JPS59179318A - Biaxial orientation blow molding method of polypropylene - Google Patents

Abstract

PURPOSE:To mold a hollow article such as a bottle made of beautiful polypropylene which is transparent, glossy and even in thickness through biaxial orientation blowing method, by eliminating completely molten crystalline substance contained in molten polypropylene in an injection cylinder by kneading the molten polypropylene prior to pouring of the same into a metal die. CONSTITUTION:Simultaneously with elimination of crystalline substance by mixing amorphous substance and crystalline substance of polypropylene in a molten state with a rotation of an injection screw uniformity of a temperature is contrived and nonuniformity of an inner temperature in a parison is eliminated. At the time of molding of the parison, a thin coating is made to form on the inner and outer surfaces of the parison by making injecting and cooling time as short as possible, and cooling is left within a limit through which the parison is capable of releasing from a metal die. The hot parison released from the metal die is adjusted immediately to a molding temperature by a heat exchanger type temperature adjusting device. A biaxial orientating hollow article, which is superior in transparency, is molded by orientation blow molding, by a method wherein an orientation blow of the article is made rapidly and let the article cool quickly.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for biaxial stretch blow molding of polypropylene, which involves continuous injection molding of polypropylene into biaxially oriented hollow articles such as bottles.

Polypropylene is a crystalline resin, and the wave red used for molding is white and in a crystalline state. The temperature at which this polypropylene can be molded is in the range of 190° to 2600°C,
When molding a hollow product such as a bottle by blow molding or in-extraction blow molding, it is desirable to set the temperature as high as possible.

In blow molding or injection blow molding, the molded nochrisone is immediately blow molded into hollow products, so all of the resulting hollow products have poor transparency and are cloudy.

To make this opaque polypropylene hollow product transparent
d. To obtain a transparent hollow product of polyethylene terephthalate, the commonly practiced biaxial stretch blow molding is adopted.

However, the hollow products of Boripro Gyren are formed by biaxial stretch blow molding, which is a method that continuously performs the stretch blow molding of hollow products from the injection molding of Yarison, that is, the method generally referred to as the hot parison method. Even if the IJson temperature is adjusted to the most suitable temperature for molding,
・41Json easily breaks during stretch blow molding, and even if a hollow product is obtained, the wall thickness of the hollow product is uneven and the transparency is uneven, making it difficult to obtain a satisfactory hollow product. There wasn't.

The opacity of the hollow product is said to be due to crystals generated during the cooling process from the molten state, and the transparency is said to vary depending on the size and degree of crystallinity in the unquality product. Therefore, if the process from injection molding to stretch blow molding of hollow products is carried out in an extremely short time, it may be possible to obtain hollow products with excellent transparency and uniform thickness. However, with the equipment currently in use, such a thing is impossible, and even now the meat is transparent, shiny, and uniform due to the 2IllI orientation. Hollow products of lysolobirene are readily available.

An object of the present invention is to mold a beautiful hollow product such as a bottle made of polynolopyrene, which is transparent, glossy, and has a uniform wall thickness throughout, by biaxial stretching blowing. Another purpose is to make holin-0-ropyrene, which can be easily molded using equipment used for injection stretch blow molding of polyethylene terephthalate and other materials.
The purpose of the present invention is to provide axial stretch blow molding.

One of the features of this invention according to the above-mentioned object is that the molten polypropylene in the injection molding is thoroughly kneaded before being injected into the mold to completely remove the crystalline material in the molten material. .

In general, the IJson molding pellet is melted by the rotation of the injection screw in a heated injection cylinder, and the molten material measured at the tip of the injection screw is poured into the mold by the forward movement of the injection screw. By injecting into.

In normal injection molding, the pellet is designed to be completely melted by the rotation of the injection screw, and is assumed to be completely melted by the time measurement is completed, and the melting state is not controlled in detail.

Crystalline resins such as polypropylene can be either unquality or crystalline depending on the degree of melting, and even if injection molding is possible by melting with an injection screw, crystalline resins may exist. It is possible. And as long as the molten yjP IJ f-mouth V-lens consists of amorphous and crystalline materials, it is not possible to obtain a transparent, shiny, biaxially oriented hollow product by stretch blowing. They discovered this.

Furthermore, even if all of the material measured at the tip of the injection screw is in a molten state, there is likely to be unevenness in temperature.

This temperature unevenness continues even when the molten material is injected into the mold, and is one of the causes of temperature unevenness in the parison. Non-uniformity in temperature can be corrected uniformly by temperature control performed before stretch blow molding, but it is due to external temperature unevenness caused by the cooled mold. It is difficult to even out internal temperature irregularities that occur before molding by short-term temperature control. And that temperature unevenness is caused by stretch blow molding.
This causes a difference in the cooling rate of the IJ-son, creating parts that are easy to stretch and parts that are difficult to stretch, resulting in damage.
Also, the transparency becomes uneven.

The above-mentioned kneading in this invention refers to mixing the amorphous and crystalline polypropylene in the molten state by rotating the injection screw after weighing, and at the same time, removes the crystalline substance by removing the crystalline substance and maintains a uniform temperature. This is to eliminate internal temperature non-uniformity in the IJ. In fact, the results of measuring the temperature of a parison molded after kneading and a parison molded normally show that the former has less temperature unevenness and still has better transparency, while the latter is noticeably cloudier than the former.

In this invention, when molding the i91J son, the injection and cooling times are kept as short as possible to form a thin skin on the inner and outer surfaces of the parison, and the cooling is kept to a limit that allows the parison to be released from the mold. .

Immediately after being removed from the mold, the parison has crystallized thin skin on its inner and outer surfaces and is slightly cloudy.
? There are uncrystallized high-temperature parts left inside the IJson,
Due to the amount of heat it holds, the thin skin on the inner and outer surfaces melts, and after a while, the OIJ son gradually becomes clearer and clearer.

Once released from the mold, the tR parison is immediately adjusted to the molding temperature using a heat exchange type temperature controller. This temperature control d,
The temperature control method invented by the present inventor (Japanese Patent Application No. 57-130)
No. 862, Japanese Patent Application No. 57-166377). By this temperature control, even slight temperature irregularities remaining in the OIJ sonon can be uniformized in a short time. In addition, the dimensions of the temperature control mold used for temperature control are ・e IJ sonon dimensions, and the area ratio is about 1.4 to 2 times. Sonon is controlled in the temperature range where it shrinks in an attempt to restore it to its original shape.

The temperature-controlled parison is in an amorphous state and transparent.

In this state, the fish bed is stretched and quenched to form a biaxially oriented hollow product with excellent transparency.

Next, examples will be described in detail. The molding was carried out using the apparatus disclosed in Japanese Patent Publication No. 53-22096.

Example 1 In an injection cylinder heated to 220°C, polypropylene coated pellets (Mitsubishi Kasei 6
200 K) was heated and melted and measured, and after the measurement was completed, the injection screw was further rotated to perform crosstalk for a short time. After kneading, the molten material was poured into a mold that had been cooled to 12° to 15°C to form a bottomed hot dilinone having the following dimensions.

Outer diameter 22 ++1++1 Inner
Diameter: J5 Thickness: 3.5 mm Overall length: 28 points, 28 recesses: 11.0 The above-mentioned hot gurinone was taken out of the mold while it was as hot as possible in a state where it could be released from the mold. -1511
The mixture was transferred to a heat exchange type temperature control device having a temperature control type disclosed in No. 75, and the temperature was immediately controlled. The temperature of the hot parison in this case was 100° to 103°C, and the temperature was controlled under the following conditions.

Temperature control mold Inner diameter: 36 Depth: 137 mm Same temperature: 6 to 7 sec Air pressure: 1 to 2 Kg/crn2 For temperature control, first insert an extension rod into the hot parison in the temperature control mold to heat the hot parison. After stretching in the axial direction to the inner bottom surface of the mold, air is blown into the IJ sonon for 6 to 7 seconds to expand it, and the outer surface of the hot parison is brought into close contact with the inner surface of the temperature mold. went. Completion of temperature control is achieved by the contraction of the e-linon that occurs when the elongated rod and air pressure pressurizing it are removed.

For this reason, the dimensions of the temperature control/spear non pulled out from the temperature control mold were 31 to 32 mm in outer diameter, 30 mm in length under the neck, and were larger than before the temperature control. Also, the temperature is 1
The temperature is as high as 13° to 120°C.

After the temperature control was completed, the IJ Sonon was immediately transferred to a blow mold and stretch blow molded into a 600me Bayer bottle with the following dimensions by conventional means. In addition, the blowing pressure at this time is 8 to 10 2/cm2, and the time is 3 to 5.5 seconds.
Met.

Bottle outer diameter (elliptical) 80 x 60 jTnl wall thickness 0.4 length total length 19
8 Length under the neck 180 Capture weight 22.2
f The above molded product was transparent, had no clouding, was still shiny, and had a uniform wall thickness.

Example 2 In this example, a 7007 oil bottle was molded using the same process as in Example 2.

Therefore, only the molding conditions will be described below.

Parison dimensions: Outer diameter: 28mm Inner diameter: 20mm
．． 6 mm wall thickness 3.7 mnl
Total length: 130 Length below neck: 118 wrl Mold temperature: 15-22°C Nogurinon temperature: 100°C Temperature-controlled mold inner diameter: 40 pieces Depth
]22 Temperature control 90°~100°C Air pressure 8 Ky/crn2 Temperature control time Q, 5~], sec Temperature control/Gurinon outer diameter 33k Neck length 119 Gate temperature
Degree: 115°C Oil bottle (molded product) Outer diameter: φ70 mm (Maxφ77) Total
Length 225mm Meat +1 0
．． 4 rnn length 2.1.3+++m weight
Amount 29.6! The molded product described in i' also had excellent transparency, was glossy, and had a uniform wall thickness distribution.

Patent originator Tsuyoshi Yoiki 11- Procedural amendment (to the examiner of the Japan Patent Office) 1. Indication of the case Patent Application No. 56330 filed in 1982. 2. Name of the invention Biaxial stretch blow molding method for polypropylene 3. Person making the amendment Relationship to the case Applicant name: Tsuyoshi Aoki 4, agent address: 1-1-5 Shimome, Minami-Aoyama, Minato-ku, Tokyo Date of amendment order (voluntary) (Date of dispatch) Showa, Month, Day 6, Amendment Contents of M/Z amendments to the detailed description of the fence invention in the scope of the subject patent claims (1) The scope of the claims will be amended as shown in the attached sheet.

(2) Specification page 8, line 17 [same temperature 6-7 sec
j "Temperature: 120-130°C Temperature control time: 6-7 sec" 2. Claims The molten polypropylene in the injection cylinder is thoroughly kneaded before being injected into the mold, and the crystalline material in the molten polypropylene is )'? IJ sonon molding is performed, the parison is released from the mold while it is as hot as possible, the temperature is controlled using a heat exchange type temperature control device, and the temperature controlled parison is immediately stretch blow molded in a blow mold. , a method for biaxially stretched polypropylene blow molding, characterized in that a desired biaxially stretched transparent hollow product is obtained.

Claims (1)

[Claims] The molten polypropylene in the injection mold is thoroughly kneaded before being injected into the mold, and the crystalline material in the molten polyzolopylene is completely removed before molding.
・F IJson is released from the mold while it is as hot as possible, heated and temperature controlled using a heat exchange type temperature control device, and the temperature control ・e
Immediately stretch blow mold the IJson in a blow mold, and
A method for biaxially stretching blow molding of polyzolopyrene, which is characterized in that a desired transparent hollow article that has been axially stretched is obtained.