JPS60127335A - Container made of polypropylene resin - Google Patents

Abstract

PURPOSE:To obtain a container, made of polypropylene (PP) by blow molding, and having improved transparency without uneven wall thickness, by incorporating PP resin having a specific melt flow index with dibenzylidenesorbitol or a derivative thereof. CONSTITUTION:A container made of polypropylene (PP) by incorporating propylene-alpha-olefin copolymer (preferably the alpha-olefin is ethylene) having 4-50g/ 10min melt flow index with dibenzylidenesorbitol expressed by the formula (R is 1-5C alkyl or alkoxyl) or a derivative thereof in an amount of 0.01-1wt%, preferably 0.1-0.5wt%, and molding the resultant resin composition by the injection drawing blow molding method to give 0.2-1mm. wall thickness in the drum part and <=9% haze expressed in terms of that for 1mm. wall thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polypropylene blow-molded container with extremely excellent transparency.

Polypropylene is a resin with excellent heat resistance, chemical resistance, safety and hygiene, and its blow molded products have excellent rigidity and impact resistance, so it is widely used in food containers, detergent containers, medical containers, etc. .

The reality is that the sky is white and hazy at best.

Conventionally, methods for improving the transparency of polypropylene molded products include adding a nucleation aid and biaxial stretching as a processing method, but blow molding usually does not allow for blow molded products with sufficient transparency. can't get it.

In addition, in the conventional blow molding method, the melt flow index (MFI) measured under condition 14 of JIS] (-7210) for polypropylene resins is at most 4
17/'10 minutes or less.

In recent years, the injection stretch blow molding method has been developed as a blow molding method for polypropylene resin (・However, with this new blow molding method, it is not possible to mold the MFI polypropylene used in the conventional blow molding method. However, it was not possible to obtain a blow-molded product with good transparency.

That is, the reality is that there are no blow-molded products that have sufficient transparency, and there is a demand for products that have the same transparency as polyvinyl chloride resin containers.

As a result of intensive research into polypropylene resin blow-molded containers with excellent transparency and no uneven thickness, the present inventors found that injection stretch blow molding can also be used as a blow molding method to produce polypropylene resin with a specific nucleation rate. It was discovered that a good polypropylene resin blow-molded container could be obtained by using a polypropylene resin composition to which a specific amount of the agent was added, and the present invention was finally completed.

That is, the present invention is a polypropylene resin container obtained by injection-infiltration blow molding of a random copolymer of propylene and α-olefin, wherein the propylene-α-olefin random copolymer has a Camelto flow index of 4.
509/'10 minutes, and contains 0.01 to 160% by weight of dibenzylidene sorbitol or its derivatives, when converted to body wall thickness 1 mm.

The polypropylene resin used in the present invention is mainly composed of brobylene, and is a copolymer with α-olefins such as ethylene, 1-butene, 1-pentene, and 1-hexene.
The FI is 4 to 509/''10. Note that it is preferable that the α-olefin is ethylene because of its excellent transparency.Moreover, polypropylene homopolymer has extremely uneven thickness and poor moldability.

MFI of propylene-α-olefin random copolymer
If the time is less than 49/'10 minutes, a blow-molded container with sufficient transparency cannot be obtained, and if it exceeds 50/710 minutes, uneven thickness will become significant, making it impossible to obtain a consistently good container. .

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

The amount used is 0.01 to 1 in polypropylene resin.
．． 0% by weight, preferably 0.1-0.5% by weight,
If it is less than 0.01% by weight, not only will sufficient transparency not be obtained, but if the MFI of the polypropylene resin is large,
Uneven thickness tends to occur, making it impossible to obtain a good blow-molded container. On the other hand, if it exceeds 1.0% by weight, the whiteness of the blow-molded container will increase, and white will bleed onto the surface, impairing transparency.

The dibenzylidene sorbitol derivative used in the present invention is a compound represented by the general formula (1) CI-1-08 H2OH (wherein R is an alkyl or alkoxy group having 1 to 5 carbon atoms), for example. Examples include di(methylbenzylidene) sorbitol, di(ethylbenzylidene) sorbitol, di(propylbenzylidene) sorbitol, di(methoxybenzylidene) sorbitol, di(ethoxybenzylidene) sorbitol, and the like.

In addition, in the present invention, antioxidants, ultraviolet absorbers,
Additives such as antistatic agents, lubricants, and colorants, other various resins, and nidistomers may be added and mixed.

The injection stretch blow molding method, which is the molding method used in 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 method used is a combination of mechanical longitudinal stretching using a rod and blow stretching using air blowing. Examples of molding machines suitable for this molding method include injection stretch blow molding machines ASB-50, ASB-150, and ASB-2 manufactured by Nittan ASB Machinery Co., Ltd.
50, ASIJ-650, etc.

In the present invention, the general conditions for performing injection stretch blow molding are as follows, taking the injection stretch blow molding machine ASB-50 as an example.

Injection molding temperature = 200-260°C Pre-blow stretching ratio: Vertical i, o ~ 1.8 times Width 1.2 ~
2.0 times preliminary blow air pressure = 3 to 7 kg/CJ
Stretching temperature adjustment Mold temperature = 90 to 140°C Stretch blow Stretch ratio: 1.2 to 3.5 times vertical, 1.2 to 6 times horizontal Stretch blow air pressure = 4 to 20 kg/cJ The blow molded container of the present invention is made of polypropylene The resin is molded by the above-mentioned injection stretch blow molding method until the body has a wall thickness of 0.2 to 1.0. , and the haze of the body is 9% or less when converted to a wall thickness of 11111L.

The haze degree of the present invention is measured by the method described in JIS K-6714, and the haze degree H of the body section converted to a wall thickness of 1WI++1 is determined by cutting a test piece, first measuring its haze degree B, Next, liquid paraffin was applied to both sides of the test piece to substantially eliminate the diffused reflection on the surface and the influence of reflection, and the haze level (internal haze level) A and the thickness of the test piece t (
+i) by the following formula in order of wall thickness.

1(=-10(B-A)) Here, ('B-A) is the amount of influence on the haziness of the surface.

Haze level L converted to wall thickness 11111L obtained in this way
(If it exceeds 9%, the transparency is insufficient, and it can be clearly seen that it is cloudy even by visual inspection.

Since the polypropylene resin container of the present invention is blow-molded, it has excellent rigidity and impact resistance, and it has much better transparency than conventional blow-molded containers, so it can be used as food containers, detergent containers, and shampoo containers. , toiletry containers, and medical containers.

The present invention will be explained below with reference to Examples.

The degree of haze is measured using a haze meter manufactured by Nippon Denshoku.
It was measured by the method described in SK-6714.

Example 1 The polypropylene resin had an ethylene content of 4% by weight and a MF'l 15';II/'10 min, and the dibenzylidene sorbitol derivative NC-4 (trademark,
Propylene containing 0.3% by weight (manufactured by Mitsui Toatsu Chemical @)
The ethylene random copolymer is molded using injection stretch blow molding machine A.
A round bottle with a body diameter of 70 mm and an internal capacity of 500 mm was molded using SB-50 under the following conditions.

Injection molding temperature: 220°C Injection molding mold temperature = 15°C Pre-blow stretching ratio: 1x vertical, 1.4x horizontal Pre-blow air pressure 5 to 9/cJ Stretching temperature adjustment mold temperature = 100°C Stretch blow stretching Magnification: 1.8 times vertical, 1.2 times horizontal Stretching blower air pressure 9kg1cr! The weight of the obtained bottle was 242, and it was a polypropylene blow-molded container with extremely excellent transparency. Further, the wall thickness of the body portion was 0.53 mm, the degree of haze B was 3.1%, and the degree of haze H converted to a wall thickness of 1 mm was 5.3%.

In Example 1, a round bottle was molded in the same manner as in Example 1, except that a polypropylene resin having the ethylene content, MFI, and nucleating agent content shown in Table 1 was used.

In Example 4, dibenzylidene sorbitol was used as the nucleating agent.

The performance of the bottle is summarized in Table 1.

Reference Example 1 Example 1 obtained by extrusion stretch blow molding using the resin used in Comparative Example 5 as the polypropylene resin
In a bottle similar to the above, the body wall thickness (n, ssmm) was uniform, but it was pale white and hazy, and the transparency was insufficient, and the haze degree B was 6.0%.

Further, the haze degree ■4 was 9.8% when converted into wall thickness 1 mmK.

The extrusion stretch blow molding method is a molding method in which a parison is obtained by cutting an extrusion-molded pipe into a certain length, which is then reheated to a stretching temperature and then stretch-blown to obtain a product. .

patent applicant Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Claims] 1) A polypropylene resin 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 509/1.
0 minutes, and contains 0.01 to i, o weight percent of dipendylidene sol beer or its derivatives, and has a haze degree of 9% when converted to a body wall thickness of 1 mm. Polypropylene resin containers that are: