JPH0272926A - 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 blowing mold has attained 100% 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 transition temperature. 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 100% 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. The preform to be used is molded by 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.

[Conventional technology]

Nowadays, 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 pre-blown material is sandwiched between a pair of half-split molds each having a protrusion for forming a handle hole, and then air is 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 part required for a blow bottle is small, an unnecessary bulge part is inevitably formed on the outside of the neck part of the bottle. There is a problem of being exposed. In addition, naturally, a large amount of bulging occurs in bottles with large internal volumes. Furthermore, in this method, the rise at the bottom cannot be ignored in many cases, which also poses a problem.

On the other hand, recently in the field of blow molding, in addition to the conventionally used so-called direct blow molding method, 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 contraction direction using a stretch bottle 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 temperature is usually about 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 a crystalline resin such as PET (polyethylene terephthalate) is used as a raw material, if the heating is performed as described above, the heated part will crystallize after molding, resulting in whitening and the handle and other parts. The problem is that distortion occurs due to the difference in crystallinity between the resin and the resin, 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 often lacking when fixing the handle to the bottle body, and the manufacturing process It also has the problem of becoming complicated.

The present inventors conducted studies with the objective of finding an excellent method for manufacturing a blow bottle with a handle using a stretch blow molding method.

(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 that has already been transferred into a blowing mold is stretched using stretch pins. When the volume of the preform reaches 80% or more and less than 100% of the internal volume of the blowing mold in the process of stretch-molding by Invented a method for manufacturing a blow bottle with a handle, which consists of pressing the part of the preform that should become the hole for the handle, and filed a patent application for this manufacturing method.
As a result of further study, we found that even if the movable plug is pushed in after the volume of the preform reaches 100% of the internal volume of the blowing mold, They discovered that an excellent bottle with a handle similar to that proposed in the above proposal can be obtained as long as the temperature of the reform is within the period until the inner wall of the blowing mold cools down to the glass transition temperature, and has completed the present invention. It's arrived.

That is, the present invention provides a method for manufacturing a stretched blow bottle in which a preform transferred into a blow mold is stretch-molded by stretching and blowing using a stretch bottle, in which the volume of the preform is equal to or smaller than the inner volume of the blow mold. 100 of
%, and until the temperature of the preform is cooled to the glass transition temperature on the inner wall of the blow mold, a pair of opposing movable plugs installed in the blow mold are used to cool the preform. A method for manufacturing a stretched blow bottle with a handle, which is characterized in that a portion of the stretched blow bottle with a handle is pressed and pinched to form a handle, and furthermore, a handle for the stretched blow bottle with a handle manufactured by the manufacturing method is In this method, a stretched blow bottle with a handle is manufactured by heating and melting the periphery of the recess to seal it, and then hollowing out the inside of the periphery.

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 orienting polymer chains when stretched and blown, and specifically include polyvinyl chloride, polypropylene, etc. ,
Examples include polyethylene terephthalate, polyacrylonitrile and polyethylene. Polyethylene terephthalate and polyvinyl chloride with a degree of polymerization of 600 to 1100 are preferable in terms of moldability and mechanical strength of the resulting bottle, have a wide temperature range at which they can be stretched, and can be fused by high-frequency dielectric bonding. Polyvinyl chloride is particularly suitable for the present invention.

Further, the preform that can be used in the present invention may be a preform molded by either blow molding or injection molding.

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

As shown in FIG. 1, a preform 1 is held between a mold 3 having a pair of opposing plugs 2 operated by hydraulic pressure or air pressure, and then a stretch bin 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 10 of the internal volume of mold 3.
After reaching 0% and before the temperature of the preform is cooled to the glass transition temperature on the inner wall of the blow mold, plug 2
The bottle 7 having the shape shown in FIG. 3 can be molded in the mold 3 by pressing the bottle into the state shown in FIG. 2, which shows the cross section taken along the line AA° in FIG.

When the preform is in contact with the inner wall surface of the mold 3 for a long time and the thermoplastic resin forming it has cooled to a temperature lower than its glass transition temperature, the plug 2 is pushed in, thereby causing the preform to This is inappropriate because the reform 1 may be destroyed or a recess 6 with uneven thickness may be formed.

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, the internal volume is 1j1
! When a large bottle as described above is targeted, it is preferable to use a bottle with a handle in which the recess 6 is hollowed out, and the bottle 7 can be extremely easily processed into such a hole punched bottle. be.

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. In order to perform heat welding over one circumference with a width of about 2 to 2 m, it is preferable that the heating part provided near the outer periphery protrudes with a width of about 0.2 to 2 m.
In particular, when the width is set to about 0.2 to 0.4 mm, the recess 6 can be cut out by fusion bonding and by operating the heating terminal with the peripheral edge of the bottle fixed by the heating terminal itself being pressed between them. This is highly desirable because it makes it possible.

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 frequency may be about 0.46 MHz, 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, the heating portion provided near the outer periphery as described above will protrude with a width of about 0.2 to 2 mm. It is preferable to use a Thomson-type heating terminal, but 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 two-wheel stretch blow molding machine (manufactured by Kogyo Co., Ltd.) was used.
A stretched blow bottle with a handle was manufactured using a BMOd model manufactured by Bekum Co., Ltd. in the following manner.

A preform molded by blow molding using the above PVC compound and having a cylindrical shape with a hemispherical bottom, a diameter of 45 mm, and a height of 250 mm is placed in a finishing mold (volume Immediately after the preform was transferred to a 1.800 mR bottle (for bottles), and while blowing air, the preform was stretched vertically to the bottom of the mold using stretch pins, and immediately after the preform became equal to the inner volume of the finishing mold. The plug is operated hydraulically,
They were butted together to form a recess for a handle, and air was blown to complete a bottle with a handle.

The concave part of the bottle has a capacity of 3 when the bottle is removed from the mold.
The outer periphery is fused using a pair of electrodes having protrusions of the same shape as the outer periphery of the concave part of a kW high-frequency welder, and then one of the electrodes is returned and the other is pushed in to punch out and the center part is scraped off. , smooth finish 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 having excellent mechanical strength in which the handle and the bottle body are integrally molded from one preform. 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 the plug 2 with the preform inserted.
FIG. 2 is a cross-sectional view taken along the line A-A in FIG. [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. 1.------Preform, 2---1..-Plug, 3---Blow mold, 4---Stretch pin, 5--------- -bropin, 6---
--・Concave part, 7・---------Bottle, 8------
heating terminal

Claims (1)

[Claims] 1. 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, wherein the volume of the preform is equal to or smaller than that of the blow mold. After reaching 100% of the internal volume, a pair of opposing movable plugs attached to the blowing mold cool the preform to the glass transition temperature on the inner wall of the blowing mold. A method for manufacturing a stretched blow bottle with a handle, characterized in that a handle is formed by pressing a portion of the preform that is to become a recess for 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.