JP2841913B2 - Parison for blow molding and blow molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a parison for blow molding and a blow molding method, and more particularly to a parison for blow molding and a blow molding method suitable for molding a product having good surface properties.

[0002]

2. Description of the Related Art In general, in blow molding, since molding pressure is lower than that in injection molding, transferability to a mold is poor, surface properties are not good, and cooling time needs to be long. . In particular, in the case of engineering plastics, which have been widely used in recent years, since the cooling and solidification time is short, the parison injected from the die is air-cooled in the air before the mold is clamped, and the surface properties are easily deteriorated. In addition, there was a problem that the parison expansion was uneven and a good product could not be obtained.

[0003] In order to cope with such a problem, various methods have been conventionally proposed.
In No. 125, a heater is provided at the lower part of the die to heat the outer surface of the parison injected to provide radiant heat, or a heater heated by irradiating the outer surface of the parison with a halogen lamp is provided. Are known.

[0004]

However, in the above-described conventional method, discoloration or deterioration due to oxidation occurs due to heating of the parison surface, and drawdown is promoted because heating of only the surface layer cannot be performed, and parison meat is accelerated. There was a drawback that molding failure was caused by deviation of the thickness distribution.

[0005] In addition, the solidified resin remaining in the vicinity of the resin discharge port during the injection of the parison may cause streak-like scratches called die lines and irregularities called melt fractures. It could not be improved by heating.

The present invention focuses on the above-mentioned conventional problems, and can provide a parison which can suppress drawdown and improve moldability even if it is a resin material which is easy to solidify by cooling. It is an object of the present invention to provide a blow molding parison and a blow molding method capable of obtaining a blow-molded product having excellent transferability and moldability to a mold and having excellent surface properties.

[0007] To achieve the above object, the parison for blow molding according to the present invention is formed by a coating layer comprising a resin layer formed parison emitted depending from die from the product main material and its outer surface a water-soluble resin , The water-soluble resin coating
The film layer is a film layer that is removed after molding.
ing.

Further, in the blow molding method according to the present invention, a parison injected and suspended from a die is formed by a resin layer composed of a main material of a product and a coating layer composed of a water-soluble resin on the outer surface of the parison, and this is formed into a mold. It was configured to blow-mould by feeding and remove the coating layer by fluid after molding to obtain a product. In this case, in the blow molding method, the cylindrical passage of the parison injection die is formed as a concentrically formed multiple passage, and is joined at the resin discharge port so that the multilayer parison can be injected. After supplying the resin material set according to the molding product to the inner peripheral side passage, and simultaneously supplying the water-soluble resin to the outermost peripheral side passage and injecting a multilayer parison, the multilayer parison is blow-molded by a mold. The surface layer can be removed by a fluid to obtain a product. Alternatively, a water-soluble resin is sprayed on the outer surface of the parison that is dripped from the die to form a surface layer film, and the parison with the surface layer film is blow-molded with a mold, and the surface layer portion is removed with a fluid to obtain a product. be able to.

[0009]

According to the above construction, the parison injected and suspended from the parison injection die has a surface coating formed of a water-soluble resin on its outer surface, so that the main product of the inner layer is insulated. As a result, even if engineering plastic or the like is used as the main material, the outer surface of the main material is not exposed to the outside air, so that cooling is suppressed and drawdown can be suppressed. Therefore, the occurrence of the parison thickness deviation before molding by the mold is prevented, and the moldability is not deteriorated.

In addition, a water-soluble resin film is formed on the parison surface of the main material of the product, blow-molded with a mold, and the surface film is removed by a fluid after the molding. Even if a surface defect is generated, a product having excellent surface properties can be formed because there is no generation on the main material on the inner layer side of the product. Furthermore, the transferability to the mold is not impaired by making the surface coating extremely thin, about 1 to 50 μm, and at the same time, the main material is gradually cooled by the heat insulation effect to form the main material surface precisely. And also the surface properties can be improved.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific examples of the blow molding parison and the blow molding method according to the present invention will be described below in detail.

FIG. 1 is a sectional view of a parison injection die for injection-molding a parison according to an embodiment. The parison injection die 10 has a die housing 12 formed of a rectangular block, and a through-hole 14 having a substantially circular cross section is formed along a vertical center line thereof. Such a through-hole 14 is opened at the lower end surface of the housing 12 in a state where the inner diameter is gradually reduced from the middle to the lower end surface of the housing 12. A mandrel 16 having a smaller diameter than the through hole 14 is inserted into the housing 12 to form a cylindrical passage 18 between the outer peripheral surface of the mandrel 16 and the inner peripheral surface of the through hole 14. ing. A die plate 20 fixed to the upper part of the die housing 12 is provided at an upper end portion of the mandrel 16. By fixing the die plate 20 to the upper surface of the die housing 12, the die plate 20 is positioned at the center of the through-hole 14. The upper end opening of the through hole 14 is sealed while the mandrel 16 is arranged. The lower end of the mandrel 16 is formed with a narrowed end in accordance with the diameter-reduced portion of the through-hole 14. In particular, a parison control mandrel 22 is attached to the end of the mandrel 16 so as to be able to enter and exit the mandrel 16. At the tip of the parison control mandrel 22, a die lip 26 which faces the opening of the through-hole 14 and forms a circular ring-shaped resin discharge port 24 with the opening of the through-hole 14 is integrally provided. Therefore,
The die gap can be arbitrarily changed by changing the amount of the parison control mandrel 22 going in and out. The die gap t can be changed by driving a control cylinder (not shown) installed above the die plate 20. The parison control mandrel 22 passes through the mandrel 16 and is driven by a control cylinder. Are linked.

In such an injection die 10, the cylindrical passage 18 is formed as a concentric multiple passage, and joins immediately before the resin discharge port 24 so that a multilayer parison can be injected. That is, the inner peripheral surface of the through-hole 14 formed inside the die housing 12 and the mandrel 1
A cylindrical die housing 30 is interposed between the outer peripheral surface of the cylindrical die 6 and the cylindrical die housing 30 to form the cylindrical passage 18 as a double passage composed of concentric inner cylindrical passages 18A and outer cylindrical passages 18B. I have. A flange 32 is integrally provided at an upper end portion of the cylindrical die housing 30, and is fixed between the main die housing 12 and the die plate 20 to hold the cylindrical die housing 30 at an intermediate portion of the cylindrical passage 18. doing. In this case, the inner cylinder passage 1
The cross-sectional area of 8A is set larger than the cross-sectional area of outer cylinder passage 18B. The lower end of the cylindrical die housing 30 is set to reach a position just before the opening of the resin discharge port 24.
The junction passage 18C for B is formed immediately before the resin discharge port 24.

In order to fill the inner and outer cylindrical passages 18A, 18B with molten resin supplied from the extruder side, independent resin inlets 34A, 34B are formed respectively. The resin inlet 34A for the inner cylinder passage 18A is connected to the flange 3
2, a resin inlet 3 opening to the outer cylinder passage 18B.
4B is perforated on the side surface of the main die housing 12. An independent external accumulator (not shown) is connected to these resin inlets 34A and 34B,
Resin is supplied independently.

The parison 36 is injected by using the parison injection die 10 as described above, and a resin set as a molded product is used as the resin charged and supplied to the inner cylindrical passage 18A of the double passage. This may be performed by using a general blow molding resin. For example, polyethylene terephthalate (PET), polyamide (PA),
Modified polyphenine oxide (PPO), polycarbonate (PC), polypheninsalphite (PPS)
Engineering thermoplastic resin or the like is used.

On the other hand, a water-soluble resin is used as the resin supplied and filled into the outer cylindrical passage 18B of the double passage.
It is made of a water-soluble polymer, especially a synthetic polymer resin, and has excellent water solubility such as polyvinyl alcohol, polyethylene glycol, polypropylene glycol, and polyvinyl ether, and alkali-soluble polyacrylic acid and water-soluble alkyd. And a polymaleic acid copolymer. The selection criteria for the outer layer resin in this case are such that there is no adverse effect such as a chemical reaction, decomposition, generation of gas, or discoloration between the outer layer resin and the inner layer resin simultaneously supplied from the inner cylinder passage 18A.

Each of the molded resin and the water-soluble resin is extruded from a separate extruder to the resin inlets 34A and 34B through the independent accumulators as well. The water-soluble resin is filled and pressurized in a separated state, and is laminated and integrated with each other in the merging passage 18C immediately before the resin discharge port 24 to form the resin discharge port 24.
The double parison 36 is ejected from. At this time, the thickness of the outer parison 36F is adjusted so that it functions as a heat insulating layer of the inner parison 36M and has a thickness of about 1 to 50 μm in order to ensure transferability to a mold. This may be performed by reducing the width of the outer cylinder passage 18B and adjusting the resin pressing speed to be lower than the inner layer side.

The parison 36 injected in this manner is hung between molding dies, pre-blown, closed, and blow-molded in a usual manner. The molded article becomes a multilayer molded article in which a water-soluble resin film is laminated on the outer surface of the original product resin. Then, this multilayer molded article is transferred to a water washing step, in which the molded primary product is washed with water, thereby dissolving and removing the water-soluble resin in the surface layer portion. This may be performed by immersing the primary product in a water tank.
By immersing in hot water or an alkaline aqueous solution at 0 to 80 ° C., the dissolution rate can be increased to remove. Alternatively, the primary product may be removed by spraying high-pressure water at 1 to 20 kg / cm ² on the surface thereof. Products, of course
For example, depending on the product that does not require heat resistance, it may not be necessary to wash and remove the water-soluble resin. In this case, the washing step is omitted. The washing time varies depending on the resin material and the washing temperature, but the dissolution treatment is completed in about 10 minutes.

The product obtained through this washing step is a single-layer resin product composed of the inner layer resin from which the water-soluble resin film on the surface layer has been removed.

FIG. 2 shows such a blow molding process.
First, a product resin and a water-soluble resin are extruded and supplied to a parison injection die (step 100). In the die, a two-layer parison is injected with the product resin on the inner layer side and the water-soluble resin on the outer layer side (step 110). Pinch and seal the upper and lower ends of the injected parison (step 12).
0), pre-blow is performed (step 130). After closing the mold (step 140) and sucking air in the cavity, high-pressure air is blown into the parison (step 15).
0). This causes the parison to follow the shape of the cavity.
Thereafter, it is cooled in the mold (Step 160), the blowing is stopped (Step 170), and the primary product of the two-layer structure is taken out (Step 180). A water-soluble resin film is formed on the surface of this product. Then, the primary product is carried out and immersed in a water tank, and is washed with water (Step 1).
90), the water-soluble resin film on the surface layer is removed and taken out as a final product (step 200).

According to the above embodiment, the parison 36 injected from the parison injection die 10 is injected in a two-layer structure of the inner parison 36M which is the original molded product and the outer parison 36F of the water-soluble resin film. The whole of the injected parison 36 is suppressed from cooling during the hanging process due to the heat insulating effect of the outer resin film. For this reason, when engineering plastic is used for the inner layer side as a product material, the drawdown is suppressed by the heat insulating action of the surface resin. As a result, parison 36
Can be prevented from changing in thickness, and mold moldability can be improved.

Also, with the injection of the parison 36, a die line may be formed on the surface of the parison 36 due to the solidified resin remaining around the resin discharge port of the die 10, or a surface defect such as melt fracture may occur. However, this surface defect is generated in the outer parison 36F. However, the parison 36 is molded in a mold with a two-layer structure, and since the surface resin is removed from the molded primary product in the washing step, the defective surface portion does not appear on the surface of the final product. In particular, in the mold, the inner layer resin is gradually cooled by the heat insulating effect of the outer layer resin film, so that the surface properties of the final product are extremely good. In addition, the outer layer coating is 1 to
Since the thickness is as thin as 50 μm, transferability to a mold is not impaired. Moreover, since the resin temperature drop of the parison 36 is small and uniform, there is no unevenness in expansion in the mold, the incidence of product defects is reduced, and the yield can be improved. Further, since there is no need to perform special processing such as heating and cooling means on the mold, there is an advantage that the burden on the molding equipment can be reduced.

In the above embodiment, the two-layer parison 36 is used.
A double cylindrical passage 18A in the die 10 for injecting
18B was formed to form a water-soluble resin coating on the outer layer. However, the cylindrical passage 18 of the die 10 was configured as a single passage, and a resin injection nozzle was arranged immediately below the die 10 to be injected. An outer layer coating can be formed by spraying a water-soluble resin on the surface of the parison. In this case,
Nozzles are arranged at equal intervals around the injection parison so as to form a coating of uniform thickness on the outer surface of the injection parison,
Care should be taken to have a uniform spray of the water-soluble resin around the parison.

With such a configuration, a draw-down suppressing effect can be obtained, and the temperature drop of the parison can be made uniform, and a slow cooling effect in the mold can be exhibited. In particular, this embodiment can cope with the conventional blow molding equipment by adding a water-soluble resin injection means,
There is an advantage that moldability can be improved by conventional equipment.

In this embodiment, the case where water is used for removing the outer coating is described, but a fluid that can dissolve a water-soluble resin other than water can be used. Also,
In the above embodiment, the two-layer parison was injected.
The cylindrical passage 18 of the die 10 can be a multiple passage like a triple passage. In this case, the water-soluble resin is supplied to the outermost passage. This can be applied when the product has a multilayer structure of different colors.

[0026]

As described above, according to the present invention,
Even if the resin material is easily cooled and solidified, it is possible to obtain a parison capable of improving the formability by suppressing the drawdown, and has a very good surface property, thereby improving the transferability to the mold and the formability. An excellent effect is obtained that a blow molded product having excellent surface properties can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional configuration diagram of a die for injecting a parison according to an embodiment.

FIG. 2 is an explanatory diagram of a blow molding process according to an example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Parison injection die 12 Main die housing 16 Mandrel 18 Cylindrical passage 18A Inner cylinder passage 18B Outer cylinder passage 18C Merging passage 24 Resin discharge port 34A, 34B Resin inlet 36 Parison 36F Outer parison of water-soluble resin 36M Inner parison

──────────────────────────────────────────────────続 き Continuing from the front page (72) Yoshiaki Kano, Inventor 1980, Kogushi-ji, Obe-shi, Ube-shi, Ube-shi, Yamaguchi Ube Industries, Ltd. Ube Resin Processing Machine Research Laboratory (56) References , B2) Special Publication 58-2053 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) B29B 11/10 B29C 49 / 04,49 / 22 B29C 49/24-49/42 B29L 9: 00,22: 00 B29C 47/20-47/28

Claims (2)

(57) [Claims] 1. A parison injected and suspended from a die is formed by a resin layer composed of a main material of a product and a coating layer composed of a water-soluble resin on an outer surface of the parison.
A blow molding parison, which is a coating layer removed after shaping. 2. A parison injected and suspended from a die is formed by a resin layer composed of a main material of the product and a coating layer composed of a water-soluble resin on the outer surface of the parison. A blow molding method, wherein the product is obtained by removing the coating layer with a fluid later.