JPH048211B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polypropylene resin blow-molded container with improved transparency and less uneven thickness. Polypropylene resin has excellent heat resistance, chemical resistance, and safety and hygiene, and its blow-molded products have excellent rigidity and impact strength, so it is widely used in food containers, detergent containers, medical containers, etc. However, blow-molded products made of polypropylene resin have insufficient transparency and do not fully satisfy market demands. Conventionally, methods for improving the transparency of polypropylene resin include adding a nucleating agent, thermal degradation in the presence or absence of an oxide, and copolymerizing α-olefin with propylene. In addition, there are known molding methods such as biaxial stretching, but with normal blow molding, even if these measures are taken, the product will look pale and hazy, and it is difficult to achieve sufficient transparency. It is not possible to obtain a blow-molded container with good properties. In addition, the polypropylene resin used in conventional blow molding has good moldability, impact resistance,
In terms of rigidity, etc., it is usually JISK-7210 condition 14.
Melt flow index (MFI) measured by
is about 4g/10 minutes at most, especially 1 to 2
g/10 minutes are often used. On the other hand, in recent years, molding machines that can be applied to polypropylene resin have been developed in the injection stretch blow molding method, and blow molded products have also been prototyped. The reality is that this is not the case. The present inventors have conducted intensive studies to obtain a polypropylene resin blow molded container with excellent transparency and no uneven thickness by injection stretch blow molding, and as a result, the polypropylene resin has a specific MFI,
Furthermore, the inventors have discovered that a good blow-molded container can be obtained by using a copolymer of propylene and α-olefin whose intrinsic viscosity and MFI have a specific relationship, and have completed the present invention. That is, the present invention is a polypropylene resin blow-molded container in which a random copolymer of propylene and α-olefin is injection-stretched and blow-molded, and the propylene-α-olefin random copolymer has a melt flow index of 4 to 50 g. /In 10 minutes,
And the relationship between the intrinsic viscosity [η] (dl/g) measured in a tetralin solution at 135°C and the melt flow index MFI (g/10 minutes) is 1.70≦logMFI+5.20log[η]≦1.95. This is a polypropylene resin blow-molded container with improved transparency and no uneven thickness. The propylene-α-olefin random copolymer used in the present invention is a random copolymer mainly composed of propylene and α-olefin such as ethylene, 1-butene, 1-pentene, and 1-hexene, and particularly, A copolymer with ethylene is preferred because it provides good transparency. Note that polypropylene homopolymer has significant thickness unevenness and poor moldability. The propylene-α-olefin random copolymer in the present invention has an MFI of 4 to 50 g/10 minutes,
It is necessary that the relationship between the intrinsic viscosity [η] (dl/g) and MFI (g/10 min) measured in a tetralin solution at 135°C is 1.70≦logMFI+5.20log[η]≦1.95. If the MFI of the propylene-α-olefin random copolymer is less than 4 g/10 minutes, sufficient transparency cannot be obtained. Furthermore, if the MFI exceeds 50 g/10 minutes, the uneven thickness becomes significant, making it impossible to stably obtain a good blow-molded container. Furthermore, if logMFI+5.20log [η] is less than 1.70, the resin tends to become sticky and a blow-molded container cannot be stably obtained. Furthermore, if it exceeds 1.95, sufficient transparency cannot be obtained. The propylene-α-olefin random copolymer satisfying 1.70≦logMFI+5.20log[η]≦1.95 can be melted and pelletized with or without adding a small amount of organic peroxide to this resin. It can be obtained by Examples of organic peroxides used for this purpose include dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, etc. Among them, those having a 10-hour half-life in the temperature range of 110 to 130°C are preferred. In the present invention, a nucleating agent can be added because the transparency is further improved. In that case, the amount is suitably 1% by weight or less based on the propylene-α-olefin random copolymer. Furthermore, additives such as antioxidants, ultraviolet absorbers, antistatic agents, lubricants, and colorants, as well as other resins and elastomers, may be added and blended. The injection stretch blow molding method, which is the molding method of the present invention, is a molding method in which a bottomed parison is molded by injection molding, and then a product is obtained by pre-blowing, stretching temperature adjustment, and stretch blowing. The stretching method is a combination of mechanical vertical stretching using a rod and air blowing. Examples of molding machines suitable for this molding method include Nissei
Injection stretch blow molding machine ASB manufactured by ASB Machinery Co., Ltd.
-50, ASB-150, ASB-250, ASB-650, etc. In the present invention, in order to obtain particularly excellent transparency, for example, an injection stretch blow molding machine is used as a molding machine.
When using ASB-50, the following conditions are desirable. Injection molding temperature: 200-260℃ Pre-blow stretch ratio: Vertical 1.0-1.8 times Width 1.2-2.0 times Pre-blow air pressure: 3-7 Kg/cm ² Stretching temperature adjustment mold temperature: 90-140℃ Stretch blow stretch ratio; Vertical 1.2 to 3.5 times horizontal stretching 1.2 to 6.0 times Blow air pressure: 4 to 20 Kg/cm ² The polypropylene resin blow-molded container of the present invention contains polypropylene resin with a stabilizer, an antistatic agent,
After adding additives such as an ultraviolet absorber, a coloring agent, and a nucleating agent, the body is usually manufactured to have a body thickness of 0.2 to 1.0 mm by the above-mentioned injection stretch blowing. In addition, it has excellent transparency, heat resistance, and impact resistance, so it can be suitably used for food containers, detergent containers, shampoo containers, toiletry containers, medical containers, etc. by taking advantage of these properties. Hereinafter, the present invention will be explained in detail with reference to Examples. Incidentally, the body haze was measured using a haze meter manufactured by Nippon Denshoku Co., Ltd. according to the method described in JIS K-6714. Example 1 A powder of a propylene-ethylene random copolymer with an ethylene content of 4% by weight is mixed with 0.01% by weight of the organic peroxide Lupazole along with additives such as antioxidants and 0.30% by weight of a nucleating agent. 101 (trade name: Lucidor, manufactured by Yoshitomi Co., Ltd.) was added, thoroughly stirred with a Henschel mixer, and then extruded at 240°C using a φ65 mm extruder to form pellets to obtain polypropylene resin pellets. The MFI of the pellets obtained was 14 g/10 min.
Also, [η] is 1.35 and logMFI + 5.20log [η] is 1.82
It was hot. This resin was molded using an injection stretch blow molding machine ASB-50 under the following conditions to create a body with a diameter of 70 mm and an inner volume.
A 500ml round bottle was molded. Injection molding temperature: 220℃ Injection mold temperature: 15℃ Pre-blow stretching ratio: 1x vertically 1.4x horizontally Pre-blowing air pressure: 5Kg/cm ² Stretching temperature adjustment mold temperature: 100°C Stretching blow stretching ratio: 1.8x vertically Horizontal 1.2 times stretching Blow air pressure: 9 Kg/cm ² The resulting bottle weighed 24 g and was a polypropylene resin blow-molded container with extremely excellent transparency. In addition, the wall thickness of the body was 0.53 mm, the haze level was 2.8%, and the transparency when the liquid was added was also good. Example 2 In Example 1, the organic peroxide Lupazole
Polypropylene resin pellets were obtained in the same manner as in Example 1, except that the amount of 101 added was changed to 0.02% by weight. Its MFI is 25g/10min, and [η] is
At 1.22dl/g, logMFI+5.20log[η] was 1.85. Using this resin, an injection stretch blow molded bottle was obtained in the same manner as in Example 1, and the wall thickness and haze of the body were measured. The measurement results are shown in Table 1. Example 3 0.02% by weight of the organic peroxide Lupazol 101 was added to a powder of propylene ethylene random copolymer having an ethylene content of 5.5% by weight along with additives such as antioxidants and 0.30% by weight of a nucleating agent. and pelletized in the same manner as in Example 1 to obtain polypropylene resin pellets. Its MFI is 41
g/10 min, [η] is 1.10, logMFI+
5.20log [η] was 1.83. Using this resin, an injection stretch blow molded bottle was obtained in the same manner as in Example 1, and the wall thickness and haze of the body were measured. The measurement results are shown in Table 1. Example 4 A powder of a propylene-ethylene random copolymer with an ethylene content of 1.5% by weight was injected with the organic peroxide Perkatox 14 (trade name, Chemical Polypropylene resin pellets were obtained in the same manner as in Example 1, except that 0.005% by weight of Polypropylene resin (manufactured by Yakuh Nouri Co., Ltd.) was added. Its MFI is 6g/10min and [η] is 1.58
The logMFI+5.20log [η] was 1.81. Using this resin, an injection stretch blow molded bottle was obtained in the same manner as in Example 1, and the wall thickness and haze of the body were measured. The measurement results are shown in Table 1. Comparative Example 1 As a polypropylene resin, ethylene content is 4
Weight% MFI2g/10min, [η]2.10dl/g,
A round bottle was molded in the same manner as in Example 1 using a propylene-ethylene random copolymer having logMFI+5.20log[η]=1.98 and containing 0.3% by weight of a nucleating agent. Table 1 shows the wall thickness and haze of the body of the obtained bottle.
Shown below. Comparative Example 2 In addition to additives such as antioxidants, 0.25% by weight of the organic peroxide Percadox 14 and 0.30% by weight of a nucleating agent were added to a propylene-ethylene random copolymer powder with an ethylene content of 2% by weight. Add
Polypropylene resin pellets were obtained in the same manner as in Example 1. Its MFI is 55g/10min, [η]
was 1.09dl/g, and logMFI+5.20log[η] was 1.93. Using this polypropylene, injection stretch blow molding was carried out in the same manner as in Example 1, but thickness deviation became significant during blow molding, and a good container could not be obtained. Comparative Example 3 In addition to additives such as antioxidants, organic peroxide Lupasol 101 was added to polypropylene homopolymer.
Polypropylene resin pellets were obtained in the same manner as in Example 1 by adding 0.10% by weight of 0.1% by weight and 0.30% by weight of a nucleating agent. Its MFI is 15g/10min, and [η] is
At 1.45 dl/g, logMFI+5.20log [η] was 2.02. Using this polypropylene, injection stretch blow molding was carried out in the same manner as in Example 1, but the thickness deviation during blow molding was significant and a good container could not be obtained. 【table】

Claims (1)

[Scope of Claims] 1. A blow-molded container made of polypropylene resin, which is made by injection stretch blow-molding a random copolymer of propylene and α-olefin, which
- The olefin random copolymer has a melt flow index of 4 to 50 g/10 minutes and an intrinsic viscosity [η] (dl/
g) and melt flow index MFI (g/10
A polypropylene resin blow-molded container with improved transparency and no uneven thickness, characterized in that the relationship between 2. The polypropylene blow container according to claim 1, wherein the α-olefin is ethylene.