JPS60125630A - Blow molded container with improved transparency - Google Patents

Abstract

PURPOSE:To improve transparency of a molded article, by making orientation blow molding of a random copolymer of propylene and ethylene whose ethylene content is 1-6wt% and a ratio between a melt flow index and extreme viscosity is in a specific relation. CONSTITUTION:A molded container whose transparency has improved is obtained by making injection orientation blow molding of a propylene-ethylene random copolymer whose ethylene content is 1-6wt% a melt flow index (MFI) is 4-50g/10min and a relation between extreme viscosity [eta]dl/g and the foregoing MFI is 1.70<=log MFI+5.20log[eta]. As the transparency becomes favorable further a nucleating agent can be kept loaded, and in this case, loading of more than 1wt% nucleating agent to the propylene-ethylene random copolymer is favorable.

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 also have excellent rigidity and impact strength, so it is widely used for 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 organic peroxide, and copolymerizing propylene with ethylene. 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, making it difficult to achieve sufficient transparency. It is not possible to obtain a durable blow molded container.

In addition, polypropylene resin used in conventional blow molding usually has a melt flow index (MFI) measured under condition 14 of JIS K-7210 in terms of moldability, impact resistance, rigidity, etc. 49
710, and in particular those with a roughness of 1 to 29/10 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 achieved excellent transparency using the injection stretch blow molding method,
As a result of intensive studies to obtain a blow-molded container made of polypropylene resin with no uneven thickness, we found that polypropylene resin has a specific 1VFI, has a specific relationship between the intrinsic viscosity and MFI, and has a specific ethylene content. The inventors have discovered that a good blow-molded container can be obtained by using a certain copolymer of propylene and ethylene, and have completed the present invention.

That is, the present invention provides a polypropylene resin blow-molded container made of a random copolymer of propylene and ethylene, which is injection-stretched and blow-molded, wherein the content of the propylene-ethylene random copolymer is 1 to 6% by weight, and Its intrinsic viscosity C1) (dl/9) and melt flow index MF measured in a tetralin solution at 135°C with a flow index of 4 to 50!7/1.0 min.
The relationship with I (g/l 0 min) is 1.70≦lOgMFI+5.201og (me≦1.9
This is a polypropylene resin blow-molded container with improved transparency and no uneven thickness.

The polypropylene resin used in the present invention is a propylene-ethylene random copolymer, and its ethylene content is 1
It is desirable for the transparency of the blow-molded product to be 6% by weight, and the MF'I is 4 to 50g/1.0 min, and the intrinsic viscosity is 1% when measured in a tetralin solution at 135°C. The relationship between [η) (dl/'7) and MFI ('; l/10 min) is 1.70≦logMFI+5.201og (ll force≦1
．． 95 is desirable.

If the ethylene content is less than 1% by weight, the uneven thickness will be significant and the moldability will be poor. Moreover, if the weight exceeds 6, the rigidity of the resulting blow container will be insufficient and it cannot be used.

If the MFI is less than 4710 minutes, sufficient transparency cannot be obtained. Also, MFI is 50! ; If it exceeds 1/10 minutes, the uneven thickness will become significant, making it impossible to stably obtain a good blow-molded container.

Also, the value of logMFI+5.201og(η) is 1,
If it is less than 70, the resin tends to become sticky and a blow-molded container cannot be stably obtained. Moreover, if it exceeds 1.95, sufficient transparency cannot be obtained.

In addition, 1.70 ≦logMFI+5.201ogC'7
), a propylene-ethylene random copolymer satisfying i 1.95 can be obtained by adding a small amount of organic peroxide to this resin, or by melting it and pelletizing it without adding a small amount of organic peroxide. can.

Organic peroxides used for this purpose include, for example, dicumyl peroxide, dibutyl peroxide,
Examples include 2,5-dimethyl-2,5-bis(butylperoxy)hexane, and among them, those having a 10-hour half-life in the temperature range of 110 to 130°C are preferred.

The highly transparent blow-molded container of the present invention cannot be obtained using a propylene-ethylene block copolymer.

In the present invention, a nucleating agent can be added because the transparency is further improved. In that case, it is appropriate that the amount is 1 weight or less relative to the propylene-ethylene random copolymer.

Furthermore, antioxidants, ultraviolet absorbers, antistatic agents, lubricants,
Additives such as colorants, 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. A combination of mechanical vertical stretching using a rod and air blowing is used. Which molding machine is suitable for the molding method? For example, the injection stretch blow molding machine As manufactured by Nissei ASB Machinery Co., Ltd.
B-50, ASB-1, 50, ASB-250, A5B
-650 etc. are mentioned.

In the present invention, in order to obtain particularly excellent transparency, for example, when an injection stretch blow molding machine AS B-50 is used as a molding machine, the following conditions are desirable.

Injection molding temperature: 200-260°C Pre-blow stretching ratio: 1.0-1.8 times vertically 1.2 times horizontally
~2.0 times preliminary blow air pressure: 3 to 7 kl? / cr&
Stretching temperature adjustment Mold temperature = 90-140°C Stretching blow Stretching ratio: 1.2-3.5 times vertically 1.2-6.0 times horizontally Stretching blowing air pressure: 4-20 kg/ff1 Made of polypropylene resin of the present invention Blow-molded containers are made by adding additives such as stabilizers, antistatic agents, ultraviolet absorbers, colorants, and nucleating agents to polypropylene resin, and then using the above-mentioned injection stretch blowing process to reduce the body wall thickness to 0.2. ~1. , Om, is manufactured. In addition, it has excellent transparency, heat resistance, and impact resistance, so it can be used to create food containers, detergent containers, shampoo containers, toiletry containers, etc.
It can be suitably used for medical containers, etc.

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 Juishoku Co., Ltd. according to the method described in JIS K-6714.

Example 1 A propylene-ethylene random copolymer powder with an ethylene content of 4% by weight was mixed with 0.01% by weight of an organic filtrate along with additives such as an antioxidant and 0.30% by weight of a nucleating agent. Oxide Lupazole 101 (trademark, manufactured by Sildor Kamine Co., Ltd.) was added, and after stirring sufficiently with Hensinopexer, the mixture was extruded at 240°C using a φ65 extruder to form pellets to obtain polypropylene resin pellets.

The MFI of the resulting beret was 14. ! 7/10 minutes, and [η] is 1.35, so log M F I +5.
201og (Isamu was 1.82.

This resin is processed by injection stretch blow molding machine ASB-50.
Molded under the following conditions, body diameter 70van, inner volume 50
0 prototype bottles were molded.

Injection molding temperature: 220°C Injection molding mold temperature: 15°C Pre-blow stretching ratio: 1x vertically, 1.4x horizontally Pre-blow air pressure: 5' to 9/cr & stretching temperature adjustment mold temperature = 100°C Stretch blow Stretch ratio: 1.8 times vertically, 1.2 times horizontally Stretch blow air pressure: 9kl? /ffl The weight of the obtained bottle was 24 kg, and it was a blow-molded container made of polypropylene resin with extremely excellent transparency. Further, the wall thickness of the body was 0.513 mm, the haze was 2.8, and the transparency when the content liquid was poured was also good.

Example 2 Polypropylene resin pellets were obtained in the same manner as in Example 1, except that the amount of organic peroxide Lupasol 101 added was changed to 0.02% by weight. The midfielder
I was 25/710 minutes, [η] was 1.22, and now IogMFI+5.201og (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 The organic peroxide Lupazol was added to a propylene-ethylene random copolymer powder having an ethylene content of 5.5% by weight together with additives such as antioxidants and 0.30% by weight of a nucleating agent. 101 was added in an amount of 0.02% by weight and pelletized in the same manner as in Example 1 to obtain polypropylene resin pellets. Its MFl is 41Cl/10min, (
77) C1. ,10te,1ogMFI+5,201o
g('7) 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 The organic peroxide Perkatox was added to a powder of propylene-ethylene random copolymer having an ethylene content of 1.5% by weight along with additives such as an antioxidant and 0.20% by weight of a nucleating agent. 14 (trademark, manufactured by Kayaku Nouri@)) to 0
．． 005 weight suspension section, and in the same manner as in Example 1, polypropylene resin pellets were obtained. Its MFI is 69710
Minute dust, [η] is 1.58, logMP I +
5.20 l og (η) was equal to 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 seismic intensity of the body were measured.

The measurement results are shown in Table 1.

Comparative Example 1 Ethylene content 4 layered part MF as polypropylene resin
I2!7710 minutes, [η) 2,10 old/ri, 1ogM
A master bottle was molded in the same manner as in Example 1 using a propylene-ethylene random copolymer with FI+5.201 og(77)-1,98 and containing 0.3 weight of nucleating agent.

Table 1 shows the wall thickness and haze of the body of the obtained bottle.

Comparative Example 2 A prohylene-ethylene random copolymer powder containing 2 parts of ethylene was added with 0.25 parts of organic peroxide Perrydox 14 in addition to additives such as antioxidants. Polypropylene It fat pellets were obtained in the same manner as in Example 1 by adding 0.30 parts by weight of a nucleating agent. The midfielder
T was 55 710 minutes, [force was 1.09 dl/9, log MPi+5,201ogr'7J was 1.93.

Using this polypropylene, in the same manner as in Example 1,
Injection stretch blow molding was carried out, but the thickness unevenness during blow molding became significant and a good container could not be obtained.

Comparative Example 3 A powder of a propylene-ethylene random copolymer having an ethylene content of 0.5 parts per weight was added with an organic peroxide Lupasol 1010.10 parts per weight a nucleating agent in addition to additives such as an antioxidant. Polypropylene resin pellets were obtained in the same manner as in Example 1 by adding 30 parts by weight. That MT”I
is 15ri710 minutes, and (77')ha is 1.33 dl
/9 Te, logMFI+5.201og (cap 11.8
It was 2.

11- Using this polypropylene, in the same manner as in Example 1,
Injection stretch blow molding was performed, but the wall thickness during blow molding was significant and a good container could not be obtained.

=12-

Claims (1)

[Scope of Claims] 1. A polypropylene resin blow-molded container obtained by injection stretch blow-molding a random copolymer of propylene and ethylene, wherein the propylene-ethylene random copolymer has an ethylene content of 1 to 6% by weight. , the melt flow index is 4 to 509710 minutes, and the intrinsic viscosity measured in a tetralin solution at 135°C is 11:v) (d I/
g) and melt flow index MFI (9710 minutes)
The relationship is 1.70≦IogMFI+5.201og('7)≦1
．． 95. A blow molded polypropylene resin container with improved transparency and no uneven thickness.