taper angle (θ) of the outer surface of the side wall is preferably 0.5 to 89.5 ° from the viewpoint of moldability. FIG. 9 shows a cross section of the blow molding preform of the present invention when the taper angle is 0.8 °, and FIG. 10 shows a cross section of the blow molding preform of the present invention when the taper angle is 45 °. Yes. The wall thickness of the side wall portion 65 and the bottom portion 66 may be uniform except for the inclined portion 67 described above, and may vary in thickness. For example, the side wall portion is thicker toward the bottom portion. It may have a distribution that increases.
[0045]
The preform can be used for stretch blow molding as it is, and in order to give heat resistance and rigidity to the mouth of the preform, the mouth is crystallized by heat treatment and whitened at the stage of the preform. Alternatively, after the preform is formed into a bottle by biaxial stretch blow molding described later, the mouth portion of the obtained plastic bottle may be crystallized and whitened.
[0046]
[Stretch blow molding]
The preform is heated to a stretching temperature, and the preform is pulled and stretched in the axial direction and blown and stretched in the circumferential direction to produce a bottle.
[0047]
Prior to stretch blow molding, the preform is preheated to a stretchable temperature by means of hot air, an infrared heater, high frequency induction heating or the like. In the case of polyester, the temperature range is 85 to 120 ° C., particularly 95 to 110 ° C.
[0048]
This preform is supplied into a stretch blow molding machine known per se, set in a mold, stretched in the axial direction by pushing a stretching rod, and blow stretched in the circumferential direction by blowing fluid. To do.
[0049]
The draw ratio in the final bottle is suitably 1.5 to 25 times in terms of area magnification, and among these, the draw ratio in the axial direction is 1.2 to 6 times, and the draw ratio in the circumferential direction is 1.2 to 4.5. It is better to double.
[0050]
In FIG. 8 (side view) showing an example of a bottle manufactured from a preform for blow molding according to the present invention, this bottle 70 has a mouth 61, a trapezoidal shoulder 71, an upper body 72, and a lower body. It consists of a part 73 and a bottom part 74. The structure and dimensions of the mouth 61 are exactly the same as those of the preform.
[0051]
The bottom portion 74 is formed by a grounding portion 75 and an upper bottom 76 that rises upward from the grounding portion. A panel part (mirror part) 77 for absorbing deformation under reduced pressure is formed on the upper body part 72 of the bottle via a rib 78. Further, a circumferential concave bead 79 for reinforcement is formed at a connection portion between the lower body portion 73 and the shoulder portion 71 and the upper body portion 72.
[0052]
The bottle manufactured from the preform for blow molding according to the present invention has the advantage that it is excellent in physical properties such as strength and impact resistance as well as excellent shape and structure expression (molding). Have.
[0053]
【Example】
[Example 1]
The invention is illustrated by the following examples. Crane which rotates polyethylene terephthalate resin EFS-7H manufactured by Kanebo Synthetic Co., Ltd. with a dryer and extrudes vertically from a nozzle with a diameter of 22 mm using an extruder with a diameter of 65 mm and L / D of 27 and rotates horizontally. The molten resin is cut horizontally to form a molten mass with a weight of 20 g, immediately transported, and dropped vertically onto the female mold in the molding machine rotating in synchronization with the cutter rotation, and the mold is moved at high speed. At the same time, it is compressed while discharging residual air in the mold while it is closed. After cooling and solidifying while applying a force of about 700 kgf, the mold is opened, blow molding with a diameter of 38 mm, a height of 63 mm, an average thickness of 3 mm, and a weight of 20 g. A preform was obtained. There was no wrinkle or whitening at the bottom of the preform and in the vicinity thereof, and a very smooth surface was observed after the residual air discharge part, but no gate residue. When the bottom of the preform was observed with polarized light, the distortion was extremely low. The preform is heated to 110 ° C. in a test stretch blow molding machine, and then stretched in the longitudinal direction in a blow mold, and then blow molded with high-pressure air of 35 atm. A bottle of 67.5 mm and an internal capacity of 380 cc was obtained. The appearance of the bottle was beautiful with no wrinkles or lines. When 350 cc of water was placed in the bottle, sealed with a cap and dropped from a height of 1.2 m, the bottle did not crack even after 15 repetitions.
[0054]
[Comparative Example 1]
A preform for blow molding was obtained under the same conditions as in the Examples except that the compression molding was performed without discharging the residual air in the mold. Wrinkles and whitening due to slight crystallization were observed at and near the bottom of the preform. The preform is heated to 110 ° C. in a test stretch blow molding machine, then stretched in the longitudinal direction in a blow mold, and blow molded with high-pressure air at 35 atm. A bottle of 67.5 mm and an internal capacity of 380 cc was obtained. The appearance of the bottle was wrinkled and streaked around the bottom and had no commercial value. When 350 cc of water was put into the bottle, sealed with a cap and dropped from a height of 1.2 m, cracking occurred from around the bottom of the bottle in 7 repetitions.
[0055]
[Comparative Example 2]
A blow-molded preform was obtained under the same conditions as in the Examples 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 and near the bottom of the preform. The preform is heated to 110 ° C. in a test stretch blow molding machine, then stretched in the longitudinal direction in a blow mold, and blow molded with high-pressure air at 35 atm. A bottle of 67.5 mm and an internal capacity of 380 cc was obtained. The appearance of the bottle was not worthy because there were large wrinkles and streaks from the bottom to the body. When 350 cc of water was put into the bottle, sealed with a cap and dropped from a height of 1.2 m, cracks occurred from the bottom of the bottle in three repetitions.
[0056]
【The invention's effect】
According to the present invention, there is no need to mold the resin into a precursor once, and molding such as a preform for blow molding without generating desirable geometric distortion due to resin volume shrinkage due to a decrease in resin temperature. The object can be compression molded.
[Brief description of the drawings]
FIG. 1 is a plan view showing the arrangement of an entire apparatus including an apparatus that can be suitably used to perform a compression molding method constructed according to the present invention.
FIG. 2 is a side view of the apparatus of FIG.
FIG. 3 is a plan view of a molten lump cutting and feeding apparatus.
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 the compression molding process.
FIG. 6 is a side sectional view for explaining each stage of a pre-molded product take-out process after compression molding.
FIG. 7 is a sectional view showing an example of a preform for blow molding.
8 is a side view showing an example of a bottle manufactured from the preform of FIG. 7. FIG.
FIG. 9 is a sectional view showing another example of a preform for blow molding.
FIG. 10 is a cross-sectional view showing still another example of a preform for blow molding.
[Explanation of symbols]
3: Compression molding equipment
32: Female type
33: Male
43: Cavity
47: Follower member
53: Core mold
57: Driven mold

Claims (1)

A method of compression molding a blow molding preform having a mouth shape and size corresponding to a mouth portion of a container and a bottomed body portion to be blow molded, wherein a molten mass of thermoplastic resin is formed into a female cavity And then moving the male mold relative to the female mold to compress the molten mass into the required shape, and further moving the male mold relative to the female mold to reduce the resin volume due to a decrease in resin temperature. contraction absorb allowed variation in the shape and size of the blow molding unit without allowed to change the shape and dimensions of the mouth portion, wherein the.

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