JPH0272927A - Manufacture of stretched blow bottle with handle - Google Patents

Abstract

PURPOSE:To contrive an improvement in mechanical strength, by a method wherein after volume of a preform transferred within a flowing mold has attained at least specific % of that of the inside of the blowing mold, a part which is to become a recessed part for a handle of the preform is pressed and placed between plugs of movable molds before a temperature of the preform is cooled down to the glass transistion temperature on an inner wall of the blowing mold. CONSTITUTION:A preform 1 is placed between molds 3 possessing a pair of plugs 2, which are actuated hydraulically or pneumatically and confronted with each other and then the bottom part of the preform 1 is ejected by a stretch pin 4. Simultaneously with this or directly after this air is blown into the preform 1 through a blow pin 5 and the preform 1 is expanded toward an inner wall of the mold 3. After volume of the preform 1 has attained at least 80% of that of the inside of the mold 3, a bottle 7 is molded within the mold 3 by pressing the plug 2 into the preform 1 before a temperature of the preform is cooled down to the glass transition temperature on an inner wall of a blowing mold. A part where a handle is to be formed is molded at a temperature lower than those for portions upper or lower than that part, in the preform to be used and the preform is molded with either a blow molding or injection molding.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Object of the invention [Field of industrial application] The present invention relates to a method for manufacturing a stretched blow bottle with a handle made of a thermoplastic resin.

[Prior Art] In recent years, plastic bottles with large internal volumes are often provided with handles to make them easier to carry.

Conventionally, in order to manufacture a plastic bottle with a handle using the blow molding method, for example, a hollow parison extruded from an extruder is provided with a bottom, air is blown into it to expand it (usually referred to as blowing), and a pre-blow is performed. Then, the buriburo is sandwiched between a pair of half-split molds having protrusions for forming a handle hole, and then air is further blown into the mold to expand it into the shape of the mold, thereby forming a hole for the handle. A commonly used method is to sandwich and close the desired portion between the protrusions of a mold to obtain a bottle with a welded hole, and then to hollow out a hole (welded portion) for the handle of the bottle.

However, since the handle is usually provided near the shoulder of the bottle, the handle needs to be large enough around the upper opening of the pre-blow to be closed by the protrusion of the mold. However, since the mouth and neck required for blow bottles are small, unnecessary ridges are inevitably formed on the outside of the neck and mouth of the bottle. There is a problem of being exposed. Further, as a matter of course, more burrs occur in bottles with larger internal volumes. Furthermore, in this method, the rise at the bottom cannot be ignored in many cases, which also poses a problem.

-4.Recently, in the field of blow molding, in addition to the so-called direct blow molding method that has traditionally been used, molded products with superior mechanical strength, transparency, gas barrier properties, etc. can be obtained by this molding method. A blow molding method called stretch blow molding method has been developed and put into practical use. In the stretch blow molding method, a preform obtained by blowing air into a parison extruded from an extruder or an injection molded preform is placed in a blow mold at a temperature higher than its glass transition temperature and at a melting point or flow rate. It is a method of stretch forming by stretching in the longitudinal direction with a stretch pin and stretching in the lateral direction by blowing at a temperature below the starting point,
Such stretching results in molecular orientation of the polymer chains of the thermoplastic resin constituting the molded product, so that a molded product having the above-mentioned excellent properties can be obtained.

Therefore, regarding plastic bottles with handles,
There has been a request to apply the above stretch blow molding method, but as mentioned above, in the stretch blow molding method,
The temperature of the preform molded in the mold must be higher than the glass transition temperature of the thermoplastic resin to be molded, but lower than the melting point or flow start point; for example, if the bottle is made of polyvinyl chloride, the resin The temperature is usually 120°C
Since the bottle is molded at a temperature below the melting point of about 100 ml, the above-mentioned direct blow molding method for producing a bottle with a handle, that is, a method using a pair of half-split molds having a protrusion for forming the handle hole. Even if this method is applied, the mouth and neck cannot be welded, and the area after removing the bulge formed on the outside of the mouth and neck is not sealed, making it impossible to obtain a usable bottle.

Furthermore, in order to solve the above-mentioned problems, if the temperature of the thermoplastic resin in the handle part is heated to a temperature higher than the melting point or flow start point using a mold etc. with a heater, the stretching effect of the heated part will be reduced. disappears, and the mechanical strength etc. of that part is significantly reduced.

In particular, when the raw material is a crystalline resin such as PET (polyethylene terephthalate), if the above heating is performed, the heated portion will crystallize after molding.
As well as whitening, distortion occurs due to the difference in crystallinity between the handle part and the resin in other parts, making it easy to break.

As mentioned above, in the stretch blow molding method, it is difficult to apply the method of forming the handle part used in the direct blow molding method, so different methods have been proposed, such as forming the handle part separately from the bottle body. A typical example is a method in which a handle is attached to a stretch-blow-molded bottle body by fitting or the like (Japanese Patent Publication No. 11218/1983).

However, in the stretched blow bottle with a handle obtained by the above method, since the handle and the bottle are not integrally molded from one preform, the reliability is likely to be lacking in fixing the handle to the bottle body, and the manufacturing process is also difficult. The problem is that it becomes complicated.

The present inventors conducted studies to find an excellent method for manufacturing a blow bottle with a handle using a stretch blow molding method, and the preform transferred into a blow mold was stretched and blown using a stretch bottle. In the process of stretch-molding, when the volume of the preform expands to a specific size, a movable plug attached to the mold, that is, a movable protrusion, opens the part of the preform that will become the hole for the handle. A stretched blow bottle with a handle is obtained by obtaining a bottle having a concave portion having a shape corresponding to a hole for a push scissor and a handle, and then sealing the concave periphery by heat welding using high-frequency dielectric heating, and then hollowing out the inside of the periphery. We have already proposed a manufacturing method for
No. 33). However, even with the above-mentioned proposed method, there is a problem that the wall thickness of the portion stretched by the plug, that is, the portion along the hole of the handle portion is thin, and the mechanical strength of that portion tends to decrease.

(B) Structure of the Invention [Means for Solving the Problems] As a result of intensive studies to solve the above problems, the present inventors have discovered that a preform transferred into a blow mold is stretched using a stretch bin. In the method for manufacturing a stretch-blown bottle by stretch-molding by blowing, the temperature of the portion of the preform where the handle is formed is maintained lower than the temperature of both the upper and lower portions of that portion, and the volume of the preform is After reaching 80% or more of the internal volume of the blow mold, and before the temperature of the preform is cooled to the glass transition temperature on the inner wall of the blow mold, the opposing By using a pair of movable plugs to push the area of the preform that should become the recess for the handle, the thickness of the area along the handle hole is reduced compared to other areas that are not stretched by the plugs. The present inventors have discovered that a bottle with a handle that is not very thin and has excellent mechanical strength can be obtained, and have completed the present invention.

That is, the present invention provides a method for manufacturing a stretch blow bottle in which a preform transferred into a blow mold is stretch-molded by stretching and blowing with a stretch bottle, and the temperature of the portion of the preform where the handle is to be formed is adjusted to that temperature. While keeping the temperature lower than both the upper and lower parts of the part and after the volume of the preform reaches 80% or more of the internal volume of the blow mold, the temperature of the preform is lowered to lower than the temperature of the blow mold. Before the inner wall is cooled to the glass transition temperature, a pair of opposing movable plugs attached to the blow mold press and sandwich the portion of the preform that will become the recess for the handle to form a handle. A method for manufacturing a stretched blow bottle with a handle, which is characterized in that, after heating and melting the peripheral edge of the concave portion for the handle of the stretched blow bottle with a handle manufactured by the manufacturing method, the peripheral edge is sealed. This is a method for manufacturing a stretched blow bottle with a handle, which is formed by hollowing out the inside of a bottle.

The present invention will be explained in more detail below.

Thermoplastic resins that can be used as bottle molding materials in the present invention include thermoplastic resins that have the property of distributing polymer chains when stretched and blown, and specifically include polyvinyl chloride, polyvinyl chloride, polypropylene,
Examples include polyethylene terephthalate, polyacrylonitrile and polyethylene. Polyethylene terephthalate and polyvinyl chloride with a degree of polymerization of 600 to 1100 are preferred in terms of moldability and mechanical strength of the bottle obtained, and polyvinyl chloride has a wide range of stretchable temperatures (polyvinyl chloride can be fused by high-frequency dielectric bonding). Vinyl is particularly suitable for the present invention.

Next, as mentioned above, the preform used in the present invention is a preform that is molded so that the temperature of the part where the handle is formed is lower than both the upper and lower temperatures of that part, and is molded by blow molding or injection molding. Preforms molded by any of these methods can be used.

A preform in which the temperature of the portion where the handle is to be formed is lower than both the upper and lower temperatures of that portion can be easily molded by adjusting the temperature distribution of the mold for molding the preform.

For example, when molding a preform made of polyvinyl chloride by blow molding, a preform having such a temperature distribution can be used by controlling the temperature of the part of the preliminary blow mold that is in contact with the part of the preform where the handle is to be formed. Molding can be easily performed by setting the temperature to be about 5 to 15°C lower than both the upper and lower temperatures, specifically, about 50°C. The temperature inside the preliminary blow mold is usually 170” to 180°C.
The bottomed parison is transferred in a heated state,
By controlling the temperature of the preliminary blow mold as described above, the temperature of the part where the handle is to be formed is lower than 120°C.
°C lower, while the upper and lower temperatures are about 12 °C
A preform molded at 0°C is obtained.

Note that the temperature of the preform at the portions that are to become the mouth and bottom of the bottle is usually much lower than the temperature at the portion where the handle is to be formed.

Hereinafter, the present invention will be described in detail using the accompanying drawings.

As shown in FIG. 1, a preform 1 is sandwiched between a mold 3 having a pair of opposing plugs 2 operated by hydraulic pressure or pneumatic pressure, and then a trench pin 4 is used to push out the bottom of the preform 1.

At the same time or immediately after that, air is blown through the blow pin 5 to expand the preform 1 toward the inner wall of the mold 3. The volume of preform 1 is 80% of the internal volume of mold 3.
% or more, and before the temperature of the preform is cooled to the glass transition temperature on the inner wall of the blowing mold, the plug 2 is moved as shown in FIG. 2, which shows the AA cross section of FIG. By pressing into this state, a bottle 7 having a shape as shown in FIG. 3 can be molded in the mold 3.

If the plug 2 is pushed in when the volume of the preform 1 is less than 80% of the internal volume of the mold 3, the recess 6 corresponding to the hole in the handle cannot be formed in the desired shape;
The bottle can be molded into a better shape by pushing in the plug 2 after the preform has expanded to the point where it has expanded at or near the point where the preform has expanded. If the plug 2 is pushed in when the thermoplastic resin forming the preform has cooled to a temperature lower than its glass transition temperature, the preform may be destroyed or a recess 6 with uneven thickness may be formed. It is inappropriate because it may cause

Further, it is preferable that the shape of the plug is gradually tapered toward its tip, as specifically shown in FIG. 2, for example.

The bottle 7 thus obtained can itself be used as a bottle with a handle.Furthermore, if a large bottle with an internal volume of 11 or more is to be used, the recess 6 may be hollowed out. It is preferable to use a bottle with a handle, and the bottle 7 can be extremely easily processed into a punched bottle.

That is, although the recess 6 in the bottle 7 is made up of a pair of plastic walls facing each other with a narrow gap in between, according to the present invention, the gap can be reduced to 0.1 mm or less, and furthermore, in a state where there is virtually no gap. Since the concave portion 6 can be made as narrow as possible, welding of the peripheral edge of the concave portion 6 can be performed extremely easily.

A method of heating and welding the peripheral edge of the recess 6 in the bottle 7 will be described.

Examples of methods that can be used as heat welding methods include high frequency dielectric bonding, ultrasonic bonding, heat sealing, and impulse sealing. If available, it is preferable to use high frequency dielectric bonding, ultrasonic bonding or impulse sealing for polyethylene terephthalate or polypropylene, and high frequency dielectric bonding, heat sealing or impulse sealing for polyacrylonitrile.

Polyvinyl chloride bottle 7 made by high frequency dielectric bonding method
The heat welding of the peripheral edge of the recess 6 will be explained in more detail.

The material of the electrode, that is, the heating terminal of the high-frequency dielectric bonding device is preferably brass, and the outer circumference of its tip is preferably slightly smaller than the circumference of the recess 6. .2 In order to perform heat welding over one circumference with a width of about 2 to 2 fences, it is preferable that the heated portion provided near the outer periphery protrudes with a width of about 0.2 to 2 mm, and in particular, the width should be set to 0.2 mm. A length of about 0.4 m is very preferable because it makes it possible to cut out the recess 6 by fusion bonding and by activating the heating terminal with the peripheral edge of the bottle fixed by the heating terminal itself pressed between them. Become something.

In addition, it is preferable that the heating terminal has a built-in heater so that the temperature is maintained at about 45 to 80°C during use, and furthermore, it prevents the generation of sparks between the heating terminals, which is a problem in high frequency dielectric bonding. It is preferable that the surface is insulatingly coated with a Teflon coating or a Teflon film, etc., for the purpose of protection.

Using a high frequency dielectric bonding device having heating terminals as described above, a pair of heating terminals 8 are pressed against the periphery of the recess 6 of the bottle 7 as shown in FIG. are heated and welded all around with a width of about 0.2 to 2 mm. For example, the frequency of the high frequency dielectric bonding device is 4
The heating time may be approximately 0.46 MI (z), and the preferred heating time varies depending on the wall thickness of the bottle, but is usually 1 to 4 seconds.

Heat welding of the peripheral edge of the concave portion 6 of the bottle 7 by the high frequency dielectric bonding method can be carried out by the method described above after the bottle 7 is taken out from the mold 3. Alternatively, the heating terminal of the high frequency dielectric bonding device can be It is also possible to incorporate it into the tip of a movable plug attached to the mold 3 and carry out the process inside the mold.

Next, a method of hollowing out the inside of the recess 6 from the bottle 7 to which the peripheral edge of the portion that will become the handle hole is welded will be described.

When the peripheral edge is welded by the high-frequency dielectric bonding method, as described above, immediately after welding, that is, when the bonded portion is still in a molten state, one of the heating terminals is pushed out while the bottle 7 is fixed, and at the same time By pulling the other heating terminal, the inside of the recess 6 can be easily hollowed out. In that case, it is preferable to use a heating terminal as described above in which the heating portion provided near the outer periphery protrudes with a width of about 0.2 to 2 mm, and it is also possible to use a Thomson type heating terminal. .

Other punching methods include, for example, a method using a punching machine or the like.

〔Example〕

A commercially available PC compound for blow molding (Aron Compound BL 2H-8VIP: Toagosei Chemical Co., Ltd. A biaxial stretch blow molding machine (manufactured by Kogyo Co., Ltd.) was used.
A stretched blow bottle with a handle was manufactured using a model 8MO4 (manufactured by Bekum) in the following manner.

The PVC compound is molded into a cylindrical parison in a molding machine with the temperature of the cylinder, adapter and die adjusted to 170-180°C.The parison is made of beryllium copper alloy and has seven equal parts in the body. It is sandwiched between preform molds each having a temperature regulating jacket and whose temperature is adjusted to the temperature shown in FIG. 5, and the upper part is cut with a cutter. Then, a blow pin is pushed through the cut portion and compressed air is blown into the cut portion to form a preform.

The formed preform is cooled and adjusted so that the temperature of the part where the handle is to be formed is lower than the temperature of both the upper and lower parts of that part, and the shape is Has a hemispherical bottom and a diameter of 4
It has a cylindrical shape with a diameter of 5 mm and a height of 250 mm.

The preform was transferred to a finishing mold (volume: 1.80 mm) having a pair of movable plugs for forming the handle.
M bottle), and while blowing air further, the preform was stretched vertically to the bottom of the mold using stretch pins, until the preform became almost equal to the internal volume of the finish mold. At this time, the plugs were actuated hydraulically and butted together to form a recess for the handle, complete air blowing, and produce a bottle with a handle.

The average wall thickness of the body of the resulting bottle other than the handle is:
While the thickness was 0.4 to 0.5 mm, the minimum thickness around the handle was 0.29 mm.

The concave part of the bottle has a capacity of 3 when the bottle is removed from the mold.
The outer periphery is fused by a pair of electrodes having protrusions of the same shape as the outer periphery of the concave part of the high-frequency welder, and then one of the electrodes is returned and the other is pushed in to punch out the inner part. It was scraped off and finished smooth on the side of the electrode.

(C) Effects of the Invention According to the present invention, it is possible to easily manufacture a stretched blow bottle with a handle, in which the handle and the bottle body are integrally molded from one preform, and the wall thickness around the handle is considerably thick. . The bottle is aesthetically pleasing due to its excellent transparency, and is suitable for long-term storage of contents due to its good gas barrier properties, and has excellent mechanical strength even with a small basis weight.

[Brief explanation of the drawing]

Figure 1 shows plug 2 with preform 1 inserted.
FIG. 2 is a longitudinal sectional view of the mold with the plug 2 pushed into the preform 1 expanded by air blowing from the blow pin 5 and stretch pin 4. [1] in FIG. 3 is a front view of a bottle 7 having a stretch-blow-molded concave portion 6, [2] in FIG. 3 is a cross-sectional view of the same bottle, and
The figure is a schematic diagram showing how the concave portion 6 of the bottle 7 is pressure-welded by high-frequency dielectric heating. Moreover, FIG. 5 is a schematic diagram showing the temperature distribution in the preform mold when the preform 1 is molded. 1--Preform, 2--Plug, 3--Blow mold, 4--Stretch pin, 5--
-Blow pin, 6・---1---Recess, 7------
Pottle, 8-curved heating terminal, 9----1.- Preform mold, 10-.- Curved bottomed balisong

Claims (1)

[Scope of Claims] 1. In a method for manufacturing a stretch blow bottle in which a preform transferred into a blow mold is stretch-molded by stretching with a stretch pin and blowing, the temperature of a portion of the preform where a handle is to be formed; While keeping the temperature lower than both the upper and lower parts of the part, and after the volume of the preform reaches 80% or more of the internal volume of the blow mold, the temperature of the preform becomes lower than the temperature of the blow mold. By the time the inner wall of the mold is cooled to the glass transition temperature, a pair of opposing movable plugs attached to the blow mold are used to press and sandwich the portion of the preform that is to become the recess for the handle. A method for producing a stretched blow bottle with a handle, the method comprising forming a stretched blow bottle with a handle. 2. A handle formed by heat-melting and sealing the peripheral edge of the handle recess of a stretched blow bottle with a handle manufactured by the manufacturing method described in claim 1, and then hollowing out the inside of the peripheral edge. A method of manufacturing a stretched blow bottle.