JPH0639554B2 - Transparent polypropylene resin container - Google Patents

Description

The present invention relates to a polypropylene resin blow molded container having improved transparency and less uneven thickness.

Polypropylene resin is excellent in heat resistance, chemical resistance and safety and hygiene, and its blow-molded product is excellent in rigidity and impact strength, and is therefore widely used in food containers, detergent containers, medical containers and the like. However, the blow-molded product of polypropylene resin has insufficient transparency and does not sufficiently satisfy the market demand.

Conventionally, as a method for improving the transparency of polypropylene resin, a method of adding a nucleating agent, a method of thermally degrading in the presence or absence of an organic peroxide, a method of copolymerizing α-olefin with propylene, etc. However, in the molding processing method, a method of biaxial stretching is known, but in the ordinary blow molding method, even if these measures are taken, the product becomes white and has a haze, It is not possible to obtain a blow-molded container with excellent transparency.

In addition, the polypropylene resin used for conventional blow molding has a melt flow index (MFI) measured under JIS K-7210 condition 14 of at most 4 g in terms of moldability, impact resistance, rigidity and the like. It is about / 10 minutes, and particularly about 1 to 2 g / 10 minutes is often used.

On the other hand, in recent years, in the injection stretch blow molding method, a molding machine that can be applied to polypropylene resin has been developed, and a blow molded product has been prototyped, but a blow molded container made of polypropylene resin with sufficient transparency and uneven thickness is obtained. The reality is that it has not been done.

As a result of intensive investigations by the inventors of the present invention to obtain a polypropylene resin blow molded container having excellent transparency and no uneven thickness,
According to the injection stretch blow molding method as a blow molding method,
A polypropylene resin blow-molded container having good transparency can be obtained by adding a specific amount of a specific nucleating agent to a polypropylene resin having a specific MFI and having a specific relationship between [η] and MFI. Therefore, the present invention was finally completed.

That is, the present invention provides a polypropylene resin blow molding container obtained by injection stretch blow molding a random copolymer of propylene and α-olefin, wherein the propylene-α-olefin random copolymer has a melt flow index of 4 to 50 g. The relationship between the intrinsic viscosity [η] (d / g) and the melt flow index MFI (g / 10 min) measured in a tetralin solution at / 10 min and at 135 ° C. is 1.70 ≦ logMFI + 5.20log [η]. ≦ 1.95, and further containing 0.01 to 1.0% by weight of dibenzylidene sorbitol or a derivative thereof, made of polypropylene resin having a haze of 9% or less when converted to a body thickness of 1 mm. It is a blow molded container.

The propylene-α-olefin random copolymer used in the present invention is a random copolymer of ethylene mainly containing propylene, 1-butene, 1-pentene, 1-hexene and the like α-olefin, and particularly, A copolymer with ethylene is preferable because it has good transparency. Note that polypropylene homopolymer has a marked uneven thickness and poor moldability.

The propylene-α-olefin random copolymer in the present invention has an MFI of 4 to 50 g / 10 minutes and an intrinsic viscosity [η] (d / g) measured in a tetralin solution at 135 ° C.
And MFI (g / 10 minutes) must be 1.70 ≦ log MFI + 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. Further, if the MFI exceeds 50 g / 10 minutes, the uneven thickness becomes remarkable, so that a stable and good blow-molded container cannot be obtained.

Further, when the value of logMFI + 5.20log [η] is less than 1.70, the resin tends to be sticky, and a stable blow-molded container cannot be obtained. If it exceeds 1.95, sufficient transparency cannot be obtained.

Incidentally, a propylene-α-olefin random copolymer satisfying 1.70 ≦ logMFI + 5.20log [η] ≦ 1.95 can be obtained by adding a small amount of an organic peroxide to a raw material resin and performing melt pelletization. .

As the organic peroxide used for this purpose, for example,
Dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane and the like can be mentioned. Among them, a 10-hour half-life is 1
Those in the temperature range of 10 to 130 ° C. are preferable.

In the present invention, it is necessary to use a nucleating agent in order to obtain excellent transparency, and dibenzylidene sorbitol or its derivative is particularly desirable as the nucleating agent.

The amount used is 0.01 to 1.0 in polypropylene resin.
% By weight, preferably 0.1-0.5% by weight, 0.01% by weight
If it is less than the above range, sufficient transparency cannot be obtained, and if the polypropylene resin has a large MFI, uneven thickness is likely to occur, and a good blow-molded container cannot be obtained. Also, 1.0
On the other hand, if the content exceeds 10% by weight, the whiteness of the blow molded container increases
In addition, the surface bleeds white, which in turn impairs transparency.

The derivative of dibenzylidene sorbitol used in the present invention has the general formula (I) (In the formula, R is an alkyl or alkoxy group having 1 to 5 carbon atoms.), For example, di (methylbenzylidene) sorbitol, di (ethylbenzylidene) sorbitol, di (propylbenzylidene). Sorbitol,
Examples thereof include di (methoxybenzylidene) sorbitol and di (ethoxybenzylidene) sorbitol.

Incidentally, in the present invention, an antioxidant, an ultraviolet absorber,
Additives such as antistatic agents, lubricants, additives such as colorants, and other various resins and elastomers may be added and mixed.

The injection stretch blow molding method, which is a molding method in the present invention, is a molding method in which a bottomed parison is molded by injection molding, and then a preliminary blow, a stretching temperature is adjusted, and a product is obtained by stretching blow. As a stretching method, a method in which mechanical longitudinal stretching by a rod and blow stretching by blowing air are combined is adopted.

A molding machine suitable for this molding method is, for example, NISSEI ASB.
Kikai Co., Ltd. injection stretch blow molding machine ASB-50, ASB-150, A
Examples include SB-250 and ASB-650.

In the present invention, the general conditions for performing injection stretch blow molding will be described by taking the injection stretch blow molding machine ASB-50 as an example.
It is as follows.

Injection molding temperature: 200 to 260 ° C Preliminary blow stretch ratio: Vertical 1.0 to 1.8 times Horizontal 1.2 to 2.0 times Preliminary blow air pressure: 3 to 7 kg / cm ² Stretching temperature adjustment mold temperature: 90 to 140 ° C Stretching blow stretch ratio: Vertical 1.2 to 3.5 times Horizontal 1.2 to 6.0 times Stretching blow air pressure: 4 to 20 Kg / cm ² The blow molding container of the present invention has a wall thickness of the body portion of 0.2 to 1.0 mm by polypropylene resin injection injection blow molding.
Blow-molded so that the body has a haze of 1 mm
It was molded so as to have a haze of 9% or less when converted to.

The haze of the present invention is measured by the method described in JIS K-6714, and the haze H of the body part converted to a wall thickness of 1 mm is cut out from a test piece to measure the haze B first. Then, by applying liquid paraffin to both surfaces of the test piece and measuring the haze (internal haze) A and the thickness t (mm) of the test piece measured in a state in which the diffuse reflection on the surface and the influence of the reflection are substantially eliminated. It is a value converted to a wall thickness of 1 mm by the following formula.

Here, (BA) is the amount of influence on the haze of the surface. It can be seen that when the haze value H converted to a wall thickness of 1 mm thus obtained exceeds 9%, the transparency is insufficient and it is visually cloudy.

Since the polypropylene resin container of the present invention is blow molded, it is excellent in rigidity and impact resistance, and is significantly excellent in transparency as compared with a conventional blow molded container. Therefore, a food container, a detergent container, Shampoo container, toiletry container,
It can be suitably used for medical containers and the like.

Hereinafter, the present invention will be described with reference to examples.

The haze is a haze meter manufactured by Nippon Denshoku Co., Ltd., JIS K-6
It was measured by the method described in 714.

Example 1 A powder of a propylene-ethylene random copolymer having an ethylene content of 4%, an additive such as an antioxidant, and an organic peroxide lupazole 101 (trademark, lucidol).
Add 0.01% by weight of Yoshitomi Co., Ltd. and 0.3% by weight of NC-4 (trademark, manufactured by Mitsui Toatsu Chemical Co., Ltd.), which is a derivative of dibenzylidene sorbitol, as a nucleating agent, and stir well with a Hensyl mixer. After that, 240 ℃ by φ65mm extruder
Was extruded into pellets to obtain polypropylene resin pellets. The MFI of the obtained pellets was 14 g / 10 minutes, [η] was 1.35, and logMFI + 5.20log [η] was 1.82.

This resin is injection stretch blow-molded by the injection stretch blow molding machine ASB-50 under the following conditions, and the body diameter is 70 mm and the capacity is 5
A round bottle of 00 cc was molded.

Injection molding temperature: 220 ° C. Injection molding Mold temperature: 15 ° C. pre-blow stretch ratio: 1 vertical fold horizontal 1.4 times pre-blow air pressure: 5Kg / cm ² stretch temperature adjusting mold temperature: 100 ° C. stretch blow stretch ratio: Vertical 1.8 Horizontal 1.2 times stretch blow air pressure: 9 kg / cm ^{2 The} obtained bottle weighed 24 g and was a polypropylene resin blow molded container having extremely excellent transparency. The wall thickness of the body was 0.53 mm, the haze B was 2.8%, and the haze H converted to a wall thickness of 1 mm was 4.3%.

Example 2 In Example 1, the amount of the nucleating agent NC-4 added was 0.10% by weight.
Polypropylene resin pellets were obtained in the same manner as in Example 1 except that Its MFI is 14g / 10 minutes, [η] is 1.34d / g, logMFI + 5.20log [η] is
It was 1.81.

An injection stretch blow-molded bottle was obtained in the same manner as in Example 1 using this resin. The wall thickness and haze of the body were measured.

The measurement results are shown in Table 1.

Example 3 A polypropylene resin pellet was obtained in the same manner as in Example 1 except that the addition amount of the organic peroxide lupazole 101 was changed to 0.02% by weight. Its MFI is 2
5g / 10min, [η] 1.22d / g, logMFI
The + 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. 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 having an ethylene content of 5.5% by weight, 0.003% by weight of an organic peroxide lupazole 101 and a nucleating agent NC-, in addition to additives such as an antioxidant. In the same manner as in Example 1 except that 0.2% by weight of 4 was added, polypropylene resin pellets were obtained. That
MFI is 8g / 10min, [η] is 1.51d / g, l
The ogMFI + 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. The wall thickness and haze of the body were measured.

The measurement results are shown in Table 1.

Example 5 Polypropylene resin pellets were obtained in the same manner as in Example 4 except that the addition amount of the organic peroxide lupazole 101 was changed to 0.20% by weight. Its MFI is 4
1g / 10min, [η] is 1.09d / g, logMFI
The + 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. The wall thickness and haze of the body were measured.

The measurement results are shown in Table 1.

Example 6 A powder of a propylene-ethylene random copolymer having an ethylene content of 1.5% by weight was added to an organic peroxide Percadox 14 (trademark, in addition to additives such as an antioxidant.
Kayaku Nouri Co., Ltd. 0.15% by weight and dibenzylidene sorbitol 0.30% by weight as a nucleating agent were added, and polypropylene resin pellets were obtained in the same manner as in Example 1.
Its MFI is 22 g / 10 minutes, and [η] is 1.23 d /
The logMFI + 5.20log [η] was 1.81 in g.

Using this resin, an injection stretch blow molded bottle was obtained in the same manner as in Example 1. The wall thickness and haze of the body were measured.

The measurement results are shown in Table 1.

Comparative Example 1 A powder of a propylene-ethylene random copolymer having an ethylene content of 4% by weight was added to an organic peroxide lupazole 101, 0.005% by weight and a nucleating agent NC-, in addition to additives such as an antioxidant acid. 4, 0.30% by weight was added, and polypropylene resin pellets were obtained in the same manner as in Example 1. That MF
I is 2 g / 10 minutes, [η] is 1.97 d / g, and log
The MFI + 5.20 log [η] was 1.83.

Using this resin, an injection stretch blow molded bottle was obtained in the same manner as in Example 1. The wall thickness and haze of the body were measured.

The measurement results are shown in Table 1.

Comparative Example 2 In a powder of propylene-ethylene random copolymer having an ethylene content of 2% by weight, in addition to additives such as an antioxidant, 0.25% by weight of organic peroxide Percadox 14 and a nucleating agent NC- 4 0.30% by weight was added and in the same manner as in Example 1, polypropylene resin pellets were obtained. That MF
I is 55 g / 10 minutes, [η] is 1.03 d / g, and
The ogMFI + 5.20log [η] was 1.81.

Using this polypropylene, injection stretch blow molding was performed in the same manner as in Example 1. However, uneven thickness was remarkable during blow molding, and a good container could not be obtained.

Comparative Example 3 Polypropylene homopolymer powder, organic peroxide Percadox 14 in addition to additives such as antioxidants
A polypropylene resin pellet was obtained in the same manner as in Example 1 except that 0.25% by weight and NC-4 0.3% by weight were added. Its MFI is 15g and [η] is 1.45d / g
The logMFI + 5.20log [η] was 2.02.

Using this resin, injection stretch blow molding was performed in the same manner as in Example 1, but uneven thickness was remarkable during blow molding,
No good container has been obtained.

Comparative Example 4 A polypropylene resin pellet was obtained in the same manner as in Example 1 except that sodium benzoate was used as the nucleating agent instead of NC-4. That MFI is 1
4g / 10min, [η] is 1.35d / g, logMFI
The + 5.20log [η] was 1.82.

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 5 A polypropylene resin pellet was obtained in the same manner as in Example 1, except that the nucleating agent was not added. That MF
I is 14 g / 10 minutes, [η] is 1.35 d / g, and
The ogMFI + 5.20log [η] was 1.82.

Using this resin, an injection stretch blow-molded bottle was obtained in the same manner as in Example 1, but uneven thickness was slightly generated. The wall thickness and haze of the body of this container were measured in the same manner as in Example 1.

The measurement results are shown in Table 1.

Comparative Example 6 A polypropylene resin pellet was obtained in the same manner as in Example 1 except that the organic peroxide rupar 101 was not added. MFI of the obtained pellets is 6.0 g / 10 minutes,
[Η] was 1.49 and logMFI + 5.20log [η] was 1.68.

This resin was injection stretch blow molded in the same manner as in Example 1 to obtain a round bottle. As a result of measuring the wall thickness and the haze of this body, the haze of 1 mm in wall thickness was 6.8%.

Comparative Example 7 In the method of Example 1, the injection-molded product before stretching had a thickness of 3 mm and a haze of 30%, and the haze of 11 mm in terms of wall thickness was 10%.

 ─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A 58-129036 (JP, A) JP-A 56-161444 (JP, A) JP-A 54-159454 (JP, A) JP-A 54- 69155 (JP, A)

Claims (2)

[Claims] 1. A blow molding container made of polypropylene resin, wherein a random copolymer of propylene and α-olefin is injection stretch blow molded, wherein the propylene-α-olefin random copolymer has a melt flow index of 4.
Intrinsic viscosity [η] (up to 50 g / 10 minutes and measured in a tetralin solution at 135 ° C. by adding an organic peroxide to the raw material propylene-α-olefin random copolymer and melt-pelletizing. dl / g) and the melt flow index MFI (g / 10 min) are set so that 1.70 <logMFI + 5.20log [η] <1.95, and dibenzylidene sorbitol or its derivative is 0.01 A polypropylene resin blow-molded container having a haze of 9% or less when converted to a body thickness of 1 mm, characterized in that the content is 1 to 1.0% by weight. 2. A polypropylene resin blow-molded container according to claim 1, wherein the α-olefin is ethylene.