JPH01283128A - Manufacture of thermoplastic resin container - Google Patents

Abstract

PURPOSE:To manufacture a thermoplastic resin container economically in a short period of time by cutting a pipe-shaped molded product into the length equivalent to two sets of containers, heating its middle section by means of a burner and bottom molding respective containers. CONSTITUTION:The length of a multi-layer pipe 16 is equivalent to the length of two sets of containers, and is in the state of a container bottom unmolded with a gas barrier resin layer in the intermediate layer. Core molds 17 and 18 are at least a couple of container retaining molding with heating and cooling functions usually, and made of metal or non-metal with the function of revolving freely. An embossing die 19 is a mold for drawing made of metal or non-metal container bottom provided close by in a space between a couple of core molds 17 and 18. The drawing die 19 has a function to move and emboss toward the center of axis of core molds 17 and 18, and should preferably have function to revolve for enhancing drawing properties. At the time of bottom molding, a pipe heating section is pressed and constricted following the revolution of a pipe to form a bottom section. Also, heating and cooling function can be provided to the embossing die 19 to further enhance molding properties.

Description

DETAILED DESCRIPTION OF THE INVENTION A.-1 The present invention relates to a method for manufacturing thermoplastic resin containers extremely easily and economically by using a burner.

B'+7)' There are many methods for manufacturing containers made of thermoplastic resin, but
Injection molding methods and extrusion molding methods are well known. Particularly, the injection molding method has become rapidly popular in recent years because it requires little capital investment and allows containers of various shapes to be obtained. On the other hand, the extrusion molding method can stably mold containers with multilayer structures, and is used in combination with direct blow technology. A method of obtaining a multilayer container by
237, Jikai 60-253513).

There is a method of using an infrared lamp to form the bottom of a cut pipe into a container. FIG. 1 shows an outline of bottom forming using this method. The cut pipe 1 is rotated and heated to a moldable temperature by the infrared lamp heating device 2, and then held in a holder and inserted into the internal mold 3h (the pipe), and then the external mold 4 is inserted into the heating pipe. The heated and molten resin is molded into a bottom shape by pressing it against the pipe.However, this method is effective when using a thick pipe with a wall thickness of about 3.0 mm, but when the wall thickness is 0.5 to 2.0 mm, It has been found that pipes as thin as .0 mm have a major drawback.In other words, in thin-walled pipes, the total amount of resin that melts during heating is small, so the bottom seal is insufficient.Melted resin It may be possible to increase the heating length of the pipe in order to increase the amount, but in that case, the shape of the pipe at the heated part would be deformed and the shape of the bottom forming part would be poor, and the first
Since the resin does not fit tightly into the external mold shown in 4 in the figure, the molten resin remains in the middle of the mold inner wall surface, resulting in an incomplete seal. Furthermore, the method using an infrared lamp has a problem in that the heating time is long.

C9 Problems to be Solved by the Present Invention The present invention solves the problems in conventional container manufacturing methods and provides a method for manufacturing thermoplastic resin containers extremely easily, quickly, and economically. It is about providing.

01 Means for Solving the Problems As a result of intensive research aimed at solving the above-mentioned problems, the present invention has revealed that when molding a container from a pipe-shaped molded product made of thermoplastic resin, it is possible to In this method, the pipe-shaped molded product is cut, and then the middle part thereof is heated with a burner to form the bottom of each container, thereby obtaining two containers at the same time.

E. More detailed explanation of Akira The greatest feature of the present invention is that when heating a pipe-shaped molded product made of thermoplastic resin, the flame of the burner is applied directly to the thermoplastic resin, thereby heating the pipe-shaped product in a short time and economically. In addition, the object is to obtain a container with good bottom sealing properties.

The present invention enables the burner heating method used in the manufacture of glass containers by adjusting the size and strength of the flame.
It was discovered that it can be used satisfactorily in the molding process of plastics, and this finding means that since plastics burn when exposed to flame, a method of molding the plastics by heating them with a burner is out of the scope of consideration. Considering all this, this is truly surprising.

Hereinafter, the bottom forming method of the present invention will be specifically explained with reference to the drawings.

FIG. 2 is a sectional view schematically showing an example of a bottom forming apparatus used in manufacturing the container of the present invention.

Reference numeral 16 indicates a multilayer pipe having a gas barrier resin layer as an intermediate layer having a length equal to the length of two containers set in this apparatus, and the container bottom is not yet formed.

17 and 18 are at least a pair of core molds for container holding molding of the apparatus of the present invention. The core molds 17 and 18 are usually made of metal or non-metal and have a heating/cooling function and a freely rotatable function. However, if separate heating and cooling means are provided externally, this core mold is not necessarily compatible with these lli.
It is not necessary to have the ability. 19 is a pair of core molds 17.
At least 1 metal or non-metallic embossing molds are provided between and adjacent to the container bottom, and these are molds for drawing the bottom of the container. The drawing mold 19 has a function of moving toward the axial center of the core molds 17 and 18 to perform stamping, and preferably has a rotation function to improve drawing performance. When forming the bottom, as the pipe rotates, the heating part of the pipe is pressed down and constricted to form the bottom part. It is also possible to provide the embossing die 19 with a heating/cooling function, which can be expected to further improve moldability. In some cases, bottom molding is possible without the molds of 17, 18, and 19, but the accuracy is somewhat poor.

A burner heating device 20 is provided in the middle of the pipe 16 so as to face the stamping die 19 for heating the middle part (molding part) of the pipe 16. Here, the middle part may be the center part (in this case, containers of approximately the same length can be obtained), or it may be a part away from the center part (in this case, containers of different lengths can be obtained). ).

FIG. 3 is a sectional view showing a state in which the molding of the container bottom is almost completed using the apparatus shown in FIG. 2, and it is now possible to take out two containers. The pipe 16 is shown in a state in which it is drawn and bottom-formed by a drawing die 19 to form a container 21 and a container 2z.

The burner used here is preferably a flammable gas burner, especially a high-performance propane and oxygen mixed type burner, and the distance between the burner and the pipe is such that the resin surface temperature of the pipe can instantly reach the heating limit temperature of the resin. (Temperature that does not cause scorching, whitening, etc. on the resin surface) or a temperature close to it, for example, in the case of polyester resin, it is preferable to set the temperature to 200 to 320 degrees Celsius, usually 5 to 100 mm, preferably is 10-80m
It is m. It is preferable to approach them at first and then gradually move them away.

The heating time using the burner is about 1 to 8 seconds, preferably about 1.5 to 6 seconds.

The wall thickness of the pipe-shaped molded product used in the present invention is 0.5 to 2.0
+n+n is even more preferable. The heating method with a burner has the advantage of rapidly raising the resin temperature by directly applying flame and processing in a short time.
If the pipe is thicker than 2.0 mm, the difference in heating temperature between the outside and inside surfaces of the pipe will be large, and the heating time will inevitably be longer, resulting in excessive melting or even combustion on the outside surface. . On the other hand, if it is less than 0.5 mm, the pipe itself will not have enough strength as a container, and it may be burned out by the burner flame, making it difficult to form the bottom.

It is more effective for the pipe-shaped molded product used in the present invention to be a multilayer laminate. It is not necessarily the case that containers obtained from single-layer pipes by the method of the invention are economically advantageous over containers obtained by the injection method. However, it is technically difficult to stably obtain multilayer laminates in large quantities at low cost using the injection method. The method of forming pipes and forming containers according to the invention is of great advantage.

Thermoplastic resin containers molded according to the present invention can be used for various purposes. By machining a threaded part on the mouth and biaxially stretching blow molding, it can be used as a filling bottle for various foodstuffs and drinking water, but in particular, it can be used as a vacuum blood collection tube in the medical field without being blown. It's promising.

Glass has traditionally been commonly used as the material for vacuum blood collection tubes, but safety issues such as hepatitis virus infection due to glass breakage have recently been pointed out, so an alternative product is available that does not break even when dropped or centrifuged. Expectations for plastic vacuum blood collection tubes are increasing.

Unfortunately, however, plastic materials have poorer barrier properties than glass against gases such as oxygen, nitrogen, carbon dioxide, and water vapor in the air, making it difficult to maintain a constant degree of vacuum for long periods of time. It has points. Therefore, by the method of the present invention, it is possible to mass-produce plastic vacuum blood collection tubes with improved barrier performance at low cost by laminating the pipes described above (laminated body having a gas barrier resin layer).

Next, a laminate preferably used in the present invention, particularly a laminate having a gas barrier resin layer, and particularly a laminate having a gas barrier resin layer as an intermediate layer will be described.

A typical example of the laminate is a laminate having thermoplastic resin layers, such as hydrophobic thermoplastic resin layers, as inner and outer layers, and a gas barrier resin layer as an intermediate layer.

Hydrophobic thermoplastic resins used for the inner and outer layers include polyolefins (polyethylene, polypropylene, etc.), styrene resins (polystyrene, etc.), vinyl chloride resins, polyamide resins, polyester resins (ethylene terephthalate polyesters, etc.), polycarbonates, etc. Polyester resin (
PES) is the best.

A typical example of PES is PET, which is an ethylene terephthalate polyester.

Here, PES is a polyester resin mainly composed of ethylene glycol and terephthalic acid, in which terephthalic acid accounts for 80 mol% or more of the acid component, preferably 90 mol% or more, and 70 mol% or more of the glycol component, preferably 90 mol% or more.
It is a polyester resin in which 0 mol% or more is ethylene glycol. Other acid components include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, naphthalene 1.4 or 2.6 dicarboxylic acid, diphenyl ether 4.4°-dicarboxylic acid, diphenyl dicarboxylic acid, and diphenoxyethane dicarboxylic acid. , adipic acid, sepatic acid, azelaic acid and aliphatic dicarboxylic acids such as decane-1,10-dicarboxylic acid, and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid. These can be used alone or in combination of two or more, and mixed with terephthalic acid in an amount of less than 20 mol % of the acid component. Other glycol components include propylene glycol, trimethylene glycol, tetramethylene glycol, diethylene glycol,
polyethylene glycol, polypropylene glycol,
Aliphatic glycols such as polytetramethylene glycol, hexamethylene glycol, dodecamethylene glycol and neopentyl glycol, alicyclic glycols such as cyclohexane dimetatool, 2.2-
Examples include bis(4-β-hydroxyethoxyphenyl)propane and other aromatic diols. These glycols are 2 in the glycol component.
It can be contained in a range of less than 0 mol%. Also,
The compositions of the inner layer PES and the outer layer PES may be the same or different. The above hydrophobic resins may be used alone or in combination of two or more. In addition, the hydrophilic resin and various other additives may be freely blended and used within the range that does not impede the purpose of the present invention. Further, the inner and outer layers made of hydrophobic resin layers may each be a single layer or may be a multilayer.

Examples of gas barrier resins used in the intermediate layer include polyvinyl alcohol, its derivatives, and EVOH.
VOH is the best. The ethylene content of EVO) is 2
It is preferably 0 to 55 mol%, more preferably 25 to 50 mol%. Further, the degree of saponification of the vinyl acetate moiety is preferably 96 mol% or more, but if it is less than 96 mol%, the gas barrier properties deteriorate. When producing EVOH, in addition to ethylene and vinyl acetate, monomers copolymerizable with these may be used for polymerization, and the monomers may be saponified as long as this does not impede the purpose of the present invention.

Furthermore, in the present invention, it is preferable to provide an adhesive layer between the inner and outer layers (eg, PES resin layer) and the intermediate layer (eg, EVOH layer). Examples of this adhesive include, for example, a graft product of an unsaturated carboxylic acid or anhydride of an ethylene-vinyl acetate copolymer, a graft product of an unsaturated carboxylic acid or anhydride of a polyolefin (such as polyethylene), a graft product of an ethylene-acrylic acid ester ( Graft products of unsaturated carboxylic acids or their anhydrides (such as ethyl acrylate), polyesters with aluminum atoms and monocarboxylic acids bonded as described in JP-A-59-115327, etc. are preferably used for the purpose of the present invention. .

A laminate having the above gas barrier resin layer as an intermediate layer is useful as a vacuum blood collection tube and as a preform of a biaxially stretched blow container. Thickness is A1 Average thickness of outer layer is B
When 1.2≦B/A≦6, preferably 1.5
It is effective to use a laminate satisfying ≦B/A≦4. Note that the average thickness here is a value measured in a cross section of a laminated pipe. One end of such a laminate is formed into a bottle, and the opening at the other end is sealed with a rubber stopper or the like to form a vacuum blood collection tube.

The present invention will be further explained below with reference to Examples.

Example 1 Polyethylene terephthalate resin ([η] = 1.0°, melting point is 250°C as measured by DSC (scanning speed 20°C/min)), ethylene content 32 mol%, saponification degree 99.5 mol% Saponified ethylene-vinyl acetate copolymer (melting point 181'C) and JP-A-59-1153
A modified polyester resin with 450 ppm of aluminum atoms and benzoic acid bonded as described in Publication No.
T), 250°C (EVOH), and 230°C (TR,), and adjust the discharge timing to 245'C.
A pipe was formed at a speed of 5 m/min by feeding it into a three-type, five-layer pipe forming die, with an outer diameter of 12111+n and a length of 24.
A pipe with a wall thickness of 0 mm and a volume of 8 ml was obtained. When measuring the thickness of each layer, the PET inner layer is 270 μm open, the adhesive inner layer is 35 μm, the EVOH layer is 85 μm, and the adhesive outer layer is 30 μm.
, the PET outer layer was 380 μm.

As shown in Fig. 2, the center part of the obtained laminated cut pipe was heated with a burner while rotating for 3 seconds, and the bottom was formed using an internal mold inserted into the pipe and a drawing mold from the outside. It was cut to obtain two blood collection tubes at the same time. The bottom part was transparent without any whitening and had a good shape.

The pressure of this blood collection tube was reduced to 5 cmHg, and the bottom sealability was evaluated by a saline absorption test immediately after and 3 days after capping with a butyl rubber cap. There was no difference between the two, and the bottom seal was completely sealed. Met.

Comparative example! A 12 cm laminated pipe obtained in the same manner as in Example 1
When the bottom was formed using an infrared lamp in the equipment shown in FIG. 1, crack-like streaks appeared on the bottom. Further, when the obtained container was subjected to a seal test, it was found that there was leakage, and the degree of vacuum had disappeared after one day.

G, [! I'1 (IIJ! According to the present invention, the bottom of a thermoplastic resin container can be formed in a short time and economically, and is particularly effective when forming the bottom of a container from a thin-walled pipe.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an outline of conventional bottle molding using an infrared lamp, where A is a cross-sectional view of a pipe (longitudinal direction);
B is a cross-sectional view when the internal mold is inserted inside the pipe, C is a cross-sectional view when the internal mold is inserted inside the pipe, and an external mold is placed outside. D is the bottom FIG. 3 is a cross-sectional view of a container that has been completely molded. FIG. 2 is a sectional view of a bottom forming apparatus used for manufacturing the container of the present invention. FIG. 3 is a cross-sectional view showing a state in which the molding of the container bottom is almost completed using the apparatus shown in FIG. 2, and it is now possible to take out two containers. 16...Multilayer mold 17.18...Core metal mold 19...Press mold 20...Burner heating device 21.22...Container Patent applicant RiRa Co., Ltd.

Claims (4)

[Claims] (1) When molding a container from a pipe-shaped molded product made of thermoplastic resin, the pipe-shaped molded product is cut into lengths equivalent to two containers, and then the middle part is heated with a burner to separate each container. 1. A method for producing a thermoplastic resin container, characterized by forming the bottom of the container to obtain two containers at the same time. (2) The method for manufacturing a thermoplastic resin container according to claim 1, wherein the pipe-shaped molded product has a wall thickness of 0.5 to 2.0 mm. (3) The method for producing a thermoplastic resin container according to claim 1 or 2, wherein the pipe-shaped molded product is a laminate having a gas barrier resin layer. (4) Claims 1 to 4, wherein the thermoplastic resin container is a vacuum blood collection tube.
3. The method for manufacturing a thermoplastic resin container according to any one of 3.